JPH0715782B2 - Video axis time-axis correction circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a time axis correction circuit for a video disc player.

BACKGROUND ART MUSE (Multiple S) that enables high-definition television signals to be transmitted by broadcasting satellites by band compression until the bandwidth becomes approximately 8 MHz.
A method called ub-Nyquist Sampling Encoding) has been proposed. According to this MUSE system, it becomes easy to record a high-definition television signal on a recording medium such as an optical video disc.

However, the bandwidth obtained by this MUSE method is about 8M.
The synchronization signal of the high-quality image signal of Hz (hereinafter referred to as the MUSE signal) is positive polarity synchronization, and the amplitude of the synchronization signal exists within the video signal level. As a result, in the MUSE signal,
As in the case of the NTSF signal, it is impossible to easily detect the sync signal by a method such as amplitude separation, and the sync separation is difficult unless the signal is reproduced on the normal time axis.
For this reason, if normal playback is not performed, the time axis correction is performed when the disc rotation is not normal, such as when starting playback from the rotation stop state during playback on the optical video disc player to the start of steady rotation. Therefore, the synchronizing signal of the video signal cannot be used. For this reason, it has been proposed to frequency-multiplex a pilot signal with a video FM modulation signal when recording a MUSE signal on a video disc, and to separate the pilot signal during reproduction to detect a time-axis error. .

As a method of correcting the time axis error detected by the pilot signal, a tangential mirror for vibrating the information reading spot light in the recording track direction is provided in the pickup of the optical video disc player. An apparatus having a structure in which a mirror is driven according to a time axis error is known. However, in such a conventional device, it is necessary to provide the pickup with a mechanism for supporting the tangential shell mirror together with the tangential mirror, and it is difficult to reduce the size of the pickup.

Therefore, CCD (Charge Ca
It has been considered to use the conventional method of correcting the time base of the NTSC signal by a variable delay element such as an upled device). However, since the CCD inputs and outputs signals with the same clock, the conventional method is to supply the demodulated video signal to the variable delay element and separate the sync signal from the video signal that has passed through the variable delay element. The delay time of the variable transfer element is controlled according to the time axis error detected by comparing the phase with the reference signal, and a video signal with no time axis error is obtained from the variable delay element. In this case, the time axis correction cannot be performed.
Also, the RF signal in which the FM-modulated MUSE signal and the pilot signal are frequency division multiplexed is supplied to the variable delay element,
It was also possible to use a pilot signal that passed through this variable delay element to detect the time-axis error and control the delay time of the variable delay element.However, because the bandwidth of the RF signal is wide, the variable delay element of the RF signal It is difficult to delay due to, and even with such a configuration, the time base correction of the MUSE signal cannot be performed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a time axis correction circuit for a video disc player, which has a simple structure and can perform time axis correction of a reproduced image signal without providing a special mechanism for a hit-up. Is.

In the time axis correction circuit of the video disc player according to the present invention, the time axis servo of the pilot signal is performed so that the time axis of the pilot signal extracted from the RF signal and the time axis of the reference signal coincide with each other, and the time axis servo is obtained. The time axis control of the image signal demodulated from the RF signal by the error signal is performed.

Examples Hereinafter, examples of the present invention will be described in detail with reference to the accompanying drawings.

In the figure, a video disc 2 is shown by a pickup 1
An RF (high frequency) signal read from the BRF is supplied to a BRF (band pass filter) 3 and a time base correction circuit 4 according to the present invention. BPF3 is an FM whose center frequency carries the MUSE signal.
It is configured to be equal to the frequency of the carrier. The MUSE signal component in the RF signal is separated and extracted by this BPF 3 and is supplied to the FM demodulator 5 to demodulate the MUSE signal. The demodulated MUSE signal is supplied to the output terminal 7 via the CCD 6 in the time axis correction circuit 4.

On the other hand, the RF signal supplied to the time axis correction circuit 4 is supplied to the BPF 8. The BPF 8 is configured so that the center frequency becomes equal to the frequency of the pilot signal, for example, 2.28 MHz. The pilot signal is separated and extracted by the BPF 8 and supplied to the CCD 9 and the frequency phase comparison circuit 10.
In the frequency / phase comparison circuit 10, the pilot signal and the reference signal output from the reference signal generation circuit 11 are compared in frequency and phase, and a frequency / phase detection signal corresponding to the frequency and phase difference between both signals is output. This frequency phase detection signal is supplied as a drive control signal to the spindle motor 13 via the phase compensation filter 12. The disk 2 is rotationally driven by the spindle motor 13, and the rotational speed of the disk 2 is controlled so that the linear velocity becomes constant, for example.

A clock pulse output from a VCO (voltage controlled oscillator) 14 is supplied to the CCDs 6 and 9. CCD6 and 9 are
It acts as a variable delay element that delays the input signal for a time corresponding to the frequency of the clock pulse. The pilot signal delayed by CCD9 is the frequency phase comparison circuit 15
Is supplied to. In the frequency / phase comparison circuit 15, the pilot signal and the reference signal output from the reference signal generation circuit 11 are compared in frequency and phase, and a frequency / phase detection signal corresponding to the frequency and phase difference between both signals is output. .
This frequency phase difference detection signal is passed through the filter 16 to VCO1
Applied to 4 as a control voltage.

In the above configuration, the frequency of the clock pulse supplied to the CCDs 6 and 9 is a value corresponding to the frequency and phase difference between the pilot signal passed through the CCD 9 and the reference signal output from the reference signal generation circuit 11, The delay time of the CCD 9 changes according to the time axis error of the pilot signal, and the time axis error of the pilot signal output from the CCD 9 is corrected. The time axis error of the MUSE signal supplied to CCD6 is the same as the time axis error of the pilot signal supplied to CCD9, and the delay time of CCD6 is equal to the delay time of CCD9. The time base of the MUSE signal output from will be corrected. In the time axis correction operation described above, that is, in the time axis servo, if time elapses from the start of the operation and the steady state is reached, the frequency of the pilot signal and the frequency of the reference signal are almost the same, and it is mainly due to the phase difference. Time axis servo is performed.

Although the MUSE signal has been described as an example, the present invention can be directly applied to the time axis correction of a video disc player for reproducing a video disc in which pilot signals are frequency-multiplexed.

As described above in detail, the time axis correction circuit of the video disc player according to the present invention includes the first variable delay element for delaying the pilot signal extracted from the RF signal by the time corresponding to the control signal, and the demodulation from the RF signal. A second variable delay element that delays the generated image signal by a time corresponding to the control signal, and a signal that corresponds to the phase difference between the pilot signal delayed by the first variable delay element and the predetermined reference signal is generated as the control signal. Since it consists of the control signal generating means, the time axis correction of the image signal can be performed by a simple configuration in which only one variable delay element is added to the conventional circuit, and the pickup can be downsized and the circuit scale can be reduced at the same time. You can do it.

[Brief description of drawings]

 FIG. 1 is a block diagram showing an embodiment of the present invention. Explanation of main part code 3,8 …… BPF 6,9 …… CCD 11 …… Reference signal generation circuit 10,15 …… Frequency phase comparison circuit 14 …… VCO

Claims (1)

[Claims] 1. A time axis correction circuit of a video disc player for reproducing an image signal frequency-multiplex-recorded on a video disc together with a pilot signal of a predetermined frequency, wherein the pilot signal is obtained from an RF signal obtained from the video disc. Extracting means for extracting, a first variable delay element for delaying the pilot signal extracted by the extracting means by a time corresponding to a control signal, and the image signal demodulated from the RF signal according to the control signal A second variable delay element for delaying by a time, and a control signal generating means for generating, as the control signal, a signal corresponding to a phase difference between the pilot signal delayed by the first variable delay element and a predetermined reference signal. Time axis correction circuit.