JPH09149317A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a natural output image by outputting a video signal where diaphragm control and gradation correction are executed based on the video signal limited in a same screen area. SOLUTION: An imaging device 102 outputs the video signal, a diaphragm 101 limits incident light quantity on the imaging device and a diaphragm driving circuit 100 drives the diaphragm. An area limiting circuit 106 limits the screen area of the video signal of the imaging device and a characteristic quantity pickup circuit 111 picks-up the feature quantity of the video signal from the video signal which is limited by an area limiting circuit. A gradation correcting circuit 113 controls gain at every luminance level of the video signal from the imaging device by feature quantity which is picked-up by the feature quantity pickup circuit so as to correct a gradation. An integration circuit 107 executes the integration of the video signal limited by the area limiting circuit. A diaphragm control means 108 controls the diaphragm driving circuit so as to make the output signal level of the imaging device fixed. A signal processing circuit 114 processes the output signal of the gradation correcting circuit so as to output the video signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device.

[0002]

2. Description of the Related Art In recent years, image pickup devices equipped with many backlight correction means have been developed. As a conventional imaging device, there is, for example, Japanese Patent Laid-Open No. 04-340875. The conventional image pickup apparatus will be described below. FIG. 12 is a block diagram of the conventional image pickup apparatus shown in the publication. In FIG. 12, 1101 is a lens, 1102 is a diaphragm mechanism, 1103 is an image sensor, 1104 is an image sensor 11.
Preamplifier that amplifies 03 output to a proper size, 1
Reference numeral 105 denotes an integrating circuit, 1106 denotes an aperture control circuit, 1107.
Is a process circuit including a gamma correction circuit and a white balance circuit, and 1108 is an automatic gain control circuit (hereinafter referred to as A
1109 is an integrating circuit, 1110 is A
AG that generates a signal for controlling the gain of the GC circuit 1108
C control circuit, 1111 is an A / D converter for A / D converting the video signal output of the AGC circuit 1108, 1112 is an A / D
A region dividing circuit that divides the converted signal into a plurality of regions,
1113 is an integrating circuit that calculates an evaluation value corresponding to the brightness of each area from the signals divided into each area, and 1114 counts the signals divided into each area by brightness,
A frequency distribution calculation circuit for obtaining a frequency distribution, 1115 is an interface circuit for inputting the output of the integration circuit 1113 and the output of the frequency distribution calculation circuit 1114 to a microcomputer,
1116 is a microcomputer, 1117 is a D / A converter that converts the digital signal output of the microcomputer 1116 into an analog signal, 1118 is a control signal generation circuit that generates a control signal according to the output of the D / A converter 1117, and 1119 is a control By the control signal output from the signal generation circuit 1118,
A gain control circuit 1120 for controlling the gain of the video signal is a signal processing circuit of the camera, and 1121 is a signal output terminal.

The operation of the conventional image pickup apparatus configured as described above will be described below. The light passing through the lens 1101 is limited in light amount by the diaphragm mechanism 1102, converted into an electric signal by the image sensor 1103, and then the preamplifier 110.
Amplified at 4. The output of the preamplifier 1104 is integrated by the integrating circuit 1105 and becomes a DC signal corresponding to the output signal level of the preamplifier 1104.
It is input to 06. The diaphragm control circuit 1106 compares the input DC signal level with the reference voltage and outputs a control signal for operating the diaphragm mechanism 1102 so that the output signal level of the preamplifier 1104 becomes constant.

On the other hand, the output of the preamplifier 1104 passes through a process circuit 1107 for gamma correction and white balance and is input to an AGC circuit 1108. The AGC circuit 1108 outputs the output of the AGC circuit 1108 to the integration circuit 1
After being integrated in 109 to form a DC signal corresponding to the output level of the AGC circuit 1108, the AGC control circuit 1110 compares it with a reference voltage and generates an AGC control signal.
The output signal level of the C circuit 1108 is kept constant.

The output of the AGC circuit 1108 is converted into a digital signal by the A / D converter 1111 and the area dividing circuit 1112 divides the screen into a plurality of areas, and the arithmetic circuit 1113 averages the video signals in the respective areas. While detecting the brightness distribution as the exposure evaluation value of each area,
The frequency distribution calculation circuit 1114 obtains the luminance distribution in each area, and the microcomputer 1116 correlates the central portion of the screen with other areas. The area having the correlation with the central portion of the screen is the main subject area, and the other areas are It is a non-main subject area.
Then, the backlight and the over-forward light are discriminated based on the ratio between the main subject area and the non-main subject area, and the gain of the video signal is controlled according to the degree. When the gain of the video signal is controlled, the gain of the portion of the video signal having a low luminance level is corrected to be higher than that of the portion of the video signal having a high luminance level. In this way, the gain control circuit 1119 corrects the gradation characteristic of the dark portion and outputs a signal with contrast, and the signal processing circuit 1
After various processing by 120, the signal output terminal 112
1, the video signal is output.

[0006]

However, in the above-mentioned conventional example, the aperture control, the AGC control, and the gradation correction control means by the gain control have different control loops, and they are independent control systems. Therefore, the extraction areas of the integration circuit and the feature quantity extraction circuit have been considered separately so as to be optimal for each control. That is, in aperture control and AGC control, video signals are extracted from different places and integrated without limiting, and in a gradation correction circuit, an area that is an area division circuit is divided into areas to obtain a feature amount and gradation correction is performed. There is.

Therefore, when a bright subject comes in from the edge of the screen, the aperture control, the AGC control, and the gradation correction react in a disjointed manner, and the aperture control and the backlight correction or the gradation correction control can be naturally linked. However, there is a problem that a natural output image cannot be obtained. The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an imaging device capable of obtaining a natural output image even when a bright subject comes in from the edge of the screen.

[0008]

According to another aspect of the present invention, there is provided an image pickup device comprising: an image pickup device for outputting a video signal; a diaphragm for controlling the amount of light incident on the image pickup device; and a diaphragm drive circuit for driving the diaphragm. An area limiting circuit for limiting the screen area of the image signal of the image sensor, a feature amount extracting circuit for extracting the image feature amount from the image signal limited by the area limiting circuit, and a feature amount extracted by the feature amount extracting circuit. The gradation correction circuit that performs gradation correction by controlling the gain for each brightness level of the video signal from the image sensor, the integration circuit that integrates the video signal restricted by the area restriction circuit, and the integration of this integration circuit According to the result, an aperture control means for controlling the aperture drive circuit so that the output signal level of the image sensor becomes constant, and a signal processing circuit for processing the output signal of the gradation correction circuit and outputting a video signal are provided. Than it is.

According to the image pickup apparatus of the first aspect, since the area limiting circuit outputs the video signal subjected to aperture control and gradation correction based on the video signal limited to the same screen area. Even when a bright subject comes in from the edge of the screen, the aperture control and the gradation correction control react at the same time, and these linked operations can be smoothly performed, so that a natural output image can be obtained.

According to another aspect of the present invention, there is provided an image pickup device for outputting an image signal, an aperture for controlling the amount of light incident on the image pickup device, a diaphragm drive circuit for driving the aperture, and a video signal from the image pickup device. Circuit for controlling the gain of the AGC circuit, AGC control means for controlling the output signal level of the AGC circuit to be constant, an area limiting circuit for limiting the screen area of the video signal of the AGC circuit, and the area limiting circuit. Grayscale by controlling the gain for each brightness level of the video signal output of the AGC circuit by the feature quantity extraction circuit that extracts the feature quantity of the image from the video signal limited by A gradation correction circuit that performs correction, an integration circuit that integrates the video signal limited by the area limiting circuit, and the output signal level of the image sensor becomes constant according to the integration result of this integration circuit. The aperture control means for controlling the aperture drive circuit as described above and the signal processing circuit for processing the output signal of the gradation correction circuit and outputting the video signal are provided, and the AGC control means is controlled based on the integration result of the integration circuit. It is a thing.

According to another aspect of the image pickup device of the present invention, an image signal subjected to aperture control, AGC control and gradation correction is output based on the image signal limited to the same screen area by the area limiting circuit. Therefore, even when a bright subject comes in from the edge of the screen, the aperture control, the AGC control, and the gradation correction control react at the same time, and these linked operations can be smoothly performed, so that a natural output image can be obtained. You can

According to a third aspect of the present invention, there is provided an image pickup device for outputting a video signal, an aperture for controlling the amount of light incident on the image pickup device, a diaphragm drive circuit for driving the aperture, and an image from the image pickup device. An AGC circuit for controlling the gain of the signal, an AGC control means for controlling the output signal level of the AGC circuit to be constant, an area limiting circuit for limiting the screen area of the video signal output of the AGC circuit, and this area. A feature amount extraction circuit for extracting a feature amount of an image from the video signal limited by the limit circuit, and an image for outputting a gradation correction coefficient by determining the degree of backlight and over-forward light from the feature amount extracted by the feature amount extraction circuit The discrimination means, the gradation correction circuit for performing gradation correction by controlling the gain for each luminance level of the video signal of the AGC circuit by the gradation correction coefficient, and the image limited by the area limiting circuit An integration circuit for integrating the signal, an aperture control means for controlling the aperture drive circuit so that the output signal level of the image sensor becomes constant according to the integration result of the integration circuit, and an image by processing the output signal of the gradation correction circuit. A signal processing circuit for outputting a signal is provided, and the AGC control means is controlled based on the integration result of the integration circuit.

According to the image pickup device of the third aspect, the same effect as that of the first aspect can be obtained. According to another aspect of the present invention, there is provided an image pickup device that outputs an image signal, an aperture that controls the amount of light incident on the image sensor, a diaphragm drive circuit that drives the aperture, and a gain of a video signal from the image sensor. An AGC circuit for controlling, an AGC control means for controlling the output signal level of the AGC circuit to be constant, an area limiting circuit for limiting the screen area of the video signal output of the AGC circuit, and a limiting by the area limiting circuit. A feature amount extraction circuit for extracting a feature amount of an image from the image signal generated, and an image determination means for determining a backlight and an over-forward light intensity from the feature amount extracted by the feature amount extraction circuit, and outputting a gradation correction coefficient, A gradation correction circuit that performs gradation correction by controlling the gain for each luminance level of the video signal of the AGC circuit by a gradation correction coefficient and the video signal limited by the area limiting circuit are integrated. A division circuit, an aperture control means for controlling the aperture drive circuit so that the output signal level of the image pickup device becomes constant by the integration result of this integration circuit, and an output signal of the gradation correction circuit to process and output a video signal. A signal processing circuit is provided, and the AGC control means is controlled based on the integration result of the integration circuit.

According to the image pickup device of the fourth aspect, there is the same effect as the second aspect. According to a fifth aspect of the present invention, in the image pickup device according to the first aspect, the second aspect, the third aspect, or the fourth aspect, the gradation correction circuit has a higher gain in the low luminance part than in the high luminance part of the video signal. The adjustment is performed.
According to the image pickup device of the fifth aspect, it is possible to obtain an output image which is rich in gradation expression with respect to the subject in the first, second, third or fourth aspect.

According to a sixth aspect of the present invention, in the image pickup device according to the first aspect, the second aspect, the third aspect, or the fourth aspect, the feature amount extracted by the feature amount extracting circuit is the brightness distribution of the screen area of one field of the video signal. It is what According to the image pickup device of claim 6, in addition to the effect of claim 1, claim 2, claim 3, or claim 4, the gradation correction of the gradation correction circuit is facilitated.

According to a seventh aspect of the present invention, in the image pickup apparatus according to the first aspect, the second aspect, the third aspect, or the fourth aspect, the range in which the area limiting circuit extracts the feature amount is the number of lines that is an integral multiple of a power of two. It is the number of pixels. According to the image pickup device of claim 7, in addition to the effect of claim 1, claim 2, claim 3, or claim 4, the circuit scale of the area limiting circuit, the integrating circuit, and the feature quantity extracting circuit can be reduced, and It is possible to easily deal with areas of any number of pixels.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the arrangement of an image pickup apparatus according to the first embodiment of the present invention. In FIG. 1, 101 is a diaphragm,
102 is an image sensor, 103 is a process circuit including a gamma correction circuit and a white balance circuit, and 104 is A
GC circuit, 105 is A / video signal of AGC circuit 104
A / D converter for D conversion, 106 is A / D converter 105
Area limiting circuit that limits the screen area of the video signal of
Reference numeral 07 is an integrating circuit for integrating the output of the area limiting circuit 106, 108 is an aperture control means for comparing the integration result of the integrating circuit 107 with a target value and controlling the aperture drive circuit 109, 109
Is an aperture drive circuit for driving the aperture 101 by the control signal of the aperture control means 108, 110 is AGC control means for generating a signal for controlling the gain of the AGC circuit 104 by the control signal of the aperture control means 108, and 111 is the area limiting circuit 106. A feature amount extraction circuit for extracting a feature amount of the video signal output from the image pickup device 112, an image discriminating means 112 for discriminating the degree of backlight and over-forward light of the input image, and outputting a gradation correction coefficient, and 113 depending on the gradation correction coefficient. Tone correction circuit for performing tone correction, 11
Reference numeral 4 is a signal processing circuit that performs signal processing of the video signal whose gradation is corrected by the gradation correction circuit 113, and 115 is the signal processing circuit 11
4 is a D / A converter for D / A converting the video signal output of No. 4.

FIG. 2 is a diagram showing an image of one field of an input video signal according to the first embodiment of the present invention. In FIG. 2, 201 is an extraction area, 202 is an effective screen, and the extraction area 201 has 512 pixels in the horizontal scanning direction H and 192 pixels in the vertical scanning direction V. FIG. 3 is a diagram showing an example of the luminance distribution extracted by the feature amount extraction circuit 111 according to the first embodiment of the present invention. In FIG.
a is a luminance distribution, b is the number of low luminance pixels, c is the number of medium luminance pixels,
d is the number of high-luminance pixels.

FIG. 4 is a block diagram of the feature quantity extraction circuit 111 according to the first embodiment of the present invention. In FIG. 4, reference numeral 401 is a comparator, 402 is a counter circuit for the number of low-luminance pixels, 403 is a counter circuit for the number of medium-luminance pixels, and 404.
Is a counter circuit for the number of high brightness pixels. FIG. 5 is a block diagram of the image discriminating means 112 according to the first embodiment of the present invention. In FIG. 5, 501 is a quantization table, 502 is an output table, and 503 is a filter circuit.

FIG. 6 is a block diagram of the gradation correction circuit 113 according to the first embodiment of the present invention. In FIG. 6, 602 is a Y1 gain generation circuit, 603 is a Y2 gain generation circuit, 604 is a luminance average circuit (LPF), 605 is an adder, 606 is a weighted average circuit, 607 is a delay circuit, and 608 is a multiplier. FIG. 7 shows gradation correction characteristics in the first embodiment of the present invention.

FIG. 8 shows gradation correction characteristics and input / output characteristics in the first embodiment of the present invention. The operation of the image pickup apparatus according to the first embodiment of the present invention configured as described above will be described below. In FIG. 1, first, the amount of light incident on the image sensor 102 is adjusted by the diaphragm 101. Next, the video signal picked up by the image pickup device 102 is subjected to gamma correction, white balance, and other processing in the process circuit 103, and then input to the AGC circuit 104. A
The output video signal of the GC circuit 104 is converted into a digital signal by the A / D converter 105. Then, the A / D converter 10
The video signal digitally converted to 0 to 255 in 5 is input to the area limiting circuit 106 and the gradation correcting circuit 113.

First, the area limiting circuit 106 limits the screen area of the video signal of the A / D converter 105, that is, the data sample area in the screen. The area limiting circuit 106 limits the video signal to a 512 × 192 screen area.
In this way, by setting the effective screen area for area restriction to the number of pixels and the number of lines that are integral multiples of powers of 2, the area restriction circuit 106, the integration circuit 107, and the feature amount extraction circuit 11
The circuit scale of the digital circuit of 1 can be reduced,
Furthermore, it is possible to easily deal with areas of any number of pixels. Then, the video signal whose screen area is limited by the area limiting circuit 106 is input to the integrating circuit 107 and the feature amount extracting circuit 111, respectively.

First, the operation relating to the aperture control will be described.
The output of the area limiting circuit 106 is integrated by the integrating circuit 107 to obtain a signal corresponding to the output level of the area limiting circuit 106, and then the diaphragm control circuit 108 compares the diaphragm with a reference value to generate a diaphragm control circuit 109. Control the
The diaphragm driving circuit 109 drives the diaphragm 101 to drive the image sensor 1
The output signal level of 02 is controlled to be constant. Further, when the aperture control range of the aperture control means 108 is exceeded, the aperture control means 108 outputs a gain control signal, and the AGC
The control means 110 controls the output signal level of the AGC circuit 104 to be constant by the AGC control signal generated by comparing the gain control signal with the reference value.

Next, the operation relating to the gradation correction control will be described. Feature amount extraction circuit 1 from the output of the area limiting circuit 106
In 11, the luminance distribution of the low luminance pixel number, the medium luminance pixel number, and the high luminance pixel number is extracted as the feature amount. Then, the image discrimination means 112 determines the gradation correction coefficient indicating the correction degree of the gradation correction characteristic for correcting the input image from the luminance distribution extracted by the feature amount extraction circuit 111.

On the other hand, the gradation correction circuit 113 obtains the corrected brightness signal Y'from the brightness signal Y of the input video signal and the gradation correction coefficient, and calculates the correction gain (Y '/ Y) to obtain the input video signal. Is matched with the correction gain in the delay circuit 607, and is multiplied by the correction gain (Y ′ / Y) in the multiplier 608 to output the gradation-corrected video signal. Finally,
The tone-corrected video signal is subjected to various signal processing by the signal processing circuit 114, and then the D / A converter 115 outputs the analog-converted video signal.

