JPH0587891B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a track jump detection and control device for an optical disk having a guide track for an optical recording/reproducing device.

Conventional configuration and its problems As an optical information recording/reproducing device, for example, an optical disk coated with or vapor-deposited with a photosensitive material is rotated, and a beam of light from a laser light source, etc. is directed onto the optical disk to a diameter of 1 μm or less. By irradiating a focused minute spot light and modulating its optical output intensity with a recording signal, changes in optical properties such as phase changes, refractive index changes, reflectance and transmittance changes due to unevenness are recorded on the optical disk. Information such as video signals and digital signals can be recorded in real time.
A device has also been proposed that can reproduce recorded information by detecting the change in the optical characteristics.

In such a device, a guide track is provided in advance in a concentric circle or a spiral shape to guide the track to be recorded in order to increase the density of the recording track, discrete partial writing or erasing, etc., and the track follows the guide track. An optical information recording and reproducing apparatus can be considered that records information on a predetermined track while applying tracking control and reproduces information from the track.

The guide track formed on the optical disk is suitably, for example, a groove-like structure having a concavo-convex shape. Information is recorded on a recording medium, such as an amorphous metal deposited on an optical disk provided with this guide track. Information is stored in the form of holes or local blackening due to evaporation of the recording medium.

The guide track is identified by the far-field pattern of the laser beam reflected by the guide track, which is biased in the light intensity distribution on both sides of the guide track. This deviation is photoelectrically converted by a photodetector having two light-receiving sections arranged so that the dividing boundary is parallel to the tangential direction of the guide track, and is applied to the tracking control means.

As an optical disk having a guide track, a structure as shown in FIG. 1 can be considered. FIG. 1 is a diagram showing a part of the disk of the optical disk 1. On the surface R side of the optical disk 1, groove-shaped guide tracks 10a to 10e with a width W, a pitch P, and a depth δ are provided in a concentric or It is carved in a spiral shape. 11a to 11e indicate grooves. A photosensitive recording material is applied from the surface R side to form a recording surface 12. The light is focused on the surface R of the light spot. During recording and reproduction, tracking control is applied so that the light spot is projected onto the groove-shaped guide track 10. During recording, the optical output of the light source is increased and the optical energy of the light spot projected onto the groove-shaped guide track 30 on the disk 1 is increased to expose the recording material coated on the guide track 10. As a result, the reflectance of the recorded portion on the groove guide track changes. By detecting this change in reflectance using a light spot with a smaller optical output than during recording, the recorded signal can be reproduced. 13 shows how the recording material inside the groove-shaped guide track is exposed to light during recording.
This case shows an example in which the recording material became black and the reflectance increased. The guide track 10a~
Specific values of the width W, pitch P, and depth δ of 10e are, for example, width W = 0.6 μm, pitch P = 1.6 μm,
Depth δ = 1000 Å (1/1 of the light wavelength of the laser light source 3)
An optical path length of about 8) is selected.

FIG. 2 is a diagram showing an optical disk and a scanning locus of a light beam when a track jump occurs.
In the optical disk 1, address signals are cut in advance in track address areas 2A and 2B as shown in FIG. 2 by means of uneven grooves, and are used for searching and identifying a required track. Usually, one or two track address areas are provided for each track. That is, when one track is being played back once, the current track address can be checked only twice per revolution.

As an example of the order in which information is recorded on the optical disk 1, as shown in FIG. 2, the current track 3 is searched, track address 2A is reproduced, and then the recording mode is entered from the recording start point 7. In other words, the laser of the light source is set to the power necessary to expose the recording medium from 7, and the light beam is modulated in accordance with the information recording signal. While the tracking servo is recording a track, it is possible that the tracking servo deviates from the current track 3 and causes a track jump while crossing other tracks, although this is rare. Possible causes include deformation of the grooves on the disk 1, scratches on the surface, or if recording is performed in sectors, the tracking servo becomes unstable at the start of recording. Track skipping also occurs when external vibrations, shocks, etc. are applied to the optical head. Even if a track jump occurs during recording, it cannot be detected until the address signal 2B is reproduced, as described above. In other words, track jump is not detected in section 6, and the information is recorded on the jump destination track 5 while the current track is mistakenly recognized as track 3. Even more inconveniently, if track jump 8 occurs, recording will be made while crossing track 4. If information has already been recorded on track 4, double writing will be performed and the information on track 4 will be destroyed. Considering that a track jump crosses many more tracks, all the information on the crossed tracks becomes double-written, leading to information loss. All crossed tracks 4 become unrecordable, even if they are unrecorded tracks. Since the damage caused by track skipping is great as described above, when track skipping occurs during recording, the recording mode must be stopped instantly.

Purpose of the Invention The present invention has been made for the purpose of preventing track skipping during recording, writing on the wrong track, or recording while crossing tracks, thereby preventing information on recorded tracks from being destroyed. It is something.

Structure of the Invention The present invention detects a track jump at the moment when a light beam jumps from a recording track by using a track crossing signal without reproducing an address signal, and instantly reduces the recording power to the reproduction power. It is designed to read the destination track address, and prevents erroneous recording caused by track skipping.2.
Double recording is prevented, the reliability of recorded data on the optical disk is improved, and error processing and recovery processing are realized with high reliability.

DESCRIPTION OF EMBODIMENTS An embodiment of an optical recording/reproducing apparatus equipped with a track jump detection control device according to the present invention will be described below with reference to FIG. The optical disk 1 is rotated by a disk motor 20. Light emitted from a light source 21 such as a semiconductor laser is collected by a condenser lens 22, and focused by an aperture lens 23 onto the optical disk 1 into a light spot of about 1 μm in diameter. The reflected light from the optical disk 1 is separated by a λ/4 plate 24 and a polarizing beam splitter 25, and guided to a two-split photodetector 26. This photodetector 26 is arranged so that its dividing line is parallel to the tracks on the optical disk 1. This two-split photodetector 26
The tracking error signal 27 passes through a tracking/jumping control circuit 28 and drives the aperture lens 23 in a direction perpendicular to the track, thereby performing tracking control. Further, the reproduction signal output 29 is used for reproduction of recorded signals and reproduction of track addresses.

A light source 21 such as a semiconductor laser is set to read power or write power by a drive circuit 30.
A recording signal such as a digital signal or a video signal is generated by a recording signal generation circuit 31, and modulates the power of the semiconductor laser during recording.

FIG. 4 is a diagram showing signal waveforms at various parts when track jump occurs. b to e in FIG. 3 are observation points of signal waveforms b to e in FIG. 4. A is a cross-sectional view of the track in the scanning direction of the light beam, as seen from the light beam. Reference numeral 40 represents a groove track, and 41 represents a flat portion between grooves, and indicates their respective levels. Each track corresponds to Figure 2. 3 represents the track currently being recorded, and the blackened portion represents the photosensitive state. When track jump 8 occurs, 4
Cross tracks A and 4B and jump to track 5
This indicates that the tracking servo is applied to. FIG. 4b shows the output waveform of the tracking error signal 27, which becomes the crossing signal.
In this manner, when the optical spot deviates from the groove tracking 40, a tracking error signal is output in the negative direction as shown in 27A, and when the optical spot enters the groove tracking 40 from the inter-groove flat portion 41, a tracking error signal is output in the positive direction as shown in 27B. This shows the case where the light beam crosses from the inside to the outside of the disk, but when the light beam crosses from the outside to the inside of the disk, the sign of the error signal is reversed. When the tracking servo is applied to the groove track 40, the level of the error signal is naturally close to zero, as shown in FIG. 4b. The moment the tracking is removed from the currently recording track 3,
In other words, by detecting the falling edge of the waveform of 27A, track jump 8 can be detected without scanning the recording beam on other tracks. Figure 4b
The waveform of the error signal 27 of
(Figure 3) uses a threshold value of 42, and the negative comparator 33 (Figure 3) uses a threshold value of 43 to compare and output the track jump detection signals 44 and 45 shown in Figures 4c and d. . This figure 4c or 2
The rise of the first pulse is the timing when the track jump 8 occurs and the beam has not yet entered the flat part 41 between the grooves. Erroneous recording can also be prevented on flat areas. When the pulse shown in FIG. 4 d occurs before the pulse shown in FIG. When this occurs, it is detected that the track has skipped outward.

In FIG. 3, the track jump pulse signals c and d in FIG. 4 are logically summed by an OR gate 34. Then, the flip-flop 35 is set with the output, the analog gate 36 is opened, and the recording signal generation circuit 31 and the semiconductor laser drive circuit 30 are cut off.
In addition, the optical power of the semiconductor laser drive circuit 30 is reduced from recording power to reproducing power. Figure 4 e
represents the optical output waveform of the semiconductor laser. During recording, the recording signal is modulated by the bias power of the PR, and the modulation is stopped at the rise of the first pulse shown in FIG. 4d, and the power is reduced to the reproduction power. CPU37
confirms the address of the jump destination track based on the input from the track address reproducing circuit 38, resets the flip-flop 35, and waits for detection of the next track jump.

FIG. 5 is a diagram illustrating the occurrence of track jump 3 during recording on the optical disk 1 having a spiral guide track. In order to increase the density of the optical disk 1, the track spacing must be narrowed. For such narrow track pitch guide tracks, it is necessary to reduce uneven bit feeding, so spiral cutting is sometimes performed. When recording data on such a spiral guide track, it is necessary to perform recording while applying tracking control to the guide track at a specific address. i.e. disk 1
A jumping operation is required in which the light beam jumps over one track every lap and moves the light beam to the leading position of the guide track. 50 is 1
It shows the jumping section that is performed every lap. Even while recording data on such a spiral guide track, unnecessary track jumps as described above may occur. Reference numeral 8 in FIG. 5 indicates a track jump, and similarly to FIG. 2, it shows a state in which the current track 3 crosses over the cross track 4 and a track jump occurs on the destination track 5.

Similar to FIG. 4, FIG. 6 is a diagram showing signal waveforms at various parts when a track jump occurs. Figure 6
a' to e' are waveforms of the same constituent parts as in FIG. 4 a to e. FIG. 7 is a block diagram of an optical recording/reproducing apparatus equipped with a track jump detection control device for an optical disk having a spiral guide track. b' to g' in FIG. 7 are observation points of signal waveforms b' to g' in FIG.
As mentioned above, 50 in FIG. 5 indicates a jumping section for continuing to apply tracking control to a specific track. a' is a cross-sectional view of the track in the scanning direction of the light beam. When the jumping operation is performed in this manner, the light spot crosses between the grooves of the guide track, so that a crossing signal 51 is detected in the tracking error signal b' in the same way as when track jumping occurs. It is necessary to prevent this crossing signal 51 from being judged as a track skip. f' in FIG. 6 shows a jumping section pulse 52 synthesized from driving pulses for jumping. If this jumping section pulse 52 and the outputs of the positive/negative comparators 32 and 33 (FIG. 6 c', d') are ANDed using an AND gate 56, a jumping section pulse formed by the crossing signal 51 is generated. It is possible to prevent signals 53 and 54 from being judged as track skip signals. Using the rising edge of the first pulse of the track jump detection signal 55 as shown in Fig. 6 g' obtained in this way, only the track jump is accurately detected, and the optical power is determined as shown in Fig. 6 e'. It is possible to reduce the read power from the recording state. 5 in Figure 7
A high-pass filter 7 removes an error voltage having a period of one rotation of the disk during tracking control, and is provided to ensure the operation of the comparators 32 and 33.

In this way, even when intermittently recording a specific track on an optical disk having a spiral guide track, track skipping can be accurately detected regardless of the jumping operation.

Effects of the Invention As described above, according to the track jump detection control device of the present invention, it is possible to detect erroneous recording by instantly detecting the occurrence of a track jump unexpectedly during recording using a track crossing signal, and reducing the recording power to the reproduction power. ,
Double recording can be prevented, and error processing and recovery processing can be realized with high reliability by reproducing the jump destination track address. Furthermore, by distinguishing the track crossing signal detected during a jumping operation in which a disk with a spiral track jumps over a track every revolution, and the crossing signal caused by the track jumping described above, Misrecording can be prevented.

Without the track jump detection control device of the present invention, a track jump cannot be detected until the track address is reproduced after the track jump occurs.
If a track jumps and crosses a track during recording, important information on the already recorded track will be destroyed, and it will also be recorded on the destination track, causing great damage to the information on the disk. According to the present invention, by utilizing the characteristics of the tracking cross signal, it is possible to detect the timing at which the optical beam jumps from the track being recorded, and the recording optical power can be instantly reduced to the reproducing power. As described above, by using the present invention, it is possible to completely prevent erroneous recording and double recording caused by unexpected track jumps, and the reliability of recorded data on optical disks can be dramatically improved. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of an optical disk equipped with a guide track, FIG. 2 is a diagram showing the optical disk and the trajectory of the light beam when the track jumps,
FIG. 3 is a block diagram of an optical recording and reproducing apparatus equipped with a track jump detection control device according to an embodiment of the present invention, FIG. 4 is a diagram showing signal waveforms of various parts when a track jump occurs, and FIG. 5 6 is a diagram illustrating the occurrence of track skipping during recording on an optical disk having a spiral guide track, and FIG. FIG. 7 is a block diagram of an optical recording/reproducing apparatus equipped with a track jump detection control device for an optical disk having a spiral guide track according to another embodiment. 1... Optical disk, 3, 4, 5, 10... Guide track, 8... Track jump section, 21...
Light source such as semiconductor laser, 26...Photodetector, 2
7... Tracking error signal, 28... Tracking/jumping control circuit, 32, 33... Positive/negative comparator, 44, 45, 55... Track jump detection signal, 50... Jumping section, 5
3,54...Jumping pulse.

Claims (1)

[Claims] 1. In an optical recording and reproducing device that records or reproduces information by focusing a laser light source on an optical disk equipped with a spiral guide track, a two-split photodetector whose dividing boundary is arranged parallel to the tangential direction of the guide track. means for receiving reflected light from an optical disk and generating a tracking error signal for applying tracking control to a spiral guide track, and for changing a laser light source to a recording power state for applying tracking control to a guide track during recording. Means for instantaneously detecting track jumps due to unexpected vibration shocks by comparing and outputting the output waveform of the tracking error signal with a comparator set to a positive threshold and a negative threshold respectively while recording information. and means for stopping the modulation of the laser light source by the recording signal during recording by the track jump detection means and changing the optical power of the laser light source from the recording state to the reproducing state; A track jump detection control device comprising: means for generating a signal indicating a one track jump section during a one track jump operation in which tracking control is applied only to the track jump, and distinguishing it from the suddenly occurring track jump.