JPH02116289A - Time base corrector - Google Patents

Abstract

PURPOSE:To control the influence of noise, to increase the accuracy of time base error detection, and to accurately remove the time base fluctuation of a reproducing signal by adding a time base error signal to be obtained as two phase comparator outputs. CONSTITUTION:N-multiplication is executed with making the leading edge of the inputted horizontal synchronization signal into a reference in a first PLL circuit 8. The N-multiplication is executed with making the trailing edge of the inputted horizontal synchronization signal into a reference in a second PLL circuit 9. The horizontal synchronization signals being multiplied in the PLL circuits 8 and 9 are respectively inputted into phase comparators 10 and 11, phase-compared with a reference signal to be generated by a reference signal generator 12, and outputted as the time base error signal. The output of the phase comparators 10 and 11 is inputted into an adder 13, after being added, inputted into a delaying quantity variable circuit 4, changes the delaying quantity of the delaying quantity variable circuit 4, and corrects the time base fluctuation. Thus, picture deterioration attributable to the time base fluctuation can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention frequency-converts the color signal of a video signal such as a consumer VTR to a low frequency range, frequency-modulates a luminance signal to a high frequency range, and records it on a magnetic recording medium. The present invention relates to a time axis correction device that can be used in a device (color under one-way type VTR) for recording and reproducing information.

2. Description of the Related Art Generally, in a consumer VTR, the color signal of a video signal is frequency-converted to a low frequency band, and the luminance signal is frequency-modulated to a high frequency band, and then recorded on a magnetic recording medium. During playback, in the process of frequency converting the low frequency converted color signal back to the original high frequency range, time axis fluctuations (phase fluctuations) included in the color signal are removed and added to the reproduced luminance signal obtained by FM demodulation. and output it to a monitor television receiver. This is because a certain amount of time axis fluctuation occurs in the magnetic recording and reproducing system of consumer VTRs, and this time axis fluctuation causes the phase of the color signal to fluctuate significantly, so it is necessary to remove this phase fluctuation. be. In addition, the time axis fluctuation included in the luminance signal is
Since its frequency is low, it is almost eliminated by the AFC circuit included in the monitor television receiver. In other words, time axis fluctuations included in the color signal are corrected, but time axis fluctuations included in the luminance signal are not corrected. Therefore, the color signal and luminance signal have different time axis fluctuations,
The high-frequency luminance signal component included in the color signal component acts as an interfering signal between the original luminance signal and causes image quality deterioration. As a means to improve this image quality deterioration, a time axis correction device is used. (For example, ``Temporal axis fluctuations and their correction methods,'' Konishi et al., Journal of the Society of Television Engineers, 495.
~503 pages, Volume 3, No. 6, 1981).

An example of a conventional time axis correction device will be described below with reference to the drawings.

FIG. 4 is a block diagram showing the main structure of a conventional time axis correction device. In FIG. 4, a video signal recorded on a magnetic recording medium 1 is reproduced by a magnetic head 2 and input to a reproduction amplifier 3.

After being amplified by the regenerative amplifier 3, the luminance signal component is input to the luminance signal demodulator 201, where it is FM demodulated and then sent to the adder 2.
03.

On the other hand, the color signal component output from the regenerative amplifier 3 is input to the color signal converter 202, where it is frequency-converted by the color subcarrier frequency (3.58 MHz) output from the PLL circuit 205, and becomes the original color signal frequency. It is input to adder 203. An adder 203 adds the demodulated luminance signal and the frequency-converted chrominance signal, and inputs the result as a composite video signal to a delay amount variable circuit 206, a time axis variation detector 207, and a horizontal synchronization signal separation circuit 204.

The horizontal synchronization signal separation circuit 204 separates the horizontal synchronization signal of the input composite video signal and inputs it to the PLL circuit 205 . The PLL circuit 205 multiplies the input horizontal synchronizing signal to 455/2 times the frequency (3.58 MHz=color subcarrier frequency) and inputs the multiplied signal to the color signal converter 202 . The color subcarrier output from the PLL circuit 205 includes time axis fluctuations, and is frequency-converted by this color subcarrier, so that the composite video signal output from the adder 203 is composed of a luminance signal and a color signal. This means that they have the same time axis fluctuation.

The time axis variation detector 207 extracts a time axis variation component from the input composite video signal output from the adder 203 and outputs it as a time axis correction signal or a clock signal that matches the time axis variation. - A simple detector compares the phase of a reference signal with a signal obtained from a burst signal or horizontal synchronization signal to detect time axis fluctuations. The composite video signal input to the variable delay amount circuit 206 constituted by a semiconductor memory or the like has its time axis fluctuation corrected by the output of the time axis fluctuation detector 207, and is outputted from the terminal 208.

Problems to be Solved by the Invention However, in the above conventional configuration, the noise component included in the output of the adder 203 is also regarded as a time axis fluctuation component,
Since an attempt is made to correct time axis fluctuations, incorrect correction may be performed due to noise components, which often causes image quality deterioration. This is particularly noticeable with respect to high frequency time axis fluctuation components (several kHz).

The present invention solves the above conventional problems, and provides a time axis correction device that can improve image quality such as color reproducibility by increasing time axis error detection accuracy and improving correction accuracy compared to conventional time axis correction devices. The purpose is to provide.

Means for Solving the Problems To achieve this object, the time axis correction device of the present invention has the following features:
A variable delay circuit that receives a reproduction signal (hereinafter referred to as a reproduction RF signal) from a magnetic recording medium of a color under-type VTR as an input signal and varies the amount of delay of this input signal, and a band that extracts a luminance signal component from the reproduction signal. Pass filter (hereinafter referred to as B
PF), a demodulator that performs FM demodulation of the luminance signal component obtained by this BPF, a horizontal synchronization signal separation circuit that separates the horizontal synchronization signal from the demodulated luminance signal, and a demodulator that performs FM demodulation of the luminance signal component obtained by this BPF; 1 PLL circuit, a second PLL circuit that multiplies the falling edge of the horizontal synchronization signal as a reference, a reference signal generation circuit that generates a reference signal for time axis fluctuation correction, and an output of the first PLL circuit. a first phase comparator that compares the phase of the reference signal with the reference signal;
a second phase comparator that compares the output of the PLL circuit with the phase of the reference signal; and an adder that adds the outputs of the first and second phase comparators and inputs the sum to the variable delay amount circuit. are doing.

Effect of the present invention With the above-described configuration, by adding the time axis error signals obtained as the outputs of two phase comparators, the influence of noise is suppressed, and the accuracy of time axis error detection is improved compared to the conventional one, and the time axis of the reproduced signal is Eliminate axis fluctuations with precision. Furthermore, since the input signal is a reproduced RF signal, time axis fluctuations of the color signal and the luminance signal are corrected at the same time.

Embodiment Hereinafter, a time axis correction device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the main structure of a time axis correction device according to a first embodiment of the present invention. In FIG. 1, a video signal recorded on a magnetic recording medium 1 is reproduced by a magnetic head 2 and input to a reproduction amplifier 3. After being amplified by the regenerative amplifier 3, the delay amount variable circuit 4
is input.

Here, the delay amount variable circuit 4 is a semiconductor memory COD.
(charge-coupled device) etc., the delay time can be controlled freely.

The output of the variable delay amount circuit 4 is output from the terminal 14 and is also input to the BPF 5. The BPF 5 extracts the luminance signal component from the RF signal and inputs it to the demodulator 6 .

The demodulator 6 demodulates the FM signal and inputs it as a baseband luminance signal to the horizontal synchronization signal separation circuit 7 (see Fig. 2).
The waveform diagram is shown in a). From the horizontal synchronization signal separation circuit 7,
Only the horizontal synchronizing signal is extracted and input to the PLL circuits 8 and 9 (a waveform diagram is shown in FIG. 2(b)).

The first PLL circuit 8 multiplies the signal by N based on the rising edge of the input horizontal synchronizing signal (the waveform diagram is shown in FIG. 2(c)). For example, if N=227.5,
The output of the PLL circuit 8 becomes a 3.58 MHz signal. Further, in the second PLL circuit 9, the falling edge of the input horizontal synchronizing signal (the waveform diagram is shown in FIG. 2(d)) is used as a reference, and similarly to the PLL circuit 8, the signal is multiplied by N. PLL
The horizontal synchronizing signals multiplied by the circuits 8 and 9 are input to phase comparators 10 and 11, respectively, and the phase is compared with the reference signal (same frequency as the output of the PLL circuits 8 and 9) generated by the reference signal generator 12. It is compared and output as a time axis error signal. The outputs of the phase comparators 1o and 11 are input to the adder 13, and after being added, are input to the variable delay amount circuit 4, and the delay amount of the variable delay amount circuit 4 is changed to correct the time axis fluctuation.

As described above, according to this embodiment, by adding two time axis error signals, reducing the influence of noise and increasing detection accuracy, it is possible to more accurately remove time axis fluctuations. Image quality deterioration caused by time axis fluctuations can be improved.

FIG. 3 is a block diagram showing the main part configuration of a time axis correction device showing a second embodiment of the present invention. The difference from Fig. 1 is that Fig. 1 constitutes a feedback type, whereas
Figure 3 shows a feedforward configuration.

The operation of the time axis correction device configured as described above will be described below. In FIG. 3, a video signal recorded on a magnetic recording medium 1 is reproduced by a magnetic head 2 and input to a reproduction amplifier 3. After being amplified by the regenerative amplifier 3, the signal is input to the variable delay amount circuit 101. The variable delay amount circuit 101 is basically the same as the variable delay amount circuit 4 shown in FIG. 1, but since it is used in a feedforward type, the overall delay time is different.

The output of the variable delay amount circuit 101 is output from the terminal 14 and is also input to the BPF 5. RF by BPF5
The luminance signal component in the signal is extracted and input to the demodulator 6. The signal is FM demodulated by the demodulator 6 and input to the horizontal synchronization signal separation circuit 7 as a baseband luminance signal. Only the horizontal synchronizing signal is taken out from the horizontal synchronizing signal separation port 7 and input to PLL circuits 8 and 9.

The first PLL circuit 8 multiplies the rising edge of the input horizontal synchronizing signal by N.

Further, the second PLL circuit 9 multiplies the signal by N using the falling edge of the input horizontal synchronizing signal as a reference. PLL
The horizontal synchronizing signals multiplied by circuits 8 and 9 are input to phase comparators 10 and 11, respectively, where the phase is compared with a reference signal generated by reference signal generator 12, and output as a time axis error signal. The outputs of the phase comparators 10 and 11 are input to the adder, and after being added, the delay amount variable circuit 101
is input to the variable delay amount circuit 101 to change the delay amount of the variable delay amount circuit 101 to correct time axis fluctuations.

As described above, according to this embodiment, by adding two time axis error signals, reducing the influence of noise and increasing detection accuracy, it is possible to more accurately remove time axis fluctuations. Image quality deterioration caused by time axis fluctuations can be improved. Furthermore, although the stability is lower than in the first embodiment, the responsiveness is faster and it is possible to follow high frequency time axis fluctuation components.

Note that in the first and second embodiments, the PLL circuit 8,
Although the frequency multiplication factor N of 9 was set to 227.5, the N may be any value.

Effects of the Invention As described above, the present invention uses a reproduced RF signal as an input signal,
a delay amount variable circuit that varies the delay amount of this input signal;
A BPF that extracts the luminance signal component in the F signal and this BP
a demodulator that performs FM demodulation of the F output; a horizontal synchronization signal separation circuit that separates the horizontal synchronization signal from the demodulated luminance signal; a PLL circuit that multiplies the rising edge of the horizontal synchronization signal as a reference; and a falling edge of the horizontal synchronization signal. 2. A PLL circuit that multiplies the edge based on the edge, a reference signal generation circuit that generates a reference signal for time axis fluctuation correction, and two phase comparators that compare the output of each PLL circuit with the phase of the reference signal.
By providing an adder that adds the outputs of two phase comparators and inputs it to the variable delay amount circuit, the influence of noise contained in the time axis error signal is reduced, and the detection accuracy is increased, allowing more accurate timing. It becomes possible to remove axis fluctuations and improve image quality, which has great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a time axis correction device according to a first embodiment of the present invention, FIG. 2 is an operation waveform diagram of the same embodiment, and FIG. 3 is a block diagram of a time axis correction device according to another embodiment of the present invention. Block Diagram FIG. 4 is a block diagram of a conventional time axis correction device. 4...Delay amount variable circuit, 5...B
PF16...Demodulator, 7...Horizontal synchronization signal separation circuit, 8.9...PLL circuit,
10.11... Phase comparator, 12...
...Reference signal generator, 13...Adder,
101...Delay amount variable circuit. Name of agent: Patent attorney Shigetaka Awano and one other person Figure <d)

Claims (2)

[Claims] (1) As an input signal, a playback signal from a magnetic recording medium recorded by frequency converting the color signal component of the video signal to a low frequency band and frequency modulating the luminance signal component to a high frequency band is used as an input signal, and this input signal is delayed. a variable delay amount circuit that varies the amount of delay; a bandpass filter that extracts a luminance signal component from the output of the variable delay amount circuit; a demodulator that demodulates the luminance signal component obtained by the bandpass filter; a horizontal synchronization signal separation circuit that separates a horizontal synchronization signal from a luminance signal; a first PLL circuit that multiplies the horizontal synchronization signal based on the rising edge of the horizontal synchronization signal; and a second PLL circuit that multiplies the horizontal synchronization signal based on the falling edge of the horizontal synchronization signal. a PLL circuit, a reference signal generation circuit that generates a reference signal for time axis fluctuation correction, a first phase comparator that compares the phase of the output of the first PLL circuit and the reference signal, and the second a second phase comparator that compares the output of the PLL circuit and the phase of the reference signal;
and an adder for adding the output of the second phase comparator and inputting the result to the variable delay amount circuit. (2) As an input signal, a playback signal from a magnetic recording medium recorded by frequency converting the color signal component of the video signal to a low frequency band and frequency modulating the luminance signal component to a high frequency band is used as an input signal, and this input signal is delayed. a delay amount variable circuit that varies the amount of delay; a bandpass filter that extracts the luminance signal component from the input signal; and a bandpass filter that extracts the luminance signal component from the input signal;
a demodulator for demodulating, a horizontal synchronizing signal separation circuit for separating a horizontal synchronizing signal from the demodulated luminance signal, a first PLL circuit for multiplying the rising edge of the horizontal synchronizing signal, and a first PLL circuit for multiplying the rising edge of the horizontal synchronizing signal; a second PLL circuit that multiplies based on the falling edge; a reference signal generation circuit that generates a reference signal for time axis fluctuation correction; and a first PLL circuit that compares the phase of the output of the first PLL circuit and the reference signal. a second phase comparator that compares the phase of the output of the second PLL circuit and the reference signal; and a second phase comparator that adds the outputs of the first and second phase comparators to the variable delay amount circuit. A time axis correction device characterized by comprising an input adder.