JP2007036353A - Image pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration in image quality by completely correcting linear deterioration for a light receiving quantity of RAW data. <P>SOLUTION: An analog signal processor 29 applies predetermined analog processing to an image pickup signal output from a CCD image sensor 16 to generate RAW data. A CPU 12 controls a CCD driver 24 via a TG 25, and changes an electronic shutter speed of the CCD image sensor 16 to gradually change the light receiving quantity. A correction data calculating program 14b in an EEPROM 14 is activated by the CPU 12, obtains a different quantity between predetermined pixel data of the RAW data generated in each light receiving quantity and an ideal straight line, and creates an LUT 14c for linear correction corresponding to the relation between the pixel data and the difference quantity. A linear correction processing circuit 37 corrects the RAW data on the basis of the LUT 14c for linear correction, and linearized RAW data are input into a digital signal processing circuit 31. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging apparatus that converts subject light into digital image data and records it on a recording medium.

  Digital cameras that convert subject light captured by a solid-state imaging device such as a CCD image sensor into digital image data and record it on a recording medium such as a built-in memory or a memory card have become widespread. The imaging signal output from the solid-state imaging device is subjected to correlated double sampling processing and amplification processing and A / D conversion processing, and is digitized.

  However, this digitized imaging signal (RAW data) receives the processing characteristics of the voltage conversion processing, correlated double sampling processing, amplification processing, and A / D conversion processing of the solid-state imaging device, and is linear with respect to the amount of received light. (Linearity) is impaired. Therefore, when digital signal processing is performed on this RAW data, image quality degradation occurs due to color misregistration and the like.

Patent Document 1 discloses a method for improving the linearity of the A / D conversion process.
JP-A-8-195877

  However, even if the method of Patent Document 1 is applied to the digital camera, linearity deterioration due to voltage conversion processing, correlated double sampling processing, amplification processing, and the like of the solid-state imaging device cannot be corrected. The image quality after signal processing is still deteriorated.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an imaging apparatus capable of completely correcting linearity deterioration with respect to the amount of received light of RAW data (digital data) and preventing image quality deterioration. And

  In order to achieve the above object, an image pickup apparatus of the present invention converts an image charge generated by a plurality of two-dimensionally arranged photoelectric conversion elements into an image pickup signal by an output amplifier and outputs the image pickup signal from the image pickup means. Digital data conversion means for performing predetermined processing on the output imaging signal and converting it into digital data, received light amount control means for changing the received light amount of the imaging means in a plurality of stages so as to include a light shielding state, and the received light A predetermined pixel data included in the digital data generated at each received light amount set by the amount control means, and an ideal straight line determined based on a difference between the pixel data in the light shielding state and a predetermined exposure state. A correction data calculating means for calculating a linearity correction data by obtaining a differential quantity and relating the differential quantity and the pixel data; and the linearity correction data Zui and is characterized in that a correcting means for correcting the digital data.

  The correction data calculation means preferably calculates the pixel data for the received light amount not set by the received light amount control means by linear interpolation.

  The digital data processing means for performing digital signal processing including gamma correction on the digital data, the linearity correction data calculated by the correction data calculation means, and the gamma correction used for the gamma correction. It is preferable to integrate the data.

  The imaging unit is a CCD image sensor including a plurality of the output amplifiers, the correction data calculating unit calculates the linearity correction data for each output amplifier, and the correction processing unit It is preferable that the digital data corresponding to each output amplifier is corrected using the linearity correction data calculated for each output amplifier.

  Further, the imaging means is provided with a plurality of output amplifiers for each horizontal transfer path, and when the linearity correction data is calculated by the correction data calculation means, the horizontal transfer path is the same photoelectric conversion element. It is preferable to distribute the signal charges transferred through the horizontal transfer path to the output amplifiers in time series.

  Further, the imaging means is provided with a plurality of horizontal transfer paths to which the output amplifier is connected, and a distribution means for distributing signal charges from the same photoelectric conversion element to the horizontal transfer paths. When the linearity correction data is calculated by the correction data calculation means, it is preferable that the distribution means distributes the signal charges output from the same photoelectric conversion element to the horizontal transfer paths in time series.

  In addition, a prism that splits incident light into a plurality of colors is provided, and the imaging unit is provided for each of the dispersed colors, and the correction data calculation unit calculates the linearity correction data for each color. The correction processing means preferably corrects the digital data corresponding to each color using the linearity correction data calculated for each color.

  It is preferable that the recording apparatus further includes a recording unit that records the digital data together with the linearity correction data.

  The image pickup apparatus of the present invention changes the light reception amount of the image pickup means in a plurality of stages so as to include a light shielding state, determines an ideal straight line, and determines a predetermined amount included in the digital data acquired for each step of the light reception amount. Since the difference amount between the pixel data and the ideal straight line is obtained, the linearity correction data corresponding to the relationship between the pixel data and the difference amount is calculated, and the digital data is corrected based on the linearity correction data. Fully corrects the linearity deterioration with respect to the received light amount of digital data, and can prevent image quality deterioration.

  Further, by calculating the pixel data for the received light amount outside the setting by linear interpolation, the number of steps of the received light amount actually changed can be reduced.

  Further, by integrating the linearity correction data and the gamma correction data, the cost of the storage medium for storing them can be reduced, and the time required for the correction process can be reduced.

  When the imaging means is a CCD image sensor having a plurality of output amplifiers, the linearity correction data is calculated for each output amplifier, and the digital data corresponding to each output amplifier is calculated for each output amplifier. By correcting using the correction data, image quality deterioration due to the characteristic difference of each output amplifier is prevented, and the image quality of the composite image is improved.

  In addition, in the case of a multi-plate CCD configuration that includes a prism that splits incident light into a plurality of colors and that has an imaging means for each of the dispersed colors, linearity correction data is calculated for each color and corresponds to each color By correcting the digital data to be used using the linearity correction data calculated for each color, image quality deterioration due to the characteristic difference between the individual image pickup means is prevented, and the color shift of the composite image is reduced.

  In FIG. 1 showing the configuration of the digital camera 10, the operation unit 11 includes a power switch 11a, a shutter button 11b, a mode switching dial 11c, and the like. The CPU 12 controls the operation of each unit via the bus line 13 based on the operation signal input from the operation unit 11. The EEPROM 14 stores a well-known gamma correction lookup table (LUT) 14a, a correction data calculation program 14b for linearity correction, which will be described later, a linearity correction LUT 14c, and the like. The RAM 15 is a working memory used during various controls.

  On the subject side of the CCD image sensor (imaging means) 16, a mechanical shutter 17, a photographic lens 18, and a diaphragm 19 are provided, and motors 20, 21, and 22 are connected to each other. The motors 20 to 22 are independently controlled by a drive signal transmitted from the motor driver 23.

  The CCD image sensor 16 photoelectrically converts (images) subject light that has passed through the mechanical shutter 17, the photographic lens 18, and the diaphragm 19 using a plurality of two-dimensionally arranged photoelectric conversion elements. A CCD driver 24 is connected to the CCD image sensor 16, and a timing generator (TG) 25 controlled by the CPU 12 is connected to the CCD driver 24.

  In the CCD image sensor 16, the electronic shutter speed (signal charge accumulation time) is controlled by a control signal for shutter speed control supplied from the CCD driver 24 and a control signal for signal charge transfer supplied from the CCD driver 24. The signal charge is converted into a voltage signal by the output amplifier based on the above, and the imaging signal corresponding to the charge amount of the signal charge is serially output to the outside. The mechanical shutter 17 and the electronic shutter controlled by the CPU 12 function as a received light amount control unit.

  Note that an RGB color filter is provided in the light receiving portion of the CCD image sensor 16 in which the photodiodes are two-dimensionally arranged, and the color arrangement of the RGB color filter is a Bayer arrangement. The CCD image sensor 16 outputs an imaging signal by a still image reading method (for example, frame reading) in the still image shooting mode, and outputs an imaging signal by a moving image reading method (for example, field reading) in the moving image shooting mode. Do. The driving frequency in each readout method is determined by the frequency of the clock pulse supplied from the TG 25 to the CCD driver 24.

  An imaging signal output from the CCD image sensor 16 is an analog signal processing unit (digital data conversion means) including a correlated double sampling circuit (CDS) 26, an auto gain control amplifier (AGC) 27, and an A / D converter 28. ) 29 is digitized.

  The CDS 26 removes the amplifier noise and reset noise of the CCD image sensor 16. The AGC 27 is an amplifier that can change the gain in a programmable manner, and a gain amount (that is, ISO sensitivity) is set by the CPU 12. The A / D converter 28 digitizes the imaging signal that has been subjected to noise removal and gain adjustment by the CDS 26 and the AGC 27 and generates RAW data (digital data). The RAW data output from the A / D converter 28 is temporarily stored in the image memory 30.

  The digital signal processing circuit 31 performs image processing such as signal interpolation, white balance adjustment, gamma correction, and luminance / color difference conversion on the RAW data stored in the image memory 30 to generate image data. The LCD driver 32 displays this image data on the liquid crystal display (LCD) 33 as a through image. The gamma correction is performed based on the gamma correction LUT 14a in the EEPROM 14. Gamma correction is a type of gradation conversion, and is performed to achieve consistency with the display system.

  The compression / decompression processing circuit 34 performs compression processing on the image data in the image memory 30 in a predetermined compression format (for example, JPEG format) when the shutter button 11b is pressed. The media controller 35 records the image data compressed by the compression / decompression processing circuit 34 on the memory card 36. The media controller 35 reads image data from the memory card 36 in the playback mode. The compression / decompression processing circuit 34 performs decompression processing on the image data read by the media controller 35, and reproduces and displays the decompressed image data on the LCD 33 via the LCD driver 32.

  The digital camera 10 has a “correction data creation mode” for creating correction data for making pixel data (QL value) constituting RAW data accurately proportional to the amount of light received by each light receiving element of the CCD image sensor 16. Yes. Under the correction data creation mode, the CPU 12 controls the operation of each unit based on the correction data calculation program 14b. The CPU 12 changes the amount of received light by controlling the mechanical shutter 17 and the electronic shutter of the CCD image sensor 16, and obtains QL values for a plurality of received amounts of light from predetermined pixels. Then, a QL value for other received light amounts is obtained by linear interpolation, a difference amount between each QL value and an ideal straight line is calculated, and a linearity correction LUT 14c corresponding to the relationship between the QL value and the difference amount is stored in the EEPROM 14. create.

  The linearity correction LUT 14c is a conversion table in which a QL value before conversion and a QL value after conversion obtained by subtracting the difference amount from the QL value are associated with each other. The linearity correction LUT 14c is created for each drive mode of the digital camera 10. As shown in FIG. 2, the drive mode is defined by a combination of ISO sensitivity, drive frequency of the CCD image sensor 16, aperture value, and setting values of the readout method of the CCD image sensor 16.

  The linearity correction processing circuit 37 performs linearity correction processing by converting the QL value of the RAW data based on the linearity correction LUT 14c corresponding to the drive mode at the time of still image shooting or moving image shooting. RAW data is input to the digital signal processing circuit 31.

  Next, a method of calculating the difference amount necessary for creating the linearity correction LUT 14c will be briefly described with reference to FIG. The graph is a graph showing the amount of received light along the horizontal axis and the QL value along the vertical axis, and A0 to A3 are measured values of the QL values for four different received light amounts S0 to S3. S0 corresponds to a light shielding state in which the mechanical shutter 17 is closed, and S3 corresponds to a saturated state in which the amount of light received by the CCD image sensor 16 is saturated (a signal charge saturation accumulation state). S1 to S3 are light reception amounts set by changing the electronic shutter speed (charge accumulation time) of the CCD image sensor 16 with the mechanical shutter 17 opened.

