JPS5987629A - Optical disk device control method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an optical disk device control system, and in particular to stable information reproduction even when the information track on the optical disk is damaged by scratches, dust, etc. This invention relates to an optical disk device control system that allows for

[Prior art]

In recent years, optical disk devices using digital optical disks have been put into practical use due to their high recording density. This device is a rotating optical disk (digital optical disk).
An information track (hereinafter simply referred to as "track") provided on the surface is tracked by an optical head, and a laser beam is used to thermally create holes ("track") in the metal film on the track.
called "bit". ), and for reproduction, a weak laser beam is irradiated and the presence or absence of reflection is detected to obtain a digital signal. The problem here is that the track pitch of digital optical discs is approximately 1.6.
Since the width is extremely narrow (μm), even small scratches or dust on the disk surface may have a negative effect on the track.

In other words, scratches, dust, defects, or destruction on the recording film cause an abnormality in the servo signal that causes the head to follow the track during recording and playback, and this causes disturbance to the servo system, causing the optical head to deviate from the track. Recording information.

The problem is that playback becomes impossible. Since optical discs are not rewritable, if the track-off occurs during recording, it is necessary to immediately detect this and stop recording. If the track off occurs during playback, there is no risk of destroying data on other tracks, but the read data is incorrect, so the track off is detected and the read data is incorrect. need to be recognized. This will be explained in more detail below.

A conventional optical disk device includes an optical disk drive device (consisting of an optical head, a control circuit for controlling the optical head's moving means 9 rotation systems and a mechanical section, and an interface circuit with a higher-level control device), and an optical disk control device. The device has the function of giving commands to the optical disk drive device and driving the mechanical part of the drive device and the optical head according to a certain procedure, and the function of processing signals recorded on the optical disk and signals reproduced. ). If the above-mentioned off-track occurs while the optical disk drive is performing a reproducing operation under the control of the control device, the half-disk drive detects the off-track and sends it to the control device.

When the control device receives this signal, it recognizes that the data it has just read is incorrect and goes to read the data again, but there is a possibility that it will go off track again. In this case, in the information recording and reproducing system using the conventional optical information processing device as described above, the re-reproduction operation (
Since the retry operation was repeated, there was a serious drawback that whenever a rack misalignment occurred, not only the data in that part but also the data subsequent to that track became unreadable. Further, even if a track-off signal is erroneously detected in a state where no track-off has actually occurred, the above-mentioned inconvenience occurs and data reproduction becomes impossible.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to eliminate the above-mentioned drawbacks of conventional optical disk devices, and to prevent tracks on optical disks from being destroyed by scratches, dust, etc. Even if the optical head goes off track, only that part of the data will be discarded.
The purpose of the subsequent steps is to provide a stable and highly reliable optical disk device control system that enables normal playback.

[Summary of the invention]

The gist of the present invention is that in an optical disk device that reproduces information by tracking a light spot on a track on an optical disk, the relative positional relationship between the track and the light spot is determined in response to the state of reflected light from the optical disk. The response characteristics of the automatically corrected tracking servo system are made variable,
The point is that the response characteristic is controlled so that the servo system does not follow the actual change in the reflected light from the optical disk while the light spot passes through the defective area on the track.

This will be explained in more detail below.

FIG. 1 shows a digital optical disc. A spiral track 2 is provided on the optical disk l,
The track 2 has an area S called a sector, which is divided into n equal parts. , So,...S. In the case of a digital optical disc, the track is along a groove pre-formed on the disc surface, and the first part of each sector has a track number and a track number, as shown in FIG.
Information such as sector number is written. This part is I
It's called D.

In an optical disk device, information is always recorded and reproduced in sectors. The optical disk control device checks the track number and sector number for each sector, and issues recording and reproduction commands to the optical disk drive device. Tracking is also performed by detecting changes in reflected light (servo information) that occur when a light spot crosses a track groove on the disk surface. .

By the way, if there are scratches, dust, etc. on the recording film on the track,
In this case, servo information for tracking may be lost, or false servo information may be generated to try to take the optical head off the track. Since the control circuit of the optical head controls the position of the optical head according to the servo information, the optical head will deviate from the track according to the time constant of the control circuit and the time constant of the track following mechanism of the head. For example, if the rotation speed of the disk is 240 r, p,
If the deviation between the center of the track and the center of the spindle (called "eccentricity") is 50 μm, the cutoff frequency of the servo system must be 1 to 1.5 KH. If a large disturbance is caused by dirt, dust, etc., the optical head will follow the disturbance.

In order to prevent this, in the present invention, the control device specifies a sector where the optical head may come off track due to the scratches or dust, and while the optical spot is scanning the specified sector, the optical head is This is to control the head so that it does not follow the actual servo information from the disk surface - to maintain the previous state to some extent.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a block diagram showing the first embodiment of the present invention, and shows an example in which the degree of amplification of the track following servo signal is changed based on the output of the off-track detection circuit.

In FIG. 3, 1 is an optical disk, and 4 is the optical disk l.
10 is an optical head, 33 is an optical disk control device, 34 is an F rank out-of-rank detection circuit, and 23 is a switch circuit.

The operating operation of the apparatus of this embodiment is exactly the same as that of a conventional optical disk apparatus. That is, a light beam emitted from a semiconductor laser 11 as a light source and controlled in the radial direction of the front light distribution disk 1 by a galvanic mirror 12 is focused onto a track of the optical disk by an objective lens 5, and is focused on a track of the optical disk with a diameter of about 1. This results in a light spot 28 of .6 μm. On the other hand, the reflected light from the optical disc is separated from the incident light by the beam splitter 6 and input to the photodetector 19. Photodetector 19 power)
Their outputs are input to the adder circuit 20 to become a signal indicating the total reflected light it, and are digitized by the peak sense circuit 50 to become the data signal 51. In addition, the force calculation circuit 20
The output is input to the detection circuit 54, and a sector mark signal 55 indicating the division of each sector is obtained.These signals are sent to the optical disk controller 33 via the interface circuits 7 and 8.

Furthermore, a track following servo signal 22 (obtained ε1) is output from the photodetector 19 through the output circuit 21. The amount of deviation is the amplifier 25 whose amplification degree is 0. Compensation circuit 2
6. A power amplifier 27) operates a galvanometer mirror 12 through a servo system to control the light spot 28 to always be at the center of the track 2. However, since the tracking range of the Garno-kuno mirror 12 is at most about ±100 μm, larger movements than this are impossible due to the magnet 14.
．． This is done by passing a current through the voice coil 13 in the magnetic field created by the magnetic field 15 to move the entire optical head 10.

During normal track following, a circuit 29 detects the movement of the galvano mirror 12 from the drive current of the galvano mirror 12.
The position of the mirror 12 is detected. This detection signal is applied to an adder circuit 17 through an analog switch 30 and a servo system compensation circuit 31, and the output thereof is sent to the voice coil 13 via a power amplifier 18 and sent to the optical head 1.
Drive o. By performing such two-stage servo, the galvanometer mirror 12 can always position the light spot 28 on the track 2 without moving almost from the neutral point.

When moving a large track, the number of tracks to be moved is instructed from the optical disc control device W33 to the access control circuit 16, and a drive signal corresponding to the number of tracks to be moved is inputted to the box and force amplifier 18 via the adder circuit 17. , whereby the optical head 10 is driven at high speed. In this case, since track following is not performed, the galvanometer mirror position signal is turned off by the analog switch 30.

The characteristic operation of the device of this embodiment will be explained below.

Now, suppose that there is a large scratch 3 running in the radial direction as shown in FIG. 1 on the track 2 of the optical disc 1-1.

When off-track occurs due to the scratch 3, the track following servo signal 22 output from the differential circuit 21 increases. This is detected by the off-track detection circuit 34, which has a semi-determining function based on two slice levels, positive and negative. The detected signal is sent to the destination disk controller 33 via the interface circuits 7 and 8.

When the optical disk control device 33 receives this signal, it stops the playback operation, performs certain processing, and then accesses the track where the track-off occurred again and starts playback.

Reproduction is performed sector by sector as described above. The optical disk control device 33 recognizes the sector on the track that has caused the off-track, and uses the sector number and the current optical head 10.
and the sector number through which it is passing are sent to the optical disk drive. The optical disk drive device receives the two signals (signal 52.
53) is received, and the sector number that caused the off-track (
The signal 52) is input to the comparison circuit 56, and the signal 52) is inputted to the comparison circuit 56, and the current optical head 10
The sector number (signal 53) through which the
Load into. The counter 32 receives the sector mark signal 55.
The output is input to the comparator circuit 56. Therefore, when the optical head 10 comes to the sector where the track-off has occurred, the inputs of the comparator circuit 56 become equal. The switch circuit 23 is switched by the output signal of the comparison circuit 56 at this time, so that the amplifier 24 is used at a smaller amplification degree than the previous amplification degree. When the sector in which the track-off has occurred is completed, the switch circuit 23 is switched again to use the amplifier 25 with the original amplification degree of 0. As a result, it is possible to avoid responding to pulse-like disturbances caused by scratches, dust, etc., and normal playback without track deviation can be performed. Needless to say, if the scratch is large, that sector cannot be reproduced, and subsequent sectors can be reproduced normally. In the above embodiment, instead of lowering the amplification degree for the entire period of one sector, it is also possible to switch the amplification degree only for the portion of the sector where the off-track signal is generated. Further, it is necessary that the time width of the disturbance caused by the scratches, dust, etc. is smaller than the time constant of the servo system.

FIG. 4 is a block diagram showing a second embodiment of the present invention, in which the same components used in the first embodiment shown in FIG. 3 are designated by the same numbers. The difference from the embodiment shown in Fig. fR3 is that the amplification degree of the track following servo signal is changed by the output of the off-track detection circuit in the previous embodiment, whereas the track following servo signal is changed by the output in this embodiment. The key point is that the signal is held in its previous state.

In FIG. 4, 35 is a sample and hold circuit.

Since the normal operation of the device of this embodiment is exactly the same as that of the previous embodiment, a description thereof will be omitted and a description of the characteristic operation will be given immediately.

Track 2 on optical disk 1 has scratch 3 as described above.
Let us consider a case where this causes the vehicle to fall off the track. This is detected by the off-track detection circuit 34, and the output signal of the comparison circuit 56 is obtained in exactly the same manner as in the previous embodiment, and this is sent to the sample hold circuit 35. The sample hold circuit 35 holds the state before the track-off occurs for the time period of the sector where the track-off occurs (or the period during which the track-off signal is output) to prevent the track-off from occurring. In this case, the galvano mirror
It is necessary to hold only the optical head 12 and turn off the drive of the entire optical head using the analog switch 30. Also,
The holding time needs to be short enough so that no off-track occurs due to the eccentricity within that time. For example, when the eccentricity is 50 ttm and the number of sectors in one track is 64, the track deviation that occurs between one sector is about 0.2 μm, and if this is the case, the entire time for one sector is There is no problem with holding.

In the above embodiments, the response to the actual occurrence of off-track has been described, but in addition to this, there are cases in which data reproduction cannot be performed due to erroneous detection of an off-track signal. In both of the above two embodiments, in such a case, the optical disk controller specifies the sector number where the track-off has occurred, and tracks only that sector, just as when the track-off actually occurs. It is possible to reproduce data while ignoring the out-of-band signal, read the ID of the next sector, and if the track number is correct, it is possible to determine that the previously read data is correct and proceed with the reproduction process.

[Effects of the Invention] As described above, according to the present invention, in an optical disc device that reproduces information by tracking a light spot on a track on an optical disc, the The response characteristic of a tracking servo system that automatically corrects the relative positional relationship between the information track and the optical spot is made variable, and while the optical spot passes through a defective area on the information track, the servo system controls the response from the optical disk. Since the response characteristics are controlled so as not to follow the actual changes in the reflected light, even if track-off occurs, only that part of the data is discarded, and normal playback is possible from the subsequent part. This has the remarkable effect of realizing a stable and highly reliable optical disk device control system.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a digital optical disc, FIG. 2 is a diagram showing a track configuration, and FIGS. 3 and 4 are configuration diagrams showing an embodiment of the present invention. 1: Optical disk, 2 Ni-Drack, 3: Scratch, 10': Optical head, 23: Switch circuit, 33: Optical disk control device, 34 Ni-Drack removal detection circuit, 35: Sample hold circuit. Patent applicant Hitachi Seisaku Shinshiki Co., Ltd. Patent attorney Masaru Isomura Disciple 1 Figure 2

Claims (1)

[Claims] α) An optical disk device that reproduces information by tracking a light spot on an information track on an optical disk,
The response characteristics of a tracking servo system that automatically corrects the relative positional relationship between the information track and the light spot in response to the state of the light and the light reflected from the disk are made variable, so that the light spot is on the information track. An optical disk device control method characterized in that the response characteristic is controlled so that the servo system does not follow an actual change in the reflected light from the optical disk while passing through a defective area.Oe) Controlling the response characteristic 2. The optical disk device control method according to claim 1, wherein the control method is performed by switching the gain of the servo system. c! 1) The optical disk device control method according to claim 1, wherein the response characteristic is controlled by holding the servo system. ′←) Control of the response characteristics is performed by storing the position of the light spot when it is detected that the light spot has deviated from the information track, and when accessing the information track again, the light spot is changed from the memorized position. 2. The optical disk device control method according to claim 1, wherein the control method is performed by detecting that the position has been reached.