JP2004023226A - Image processor, camera device and its method for controlling exposure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform proper backlight correction regardless of the position of a main object in an automatic exposure control of a camera device. <P>SOLUTION: An optical detector part 250 calculates an integrated value for each detection frame and transfers the integrated value to a microcomputer 140. The microcomputer 140 divides the integrated value for each detection frame by the number of pixels of each detection frame, calculates an integrated value of one image for each detection frame, selects the maximum integrated value for one pixel among integrated values for one pixel for each detection frame, and divides the maximum integrated value for one pixel by the integrated value for one pixel for each detection frame to thereby calculate a base coefficient for each detection frame. Then, the base coefficient for each detection frame is multiplied by a prescribed constant k to thereby calculate a coefficient for exposure determination for each detection frame. Subsequently, integration data of each detection frame is multiplied by the coefficient for exposure determination to determine an image state, and an exposure time is determined by the determination result to perform an automatic exposure operation. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image processing apparatus, a camera apparatus, and an exposure control method for performing signal processing for performing automatic exposure optimization control by determining the state of an input image due to the influence of backlight or the like at the time of capturing an object.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, when an image of a subject is captured by a camera device having an automatic exposure (AE) function, a plurality of detection frames are set in advance in an image frame, and the luminance of the input image for each detection frame is detected to detect the input image. A method is known in which the state is determined and the exposure time is controlled.
For example, if imaging is performed in a backlight state, incident light from a main subject to be photographed becomes small, resulting in an image having a partially low luminance. Therefore, the image is determined using the detection frame as described above, and is determined as much as possible. Backlight correction is performed to control the exposure time longer so that the image of the main subject becomes clearer.
[0003]
FIG. 4 is an explanatory diagram illustrating an example of a conventional detection frame.
As illustrated, in this example, five detection frames are provided for one image frame 10. Here, the detection frame on the upper side in the figure is the detection frame 0, the detection frame on the lower side is the detection frame 1, the detection frame on the middle left is the detection frame 2, the detection frame on the middle right is the detection frame 3, and the center detection frame is the detection frame 3. The detection frame 4 will be described.
Exposure determination coefficients are set in advance in each of the detection frames 0 to 4. That is, in normal photographing, it is general that the main subject is located at the center. Therefore, based on this, by weighting the central detection frame 4 and other peripheral detection frames 0 to 3, The backlight state of the image can be properly determined.
That is, in the example of FIG. 4, the coefficient of the detection frame 0 is 1, the coefficient of the detection frame 1 is 2, the coefficient of the detection frame 2 is 3, the coefficient of the detection frame 3 is 3, and the coefficient of the detection frame 4 is 5. I have.
Then, the integrated value of the image signal obtained from each detection frame is multiplied by the exposure determination coefficient of each detection frame, and the multiplied values are compared and determined, thereby determining the backlight state of the image and the like, and according to the determination result. By controlling the exposure time and controlling the gain, optimal exposure correction is obtained.
[0004]
[Problems to be solved by the invention]
However, in the above-described conventional technology, since the image is determined by assigning a fixed coefficient to each detection frame, the determination is performed with the position of the main subject limited to the center detection frame, and an appropriate position is determined when the position of the main subject is shifted. There is a problem that image determination cannot be performed and exposure control for obtaining effective backlight correction cannot be performed.
Also, instead of using the simple method based on the detection frame as described above, if a circuit for calculating a histogram of each pixel signal (hist integration circuit) is used, the backlight state can be corrected regardless of the position of the main subject. This method has a problem that a Hist integration circuit is required, the configuration is complicated, and the system becomes expensive.
[0005]
Therefore, an object of the present invention is to provide an image processing apparatus, a camera apparatus, and an image processing apparatus that can realize automatic exposure control capable of performing appropriate backlight correction without using a Histo integration circuit, regardless of the position of a main subject. An object of the present invention is to provide an exposure control method.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an image input means for inputting an image signal, and for an image signal input by the image input means, divides an image frame into image frames and sets an integral value of the image signal for each detection frame set. Integrating means for calculating, dividing means for dividing the integrated value of the image signal for each detection frame by the number of pixels for each detection frame, and calculating one pixel integrated value for each detection frame; Coefficient setting means for setting an exposure determination coefficient for each detection frame based on one pixel integrated value for each detection frame, and determination for determining the state of the image signal based on the exposure determination coefficient set by the coefficient setting means Means.
[0007]
The present invention also provides an integration step of calculating an integrated value of an image signal for each detection frame set by dividing an image frame with respect to an input image signal, and calculating an integrated value of the image signal for each detection frame for each detection frame. Dividing by the number of pixels of each detection frame to obtain an integral value of one pixel for each detection frame, and setting an exposure determination coefficient of each detection frame based on the one pixel integral value of each detection frame calculated by the division step. And a determining step of determining the state of the image signal based on the exposure determining coefficient set in the coefficient setting step.
[0008]
Further, the present invention provides an image input means for inputting an image signal, and an integration means for calculating an integrated value of the image signal for each detection frame set by dividing an image frame with respect to the image signal input by the image input means. Dividing means for dividing the integrated value of the image signal for each detection frame by the number of pixels for each detection frame, and calculating one pixel integrated value for each detection frame; Coefficient setting means for setting an exposure determination coefficient for each detection frame based on the pixel integration value; and automatic exposure control for performing exposure control by determining the state of the image signal based on the exposure determination coefficient set by the coefficient setting means. Exposure control means.
[0009]
The present invention also provides an integration step of calculating an integrated value of an image signal for each detection frame set by dividing an image frame with respect to an image signal input by an image input unit, and an integrated value of the image signal for each detection frame. Is divided by the number of pixels for each detection frame, and a dividing step for obtaining a one-pixel integrated value for each detection frame, and an exposure of each detection frame based on the one-pixel integrated value for each detection frame calculated in the dividing step. A coefficient setting step of setting a determination coefficient; and an automatic exposure control step of determining a state of the image signal based on the exposure determination coefficient set in the coefficient setting step and performing exposure control. .
[0010]
According to the image processing apparatus, the camera apparatus, and the exposure control method of the present invention, an input image signal is divided into image frames, and an integral value of the image signal is calculated for each of the detection frames set to calculate a pixel value for each of the detection frames. Automatic exposure control that can perform appropriate backlight correction regardless of the position of the main subject because the exposure judgment coefficient for each detection frame is set based on the integral value of one pixel divided by the number Can be realized without using the Histo integration circuit.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an image processing device, a camera device, and an exposure control method according to the present invention will be described.
The camera device according to the present embodiment performs backlight correction control using each detection frame in the CCD image pickup device, and is added to each detection frame as an automatic exposure control method when capturing an image of a subject in a backlight state. By controlling the coefficient (exposure determination coefficient) based on one pixel integrated value of each detection frame, appropriate backlight correction can be performed regardless of the position of the main subject.
[0012]
FIG. 1 is a block diagram illustrating a configuration example of a camera device according to an embodiment of the present invention.
As shown in the figure, the camera device of the present embodiment includes a CCD image pickup device 110, a CDS / AGC circuit 120, a digital signal processing circuit (camera DSP; digital signal processor) 130, a microcomputer 140, a timing generator 150.
[0013]
The CCD image pickup device 110 converts an optical signal imaged through a lens (not shown) from the front of the camera into an electric signal and outputs it as an image signal. Note that the imaging means is not limited to the CCD imaging element 110, and a CMOS sensor type imaging element or other imaging means may be used.
The CDS / AGC circuit 120 performs pixel noise removal by CDS (correlated double sampling) and gain adjustment by AGC on the image signal output from the CCD image sensor 110, and outputs the signal to the digital signal processing circuit 130. I do.
A digital signal processing circuit (camera DSP) 130 converts an image signal input from the CDS / AGC circuit 120 into a digital signal, separates the image signal into a chrominance signal and a luminance signal, performs various kinds of digital signal processing, and then converts the analog signal into an analog signal. And sends it to the output unit at the subsequent stage. The detailed configuration will be described later.
[0014]
The microcomputer 140 performs various control operations in the camera device of the present embodiment, in particular, arithmetic processing for automatic exposure control in the present embodiment, and details of the processing will be described later.
The timing generator (TG) 150 supplies various timing signals for operating each unit of the camera device of the present example.
[0015]
Next, the configuration of the digital signal processing circuit 130 that is a feature of the camera device of the present example will be described.
As shown in FIG. 1, the digital signal processing circuit 130 includes an A / D converter 210, a signal processor 220 (a color signal processor (C processor) 221 and a luminance signal processor (Y processor) 222), It has a gain amplifier 230, D / A converters 241 and 242, and an optical detector (OPD) unit 250.
[0016]
The A / D converter 210 converts an analog image signal input from the CDS / AGC circuit 120 into a digital image signal, and outputs the digitized image signal to the signal processor 220.
Although omitted in FIG. 1, the signal processing unit (signal processing means) 220 converts the input image signal into color signals (C) of R (red), G (green), and B (blue) and a luminance signal (Y). And a color separation unit that separates the color signal and the luminance signal into the color signal processing unit 221 and the luminance signal processing unit 222 to perform digital signal processing on each of the color signal and the luminance signal.
The color signal processed by the color signal processing unit 221 is converted into an analog signal by the D / A conversion unit 241, and the luminance signal processed by the luminance signal processing unit 222 is controlled by the luminance gain amplifier 230 to control the gain. The signal is converted into an analog signal by the A conversion unit 242, and is output to a subsequent circuit.
[0017]
The optical detector (color change detecting unit) 250 detects the color signal and the luminance signal acquired by the signal processing unit 220 and outputs the integrated value (OPD data) to the microcomputer 140.
In this example, in order to perform the above-described automatic exposure control (backlight correction), each detection frame is integrated by integrating image data (luminance signal) for each of detection frames 0 to 4 set by dividing an image frame into five. It is assumed that the integral data for each is sent to the microcomputer 140.
[0018]
The microcomputer 140 performs various kinds of arithmetic processing by software based on the integrated value (OPD data) output by the optical detector 250. In particular, in this example, the microcomputer 140 performs backlight correction according to the state of an image. The exposure determination coefficient to be assigned to each of the detection frames 0 to 4 is calculated using the integrated data of each of the detection frames 0 to 4 from the optical detector 250, and the automatic exposure time determination process using the coefficient is performed. Is what you do.
The arithmetic processing for the automatic exposure is shown in blocks (steps S1 to S3) of the microcomputer 140 shown in FIG. Hereinafter, based on the description in this block, an outline of the arithmetic processing in this example will be described.
[0019]
First, in step S1 of the microcomputer 140, the integral value (luminance integrated data) of each detection frame is divided by the number of pixels of each detection frame to calculate one image integral value of each detection frame.
Next, in step S2 of the microcomputer 140, the largest one-pixel integration value (maximum one-pixel integration value) is selected from the one-pixel integration values of each detection frame, and the selected maximum one-pixel integration value is determined for each detection frame. The base coefficient of each detection frame is determined by dividing the frame by one pixel integrated value.
Next, in step S3 of the microcomputer 140, the exposure determination coefficient for each detection frame is calculated by multiplying the base coefficient of each detection frame by a predetermined constant k.
[0020]
Thereafter, by the same processing as in the prior art, the integrated data of each detection frame is multiplied by an exposure determination coefficient to perform an image state determination process, an exposure time is determined based on the determination result, and an automatic exposure operation is performed.
In this way, a detection frame having a large integral value per pixel is determined to be a high-luminance frame, and by reducing the coefficient by which each detection frame used to determine the image state is multiplied, regardless of the position of the main subject, Enables backlight correction.
[0021]
Next, a specific description will be given of a method of obtaining an exposure determination coefficient to multiply each detection frame from one pixel integrated value of each detection frame.
FIG. 2 is an explanatory diagram showing a specific example of the coefficient calculation value in this example.
First, it is assumed that the integration value and the number of pixels of each detection frame are values as shown in FIG.
First, as shown in FIG. 2B, after calculating one pixel integrated value of each detection frame, the largest one pixel integrated value is searched (in the example of FIG. 2, 2.5 of the detection frame 4).
Next, after searching for the maximum one-pixel integration value, the maximum one-pixel integration value is divided by the one-pixel integration value of the detection frame 0 as shown in FIG. 2C, and the quotient is multiplied by the detection frame 0. Base coefficient. The same processing is performed on the detection frames 1 to 4.
