JPH0356040B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a time axis correction device for a reproduced signal,
In particular, the present invention relates to a time axis correction device for a reproduced color video signal obtained from a recording medium such as a video disk.

In playback devices such as video disc players, a time axis correction device that corrects the time axis of a playback signal is essential in order to obtain high quality color images. This time axis correction device eliminates the time axis error of the reproduced signal by controlling the movement of a reading pickup in the track tangential direction of the recording disk using a time axis error signal corresponding to the amount of time axis error of the reproduced signal, for example. It is structured as follows. Such a time axis correction device uses a phase difference signal obtained by phase comparison of a reproduced horizontal synchronization signal in a reproduced color video signal and a reference horizontal synchronization signal, and a reproduced color burst signal and a reference color sub signal in a reproduced color video signal. A device is already known that has a configuration in which a signal obtained by amplifying and adding and combining a phase difference signal obtained by phase comparison of a carrier signal is used as a time axis error signal. In such conventional time base correction devices, in order to precisely match the phase of the reproduced horizontal synchronizing signal with the phase of the reference horizontal synchronizing signal, a phase difference signal obtained by comparing the phases of the reproduced and reference horizontal synchronizing signals is amplified. When the gain of the amplifier is increased, a steady-state error occurs between the phases of the reproduced color burst signal and the reference color subcarrier signal. Conversely, in order to precisely match the phase of the reproduced color burst signal with the phase of the reference color subcarrier signal, a phase difference signal obtained by phase comparison of the reproduced color burst signal and the reference color subcarrier signal is used. When the gain of the amplifying amplifier is increased, a steady error occurs between each phase of the reproduction and reference horizontal synchronizing signals, making it difficult to perform accurate time axis correction.

Therefore, a time axis correction device as shown in FIG. 1, which enables relatively accurate time axis correction, was also devised by the inventor of the present application. In Figure 1,
A reproduced color video signal is supplied to a horizontal sync separator 1 and a phase comparator 2. Horizontal sync separator 1
separates and outputs the reproduced horizontal synchronizing signal from the reproduced color video signal, and also generates a burst gate pulse consisting of pulses that are generated during the existence time of the color burst signal in the reproduced color video signal after a predetermined time has elapsed from the reproduced horizontal synchronizing signal. It is also configured to output. The reproduced horizontal synchronization signal output from the horizontal synchronization separator 1 is sent to the phase comparator 3.
The phase is compared with the 15.75KHz reference horizontal synchronization signal.
A signal corresponding to the phase difference between the reproduced and reference horizontal synchronizing signals outputted from the phase comparator 3 is amplified by an amplifier 4 and then supplied to an adder 5 .

On the other hand, in the phase comparator 2, the reproduced color video signal is phase-compared with a reference color subcarrier signal of 3.58 KHz. The output of this phase comparator 2 is supplied to a sample hold circuit 6. The burst gate pulse outputted from the horizontal sync separator 1 is supplied to the sample hold circuit 6 as a sampling pulse. The sample and hold circuit 6 holds and outputs a signal voltage corresponding to the phase difference between the reproduced color burst signal and the reference color subcarrier signal at the output of the phase comparator 2. This signal voltage is amplified by an amplifier 7 and then sent to an adder 5 via an analog switch 8.
and the output of the phase comparator 3 which is amplified by the amplifier 4 and combined. The analog switch 8 is configured to be in an open state when, for example, a low level signal is supplied to the control input terminal. The control input terminal of this analog switch 8 is supplied with the output of the window comparator 9. The output of the phase comparator 3 is supplied to the window comparator 9. Window comparator 9
is configured to generate, for example, a high level signal when the input voltage is within a voltage range determined by two mutually different reference voltages, and to generate, for example, a low level signal when the input voltage is outside the voltage range. There is.

The output of the adder 5 is then supplied as a time-axis error signal to a spindle motor (not shown) for rotating the recording disk via an equalizer amplifier 10, and at the same time, a button that controls the position of the information reading laser beam in the tangential direction of the recording track. It is supplied to a drive coil 12 that drives a Zentral mirror 11.

