JPH04114326A - Optical disk driving device - Google Patents

Abstract

PURPOSE:To enlarge an allowable degree to the warp of an optical disk by inclining a motor to rotate the optical disk corresponding to the inclination of the optical disk. CONSTITUTION:An inclination detecting means 2 is composed of LED 21a and 21b and photodetectors 22a and 22b. Corresponding to the value of an additive output signal TC showing the inclination of an optical disk 1, the number of pulses applied to a correction motor 8 is set in advance, the pulse number of drive signals are applied to turn the correction motor 8. When the correction motor 8 is turned, a worm 81 is turned, a gear part 17a engaged to the worm 81 is turned upward or downward with a pin 16 as a center, a motor 14 is inclined, and the optical disk 1 is inclined. Thus, even when the optical disk 1 is warped, the optical axis is made almost orthogonal to a recording layer 11 of the optical disk 1.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical disc drive device that accesses an optical disc, and in particular, to a device that corrects a deviation in the surface angle between the optical disc and the optical axis of an optical head caused by warping of the optical disc. Regarding technology.

[Prior art] A magneto-optical disk has a substrate made of glass or acrylic resin,
It is composed of a multilayer body made of different materials, including a recording layer made of an amorphous alloy and a protective layer made of an ultraviolet curing resin. Since these layers have different coefficients of thermal expansion and moisture absorption characteristics, there is a problem in that the magneto-optical disk may warp depending on changes in temperature and humidity. This problem similarly occurs with read-only optical discs such as CDs and LDs, and write-once optical discs.

In an optical disc, it is necessary to arrange an optical head such that the optical axis of the optical head is perpendicular to the recording surface of the optical disc.

In an optical disk drive device, the inclination and warpage of the optical disk impose major constraints on the device. For example, if an optical disk warps and the angle between the optical axis of the optical head and the recording surface deviates beyond the allowable range, the focused spot will not form a perfect circle on the recording surface, resulting in so-called coma aberration. , abnormalities such as data reproduction errors and tracking servo system offsets occur, reducing the reliability of the device.

For this reason, the current optical disc standards limit the deviation to 90°.
The problem of warpage is solved by strictly specifying a narrow tolerance range of ±7 mrad, which is a major obstacle in improving the yield of optical disks.

[Problem to be solved by the invention]

Therefore, if the angular deviation between the optical axis and the recording surface can be corrected on the equipment side, the tolerance range for optical disc warping and tilting will be widened, making it possible to improve the yield of optical discs and improving the reliability of the equipment. can be done.

As a conventional optical disk drive device that corrects the deviation,
There is a known device that detects the tilt of an optical disc and corrects the tilt of the optical head (optical pickup) to be parallel to the tilt of the optical disc according to the detected tilt (for example, Radio Technology Selection 198 "Optical Disc Technology" by Noboru Murayama). , Hiroshi Koide,
Co-authored by Kazusaku Yamada and Makoto Kunikane, page 92).

In the above-mentioned apparatus, since the inclination of the optical head is corrected by including a moving system for moving the beam in the radial direction, the structure of the correction system is complicated, and a high-output drive system is required.

Recently, in order to increase the access speed of optical discs, a separation optical head has been developed in which only the objective lens and reflection mirror of the optical head are moved in the radial direction of the optical disc, and the laser light source, optical system, and detection system are fixed. There is. Since the separation optical head is heavier than an integrated type, it is conceivable to correct only the moving part according to the inclination of the optical disk.

However, tilting the movable part causes optical axis misalignment between it and the fixed part, which is difficult in practice. Therefore, it is necessary to correct the tilt of the entire separate optical head, which is heavier than an integrated optical head, and the configuration of the correction system becomes more complex, and its drive system requires a large output, making the device larger. There was a problem.

The present invention was developed in view of the above circumstances, and by tilting a motor that rotates not an optical head but a lighter optical disk according to the inclination of the optical disk, it is possible to achieve an acceptable correction system with a simple structure and a small output. To provide an optical disc drive device which can reliably reproduce even an optical disc that has warped more than the range and has a high tolerance for warping of the optical disc.

[Means to solve the problem]

The optical disc drive device according to the present invention includes a drive unit for driving a motor for rotationally driving an optical disc in a plane including the optical axis in accordance with the inclination of the recording surface of the optical disc with respect to a plane intersecting the optical axis of the optical head detected by the inclination detection unit. It is made to tilt more.

[Effect]

In the present invention, the motor for rotationally driving the optical disc is tilted including the optical axis in accordance with the tilt of the recording surface of the optical disc with respect to the plane intersecting the optical axis of the irradiation light of the optical head detected by the tilt detection means, The recording surface and the surface intersecting the optical axis are kept substantially parallel, and even if the optical disc is warped, it can be accessed.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof.

FIG. 1 is a perspective view showing the main structure of an optical disk drive device according to the present invention, and FIG. 2 is a block diagram showing the structure of a tilt detecting means. In the figure, 1 is an optical disk, and as shown in FIG. 2, the optical disk 1 has a recording layer 11 made of an amorphous alloy and a protective layer 12 made of an ultraviolet curing resin laminated in sequence on a substrate 10 made of glass or acrylic resin. The bases vi, 10 and each layer 11, 12 have different thermal expansion coefficients and moisture absorption characteristics. optical disc 1
A metal hub 13 is attached to the center of the optical disc 1, and the hub 13 is attracted by a magnet (not shown) in a turntable 14a fixed to a rotating shaft 14b of a motor 14 for rotating the optical disc. It is fixed to the turn table 14a. A tilting portion 17 having a dogleg shape in side view is attached to the bottom of the motor 14 for tilting the motor. The tilting part 17 has a gear part 17a formed from a part of a worm wheel carved on the outside of one side, and a hinge 17b for rotation fixed on the outside of the other side. The gear part 17a meshes with a worm 81, and the rotation of the worm 81 rotated by the correction motor 8 causes the gear part 17a to move up and down, and the motor 17 moves around the pin 16 rotatably fitted into the hinge 17b. Tilt. The bin 16 is fixedly supported by a bracket 16 surrounding the main frame of the device (not shown).

The correction motor 8 uses a pulse motor, and is attached to a motor mounting bracket 82 that is U-shaped in plan view. The motor mounting bracket B2 is provided with guide parts on both sides thereof, and slidable guide shafts 84, 84 are fitted inside the guide parts, so that the motor mounting bracket 82 can freely move in the direction of approaching and separating from the motor 14. It becomes. The guide shaft 84.84 has its base end fixed to the main frame, and a spring 83.83 is interposed between the main frame and the motor mounting bracket 82. As a result, the motor mounting bracket 82 is always urged in the direction of contacting the motor 14. This is the worm 81 and gear part 17
This is to keep the gear part 17a in constant contact with the gear part 17a at a constant pressure even when the gear part 17a moves up and down.

An optical head 3 is provided at a position facing the tilting section 17 and the motor 14. The optical head 3 is a separation type optical head, which generates a laser beam with a predetermined diameter (for example, several ml diameter), projects it in the radial direction of the optical disk l, receives reflected light from the optical disk, and calculates the amount of light. It consists of a fixed head 30 for detection, a yoke 33 attached to the base of the fixed head 30 or a near motor, and a movable head 31 winding a voice coil (not shown) or provided on a carriage 32 of the near motor. The moving head 31 has a reflecting mirror 35 that reflects the projected laser beam in the direction of the optical disk 1, and an objective lens 34 that focuses the laser beam on the recording J'511 of the optical disk 1 into a spot light with a diameter of 1 μm.
The optical axis of the objective lens 34 is approximately perpendicular to the recording layer ll of the optical disc. The objective lens 34 can be moved minutely in the direction toward and away from the optical disc 1 and in the radial direction of the optical disc 1, and is moved in each direction by a focus error signal and a tracking error signal.

As shown in FIG. 2, two LEDs 21a and 21b are arranged side by side on the moving head 31. LED 21a, 2
1b is an optical disc 1 at a predetermined angle on the inner circumferential side and the outer circumferential side, respectively.
Emits light towards. The reflected light from optical disk 1 is 2
The light is detected separately by photodetectors 22a and 22b having separate light-receiving surfaces. These LEDs 21a, 21b and photodetectors 22a, 22b constitute the tilt detection means 2.

The photodetectors 22a and 22b output four electrical signals PDI to PD4 corresponding to the amount of light received on each light receiving surface, and the photodetectors 22a and 22b detect the optical disk 1 at a predetermined distance from the moving head 31. When the optical axis of the light irradiated onto the optical disk 1 by the moving head 31 is perpendicular to the recording surface, the two light receiving surfaces are arranged so that the amount of light received by the two light receiving surfaces is equal. Therefore, at that time, the electrical signals PDI, PO2 and P
O2 and PO2 have the same thickness. Electric signals PDI to PD4 from each light receiving surface are transmitted to amplifiers 4a, 4b and 4.
The two subtraction outputs RCa and RCb are supplied to an adder 6. This addition output signal TC becomes a signal corresponding to the inclination between the optical axis and the recording surface.

The addition output signal TC is applied to the correction control circuit 7, where a drive signal corresponding to the value of the addition output signal TC is generated and applied to the correction motor 8.

Next, the tilt detection and correction operations of the optical disk drive device of the present invention configured as described above will be explained. This operation is performed, for example, when the optical disc 1 is loaded into the device or when the temperature change exceeds a predetermined value. In the case of a 130 am optical disc, the optical disc 1 is moved to a radius of 45 tI, and the tilt of the optical disc 1 caused by warpage of the optical disc 1, foreign matter on the turntable 14a, etc. is detected there.

Here, in this embodiment, LEDs 21a, 21b and a photodetector 22a.

The reason why the inclination detection means 21 of 22b is provided will be explained. The tilt of the optical disc 1 is determined by the LED and photodetector 1.
Although it is possible to detect using the tilt detection means 2 of the set,
In this case, the output of the photodetector changes depending on the inclination, and also changes when the distance between the optical head 3 and the optical disk 1 changes, that is, when the optical head and the optical disk 1 move in parallel. For example, when detecting the tilt using the LED 21a and the photodetector 22a, when the optical disc 1 tilts upward to the right in FIG. =PD1-PD2) is positive, but the output RCa of the subtracter 5a also becomes positive when the optical disk 1 approaches the movable head 31 by parallel movement, and these cannot be discriminated in the case of one set.

On the other hand, if there are two sets of LEDs and photodetectors, and the irradiation directions of the LEDs are different in the radial direction, the output RCa(-PDl-PO2) of the subtractor 5a will be
The output RCb (=PD3-PO2) of the adder 6 and 5b both become positive, and the output signal TC of the adder 6 becomes positive, but when the optical disk 1 approaches the moving head 31, the output RCa is positive and the output 1? cb becomes negative, and the output signal TC of the adder 6 becomes approximately zero. This makes it possible to distinguish between tilt and parallel movement.

The number of pulses to be applied to the correction motor 8 is set in advance in accordance with the value of the addition output signal TC indicating the inclination of the optical disc 1, and the correction motor 8 is rotated by applying a drive signal of that number of pulses. When the correction motor 8 rotates, the worm 81 rotates, and the gear portion 17a meshing with the worm 81 rotates upward or downward about the pin 16, causing the motor 14 to tilt and the optical disc 1 to be tilted.

As a result, even if the optical disc 1 is warped, the optical axis and the recording layer 11 of the optical disc 1 are substantially orthogonal, coma aberration does not occur, the spot light becomes a substantially perfect circle, and reproduction errors and tracking errors are reduced.

In addition, LEDs 21a, 21b and photodetectors 22a, 2
When the inclination is detected by the two sets of inclination detection means 2 of 2b, by providing a new subtracter for subtracting the outputs of the subtracters 5a and 5b, this subtractor outputs a signal corresponding to the amount of parallel movement. Therefore, it becomes possible to use this as a focus error signal.

In this embodiment, a step motor is used as the tilting driving means, but the present invention is not limited to this, and it goes without saying that other actuators such as a linear motor and a solenoid can also be used.

Further, in the present embodiment, the tilting mechanism is configured with a worm and a worm wheel, but this is just an example, and any mechanism that can be tilted may be used.

Furthermore, although this embodiment has been explained using a separate optical head as an example,
It goes without saying that the present invention can also be applied to an integrated optical head.

〔Effect of the invention〕

As detailed above, in the present invention, the motor for rotating the lighter optical disk rather than the optical head is tilted according to the tilt of the optical disk, so a low-output drive system is used and the configuration is simple. It has excellent effects such as being able to correct the tilt of the optical disc.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing the structure of an optical disk drive device according to the present invention, and FIG. 2 is a block diagram showing the structure of a tilt detecting means. I... Optical disk 2... Tilt detection means 3... Optical head 8... Correction motor 11... Recording layer 14.
...Motor 17...Tilt part 21a, 21b...
LED22a, 22b -"Photodetector In the diagram, the same reference numerals indicate the same or corresponding parts. Agent Masuo Oiwa

Claims (1)

[Claims] (1) An optical head that faces one surface of an optical disk and is movable in the radial direction of the optical disk, irradiates the optical disk with light and detects the reflected light, and the optical head that irradiates the optical disk with light. a tilt detection means for detecting the tilt of the recording surface of the optical disc with respect to a plane intersecting the optical axis of the optical disk; In an optical disk drive device, the correction means includes means for tiltably supporting a motor that rotationally drives the optical disk within a plane including the optical axis; What is claimed is: 1. An optical disc drive apparatus comprising: a drive means for causing the drive to move; and a means for controlling the drive means in accordance with the detected tilt.