JP2596209B2 - Eccentricity removal method for optical disk - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus that performs recording, reproduction, and erasure of information using a laser beam.

[Conventional technology]

The optical disk recording / reproducing method using a laser beam is capable of large-capacity recording / reproducing and non-contact high-speed access, and has thus been put to practical use as a large-capacity memory. The optical disk is a read-only type that is known as a compact disk or laser disk, a write-once type that can be recorded by the user,
And rewritable types that can be repeatedly recorded by the user. The rewritable type is expected to replace a magnetic disk as an external memory for a computer or to be applied as a document / image file.

Generally, a method of recording / reproducing information on an optical disk is to irradiate a laser beam onto an optical disk rotating at a high speed and follow the guide beam (hereinafter, referred to as a pre-groove) formed in a spiral shape inside the optical disk so as to follow the information. Record and play back. In the conventional method, the laser light is focused on the recording film of the disk, and the laser light is moved in the radial direction of the disk so that the laser light follows the pregroove. Further, regarding the eccentricity of the disk, the eccentricity was removed only by the mechanical accuracy of the disk rotating portion and the disk clamping portion.

[Problems to be solved by the invention]

However, when the laser light is moved in the radial direction of the disk so that the laser light follows the pregroove of the optical disk, a method of moving the condenser lens 14 by the magnet coil 13 as shown in FIG. As shown in (1), there is a method of moving the laser beam 16 by using the galvanomirror 17, but the range in which the laser beam 16 can follow is about 100 μm, and it cannot follow the eccentricity of the disk exceeding 100 μm. Also, even if the disc is rotating at high speed even with an eccentricity of 100 μm or less, depending on the spring constant of the spring 15 supporting the condenser lens 14 and the galvanometer mirror 17 and the weight of the condenser lens 14 and the galvanometer mirror 17,
There were times when I could not follow. If the laser beam 16 cannot follow the pre-groove of the disk, it will not be possible to read information recorded on the disk or write information on the disk, and will not function as an optical disk device.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disk device which can solve the above-mentioned drawbacks and can minimize the eccentricity of an optical disk when the optical disk device is mounted.

Another object of the present invention is to provide an optical disk eccentricity removing method using the optical disk device.

[Means for solving the problem]

The present invention relates to an optical disc apparatus for recording / reproducing and erasing information by using a laser beam, comprising: an eccentricity removing section which contacts an outermost periphery of the optical disc and moves the optical disc in a radial direction; An eccentricity removal method for an optical disk using an optical disk device comprising: an eccentricity amount detection unit for generating a sine wave; and a drive circuit for moving the eccentricity removal unit so that the sine wave of the first cycle becomes zero. Then, the optical disc is moved in the radial direction by bringing the eccentricity removing section into contact with the outer circumference of the optical disc such that a sine wave of one cycle of the track error signal for one round of the optical disc becomes zero.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a configuration of an embodiment of an optical disk device according to the present invention. The optical disc apparatus includes an eccentricity removing tool 6 that contacts the outermost peripheral portion of the optical disc 1 and moves the optical disc 1 in a radial direction, a driving unit 5 that moves the eccentricity removing tool 6, and a driving circuit that moves the driving unit 5 4, an optical head 2, a filter 3, and a track servo circuit 10. Reference numeral 8 denotes a clamp unit for clamping the optical disc 1, reference numeral 9 denotes a rotating shaft, and reference numeral 7 denotes a rotary motor. The optical head 2 and the filter 3 constitute an eccentricity detection unit for the optical disk.

Since the eccentricity removing tool 6 is a portion that directly contacts the outermost peripheral side surface of the rotating disk 1, the shape is desirably a cylindrical shape as shown in FIG. . Further, the eccentricity removing tool 6 is attached to the drive unit 5 and can be moved toward the center of the disk by the power of the drive unit 5. A voice coil, a linear motor, or the like is used as a power source of the driving unit 5. As shown in FIG. 3, the diameter of the rotating shaft 9 of the clamp portion 8 of the disc is smaller than the inner diameter of the center hole 18 of the disc 1 by about 100 μm. In this case, the disc 1 is shifted from the rotation shaft, but the disc 1 is pressed by the spring 15 so that the disc 1 does not deviate from the rotation shaft 9 with the rotation torque of the motor 7.

When the optical disk 1 is mounted on the optical disk device and the disk is rotated, and the laser beam emitted from the optical head 2 is made to follow the pre-groove of the optical disk 1, the optical head 2
Thus, a track error signal can be obtained. If the optical disk itself is eccentric, or if eccentricity occurs when the optical disk is mounted on the optical disk device, as shown in FIG. Waves are generated. The greater the eccentricity of the disk, the greater the difference between the peak and valley of the sine wave as shown in FIG. 4 (b), and the smaller the eccentricity, the greater the difference between the ridge and valley of the sine wave as shown in FIG. 4 (c). Is smaller. When the eccentricity disappears, no sine wave is generated as shown in FIG. 4 (d). Returning to the description of FIG.

The optical disk 1 is mounted on the optical disk device, the disk is rotated at a low speed, and the laser beam emitted from the optical head 2 is made to follow the pre-groove of the optical disk 1. The rotation speed of the optical disk is preferably 10 rpm to 100 rpm. Next, the track error signal obtained from the optical head 2 is extracted by the filter 3 as a sine wave of one cycle for one round of the disk. Based on the sine wave obtained by the filter 3, the eccentricity removing tool 6 connected to the drive unit 5 is brought into contact with the outermost side surface of the disk by the drive circuit 4, and the signal obtained by the filter 3 is reduced to zero. By pressing the outermost peripheral side of the disk so that the optical disk 1 is shifted from the rotation axis 9, the center of the optical disk coincides with the center of the rotation axis, and the eccentricity is removed. The normal tracking operation is performed by a track servo circuit 10 to which a track error signal is input via the filter 3.
Is performed by outputting a track servo signal and thereby moving the optical head 2.

It is desirable to perform the above-described eccentricity removal operation before reading / writing information from / to the optical disk. Even if the optical disc 2 and the rotating shaft 9 have an eccentricity of 100 μm or more, if the laser beam emitted from the optical head 2 follows the pre-groove of the optical disc 1 and the eccentricity removing operation is started at the same time, There is no problem that the light emitted from the head 2 cannot follow the pre-groove of the optical disk 1 completely.

Attempting to remove all the eccentricity of the disk during one rotation of the disk may increase the impact on the disk, so the eccentricity was removed little by little during multiple rotations of the disk, and the eccentricity became zero. At this point, the optical disk is rotated to the number of rotations necessary for recording and reproducing information. One cycle of the sine wave for one round of the disk obtained from the optical head is
As shown in FIG. 5, the value of the eccentricity of the disk on the straight line A connecting the center 11 at the time of rotation 9 and the laser beam emitting portion 12 of the optical head 2 is shown. It is desirable that the place of contact is point B or point C where the extension of the straight line A and the outer peripheral edge of the optical disc 1 intersect.

〔The invention's effect〕

As described above, the present invention includes an eccentricity removing unit which moves the optical disk in the radial direction by contacting the outermost peripheral portion of the optical disk by power inside the optical disk device according to the present invention, based on the track error signal obtained from the optical head. The eccentricity of the disk is calculated, the eccentricity removal part is brought into contact with the outermost periphery of the disk, and further pressure is applied in the radial direction to move the optical disk from the center axis by the eccentricity of the disk obtained based on the track error signal By doing so, the eccentricity of the optical disk can be removed.

Therefore, the burden of causing the laser light emitted from the optical head to follow the pre-groove of the optical disk is reduced, and information can be recorded / reproduced / erased stably even when the optical disk rotates at a high speed. Therefore, there is an effect that it is possible to provide a highly reliable optical disk device that solves the problem that information cannot be recorded / reproduced / erased.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of an optical disk device, FIG. 2 is a diagram showing an optical disk eccentricity removing unit, FIG. 3 is a diagram showing an optical disk clamp unit, and FIG. 4 is a diagram showing a track error signal obtained from an optical head. FIG. 5 is a diagram showing a position at which the optical disk eccentricity removing tool and the optical disk are brought into contact with each other. FIGS. 6 and 7 are schematic views of a main part of a conventional optical disk device. DESCRIPTION OF SYMBOLS 1 ... Optical disk 2 ... Optical head 3 ... Filter 4 ... Drive circuit 5 ... Drive part 6 ... Eccentricity removal tool 7 ... Rotary motor 8 ... Clamp part 9 ... Rotary axis 10 ... Track servo circuit 11 ... Center of rotation axis 12 ... Laser beam emitting part 13 ... Magnet coil 14 ... Condenser lens 15 ... Spring 16 ... Laser beam 17 ... Galvanometer mirror 18 ... Center hole

Claims (1)

(57) [Claims] 1. An optical disk apparatus for recording / reproducing and erasing information by using a laser beam, comprising: an eccentricity removing section which contacts an outermost peripheral portion of an optical disk and moves the optical disk in a radial direction; An eccentricity removing method for an optical disk using an optical disk device comprising: an eccentricity detecting means for generating a sine wave of the formula (1); and a drive circuit for moving the eccentricity removing unit so that the sine wave of one cycle becomes zero. An eccentricity removing unit that contacts the outer circumference of the optical disk such that a sine wave of one cycle of the track error signal for one rotation of the optical disk becomes zero, and moves the optical disk in a radial direction.