JPH0582667B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a pick-up return device, which is particularly useful for quickly returning a pick-up to a jump starting position when a track jump occurs in a compact disk device (CD device) or the like. Regarding a pick-up recovery device that can be used.

<Prior Art> In a CD device, it is necessary to correctly position the beam spot on a track with a pitch of 1.6 μm, and to move the spot correctly on the track in accordance with the rotation of the disk. The positioning accuracy must be controlled to within ±0.1 μm, and it must be possible to correct position errors up to ±70 μm. For this reason, the CD device is equipped with a tracking servo mechanism, which generates a tracking signal having a voltage value according to the deviation between the spot position and the track, and performs servo control using the tracking signal to track the beam spot. The spot is positioned directly above the disk, and the spot is moved in accordance with the rotation of the disk to accurately track the track.

By the way, car-mounted CD devices are subject to the vibrations of the car. Therefore, the vibration may cause the pickup to jump over several tracks. When such a track jump occurs, if no action is taken, the play will be restarted from the place where the track jump occurred, resulting in skipping and causing discomfort to the listener.

Conventionally, such truck jumps are detected and the pickup is returned to the position where the jump occurred.

That is, conventionally, time information (total elapsed time) obtained from subcode information is monitored, discontinuity in the elapsed time is detected to detect the occurrence of a track jump, and the time information at the jump start position is then detected. This is used to return the pickup to the jump starting position.

<Problems to be Solved by the Invention> However, in such conventional examples, discontinuity in time information is detected after a track jump occurs.
There is a problem in that the detection of a track jump is delayed, and moreover, it takes time for processing to recover using the time information of the subcode, and the time during which the sound stops becomes longer.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pickup return device that can quickly detect a truck jump and return the pickup to the truck jump starting position in a short period of time.

<Means for solving the problem> Fig. 1 includes the pick-up return device of the present invention.
FIG. 2 is a block diagram of main parts of a CD device.

1 is a compact disk, 2 is a pick-up,
4 is a signal processing circuit, 5 is a tracking servo circuit, 6 is a pick-up feed circuit, 7 is a feed motor, 8 is a rotation speed control section, 9 is a spindle motor, 21 is an envelope detection section, 22 is a tracking jump detection section, 23 is a tracking counter,
24 is a flaw detection circuit.

<Operation> When a tracking jump occurs, the amount of change in the envelope of the RF signal RFS output from the pickup 2 exceeds a predetermined level, and moreover, the tracking error signal TRE crosses the predetermined level.

Therefore, in the present invention, the envelope waveform of the output signal (RF signal) of the pickup 2 is detected and outputted by the envelope detection circuit 21, and the envelope waveform signal is detected and outputted by the truck jump detection section 22.
The amount of change in RFS has exceeded a predetermined level,
The occurrence of a track jump is detected when the tracking error signal TRE crosses a predetermined level, and one track jump pulse TJP is generated each time one track is jumped.

The tracking counter 23 counts the track jump pulse TJP and calculates the number N of tracks that have jumped.
monitor.

After the track jump is completed, the signal processing circuit 4 inputs a number of kick pulses equal to the count value of the tracking counter 23 as the sending signal PSS to the pickup sending circuit 6 to return the pickup to the jump starting position.

In addition, if the track jump occurs due to scratches on the disk, if you return it to the same location, the track jump will occur again due to the scratch.
Return the pickup to a track position one track outside the jump start track.

<Embodiment> FIG. 1 is a block diagram of the main parts of a CD device including a pickup recovery device according to the present invention.

1 is a compact disk, 2 is a pick-up,
3 is a waveform processing circuit, 4 is a signal processing circuit, 5 is a tracking servo circuit, 6 is a pick-up feed circuit, 7 is a feed motor, 8 is a rotational speed control section, 9 is a spindle motor, 10 is an operation panel, and 11 is a display. 12 is a DA converter, 13 is an audio circuit, 14 is an RF amplifier, 21 is an envelope detection circuit, 22 is a tracking jump detection section, 23 is a tracking counter, and 24 is a scratch detection circuit.

The tracking servo circuit 5 includes a tracking error calculation circuit 5a, a tracking phase correction circuit 5b, and a tracking actuator drive circuit 5c.

