JPH0520810A - Time-axis control system - Google Patents

Abstract

PURPOSE:To make the fine adjustment of a time axis easy and to make a dynamic range wide by a method wherein the error of the time axis is made continuous before and after a jump operation by changing the generation phase of a reference synchronizing signal and a time constant is initialized during the jump operation. CONSTITUTION:When a tracking control operation and a jump operation are performed alternately and an information readout point is transferred, the generation phase of a reference synchronizing signal is changed by using a transfer change means 22, and the phase difference between a replay synchronizing signal and the reference synchronizing signal is made nearly continuous. Thereby, the fine adjustment of a time axis can be performed smoothly. At the same time, a time-constant means is initialized so that a signal generated from the time-constant means is set to a prescribed value by an initialization means 23 during the jump operation. Thereby, it is possible to prevent the dislocation of an operating point from being stored and to make a dynamic range wide. The operation is weakened and returned to a normal operation when both means 22, 23 are synchronized by the control signal of a control-signal generation means 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time axis control system for recording or reproducing information such as video signals and audio signals on a recording medium such as a disk or a magnetic tape.

[0002]

2. Description of the Related Art For example, as a time axis control system in a video disc player, there is one shown in FIG. 1
Is a video disk, which is rotationally driven by the spindle motor 2. A signal reproduced by a pickup (not shown) as signal recording / reproducing means is demodulated by the demodulation circuit 3 and then CCD as means for finely adjusting the time axis.
It is output via (charge transfer device) 4. On the other hand, a part of the output is synchronously separated and supplied to the circuit 5 for removing the equalized pulse, and a pulse synchronized with the reproduced horizontal synchronizing signal is obtained.
This pulse is input to the phase comparator 6 and has the same frequency as the reproduced horizontal synchronizing signal (15.734K in the case of the NTSC system).
Hz, 15.625 KHz in the case of the PAL system) is phase-compared with the output of the reference oscillator 7, and its error output is supplied to the motor 2 via the amplifier 8, the equalizer 9, the amplifier 10, the equalizer 11, and the amplifier 12. Is becoming Further, the equalizer 9 defines the total gain characteristic in the fine adjustment loop on the time axis described later, and the high frequency component of the input error output is relatively attenuated as compared with the low frequency component. A clock constant applied to the CCD is controlled by including a time constant means for generating an output and supplying this output to a VCO (voltage controlled oscillator) 13. That is, the CCD adjusts the time axis of the reproduction signal according to the output of the equalizer 9. Then, according to the above configuration, the time axis coarse adjustment is performed by the loop of the demodulation circuit 3, the CCD 4, the sync separation circuit 5, the phase comparator 6, the amplifier 8, the equalizer 9, the amplifier 10, the equalizer 11, the amplifier 12, and the motor 2. Performed by the sync separation circuit 5, the phase comparator 6, the amplifier 8, the equalizer 9, the VCO 13, and the CC.
The time axis is finely adjusted in the loop of D4.

When the pickup is made to perform a so-called scan operation in which the operation of jumping over one or more tracks and the tracking servo operation of following the tracks are alternately repeated while the time axis control is performed by such a system, a monitor is displayed. The video signal in the track following period is reproduced in a state where the page of the book is turned over. However, the positions of the vertical sync signal and the horizontal sync signal are aligned in the disk radial direction C
There is no problem for AV (constant angular velocity) discs, but for CLV (constant linear velocity) discs and CAA (constant angular acceleration) discs that are not aligned, the phase of the signal before and after the track jump operation becomes discontinuous, and every jump In addition, a large error signal was generated in the player's time axis servo system, and it took a relatively long time to stabilize it again.
Further, since the CCD may malfunction due to exceeding the correction operation range, when the time axis error becomes relatively large, the CCD loop as the fine adjustment means is turned off, and the spindle as the coarse adjustment means. Only the servo loop was operating. As a result, the image on the monitor cannot be color-synchronized, resulting in a black and white image. Further, even if the scan operation is stopped and the normal play operation is resumed, it takes a relatively long time for the time axis control to be stable and the time axis error to be small. There were many

In order to eliminate some of these drawbacks,
For example, there is a technique disclosed in Japanese Patent Laid-Open No. 58-98881. This has the effect of holding the frequency division counter by the gate pulse which includes the interlace period and which is synchronized with the reproduction horizontal synchronizing pulse, and smoothly continues without disturbing the time axis error.

