JP2003263749A - Optical information recording device and optical information recording / reproducing device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To record or reproduce information using holography, and to make an optical system small without reducing the amount of information. SOLUTION: During recording, an information light 61 generated by a spatial light modulator and a recording reference light 62 generated by a phase spatial light modulator pass through a two-segment optical rotation plate 32 to form an information recording layer of a recording medium. 3 is radiated coaxially from one surface side so as to have the smallest diameter on the reflection surface 5a,
Information is recorded on the information recording layer 3. 2 split optical rotation plate 32
Rotates the passing light in a different direction for each region obtained by dividing the cross section of the light beam into two. The two-part optical rotation plate 32 is disposed at a position conjugate with the position at which the spatial light modulator is disposed.
Further, the phase spatial light modulator is disposed at a position conjugate with the position at which the two-part optical rotation plate 32 is disposed.

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 apparatus for recording information on a recording medium using holography, and an optical information recording apparatus for recording information on the recording medium using holography and reproducing information from the recording medium. The present invention relates to an information recording / reproducing device.

[0002]

2. Description of the Related Art Holographic recording in which information is recorded on a recording medium by utilizing holography generally causes light having image information and reference light to be superposed inside the recording medium, and interference caused at that time is generated. This is done by writing the pattern on a recording medium. At the time of reproducing the recorded information, by irradiating the recording medium with the reference light, the image information is reproduced by the diffraction due to the interference pattern.

In recent years, volume holography, particularly digital volume holography, has been developed in the practical range and has attracted attention for ultra-high density optical recording. Volume holography is a method of writing interference patterns three-dimensionally by positively utilizing the thickness direction of the recording medium.
There is a feature that the diffraction efficiency can be increased by increasing the thickness and the recording capacity can be increased by using the multiplex recording. The digital volume holography is a computer-oriented holographic recording method in which the image information to be recorded is limited to a binarized digital pattern while using the same recording medium and recording method as the volume holography. In this digital volume holography, image information such as an analog picture is digitized once and developed into two-dimensional digital pattern information.
This is recorded as image information. During playback, by reading and decoding this digital pattern information,
The original image information is restored and displayed. As a result, even if the signal-to-noise ratio (hereinafter referred to as the SN ratio) during reproduction is somewhat poor, by performing differential detection or coding the binarized data and performing error correction, it is possible to faithfully reproduce the original signal. It becomes possible to reproduce the information of.

[0004]

In the conventional optical information recording / reproducing method using holography, if the reproducing reference light is incident on the photodetector for detecting the reproducing light, the SN ratio of the reproducing information is also increased. However, there was a problem of deterioration. Therefore, in the conventional optical information recording / reproducing method, the reproducing light and the reproducing reference light can be spatially separated at the time of reproducing, and the information light and the recording reference light form a predetermined angle at the time of recording. It is often incident on the recording medium.
As a result, the reproduction light generated during reproduction travels in a direction forming a predetermined angle with respect to the reproduction reference light, so that the reproduction light and the reproduction reference light can be spatially separated.

However, as described above, the information light and the recording reference light are made incident on the recording medium at a predetermined angle during recording, and the reproducing light and the reproducing reference light are spatially separated during reproduction. If this is done, there is a problem that the optical system for recording and reproducing becomes large.

In Japanese Unexamined Patent Publication No. 10-124872, information light and recording reference light are placed at different positions in the thickness direction of the information recording layer on the information recording layer on which information is recorded by using holography. There is disclosed a technique of recording an interference pattern between the information light and the recording reference light on the information recording layer by irradiating the information recording layer from the same surface side so as to converge. Further, the above-mentioned publication discloses a technique for separating the reproduction light and the reproduction reference light by using a two-divided optical rotation plate provided in the recording / reproduction optical system.
The two-divided optical rotation plate rotates the passing light in different directions for each of the regions obtained by dividing the cross section of the light flux into two.

By the way, when the above-mentioned two-division optical rotator is used, the information light passes through the two-division optical rotator, so that the image of the boundary line between the two regions of the two-division optical rotator overlaps the image of the information light.
As a result, on the information recording layer, in addition to the image of the information light, the image of the boundary line of the two-part optical rotatory plate is recorded so as to be superimposed on the image. Here, depending on the arrangement of the two-part optical rotatory plate in the recording / reproducing optical system, the image of the boundary line of the two-part optical rotatory plate recorded on the information recording layer may be a blurred image. In that case, there is a problem that the image of the boundary line may cause a part of the information carried by the information light to be lost.

The present invention has been made in view of the above problems, and an object thereof is to record information by utilizing holography and to make a recording optical system small without reducing the amount of information. An object of the present invention is to provide an optical information recording device and an optical information recording / reproducing device that can be used.

[0009]

An optical information recording apparatus of the present invention is an information recording layer in which information is recorded by utilizing holography and light for recording or reproducing information is irradiated from one surface side. And a device for recording information on a recording medium having a reflection surface disposed on the other surface side of the information recording layer, the device having a spatial light modulator, the spatial light modulator Information light generating means for generating information light carrying information, recording reference light generating means for generating recording reference light, and interference due to interference between the information light and the recording reference light in the information recording layer. A recording optical system that irradiates the information recording layer with the information light generated by the information light generating means and the recording reference light generated by the recording reference light generating means so that information is recorded by the pattern, The recording optics The cross section of the bundle is divided into two areas, and each of the areas has a two-part optical rotation plate that rotates in different directions. The two-part optical rotation plate is arranged at a position conjugate with the position where the spatial light modulator is arranged. Means a recording reference light having a predetermined first polarization direction and information light having a second polarization direction different from the first polarization direction, each being rotated by a two-division optical rotation plate, and incident on a reflecting surface. The polarization direction of the information light before being reflected and the polarization direction of the recording reference light after being reflected by the reflecting surface match, and the polarization direction of the recording reference light before entering the reflecting surface and the information light after being reflected by the reflecting surface So that they coincide with each other, the polarization directions of the information light and the recording reference light are made different for each region, and the recording optical system further supplies the information light and the recording reference light to the information recording layer in one direction. Information light before it is incident on the reflecting surface coaxially and convergently from the surface side of An interference pattern resulting from interference between the recording-specific reference light reflected by the reflecting surface,
Also, information is recorded on the information recording layer by an interference pattern due to interference between the recording reference light before entering the reflecting surface and the information light after reflecting on the reflecting surface.

In the optical information recording apparatus of the present invention, the recording light of the first polarization direction and the information light of the second polarization direction are rotated by the two-divided optical rotator before being incident on the reflecting surface. The information light and the recording reference light after being reflected by the reflecting surface have the same polarization direction, and the recording reference light before entering the reflecting surface and the information light after having been reflected by the reflecting surface have the same polarization direction. As described above, the polarization directions of the information light and the recording reference light are changed for each area. The information beam and the reference beam for recording are
The information recording layer is irradiated so as to be coaxial and converge from one surface side. Then, the interference pattern due to the interference between the information light before entering the reflecting surface and the recording reference light after reflecting on the reflecting surface, and the recording reference light before entering the reflecting surface and the reflecting on the reflecting surface Information is recorded on the information recording layer by the interference pattern due to the interference with the information light after that. Further, in the optical information recording apparatus of the present invention, the image of the information light formed by the spatial light modulator is formed on the two-divided optical rotation plate.

In the optical information recording apparatus of the present invention, the recording reference light generating means has a phase spatial light modulator, and the phase spatial light modulator is arranged at a position conjugate with the position where the two-divided optical rotation plate is arranged. The recording reference light generating means may generate the recording reference light whose phase is spatially modulated by using the phase spatial light modulator.

The optical information recording / reproducing apparatus of the present invention records information by utilizing holography, and an information recording layer on which light for recording or reproducing information is irradiated from one surface side, and this information recording layer. While recording information on a recording medium having a reflection surface arranged on the other surface side of the layer,
An apparatus for reproducing information from a recording medium, which has a spatial light modulator, uses the spatial light modulator to generate information light carrying information light, and recording reference light. A recording reference light generating means for generating, a reproducing reference light generating means for generating a reproducing reference light, and at the time of recording information,
The information light generated by the information light generating means and the recording reference generated by the recording reference light generating means so that the information is recorded on the information recording layer by the interference pattern due to the interference between the information light and the recording reference light. By irradiating the information recording layer with light, and by irradiating the information recording layer with the reproducing reference light generated by the reproducing reference light generating means at the time of reproducing the information, the reproducing reference light is irradiated. The recording / reproducing optical system includes a recording / reproducing optical system that collects the reproducing light generated from the information recording layer, and a detection unit that detects the reproducing light collected by the recording / reproducing optical system. A two-divided optical rotation plate that rotates in different directions is provided for each of the regions obtained by dividing the cross-section into two, and the two-divided optical rotation plate is arranged at a position conjugate with the position where the spatial light modulator is arranged.

