JPS59140785A - Time-axis correcting device for reproduced signal - Google Patents

Abstract

PURPOSE:To make sufficiently precise time-axis corrections by detecting the phase difference between a reproduced and a reference horizontal synchronizing signal with relatively high precision, and outputting the phase difference signal between a reproduced burst signal and a reference color subcarrier signal only when said detection signal of the phase difference is present. CONSTITUTION:The reproduced horizontal synchronizing signal outputted by a horizontal synchronous separator 1 and the reference horizontal synchronizing signal are compared with each other by a phase comparator 3 and also a phase comparator 13 which has higher precision and a narrower phase comparison range than the phase comparator 3 also makes a phase comparison. When the phase difference obtained by the phase comparison of the phase comparator 13 is extremely small, the output of a window comparator 13 goes up to a high level for the first time and a changeover switch 15 is switched. consequently, a signal corresponding to the phase difference between the reference subcarrier signal and reproduced color burst signal is selected by the changeover switch 15 and outputted as a time-axis error signal.

Description

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

In a playback device such as a video disk player, a time axis correction device that corrects the time axis of a playback signal is essential in order to obtain a high quality color image. This time axis correction device has a configuration in which, for example, the movement of a reading pickup in the track tangential direction of the recording disk is controlled by a time axis error signal corresponding to the amount of time axis error of the reproduced signal to eliminate the time axis error of the reproduced signal. It has become. As such a time axis correction device, a phase difference signal obtained by phase comparison of the reproduced horizontal synchronization signal in the reproduced color video signal and the reference horizontal synchronization signal, and the reproduced color burst signal and the reference color TV carrier signal in the reproduced color video signal are used. A device is already known that has a configuration in which a signal obtained by amplifying and adding and synthesizing the phase difference signal obtained by the phase comparison is used as a time axis error signal. In such a conventional time base correction device, an amplifier is used to amplify a phase difference signal obtained by comparing the phases of the reproduced and reference horizontal synchronizing signals in order to precisely match the phase of the reproduced horizontal synchronizing signal with the phase of the reference horizontal synchronizing signal. Increasing the gain of the reproduced color burst signal causes a steady error between each phase of the reference color safunicarrier signal. Conversely, in order to precisely match the phase of the reproduced color burst signal with the phase of the reference color subcarrier signal, an amplifier is used to amplify the phase difference signal obtained by comparing the phases of the reproduced color burst signal and the reference color subcarrier signal. When the gain 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, the inventor of the present application has devised a time axis correction device as shown in FIG. 1, which enables relatively accurate time axis correction. In FIG. 1, a reproduced color video signal is supplied to a horizontal sync separator 1 and a phase comparator 2. In FIG. The horizontal sync separator 1 separates and outputs a reproduced horizontal sync signal from the reproduced color video signal, and also separates and outputs a pulse generated over the existence time of the color burst signal in the reproduced color video signal after a predetermined time has elapsed since the reproduced horizontal sync signal. The configuration also outputs a burst gate pulse consisting of:

The reproduced horizontal synchronizing signal output from the horizontal synchronizing separator 1 is phase-compared with a reference horizontal synchronizing signal of 1'5.75 in phase comparator 3. The signal corresponding to the phase difference between the reproduction and reference horizontal synchronization signals output from the phase comparator 3 is
After being amplified by an amplifier 4, it is supplied to an adder 5.

On the other hand, in the phase comparator 2, the phase of the reproduced color video signal is compared with the reference color subcarrier signal of 358MH7. The output of the phase comparator 2 is supplied to a sample and hold circuit 6. The burst pulse output 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 Vermi No. 4 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 supplied to an adder 5 via an analog switch 8, where it is added and combined with the output of the phase comparator 3 which has been amplified by the amplifier 4. 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 output of the window comparator 9 is supplied to the control input terminal of the analog switch 8. The output of the phase comparator 3 is supplied to the window comparator 9. The 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 different reference voltages, and to generate, for example, a low level signal when the input voltage is outside the voltage range. It is being done.

Then, the output of the adder 5 is supplied as a time-axis error signal to a spindle motor (not shown) for rotating the recording disk via an equalizer amplifier 10, and the information is transmitted along with φ to the entire position of the laser beam in the tangential direction of the recording track. It is supplied to a drive coil 12 that drives a tangential mirror 11 to be controlled.

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 falls within a voltage range determined by the reference voltage in the window comparator 9. If so, the output of the window comparator 9 becomes high level and the analog switch 8 is turned on only when the phase difference between the reproduced and reference horizontal synchronizing signals becomes equal to or less than a predetermined phase difference. 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 adjusted. Even if a steady error occurs between each phase, the analog switch 8 acts to prevent the phase difference between the reproduced and reference horizontal synchronizing signals from exceeding the required difference. As a result, the phases of the reference subcarrier signal and the reproduced color burst signal can be precisely 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. Become.

