JPH0450701Y2 - - Google Patents

Description

[Detailed description of the invention] <Technical field> The invention relates to a contour compensation circuit installed in video cameras and the like to improve the sharpness of images. The present invention relates to a contour compensation circuit that forms a contour-compensated video signal from a video signal.

<Prior Art> FIG. 3 is a block diagram of a conventional example, and FIG. 4 is a signal waveform diagram of each part. In FIG. 3, reference numeral 1 denotes a white signal compression circuit that compresses the white part of the video signal in order to widen the dynamic range of the object part (highlight part) with high brightness. In this white signal compression circuit 1, for example, the white part of the video signal having a predetermined level L or higher shown in FIG.
It is output as a video signal shown in Figure B. The video signal white-compressed by the white signal compression circuit 1 is amplified by the amplifier circuit 2, and then delayed by 1H (H is a horizontal scanning period), a first delay circuit 3 and a comb filter circuit 1.
given to 0. The video signal delayed by 1H in the first delay circuit 3 is further delayed by 1H in a second delay circuit 4, and in a third delay circuit 7 for timing adjustment.
and comb filter circuit 10, respectively. The comb filter circuit 10 reduces noise components based on the outputs of the amplifier circuit 2, the first delay circuit 3, and the second delay circuit 4, and outputs the video signal shown in FIG. 4B.

Based on the white-compressed video signal shown in FIG. 4B from the comb filter circuit 10, the contour compensation signal forming circuit 6 forms the contour compensation signal shown in FIG. 4C. This contour compensation signal is applied to the mixing circuit 8, where it is mixed with the video signal shown in FIG. 4B from the third delay circuit 7 to form the contour compensated signal shown in FIG. 4D. A video signal is output.

In such a conventional contour compensation circuit, the white portion is compressed by the white signal compression circuit 1, and the contour compensation signal is formed based on this compressed video signal, so that the signal shown in FIG. 4D is generated. The disadvantage is that contour compensation for white areas is insufficient, resulting in images with low sharpness.

<Purpose of the invention> The present invention has been made in view of the above-mentioned points, and an object thereof is to improve sharpness by sufficiently performing contour compensation in white areas.

<Configuration of the invention> In order to achieve the above-mentioned object, the invention includes a sampling circuit that extracts a video signal portion to be white-compressed at a predetermined level or higher from a video signal input to a white signal compression circuit; a first mixing circuit for mixing the extracted video signal portion and the white-compressed video signal from the white signal compression circuit; and a contour compensation signal forming circuit for forming a contour compensation signal based on the output of the first mixing circuit. and a second mixing circuit that mixes the contour compensation signal and the white-compressed video signal and outputs a contour-compensated video signal.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of one embodiment of the present invention, and parts corresponding to the conventional example of FIG. 3 are given the same reference numerals. Moreover, FIG. 2 is a signal waveform diagram of each part of FIG. 1. In Figure 1, 1
2 is a white signal compression circuit; for example, when the video signal shown in FIG. 2A is input, the white portion of a predetermined level L or higher is compressed to become the video signal shown in FIG. 2B. The video signal compressed in white by the white signal compression circuit 1 is amplified by the amplifier circuit 2, and is 1H
The signal is applied to a first delay circuit 3 and a comb filter circuit 5, respectively. In the first delay circuit 3
The video signal delayed by 1H is further processed by a second delay circuit for delaying it by 1H and a third delay circuit for timing adjustment.
The signal is applied to delay circuit 7 and comb filter circuit 5, respectively.

Reference numeral 9 denotes a sampling circuit that extracts the video signal portion to be white-compressed at a predetermined level L or higher from the video signal shown in FIG. 4A that is input to the white signal compression circuit 1, as shown in FIG. The resulting video signal portion is applied to a comb filter circuit 5.

The comb filter circuit 5 includes an amplifier circuit 2, a first delay circuit 3, and a second delay circuit 4, as in the conventional example.
Based on the video signal from the sampling circuit 9, the noise component is reduced to form the video signal shown in FIG.
By mixing the video signal portion shown in FIG. 2C from FIG. 2B with the white compressed video signal of FIG.
A video signal shown in is formed and output to the contour compensation signal forming circuit 6. That is, the comb filter circuit 5 of this embodiment has a function as a first mixing circuit that mixes the video signal portion extracted by the extraction circuit 9 and the video signal white-compressed by the white signal compression circuit 1.

The contour compensation signal forming circuit 6 forms the contour compensation signal shown in FIG. 2E based on the video signal of FIG. 2D from the comb filter circuit 5 and outputs it to the mixing circuit 8, as in the conventional example do.

The white-compressed video signal is mixed with the white-compressed video signal extracted by the sampling circuit 9, and based on this mixed video signal, the contour compensation signal forming circuit 6 generates a contour compensation signal. 4. Compared to the conventional example shown in Figure 4C,
As shown in Figure E, the outline is sufficiently compensated even in the area where white compression is applied.
Image sharpness in highlight areas is improved.

In the mixing circuit 8 serving as the second mixing circuit, the video signal shown in FIG. 2B whose timing has been matched by the third delay circuit 7 and the contour compensation signal shown in FIG. As shown in the figure, a video signal with sufficient contour compensation is output even in the white-compressed portion.

In the above embodiment, the comb filter circuit 5 also serves as the first mixing circuit for mixing the video signal portion extracted by the extraction circuit 9 and the white compressed video signal from the white signal compression circuit 1. However, the present invention is not limited to this, and it goes without saying that the comb filter circuit 5 may be replaced with a separate mixing circuit.

<Effects of the invention> As described above, according to the invention, the video signal portion to be white-compressed at a predetermined level or higher is extracted from the video signal input to the white signal compression circuit, and the white-compressed portion is applied to the extracted video signal portion. Since the mixed video signals are mixed and the contour compensation signal is formed based on this mixed video signal, the contour compensation of the white areas is also sufficiently performed, and the sharpness of the highlight areas is also improved. The result is an easy-to-read image.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention;
1, FIG. 3 is a block diagram of a conventional example, and FIG. 4 is a signal waveform diagram of each part in FIG. 3. DESCRIPTION OF SYMBOLS 1... White signal compression circuit, 5... Comb filter circuit (first mixing circuit), 6... Contour compensation signal forming circuit, 8... Mixing circuit (second mixing circuit), 9... Sampling circuit.

Claims (1)

[Claims for Utility Model Registration] A sampling circuit for extracting a video signal portion to be white-compressed at a predetermined level or higher from a video signal input to a white signal compression circuit; and the video signal portion extracted by the sampling circuit and the white. a first mixing circuit that mixes the white-compressed video signal from the signal compression circuit; an outline compensation signal forming circuit that forms an outline compensation signal based on the output of the first mixing circuit; and the outline compensation signal and the white A contour compensation circuit comprising: a second mixing circuit that mixes compressed video signals and outputs a contour-compensated video signal.