JP2515721B2 - Optical disk device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an optical disc device capable of automatically detecting the unevenness of a guide groove provided on a disk and automatically switching the polarities of a track tracking servo. The present invention relates to an optical disk device capable of stably recording and reproducing a signal without being restricted by the unevenness of the.

[Background of the Invention]

A method for recording and reproducing information by previously providing a guide groove on a disc is described in JP-A-54-130102. In this device, the light beam in the guide groove is traced by detecting the diffraction pattern of the reflected light from the guide groove with a two-divided photodetector installed in the far feed area in the optical head, and detecting the two differential outputs as a track shift signal. The beam can be moved as, for example, by feeding back to a galvanometer mirror or a lens actuator. This track shift method is well known as a bushable method. This track deviation signal is 0 when the spot is located at the center of the track (guide groove), and + or-when the spot is displaced from the center of the track.
The servo loop is formed so that this signal is always 0. Further, since the track shift signal has different polarities with respect to the signal shift depending on the groove of the guide groove or between the grooves, and the shape of the guide groove is concave or convex, it is necessary to consider the polarity of the servo loop in each case.

This does not cause any problem when recording and reproducing the same type of disk, but if there are many types of disks used, such as between grooves and above grooves, or concave and convex, it is necessary to switch the polarity according to each case. In addition, when two types of shapes are attached as the same disk, if the wrong disk device is used, information cannot be normally recorded / reproduced.

[Object of the Invention]

The object of the present invention is to solve the above problems by automatically detecting the unevenness of the guide groove of the disk, eliminating the trouble of switching the polarity of the servo loop for each disk, and recording / reproducing due to an error in the disk device. It is to provide an optical disk device that can solve the problem of being impossible.

[Outline of Invention]

The feature of the present invention is that when the optical spot is projected from the mirror surface portion into the guide groove at the start end of the guide groove of the disc (the innermost or outermost portion of the guide groove, which is called the home position of the optical head). The polarity of the track deviation detection signal is detected, and this signal is used as the polarity switching signal of the track tracking servo loop.

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 (semiconductor laser or gas laser) becomes a parallel light flux by the coupling lens 2, passes through the polarizing prism 3, and further passes through the quarter wavelength plate 4, the galvanometer mirror 5, and the focusing lens 6 to the disk 7. It is narrowed down as a minute spot of about 1 μm. A guide groove 71 is previously formed in a concave or convex shape on the disk 7, and a light spot is located on the groove of the guide groove 71 or between the grooves to record / reproduce information. The light reflected by the disk 7 is again focused on the lens 6, the galvanometer mirror 5,
After passing through the quarter-wave plate 4, the optical path is separated by the polarization prism 3 and guided to the signal detection system. In the signal detection system, a half prism 8 separates a track shift detection system 9 on the transmission side and an automatic focus detection system 10 on the reflection side. (The autofocus system 10 is not directly related to the present invention, so the description is omitted). A two-divided detector 11 is installed in the track deviation detection system 9, receives reflected diffracted light from the guide groove, and the output thereof is a track deviation servo circuit 13 as a track deviation detection signal by a differential amplifier 12.
Be led to. The track shift servo circuit 13 performs tracking and tracking by driving the galvano mirror 5 after performing amplification and phase compensation.

