JPH0531880B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for reproducing color television signals from a disc-shaped recording medium (hereinafter referred to as disks) in which color television signals are recorded on concentric or spiral recording tracks. The present invention relates to a reproducing apparatus, and is particularly characterized by a correction apparatus that removes a time axis fluctuation component from a reproduced signal.

Conventional configuration and its problems For example, in a playback device that plays back a disc in which a frequency-modulated NTSC color television signal is recorded one frame per revolution, changes in the rotational speed of the spindle motor that drives the turntable occur. Due to eccentricity and warpage of the record, errors occur in the relative speed between the pickup and the disk-shaped recording medium, and the reproduced signal is subject to time axis fluctuations.

To compensate for this, in optical video disc devices, the rotational speed of the spindle motor is controlled to be constant by phase comparison between the reproduction horizontal synchronizing signal and the reference signal, and track eccentricity and warping are controlled by a tangential mirror. The reproducing laser beam is directed in the track direction to make corrections (hereinafter this control will be referred to as TBC servo). However, there are mechanical limits to the response of spindle motors and tangential mirrors to temporal fluctuations, and there is an error (residual time axis error) that cannot respond to instantaneous temporal fluctuations, which causes unevenness on the playback screen. ing.

FIG. 1 is a block diagram of a conventional residual time axis error correction device, in which a composite color video signal reproduced from a disk and demodulated is input to a variable delay line device 1. The variable delay line device 1 inputs an oscillator that generates a clock signal whose voltage is controlled by the residual time axis error signal output from the residual time axis error detection circuit 5, and a delay whose size is determined by the frequency of the clock signal. to a composite color video signal of
It is made of CCD delay lines, etc. Variable delay line device 1
The composite color video signal passed through is supplied to a band pass filter 2, the chroma signal component is extracted and supplied to a gate circuit 4, and the burst gate pulse signal generated by a burst gate pulse generation circuit 3 is sent to the gate circuit. 4 is entered,
Only the burst signal component is output from the gate circuit 4. This burst signal component is input to a residual time axis error detection device 5 to detect a residual time axis error signal, and this signal is input to a variable delay line device 1 to control the delay time of the composite color video signal and control the residual time axis. Eliminate errors.

However, in the above-mentioned residual time axis error correction device, during special playback such as slow playback, fast playback, or static playback of the screen, the optical pickup moves to the next track in the radial direction by the kick pulse, but the disk is based on the NTSC system. Since the composite color video signal is recorded one frame per round, the phase of the chroma signal component is reversed, causing a large residual time axis error until it is corrected by the TBC servo. In addition, since there is no burst signal during the vertical blanking period of a composite color video signal, the residual time axis error immediately before that period is sampled and held, so the next time the burst signal appears, the residual time axis error will be large. Become. For this reason, the residual time axis error correction device handles a small time axis error compared to the TBC servo, so the dynamic range is narrower, so if you try to increase the color unevenness compensation rate, the control becomes unstable and oscillates. There was a problem with image quality loss.

Purpose of the Invention In view of the above, the purpose of the present invention is to disable the residual time axis error detection circuit by turning off the burst gate circuit during the vertical retrace pulse signal period and the hard pulse signal period during special playback, and to disable the TBC.
By operating the residual time axis error detection circuit after the servo becomes stable, the color unevenness correction rate can be increased even during special playback.

Structure of the Invention According to the present invention, the burst gate circuit is turned on during the burst signal period excluding the vertical blanking period and a period extended by a certain period from the edge of the starting point of the kick pulse, and the residual time axis error detection circuit operates. The color unevenness correction rate can be increased during special playback.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 2 and 3. The reproduced and FM demodulated composite color video signal is input to a variable delay line device 1, and the variable delay line device 1 is connected to a residual time axis error detection circuit 5.
imparts a delay to the input composite color video signal of an amount determined by the output residual time axis error signal. The composite color video signal that has passed through the variable delay line device 1 is supplied to a bandpass filter 2, where the chroma signal component is extracted. At the same time, the burst pulse signal A is input to the burst gate pulse generation circuit 3 and the vertical blanking pulse generation circuit 6, and a burst pulse signal A is a pulse signal of the burst signal period, and a vertical blanking pulse signal B is a pulse signal of the vertical blanking period. is obtained. The pick pulse C that forces the pick up to move to the adjacent track is
The delay circuit 7 is inputted and outputs a kick pulse signal D which is delayed for a certain period from the starting edge of the kick pulse. The NOR circuit 8 takes the NOR of the vertical retrace pulse signal B and the kick pulse signal strength, and the AND of the output signal and the burst pulse signal A is obtained by the AND circuit 9, resulting in the burst gate pulse signal E. is obtained, and the gate circuit 4 outputs the burst signal component, which is the chroma signal component excluding the vertical retrace pulse signal period and the hard pulse signal period, by the burst gate pulse signal E, and outputs the burst signal component to the residual time axis error detection circuit 5. is input. When a burst signal exists, the residual time axis error detection circuit 5 compares the phase with a reference signal and outputs the comparison voltage value as a residual time axis error signal. Sample and hold the time axis error and output it. For this reason, in special reproduction, the residual time axis error detection circuit 5 operates after the TBC servo is stabilized, so the residual time axis error at the time of operation is small. The residual time base error signal output from the residual time base error detection circuit 5 is input to the variable delay line device 1, and controlled to remove the residual time base error.

Effects of the Invention As described above, according to the present invention, the residual time axis error detection circuit operates only during special playback.
Since the TBC servo is stabilized, the residual time axis error is small at that point, so it is possible to increase the color unevenness correction rate and obtain high-quality images without color unevenness.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional time axis variation component correction device, Fig. 2 is a block diagram showing an embodiment of the time axis variation component correction device of the present invention, and Fig. 3 is an operating waveform diagram of the same device. be. 1... variable delay line device, 2... band pass filter, 3... burst pulse generation circuit, 4...
Gate circuit, 5...Residual time axis error detection circuit, 6
...Vertical retrace pulse generation circuit, 7...Delay circuit.

Claims (1)

[Claims] 1. Means for rotationally driving a disc-shaped recording medium on which a color video signal is recorded as concentric or spiral recording tracks, pickup means for reproducing the color video signal from the disc-shaped recording medium, and a control signal to be applied. variable delay means whose delay amount changes according to the input signal and receives the reproduced signal from the pickup means as an input signal; means for creating a burst pulse corresponding to a burst signal period from the output of the variable delay means; vertical blanking pulse generating means for extracting a vertical blanking pulse signal corresponding to the vertical blanking period from the output of the means;
means for producing a kick pulse signal extended for a fixed period from the edge of the starting point of the kick pulse for moving the pick-up means to an adjacent track; and a vertical blanking period from the burst pulse signal, the vertical blanking pulse signal and the kick pulse signal; a logic means for generating a burst gate pulse signal which is a burst pulse signal prohibited during the hard pulse signal period; a burst gate circuit for extracting only the burst signal from the output of the variable delay means by the burst gate pulse signal; and an output of the burst gate circuit. When a burst signal exists in the signal, the phase comparison output with the reference signal is output as a residual time axis error, and when there is no burst signal, the immediately preceding residual time axis error is sampled and held and output. , and time-base error detection means for applying the error signal to the variable delay means as a control signal.