JPH0548537B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical digital disk player, which has particularly good vibration resistance and prevents scratches on the disk.
This invention relates to a focusing or tracking servo circuit that is less likely to malfunction due to dust.

Conventional configuration and its problems The biggest problem when an optical digital disk player is installed in a vehicle is vibration resistance. In principle, vibration resistance can be improved by increasing the gains of the tracking servo and focus servo servo circuits, but as a result, tracking jumps or loss of focus due to scratches or dust on the disk become more likely to occur.

As a way to solve this problem, the frequency components of the focus error signal or tracking error signal due to vibrations are mostly low frequency components (100Hz or less), whereas the frequency components of the focus error signal or tracking error signal due to scratches or dirt on the disk, etc. Focusing on the fact that there are many high frequency components (above 1KHz), we extracted the low frequency components in the error signal.
The magnitude of the vibration can be determined by the magnitude of this level.
When the level is low, the vibration is assumed to be small, and the gain of the servo circuit is reduced to reduce interference with the servo circuit due to scratches and dirt on the disk, and as the level increases, the vibration is assumed to be large. One possible method is to increase the gain of the servo circuit to withstand the problem.

However, with this method, the frequency components of tracking or focus error signals due to disk eccentricity or surface runout are also low frequency components (100Hz or less).
Since there are many problems, there is a problem in that even if the low frequency component is simply extracted, it is not possible to distinguish whether it is caused by vibration or eccentric surface runout of the disk.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and provide a servo circuit for a digital disk player that is capable of achieving both vibration resistance, scratch resistance, and dust resistance.

Structure of the Invention In order to achieve the above object, a servo circuit for a digital disk player of the present invention includes an error signal generation means for generating a tracking error signal and a focus error signal, and a means for extracting a low frequency component from the error signal. , a delay means for delaying the extracted low frequency component by the time required for one rotation of the disk, means for taking the difference between the input signal and the output signal of the delay means, and a gain control signal corresponding to the difference level from the means for taking the difference. and an amplifying means for amplifying the output of the error signal generating means, the amplification gain of which is controlled by a gain control signal,
The low frequency component of the error signal component is input to the delay circuit, and the difference between the output and the output of the delay circuit delayed by the time equivalent to one rotation of the disk is taken, and the gain is controlled according to this difference signal level, and the vibration When the vibration is small, the servo gain is lowered to the extent necessary to withstand the vibration, and as the vibration increases, the servo gain is lowered to the extent necessary to withstand the vibration. The servo gain can be increased up to a certain level, and it is resistant to scratches and dirt.

DESCRIPTION OF THE EMBODIMENTS A case where the present invention is applied to a tracking servo circuit will be described below using FIG. 1 as an example.

In the figure, 1 is an optical pickup;
A is an optical detector located in the optical pickup 1 and detects the reflected light from the disk of the laser beam emitted from the optical pickup 1, and 1B is a tracking device located in the optical pickup 1 that controls tracking of the laser beam emitted from the optical pickup 1. actuator coil for

2 is a tracking error signal generation circuit that generates a tracking error signal from the output of the optical detector 1A, 3 is a phase correction circuit that performs phase correction so that the operation of the entire tracking loop 9 is stable, and 4 is a phase correction circuit. This is a variable gain amplifier that amplifies the output signal of the circuit 3 and outputs a drive signal for the tracking actuator coil 1B, and its gain is controlled by the output of a gain control signal generation circuit 8, which will be described later. 5 is a low-pass filter for extracting low-frequency components from the output signal of the phase correction circuit 3; 6 is a delay circuit that delays the output of the low-pass filter 5 by a time corresponding to one rotation of the disk; 7 is a low-pass filter. A difference circuit 8 takes the difference between the output of 5 and the output of the delay circuit 6, and 8 is a gain control signal generation circuit that corresponds to the output level of the difference circuit 7 and outputs a gain control signal for controlling the gain of the amplifier 4. .

In the above configuration, the error signal component due to disk eccentricity is removed from the output of the difference circuit 7, and therefore the gain control signal generation circuit is provided with a signal corresponding to the magnitude of the tracking error signal mainly due to vibration (vibration magnitude). Since a signal is input, the variable gain of the amplifier 4, in other words, the loop gain, can be controlled with a gain corresponding to the magnitude of vibration.

Effects of the Invention As is clear from the above explanation, according to the present invention, it is possible to control the servo circuit gain in accordance with the magnitude of vibration while eliminating the effects of disk eccentricity and surface runout, and as a result, The loop gain is normally controlled to a level that is not easily affected by scratches or dust on the disk, and only when vibration is added.
It is possible to provide a servo circuit that can control the gain necessary to withstand applied vibrations, is resistant to scratches and dirt on the disk, and has good vibration resistance.
Effective for portability.

[Brief explanation of drawings]

The figure is a block diagram of a servo circuit of a digital disk player showing an embodiment of the present invention. 1... Optical pickup, 1A... Optical detector, 1B... Tracking actuator coil, 2... Tracking error signal generation circuit, 3
... Phase correction circuit, 4 ... Amplifier, 5 ... Low-pass filter, 6 ... Delay circuit, 7 ... Parallel circuit, 8 ...
Gain control signal generation circuit.

Claims (1)

[Claims] 1. In a digital disk player that reads out signals by irradiating a light beam onto a disk on which digital signals are recorded, an error signal generation means for generating a tracking error signal and a focus error signal, and a low frequency signal from among the error signals. a means for extracting a component, a delay means for delaying the extracted low frequency component by the time required for one rotation of a disk, a means for taking a difference between an input signal and an output signal of the delay means, and a means for taking the difference. A servo for a digital disk player, comprising means for outputting a gain control signal corresponding to a difference level, and an amplification means for amplifying the output of the error signal generation means, the amplification gain of which is controlled by the gain control signal. circuit.