JPS6029275B2 - Image quality improvement circuit for color television receivers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for improving the image quality of a color television receiver.

Current color television signals are sent with a color difference signal superimposed on a luminance signal.

The luminance signal is a signal that represents the brightness and darkness of an image and is sent in a frequency band of approximately 4.9 MHz, but the color difference signal is a signal that represents the hue and saturation of an image and is only sent in a frequency band of 0.5 to 1.5 MHz. I don't get hit. For this reason, in the image reproduced on a color television receiver, the boundaries where the luminance changes greatly are clear, but the boundaries where the color changes are not clear. SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a color television receiver that can reproduce images with clear outlines even at boundaries where colors change.

The present invention focuses on the fact that, in the case of images sent from normal broadcasting stations, the brightness also changes somewhat at the boundaries where the colors change, and the present invention uses the Takagi component of the brightness signal, that is, the outline of the image, to distinguish between the color boundaries. The feature is that it reproduces the color of the image and sharpens the outline of the image where the color changes.

An embodiment of the present invention is shown in FIG.

In the figure, 1 is a high-pass filter, 2 is a trigger generation circuit, 3 is a delay circuit, 4 is a switch changeover circuit, and 5 is a comparison circuit.
Since the luminance signal Y has a frequency component up to 4.8 MHz as shown in FIG. 2a, the signal waveform has a sharp rise even in the contour portion of a colored image. This waveform a passes through the high-pass filter shown in FIG. 1, and as shown in waveform b shows only the Takagi component of the luminance signal, and is slightly delayed. On the other hand, the color difference signal C is divided into a signal supplied to the switch changeover circuit 4 through the delay circuit 3 and a signal supplied directly to the switch changeover circuit 4. The latter signal has the waveform shown in FIG. 2c, and the former has the waveform shown at d. As can be seen from the figure, the color difference signal waveforms c and d have a frequency band of 0.5.
Since it is approximately 1.8 MHz, the waveform is quite gentle. It will also be understood that the waveforms c and d are temporally located before and after the waveform b of the high-frequency component of the luminance signal. The color difference signal waveform d on the delayed side is first output by the switch changeover circuit 4, and then the switch is turned off from the trigger generation circuit 2 by the Takagi component bl of the luminance signal, that is, a signal indicating the outline position of the image. A switching signal is given to the fusuma circuit 4, and the color difference signal waveform c that is not delayed
is switched so that it is output. Thereafter, when the comparison circuit 5 compares the waveform c and the waveform d, when the waveform c and the waveform d match, the switching signal f is again given to the switch switching sliding door circuit 4, and the switching is made so that the color difference signal waveform d is outputted. . Further, the switch switching circuit 4 is activated by the Takagi component b2 of the luminance signal, and the color difference signal output e is switched from the waveform d to the waveform c. In this way, the color difference signal waveform is switched from d to c every time the Takagi component of the luminance signal comes, and the color difference signal waveform is switched from c to d every time the waveforms match in the comparison circuit 5.

As a result, the color difference signal output becomes as shown in waveform e in FIG. 2, and an image with clear outlines can be obtained even at color boundaries. By using the present invention, it is possible to provide a color television receiver that can clearly reproduce the contours of colored images, and it is possible to obtain beautiful images that have never been seen before.

Note that in the above, the delayed color difference signal C and
Although an example has been described in which the color difference signals are divided into two, one without delay and the other with no delay, it will be easily understood that in general, it is sufficient that there is a predetermined delay time difference between the two divided color difference signals.

Therefore, the term delay time in this specification also includes zero delay time. It is also clear that the same effects as the present invention can be obtained by dividing the color difference signals into three or more systems with different delay time differences.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram of each part thereof. 1...Takagi filter, 2...Trigger generation circuit, 3...Delay circuit, 4...Switch switching circuit, 5...Comparison circuit. O Zuko 2

Claims (1)

[Claims] 1 means for determining the position indicating the outline of an image from the luminance signal;
A means for dividing the color difference signal into two systems each having a different delay time, a means for switching between the color difference signals having different delay times, and a means for comparing the color difference signals having different delay times is provided. The color difference signal with a large delay time is switched to the color difference signal with a small delay time at the outline position, and when the two color difference signals match, the color difference signal with a small delay time is switched to the color difference signal with a large delay time and output. An image quality improvement circuit for a color television receiver, characterized by: