JPH11126335A - Optical information recording medium, optical information recording apparatus and method, and optical information reproducing apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to record information at a higher density. SOLUTION: The optical information recording medium 1 has plural information recording layers 2 which are laminated in a thickness direction, are respectively recorded with information by interference patterns by the interference of information light carrying the information and reference light for recording and generate the reproducing light corresponding to the recorded information when irradiated with reference light for reproducing and positioning layers 3 which are used for positioning of the information light to the respective information recording layers 2, the reference light for recording and the reference light for reproducing. The optical information recording and reproducing device executes recording and reproducing by accessing the desired information recording layers 2 by using the positioning layers 3 of the optical information recording medium 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium on which information is recorded using holography, an optical information recording apparatus and method for recording information on the optical information recording medium, and information from the optical information recording medium. The present invention relates to an optical information reproducing apparatus and method for reproducing information.

[0002]

2. Description of the Related Art In general, holographic recording in which information is recorded on a recording medium using holography is performed by superimposing light having image information and reference light inside a recording medium, and generating interference at that time. This is performed by writing stripes on a recording medium. When reproducing the recorded information, the recording medium is irradiated with reference light, whereby the image information is reproduced by diffraction due to interference fringes.

In recent years, volume holography, especially digital volume holography, has been developed in the practical range for ultra-high-density optical recording, and has attracted attention. Volume holography is a method of writing interference fringes three-dimensionally by actively utilizing the thickness direction of the recording medium. Increasing the thickness increases the diffraction efficiency, and using multiplex recording to increase the storage capacity. There is a feature that can be achieved. And
Digital volume holography is a computer-oriented holographic recording method that uses the same recording medium and recording method as volume holography, but limits image information to be recorded to binary digital patterns. In this digital volume holography, for example, image information such as an analog picture is once digitized, developed into two-dimensional digital pattern information, and recorded as image information. At the time of reproduction, this digital pattern information is read out and decoded to return to the original image information for display. Thereby, even if the SN ratio (signal-to-noise ratio) is somewhat poor at the time of reproduction, the original information can be reproduced very faithfully by performing differential detection or encoding the binary data to correct errors. It becomes possible.

FIG. 34 is a perspective view showing a schematic configuration of a recording / reproducing system in conventional digital volume holography. This recording / reproducing system includes a spatial light modulator 10 for generating an information light 102 based on two-dimensional digital pattern information.
1, a lens 103 for condensing the information light 102 from the spatial light modulator 101 and irradiating the hologram recording medium 100 with the information light 102. Reference light irradiating means (not shown) for irradiating light 104, CCD (charge coupled device) array 107 for detecting reproduced two-dimensional digital pattern information, and reproduction light 105 emitted from hologram recording medium 100 And a lens 106 for condensing the light and irradiating the light onto the CCD array 107. For the hologram recording medium 100, a crystal such as LiNbO ₃ is used.

In the recording / reproducing system shown in FIG. 34, at the time of recording, information such as an original image to be recorded is digitized, and a signal of 0 or 1 is further arranged two-dimensionally to generate two-dimensional digital pattern information. . One piece of two-dimensional digital pattern information is called page data. Here, it is assumed that page data # 1 to #n are multiplex-recorded on the same hologram recording medium 100. In this case, first, the spatial light modulator 101 selects transmission or light blocking for each pixel based on the page data # 1, whereby the spatially modulated information light 1 is selected.
02 is generated and irradiated on the hologram recording medium 100 via the lens 103. At the same time, the hologram recording medium 10
0, the reference light 1 from a direction θ1 substantially orthogonal to the information light 102.
04, and inside the hologram recording medium 100,
The interference fringes formed by the superposition of the information beam 102 and the reference beam 104 are recorded. In order to increase the diffraction efficiency, the reference light 104 is transformed into a flat beam by a cylindrical lens or the like, and the interference fringes are changed to the hologram recording medium 100.
To be recorded in the thickness direction. At the time of recording the next page data # 2, the reference light 104 is irradiated from the angle θ2 different from θ1, and the reference light 104 and the information light 1 are irradiated.
02 can be multiplex-recorded on the same hologram recording medium 100. Similarly, at the time of recording other page data # 3 to #n, information is multiplex-recorded by irradiating the reference beam 104 from different angles θ3 to θn. A hologram in which information is multiplex-recorded is called a stack. In the example shown in FIG. 34, the hologram recording medium 100 has a plurality of stacks (stack 1, stack 2,..., Stack m,...).

In order to reproduce any page data from the stack, the stack may be irradiated with the reference beam 104 having the same incident angle as when the page data was recorded. Then, the reference light 104 is selectively diffracted by an interference fringe corresponding to the page data, and a reproduction light 105 is generated. This reproduction light 105 is transmitted through a lens 106
, And the two-dimensional pattern of the reproduction light is detected by the CCD array 107. Then, the information such as the original image is reproduced by decoding the detected two-dimensional pattern of the reproduction light in a manner reverse to that at the time of recording.

[0007]

In the configuration shown in FIG. 34, information can be multiplex-recorded on the same hologram recording medium 100. However, in order to record information at an extremely high density, the hologram recording medium 100 must be The positioning of the information light 102 and the reference light 104 becomes important. However, in the configuration shown in FIG.
Since there is no information for positioning in the hologram recording medium 100, the information beam 102 and the reference beam 10
The positioning of 4 can only be performed mechanically, and high-precision positioning is difficult. Therefore, the removability (easiness of transferring the hologram recording medium from one recording / reproducing apparatus to another recording / reproducing apparatus and performing the same recording / reproducing) is poor, and random access is difficult and high-density recording is difficult. There is a problem that is. Further, in the configuration shown in FIG. 34, since the optical axes of the information light 102, the reference light 104, and the reproduction light 105 are spatially arranged at mutually different positions, there is a problem that the optical system becomes large. .

In the patent application (Japanese Patent Application No. 9-104614) filed earlier, the present applicant irradiates a disc-shaped recording medium with information light and reference light.
A technique for recording information by an interference pattern due to the interference between the information light and the reference light has been proposed.

In this technique, an interference pattern is volumetrically recorded on a hologram layer in a recording medium. In other words, a volume hologram is formed on the hologram layer.
However, in this technique, although a volume hologram is formed using the thickness direction of the recording medium, only one volume hologram is formed in the thickness direction of the recording medium.
It is not efficient in terms of recording capacity.

It is conceivable to increase the thickness of the hologram layer in order to improve the recording capacity. However, if the entire hologram layer in the thickness direction is to be used, the amount of light is reduced, or the recording area (volume hologram) of one unit is reduced. This is not effective because, for example, it becomes difficult to perform high density recording.

Although it is conceivable to increase the number of pixels of the spatial light modulator to increase the amount of data per unit recording area, the number of pixels of the spatial light modulator is limited, and it is dramatically increased. It is difficult to increase the recording density.

Conventionally, in an optical disk device, a technique of recording a plurality of pits in the thickness direction of the optical disk has also been proposed (see "Electronics", May 1996, pp. 96-99). However, in this technique, the thickness of the substrate up to the pit changes in accordance with the position of the pit in the thickness direction, and as a result, the aberration also changes in accordance with the change in the thickness of the substrate. However, it is difficult to obtain good optical characteristics. It is also conceivable to perform aberration correction according to the position of the pit in the thickness direction, but this is not practical.

In general, when recording a plurality of information in the thickness direction of a recording medium, there is a problem that it is difficult to form position information for each position in the thickness direction. Therefore, conventionally, it has been difficult to precisely control the information recording position in the thickness direction of the recording medium, and it has been difficult to precisely record information in the thickness direction of the recording medium.

The present invention has been made in view of such a problem, and an object of the present invention is to provide an optical information recording medium on which information is recorded by using holography, which can record information at a higher density. Optical information recording medium, optical information recording apparatus and method capable of recording information at a high density on this optical information recording medium, and information recorded at a high density An object of the present invention is to provide an optical information reproducing apparatus and method capable of reproducing information from an optical information recording medium.

[0015]

An optical information recording medium according to the present invention is laminated in a thickness direction, and each of the optical information recording media is formed by using holography by an interference pattern caused by interference between an information light carrying information and a recording reference light. Information is recorded,
A plurality of information recording layers for generating reproduction light corresponding to recorded information when irradiated with reproduction reference light; information light, recording reference light, and reproduction reference light for each information recording layer; And a plurality of positioning layers used for positioning.

An optical information recording apparatus according to the present invention is an optical information recording apparatus for recording information on the optical information recording medium, wherein an interference between the information light and the recording reference light occurs on an arbitrary information recording layer. A recording optical system for irradiating the information light and the reference light for recording while converging it on an arbitrary information recording layer, and an information recording layer on which information is to be recorded so that information is recorded by an interference pattern due to And position control means for controlling the positions of the information light and the recording reference light with respect to the information recording layer on which information is to be recorded, using the corresponding positioning layer.

An optical information recording method according to the present invention is an optical information recording method for recording information on the optical information recording medium, wherein a positioning layer corresponding to the information recording layer on which information is to be recorded is used. Irradiating the information light and the recording reference light onto the information recording layer on which information is to be recorded while converging the information light and the recording reference light on the information recording layer on which the information is to be recorded. Then, the information is recorded on the information recording layer in which the information is to be recorded by an interference pattern caused by the interference between the information light and the recording reference light.

An optical information reproducing apparatus according to the present invention is an optical information reproducing apparatus for reproducing information from the above-mentioned optical information recording medium. While irradiating while converging the reference light for reproduction, a reproduction optical system for collecting reproduction light generated from the information recording layer by being irradiated with the reproduction reference light,
Position control means for controlling the position of the reference light for reproduction with respect to the information recording layer from which information is to be reproduced by using a positioning layer corresponding to the information recording layer from which information is to be reproduced, and the reproduction collected by the reproduction optical system. And a detecting means for detecting light.

An optical information reproducing method according to the present invention is an optical information reproducing method for reproducing information from the optical information recording medium, wherein a positioning layer corresponding to the information recording layer from which information is to be reproduced is used. While controlling the position with respect to the information recording layer in which information is to be reproduced, the information recording layer in which information is to be reproduced is irradiated with the reproduction reference light corresponding to the recording reference light at the time of recording while converging. The reproducing light generated from the information recording layer by the irradiation of the reproducing reference light is collected, and the reproducing light is detected to reproduce the information.

In the optical information recording medium of the present invention, the positioning of the information light, the recording reference light and the reproduction reference light with respect to each information recording layer is performed by using the positioning layer, and information is recorded on the information recording layer. And reproduction of information from the information recording layer.

In the optical information recording apparatus according to the present invention, the position control means uses the positioning layer corresponding to the information recording layer on which information is to be recorded, and the information light and recording medium for the information recording layer on which information is to be recorded. The position of the reference beam is controlled, and the recording optical system irradiates the information recording layer on which information is to be recorded with the information beam and the recording reference beam while being converged, thereby causing interference between the information beam and the recording reference beam. The information is recorded by the interference pattern of.

In the optical information recording method of the present invention, the position of the information light and the recording reference light with respect to the information recording layer on which information is to be recorded is determined using the positioning layer corresponding to the information recording layer on which information is to be recorded. The information beam and the reference light for recording are irradiated while being converged on the information recording layer on which the information is to be recorded, and the information is recorded by an interference pattern due to the interference between the information light and the reference light for recording.

In the optical information reproducing apparatus of the present invention, the position control means uses the positioning layer corresponding to the information recording layer from which the information is to be reproduced, and the reproduction reference light for the information recording layer from which the information is to be reproduced. The position is controlled, and the reproducing optical system irradiates the information recording layer from which information is to be reproduced, while converging the reproducing reference light corresponding to the recording reference light at the time of recording with the reproducing reference light. The reproduction light generated from the information recording layer by the irradiation is collected, and the reproduction light is detected by the detecting means to reproduce the information.

In the optical information reproducing method of the present invention, the position of the reproduction reference light with respect to the information recording layer from which information is to be reproduced is controlled by using the positioning layer corresponding to the information recording layer from which information is to be reproduced, The information recording layer from which information is to be reproduced is irradiated with the reproduction reference light corresponding to the recording reference light at the time of recording while being converged, and is irradiated from the information recording layer by being irradiated with the reproduction reference light. The generated reproduction light is collected, and this reproduction light is detected,
The information is reproduced.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a pickup in an optical information recording device according to a first embodiment of the present invention and an optical information recording / reproducing device as an optical information reproducing device, and an optical information recording medium according to the first embodiment of the present invention. FIG. 2 is an explanatory diagram showing the configuration, FIG. 2 is a block diagram showing the entire configuration of the optical information recording / reproducing apparatus according to the present embodiment, and FIG. 3 is an explanatory diagram showing the configuration of the optical information recording medium according to the present embodiment.

First, the configuration of the optical information recording medium according to the present embodiment will be described with reference to FIG. The optical information recording medium 1 is laminated in the thickness direction, and information is recorded by using an interference pattern between an information light carrying information and a recording reference light by using volume holography. A plurality of information recording layers 2 for generating reproduction light corresponding to recorded information when irradiated with reference light; information light, recording reference light, and reproduction reference light for each information recording layer 2 And a positioning layer 3 used for positioning. The information recording layers 2 and the positioning layers 3 are alternately laminated, and the two outermost layers of the optical information recording medium 1 are
It has become. Each surface of the two outermost positioning layers 3 of the optical information recording medium 1 is preferably coated with an antireflection film. The entire optical information recording medium 1 is formed in a disk shape. Although FIG. 3 shows an example in which the information recording layer 2 has five layers, the number of the information recording layers 2 is not limited to this.