However, in the conventional time axis stop≠-coma motion correction device as described above, the comparison range of the phase comparator 3 usually needs to be about 40μ, and the output voltage range of the phase comparator 3 is limited. Therefore, even if the voltage range determined by the two reference voltages in the window comparator 9 is set as narrow as possible within the range that allows stable voltage comparison, the phase difference between the reproduction and reference horizontal synchronizing signals will be approximately 3μ8 or less. Therefore, it was not possible to perform sufficiently accurate time axis correction.

That is, as shown in FIG. 2, if the color burst signal 0. Even if the phase of B completely matches the phase of the reference color subcarrier signal (α), there is a difference in phase between the reference horizontal synchronization signal (b) and the reproduced horizontal synchronization signal PBH in the reproduced color video signal (1). A deviation Δt may occur.

This means that the fluctuation phase error between the reference horizontal synchronization signal and the reproduced horizontal synchronization signal can be suppressed to only 3 μs, and this value is 1
This is because it is considerably larger than the wavelength of 280 ns.

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 axis correction device that can perform sufficiently accurate time axis correction, and is to provide a time axis correction device that can be applied to the so-called external synchronization method.

The time axis correction device for a reproduced signal according to the present invention detects a phase difference between a reproduced horizontal synchronizing signal in a reproduced color video signal and a reference horizontal synchronizing signal using two phase difference detecting means having different accuracies, and When it is detected by the output of one of the phase difference detection means having relatively high accuracy that the phase difference between the reproduction and reference horizontal synchronization signals is outside a predetermined range, the outputs of the two phase difference detection means are added and combined. is used as a time axis error signal, and when it is detected by the output of one of the above that the phase difference between the reproduction and reference horizontal synchronizing signals is within a predetermined range, the other of the two phase difference detection means has relatively low accuracy. The output signal is added and synthesized with a signal corresponding to the phase difference between the reproduced color burst signal and the reference subcarrier signal to generate a time axis error signal.

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

As shown in FIG. 3, a horizontal sync separator 1, a phase comparator 2,
3, amplifier 4, 7, adder 5, sample hold circuit 6
, equalizer amplifier 10, and drive coil JJ/12 for driving Tansen Yarmirror 11 are connected in the same manner 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 higher in accuracy than the phase comparator 3, and the phase comparison range is relatively narrow (for example, ±1μ5ec). Phase comparator 1
3 was also detected. The output of the phase comparator 13 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. Signal changeover switch 1
The output of the amplifier 7 is supplied to the other input terminal of the signal changeover switch 15, and the output of the window comparator 9 is supplied to the control input terminal of the signal changeover switch 15. 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 that is 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. 4(B) with respect to the input/output characteristics of the phase comparator 3 as shown in FIG. 4(4), the phase comparison It is possible to make the output of the window controller 9 change from a low level to a high level only when the phase difference between the reproduced and reference horizontal synchronizing signals, which are phase-compared in the device 13, becomes an extremely small difference of about 1071 seconds. can. Then, the phase difference between the reproduction and reference horizontal synchronization signals is several i.
When the difference becomes extremely small on the order of 0 rLsec, the signal changeover switch 15 selectively outputs the output of the amplifier 7 instead of the output of the amplifier 14, that is, a signal corresponding to the phase difference between the reference subcarrier signal and the reproduced color burst signal. This signal is then applied to the spindle motor and drive coil 12 (not shown) as a time axis error signal. Therefore, after the phase of the horizontal synchronization signal accurately 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 a long time.

In the above example, the time axis error signal is applied to the spindle motor and drive coil 12 (not shown), but the time axis error signal delays the reproduced color video signal (COD (charge coupled device)). It is supplied to a VOO (voltage controlled oscillator) that generates a clock pulse for controlling the delay amount of a controlled delay device such as
The time axis of the color video signal may be corrected. 'Furthermore, in the above embodiment, the explanation has been made regarding the time axis correction device for the color video signal of the NTSC system, but the present invention is applicable to the time axis system of the color video signal of other systems such as the PAL system. It can also be applied to a nose = age correction device.

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. This makes it possible to sufficiently reduce 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, thereby 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 selective switching is performed, no uneven color shift will occur on the screen of the playback monitor. Therefore, images from multiple color video signal reproduction devices! It becomes possible to perform screen composition etc. using the output.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a time axis correction device for a reproduced signal, and FIG. 2 is a diagram showing a phase shift of a reproduced horizontal synchronization signal.
FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. 4 is a diagram showing the input/output characteristics of each of the phase comparators 3 and 13 in the device shown in FIG. Explanation of symbols of main parts l...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 Applicant Pioneer Corporation Agent Patent attorney Motohiko Fujimura

Claims (1)

[Claims] 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; a second phase difference detection means for detecting a phase difference of the reference horizontal synchronization signal with relatively high precision to generate a second phase difference signal; and a reproduction burst signal in the reproduction color video signal and a reference color subcarrier signal. a third phase difference detection means for detecting a phase difference between the two and generating a third phase difference signal; selectively outputting the second phase difference signal when a certain thing is detected, and when it is detected that the phase difference between the reproduced horizontal synchronization signal and the reference horizontal synchronization signal is within the predetermined range; a signal selection means for selectively outputting three phase difference signals, 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 reproduction signal. Signal time axis correction device.