JP2002269789A - Optical disk drive - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce the cost of an optical system by using a configuration capable of tilt detection without using a light source dedicated to tilt detection,
An optical disk drive device that can be easily miniaturized is realized. SOLUTION: Between a laser light source 1 and an objective lens 5,
An optical disc having a beam splitter 3 that transmits light from the laser light source 1 and guides it to the objective lens 5 and reflects light reflected by the optical disk 6 and returned through the objective lens 5 and guides the light to the light receiving element 9 for signal detection. In the drive device, a part of the light traveling from the laser light source 1 toward the objective lens 5 is reflected by the beam splitter 3 and irradiates the optical disk 6, and the reflected light is incident on a plurality of divided light receiving elements 10 for tilt detection. The relative inclination between the recording surface of the optical disk 6 and the objective lens 5 is detected based on the output signals of the plurality of light detecting elements 10 for tilt detection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for correcting a relative inclination between a recording surface of an optical disc and an objective lens in an optical disc drive for recording, reproducing, or erasing information on an optical disc such as a CD or DVD. .

[0002]

2. Description of the Related Art FIG. 8 shows a configuration example of a conventional optical disk drive. In the figure, reference numeral 6 denotes an optical disk, and 1 denotes a semiconductor laser. Light emitted from the semiconductor laser 1 in parallel to the optical disk 6 is converted into parallel light by the coupling lens 2, passes through the beam splitter 3, and is reflected at right angles to the optical disk 6 by the reflection mirror 4. The light is condensed as a minute spot on the recording surface of the optical disk 6 by the objective lens 5. This light is used for reproducing, recording, or erasing information. The light reflected back from the optical disk 6 is returned to parallel light again by the objective lens 5, reflected by the reflection mirror 4 and returned to the beam splitter 3. The returned light is condensed by the beam splitter 3 into the condenser lens 7.
After being reflected to the side and condensed by the condenser lens 7 and given astigmatism by the cylindrical lens 8, the light enters the signal detection light-receiving element 9. From the output of the signal detection light receiving element 9,
An information signal, a focus error signal, and a track error signal are detected. In general, in an optical disk drive of this type, when the capacity of the optical disk is increased, the numerical aperture (N
A) must be increased. That is, the relationship between the spot diameter of the laser beam irradiated on the optical disc and the NA is expressed by the following equation (1). Spot diameter (φ) = K · (λ / NA) (1) where K is a constant and λ is the wavelength of the laser beam. This equation (1) indicates that it is necessary to reduce the wavelength λ or increase the NA to reduce the spot diameter. However, when the NA of the objective lens increases, the degree of coma aberration increases in proportion to the cube of the NA due to the relative inclination of the optical disk and the optical pickup, and a good spot cannot be obtained. That is, N of the objective lens
The relationship between A and coma is represented by the following equation (2). Coma Aberration ∝ (NA) ³ ... (2) Also, since the optical disk is inevitably warped, there is a difference in the amount of warping between the inner and outer circumferences of a single optical disk. There are also individual differences. Therefore, in the conventional optical disk drive, the tilt sensor 13 is attached to the optical pickup, and the relative tilt (tilt) between the optical disk 6 and the optical pickup is determined based on the output of the tilt sensor 13.
Is detected and the correction is performed.

[0003]

However, since the tilt sensor 13 has a light source (LED) and a light receiving element, the conventional optical disk drive is used for reproducing, recording, or erasing information on the optical disk. In addition to the light source, that is, the semiconductor laser, a configuration is provided that includes a light source dedicated to tilt detection. Further, since the tilt sensor 13 is configured by enclosing a light source and a light receiving element in a package, the parts themselves are large. Therefore, the provision of the tilt sensor 13 has a problem that the optical system of the optical disk drive becomes expensive and large. SUMMARY OF THE INVENTION An object of the present invention has been made in view of the above circumstances. An optical disc drive device which is easy to reduce the cost and size of an optical system by adopting a configuration capable of tilt detection without using a light source dedicated to tilt detection. It is to realize. Furthermore, by adopting a configuration capable of detecting the amount of laser light simultaneously with tilt detection, an optical disk drive device with a smaller optical system is realized. Further, the size of the apparatus can be further reduced by integrating the light receiving element for detecting the tilt and the light receiving element for detecting the amount of laser light.

[0004]

According to a first aspect of the present invention, there is provided an information processing apparatus for recording, reproducing, or erasing information by condensing light from a laser light source on an optical disk with an objective lens. An optical disc drive device for performing, between the laser light source and the objective lens, light transmitted from the laser light source and guided to the objective lens, and light reflected from the optical disc and returned through the objective lens. An optical disk drive device provided with a beam splitter that reflects light from the light source to the light receiving element for signal detection, and irradiates the optical disk by reflecting a part of light from the light source toward the objective lens with the beam splitter. The light is incident on a plurality of divided light receiving elements for tilt detection, and the light is output by the plurality of tilt detecting light receiving elements. Wherein the recording surface of the disk and configured the to detect a relative inclination between the objective lens. According to a second aspect of the present invention, in the optical disk drive device of the first aspect, an angle θ between a normal to an end surface of the beam splitter facing the optical disk and an optical axis of the objective lens is 0 ° <θ <. It is characterized by 90 °. According to a third aspect of the present invention, in the optical disk drive device according to the first aspect, the angle between the optical axis of the objective lens and the optical axis of the reflected light reflected toward the optical disk by the beam splitter is set to 0. ° <θ <
It is characterized by 90 °. According to a fourth aspect of the present invention, in the optical disk drive device according to any one of the first to third aspects, a part of the light reflected toward the optical disk by the beam splitter is a light receiving element for detecting a laser output. And a laser output of the laser light source is detected based on an output signal of the light-receiving element for detecting a laser output. According to a fifth aspect of the present invention, in the optical disk drive device according to any one of the first to fourth aspects, the light receiving element for detecting the tilt and the light receiving element for detecting the laser output are arranged close to or integrally with each other. It is characterized by having been provided. According to a sixth aspect of the present invention, in the optical disk drive of the fifth aspect, the light receiving element for detecting the tilt and the light receiving element for detecting the laser output are sealed in one package. .

[Detailed Description of the Invention] Hereinafter, embodiments of the present invention will be described. FIG. 1 is a schematic configuration diagram showing an example of an embodiment of an optical disk drive device according to the present invention. The light emitted from the semiconductor laser 1 is converted into substantially parallel light by the coupling lens 2 and then passes through the beam splitter 3.
The light is reflected at right angles to the optical disk 6 by the reflection mirror 4, and is collected as a minute spot on the recording surface of the optical disk 6 by the objective lens 5. This light is used for reproducing, recording, or erasing information. The light reflected back by the optical disk 6 is returned to the parallel light again by the objective lens 5, reflected by the reflection mirror 4 and returned to the beam splitter 3. The returned light is reflected by the beam splitter 3 toward the condenser lens 7, condensed by the condenser lens 7, given astigmatism by the cylindrical lens 8, and then enters the signal detection light-receiving element 9. . An information signal, a focus error signal, and a track error signal are detected from the output of the light detecting element 9 for signal detection.

On the other hand, a part of the light emitted from the semiconductor laser 1 is reflected by the beam splitter 3 and is incident on the optical disk 6, and the reflected light is incident on the light receiving element 10 for tilt detection. When the relative tilt between the optical disc 9 and the optical system changes, the position of light incident on the light receiving element 10 for tilt detection changes. The light receiving element 10 for tilt detection is divided into two as shown in FIG. 2, for example, and the amount of tilt can be detected by the differential output. In FIG. 2, the solid line indicates the position where light is incident on the light receiving element 10 for tilt detection when the tilt is not generated, and the dotted line indicates the position where the tilt is generated. By tilting the entire optical system with respect to the optical disk 6 in accordance with the detected amount of tilt, tilt can be reduced, coma of spots on the disk surface can be suppressed, and good reproduction, recording, or erasing can be performed. Become like (Corresponding to claim 1)

[0007] The tilt detection area is desirably in the vicinity of the objective lens 5. Therefore, as shown in FIG. 3, the end surface of the beam splitter 3 on the optical disk 6 side is inclined by cutting it obliquely, so that the light is refracted from the beam splitter 3 and exits, and enters near the objective lens 5. So that By setting the angle θ between the normal 3-1 of the end surface of the beam splitter 3 on the optical disk 6 side and the optical axis 5-1 of the objective lens 5 to be 0 ° <θ <90 °, the beam splitter 3 Can reach the vicinity of the objective lens 5. Instead of tilting the end face of the beam splitter 3 on the optical disk 6 side, as shown in FIG. 4, the beam axis of the reflected light reflected by the reflecting surface of the beam splitter 3 and the objective lens 5 The refracted light from the beam splitter 3 can also reach the vicinity of the objective lens 5 by making the angle θ ′ with the optical axis 5-1 0 ° <θ ′ <90 °. (Corresponding to claim 3)