When recording information, the recording / reproducing optical system outputs a recording reference light having a predetermined first polarization direction and an information light having a second polarization direction different from the first polarization direction, respectively.
The information light before being incident on the reflecting surface and the recording reference light after being reflected by the reflecting surface have the same polarization direction after being rotated by the split optical rotator and reflected by the recording reference light before entering the reflecting surface. So that the polarization directions of the information light after being reflected by the surface match.
The polarization directions of the information light and the recording reference light are made different for each region.

When recording information, the recording / reproducing optical system further irradiates the information recording layer with the information light and the recording reference light so that the information recording layer is coaxially converged from one surface side, and the reflection surface is irradiated with the information light. An interference pattern due to interference between the information light before incidence and the recording reference light after being reflected by the reflecting surface, and the recording reference light before entering the reflecting surface and the information light after being reflected by the reflecting surface The information is recorded on the information recording layer by the interference pattern due to the interference of.

When reproducing information, the recording / reproducing optical system rotates the reproduction reference light of the first polarization direction by the two-division optical rotation plate and converts it into reproduction reference light having a different polarization direction for each area. The reproducing reference light is irradiated onto the information recording layer so as to be converged in the same manner as the recording reference light, and the reproducing light and the return light by the reproducing reference light reflected by the reflecting surface are divided by a two-divided optical rotation plate. Rotate the light to make the first
The entire cross section of the reproduction light and the light flux with the polarization direction of
To return light having a second polarization direction different from the polarization direction. The recording / reproducing optical system further irradiates the reproducing reference light and collects the reproducing light so that the reproducing reference light and the reproducing light are coaxially arranged at the time of reproducing the information. Do from the side.

In the optical information recording / reproducing apparatus of the present invention, at the time of recording information, the reference light for recording having the first polarization direction and the information light having the second polarization direction are rotatively reflected by the two-division rotatory plate. The information light before entering the surface and the recording reference light after being reflected by the reflecting surface have the same polarization direction, and the recording reference light before entering the reflecting surface and the information light after being reflected by the reflecting surface The polarization directions of the information light and the recording reference light can be changed for each region so that the polarization directions of the two become the same. The information light and the recording reference light are irradiated onto the information recording layer from one surface side so as to be coaxial and converged. And
An interference pattern due to interference between the information light before entering the reflecting surface and the recording reference light after reflecting on the reflecting surface, and the recording reference light before entering the reflecting surface and after reflecting on the reflecting surface Information is recorded on the information recording layer by the interference pattern due to the interference with the information light. Further, in the optical information recording / reproducing apparatus of the present invention, the image of the information light formed by the spatial light modulator is formed on the two-divided optical rotation plate.

Further, in the optical information recording / reproducing apparatus of the present invention,
At the time of reproducing information, the reproduction reference light having the first polarization direction is rotated by the two-divided optical rotation plate and converted into reproduction reference light having a different polarization direction for each region, and the reproduction reference light is recorded. The information recording layer is irradiated so as to converge like the reference light for use. Further, the reproduction light and the return light due to the reproduction-specific reference light reflected by the reflecting surface are rotated by the two-divided optical rotation plate, and the reproduction light and the entire cross section of the light flux having the first polarization direction for the entire cross section of the light flux are It is converted into return light having a second polarization direction different from the one polarization direction. Irradiation of the reproduction reference light and collection of the reproduction light are performed from one surface side of the information recording layer so that the reproduction reference light and the reproduction light are arranged coaxially.

Further, in the optical information recording / reproducing apparatus of the present invention, the recording reference light generating means and the reproducing reference light generating means have a common phase spatial light modulator, and the phase spatial light modulator has a two-division optical rotation. The recording reference light generating means is arranged at a position conjugate with the position where the plate is arranged, and the recording reference light generating means generates a recording reference light whose phase is spatially modulated by using a phase spatial light modulator, and reproduces the reference light. The light generation means may generate a reproduction reference light whose phase is spatially modulated using a phase spatial light modulator.

In the optical information recording / reproducing apparatus of the present invention, the recording / reproducing optical system further includes the reproduction light after passing through the two-division optical rotation plate and the return after passing through the two-division optical rotation plate due to the difference in the polarization direction. It may have a polarized light separating means for separating light.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, the configuration of an optical information recording / reproducing apparatus according to an embodiment of the present invention will be described with reference to FIGS. The optical information recording / reproducing apparatus according to this embodiment includes the optical information recording apparatus according to this embodiment. FIG. 1 is an explanatory diagram showing a configuration of a main part of an optical head in the optical information recording / reproducing apparatus according to the present embodiment. FIG. 2 is a plan view showing the movable portion of the optical head and its periphery. FIG. 3 is an explanatory diagram showing the light emitting portion of the optical head and the recording medium in the optical information recording / reproducing apparatus according to the present embodiment. FIG. 4 is an explanatory diagram showing an optical system for controlling the position of the optical head. FIG. 5 is an explanatory diagram showing a recording medium used in this embodiment. FIG. 6 is a block diagram showing the overall configuration of the optical information recording / reproducing apparatus according to the present embodiment.

First, the structure of the recording medium used in the present embodiment will be described with reference to FIGS. 3 and 5. As shown in FIG. 3, the recording medium 1 according to the present embodiment has a disk-shaped transparent substrate 2 formed of polycarbonate or the like, and a transparent substrate 2 on the side opposite to the light entrance / exit side. The information recording layer 3, the transparent substrate 4, and the reflective layer 5 are arranged in this order from the substrate 2. An air gap layer may be provided instead of the transparent substrate 4. The information recording layer 3 is a layer in which information is recorded by utilizing holography, and is a hologram in which 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. It is made of material. As the hologram material, for example, photopolymers HRF-6 manufactured by Dupont can be used.
00 (product name), a photo polymer ULSH-500 (product name) manufactured by Aprilis (Aprils), or the like is used. The reflective layer 5 is made of, for example, aluminum. The surface of the reflective layer 5 on the transparent substrate 4 side is a reflective surface 5a that reflects light for recording or reproducing information.

FIG. 5 shows a part of one track on the recording medium 1. The recording medium 1 has a disk shape and has a plurality of tracks TR. Each track TR
, A plurality of address / servo areas 6 are provided at equal intervals. 1 between adjacent address / servo areas 6
One or more information recording areas 7 are provided. Figure 5
Shows an example in which four information recording areas 7 are provided at equal intervals between adjacent address / servo areas 6.

In the address / servo area 6, information for generating a basic clock that serves as a reference for the timing of various operations in the optical information recording / reproducing apparatus, information for performing focus servo by the sampled servo system, and sampled Information for performing tracking servo by the servo system and address information are recorded in advance by embossed pits or the like. Note that focus servo may be performed using the reflecting surface 5 a of the recording medium 1 without recording information for performing focus servo in the address / servo area 6. The address information is information for identifying each information recording area 7.

Next, the configuration of the optical information recording / reproducing apparatus according to the present embodiment will be described with reference to FIG. The optical information recording / reproducing apparatus 10 controls a spindle 81 to which the recording medium 1 is attached, a spindle motor 82 for rotating the spindle 81, and a spindle motor 82 so as to keep the number of rotations of the recording medium 1 at a predetermined value. A spindle servo circuit 83 and a slider 93 for moving the spindle motor 82 in the horizontal direction are provided. The optical information recording / reproducing apparatus 10 further irradiates the recording medium 1 with the information light and the recording reference light to record information, and irradiates the recording medium 1 with the reproducing reference light to reproduce the reproduction light. And an optical head 11 for reproducing information recorded on the recording medium 1.

The optical information recording / reproducing apparatus 10 further includes a detection circuit 85 for detecting the focus error signal FE, the tracking error signal TE and the reproduction signal RF from the output signal of the optical head 11, and the detection circuit 85. Based on the focus error signal FE, the focus servo circuit 86 that drives the actuator in the optical head 11 to move the objective lens in the optical head 11 in the thickness direction of the recording medium 1 to perform focus servo, and the detection circuit 85. A tracking servo circuit 87 that drives a linear motor in the optical head 11 based on the tracking error signal TE detected by the above to move the objective lens in the radial direction of the recording medium 1 to perform tracking servo; Based on the command from the controller described later And controls the rider 93, and a slide servo circuit 88 for performing a slide servo for moving the spindle motor 82 in the horizontal direction.

