JPH0817501B2 - Time axis fluctuation correction device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reproducing apparatus such as a VTR or a video disc, and a time axis fluctuation correcting apparatus for removing a time axis fluctuation component of a reproduced composite video signal reproduced from a recording medium. Regarding

2. Description of the Related Art As a conventional time axis fluctuation correction device, for example, Japanese Patent Laid-Open No.
The method shown in Japanese Patent Laid-Open No. 60-216691 "Time axis fluctuation correction device" is known. Hereinafter, a conventional time axis fluctuation correction device will be described with reference to the drawings.

FIG. 5 shows a block diagram of a conventional time axis fluctuation correcting device. In FIG. 5, 10 is an input terminal of the device,
20 is an output terminal of the device, 30 is a variable delay element 31 composed of a CCD or the like, a horizontal sync separation circuit for extracting a horizontal sync signal from the reproduced composite video signal and refining the burst gate signal, and 32 is a horizontal sync. A horizontal phase difference detection circuit for detecting a phase error of a signal, a phase compensation circuit 35 composed of an active filter and the like, and a voltage controlled oscillation circuit (VCO) 36 capable of changing an oscillation frequency by a voltage. Further, 40 is a phase correction circuit that corrects the phase shift of the color subcarrier of the reproduced composite video signal, 41 is a burst separation circuit that extracts the burst signal from the reproduced composite video signal, and 42 is a burst that detects the phase error of the burst signal. A phase difference detection circuit, 43 is a reference signal generation circuit for generating a reference horizontal synchronizing signal and a reference burst signal, 33 is an adder, and 34 is a low pass filter (LPF).

In FIG. 5, a variable delay element 30, a horizontal sync separation circuit
31, horizontal phase difference detection circuit 32, low pass filter (LPF) 3
3, adder 34, phase compensation circuit 35, voltage controlled oscillator circuit (VC
O) 36 blocks make up a course TBC and remove the time-axis fluctuation component contained in the reproduced composite video signal up to the phase shift of the burst signal (up to about ± 140 ns or less). Further, a fine TBC is composed of three blocks of a phase correction circuit 40, a burst separation circuit 41, and a burst phase difference detection circuit 42, and the phase shift of the burst signal is about the maximum (±
The time-axis fluctuation component in the reproduced composite video signal that has been reduced to 140 ns) or less is further accurately removed.

The operation of the conventional time-axis fluctuation correction device configured as described above will be described below with reference to FIG.

The reproduced composite video signal including the time-axis fluctuation component input from the input terminal 10 of the device passes through the variable delay element 30 and is sent to the horizontal sync separation circuit 31, the burst separation circuit 41, and the phase correction circuit 40. The horizontal sync separation circuit 31 separates the horizontal sync signal in the reproduced composite video signal, sends it to the horizontal phase difference detection circuit 32, and generates a burst gate signal to send it to the burst separation circuit 41.