The information recording layer 2 is formed of a hologram material whose optical characteristics such as a refractive index, a dielectric constant, and a reflectance change according to the intensity of light when the light is irradiated. As a hologram material, for example, Dupont
t) Photopolymers manufactured by the company
HRF-600 (product name) or the like is used. The positioning layer 3 is formed of a transparent material such as polycarbonate.

On each surface of the positioning layer 3 facing the information recording layer 2, a plurality of address servo areas 6 extending linearly in the radial direction are provided at predetermined angular intervals. Is a data area 7. In the address servo area 6, information for performing focus servo and tracking servo by a sampled servo method and address information are recorded in advance by emboss pits or the like. The focus servo can be performed based on light emitted from a pickup, which will be described later, and reflected by the reflective surface, with the boundary surface between the information recording layer 2 and the positioning layer 3 as a reflective surface. When the refractive index of the information recording layer 2 and the positioning layer 3 are close to each other and the desired reflectance cannot be obtained at the interface between the information recording layer 2 and the positioning layer 3, the information is adjusted so that the desired reflectance is obtained. A dielectric multilayer film using AlN or the like may be provided between the recording layer 2 and the positioning layer 3. For example, wobble pits can be used as information for performing the tracking servo. In the present embodiment, the address information includes information on the number of layers of the corresponding information recording layer 2 in the thickness direction, in addition to the information on the track and the sector.

Next, the configuration of the optical information recording / reproducing apparatus according to this embodiment will be described. As shown in FIG. 2, the optical information recording / reproducing apparatus 10 includes a spindle 81 on which the optical information recording medium 1 is mounted, a spindle motor 82 for rotating the spindle 81, and a rotation speed of the optical information recording medium 1. And a spindle servo circuit 83 for controlling the spindle motor 82 so as to maintain the value of The optical information recording / reproducing apparatus 10 further irradiates the optical information recording medium 1 with information light and recording reference light to record information, and irradiates the optical information recording medium 1 with reproduction reference light. A pickup 11 for detecting the reproduction light and reproducing the information recorded on the optical information recording medium 1; and a light input / output position of the pickup 11 can be moved in a radial direction of the optical information recording medium 1. And a driving device 84. The pickup 11 is formed, for example, in an arm shape in which a light input / output unit rotates about a predetermined rotation axis. In this case, the driving device 84
Is a device for rotating.

The optical information recording / reproducing apparatus 10 further receives a focus error signal FE,
A detection circuit 85 for detecting the tracking error signal TE and the reproduction signal RF; and driving an actuator in the pickup 11 based on a focus error signal FE detected by the detection circuit 85 and a command from a controller described later. A focus servo circuit 86 that moves the objective lens in the thickness direction of the optical information recording medium 1 to control focus servo and a transition from an arbitrary information recording layer 2 to another information recording layer 2, and is detected by a detection circuit 85. A tracking servo circuit 87 that drives an actuator in the pickup 11 based on the tracking error signal TE to move the objective lens in the radial direction of the optical information recording medium 1 to perform tracking servo; Based on directives from Seek control circuit 8 for controlling the seek the dynamic device 84 is controlled to move the input and output position of light in the pickup 11 in the radial direction of the optical information recording medium 1
8 is provided.

The optical information recording / reproducing apparatus 10 further decodes output data of a CCD array, which will be described later, in the pickup 11 to reproduce data recorded in the data area 7 of the optical information recording medium 1 and to detect a data stored in the detection area. A signal processing circuit 89 for reproducing a basic clock or determining an address from a reproduced signal RF from the optical disc 85;
And a controller 90 for controlling the whole of the device. The controller 90 receives the basic clock and address information output from the signal processing circuit 89 and controls the pickup 11, the spindle servo circuit 83, the seek control circuit 88, and the like. The spindle servo circuit 83 receives the basic clock output from the signal processing circuit 89.

Detection circuit 85, focus servo circuit 8
6, the tracking servo circuit 87 and the seek control circuit 88 correspond to the position control means in the present invention.

As shown in FIG. 1, the pickup 11
Is an objective lens 12A arranged so as to face one surface of the optical information recording medium 1 when the optical information recording medium 1 is fixed to the spindle 81; An actuator 13A that can move in the thickness direction and the radial direction, and a two-divided optical rotation plate 14A, a prism block 15A, and a spatial light that are sequentially arranged from the objective lens 12A side on the opposite side of the optical information recording medium 1 in the objective lens 12A. A modulator 16, a collimator lens 17, a laser coupler 20, a convex lens 18A and a CCD array 19 disposed on the side of the prism block 15A.
A is provided.

The pickup 11 further includes a spindle 8
When the optical information recording medium 1 is fixed to the optical information recording medium 1, the objective lens 12B is disposed so as to face the other surface of the optical information recording medium 1;
13B movable in the thickness direction and the radial direction of the optical information recording medium 1 in the objective lens 12B
On the opposite side, a two-segment optical rotation plate 14B, a prism block 15B, a convex lens 18B, and a CCD array 19B are provided in order from the objective lens 12B side.

Each of the two split optical rotation plates 14A and 14B is the optical rotation plate 1 arranged on the upper side of the optical axis in FIG.
4AR and 14BR, and optical rotation plates 14AL and 14BL arranged in the lower part of the optical axis in FIG. Each of the optical rotation plates 14AR, 14BR, 14AL, and 14BL is configured by sealing liquid crystal between, for example, two transparent electrode substrates. When no voltage is applied between the two transparent electrode substrates (hereinafter, referred to as off), the optical rotation plates 14AR and 14BR rotate the polarization direction of incident light by -45 °, and apply a voltage between the two transparent electrode substrates. Is applied (hereinafter referred to as ON), the direction of polarization of incident light is not rotated. On the other hand, when the optical rotation plates 14AL and 14BL are turned off, the polarization direction of the incident light is rotated by + 45 °, and when turned on, the polarization direction of the incident light is not rotated.

The normal direction of the prism block 15A between the two-divided optical rotation plate 14A and the spatial light modulator 16 is 45 degrees with respect to the optical axis direction between the two-divided optical rotation plate 14A and the spatial light modulator 16. A polarizing beam splitter surface 15Aa arranged at an angle and a reflecting surface 15Ab arranged in a direction in which light from the spatial light modulator 16 is reflected by the polarizing beam splitter surface 15Aa and parallel to the polarizing beam splitter surface 15Aa. have.

The prism block 15B has a polarizing beam splitter surface 15Ba disposed parallel to the polarizing beam splitter surface 15Aa of the prism block 15A between the two-part optical rotation plate 14B and the convex lens 18B.
And a reflecting surface 15Bb that is arranged at a position where the light from the reflecting surface 15Ab in the prism block 15A is incident and is parallel to the polarizing beam splitter surface 15Ba.

The reflecting surfaces 15Ab and 15Bb of the prism blocks 15A and 15B are disposed on the sides of the optical information recording medium 1, and light traveling from the reflecting surface 15Ab toward the reflecting surface 15Bb is directed to the sides of the optical information recording medium 1. It is designed to pass.

The spatial light modulator 16 has a large number of pixels arranged in a lattice pattern, and spatially modulates light by a difference in polarization direction by selecting a polarization direction of emitted light for each pixel. You can do it. Specifically, the spatial light modulator 16 has, for example, the same configuration as that of a liquid crystal display element utilizing the optical rotation of liquid crystal, except for a polarizing plate. Here, when turned off, the spatial light modulator 16 rotates the polarization direction by + 90 ° for each pixel, and does not rotate the polarization direction when turned on. As the liquid crystal in the spatial light modulator 16, for example, a ferroelectric liquid crystal having a high response speed (on the order of microsecond) can be used. This enables high-speed recording, for example, 1
It is possible to record information for a page in several μ or less. The CCD arrays 19A and 19B are respectively
It has a large number of pixels arranged in a grid.

In the pickup 11 shown in FIG.
The laser coupler 20 is provided with S-polarized light (the polarization direction is
Laser light having a linear polarization perpendicular to the paper surface of FIG. 1) is emitted, and this laser light is converted into a parallel light flux by a collimator lens 17, passes through a spatial light modulator 16,
The light is incident on the 5A polarization beam splitter surface 15Aa. Here, the light that has passed through the off-pixels of the spatial light modulator 16 becomes P-polarized light (linearly polarized light whose polarization direction is parallel to the incident surface), passes through the polarizing beam splitter surface 15Aa, and passes through the two-segment optical rotation plate 14A. And the objective lens 12A
And irradiates the optical information recording medium 1. On the other hand, the light that has passed through the ON pixel of the spatial light modulator 16 remains S-polarized light, is reflected by the polarization beam splitter surface 15Aa, is further reflected by the reflection surface 15Ab, is incident on the prism block 15B, and is reflected by the reflection surface. Fifteen
Bb, the light is sequentially reflected by the polarization beam splitter surface 15Ba, passes through the split optical rotation plate 14B, is condensed by the objective lens 12B, and is irradiated on the optical information recording medium 1.

Objective lens 12A from optical information recording medium 1
The light traveling toward the side is reflected by the objective lens 12A,
A sequentially passes through and enters the polarization beam splitter surface 15Aa of the prism block 15A. S-polarized light of this light is polarized beam splitter surface 1
5Aa, reflected by the convex lens 18A,
The light is incident on the D array 19A. On the other hand, among the light traveling from the optical information recording medium 1 toward the objective lens 12A, the P-polarized light is polarized light beam splitter surface 15Aa.
, Passes through the spatial light modulator 16, is condensed by the collimator lens 17, and enters the laser coupler 20.

Objective lens 12B from optical information recording medium 1
The light traveling to the side is divided by the objective lens 12B and the two-part optical rotation plate 14
B, and sequentially enters the polarization beam splitter surface 15Ba of the prism block 15B. S-polarized light of this light is polarized beam splitter surface 1
The P-polarized light reflected by 5Ba is transmitted through the polarization beam splitter surface 15Ba, is collected by the convex lens 18B, and is incident on the CCD array 19B.

In the pickup 11 shown in FIG. 1, the recording optical system 91 includes the laser coupler 20 and the collimator lens 1.
7, spatial light modulator 16, prism blocks 15A, 15
B, 2 split optical rotation plates 14A, 14B, objective lens 12A,
12B. In the pickup 11 shown in FIG. 1, there are two reproduction optical systems, a reproduction optical system 92 and a reproduction optical system 93. The reproduction optical system 92 includes the laser coupler 20, the collimator lens 17, the spatial light modulator 1
6, prism block 15A, two-part optical rotation plate 14A, objective lens 12A, convex lens 18A, CCD array 19A
It is composed of The reproduction optical system 93 includes the laser coupler 2
0, a collimator lens 17, a spatial light modulator 16, prism blocks 15A and 15B, a two-part optical rotation plate 14B, an objective lens 12B, a convex lens 18B, and a CCD array 19B.

FIG. 4 is a perspective view showing the structure of the laser coupler 20 in FIG. 1, and FIG. 5 is a side view of the laser coupler 20. As shown in these figures, the laser coupler 20
Semiconductor substrate 2 on which photodetectors 25 and 26 are formed
1 and a prism 22 arranged on the semiconductor substrate 21 so as to cover the photodetectors 25 and 26 and bonded to the semiconductor substrate 21 at a position different from the position where the photodetectors 25 and 26 are formed on the semiconductor substrate 21. The semiconductor device includes a semiconductor element 23 arranged and bonded on a semiconductor substrate 21 and a semiconductor laser 24 bonded on the semiconductor element 23. The semiconductor laser 24 emits forward laser light in the horizontal direction toward the prism 22 and emits backward laser light in a direction opposite to the forward laser light. Semiconductor laser 2 of prism 22
On the side of the semiconductor laser 2, a slope is formed.
4 reflects part of the forward laser light from the semiconductor substrate 2
1 and a semi-reflective surface 22a that transmits a part of the return light from the optical information recording medium 1. The upper surface of the prism 22 is a total reflection surface 22b that totally reflects light passing through the prism 22, as shown in FIG. In the semiconductor element 23, a photodetector 27 that receives a backward laser beam from the semiconductor laser 24 is formed. The output signal of the photodetector 27 is used to automatically adjust the output of the semiconductor laser 24. Various amplifiers and other electronic components are built in the semiconductor substrate 21. The semiconductor element 23 has built-in electronic components such as an amplifier for driving the semiconductor laser 24.

The laser coupler 20 shown in FIGS. 4 and 5
1, a part of the forward laser light from the semiconductor laser 24 is reflected by the semi-reflective surface 22a of the prism 22, and is incident on the collimator lens 17 in FIG. A part of the return light from the optical information recording medium 1 collected by the collimator lens 17 passes through the semi-reflective surface 22a of the prism 22, and is guided into the prism 22,
It is directed to the photodetector 25. A semi-reflective film is formed on the photodetector 25, and a part of the light guided into the prism 22 passes through the semi-reflective film on the photodetector 25 and is incident on the photodetector 25, and the other part is a photodetector. The light is reflected by the semi-reflective film on the surface 25, further reflected by the total reflection surface 22 b of the prism 22, and incident on the photodetector 26.

Here, as shown in FIG.
The light guided into the light source 2 is once converged so as to have the smallest diameter in the middle of the optical path between the photodetectors 25 and 26. When the light from the laser coupler 20 is in a focused state where the light converges on the boundary surface between the arbitrary information recording layer 2 and the positioning layer 3 in the optical information recording medium 1 so as to have the smallest diameter, the light enters the photodetectors 25 and 26. The diameters of the light become equal, and when out of focus, the diameters of the light incident on the photodetectors 25 and 26 are different. Since the changes in the diameter of the light incident on the photodetectors 25 and 26 are in opposite directions, a focus error signal can be obtained by detecting a signal corresponding to the change in the diameter of the light incident on the photodetectors 25 and 26. As shown in FIG. 4, each of the photodetectors 25 and 26 has a light receiving unit divided into three. The light receiving unit in the photodetector 25 is A1,
C1, B1, the light receiving portion of the photodetector 26 is A
2, C2 and B2. C1 and C2 are respectively A
It is a light receiving section in the central portion between 1, B1 and between A2, B2.
The dividing line between the light receiving sections is arranged so as to be parallel to the direction corresponding to the track direction in the optical information recording medium 1. Therefore, between the light receiving portions A1, B1 and A2,
From the output difference between B2, a tracking error signal can be obtained by the push-pull method.

The control of the output of the semiconductor laser 24 in the laser coupler 20 and the control of the two-segment optical rotation plates 14A and 14B and the spatial light modulator 16 are illustrated under the control of the controller 90 in FIG. This is done by a drive circuit that does not.

FIG. 6 shows a detection circuit 85 for detecting a focus error signal, a tracking error signal and a reproduction signal based on the outputs of the photodetectors 25 and 26.
FIG. 3 is a block diagram showing the configuration of FIG. This detection circuit 85
An adder 31 for adding the respective outputs of the light receiving sections A1 and B1 of the photodetector 25, a gain adjusting amplifier 32 for adjusting the gain of the output of the adder 31, and a gain for adjusting the gain of the output of the light receiving section C1 of the photodetector 25. Adjustment amplifier 33
And a subtractor 34 for calculating the difference between the output of the gain adjustment amplifier 32 and the output of the gain adjustment amplifier 33;
And a gain adjustment amplifier 36 for adjusting the gain of the output of the adder 35, a gain adjustment amplifier 37 for adjusting the gain of the output of the light receiving section C2 of the photodetector 26, and an output of the gain adjustment amplifier 36 and the gain adjustment amplifier 37. A subtractor 38 for calculating a difference between the output and a subtractor 39 for calculating a difference between an output of the subtractor 34 and an output of the subtractor 38 to generate a focus error signal FE.

The detection circuit 85 further includes a subtractor 40 for calculating the difference between the output of the light receiving section A1 of the photodetector 25 and the output of the light receiving section B1, and the light receiving section A of the photodetector 26.
Subtractor 4 for calculating the difference between the output of the light receiving section B2 and the output of the light receiving section B2
1 and a subtractor 4 that calculates the difference between the output of the subtractor 40 and the output of the subtractor 41 to generate the tracking error signal TE.
2 is provided. The detection circuit 85 further includes the adder 31
An adder 43 for adding the output of the light receiving unit C1 to the output of
An adder 44 that adds the output of the adder 35 and the output of the light receiving unit C2, and an adder 45 that adds the output of the adder 43 and the output of the adder 44 to generate a reproduction signal RF. . In the present embodiment, the reproduction signal RF is a signal obtained by reproducing information recorded in the address servo area 6 on the optical information recording medium 1.

Next, the operation of the optical information recording / reproducing apparatus and the optical information recording medium according to this embodiment will be described with reference to FIGS.
The recording and the reproduction will be described separately. The following description also serves as an explanation of the optical information recording method and the optical information reproducing method according to the present embodiment. During servo, during recording,
At any time during reproduction, the optical information recording medium 1 is controlled by the spindle motor 82 to be controlled so as to maintain a specified number of rotations.

First, the operation at the time of servo will be described.
FIG. 7 is an explanatory diagram showing the state of the pickup 11 during servo, and FIG. 8 is an explanatory diagram showing the state of light during servo. As shown in these figures, at the time of servo, all the pixels of the spatial light modulator 16 are turned off, and the two-part optical rotation plate 1 is turned off.
4A, 14B optical rotation plates 14AR, 14AL, 14B
R and 14BL are all turned on. Laser coupler 20
Is set to a low output for reproduction. The controller 90 predicts the timing at which the output light of the objective lens 12A passes through the address servo area 6 based on the basic clock reproduced from the reproduction signal RF, and outputs the output light of the objective lens 12A to the address servo area. During the passage through 6, the above settings are made.

At the time of servo operation, the S-polarized laser light emitted from the laser coupler 20 is converted into a parallel light beam by the collimator lens 17 and enters the spatial light modulator 16. Here, since all the pixels of the spatial light modulator 16 are turned off, the light that has passed through the spatial light modulator 16 has its polarization direction rotated by + 90 ° and becomes P-polarized light. This P-polarized light is
Polarizing beam splitter surface 15 of prism block 15A
The light passes through Aa and is incident on the split optical rotation plate 14A. Here, since the optical rotation plates 14AR and 14AL of the two-part optical rotation plate 14A are both turned on, the light is not affected at all and the light is not affected.
The light passes through the split optical rotation plate 14A. The light that has passed through the two-part optical rotation plate 14A is condensed by the objective lens 12A, is converged so as to have the smallest diameter in the optical information recording medium 1, and is irradiated on the information recording medium 1. This light is applied to the information recording medium 1
At the boundary between the arbitrary information recording layer 2 and the position information layer 3 at that time, the light is modulated by emboss pits in the address servo area 6 and the objective lens 12
Come back to A side. This return light is converted into a parallel light beam by the objective lens 12A, and is not affected at all.
A, passes through the polarization beam splitter surface 15Aa of the prism block 15A, passes through the spatial light modulator 16, rotates the polarization direction by + 90 °, becomes S-polarized light again, and enters the laser coupler 20, Photo detector 2
5 and 26. Then, based on the outputs of the photodetectors 25 and 26, the detection circuit 85 shown in FIG. 6 generates a focus error signal FE, a tracking error signal TE, and a reproduction signal RF.
Based on these signals, focus servo and tracking servo are performed, and the reproduction of the basic clock and the determination of the address are performed.

In the present embodiment, the actuators 13A and 13B are controlled by the focus servo circuit 86 so as to be interlocked, and the convergence position of each light from the objective lenses 12A and 12B (the position where the light flux has the smallest diameter). But,
It moves while maintaining a predetermined positional relationship. When information is recorded or reproduced on the desired information recording layer 2, as shown in FIG. 8, light from the objective lens 12 </ b> A is applied to the desired information recording layer 2 and the information recording layer 2. 8 converges so as to have the smallest diameter on the boundary surface with the positioning layer 3 adjacent on the back side when viewed from the objective lens 12A side, and although not shown in FIG. Is not converged so as to have the smallest diameter on the boundary surface between the desired information recording layer 2 and the positioning layer 3 adjacent to the information recording layer 2 on the back side as viewed from the objective lens 12B side. Then, a focus servo is performed. Hereinafter, this state,
It is called a focused state for a desired information recording layer 2.

Since the address / servo area 6 includes information on the number of layers corresponding to the information recording layer 2 in the thickness direction, the controller 90 starts focus servo and records any information. After the layer 2 is in focus, the information recorded in the address / servo area 6 indicates which layer the information recording layer 2 is. After the controller 90 is brought into a focused state with respect to an arbitrary information recording layer 2 by the focus servo,
The focus servo circuit 86 is controlled to move the light convergence position by a predetermined unit in the thickness direction with the thickness obtained by adding the thickness of the information recording layer 2 and the thickness of the position information layer 3 as one unit. By performing the focus servo, it is possible to bring the other information recording layer 2 into a focused state.

In the above setting at the time of servo,
The configuration of the pickup 11 is a CD (compact disc), a DVD (digital video disc), an HS
The configuration is the same as that of a pickup for recording and reproduction on a normal optical disk such as a (hyper storage disk). Therefore, the optical information recording / reproducing device 10 according to the present embodiment can be configured to have compatibility with a normal optical disk device.

Next, the operation at the time of recording will be described. FIG. 9 is an explanatory diagram showing the state of the pickup 11 during recording, and FIG. 11 is an explanatory diagram showing the state of light during recording. As shown in these figures, at the time of recording, the spatial light modulator 16 turns on (0) for each pixel according to the information to be recorded.
°) and off (+ 90 °). In the present embodiment, 1-bit information is expressed by two pixels. In this case, one of the two pixels corresponding to one bit of information is always turned on and the other is turned off. Also, the two-part optical rotation plates 14A, 1
4B optical rotation plates 14AR, 14AL, 14BR, 14B
L is all turned off. The output of the light emitted from the laser coupler 20 is pulsed to a high output for recording. Note that the controller 90 predicts the timing at which the emitted lights of the objective lenses 12A and 12B pass through the data area 7 based on the basic clock reproduced from the reproduced signal RF, and outputs the emitted lights of the objective lenses 12A and 12B in the data area. During the passage through 7, the above setting is made. Objective lenses 12A, 12B
While the outgoing light passes through the data area 7, focus servo and tracking servo are not performed, and the objective lenses 12A and 12B are fixed.

Here, A-polarized light and B-polarized light used in the following description are defined as follows. In the present embodiment, as shown in FIG. 10, the A-polarized light is a linearly polarized light obtained by rotating the S-polarized light by −45 ° or the P-polarized light by + 45 ° when viewed from the objective lens 12A side, and the B-polarized light. Indicates that the S-polarized light is + 45 ° or the P-polarized light is −
Linear polarization is obtained by rotating the polarization direction by 45 °. Therefore,
When viewed from the objective lens 12B side, the A-polarized light is a linearly polarized light obtained by rotating the S-polarized light by + 45 ° or the P-polarized light by −45 °, and the B-polarized light is obtained by converting the S-polarized light to −45 ° or P-polarized light. Is a linearly polarized light obtained by rotating the polarization direction by + 45 °. The polarization directions of the A polarized light and the B polarized light are orthogonal to each other.

At the time of recording, the S-polarized laser light emitted from the laser coupler 20 is converted into a parallel light beam by the collimator lens 17 and enters the spatial light modulator 16. Here, the light passing through the turned-on pixel of the spatial light modulator 16 remains S-polarized without rotating the polarization direction, and the light passing through the turned-off pixel has a polarization direction of +.
The light is rotated by 90 ° to become P-polarized light.

The P-polarized light from the spatial light modulator 16 is applied to the polarization beam splitter surface 15A of the prism block 15A.
a through the optical rotation plate 14A. Here, since the optical rotation plates 14AR and 14AL of the two-part optical rotation plate 14A are both turned off, the light that has passed through the optical rotation plate 14AR is rotated by -45 ° in the polarization direction and becomes B-polarized light.
The light that has passed through the optical rotation plate 14AL has its polarization direction rotated by + 45 ° and becomes A-polarized light. The light from the two-part optical rotation plate 14A has the smallest diameter on the boundary surface between the desired information recording layer 2 and the positioning layer 3 adjacent to the information recording layer 2 on the back side when viewed from the objective lens 12A side. Converge so that

The S-polarized light from the spatial light modulator 16 is applied to the polarization beam splitter surface 15A of the prism block 15A.
Then, the light is reflected by the reflection surface 15Ab, is further reflected by the reflection surface 15Ab, is incident on the prism block 15B, is sequentially reflected by the reflection surface 15Bb and the polarization beam splitter surface 15Ba, and is incident on the two-segment optical rotation plate 14B. Here, since the optical rotation plates 14BR and 14BL of the two-part optical rotation plate 14B are both turned off, the light that has passed through the optical rotation plate 14BR is rotated by −45 ° in the polarization direction to become B-polarized light, and the optical rotation plate 14BL is The transmitted light has its polarization direction rotated by + 45 ° and becomes A-polarized light. 2
The light from the split optical rotation plate 14B has the smallest diameter on the boundary surface between the desired information recording layer 2 and the positioning layer 3 adjacent to the information recording layer 2 on the back side when viewed from the objective lens 12B side. Converge as follows.

As shown in FIG. 11, in the desired information recording layer 2, the B-polarized light from the optical rotation plate 14AR and the optical rotation plate 14
The B-polarized light from the BR interfered with the A-polarized light from the optical rotation plate 14AL and the A-polarized light from the optical rotation plate 14BL interfered, and the output of the output light from the laser coupler 20 became high. Sometimes, interference patterns due to these lights are volumetrically recorded in the information recording layer 2, and a reflection type (Lipman type) volume hologram 58 is formed. In addition, A polarized light and B
The polarized lights do not interfere with each other because their polarization directions are orthogonal to each other. Thus, in the present embodiment, the light beam is split into two,
Since the polarization directions of the light in the respective regions are orthogonal to each other, it is possible to prevent the occurrence of extra interference fringes and to prevent a reduction in the SN (signal to noise) ratio.

Further, in the present embodiment, the two-rotation optical rotation plate 14 irradiating the information recording layer 2 from opposite directions is used.
The light from A and the light from the split optical rotation plate 14B have patterns complementary to each other.
It can be regarded as an information light carrying information to be recorded in the information light. When the light from the two-part optical rotation plate 14A is viewed as information light, the light from the two-part optical rotation plate 14B becomes the reference light for recording. Conversely, when the light from the two-part optical rotation plate 14B is viewed as the information light. The light from the two-part optical rotation plate 14A becomes the recording reference light.

In this embodiment, since the recording reference light is also light that has been spatially modulated by the spatial light modulator 16, when viewing one section of the information recording layer 2, the information light in pixel units is obtained. Some information light does not cause interference fringes because there is no pixel-based recording reference light. However, even with such information light, the pixel-based recording reference light is necessarily generated in the information recording layer 2. Since no interference fringes are generated through the existing portion, no problem occurs. In the spatial light modulator 16,
One-bit information is expressed by two pixels, and one of two pixels corresponding to the one-bit information is turned on and the other is turned off. Therefore, the light amount of the recording reference light is substantially constant regardless of the content of the information. FIG. 12 conceptually shows how the recording reference light 55 in pixel units and the information light 56 in pixel units interfere volumetrically in the information recording layer 2.
In this figure, for simplicity, the recording-specific reference light 5 in pixel units is used.
5 shows an example in which 5 and information light 56 in pixel units are alternately arranged. In this example, the pixel-based recording reference light 55 is convergent light having different angles θ ₁ , θ ₃ ,..., Θ _n-3 , θ _n-1 , and the pixel-based information light 56 has different angles. It is convergent light having θ ₂ , θ ₄ ,..., θ _n-2 , θ _n . As can be seen from this figure, the information light 5 in each pixel unit
6 always generates an interference fringe in the information recording layer 2 by intersecting with the recording reference light 55 of any pixel unit.

Next, the operation at the time of reproduction will be described. FIG. 13 is an explanatory diagram showing the state of the pickup 11 during reproduction, and FIGS. 14 and 15 are explanatory diagrams showing the state of light during reproduction. As shown in these figures, at the time of reproduction, the spatial light modulator 16 selects a state in which all pixels are off (+ 90 °) and a state in which all pixels are on (0 °) as necessary. The optical rotation plates 14AR, 14AL, 14BR, and 14BL of the two split optical rotation plates 14A and 14B are all turned off. The output of the light emitted from the laser coupler 20 is set to a low output for reproduction. Note that the controller 90 predicts the timing at which the light emitted from the objective lenses 12A and 12B passes through the data area 7 based on the basic clock reproduced from the reproduction signal RF, and the objective lenses 12A and 12B
The above setting is made while the outgoing light passes through the data area 7. While the light emitted from the objective lenses 12A and 12B passes through the data area 7, focus servo and tracking servo are not performed, and the objective lenses 12A and 12B are fixed.

When all the pixels of the spatial light modulator 16 are off, the reproduction optical system 92 reproduces information. At this time, the S-polarized laser light emitted from the laser coupler 20 is converted into a parallel light beam by the collimator lens 17, and the polarization direction is + 90 ° by the spatial light modulator 16.
Rotated to P-polarized light. The P-polarized light from the spatial light modulator 16 passes through the polarization beam splitter surface 15Aa of the prism block 15A, and as shown in FIG.
The light enters the split optical rotation plate 14A. Here, the two-part optical rotation plate 1
Since the optical rotation plates 14AR and 14AL of 4A are both turned off, the light passing through the optical rotation plate 14AR has a polarization direction of-.
Light that has been rotated by 45 ° to become B-polarized light and passed through the optical rotation plate 14AL has its polarization direction rotated by + 45 ° to become A-polarized light. The light from the two-part optical rotation plate 14A has the smallest diameter on the boundary surface between the desired information recording layer 2 and the positioning layer 3 adjacent to the information recording layer 2 on the back side when viewed from the objective lens 12A side. Converge so that

The volume hologram 58 in the information recording layer 2
Thus, the reproduction light is generated when the light from the two-part optical rotation plate 14A is regarded as the reproduction reference light. More specifically, in the upper half region of the volume hologram 58 in FIG. 14, B-polarized light from the optical rotation plate 14AR is irradiated,
At the time of recording, reproduced light corresponding to the light emitted from the optical rotation plate 14BR of the two-part optical rotation plate 14B is generated. This reproduction light is B-polarized light, is condensed by the objective lens 12A, passes through the optical rotation plate 14AL of the two-part optical rotation plate 14A, and
It becomes polarized light. Similarly, in the lower half region of the volume hologram 58 in FIG. 14, the A-polarized light from the optical rotation plate 14AL is irradiated, and the two-rotation optical rotation plate 14 is recorded.
A reproduction light corresponding to the light emitted from the B optical rotation plate 14BL is generated. This reproduction light is A-polarized light, is condensed by the objective lens 12A, passes through the optical rotation plate 14AR of the two-part optical rotation plate 14A, and becomes S-polarized light. These S-polarized reproduction lights are reflected by the polarization beam splitter surface 15Aa of the prism block 15A, are collected by the convex lens 18A, and form an image on the CCD array 19A. In this manner, on the CCD array 19A, the spatial light modulator 1
Only the portion corresponding to the pixel that was turned on in 6 is brightly illuminated, and its two-dimensional pattern is the CCD array 19A.
And the information is reproduced.

On the other hand, when all the pixels of the spatial light modulator 16 are on, the reproduction optical system 93 reproduces information. At this time, the S-polarized laser light emitted from the laser coupler 20 is converted into a parallel light beam by the collimator lens 17, and remains in the S-polarized light without the polarization direction being rotated by the spatial light modulator 16. The S-polarized light from the spatial light modulator 16 is reflected by the polarization beam splitter surface 15Aa of the prism block 15A, and further reflected by the reflection surface 15Ab.
, And is incident on the prism block 15B, is sequentially reflected on the reflection surface 15Bb and the polarization beam splitter surface 15Ba, and is incident on the two-rotation optical rotation plate 14B. Here, since the optical rotation plates 14BR and 14BL of the two-part optical rotation plate 14B are both turned off, the light passing through the optical rotation plate 14BR is rotated by -45 ° in the polarization direction to become B-polarized light, and the optical rotation plate 14
The light passing through BL has its polarization direction rotated by + 45 °,
It becomes A polarized light. Light from the two-part optical rotation plate 14B is applied to the desired information recording layer 2 and the objective lens 1 with respect to the information recording layer 2.
On the boundary surface with the positioning layer 3 adjacent on the back side when viewed from the 2B side, the light converges so as to have the smallest diameter.

Volume hologram 58 in information recording layer 2
Thus, the reproduction light is generated when the light from the two-part optical rotation plate 14B is regarded as the reproduction reference light. More specifically, in the upper half region of the volume hologram 58 in FIG. 15, the B-polarized light from the optical rotation plate 14BR is irradiated,
At the time of recording, reproduction light corresponding to the light irradiated from the optical rotation plate 14AR of the two-part optical rotation plate 14A is generated. This reproduction light is B-polarized light, is condensed by the objective lens 12B, passes through the optical rotation plate 14BL of the two-part optical rotation plate 14B, and
It becomes polarized light. Similarly, in the lower half region of the volume hologram 58 in FIG. 15, the A-polarized light from the optical rotation plate 14BL is irradiated, and the two-rotation optical rotation plate 14
A reproduction light corresponding to the light irradiated from the optical rotation plate 14AL of A is generated. This reproduction light is A-polarized light, is condensed by the objective lens 12B, passes through the optical rotation plate 14BR of the two-part optical rotation plate 14B, and becomes P-polarized light. The P-polarized reproduction light passes through the polarization beam splitter surface 15Ba of the prism block 15B, is collected by the convex lens 18B, and forms an image on the CCD array 19B. In this manner, on the CCD array 19B, the spatial light modulator 1
Only the portion corresponding to the pixel that was off in 6 is illuminated brightly, and its two-dimensional pattern is the CCD array 19B.
And the information is reproduced.

In the present embodiment, information may be reproduced by the reproduction optical system 92 with all the pixels of the spatial light modulator 16 turned off, or with all the pixels of the spatial light modulator 16 turned on. The information may be reproduced by the reproduction optical system 93. Further, in the present embodiment, for one recording area (volume hologram 58), all pixels of the spatial light modulator 16 are switched off and all pixels of the spatial light modulator 16 are switched on. It is also possible to irradiate two types of reference light for reproduction in a time-division manner and reproduce the information using both the reproduction optical systems 92 and 93. In this case, the reproduction optical system 9 is used for one recording area (volume hologram 58).
Since the two reproduction lights obtained in 2, 93 have complementary patterns, information can be reproduced by so-called differential detection by calculating the difference between the two reproduction lights. When information is reproduced by differential detection as described above, specifically, the signal processing circuit 89 in FIG.
Thus, the output signals of the CCD arrays 19A and 19B are corrected to match the size, position and signal level of each pattern detected by the CCD arrays 19A and 19B, and the difference between the corrected signals is calculated. To play the information.

In the present embodiment, since the optical information recording medium 1 has a plurality of stacked information recording layers 2, the reproduction reference light passes through the plurality of information recording layers 2 during reproduction. However, since the angle formed by the reference light for reproduction with respect to the information recording layer 2 from which information is to be reproduced and the angle formed by the reference light for reproduction with respect to the other information recording layers 2 are different, the information is reproduced. It is possible to reproduce information only from the information recording layer 2. Hereinafter, this is shown in FIG.
6 and FIG. 17 will be described in detail.

First, with reference to FIG. 16, the relationship between the relief in the volume hologram and the incident angle to the relief will be described (for details, see Koyama and Nishihara, "Lightwave Electronics" (Corona)). ). Now, as shown in FIG. 16, the thickness T at which the relief 132 is
Angle hologram 131 with relief 132
_{At i} , consider the case where light 133 of wavelength λ ₀ is incident. The relief 132 in the volume hologram 131
The refractive index distribution n (x) in a direction x orthogonal to the following expression is represented by the following equation.

N (x) = n ₀ + n ₁ sin (K × x) K = 2π / Λ

The intensity I ₁ of the first-order diffracted light by the volume hologram 131 is obtained by the following equation.

I ₁ = {κT ・ (sin σ / σ)} ² where κ = πn ₁ / λ ₀ σ = (1/4) √ ｛Q ² (1-2α) ² +4 (2κ
T) ² ｝ Q = 2πλ ₀ T / n ₀ Λ ² α = (− ／) · (sin θ _i / sin θ _B ).

Here, θ _B is a Bragg angle, which satisfies the following equation.

2Λsin θ _B = λ ₀ / n ₀

Here, λ ₀ ≒ 0.5 μm, Λ ≒ λ ₀ , T
{50}, n ₁ ≒ 1/100, cos θ _B ≒ 1, n ₀
Assuming 1.5, the diffraction intensity I ₁ is given by the following equation.

I ₁ ≒ ｛(πn ₁ T / λ ₀ ) Sinc (π
λ ₀ Tδ / 2n ₀ Λ ² )｝ ² sin θ _i = sin (θ _B + δ) Sinc (x) = sinx / x

Here, δ represents a deviation from the Bragg angle. FIG. 17 shows the function Sinc ² (x). Also, with δ = 0 as the center, from the δ when the diffraction intensity I ₁ first becomes 0 on the negative side, the diffraction intensity I ₁ on the positive side is obtained.
Separation width Δ which is the width up to δ when ₁ first becomes 0
Is given by the following equation:

Δ = 4n ₀ Λ ² / λ ₀ T

As described above, in the volume hologram 131,
It can be seen that the reproduction light is obtained only when the light 133 enters the relief 132 near the Bragg angle. From this, each information recording layer 2 of the optical information recording medium 1 can generate the reproduction light only when the reproduction reference light is irradiated at an angle near the same angle as the recording reference light at the time of recording. It can be seen that it is possible to reproduce information only from the information recording layer 2 from which information is to be reproduced.

When the two-dimensional pattern of the reproduction light is detected by the CCD arrays 19A and 19B, the reproduction light and the CCD arrays 19A and 19B are accurately positioned, or the reproduction light is detected from the detection data of the CCD arrays 19A and 19B. It is necessary to recognize the reference position in this pattern. In the present embodiment, the latter is adopted. Here, FIG.
8 and FIG. 19, the CCD arrays 19A, 19A
A method of recognizing the reference position in the reproduction light pattern from the B detection data will be described. As shown in FIG. 18A, the aperture of the pickup 11 is 2
The divided optical rotation plates 14A and 14B divide the light into two regions 71L and 71R that are symmetric about the optical axis. Furthermore,
As shown in FIG. 18B, the aperture is divided into a plurality of pixels 72 by the spatial light modulator 16. The pixel 72 is the minimum unit of the two-dimensional pattern data.
In this embodiment, one pixel of digital data “0” or “1” is represented by two pixels, and one of two pixels corresponding to one-bit information is turned on and the other is turned off.
If both pixels are on or both off, error data is generated. Expressing 1-bit digital data with two pixels as described above has advantages such as an increase in data detection accuracy by differential detection. FIG.
(A) shows a set 73 of two pixels corresponding to 1-bit digital data. The area where the set 73 exists is hereinafter referred to as a data area. In the present embodiment, 2
Utilizing that error data is obtained when both pixels are on or both off, reference information indicating a reference position in the reproduction light pattern is included in the information light. That is, as shown in FIG. 19B, a cross-shaped area composed of a portion having a width of two pixels parallel to the dividing line of the two-part optical rotation plates 14A and 14B and a portion having a width of two pixels perpendicular to the dividing line. At 74, error data is intentionally arranged in a predetermined pattern. This error data pattern is hereinafter referred to as a tracking pixel pattern. This tracking pixel pattern becomes reference position information. FIG.
In FIG. 9B, reference numeral 75 denotes an ON pixel, and reference numeral 76 denotes an OFF pixel. In addition, the area 77 of four pixels at the center is always turned off.

When the tracking pixel pattern and the pattern corresponding to the data to be recorded are combined, FIG.
A two-dimensional pattern as shown in FIG. In the present embodiment, among the regions other than the data region, the upper half in the figure is turned off and the lower half is turned on, and pixels in the data region that are in contact with the region other than the data region are other than the data region. It is turned on when the state opposite to the area, that is, the area other than the data area is off, and turned off when the area other than the data area is on. This allows
From the detection data of the CCD arrays 19A and 19B, it is possible to more clearly detect the boundary of the data area.

At the time of recording, an interference pattern between the information light spatially modulated according to the two-dimensional pattern as shown in FIG. 20A and the recording reference light is recorded on the information recording layer 2.
As shown in FIG. 20B, the pattern of the reproduction light obtained at the time of reproduction has lower contrast and lower SN ratio than at the time of recording. At the time of reproduction, the patterns of the reproduction light as shown in FIG. 20B are detected by the CCD arrays 19A and 19B, and the data is discriminated. To determine the data.

FIG. 21A conceptually shows the contents of data determined from the reproduction light pattern. In the figure, areas denoted by reference numerals such as A-1-1 represent 1-bit data. In the present embodiment, the data area is
The four regions 78A and 78 are divided by dividing the region 74 of the cross into which the tracking pixel pattern is recorded.
B, 78C and 78D. And FIG.
As shown in (b), the diagonal areas 78A and 78C are combined to form a rectangular area, and similarly, the diagonal areas 78B and 78C are formed.
A rectangular area is formed by combining 78D, and an ECC table is formed by arranging two rectangular areas vertically. The ECC table is a data table formed by adding an error correction code (ECC) such as a CRC (cyclic redundancy check) code to data to be recorded. FIG. 21B shows an example of an ECC table with n rows and m columns, and other arrangements can be freely designed. The data array shown in FIG. 21A uses a part of the ECC table shown in FIG. 21B, and the data array shown in FIG.
Portions of the CC table that are not used in the data array shown in FIG. 21A have constant values regardless of the data contents. At the time of recording, E as shown in FIG.
The CC table is decomposed into four areas 78A, 78B, 78C, and 78D as shown in FIG. 21A and recorded on the optical information recording medium 1, and at the time of reproduction, an array as shown in FIG. The data of FIG.
The ECC table as shown in FIG.
Data is reproduced by performing error correction based on the CC table.

The recognition of the reference position (tracking pixel pattern) and the error correction in the reproduction light pattern as described above are performed by the signal processing circuit 89 in FIG.

As described above, according to the optical information recording medium 1 and the optical information recording / reproducing apparatus 10 according to the present embodiment, the optical information recording medium 1 in which the information recording layers 2 and the positioning layers 3 are alternately stacked. The position of the information light and the recording reference light is controlled using the positioning layer 3 corresponding to the information recording layer 2 on which information is to be recorded, and the information is recorded on the information recording layer 2 on which information is to be recorded. Since the light and the recording reference light are irradiated while being converged, information is recorded on the information recording layer 2 on which information is to be recorded by an interference pattern due to interference between the information light and the recording reference light. Also in the thickness direction of the recording medium 1, a plurality of pieces of information (volume hologram) can be recorded while controlling the position accurately, and information can be recorded at a higher density.

Further, according to the optical information recording medium 1 and the optical information recording / reproducing apparatus 10 according to the present embodiment, the optical information recording medium 1 in which the information recording layers 2 and the positioning layers 3 are alternately laminated.
, While controlling the position of the reproduction reference light using the positioning layer 3 corresponding to the information recording layer 2 from which information is to be reproduced, the reproduction reference light is transmitted to the information recording layer 2 from which information is to be reproduced. Is converged, the reproduction light generated from the information recording layer 2 by the irradiation of the reproduction reference light is collected, and the reproduction light is detected to reproduce the information. The information can be reproduced with higher accuracy than the optical information recording medium 1 in which a plurality of pieces of information are recorded at a high density.

Further, according to the present embodiment, since the positioning of the light for recording or reproduction can be performed with high accuracy, the removable property is good, the random access is easy, and the recording capacity and transfer rate are reduced. Can be bigger.

Further, according to the present embodiment, information can be reproduced by differential detection using both of the reproduction optical systems 92 and 93, whereby the DC noise component superimposed on the reproduction light can be reduced. The cancellation can improve the SN ratio, and the information detection accuracy can be improved.

In the present embodiment, information is recorded by irradiating a desired information recording layer 2 with convergent information light and recording reference light during recording, and the desired information recording layer 2 is reproduced during reproduction. The information is reproduced by irradiating the reproduction reference light corresponding to the recording reference light while convergence is performed. Therefore, at the time of reproduction, the angle formed by the reproduction reference light with respect to a desired information recording layer 2 is determined. Since the angle formed by the reproduction reference light with respect to the other information recording layers 2 is different, it is possible to reproduce information only from the desired information recording layer 2,
While recording a plurality of information in the thickness direction of the optical information recording medium 1, the ability to separate the plurality of information is high.

Further, according to the present embodiment, the objective lenses 12A, 12B are controlled by the actuators 13A, 13B.
Only by changing the convergence position of the light from the optical information recording medium 1
Can be accessed at high speed.

Further, according to the present embodiment, each time the information recording layer of the optical information recording medium 1 is accessed, the aberration that occurs in the incoming and outgoing light changes. The corrected aberration is corrected (canceled) by the aberration generated with respect to the reproduction light at the time of reproduction, so that the aberration can be favorably obtained over a wide range in the thickness direction without performing the aberration correction according to the information recording layer to be accessed. Optical characteristics can be obtained.

The optical information recording medium 1 according to the present embodiment can be easily manufactured by alternately laminating the information recording layers 2 and the positioning layers 3.

Further, in this embodiment, since the information recording layer 2 is irradiated with two light beams which converge from directions opposite to each other, a region near the convergence position of the two light beams where the light amount becomes large is selected. Information can be recorded in an efficient manner.

According to the present embodiment, the reference position information indicating the reference position in the reproduction light pattern is included in the information light, so that the reproduction light pattern can be easily recognized.

FIG. 22 is an explanatory diagram showing a configuration of a main part of an optical information recording / reproducing apparatus according to the second embodiment of the present invention. The optical information recording / reproducing apparatus according to the present embodiment is an example in which focus servo and tracking servo are performed by moving the optical information recording medium 1. In the optical information recording / reproducing apparatus according to the present embodiment, FIG.
Are not provided. In the optical information recording / reproducing apparatus according to the present embodiment, as shown in FIG. 22, an ultrasonic linear motor 95 is provided on a base member 94 of the optical information recording / reproducing apparatus.
The ultrasonic linear motor 95 has a stator 96 fixed to a base member 94 and a slider (rotor) 97 movable on the stator 96 in a horizontal direction. An actuator 98 using a piezoelectric element that can expand and contract in the vertical direction is mounted on the slider 97, and a spindle motor 82 is fixed on the actuator 98.

The actuator 98 is controlled by the focus servo circuit 86 in FIG. 2, and the ultrasonic linear motor 95 is controlled by the tracking servo circuit 8 in FIG.
7 is controlled.

In this embodiment, the focus servo is
Actuator 98 by focus servo circuit 86
By moving the optical information recording medium 1 up and down. The tracking servo is performed by an ultrasonic linear motor 9 by a tracking servo circuit 87.
5 by controlling the optical information recording medium 1 in the horizontal direction.

Other configurations, operations and effects of the present embodiment are the same as those of the first embodiment.

Next, a third embodiment of the present invention will be described. In this embodiment, the same optical information recording medium 1 as in the first embodiment is used. The overall configuration of the optical information recording / reproducing apparatus according to the present embodiment is the same as that of FIG. 2 except that the configuration of the pickup is different.

FIG. 23 is an explanatory diagram showing the configuration of a pickup in the optical information recording / reproducing apparatus according to the present embodiment. Hereinafter, the same members as those in the pickup shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.
The pickup 111 according to the present embodiment includes an objective lens 12A arranged to face one surface of the optical information recording medium 1 when the optical information recording medium 1 is fixed to the spindle 81, and an objective lens 12A 13A, which is movable in the thickness direction and the radial direction of the optical information recording medium 1, and a two-divided optical rotation plate 14A which is disposed on the opposite side of the optical information recording medium 1 in the objective lens 12A from the objective lens 12A side. , Prism block 112, 1
13, a spatial light modulator 16, a collimator lens 17, and a laser coupler 20. Prism block 11
A convex lens 114 is provided between the lenses 2 and 113.

The pickup 111 further includes an objective lens 12B arranged to face the other surface of the optical information recording medium 1 when the optical information recording medium 1 is fixed to the spindle 81, and an objective lens 12B 13B, an actuator 13B capable of moving the optical information recording medium 1 in the thickness direction and the radial direction, and a two-segmented optical rotation plate 14C disposed on the opposite side of the optical information recording medium 1 in the objective lens 12B from the objective lens 12B side. , Prism blocks 115 and 11
6 and a CCD array 119B. A half-wave plate 117 is provided between the prism blocks 115 and 116.
And a convex lens 118 are provided. A CCD array 119A is provided on the side of the prism block 116.

The two-rotation optical rotation plate 14C has an optical rotation plate 14CR arranged on the upper part of the optical axis in FIG. 23 and an optical rotation plate 14CL arranged on the lower part of the optical axis in FIG. Each of the optical rotation plates 14CR and 14CL is configured by enclosing liquid crystal between, for example, two transparent electrode substrates. When the optical rotation plate 14CR is turned off, the polarization direction of the incident light is rotated by + 45 °, and when turned on, the polarization direction of the incident light is not rotated. On the other hand, the optical rotation plate 14
When the CL is turned off, the polarization direction of the incident light is rotated by -45 °, and when turned on, the polarization direction of the incident light is not rotated.

The prism block 113 has a polarization beam splitter surface 113a whose normal direction is inclined at 45 ° with respect to the optical axis direction between the two-segment optical rotation plate 14A and the spatial light modulator 16; The light modulator 16 has a reflection surface 113b that is arranged in a direction in which light from the optical modulator 16 side is reflected by the polarization beam splitter surface 113a and is parallel to the polarization beam splitter surface 113a.

The prism block 112 has its normal direction inclined by 45 ° with respect to the optical axis direction between the two-segment optical rotation plate 14A and the spatial light modulator 16, and Polarizing beam splitter surface 1 arranged at an angle of 90 ° with respect to
12a and a reflecting surface 112b that is arranged at a position where light from the reflecting surface 113b of the prism block 113 is incident and is parallel to the polarizing beam splitter surface 112a.
The convex lens 114 is a reflection surface 1 of the prism block 113.
13b and the reflecting surface 112b of the prism block 112.

The prism block 115 has a polarization beam splitter surface 115a whose normal direction is inclined by 45 ° with respect to the optical axis direction of the objective lens 12B and the two-segment optical rotation plate 14C, and a two-segment optical rotation plate 14C. It is arranged in a direction in which light from the side is reflected by the polarizing beam splitter surface 115a, and has a reflecting surface 115b parallel to the polarizing beam splitter surface 115a.

The prism block 116 has its normal direction inclined by 45 ° with respect to the optical axis direction of the objective lens 12B and the split optical rotation plate 14C, and 90 ° with respect to the polarization beam splitter surface 115a of the prism block 115. Polarized beam splitter surface 1 arranged at an angle
16a and a reflecting surface 116b that is arranged at a position where light from the reflecting surface 115b of the prism block 115 is incident and is parallel to the polarizing beam splitter surface 115a.
The half-wave plate 117 is connected to the polarizing beam splitter surface 115 a of the prism block 115 and the prism block 11.
6 of the polarization beam splitter surface 116a. The convex lens 118 has a reflecting surface 115 b of the prism block 115 and a reflecting surface 11 of the prism block 116.
6b.

Each of the CCD arrays 119A and 119B has a large number of pixels arranged in a grid. C
The CD array 119A is arranged in a direction in which light passing through the half-wave plate 117 is reflected by the polarizing beam splitter surface 116a of the prism block 116, and the CCD array 119B is arranged so that light passing through the convex lens 118 is Are reflected by the reflection surface 116b, and are further reflected by the polarization beam splitter surface 116a.

In the pickup 111 shown in FIG. 23, the laser coupler 20 emits S-polarized laser light,
This laser light is converted into a parallel light flux by the collimator lens 17, passes through the spatial light modulator 16, and is incident on the polarization beam splitter surface 113 a of the prism block 113. Here, the light that has passed through the OFF pixel of the spatial light modulator 16 becomes P-polarized light, transmits through the polarization beam splitter surface 113a, enters the prism block 112, transmits through the polarization beam splitter surface 112a, and is split into two optical rotations. After passing through the plate 14A, by the objective lens 12A,
The light is converged so as to have the smallest diameter in the optical information recording medium 1 and is irradiated onto the optical information recording medium 1. On the other hand, the light that has passed through the ON pixels of the spatial light modulator 16 is S
The polarized lens remains as it is, and is reflected by the polarizing beam splitter surface 113a, further reflected by the reflecting surface 113b, and
After being condensed by the laser beam 14, the light is incident on the prism block 112, and is reflected by the reflection surface 112 b and the polarization beam splitter surface 11.
The light is sequentially reflected at 2a, passes through the two-segment optical rotation plate 14A, and has the smallest diameter at a position closer to the near side than the light that has passed through the off pixel of the spatial light modulator 16 in the optical information recording medium 1 by the objective lens 12A. The light is converged so as to irradiate the optical information recording medium 1.

The objective lens 12A from the optical information recording medium 1
The return light to the side is supplied to the objective lens 12A,
A sequentially passes through A and enters the polarization beam splitter surface 112a of the prism block 112. The P-polarized light of the return light passes through the polarizing beam splitter surface 112a, further passes through the polarizing beam splitter surface 113a of the prism block 113, passes through the spatial light modulator 16, and is collected by the collimator lens 17. The light is emitted and enters the laser coupler 20.

The reproduction light emitted from the optical information recording medium 1 to the objective lens 12B side passes through the objective lens 12B and the two-segment optical rotation plate 14C in order, and is incident on the polarization beam splitter surface 115a of the prism block 115. ing. The P-polarized light of the reproduced light is transmitted through the polarization beam splitter surface 115a, and the polarization direction is rotated by 90 ° by the half-wave plate 117 to become S-polarized light.
Polarization beam splitter surface 11 of prism block 116
The light is reflected by 6a and enters the CCD array 19A. On the other hand, the S-polarized light of the reproduction light is reflected by the polarization beam splitter surface 115a, further reflected by the reflection surface 115b, collected by the convex lens 118 into a parallel light flux, and then enters the prism block 116. , Reflecting surface 116b, polarizing beam splitter surface 116a
Are sequentially reflected and incident on the CCD array 19B.

In the pickup 111 shown in FIG.
The recording optical system 121 includes a laser coupler 20, a collimator lens 17, a spatial light modulator 16, and a prism block 11.
3, 112, a convex lens 114, a split optical rotation plate 14A, and an objective lens 12A. In the pickup 111 shown in FIG. 23, the reproduction optical system 122 is constituted by the entire optical system of the pickup 111.

Next, the operation of the optical information recording / reproducing apparatus and the optical information recording medium according to the present embodiment will be described with reference to FIGS.
The recording and the reproduction will be described separately. Note that the optical information recording medium 1 is controlled by the spindle motor 82 to be controlled so as to maintain a specified number of rotations in any of servo, recording, and reproduction.

First, the operation at the time of servo will be described.
FIG. 24 is an explanatory diagram showing the state of the pickup 111 during servo. At the time of servo, all the pixels of the spatial light modulator 16 are turned off, and the optical rotation plates 14AR, 14AL, 14CR, and 14CL of the two-part optical rotation plates 14A and 14C are all turned on. The output of the output light of the laser coupler 20 is
Set to low output for playback. The controller 90
Predicts the timing at which the light emitted from the objective lens 12A passes through the address servo area 6 based on the basic clock reproduced from the reproduction signal RF.
The above setting is made while the outgoing light passes through the address servo area 6.

At the time of servo, the S-polarized laser light emitted from the laser coupler 20 is converted into a parallel light beam by the collimator lens 17 and enters the spatial light modulator 16. Here, since all the pixels of the spatial light modulator 16 are turned off, the light that has passed through the spatial light modulator 16 has its polarization direction rotated by + 90 ° and becomes P-polarized light. This P-polarized light is
Polarizing beam splitter surface 11 of prism block 113
3a and the polarized beam splitter surface 112a of the prism block 112 are sequentially transmitted and incident on the two-part optical rotation plate 14A. Here, the optical rotation plate 14AR of the two-part optical rotation plate 14A,
Since both light sources 14AL are turned on, the light passes through the split optical rotation plate 14A without any influence. The light that has passed through the two-part optical rotation plate 14A is condensed by the objective lens 12A, is converged so as to have the smallest diameter in the optical information recording medium 1, and is irradiated on the information recording medium 1. This light is applied to any information recording layer 2 and position information layer 3 in the information recording medium 1.
At this time, the light is reflected by the emboss pits in the address servo area 6 and returns to the objective lens 12A side. This return light is converted into a parallel light beam by the objective lens 12A, passes through the two-rotation optical rotation plate 14A without any influence, and passes through the polarization beam splitter surface 112a of the prism block 112 and the prism block 113.
, Sequentially pass through the polarization beam splitter surface 113a, pass through the spatial light modulator 16, rotate the polarization direction by + 90 °, become S-polarized light again, enter the laser coupler 20, and are detected by the photodetectors 25 and 26. You. Then, based on the outputs of the photodetectors 25 and 26, the detection circuit 85 shown in FIG. 6 generates a focus error signal FE, a tracking error signal TE, and a reproduction signal RF. While the tracking servo is performed, reproduction of the basic clock and determination of the address are performed.

The optical information recording medium 1 during servo operation
The state of light inside is the same as in FIG. In the present embodiment, the actuators 13A and 13B are controlled by the focus servo circuit 86 so as to be interlocked, and the convergence position (the position where the light beam has the smallest diameter) of each light from the objective lenses 12A and 12B is set to a predetermined position. They move while maintaining the relationship. Then, the desired information recording layer 2
In the case where information is recorded or reproduced from the objective lens 12A, light from the objective lens 12A is applied to the desired information recording layer 2 and the objective lens 12 as shown in FIG.
On the boundary surface with the positioning layer 3 adjacent on the back side as viewed from the A side, the object lens 1 converges so as to have the smallest diameter.
2B, the divergent light having the smallest diameter on the boundary surface between the desired information recording layer 2 and the positioning layer 3 adjacent to the information recording layer 2 on the back side as viewed from the objective lens 12B side is defined as a parallel light flux. Thus, focus servo is performed. Hereinafter, this state is referred to as a focused state for the desired information recording layer 2.

Next, the operation at the time of recording will be described. FIG. 25 is an explanatory diagram showing the state of the pickup 111 during recording, and FIG. 26 is an explanatory diagram showing the state of light during recording. As shown in these figures, at the time of recording, the spatial light modulator 16 selects ON (0 °) or OFF (+ 90 °) for each pixel according to the information to be recorded. In the present embodiment, as in the first embodiment, one-bit information is expressed by two pixels. In this case, one of the two pixels corresponding to one bit of information is always turned on and the other is turned off.
Each of the optical rotation plates 14A of the two-part optical rotation plates 14A and 14C.
R, 14AL, 14CR, 14CL are all turned off. The output of the light emitted from the laser coupler 20 is pulsed to a high output for recording. The controller 90 predicts the timing at which the light emitted from the objective lens 12A passes through the data area 7 based on the basic clock reproduced from the reproduction signal RF, and the light emitted from the objective lens 12A passes through the data area 7. During this time, the above settings are used. While the light emitted from the objective lens 12A passes through the data area 7, focus servo and tracking servo are not performed, and the objective lenses 12A and 12B are fixed.

At the time of recording, the S-polarized laser light emitted from the laser coupler 20 is converted into a parallel light beam by the collimator lens 17 and enters the spatial light modulator 16. Here, the light passing through the turned-on pixel of the spatial light modulator 16 remains S-polarized without rotating the polarization direction, and the light passing through the turned-off pixel has a polarization direction of +.
The light is rotated by 90 ° to become P-polarized light.

The P-polarized light from the spatial light modulator 16 is applied to the polarization beam splitter surface 113 of the prism block 113.
a and the polarization beam splitter surface 112a of the prism block 112, and sequentially enter the two-rotation optical rotation plate 14A. Here, the optical rotation plates 14AR, 1 of the two-part optical rotation plate 14A are provided.
Since both 4ALs are turned off, the light passing through the optical rotation plate 14AR is rotated by -45 ° in the polarization direction to become B-polarized light, and the light passing through the optical rotation plate 14AL has the polarization direction +
It is rotated by 45 ° and becomes A-polarized light. This light is applied to the desired information recording layer 2 and the objective lens 12 to the information recording layer 2.
On the boundary surface with the positioning layer 3 adjacent on the back side as viewed from the A side, the light converges to have the smallest diameter.

The S-polarized light from the spatial light modulator 16 is applied to the polarization beam splitter surface 113 of the prism block 113.
Then, the light is reflected by the reflective surface 113a, further reflected by the reflective surface 113b, and condensed by the convex lens 114, and then enters the prism block 112.
The light is sequentially reflected by a and enters the two-segment optical rotation plate 14A. Here, the optical rotation plates 14AR and 14AL of the two-part optical rotation plate 14A.
Are turned off, the light that has passed through the optical rotation plate 14AR has its polarization direction rotated by −45 ° to become A-polarized light, and the light that has passed through the optical rotation plate 14AL has a polarization direction of + 45 °.
Rotated by ° to become B-polarized light. This light converges to have the smallest diameter on the boundary surface between the desired information recording layer 2 and the positioning layer 3 adjacent to the information recording layer 2 on the near side as viewed from the objective lens 12A side.

As shown in FIG. 26, in the desired information recording layer 2, the B-polarized light from the optical rotation plate 14AR and the optical rotation plate 14
The B-polarized light from the AL interferes with the A-polarized light from the optical rotation plate 14AR and the A-polarized light from the optical rotation plate 14AL interferes, and the output of the emitted light from the laser coupler 20 becomes high. Sometimes, an interference pattern due to these lights is volumetrically recorded in the information recording layer 2, and a transmission type (Fresnel type) volume hologram 59 is formed. The A-polarized light and the B-polarized light do not interfere with each other because their polarization directions are orthogonal to each other. Thus, in the present embodiment, the light beam is split into two,
Since the polarization directions of the light in the respective regions are made orthogonal to each other, it is possible to prevent the occurrence of extra interference fringes and prevent the SN ratio from lowering.

In the present embodiment, the light converging so as to have the smallest diameter at the back of the information recording layer 2 where information is to be recorded and the light that converges at the front of the information recording layer 2 where information is to be recorded. Light that converges to have the smallest diameter has complementary patterns to each other, and can be regarded as information light carrying information to be recorded on the information recording layer 2.
When the light converging so as to have the smallest diameter on the back side of the information recording layer 2 is viewed as information light, the light converging so as to have the smallest diameter on the front side of the information recording layer 2 is the recording reference light. Conversely, when the light converging so as to have the smallest diameter on the front side of the information recording layer 2 is regarded as the information light, the light converging so as to have the smallest diameter on the back side of the information recording layer 2 is recorded. Reference light.

Next, the operation at the time of reproduction will be described. FIG. 27 is an explanatory diagram showing the state of the pickup 111 during reproduction, and FIGS. 28 and 29 are explanatory diagrams showing the state of light during reproduction. As shown in these figures, at the time of reproduction, the spatial light modulator 16 selects a state in which all pixels are off (+ 90 °) and a state in which all pixels are on (0 °) as necessary. The optical rotation plates 14AR, 14AL, 14CR, and 14CL of the two split optical rotation plates 14A and 14C are all turned off. The output of the output light of the laser coupler 20 is
Low output for playback. In addition, the controller 90
Based on the basic clock reproduced from the reproduction signal RF,
The timing at which the light emitted from the objective lens 12A passes through the data area 7 is predicted, and the above setting is made while the light emitted from the objective lens 12A passes through the data area 7. While the light emitted from the objective lens 12A passes through the data area 7, the focus servo and the tracking servo are not performed.
The objective lenses 12A and 12B are fixed.

When all the pixels of the spatial light modulator 16 are off, the S-polarized laser light emitted from the laser coupler 20 is converted into a parallel light beam by the collimator lens 17, and the polarization direction is changed by the spatial light modulator 16. The light is rotated by + 90 ° to become P-polarized light. The P-polarized light from the spatial light modulator 16 is transmitted through the polarizing beam splitter surface 113a of the prism block 113 and the polarizing beam splitter surface 112a of the prism block 112 in this order, and is split into two optical rotation plates 14A.
Incident on. Here, as shown in FIG. 28, since both the optical rotation plates 14AR and 14AL of the two-part optical rotation plate 14A are turned off, the light passing through the optical rotation plate 14AR is rotated by -45 ° in the polarization direction. B-polarized light, optical rotation plate 14A
The light passing through L has its polarization direction rotated by + 45 °, and A
It becomes polarized light. This light converges to have the smallest diameter on the boundary surface between the desired information recording layer 2 and the positioning layer 3 adjacent to the information recording layer 2 on the back side when viewed from the objective lens 12A side.

As shown in FIG. 28, from the volume hologram 59 in the information recording layer 2, the light that converges so as to have the smallest diameter on the back side of the information recording layer 2 is reproduced when viewed as the recording reference light. Light is generated. The reproduction light in this case is divergent light having the smallest diameter on the front side of the information recording layer 2. More specifically, the volume hologram 59 in FIG.
In the upper half region, the B-polarized light from the optical rotation plate 14AR is irradiated, and from the optical rotation plate 14AL of the two-part optical rotation plate 14A during recording, the light having the smallest diameter on the front side of the information recording layer 2 is emitted. Is generated. This reproduction light is B-polarized light, and is condensed by the objective lens 12B to become a parallel light flux.
The light passes through the CR and becomes P-polarized light. Similarly, in the lower half region of the volume hologram 59 in FIG.
The A-polarized light from the 4AL is irradiated, and is irradiated from the optical rotation plate 14AR of the 2-split optical rotation plate 14A at the time of recording, and reproduction light corresponding to the light having the smallest diameter on the front side of the information recording layer 2 is generated. . This reproduction light is A-polarized light, is condensed by the objective lens 12B, becomes a parallel light beam, passes through the optical rotation plate 14CL of the two-part optical rotation plate 14C, and becomes P-polarized light. The P-polarized reproduction light is supplied to the prism block 11.
5 is transmitted through the polarization beam splitter surface 115a, and the polarization direction is rotated by 90 ° by the half-wave plate 117, so that S
The light becomes polarized light, is reflected by the polarization beam splitter surface 116a of the prism block 116, and is
An image is formed on 9A. Thus, the CCD array 119
On A, only the portion corresponding to the pixel that was turned on in the spatial light modulator 16 at the time of recording is illuminated brightly.
The dimensional pattern is detected by the CCD array 119A, and information is reproduced.

On the other hand, when all the pixels of the spatial light modulator 16 are in the ON state, the S-polarized laser light emitted from the laser coupler 20 is converted into a parallel light beam by the collimator lens 17 and is polarized by the spatial light modulator 16. The direction remains unpolarized without being rotated. S from the spatial light modulator 16
The polarized light is reflected by the polarization beam splitter surface 113a of the prism block 113, further reflected by the reflection surface 113b, enters the prism block 112, and is reflected by the reflection surface 11b.
2b, the light is sequentially reflected by the polarizing beam splitter surface 112a, and enters the two-segment optical rotation plate 14A. Here, as shown in FIG. 29, the optical rotation plates 14AR and 14AR of the two-part optical rotation plate 14A are provided.
Since both 14AL are turned off, the optical rotation plate 14AR
, The polarization direction is rotated by −45 ° and becomes A-polarized light, and the light that has passed through the optical rotation plate 14AL is rotated by + 45 ° and becomes B-polarized light. This light is applied to a desired information recording layer 2 and the objective lens 1 to the information recording layer 2.
On the boundary surface with the adjacent positioning layer 3 on the near side as viewed from the 2A side, the light converges so as to have the smallest diameter.

As shown in FIG. 29, from the volume hologram 59 in the information recording layer 2, the light that converges so as to have the smallest diameter in front of the information recording layer 2 when viewed as the recording reference light is reproduced. Light is generated. The reproduction light in this case is divergent light having the smallest diameter on the inner side of the information recording layer 2. More specifically, the volume hologram 59 in FIG.
In the upper half region, light of B-polarized light from the optical rotation plate 14AL is irradiated, and is irradiated from the optical rotation plate 14AR of the two-part optical rotation plate 14A during recording, and the light having the smallest diameter on the inner side of the information recording layer 2 Is generated. The reproduced light is B-polarized light, is condensed by the objective lens 12B, becomes a slightly diffused light flux, passes through the optical rotation plate 14CL of the two-part optical rotation plate 14C, and becomes S-polarized light. Similarly, FIG.
In the lower half region of the volume hologram 59 in FIG. 9, the A-polarized light from the optical rotation plate 14AR is irradiated and emitted from the optical rotation plate 14AL of the two-part optical rotation plate 14A during recording. Reproduction light corresponding to the light having the smallest diameter is generated. This reproduction light is A-polarized light, is condensed by the objective lens 12B and slightly diffuses, passes through the optical rotation plate 14CR of the two-part optical rotation plate 14C, and becomes S-polarized light. The S-polarized reproduction light is reflected by the polarization beam splitter surface 115a of the prism block 115, further reflected by the reflection surface 115b, and
The light is condensed by 18 and becomes a parallel light beam, which is reflected on the reflecting surface 116b of the prism block 116 and the polarizing beam splitter surface 116a in order, and forms an image on the CCD array 119B. In this way, on the CCD array 119B, only the portion corresponding to the pixel that was turned off in the spatial light modulator 16 at the time of recording is illuminated brightly, and its two-dimensional pattern is detected by the CCD array 119B, and information is reproduced. Will be

In this embodiment, information may be reproduced by the CCD array 119A with all the pixels of the spatial light modulator 16 turned off, or the CCD may be set with all the pixels of the spatial light modulator 16 turned on. Information may be reproduced by the array 119B. Further, in the present embodiment, 1
For each unit recording area (volume hologram 59), two types of reference light for reproduction are time-divided by switching between a state where all the pixels of the spatial light modulator 16 are off and a state where all the pixels of the spatial light modulator 16 are on. For example, half of all the pixels of the spatial light modulator 16 are turned off and half of the pixels are turned on, and two kinds of reference light for reproduction are simultaneously irradiated so that both of the CCD arrays 119A and 119B are used. Information can also be reproduced. In this case, the CCD arrays 119A and 11A for one recording area (volume hologram 59).
Since the two reproduction lights obtained in 9B have patterns complementary to each other, the difference between the two reproduction lights is obtained as in the first embodiment, and the information is obtained by so-called differential detection. Can be played.

Other structures, operations and effects of the present embodiment are the same as those of the first embodiment.

FIG. 30 is an explanatory diagram showing the structure of a pickup in an optical information recording / reproducing apparatus according to the fourth embodiment of the present invention. The optical information recording / reproducing apparatus according to the present embodiment uses the optical system of the pickup according to the third embodiment, and controls the focus servo and the tracking servo by moving the collimator lens 17 instead of the objective lenses 12A and 12B. This is an example in which it is performed. In the optical information recording / reproducing apparatus according to the present embodiment, the actuators 13A and 13B shown in FIG. 23 are not provided. Instead, in the optical information recording / reproducing apparatus according to the present embodiment, as shown in FIG. 30, the collimator lens 17 is moved in the direction corresponding to the thickness direction of the optical information recording medium 1 and the direction corresponding to the radial direction. With a possible actuator 123. The actuator 123 is controlled by the focus servo circuit 86 and the tracking servo circuit 87 in FIG.

In this embodiment, the focus servo is
The actuator 12 is controlled by the focus servo circuit 86.
3 by moving the collimator lens 17 in a direction corresponding to the thickness direction of the optical information recording medium 1. The tracking servo controls the actuator 123 by the tracking servo circuit 87,
This is performed by moving the collimator lens 17 in a direction corresponding to the radial direction of the optical information recording medium 1.

Instead of moving the collimator lens 17, a lens is provided on the optical path common to the two optical paths in the recording optical system 121, and this lens is moved to perform focus servo and tracking servo. It may be.

The other structures, operations and effects of the present embodiment are the same as those of the third embodiment.

It is to be noted that, similarly to the second embodiment, the optical system of the pickup according to the third embodiment is used to move the optical information recording medium 1 so as to perform focus servo and tracking servo. It is also possible to configure an information recording / reproducing device.

Next, a fifth embodiment of the present invention will be described with reference to FIGS. The present embodiment is an example in which a plurality of pieces of information can be recorded in one information recording layer 2 in the optical information recording medium 1 in the thickness direction. FIG. 31 shows a recording area in one information recording layer 2 in the optical information recording medium 1. In this figure,
Each area represented by a diamond represents a recording area 201. As described above, in the present embodiment, one information recording layer 2 is virtually divided into a plurality of layers (an example of seven layers is shown in FIG. 31), and each layer can be selectively accessed. And

The following two methods can be considered as a method of selectively accessing each of a plurality of layers in one information recording layer 2. In the first method, as shown by a solid line in FIG. 32, the light 211 from the objective lens 12A is in a focused state on one end surface of an arbitrary information recording layer 2,
The focus servo circuit 86 is controlled so that the light 211 from the objective lens 12A is focused on one end surface of the adjacent information recording layer 2 until the light 211 from the objective lens 12A is focused as shown by a broken line. The convergence position of the light 211 is moved at a constant speed, and the light 211 is moved at an arbitrary timing during the movement.
Is stopped, and an in-focus state is set at an arbitrary position in the thickness direction in the information recording layer 2. In this case, from a state in which the light 211 from the objective lens 12A is in a focused state on one end surface of an arbitrary information recording layer 2 to a state in which the light 211 is in a focused state on one end surface of an adjacent information recording layer 2 Light 2
Since the time required to move the convergence position of the light 11 is determined in advance, by controlling the time from the start of the movement of the convergence position of the light 211 to the stop of the movement, the thickness in the information recording layer 2 is controlled. An in-focus state can be set at any position in the direction.

The second method is to add an arbitrary offset amount to the focus error signal FE during the focus servo operation. FIG. 33 shows an optical information recording medium 1
4 shows an example of the relationship between the focus position of the light from the objective lens 12A and the focus error signal FE in the thickness direction of FIG. In this example, when the convergence position of the light from the objective lens 12A is on one end surface of an arbitrary information recording layer 2, the focus error signal FE becomes 0, and the convergence position of the light shifts in one direction from that state. And the focus error signal FE changes in the positive direction, and the focus error signal FE changes in the negative direction when the light convergence position shifts in the other direction. The focus servo operates so that the focus error signal FE becomes 0. Therefore, by adding an arbitrary offset amount to the focus error signal FE, the convergence position of the light from the objective lens 12A can be changed.
It can be held at any position in the information recording layer 2 in the thickness direction. For example, as shown in FIG. 33, when no offset is added to the focus error signal FE,
Assuming that the value of the focus error signal FE when the light convergence position is at the position indicated by the symbol P ₁ is V ₁ , the offset amount with respect to the focus error signal FE is −V _1.
The addition of, so that the convergence position of the light is held in the position P _1.

Note that the address of each recording area 201 in the track direction is estimated and determined from the address represented by the preceding and following address pits in the track direction of the recording area 201 and the distance from the preceding and following address pits. To Other configurations and operations in the present embodiment are the same as those in the first to fourth embodiments.

According to the present embodiment, the optical information recording medium 1
In one of the information recording layers 2, a plurality of pieces of information can be recorded in the thickness direction, and as shown in FIG.
In the information recording layer 2, the recording area 201 can be densely arranged.
It is possible to record information at a higher density than in the embodiment.

The present invention is not limited to the above embodiments. For example, in the optical information recording medium 1, a positioning layer 3 in which address information and the like are recorded in advance by emboss pits is provided between the information recording layers 2. Instead of providing a semi-reflective film for obtaining a predetermined reflectance for performing focus servo, the information recording layer is formed in the address servo area 6 while performing focus servo using this semi-reflective film. The portion close to the semi-reflective film 2 may be selectively irradiated with high-power laser light, and the refractive index of the portion may be selectively changed to record address information or the like to perform formatting. . In this case, the semi-reflective film and the portion of the information recording layer 2 close to the semi-reflective film correspond to the positioning layer in the present invention.

The element for detecting information recorded on the information recording layer 2 is not a CCD array but a smart optical sensor (eg, a MOS solid-state image pickup element and a signal processing circuit integrated on a single chip). Document "O plus
E, September 1996, No. 202, pages 93-99 ". ) May be used. Since this smart optical sensor has a high transfer rate and a high-speed calculation function, high-speed reproduction can be performed by using this smart optical sensor. For example, reproduction at a transfer rate of the order of G bits / second can be performed. Becomes possible.

In particular, when a smart optical sensor is used as an element for detecting information recorded on the information recording layer 2, address information and the like are embossed in the address servo area 6 of the optical information recording medium 1. Instead of recording in advance, address information and the like of a predetermined pattern are recorded in advance in the same manner as in the recording using holography in the data area 7, and the pickup is set to the same state as during reproduction during servo operation. The address information and the like may be detected by a smart optical sensor. In this case, the basic clock and the address can be obtained directly from the detection data of the smart optical sensor. The tracking error signal can be obtained from information on the position of the reproduction pattern on the smart optical sensor. The focus servo can be performed by driving an objective lens or the like so that the contrast of the reproduction pattern on the smart optical sensor is maximized. Also, at the time of reproduction, it is possible to perform focus servo by driving an objective lens or the like so that the contrast of the reproduction pattern on the smart optical sensor is maximized.

When the light beam is modulated in accordance with the information to be recorded, in each of the embodiments, the light beam is modulated by the difference in polarization. In addition, the light beam may be modulated by the light intensity or phase difference. Good.

[0145]

As described above, according to the optical information recording medium according to the first or second aspect, the information light and the reference light for recording are stacked in the thickness direction and each carry information by using holography. A plurality of information recording layers for generating reproduction light corresponding to the recorded information when information is recorded by an interference pattern due to interference with the information and reproducing reference light is irradiated; With a plurality of positioning layers used for positioning the information light for the layer, the reference light for recording and the reference light for reproduction, it is possible to record a plurality of information in the thickness direction of the optical information recording medium, There is an effect that information can be recorded at a higher density.

According to the optical information recording device of any one of claims 3 to 8, the position control means uses the positioning layer corresponding to the information recording layer in which information is to be recorded on the optical information recording medium, and The position of the information light and the recording reference light with respect to the information recording layer on which information is to be recorded is controlled, and the information light and the recording reference light are converged on the information recording layer on which information is to be recorded by the recording optical system. As it was made to irradiate, the information was recorded by the interference pattern due to the interference between the information light and the recording reference light,
It is possible to record a plurality of pieces of information in the thickness direction of the optical information recording medium, and it is possible to record information at a higher density.

According to the optical information recording apparatus of the present invention, the information light and the recording reference light have patterns complementary to each other. There is an effect that the detection accuracy can be improved.

According to the optical information recording apparatus of the present invention, the position control means controls the positions of the information light and the recording reference light by selecting a position in the thickness direction in one information recording layer. Therefore, it is possible to record a plurality of pieces of information in one information recording layer in the thickness direction in one information recording layer, and it is possible to record information at a higher density.

According to the optical information recording method of the ninth aspect,
In the optical information recording medium, information is recorded by controlling the positions of the information light and the recording reference light with respect to the information recording layer on which information is to be recorded, using a positioning layer corresponding to the information recording layer on which information is to be recorded. The information recording layer to be recorded is irradiated with the information light and the recording reference light while being converged, and information is recorded by an interference pattern due to interference between the information light and the recording reference light. It is possible to record a plurality of pieces of information in the thickness direction of the medium, and it is possible to record information at a higher density.

According to the optical information reproducing apparatus of any one of claims 10 to 16, the position control means uses the positioning layer corresponding to the information recording layer from which information is to be reproduced on the optical information recording medium. By controlling the position of the reference light for reproduction with respect to the information recording layer from which information is to be reproduced,
The reproduction optical system irradiates the information recording layer from which information is to be reproduced, while converging the reproduction reference light corresponding to the recording reference light at the time of recording, and irradiates the reproduction reference light. The reproducing light generated from the information recording layer is collected, and the reproducing light is detected by the detecting means to reproduce the information. Therefore, a plurality of pieces of information are recorded in the thickness direction, and the information is recorded at a high density. There is an effect that information can be reproduced with higher accuracy from the optical information recording medium thus obtained.

Further, according to the optical information reproducing apparatus of the twelfth aspect, the information information reproducing apparatus has the mutually complementary patterns, and the recording medium and the information light irradiated from opposite directions so as to converge at different positions in the thickness direction. Using an optical information recording medium in which information is recorded on the information recording layer by an interference pattern due to interference with the reference light for reproduction, the reproducing optical system corresponds to the information light and the recording reference light during recording from both sides of the information recording layer 2
One reproduction reference light is irradiated, two reproduction lights obtained from both sides of the information recording layer are collected, and the detecting means detects the two reproduction lights and reproduces information based on a difference between the two reproduction lights. With this configuration, it is possible to further improve the information detection accuracy by the differential detection.

Further, according to the optical information reproducing apparatus of the present invention, the information light and the recording medium have mutually complementary patterns and are recorded with the information light irradiated from opposite directions so as to converge at different positions in the thickness direction. Using an optical information recording medium in which information is recorded on the information recording layer by an interference pattern due to interference with the reference light for recording, the reproducing optical system uses the information light and the recording reference light for recording from the same side of the information recording layer. Are irradiated with two reference light beams for reproduction, and two reproduction light beams obtained from the opposite surface of the information recording layer are collected.
Since the two reproduction lights are detected and the information is reproduced based on the difference between the two reproduction lights, it is possible to further improve the detection accuracy of the information by the differential detection.

According to the optical information reproducing apparatus of the present invention, the position control means controls the position of the reproducing reference light by selecting a position in the thickness direction in one information recording layer. Therefore, it is possible to reproduce information more accurately from an optical information recording medium in which a plurality of pieces of information are recorded in one information recording layer in the thickness direction.

According to the optical information reproducing method of the seventeenth aspect, in the optical information recording medium, using the positioning layer corresponding to the information recording layer in which the information is to be reproduced, the reproduction to the information recording layer in which the information is to be reproduced is performed. By controlling the position of the reference light for the information recording layer where information is to be reproduced,
At the time of recording, the reproduction reference light corresponding to the recording reference light is irradiated while being converged, and the reproduction light generated from the information recording layer due to the irradiation of the reproduction reference light is collected and detected. Then, since the information is reproduced, a plurality of pieces of information are recorded in the thickness direction, and the information can be reproduced with higher accuracy than the optical information recording medium on which the information is recorded at a high density. To play.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a pickup and an optical information recording medium in an optical information recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an overall configuration of the optical information recording / reproducing apparatus according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a configuration of the optical information recording medium according to the first embodiment of the present invention.

FIG. 4 is a perspective view showing a configuration of the laser coupler in FIG. 1;

FIG. 5 is a side view of the laser coupler in FIG. 1;

FIG. 6 is a block diagram illustrating a configuration of a detection circuit in FIG. 2;

FIG. 7 is an explanatory diagram illustrating a state of the pickup illustrated in FIG. 1 during servo.

FIG. 8 is an explanatory diagram showing a state of light in the pickup in the state shown in FIG. 7;

FIG. 9 is an explanatory diagram illustrating a state of the pickup illustrated in FIG. 1 during recording.

FIG. 10 is an explanatory diagram for explaining polarized light used in the first embodiment of the present invention.

FIG. 11 is an explanatory diagram showing a state of light in the pickup in the state shown in FIG. 9;

12 is an explanatory diagram conceptually showing a state of interference in the information recording layer shown in FIG.

FIG. 13 is an explanatory diagram showing a state of the pickup shown in FIG. 1 during reproduction.

FIG. 14 is an explanatory diagram showing a state of light in the pickup in the state shown in FIG. 13;

FIG. 15 is an explanatory diagram showing a state of light in the pickup in the state shown in FIG. 13;

FIG. 16 is an explanatory diagram for describing a relationship between a relief in a volume hologram and an incident angle with respect to the relief.

FIG. 17 is an explanatory diagram showing a function Sinc ² (x) for explaining diffraction intensity in the volume hologram shown in FIG. 16;

18 is an explanatory diagram for describing a method of recognizing a reference position in a reproduction light pattern from detection data of the CCD array in FIG. 1;

FIG. 19 is an explanatory diagram for describing a method of recognizing a reference position in a reproduction light pattern from detection data of the CCD array in FIG. 1;

FIG. 20 is an explanatory diagram showing a pattern of information light and a pattern of reproduction light in the pickup shown in FIG. 1;

21 is an explanatory diagram showing the contents of data determined from the pattern of the reproduction light detected by the pickup shown in FIG. 1 and an ECC table corresponding to the data.

FIG. 22 is an explanatory diagram showing a configuration of a main part of a pickup in an optical information recording / reproducing apparatus according to a second embodiment of the present invention.

FIG. 23 is an explanatory diagram showing a configuration of a pickup in an optical information recording / reproducing device according to a third embodiment of the present invention.

FIG. 24 is an explanatory diagram showing a state of the pickup shown in FIG. 23 during servo.

FIG. 25 is an explanatory diagram showing a state of the pickup shown in FIG. 23 during recording.

FIG. 26 is an explanatory diagram showing a state of light in the pickup in the state shown in FIG. 25.

FIG. 27 is an explanatory diagram illustrating a state during reproduction of the pickup illustrated in FIG. 23;

FIG. 28 is an explanatory diagram showing a state of light in the pickup in the state shown in FIG. 27;

FIG. 29 is an explanatory diagram showing a state of light in the pickup in the state shown in FIG. 27;

FIG. 30 is an explanatory diagram showing a configuration of a pickup in an optical information recording / reproducing apparatus according to a fourth embodiment of the present invention.

FIG. 31 is an explanatory diagram showing a recording area in one information recording layer in an optical information recording medium according to a fourth embodiment of the present invention.

FIG. 32 is an explanatory diagram for explaining a method of selectively accessing each of a plurality of layers in one information recording layer in the fourth embodiment of the present invention.

FIG. 33 is an explanatory diagram for explaining a method of selectively accessing each of a plurality of layers in one information recording layer in the fourth embodiment of the present invention.

FIG. 34 is a perspective view showing a schematic configuration of a recording / reproducing system in conventional digital volume holography.

[Explanation of symbols]

1 optical information recording medium, 2 information recording layer, 3 positioning layer, 6 address servo area, 7 data area,
10 ... optical information recording / reproducing device, 11 ... pickup, 12
A, 12B: Objective lens, 13A, 13B: Actuator, 14A, 14B: Two-part optical rotation plate, 15A, 15B
... Prism block, 16 ... Spatial light modulator, 19A, 1
9B: CCD array, 20: Laser coupler.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G11B 7/135 G11B 7/135 A 7/24 501 7/24 501Z

Claims (17)

[Claims] 1. Information is recorded by an interference pattern caused by interference between an information light carrying information and a recording reference light, and the reproduction reference light is irradiated by using holography. A plurality of information recording layers for generating reproduction light corresponding to the recorded information when the information light is used for positioning the information light, the recording reference light, and the reproduction reference light for each information recording layer. An optical information recording medium comprising: a plurality of positioning layers. 2. The optical information recording medium according to claim 2, wherein said information recording layer and said positioning layer are alternately laminated. 3. Information is recorded by an interference pattern caused by interference between an information light carrying information and a recording reference light, and the reproduction reference light is irradiated by using holography. A plurality of information recording layers for generating reproduction light corresponding to recorded information, and used for positioning of the information light, recording reference light, and reproduction reference light for each information recording layer. An optical information recording device for recording information on an optical information recording medium having a plurality of positioning layers, wherein an information pattern is recorded on an arbitrary information recording layer by an interference pattern caused by interference between the information light and the recording reference light. Corresponds to the recording optical system for irradiating the information light and reference light for recording while converging it to any information recording layer so that information is recorded, and the information recording layer to record information That using a positioning layer, an optical information recording apparatus characterized by comprising a position control means for controlling the position of the information light and the recording-specific reference light with respect to the information recording layer to be recorded information. 4. The recording optical system irradiates the information light and the recording reference light from opposite directions to the information recording layer so as to converge at different positions in the thickness direction. The optical information recording device according to claim 3. 5. The recording optical system irradiates the information beam and the recording reference beam from the same surface side so as to converge on the information recording layer at different positions in the thickness direction. The optical information recording device according to claim 3. 6. The optical information recording apparatus according to claim 3, wherein the information light and the recording reference light have mutually complementary patterns. 7. The position control means controls the positions of the information light and the recording reference light based on the light radiated on the information recording layer by the recording optical system and reflected on the information recording layer. The optical information recording apparatus according to claim 3, wherein 8. The apparatus according to claim 3, wherein said position control means further controls the positions of the information light and the recording reference light by selecting a position in the thickness direction in one information recording layer. Optical information recording device. 9. Laminating in the thickness direction, the information is recorded by an interference pattern of interference between the information light carrying information and the recording reference light using holography, and the reproduction reference light is irradiated. A plurality of information recording layers for generating reproduction light corresponding to recorded information, and used for positioning of the information light, recording reference light, and reproduction reference light for each information recording layer. An optical information recording method for recording information on an optical information recording medium having a plurality of positioning layers, wherein the information is recorded using a positioning layer corresponding to the information recording layer on which information is to be recorded. While controlling the positions of the information light and the recording reference light with respect to the information recording layer on which information is to be recorded, the information light and the recording reference light are focused on the information recording layer on which information is to be recorded. And irradiating the optical information recording method comprising recording information of an interference pattern resulting from interference between the information recording layer in the information light to be recorded information and recording-specific reference light. 10. Information is recorded by an interference pattern caused by interference between an information light carrying information and a recording reference light by using holography, and the reproduction reference light is radiated. A plurality of information recording layers for generating reproduction light corresponding to recorded information, and used for positioning of the information light, recording reference light, and reproduction reference light for each information recording layer. An optical information reproducing apparatus for reproducing information from an optical information recording medium having a plurality of positioning layers, wherein a reproduction reference light corresponding to a recording reference light at the time of recording is formed on an arbitrary information recording layer. While irradiating while converging,
Information is reproduced using a reproduction optical system for collecting reproduction light generated from the information recording layer by irradiation with the reproduction reference light, and a positioning layer corresponding to the information recording layer from which information is to be reproduced. An optical information reproducing apparatus comprising: position control means for controlling a position of a reproduction reference light with respect to an information recording layer to be obtained; and detection means for detecting reproduction light collected by the reproduction optical system. 11. The optical information reproducing apparatus according to claim 10, wherein the reproducing optical system irradiates the reproducing reference light and collects the reproducing light from the same side of the information recording layer. 12. The information recording layer of the optical information recording medium has mutually complementary patterns, and the information light and the recording medium irradiated from opposite directions to converge at different positions in the thickness direction. Information is recorded by an interference pattern due to interference with the reference light, and the reproduction optical system includes:
From both sides of the information recording layer, two reproduction reference lights corresponding to the information light at the time of recording and the reference light for recording are irradiated, and two reproduction lights obtained from both sides of the information recording layer are collected. 11. The optical information reproducing apparatus according to claim 10, wherein two reproducing lights are detected, and information is reproduced based on a difference between the two reproducing lights. 13. The optical information reproducing apparatus according to claim 10, wherein the reproducing optical system irradiates the reproducing reference light and collects the reproducing light from opposite directions in the information recording layer. 14. The information recording layer of the optical information recording medium has a pattern complementary to each other, and the information light irradiated from the same side and the recording light are converged at different positions in the thickness direction. Information is recorded by an interference pattern due to interference with the reference light, and the reproduction optical system irradiates two reproduction reference lights corresponding to the information light and the recording reference light during recording from the same surface side of the information recording layer. Collecting two reproduction light beams obtained from opposite surfaces of the information recording layer, wherein the detecting means detects the two reproduction light beams and reproduces information based on a difference between the two reproduction light beams. Claim 1
0. The optical information reproducing apparatus according to item 0. 15. The apparatus according to claim 1, wherein the position control means controls the position of the reference light for reproduction based on light irradiated on the information recording layer by the reproduction optical system and reflected on the information recording layer. Item 11. An optical information reproducing apparatus according to Item 10. 16. The optical information according to claim 10, wherein said position control means further controls a position of a reference light for reproduction by selecting a position in a thickness direction in one information recording layer. Playback device. 17. Information is recorded by an interference pattern due to interference between an information light carrying information and a recording reference light by using holography, and the reproduction reference light is radiated. A plurality of information recording layers for generating reproduction light corresponding to recorded information, and used for positioning of the information light, recording reference light, and reproduction reference light for each information recording layer. An optical information reproducing method for reproducing information from an optical information recording medium comprising a plurality of positioning layers, wherein the information is reproduced using a positioning layer corresponding to the information recording layer from which information is to be reproduced. While controlling the position with respect to the information recording layer, while converging the reproduction reference light corresponding to the recording reference light at the time of recording to the information recording layer where information is to be reproduced. While morphism collects reproduction light reproducing reference beam is generated from the information recording layer by being irradiated, the optical information reproducing method comprising reproducing the information by detecting the reproduction light.