JPS5826105B2 - jitter hoshiyosouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal reproducing apparatus such as a magnetic drum, a magnetic disk, or a recording disk in which the video signal is carved into grooves, and provides an apparatus for accurately compensating for jitter.

When playing back a video signal from a disk, drum, etc. on which a video signal has been recorded, jitter occurs, which causes the image to fluctuate due to uneven relative speed between the recording surface of the disk or drum and the pickup device that converts the recorded signal into an electrical signal. .

During reproduction, this relative velocity unevenness may be due to surface runout, eccentricity, vibration, rotational unevenness, etc. of the recording disk or drum, and during recording, it may be due to recording errors, rotational unevenness of the recorder, etc.

In order to obtain good images with current color receivers, the above jitter must be suppressed to within about 0.01%.

In order to minimize the above-mentioned causes during video signal recording and playback, jitter can be reduced to some extent by improving the accuracy of each part of the recording and playback equipment. The value of the machine will increase, and mass production will become worse.

For this reason, a jitter compensation device moves the pickup device in the rotational direction or counter-rotation direction of the recording disk or drum so as to cancel out the jitter, and always keeps the error in the relative speed between the pickup device and the recording disk or drum within a certain value. was considered.

This jitter compensation device is a closed-loop control system that compares the vertical or horizontal synchronization signal in the reproduced signal with a reference signal, detects an error in the phase of the reproduced signal, and uses this detected error to move the pickup device to cancel the jitter. be.

FIG. 1 shows an example of the configuration of the jitter compensation device described above.

1 is a motor with a constant rotation speed (for example, 450r, p
, m).

2 is a turntable and has large inertia so as to reduce uneven rotation of the motor 1.

3 is a recording disk placed on the turntable 2, and a video signal is recorded on the upper surface thereof.

4 is a pickup device for taking out the video signal recorded on the recording disk 3;

Reference numeral 5 designates a synchronization separation circuit that separates horizontal or vertical synchronization signals from the video signal taken out by the pickup device 4, and reference numeral 6 designates a frequency discrimination circuit that converts frequency fluctuations of the separated synchronization signals into voltage fluctuations.

Reference numeral 7 denotes a compensation and drive circuit that appropriately compensates the output voltage of the frequency discrimination circuit 6 and amplifies it to the power necessary to drive the pickup device.

8 is the recording disk 30 by the output of the compensation and drive circuit 7.
This is a pickup drive device that moves the pickup device 4 in a rotational direction or a counter-rotation direction, and uses a solenoid coil.

Here, since the pickup driving device 8 converts electrical force into mechanical force, the frequency characteristics of the pickup driving device 8 become a problem in order to accurately compensate for jitter.

Now, if the recording disk 3 is rotating at 45Q1-, pom, the fundamental wave of jitter due to eccentricity of the recording disk 3, etc.7.
It becomes 5 Hz.

Therefore, the jitter frequency is about 7.5 to about 100 Hz.

In addition, the frequency characteristics of the pickup drive device 80 are as follows.
Two types are possible.

That is, firstly, when the natural fundamental frequency of the pickup driving device 8 is lower than the above-mentioned jitter frequency (for example, 5 to 6 Hz), and secondly, when the above-mentioned jitter frequency or a frequency near it and the pickup driving device 8 are When the natural fundamental frequencies are almost equal (e.g. 60-100Hz)
, Thirdly, when the natural frequency of the pickup driving device 8 is considerably higher than the above-mentioned jitter frequency (for example, I K
Hz) is considered.

Among these three frequency characteristics, the one having the second frequency characteristic allows for the most accurate jitter compensation.

From the above, the conventional jitter compensation device for a video signal reproducing device is provided with a pickup drive device having a natural resonant frequency approximately equal to the jitter frequency.

However, since the pickup drive device has a natural resonant frequency, it does not operate accurately in accordance with the jitter compensation signal, and jitter remains in the reproduced image.

This will be explained with reference to FIG.

In Fig. 3, the vertical axis indicates g; the phase shift of the pickup drive device relative to the jitter compensation signal and θ; the horizontal axis indicates f; the frequency of the jitter compensation signal. .

Further, the solid line shows the displacement-frequency characteristic, and the broken line shows the phase-frequency characteristic.5 It can be seen from FIG. 3 that the pickup drive device resonates at the frequency fo.

The present invention solves the above-mentioned conventional drawbacks by adding a braking device that applies appropriate braking to the pickup drive device to accurately compensate for jitter, and will be described in detail below.

FIG. 2 shows a part of the compensation and drive circuit T and the pickup drive device, and in FIG.
is an amplification stage, and 101 is an operational amplifier.

102 is an input resistance of the operational amplifier 101, 103,
104 are a feedback resistor and a feedback capacitor, respectively; 10
5 is a grounding resistance.

Also, the gain and frequency characteristics of the operational amplifier 101 are determined by the resistance 1
02, 103 and capacitor 104.

Reference numeral 200 is a buffer stage composed of Darlington-connected NPN transistors 201 and 202 and emitter followers of PNP transistors 203 and 204.

205 and 206 are transistors 201 and 203, respectively.
is the bias resistance.

207 and 208 are noise eliminating capacitors connected in parallel to resistors 205 and 206, respectively.

209-212 are diodes, and 213-216 are emitter resistors, respectively.

300 is a bridge stage, in which a solenoid coil 301 and a resistor 302 of the pickup drive device are connected in series, a resistor 303, a semi-fixed resistor 304, and a capacitor 306 connected in parallel with a resistor 305 are connected to the solenoid coil 3.
01 and the resistor 302 are connected in parallel.

Also, each resistor and capacitor are connected to the solenoid coil 3.
It is determined that the permanent magnet actuator (not shown) in 01 is balanced when it is at rest, that is, when the pickup is not moving to compensate for jitter.

That is, the relationship between each impedance of the bridge stage 300 is determined to be expressed by the following equation.

Z301 'Z305 ==Z3o3'' Z302
"""""""・(1) However, Z301 is the impedance when the actuator in the solenoid coil 301 is stopped, Z302 is the resistance value of the resistor 302, and z3os is the resistance of the resistor 303 and the semi-fixed resistor 304. The sum of the values, Z305, is the impedance of the resistor 305 and capacitor 306 connected in parallel.

Mata capacitor 306 is solenoid co/I'/l/30
The frequency characteristics of the bridge stage 300 are compensated by an inductance of 1, and its capacitance c3o 1
is given by the following equation.

Caoa=L3ot/R305・R301--・
-・・・(2) However, LaO2 is solenoid coil 30
1 inductance, R301 is solenoid coil 30
1, and R3o5 is the resistance value of the resistor 305.

400 is a differential amplification stage composed of resistors 401, 402, 403, a semi-fixed resistor 404, a capacitor 405, and an operational amplifier 406.

The gain and frequency characteristics of the differential amplifier stage 400 are determined by the resistor 401.
．． 403 and capacitor 405.

Further, the output of the operational amplifier 406 is negatively fed back to the input circuit of the amplifier stage 1000 via a resistor 407 and a capacitor 408.

Next, the operation of the jitter compensation device of the present invention will be explained.

Motor 1 rotates and drives turntable 2.

Then, the pickup device 4 picks up the video signal recorded on the recording disk placed on the turntable 2.

A horizontal or vertical synchronization signal is separated from the video signal taken out by the pickup device 4 by a synchronization separation circuit 5.

Frequency fluctuations of the synchronization signal separated by the synchronization separation circuit 5 are changed into voltage fluctuations by the frequency discrimination circuit 6.

Next, the output of the frequency discrimination circuit 6 is given appropriate compensation and then input to the amplification stage 100.

The output of amplifier stage 100 passes through buffer stage 200 and is input to bridge stage 300 .

The solenoid coil 301 is driven according to the voltage fluctuation, that is, the jitter compensation signal applied to this bridge stage 300, and the permanent magnet actuator (
(not shown) moves.

When the actuator of the solenoid coil 301 moves, a reverse induced voltage appears in the solenoid coil 301, and the bridge stage 3
00 is out of balance.

Therefore, a potential difference appears between A and B of bridge stage 300, this potential difference is amplified by differential amplification stage 400, and is negatively fed back to amplification stage 100 via resistor 407 and capacitor 408.

Therefore, the pickup drive device is properly braked and operates accurately according to the jitter compensation signal.

This will be explained with reference to FIG.

In FIG. 4, the vertical axis represents g: the displacement amount of the pickup driving device with respect to the jitter compensation signal, and θ represents the phase shift of the pickup driving device with respect to the phase of the jitter compensation signal, and the horizontal axis represents the frequency of the jitter compensation signal.

The solid line represents the displacement vs. frequency characteristics, and the broken line represents the phase vs. frequency characteristics.

As is clear from FIG. 4, the resonance wave number f of the pickup 1 drive device.

However, it can be seen that the pickup drive device does not cause resonance.

As described above, the jitter compensation device of the present invention applies appropriate braking to the video signal pickup device and drives it, so that jitter compensation can be easily and accurately performed.

Furthermore, in the present invention, the amplitude frequency characteristics of the pickup device itself, which is the controlled object, are improved, and the characteristic resonance frequency f as shown in FIG. 3 is improved.

By suppressing this, the movement of the pickup device in response to the jitter compensation signal (control signal) can be made more faithful, and stable operation can be expected without deterioration of control accuracy and response characteristics.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a jitter compensation device in a conventional example and an embodiment of the present invention, Fig. 2 is a wiring diagram of main parts in an embodiment of the jitter compensation device of the present invention, and Fig. 3 is a characteristic of the conventional example. 4 are characteristic diagrams of an embodiment of the jitter compensation device of the present invention. 3...Recording disc, 4...Pickup device, 5...Synchronization separation circuit, 6...Frequency discrimination circuit, T...Compensation and amplifier circuit, 8
...Pickup 1 drive circuit.

Claims (1)

[Claims] 1. A pickup device that takes out a video signal recorded from a rotationally driven recording medium, a jitter detection device that creates a detection signal according to the jitter of the output signal of this pickup device, and amplifies the detection signal of the jitter detection device. and a pickup drive device that moves the pickup device in a direction to cancel jitter according to the output of the amplifier, wherein the pickup drive device has the output of the amplifier applied to a solenoid coil; An actuator made of a permanent magnet is constituted by a solenoid connected to the pickup device, and a back electromotive force generated in the solenoid coil according to the moving speed of the permanent magnet is fed back to the amplifier as a negative feedback signal. A jitter compensation device characterized by: