JPH04336880A - Contour correction circuit - Google Patents

Abstract

PURPOSE:To realize the contour correction circuit in a color video camera which varies the contour correction quantity and the processing range of the coring processing to an optimum range in response to the image pickup condition. CONSTITUTION:An inputted video signal is fed to a high frequency component extraction circuit 1. The circuit 1 extracts a high frequency component signal from the inputted video signal, and the result is fed to a contour correction signal extract circuit 2. The circuit 2 eliminates a small amplitude signal within a coring width to eliminate a noise component from the supplied high frequency signal to make a characteristic signal, and the resulting signal is fed to a multiplier 3. In this case, the contour correction area and the width (coring width) of the noise area are given externally and latched by a 1st storage circuit 6a and the result is fed to the circuit 2. The multiplier 3 multiplies the signal from the circuit 2 with an optional contour correction coefficient given externally and latched by a 2nd storage circuit 6b and gives the resulting signal to an adder circuit 4. The adder circuit 4 adds the signal fed from the multiplier 3 and the original video signal, and the sum signal is outputted to be a signal subjected to contour correction and noise elimination.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour correction circuit used in a color video camera to improve the sharpness of a captured image.

0002

2. Description of the Related Art Contour correction circuits are circuits used in color video cameras that correct spatial frequency characteristics degraded by lenses, crystal filters, etc., and improve the sharpness of images.

Conventional contour correction circuits include a contour correction signal generation circuit for emphasizing contours, and a circuit for reducing small-amplitude high-frequency noise components (hereinafter referred to as noise components) contained in the contour correction signals. It consists of a clip circuit for In order to improve the sharpness of the image, if the contour correction signal generation circuit generates a signal that emphasizes the high frequency components of the input signal, noise components will also increase and the S/N will deteriorate, so a base clip circuit is used. Then, noise components whose level is lower than the clip level (hereinafter referred to as coring width in the sense of the range to which coring processing is applied) are removed from the signal that emphasizes the high frequency components of the input signal. Thereby, even if contour correction is performed, noise components are removed and S/N ratio does not deteriorate.

[0004] As a document describing this type of device, for example, JP-A-58-38074 can be mentioned.

[0005]

[Problems to be Solved by the Invention] In color video cameras, AGC is used to keep the input signal level constant.
(automatic gain control) circuit is used, and the AGC amount varies depending on the shooting conditions. For example, when the input signal level decreases, such as during low illumination, the AGC amount increases to keep the signal level constant, greatly amplifying the video signal. Then, in addition to the video signal, the noise component is also amplified.
/N deteriorates. In order to perform contour correction without causing S/N deterioration, it is necessary to increase the coring width of the base clip circuit to remove more noise components.

In the opposite case, if noise is removed under high illumination using the same coring width as under low illumination, not only noise components but also signals that require small amplitudes will be removed, resulting in an unnatural image. turn into. Therefore, in the above-mentioned conventional technology, the amount of contour correction and the coring width for removing noise components satisfy each imaging condition to some extent.
It is set to a certain moderate value.

SUMMARY OF THE INVENTION An object of the present invention is to provide a contour correction circuit that can change the contour correction amount and coring width at any time in a color video camera to optimize them for photographing conditions.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a first means for extracting and outputting a high frequency component from an input video signal, and a coring width value (limit range) given from the outside. ) for removing a small-amplitude signal portion containing a noise component from the high-frequency component (output of the first means) of the input video signal, and extracting and outputting the remaining signal portion as a signal portion for contour correction; , a third means for multiplying the signal to be contour corrected (output of the second means) by an externally applied contour correction coefficient; and the original input video signal and the signal output from the multiplier (third means). and a fourth means for adding together the contour correction circuit.

[0009] As a means for externally providing the above coefficients,
For example, a microcomputer or the like is used.