The track jump detection section 22 has a waveform shaping circuit 22a, a zero cross detection circuit 22b, an AND gate 22c, and a jump direction detection circuit 22d.

As shown in FIG. 2, the scratch detection circuit 24 includes a peak hold circuit 24a that detects and holds the peak value of the envelope waveform signal RFE output from the envelope detection circuit 21, and a threshold that sets a predetermined threshold level. It has a threshold level setting section 24b and a comparator 24c that generates a flaw signal IJS when the peak value exceeds the threshold level.

Acoustic signals are digitally recorded on the compact disc 1, and control data called frame synchronization signals and subcoding are recorded for each predetermined number of data.

Pickup 2 optically reads the digital information recorded on compact disc 1.
The signal is input to the waveform processing circuit 3 via the RF amplifier 14. The waveform processing circuit 3 amplifies the RF signal output from the RF amplifier 14, shapes the waveform at a predetermined slice level, and inputs the signal obtained by waveform shaping (referred to as an EFM signal) to the signal processing circuit 4.

The signal processing circuit 4 demodulates the EFM signal and
After separating the audio data and sub-coding and subjecting the audio data to error detection/correction processing, the DA converter 12 performs DA conversion and outputs the audio data to the audio circuit 13.
Output to. Further, the signal processing circuit 4 analyzes the Q channel of the sub-coding, extracts data indicating the current song number, elapsed time for each song, total elapsed time, etc., and displays it on the display device 11 as appropriate. Random access processing is performed based on information input from the operation panel 10.

The tracking servo circuit 5 includes a tracking error signal calculation circuit 5a, a tracking phase correction circuit 5b, and a tracking actuator drive circuit 5c, and uses the detection signal derived from the pickup 2 to generate a tracking error signal. The laser beam is generated and the tracking actuator TAC is driven to move the objective lens OBL in the horizontal direction and control the laser beam spot to be at the center of the pit. That is, the output current from the pin photodiode read out by the pickup 2 is calculated by the tracking error signal calculation circuit 5a.
It is converted and further calculated to become the tracking error signal TRE. Thereafter, the tracking phase correction circuit 5b performs phase correction in accordance with the characteristics of the tracking actuator of the pickup 2.
Based on the phase-corrected signal, the tracking actuator drive circuit 5c drives the tracking actuator TAC to position the beam spot on the track.

The pick-up feed circuit 6 is used by the signal processing circuit 6 when positioning the pick-up 2 at a predetermined target position (access position) or when moving the pick-up 2 to follow a track during performance.
The feed motor 7 is rotated based on the feed signal PSS and the tracking error signal TRE' given from the controller.

The CLV circuit 8a of the rotational speed control section 8 generates an EFM signal and a crystal oscillator built in the signal processing circuit 4.
A drive signal for rotating the spindle motor 9 at a constant linear velocity is generated using the 4.3218 MHz clock signal CLS, and the drive circuit 8b rotates the spindle motor 9 based on the drive signal.

The envelope detection circuit 21 detects and outputs an envelope waveform signal RFE corresponding to the envelope waveform of the RF signal (RFS) output from the RF amplifier 14.

The tracking jump detection section 22 detects that a tracking jump has occurred when the amount of change in the envelope waveform signal RFE exceeds a predetermined level and the tracking error signal TRE crosses zero.

That is, the envelope waveform signal RFE is sliced at a predetermined level in the waveform shaping circuit 22a,
When the envelope waveform signal RFE is at a predetermined level or higher, a high level (“1”) signal EV is output.
On the other hand, the zero cross detection circuit 22b is composed of a comparator with hysteresis (window comparator), and as shown in _FIG . 1”),
When the threshold level S _L on the L side becomes lower than that, a signal ZCR that becomes low level (="0") is output. AND gate 22c is waveform shaping circuit 22a
When a high level signal EV is output from
High level signal from zero cross detection circuit 22b
If ZCR occurs, it is assumed that a truck jump has occurred and a truck jump pulse TJP is output.

Now, in an ideal state where there is no scratch on the disk and no vibration, the signal EV and the signal ZCR are both at low level ("0") as shown in Figure 4 A to F, and the track jump pulse TJP is Of course, this does not occur.

On the other hand, if pickup 2 causes a track jump due to scratches on the disk or large vibrations, the envelope waveform signal RFE changes to
As shown in the figure, an alternating waveform whose period is the time of crossing one track is shown. The tracking error signal TRE also has an alternating waveform whose phase leads or lags the envelope waveform signal RFE by π/2.
Therefore, every time a track jump occurs, the envelope waveform signal RFE changes by more than a predetermined level.
In addition, since the tracking error signal crosses zero, one tracking jump pulse TJP is generated for each tracking jump. Thereby, even during a truck jump, the truck jump can be detected quickly and reliably.

Track jump pulses TJP generated from the track jump detector 22 are counted by a tracking counter 23. Note that the count value N is equal to the number of tracks jumped by the pick-up.

The envelope waveform signal RFE output from the envelope detection circuit 21 is input to the track jump detection section 22 and also input to the scratch detection circuit 24 to detect scratches on the track. That is, when a scratch on the track is detected, the scratch detection circuit 24 outputs a high level scratch signal IJS.

A processor built into the signal processing circuit 4 reads the count value N and the scratch signal IJS from the tracking counter 23 and the scratch detection circuit 24, respectively.

Then, the scratch signal IJS is at low level (="0")
If so, it is assumed that the track jump is caused by vibration rather than a scratch on the disk, and the count value N is
A number of kick pulses equal to PSS are input to the pick-up sending circuit 6 as sending pulses PSS to perform pick-up 2, jump in the N track, jump start direction, and return to the jump start position.

On the other hand, if the scratch signal IJS is at a high level (="1"), it is determined that the track jump is caused by a scratch on the disk.

Now, if a truck jump occurs due to a scratch, when the pickup is returned to the same location, the truck jump may occur again due to the scratch. Therefore, when a track jump occurs in the outer circumferential direction due to a scratch, the number of tracks that is one less than the count value N, that is, (N-1) tracks, is jumped, and the track position is one track outside the jump start track. Restore Pickup.

In addition, when the track jumps inward due to a scratch, the number of tracks that is one more than the count value N, that is, (N+1) tracks, is jumped, and the pick-up is returned to a track position that is one track outside of the jump start track. .

Note that whether the signal has jumped outward or inward can be determined by monitoring the phases of the envelope waveform signal RFE and the tracking error signal TRE (by monitoring which one is the leading phase). Therefore, the jump direction detection circuit 22d of the track jump detection section 22 is configured to identify the jump direction and input the jump direction signal JDS to the signal processing circuit 4.

Although described in detail above, the present invention is not limited to the embodiments and can be modified in various ways within the scope of the claims. It may be configured as follows.

<Effects of the Invention> As described above, according to the present invention, a track jump can be detected even during a jump, and the number of tracks jumped can be recognized, so that it is only necessary to return the pick-up to the start direction of the jump of that number immediately after the jump ends. The time it takes to return to the original location can be shortened, and the time when no sound is produced can be shortened.

In the case of a track jump due to a scratch, by configuring the pickup to return to a track one track outside the jump start track, it is possible to prevent a track jump from occurring again due to the same scratch.

[Brief explanation of the drawing]

FIG. 1 includes the pick-up return device of the present invention.
A block diagram of the main parts of the CD device, Fig. 2 is a block diagram of the scratch detection circuit, Fig. 3 is a waveform diagram explaining the operation of the zero-cross detection circuit, Fig. 4 is a waveform diagram of each part in an ideal state, and Fig. 5 is a track diagram. FIG. 3 is a waveform diagram of various parts during jump. 1...Compact disk, 2...Pickup, 4...Signal processing circuit, 5...Tracking servo circuit, 6...Pickup feed circuit, 7...
Feed motor, 21... Envelope detection circuit, 2
2...Track jump detection section, 22a...Waveform shaping circuits 22a, 22b...Zero cross detection circuit, 22d...Jump direction detection circuit, 23...
Tracking counter, 24...flaw detection circuit.

Claims (1)

[Scope of Claims] 1. A pick-up that reads digitally recorded signals from a disk and outputs the same; a track jump detection circuit that generates one track jump pulse each time the pick-up jumps one track; A pick-up return device comprising: counting means for counting jump pulses; and means for returning the pick-up to the jump start position by jumping a number of tracks equal to the count value in the jump start direction.