JPS5834609Y2 - signal regenerator - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a reproducing device that uses a pickup means to reproduce signals from a disk-shaped recording medium that is driven one rotation, and the relative speed between the disk-shaped recording medium and the pickup means is always constant. It is intended to be controlled so that it remains constant.

For example, when a video signal is reproduced from a recording disk on which a video signal has been recorded, a time axis fluctuation component (jitter) occurs in the reproduced video signal due to eccentricity of the recording disk, uneven rotation of a rotational drive motor, and the like.

In order to obtain high-quality reproduced images on a normal color television receiver, the jitter of the luminance signal system must be at least 0.0.
It is necessary to suppress it to 1% (P-P) or less.

However, it is extremely difficult to suppress jitter to 0.01% or less by increasing the accuracy of the disk and the drive system for the disk, which poses a problem in mass production of the disk and its reproducing device.

The present invention eliminates jitter in the reproduced signal by controlling changes in the relative speed between the disk and the pickup caused by eccentricity of the disk or uneven rotation of the drive system by moving the pickup in its relative running direction. In particular, the structure is such that stable control operation can be expected even if there is a short-term dropout signal (dropout) due to a scratch on the recording disk or the like.

One embodiment will be described below with reference to the drawings.

In FIG. 1, 1 is a video signal recording disk (hereinafter referred to as a disk), and 2 is a turntable which is driven by a disk rotation motor 3 and rotates together with the disk 1.

4 is a pickup means for detecting the disc signal, 5 is an amplifier for amplifying the picked up signal, 6 is a limiter amplifier used when the disc signal is recorded as an FM signal, and 7 is the same <FM demodulation The video signal reproduced from the disc 1 (in this embodiment, an NTSC signal will be described) is obtained at the output terminal 14.

8 extracts a horizontal synchronization signal with a synchronization separation circuit, and the extracted horizontal synchronization signal is sent to a chroma burst signal extraction circuit 10.
The signal from the NTSC signal that has passed through the 9 bandpass filters is separated from the NTSC signal.

20 is a PLL loop, in which the phase of the burst signal and the output of the voltage controlled oscillator (VCO) 12 are compared by a phase comparator 11, and the output corresponding to the phase difference is passed through a filter 13 to control the tube frequency of the VCO 12. .

Since the output of the phase comparator 11 is the one that detects the jitter of the disk 1, it is sent to the compensation circuit 15 and the drive amplifier 16.
A pickup driving means 17 for moving the pickup means 1 along the recording track is driven via the recording head.

That is, the jitter in the reproduced video signal is compensated for by displacing the pickup means on the recording track of the disk in accordance with the jitter in the reproduced signal.

By the way, if there is a dropout due to scratches or the like on the rotating disk, it will appear in the phase comparator 11 as a disturbance signal unrelated to jitter, and the pickup means 4 will be driven by this disturbance signal, significantly reducing the image quality of the reproduced video signal. Let's lower it.

When this disturbance signal was analyzed in detail, it was found that the disturbance signal due to the dropout that occurred in the 11 phase comparators was caused by the VCO 12
oscillation frequency to a large extent, thereby extending the duration of the disk dropout.

It was also found that the initial disturbance signal was greatly increased.

Furthermore, it has been found that when a disc is scratched, the dropout caused by the scratch appears in synchronization with the rotational frequency of the disc.

Therefore, the present invention significantly reduces the occurrence of the above-mentioned disturbance signal by configuring the filter 13 so that the gain attenuates at least at the rotation frequency of the disk 1 (for example, 30 Hz in the case of 1800 ROM). It is something.

That is, according to this configuration, the rotational frequency of the disk (3
This prevents the oscillation frequency from being significantly shifted by a disturbance signal due to dropout occurring at 0 Hz).

As an example of this filter, one of the type shown in FIG. 3 having the characteristics shown in FIG. 2 can be used.

If the disk rotation is 30Hz, the fl shown in Figure 2
Favorable results can be obtained by setting the frequency to 30 Hz or less.

As described above, according to the present invention, even if there is a dropout due to a scratch on the disk, the pickup means is not driven by the dropout, and stable jitter compensation can always be performed.

In the button embodiment, we have explained the case where the control system is configured using a burst signal in the reproduced signal, but it is also possible to use a constant period signal such as a horizontal synchronization signal or a pilot signal inserted in advance during recording. It has a great effect.

[Brief explanation of the drawing]

FIG. 1 is an electrical block diagram showing one embodiment of the present invention, FIG. 2 is a diagram showing filter characteristics used in the present invention, and FIG. 3 is a diagram showing an example of a low-pass filter. 1... Disc (recording medium), 4... Pickup, 5.6... Amplifier, 7... FM demodulator, 8...
Horizontal synchronization separation circuit, 9... Blue band filter, 10... Burst gate, 11... Phase comparator, 12... Variable oscillator, 13... Filter, 14... Output terminal,
15...Compensation circuit, 16...Drive amplifier, 17...
-Pickup drive means.

Claims (1)

[Scope of utility model registration request] a driving means for rotationally driving a disk-shaped recording medium on which a signal including a periodic signal having a constant period is recorded on a recording track;
a pickup means for reproducing a signal from a recording track of the disc-shaped recording medium; a variable oscillator whose oscillation frequency changes according to a control signal; and the periodicity in the output of the variable oscillator and the reproduced signal from the pickup means. and a phase comparison means for comparing the phases of the two signals, and a filter whose gain is attenuated by multiplying the output of the phase comparison means according to the phase difference between the two signals by the rotational frequency of the recording medium, and outputting the control signal as the variable signal. A signal reproducing device comprising: means for applying an voltage to an oscillator; and means for moving the pickup means in the recording track direction of the disc-shaped recording medium in accordance with the output of the phase comparison means.