JPH0467698B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a disturbance information reproducing device that reproduces disturbance information in the servo of a DAD (digital audio disc) player.

[Technical background of the invention and its problems]

Conventionally, a disk scratch detection circuit as shown in FIG. 4 has been used. In other words, the RF signals, which are all the summed signals of the four-division detector, are AC-coupled by the capacitor 10 (FIG. 5A), and the waveform shaping circuit 11
to keep the amplitude offset voltage constant. One of these signals is converted into a digital signal by an EFM (eight foot modulation) signal generation circuit 12.

On the other hand, an envelope detection circuit 13 extracts the envelope signal of the RF signal as shown in FIG. 5B, and a signal comparison circuit 14 detects that the signal has fallen below a certain level, as shown in FIG. 5C. Generate timing pulse. When this timing pulse occurs, it may be due to scratches on the disk, etc.
This is when a large change appears in the envelope of the RF signal, and at this time it is better to lower the open loop gain of the DAD player's tracking servo to prevent tracking jumps from occurring due to scratches.

Therefore, a tracking error signal as shown in FIG. Tracking servo phase compensation circuit 1
9 is input. This servo phase compensation circuit 19 compensates the phase characteristics of the servo system and outputs it to the tracking actuator driver DR.

With the above circuit configuration, when the RF signal disappears due to a scratch as shown in the signal waveform in Figure 5, a timing pulse as shown in Figure 5C is generated for that time, and the open loop gain of the tracking servo is increased. lower it (Fig. 5D).

In the above method, for normal servo operation, the open loop gain of the servo is set to a property (increasing the open loop gain) that makes it difficult to cause track jumps due to vibrations, etc.

FIG. 6 shows another example of a conventional disk scratch detection circuit. In the case of Fig. 6, contrary to the case of Fig. 4, for normal servo operation, the characteristics are set so that track jumps do not easily occur due to scratches on the disk (the open loop gain is lowered), and vibrations are detected. This increases the open loop gain and makes it difficult for track jumps to occur due to vibration.

That is, the tracking error signal generated from the photodetector signal (FIG. 7A) is input to the tracking servo phase compensation circuit 21 through the amplifier 20 whose gain is reduced in normal operation.

On the other hand, the tracking error signal is also input to the signal comparison circuit 22, which detects that the tracking error signal exceeds the slice level as shown in FIG. 7A and outputs a signal as shown in FIG. 7B. The multivibrator 23 is activated to generate pulses for a certain period of time as shown in FIG. 7C. Then, while this pulse is being output, the analog switch 24 is turned on to increase the open loop gain of the tracking servo (FIG. 7D).

With the above circuit configuration, vibrations are detected as shown in the signal waveform of FIG. 7, and the gain is increased for a certain period of time to make it difficult to cause a track jump.

As mentioned above, flaws can be detected in Figure 4, but in the case of vibration, the RF signal also fluctuates as shown in Figure 7, so the open loop gain should not be lowered at this time, but detection and lower the open loop gain. This makes it easy for track jumps to occur during vibration.

In addition, vibration can be detected in Figure 6, but if the disk is scratched, the tracking error signal will also fluctuate as shown in Figure 7, so in this case too, false detection will occur and the gain will be increased. This makes it easier for truck jumps to occur. In this way, each has the drawback of malfunctioning due to vibration or scratches.

[Purpose of the invention]

This invention was made to eliminate the above-mentioned conventional drawbacks, and it controls the tracking servo to have appropriate characteristics for each disturbance without erroneously detecting scratches on the disk. To provide a disturbance information reproducing device capable of stably reproducing a disk by making track jump less likely to occur.

[Summary of the invention]

The disturbance information reproducing device of the present invention uses a first circuit to extract a recording signal recorded on the signal recording surface of a disk from a three-beam laser pickup, and also extracts low frequency components of two sub-beam signals obtained from the laser pickup. A third circuit detects sudden changes in the output signals of the first and second circuits, and only the envelope-detected signal of the recording signal among the inputs of this third circuit suddenly changes. When the change occurs, it is judged as an external vibration, and the fourth circuit controls to increase the open loop gain of the tracking servo system circuit for making the laser pickup follow the information signal on the track on the recording surface. When both inputs of the circuit suddenly change, it is determined that the disk is scratched and the gain is controlled to be lowered.

[Embodiments of the invention]

Embodiments of the disturbance information reproducing device of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment. In FIG. 1, numerals 30 and 31 are sub-beam detectors of the laser pickup, which are attached to the optical head. Further, 32 is a four-division detector, and the output of this four-division detector 32 is inputted to a waveform shaping circuit 35 via an amplifier 33 and a capacitor 34.

The output of the waveform shaping circuit 35 is sent to an EFM signal generation circuit 36, from which an EFM signal is output, and the output of the waveform shaping circuit 35 is also input to an envelope detection circuit 37. ing. The output of the envelope detection circuit 37 is input to a signal comparison circuit 38, and when the output of the envelope detection circuit 37 is below a predetermined level, the signal comparison circuit 38 outputs an output, and the output is output to the mono multivibrator 42. There is.

On the other hand, the outputs of the sub-beam detectors 30 and 31 are sent to an adder 39 and a subtracter 43, respectively. The output of the adder 39 is input to a signal comparison circuit 41 through a low-pass filter 40. The output of the signal comparison circuit 41 is compared with a predetermined level and the output of the low-pass filter 40, and when the output of the low-pass filter 40 is below a predetermined value, a pulse is generated from the signal comparison circuit 41 to reset the mono-multivibrator 42. It's becoming like that.

The output of this mono multivibrator 42 controls the opening and closing of the analog switch 46.
By opening and closing this analog switch 46, the gain of the variable gain amplifier 44 is controlled.

On the other hand, the output of the subtracter 43 is amplified by the variable gain amplifier 44 and then input to the tracking servo phase compensation circuit 45. The output of the tracking servo phase compensation circuit 45 is output to a tracking actuator driver (not shown).

Next, the operation of the disturbance information reproducing apparatus of the present invention configured as described above will be explained. All the summed signals of the 4-division detector 32 are sent to the amplifier 33.
The signal is amplified by the capacitor 34, excess DC components are removed by the capacitor 34, and the signal is input to the waveform shaping circuit 35. The signal given a constant amplitude and DC offset by the waveform shaping circuit 35 is input to the EFM generation circuit 36.
converted into a digital signal.

One of the waveform-shaped RF signals (recorded signals) (FIG. 2A) is envelope-detected by the envelope detection circuit 37, and its output is as shown in FIG. 2B, and is input to the signal comparison circuit 38. . The signal comparison circuit 38 detects that the output of the envelope detection circuit 37 is below a certain level and outputs the pulse shown in FIG. 2D. This pulse is input to the set terminal (trigger terminal) of the mono multivibrator 42. As a result, the signal is output from the mono multivibrator 42, the analog switch 46 is opened, and the gain of the variable gain amplifier 44 is lowered.

On the other hand, two sub-beam detectors 30 and 31
The signals are added by an adder 39, and high-frequency pit signal components are removed by a low-pass filter 40. A signal comparison circuit 41 detects that the output signal of the low-pass filter 40 has become below a certain level, and generates a pulse in the same manner as the signal comparison circuit 38.
This pulse is input to the reset terminal of the mono multivibrator 42 (a terminal for forcibly reducing the output of the mono multivibrator to zero).

In addition, two sub-beam detectors 30 and 31
The output of is subtracted by a subtracter 43 to produce a tracking error signal, which is input to a variable gain amplifier 44. The gain of this variable gain amplifier 44 is reduced in a normal state. This variable gain amplifier 44
The output is input to the tracking servo phase compensation circuit 45. The output of the mono multivibrator 42 is connected to an analog switch 46 to control the gain of the variable gain amplifier 44.

In this embodiment, only vibration is detected, and at this time an operation is performed to increase the open loop gain of the tracking servo. In the event of a scratch, the analog switch 46 remains off, so under normal conditions the open loop gain of the tracking servo must be lowered to create a state in which tracking jumps are less likely to occur due to scratches on the disk.

As can be seen from the signal waveform in FIG. 2, the envelope of the RF signal changes both in the case of scratches and in the case of vibration. When operated, the open loop gain of the tracking servo increases.

However, if the disc is scratched, the low frequency components of the sub-beam sum signal will fluctuate greatly.
The signal comparison circuit 41 that has detected this applies a pulse shown in FIG. 2E to the reset terminal of the mono multivibrator 42, and the mono multivibrator 42 is reset.

In this invention, the low frequency component of the sub-beam addition signal is at a certain level (total reflection level) unless the focus servo is off, and there are no large or sudden fluctuations. There is.

The time width of the output pulse of the mono-multivibrator must be such that when the laser beam spot begins to deviate from the disk track due to vibration, the servo gain is increased so that it can stably converge on the track that is about to deviate. It is.

In this way, the disturbance information reproducing device of the present invention has the following features:
Disc scratches and external vibrations are identified, and the tracking servo characteristics are switched to those appropriate for each case, allowing stable disc playback.

FIG. 3 is a block diagram showing only the essential parts of another embodiment of the invention. In the case of Fig. 3, even if the open loop gain of the servo is not lowered to make it difficult for the tracking servo to jump in the normal state due to scratches on the disk, the addition signal of the sub-beam will be lowered in the case of a scratch. If the frequency component suddenly changes, it can be detected that it is a flaw, so the mono multivibrator 42 is reset with the pulse signal output from the signal comparison circuit 41, the analog switch 49 is turned on, and the gain is adjusted using the resistors 47 and 48. It attenuates the output of the variable amplifier 44 and is connected to a tracking servo phase compensation circuit 45. The operation in the case of vibration is the same as that in the embodiment shown in FIG. 1, so a description thereof will be omitted.

〔Effect of the invention〕

As explained above, according to the disturbance information reproducing apparatus of the present invention, scratches on the disk and external vibrations are identified by monitoring both the envelope of the RF signal and the low frequency component of the summed signal of two sub-beams, and the former In the latter case, the open-loop gain of the tracking servo is lowered, and in the latter case, the open-loop gain is raised. Therefore, the tracking servo is adjusted in response to each disturbance, whether it is scratches or vibrations. It is possible to control the characteristics of the disc appropriately and play discs stably.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the disturbance information reproducing apparatus of the present invention, FIG. 2 is a signal waveform diagram of each part for explaining the operation of the above disturbance information reproducing apparatus, and FIG.
The figure is a block diagram showing only the essential parts of another embodiment of the disturbance information reproducing device of the present invention, FIG. 4 is a block diagram of a conventional disk scratch detection circuit, and FIG. 5 is a disk scratch detection circuit shown in FIG. 4. A signal waveform diagram of each part to explain the operation of the circuit. Figure 6 is a block diagram showing only the main parts of another conventional disc scratch detection circuit. Figure 7 is a diagram of the disc scratch detection circuit of Figure 6. FIG. 4 is a signal waveform diagram of each part for explaining the operation. 30, 31...Sub beam detector, 32...4
Split main beam detector, 33...amplifier, 3
4... Capacitor, 35... Waveform shaping circuit, 37... Envelope detection circuit, 38, 41... Signal comparison circuit, 39... Adder, 40... Low pass filter, 4
2...Mono multivibrator, 43...Subtractor, 4
4...Variable gain amplifier, 46, 49...Analog switch, 47, 48...Resistor.

Claims (1)

[Claims] 1. A first circuit for extracting the recorded signal from a three-beam laser pickup for optically reproducing information recorded on the signal recording surface of the disk, and a low frequency of two sub-beam signals obtained from the laser pickup. a second circuit for extracting the component; a circuit capable of varying the open loop gain of a tracking servo system circuit for causing the laser pickup to follow the information signal on the track of the recording surface; A third circuit detects a sudden change in the output signal of the circuit, and when only the envelope-detected signal of the recording signal among the inputs of this third circuit changes suddenly, it is determined to be external vibration and the above-mentioned vibration is detected. A fourth circuit controls to increase the gain of the gain variable circuit, and determines that there is a scratch on the disk when both of the inputs of the third circuit suddenly change, and controls the gain to decrease. Disturbance information reproducing device.