[0005]

However, even in the case of the technique disclosed in the above publication, when the scanning operation is repeated, the disturbance of the time axis may occur and the color loss may occur in the image on the monitor. It was That is, in the case of the scanning operation, the tracking servo loop open pulse is generated to return the mirror near the center of the field of view when the tracking mirror forming a part of the signal recording / reproducing means reaches the limit of the field of view. , It has nothing to do with the cycle of the time axis error. Therefore, when the scanning operation is repeated, even if the time axis error is smoothly connected, the CCD is to correct the time axis error that occurs after the connection (after the jump), and the operating point before the connection (before the jump) The operation will start from (with an offset). In other words, since the time axis error correction permissible range by the CCD is finite, performing the fine adjustment of the time axis error after jumping in the state of having an offset means that the CCD time axis error correction permissible range (dynamic The range) will be substantially narrowed. Further disadvantageously, since the radial position from the center immediately before and after the jump extends over a considerable number of tracks, in the case of a CLV disc, it is necessary to follow the spindle rotation at a speed corresponding to this radial difference. Since the response is slow, the CCD with fast response operates to cover this. As a result, when such a state is repeated, the offset (deviation of the operating point) is gradually accumulated and increased, and there is no problem if the amount is corrected by the spindle motor that rotates the disk, but if it occurs in a short time. Cannot be absorbed by the response of the spindle motor, and finally the CCD reaches its limit, causing color loss and disturbance of the time axis.

Therefore, according to the present invention, the time axis fine adjustment of the reproduction signal in the video disc player can be smoothly performed, and the dynamic axis which is the correction allowable range of the time axis error can be widened as much as possible. The purpose is to provide a control method.

[0007]

In order to solve the above-mentioned problems, the present invention changes the generation phase of the reference synchronization signal so that the time axis error is continuous before and after the interlacing operation, and the interlacing operation is performed. It is characterized in that it is configured to initialize the time constant means therein.

That is, the present invention is a time axis control system for performing coarse adjustment and fine adjustment of the time axis according to the relative speed of the recording medium and the information reading point for scanning the recording medium, and a reproduction signal Sync separation means for extracting the included reproduction synchronization signal, reference signal generation means for generating a reference synchronization signal, phase comparison means for generating a phase difference signal between the reproduction synchronization signal and the reference synchronization signal, and the phase difference Time provided with time constant means for generating a signal in which the high frequency component of the signal is relatively attenuated as compared with the reduction component, and time axis fine adjustment means for finely adjusting the time axis of the reproduction signal according to the signal In the axis control device, when the information reading point is transferred while alternately repeating the tracking control operation so that the information reading point follows the track formed on the recording medium and the jumping operation over the track. A phase changing means (22) for changing the generated phase of the reference synchronization signal so that the phase difference before and after the jumping operation is substantially continuous; and at least during a period when the tracking servo loop in the jumping operation is opened. An initialization means (23) for initializing the time constant means so that the signal has a predetermined value, and a control signal generation means for generating a control signal for synchronously deactivating the phase changing means and the initialization means. (25), and is comprised.

[0009]

According to the present invention having the above structure, the phase changing means (22) is used when the information reading point on the recording medium is transferred while alternately repeating the tracking control operation and the track jumping operation for the track on the recording medium. ) Is used to change the generation phase of the reference synchronization signal so that the phase difference between the reproduction synchronization signal and the reference synchronization signal before and after the track jumping operation is substantially continuous. Fine adjustment of the time axis can be performed smoothly. At the same time, during the track jumping operation, the initialization means (23) controls the time constant means so that the signal generated from the time constant means becomes a predetermined value at least during the period when the tracking servo loop is opened. In order to initialize, the deviation of the operating point of the time axis fine adjustment means (offset) is prevented from being accumulated, and the operation start position of the time axis fine adjustment means is set to the widest correction range of the time axis error, that is, the dynamic range. It is possible to automatically set the center of the operating point. In the above operation, the control signal from the control signal generating means (25) synchronously deactivates the phase changing means (22) and the initializing means (23), that is, the operation is stopped. It is possible to return to normal operation in synchronization.

In this way, the continuity of the phase difference between the reproduction synchronizing signal and the reference synchronizing signal before and after the jumping operation is maintained,
Moreover, in order to erase the offset of the operating point of the time axis fine adjustment means by initializing the time constant means during the track jumping operation,
It is possible to prevent the disturbance of the time axis and the occurrence of color loss due to the alternate repetition of the tracking control operation and the track jump operation.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments according to the present invention will be described with reference to the drawings. FIG. 1 shows the basic configuration of the present invention. The parts corresponding to those in FIG. 6 are denoted by the same reference numerals, and detailed description thereof will be omitted. In this system, the means for supplying the reference horizontal synchronizing pulse to the phase comparator 6 outputs the reference signal having a frequency N times the horizontal synchronizing signal.
And a frequency divider 21 that divides the output by 1 / N. Reference numerals 22 and 23 denote switches, which are opened and closed by a pulse width expansion circuit 24 and a D flip-flop 25.
It is controlled by a drive circuit consisting of

Now, the operation will be described. CCD4
Since the time axis control is performed by the fine adjustment system by and the coarse adjustment system by the spindle motor 2 as in the case of FIG. 6, only the points different from the case of FIG. 6 will be described.

The signal input to the pulse width expansion circuit 24 is a pulse for opening the tracking servo loop when the mirror reaches near the field limit during the search operation (FIG. 2b). When this pulse is input, a pulse having a longer width is output by the pulse width expansion circuit 24 (FIG. 2c). Even if the tracking servo loop is closed again after the pulse for opening the tracking servo loop is closed and the pickup is switched to follow the track on the disk, the tracking servo loop is not immediately stable due to inertia or the like. The width of the pulse output by the circuit 24 is determined in consideration of the time required for this stabilization. Therefore, when the pulse of the circuit 24 is completed, the tracking servo is already locked in, and the tracking error is sufficiently small. The pulse whose width has been expanded is input to the data terminal D, and the reproduction horizontal sync pulse extracted by the sync separation circuit 5 is input to the clock terminal CK. Therefore, the output of the D-type flip-flop 25 is expanded. A leading edge is generated when the first reproduction horizontal sync pulse is input after the arrival of the pulse, and a trailing edge is generated when the first reproduction horizontal sync pulse is input after the end of the expansion pulse. That is, the enlarged pulse synchronized with the reproduction horizontal synchronizing signal is output from the flip-flop 25. When the flip-flop 25 outputs a pulse, the switch 22 is open and the switch 23 is closed during that time. When the switch 22 is opened, the counter constituting the frequency divider 21 is not supplied with the pulse from the oscillator 20, and the counter holds the count value at that time. Therefore, the reference horizontal synchronizing pulse is not input to the phase comparator 6 from the frequency divider 21 during this period, and the output of the phase comparator 6 tends to make the rotation of the motor 2 slower. However, the time constant circuit of the equalizer 9 is used. Is discharged by the switch 23, the output after passing through the equalizer 9 becomes substantially the same as when the time base error is zero. As a result, the spindle motor 2 and the CCD 4 operate in the same way as when the error signal is zero.

On the other hand, when the pulse of the flip-flop 25 ends, the switch 22 is closed again. The time required for the jumping operation is relatively short, and the motor 2 having a relatively large inertia cannot make a rapid response during that time. Therefore, the speed immediately after the jumping is almost the same as the speed immediately before the jumping. Therefore, the phase of the reference horizontal sync pulse with respect to the playback horizontal sync pulse immediately before the jump is held as a counter value, and the counter is restarted in synchronization with the playback horizontal sync pulse obtained immediately after the jump, so that the reference horizontal is instantaneously The same effect can be obtained as when the sync pulse and the reproduction horizontal sync pulse are matched to the same phase as they were just before the jump, so that continuity of the time axis error can be secured.

When the switch 23 is opened by the end of the pulse of the flip-flop 25, the CCD 4 performs the fine adjustment operation of the time axis again from the operation center point thereof, and therefore the offset (operation) is repeated by repeating the interlacing operation. The deviation of points does not accumulate. At this time, the motor 2 is also normally supplied with the correction signal of the time axis error signal. Therefore, during this period, the color image can be viewed on the monitor.