The ideal straight line L is a straight line connecting the coordinates (S3, B3) and the origin (S0, 0), and is defined as B3 = A3-A0. That is, B3 is a value obtained by subtracting the dark current component in the light shielding state from the QL value in the saturated state. The QL values B1 and B2 on the ideal straight line L in S1 and S2 are expressed as follows by proportional calculation.
B1 = (A3-A0). (S1-S0) / (S3-S0)
B2 = (A3-A0). (S2-S0) / (S3-S0)

  Accordingly, by subtracting B1 and B2 from A1 and A2, respectively, the difference amount with respect to the actually measured QL value is obtained. The difference amount with respect to other QL values is calculated by calculating the QL values between A0 to A1, between A1 and A2, and between A2 and A3 by linear interpolation, and the difference between each calculated QL value and the ideal straight line L is as above. It is obtained by calculating by the same calculation. Note that the actual number of QL values and the number calculated by correction interpolation may be set as appropriate.

  The linearity correction operation of the digital camera 10 configured as described above will be described based on the flowchart of FIG. When the power switch 11a is operated to turn on the power (step S100), and then the mode switching dial 11c is operated to set the correction data creation mode (Yes in step S101), the correction data calculation program 14b is activated. At the same time, the parameter M is set to “M = 1” (step S102), and the drive mode (M = 1) shown in FIG. 2 is set under the control of the CPU 12 (step S103).

  First, imaging is performed in a light-shielded state with the mechanical shutter 17 closed, and predetermined pixel data (QL value) is acquired from the RAW data output from the analog signal processing unit 29 (step S104). Next, in a state where the mechanical shutter 17 is opened, imaging is sequentially performed under a plurality of exposure conditions including a signal charge saturation state, and a QL value is similarly acquired under each exposure condition (step S105). This exposure condition is set by changing the electronic shutter speed of the CCD image sensor 16 in a plurality of stages.

  Next, based on the QL values acquired in steps S104 and S105, other QL values are calculated by the above-described linear interpolation (step S106). Thereafter, an ideal straight line L as shown in FIG. 3 is set based on the QL value in the light-shielding state obtained in step S105 and the QL value in the saturated state obtained in step S105. A difference amount from the QL value is calculated (step S107). Based on the difference amount, a linearity correction LUT 14c is created (step S108). Thereafter, steps S103 to S108 are repeatedly executed until the parameter M reaches the maximum number K of drive modes. Thereby, the LUT 14c for linearity correction is created for all drive modes.

  The linearity correction LUT 14c thus obtained is used by the linearity correction processing circuit 37 during still image shooting or moving image shooting. The linearity correction processing circuit 37 converts each QL value of the RAW data based on the linearity correction LUT 14c corresponding to the drive mode, performs linearity correction processing, and converts the corrected RAW data into a digital signal processing circuit. 31. Since the RAW data in which the linearity deterioration with respect to the amount of received light is completely corrected is input to the digital signal processing circuit 31, image quality deterioration due to digital signal processing is reduced.

  In the above embodiment, in addition to the linearity correction LUT 14c, a gamma correction LUT 14a used for gamma correction is separately provided. However, the present invention is not limited to this, and the linearity correction LUT 14c and the gamma correction LUT 14a are provided. It is also possible to integrate. When the input / output relationship of the linearity correction LUT 14c is expressed as a function Y = Lin (X) and the input / output relationship of the gamma correction LUT 14a is expressed as a function Y = γ (X), The relationship is Y = γ (Lin (X)). Here, X represents an input value, and Y represents an output value.

  In the above-described embodiment, the linearity correction LUT 14c is provided in the EEPROM 14 for linearity interpolation. However, the present invention is not limited to this, and instead of the linearity correction LUT 14c, the QL corresponding to the received light amount is changed. Only the actual measurement value may be stored in the EEPROM 14, and the linearity correction processing circuit 37 may perform all the above-described linear interpolation, difference amount calculation, and correction processing. The processing procedure of the linearity correction processing circuit 37 in this case is shown in FIG. It is assumed that measured values A0 to A3 of the QL values shown in FIG. 3 are stored in the EEPROM 14 in association with the received light amounts S0 to S3. The actual measurement values A0 to A3 are obtained in the correction data creation mode.

