JPS6072494A - Servo control circuit of video disc player - Google Patents

Abstract

PURPOSE:To realize servo control stable at all times by providing a noise eliminating circuit eliminating noise component exceeding a peak potential of a horizontal synchronizing signal to a front-stage of a clamp circuit constituting a servo control circuit to have only to add a simple circuit. CONSTITUTION:An output of a video amplifier 5 is inputted to a base of a transistor (TR) Q1 in a noise eliminating circuit 6 and an output is given from the emitter to a clamp circuit 7. When a base potential of a TRQ2 is lower than a base potential of the TRQ1, the Q2 is cut off, and when the base potential of the Q1 is lower than the base potential of the Q2, the Q1 is cut off and Q2 is activated, then a voltage lower than the base potential of the Q2 by a base-emitter voltage of the Q2 appears to each emitter of the Q1, Q2, and when the base potential of the Q2 is set to a proper value by voltage dividing resistors R2, R3, the potential of the horizontal synchronizing signal of the video signal inputted to the base of the Q1 and the base potential of the Q2 are made equal and a noise having a level lower than the potential of the horizontal synchronizing signal is not outputted to the clamp circuit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a servo control circuit for a video disc player, particularly for special playback such as a double-speed playback mode.

The present invention also relates to a servo control circuit for a video disc player that prevents instability of the servo mechanism due to noise contamination during track jumps during random access such as high-speed search.

In the case of a video disc player, especially an optical video disc player with a pickup using laser light,
It is widely used because operations such as random access can be easily performed, but at the same time, stable servo control is required for the control system such as the disk spindle motor to ensure normal operation of the device at all times during the playback process. Ru. Therefore, the recorded information detected by the pickup (m7, that is, the horizontal synchronization signal of the video signal obtained from the detected FM signal) is separated by means of time-axis servo in the control system, and the servo control signal is generated based on this signal. What I try to get is common.

However, in the case of special playback, random access, etc., there are many opportunities to perform so-called track jumps in which the pickup is moved in the radial direction of the disc. Now. For this reason, as in the case of full dropout, when the signal is missing, noise is included in the video signal.

The noise generated in this way is more pronounced than during normal playback.
, for example, in the case of high calyx←chi, the faster the moving speed of the pickup, the more noticeable it becomes. The effects of such noise generation appear particularly in the clamp circuit provided in the separation process of the horizontal synchronizing signal, and as the DC level of the video signal fluctuates, the peak level of the horizontal synchronizing signal included therein also fluctuates. As a result, a period occurs during which it is impossible to separate the horizontal synchronizing signal, and stable control of the sensor 11≦ cannot be performed at all times.

3.7) Yo □ Huie. Yo, □2□16-8 then,
Key Dokura: Clamps only for the necessary period when crystallization occurs.
Possible methods include a canceling method that adds artificial noise (a6) that has the opposite phase to the noise, but all of these have disadvantages such as complicated circuit configurations and lack of reliability of operation, and are not very versatile. It is something.

The present invention was made by focusing on these conventional problems, and by using a simple circuit configuration to avoid the effects of noise that is introduced when the pickup in a video disc player operates at high speed, it is possible to An object of the present invention is to provide a servo control circuit for a video disc player that can perform stable servo control.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

First, to explain the configuration, in FIG.

A photoelectric conversion section 3' that converts the gloss and recorded information optically read from the pickup 3 into electrical signals is faced.

Then, the detected FM signal outputted from the photoelectric conversion section 3' becomes a demodulated video signal in the pulse count demodulation circuit 4. It is assumed that the horizontal synchronization signal included in this demodulated video signal appears on the negative side of the black level, and the related noise will be explained below with its peak appearing on the negative side of this horizontal synchronization signal.1. .

In this way, the obtained video signal is input to a noise removal circuit 6, which will be described in detail later, via a video amplifier 5.
Flat synchronous signal? Noise generation □ and noise at a potential lower than the peak potential are removed. The output of the noise canceling circuit 6 is input to the clamp circuit 7, and the output of the clamp circuit 7 is filtered to the horizontal synchronizing signal separating circuit 8. Then, the separated horizontal synchronization signal is inputted to the time axis and the phase ratio is compared with a predetermined reference signal, and the phase ratio obtained according to this phase comparison is Hazu spindle motor 2 and pick 7 y i 31 zo'' se, ''9° pa 6・=
Jt L: , ni°・L:'1H) Lt%l-", 21
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U e y 97 y '/'39'''1''? ,'go1
″-=y (1) f'J lx ff; i row 4″ 1st 0-9°・1st, ni, no:, please refer to Figure 2 for the details of the ise removal date path 6: , etc. will be explained. In FIG. 11, VCC is a circuit power supply, and this circuit source VCC has an NPN type transistor whose emitter is grounded via a resistor R1.

In addition, the collector of a transistor q2q) is connected to the circuit power supply Vcc, and its emitter is
Connected to the emitter of: One more thing!・The base of transistor Q2 has partial pressure:? Connection between anti-R2 and R:1・0゛ connection atLi'H'1. s″″′1 now Lmm
R12 (7J-"11 (one circuit connected to the power supply Vcc; one end of the R circuit connected to the ground): constructed in this manner) is connected to the base of the transistor Q1. The output of the 1+' amplifier 5 is input and output to the emitter 1 and output clamp circuit 7. Under normal conditions, the transistor Q1 acts as an emitter 1 and a follower 1. In other words, when the base 1 potential of transistor Q121, which is the divided potential of R211 (a'), is low, the base voltage of transistor Q121 becomes low. However, conversely, the base voltage of transistor 1 is lower than the base voltage of transistor Q2: 1~
Transistor Q1 is in the twelfth state and transistor Q2 is in the active state. For this reason.

A potential lower than the base potential of the transistor Q2 by the base-emitter voltage of the transistor Q2 appears at each emitter of the transistors Ql and C)2. Therefore, when the base potential of the 1-heran sister 02 is set to an appropriate value by the voltage dividing resistors 11z and lta,
The potential of the horizontal synchronizing signal of the video signal input to the base of the transistor Q2 is equal to the base potential of the transistor Q2, and noise lower than the potential of the horizontal synchronizing signal is not output to the clamp circuit 7.

The operation of the noise removal circuit 6 will be described in more detail with reference to FIG. 3. As shown in FIG. 3(a), the video signal Vs containing noises Nt, N2... When manually applied, noise components that are more negative than the peak potential of the horizontal synchronizing signal IIs are removed, as shown in FIG. 3(b).

As a result, the DC level of the video signal Vs does not fluctuate in the clamp circuit 7, and the horizontal synchronization signal Its is reliably transmitted from the horizontal synchronization signal separation circuit 8 in each horizontal synchronization period as shown in FIG. It starts to look like A. Note that, as shown in FIG. 3C, noise components that do not reach the peak potential of the horizontal synchronization signal Hs are also output from the horizontal synchronization signal separation circuit 8, but such noise components can also appear during normal playback. There is no problem in removing it, as well-known removal measures can be taken.

In the above embodiment, the case where the horizontal synchronizing signal appears on the negative side of the black level of the video signal has been explained, but the present invention also works in the case of the opposite polarity, and in this case, the 1-transistor Q1 in the embodiment ,02 respectively as P
It is sufficient if it is composed of NP type.

Furthermore, in the description of the two embodiments, emphasis has been placed on the noise removal circuit 6, but the other circuit configurations are conventionally known and do not require a detailed explanation.

As explained above, according to the present invention, a noise removal circuit for removing noise components exceeding the peak potential of a horizontal synchronizing signal is provided before the clamp circuit that constitutes the servo control circuit of a video disc player. The time axis servo control based on the horizontal synchronization signal can be performed stably and reliably at all times without being affected by noise. Moreover, this can be achieved by simply adding a simple circuit, and loss 1 hairs can be avoided. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating a servo control circuit for a video disc player according to the present invention, FIG. 2 is a circuit diagram illustrating an embodiment of a noise removal circuit, and FIG. 3 is a block diagram illustrating the operation of the noise removal circuit. FIG. ■...Tiff, 4. Pulse count demodulation circuit, 6. Noise removal circuit, 7. Clamp circuit, 8. Horizontal synchronization signal separation circuit, 9. Time axis servo circuit. Figure 2 Figure 3

Claims (1)

[Scope of Claims] A demodulation circuit that demodulates a recording information signal detected from a disk into a video signal, a clamp circuit that clamps an output signal of the modulation circuit, and a horizontal output signal from the output signal of the clamp circuit. a horizontal synchronization signal separation circuit that separates a synchronization signal; and a time axis servo that controls the time axis of the control system of the disk according to the comparison output by comparing the output signal of the horizontal synchronization signal separation circuit with a reference signal. circuit, and a noise removal circuit for removing noise components having a signal level higher than the (i?'';J level of the horizontal synchronization signal) is provided between the demodulation circuit and the clamp circuit v11. Disc player servo control circuit.