The horizontal phase difference detection circuit 32 detects the phase difference between the reference horizontal sync signal generated by the reference signal generation circuit 43 and the horizontal sync signal in the reproduced composite video signal sent from the horizontal sync separation circuit 31. , To the adder 34. Further, the burst separation circuit 41 separates the burst signal in the reproduced composite video signal and sends it to the burst phase difference detection circuit 42. The burst phase difference detection circuit 42 detects the phase difference between the reference burst signal generated by the reference signal generation circuit 43 and the burst signal in the reproduced composite video signal sent from the burst signal separation circuit 41, and the LPF33 To the phase correction circuit 40. The LPF 33 extracts only the low frequency component of the burst phase difference signal and sends it to the adder 34. The adder 34 adds the horizontal sync phase difference signal sent from the horizontal phase difference detection circuit 32 and the low frequency component of the burst phase difference signal sent from the LPF 33, and the phase compensation circuit
Send to 35. In the phase compensation circuit 35, the time axis fluctuation component in the reproduced composite video signal and the course having the feedback loop
The phase difference signal from the adder 34 is amplified and phase-compensated in consideration of the operating characteristics such that the TBC does not oscillate, and then sent to the VCO 36. The VCO 36 is a voltage control type oscillation circuit, and changes the oscillation frequency according to the phase difference signal sent from the phase compensation circuit 35. The variable delay element 30 changes the delay amount according to the change in the oscillation frequency of the VCO 36, and removes the time axis fluctuation component in the reproduced composite video signal. On the other hand, the phase correction circuit
At 40, the phase of the color subcarrier is changed according to the burst phase difference signal detected by the burst phase difference detection circuit 42, so that the time-axis fluctuation component in the reproduced composite video signal is accurately removed. The burst phase difference signal detected by the burst phase difference detection circuit 42 is returned to the coarse TBC through the LPF 33 so that the phase correction circuit 40 can operate within the phase difference (up to ± 140 ns) of the burst signal. Is. Further, the reference signal generating circuit 43 generates a reference burst signal and a horizontal synchronizing signal by dividing the frequency of the signal generated by using the crystal oscillator.

The time-axis fluctuation correction device is configured with the above configuration, the reproduction composite video signal including the time-axis fluctuation component input from the input terminal 10 of the device, the time-axis fluctuation component is removed by the coarse TBC and the fine TBC, the device The output terminal 20 outputs the composite video signal synchronized with the reference burst signal and the reference horizontal synchronizing signal generated by the reference signal generating circuit 43.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, as described above, in the conventional time-axis fluctuation correction device configured, the phase comparison operation is always performed on the burst signal in the reproduced composite video signal, and the burst phase difference signal is used. Since the variable delay element 30 and the phase correction circuit 40 shown in FIG. 5 are driven, the amplitude of the burst signal is disturbed or lost due to dropout, deterioration of S / N, deterioration of frequency characteristics, etc. In the abnormal state of, the burst signal phase comparison operation malfunctions, and the variable delay element 30 and the phase correction circuit 40 shown in FIG.
However, since it is driven by an erroneous phase difference signal, there is a problem that the time axis fluctuation cannot be sufficiently corrected.

The present invention has been made in view of the above point, and even when the amplitude of the burst signal in the reproduced composite video signal is disturbed,
Without significantly disturbing the phase difference signal of the burst signal,
The present invention provides an apparatus that appropriately corrects fluctuations in the time axis.

Means for Solving the Problems In order to solve the above problems, the time-axis variation correction apparatus of the present invention detects whether or not the amplitude of the burst signal is normal by providing a burst detection circuit in the reproduction composite video signal system. , The phase difference signal of the burst signal is sampled by this detection signal, and when the burst signal in the reproduced composite video signal is detected, the phase difference signal of the burst signal is sampled and output to reproduce the composite video image. When the burst signal in the signal is not detected, the phase difference signal of the burst signal is disturbed by holding the normal state (previous value hold) without sampling the phase difference signal of the burst signal. To prevent the

Effect The present invention is configured to perform sampling or holding of the phase difference signal of the burst signal in the reproduced composite video signal according to whether the burst signal is normal or not by the configuration described above. When the burst signal amplitude is disturbed or lost due to deterioration or frequency characteristic deterioration, the phase difference signal of the burst signal is held and output at the normal value. Therefore, the operations of the phase correction circuit and the variable delay element are not disturbed, and appropriate time-axis fluctuation correction can be performed.

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

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In FIG. 1, 10 is an input terminal of the device, 20 is an output terminal of the device, 30 is a variable delay element composed of a CCD or the like, 31 is a horizontal sync signal from the reproduced composite video signal, and a burst gate. A horizontal sync separation circuit for generating a signal, 32 a horizontal phase difference detection circuit for detecting a phase error of the horizontal sync signal, 33 a low pass filter (LPF), 34 an adder, 35 an active filter, etc. The phase compensation circuit 36 is a voltage controlled oscillator (VCO) whose oscillation frequency can be varied by voltage. Further, 40 is a phase correction circuit that corrects the phase of the color subcarrier of the reproduced composite video signal, 41 is a burst separation circuit that extracts a burst signal from the reproduced composite video signal, and 43 is a reference horizontal synchronizing signal and a burst signal. A reference signal generation circuit, 44 is a burst abnormality detection circuit that detects whether the burst signal in the reproduced composite video signal is normal, and 45 is a burst phase difference detection circuit that detects a phase error of the burst signal. In FIG. 1, blocks with the same numbers as in FIG. 5 indicate the same circuit blocks.

The operation of the time-axis fluctuation correction apparatus of the present invention configured as described above will be described below with reference to FIG.

In FIG. 1, a variable delay element 30, a horizontal sync separation circuit
31, horizontal phase difference detection circuit 32, low pass filter (LPF) 3
3, adder 34, phase compensation circuit 35, voltage controlled oscillator circuit (VC
O) 36 blocks make up a course TBC and remove the time-axis fluctuation component contained in the reproduced composite video signal up to the phase shift of the burst signal (up to about ± 140 ns or less).

Further, a fine TBC is composed of four blocks of a phase correction circuit 40, a burst separation circuit 41, a burst abnormality detection circuit 44, and a burst phase difference detection circuit 45, and a coarse TBC phase shift of the burst signal (max. ) The time-axis fluctuation component in the reproduced composite video signal removed up to the following is further accurately removed.

The course TBC has exactly the same configuration as the conventional time axis fluctuation correction device shown in FIG. 5, and the horizontal synchronization phase difference signal obtained by detecting the phase difference of the horizontal synchronization signal in the reproduced composite video signal and the fine TBC. After adding the low-frequency components of the burst phase difference signal obtained in step 1 and performing phase compensation and amplification, the voltage-controlled oscillation circuit (VCO) 36 is controlled, and the delay amount of the variable delay element 30 is controlled. The time-axis fluctuation component contained in the video signal is adjusted to the phase shift of the burst signal (maximum ±
(About 140ns) or less. On the other hand, in the fine TBC, first, the reproduction composite video signal from which the time axis fluctuation component has been removed to the phase shift degree of the burst signal (maximum ± about 140 ns) or less in the coarse TBC is input and sent to the phase correction circuit 40. It is sent to the burst separation circuit 41 and the burst abnormality detection circuit 44. The burst separation circuit 41 separates the burst signal in the reproduced composite video signal and sends it to the burst phase difference detection circuit 45 as a reproduced burst signal. Further, the burst abnormality detection circuit 44 detects whether or not the burst signal in the reproduced composite video signal is normal, and sends a sampling pulse to the burst phase difference detection circuit 45. The burst phase difference detection circuit 45 detects the phase difference between the reproduction burst signal from the burst separation circuit 41 and the reference burst signal from the reference signal generation circuit 43, and reproduces according to the sampling pulse from the burst abnormality detection circuit 44. If the burst signal in the composite video signal is detected normally, sampling is performed.If the burst signal in the playback composite video signal is not detected normally, hold the previous value and correct the phase. It is sent to a circuit 40 and a low pass filter (LPF) 33. The phase correction circuit 40 accurately corrects the time base fluctuation of the reproduced composite video signal by changing the phase of the color subcarrier in the reproduced composite video signal. Further, the reference signal generation circuit 43 obtains the reference burst signal and the reference horizontal synchronizing signal by dividing the oscillation frequency of the crystal oscillator.

FIG. 2 is a block diagram showing details of the burst abnormality detection circuit 44 and the burst phase difference detection circuit 45 in the time axis fluctuation correction apparatus of the present invention shown in FIG. FIG. 3 is a signal line diagram showing the operation of the burst abnormality detection circuit 44 of the time axis fluctuation correction apparatus of the present invention shown in FIG. 2, and FIG. 4 is the time axis of the present invention shown in FIG. FIG. 6 is a signal diagram showing the operation of the burst phase difference detection circuit 45 of the fluctuation correction device.

In FIG. 2, 441 is an input terminal to which the output video signal of the variable delay line 30 shown in FIG. 1 is input, and 442 is a burst gate signal generated by the horizontal sync separation circuit 31 shown in FIG. An input terminal, 451 is an input terminal to which the output terminal of the burst separation circuit 41 shown in FIG. 1 is input, and 452 is the first
An input terminal to which the reference burst signal generated by the reference signal generation circuit 43 shown in the figure is input, 456 is an output terminal for outputting the output signal of the burst phase difference detection circuit 45 shown in FIG. 1, and 443 is a color signal. A bandpass filter (BPF) to extract
444 is an amplifier that amplifies the amplitude of the color signal, 445 is a burst gate that sets the signal other than the burst period to the GND potential, 446 is an absolute value circuit (ABS) that takes the absolute value of the signal, and 447 is compared with the reference potential for comparison. A comparator that outputs the result, 448 is a low pass filter (LPF) that extracts low frequency components, 453 is a phase comparator that detects the phase difference between the burst signal in the reproduced video signal and the reference burst signal, and 454 is A switch for sampling the comparison output of the phase comparator 453, 455 is a switch 454.
This is a capacitor that holds the sampling output at.

The operation of the burst abnormality detection circuit 44 will be described below with reference to FIGS. 2 and 3. From the reproduced composite video signal (signal A in FIG. 3) input from the input terminal 441 shown in FIG. 2, the color signal B is extracted by the bandpass filter (BPF) 443. (Signal B in FIG. 3) Next, after being amplified by the amplifier 444 to stabilize the operation of the next stage, the burst gate 4
At 45, the signal other than the burst period is fixed to the GND potential, and the absolute value circuit (ABS) 446 converts it to an absolute value, which is signal C (Fig. 3 signal C).
Becomes Next, the signal C is applied to the reference voltage V by the comparator 447.
It is compared with o and becomes a signal D (signal D in FIG. 3). Further, the low-pass filter (LPF) 448 extracts the low-frequency component of the signal D into a signal E (signal E in FIG. 3), and the switch 454.
Control signal. This control signal E
Is obtained by comparing the signal C with the reference voltage Vo by the comparator 447 in FIG. 2 like the signal C shown in FIG. 3, the burst signal in the reproduced video signal A (signal A in FIG. 3) is obtained. If the amplitude of the signal C is disturbed as in the section b of the signal A shown in FIG. 3, the amplitude of the signal C is also disturbed, and
The section in which the signal C shown in the figure is larger than the reference potential Vo decreases, and the sampling pulse does not appear in the section b like the signal E shown in FIG.

At this time, the signal Z at the output terminal 456 shown in FIG.
The state is shown in FIG. The operation of the burst phase difference detection circuit 45 in FIG. 2 will be described below with reference to FIGS. 2 and 4. The burst signal in the reproduced code video signal input from the input terminal 451 and the reference burst signal input from the input terminal 452 are phase-compared by the phase comparator 453, and become the signal X (signal X in FIG. 4). This signal X is sampled by switch 454 and capacitor 455 and signal Z
(Signal Z in FIG. 4). Since this signal Z is sampled by the control signal E shown in FIG. 3, when the burst signal is normally detected in the reproduced composite video signal like the signal Z shown in FIG. 4, it is sampled and output. If the burst signal in the reproduced composite video signal is not detected normally, the value in the normal state is held.

As described above, according to this embodiment, the burst phase difference detection circuit 45 shown in FIG. 2 outputs a signal corresponding to the phase difference of the burst signal when the burst signal in the reproduced composite video signal is normal. , A signal that holds a normal value without outputting an erroneous signal X (X in Fig. 4) even when the burst signal amplitude is disturbed due to dropout, S / N deterioration, or frequency characteristic deterioration. Since Z (Z in FIG. 4) is output, the time axis fluctuation component can be removed without malfunctioning in the coarse TBC and fine TBC shown in FIG.

As described above, according to the time axis fluctuation correction apparatus of the present invention, it is detected whether the amplitude of the burst in the reproduced composite video signal is normal, and the phase comparison of the burst signals is performed using this detection signal. By configuring the output to be sampled, bursts in the playback composite video signal can be dropped out or
Even if the burst signal amplitude is disturbed or lost due to S / N deterioration or frequency characteristic deterioration, the phase comparison output of the burst signal can reliably detect only when the burst signal is abnormal. The value of the last normal state is held and output.
BC can remove the time-axis fluctuation component without malfunction, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a time axis fluctuation correcting apparatus according to the present invention, and FIG. 2 is an example of a burst detection circuit and a burst phase difference detecting circuit in the time axis fluctuation correcting apparatus according to the present invention shown in FIG. FIG. 3 is a block diagram showing the details of the embodiment, FIG. 3 is a signal diagram showing the operation of the burst detection circuit shown in FIG. 2, and FIG. 4 is a signal showing the operation of the burst phase difference detection circuit shown in FIG. FIG. 5 is a block diagram showing an outline of a conventional time axis fluctuation correction device. 10 …… input terminal, 20 …… output terminal, 30 …… variable delay element, 31 …… horizontal sync separation circuit, 32 …… horizontal phase difference detection circuit, 33 …… low pass filter (LPF), 34 …… Adder, 3
5 …… Phase compensation circuit, 36 …… Voltage controlled oscillator circuit, 40 ……
Phase correction circuit, 41 ... Burst separation circuit, 42, 45 ... Burst phase difference detection circuit, 43 ... Reference signal generation circuit, 44 ...
... Burst detection circuit, 441,442 ... Burst detection circuit 44
, 451, 452 ... Burst phase difference detection circuit 45 input terminal, 456 ... Burst phase difference detection circuit 45 output terminal, 443 ... Bandpass filter (BPF), 444 ... Amplifier, 445 ... Burst gate , 446 …… Absolute value circuit (AB
S), 447 ... Comparator, 448 ... Low-pass filter (LPF), 453 ... Phase comparator, 454 ... Switch, 455 ...
... Capacitor, A ... input signal of band pass filter (BPF) 443 in Fig. 2, B ... output signal of band pass filter (BPF) 443 in Fig. 2, C ... absolute value circuit (Fig. 2) ABS) 446 output signal, D ... output signal of comparator 447 in FIG. 2, E ... output signal of low pass filter (LPF) 448 in FIG. 2, X ... phase comparator 453 in FIG. , The output signal of the burst phase difference detection circuit 45 in FIG.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kiyoshi Uchimura 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Kazuya Ueda, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP 57-169999 (JP, A) JP 60-216691 (JP, A) Actual opening 59-180577 (JP, U) Actual opening 61-14578 (JP, U)

Claims (1)

[Claims] 1. A time axis fluctuation correction apparatus for removing time axis fluctuations by controlling the delay amount of a variable delay element provided in the reproduction composite video signal system according to the time axis fluctuation component in the reproduction composite video signal. In burst reproduction means for extracting a burst signal in the reproduced composite video signal, reference signal generation means for generating a reference burst signal, burst signal extracted by the burst extraction means and generated by the reference signal generation means The phase difference detection means for detecting a phase difference between the burst signal and the reference burst signal, and the burst abnormality detection means for detecting whether or not the amplitude of the burst signal in the reproduced composite video signal is normal. The abnormality detecting means includes absolute value means for taking an absolute value of a signal, reference potential comparing means for comparing the output of the absolute value means with a reference potential, and the reference potential ratio. And a holding means for sampling and holding the output of the phase difference detecting means in accordance with the output of the burst abnormality detecting means. A time axis fluctuation correction device characterized by the above.