In the above configuration, when the phase difference between the reproduced and reference horizontal synchronizing signals whose phases are compared in the phase comparator 3 becomes less than a predetermined difference, the output voltage of the phase comparator 3 is determined by the reference voltage in the window comparator 9. If the voltage is within the range, the window comparator 9 will only operate when the phase difference between the reproduction and reference horizontal synchronizing signals becomes less than the predetermined phase difference.
The output becomes high level and the analog switch 8 is turned on. Then, a signal corresponding to the phase difference between the reference subcarrier signal and the reproduced color burst signal begins to be applied as a time axis error signal to the spindle motor and drive coil 12 (not shown). Therefore, in order to precisely match the phases of the reference subcarrier signal and the reproduced color burst signal, by increasing the gain of the amplifier 7 that amplifies the signal according to the phase difference between the two signals, the reproduced and reference horizontal synchronizing signals are Even if a steady error occurs between each phase of the signal, the analog switch 8 acts so that the phase difference between the reproduced and reference horizontal synchronizing signals does not exceed a predetermined difference. As a result, the phases of the reference subcarrier signal and the reproduced color burst signal can be accurately matched, and the phase difference between the reproduced and reference horizontal synchronization signals can be kept below a predetermined difference, making it possible to perform relatively accurate time axis correction. .

However, in the conventional time base correction device as described above, the comparison range of the phase comparator 3 is usually
Since a range of about 40 μsec is required and the output voltage range of the phase comparator 3 is limited, the voltage range determined by the two reference voltages in the window comparator 9 is set within the range in which stable voltage comparison can be made. Even if the setting was made as narrow as possible, the phase difference between the reproduction and reference horizontal synchronizing signals could not be reduced to less than about 3 μs, making it impossible to perform sufficiently accurate time axis correction.

That is, even if the phase of the color burst signal CB in the reproduced color video signal c completely matches the phase of the reference color subcarrier signal a as shown in FIG. 2, the reference horizontal synchronization signal b and the reproduced color Playback horizontal synchronization signal PBH in video signal c
A phase shift Δt may occur between the two.

This means that the fluctuation phase error between the reference horizontal synchronization signal and the reproduced horizontal synchronization signal can be suppressed to only about 3 μs.
This value is the color subcarrier signal (f _SC = 3.58M
This is because it is considerably larger than 280 ns, which is one wavelength of Hz).

Therefore, it has not been possible to perform time axis correction that can be applied to a so-called external synchronization method in which the playback outputs of two or more video playback devices are synchronized with the same reference signal and the outputs of each video playback device are synchronized with each other. This is because each video output has a different phase shift Δt, making it impossible to synchronize the horizontal synchronizing signal.

Therefore, an object of the present invention is to provide a time base correction device that can perform sufficiently accurate time base correction, and is to provide a time base correction device that can be applied to a so-called external synchronization method.

The playback signal time axis correction device according to the present invention adjusts the phase difference between the playback horizontal synchronization signal and the reference horizontal synchronization signal in the playback color video signal with two different accuracies.
The phase difference between the reproduction and reference horizontal synchronizing signals is detected to be outside a predetermined range by the output of one of the two phase difference detection means, which has relatively high accuracy. At this time, the outputs of the two phase difference detection means are added and synthesized to form a time axis error signal, and it is detected by the output of one of the above that the phase difference between the reproduction and reference horizontal synchronization signals is within a predetermined range. When the output of the other of the two phase difference detection means having relatively low precision is added and synthesized with a signal corresponding to the phase difference between the reproduced color burst signal and the reference subcarrier signal, a time axis error signal is obtained. It's summery.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 3 and 4.

As shown in FIG. 3, the drive coil 12 that drives the horizontal sync separator 1, phase comparators 2, 3, amplifiers 4, 7, adder 5, sample and hold circuit 6, equalizer amplifier 10, and tangential mirror 11 is They are connected in the same way as in FIG. however,
In this example, the phase difference between the reproduced horizontal synchronization signal output from the horizontal synchronization separator 1 and the reference horizontal synchronization signal is more accurate than the phase comparator 3, and the phase comparison range is relatively narrow (for example, ±1 μsec). Vessel 13
It has also been detected in This phase comparator 13
The output is supplied to the window comparator 9, amplified by the amplifier 14, and then supplied to one input terminal of the signal changeover switch 15. The other input terminal of the signal changeover switch 15 is supplied with the output of the amplifier 7, and the control input terminal of the signal changeover switch 15 is supplied with the output of the window comparator 9. The signal changeover switch 15 selectively outputs the output of the amplifier 14 supplied to one input terminal when a low level signal is supplied to the control input terminal, and when a high level signal is supplied to the control input terminal. The configuration is such that the output of the amplifier 7 supplied to the other input terminal is selectively output.

