JPS63311632A - Tracking servo device for disk reproducing device - Google Patents

Abstract

PURPOSE:To produce a tracking actuator control signal to detect dust or flaw on a track and to cope with it by splitting the frequency band of a tracking error signal. CONSTITUTION:A high pass filter 16 receives a tracking error signal as an input signal, the frequency band of the signal is split to detect only the high frequency component of the tracking error signal to form an output signal caused by the effect of dust and flaw. Then a control signal generating circuit 17 outputs a control signal restoring a tracking actuator to a prescribed position for a prescribed period only when a signal is outputted from the high pass filter 16 and shields an input signal from a servo amplifier 12 while the control signal is outputted. Then the signal selection circuit 14 passes the signal when the output signal of the control signal generating circuit 11 is inputted. Thus, the presence of dust and flaw on the track is detected clearly and track jump, instability of the tracking servo circuit and switching noise caused by dust and flaw are avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a tracking servo device for a disc playback device that can set stable tracking servo control inputs.

2. Description of the Related Art Conventionally, in a tracking servo device of an information recording disk reproducing device, importance has been placed on a method of processing a tracking error signal for dust and S on a track, and a method of setting a servo loose gain.

Hereinafter, a conventional tracking servo device will be explained with reference to the drawings. FIG. 3 shows a block diagram of a conventional tracking servo device. In FIG. 3, 1 is a photodetector that detects the amount of light, 2.3.4.5 is an amplifier connected to photodetector 1, θ is a summing amplifier connected to amplifiers 4 and 6, and 8 9.1 is a level detector connected to the differential amplifier 7; 11 is a selection circuit connected to the level detector 8; 16 is a switch operated by the selection circuit 11; 12 is a servo amplifier connected by the switch 16; 9.1
0 is a low-pass filter (hereinafter referred to as a low-pass filter) attached to the differential amplifier 7, and 13 is a tracking actuator drive circuit connected to the servo amplifier 12.

The operation of the tracking servo device configured as described above will be described below.

The tracking servo device operates according to the amount of light that is incident on the light receiving areas A and B of the light that is incident on the photodetector 1 . Next, each current having a magnitude corresponding to the amount of incident light from the photodetector 1 is inputted to amplifiers 2 and 3 and converted into a voltage. The outputs of these amplifiers 2 and 3 are calculated by a differential amplifier 7, and a tracking error signal is output. When tracking without dirt or g% on the track, the switch 16 is connected to contact a;
The loop cane of the servo loop is set to the optimum value for tracking by the low-pass filter 1o and the servo amplifier 12, and is output to the tracking actuator drive circuit 13.

Next, when tracking with dust or scratches on the track, the level fluctuation of the tracking error signal of the differential amplification booklet increases. Next, when a level change is detected by the level detector 8, the selection circuit 11 connects the switch 16 to the contact point S. Then, a voltage set to increase the loop gain by the low-pass filter 9 and the servo amplifier 12 is output to the tracking actuator and drive circuit 13. Calorie calculation amplifier 6 receives the output signals of amplifiers 4 and 6 and outputs an information signal.

The problem that the invention aims to solve However, the above configuration is garbage.

The flaw is detected as the level of the output signal of the differential amplifier 7, and if the level becomes large, the 1/bell fluctuation can be reduced by increasing the servo loop gain, but the subsequent servo loop may become unstable. The problem was that it became unstable, making truck jumps and excavations more likely to occur due to dirt and unevenness. Furthermore, since the gain of the servo loop is set by a switch, there is a problem in that the servo circuit is adversely affected by switching noise.

In view of the above-mentioned problems, the present invention provides a tracking servo device for a disk reproducing device that can set a control input signal to realize a stable servo loop and prevent the adverse effects of switching noise on the servo circuit.

Means for Solving the Problems In order to achieve this object, the tracking servo device of the disc playback device of the present invention includes a high-pass filter that divides the frequency band of the tracking error signal and detects only high frequency components. , a control signal generation circuit whose input signal is the output signal of the high-pass filter, a signal selection circuit whose input signals are the output signal of the control signal generation circuit and the output signal of the servo amplifier, and the signal selected by the signal selection circuit. The structure includes a drive circuit that drives the tracking actuator based on the signal.

This configuration works by dividing the frequency band of the tracking error signal to eliminate debris on the track.

Scratches can be detected and tracking actuator control signals can be generated to address the situation.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of a tracking servo device of a disc playback device in one embodiment of the present invention. In FIG. 1, 16 is a high-pass filter (hereinafter referred to as a bypass filter), 17 is a control signal generation circuit, and 14
is a signal selection circuit. Note that 1 is a photodetector, 2, 3,
4.5 is an amplifier, e is a summing amplifier, 7 is a differential amplifier, 1
2 is a servo amplifier, and 13 is a tracking actuator drive circuit, which have the same configuration as the conventional example.

The operation of the tracking servo device configured as described above will be described below. The bypass filter 16 uses the tracking error signal as an input signal,
The frequency band of the signal is divided, and only the high frequency components of the tracking error signal caused by dust and scratches are detected and output signals. Next, the control signal generation circuit 17
Only when a signal is output from the innos filter 16,
A control signal for returning the tracking actuator to a predetermined position is output for a certain period of time, and input signals from the servo amplifier 12 are blocked during the period when the control signal is output. The signal selection circuit 14 allows the output signal of the control signal generation circuit 11 to pass while the signal is being input. Figure 2 a is
The tracking error signal waveform is shown, and FIG. 10C shows an output signal of the bypass filter 16, and FIG. 2C shows an example of the control signal. Note that the control signal is a low frequency domain signal that can be sufficiently followed by the tracking actuator.

As described above, according to this embodiment, the bypass filter 16
This makes it possible to clearly detect the presence of dirt and scratches on the track. Furthermore, the control signal generating circuit 11 can avoid track jumps caused by dust or scratches on the track, instability of the tracking servo circuit, and switching noise.

Effects of the Invention The present invention can easily detect the presence of dust and scratches on a track from a tracking error signal by providing a high-pass filter, and furthermore, by providing a control signal generation circuit and a signal selection circuit. Feedforward control is performed for a certain period of time, and the excellent effect of eliminating switching noise and instability of the tracking servo circuit such as track jumps and excavations caused by dirt on the track and fs can be obtained. It is possible to realize a tracking servo device for a disc playback device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a tracking servo device of a disc playback device according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram of the main parts of the same device, and FIG. 3 is a diagram of a tracking servo device of a conventional disc playback device. FIG. 1...Photodetector, 2...Amplifier, 3.
...Amplifier, 4...Amplifier, 6...
...Amplifier, 6...Summing amplifier, 7...
Differential amplifier, 12... Servo amplifier, 13...
...Tracking actuator drive circuit, 14.
... Signal selection QO path, 16 ...) Ibus filter, 17 ... Control signal generation circuit.

Claims (3)

[Claims] (1) A high-pass filter that divides the frequency band of a tracking error signal obtained from a track of a disk on which information is recorded and detects only high-frequency components; and an output signal of the high-pass filter that is used as an input signal. a control signal generation circuit, a signal selection circuit whose input signals are an output signal of the control signal generation circuit and an output signal of a servo amplifier, and a drive for driving a tracking actuator based on the signal selected by the signal selection circuit. A tracking servo device for a disc playback device, characterized by comprising a circuit. (2) The control signal generation circuit outputs an arbitrarily set signal for driving the tracking actuator to a desired position only when the output signal of the high-pass filter is input. A tracking servo device for a disc playback device according to scope 1. (3) The tracking servo device for a disk reproducing device according to claim 1, wherein the signal selection circuit allows the input signal to pass only when the output signal of the control signal generation circuit is input.