The optical information recording / reproducing apparatus 10 further moves the irradiation positions of the information light and the recording reference light in the direction substantially along the track at the time of recording the information.
A tracking control circuit 94 for controlling the irradiation positions of the information light and the recording reference light is provided so that the irradiation positions of the information light and the recording reference light follow one moving information recording area 7 for a predetermined period. .

The optical information recording / reproducing apparatus 10 further decodes output data of a solid-state image pickup device, which will be described later, in the optical head 11 to reproduce or detect data recorded in the information recording area 7 of the recording medium 1. A signal processing circuit 89 for reproducing a basic clock and determining an address from a reproduction signal RF from the circuit 85, a controller 90 for controlling the entire optical information recording / reproducing apparatus 10, and various instructions to the controller 90. And an operation unit 91 for giving The controller 90 inputs the basic clock and address information output from the signal processing circuit 89, and controls the optical head 11, the spindle servo circuit 83, the slide servo circuit 88, the follow-up control circuit 94 and the like. The spindle servo circuit 83 has a signal processing circuit 89.
The basic clock that is output is input. The controller 90 is a CPU (central processing unit), R
It has an OM (Read Only Memory) and a RAM (Random Access Memory), and the CPU realizes the function of the controller 90 by executing the program stored in the ROM using the RAM as a work area. It has become.

Next, with reference to FIG. 1, the structure of the main part of the optical head 11 in the present embodiment will be described.
The optical head 11 includes a light source device 12 that emits coherent linearly polarized laser light, and a collimator lens 13, mirrors 14, 2 that are sequentially arranged on the optical path of light emitted from the light source device 12 from the light source device 12 side. Sub-wave plate 15
And a polarization beam splitter 16. As the light source device 12, for example, a semiconductor laser that emits green light of a single wavelength is used. Green light has a wavelength of about 4
It refers to light within the range of 92 nm to 577 nm. The polarization beam splitter 16 has a polarization beam splitter surface 16a that reflects S-polarized light and transmits P-polarized light. Note that S-polarized light means that the polarization direction is the plane of incidence (paper surface of FIG. 1)
Is a linearly polarized light that is perpendicular to, and P-polarized light is a linearly polarized light whose polarization direction is parallel to the incident surface.

The optical head 11 further includes the half-wave plate 1
The polarization beam splitter 16 is provided with a half-wave plate 17 and a polarization beam splitter 18 arranged in order from the polarization beam splitter 16 side in the traveling direction of the light that has entered the polarization beam splitter 16 and transmitted through the polarization beam splitter surface 16a. There is. The polarization beam splitter 18 reflects the S-polarized light and transmits the P-polarized light.
8a.

The optical head 11 further comprises a half-wave plate 1
A quarter that is sequentially arranged from the polarization beam splitter 18 side in the traveling direction of the light that has entered the polarization beam splitter 18 from the 7 side and is reflected by the polarization beam splitter surface 18a.
A wave plate 19 and a reflective spatial light modulator 20 are provided. The reflection-type spatial light modulator 20 has a large number of pixels arranged in a grid pattern, and selects a state in which light passes through or a state in which light is blocked for each pixel so that the light is spatially divided according to the light intensity. Information light carrying information can be generated by modulating the information.

The optical head 11 further includes the quarter-wave plate 1
The half-wave plate 21, the convex lens 22, the pinhole 23, which are sequentially arranged from the polarization beam splitter 18 side in the traveling direction of the light that has entered the polarization beam splitter 18 from the 9 side and transmitted through the polarization beam splitter surface 18a, Convex lens 2
4 and a polarization beam splitter 25. The polarization beam splitter 25 has a polarization beam splitter surface 25a that reflects S-polarized light and transmits P-polarized light.

The optical head 11 further includes the half-wave plate 1
The polarization beam splitter 16 is provided with a phase spatial light modulator 26 and a polarization beam splitter 27, which are sequentially arranged from the polarization beam splitter 16 side in the traveling direction of the light entering the polarization beam splitter 16 and reflected by the polarization beam splitter surface 16a. There is. The phase spatial light modulator 26 has a large number of pixels arranged in a lattice, and the phase of the light can be spatially modulated by selecting the phase of the emitted light for each pixel. ing. A liquid crystal element can be used as the phase spatial light modulator 26. The polarization beam splitter 27 has a polarization beam splitter surface 27a that reflects S-polarized light and transmits P-polarized light.

The optical head 11 is further moved in the traveling direction of the light incident on the polarization beam splitter 27 from the phase spatial light modulator 26 side and reflected by the polarization beam splitter surface 27a.
It includes a half-wave plate 28, a convex lens 29, and a convex lens 30, which are sequentially arranged from the polarization beam splitter 27 side. The light that has passed through the convex lenses 29 and 30 travels in the direction orthogonal to the traveling direction of the light that enters the polarization beam splitter 25 from the side of the convex lens 24 and enters the polarization beam splitter 25.

The optical head 11 further enters the polarization beam splitter 25 from the convex lens 24 side and is reflected by the polarization beam splitter surface 25a, and enters the polarization beam splitter 25 from the convex lens 30 side to the polarization beam splitter surface 25a. A short wavelength pass filter 31, a two-divided optical rotation plate 32, and a dichroic mirror 33, which are arranged in order from the polarization beam splitter 25 side, are provided in the traveling direction of the light that has passed through. The short wavelength pass filter 31 passes green light and blocks red light. Red light refers to light having a wavelength in the range of approximately 622 nm to 770 nm. The two-part optical rotation plate 32 has an optical rotation plate 32R arranged on the right side portion of the optical axis in FIG. 1 and an optical rotation plate 32L arranged on the left side portion of the optical axis. Polarizing plate 32
R rotates the polarization direction by −45 °, and the optical rotation plate 32L rotates the polarization direction by + 45 °. The dichroic mirror 33 reflects green light and allows red light to pass through.

In the present embodiment, the two-part optical rotation plate 32 is
The reflective spatial light modulator 20 is arranged at a position conjugate with the position at which the reflective spatial light modulator 20 is arranged. More specifically, the reflective spatial light modulator 20 has an image forming surface that forms an image corresponding to information, and the image forming surface and the two-divided optical rotation plate 32 are conjugate with each other with respect to the optical system between them. It is located in a different position. Therefore, the image formed by the reflective spatial light modulator 20 is formed on the two-divided optical rotation plate 32.

Further, in this embodiment, the phase spatial light modulator 26 is arranged at a position conjugate with the position where the two-divided optical rotation plate 32 is arranged. More specifically, the phase spatial light modulator 26 has an image forming surface that forms an image in which the phase is spatially modulated, and the image forming surface and the two-divided optical rotation plate 32 are
With respect to the optical system between them, they are arranged at positions conjugate with each other. Therefore, the image formed by the phase spatial light modulator 26 is formed on the two-divided optical rotation plate 32.

The optical head 11 further includes a two-part optical rotation plate 32.
The dichroic mirror 3 enters the dichroic mirror 33 from the side and is reflected by the dichroic mirror 3 in the traveling direction.
A convex lens 34, a convex lens 35, and a mirror 36, which are sequentially arranged from the third side, are provided.

The light that enters the mirror 36 from the convex lens 35 side and is reflected by the mirror 36 enters the movable portion shown in FIG.

The optical head 11 further includes the half-wave plate 2
The imaging lens 37, the imaging lens 38, and the solid-state imaging device 39, which are sequentially arranged from the polarization beam splitter 27 side in the traveling direction of the light that has entered the polarization beam splitter 27 from the 8 side and transmitted through the polarization beam splitter surface 27a. I have it. As the solid-state image pickup device 39, for example, CCD or MO
An S-type solid-state image sensor is used.

The optical head 11 further includes the position control optical system shown in FIG. This position control optical system
On the side of the dichroic mirror 33 opposite to the convex lens 34, a red transmission filter 42, a beam splitter 43, a collimator lens 44, and a light source device 45 are sequentially arranged from the dichroic mirror 33 side. The beam splitter 43 has a semi-reflective surface 4 whose normal direction is inclined by 45 ° with respect to the optical axis direction of the collimator lens 44.
3a. The red transmission filter 42 passes red light and blocks light in other wavelength regions. As the light source device 45, for example, a semiconductor laser that emits single wavelength red light is used. The optical head 11 is
Further, from the collimator lens 44 side, the beam splitter 4
3 is provided with a photodetector 46 arranged in the traveling direction of the light reflected by the semi-reflecting surface 43a. The photodetector 46 is used to monitor the amount of light emitted from the light source device 45 and automatically adjust the amount of light emitted from the light source device 45.

