JPS58215767A - Tracking servo control device for disc playback device - Google Patents

Abstract

PURPOSE:To control the gain of a tracking circuit stably and surely, by detecting address information in an information track being read on a recording medium and correcting the level of a tracking error signal according to the detected address information. CONSTITUTION:The tracking error signal from a disc shaped recording medium is detected by inputting an output of a photodiode 1 to a differential amplifier 2. Then, an output through a phase compensating circuit 4 and an amplifier 5 via a gain control circuit 3 and an output of a zero cross detector 10 and a jump pulse generator 11 are summed 7 and applied to a tracking mirror drive coil 9. Further, an address signal demodulated at an FM demodulating circuit 13 via a preamplifier 12 and inserted in the vertical blanking period of a video signal at an address code extracting circuit 14 is extracted and demodulated at a demodulating circuit 15. The demodulated data is inputted to a microcomputer 16, which discriminates the disc and controls the special reproduction. In this way, the tracking circuit is gain controlled stably and surely.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking control device for information reading means in a disc playback device such as a video disc player, and more particularly to gain adjustment of a tracking servo system on the inner and outer peripheries of a disc.

As an example of a method for recording information on a video disc, depressions called pits are arranged on the disc surface to form concentric or spiral tracks, and information is recorded based on the length and spacing of these pits. There is something.

To read information from a disc, for example, a light reading means (
This is done by demodulating reflected light or transmitted light from the recording surface, which is modulated depending on the presence or absence of pits on the disc. In this information recording disk reading device, a so-called tracking servo control device is provided to control the rotation of a deflection tracking mirror so that the irradiated light accurately tracks the information track on the disk.

FIG. 1 is a circuit diagram showing a conventional tracking support control device for a disc playback device.

In the figure, %1 is a photodiode, 2 is a differential amplifier, 6 is a gain control circuit, 4 is a phase compensation circuit, 5 is an amplifier circuit, 6 is a tracking on/off switch, 7 is an adder circuit, 8 is a drive circuit, 9 is a mirror drive coil, 10 is a zero cross detector, and 11 is a jump pulse generator.

Next, the operation will be explained. Of the six beams (0th order light, ±1st order light) separated by a diffraction grating (not shown), the spots on both sides (±1st order) are received by the tracking detection pattern of photodiode 1, and this signal is The signal is input to the dynamic amplifier 2.

The tracking error signal obtained here is the gain control circuit 3
1 phase compensation circuit 4, amplifier 5, addition circuit 7, drive circuit 8
The signal is applied to the tracking mirror drive coil 9 through the signal, and the deflection angle of the tracking mirror (not shown) is controlled so that the tracking error signal becomes zero.

The tracking error signal obtained by the differential amplifier 2 is
Generally, the output level differs between the inner and outer circumferences of the disk, as shown in FIG. 2, due to the degree of modulation and the mechanical off-center position during movement of the reading means (pickup). The gain control circuit 3 is
This level fluctuation is only to be corrected, and conventionally, gain control has been performed by detecting it with a reproduction position tii'v microswitch of the reading means (pickup) or a variable resistance element that moves in conjunction with the reading means. However, this method has problems in that it is not possible to finely adjust the gain, and that the mechanical system is complex and the cost is high.

The purpose of the present invention is to solve the above-mentioned drawbacks of the prior art.
An object of the present invention is to provide a device which stably and reliably performs gain control of a tracking control device with a simple configuration without using a mechanical system.

In the present invention, the reproduction position t of the reading means is detected from the address signal inserted in each vertical retrace period of the video signal,
A method was adopted in which this signal was used to control the gain of the tracking control device.

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

FIG. 4 is a block diagram showing one embodiment of the present invention. In this figure, parts having the same functions as those in FIG. 1 are labeled with the same number. In addition, 12 is a preamplifier circuit,
16 is an FM demodulation circuit, 14 is a code extraction circuit, and 15 is a code demodulation circuit.

16 is a micro-comb router.

Next, the operation will be explained. The main spot (0th order light) is received by the signal detection pattern of the photodiode 1, amplified by the preamplifier 12, and demodulated by the FM demodulation circuit 13. Although not shown here, the main spot is received by the signal processing circuit and The address code is input to the address code extraction circuit 14. The address code extraction circuit 14 extracts only the address signal A inserted within the vertical retrace period of the video signal shown in FIG. 3, and the demodulation circuit 15 demodulates it. The demodulated data is input to a microcomputer 16 that controls the entire video disc player, and the micro combiator 16 determines the format and controls special playback based on this data.

When controlling the gain of the tracking control circuit by dividing the playback range from the innermost circumference to the outermost circumference of the disk into eight parts, for example, 3-bit information is sufficient as a control signal, and this 3-bit signal The signal is input from the microcombiner 16 to the D/A converter 17. Gain control circuit 3 is controlled by the output of this D/A converter 17. For example, for a CAV disk with a constant rotation speed, the address information is 5.
Track numbers up to 4000 are recorded, but from 0 to
6750) To the rack (000)we6751~1
3500) up to the rack (001), and 6750)
Bits are switched for each rack. On the other hand, C with constant linear velocity
On LV discs, the playback time is recorded as address information, 0 to 7 minutes is (ODD)z, 8 minutes to 1
For up to 5 minutes, the bits should be changed from (001)1 to approximately every 7 minutes.

As explained above, according to the present invention, a tracking circuit can be stably and reliably achieved by using the address signal conventionally used for disc discrimination or special playback, and with a simple configuration that only requires a D/A converter. gain control becomes possible.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a conventional tracking servo control device for a disc playback device, Fig. 2 is a graph showing the relationship between the playback position on the disc and the tracking error output, and Fig. 3 is a graph showing the relationship between the playback position on the disc and the tracking error output. FIG. 4 is an explanatory diagram showing the address signal insertion position *V, and FIG. 4 is a four-dimensional diagram showing an embodiment of the present invention. Code explanation 1: Photodiode 2: Differential amplifier 3: Gain control circuit 9: Mirror drive coil 10: Zero cross detector 11: Jump pulse generator 6: Tracking on/off switch 17: D/A converter 8 people Patent Attorney 1 Thin 1) Wa・In”-Sachi A No. 2 Zuama 3 Enku 廿Se

Claims (1)

[Claims] 1. Tracking error detection means of the information reading means for reading information from a disk-shaped recording medium; a gain control circuit for correcting the level of the detected tracking error signal; and a gain control circuit for correcting the level of the detected tracking error signal; A tracking servo control device for a disk reproducing device comprising a tracking control means for controlling tracking of an information reading means, a means for detecting address information in an information track being read by the information reading means on the recording medium; A tracking servo control device for a disk reproducing device, comprising means for adjusting the gain of the gain control circuit according to detected address information.