Next, an example of the guide groove unevenness detection circuit 14 will be described with reference to FIG. (A) shows the circuit diagram, (b) shows the waveform of each part when the guide groove is convex, and (c) shows the waveform of each part when the guide groove is concave. First, in the case of a convex, the track shift signal TR when the beam is moved from the mirror surface portion into the guide groove at the outermost or innermost circumference of the disk is shown. In practice, since the optical head itself needs to be moved to the home position at the innermost circumference or outermost circumference of the guide groove after the disc is rotated, the track deviation signal at this movement is used. Two comparators COM1 (141), CO for the obtained track shift signal TR
M2 (142) is provided and voltage comparison is performed at comparator levels C1 and C2. The outputs A and B obtained at that time are the timing when the A pulse precedes. A, B2 signal and A + B signal C are J-
K flip 143 (eg TI SN74112) J, K, CK
Each is input as an input, and unevenness is detected. The outputs D and E of the JK flip-flop 143 are "Hi" and "Lo", respectively, when the guide groove is convex as shown in the figure. Since this level must be determined when entering the guide groove, the data latch 144 is provided after the JK flip-flop 143, and the output F of the monostable vibrator MM1 (145) and the output G of the MM2 (146) are output from the rising timing of the A + B signal C. It is generated and at this timing G, the unevenness detection levels D ′ and E ′ are determined. At the same time, the input to MM1 (145) is gated by RS flip-flop 147.

The case of concave (c) can be explained in the same manner as the case of convex (b). In the case of the concave, the track shift signal TR has a different polarity from that in the case of the convex, and the signals A and B detected by the comparators COM1 (141) and COM2 (142) are as shown in FIG. The outputs D and E of the JK flip-flop 143 are "Lo" and "Hi", contrary to the case of the convex. This level is determined in the same manner as the operation described for the convex case.

Next, the role of the unevenness detection signal in the track shift servo circuit 13 will be described with reference to FIG. The track shift signal TR passes through the amplifier 131 and the phase compensation circuit 132, and is input to the two analog switches 133. At this time, in order to switch the polarity, one is left as it is
Be entered via. In the analog switch 133, the above-mentioned unevenness detection signal levels D'and E'are applied to the respective switch control terminals. For example, when using DG201 from Siliconix as an analog switch, the level is "Lo".
Since the switch is turned on at the time of, the input is as it is in the case of convex, and the inverted input is turned on in the case of concave, and the polarities are switched between concave and convex. After that, there is further an analog switch 135, which is supplied with a control signal for turning on the track loop from the upper level, and the track deviation servo circuit 13 becomes a closed loop to start track tracking.
In addition, regarding the switching of the tracking on the groove of the guide groove and between the grooves,
It is necessary to provide the track shift servo circuit 13 with an analog switch similar to that for the unevenness detection signal and manually switch the polarity in advance.

〔The invention's effect〕

As described above, according to the present invention, it is possible to automatically detect whether the guide groove for recording / reproducing information is concave or convex. Therefore, a normal signal can be obtained regardless of whether a concave or convex disk is mounted. Recording and reproduction becomes possible. In addition, even in a disk form in which concave and convex shapes are attached to each other on both sides, it is possible to detect the front and back sides, and it is possible to determine the front and back sides. The problem of erroneous operation is eliminated, and the reliability in terms of device utilization is improved. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a view showing an example of a guide groove unevenness detecting circuit used in the present invention, and FIG. 3 is an example of a track shift servo circuit used in the present invention. It is a figure. 5 ... Galvano mirror, 6 ... Focusing lens, 7 ...
Disk, 9 ... Track deviation detection system, 11 ... Divided photodetector, 12 ... Differential amplifier, 13 ... Track deviation servo circuit, 14 ... Guide groove unevenness detection circuit.

Claims (1)

(57) [Claims] 1. An optical system for irradiating an optical spot having an approximately concentric track with a light spot, a track signal detecting means for receiving a reflected light of the light spot from the track to detect a track signal, and the track signal. A servo signal based on the servo signal and driving at least a part of the optical system based on the servo signal to move the light spot; and a track from the mirror surface portion on the outermost or innermost circumference of the optical disc. Detects the polarity of the track signal when the light spot rushes into the specified guide groove,
The control means has means for specifying whether the type of the guide groove on the optical disk surface for recording or reproducing is concave or convex based on the polarity, and the control means responds to the kind of the guide groove for the specified optical disk surface. An optical disk device, wherein a servo signal having a different polarity is formed, an optical spot follows a track based on the servo signal having a polarity corresponding to the type of the guide groove, and the optical disk surface is recorded or reproduced.