JPH0850731A - Optical disk drive - Google Patents

Abstract

(57) [Summary] [Object] To detect the tilt of an optical disk with respect to the optical head by using the beam of the optical head, simplify the structure of the disk tilt detector, and improve the detection sensitivity. [Structure] A light beam 10 is directed toward a medium surface 6 of an optical disk.
Is irradiated. At this time, the light beam 10 is incident on the tilt beam detecting means 12 via the collimator lens 9 and the beam splitter 3. At this time, the first-order diffracted light is defocused to form the tilt detection light beam 1, and this light is made incident on the medium surface 6. Next, this reflected light is bent by the beam splitter 3 and is incident on the detection unit 8 including the reproduction signal detection unit 13. If the optical disc 5 has a tilt, the tilt detector 8
A signal is obtained from a and gives a control signal to the actuator 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device for detecting the inclination of a disk surface when optically recording or reproducing information.

[0002]

2. Description of the Related Art In an optical disk device, the optical axis of an objective lens of an optical head is set to be perpendicular to the optical disk. However, when the disk surface is tilted due to deformation of the optical disk, so-called disk tilt, the perpendicularity of the optical head to the recording surface of the optical disk is lost, and the objective lens cannot exert its original performance. In this case, the crosstalk of the reproduced signal is increased and the reading performance is deteriorated. Therefore, in order to prevent such a phenomenon, some optical disc devices detect the disc tilt and perform vertical adjustment by tilting the optical head based on the detection signal.

A conventional optical disc device having a disc tilt detecting function will be described with reference to FIG. As shown in FIG. 11A, the optical disk device is provided with a disk drive means 15, on which the optical disk 5 is placed or clamped. An optical head 40 is provided so as to be movable in the radial direction of the optical disc 5 in order to record or reproduce information on the track of the optical disc 5, and the optical head 40 is driven by an optical head drive means (not shown).

The optical head 40 is provided with a collimator lens 9 for collecting the light beam from the semi-moving body laser and an objective lens 4 for focusing the light beam on the medium surface 6 of the optical disk 5. . Further, these lenses have a function of condensing the reflected light and guiding the reflected light to the detector when reproducing the information recorded on the medium surface 6.

As shown in FIG. 11A, the optical head 40
Is provided with a tilt detector 41 for detecting a disc tilt. The conventional tilt detector 41 includes a light emitter 42
The light beam 43 output from the optical disc 5 is reflected by the lower surface of the optical disc 5 and is received by the light receiver 44. When the disc tilt occurs, the traveling direction of the light beam 43 after being reflected by the optical disc 5 changes, so that the light receiving member 44
The irradiation position of changes. FIG. 11B is a plan view of the optical head 40. As shown in this figure, the light receiving body 44 has divided light receiving portions 45 and 46, and if there is a disc tilt, the light receiving amounts of the light receiving portions 45 and 46 are different from each other. Processing tilt information.

[0006]

This method is used in the optical head 4
Since the slight inclination of the optical disk 5 with respect to the optical axis of 0 is detected by the slight displacement of the light beam 43, the detection accuracy cannot be improved. There is also a drawback that an optical system including the light emitting body 42 and the light receiving body 44 must be separately provided in order to detect the disc tilt. As described above, in the optical disk device, the tilt of the disk is the main factor of signal deterioration, and it is important to suppress it as much as possible.

The present invention has been made in view of such conventional problems, and detects the relative tilt between the optical head and the optical disk with high accuracy and controls the attitude of the optical head. It is an object of the present invention to provide an optical disc device capable of stably recording or reproducing information.

[0008]

According to the invention of claim 1 of the present application, a laser light source for outputting a coherent light beam, a disk drive means for rotationally driving an optical disk, and a light beam for recording and reproducing information. And an optical head including an objective lens for focusing the light on an optical disc, wherein a part of a light beam of a laser light source is used as a tilt detection light beam and an objective is applied to a medium surface of the optical disc rotated by the disc driving means. Tilt beam forming means for converting into a defocused state via a lens, reproduction signal detecting means for receiving reflected light from the optical disc and detecting information recorded on the medium surface, and tilt reflected by the optical disc. Tilt detecting means for receiving the detected light beam and detecting the disc tilt of the optical disc from the change in the light receiving angle, It is characterized in that it comprises.

According to a second aspect of the present invention, there is provided a laser light source for outputting a coherent light beam, a disk drive means for rotationally driving the optical disk, and an objective for focusing the light beam on the optical disk for recording and reproducing information. An optical disk device having an optical head including a lens, wherein a reproduction signal detecting means for receiving reflected light from the optical disk and detecting information recorded on the medium surface, and a reflection signal reflected on the surface of the optical disk. Tilt detection means for receiving light as a tilt detection light beam and detecting the disc tilt of the optical disk from changes in the light reception angle.

According to the invention of claim 3 of the present application, a laser light source for outputting a coherent light beam, a disk drive means for rotationally driving the optical disk, and an objective for focusing the light beam on the optical disk for recording and reproducing information. An optical disk device having an optical head including a lens, wherein a part of a light beam of a laser light source is used as a tilt detection light beam, and a focus shift occurs via an objective lens with respect to a medium surface of an optical disk rotated by a disk drive means. Tilt beam forming means for converting a part of the light beam of the laser light source in a direction different from the incident direction, and the reflected light from the optical disc to receive the information recorded on the medium surface. The reproduction signal detecting means for detecting and the tilt detection light beam reflected by the optical disk are received, and the light is detected from the change in the light receiving angle. A tilt detecting means for detecting the disc tilt of the disc; and a lens tilt detecting means for receiving the reflected light by the tilt beam forming means and detecting the tilt of the objective lens from the change of the light receiving position. It is a thing.

According to a fourth aspect of the present invention, there is provided a laser light source for outputting a coherent light beam, a disk drive means for rotationally driving the optical disk, and an objective for focusing the light beam on the optical disk for recording and reproducing information. An optical disk device having an optical head including a lens, wherein a part of a light beam of a laser light source is used as a tilt detection light beam, and a focus shift occurs via an objective lens with respect to a medium surface of an optical disk rotated by a disk drive means. Tilt beam forming means for converting the state to the above state, reproduction signal detecting means for receiving the reflected light from the optical disk and detecting the information recorded on the medium surface, and the optical axis of the tilt detecting light beam reflected by the optical disk. Is deflected to a position different from the focusing position of the light by the reproduction signal detecting means, and is deflected by the image forming correction means. It was by receiving the tilt detection light beam, the change of the light receiving angle, and is characterized in that it comprises a tilt detection means for detecting disc tilt of the optical disk, the.

According to a fifth aspect of the present invention, there is provided a laser light source for outputting a coherent light beam, a disk drive means for rotationally driving the optical disk, and an objective for focusing the light beam on the optical disk for recording and reproducing information. An optical disk device having an optical head including a lens, wherein a part of a light beam of a laser light source is used as a tilt detection light beam, and a focus shift occurs via an objective lens with respect to a medium surface of an optical disk rotated by a disk drive means. Tilt beam forming means for converting to a state, reproduction signal detecting means for receiving the reflected light from the optical disk and detecting the information recorded on the medium surface, and receiving the tilt detecting light beam reflected by the optical disk. Then, a reflection means for reflecting this optical axis to a position different from the reproduction signal detection means, and a tilt detection reflected by the reflection means Receiving the beam from the change of the light receiving angle, and is characterized in that it comprises a tilt detection means for detecting disc tilt of the optical disk, the.

[0013]

According to the invention of claim 1 of the present application having such a feature, the tilt beam forming means uses a part of the light beam of the laser light source as the tilt detection light beam to defocus the state through the objective lens. And is incident on the medium surface of the optical disc. If the optical disc has a disc tilt, the tilt detection light beam reflected by the medium surface is incident on the tilt detection means, and the disc tilt of the optical disc is detected from the change in the light receiving angle. On the other hand, the information recorded on the medium surface is detected from the main beam by the reproduction signal detecting means.

According to the invention of claim 2 of the present application, a part of the light beam of the laser light source is incident on the surface of the optical disc in a defocused state via the objective lens. The tilt detecting means receives the reflected light on the surface of the optical disc as a tilt detection beam, and detects the disc tilt of the optical disc from the change in the light receiving angle. On the other hand, the information recorded on the medium surface is detected from the main beam by the reproduction signal detecting means.

