JP2972406B2 - Video signal processing circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing circuit, and more particularly to a video signal processing circuit having a separation circuit for separating a composite video signal into a luminance signal and a chrominance signal.

[0002]

2. Description of the Related Art Conventionally, when a composite video signal is projected as an image on a color TV monitor, the composite video signal is separated into a luminance signal and a chrominance signal using a band-pass filter, a band gap filter, and the like. For example, after adjusting the brightness and contrast, and if it is a color signal, adjusting the hue and color density, etc., control the mutual phase of these two signals and display an image on a TV monitor based on these signals. Or recording on a VTR.

FIG. 5 is a block diagram showing an example of conventional processing of a composite video signal. A composite video signal 62 is input from a composite video signal input terminal 61 to a Y / C separation circuit 63. After the composite video signal 62 is separated into a luminance signal and a chrominance signal by a Y / C separation / adjustment circuit 63, the luminance signal and the contrast of the separated luminance signal are adjusted, and the separated color signal is a hue and a color signal. The density is adjusted, and the luminance signal 6
4a and the color signal 65 are obtained. The bandwidth of the circuit through which the luminance signal passes is 5 MHz or more, but the bandwidth of the circuit through which the chrominance signal passes is about 0.5 to 1 MHz. For this reason, there is a difference in the transmission speed of each signal, and when the image is projected on the picture tube without performing phase adjustment, the output of the color signal having a narrow bandwidth is delayed by about 0.8 to 1 μsec from the output of the luminance signal. To reach. Therefore, it is necessary to delay the luminance signal output reaching the picture tube by using a delay line so as to match the time when the color signal reaches the picture tube. In the circuit diagram shown in FIG. 5, since the luminance signal 64a has a phase advanced from the color signal 65, the luminance signal 64a is input to a delay circuit 66 using a fixed delay line to reduce the phase difference. The configuration is such that a luminance signal 64 whose phase is controlled so that there is no phase difference with the signal 65 is obtained. The luminance signal 64 and the chrominance signal 65 output from the delay circuit 66 are output to a luminance signal output terminal 67 and a chrominance signal output terminal 68, respectively. Then, the luminance signal 64
An image is displayed on a color TV monitor or recorded on a VTR based on the color signal 65 and the color signal 65.

[0004]

However, in the conventional video signal processing circuit, if the phase control is not performed despite the relative phase difference between the luminance signal and the chrominance signal, the color image is not displayed on the screen. There is a problem that it appears as a gap.

FIGS. 6 to 8 are diagrams showing waveforms and images of a composite video signal, a luminance signal, and a color signal when color shift occurs and when color shift does not occur.

In the case of the image 71 shown in FIG. 6, a composite video signal on a scanning line at a position connecting the point A and the point B is represented by reference numeral 72. When this signal is Y / C-separated and there is no phase difference between the luminance signal 74 and the color signal 75 as shown in FIG. The screen will not be misaligned. However, as shown in FIG. 8, when a phase difference 77 occurs between the luminance signal 74a and the color signal 75a, a color shift like the image 76 occurs.

Therefore, in the conventional video signal processing circuit, in order to prevent color shift, each time the separation circuit is changed in accordance with the performance and specifications to be realized, the separation method of the luminance signal and the chrominance signal, and the The control is changed based on the delay of a necessary filter or the like. Therefore, it is necessary to change and add a circuit for control.

Further, when the signal delay time during use of the apparatus is slightly changed due to the power supply voltage characteristic and the temperature characteristic, or when the luminance signal and the chrominance signal are displaced due to signal processing in a video recording and reproducing operation process, etc. There is. In such a case, if a signal shift is generally about 100 nsec or more, when a horizontal resolution is displayed on a 800 color TV monitor, a color shift occurs on one vertical line reflected on the monitor.

The present invention has been made in view of the above problems, and has been made in consideration of the above-described problems, and has been made in consideration of the above-described problems. It is intended to provide a circuit.

[0010]

Means for Solving the Problems A video signal processing circuit according to the present invention, the period of the color burst signal of the composite video signal
A phase reference signal in the frequency band of the luminance signal, or
During the horizontal synchronizing signal period of the composite video signal,
To superimpose the phase reference signal in the frequency band of the
A reference signal superimposing circuit, and a circuit in which the phase reference signal is superimposed.
Y / C separation for separating composite video signal into luminance signal and color signal
A circuit, a phase reference signal included in the luminance signal, and the color
A color burst signal or the color signal contained in the signal
And the horizontal reference signal included in the luminance signal.
Depending on the phase difference from the synchronization signal, the luminance signal or the color
A phase control circuit for controlling the phase of the signal .

[0011]

In the present invention, a composite signal obtained by superimposing a phase reference signal on a composite video signal is separated into a luminance signal and a chrominance signal by a Y / C separation circuit. And the phase control circuit
Based on the phase reference signal, burst signal or synchronization signal, the phases of the luminance signal and the color signal are compared. If the phase of the luminance signal is early, the luminance signal is delayed, and if the phase of the color signal is early, the color is By delaying the signal, a signal in which both phases are matched is output. Thus, color shift can be prevented without changing the circuit as in the related art.

[0012]

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram of a video signal processing circuit according to an embodiment of the present invention, and FIG. 2 is a signal waveform diagram in the video signal processing circuit of the present embodiment. A phase reference signal superimposing circuit 3 superimposes a phase reference signal 21 on a composite video signal 2 input from a composite video signal input terminal 1 during a burst signal period 22. The composite video signal 4 on which the phase reference signal 21 is superimposed is separated by the Y / C separation adjustment circuit 5 into two signals, that is, a luminance signal 6 and a chrominance signal 7. Y / C
The Y / C separation method by the separation adjustment circuit 5 is performed by a method using a comb filter using a CCD delay line. A phase reference signal 21 is superimposed on the luminance signal 6.

The phase control circuit 8 compares the phase of the phase reference signal 21 contained in the luminance signal 6 with the phase of the burst signal 23 contained in the chrominance signal 7, and if the luminance signal has the earlier phase, delays the luminance signal. If the phase of the color signal is earlier, the luminance signal 6 and the color signal 7 are selectively delayed so that the color signal is delayed, and then the phase reference signal 21 is removed. As a result, the phase control circuit 8 generates the luminance signal 9 after the phase control and the color signal 10 after the phase control.

As shown in the waveform diagram of FIG. 2, the phase of the luminance signal 6 is faster than that of the chrominance signal 7 by the phase difference 24.
There is no phase difference between the luminance signal 9 and the chrominance signal 10 after the control. Then, the luminance signal 9 and the chrominance signal 10 are output from the luminance signal output terminal 11 and the chrominance signal output terminal 12, respectively.

By the above operation, the luminance signal 6 and the chrominance signal 7
Is corrected by the phase control by the Y / C separation adjusting circuit 5, and the phenomenon of color shift is minimized.

Next, a second embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 3 shows a second embodiment of the invention.
It is a block diagram of a video signal processing circuit according to the embodiment of the
FIG. 4 is a signal waveform diagram of the video signal processing circuit according to the present embodiment. The phase reference signal 51 is superimposed on the composite video signal 32 input from the composite video signal input terminal 31 during the synchronization signal period 52 by the phase reference signal superimposing circuit 33. The phase reference signal 51 has the same fsc (= 3.
(58 MHz) is a signal generated during the synchronization signal period 52. The composite video signal 34 on which the phase reference signal 51 is superimposed is converted by the A / D conversion circuit 43 into a digital composite video signal 34a. The digital composite video signal 34a is separated by the Y / C separation adjustment circuit 35 into two signals, namely, a digital luminance signal 36 and a digital chrominance signal 37. The Y / C separation method in the Y / C separation adjustment circuit 35 is a three-dimensional Y using digital memory.
/ C separation method. The digital luminance signal 36 and the digital chrominance signal 37 are input to a phase control circuit 38.

The phase control circuit 38 includes a synchronizing signal 52 and a digital chrominance signal 37 included in the digital luminance signal 36.
Is compared with the phase reference signal 51 included in the digital luminance signal so that the luminance signal is delayed when the luminance signal is earlier in phase, and the color signal is delayed when the chrominance signal is earlier in phase. 36 and the digital chrominance signal 37 are delayed, after which the phase reference signal is removed. As a result, the phase control circuit 38 generates the digital luminance signal 39a after the phase control and the digital color signal 40a after the phase control. The digital luminance signal 39a and the digital chrominance signal 40a after the control are converted into analog luminance signals 39 and chrominance signals 40 by D / A conversion circuits 44 and 45, respectively. These analog signals are output to a luminance signal output terminal 41 and a chrominance signal, respectively. Output from the output terminal 42.

By the above operation, the Y / C separation adjusting circuit 3
5, the digital luminance signal 36 and the digital chrominance signal 3
7 is corrected by the phase control circuit 38 to minimize the color shift phenomenon.

In the first embodiment, since the delay processing of the analog signal is performed, as the delay time becomes longer,
Adverse effects such as signal degradation are likely to occur. However, in the second embodiment, since the digital signal is delayed, there is an advantage that the signal does not deteriorate due to the delay.

The phase comparison is performed as in the above embodiment.
When comparing the phase of the phase reference signal included in the luminance signal with the burst signal included in the color signal, or comparing the phase of the synchronization signal included in the luminance signal with the phase reference signal included in the color signal Not limited to this case, the phase reference signal in the luminance signal may be compared with the phase reference signal in the chrominance signal.
The phase control may control either the luminance signal or the chrominance signal, or may control both phases.

[0022]

According to the present invention, Y is controlled by the phase control circuit.
Since the phase of the color signal and / or the luminance signal after the / C separation is controlled, unlike the related art, the phase control required for each circuit change to eliminate the color shift becomes unnecessary, and the Y / C separation after the Y / C separation is unnecessary. Since it is not necessary to adjust the delay times of the luminance signal and the chrominance signal, there is no need to change or add a circuit for control. Therefore, the man-hour for designing the adjustment circuit and the man-hour for fine adjustment required at the time of manufacturing the device, which are required at the time of designing the device, become unnecessary, and the adjustment can be eliminated. Can be reduced. Further, the present invention is also applicable to a case where a slight change occurs between a luminance signal and a color signal due to a subtle change due to a power supply voltage characteristic and a temperature characteristic of each signal delay time when the device is used, or a video recording and reproducing operation. If the accuracy of the phase adjustment is set to 100 ns or less, the phase can be automatically adjusted in real time within a range in which the color TV monitor with a horizontal resolution of 800 is inconspicuous enough to obtain an image with less color shift. The effect is that it is possible.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a video signal processing circuit according to a first embodiment of the present invention.

FIG. 2 is a signal waveform diagram when a composite video signal is detected by the system of the embodiment in the embodiment.

FIG. 3 is a block diagram illustrating a video signal processing circuit according to a second embodiment of the present invention.

FIG. 4 is a signal waveform diagram of a video signal processing circuit in the present embodiment.

FIG. 5 is a block diagram showing an example of a conventional circuit for separating a composite video signal into a luminance signal and a chrominance signal.

FIG. 6 is a schematic diagram showing waveforms and images of a composite video signal, a luminance signal, and a color signal.

FIG. 7 is a schematic diagram showing a waveform and an image when no color shift occurs.

FIG. 8 is a schematic diagram showing a waveform and an image when color misregistration occurs.

[Explanation of symbols]

1, 31, 61; composite video signal input terminal 3, 33; phase reference signal superimposing circuit 5, 35; Y / C separation adjusting circuit 8, 38; phase control circuit 11, 41, 67; luminance signal output terminal 12, 42 68, color signal output terminal 43; A / D conversion circuits 44, 45; D / A conversion circuit 63; Y / C separation circuit 66; delay circuits 2, 32, 62; composite video signals 4, 34; (A superimposed phase reference signal) 34a; digital composite video signal (a superimposed phase reference signal) 6; luminance signal (before phase control) 36; digital luminance signal (before phase control) 7; color signal (phase control) Before) 37; Digital color signal (before phase control) 39a; Digital luminance signal (after phase control) 9, 39; Luminance signal (after phase control) 40a; Digital color signal (after phase control) 10, 40; (After phase control) 74, 74a; Luminance signal 75, 75a; Color signal 21; Phase reference signal 22; Burst signal period 23; Burst signal 71; Example of TV image 73; Example of TV image (without color shift) 76; an example of a TV image (with color shift)

Continuation of the front page (56) References JP-A-64-49495 (JP, A) NHK Television Technical Textbook (1), edited by The Japan Broadcasting Corporation, published by The Japan Broadcasting Publishing Association (April 10, 2001)

Claims (2)

(57) [Claims] 1. The period of a color burst signal of a composite video signal.
A phase reference signal in the frequency band of the luminance signal
Is a color bar during the horizontal synchronizing signal of the composite video signal.
Superimpose the phase reference signal in the frequency band of the burst signal
A phase reference signal superimposing circuit, wherein the phase reference signal is superimposed;
Y / C for separating a composite video signal into a luminance signal and a chrominance signal
A separating circuit, and a phase reference signal included in the luminance signal,
Color burst signal included in the color recording signal or the color
Phase reference signal included in the signal and the luminance signal
Depending on the phase difference with the horizontal synchronization signal, the luminance signal or the previous
A video signal processing circuit comprising: a phase control circuit that controls a phase of the color recording signal . 2. An A / D conversion circuit for converting an output of the phase reference signal superimposing circuit into a digital signal, and a D / A conversion circuit for converting an output of the phase control circuit into an analog signal; The video signal processing circuit according to claim 1, wherein the / C separation circuit and the phase control circuit perform processing on a digital signal.