JPS63204558A - Correcting circuit for time axis of video disk player - Google Patents

Abstract

PURPOSE:To correct a time axis without forming a specific mechanism by executing the time axis servo of a pilot signal so that the time axis of the pilot signal extracted from an RF signal coincides with that of a reference signal and controlling the time axis of an image signal demodulated from the RF signal on the basis of an obtained error signal. CONSTITUTION:A time axis correcting circuit consists of the 1st variable delay element 9 for delaying a pilot signal extracted from an RF signal by the time corresponding to a control signal, the 2nd variable delay element 6 for delaying an image signal demodulated from the RF signal by the time corresponding to the control signal and a control signal generating means 15 for generating a signal corresponding to a phase difference between the pilot signal delayed by the element 9 and a prescribed reference signal. The time axis of the image signal can be corrected by the simple constitution, a pickup can be miniaturized and the size of the circuit can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a time axis correction circuit for a video disc player.

Once a high-definition television signal has passed, the bandwidth is compressed to a bandwidth of approximately 8M)-1z, making it possible to transmit it by broadcasting satellite.
US E (Multiple 5ub-Nyqui
A method called ``st Sampling Encoding'' has been proposed. According to this MUSE method,
It also becomes easier to record high-definition television signals onto recording media such as optical video discs.

However, the bandwidth obtained by this MLISE method is a high-quality image signal with a bandwidth of approximately 8 MH2 (hereinafter referred to as MtJ S E
The synchronization signal (referred to as "signal") is positive synchronization, and the amplitude of the synchronization signal exists within the video signal level. As a result, M.U.
In SE signals, it is impossible to easily detect the synchronization signal using methods such as amplitude separation as in the case of conventional NTSC Shintan, and synchronization separation cannot be performed unless the signal is being reproduced on the normal time axis. Have difficulty. For this reason, when normal playback is not being performed, especially when the disc is not rotating normally, such as when starting from a stopped state to steady rotation during playback on an optical video disc player, time axis correction is required. In this case, the synchronization signal of the video signal cannot be used. For this reason, it has been proposed to frequency-multiplex a pilot signal onto the video FM modulation signal when recording the MUSE signal on a video disc, and to separate this pilot signal during playback to detect time axis errors. .

In addition, as a method of correcting the time @ error detected by this pilot signal, a tangential mirror for vibrating the spot light for information reading in the direction of the recording track is provided in the pickup of the optical video disc player. 2. Description of the Related Art A device configured to drive a dential mirror according to a time axis error is known. However, in such a conventional device, it is necessary to provide the pickup with a tangential mirror as well as a mechanism for supporting the tangential mirror, which has the disadvantage that it is difficult to miniaturize the pickup.

In addition, a circuit that writes video data to a FIFO (first-in, first-out memory) at a cycle corresponding to a time axis error, and reads video data from the FIFO at a constant cycle to correct the time @ error is also known. There is. However, in a circuit that uses this FIFO to perform time axis correction, a circuit that controls memory addresses, etc., and an A/D
(Analog-digital) converter, D/Δ converter, etc. are required, resulting in a complicated configuration.

Therefore, COD (Charoc Couple), which does not require address control and can delay analog signals,
NTSC using variable delay elements such as
Consideration has been given to using conventional methods to perform time axis correction of the system signals. However, in COD, signal input and output are performed using the same clock, so the conventional method is to supply the demodulated video signal to a variable delay element and separate the synchronization signal from the video signal that has passed through the variable delay element. The delay time of the variable delay element is controlled according to the time axis error detected by comparing the phase with the reference signal, and the time @
The configuration is such that a video signal without errors is obtained, and time axis correction cannot be performed when the pilot signal is frequency multiplexed. In addition, the RF multiplied signal in which the FM modulated MUSE signal and the pilot signal are frequency division multiplexed is supplied to a variable delay element, and the time axis error is detected by the pilot signal that has passed through the variable delay element, thereby delaying the variable delay element. A configuration that controls the time has been considered, but since the RF multiple signal bandwidth is wide, it is difficult to delay using the RF multiple signal variable delay element, and even with such a configuration, it is not possible to perform time axis correction of the MUSE signal. It cannot be done.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a time axis correction circuit for a video disc player that has a simple configuration and is capable of correcting the time axis of a reproduced image signal without providing a special mechanism to the pickup. It is.

In the time base correction circuit of the video disc player according to the present invention, the time base servo of the pilot signal is performed so that the time base of the pilot signal extracted from the RF multiplied signal and the reference signal are made to match, and the time base servo of the pilot signal is The time axis control of the image signal demodulated from the RF multiplied signal is performed using the error signal generated.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

In the figure, the video disc 2 is picked up by the pickup 1.
An RF (high frequency) signal read from is supplied to a BPF (band pass filter) 3 and a time axis correction circuit 4 according to the present invention. The BPF 3 is configured such that the center frequency is equal to the frequency of the FMwI transmission carrying the MUSE signal. This BPF3 allows the MU in the RF signal to
The SE signal component is separated and extracted and supplied to the FM demodulator 5, where the MUSE signal is demodulated. The demodulated MUSE signal is supplied to the output terminal 7 via the CCD 6 in the time base correction circuit 4.

On the other hand, the RF multiplied signal supplied to the time axis correction circuit 4, BP
Supplied to F8. The BPF 8 is configured such that the center frequency is equal to the pilot signal frequency, for example, 2°28 M l−(z).

The pilot signal is separated and extracted by this BPF 8 and is supplied to the CCD 9 and the frequency phase comparison circuit 10 . In the frequency and phase comparison circuit 1o, the frequency and phase of the pilot signal and the reference signal outputted from the reference signal generation circuit 11 are compared, and a frequency and phase detection signal corresponding to the frequency and phase difference between the two signals is outputted. This frequency phase detection signal is supplied to the spindle motor 13 as a drive control signal via a 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, for example, the linear velocity is constant.

CCDs 6 and 9 are supplied with clock pulses output from a VCO (voltage controlled oscillator) 14. CCD
6 and 9 act as variable delay elements that delay the input signal by a time corresponding to the frequency of this clock pulse. The pilot signal delayed by the CCD 9 is supplied to a frequency phase comparison circuit 15. The frequency and phase comparison circuit 15 compares the frequency and phase of this pilot signal and the reference signal output from the reference signal generation circuit 11, and outputs a frequency and phase detection signal according to the frequency and phase difference between the two signals. . This frequency phase difference detection signal is
A control pressure of 1 m is applied to the vcoi 4 via the filter 16.

In the above configuration, the frequency of the clock pulses supplied to the CCDs 6 and 9 has a value corresponding to the frequency and phase difference between the pilot signal that has 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. Furthermore, the time axis error of the MUSE signal supplied to the CCD 6 is the same as the time axis error of the pilot signal supplied to the CCD 9, and the delay time of the CCD 6 is equal to that of the CCD 9. The time axis of the MUSE signal output from the MUSE signal will be corrected.

Although the explanation has been given using the M LJ SE signal as an example, the present invention can be directly applied to time axis correction of a video disc player that plays back a video disc in which pilot signals are frequency multiplexed.

As described in detail above, the time axis correction circuit of the video disc player according to the present invention has a first circuit that delays the pilot signal extracted from the RF multiplied signal by a time corresponding to the ii' control signal.
a variable delay element; a second variable delay element that delays the image signal demodulated from the RF multiplied signal by a time corresponding to the control signal;
The control signal generating means generates, as a control signal, a signal corresponding to the phase difference between the pilot signal delayed by the first variable delay element and a predetermined reference signal, so that one variable delay element can be added to the conventional circuit. With a simple addition, the time axis correction of the image signal can be performed, making it possible to downsize the pickup and at the same time reduce the circuit scale.

[Brief explanation of the drawing]

The figure is a block diagram showing one embodiment of the present invention. Explanation of symbols of main parts 3.8...BPF 6.9...C0D 11...Reference signal generation circuit 10.15...Frequency phase comparison circuit 14...
...VCO

Claims (1)

[Claims] A time axis correction circuit for a video disc player that reproduces an image signal frequency-multiplexed and recorded on a video disc together with a pilot signal of a predetermined frequency, the circuit comprising extraction means for extracting the pilot signal from an RF signal obtained from the video disc. , a first variable delay element that delays the pilot signal extracted by the extraction means by a time corresponding to the control signal; and a first variable delay element that delays the image signal demodulated from the RF signal by a time corresponding to the control signal. A time axis correction circuit comprising: two variable delay elements; and a control signal generating means for generating, as the control signal, a signal according to a phase difference between the pilot signal delayed by the first variable delay element and a predetermined reference signal.