JP2502657B2 - Time axis correction device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time axis correction device for a chroma signal of a composite video signal or a chroma signal of balanced modulation.

Conventional technology Composite video signals played directly from the heads and disks of packaged video equipment such as VTRs and video disks generally fluctuate in the time axis direction due to tape expansion / contraction, disk eccentricity, and input system accuracy. (Hereinafter, referred to as time axis fluctuation). When a composite video signal including this time-axis fluctuation is reproduced by a color television receiver, the reproduced image often vibrates horizontally (hereinafter referred to as jitter), or uneven color, color tint, or color does not occur. Therefore, in a VTR, a video disc, or the like, the directly reproduced composite video signal is subjected to time-axis correction or the like and then output as an output signal from the device.

A general configuration of the time axis correction device and its operation will be described using a conventional example.

FIG. 5 is a block diagram showing an example of the configuration of a conventional time axis correction device. 51 is an input terminal to which a composite video signal including time axis fluctuation is input, 52 is a delay element CCD, 53 is a chroma TBC (Ti
me Base Corrector, 54 is a sync separation circuit, 55 is an HD (horizontal sync) phase comparison circuit, and 56 is
VCO (voltage controlled oscillator), 57 horizontal phase comparison signal output terminal, 58 horizontal sync reference signal input terminal, 59 burst extraction circuit, 60 chroma phase comparison circuit, 61 chroma reference signal input terminal, and 62 time It is an output terminal of a composite video signal from which axis fluctuation is removed.

6 is a block diagram showing an example of the configuration of the chroma TBC circuit 53 of FIG. 5, and 71 is the input of the composite video signal in which the time base fluctuation of the luminance signal which is the output of the CCD 52 of FIG. 5 is suppressed. Input terminal, 72 is an adder, 73 is a chroma phase circuit,
Reference numeral 74 is an input terminal for the chroma phase comparison signal, and 75 is an output terminal for outputting the composite video signal from which the time base fluctuation of the chroma signal is removed. FIG. 7 is a vector diagram showing the operation of FIG.

The composite video signal with time-axis fluctuation input from the input terminal 51 of FIG. Separation circuit 54, and burst sampling circuit 5
Input to 9. The sync separation circuit 54 separates the sync signal from the composite video signal and supplies it to the HD phase comparison circuit 55 and the burst sampling circuit 59. The HD phase comparison circuit 55 compares the phases of the horizontal sync reference signal input from the horizontal sync reference signal input terminal 58 and the separated sync signal, and the phase difference is used as the horizontal phase comparison signal to determine the horizontal phase comparison signal. Supply to output terminal 57 and VCO 56. The VCO56 changes the oscillation frequency according to the voltage change of the horizontal phase comparison signal,
Add to D52. The CCD 52 delays and outputs the input composite video signal accompanied by the time base fluctuation according to the clock frequency from the VCO 56. In this way, by controlling the delay amount by the CCD for each H (horizontal synchronization signal) with the horizontal phase comparison signal, the time axis fluctuation can be largely eliminated. However, even in this case, when reproduced by the color television receiver, it is not possible to completely remove color unevenness or color gamut.

Therefore, the burst signal included in the composite video signal is extracted by the burst sampling circuit 59 shown in FIG. 5 by the burst gate signal obtained from the synchronization signal from the synchronization separation circuit 54.
The phase is compared with the phase of the chroma reference signal input from the chroma reference signal input terminal 61 by the chroma phase comparison circuit 60,
Chroma TBC circuit 5 using the phase difference as the chroma phase comparison signal.
Enter in 3. The chroma TBC circuit 53 uses the chroma phase comparison signal to suppress the change in the chroma phase of the composite video signal from the CCD 52 from which the change in the time axis is largely eliminated, thereby changing the time axis of both the luminance signal and the chroma signal. The composite video signal almost removed from is obtained and output from the output terminal 62.