The optical head 11 further includes a convex lens 47, a cylindrical lens 48, and a four-division photodetector 49, which are arranged in this order from the beam splitter 43 side, on the side of the beam splitter 43 opposite to the photodetector 46. . The four-division photodetector 49 has four light receiving portions divided by a division line parallel to the direction corresponding to the track direction in the recording medium 1 and a division line in a direction orthogonal to the division line. The cylindrical lens 48 is arranged such that the central axis of its cylindrical surface forms 45 ° with respect to the dividing line of the 4-division photodetector 49.

Next, the structure of the movable portion of the optical head 11 will be described with reference to FIGS. Optical head 11
The movable part 200 has an objective lens 41 and a mirror 40 that form a part of a recording / reproducing optical system. As shown in FIG. 3, the objective lens 41 is the transparent substrate 2 of the recording medium 1.
The mirror 40 is arranged on the side of the objective lens 41 opposite to the recording medium 1.

The movable part 200 of the optical head 11 has a first movable part 201 and a second movable part 202. The main body of the optical information recording / reproducing apparatus has two rails 211 extending in the radial direction of the recording medium 1 (left and right direction in FIG. 2).
Is attached. The first movable part 201 is
It is supported by a book rail 211 so as to be movable in the radial direction of the recording medium 1. Further, the optical head 11 has a first
Linear motor 212 for moving the movable part 201 of the optical information recording / reproducing apparatus in the radial direction of the recording medium 1.
have.

The first movable portion 201 has two rails 2 extending in the tangential direction of the track (vertical direction in FIG. 2).
21 is attached. The second movable portion 202 is supported by the two rails 221 so as to be movable in the tangential direction of the track. The optical head 11 also includes a linear motor 222 that moves the second movable portion 202 in the tangential direction of the track with respect to the first movable portion 201.

The objective lens 41 is attached to the second movable portion 202.
A support plate 203 that supports the recording medium 1 movably in a direction perpendicular to the surface of the recording medium 1 (direction orthogonal to the paper surface in FIG. 2) is attached. The optical head 11 also has an actuator 231 that moves the objective lens 41 in a direction perpendicular to the surface of the recording medium 1 with respect to the second movable portion 202.

The mirror 40 is fixed to the first movable portion 201. Light incident on the mirror 36 from the convex lens 35 side in FIG. 2 and reflected by the mirror 36 enters the mirror 40 shown in FIG. 3 and is reflected thereby. The light reflected by the mirror 40 is condensed by the objective lens 41 and applied to the recording medium 1. Further, the light incident on the objective lens 41 from the recording medium 1 side is
The light is condensed by the objective lens 41, is sequentially reflected by the mirrors 40, 36, and is convex lens 35 and convex lens 34.
Through in order.

In the optical head 11 according to this embodiment,
By the actuator 231, the position of the objective lens 41 can be changed in the direction perpendicular to the surface of the recording medium 1, and thus focus servo can be performed. Further, in the optical head 11, the position of the objective lens 41 can be changed in the radial direction of the recording medium 1 by the linear motor 212, and thus tracking servo can be performed. Further, in the optical head 11, the position of the objective lens 41 can be changed by the linear motor 222 in the tangential direction of the track, that is, in the direction substantially along the track. This makes it possible to control the irradiation positions of the information light and the recording reference light to follow the information recording area 7. The desired track is accessed by moving the spindle motor 82 in the horizontal direction by the slider 93.

The actuator 231 is driven by the focus servo circuit 86 shown in FIG. The linear motor 212 is driven by the tracking servo circuit 87 shown in FIG. The linear motor 222 is driven by the tracking control circuit 94 shown in FIG. Further, the slider 93 is adapted to be driven by the slide servo circuit 88 shown in FIG.

The light source devices 12, 4 in the optical head 11 are
5, reflective spatial light modulator 20 and phase spatial light modulator 2
6 is controlled by the controller 90 in FIG. The controller 90 holds information on a plurality of modulation patterns for spatially modulating the phase of light in the phase spatial light modulator 26. Further, the operation section 91 can select an arbitrary modulation pattern from a plurality of modulation patterns. Then, the controller 90 provides the phase spatial light modulator 26 with information of the modulation pattern selected by itself or the modulation pattern selected by the operation unit 91 according to a predetermined condition,
The phase spatial light modulator 26 is adapted to spatially modulate the phase of light with a corresponding modulation pattern in accordance with the information on the modulation pattern provided from the controller 90.

Next, the optical head 1 shown in FIGS.
The outline of the operation of the first optical system will be described. Light source device 1
2 emits linearly polarized green light of S polarization or P polarization. The light emitted from the light source device 12 is collimated by the collimator lens 13 into a parallel light flux, which is reflected by the mirror 14 and then 2
The light passes through the half-wave plate 15 and its polarization direction is rotated by 45 ° to become light including an S-polarized component and a P-polarized component. This light enters the polarization beam splitter 16. Of the light incident on the polarization beam splitter 16, the P-polarized component is the polarization beam splitter surface 1 of the polarization beam splitter 16.
6a, and the S-polarized component is polarized beam splitter 16
Is reflected by the polarized beam splitter surface 16a.

The P-polarized light that has passed through the polarization beam splitter surface 16a is rotated by 90 ° by the half-wave plate 17 to become S-polarized light. This light is reflected by the polarization beam splitter surface 18 a of the light beam splitter 18, passes through the quarter wavelength plate 19, becomes circularly polarized light, and enters the spatial light modulator 20. The intensity of the light incident on the spatial light modulator 20 is spatially modulated by the spatial light modulator 20, and the information light is emitted from the spatial light modulator 20. The information light emitted from the spatial light modulator 20 passes through the quarter-wave plate 19 to become P-polarized light, and passes through the polarization beam splitter surface 18 a of the polarization beam splitter 18. This light passes through the half-wave plate 21 and becomes S-polarized light. This light passes through the convex lens 22, the pinhole 23, and the convex lens 24 in order, enters the polarization beam splitter 25, is reflected by the polarization beam splitter surface 25a, and is reflected by the short wavelength pass filter 3
Incident on 1.

On the other hand, the S-polarized light reflected by the polarization beam splitter surface 16a enters the phase spatial light modulator 26. The phase spatial light modulator 26 spatially modulates the phase of light by setting the phase of outgoing light for each pixel to one of two values that differ from each other by π (rad), for example. Has become. The light modulated by the phase spatial light modulator 26 becomes recording reference light or reproduction reference light. The outgoing light of the phase spatial light modulator 26 enters the polarization beam splitter 27, and the polarization beam splitter surface 27a
Is reflected by. This light has its polarization direction rotated by 45 ° by the half-wave plate 28, and then the convex lens 2
After passing through 9 and 30, it enters the polarization beam splitter 25. A part of this light passes through the polarization beam splitter surface 25a and enters the short wavelength pass filter 31.

The light emitted from the polarization beam splitter 25 and incident on the short wavelength pass filter 31 is information light, recording reference light or reproduction reference light. Also, these lights are green lights. These lights pass through the short wavelength pass filter 31 and the two-divided optical rotation plate 32, are reflected by the dichroic mirror 33, pass through the convex lenses 34 and 35 in order, and are reflected in order by the mirrors 36 and 40, and the objective lens 4
It is condensed by 1 and is irradiated onto the recording medium 1. The information light, the recording reference light and the reproducing reference light are converged so as to be coaxial with the information recording layer 3 of the recording medium 1 from one surface side and have the smallest diameter on the reflecting surface 5a. Is irradiated.

The return light from the recording medium 1 corresponding to the green light applied to the recording medium 1 is converted into a parallel or nearly parallel light beam by the objective lens 41, and the mirrors 40 and 36, the convex lenses 35 and 34, and the dichroic mirror 33. It is incident on the polarization beam splitter 25 via the two-divided optical rotation plate 32 and the short wavelength pass filter 31. As will be described later in detail, the light incident on the polarization beam splitter 25 includes S-polarized light and P-polarized light. Of these, the S-polarized light is reflected by the polarization beam splitter surface 25a, and the P-polarized light passes through the polarization beam splitter surface 25a. The P-polarized light that has passed through the polarization beam splitter surface 25a is reflected by the convex lens 3
After passing through 0 and 29, the polarization direction thereof is rotated by 45 ° by the half-wave plate 28, and then enters the polarization beam splitter 27. A part of this light passes through the polarization beam splitter surface 27a, passes through the imaging lenses 37 and 38, and enters the solid-state image sensor 39.

On the other hand, the red light emitted from the light source device 45 is collimated by the collimator lens 44 and then enters the beam splitter 43. Part of the light that has entered the beam splitter 43 is reflected by the semi-reflective surface 43a and enters the photodetector 46, and the other part of the light passes through the semi-reflective surface 43a. The light that has passed through the semi-reflective surface 43a serves as position control light. This position control light passes through the red transmission filter 42 and the dichroic mirror 33 in this order, and further, the convex lens 3
4 and 35 in order, reflected in order by mirrors 36 and 40, and condensed by the objective lens 41 to obtain the recording medium 1
Is irradiated. The position control light is reflected by the reflection surface 5 of the recording medium 1.
The recording medium 1 is irradiated so as to have the smallest diameter on a and converge.

The return light from the recording medium 1 corresponding to the red light applied to the recording medium 1 is collimated by the objective lens 41, passes through the mirrors 40 and 36 and the convex lenses 35 and 34, and enters the dichroic mirror 33. To do. This light is
After passing through the dichroic mirror 33 and the red transmission filter 42 in order, the light enters the beam splitter 43. Part of the light incident on the beam splitter 43 is a semi-reflecting surface 43a.
Is reflected by the convex lens 47 and the cylindrical lens 48.
After being sequentially passed through, the light is detected by the four-division photodetector 49. The focus error signal FE, the tracking error signal TE, and the reproduction signal RF are generated by the detection circuit 85 based on the output of the 4-division photodetector 49. Then, based on these signals, focus servo and tracking servo for controlling the positions of the information light, the recording reference light and the reproduction reference light with respect to the recording medium 1 are performed, and the reproduction of the basic clock and the determination of the address are performed. Be seen.

Here, with reference to FIG. 7, A-polarized light and B-polarized light used in the following description will be defined as follows. That is, as shown in FIG. 7, the A-polarized light has an S-polarized light of −45 °.
Alternatively, the P-polarized light is linearly polarized light whose polarization direction is rotated by + 45 °, and the B-polarized light is S-polarized light by + 45 ° or P-polarized light by -45 °.
° Linearly polarized light with the polarization direction rotated. The polarization directions of the A-polarized light and the B-polarized light are orthogonal to each other.

Next, the operation of the optical information recording / reproducing apparatus according to the present embodiment will be described in order of servo operation, information recording operation, and information reproduction operation.

First, the operation during servo will be described with reference to FIG. FIG. 8 is an explanatory diagram showing the state of light during servo. Note that FIG. 8 shows only the dichroic mirror 33 and the objective lens 41 as the optical components. During servo, the light source device 45 emits red light and the light source device 12 does not emit green light. Light source device 45
As described above, the position control light 51, which is the emitted light of the collimator lens 44, the beam splitter 43, the red transmission filter 42, the dichroic mirror 33, and the convex lens 3 are emitted.
The recording medium 1 is irradiated from the objective lens 41 through the mirrors 4, 35 and the mirrors 36, 40. This position control light 51 is
The objective lens 41 is reflected by the reflection surface 5a of the recording medium 1,
It is detected by a four-division photodetector 49 through the mirrors 40 and 36, the convex lenses 35 and 34, the dichroic mirror 33, the red transmission filter 42, the beam splitter 43, the convex lens 47, and the cylindrical lens 48. The focus error signal FE, the tracking error signal TE, and the reproduction signal RF are generated by the detection circuit 85 based on the output of the 4-division photodetector 49. Then, based on these signals, focus servo and tracking servo are performed, and the basic clock is reproduced and the address is determined. In the present embodiment, the focus servo is performed so that the position control light 51 has the smallest diameter on the reflection surface 5a of the recording medium 1 and converges.

The controller 90 predicts the timing at which the light emitted from the objective lens 41 passes through the address servo area 6 based on the basic clock reproduced from the reproduction signal RF, and the light emitted from the objective lens 41 undergoes the address servo. While passing through the area 6, the above setting is made.

Next, the operation of recording information will be described with reference to FIG. FIG. 9 is an explanatory diagram showing a light state at the time of recording information. Note that FIG. 9 shows only the polarization beam splitter 25, the two-divided optical rotation plate 32, and the objective lens 41 as optical components.

At the time of recording information, the light source device 12 emits green light and the light source device 45 does not emit red light. The output of the light emitted from the light source device 12 is controlled to a high output for recording for a certain period of time under the control of the controller 90. Further, the light emitted from the objective lens 41 is the address / servo area 6
Focus servo and tracking servo are not performed while passing through the areas other than. During this time, the objective lens 4
1 is fixed to the position determined by the focus servo and the tracking servo performed immediately before.

The light emitted from the light source device 12 is split into two light beams by the polarization beam splitter 16. One of the light fluxes is modulated by the spatial light modulator 20 to be the information light 61.
Becomes The other light flux is modulated by the phase spatial light modulator 26 to become the recording reference light 62. The information light 61 and the recording reference light 62 are combined by the polarization beam splitter 25 and are incident on the two-divided optical rotation plate 32 together. The information light 61 is S-polarized light and the recording reference light 62 is P-polarized light before entering the two-split optical plate 32.

The information light 61R that has passed through the optical rotation plate 32R of the two-divided optical rotation plate 32 becomes A-polarized light, and the information light 61L that has passed through the optical rotation plate 32L of the two-divided optical rotation plate 32 becomes B-polarized light. On the other hand, the recording reference light 62R that has passed through the optical rotation plate 32R of the two-divided optical rotation plate 32 becomes B-polarized light, and the recording reference light 62L that has passed through the optical rotation plate 32L of the two-divided optical rotation plate 32 becomes A-polarized light.

Information light 61 which has passed through the two-divided optical rotation plate 32.
The R, 61L and the recording reference beams 62R, 62L are condensed by the objective lens 41, and are recorded on the recording medium 1.
Irradiate coaxially from the same side. Information light 61R, 61
The L and the recording reference lights 62R and 62L have the smallest diameter on the reflection surface 5a and converge.

After passing through the optical rotation plate 32R, the information light 61R incident on the recording medium 1 is A-polarized. Further, the recording reference light 62L incident on the recording medium 1 after passing through the optical rotation plate 32L is also A-polarized. The A-polarized recording reference light 62L is reflected by the reflecting surface 5a of the recording medium 1 and before being reflected by the reflecting surface 5a in the information recording layer 3.
It passes through the same area as the polarized information light 61R. Since the polarization directions of these lights 61R and 62L coincide with each other, they interfere with each other to form an interference pattern. In addition, A-polarized information light 61R
Is reflected by the reflecting surface 5a of the recording medium 1 and the information recording layer 3
Inside, the light passes through the same area as the A-polarized recording reference light 62L before being reflected by the reflecting surface 5a. These light 61
Since the R and 62L also have the same polarization direction, they interfere with each other to form an interference pattern. Therefore, in the information recording layer 3, the A-polarized information light 61R and the reflection surface 5 before entering the reflection surface 5a.
The interference pattern due to the interference of the A-polarized light with the recording reference light 62L after being reflected by a, and the A before being incident on the reflecting surface 5a.
An interference pattern due to interference between the polarized recording reference light 62L and the A-polarized information light 61R after being reflected by the reflecting surface 5a is volumetrically recorded.

Similarly, the information light 61L incident on the recording medium 1 after passing through the optical rotation plate 32L is B-polarized.
Further, the recording reference light 62R incident on the recording medium 1 after passing through the optical rotation plate 32R is also B-polarized. The B-polarized recording reference light 62R is reflected by the reflection surface 5a of the recording medium 1 and passes through the same area as the B-polarized information light 61L in the information recording layer 3 before being reflected by the reflection surface 5a. These lights 61L and 62R have the same polarization direction and thus interfere with each other to form an interference pattern. The B-polarized information light 61L is reflected by the reflection surface 5a of the recording medium 1 and passes through the same area as the B-polarized recording reference light 62R in the information recording layer 3 before being reflected by the reflection surface 5a. To do. Since the polarization directions of these lights 61L and 62R are also the same, they interfere with each other to form an interference pattern. Therefore, in the information recording layer 3, the B-polarized information light 61L before entering the reflecting surface 5a and the B-polarizing recording reference light 62 after being reflected by the reflecting surface 5a.
The interference pattern due to the interference with R and the interference pattern due to the interference between the B-polarized recording reference light 62R before entering the reflecting surface 5a and the B-polarized information light 61L after being reflected by the reflecting surface 5a are volume. Will be recorded.

The information light 61 that has passed through the optical rotation plate 32R
R and the information light 61L that has passed through the optical rotation plate 32L do not interfere with each other because their polarization directions differ by 90 °. Similarly, the optical rotation plate 32
The recording reference light 62R that has passed through R and the recording reference light 62L that has passed through the optical rotation plate 32L do not interfere because the polarization directions differ by 90 °.

Further, in the present embodiment, by changing the modulation pattern of the phase of the recording reference light for each information to be recorded, a plurality of pieces of information are recorded at the same location of the information recording layer 3 by the phase encoding multiplex system. Multiple recording is possible.

Next, the operation at the time of reproducing information will be described with reference to FIG. FIG. 10 is an explanatory diagram showing the state of light when reproducing information.

When reproducing information, the light source device 12 emits green light and the light source device 45 does not emit red light. The output of the light emitted from the light source device 12 is set to a low output for reproduction under the control of the controller 90. In addition, the objective lens 4
While the emitted light of 1 passes through the area other than the address servo area 6, the focus servo and the tracking servo are not performed. During this time, the objective lens 41 is fixed at the position determined by the focus servo and the tracking servo performed immediately before.

In the spatial light modulator 20, all pixels are in a state of blocking light. The light emitted from the light source device 12 is split into two light beams by the polarization beam splitter 16. One light flux is blocked by the spatial light modulator 20. The other light flux is modulated by the phase spatial light modulator 26 to become the reproduction reference light 71. The reproduction reference light 71 passes through the polarization beam splitter 25 and enters the two-part optical rotation plate 32. Before entering the two-division optical rotation plate 32, the reproduction reference light 71 is P-polarized light.

The reproduction reference light 71R that has passed through the optical rotation plate 32R of the two-division optical rotation plate 32 becomes B-polarized light, and the two-division optical rotation plate 3
The reproduction reference light 71L that has passed through the second optical rotation plate 32L becomes A-polarized light.

The reproduction reference lights 71R and 71L that have passed through the two-divided optical rotation plate 32 are condensed by the objective lens 41 and are applied to the recording medium 1. Reference light for reproduction 71R, 7
1L is information light 61R, 61L and recording reference light 62
The R and 62L have the smallest diameter and converge at the same position, that is, the smallest diameter on the reflecting surface 5a and converge.

The reproduction reference light 71R incident on the recording medium 1 after passing through the optical rotation plate 32R is B-polarized. On the other hand, the reproduction reference light 71L incident on the recording medium 1 after passing through the optical rotation plate 32L is A-polarized. In the information recording layer 3, the reproduction reference light before being reflected by the reflection surface 5a generates reproduction light that travels to the side opposite to the reflection surface 5a, and the reproduction reference light after being reflected by the reflection surface 5a. The light generates reproduction light that travels toward the reflecting surface 5a. The reproduction light traveling on the side opposite to the reflection surface 5a is emitted from the recording medium 1 as it is, and the reproduction light traveling on the side on the reflection surface 5a is reflected by the reflection surface 5a and emitted from the recording medium 1.

The reproduction light is made into a parallel light flux by the objective lens 41, and then enters the two-divided optical rotation plate 32. here,
Reproduction light 72 incident on the optical rotation plate 32R of the two-division optical rotation plate 32
R is B-polarized light before entering the optical rotation plate 32R, and is P-polarized light after passing through the optical rotation plate 32R. On the other hand, the reproduction light 72L incident on the optical rotation plate 32L of the two-divided optical rotation plate 32 is A-polarized before entering the optical rotation plate 32L, and thus the optical rotation plate 32L.
After passing through, it becomes P-polarized light. In this way, the reproduction light after passing through the two-part optical rotation plate 32 becomes P-polarized light for the entire cross section of the light beam. The reproduction light that has passed through the two-divided optical rotation plate 32 enters the solid-state imaging device 39. Imaging lenses 37, 38
Is configured to form an image carried by reproduction light on the solid-state image pickup device 39.

On the solid-state image pickup device 39, a light intensity pattern formed by the spatial light modulator 20 during recording is imaged, and information is reproduced by detecting this pattern. When a plurality of pieces of information are recorded in the information recording layer 3 by changing the modulation pattern of the recording reference light, only the information corresponding to the modulation pattern of the reproducing reference light is included in the plurality of pieces of information. Is played.

On the other hand, the reproduction reference light 71R that has entered the recording medium 1 after passing through the optical rotation plate 32R is reflected by the reflecting surface 5a, is emitted from the recording medium 1, passes through the optical rotation plate 32L, and is S-polarized. Is converted to the return light. Also, the optical rotation plate 32
After passing through L, the reference beam for reproduction 7 incident on the recording medium 1
1L is reflected by the reflection surface 5a, emitted from the recording medium 1, passes through the optical rotation plate 32R, and is converted into S-polarized return light. In this way, the return light after passing through the two-part optical rotation plate 32 becomes S-polarized light for the entire cross section of the light flux. This return light is reflected by the polarization beam splitter surface 25a of the polarization beam splitter 25 and therefore does not enter the solid-state image sensor 39.

Next, the operation of the optical head 11 at the time of recording information will be described with reference to FIG. Figure 11
Shows the movement of the track TR and the movement of the irradiation position 101 of the information light and the recording reference light when recording information. In FIG. 11, the symbol R represents the moving direction of the recording medium 1. Note that, in FIG. 11, the irradiation position 101 is shown not to overlap the track TR for convenience, but in reality, the irradiation position 101 overlaps the track TR.

In this embodiment, as shown in FIG. 11A, before the information is recorded in the information recording area 7 of the recording medium 1, the irradiation position 101 is higher than the neutral position in the recording medium 1.
Is moved in a direction opposite to the moving direction R (hereinafter, also referred to as a forward direction). At that time, the irradiation position 101 passes through the address servo area 6, and the information recorded in the address servo area 6 is detected by the optical head 11.

Next, as shown in FIG. 11B, when the irradiation position 101 reaches the end E1 of the moving range in the forward direction,
The irradiation position 101 is now moved in the moving direction R of the recording medium 1 (hereinafter, also referred to as the delay direction). Irradiation position 10
Immediately after the start of the movement of 1 in the delay direction, the moving speed of the irradiation position 101 is lower than the moving speed of the desired information recording area 7 in which information should be recorded. Therefore, in time, the irradiation position 101
Overlap the desired information recording area 7.

As shown in FIG. 11C, irradiation position 1
When 01 overlaps the desired information recording area 7, irradiation position 1
The moving speed of 01 is adjusted to be equal to the moving speed of the information recording area 7. As a result, the irradiation position 1 is set so that the irradiation position 101 follows the desired information recording area 7.
01 is moved.

Next, as shown in FIG. 11D, when the irradiation position 101 reaches the end E2 of the moving range in the delay direction,
The irradiation position 101 is again moved in the forward direction, as shown in FIG.
The operation shown in (a) is performed. In this way, FIG.
The operations shown in 1 (a) to (d) are repeatedly executed.

As described above, in the present embodiment, the irradiation position 101 is moved so that the irradiation position 101 of the information light and the recording reference light follows one moving information recording area 7 for a predetermined period. It As a result, one information recording area 7 continues to be irradiated with the information light and the recording reference light for a predetermined period, and information is recorded in this information recording area 7 by the interference pattern due to the interference between the information light and the recording reference light. To be done.

As described above, in the present embodiment,
At the time of recording information, the information light and the recording reference light are irradiated onto the information recording layer 3 coaxially from one surface side and with the smallest diameter on the reflecting surface 5a and converge.

When recording information, the recording reference light having the first polarization direction (P-polarized light) and the information light having the second polarization direction (S-polarized light) different from the first polarization direction (P-polarized light) are recorded. But,
The cross section of the light flux is divided into
Optical rotation is performed in different directions for each of the divided areas. Thereby, for each of the information light and the recording reference light, in the same area in the information recording layer 3, the polarization of the information light before entering the reflecting surface 5a and the polarization of the recording reference light after being reflected by the reflecting surface 5a Polarization is performed for each region obtained by dividing the cross section of the light flux into two so that the directions of the light beams are the same and the polarization directions of the recording reference light before entering the reflecting surface 5a and the information light after being reflected by the reflecting surface 5a match. The directions are set to be different. As a result, in the information recording layer 3, the information light before entering the reflecting surface 5a and the reflecting surface 5a.
The interference pattern due to the interference with the recording reference light after being reflected by a is recorded, and the interference between the recording reference light before entering the reflecting surface 5a and the information light after being reflected by the reflecting surface 5a is recorded. Interference pattern is recorded.

During reproduction of information, the information recording layer 3 is arranged such that the reproduction reference light has the smallest diameter and converges at the same position where the information light and the recording reference light have the smallest diameter and converge. Is irradiated. Further, during reproduction of information, irradiation of the reproduction reference light and collection of the reproduction light are performed from one surface side of the information recording layer 3, and the reproduction reference light and the reproduction light are arranged coaxially.

During reproduction of information, the reproduction reference light of the first polarization direction (P-polarized light) is rotated by the two-divided optical rotation plate 32 in different directions for each of the regions into which the cross section of the light beam is divided into two. The information recording layer 3 is irradiated with the converted reference light which has a different polarization direction for each area. Further, the reproduction light and the return light due to the reproduction reference light reflected by the reflection surface 5a are rotatively rotated in different directions for each region by the two-division optical rotator 32, and the first polarization direction ( P-polarized) reproduction light and the entire cross section of the light beam
Is converted into the return light having the polarization direction (S polarization). Thereby, it becomes possible to separate the reproduction light and the return light by the polarization beam splitter 25 as the polarization separation means, and as a result, it is possible to improve the SN ratio of the reproduction information.

Further, in the present embodiment, the information light can carry information by using the entire cross section of the light flux, and similarly, the reproduction light can also carry information by using the entire cross section of the light flux. it can.

By the way, the two-part optical rotatory plate 32 has a boundary line between two regions, that is, one boundary line that divides the two optical rotatory plates 32R and 32L. The information light passes through the two-part optical rotation plate 32. Therefore, the image of the boundary line of the two-part optical rotation plate 32 overlaps the image of the information light. As a result, the information recording layer 3
In addition to the image of information light,
An image of the boundary line of the divided optical rotation plate 32 is recorded. Here, depending on the arrangement of the two-part optical rotation plate 32 in the recording / reproducing optical system, the image of the boundary line of the two-part optical rotation plate 32 recorded on the information recording layer 3 may be a blurred image. When that happens,
The image of the boundary line of the two-part optical rotation plate 32 may cause a part of the information carried by the information light to be missing.

On the other hand, in the present embodiment, the two-divided optical rotation plate 32 is arranged at a position conjugate with the position where the reflection type spatial light modulator 20 is arranged. Therefore, the image of the information light formed by the reflective spatial light modulator 20 is formed on the two-divided optical rotation plate 32. Therefore, if the recording / reproducing optical system is designed so that the image of the information light is clearly recorded on the information recording layer 3, the image of the boundary line of the two-part optical rotatory plate 32 is also clearly displayed on the information recording layer 3. That is, it is recorded as an image of a thin line.

Here, the reflective spatial light modulator 20 has a plurality of grid-like boundary lines that divide each pixel. 12
Is an image 111 of a plurality of grid-like boundary lines in the reflective spatial light modulator 20 and an image 11 of a boundary line of the two-divided optical rotation plate 32.
It shows conceptually that 2 and 2 overlap. Figure 1
As shown in FIG. 2, the reflective spatial light modulator 20 and the reflective spatial light modulator 20 are arranged so that one image of the boundary lines of the reflective spatial light modulator 20 overlaps with the image 112 of the boundary line of the two-divided optical rotation plate 32. If the two-division optical rotation plate 32 is aligned, the two-division optical rotation plate 32
The image 112 of the boundary line of 1 has almost no influence on the image of the information light, and the information carried by the information light is not lost.

Further, in this embodiment, the phase spatial light modulator 26 is arranged at a position conjugate with the position where the two-divided optical rotation plate 32 is arranged. Like the reflective spatial light modulator 20, the phase spatial light modulator 26 also has a plurality of grid-like boundary lines that divide each pixel. Images of a plurality of grid-like boundary lines of the phase spatial light modulator 26 are formed on the two-divided optical rotation plate 32. Therefore, the phase spatial light modulator 26 and the two-divided optical rotation plate 32 are aligned so that one image of the plurality of boundary lines of the phase spatial light modulator 26 overlaps with the image 112 of the boundary line of the two-divided optical rotation plate 32. If so, the image 1 of the boundary line of the two-part optical rotation plate 32
12 has almost no effect on the modulation pattern generated by the phase spatial light modulator 26, and does not affect the multiplex recording by the phase encoding multiplex system.

From the above, according to the present embodiment,
Information can be recorded and reproduced using holography, and an optical system for recording and reproduction can be made small without reducing the amount of information.

Further, in the present embodiment, the irradiation positions of the information light and the recording reference light are set so that the irradiation positions of the information light and the recording reference light follow one moving information recording area 7 for a predetermined period. To move. As a result, one information recording area 7 is continuously irradiated with the information light and the recording reference light for a predetermined period. Therefore, according to the present embodiment, the information recording area 7 is not displaced from the irradiation positions of the information light and the recording reference light, and the information is recorded for a sufficient time in the information recording area 7. It is possible to irradiate the recording area 7 with the information light and the recording reference light. As a result, according to the present embodiment, for example, a semiconductor laser which is a practical light source is used to rotate the recording medium 1 having the plurality of information recording areas 7 while rotating the respective information recording areas 7.
It is possible to record information using holography.

The present invention is not limited to the above embodiment, and various modifications can be made. For example, in the embodiment, the information is multiplexed and recorded by the phase encoding multiplex system, but the present invention includes the case where the multiplex recording by the phase encoding multiplex system is not performed. Further, in the embodiment, during recording of information, the information light and the recording reference light are so arranged that the irradiation position of the information light and the recording reference light follows one moving information recording area 7 for a predetermined period. Although the irradiation position is controlled, the present invention includes the case where such control is not performed.

[0097]

As described above, claim 1 or 2
In the optical information recording device described above or the optical information recording / reproducing device according to any one of claims 3 to 5, the information light and the recording reference light are converged from one surface side with respect to the information recording layer of the recording medium. It is irradiated to do. Further, in the present invention,
The information light can carry information using the entire cross section of the light flux. Further, in the present invention, the image of the information light formed by the spatial light modulator is formed on the two-divided optical rotation plate.
Therefore, the image of the boundary line between the two areas on the two-divided optical rotator can be superimposed on the image of the information light and recorded clearly on the information recording layer, that is, as an image of a thin line. This makes it possible to prevent the information carried by the information light from being lost. From these facts, according to the present invention, it is possible to record information by utilizing holography, and it is possible to configure an optical system for recording small without reducing the amount of information. Play.

In the optical information recording apparatus according to the second aspect or the optical information recording / reproducing apparatus according to the fourth aspect, a phase spatial light modulator for generating the recording reference light whose phase is spatially modulated. It is arranged at a position conjugate with the position where the two-divided optical rotation plate is arranged. Therefore, according to the present invention, there is an effect that it is possible to prevent the image of the boundary line on the two-part optical rotation plate from affecting the multiplex recording by the phase-encoding multiplex system.

Further, in the optical information recording / reproducing apparatus according to the fifth aspect, the recording / reproducing optical system has a difference in polarization direction.
It has a polarization separation means for separating the reproduction light after passing through the split optical rotation plate and the return light after passing through the two-division optical rotation plate.
Therefore, according to the present invention, the reproduction light and the return light can be separated, and as a result, the SN ratio of the reproduction information can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a main part of an optical head in an optical information recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view showing a movable portion of an optical head and its surroundings in an optical information recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a light emitting portion of an optical head and a recording medium in an optical information recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an optical system for controlling a position of an optical head in an optical information recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a recording medium used in an embodiment of the present invention.

FIG. 6 is a block diagram showing an overall configuration of an optical information recording / reproducing device according to an embodiment of the present invention.

FIG. 7 is an explanatory diagram for explaining polarized light used in one embodiment of the present invention.

FIG. 8 is an explanatory diagram for explaining an operation during servo of the optical information recording / reproducing device according to the embodiment of the present invention.

FIG. 9 is an explanatory diagram for explaining an operation at the time of information recording of the optical information recording / reproducing device according to the embodiment of the present invention.

FIG. 10 is an explanatory diagram for explaining an action at the time of information reproduction of the optical information recording / reproducing device according to the embodiment of the present invention.

FIG. 11 is an explanatory diagram for explaining the movement of the track and the movement of the irradiation position of the information light and the recording reference light during information recording of the optical information recording / reproducing apparatus according to the embodiment of the present invention.

FIG. 12 is a view showing an image of a plurality of grid-like boundary lines of a reflective spatial light modulator in an optical information recording / reproducing apparatus according to an embodiment of the present invention and an image of a boundary line of a two-divided optical rotatory plate. It is explanatory drawing which shows a mode.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Recording medium, 3 ... Information recording layer, 5 ... Reflective layer, 5a ... Reflective surface, 11 ... Optical head, 12 ... Light source device, 20 ... Spatial light modulator, 25 ... Polarization beam splitter, 26 ... Phase spatial light modulation Vessel, 32 ... 2 division optical rotation plate, 39 ... solid-state image sensor,
41 ... Objective lens, 45 ... Light source device.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hideyoshi Horimei             2-5-1, Shin-Yokohama, Kohoku Ward, Yokohama City, Kanagawa Prefecture             No. 13 Building, 7th floor, Opto Corporation             In the air (72) Inventor Masaharu Kinoshita             2-5-1, Shin-Yokohama, Kohoku Ward, Yokohama City, Kanagawa Prefecture             No. 13 Building, 7th floor, Opto Corporation             In the air (72) Inventor Hayashi Jinmei             2-5-1, Shin-Yokohama, Kohoku Ward, Yokohama City, Kanagawa Prefecture             No. 13 Building, 7th floor, Opto Corporation             In the air (72) Inventor Kozo Matsumoto             173-1 Asana, Asaba-cho, Iwata-gun, Shizuoka             Oh, inside Hamamatsu Manufacturing Co., Ltd. (72) Inventor Atsushi Kitamura             173-1 Asana, Asaba-cho, Iwata-gun, Shizuoka             Oh, inside Hamamatsu Manufacturing Co., Ltd. (72) Inventor Hideki Kato             173-1 Asana, Asaba-cho, Iwata-gun, Shizuoka             Oh, inside Hamamatsu Manufacturing Co., Ltd. F term (reference) 2K008 AA04 BB04 DD13 HH11 HH13                 5D090 AA01 BB17 CC01 CC04 CC16                       DD03 FF03 KK06 KK11 KK12                       KK15                 5D118 AA01 BA01 BB03 CA11 CA13                       CD02 CD03 CG04 CG26 CG32                 5D119 AA01 BA01 BB02 DA01 DA05                       EA02 EA03 EC25 EC43 EC47                       EC48 JA27                 5D789 AA01 BA01 BB02 DA01 DA05                       EA02 EA03 EC25 EC43 EC47                       EC48 JA27

Claims (5)

[Claims] 1. An information recording layer on which information is recorded by utilizing holography and at the same time a light for recording or reproducing information is irradiated from one surface side, and an information recording layer arranged on the other surface side of this information recording layer. An optical information recording device for recording information on a recording medium having a reflective surface, the optical information recording device having a spatial light modulator, the information light carrying information using the spatial light modulator. And an information light generating unit for generating a recording reference light, and information is recorded on the information recording layer by an interference pattern due to interference between the information light and the recording reference light. A recording optical system for irradiating the information recording layer with the information light generated by the information light generating means and the recording reference light generated by the recording reference light generating means, wherein the recording optical system is The passing light is cut off A two-divided optical rotation plate that rotates in different directions in each of the two divided regions, the two-divided optical rotation plate being arranged at a position conjugate with the position where the spatial light modulator is arranged, and the recording optical system. Means a recording reference light having a predetermined first polarization direction and information light having a second polarization direction different from the first polarization direction, which are rotated by the two-divided optical rotation plate, respectively, Of the information light before being incident on the reflection reference surface and the recording reference light after being reflected on the reflection surface are aligned with each other, and the recording reference light before entering the reflection surface and the information light after being reflected on the reflection surface. In order to match the polarization directions, for each of the information light and the recording reference light, the polarization direction is different for each of the regions, the recording optical system further, the information light and the recording reference light, the information The recording layer is illuminated so as to be coaxial and converge from the one surface side. The interference pattern due to the interference between the information light before it is incident on the reflecting surface and the recording reference light after it is reflected on the reflecting surface, and the recording reference light before it is incident on the reflecting surface and it is reflected by the reflecting surface. An optical information recording device, characterized in that information is recorded on the information recording layer by an interference pattern due to interference with the information light after being irradiated. 2. The recording reference light generation means has a phase spatial light modulator, and the phase spatial light modulator is arranged at a position conjugate with a position where the two-divided optical rotation plate is arranged, 2. The optical information recording apparatus according to claim 1, wherein the reference light generating unit generates the recording reference light whose phase is spatially modulated by using the phase spatial light modulator. 3. An information recording layer on which information is recorded by utilizing holography and at the same time a light for recording or reproducing information is irradiated from one surface side, and an information recording layer arranged on the other surface side of this information recording layer. An optical information recording / reproducing apparatus for recording information on a recording medium having a reflection surface and reproducing the information from the recording medium, the spatial information modulator having a spatial light modulator. An information light generating means for generating information light carrying information, a recording reference light generating means for generating a recording reference light, a reproducing reference light generating means for generating a reproducing reference light, and At the time of recording, the information light generated by the information light generation means and the recording reference light generation means such that information is recorded on the information recording layer by the interference pattern due to the interference between the information light and the recording reference light. Generated by With a recording reference beam is irradiated on the information recording layer, at the time of reproduction of information is irradiated with reference light for reproduction generated by the reproduction reference light generation means with respect to said information recording layer,
A recording / reproducing optical system that collects reproducing light generated from the information recording layer when the reproducing reference light is irradiated; and a detection unit that detects the reproducing light collected by the recording / reproducing optical system, The recording / reproducing optical system has a two-part optical rotation plate that rotates the passing light in different directions for each region obtained by dividing the cross section of the light flux into two parts. The two-part optical rotation plate is provided with the spatial light modulator. The recording / reproducing optical system is arranged at a position conjugate with a predetermined position when recording information.
The recording reference light having the polarization direction of 2 and the information light having the second polarization direction different from the first polarization direction, respectively.
The information light before being incident on the reflecting surface and the recording reference light after being reflected by the reflecting surface have the same polarization direction after being rotated by the split optical rotator and reflected by the recording reference light before entering the reflecting surface. So that the polarization directions of the information light after being reflected by the surface match.
With respect to each of the information light and the recording reference light, the polarization direction is made different for each of the areas, and the recording / reproducing optical system further adds the information light and the recording reference light to the information recording layer when recording information. Irradiating so as to be coaxial and convergent from the one surface side, an interference pattern due to interference between the information light before entering the reflecting surface and the recording reference light after being reflected by the reflecting surface, and Information is recorded on the information recording layer by an interference pattern due to the interference of the reference light for recording before entering the reflecting surface and the information light after being reflected on the reflecting surface, and the recording / reproducing optical system, at the time of reproducing the information. , The reproduction reference light having the first polarization direction is rotated by the two-divided optical rotation plate to be converted into reproduction reference light having a different polarization direction for each region, and the reproduction reference light is used for the recording. To converge like the reference beam While irradiating the information recording layer, the reproduction light and the return light of the reproduction reference light reflected by the reflection surface are rotated by the two-divided optical rotator so that the entire cross section of the light beam has the first polarization direction. The reproduction light and the return light having a second polarization direction different from the first polarization direction in the entire cross section of the reproduction light are converted into the reproduction light and the recording / reproduction optical system further reproduces the reference light for reproduction. An optical information recording / reproducing apparatus, wherein the reproduction reference light is irradiated and the reproduction light is collected from the one surface side so that the reproduction light is coaxially arranged. 4. The recording reference light generation means and the reproduction reference light generation means have a common phase spatial light modulator, and the phase spatial light modulator has a position where the two-split optical polarization plate is arranged. The recording reference light generation unit is arranged at a conjugate position, the recording reference light generation unit uses the phase spatial light modulator to generate recording reference light whose phase is spatially modulated, and the reproduction reference light generation unit is 4. The optical information recording / reproducing apparatus according to claim 3, wherein the phase spatial light modulator is used to generate a reproduction reference light whose phase is spatially modulated. 5. The recording / reproducing optical system further separates the reproduction light after passing through the two-divided optical rotation plate and the return light after passing through the two-divided optical rotation plate, depending on the difference in polarization direction. The optical information recording / reproducing apparatus according to claim 3, further comprising a polarized light separating means.