Then, after the base coefficients of the detection frames 0 to 4 are derived, as shown in FIG. 2D, the base coefficients are multiplied by a predetermined constant k, so that the detection coefficients of the detection frames 0 to 4 are obtained. The exposure correction coefficient is determined, and the integrated value of each detection frame is multiplied to adjust the backlight correction effect.
[0022]
In the algorithm of the present embodiment as described above, the brightness level of each detection frame is constantly monitored, and the exposure control with the above-described coefficient calculation and the backlight correction effect is performed. No matter where the image moves, an appropriate amount of backlight correction can always be calculated, and optimal exposure control can be performed.
FIG. 3 is an explanatory diagram illustrating an example of a change in integrated data of each detection frame when the position of the main subject has moved.
In FIG. 3A, the detection frame 4 is the brightest and the detection frame 1 is the darkest, but in FIG. 3B, the detection frame 4 is the darkest due to the movement of the main subject.
Therefore, the base coefficient of each of the detection frames 0 to 4 changes as shown in FIG. 3 (C) to FIG. 3 (D), and becomes a value following the movement of the main subject.
As a result, in the conventional backlight correction algorithm that is performed without being aware of the position of the main subject, the Hist integration circuit was conventionally required, but in this example, the Hist integration circuit is used without using the Hist integration circuit. The same effect as the backlight correction can be realized.
[0023]
In the above example, the case where the present invention is applied to a camera device using a CCD image sensor and its exposure control method has been described. However, the present invention is directed to a camera device having a configuration separated from an image pickup means and its exposure control method. The present invention is also applicable to an image processing apparatus and an image processing method that perform arithmetic processing for exposure control based on an input image.
Further, as a method of exposure control, not only adjustment of the exposure time but also gain adjustment of the image signal can be used.
[0024]
【The invention's effect】
As described above, according to the image processing apparatus and the image processing method of the present invention, an integrated value of an image signal is calculated for each detection frame set by dividing an image frame for an input image signal, and Divided by the number of pixels, and the exposure determination coefficient of each detection frame is set based on the integrated value of one pixel, so that it can effectively follow the luminance fluctuation accompanying the movement of the main subject included in the input image signal. This makes it possible to determine the state of the image signal, and to perform, for example, an appropriate backlight correction process.
[0025]
Further, according to the camera apparatus and the exposure control method of the present invention, an input image signal is divided into image frames, and an integral value of the image signal is calculated for each of the detection frames set, and the number of pixels for each detection frame is calculated. Dividing and setting the exposure determination coefficient for each detection frame based on the integrated value of one pixel, automatic exposure control effectively follows the luminance fluctuation accompanying the movement of the main subject included in the input image signal The automatic exposure control that can perform, for example, appropriate backlight correction regardless of the position of the main subject can be realized without using the Hist integration circuit.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration example of a camera device according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a specific example of a coefficient calculation value in the camera device shown in FIG.
3 is an explanatory diagram showing an example of a change in integrated data of each detection frame when the position of a main subject moves in the camera device shown in FIG. 1;
FIG. 4 is an explanatory diagram illustrating an example of a detection frame in a conventional camera device.
[Explanation of symbols]
110 CCD image sensor 120 CDS / AGC circuit 130 Digital signal processing circuit 140 Microcomputer 150 Timing generator 210 A / D converter 220 Signal processor 221: a color signal processing unit, 222: a luminance signal processing unit, 230: a luminance gain amplifier, 241, 242, a D / A conversion unit, 250: an optical detector (OPD) unit.

Claims (14)

Image input means for inputting an image signal;
Integrating means for calculating an integrated value of the image signal for each detection frame set by dividing the image frame for the image signal input by the image input means,
Dividing means for dividing the integrated value of the image signal for each detection frame by the number of pixels for each detection frame, and obtaining one pixel integrated value for each detection frame,
Coefficient setting means for setting an exposure determination coefficient of each detection frame based on one pixel integrated value for each detection frame calculated by the dividing means,
Determining means for determining the state of the image signal based on the exposure determination coefficient set by the coefficient setting means,
An image processing apparatus comprising: The coefficient setting means selects the largest one-pixel integrated value from the one-pixel integrated value of each detection frame, and divides the selected largest one-pixel integrated value by the one-pixel integrated value of each detection frame. The image processing apparatus according to claim 1, wherein a base coefficient of each detection frame is obtained, and an exposure determination coefficient of each detection frame is calculated by multiplying the base coefficient by a predetermined constant. A color separation unit that separates an image signal input by the image input unit into a color signal and a luminance signal, and using a luminance signal obtained by the color separation unit, one pixel integration value for each of the detection frames, and The image processing apparatus according to claim 1, wherein the calculation of the exposure determination coefficient is performed. An integration step of calculating an integrated value of the image signal for each detection frame set by dividing the image frame with respect to the input image signal;
A dividing step of dividing the integrated value of the image signal for each detection frame by the number of pixels for each detection frame, and obtaining one pixel integrated value for each detection frame;
A coefficient setting step of setting an exposure determination coefficient of each detection frame based on the one-pixel integrated value for each detection frame calculated by the division step,
A determining step of determining the state of the image signal based on the exposure determining coefficient set by the coefficient setting step,
An image processing method comprising: The coefficient setting step is to select the largest one-pixel integration value from the one-pixel integration value of each detection frame, and divide the selected largest one-pixel integration value by the one-pixel integration value of each detection frame. 5. The image processing method according to claim 4, wherein a base coefficient of each detection frame is obtained, and an exposure determination coefficient of each detection frame is calculated by multiplying the base coefficient by a predetermined constant. A color separation step of separating the input image signal into a color signal and a luminance signal, and using the luminance signal obtained by the color separation step, one pixel integrated value for each detection frame, and the exposure determination coefficient 5. The image processing method according to claim 4, wherein the calculation is performed. Image input means for inputting an image signal;
Integrating means for calculating an integrated value of the image signal for each detection frame set by dividing the image frame for the image signal input by the image input means,
Dividing means for dividing the integrated value of the image signal for each detection frame by the number of pixels for each detection frame, and obtaining one pixel integrated value for each detection frame,
Coefficient setting means for setting an exposure determination coefficient of each detection frame based on one pixel integrated value for each detection frame calculated by the dividing means,
Automatic exposure control means for determining the state of the image signal based on the exposure determination coefficient set by the coefficient setting means, to perform exposure control,
A camera device comprising: 8. The camera device according to claim 7, wherein said image input means is means for inputting an image signal from an image pickup means for picking up an image of a subject. The coefficient setting means selects the largest one-pixel integrated value from the one-pixel integrated value of each detection frame, and divides the selected largest one-pixel integrated value by the one-pixel integrated value of each detection frame. 8. The camera device according to claim 7, wherein a base coefficient of each detection frame is obtained, and an exposure determination coefficient of each detection frame is calculated by multiplying the base coefficient by a predetermined constant. A color separation unit that separates an image signal input by the image input unit into a color signal and a luminance signal, and using a luminance signal obtained by the color separation unit, one pixel integration value for each of the detection frames, and The camera apparatus according to claim 7, wherein the exposure determination coefficient is calculated. An integration step of calculating an integration value of the image signal for each detection frame set by dividing the image frame with respect to the image signal input by the image input unit;
A dividing step of dividing the integrated value of the image signal for each detection frame by the number of pixels for each detection frame, and obtaining one pixel integrated value for each detection frame;
A coefficient setting step of setting an exposure determination coefficient of each detection frame based on the one-pixel integrated value for each detection frame calculated by the division step,
Automatic exposure control step of determining the state of the image signal based on the exposure determination coefficient set by the coefficient setting step, and performing exposure control,
An exposure control method for a camera device, comprising: 12. The exposure control method for a camera device according to claim 11, wherein said image input means is means for inputting an image signal from an image pickup means for picking up an image of a subject. The coefficient setting step is to select the largest one-pixel integration value from the one-pixel integration value of each detection frame, and divide the selected largest one-pixel integration value by the one-pixel integration value of each detection frame. 12. The exposure control method for a camera device according to claim 11, wherein a base coefficient of each detection frame is obtained, and an exposure determination coefficient of each detection frame is calculated by multiplying the base coefficient by a predetermined constant. A color separation step of separating an image signal input by the image input unit into a color signal and a luminance signal, and using a luminance signal obtained by the color separation step, one pixel integration value for each detection frame, and 12. The exposure control method for a camera device according to claim 11, wherein the calculation of the exposure determination coefficient is performed.

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