Next, the chroma TBC circuit 53 will be described in detail with reference to FIGS. 6 and 7. The composite video signal from the CCD 52 is input from the input terminal 71 of FIG. 6, and is input to the adder 72 and the chroma phase shift circuit 73. In the chroma phase shift circuit 73, only the chroma signal component in the composite video signal is extracted, and for example, the extracted chroma signal is vectored (O, Vn).
Then, as in the chroma correction vectors (O, Vx), (O, Vy) and (O, Vz), the amplitude and phase are controlled by the chroma phase comparison signal input from the input terminal 74, and then the adder 72 Supply to. In the adder 72, the vector (O, Vn) of the chroma signal in the composite video signal and the chroma correction vectors (O, Vx), (O, Vy), and (O, Vz) shown in FIG.
Are added and the vectors (O, Vx), (O, Vy) and (O, Vz) that suppress the temporal fluctuation of the chroma phase are combined, and the composite video signal from which the temporal fluctuation of the chroma signal has been removed. Is output from the output terminal 75 (see JP-A-58-29104, etc.).

However, in the above-mentioned configuration, the chroma with the time axis fluctuation removed as shown in FIG. 7 reproduction chroma vectors (O, Vx), (O, Vy) and (O, Vz). Since the amplitude of the signal changes, there is a problem in that color unevenness occurs on the reproduction screen and a good image quality cannot be obtained.

In view of this point, the present invention adds the chroma signal in the composite video signal in a state where the chroma signal in the composite video signal is amplitude-controlled with the chroma phase comparison signal and the original chroma signal has a relatively constant phase difference. By doing so, the fluctuation of the time axis is removed and the fluctuation of the amplitude of the reproduced chroma signal is suppressed,
It is an object of the present invention to provide a time axis correction device that minimizes image quality distortion.

Means for Solving the Problems The present invention controls the amplitude of a chroma signal in a composite video signal including an input time axis fluctuation according to a chroma phase comparison signal, and has a constant phase difference from the chroma signal. It is a time axis correction device that is designed to be added together.

With the above-described configuration, the present invention controls the amplitude of the chroma signal in the composite video signal including the time base fluctuation according to the chroma phase comparison signal that fluctuates according to the time base fluctuation, and maintains a constant position with the chroma signal. By adding with the phase difference, it is possible to suppress the time base fluctuation and the amplitude fluctuation of the reproduced chroma signal and reproduce the image in which the distortion of the image quality is reduced as much as possible.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a time axis correction device according to a first embodiment of the present invention, in which 1 is, as described in the conventional example,
Input terminal of composite video signal with remaining time axis fluctuation, 2 phase shift circuit for giving phase change, 3 adder, 4 chroma extraction circuit, 5 amplitude control circuit, 6 chroma phase comparison signal input terminal, Reference numeral 7 denotes an output terminal of the composite video signal from which the time base fluctuation is removed. FIG. 2 is a vector diagram showing the operation of FIG.

 This will be described below with reference to FIGS. 1 and 2.

The composite video signal remaining on the time base fluctuation input from the input terminal 1 of FIG. 1 is input to the phase shift circuit 2 and the chroma extracting circuit 4. The chroma extracting circuit 4 extracts the chroma signal from the composite video signal and adds it to the amplitude control circuit 5. In the amplitude control circuit 5, the chroma correction vectors (O, Va), (O, Vo), and (O) shown in FIG. 2 are received according to the chroma phase signal obtained from the input terminal 6 in the same manner as in the conventional example. ,
The amplitude of the chroma signal is controlled like Vb). Here, the offset vector (O, Vo) is provided in consideration of the ease of control and the dynamic range. In the phase shift circuit 2, the composite video signal and the output signal from the amplitude control circuit 5 have a constant phase (for example, if the vector indicating the chroma signal in the composite video signal is the vector (O, Vn) in FIG. ) Phase shift and add to adder 3. In the adder 3, the composite video signal phase-shifted as described above and the chroma correction signal from the amplitude control circuit 5 are vector-added as shown in FIG. 2, and the composite video signal from which the time base fluctuation is removed is output from the output terminal 7. Output. It can be seen from FIGS. 2 and 7 that the amplitude variation of the reproduced chroma signal is also suppressed according to the present embodiment.

FIG. 3 shows a time axis correction apparatus according to the second embodiment of the present invention. As with FIG. 1, 31 and 36 are input terminals, 32 is a phase shift circuit, 33 is an adder, 34 is a chroma extracting circuit, and 35 is Is an amplitude control circuit, 37 is an output terminal, 38 is an amplifier, and 39 is a subtractor. FIG. 4 is a vector diagram showing the operation of FIG. In this embodiment, compared to the first embodiment, the amplitude variation of the reproduced chroma signal is further reduced, and at the same time, the suppression amount (dynamic range) of the time axis variation is increased.

This will be described below with reference to FIGS. 3 and 4. Here, the operation other than the amplifier 38 and the subtractor 39 is the same as that of the first embodiment, and will be omitted. The chroma signal from the chroma extracting circuit 34 is applied to the amplitude control circuit 35 and the amplifier 38. The chroma correction signal whose amplitude is controlled by the chroma phase comparison signal in the amplitude control circuit 35 is subtracted from the chroma signal from the amplifier 38 by the subtractor 39, and the offset point (the position of the chroma correction signal when there is no time base fluctuation) is It becomes the origin O shown in FIG. Therefore, due to the phase difference of the chroma signal due to the time axis fluctuation, the reproduction vector is centered on the vector (O, Vn) of the chroma signal, for example, the reproduction vector ((O, Vn
d), (O, Vf), it will go around positive and negative,
It can be seen from the comparison between FIG. 7 and FIG. 7 that it is possible to suppress fluctuations in time axis and fluctuations in color density as much as possible.

As described above, in the present embodiment, as the means for suppressing the time base fluctuation included in the chroma signal, the chroma signal having a constant relative phase with respect to the original chroma signal is amplitude-controlled by the chroma phase comparison signal and then added. As a result, fluctuations in the time axis of the chroma signal can be suppressed as much as possible, and fluctuations in color amplitude during reproduction can be suppressed, so that a good reproduced image can be obtained.

Although the phase shift circuit is inserted on the composite video signal side in this embodiment, it may be inserted on the chroma correction signal side.

Further, the present embodiment is effective not only for the composite video signal including the time base fluctuation but also for the chroma signal which is balanced and modulated.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to remove the time base fluctuation of the chroma signal with a simple configuration, suppress the amplitude fluctuation of the reproduced chroma signal, and obtain good jitter and color unevenness. Images can be reproduced and their industrial value is great.

[Brief description of drawings]

FIG. 1 is a block diagram of a time axis correction device of the first embodiment of the present invention, FIG. 2 is a vector diagram showing the operation of the first embodiment, and FIG. 3 is of the second embodiment of the present invention. FIG. 4 is a vector diagram showing the operation of the time axis correction device, FIGS. 5 and 6 are configuration diagrams of a conventional time axis correction device, and FIG. 7 is a vector diagram showing the operation of FIG. Is. 2,32 ...... Phase shift circuit, 3,33,72 …… Adder, 4,34 …… Chroma extraction circuit, 5,35 …… Amplitude control circuit, 38 …… Amplifier, 39
...... Subtractor, 52 …… CCD, 53 …… Chroma TBC circuit, 54 ……
Sync separation circuit, 55 …… HD phase comparison circuit, 56 …… VCO, 59
…… Burst sampling circuit, 60 …… Chroma phase comparison circuit, 73
...... Chroma phase shift circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuya Ueda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP 61-196693 (JP, A) JP 58 -29104 (JP, A)

Claims (1)

(57) [Claims] 1. A time axis correction device using a composite video signal or a balanced-modulated macro signal as an input signal, wherein a first macro signal in the composite video signal and an amplitude of the first macro signal are compared to the first macro signal. The second chroma signal obtained by controlling the chroma phase comparison signal indicating the phase difference between the first chroma signal and the chroma reference signal has a constant phase relationship, and the first chroma signal and the second chroma signal. A time axis correction device characterized in that signals are added.