In the above configuration, if the input/output characteristics of the phase comparator 13 are made as shown in FIG. 4B with respect to the input/output characteristics of the phase comparator 3 as shown in FIG. The output of the window comparator 9 can be made to change from a low level to a high level only when the phase difference between the reproduced and reference horizontal synchronizing signals to be compared becomes an extremely small difference of about several tens of nanoseconds. Then, when the phase difference between the reproduced and reference horizontal synchronizing signals becomes extremely small, on the order of several tens of nanoseconds, the output of the amplifier 7, that is, the phase difference between the reference subcarrier signal and the reproduced color burst signal, will be used instead of the output of the amplifier 14. The signal is selectively output from the signal changeover switch 15 and applied as a time axis error signal to the spindle motor and drive coil 12 (not shown). Therefore, after the phase of the horizontal synchronization signal precisely matches, time axis correction based on the phase of the subcarrier signal is started, and time axis correction is performed to maintain the absolute phase of the reproduced color burst signal with respect to the reference horizontal synchronization signal. It will be done.

In the above embodiment, the time axis error signal is applied to the spindle motor and drive coil 12 (not shown), but the time axis error signal may also be applied to a CCD (charge coupled device) or the like that delays the reproduced color video signal. The signal may be supplied to a VCO (voltage controlled oscillator) that generates a clock pulse for controlling the amount of delay of a controlled delay device, thereby correcting the time axis of the reproduced color video signal. Further, in the above embodiment, a time axis correction device for an NTSC color video signal has been described, but the present invention can also be applied to a time axis correction device for other color video signals such as a PAL system.

As described above, according to the present invention, the comparative output of the relatively accurate phase comparison means for detecting the phase difference between the reproduced and reference horizontal synchronizing signals can be set as narrow as possible within the range that allows stable level comparison. Only when the level falls within a predetermined level range, a signal corresponding to the phase difference between the reference subcarrier signal and the reproduced color burst signal is added to the time axis error signal and output. Not only the phase difference between the reproduction signal and the reference horizontal synchronization signal but also the phase difference between the reproduction signal and the reference horizontal synchronization signal can be made sufficiently small, making it possible to perform sufficiently accurate time axis correction. Therefore, it is possible to provide the reproduction signal time axis correction apparatus according to the present invention in a plurality of reproduction apparatuses, and to precisely synchronously couple each output signal to a common external synchronization signal. Video signals that are accurately synchronously combined with each other have no phase shift in the color subcarrier signal representing the hue, and even if selectively switched, no color unevenness or color shift will occur on the screen of the playback monitor. Therefore, it becomes possible to perform screen composition, etc. using image outputs from a plurality of color video signal reproducing devices.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a time axis correction device for a reproduced signal, FIG. 2 is a diagram showing a phase shift of a reproduced horizontal synchronizing signal, and FIG. 3 is a block diagram showing an embodiment of the present invention. FIG. 4 is a diagram showing the input/output characteristics of each of the phase comparators 3 and 13 in the device of FIG. 3. Explanation of symbols of main parts, 1...Horizontal sync separator, 2, 3, 13...Phase comparator, 4, 7, 14
...Amplifier, 5...Adder, 6...Sample hold circuit, 9...Window comparator, 15...
...Signal changeover switch.

Claims (1)

[Claims] 1. A first phase difference detection means for generating a first phase difference signal by detecting a phase difference between a reproduced horizontal synchronizing signal and a reference horizontal synchronizing signal in a reproduced color video signal with relatively low accuracy; and the reproduced horizontal synchronizing signal. a second phase difference detection means for detecting a phase difference between the reference horizontal synchronization signal and the reference horizontal synchronization signal with relatively high precision to generate a second phase difference signal; a third phase difference detection means for detecting a phase difference with the rear signal to generate a third phase difference signal; and a third phase difference detection means for detecting a phase difference with the rear signal and generating a third phase difference signal; selectively outputs the second phase difference signal when it is detected that the signal is outside the predetermined range, and detects that the phase difference between the reproduced horizontal synchronization signal and the reference horizontal synchronization signal is within the predetermined range. signal selection means for selectively outputting the third phase difference signal when the third phase difference signal is detected, and the first phase difference signal and the output of the signal selection means are added to form a time axis error signal of the reproduced signal. A reproduction signal time axis correction device characterized by: