JPH0711870B2 - Optical information recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus such as an optical disk device, and more particularly to an amplitude fluctuation of a track deviation detection signal due to recording pits in a write-once optical disk and a cross track system. The present invention relates to an optical information recording / reproducing device suitable for preventing deterioration of a group signal in an adopted access system.

[Background of the Invention]

An apparatus for providing a guide groove on a recording disk in advance and recording / reproducing information along the guide groove is disclosed in Japanese Patent Laid-Open No. 54-130102.
It is described in. In this device, the light beam in the guide groove is traced by detecting a reflection diffraction pattern from the guide groove with a two-divided photodetector, and the differential output thereof can be used as a track deviation detection signal to move the light beam, for example, a galvanometer mirror or This is done by feeding back to the lens actuator. This method is well known as the Push-Pull method, but when recording or reproducing information by thermally forming a hole in the recording film, the information signal reproduced in the track deviation detection signal during reproduction. , And the frequency band of the track deviation detection circuit is lower by about two digits compared to the frequency band of the information signal, the information signal components are in an averaged form, and as a result, the amplitude of the track deviation detection signal decreases. Become. In this case, the track tracking becomes unstable, and as a method for preventing this, there is a method for preventing the track deviation detection signal from being lowered due to a hole recorded by using a peak hold circuit as described in Japanese Patent Application No. 56-138583. However, in recent years, there is a tendency to reduce the recording pit interval for higher density, and in this case, the information signal has an optical frequency characteristic. However, there is a problem that the track shift detection signal is lowered due to the decrease of the level.

Further, as an access method, there is a cross track counting method in which track tracking is performed by counting the number of guide grooves that pass while moving the optical head. For details, see Japanese Patent Application
As described in JP-A-56-187869, even in this case, if the information signal has an optical frequency characteristic, the guide groove level changes when the optical head moves, and a track count error occurs. In particular, when information is recorded between guide grooves, which is referred to as inter-groove recording described in Japanese Patent Application No. 59-133156, the level between guide grooves is close to other guide grooves due to frequency deterioration of the information signal. There is a problem that it may fluctuate and a large track count error occurs.

[Object of the Invention]

An object of the present invention is to provide an emphasis circuit in order to correct a decrease due to frequency characteristics of information signals mixed in the track deviation detection circuit, to reduce the track deviation detection signal and guide groove level at the time of cross track counting. An object of the present invention is to provide an optical information recording / reproducing apparatus capable of eliminating fluctuations and stably recording and reproducing information.

[Outline of Invention]

In the optical information recording / reproducing apparatus of the present invention, when a write-once optical disc that thermally records information by using a laser beam is used, a track deviation detection signal and a cross track count time are detected depending on frequency characteristics of mixed information signals. In order to prevent the fluctuation of the guide groove level, an emphasis circuit for correcting the frequency characteristic is provided.

Example of Invention

The first embodiment of the present invention will be described below with reference to FIG.
The light emitted from the laser light source 1 passes through the coupling lens 2, the polarizing prism 3, the 1/4 wavelength plate 4 and the galvano mirror 5, and is narrowed down on the disk 7 by the narrowing lens 6 as a minute spot of about 1 μm. A guide groove 71 is previously formed on the disk 7, and the spot is located on the groove of the guide groove 71 or between the grooves to record / reproduce information. The disk 7 is a write-once optical disk, and information is recorded by making holes in the recording film by a high-power laser beam. The light reflected by the disc 7 is a focusing lens 6, a galvanometer mirror
In the signal detection system in which the optical path is separated by the polarization prism 3 through the 5,1 / 4 wavelength plate 4 and guided to the signal detection system, the beam splitter 8 is used to detect the defocus on the reflection side and the track deviation detection system for the transmission example. Is separated into The defocus detection system is composed of a convex lens 9, a knife edge 10 and a photodetector 11, but since it is not directly related to the present invention, its explanation is omitted. The track shift detection system is composed of a convex lens 12 which is a rotation target and a two-division photodetector 13.The sum signal of the two signals of the two-division photodetector 13 is for information signal detection, and its differential output is The track deviation detection signal is introduced to the track deviation detection circuit 14 and the drive circuit 15 (including the phase compensation circuit), and the galvano mirror 5 is activated to track the track.

Next, an example of the track shift detection circuit 14 will be described with reference to FIG. A circuit 141 for the output from the element 131 and a circuit 142 for the output from the element 132 of the two-split photodetector 13.
Are completely the same, the case of the circuit 141 will be described here. The output from the element 131 is subjected to current-voltage conversion by the resistor 21, then cut by direct current (DC) by the low-pass amplifier 22 and the capacitor 23, and applied to the high-pass amplifier 25 having the feedback resistor 24. The output of the high frequency amplifier 25 is processed through the emphasis circuit 26 and the peak hold circuit 27, and then processed by the low frequency amplifier.
The sum from the output from 22 is added by the adder 28, effectively acting as a direct current (DC) amplifier having a high band. Circuit
The outputs of 141 and the circuit 142 are differentiated by the differential amplifier 29 to become a track shift detection signal. The effects of the emphasis circuit and the peak hold circuit will be described with reference to FIG. (A) is a light spot on the disk 7 and a guide groove 71.
(B) shows the waveforms in the circuits 141 and 142 when information is recorded between the grooves, and (c) shows the waveform relating to the output of the differential amplifier 29. Further, in the waveform, the left side (I) is the case where there is no signal deterioration due to frequency characteristics in the mixed information signals, and the right side (II) is the case where there is signal deterioration due to the frequency characteristics. First, in the case of (I), the emphasis circuit is not required and the peak hold circuit is required. If there is no peak hold circuit, the waveform is as shown by the broken line, so the guide groove level fluctuates in (b), and (c)
Then, the amplitude of the track deviation detection signal decreases.
However, the problem described above can be solved by using the peak hold circuit described in Japanese Patent Application No. 56-138583. However, if there is deterioration due to frequency characteristics as in (II), fluctuations in the guide groove level and a decrease in track deviation detection signal amplitude occur as shown by the broken line even if there is a peak hold circuit. In the present invention, an emphasis circuit is provided to solve this problem. As the configuration of the emphasis circuit, (a) phase advance circuit and (b) cosine equalization circuit as shown in FIG. 4 can be used. In particular, in (b), since the frequency characteristics of the inner and outer circumferences of the optical disc are largely different, the gain of the inner and outer circumferences can be changed by using the track address to correct it, and the emphasis amount can be optimized. FIG. 5 shows the relationship between the optical frequency characteristic of the optical head and the frequency characteristic of the emphasis circuit. The frequency of the information signal (for example, when the 2-7 modulation method is adopted, if the bit frequency is fb, fb / 1.5 to fb /
The gain and rise frequency of the emphasis circuit (in this example, fo /
6) is set. When such an emphasis circuit is used, the amplitude decrease due to the frequency characteristic of the information signal in FIG. 3 (II) is corrected, so that the fluctuation of the guide groove level and the track deviation detection signal amplitude decrease as shown by the thick solid line. It can be prevented and stable track tracking can be performed.

FIG. 6 shows a case where the present invention is applied to a mirror surface offset method described in Japanese Patent Application No. 57-125702, in which the offset generated in the track deviation detection signal due to the inclination of the disk is corrected by the mirror surface portion provided in the guide groove. Show. The basic structure is the second
Although the same as the figure, the level of the mirror surface portion showing the information of the disc tilt appearing in the track deviation detection signal is obtained by using the output after the peak hold circuit on the high frequency amplifier side.
Both outputs on the second side are differentially detected by the differential amplifier 30.
After that, the sample hold circuit 31 detects only the mirror surface level by using the timing signal for detecting the mirror surface portion made from the information signal, and the output from the differential amplifier 29 for the track deviation detection signal and the sample hold circuit 31 After the gain of the output is adjusted, the differential amplifier 32 operates to obtain a track deviation detection signal in which the offset due to the disc tilt is corrected.

FIG. 7 shows a case where the present invention is applied to the cross track counting method described in Japanese Patent Application No. 56-187869. In this case as well, the basic configuration is the same as in FIG. 2, but the guide groove level signal used for direction discrimination uses the output of the circuits 141 and 142 added by the adder 33. As described with reference to FIG. 3, this signal causes a change in the guide groove level signal when the mixed information signal is deteriorated due to the frequency characteristic, and in particular, during groove recording, the fluctuation becomes large and a cross track count error occurs. It causes problems such as However, since the guide groove level signal is stabilized by adopting the emphasis circuit of the present invention for the deterioration of the information signal due to the frequency characteristic, it is possible to perform the access by the stable cross track count method.

In the above explanation, two low-pass amplifiers and two high-pass amplifiers are used as amplifiers of the track deviation detection circuit, and the cut-off frequency fc ₁ of the low-pass amplifier and the low-pass cut-off frequency fc ₂ of the high-pass amplifier are assumed to be the same, and the apparent high band Although the case where the amplifier is used as a DC amplifier has been described, it goes without saying that the effect is the same even if one high band direct current (DC) amplifier is used. Also,
The push-pull method has been described as the track deviation detection method, but the same effect can be obtained with other methods (for example, the 3-spot method), and the same can be applied to the recording / reproducing apparatus and the reproduction-only apparatus. It should be noted that the read-only device adopting the 3-spot method may have a configuration in which a high frequency amplifier, an emphasis circuit and a peak hold circuit are combined.

〔The invention's effect〕

As described above, according to the present invention, stable track tracking and optical head access can be achieved by correcting the signal drop due to the frequency characteristic of the information signal mixed in the track deviation detection signal by using the emphasis circuit. Is possible.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the first embodiment of the present invention, FIG. 2 is a diagram for explaining a track deviation detection circuit, FIG. 3 is a diagram for explaining the effect of the emphasis circuit, and FIG. 4 is for the emphasis circuit. FIG. 5 is a diagram illustrating a configuration example, FIG. 5 is a diagram illustrating a relationship between frequency characteristics of an optical head and an emphasis circuit, FIG. 6 is a diagram illustrating a second embodiment of the present invention, and FIG. 7 is a diagram illustrating the present invention. It is a figure explaining a 3rd Example. 13 …… Two-division photodetector, 14 …… Track shift detection circuit,
26 …… Emphasis circuit, 27 …… Peak hold circuit,
29 …… Operating amplifier, 31 …… Sample and hold circuit.

Claims (4)

[Claims] 1. A laser light source, an optical means for guiding a light beam emitted from the laser light source onto a disk, a detecting means for detecting a light beam reflected from the disk, and the disk based on an output from the detecting means. In an optical information recording / reproducing apparatus for recording or reproducing information on the disc while tracing the upper track, the track deviation detection circuit for processing the track deviation detection signal based on the output of the detecting means detects the above-mentioned detection. An optical information recording / reproducing apparatus comprising: an emphasis circuit that corrects the deterioration of the frequency characteristic of the output from the means, and a peak hold circuit that detects the envelope of the output signal from the emphasis circuit. 2. The track deviation detection circuit has a low-frequency amplifier and a high-frequency amplifier, and an output obtained by processing the output of the high-frequency amplifier with the emphasis circuit and the peak hold circuit, The optical information recording / reproducing apparatus according to claim 1, further comprising means for adding the output obtained from the low-pass amplifier. 3. The optical information recording / reproducing apparatus according to claim 1 or 2, wherein the emphasis circuit is a circuit for advancing a phase. 4. The optical information recording / reproducing apparatus according to claim 1 or 2, wherein the emphasis circuit is a cosine equivalent circuit.