As described above, according to the first embodiment, the video signal subjected to the aperture control, the AGC control and the gradation correction based on the video signal limited to the same screen area by the area limiting circuit 106. Since it is output, even when a bright subject comes in from the edge of the screen, the video signal of the same screen area is sampled and controlled, so aperture control, AGC control, and gradation correction control respond simultaneously. Since these linked operations can be performed smoothly, a natural output image can be obtained.

Further, the area of the area limiting circuit 106 is set to 2
By setting the number of pixels, for example, the number of horizontal pixels and the number of lines, for example, the number of vertical lines, which are integral multiples of the power of, the digital circuit scale can be reduced, and an area of any number of pixels can be easily accommodated. Next, the operation related to the gradation correction control will be described in detail. First, the operation of the feature amount extraction circuit 111 will be described in detail with reference to FIG. The brightness signal Y of the input video signal is compared with the threshold value 1 and the threshold value 2 by the comparator 401.
It is compared with (threshold value 1 <threshold value 2). Luminance signal Y is threshold 1
When it is smaller, the low brightness count signal is output. When the luminance signal Y is between the threshold 1 and the threshold 2, the medium luminance count signal is output. When the luminance signal Y is larger than the threshold value 2, a high luminance count signal is output. This low brightness count signal,
The counter circuits 402 to 404 count the number of pixels in the effective screen of one field according to the medium-luminance count signal and the high-luminance count signal, and output the low-luminance pixel number, the medium-luminance pixel number, and the high-luminance pixel number, respectively.

FIG. 2 shows an image of one field 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 large degree of backlight. The feature amount extraction circuit 111 performs the low-luminance pixel number, the medium-luminance pixel number, for the 1-field image 512 × 192 dots of the effective screen 201 of FIG. When the distribution of the number of high-brightness pixels is obtained, the brightness distributions shown by reference signs b, c, and d in FIG. 3 are obtained. In this way, the circuit scale of the digital circuits of the area limiting circuit 106, the integrating circuit 107, and the feature amount extracting circuit 111 is reduced by setting the effective screen area of the area limiting to the number of pixels and the number of lines that are integral multiples of powers of two. Further, it is possible to easily deal with areas of any number of pixels. Reference numeral b shown in FIG.
Looking at the luminance distributions of c and d, the peak is 2 with low luminance and high luminance.
It can be inferred that the object is a backlit subject because it is formed at a location.

The operation of the image discrimination means 112 will be described in detail with reference to FIG. The quantization table 501 uses the low-luminance pixel number, the medium-luminance pixel number, and the high-luminance pixel number supplied from the feature amount extraction circuit 111 as addresses to quantize data for a forward-light subject, quantized data for a backlight subject, and dark. The quantized data for the subject is stored. In the output table 502, the quantized data of the quantization table 501 is used as an address, and a gradation correction coefficient indicating a degree of correction for a normal-light subject, a gradation correction coefficient indicating a degree of correction for a backlight subject, and a degree of correction for a dark subject are shown. The gradation correction coefficient and the like are stored. Therefore, when the number of low-luminance pixels, the number of medium-luminance pixels, and the number of high-luminance pixels are input from the feature amount extraction circuit 111 to the image discrimination unit 112, a gradation correction coefficient indicating one degree of correction for the input image is determined. To do. In this way, the table size can be reduced by forming the image discrimination means 112 in a two-stage table configuration. A filter circuit 5 is provided so that this gradation correction coefficient can maintain continuity with the previous field or previous frame.
Filter processing is performed at 03 and a gradation correction coefficient is output.

The operation of the gradation correction circuit 113 will be described in detail below with reference to FIG. First, the luminance signal Y of the video signal is input. The luminance signal Y is supplied to the Y1 gain generation circuit 602 and the Y2 gain generation circuit 603. The Y1 gain generation circuit 602 outputs a first correction gain (Y1 / Y) from the input luminance signal Y and Y1 corrected by the first gradation correction characteristic. Similarly, from the Y2 gain generation circuit 603, the second
The correction gain (Y2 / Y) is output. On the other hand, the luminance signal Y
The average value detection circuit (LPF) 604 finds the luminance average value Ya, the adder 605 adds the luminance average value Ya and the gradation correction coefficient, and outputs the X signal. Finally, the weighted average circuit 60
6 performs a weighted average of the first correction gain and the second correction gain by the relational expression (1) using the X signal to obtain the correction gain (Y ′
/ Y) is output.

(Y ′ / Y) = {(Y1 / Y) · (255−X) + (Y2 / Y) · X} / 255 (1) In the first embodiment, the first correction gain (Y1
/ Y) by the equation (2) and the second correction gain (Y2 / Y) by the equation (3). (Y1 / Y) = {1/256 ² · (Y-256) ³ +255} / Y (2) (Y2 / Y) = Y / Y (3) FIG. 7 shows the first embodiment. 3 shows the gradation correction characteristics in FIG. Y1 is the first gradation correction characteristic, and Y2 is the second gradation correction characteristic. For example, when the gradation correction coefficient is 0, the gradation correction characteristic becomes the characteristic a in FIG. 7 from the relational expression (1). Similarly, when the gradation correction coefficient becomes positive, the gradation correction characteristic becomes the characteristic c in FIG. Similarly, when the gradation correction coefficient becomes negative, the gradation correction characteristic becomes like the characteristic b in FIG. By changing the gradation correction coefficient in this way, the gradation correction characteristics can be easily and continuously changed. As for the gradation correction characteristic, as the gradation correction coefficient is changed, the correction gains of the low-luminance portion and the middle-luminance portion gradually increase, and finally the overall correction gain increases. Therefore, the gradation correction characteristic of Y2 in FIG. 7 is applied to the normal light subject, the gradation correction characteristic of the characteristic a in FIG. 7 is applied to the backlight subject, and the gradation correction characteristic of Y1 in FIG. 7 is applied to the dark subject. By performing gradation correction with the correction characteristic, it is possible to perform gradation correction with rich gradation expression for all subjects.

FIG. 8 shows gradation correction characteristics and input / output characteristics. When the luminance average value Ya obtained by the average value detection circuit 604 is equal to the luminance signal Y of the target pixel, the gradation correction characteristic of the characteristic a in FIG. 8 is obtained, and when the luminance average value Ya is lower than the luminance signal Y of the target pixel. With the gradation correction characteristic of the characteristic b in FIG. 8,
When the luminance average value Ya is higher than the luminance signal Y of the pixel of interest, the gradation correction characteristic of characteristic c in FIG. 8 is used to adaptively change the gradation correction characteristic on a pixel-by-pixel basis to perform gradation correction, thereby obtaining a correction gain. It is possible to obtain an output signal rich in gradation expression by performing gradation correction so as to maintain the contrast even when the inclination of is small.

As described above, according to this embodiment,
The image pickup apparatus according to the present invention includes a diaphragm 101 and an image pickup element 102.
A process circuit 103 including a gamma correction circuit and a white balance circuit, an AGC circuit 104, an AG
The A / D converter 105 for A / D converting the video signal output of the C circuit 104, the area limiting circuit 106 for limiting the screen area of the video signal output of the A / D converter 105, and the output of the area limiting circuit 106 An integrating circuit 107 that performs integration, an aperture control unit 108 that controls an aperture driving circuit by comparing an integration result of the integrating circuit 107 with a target value, and an aperture driving circuit 1 that drives the aperture 101 by a control signal of the aperture controlling unit 108.
09 and the control signal from the aperture control means 108
The AGC control means 110 for generating a signal for controlling the gain of the circuit 104, the feature amount extraction circuit 111 for extracting the feature amount of the video signal output from the area limiting circuit 106, and the backlight and over-forward light intensity of the input image are determined. Image discrimination means 112 that outputs a gradation correction coefficient, a gradation correction circuit 113 that performs gradation correction according to the gradation correction coefficient, and a gradation correction circuit 113.
The signal processing circuit 114 that performs the signal processing of the video signal whose gradation is corrected by
A D / A converter 115 for A conversion is used to output a video signal that has been subjected to aperture control, AGC control, and gradation correction based on the video signal limited to the same screen area by the area limiting circuit 106. Therefore, the above-mentioned effects can be obtained.

The gradation correction circuit according to the first embodiment of the present invention includes a Y1 gain generation circuit 602, a Y2 gain generation circuit 603, a luminance averaging circuit (LPF) 604,
With the configuration of the adder 605, the weighted average circuit 606, the delay circuit 607, and the multiplier 608, the correction gain is generated by the gradation correction coefficient.
Since it is not necessary to have an extra ROM or the like for storing several kinds of gradation correction characteristics, the circuit scale can be made very small.

By changing the gradation correction coefficient, it is possible to generate gradation correction characteristics of forward and backlit subjects, so that the gradation is not destroyed for all subjects from the backlit subject to the backlit subject. It is possible to obtain an output image with rich gradation expression over the entire area. In addition, since the gradation correction characteristic can be continuously changed, natural gradation correction can be performed on a moving image.

When the input signal is large, the gradation correction characteristic is set so that the input signal becomes an output signal almost as it is, so that the gradation of the high-brightness part is conventionally reproduced by auto knee control and the like can be reproduced clearly. can do. An image pickup apparatus according to the second embodiment of the present invention is shown in FIG. FIG. 9 is a block diagram showing the arrangement of the image pickup apparatus according to the second embodiment. Compared with the first embodiment, the difference is mainly that the AGC circuit 104 and the AGC control means 110 are not provided, but the other configurations are the same.

That is, in FIG. 9, 901 is a diaphragm,
902 is an image sensor, 903 is a process circuit including a gamma correction circuit, a white balance circuit, and the like, and 904 is an A / D converter for A / D converting an output video signal of the process circuit 903.
D converter, 905 is an area limiting circuit that limits the screen area of the output video signal of the A / D converter 904, 906 is an integrating circuit that integrates the output of the area limiting circuit 905, and 907 is the integration result of the integrating circuit 906. A diaphragm control means for controlling the diaphragm drive circuit by comparing it with a value, and 908 is a diaphragm control means 90.
7. A diaphragm driving circuit for driving the diaphragm 901 by the control signal 7; 909, a characteristic amount extracting circuit for extracting a characteristic amount of the video signal output from the area limiting circuit 905; and 910, for determining the degree of backlight and over-forward light of the input image. An image discrimination unit that outputs a gradation correction coefficient, a reference numeral 911 is a gradation correction circuit that performs gradation correction according to the gradation correction coefficient, and a reference numeral 912 is signal processing of a video signal whose gradation is corrected by the gradation correction circuit 911. A signal processing circuit 913 outputs the video signal output of the signal processing circuit 912 to D /
It is a D / A converter that performs A conversion.

The operation of the image pickup apparatus of the second embodiment of the present invention constructed as above will be described below. In FIG. 9, first, an image sensor 902 is formed by a diaphragm 901.
Adjust the amount of light incident on. Next, the image signal picked up by the image pickup element 902 is processed by a process circuit 903 such as gamma correction and white balance, and then the process circuit 903.
The video signal output of is converted into a digital signal by the A / D converter 904. Then, the A / D converter 904 outputs 0 to 255.
The area limiting circuit 905 converts the video signal digitally converted into
Is input to the gradation correction circuit 911.

The area limiting circuit 905 is the A / D converter 90.
The screen area of the video signal output of 4 is limited. The area limiting circuit 905 limits the video signal to a 512 × 192 screen area. In this way, the effective screen area of area restriction is set to 2
By setting the number of pixels and the number of lines that are integral multiples of the power of, the circuit scale of the digital circuits of the area limiting circuit 905, the integrating circuit 906, and the feature amount extracting circuit 909 can be reduced, and even in areas of any number of pixels. It can be dealt with easily. Then, the area limiting circuit 905
The video signal whose screen area is limited by the integration circuit 9
06 and the feature amount extraction circuit 909, respectively.

The operation relating to the aperture control will be described. The output of the area limiting circuit 905 is integrated by an integrating circuit 906 to obtain a signal corresponding to the output level of the area limiting circuit 905, and then the diaphragm control circuit 907 compares the signal with a reference value to generate a diaphragm control signal by a diaphragm control circuit 908. The aperture drive circuit 908 drives the aperture 901 so that the output signal level of the image sensor 902 becomes constant.

Next, the operation relating to the gradation correction control will be described. From the output of the area limiting circuit 905, the feature amount extraction circuit 9
In 09, the brightness distribution of the number of low-luminance pixels, the number of medium-luminance pixels, and the number of high-luminance pixels is extracted as a feature amount. Then, the image discrimination unit 910 determines the gradation correction coefficient indicating the correction degree of the gradation correction characteristic for correcting the input image from the luminance distribution extracted by the feature amount extraction circuit 909.

On the other hand, the gradation correction circuit 911 obtains the corrected brightness signal Y'from the brightness signal Y of the video signal input and the gradation correction coefficient, calculates the correction gain (Y '/ Y), and inputs the video signal. The delay circuit 607 shown in FIG. 6 matches the timing with the correction gain, and the multiplier 608 multiplies the correction gain (Y ′ / Y) and outputs the gradation-corrected video signal output. Finally, the gradation-corrected video signal is subjected to various signal processing by the signal processing circuit 912, and then the analog-converted video signal is output from the D / A converter 913.

As described above, according to the second embodiment, a video signal subjected to aperture control and gradation correction based on the video signal limited to the same screen area by the area limiting circuit 905 is output. Even when a bright subject comes in from the edge of the screen, the video signal of the same screen area is sampled and controlled, so that aperture control and gradation correction control react simultaneously. Since the interlocking operation can be performed smoothly, a natural output image can be obtained. Further, by setting the area of the area limiting circuit 905 to the number of pixels and the number of lines that are integral multiples of powers of 2, the digital circuit scale can be reduced, and an area of any number of pixels can be easily dealt with.

An image pickup device according to the third embodiment of the present invention is shown in FIGS. The third embodiment is different from the first embodiment mainly in the gradation correction circuit, but is otherwise the same as the first embodiment and the second embodiment. That is, FIG. 10 is a block diagram showing the configuration of the image pickup apparatus according to the third embodiment of the present invention. In FIG. 10, 1001 is a diaphragm, 1002 is an image sensor, 1003 is a process circuit including a gamma correction circuit and a white balance circuit, and 1004 is an A / D converter for A / D converting the video signal output of the process circuit 1003. , 1005 is a gradation correction circuit for performing gradation correction according to the gradation correction coefficient, 10
Reference numeral 06 is an area limiting circuit that limits the screen area of the luminance signal, 1007 is an integrating circuit that integrates the output of the area limiting circuit 1006, and 1008 is an aperture control that controls the aperture drive circuit by comparing the integration result of the integrating circuit 1007 with a target value. means,
Reference numeral 1009 denotes a diaphragm drive circuit for driving the diaphragm 1001 by a control signal from the diaphragm control means 1008, 1010 a characteristic quantity extraction circuit for extracting a characteristic quantity of the video signal from the area limiting circuit 1006, and 1011 a backlight and over-luminosity of the input image. Image discrimination means for discriminating the result and outputting the gradation correction coefficient, 1
Reference numeral 012 is a signal processing circuit that performs signal processing of the video signal whose gradation is corrected by the gradation correction circuit 1005, and 1013 is a D / A converter that performs D / A conversion of the video signal output of the signal processing circuit 1012.

FIG. 11 is a block diagram of a gradation correction circuit according to the third embodiment of the present invention. In FIG. 11, 601 is a Y matrix circuit, 602 is a Y1 gain generation circuit, 603 is a Y2 gain generation circuit, 604 is a luminance average circuit (LPF), 605 is an adder, 606 is a weighted average circuit, 607 is a delay circuit, and 608. Is a multiplier.

The operation of the image pickup apparatus of the third embodiment of the present invention configured as described above will be described below. In FIG. 10, first, the image sensor 1 is formed by the diaphragm 1001.
The amount of light incident on 002 is adjusted. Next, the image sensor 100
The video signal captured in 2 is subjected to gamma correction, white balance, and other processing in the process circuit 1003, and the video signal output of the process circuit 1003 is converted into a digital signal by the A / D converter 1004.

The R, G, and B signals converted into digital data of 0 to 255 are input to the gradation correction circuit 1005 as input video signals. These color data show white when R signal = G signal = B signal = 255, and show that the larger the value, the brighter. From these R signal, G signal, and B signal, the Y matrix circuit 60
1 calculates the luminance signal Y. When the luminance of the input video signal is Y, for example, Y = 0.30R + 0.59G + 0.11B (4) (4)
Value. The calculated luminance signal Y is the area limiting circuit 1
006 is input. Then, the area limiting circuit 1006
The video signal whose area is restricted by is input to the integration circuit 1007 and the feature amount extraction circuit 1010.

First, the area limiting circuit 1006 limits the screen area of the video signal output of the A / D converter 1004.
The area limiting circuit 1006 limits the video signal to a 512 × 192 screen area. In this way, by setting the effective screen area for area restriction to the number of pixels and the number of lines that are integral multiples of powers of 2, the area restriction circuit 1006 and the integration circuit 10
07 and the feature amount extraction circuit 1010 can reduce the circuit scale of the digital circuit, and can easily cope with an area of any number of pixels. Then, the image signal whose screen area is limited by the area limiting circuit 1006 is integrated by the integrating circuit 1007 and the feature amount extracting circuit 1010.
Respectively. First, the operation related to aperture control will be described. The output of the area limiting circuit 1006 is used as the integrating circuit 1
After being integrated in 007 to obtain a signal corresponding to the output level of the area limiting circuit 1006, the aperture driving circuit 1009 controls the aperture driving circuit 1009 by the aperture control signal generated by comparing with the reference value in the aperture control means 1008. Aperture 100
1 is controlled to control the output signal level of the image sensor 1002 to be constant.

Next, the operation relating to the gradation correction control will be described. From the output of the area limiting circuit 1006, the feature amount extraction circuit 1010 uses the low luminance pixel number, the medium luminance pixel number as the feature amount,
And the luminance distribution of the number of high luminance pixels is extracted. Then, the image discrimination unit 1011 determines a gradation correction coefficient indicating the correction degree of the gradation correction characteristic for correcting the input image from the luminance distribution extracted by the feature amount extraction circuit 1010.

On the other hand, the gradation correction circuit 1005 causes the luminance signal Y
Then, the corrected luminance signal Y ′ is calculated from the gradation correction coefficient and the correction gain (Y ′ / Y) is calculated, and the input video signal R
The signal, the G signal, and the B signal are timed with the correction gain in the delay circuit 607, and are multiplied by the correction gain (Y ′ / Y) in the multiplier 608, and the R ′ signal which is the gradation-corrected video signal output. , G ′ signal and B ′ signal are output. In this way, by multiplying the R signal, G signal, and B signal by the same correction gain, gradation correction with good color reproducibility can be performed. Finally, after the gradation-corrected video signal is subjected to various signal processing by the signal processing circuit 1012, the D / A converter 1013 outputs the analog-converted video signal.

As described above, according to the third embodiment, the area limiting circuit 1006 outputs the video signal subjected to aperture control and gradation correction based on the video signal limited to the same screen area. Even when a bright subject comes in from the edge of the screen, the video signal of the same screen area is sampled and controlled, so aperture control and gradation correction control react at the same time and these are linked. Since the operation can be performed smoothly, a natural output image can be obtained. Further, by setting the area of the area limiting circuit 1006 to the number of pixels and the number of lines that are integral multiples of powers of 2, the digital circuit scale can be reduced, and an area of any number of pixels can be easily accommodated.

Although the luminance signal Y, R signal, G signal and B signal are used as the input video signal in the above-mentioned embodiment, these luminance signals Y, R signal, G signal and B signal are used. Alternatively, a similar effect can be obtained by using a luminance signal, a color difference signal, a composite signal, and a signal obtained by combining a luminance signal and a color signal as an input video signal.

The gradation correction circuit multiplies each of the input video signals by a correction gain to perform gradation correction. However, instead of the correction gain (Y '/ Y), the correction value (Y'-Y )
Even if is added to each of the input video signals, the same effect can be obtained. Further, although the description has been given by analog-digital converting the input video signal into 8 bits, the number of quantization bits may be another value, and the number of processing bits of the correction gain generation circuit or the like can be configured according to the number of quantization bits. .

Further, the feature quantity extraction circuit outputs the number of pixels of three brightness levels, but the threshold value of each level may be different, or the number of levels may not be three. Further, the feature amount extraction circuit counted the number of pixels for an effective screen of 192 lines with 512 horizontal pixels, but the number of counted pixels may be different if it is an integer multiple of a power of 2, or a signal indicating the number of pixels. The number of bits may be any number as long as the characteristics of the input image are known.

Further, the correction coefficient determining circuit for determining the correction coefficient discriminates the input image by using the luminance distribution as the characteristic amount, but instead of the luminance distribution, another characteristic amount, for example, R signal, G
Each distribution of the signal and the B signal or any one of them may be used. Also, the effective screen of the image data is divided into blocks, and the luminance signal, the R signal, and the G signal of each block.
Signals, B signals, maximum values, average values, minimum values, etc. of color difference signals are used as the characteristic amounts, and the method is not limited to the above method as long as the characteristic amounts can classify images.

Further, the correction coefficient determining circuit may be a method using a neural network, a method using fuzzy control, a method using template matching, or the like as long as it is a method capable of determining an image and determining a gradation correction characteristic. It is not limited. In each of the embodiments, in the gradation correction circuit, the feature amount extraction circuit is used for aperture control and AG.
If the gain is controlled for each luminance level of the video signal from the image sensor by the feature amount extracted from the video signal controlled by the area control circuit used for C control or the like, it is not limited to the case of the image discrimination means, For example, a conventional example may be applied.

[0057]

According to the image pickup device of the first aspect, an image signal subjected to aperture control and gradation correction based on the image signal limited to the same screen area by the area limiting circuit is output. Therefore, even when a bright subject comes in from the edge of the screen, the aperture control and the gradation correction control react at the same time, and these linked operations can be smoothly performed, so that a natural output image can be obtained.

According to the image pickup device of the second aspect, an image signal subjected to aperture control, AGC control, and gradation correction based on the image signal limited to the same screen area by the area limiting circuit is output. Therefore, even when a bright subject comes in from the edge of the screen, the aperture control, the AGC control, and the gradation correction control react at the same time, and these linked operations can be smoothly performed, so that a natural output image can be obtained. You can

According to the image pickup device of the third aspect, the same effect as that of the first aspect can be obtained. According to the imaging device of claim 4,
This has the same effect as the second aspect. According to the image pickup device of claim 5, in claim 1, claim 2, claim 3, or claim 4, the gradation correction circuit has a higher gain in the low-luminance portion than in the high-luminance portion of the video signal. Since the gradation correction is performed in the above, it is possible to obtain an output image in which gradation expression is rich with respect to the subject in claim 1, claim 2, claim 3, or claim 4.

According to the sixth aspect of the image pickup device, in the first, second, third or fourth aspect, the characteristic amount extracted by the characteristic amount extraction circuit is stored in the screen area of one field of the video signal. Since the luminance distribution is used, the gradation correction of the gradation correction circuit is facilitated in addition to the effects of claim 1, claim 2, claim 3, or claim 4. According to the imaging device of claim 7, claim 1, claim 2, claim 3 or claim 4
In the above, the area where the area limiting circuit extracts the feature quantity is set to 2
Since the number of lines and the number of pixels are integral multiples of the power of, the circuit size of the area limiting circuit, the integrating circuit, and the feature quantity extracting circuit is small in addition to the effect of claim 1, claim 2, claim 3, or claim 4. In addition, it is possible to easily deal with areas of any number of pixels.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image pickup apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an image of one field of an input video signal.

FIG. 3 is an explanatory diagram showing an example of a luminance distribution extracted by a feature amount extraction circuit.

FIG. 4 is a block diagram of a feature quantity extraction circuit.

FIG. 5 is a block diagram of an image determining unit.

FIG. 6 is a block diagram of a gradation correction circuit.

FIG. 7 is a gradation correction characteristic diagram.

FIG. 8 is an explanatory diagram showing gradation correction characteristics and input / output characteristics.

FIG. 9 is a block diagram of an image pickup apparatus according to a second embodiment.

FIG. 10 is a block diagram of an image pickup apparatus according to a third embodiment.

FIG. 11 is a block diagram of the gradation correction circuit.

FIG. 12 is a block diagram showing a configuration of an image pickup apparatus in a conventional example.

[Explanation of symbols]

 101, 901, 1001 Aperture 102, 902, 1002 Image sensor 103, 903, 1003 Process circuit 104 AGC circuit 105, 904, 1004 A / D converter 106, 905, 1006 Area limiting circuit circuit 107, 906, 1007 Integrating circuit 108 , 907, 1008 Aperture control means 109, 908, 1009 Aperture drive circuit circuit 110 AGC control means 111, 909, 1010 Feature amount extraction circuit 112, 910, 1011 Image discrimination means 113, 911, 1005 Gradation correction circuit 114, 912, 1012 signal processing circuit

Claims (7)

[Claims] 1. An image sensor for outputting a video signal, a diaphragm for controlling the amount of light incident on the image sensor, a diaphragm drive circuit for driving the diaphragm, and an area for limiting a screen area of the video signal of the image sensor. A limit circuit, a feature amount extraction circuit that extracts a feature amount of an image from the video signal limited by the area limit circuit, and a feature amount extracted by the feature amount extraction circuit for each luminance level of the video signal from the image sensor. A gradation correction circuit that performs gradation correction by controlling gain, an integration circuit that integrates the video signal limited by the area limiting circuit, and an output signal level of the image sensor based on the integration result of the integration circuit. An image pickup apparatus comprising: an aperture control unit that controls the aperture drive circuit so that the aperture is constant; and a signal processing circuit that processes an output signal of the gradation correction circuit and outputs a video signal. 2. An image sensor for outputting a video signal, a diaphragm for controlling the amount of light incident on the image sensor, a diaphragm drive circuit for driving the diaphragm, and an AGC for controlling the gain of the video signal from the image sensor. Circuit, AGC control means for controlling the output signal level of the AGC circuit to be constant, an area limiting circuit for limiting the screen area of the video signal of the AGC circuit, and a video signal limited by the area limiting circuit A feature amount extraction circuit for extracting a feature amount of an image from
The AGC is calculated according to the characteristic amount extracted by the characteristic amount extraction circuit.
A gradation correction circuit that performs gradation correction by controlling the gain for each luminance level of the video signal output of the circuit, an integration circuit that integrates the video signal limited by the area limiting circuit, and an integration result of the integration circuit. And a signal processing circuit for processing the output signal of the gradation correction circuit and outputting a video signal, the aperture control means controlling the aperture drive circuit so that the output signal level of the image sensor becomes constant. An imaging device for controlling the AGC control means based on an integration result of an integration circuit. 3. An image sensor for outputting a video signal, a diaphragm for controlling the amount of light incident on the image sensor, a diaphragm drive circuit for driving the diaphragm, and an area for limiting a screen area of the video signal of the image sensor. A limit circuit, a feature amount extraction circuit that extracts a feature amount of an image from the video signal limited by the area limit circuit, and a backlight amount and an over-forward light level from the feature amount extracted by the feature amount extraction circuit to determine the gradation. An image discrimination unit that outputs a correction coefficient, a gradation correction circuit that performs gradation correction by controlling a gain for each brightness level of a video signal from the image pickup device by the gradation correction coefficient, and the area limiting circuit. An integration circuit for integrating the limited video signal output, an aperture control means for controlling the aperture drive circuit so that the output signal level of the image sensor becomes constant according to the integration result of the integration circuit, and the gradation An image pickup apparatus comprising: a signal processing circuit that processes an output signal of a correction circuit and outputs a video signal. 4. An image sensor for outputting a video signal, a diaphragm for controlling the amount of light incident on the image sensor, a diaphragm drive circuit for driving the diaphragm, and an AGC for controlling the gain of the video signal from the image sensor. Circuit, AGC control means for controlling the output signal level of the AGC circuit to be constant, an area limiting circuit for limiting the screen area of the video signal output of the AGC circuit, and an image limited by the area limiting circuit. A characteristic amount extraction circuit for extracting a characteristic amount of an image from a signal, an image discriminating means for discriminating backlight and over-forward light intensity from the characteristic amounts extracted by the characteristic amount extraction circuit, and outputting a gradation correction coefficient; A gradation correction circuit that performs gradation correction by controlling the gain for each brightness level of the video signal of the AGC circuit with a correction coefficient, and a product that integrates the video signal restricted by the area restriction circuit. A dividing circuit, diaphragm control means for controlling the diaphragm driving circuit so that the output signal level of the image pickup device becomes constant according to the integration result of the integrating circuit, and the output signal of the gradation correcting circuit to process a video signal. An image pickup apparatus comprising a signal processing circuit for outputting, and controlling the AGC control means based on an integration result of the integration circuit. 5. The gradation correction circuit performs gradation correction so that the gain of the low-luminance portion of the video signal is higher than that of the high-luminance portion of the video signal. 4. The imaging device according to 4. 6. The image pickup device according to claim 1, claim 2, claim 3, or claim 4, wherein the feature amount extracted by the feature amount extraction circuit is a luminance distribution in a screen area of one field of a video signal. 7. The image pickup apparatus according to claim 1, claim 2, claim 3, or claim 4, wherein the area limiting circuit extracts the feature quantity in a range of the number of lines and the number of pixels that are integral multiples of a power of two.