JP3184309B2 - Gradation correction circuit and imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to gradation correction in which a main subject becomes a blurred image without gradation in backlit photographing or the like, and a gradation rich expression image can be obtained. The present invention relates to a circuit and an imaging device.

[0002]

2. Description of the Related Art In recent years, many tone correction circuits have been developed. A conventional gradation correction circuit is disclosed in, for example,
No. 139080 discloses an image processing apparatus.

Hereinafter, a conventional gradation correction circuit will be described. FIG. 16 is a functional block diagram of a conventional gradation correction circuit. In FIG. 16, reference numeral 1301 denotes an R signal gradation correction unit, 1302 denotes a G signal gradation correction unit, 1303 denotes a B signal gradation correction unit, 1304 denotes a luminance signal histogram creating unit, and 1305 denotes a cumulative luminance distribution curve creating unit.

The operation of the conventional gradation correction circuit configured as described above will be described below.

First, R, G, and B signals converted into digital data of 0 to 255 are input. These color data indicate white when R = G = B = 255, and the larger the value, the brighter the color. Set the luminance of the input video signal to Y
Then, for example, Y = 0.30R + 0.59G + 0.
11B, which can be obtained from 0 to 255
Value. With this relational expression, the luminance is obtained over the entire area of one frame of the effective screen.
When the luminance signal histogram creation unit 1304 finds the distribution of luminance levels for × 480 dots, a luminance histogram is obtained. When the cumulative luminance distribution curve creating means 1305 calculates the cumulative luminance histogram for the image data, a cumulative luminance distribution curve is obtained.

When the horizontal axis H of the cumulative luminance distribution curve is normalized so that the input luminance level is 0 to 255 and the value of the vertical axis V is also 0 to 255, a relational expression showing this curve is obtained. . If this relational expression is V = F (H), V can be obtained as a value obtained by gamma-converting the input luminance level H. By this relational expression, the R signal tone correction unit 130
1, G signal tone correction unit 1302, B signal tone correction unit 13
03 performs gradation correction by performing the same gamma conversion on the R, G, and B signals. In this way, the cumulative luminance distribution curve is represented by R, G, B
By commonly using the signals, it is possible to obtain an output image with good color balance and gradation correction over the entire range.

[0007]

However, in the above-mentioned conventional example, there is no problem with a video having a small degree of backlight such as a television signal, but this processing is performed on an image with a large degree of backlight captured by a consumer camera or the like. Is performed, the correction is performed so that the gradation is uniform over the entire screen, so that the portion without gradation is sharply expanded, so that a false contour occurs or the portion with good gradation is crushed. There is a problem that an unnatural image is formed. In addition, there is also a problem that noise is noticeable because the gain of the low luminance portion is increased in order to reproduce the gradation of the dark portion.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. Even in an image having a large degree of backlight, a false contour is not generated, gradation is not crushed, and noise in a low luminance portion is inconspicuous. It is an object of the present invention to provide a gradation correction circuit capable of obtaining an output image rich in gradation expression over the entire region.

[0009]

In order to achieve this object, a gradation correction circuit according to the present invention comprises a low- pass filter for separating low-frequency components of an input video signal, and a low-pass filter for the low-pass filter.
When the output signal is larger than a predetermined value, the gradation correction curve
And a high-pass filter that separates high-frequency components of the input video signal, and a gradation correction processing unit that separates high-frequency components of the input video signal. And an adder for adding the signal and the output signal of the high-pass filter to output an output video signal.

The tone correction circuit according to the present invention further comprises a low- pass filter for separating low-frequency components of the input video signal;
When the output signal of the band-pass filter is larger than a predetermined value,
A tone correction processing unit that limits a gain of a tone correction curve and tone-corrects an output signal of the low-pass filter; a high-pass filter that separates a high-frequency component of the input video signal; A non-linear processing section for performing non-linear processing on an output signal of the pass filter; and an adder for adding an output signal of the gradation correction processing section and an output signal of the non-linear processing section and outputting an output video signal.

The tone correction circuit according to the present invention further comprises a low- pass filter for separating low-frequency components of the input video signal;
When the output signal of the band-pass filter is larger than a predetermined value,
A tone correction processing unit that limits a gain of a tone correction curve and tone-corrects an output signal of the low-pass filter; a high-pass filter that separates a high-frequency component of the input video signal; A non-linear processing unit that performs non-linear processing on an output signal of the pass filter, and a gain adjustment unit that performs gain adjustment on the output signal of the non-linear processing unit in accordance with the gradation correction of the gradation correction unit.
An adder for adding an output signal of the gradation correction processing unit and an output signal of the gain adjustment unit and outputting an output video signal.

An image pickup apparatus with a gradation correction function according to the present invention is a solid-state image pickup device, an analog circuit for extracting an input video signal from the solid-state image pickup device, and a low-pass filter for separating low-frequency components of the input video signal. And the low-pass filter
When the output signal is larger than the predetermined value, the gradation correction curve
A gradation correction processing unit for limiting a gain and correcting a gradation of an output signal of the low-pass filter; a contour extraction filter for extracting a contour component of the input video signal; and a non-linear processing of an output signal of the contour extraction filter A non-linear processing unit, a gain adjustment unit that adjusts a gain of an output signal of the non-linear processing unit according to the gradation correction of the gradation correction unit, an output signal of the gradation correction processing unit, and an output of the gain adjustment unit. And an adder for adding the signals and outputting an output video signal.

[0013]

The tone correction circuit according to the present invention has the above-described configuration.
The low-pass filter separates only the low-frequency components of the input video signal, and the tone correction processing unit performs tone correction. On the other hand, only the high-frequency component of the input video signal is separated by the high-pass filter. Since gradation correction is not performed for the high-frequency component, the gradation of the detail portion can be maintained. Finally, by adding the output signal of the gradation correction processing unit and the output signal of the high-pass filter by the adder, it is possible to perform gradation correction with rich gradation.

Further, according to the tone correction circuit of the present invention, only the low-frequency component of the input video signal is separated by the low-pass filter, and the tone correction is performed by the tone correction processing unit.
On the other hand, only a high-frequency component of the input video signal is separated by a high-pass filter, and a noise component is removed by a non-linear processing unit. Since gradation correction is not performed for the high-frequency component, the gradation of the detail portion can be maintained. Lastly, by adding the output signal of the gradation correction processing unit and the output signal of the non-linear processing unit by an adder, it is possible to perform gradation correction rich in gradation with reduced noise in a low luminance portion.

Further, in the gradation correction circuit of the present invention, only the low-frequency component of the input video signal is separated by the low-pass filter, and the gradation correction is performed by the gradation correction processing section.
On the other hand, only a high-frequency component of the input video signal is separated by a high-pass filter, and a noise component is removed by a non-linear processing unit. Further, in order to correct the gradation of a portion where the gradation is compressed by the gradation correction processing unit, the gain adjustment unit performs gain adjustment on the high-frequency component passed through the non-linear processing unit. Since gradation correction is not performed for the high-frequency component, the gradation of the detail portion can be maintained.
Finally, by adding the output signal of the tone correction processing unit and the output signal of the gain adjustment unit with an adder, it is possible to perform tone correction rich in tone expression in which noise in a low luminance portion is suppressed.

Further, according to the imaging apparatus having the gradation correction function of the present invention, the analog circuit takes in the input video signal from the solid-state imaging device. Only the low-frequency component of the input video signal is extracted by the low-pass filter, and the tone correction processing unit performs tone correction. On the other hand, only a contour component of the input video signal is extracted by a contour extraction filter, and a noise component is removed by a non-linear processing unit. Further, in order to correct the gradation property of the portion where the gradation is compressed by the gradation correction processing section, the gain component is gain-adjusted by the gain adjustment section through the non-linear processing section. Since the gradation correction is not performed on the contour component, the gradation of the detail part can be maintained. Finally, by adding the output signal of the tone correction processing unit and the output signal of the gain adjustment unit with an adder, it is possible to perform tone correction rich in tone expression in which noise in a low luminance portion is suppressed.

[0017]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a gradation correction circuit according to a first embodiment of the present invention. In FIG. 1, 101 is a low-pass filter (LPF), 102 is a gradation correction processing unit, 103 is a high-pass filter (HPF),
104 is a non-linear processing unit, 105 is an adder, 106 is a histogram creating means, and 107 is a gradation correction curve determining means.

FIG. 2 is a block diagram of a video-integrated camera (image pickup apparatus) using a gradation correction circuit according to an embodiment of the present invention. In FIG. 2, reference numeral 301 denotes a CCD camera head, 302 denotes an analog-digital converter (A / D converter), 303 denotes a gradation correction circuit, 304 denotes a signal processing circuit,
305 is a digital-analog converter (D / A converter),
306 is an encoder circuit, and 307 is a VTR circuit.

FIG. 3 is a diagram showing an image of one frame of the input video signal. Reference numeral 401 denotes an effective screen. Active screen 4
The number of samples of 01 is 640 points in the horizontal H direction and 480 points in the vertical V direction.

FIG. 4 is a diagram showing a histogram of a luminance signal of an effective screen and a gradation correction curve. FIG. 4A shows a histogram of a luminance signal, and FIG. 4B shows a gradation correction curve.

FIG. 5 is a diagram showing the non-linear processing characteristics of the non-linear processing section in the embodiment of the present invention. FIG. 5d shows the nonlinear processing characteristics, and FIG. 5e shows the coring value.

FIG. 6 is a signal diagram of a gradation correction circuit according to the first embodiment of the present invention. 6A shows an input video signal, and FIG. 6B shows a low-pass filter (LPF) 101.
(C) is a high-pass filter (HPF) 10
3, (d) is the output signal of the gradation correction processing unit 102, (e) is the output signal of the non-linear processing unit 104, and (f) is the output video signal of the gradation correction circuit 303.

The operation of the video-integrated camera using the gradation correction circuit according to the first embodiment of the present invention configured as described above will be described below.

In FIG. 2, first, R, G, and B signals are fetched from the CCD camera head unit 301 as input video signals. The R, G, B signals are converted into digital data of 0 to 255 by the analog-digital converter 302. The R, G, and B signals converted into the digital data of 0 to 255 are used as input video signals as gradation correction circuits 30.
3 is input. The tone correction circuit 303 separates an input video signal into a high-frequency component and a low-frequency component, and removes a high-frequency noise component. On the other hand, tone correction is performed only for the low-frequency component. Then, the high-frequency component from which the noise component has been removed and the low-frequency component whose gradation has been corrected are added, and output as R, G, B signals whose gradation has been corrected. The signal processing circuit 304 performs signal processing such as aperture correction processing on the R, G, and B signals subjected to the gradation correction.
The processed digital R, G, B signals are converted to digital signals.
An analog converter 305 converts the signals into analog R, G, B signals. Next, the encoder circuit 306 converts the R, G, and B signals into a Y signal (luminance signal) and a C signal (color signal). Finally, the VTR circuit 307 records on the video tape.

Next, referring to FIG. 1 and FIG.
03 will be described in detail. First, R, G, and B signals converted into digital data of 0 to 255 are input as input video signals. These color data are R = G = B = 25
A value of 5 indicates white, and a larger value indicates a brighter color. Assuming that the luminance of the input video signal is Y, for example,
It can be obtained by the relational expression of Y = 0.30R + 0.59G + 0.11B, and again takes a value of 0 to 255.

FIG. 3 shows an image of one frame of the input video signal. This image is an example of a subject in which a person stands in front of a window and has a high degree of backlight. When the histogram creating unit 106 obtains the luminance level distribution for one frame image 640 × 480 dots of the effective screen 401 of FIG. 3 over the entire area of the effective screen by the above relational expression, it is shown in FIG. Such a luminance histogram is obtained. Looking at the luminance histogram (a in FIG. 4), two peaks are formed, and it can be estimated that the subject is a backlight subject and the degree of the backlight is. Thus, the gradation correction curve determining means 107
Performs image recognition using the luminance histogram as a feature amount, and determines a gradation correction curve most suitable for the input image.

A low-pass filter (LPF) 101
Accordingly, only the low-frequency component (FIG. 6B) is extracted from the input video signal (FIG. 6A), and the gradation correction processing unit 102
To supply. Then, the tone correction processing unit 102 performs tone correction on the R, G, and B signals of only the low-frequency component using the same determined tone correction curve (for example, (d) of FIG. 6). As described above, since the gradation correction is performed only on the low-frequency component of the input video signal, the gradation correction can be performed without losing the gradation of the detail portion such as the edge component. In addition, by using the gradation correction curve commonly for the R, G, and B signals, it is possible to obtain an output image with good color balance and rich gradation expression over the entire range.

Hereinafter, the noise removal processing of the nonlinear processing unit 104 will be described with reference to FIG. On the other hand, the high-pass filter 103 extracts only the high-frequency component ((c) in FIG. 6) from the input video signal ((a) in FIG. 6) and supplies it to the nonlinear processing unit 104. Due to the nonlinear processing characteristic shown in FIG. 5D, when the absolute value of the high frequency component of the input video signal is smaller than the coring value (e in FIG. 5), the nonlinear processing unit 104 turns the output signal to zero, and the absolute value becomes When the value is large, if the high frequency component of the input video signal is positive, the output signal has a value obtained by subtracting the coring value (e in FIG. 5) from the high frequency component of the input video signal. If the high frequency component of the input video signal is negative, the output signal has a value obtained by adding the coring value (e in FIG. 5) to the high frequency component of the input video signal. In this way, as shown in FIG. 6E, the high frequency component (FIG.
(C)) removes noise components smaller than the coring value (e in FIG. 5). The high-frequency component of the input video signal performs only noise removal and does not perform gradation correction, so that the gradation of the detail portion is kept as it is. In addition, the coring value (FIG. 5)
The degree of noise removal can be adjusted by adjusting the size of e).

At this time, the configuration of the high-pass filter 103 is such that the relationship of 1−low-pass filter 101 is satisfied.
A low-pass filter 101 and a high-pass filter 103 are configured. By doing so, when the output of the low-pass filter 101 and the output of the high-pass filter 103 are finally added, the magnitude of the input video signal can be restored.

Finally, the output signal of the gradation correction processing section 102 and the output signal of the non-linear processing section 104 are added by an adder 105 to output an output video signal (FIG. 6 (f)). In this manner, false contours do not occur even in images with a large degree of backlight, gradation is not crushed, noise is small,
An output image with good color balance and rich gradation expression over the entire area can be obtained.

FIG. 7 is a block diagram showing a more specific configuration example of the gradation correction circuit in the first embodiment of the present invention shown in FIG. In FIG. 7, a tone correction curve determining means 1
07 is an input means 108, a microcomputer 109, a microcomputer 1
The ROM 110 stores a program 09 and a template showing characteristics of the gradation correction curve to be selected, and the RAM 111 stores a luminance histogram.

FIG. 8 is a detailed block diagram of the gradation correction processing section 102 according to the embodiment of the present invention. In FIG. 8, 1
001 is an α clip circuit for clipping with a value α, 1002
Is a β clipping circuit that clips with a value β, 1003 is a multiplier, 1004 is a subtractor, 1005 is an adder, 1006 is a gain adjuster, 1007 is a large signal selector circuit, 100
8 is a selector circuit.

FIG. 9 is a characteristic diagram showing a gradation correction curve of the gradation correction processing section 102 in the embodiment of the present invention.

FIG. 10 is a flowchart showing a procedure for determining a gradation correction curve in the embodiment of the present invention.

Hereinafter, the operation of the gradation correction circuit 303 will be described in detail with reference to FIG. First, the R, G, and B signals converted into digital data of 0 to 255 are input to the gradation correction processing unit 303 as input video signals. This input video signal is supplied to a histogram creation means 106 and a low-pass filter (L
PF) 101 and a high-pass filter (HPF) 103.

The operation of the microcomputer 109 for determining the gradation correction curve using the template matching method will be described with reference to FIGS. Histogram creating means 106
Calculates a luminance signal from an input video signal and calculates a luminance histogram for an effective screen of one frame. Then, the microcomputer 109 reads the luminance histogram into the RAM 111. Next, the distance between the template indicating the characteristic of the gradation correction curve to be selected in the ROM 110 and the luminance histogram read into the RAM 111 is obtained. Next, a tone correction curve that minimizes the distance is selected. Finally, the gain of the selected gradation correction curve is set in the gradation correction processing unit 102.

FIG. 8 is a detailed block diagram of the gradation correction processing section 102 according to the embodiment of the present invention. FIG. 9 is a characteristic diagram illustrating a gradation correction curve of the gradation correction processing unit 102 according to the embodiment of the present invention.

8 and 9, the gradation correction processing unit 10
When a gain is input, the input signal is multiplied by the input gain when the input signal is smaller than the value α, and becomes an output signal (a in FIG. 9). When the input signal has a value between the values α and β, Is an output signal (b in FIG. 9) having an offset slope of 1 obtained by multiplying the input gain by the value α. When the input signal is larger than the value β, the signal having the offset slope of 1/2 of the b signal in FIG. A tone correction curve (see FIG. 9) is automatically generated so that a larger signal becomes an output signal (c in FIG. 9), and tone correction can be performed on an input signal in real time.
Further, by providing the gradation correction processing unit 102 which generates a gradation correction curve of a polygonal line as shown in FIG. 8, an extra ROM or the like for storing several types of gradation correction curves is not required. Because it is good, the circuit scale can be very small. In addition, when the input signal is large, the tone correction curve is configured so that the input signal becomes an output signal almost as it is, so that the place where the tone of the high-brightness part has been lost by the conventional auto knee control or the like can be reproduced clearly. Can be.

The low-pass filter 101 separates low-frequency components from the input video signal. Then, the gradation correction processing unit 102 performs gradation correction only for the low-frequency component. in this way,
Since the tone correction is performed only on the low-frequency component of the input video signal, the tone correction can be performed without losing the tone of the detail part such as the edge component. Further, the gradation correction curve is represented by R,
By commonly using the G and B signals, it is possible to obtain an output image with good color balance and rich in gradation expression over the entire range.

On the other hand, the high-pass filter 103 extracts high-frequency components from the input video signal. Then, the non-linear processing unit 104 removes a noise component smaller than the coring value of the high frequency component of the input video signal according to the non-linear processing characteristics. The high frequency component of the input video signal performs only noise removal,
Since gradation correction is not performed, the gradation of the detail portion is kept as it is. In addition, the degree of noise removal can be adjusted by adjusting the magnitude of the coring value.

Finally, the adder 105 adds the high-frequency component from which the noise component has been removed and the low-frequency component whose tone has been corrected, and outputs the R, G, B signals whose tone has been corrected.

At this time, the configuration of the high-pass filter 103 is such that the relationship of 1−low-pass filter 101 is satisfied.
A low-pass filter 101 and a high-pass filter 103 are configured. By doing so, when the output of the low-pass filter 101 and the output of the high-pass filter 103 are finally added, the magnitude of the input video signal can be restored.

In this way, an output image in which no false contour is generated, the gradation is not crushed, the noise is small, the color balance is good, and the gradation expression is rich over the entire area is obtained even for an image having a large degree of backlight. be able to.

As described above, according to the present embodiment, the gradation correction circuit of the present invention includes a low-pass filter 101, a gradation correction processing unit 102, a high-pass filter 103, a nonlinear processing unit 104, Adder 105 and histogram creating means 1
06 and the gradation correction curve determining means 107, the false contour does not occur, the gradation is not crushed, the noise component is suppressed, the color balance is good, and the gradation is expressed over the entire area even in an image with a large degree of backlight. Rich output image can be obtained.

The tone correction processing unit 102 in the tone correction circuit of the present invention is provided with an α clipping circuit 1001 for clipping with a value α and a β clipping circuit 10 for clipping with a value β.
02, a multiplier 1003, a subtractor 1004, an adder 1005, a gain adjuster 1006, a large signal selector circuit 1007, and a selector circuit 1008.
A gradation correction processing unit 102 that generates a gradation correction curve of a polygonal line
By doing so, it is not necessary to have an extra ROM or the like for storing several types of gradation correction curves, so that the circuit scale can be made very small. In addition, when the input signal is large, the tone correction curve is configured so that the input signal becomes an output signal almost as it is, so that the place where the tone of the high-brightness part has been lost by the conventional auto knee control or the like can be reproduced clearly. Can be.

FIG. 11 is a block diagram showing a configuration of the gradation correction circuit 303 according to the second embodiment of the present invention. FIG.
The difference from the first embodiment shown in FIG.
1 is newly provided.

Hereinafter, the gradation correction circuit 303 will be described with reference to FIG.
Will be described in detail. First, R, G, and B signals converted into digital data of 0 to 255 are input as input video signals. These color data are R = G = B = 255.
Indicates white, and the larger the value, the brighter. Assuming that the luminance of the input video signal is Y, for example, Y
= 0.30R + 0.59G + 0.11B, which is also a value from 0 to 255. According to this relational expression, an image 640 of one frame of the effective screen of the input video signal of FIG.
Histogram creation means 106 for × 480 dots
When a luminance level distribution is obtained, a luminance histogram as shown in FIG. 4A is obtained. Looking at the luminance histogram (a in FIG. 4), two peaks are formed, and it can be estimated that the subject is a backlight subject and the degree of the backlight is. In this way, the gradation correction curve determination unit 107 performs image recognition using the luminance histogram as a feature amount, and determines a gradation correction curve most suitable for the input image.

Also, the low-pass filter 101
Only the low-frequency component is extracted from the input video signal and supplied to the gradation correction processing unit 102. Then, the gradation correction processing unit 102
Performs tone correction on the R, G, and B signals of only the low-frequency component using the same determined tone correction curve. As described above, since the gradation correction is performed only on the low-frequency component of the input video signal, the gradation correction can be performed without losing the gradation of the detail portion such as the edge component. Further, the gradation correction curve is represented by R, G, B
By commonly using the signals, it is possible to obtain an output image with good color balance and rich gradation expression over the entire area.

The operation of the nonlinear processing section 104 is the same as in the first embodiment. FIG. 12 is a diagram showing gain characteristics of a high frequency component of a video signal. FIG. 12C shows a gain characteristic. Hereinafter, gradation correction by gain adjustment of the gain adjustment unit 201 will be described with reference to FIG.

The output signal of the non-linear processing unit 104 is supplied to the gain adjustment unit 201. The gain adjustment unit 201 is configured as shown in FIG.
The high frequency component is corrected with the gain characteristic as shown in FIG.
This gain characteristic corresponds to the gradation correction curve shown in FIG.
The gain characteristic is such that the gain is gradually increased for the luminance level at which the gradation correction of gradation compression is performed. In this way, the part where the low-frequency component is gradation-compressed and the gradation disappears,
By increasing the gain of the high frequency component, the gradation can be compensated. Similarly, by performing gain adjustment to gradually lower the gain for the luminance level at which the gradation correction of the gradation expansion is performed, the portion where the low-frequency component is subjected to the gradation expansion and the portion where the gradation is excessively increased can be obtained. By lowering the gain of the high frequency component, it is possible to correct the gradation to an appropriate level. Also, when the input video signal is smaller than an arbitrary fixed value, the noise component in a low-brightness dark part is suppressed by performing gain adjustment so as to reduce the gain of a high-frequency component in proportion to the size of the input video signal. Can also.

At this time, the high-pass filter (HPF) 1
03 is composed of 1-low-pass filter (LPF) 101
So that the low-pass filter (LPF) 10
1 and a high-pass filter (HPF) 103. By doing so, finally a low-pass filter (LP
F) Output of 101 and high-pass filter (HPF) 103
Can be returned to the size of the input video signal when the outputs of the above are added.

Finally, the output signal of the tone correction processing section 102 and the output signal of the gain adjustment section 201 are added by the adder 105 to output an output video signal. In this way, false contours do not occur even in images with a large degree of backlight, gradation is not destroyed, noise components in low-luminance dark areas are suppressed, color balance is good, and gradation expression is rich over the entire area. An output image can be obtained.

FIG. 13 is a block diagram showing a more specific configuration example of the tone correction circuit 303 in the second embodiment of the present invention shown in FIG. In FIG. 13, the gradation correction curve determination means 107 includes an input means 108, a microcomputer 10
9. ROM 11 for storing a program of the microcomputer 109 and a template showing characteristics of the gradation correction curve to be selected.
0 and a RAM 111 for storing a luminance histogram.

Hereinafter, the gradation correction circuit 303 will be described with reference to FIG.
Will be described in detail. First, the R, G, and B signals converted into digital data of 0 to 255 are input to the gradation correction processing unit 303 as input video signals. This input video signal is supplied to a histogram creation means 106 and a low-pass filter (L
PF) 101 and a high-pass filter (HPF) 103.

The operation of the microcomputer 109 for determining the gradation correction curve by using the template matching method will be described with reference to FIGS. Histogram creating means 10
6 obtains a luminance signal from the input video signal and obtains a luminance histogram for an effective screen of one frame. Then, the microcomputer 109 reads the luminance histogram into the RAM 111. Next, the distance between the template indicating the characteristic of the gradation correction curve to be selected in the ROM 110 and the luminance histogram read into the RAM 111 is obtained. Next, a tone correction curve that minimizes the distance is selected. Finally, the gain of the selected gradation correction curve is set in the gradation correction processing unit 102.

8 and 9, the gradation correction processing unit 10
When a gain is input, the input signal is multiplied by the input gain when the input signal is smaller than the value α, and becomes an output signal (a in FIG. 9). When the input signal has a value between the values α and β, Is an output signal (b in FIG. 9) having an offset slope of 1 obtained by multiplying the input gain by the value α. When the input signal is larger than the value β, the signal having the offset slope of 1/2 of the b signal in FIG. A tone correction curve (see FIG. 9) is automatically generated so that a larger signal becomes an output signal (c in FIG. 9), and tone correction can be performed on an input signal in real time.
Further, by providing the gradation correction processing unit 102 which generates a gradation correction curve of a polygonal line as shown in FIG. 8, an extra ROM or the like for storing several types of gradation correction curves is not required. Because it is good, the circuit scale can be very small. In addition, when the input signal is large, the tone correction curve is configured so that the input signal becomes an output signal almost as it is, so that the place where the tone of the high-brightness part has been lost by the conventional auto knee control or the like can be reproduced clearly. Can be.

The low-pass filter 101 separates low-frequency components from the input video signal. Then, the gradation correction processing unit 102 performs gradation correction only for the low-frequency component. in this way,
Since the tone correction is performed only on the low-frequency component of the input video signal, the tone correction can be performed without losing the tone of the detail part such as the edge component. Further, the gradation correction curve is represented by R,
By commonly using the G and B signals, it is possible to obtain an output image with good color balance and rich in gradation expression over the entire range.

On the other hand, the high-pass filter 103 extracts high-frequency components from the input video signal. Then, the non-linear processing unit 104 removes a noise component smaller than the coring value of the high frequency component of the input video signal according to the non-linear processing characteristics. The high frequency component of the input video signal performs only noise removal,
Since gradation correction is not performed, the gradation of the detail portion is kept as it is. In addition, the degree of noise removal can be adjusted by adjusting the magnitude of the coring value.

Next, the multiplier 201 of the gain adjustment unit performs gain correction of the high frequency component of the input video signal in conjunction with the gradation correction processing of the gradation correction processing unit 102. As shown in FIG. 9, the gradation correction curve of the gradation correction processing unit 102 is the value β of the input signal.
, The microcomputer 109 sets the multiplier 201 of the gain adjustment unit so that the gain characteristic becomes such that the gain gradually increases at the value β. As described above, the gradation where the low-frequency component is subjected to the gradation compression and the gradation disappears can be compensated for by increasing the gain of the high-frequency component. Further, by simplifying the gradation correction curve, gain control can be easily performed with a simple configuration.

Finally, the adder 105 removes the noise component, adds the high-frequency component whose gain has been adjusted, and the low-frequency component whose tone has been corrected, and outputs the R, G, B signal whose tone has been corrected.

At this time, the configuration of the high-pass filter 103 is such that the relationship of 1−low-pass filter 101 is satisfied.
A low-pass filter 101 and a high-pass filter 103 are configured. By doing so, when the output of the low-pass filter 101 and the output of the high-pass filter 103 are finally added, the magnitude of the input video signal can be restored.

In this way, an output image in which no false contour is generated, the gradation is not crushed, the noise is small, the color balance is good, and the gradation expression is rich over the entire area is obtained even for an image with a high degree of backlight. be able to.

In this embodiment, the nonlinear processing section 1
Although the description has been made using FIG. 04, even if the non-linear processing unit 104 is deleted, noise components cannot be removed, and false contours do not occur even in an image with a high backlight level. It is possible to obtain an output image with good color balance and rich gradation expression over the entire area.

As described above, according to the present embodiment, the gradation correction circuit of the present invention comprises a low-pass filter 101, a gradation correction processing unit 102, a high-pass filter 103, a nonlinear processing unit 104, Gain adjuster 201, adder 105,
With the configuration of the histogram creating means 106 and the tone correction curve determining means 107, a false contour does not occur even in an image having a large degree of backlight, tone is not crushed, and noise components in dark portions with low luminance are suppressed, An output image with good color balance and rich gradation expression over the entire area can be obtained.

The tone correction processing unit 102 in the tone correction circuit of the present invention has an α clipping circuit 1001 for clipping with a value α and a β clipping circuit 10 for clipping with a value β.
02, a multiplier 1003, a subtractor 1004, an adder 1005, a gain adjuster 1006, a large signal selector circuit 1007, and a selector circuit 1008.
A gradation correction processing unit 102 that generates a gradation correction curve of a polygonal line
By doing so, it is not necessary to have an extra ROM or the like for storing several types of gradation correction curves, so that the circuit scale can be made very small. In addition, when the input signal is large, the tone correction curve is configured so that the input signal becomes an output signal almost as it is, so that the place where the tone of the high-brightness part has been lost by the conventional auto knee control or the like can be reproduced clearly. Can be.

FIG. 14 is a block diagram showing the configuration of an image pickup apparatus with a gradation correction function according to the third embodiment of the present invention. In FIG. 14, reference numeral 901 denotes a solid-state imaging device; 902, an analog circuit; 903, an analog-digital converter (A
/ D converter), 904 is a low-pass filter (LPF),
905 is a gradation correction processing unit, 906 is a contour extraction filter,
907 is a nonlinear processing unit, 908 is a gain adjustment unit, 909
Is an adder, 910 is a digital-analog converter (D / A
911, an encoder circuit, 912, a histogram creation unit, and 918, a gradation correction curve determination unit.

The operation of the image pickup apparatus with a gradation correction function according to the third embodiment of the present invention having the above-described configuration will be described below.

First, the analog circuit 902 takes in the R, G, and B signals from the solid-state imaging device 901 as input video signals. These R, G and B signals are converted to analog-digital converter 9
03 is converted into digital data of 0 to 255. R converted into digital data of 0 to 255,
The G and B signals are used as input video signals as the histogram creation means 912, the low-pass filter 904, and the contour extraction filter 9.
06.

The histogram creating means 912 obtains a luminance signal from the input video signal and obtains a luminance histogram for an effective frame of one frame. Then, the gradation correction curve determination unit 918 determines a gradation correction curve from the luminance histogram and sets the gradation correction curve in the gradation correction processing unit 905.

The low-pass filter 904 separates low-frequency components from the input video signal. Then, the gradation correction processing unit 90
5 performs tone correction only for the low-frequency component according to the tone correction curve determined by the tone correction determining means 918. As described above, since the gradation correction is performed only on the low-frequency component of the input video signal, the gradation correction can be performed without losing the gradation of the detail portion such as the edge component. Further, the gradation correction curve is represented by R, G, B
By commonly using the signals, it is possible to obtain an output image with good color balance and rich gradation expression over the entire area.

On the other hand, the contour extraction filter 906 extracts a contour component from the input video signal. Then, the nonlinear processing unit 907 removes noise components of the contour components of the input video signal according to the nonlinear processing characteristics. When the absolute value of the contour component of the input video signal is smaller than the coring value, the output signal is zero. When the absolute value is large, if the contour component of the input video signal is positive, the output signal is the contour of the input video signal. The value is obtained by subtracting the coring value from the component. If the contour component of the input video signal is negative, the output signal has a value obtained by adding the coring value to the contour component of the input video signal. In this way, a noise component smaller than the coring value of the contour component of the input video signal is removed. Since the contour component of the input video signal performs only noise removal and does not perform gradation correction, the gradation of the detail portion is kept as it is. In addition, the degree of noise removal can be adjusted by adjusting the magnitude of the coring value.

Next, the gain adjustment unit 908 performs gain correction of the contour component of the input video signal in conjunction with the gradation correction processing of the gradation correction processing unit 905. This gain characteristic is such that the gain is gradually increased with respect to the luminance level at which the gradation correction of gradation compression is performed on the gradation correction curve. As described above, the gradation where the low-frequency component is gradation-compressed and the gradation disappears can be compensated for by increasing the gain of the contour component. Similarly, by performing gain adjustment to gradually lower the gain for the luminance level at which the gradation correction of the gradation expansion is performed, the portion where the low-frequency component is subjected to the gradation expansion and the portion where the gradation is excessively increased can be obtained. By lowering the gain of the contour component, it is possible to correct to an appropriate gradation. Also, when the input video signal is smaller than any given value,
By performing gain adjustment so as to lower the gain of the contour component in proportion to the magnitude of the input video signal, it is also possible to suppress noise components in dark portions with low luminance.

Finally, an adder 909 adds the contour component whose noise component has been removed and the gain has been adjusted and the low-frequency component whose tone has been corrected, and outputs the R, G and B signals whose tone has been corrected.
The digital-analog converter 910 converts the digital R, G, and B signals subjected to the gradation correction into analog R, G, and B signals. Next, the encoder circuit 911 converts the R, G, and B signals into a Y signal (luminance signal) and a C signal (color signal), and outputs the output signal as a gradation-corrected output video signal. This output video signal can be recorded on a video tape by a VTR or displayed on a monitor.

FIG. 15 is a block diagram showing a more specific configuration example of the gradation correction curve determining means 918 according to the third embodiment of the present invention. 15, a gradation correction curve determination unit 918 includes an input unit 913, a microcomputer 914, a ROM 915 for storing a program of the microcomputer 914 and a template showing characteristics of the gradation correction curve to be selected, and RAMs 916 and 917 for storing a luminance histogram. Is bus 91
7.

The operation of the image pickup apparatus with a gradation correction function according to the third embodiment of the present invention having the above-described configuration will be described below.

First, the analog circuit 902 takes in the R, G, and B signals from the solid-state imaging device 901 as input video signals. These R, G and B signals are converted to analog-digital converter 9
03 is converted into digital data of 0 to 255. R converted into digital data of 0 to 255,
The G and B signals are used as input video signals as a histogram creating means 912, a low-pass filter 904, and an
06.

The operation in which the microcomputer 914 determines the gradation correction curve using the template matching method will be described with reference to FIGS. Histogram creating means 91
2 obtains a luminance signal from the input video signal and obtains a luminance histogram for an effective screen of one frame. Then, the microcomputer 914 reads the luminance histogram into the RAM 916. Next, the distance between the template in the ROM 915 indicating the characteristic of the gradation correction curve to be selected and the histogram in the RAM 916 is determined. Next, a tone correction curve that minimizes the distance is selected. Finally, the gain of the selected gradation correction curve is set in the gradation correction processing unit 905.

FIG. 8 is a detailed block diagram of the gradation correction processing unit 905 of the image pickup apparatus with a gradation correction function according to the embodiment of the present invention. FIG. 9 is a characteristic diagram illustrating a gradation correction curve of the gradation correction processing unit according to the embodiment of the present invention.

In FIGS. 8 and 9, the gradation correction processing section 90
When a gain is input, when the input signal is smaller than the value α, an output signal obtained by multiplying the input signal by the input gain (FIG. 9)
a), and when the input signal has a magnitude between the value α and the value β, the output signal has an offset slope of 1 obtained by multiplying the input gain by the value α (FIG. 9B), and the input signal is larger than the value β. 9b, a tone correction curve (see FIG. 9) is automatically generated so that the larger of the signal having the slope of the offset of the signal 1/2 and the input signal becomes the output signal (FIG. 9c). To perform tone correction in real time. Also,
By using the gradation correction processing unit 905 that generates a gradation correction curve of a broken line as shown in FIG. 8, it is not necessary to have an extra ROM or the like for storing several types of gradation correction curves. Also, the circuit scale can be made very small.
In addition, when the input signal is large, the tone correction curve is configured so that the input signal becomes an output signal almost as it is, so that the place where the tone of the high-brightness part has been lost by the conventional auto knee control or the like can be reproduced clearly. Can be.

The low-pass filter 904 separates low-frequency components from the input video signal. Then, the tone correction processing unit 905 performs tone correction only for the low-frequency component. in this way,
Since the tone correction is performed only on the low-frequency component of the input video signal, the tone correction can be performed without losing the tone of the detail part such as the edge component. Further, the gradation correction curve is represented by R,
By commonly using the G and B signals, it is possible to obtain an output image with good color balance and rich in gradation expression over the entire range.

On the other hand, the contour extraction filter 906 extracts a contour component from the input video signal. Then, the nonlinear processing unit 907 removes a noise component smaller than the coring value of the contour component of the input video signal according to the nonlinear processing characteristics. The contour component of the input video signal performs only noise removal,
Since gradation correction is not performed, the gradation of the detail portion is kept as it is. In addition, the degree of noise removal can be adjusted by adjusting the magnitude of the coring value.

Next, the multiplier 908 of the gain adjustment unit performs gain correction of the contour component of the input video signal in conjunction with the gradation correction processing of the gradation correction processing unit 905. As shown in FIG. 9, the gradation correction curve of the gradation correction processing unit 905 is represented by the value β of the input signal.
, The microcomputer 914 sets the multiplier 908 of the gain adjustment unit such that the gain characteristic becomes such that the gain gradually increases at the boundary of the value β. As described above, the gradation where the low-frequency component is gradation-compressed and the gradation disappears can be compensated for by increasing the gain of the contour component. Further, by simplifying the gradation correction curve, gain control can be easily performed with a simple configuration.

Finally, an adder 909 adds the contour component whose noise component has been removed and the gain has been adjusted and the low-frequency component whose tone has been corrected, and outputs the resultant signal as a tone-corrected R, G, B signal.
The digital-analog converter 910 converts the digital R, G, and B signals subjected to the gradation correction into analog R, G, and B signals. Next, the encoder circuit 911 converts the R, G, and B signals into a Y signal (luminance signal) and a C signal (color signal), and outputs the output signal as a gradation-corrected output video signal. This output video signal can be recorded on a video tape by a VTR or displayed on a monitor.

At this time, the configuration of the contour extraction filter 906 is such that the relationship of 1−low-pass filter 904 is obtained.
A low-pass filter 904 and a contour extraction filter 906 are configured. For example, the configuration of the low-pass filter 904 is changed to LP
F (z) = (z− ² + 2 + z ² ) / 4 and the configuration of the contour extraction filter 906 is APF (z) = (− z ⁻² + 2−z ² ) /
Assuming that 4, then LPF (z) + APF (z) = 1. With such a configuration, when the output of the low-pass filter 904 and the output of the contour extraction filter 906 are finally added, the size of the input video signal can be restored.

In this way, even for an image having a large degree of backlight, false contours are not generated, gradation is not destroyed, noise components in low-luminance dark areas are suppressed, and gradation is expressed over the entire area with good color balance. Rich output image can be obtained. Further, by sharing the gradation correction circuit and the aperture processing circuit for performing contour correction, the circuit scale can be reduced.

As described above, according to the present embodiment, the imaging apparatus with the gradation correction function of the present invention includes a solid-state imaging device 901, an analog circuit 902, and an analog-digital converter 903.
, A low-pass filter 904, and a gradation correction processing unit 905
, A contour extraction filter 906, and a non-linear processing unit 907
, A gain adjustment unit 908, an adder 909, a digital-analog converter 910, an encoder circuit 911, a histogram creation unit 912, and a gradation correction curve determination unit 91.
With the configuration of 8, a false contour does not occur even in an image with a large degree of backlight, gradation is not destroyed, noise components in dark portions with low luminance are suppressed, color balance is good, contour is corrected, and gradation is corrected over the entire area. A rich output image can be obtained. Further, by sharing the gradation correction circuit and the aperture processing circuit for performing contour correction, the circuit scale can be reduced.

The tone correction processing unit 905 in the tone correction circuit of the present invention is provided with an α clipping circuit 1001 for clipping with a value α and a β clipping circuit 10 for clipping with a value β.
02, a multiplier 1003, a subtractor 1004, an adder 1005, a gain adjuster 1006, a large signal selector circuit 1007, and a selector circuit 1008.
A gradation correction processing unit 102 that generates a gradation correction curve of a polygonal line
By doing so, it is not necessary to have an extra ROM or the like for storing several types of gradation correction curves, so that the circuit scale can be made very small. In addition, when the input signal is large, the tone correction curve is configured so that the input signal becomes an output signal almost as it is, so that the place where the tone of the high-brightness part has been lost by the conventional auto knee control or the like can be reproduced clearly. Can be.

In this embodiment, the nonlinear processing unit 1
Although the description has been made using FIG. 04, even if the non-linear processing unit 104 is deleted, noise components cannot be removed, and false contours do not occur even in an image with a high backlight level. It is possible to obtain an output image with good color balance and rich gradation expression over the entire area.

In this embodiment, the description has been made using the low-pass filter 101.
Even if 01 is deleted, the contour component is corrected by the output signal of the high-pass filter 103, so that a false contour does not occur even in an image having a large degree of backlight, gradation is not destroyed, and color balance is not changed. It is possible to obtain an output image rich in gradation expression over the entire area.

In this embodiment, the input video signal is inputted from the CCD camera head 301 because the gradation correction circuit applied to the video integrated camera has been described. Other media such as a laser disk, a video tape, and a magnetic disk for analog image recording, and a magnetic disk or an optical disk such as a hard disk for digital recording after analog-digital conversion. The present invention is not limited to this embodiment as long as image data of a frame or one field can be taken out by the gradation correction circuit 303.

In this embodiment, the gradation correction circuit 3
R, G, and B signals were used for the input video signal of No. 03,
The same effect can be obtained by using a luminance signal of a luminance signal and a color difference signal instead of the G and B signals for the input video signal.

In this embodiment, the image recognition is performed using the luminance histogram as a characteristic amount. However, instead of the luminance histogram, another characteristic amount, for example, a histogram of each of the R, G, and B signals or any one of the histograms is used. And the effective screen of image data is divided into blocks, and the maximum value, average value, minimum value, and the like of the luminance signal, RGB signal, and color difference signal of each block are used as feature amounts. If so, it is not limited to this method.

In the present embodiment, the image recognition is performed by a method using a neural network, a method using fuzzy control, a method using template matching, or any other method that can determine a correction curve by recognizing an image. It is not limited.

In this embodiment, the most appropriate gradation correction curve for the input image is determined by image recognition based on the characteristic amount of the luminance histogram. The method is not limited to a single method as long as the method can perform gradation correction, such as a corrected gradation correction curve or a broken line gradation correction curve obtained by changing some gains.

In this embodiment, the nonlinear processing unit 1
The non-linear processing characteristics of No. 04 have been described using the coring characteristics, but the method is not limited to this method as long as the non-linear processing characteristics can remove noise components instead of the coring characteristics.

[0097]

As described above, the gradation correction circuit according to the present invention
The optimal gradation correction curve can be automatically determined by image recognition based on the feature amount obtained from the input video signal, and the simple configuration allows no false contour to be generated even for an image with a large degree of backlight. It is possible to obtain an output image in which the tone is not crushed, the noise component is suppressed, the color balance is good, and the gradation expression is rich over the entire range. Further, it is possible to obtain an output image rich in gradation expression over the entire screen where noise in a dark portion is inconspicuous.

Further, the image pickup apparatus with gradation correction function of the present invention suppresses noise components in dark portions where dark contours are not generated, gradation is not destroyed, and brightness is low, even in an image having a large degree of backlight. An output image with good balance, contour correction, and rich gradation expression over the entire area can be obtained. Further, by sharing the gradation correction circuit and the aperture processing circuit for performing contour correction, the circuit scale can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a gradation correction circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a video integrated camera using the gradation correction circuit in FIG. 1;

FIG. 3 is a diagram showing one frame image of an input video signal in the first embodiment.

FIG. 4 is a diagram showing a luminance histogram and a gradation correction curve in the first embodiment.

FIG. 5 is a characteristic diagram showing nonlinear processing characteristics of the nonlinear processing unit according to the first embodiment.

FIG. 6 is a signal diagram of a gradation correction circuit according to the first embodiment.

FIG. 7 is a block diagram showing a specific configuration of a gradation correction curve determining unit in the first embodiment.

FIG. 8 is a block diagram illustrating a configuration of a gradation correction processing unit according to the embodiment of the present invention.

9 is a characteristic diagram illustrating a gradation correction curve of a gradation correction processing unit in FIG.

FIG. 10 is a flowchart showing an operation procedure of a gradation correction curve determination unit in FIG. 7;

FIG. 11 is a block diagram showing a configuration of a gradation correction circuit according to a second embodiment of the present invention.

FIG. 12 is a diagram showing gain characteristics of a high frequency component in the second embodiment.

FIG. 13 is a block diagram showing a specific configuration of a gradation correction curve determining unit in the second embodiment.

FIG. 14 is a block diagram illustrating a configuration of an imaging device with a gradation correction function according to a third embodiment of the present invention.

FIG. 15 is a block diagram showing a specific configuration of a gradation correction curve determining unit in the third embodiment.

FIG. 16 is a block diagram showing a functional configuration of a gradation correction circuit in a conventional example.

[Explanation of symbols]

 101,904 Low-pass filter 102,905 Tone correction processing unit 103 High-pass filter 104,907 Non-linear processing unit 105,909,1005 Adder 106 Histogram creation unit 107 Tone correction curve determination unit 201,908 Gain adjustment unit 401 Effective screen 901 Solid-state imaging device 902 Analog circuit 906 Contour extraction filter 1001 α clip circuit 1002 β clip circuit 1003 Multiplier 1004 Subtractor 1006 Gain adjuster 1007 Large signal selector circuit 1008 Selector circuit 1301 R signal tone correction section 1302 G signal Gradation correction unit 1303 B signal gradation correction unit 1304 Luminance signal histogram creation unit 1305 Cumulative luminance distribution curve creation unit

Claims (17)

(57) [Claims] 1. A feature amount extracting unit for extracting a feature amount of an input video signal; a tone correction curve determining unit for determining a tone correction curve from the feature amount; and separating a low-frequency component of the input video signal. A low-pass filter, and a signal output from the low-pass filter when the output signal is larger than a predetermined value.
In this case, the tone correction music in which the gain of the tone correction curve is limited.
The line complements the output signal of the low-pass filter with a line.
A tone correction processing unit that corrects, 1-a high-pass filter that separates high-frequency components of the input video signal in a configuration having a relationship of the low-pass filter, and an output signal of the tone correction processing unit. An adder for adding an output signal of the high-pass filter, wherein a tone-corrected output video signal is obtained from the adder output. 2. A feature amount extracting unit for extracting a feature amount of an input video signal; a tone correction curve determining unit for determining a tone correction curve from the feature amount; and separating a low-frequency component of the input video signal. A low-pass filter, and a signal output from the low-pass filter when the output signal is larger than a predetermined value.
In this case, the tone correction music in which the gain of the tone correction curve is limited.
The line complements the output signal of the low-pass filter with a line.
A gradation correction processing unit to correct the signal; 1-a high-pass filter for separating a high-frequency component of the input video signal in a configuration having a relationship of the low-pass filter; and a non-linear output signal of the high-pass filter. A non-linear processing unit for processing; and an adder for adding an output signal of the gradation correction processing unit and an output signal of the non-linear processing unit, and obtaining an output video signal corrected in gradation from the adder output. And a gradation correction circuit. 3. A feature amount extracting unit for extracting a feature amount of an input video signal; a tone correction curve determining unit for determining a tone correction curve from the feature amount; and separating a low-frequency component of the input video signal. A low-pass filter, and a signal output from the low-pass filter when the output signal is larger than a predetermined value.
In this case, the tone correction music in which the gain of the tone correction curve is limited.
The line complements the output signal of the low-pass filter with a line.
A gradation correction processing unit to correct the signal; 1-a high-pass filter for separating a high-frequency component of the input video signal in a configuration having a relationship of the low-pass filter; and a non-linear output signal of the high-pass filter. A nonlinear processing unit that performs processing, a gain adjustment unit that adjusts a gain of an output signal of the nonlinear processing unit, and an adder that adds an output signal of the gradation correction processing unit and an output signal of the gain adjustment unit, A gradation correction circuit for obtaining an output video signal whose gradation has been corrected from the adder output. 4. A feature amount extracting unit for extracting a feature amount of an input video signal; a tone correction curve determining unit for determining a tone correction curve from the feature amount ; , The gradation
The gradation correction curve with the gain of the correction curve limited
A gradation correction processing unit that performs gradation correction on the input video signal, a high-pass filter that separates high-frequency components of the input video signal, and a non-linear processing unit that performs non-linear processing on an output signal of the high-pass filter. A gain adjustment unit that adjusts the gain of the output signal of the non-linear processing unit according to the gradation correction of the gradation correction processing unit; and an addition that adds the output signal of the gradation correction processing unit and the output signal of the gain adjustment unit. And a tone correction circuit for obtaining an output video signal whose tone is corrected from the adder output. 5. The gradation correction circuit according to claim 1, wherein the high-pass filter is configured as a contour extraction filter for extracting a contour component from an input video signal. 6. An α-clip circuit for clipping an input signal with a value α, a multiplier for multiplying an output signal of the α-clip circuit with a gain input, and clipping an input signal with a value β. a β clip circuit, a first subtractor for subtracting an output signal of the α clip circuit from an output signal of the β clip circuit, and a second adder for adding an output signal of the multiplier and an output signal of the first subtractor. A second adder for subtracting the output signal of the β clip circuit from an input signal; a gain adjuster for adjusting a gain of an output signal of the second subtractor; Adder for adding the output signal of the adder and the output signal of the gain adjuster; a large signal selector circuit for selecting a larger one of the input signal and the output signal of the second adder; Is less than the value α The output signal of the multiplier, the output signal of the first adder when the input signal has a magnitude between values α and β, and the output signal of the large signal selector circuit when the input signal is greater than the value β. 2. A selector circuit according to claim 1, wherein said selector circuit selects a signal.
5. The gradation correction circuit according to 2, 3, or 4. 7. The gradation correction circuit according to claim 1, wherein the feature quantity extracted by the feature quantity extracting means is a histogram. 8. For an input video signal level at which a tone correction processing section performs tone correction of tone compression, a gain adjusting section sets a high frequency component or an outline of the input video signal according to the degree of tone correction. 5. The gradation correction circuit according to claim 3, wherein gain adjustment for increasing the gain of the component is performed. 9. A gain adjustment section for a high-frequency component or an outline of an input video signal according to a degree of gradation correction for an input video signal level at which a gradation correction processing section performs gradation correction of gradation expansion. 5. The gradation correction circuit according to claim 3, wherein gain adjustment for lowering the component gain is performed. 10. When the input video signal level is smaller than a predetermined value, a gain adjustment unit performs gain adjustment to decrease the gain of a high-frequency component or an outline component of the input video signal in proportion to the magnitude of the input video signal level. The gradation correction circuit according to claim 3, wherein: 11. A solid-state imaging device, an analog circuit for extracting an input video signal from the solid-state imaging device, a feature extraction unit for extracting a feature of the input video signal, and determining a gradation correction curve from the feature. A low-pass filter for separating low-frequency components of the input video signal; and a low-pass filter when the output signal of the low-pass filter is larger than a predetermined value.
In this case, the tone correction music in which the gain of the tone correction curve is limited.
The line complements the output signal of the low-pass filter with a line.
A gradation correction processing unit for correcting; 1-a contour extraction filter for extracting a contour component of the input video signal in a configuration having a relationship of the low-pass filter; and non-linear processing for nonlinearly processing an output signal of the contour extraction filter. A gain adjustment unit that adjusts the gain of the output signal of the nonlinear processing unit; and an adder that adds the output signal of the gradation correction processing unit and the output signal of the gain adjustment unit. An image pickup apparatus, which obtains an output video signal whose gradation has been corrected. 12. A solid-state imaging device, an analog circuit for extracting an input video signal from the solid-state imaging device, a feature extraction unit for extracting a feature of the input video signal, and determining a gradation correction curve from the feature. A tone correction curve determining means for determining the tone when the input video signal is larger than a predetermined value.
The gradation correction curve with the gain of the correction curve limited
A gradation correction processing unit that performs gradation correction on the input video signal; a contour extraction filter that extracts a contour component of the input video signal; a non-linear processing unit that performs non-linear processing on an output signal of the contour extraction filter; A gain adjustment unit that adjusts the gain of the output signal according to the tone correction of the tone correction processing unit; and an adder that adds the output signal of the tone correction processing unit and the output signal of the gain adjustment unit. And an image pickup device for obtaining an output video signal whose gradation has been corrected from the adder output. 13. A gain adjustment unit for a high-frequency component or an outline of an input video signal according to a degree of gradation correction for an input video signal level at which a gradation correction processing unit performs gradation correction of gradation compression. 13. The imaging apparatus according to claim 11, wherein gain adjustment for increasing a gain of the component is performed. 14. For an input video signal level at which a gradation correction processing section performs gradation correction of gradation expansion, a gain adjustment section sets a high-frequency component or contour of the input video signal according to the degree of gradation correction. 13. The imaging apparatus according to claim 11, wherein gain adjustment for lowering a component gain is performed. 15. When the input video signal level is smaller than a predetermined value, the gain adjustment unit performs gain adjustment to decrease the gain of a high-frequency component or an outline component of the input video signal in proportion to the magnitude of the input video signal level. The imaging device according to claim 11, wherein: 16. A tone correction processing unit, an α clip circuit for clipping an input signal with a value α, a multiplier for multiplying an output signal of the α clip circuit by a gain input, and clipping an input signal with a value β. a β clip circuit, a first subtractor for subtracting an output signal of the α clip circuit from an output signal of the β clip circuit, and a second adder for adding an output signal of the multiplier and an output signal of the first subtractor. A second adder for subtracting the output signal of the β clip circuit from an input signal; a gain adjuster for adjusting a gain of an output signal of the second subtractor; Adder for adding the output signal of the adder and the output signal of the gain adjuster; a large signal selector circuit for selecting a larger one of the input signal and the output signal of the second adder; Is smaller than the value α The output signal of the multiplier, the output signal of the first adder when the input signal has a magnitude between values α and β, and the output signal of the large signal selector circuit when the input signal is greater than the value β. 12. A selector circuit for selecting an output signal.
Or the imaging device according to 12. 17. A feature amount extracted by the feature amount extracting means is a histogram.
3. The imaging device according to 2.