0010

[Operation] In the above contour correction circuit, the first means extracts high frequency components from the input video signal using a band pass filter or the like. The second method is to set the output to zero for inputs other than the region of the signal to be contour corrected, that is, within the coring width given from the outside, as shown in the characteristics of FIG. 3, which will be described later, to eliminate noise components. Removes small amplitude signals. The third means changes the slope of the characteristic of the signal to be subjected to contour correction using a contour correction coefficient provided from the outside. For example, if it is desired to emphasize the contour, the slope of the characteristic of the contour correction area is made steeper. The fourth means adds the original input video signal and the signal output from the multiplier (third means), and outputs a signal with noise components reduced and contours corrected.

[0011] By each of the above-mentioned means, the input video signal becomes a signal subjected to contour correction and noise reduction. Furthermore, the contour correction and coring width can be always optimized by adjusting the coring width value (limit range) and coefficient values given externally according to each shooting condition, making it easy to improve image quality. can.

0012

Embodiment A first embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram showing the configuration of a contour correction circuit as a first embodiment of the present invention.
, a contour correction signal extraction circuit 2, a multiplier 3, an addition circuit 4, and storage circuits 6a and 6b.The operation thereof will be explained below.

A video signal input from an input terminal is supplied to a high frequency component extraction circuit 1. The high frequency component extraction circuit 1 extracts a high frequency component signal from the input video signal,
The signal is supplied to the contour correction signal extraction circuit 2. The contour correction signal extraction circuit 2 removes noise components from the supplied high frequency signal by removing small amplitude signals within the coring width, converts the signal into a signal having the characteristics shown in FIG. 3, and supplies the signal to the multiplier 3. . FIG. 3 is an input/output characteristic diagram of the contour correction signal extraction circuit 2.

At this time, the width of the contour correction area and the noise area (
The value of coring width) is given from the outside, is held in the first storage circuit 6a, and is supplied to the contour correction signal extraction circuit 2. The multiplier 3 multiplies the signal supplied from the contour correction signal extraction circuit 2 by an arbitrary contour correction coefficient given from the outside and held in the second storage circuit 6b, and supplies the signal to the addition circuit 4. The adder circuit 4 adds the signal supplied from the multiplier 3 and the original video signal, performs contour correction, and outputs a signal that has been subjected to noise removal.

FIG. 5 shows the input/output characteristics of the first embodiment of the present invention shown in FIG. In this figure, the signal characteristics (inclination K1) of the contour correction area and the coring width (W) that determines the two areas are changed by arbitrary values given from the outside. According to this embodiment, by changing the values of the contour correction coefficient and coring width given from the outside according to the imaging conditions, it is possible to easily change the contour correction characteristics and improve the sharpness of the image. can.

FIG. 2 shows a second embodiment. FIG. 2 is a block diagram showing the configuration of a contour correction circuit as a second embodiment of the present invention. , a noise extraction circuit 5, and memory circuits 6a, 6b, and 6c, and the operation thereof will be described below.

A video signal input from an input terminal is supplied to a high frequency component extraction circuit 1. The high frequency component extraction circuit 1 extracts a high frequency component signal from the input video signal,
The signal is supplied to the contour correction signal extraction circuit 2 and the noise extraction circuit 5. The contour correction signal extraction circuit 2 removes noise components from the supplied high frequency signal by removing small amplitude signals within the coring width, converts the signal into a signal having the characteristics shown in FIG. 3, and outputs the signal to the first multiplier. 3a.

The first multiplier 3a adds a second signal supplied from the outside to the signal supplied from the contour correction signal extraction circuit 2.
The multiplied signal is multiplied by an arbitrary contour correction coefficient held in the storage circuit 6b, and is supplied to the addition circuit 4.

On the other hand, the noise extraction circuit 5 passes a small amplitude signal within the coring width, and outputs a signal at a constant level when the width exceeds the coring width.
It is supplied to the second multiplier 3b. FIG. 4 is a characteristic diagram showing the input/output characteristics of the noise extraction circuit 5. the second multiplier 3
At b, the signal supplied from the noise extraction circuit 5 is multiplied by an arbitrary noise coefficient given from the outside and held in the third storage circuit 6c, and the multiplied signal is supplied to the addition circuit 4.

At this time, the width of the contour correction area and the noise area (
The value of coring width) is given from the outside, is held in the first storage circuit 6a, and is supplied to the contour correction signal extraction circuit 2 and the noise extraction circuit 5. The adding circuit 4 adds the signals supplied from the first multiplier 3a and the second multiplier 3b and the original input video signal to obtain a signal that has been subjected to contour correction and noise reduction. and output it. FIG. 6 shows the input/output characteristics of the second embodiment of the present invention shown in FIG.

In FIG. 6, the characteristics of the signal in the contour correction area (slope K1) and the characteristics of the signal in the noise area (slope K2) are shown.
), the coring width (W) that determines the two regions is changed by an arbitrary value given from the outside.

According to this embodiment, the same effects as in the first embodiment can be obtained. In addition, depending on the coring width, you can finely set the amount of noise reduction using the noise coefficient, rather than removing all the noise, so you can finely adjust the degree to which small amplitude signals that are lost with noise reduction remain, resulting in a natural sound. This is effective in obtaining images. Furthermore, the contour correction coefficient, noise coefficient, and coring width can be set externally, and each characteristic can be changed independently, which has the effect of easily setting the optimum image quality according to each imaging condition.

[0023]

[Effects of the Invention] As explained above, according to the present invention,
Since the contour correction characteristics and coring width can be changed using externally supplied coefficient values, we have developed a contour correction circuit that can always change these values to the optimal values according to the shooting conditions to improve image quality. It can be realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the invention.

FIG. 3 is an input/output characteristic diagram of the contour correction signal extraction circuit.

FIG. 4 is an input/output characteristic diagram of the noise extraction circuit.

FIG. 5 is an input/output characteristic diagram of the contour correction circuit shown in FIG. 1;

FIG. 6 is an input/output characteristic diagram of the contour correction circuit shown in FIG. 2;

[Explanation of symbols]

1... High frequency component extraction circuit, 2... Contour correction signal extraction circuit,
3, 3a, 3b... Multiplier, 4... Addition circuit, 5... Noise extraction circuit, 6a, 6b, 6c... Memory circuit

Claims (2)

[Claims] 1. A first signal extraction means for inputting a video signal, extracting a high frequency component from the input video signal, and outputting the extracted high frequency component.
1), a first storage means (6a) for storing a limit range given from the outside, and a limit read out from the first storage means by inputting the high frequency component outputted from the first signal extraction means. a second signal extraction means (2) for suppressing and not outputting high frequency components at a level within the limit range and outputting high frequency components at a level outside the limit range as a contour correction signal; a second storage means (6b) for storing coefficient values given from
and a multiplication means (3) which receives the contour correction signal output from the second signal extraction means, multiplies the contour correction signal by a coefficient value read from the second storage means, and outputs the result.
and an addition means (4) for adding the output from the multiplication means and the input video signal and outputting the result. 2. A first signal extracting means for inputting a video signal, extracting a high frequency component from the input video signal, and outputting the extracted high frequency component.
1), a first storage means (6a) for storing a limit range given from the outside, and a limit read out from the first storage means by inputting the high frequency component outputted from the first signal extraction means. a second signal extracting means (2) for suppressing and not outputting the high frequency component at a level within the limit range and outputting the high frequency component at a level outside the limit range as a contour correction signal; The high frequency component outputted from the first signal extraction means is input, and according to the limit range read from the first storage means, the high frequency component at the level of the limit range is output as a noise component, but within the limit range. a third signal extracting means (5) for outputting a high frequency component at an external level as a signal limited to a certain level; a second storage means (6b) for storing a first coefficient value given from the outside; a first multiplication means (3a ), a third storage means (6c) for storing a second coefficient value given from the outside, and a signal output from the third signal extraction means is inputted and read out from the third storage means. a second multiplication means (3b) that multiplies the signal by a second coefficient value and outputs the result; and adds the output from the first multiplication means, the output from the second multiplication means, and the input video signal. an addition means (4) for outputting a contour correction circuit.