JPH0320829B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crosstalk detection device, and more particularly to a crosstalk detection device in a recorded information reproducing device.

In general, in a recorded information reproducing apparatus, a so-called crosstalk phenomenon occurs in which information on a track adjacent to a read recording track being tracked is adversely affected, making it difficult to reproduce information favorably. In optical information reproducing devices, aberrations are introduced into the beam due to aberrations in the reading lens and a certain relative tilt angle between the optical axis of the pickup beam for reading and the disk as the recording medium. Then,
It has been found that distortion occurs in the shape of the pick-up spot converged on the recording track, causing the above-mentioned crosstalk phenomenon.

There are various causes of the relative inclination angle between the pick-up beam optical axis and the recording disk. For example, the recording disk becomes umbrella-shaped due to changes over time;
This is caused by the tilting of the disk rotation axis due to changes in the shape of the disk rotation axis fixing chassis of the playback device, and the occurrence of crosstalk is unavoidable since it is a problem that occurs after the product is shipped. Therefore, it is desired to develop a device that automatically detects the occurrence of crosstalk and prevents it.

An object of the present invention is to provide a crosstalk detection device that can automatically detect the amount of crosstalk and the direction in which it occurs in a recorded information reproducing device.

The crosstalk detection device according to the present invention uses information detection points to track a recording track of a disk in which a frequency modulated signal including a constant frequency section that appears at a constant time interval is recorded so that the linear velocity of the recording track is constant. A crosstalk detection device in a recorded information reproducing device that reads the frequency modulation signal while reading the frequency modulation signal, the device comprising: a demodulation circuit that demodulates the frequency modulation signal read from the disk; and a demodulation circuit that corresponds to the constant frequency section in the demodulation signal. a gate circuit for extracting a portion; an envelope detection circuit for envelope-detecting the output of the gate means; a peak-hold circuit for peak-holding the output signal of the envelope detection means; and a following operation of the information detection point for the recording track. and a synchronous detection circuit that synchronously detects the output of the peak hold circuit using the generated vibration signal, and is characterized in that the output of the synchronous detection circuit is used as a crosstalk detection signal.

To describe the principle of the present invention, in a certain recording section of a recording track in which information having a fixed frequency, for example, 7.5 MHz FM carrier frequency (corresponding to the sync chip level) is recorded, for example, a luminance information component from an adjacent track is recorded. If the carrier leaks as crosstalk, the beat component of the difference between the constant frequency of 7.5 MHz and the leaked carrier frequency will be superimposed on the reproduced signal obtained by FM detection of this. Therefore, crosstalk can be detected by detecting the beat component of the detection output within the recording section of the constant FM carrier frequency (for example, the section corresponding to the horizontal synchronizing signal).

On video discs recorded using the CLV (constant linear velocity) recording method, etc., so that the period corresponding to the recording of the synchronization signal is not aligned on the same radius line of the adjacent track, the brightness information of the adjacent track is recorded in the playback period of the horizontal synchronization signal. jumps in as crosstalk, so crosstalk can be easily detected using the above method. Note that as a recording method other than the CLV method, there is also a method in which recording is performed at a constant rotation speed that is slightly shifted from a frequency that is a fraction of the vertical synchronization frequency.

The present invention will be explained below using the drawings.

FIG. 1 is a circuit block diagram of one embodiment of the present invention, in which a reproduced information signal from a pickup (not shown) is converted into a composite video signal in a video detector 1. This detection output is a BPF that selectively extracts the beat component frequency due to the crosstalk mentioned above.
(Bandpass filter) 2 and gated in gate circuit 3. This gate circuit 3 operates to gate only the horizontal synchronizing signal period of the detected signal, and a gate signal generator 4 is provided for this purpose.

The beat component contained in the horizontal synchronizing signal is envelope-detected by an envelope detector 5, and the output B is peak-held in a hold circuit 6 for each horizontal period. This output C is synchronously detected by the synchronous detector 7 and becomes a detection output D corresponding to the amount of crosstalk and its generation direction, which becomes a control signal for the crosstalk removal device 8.

On the other hand, in a playback device, a tracking servo (not shown) is used to slightly deviate a pick-up detection point (hereinafter referred to as a pick-up spot) in a direction substantially orthogonal to the recording track so that the pick-up spot always accurately tracks the track. equipment is provided. The servo signal in this tracking servo device has a main component with a frequency (approximately 30 Hz) determined by the rotation speed due to the eccentricity of the recording disk. It vibrates and biases the pick-up spot to enable accurate tracking.

In this embodiment, the mirror drive signal A for pick-up spot deviation is used as another input to the synchronous detector 7 via an LPF (low pass filter) 9 and a waveform shaping circuit 10.

Each of A to D in FIGS. 2 and 3 shows the waveform of each signal A to D of the circuit block in FIG. 1, respectively. First, referring to FIG. 2, this example shows a case where the crosstalk generation direction is from one of both adjacent tracks, and in the case of a waveform like the tracking mirror drive signal A, each horizontal synchronization signal It can be seen that the envelope waveform of the beat component for each period fluctuates as shown in B. Therefore, the peak hold output becomes as shown in C. In the synchronous detector 7, if the DC cut component of this peak hold output C is multiplied by the tracking mirror drive component A, the synchronous detection output will be at a predetermined level of positive polarity as D. It becomes a signal.

Next, referring to FIG. 3, this example shows a case where the crosstalk generation direction is from another adjacent track, and the output of the envelope detector 5 is as shown in B. This has a phase difference of 180° with respect to Figure 2B.
The waveform is shifted. Therefore, the output after synchronously detecting the peak hold output C and the tracking mirror drive signal A becomes a signal of negative polarity and a predetermined level as shown in D.

That is, the output of the synchronous detector 7 provides a detection output D having a level proportional to the amount of crosstalk and a polarity corresponding to the direction in which the crosstalk occurs.

FIG. 4 is a circuit block diagram of another embodiment of the present invention, in which parts equivalent to those in FIG. 1 are designated by the same reference numerals. In this example, crosstalk is detected using a so-called wobbling method in which a pickup biasing mirror is forcibly vibrated slightly from the outside at a predetermined period. Therefore, if the same signal A as the tracking mirror wobbling signal is input to the synchronous detector 7, the same waveform as shown in FIGS. 2 and 3 will be obtained, and the same waveform as that shown in FIG. 1 will be obtained. They operate in the same way. Note that in this wobbling method, the amplitude of the forced oscillation is minute, so it does not affect the playback screen in any way.

5A and 5B are block diagrams showing specific examples of the crosstalk removing device 8 shown in FIGS. 1 and 4, respectively. In the example shown in A, an amplifier 41 amplifies a detection signal having the crosstalk amount and generation direction as information from the crosstalk detector (indicated by 40) in FIG. The mechanism 42 that adjusts the relative angle of the two is drive-controlled to eliminate crosstalk. As the mechanism 42,
For example, the optical axis of the pickup beam may be tilted by tilting the support section that supports the pickup mechanism, or the tilt of the mounting section on which the recording disk is placed may be controlled.

In the system shown in FIG. 5B, the detection signal from the crosstalk detector 40 is applied to a so-called slider servo system that moves the pickup mechanism in a direction perpendicular to the recording track. That is, this detection signal is amplified by an amplifier 41 and passed through an integrator 43 to a drive circuit 44 for the slider motor M.
1 drive input. Further, in general, a tracking error signal from a tracking error signal generator 45 drives a tracking mirror 48 by an amplifier 46 and a drive coil 47 to perform tracking servo control. Since the structure is such that servo control of the slider motor is performed according to the DC component of the error signal, tracking can be performed by forcibly adding a signal according to the detected amount and direction of crosstalk to this slider servo system. The steady-state negative slope of the mirror 48 is always controlled according to the crosstalk and operates so that the crosstalk is minimized.

FIG. 6 shows a specific example of the hold circuit 6 in FIGS. 1 and 4, and the output B of the envelope detector 5 is held at the highest level output during the hold signal arrival period in the peak hold circuit 61. be done. This output is sampled by a sample hold circuit 62 and held by a hold circuit 6.
The output is C. Here, the peak hold circuit 6
1 is reset at the end of the hold signal, and new data can be held for each signal. When crosstalk is detected during the hold signal arrival period, the sample and hold circuit 62 is triggered at the end of the sampling pulse obtained by shaping the detection output B, and the output C of the hold circuit 6 is triggered.
change. In addition, the sample hold circuit 62
is equipped with a discharge circuit having a predetermined constant, and will not malfunction even if crosstalk no longer occurs.

With the above configuration, an appropriate output can be obtained even if no crosstalk is detected during the period in which the hold signal arrives in a relatively short time.

As described above, according to the present invention, the amount and direction of crosstalk can be automatically detected, so that it is suitable for use in a recorded information reproducing apparatus. Note that it is applicable not only to optical type reproducing apparatuses but also to electrostatic type reproducing apparatuses and the like.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
3 and 3 are waveform diagrams showing the operation of the block in FIG. 1, FIG. 4 is a block diagram of another embodiment of the present invention, and FIGS. FIG. 6 is a diagram showing a specific example of the hold circuit shown in FIGS. 1 and 4. FIG. Explanation of symbols of main parts, 1...Detector, 3...
Gate circuit, 5... Envelope detector, 6...
Hold circuit, 7...synchronous detector.

Claims (1)

[Claims] 1. A recording track of a disk in which a frequency modulated signal including a constant frequency section that appears at a constant time interval is recorded so that the linear velocity of the recording track is constant is followed by an information detection point. A crosstalk detection device in a recorded information reproducing device that reads the frequency modulation signal, the device comprising: a demodulation circuit that demodulates the frequency modulation signal read from the disk; and a portion of the demodulation signal that corresponds to the constant frequency section. a gate circuit for extracting; an envelope detection circuit for envelope-detecting the output of the gate means; a peak-hold circuit for peak-holding the output signal of the envelope detection means; and causing the information detection point to follow the recording track. A crosstalk detection device comprising: a synchronous detection circuit that synchronously detects the output of the peak hold circuit using a vibration signal, the output of the synchronous detection circuit being used as a crosstalk detection signal. 2. The frequency modulated signal is a signal obtained by frequency modulating a carrier wave using a composite video signal, and the portion corresponding to the constant frequency section is a horizontal retrace period. Crosstalk detection device according to item 1. 3. The crosstalk detection device according to claim 1, wherein the vibration signal is a tracking error signal or a predetermined frequency signal.