As shown in FIG. 5, a part of light emitted from the end face of the beam splitter 3 on the optical disk 6 side is used for tilt detection, and a part of the light is incident on a light receiving element 11 for laser output detection. The laser output of the semiconductor laser 1 may be controlled according to the output of the light receiving element 11. With this configuration, the beam splitter 3
The reflected light from the light source can be used effectively, and the light receiving element 10 for detecting the tilt and the light receiving element 11 for detecting the laser output can be arranged close to each other. Turning is easy. As shown in FIG. 6, by integrating the light receiving element 10 for detecting tilt and the light receiving element 11 for detecting laser output as shown in FIG. 6, further downsizing of the apparatus and crawling of signal lines are achieved. Turning is easy. 10-1 and 11-1 in the figure are light receiving surfaces of the respective light receiving elements. As shown in FIG. 7, a light receiving element 10 for detecting a tilt and a light receiving element 11 for detecting a laser output are sealed in the same package to constitute one light receiving element 12. This makes it easier to reduce the size of the device. (Corresponding to claim 6)

[0009]

As described above, according to the present invention,
Since an apparatus configuration capable of tilt detection without using a light source dedicated to tilt detection is employed, it is possible to realize an optical disk drive apparatus in which the cost and size of the optical system can be easily reduced. Further, since the beam splitter is configured so that the light for tilt detection is incident on the optical disk surface near the objective lens, it is possible to detect the tilt near the objective lens which causes spot coma aberration. Further, by adopting a configuration in which the laser light amount can be detected simultaneously with the tilt detection, it is possible to realize an optical disk drive device with a smaller optical system. In addition, since a part of the light separated for tilt detection is used for laser output detection, tilt detection and laser output detection can be performed by effectively using light from a laser light source. Further, by arranging the light receiving element for tilt detection and the light receiving element for laser output detection close to each other or integrally with each other, the size of the apparatus can be further reduced. By enclosing the light receiving element for tilt detection and the light receiving element for laser output detection in one package, it is possible to further reduce the size, thickness, and cost of the device.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of an embodiment of an optical disk drive device according to the present invention.

FIG. 2 is an explanatory diagram of a structure of a light receiving element for tilt detection and a principle of tilt detection.

FIG. 3 is an explanatory diagram of an angle θ between a normal to an end surface of an optical disk side of a beam splitter and an optical axis of an objective lens.

FIG. 4 is an explanatory diagram of an angle θ ′ between a ray axis of reflected light reflected by a reflection surface of a beam splitter and an optical axis of an objective lens.

FIG. 5 is a schematic configuration diagram showing another example of the embodiment of the optical disk drive device according to the present invention.

FIG. 6 is a schematic configuration diagram showing an example in which a light receiving element for detecting tilt and a light receiving element for detecting laser output are integrated.

FIG. 7 is a schematic configuration diagram showing an example in which a light receiving element for tilt detection and a light receiving element for laser output detection are sealed in the same package and configured as one light receiving element.

FIG. 8 is a schematic configuration diagram showing an example of a conventional optical disk drive device.

[Explanation of symbols]

 1: Semiconductor laser (laser light source) 2: Coupling lens 3: Beam splitter 4: Reflection mirror 5: Objective lens 6: Optical disk 7: Condensing lens 8: Cylindrical lens 9: Light detecting element for signal detection 10: Tilt detection Photodetector 11: Photodetector for detecting laser output

Claims (6)

[Claims] 1. An optical disk drive device for recording, reproducing, or erasing information by condensing light from a laser light source on an optical disk with an objective lens, wherein an optical system is provided between the laser light source and the objective lens. An optical disc drive device including a beam splitter that transmits light from the laser light source and guides the light to the objective lens, and reflects light reflected by the optical disk and returned through the objective lens to guide the light to a light receiving element for signal detection. In, a part of the light traveling from the light source toward the objective lens is reflected by the beam splitter and irradiated on the optical disc,
The reflected light is made incident on a plurality of divided light receiving elements for tilt detection, and the relative tilt between the recording surface of the optical disc and the objective lens is detected based on output signals of the plurality of light receiving elements for tilt detection. An optical disk drive device characterized in that it is configured as described above. 2. An angle θ between a normal line of an end face of the beam splitter facing the optical disk and an optical axis of the objective lens is set to 0 ° <θ <90 °.
An optical disk drive device according to any one of the preceding claims. 3. An angle between a light axis of reflected light reflected toward the optical disk by the beam splitter and an optical axis of the objective lens is 0 ° <θ <90 °. 2. The optical disk drive device according to 1. 4. A part of the light reflected toward the optical disk by the beam splitter is made incident on a light-receiving element for detecting a laser output, and a laser of the laser light source is output based on an output signal of the light-receiving element for detecting the laser output. 4. The optical disk drive device according to claim 1, wherein an output is detected. 5. The optical disk drive device according to claim 1, wherein the light receiving element for detecting the tilt and the light receiving element for detecting the laser output are provided close to or integrally with each other. . 6. The optical disk drive according to claim 5, wherein the light receiving element for detecting the tilt and the light receiving element for detecting the laser output are enclosed in one package.