Further, according to the invention of claim 3 of the present application, the tilt beam forming means converts a part of the light beam of the laser light source as a tilt detection light beam into a defocused state through the objective lens, and the optical disc. Incident on the medium surface of. If there is a disc tilt of the optical disc rotated by the disc drive means, the tilt detection light beam reflected on the medium surface is incident on the tilt detection means formed on the same substrate as the reproduction signal detection means, and the optical disc changes from the change of the light receiving angle. Disc tilt is detected. Further, a reflecting surface is provided integrally with the tilt beam forming means so that a part of the light beam of the laser light source is reflected in a direction different from the incident direction. Therefore, if the optical axis of the objective lens is tilted, the lens tilt detection means can detect the tilt. Therefore, the optical axis of the optical head can be corrected according to the disc tilt.

According to the invention of claim 4 of the present application, the tilt beam forming means converts a part of the light beam of the laser light source as a tilt detection light beam into an out-of-focus state via the objective lens, and the optical disc. Incident on the medium surface of. If the optical disc has a disc tilt, the tilt detection light beam reflected by the medium surface is deflected by the image formation correction means to a position different from that of the signal detection means. This tilt detection light beam is incident on the tilt detection means formed on the same substrate at a position separated from the reproduction signal detection means, and the disk tilt of the optical disk is detected from the change in the light receiving angle.

Further, according to the invention of claim 5 of the present application, the tilt beam forming means converts a part of the light beam of the laser light source as a tilt detection light beam into a defocused state through the objective lens, and the optical disc. Incident on the medium surface of. If there is a disc tilt of the optical disc rotated by the disc drive means, the tilt detection light beam reflected by the medium surface is reflected by the reflection means to a position different from the signal detection means. This tilt detection light beam is made incident on the tilt detection means at a position different from the reproduction signal detection means, and the disk tilt of the optical disk is detected from the change in the light receiving angle.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the optical disk device of the present invention, a tilt detection light beam of an optical disk is irradiated substantially coaxially in addition to a reproduction light beam (main beam) by using the same light source to detect the disk tilt. ing. Specifically, when the light beam is focused on the optical disk 5, the tilt detection light beam is focused on a position which is an outer peripheral portion of the optical axis of the reproduction (including recording) light beam. By doing so, the tilt detection light beam irradiates the medium surface of the optical disc 5 in a defocused state, and the reflected return light of the optical disc 5 moves in a direction orthogonal to the optical axis of the main beam according to the disc tilt. . The present invention utilizes this movement of the reflected return light to detect the disc tilt.

FIG. 1 is an explanatory diagram showing the principle of disc tilt detection in the optical disc apparatus of each embodiment of the present invention. As shown in FIG. 1A, the tilt detection light beam 1 narrowed down by the objective lens 4 first irradiates the medium surface 6 of the optical disc 5 in a defocused state. After the tilt detection light beam 1 is reflected by the medium surface 6, it reaches the tilt detector 8a via the objective lens 4 and the detection lens 7. here,
When the optical disc 5 has a disc tilt, the equivalent light emitting point A on the optical disc side shown in the figure can be located at a position displaced from the optical axis B of the optical head. Therefore, the center line C of the tilt detection light beam 1 on the tilt detector 8a is also displaced from the optical axis B.

As shown in FIG. 1B, the tilt detector 8
a is composed of four photodetector elements d1 to d4. If the center line C of the tilt detection light beam 1 is biased toward the photodetection elements d2 and d3 as shown in the figure, there will be a difference in output between the photodetection elements d2 and d3 and the photodetection elements d1 and d4. By detecting the difference in the amount of received light, the position of the tilt detection light beam 1 can be known, and the disc tilt amount can be known from this. Here, the smaller the beam diameter of the tilt detection light beam 1 on the tilt detector 8a, the larger the difference in the amount of light received by each photodetection element of the tilt detector 8a. As described above, the tilt detection sensitivity can be freely set to high sensitivity depending on the size of the beam diameter of the tilt detection light beam 1. When the tilt detection light beam 1 is focused on the medium surface 6, the equivalent light emitting point A on the disc side does not laterally shift even if the disc tilt occurs. Therefore, it is necessary to irradiate the medium surface 6 with the light beam in a defocused state.

Next, an optical disk device according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a partial cross-sectional view showing the configuration of the main part of the optical disc device of the first embodiment. FIG. 3 is a plan view showing the structure of the detector 8 which receives the tilt detection light beam and the main beam. The light beam 10 emitted from the semiconductor laser 2 is collimator lens 9
Then, it becomes parallel light, is transmitted through the beam splitter 3, and is incident on the tilt beam forming means 12 composed of a hologram plate. The tilt beam forming means 12 is formed by forming a large number of concentric diffraction gratings on a transparent substrate, for example.
It is called a zone plate.

When the light beam 10 passes through the tilt beam forming means 12, the tilt detection light beam 1 which is the first-order diffracted light shown by the broken line is output in addition to the main beam 11 which is the 0th-order light of the zone plate. . In this case, as shown in FIG. 3, the tilt detection light beam 1 is incident on the detection unit 8 substantially coaxially with the main beam 11, and the incident region is a circular range including the main beam 11.

As shown in FIG. 1, the tilt detection light beam 1 is narrowed down by the objective lens 4 toward the medium surface 6 of the optical disk 5. The optical disk 5 is fixed to the disk drive means 15 and rotates like the conventional example. Main beam 11 and tilt detection light beam 1 reflected by the optical disk 5
Is again collimated by the objective lens 4, enters the beam splitter 3, and is reflected to the detection lens 7 side. The reflected light from the medium surface 6 which is the 0th order diffracted light is focused by the detection lens 7 and is incident on the reproduction signal detection unit 13 shown in FIG. The output of the reproduction signal detector 13 is applied to a focus and tracking control circuit (not shown) and processed as a reproduction signal.

On the other hand, the tilt detection light beam 1 is incident on the light detection elements 14a to 14d of the detection unit 8 of FIG. As shown in the figure, the tilt detection light beam 1 is emitted from the reproduction signal detection unit 1
The light is incident on a part of the photo-detecting elements 14a to 14d which are tilt detectors 8a arranged around No. 3. Then, when there is a disc tilt, the tilt detection light beam 1 moves on the light receiving surface. The tilt error signal is obtained by the output difference between the photodetectors 14c and 14d for the movement in the x direction and the output difference between the photodetectors 14a and 14b for the movement in the y direction.

Next, an optical disk device according to the second embodiment of the present invention will be described. FIG. 4A is an explanatory diagram showing the operating principle of the optical disc device of the second embodiment, and FIG. 4B is an explanatory diagram showing the configuration of the detection unit 8. Semiconductor laser 2
Since the structure of the optical system including is the same as that of the first embodiment, the description is omitted.

Although the tilt beam 1 is formed from the entire region of the light beam 10 in the above-described first embodiment, a part of the light beam 10 is formed as shown in FIG. 4A as the optical disk device of the second embodiment. Then, the tilt detection light beam 1 is formed. In the tilt beam forming means 12 of FIG. 4, the outside of the light beam 10 is used as the tilt detection beam 1 and the inside thereof is used as the main beam 11. At this time, as the tilt beam forming means 12,
A spherical or aspherical lens can be used in addition to the hologram plate.

When using a hologram plate, the main beam 11
It is desirable that the beam is formed from 0th-order light and the tilt light detection beam 1 is formed from 1st-order diffracted light. When a spherical or aspherical lens is used for the tilt beam detection means 12, the surface shapes of the main beam 11 and the tilt detection light beam 1 are changed. In this case, the tilt detection light beam 1 on the detection unit 8
Has a ring shape as shown in FIG. Therefore, since the tilt detection light beam 1 does not enter the signal reproduction detection unit 13, there is an advantage that the reproduction signal is not affected by the tilt detection light beam 1. Although the tilt beam forming means 12 is inserted between the objective lens 4 and the beam splitter 3 here, the collimator lens 9 and the beam splitter 3 are included.
The same effect can be obtained by putting it in between.

In the case of the distribution of the tilt detection light beam 1 and the main beam 11 as shown in FIG. 4, the light receiving state at the detector 8 becomes a ring shape as shown in FIG. 4 (b). In this case, since the tilt detection light beam 1 does not enter the reproduction signal detector 13, the tilt detection light beam 1 does not affect the reproduction signal.

Next, an optical disk device which achieves the same effect without using the tilt beam forming means 12 will be described as a third embodiment with reference to the drawings. FIG. 5 is a cross-sectional view showing the configuration of the optical disk device of the third embodiment. The same parts as those in the first embodiment are designated by the same reference numerals, and their description will be omitted.
In the figure, the light beam 10 emitted from the semiconductor laser 2 is collimated by the collimator lens 9 and transmitted through the beam splitter 3. Then, this light beam 10 is reflected by the objective lens 4
Then, it is narrowed down to the medium surface 6 of the disk 5. Next, the main beam 11 reflected by the medium surface 6 follows the same optical path as in the first embodiment, and the detection unit 8 including the reproduction signal detection unit 13
Is input to Then, the reproduction signal detector 13 obtains a control signal and a reproduction signal for the optical head.

In this embodiment, the reflected light of the main beam 11 on the disk surface 5a as shown by the broken line in FIG. 5 is used as the tilt detection light beam 1. Since the light beam 10 irradiating the disk surface 5a is incident in a defocused state, the same effect as the tilt beam forming means 12 of the first embodiment is produced. The optical path of the tilt detection light beam 1 and the tilt error detection method are the same as in the first embodiment. In this case, it is not necessary to separately provide the tilt beam forming means 12, so that the optical disk device has a simple structure.

Next, a method of further increasing the disc tilt detection sensitivity in the optical disc apparatus of the third embodiment will be described. As shown in FIG. 6, the image forming correction means 30 is provided in front of the detection lens 7. The image forming correction means 30 acts on the tilt detection light beam 1 located on the outer peripheral side of the main beam 11 and has a function of changing the image forming position. The image forming correction means 30 can be composed of a ring-shaped lens and a prism or hologram. By this image forming correction means 30,
The beam diameter of the tilt detection light beam 1 on the tilt detector 32 provided in the detection unit 31 can be changed. Therefore, by appropriately reducing the beam diameter of the tilt detection light beam 1, the disc tilt detection sensitivity can be increased.

FIG. 7 is a plan view showing an example of the structure of the detecting section 31 at this time. As shown in the figure, the detector 31 is provided with a photodetector element divided into four as the tilt detector 32, and the tilt detection spot 34 is made incident on this portion.
Further, as shown in FIG. 7, a reproduction signal detection unit 33 is provided in the other portion of the tilt detector 32, and the main beam is made incident on the photodetection element divided into four. In this case, the lateral movement amount of the tilt detection spot 34 does not change with respect to the disc tilt. Therefore, the smaller the beam diameter of the tilt detection spot 34 is,
The difference in the amount of light received by each of the four photodetector elements is increased, and the detection sensitivity can be increased. The installation position of the image forming correction means 30 is not limited to the light source side of the detection lens 7, and may be the detection unit 31 side.

Next, as another method for further increasing the disc tilt detection sensitivity, the optical disc apparatus of the fourth embodiment will be described. FIG. 8 is a cross-sectional view showing the structure of the optical disk device of the fourth embodiment. The same parts as those in the first and second embodiments are designated by the same reference numerals and their description will be omitted. As shown in the figure, the ring-shaped reflector 3 is provided in front of the reproduction signal detector 33.
5 is installed as a reflection means. The reflector 35 is the main beam 1
The part where 1 is incident is cut out, and the main beam 11
Is transmitted as it is, and only the tilt detection light beam 1 around the main beam 11 is reflected. On the other hand, the tilt detection beam 1 reflected on the outer peripheral portion of the reflection plate 35 is guided to the tilt detector 32 provided at a place different from the reproduction signal detection unit 33. The tilt detector 32 has a tilt detection spot 34.
Is arranged in a position such that is sufficiently small. Even in this case, the disc tilt can be detected with high sensitivity.

Next explained is an optical disk device according to the fifth embodiment in which the inclination of the objective lens 4 is simultaneously detected. As shown in FIG. 9, the objective lens 4 and the tilt beam forming means 12 are supported by a lens holder 19. This lens holder 19 is driven by an actuator 20 for focus and tracking control.
It is controlled to make a slight movement in the direction. At this time, the optical axis may be tilted due to nonuniformity of the driving force of the actuator 20. The influence of the tilt of the objective lens 4 on the reproduction signal is the same as in the case of the disc tilt described above. Therefore, it is important to prevent this.

The tilt beam forming means 12 of the fifth embodiment is attached at a slight inclination with respect to the optical axis of the lens holder 19. In this way, the reflected light 17 of the light beam 10 by the surface 16 of the tilt beam forming means 12 on the semiconductor laser 2 side is biased to the outer peripheral portion of either one of the main beams 11. Therefore, as shown in FIG. 10, if the lens tilt detector 18 is provided on one side of the substrate on the substrate of the detector 8 including the reproduction signal detector 13 and the tilt detector, the reflected light 17
The bias of can be detected.

When the objective lens 4 tilts, the tilt beam forming means 12 also tilts, and accordingly, the reflected light 17 moves on the lens tilt detecting section 18. As shown in FIG. 10, the tilt of the objective lens 4 can be detected by dividing the lens tilt detection unit 18 into four and detecting the difference in the amount of light received by each photodetector. This makes it possible to detect the tilt of the objective lens 4 only by adding the lens tilt detection unit 18 to the detection unit 8.

The disc tilt detection output and the lens tilt detection output obtained in this way are output to the difference circuit 21 shown in FIG.
And is converted into a control signal via the drive circuit 22. In order to prevent the influence of both the disc tilt and the tilt of the objective lens 4, the actuator 20 is controlled so that the difference between the disc tilt detection output and the objective lens tilt detection output is always zero. Here, the actuator 20,
The difference circuit 21 and the drive circuit 22 constitute a lens inclination correction means, and optimally control the attitudes of the optical disk 5 and the optical head 40. The lens tilt correction means can be realized by generating an asymmetric focus driving force of the actuator 20, or a drive coil for tilt correction may be newly provided. Also, a means for inclining the entire optical head 40 may be used.

[0038]

As described above, according to the present invention, the optical system for detecting the disc tilt can be used in common with most of the optical system for the main beam for recording / reproducing a signal on / from the medium surface of the optical disc. Therefore, the optical head can be downsized, and an optical disk device that accurately detects the tilt of the optical disk to record or reproduce information can be realized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an operation principle of an optical disk device according to each embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the configuration of the optical disk device in the first embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of a tilt detection beam in the optical disc device of the first embodiment.

FIG. 4 is a configuration diagram of a detection unit that receives a tilt detection beam in the optical disc device of the second embodiment.

FIG. 5 is a cross-sectional view showing a configuration of an optical disc device according to a third embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a configuration of an image forming correction means of an optical disc device in a third embodiment.

FIG. 7 is an explanatory diagram showing a configuration of a detection unit of an optical disc device in a third embodiment.

FIG. 8 is a sectional view showing a configuration of an optical disk device according to a fourth embodiment of the present invention.

FIG. 9 is a cross-sectional view showing the structure of the optical disc device in the fifth embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a configuration of a detection unit of an optical disc device according to a fifth embodiment.

FIG. 11 is a configuration diagram of a tilt detector in a conventional optical disc device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tilt detection light beam 2 Semiconductor laser 3 Beam splitter 4 Objective lens 5 Optical disk 5a Disk surface 6 Medium surface 7 Detection lens 8, 31 Detection part 8a Tilt detector 9 Collimator lens 10 Light beam 11 Main beam 12 Tilt beam forming means 13, 33 reproduction signal detection unit 14a to 14d, d1 to d1, 32 light detection element 15 disk drive unit 17 reflected light 18 lens tilt detection unit 19 lens holder 20 actuator 21 difference circuit 22 drive circuit 30 imaging correction unit 31, 32 tilt detection Instrument 34 Tilt detection spot 35 Reflector 40 Optical head

Claims (9)

[Claims] 1. A laser light source for outputting a coherent light beam, a disk drive means for rotationally driving an optical disk, and an optical head including an objective lens for focusing the light beam on the optical disk for recording and reproducing information. And a part of a light beam of the laser light source is used as a tilt detection light beam, and a state of defocusing is performed via the objective lens with respect to a medium surface of the optical disc rotated by the disc driving means. Tilt beam forming means for converting, reproduction signal detecting means for receiving reflected light from the optical disc and detecting information recorded on the medium surface, and receiving the tilt detecting light beam reflected by the optical disc. And tilt detecting means for detecting the disk tilt of the optical disk from the change in the light receiving angle. An optical disk device characterized in that. 2. A laser light source for outputting a coherent light beam, a disk drive means for rotationally driving an optical disk, and an optical head including an objective lens for focusing the light beam on the optical disk for recording and reproducing information. And a reproduction signal detecting means for receiving the reflected light from the optical disc and detecting the information recorded on the medium surface, and a tilt detection for the reflected light reflected on the surface of the optical disc. An optical disc apparatus comprising: a tilt detecting unit that receives a light beam and detects a disc tilt of the optical disc based on a change in a light receiving angle. 3. A laser light source for outputting a coherent light beam, a disk drive means for rotationally driving an optical disk, and an optical head including an objective lens for focusing the light beam on the optical disk for recording and reproducing information. And a part of a light beam of the laser light source is used as a tilt detection light beam, and a state of defocusing is performed via the objective lens with respect to a medium surface of the optical disc rotated by the disc driving means. Tilt beam forming means for converting and reflecting a part of the light beam of the laser light source in a direction different from the incident direction, and receiving reflected light from the optical disc to detect information recorded on the medium surface. Reproducing signal detecting means for receiving the tilt detection light beam reflected by the optical disc, A tilt detecting unit that detects a disc tilt of the optical disc based on the change, and a lens tilt detecting unit that receives the reflected light from the tilt beam forming unit and detects the tilt of the objective lens from the change of the light receiving position are provided. An optical disk device characterized by the above. 4. A laser light source for outputting a coherent light beam, a disk drive means for rotationally driving an optical disk, and an optical head including an objective lens for focusing the light beam on the optical disk for recording and reproducing information. And a part of a light beam of the laser light source is used as a tilt detection light beam, and a state of defocusing is performed via the objective lens with respect to a medium surface of the optical disc rotated by the disc driving means. Tilt beam forming means for converting, reproduction signal detecting means for receiving reflected light from the optical disc and detecting information recorded on the medium surface, and optical axis of the tilt detecting light beam reflected by the optical disc. The image formation correction means for deflecting the light beam to a position different from the focus position of the light by the reproduction signal detection means, The tilt detection light beam deflected by a positive means by receiving, from the change of the acceptance angle, the optical disk apparatus characterized by comprising a tilt detection unit, a detecting disc tilt of the optical disc. 5. A laser light source for outputting a coherent light beam, a disk drive means for rotationally driving an optical disk, and an optical head including an objective lens for focusing the light beam on the optical disk for recording and reproducing information. And a part of a light beam of the laser light source is used as a tilt detection light beam, and a state of defocusing is performed via the objective lens with respect to a medium surface of the optical disc rotated by the disc driving means. Tilt beam forming means for converting, reproduction signal detecting means for receiving reflected light from the optical disc and detecting information recorded on the medium surface, and receiving the tilt detecting light beam reflected by the optical disc. A reflecting means for reflecting the optical axis to a position different from the reproduction signal detecting means, and a reflecting means for reflecting the optical axis. Wherein receiving the tilt detection light beam, the change of the acceptance angle, the optical disk apparatus characterized by comprising a tilt detection unit, a detecting disc tilt of the optical disc. 6. The optical disk device according to claim 4, wherein the reproduction signal detecting means and the tilt beam detecting means are arranged on the same plane. 7. The tilt beam forming means is a hologram plate which receives a light beam of the laser beam and outputs diffracted lights of 0th order and 1st order into different spaces. The optical disk device according to any one of 1, 3, 4, and 5. 8. The tilt beam forming means receives a light beam of the laser beam, forms a tilt detection light beam from a part thereof, and forms a reproduction main beam from another part. Any one of claims 1, 3, 4, and 5
Optical disc device according to the item. 9. The optical axis of the optical head is adjusted so that the difference between the disc tilt detection output detected by the tilt detection means and the lens tilt detection output detected by the lens tilt detection means is minimized. 4. The optical disk device according to claim 3, further comprising a lens tilt correction means.