JPH08307775A - Image pickup device - Google Patents

Abstract

PURPOSE: To clamp image data by eliminating the dark current of an image pickup element and the influence of noise. CONSTITUTION: At first, an image pickup is performed in a state that a shutter 2 is closed. As for the image data obtained at this time, the average value of the data of plural parts within the valid area of the image pickup element 4 is determined in an arithmetic unit 19 and is stored after the signal level of the light shielding area of the image pickup element 4 is clamped to a prescribed level in a clamp circuit 9. Next, the shutter 2 is opened and closed and a this photographing is performed. The image data obtained at this time is clamped because the average value stored in the arithmetic unit 19 is subtracted after the signal level of the light shielding area is clamped to a prescribed level in the clamp circuit 9.

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 such as a digital still electronic camera.

[0002]

2. Description of the Related Art In recent years, memory ICs and analog-to-digital conversion ICs, which play an important role in establishing digital technology, have been remarkably improved in performance and reduced in cost. Therefore, video cameras, electronic still cameras, etc. Also, digitized products are becoming popular. FIG. 5 is a block diagram showing the configuration of a conventional digital electronic still camera. In the figure, 1 is an optical lens for forming an optical image of a subject, 2 is a lens shutter having a diaphragm function and a shutter function, 3 is a drive circuit for each part of a mechanical system, and 4 is an optical signal of the subject. An image sensor 5 using a CCD for conversion is a timing signal generation circuit (hereinafter T) for generating a timing signal necessary for driving the image sensor 4.
G) and 6 are image pickup element drive circuits for amplifying the signal from the TG 5 to a level required to drive the image pickup element 4, and 7 is an image pickup element 4
Is a CDS circuit for removing the output noise of the signal, 8 is an AGC circuit for amplifying the output signal of the CDS circuit 7, and 9 is a clamp circuit for fixing the zero (black) level of the amplified signal.

Reference numeral 10 is an A / D converter for converting an analog signal into a digital signal, 11 is an image pickup signal processing circuit, and 12 is a recording medium, for example, a memory card or a hard disk is used. Reference numeral 13 is an interface circuit for recording a signal on the recording medium 12, 14 is a signal processing control CPU for controlling the imaging signal processing circuit 11, 15 is a CPU for controlling the mechanism and the operation unit, and 16 is an operation assistant. And an operation display section for indicating the state of the camera, 17 is an operation section for controlling the camera from the outside, and 18 is for obtaining an aperture value and a shutter speed for performing proper exposure of the image sensor 4. An AE light receiver for measuring the brightness of a subject.

FIG. 6 is a block diagram showing in detail the configuration of the image pickup signal processing 11 of FIG. 5, and 101 is a color separation circuit for separating the output signal of the image pickup device 4 into signals c1 and c2 for each color,
Reference numeral 102 denotes RO, GO, from the color-separated signals c1 and c2.
A color matrix circuit for deriving each primary color signal of BO, 103
Is a white balance correction circuit that corrects the levels of the RO, GO, and BO primary color signals in accordance with the color temperature of the light source that illuminates the subject, and 104 is a color difference signal RY from the corrected R, G, and B signals. Color difference signal deriving circuit for deriving BY
Reference numeral 05 is a low-frequency luminance signal correction value derivation circuit that derives a signal YL that corrects the color component of the luminance signal from the R, G, and B signals that are also corrected, and 106 removes the color modulation signal that is superimposed on the image pickup signal. A color modulation trap circuit, 107 is a horizontal aperture circuit that emphasizes horizontal contours, 108 is a vertical aperture circuit that emphasizes vertical contours, and 109 is a signal obtained by adding each signal whose contours have been emphasized and a through signal. Y
An adder for obtaining O and a subtracter 110 for subtracting YL from the signal YO.

Next, the operation of the conventional example will be described with reference to FIGS. When the photographer gives an instruction to start photographing through the operation unit 17, the camera starts the photographing operation. First, the AE light receiver 18
The brightness of the subject is measured by the CPU 15, and the aperture value and the shutter speed of the lens shutter 2 are obtained by the mechanical / operation unit control CPU 15 based on the measured values. The mechanical / operation unit control CPU 15 controls the mechanical system drive circuit 3 based on the obtained control value to drive the lens shutter. In this way, the optical image of the subject is formed on the image area of the image sensor 4 with an appropriate amount of light. The image sensor 4 is operated by a drive signal obtained by amplifying the output of the TG 5 by the image sensor drive circuit 6. The operation of the TG 5 is controlled by the mechanical / operating unit control CPU 15.

The output of the image pickup device 4 driven in this way is subjected to noise reduction by the CDS circuit 7 and then output to the AG
It is amplified to an appropriate level by the C circuit 8. Next, the clamp circuit 9 clamps the black level portion of the output of the AGC circuit 8 to an appropriate potential. After such processing is performed, the image pickup signal output is converted into a digital signal by the A / D converter 10 and input to the image pickup signal processing circuit 11. In the image pickup signal processing circuit 11, a predetermined luminance signal processing described below,
Color signal processing is performed, and further, an image signal is obtained through signal conversion processing into a predetermined format (not shown), and this image signal is recorded on the recording medium 12 via the recording medium I / F 13.

In FIG. 6, an image pickup device output signal (image pickup signal) is inputted from the A / D converter 10 to the image pickup signal processing circuit 11. In the case of the generally used complementary color checkered filter array image sensor 4, this signal is a dot-sequential signal of (Mg + Y1) and (G + Cy) in the ODD field, and (G + Y1) in the EVEN field. ) (Mg + Cy) dot-sequential signals are line-sequential signals. In the image pickup signal processing circuit 11, first, the color separation circuit 101 converts the image pickup signal into each color signal c1.
((Mg + Y1) and (G + Y1) line sequential signals) and c2
(Separated into (G + Cy) and (MG + Cy) line-sequential signals.

The separated signals c1 and c2 are converted into respective primary color signals RO, GO and BO in the color matrix circuit 102 by line synchronization and matrix calculation, and the WB correction circuit 103.
Sent to In the WB correction circuit 103, the signal processing control C
The color temperature of the light illuminating the subject is corrected by the WB control signal sent from the PU 14. Corrected RGB
The color difference signal deriving circuit 104 derives color difference signals R-Y and B-Y from the signals. On the other hand, in the low-frequency luminance signal correction value deriving circuit 105, in order to improve the reproducibility of the brightness for each color, the correction signal YL for correcting the color component ratio forming the luminance signal is derived based on the RGB signal. .

On the other hand, the image pickup signal from the A / D converter 10 is also input to the color modulation amount trap circuit 106 to attenuate the modulated color signal superimposed on the luminance signal. From the output, the horizontal aperture circuit 107 and the vertical aperture circuit 1
08, an aperture signal whose contour is emphasized is derived, and is added to the through luminance signal by the adder 109. The subtraction unit 110 subtracts the correction value YL from the added signal YO to obtain the corrected luminance signal Y.
Is obtained.

FIG. 7 is a diagram showing the structure of the image pickup device 4.
Reference numeral 71 is a photodiode for photoelectric conversion, 72 is a vertical CCD for transferring the charges of the photodiode, 73 is a horizontal CCD for transferring the charges for each line transferred from the vertical CCD 72, and 74 is a transfer from the horizontal CCD 73. It is an output amplifier for converting the charge of each pixel into a voltage signal. The entire pixel area formed by the photodiode 71 and the vertical pixel is composed of two areas, the area indicated by 75 is an effective area for converting the formed optical image into a charge signal, and the area indicated by 76 is black. This is a light-shielding region formed by shielding the pixel surface with an aluminum layer in order to clarify the level reference. FIG. 7 is a block diagram of a CCD image pickup device called an interline system, but other image pickup devices, for example, a frame transfer CCD image pickup device, MO
Also in the S-type image pickup device, the amplification type image pickup device, and the like, the effective region and the light shielding region are configured in the same manner.

In the conventional digital still electronic camera using such an image pickup device, the clamp circuit 9 clamps the signal of the light-shielded area 76 of the image pickup signal and fixes it to an arbitrary potential, and then the AD converter 10 is fixed. Is entered.

[0012]

However, the above-mentioned conventional digital still electronic camera has the following problems. When shooting is performed with the image sensor completely shielded from light, the signal levels of the effective region 75 and the light-shielded region 76 should be essentially the same, but the signal levels of the two regions may differ at high temperatures. is there. This is because the state of the semiconductor surface of the pixel is different from the part without the aluminum layer because the aluminum layer is formed on the pixel surface,
For this reason, this is caused by the difference in the amount of dark current generated in the two regions, or the potential difference between the two regions in the amplification type imaging device. When an image signal is created by processing a signal having such a dark level difference between the light-shielded area and the effective area, the black balance and the white balance are deviated, and an image with correct color reproduction cannot be obtained.

The present invention addresses the above-mentioned problems, and realizes an image pickup apparatus such as a digital still electronic camera which is excellent in color reproducibility, has little noise, and can obtain a high-quality image. With the goal.

[0014]

According to the present invention, an image pickup device for picking up a subject image through a shutter to obtain image data, and a first image obtained by the image pickup device by taking an image with the shutter closed. A storage unit that stores data and a zero level of the second image data obtained from the image sensor by the image pickup performed by opening and closing the shutter is clamped by using the first image data stored in the storage unit. And clamping means.

[0015]

According to the present invention, the first image data obtained by the first photographing performed while the shutter is closed is stored in the storage means, and the second image data obtained by opening and closing the shutter next is: The clamp processing is performed so that the zero level becomes the data value stored in the storage means.

[0016]

The first to eighth embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a digital electronic camera according to the first embodiment of the present invention. In the figure, the elements having the same functions as those in FIG. 5 showing the conventional example are denoted by the same reference numerals, and the duplicated description will be omitted. In FIG. 1, an A / D converter 10 and an imaging signal processing circuit 1
An arithmetic unit 19 is added between 1 and 1. This calculator 1
9 is the average processing, addition, and subtraction of arbitrary data,
It is an arithmetic unit having a memory for storing arbitrary data as a storage means.

FIG. 2 is a timing chart for explaining the operation of the digital electronic camera. When the photographer gives an instruction to start photographing through the operation unit 17, the photographing start trigger signal shown in FIG. 2 is sent to the mechanical and operation unit control CPU 15, and the camera starts the photographing operation. First, the vertical CCDs of the image sensor 4 are cleared, while the AE light receiver 17 measures the brightness of the subject,
Based on the measured value, the aperture value and shutter speed of the lens shutter 2 are obtained by the mechanical / operation unit control CPU 15. Subsequently, with the shutter closed, the image pickup device 4 is driven by the electronic shutter pulse and the charge read pulse while being provided with a charge accumulation time similar to that actually taken with the aperture value and the shutter speed obtained above. . The output of the image pickup device 4 thus accumulated and read is subjected to noise reduction by the CDS circuit 7 and amplified by the AGC circuit 8 so as to have an appropriate output level so that the black level becomes an appropriate potential. Then, the clamp circuit 9 clamps the signal of the light-shielded area 76 in the output signal.

After such processing, the image pickup signal output is converted into a digital signal by the A / D converter 10. A
The data of a plurality of areas in the effective area 75 of the / D-converted dark data are taken into the memory of the computing unit 19, and the average value X of these data is calculated. Therefore, the average value X indicates dark current and noise.

Next, actual photographing is performed. The subject image is exposed on the image sensor 4 with the shutter speed and the aperture value which are obtained in advance. The image sensor 4 converts this into electric charge and sequentially outputs it as a voltage signal. The output of the image sensor 4 driven in this way is subjected to noise reduction by the CDS circuit 7,
The AGC circuit 8 amplifies the output level to an appropriate output level, and the clamp circuit 9 adjusts the black level to an appropriate potential.
Thus, the signal in the light-shielded area 76 is clamped to the same level as the first clamp.

After such processing, the image pickup signal output is converted into a digital signal by the A / D converter 10. Each converted pixel data is input to the calculator 19,
The average value X calculated previously is subtracted. That is, it means that the digital data has been clamped for calculation. Here, in reality, since there is data lower than X, if it is, for example, 10-bit data, addition of about 30 is added to the data of each subtracted pixel. The data processed in this manner is input to the image pickup signal processing circuit 11, where predetermined luminance signal processing and color signal processing are performed as in the conventional example, and further, signal conversion processing into a predetermined format (not shown) is performed. , Is recorded on the recording medium 12 via the recording medium I / F 13.

By performing the digital clamp operation as described above, the zero level of the image data is always fixed, so that an image with good black balance and white balance and good color reproducibility can be obtained.

In the above description, the dark data is extracted in a plurality of areas within the effective area 75 in the first image pickup, but the effect can be sufficiently obtained even if it is set in any one area. Further, by calculating the average value X of the dark data to one digit of the decimal point, expanding this bit and performing digital clamp, it is possible to perform clamp with higher precision. This is also effective in each of the embodiments described below, and is particularly effective in a clamp performed for each line.

Next, a second embodiment will be described. There is an image pickup signal processing circuit configured to perform dark level clamping again in the image pickup signal processing circuit 11. In the image pickup signal processing circuit 11 having such a configuration, the value of the dark area is different from the zero level of the image data in the case of the first embodiment, so that the correct clamping is not performed. Therefore, in the second embodiment, means for making the difference between the dark level and the effective black level the same is provided.

Similar to the first embodiment, the first photographing is performed in the light-shielded state, the output signal of the image pickup device 4 is subjected to CDS, amplification and clamp processing, and then digitalized by the A / D converter 10. Converted to a signal. Of the A / D converted data, the data of a plurality of areas within the effective area 75 and the data of a plurality of areas within the light-shielding area 76 are loaded into the memory of the computing unit 19, and the average value of the data of the light-shielding area 76 is stored in each. X
d, the average value Xe of the data in the effective area 75 is calculated.

Next, main photographing is performed in the same manner as in the conventional example, the image pickup signal from the image pickup device 4 is subjected to CDS, amplification and clamp processing, and then converted into a digital signal by the A / D converter 10. Each pixel data is input to the arithmetic circuit 19, and the previously obtained Xd is subtracted from the data of the light-shielded area 76, and the previously obtained Xe is subtracted from the data of the effective area 75. Here, in reality, since there is data lower than Xd and Xe, for example, if it is 10-bit data, about 30 plus is added to each subtracted pixel data. The data processed in this manner is input to the image pickup signal processing circuit 11, where predetermined luminance signal processing and color signal processing are performed as in the conventional example, and further, signal conversion processing into a predetermined format (not shown) is performed. , Is recorded on the recording medium 12 via the recording medium I / F 13.

Next, a third embodiment will be described. First
Similarly to the embodiment described above, the first light-shielded image capturing is performed, the output signal of the image sensor 4 is subjected to CDS, amplification, and clamp processing, and then converted into a digital signal by the A / D converter 10. Effective area 75 of A / D converted data
The data of a plurality of areas in the light-shielding area 76 and the data of a plurality of areas in the light-shielding area 76 are taken into the memory of the calculator 19, and the average value Xd of the data of the light-shielding area 76 and the average value Xe of the data of the effective area 75 are calculated respectively. And the difference Xs = Xe
-Xd is calculated.

Next, the main photographing is performed in the same manner as in the conventional example, the image pickup signal from the image pickup device 4 is subjected to CDS, amplification and clamp processing, and then converted into a digital signal by the A / D converter 10. Each pixel data is input to the calculator 19, and the previously obtained Xs is added to the data of the light shielding area 76. The data processed in this manner is used as the image pickup signal processing circuit 11
To a recording medium 12 through a recording medium I / F 13 and a predetermined luminance signal processing and a color signal processing as in the conventional example. To be done.

Although the difference between the zero level of the light-shielding area 76 and the effective area 75 is corrected (clamped) in the light-shielded area 76 here, it may be corrected (clamped) in the effective area 75. However, it is advantageous to correct (clamp) in the light-shielded area 76 because the processing amount is small.

Next, a fourth embodiment will be described. FIG.
FIG. 3 is a block diagram showing the configuration of the digital electronic camera of this embodiment. Reference numeral 20 denotes a D / A converter for actually converting the clamp level value data instructed by the arithmetic unit 19 into a voltage and inputting it to the clamp circuit 9. The other parts have the same structure as in FIG.

As in the case of the first embodiment, the first photographing is performed in the light-shielded state, and the output signal of the image pickup device 4 is subjected to CDS and amplification processing so that the black level becomes an appropriate potential V1. The clamp circuit 9 clamps the signal in the light shielding area 76. The clamped image pickup signal is converted into a digital signal by the A / D converter 10. Of the A / D-converted data, the data of a plurality of areas in the effective area 75 and the data of a plurality of areas in the light shielding area 76 are taken into the memory of the arithmetic unit 19, and the average value Xd of the data in the light shielding area 76 is stored in each of them. The average value Xe of the data in the effective area 75 is calculated, and the difference Xs = Xe−Xd is calculated. Based on this value, the clamp level correction voltage amount is input to the D / A converter 20 as data, and the D / A converter 20 outputs the voltage V2 according to this data.

Next, the main photographing is performed in the same manner as in the conventional example, the output signal of the image pickup device 4 is subjected to CDS and amplification processing, and then the signal of the light shielding area 76 is provided by the clamp circuit 9 so that the black level becomes the potential V2. Clamp. The image pickup signal output subjected to the clamp processing is converted into a digital signal by the A / D converter 10. The digital image data is directly input to the image pickup signal processing circuit 11, subjected to predetermined luminance signal processing and color signal processing as in the conventional example, and further subjected to signal conversion processing into a predetermined format (not shown) to obtain a recording medium. I / F
It is recorded on the recording medium 12 via 13.

Next, a fifth embodiment will be described. Figure 7
In the image sensor 4 using the interline CCD as described above, there is a so-called smear phenomenon due to the light entering from the pixel opening reaching the vertical CCD 72 and being photoelectrically converted by the vertical CCD 72. With an electronic still camera,
Since the mechanical shutter is used, after the mechanical shutter is closed, the photodiode 71 of the image sensor 4 is
From the vertical CCD just before the charge is read from the vertical CCD 72
By transferring 72 at a high speed, unnecessary charges that become smear components are discarded.

The difference between the 0 level of the light-shielding area 76 and the 0 level of the effective area 75 of the image pickup device 4 pointed out as a problem of the conventional electronic still camera is mainly the vertical C of both areas.
This is due to the generation of dark charges on the CD 72. For this reason, in the electronic still camera that performs high-speed charge removal of the vertical CCD 72 immediately before the charge is read from the photodiode 71 to the vertical CCD 72, the photodiode 71 is used to remove the vertical CCD.
Since the difference between the 0 level of the light-shielding area 76 and the 0 level of the effective area 75 increases in proportion to the time from the reading of charges to 72 through the horizontal CCD 73, the line that is read out later is shaded. 0 in area 76
The difference between the level and the 0 level of the effective area 75 becomes large.

Therefore, in the image pickup device 4 which is cleared at high speed just before the reading to the vertical CCD 73, the operation of each embodiment described so far in this embodiment is performed for each line. That is, the correction (clamp) amount calculated and stored in the arithmetic unit 19 is the correction (clamp) amount for each line, and the correction (clamp) is also performed for each line.

Next, a sixth embodiment will be described. Recently, many image pickup devices having a large number of pixels have been manufactured, but in such an image pickup device, charge reading must be performed at high speed. However, the output line (horizontal C
It is often practiced to provide a plurality of CDs 73). In such an image pickup device, the difference in zero level between the light-shielding region 76 and the effective region 75 of the image pickup device is different for each output due to the reason that the gains of the output amplifiers 74 of the respective output lines do not match. Therefore, in this embodiment, the operation of each embodiment described so far is performed for each output system. That is, the correction (clamp) amount calculated and stored in the computing unit 19 is the correction (clamp) amount for each output system, and the correction (clamp) is also performed for each output system.

Next, a seventh embodiment will be described. It is not only the difference in the zero level between the light-shielding region 76 and the effective region 75 that causes a problem in the characteristics of the image sensor at high temperatures. As described above, the difference in the zero level between the light-shielding area 76 and the effective area 75 is that the amount of dark charge generated by the vertical CCD 72 in each area is different. The vertical CCD 7 in the light-shielded area 76 and the effective area 75 is generated.
Although it is much smaller than the difference in the amount of dark charge generated in No. 2, it has a slight difference. For this reason, a thin vertical stripe appears in an image obtained by photographing the image pickup device using such an image pickup element under high temperature, resulting in a poor quality image.

This embodiment is applied to such an image pickup device, and the correction (clamp) data used in the arithmetic unit 19 is the average value of the data of a plurality of lines during darkness. FIG. 4 shows the drive timing of the image sensor according to the present embodiment. When the photographer gives an instruction to start photographing through the operation unit 17, the camera starts the photographing operation. First, the image sensor 4
Driving of the vertical CCD 72 and the horizontal CCD 73 starts. At the same time, the luminance of the subject is measured by the drive AE light receiver 17, and the aperture value and shutter speed of the lens shutter 2 are calculated by the mechanical / operation unit control CPU 15 based on the measured values.

When the vertical CCD drive pulse exceeds the number of pulses for sending the total number of transfer stages, the image signal output subjected to the CDS, amplification and clamp processing is converted into a digital signal in the A / D converter 10. As for the digitized image data, a plurality of lines of data are taken into the memory of the calculator 19, and the average value of the data of the pixels of the same rank on each line is calculated. In other words, the average dark level of each vertical line is calculated. In this case, the larger the number of lines required to obtain the average value, the better, and it has been confirmed that effective correction (clamping) can be performed by obtaining the average value of about 100 lines.

In this way, the data for the horizontal n lines are fetched, and when the calculation of the average value is completed, shooting is performed with the previously determined aperture value and shutter speed, as in the conventional example. The image pickup signal from the image pickup device 4 is C
DS, amplification, clamp processing, and A / D conversion are performed. The digital pixel data is input to the calculator 19, and the dark area data is subtracted from the previously calculated average dark value of the corresponding vertical line. The data processed in this manner is input to the image pickup signal processing circuit 11, where predetermined luminance signal processing and color signal processing are performed as in the conventional example, and further, signal conversion processing into a predetermined format (not shown) is performed. , Is recorded on the recording medium 12 via the recording medium I / F 13.

Here, unlike the previous embodiments, the dark data fetch timing of this embodiment is different. The vertical stripe that is the target of correction here is vertical C
Since the phenomenon caused by the CD and at a very low level in terms of level is handled, the white scratches or the like of the photodiode 71 have a strong influence as an error factor. This is because I took out only. In the dark data reading of the present embodiment, the time of actual photographing is the same as the accumulation time in the vertical CCD 72, and the necessary correction data can be obtained with this. In addition, it is possible to reduce the time required for the actual shooting.

The difference in 0 level between the light-shielding area 76 and the effective area 75, which has been a problem in each of the previous embodiments, is mostly due to the vertical CCD 72 in the interline CCD. Also, the expected effect can be obtained by setting the operation timing similar to that of the present embodiment.
However, in an image pickup device other than the interline CCD, for example, a frame transfer CCD, an XY address sensor, etc., the operation timing must be as described in the first to seventh embodiments. .

Next, an eighth embodiment will be described. CC
Although not so much in the D-type image pickup device, uneven output in the area when light is blocked is observed in the amplification type image pickup device. This is a phenomenon usually called dark shading and draws a smooth change curve. In such a clamp of the image pickup device, a plurality of data are fetched from a plurality of portions in the area as the image data at the time of the first light shielding, the average value of the data of each portion is calculated, and the averaged area The correction value of each pixel that estimates the state of dark shading in the area from the dark data of multiple parts, or divides the area into blocks and stores the correction value as a correction value for each block, and the second main captured image The signals are corrected (clamped) with the corresponding correction values. By doing so, it is possible to obtain reliable image data of a black level even in an image sensor having a swell (shading) in the dark output.

In each of the embodiments described above, the dark information is first obtained, and then the main photographing is performed. If an image memory for temporarily storing all images is built in the main body, this order may be reversed. In the sense of protecting against blurring during shooting, this method is rather preferable. In this case, the memory for storing all images has a capacity slightly larger than that for all images, so that the data necessary for clamping can be stored at a specific address of this memory, especially There is no need to have a separate memory for use. Whether or not to have a memory dedicated to the clamp may be determined depending on the system configuration.

Further, since the output difference between the light-shielding area 76 and the effective area 75, which is a problem to be solved in the present invention, is a problem at high temperature, the temperature in the image pickup device or the image pickup apparatus is not fixed in each of the above embodiments. You may make it operate | move when it becomes more than the temperature set up beforehand.

[0045]

As described above, according to the present invention, the image data of the main photographing is clamped with the image data of the image sensor in the light-shielded state as the zero reference, so that the color reproduction is excellent and the noise An image pickup device capable of obtaining a small number of images can be realized.

[Brief description of drawings]

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

FIG. 2 is a timing chart showing the operation of the embodiment.

FIG. 3 is a block diagram showing another embodiment of the present invention.

FIG. 4 is a timing chart showing the operation of another embodiment.

FIG. 5 is a block diagram showing a configuration of a conventional digital still electronic camera.

FIG. 6 is a block diagram showing a configuration of an image pickup signal processing circuit.

FIG. 7 is a configuration diagram of an image sensor.

[Explanation of symbols]

 2 Shutter and shutter 4 Image sensor 9 Clamp circuit 19 Operation unit 20 D / A converter

Claims (22)

[Claims] 1. An image pickup device for picking up an image of a subject through a shutter to obtain image data; a storage unit for storing first image data obtained from the image pickup device by image pickup performed with the shutter closed; An image pickup apparatus comprising: clamp means for clamping, using the first image data stored in the storage means, the zero level of the second image data obtained from the image pickup device by image pickup performed by opening and closing the shutter. 2. The first image data is image data of a partial region of the image sensor, and the first image data is the first image data as a reference for clamping the zero level of the second image data.
The image pickup apparatus according to claim 1, wherein an average value of the image data is used. 3. The reference for clamping the zero level of the second image data, wherein the first image data is image data of one or more pixels in a plurality of portions in the entire area of the image pickup device. The image pickup apparatus according to claim 1, wherein an average value of the first image data is used as. 4. The first image data is data composed of part of the light-shielding area of the image sensor or the whole image data and part of the effective area of the image sensor or the whole image data. Yes, the difference between the average value of the image data of the effective area and the average value of the image data of the light-shielded area is used as a reference for clamping the zero level of the second image data. The image pickup apparatus according to claim 1, wherein one of the data is clamped. 5. The image of the same vertical line of the first image data as the reference for clamping the zero level of the second image data, wherein the first image data is image data of a plurality of horizontal lines. The image pickup apparatus according to claim 1, wherein the average value of the data is used to clamp the signals of the vertical position corresponding to each of them. 6. The first image data is image data of a plurality of pixels in a plurality of portions in the entire area of the image pickup device, the data of each portion is averaged, and the entire area is obtained from the averaged data. Corresponding to each pixel obtained by shape estimation from the first image data as a reference for clamping the zero level of the second image data. The image pickup apparatus according to claim 1, wherein data is used. 7. The image pickup apparatus according to claim 1, wherein the clamp is performed for each line of the image pickup element. 8. The image pickup apparatus according to claim 1, wherein the image pickup element is an image pickup element having a plurality of output lines, and the clamp is performed for each output image data of each output line. 9. An image pickup device for obtaining an image data by picking up an optical image of a subject through a shutter, and a storage means for storing first image data obtained from the image pickup device by image pickup performed with the shutter closed. An image pickup apparatus comprising: clamp means for subtracting the first image data stored in the storage means from second image data obtained from the image pickup device by image pickup performed by opening and closing the shutter. 10. The first image data is image data of a partial area of the image sensor, and the numerical value subtracted from the second image data is an average value of the first image data. Item 9. The imaging device according to item 9. 11. The first image data is image data of one or more pixels in each of a plurality of portions in the entire area of the image sensor, and a numerical value subtracted from the second image data is the first image data. The image pickup apparatus according to claim 9, wherein the image data is an average value of the image data. 12. The data comprising the first image data, which is part of the light-shielding area of the image sensor or the whole image data, and part of the effective area of the image sensor or the whole image data. Yes, the value obtained by subtracting the average value of the image data of the light shielding area from the average value of the image data of the effective area of the first image data is added to the image data of the light shielding area of the second image data, or A value obtained by subtracting a value obtained by subtracting the average value of the image data of the effective area from the average value of the image data of the light shielding area of the first image data with respect to the image data of the light shielding area of the second image data. Item 9
The imaging device described. 13. The first image data is image data of a plurality of horizontal lines, and the numerical value subtracted from the second image data is an average value of image data of the same vertical line of the first data. 10. The image pickup apparatus according to claim 9, wherein the clamp means clamps signals corresponding to respective vertical positions. 14. The first image data is image data of each of a plurality of pixels in a plurality of portions in the entire area of the image pickup device, data of each portion is averaged, and the entire area is calculated from the average data. The data corresponding to each pixel obtained by estimating the shape of the signal level when light is shielded and subtracted from the second image data is obtained by estimating the shape of the signal level. 9. The imaging device according to item 9. 15. The image pickup apparatus according to claim 9, wherein the clamp performed by the clamp means is performed for each line of the image pickup device. 16. The image pickup apparatus according to claim 9, wherein the image pickup element is an image pickup element having a plurality of output lines, and the clamping means clamps each output image data of each output line. 17. The shutter is opened and closed the first time to store the image data in the storage means, and the second time the shutter is closed, the image data serving as a reference for the clamp is stored in the storage means and stored. The image pickup apparatus according to claim 9, wherein clamping is performed using two pieces of image data. 18. An image pickup device for obtaining a first image data by picking up a subject image through a shutter, a clamp means for clamping a signal level of a light shielding region of the image pickup device, and an image pickup performed with the shutter closed. An arithmetic unit that calculates and stores data of a difference between an average value of image data obtained from the effective area and an average value of image data obtained from the light-shielded area of the second image data obtained from the image sensor. The arithmetic means is configured to change the clamp level when the clamp means clamps the signal level of the light-shielded area obtained by imaging performed by opening and closing the shutter according to the stored difference data. Image pickup device. 19. The first and second image data are stored in different addresses of a common memory.
The imaging device according to claim 1. 20. The method according to claim 1, wherein the first and second image data are stored in separate memories.
The imaging device according to the item. 21. Clamping reference data obtained by an average value of image data obtained by opening and closing the shutter is bit extended data, and clamping is performed using the bit extended data. ~ 18
The imaging device according to claim 1. 22. The imaging device according to claim 1, wherein the clamp is performed at a specific temperature or higher.