FIG. 3 shows one implementation of the equalizer 9 in FIG.
Shows an example. The equalizer 9 is a capacitor C₁, C
₂, Resistance R₁, R₂, An operational amplifier 26
Frequency f₀Active low-pass filter 27
Anti-R₃, R_Four, Capacitor C ₃, Operational amplifier 28
Low-range gain up equalizer 29 and resistor R_Five,
R ₆, Capacitor C_FourPhase lead compensation circuit 30
It is composed of Its comprehensive characteristic diagram is as shown in Fig. 4.
It has become. The frequencies in the figure are as follows.
It

F ₀ = 1 / 2π (C ₁ C ₂ R ₁ R ₂ ) ^1/2 f ₁ = 1 / 2π (R ₃ + R ₄ ) C ₃ f ₂ = 1 / 2π R ₄ C ₃ f ₃ = 1 / 2π (R ₅ + R ₆ ) C ₄ f ₄ = 1 / 2πR ₅ C _{4 As} described above, when there are a plurality of time constant circuits in the CCD loop, all of them may be discharged, but practically the most is possible. It is efficient and effective to discharge the part having a large time constant. Therefore, in this embodiment, both ends of the capacitors C ₁ and C ₂ are short-circuited by the switches 23A and 23B, respectively.

In FIG. 5, in the case of FIG. 1, the sync separation circuit 5, the phase comparator 6, the amplifier 8 and the equalizer 9 are shared by the CCD loop as the fine adjustment loop and the spindle loop as the coarse adjustment loop. On the other hand, in each of these loops, the sync separation circuits 5a, 5b,
The phase comparators 6a and 6b, the amplifiers 8a and 8b, and the equalizers 9a and 9b are independent of each other. It is obvious that the present invention can be implemented even in such a case.
However, even if the switch 23a provided in the equalizer 9a is omitted, there is no problem in practical use. However, since the spindle motor 2 has a relatively large inertia and therefore cannot make a rapid response, if the frequency divider (counter) 21 does not output the reference horizontal synchronization pulse during that time if the jumping time is short, This is because the rotation of the spindle motor 2 hardly changes.

In the above embodiment, the time constant means of the equalizer that determines the delay amount of the reproduction signal by the CCD is discharged so that the time axis error becomes substantially the same as when the time axis error is zero. Although the fine adjustment operation of the time axis is started again from the operation center point, the polarity of occurrence of the operating point offset of the CCD is determined by the feed direction of the information reading point, so the CCD operation is determined according to this feed direction. It goes without saying that a sufficient dynamic range can be secured even if the time constant means of the equalizer is initialized so that the fine adjustment of the time axis is started from a position deviated from the center point.

[0020]

As described above, according to the present invention, the time axis error is made continuous before and after the interlacing operation by the configuration in which the generation phase of the reference synchronization signal is changed, and the time constant means during the interlacing operation. Is initialized, the time axis fine adjustment can be smoothly performed from the operation center point of the time axis fine adjustment means, and the lack of the dynamic range does not occur.

[Brief description of drawings]

FIG. 1 is a block diagram of the system of the present invention.

FIG. 2 is a waveform diagram for explaining it.

FIG. 3 is a circuit diagram showing an embodiment of an equalizer.

FIG. 4 is a characteristic diagram thereof.

FIG. 5 is a block diagram of another embodiment of the present invention.

FIG. 6 is a block diagram of a conventional method.

[Explanation of symbols]

 4 ... CCD 5 ... Sync separation circuit 6 ... Phase comparator 9 ... Equalizer 13 ... VCO 20 ... Oscillator 21 ... Divider 24 ... Pulse width expansion circuit 25 ... D flip-flop

Claims (1)

Claim: What is claimed is: 1. A time axis control method for performing coarse adjustment and fine adjustment of a time axis according to a relative speed of a recording medium and an information reading point for scanning the recording medium. Sync separation means for extracting a reproduction synchronization signal included in the signal; reference signal generation means for generating a reference synchronization signal; phase comparison means for generating a phase difference signal between the reproduction synchronization signal and the reference synchronization signal; The phase difference signal is provided with a time constant means for generating a signal in which the high frequency component is relatively attenuated as compared with the reduction component, and a time axis fine adjustment means for finely adjusting the time axis of the reproduction signal according to the signal. In the time axis control device, the information reading point is transferred while alternately repeating the tracking control operation so that the information reading point follows the track formed on the recording medium and the jumping operation over the track. In this case, a phase changing means (22) for changing the generated phase of the reference synchronization signal so that the phase difference before and after the jumping operation is substantially continuous, and at least a period during which the tracking servo loop in the jumping operation is opened. At 23, an initialization means (23) for initializing the time constant means so that the signal becomes a predetermined value, and a control signal generation for generating a control signal for synchronously deactivating the phase changing means and the initialization means. Means (25),
A time axis control device comprising: