JP2000059651A - Edge enhancement circuit - Google Patents

Abstract

(57) [Problem] To provide an outline emphasis circuit for suppressing unnecessary outline emphasis signals in a dark part of an image without impairing outline emphasis in a bright part of the image. SOLUTION: Means for extracting a first contour enhancement signal from a video signal, means for supplying the video signal and generating a function according to an input level, and first contour enhancement according to an output level of the level detection circuit Means for controlling the amount of clipping based on the absolute value level of the signal to output a second contour emphasizing signal; and adding a second contour emphasizing signal to the video signal to obtain a contour emphasizing signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a contour emphasizing circuit for generating a contour emphasizing signal for emphasizing a contour portion of a picked-up image based on a picked-up video signal.

[0002]

2. Description of the Related Art A contour portion of a picked-up image is detected from a picked-up video signal, and the video signal of the detected contour portion is emphasized. There is a problem that a clear image cannot be obtained due to a shortage of the enhancement amount in a portion, and an unnatural video signal is generated in a portion having a higher contrast because the enhancement amount is too large.

As a conventional technique for solving the above-mentioned problem, there is a technique disclosed in Japanese Patent Application Laid-Open No. 63-31875, for example. Using this conventional technique, by applying nonlinear processing to the contour enhancement signal extracted from the video signal and adding it to the original video signal, natural contour enhancement is performed on a low-contrast image or a high-contrast image. Will be.

For example, when a video signal as shown in FIG. 5 (a) is contour-enhanced by this conventional technique, the contour-enhanced signal is generated as a contour-enhanced signal as shown in FIG. 5 (b). You. The amplitude of each of the contour emphasizing signals at points A, B, and C in this figure has the same amplitude, and the effect of suppressing the contour emphasizing signal at point D from having a large amplitude can be obtained. That is, not all large-amplitude contour enhancement signals necessarily cause excessive contour enhancement.

However, only the black-side contour emphasis signal in the dark part (points A and D) of the image is suppressed, and the large-amplitude contour emphasis signal in the light part and the middle part (points B and C) is left as it is. To get a clearer image. in this case,
This is because the contour is less conspicuous when the amount of contour is the same level in the bright part than in the dark part of the image visually, and this is for the purpose of enhancing the contour suitable for the effect. In this case, when the above-described conventional technique is used, the contour enhancement signal is applied to the contour enhancement signal regardless of the dark portion or the bright portion, so that the contour enhancement signal at (B, C) may be insufficient. . For this reason, it is necessary to add clip processing to the contour emphasizing signal according to the video signal level. As in this conventional technique, simply performing non-linear processing on the contour emphasizing signal extracted from the video signal may cause the contour emphasis depending on the video level. However, there is a disadvantage that the contour of the bright part of the image is insufficient.

[0006]

In the above-mentioned prior art,
As the absolute value level of the contour emphasis signal increases, nonlinear processing is performed to gradually reduce the input / output gain of the contour emphasis signal, so that depending on the level of the video signal, excessive contour emphasis may not be obtained. On the contrary, there is a problem that the contour is unnaturally emphasized.

The present invention solves this drawback by converting a contour-enhanced signal, which has been subjected to a compression process such that the amplitude of the contour-enhanced signal is gradually compressed to an absolute level in accordance with the level of the video signal, into the original video signal. It is an object of the present invention to realize a device that obtains an outline emphasis signal by addition.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a contour emphasizing circuit for performing a contour emphasizing process on a video signal in accordance with a luminance level change amount of the video signal.
The outline emphasis of a video signal part having a lower luminance level is emphasized less, and the outline emphasis of a video signal part having a higher luminance level is emphasized more.

According to the present invention, in order to solve the above-mentioned problems, a means for extracting a first contour emphasis signal from a video signal,
Means for supplying the video signal and generating a function in accordance with the input level; a first means in accordance with the output level of the level detection circuit;
The compression amount is controlled by the absolute value level of the
Means for outputting a contour-enhanced signal, and adding a second contour-enhanced signal to the video signal to obtain a contour-enhanced signal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. In FIG. 1, an input video signal is supplied from an input terminal 1 to a contour enhancement signal generation circuit 2, a level detection circuit 3, and a video signal addition circuit 5. Edge enhancement signal generation circuit 2
Extracts a contour emphasizing signal from the input video signal and outputs it to the compression circuit 4 as a first contour emphasizing signal. The level detection circuit 3 outputs a signal processed with input / output characteristics as shown in FIG. 2 from the input video signal, and the processed signal is input to the compression circuit 4.

The compression circuit 4 is a compression circuit having input / output characteristics as shown in FIG. 3, which clips the amplitude of the first contour emphasizing signal at a predetermined absolute value and outputs a clipped video signal. At this time, the value to be clipped is determined according to the value of the signal (compressed signal) input from the level detection circuit 3.

Next, a configuration example of the compression circuit 4 and its operation will be described with reference to FIG.
This will be described in detail with reference to FIG. The input terminal 7 of the compression circuit 4
, The above-mentioned first contour emphasis signal is inputted, and the above-mentioned compressed signal b is inputted to the input terminal 8. The first contour emphasizing signal is input to the absolute value converting circuit 9, where the absolute value signal a and the sign signal s obtained by being converted into absolute values are output. Then, both the absolute value signal a and the compressed signal b are input to the selector circuit 10 and the comparison circuit 11, respectively, and the code signal s is input to the code conversion circuit 12. Comparison circuit 1
As a result of the comparison at 1, when a ≧ b, the absolute value signals a, a <
At b, a control signal for selecting the compression signal b is input to the selector circuit 10, and the selector circuit 10 outputs one of the absolute value signal a and the sign signal s according to the control signal.

The code conversion circuit 12 receives the output signal c and the code signal s of the selector circuit 10 and converts the output signal c, which has been converted into an absolute value, into a signal having a polarity corresponding to the code signal s. The returned signal is output from the output terminal 13 to the subsequent stage.

By the above operation, in the present invention, as shown in FIG. 4 (c), the contour emphasis signal at the dark portion (A, D) is suppressed and the contour emphasis signal at the light portion (B, C) is sufficiently obtained. The problem can be left, and the shortage of the outline enhancement of the bright part of the image, which is a problem in the related art, can be solved.

[0015]

As described above, when the present invention is used, an unnecessary edge enhancement signal existing in a dark portion of an image can be suppressed without impairing the edge enhancement of a bright portion of the image, and a higher quality image can be obtained. Obtainable.

[Brief description of the drawings]

FIG. 1 is a diagram showing a block configuration of an outline emphasizing circuit according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of input / output characteristics of a level detection circuit 3 according to the present invention.

FIG. 3 is a diagram showing an example of input / output characteristics of a compression circuit 4 according to the present invention.

FIG. 4 is a diagram illustrating an outline emphasis signal of an outline emphasis circuit according to one embodiment of the present invention.

FIG. 5 is a diagram illustrating an outline emphasis signal of a conventional outline emphasis circuit.

FIG. 6 is a diagram showing a block configuration example of a compression circuit in the contour emphasizing circuit of FIG. 1;

[Explanation of symbols]

1, 7, 8: input terminal, 2: contour enhancement signal generation circuit,
3: Level detection circuit, 4: Compression circuit, 5: Addition circuit, 6, 13: Output terminal, 9: Absolute value conversion circuit, 1
0: selector circuit, 11: comparison circuit, 12: code conversion circuit.

Claims (1)

[Claims] 1. An outline emphasis circuit that performs an outline emphasis process on a video signal according to a luminance level change amount of the video signal.
A contour emphasizing circuit characterized in that the contour emphasis of a video signal part having a lower luminance level is emphasized less and the contour emphasis of a video signal part having a higher luminance level is emphasized more.