  In FIG. 5, the linearity correction processing circuit 37 first selects one pixel from the RAW data output from the analog signal processing unit 29 after imaging the subject light by the CCD image sensor 16 (step S200). QL value is acquired from (step S201). Next, it is determined whether the QL value belongs to any one of A0 to A1, A1 to A2, and A2 to A3 (steps S202 and S203), and the interval to which the QL value belongs is linearly interpolated and the above-mentioned ideal A straight line L is set (step S204). Then, a difference amount of the QL value from the ideal straight line L is calculated (step S205), and the QL value is converted into a value on the ideal straight line L by subtracting the difference amount from the QL value (step S206). . Thereafter, steps S201 to S206 are executed for the other pixels, and if the final pixel is reached (Yes in step S207), the correction process is completed. As a result, the linearity deterioration that is the amount of received light of RAW data is corrected.

  In the above embodiment, the CCD image sensor 16 is described assuming that the imaging signal is serially output from one output amplifier. However, the present invention is not limited to this, and the output of the imaging signal is not limited thereto. The present invention can also be applied to a case where the CCD image sensor 16 is configured to output image pickup signals from a plurality of output amplifiers in order to increase the speed.

  As shown in FIG. 6, when a plurality of output amplifiers 40 are provided in the CCD image sensor 16, a set of CDS 26, AGC 27, and A / D converter 28 are provided for each output amplifier 40. The process of creating the linearity correction LUT 14c shown in FIG. That is, in the shooting mode (still image or moving image shooting mode), the RAW data corresponding to each output amplifier 40 is corrected using the linearity correction LUT 14c created for each output amplifier 40 in the correction data creation mode. . As a result, image quality deterioration due to the characteristic difference between the individual output amplifiers 40 is prevented, the image quality of the composite image is improved, and horizontal stripes, moving image flicker, and the like are reduced.

  7 and 8 show specific examples of the CCD image sensor 16 having a plurality of output amplifiers. In FIG. 7A, two output amplifiers 40 are connected to the output stage of a horizontal transfer path (HCCD) 51 arranged along the lower side of the light receiving unit 50. In the photographing mode, the signal charge transferred from the photoelectric conversion element (photodiode: PD) 50a of the light receiving unit 50 to the HCCD 51 is located in the odd number column and the signal charge output from the PD 50a located in the even number column. It is divided into signal charges output from the PD 50a and output as image signals from the output amplifiers 40 in parallel.

  On the other hand, in the correction data creation mode, as shown in FIG. 7B, the signal charges output from the same PD 50a are distributed to the output amplifiers 40 in time series by the HCCD 51, and from the output amplifiers 40, respectively. Output as an imaging signal. That is, the signal charge is transferred to one output amplifier 40 in the first charge transfer period, and the signal charge is transferred to the other output amplifier 40 in the second charge transfer period. Thus, by making the signal charge supply source to each output amplifier 40 the same in the correction data creation mode, the difference in the amount of received light due to the variation in the light receiving characteristics of the PD 50a can be eliminated, and more accurate linearity can be achieved. The correction LUT 14c can be created. The number of output amplifiers 40 connected to the HCCD 51 is not limited to two and may be three or more.

  In FIG. 8A, the light receiving unit 50 is divided into two regions in the horizontal direction, and an HCCD 51 is provided for each region. The signal charges output from the PDs 50a belonging to each group are horizontally transferred by the HCCDs 51 and output from the output amplifiers 40 as imaging signals. A line memory (LM) 60 is provided between the light receiving unit 50 and each HCCD 51. As shown in FIG. 8, the LM 60 transfers the signal charge input from each region of the light receiving unit 50 to one HCCD 51 corresponding to the vertical direction as it is, and as shown in FIG. It is also possible to transfer the charges to the other HCCD 51 after moving the charges in the horizontal direction. The LM 60 functions as a distribution unit that distributes signal charges to the HCCDs 51.

  In the shooting mode, as shown in FIG. 8A, the signal charge output from the PD 50a is transferred to the corresponding HCCD 51 via the LM 60 and output as an imaging signal from the output amplifier 40 of each HCCD 51. The

  On the other hand, in the correction data creation mode, as shown in FIG. 8B, the signal charges output from the same PD 50a located in either the left or right region are distributed to the left and right HCCDs 51 in time series by the LM 60. Then, it is output from the output amplifier 40 of each HCCD 51 as an imaging signal. That is, in the first charge transfer period, the signal charge output from the PD 50a is transferred as it is to the one HCCD 51 corresponding to the vertical direction by the LM 60, and in the second charge transfer period, it is the same as the first charge transfer period. The signal charge output from the PD 50 a is moved in the horizontal direction by the LM 60 and then transferred to the other HCCD 51. Thus, by making the signal charge supply source to each output amplifier 40 the same in the correction data creation mode, the difference in the amount of received light due to the variation in the light receiving characteristics of the PD 50a can be eliminated, and more accurate linearity can be achieved. The correction LUT 14c can be created. The area division of the light receiving unit 50 is not limited to two divisions and may be three or more divisions, and the HCCD 51 and the output amplifier 40 may be provided for each divided area.

  7 and 8, the HCCD 51 is arranged along one side of the light receiving unit 50. However, the present invention is not limited to this, and the HCCD 51 is arranged along two sides sandwiching the light receiving unit 50. The present invention can also be applied to cases.

  In the above-described embodiment, the QL value in the light shielding state is acquired by closing the mechanical shutter 17 in the correction data creation mode. However, the present invention is not limited to this, and as shown in FIG. An optical black (optical black: OB) region 70 in which the PD 50a is shielded by a metal layer or the like may be provided in the peripheral portion of the light source, and the QL value in a light shielding state may be acquired based on the signal charge from the OB region 70.

  In the above embodiment, a single plate system in which a single color filter is applied to each photodiode arranged in a two-dimensional manner in the CCD image sensor 16 is described as an example. However, the present invention is not limited to this. Instead of the CCD image sensor 16, the present invention is also applied to the case of a multi-plate system using a prism that separates subject light into a plurality of colors and a plurality of CCD image sensors that receive the separated colors of light. can do.

  In FIG. 10, the prism 80 splits the subject light incident through the diaphragm 19 into red (R) light, green (G) light, and blue (B) light. Three CCD image sensors 81 provided behind the prism 80 image each of R, G, and B subject light that has been split. A set of CDS 26, AGC 27, and A / D converter 28 is provided for each CCD image sensor 81, and the process of creating the linearity correction LUT 14c shown in FIG. That is, in the shooting mode (still image or moving image shooting mode), the linearity correction LUT 14c created for each CCD image sensor 81 (for each color) in the correction data creation mode is used and corresponds to each CCD image sensor 81. RAW data correction (corresponding to each color) is performed. As a result, image quality deterioration due to the characteristic difference between the individual CCD image sensors 81 is prevented, and color shift of the composite image is reduced.

  In the above embodiment, image data generated by performing linearity correction processing, digital signal processing, and compression processing on the RAW data output from the analog signal processing unit 29 at the time of shooting is recorded in the memory card 36. However, as shown in the flowchart of FIG. 11, RAW data obtained through imaging and analog signal processing is converted into a linearity correction LUT corresponding to the drive mode and the drive mode information (ISO sensitivity, drive). (Frequency, aperture value, readout method) may be recorded on the memory card 36. When the RAW data is read from the memory card 36 in the reproduction mode, the linearity correction LUT added to the RAW data is recorded in the EEPROM 14 and the linearity correction processing circuit 37 stores the RAW data. Correction processing is performed.

It is a block diagram which shows the electric constitution of the digital camera to which this invention is applied. It is a figure which shows an example of a drive mode. It is a graph which shows the measurement data and ideal curve of QL value with respect to the amount of received light. It is a flowchart which shows the process sequence of correction data creation mode. It is a flowchart which shows the process sequence which a linearity correction process circuit performs when not providing the linearity correction LUT. It is a block diagram which shows the structure of the analog signal processing part with respect to the CCD image sensor which has several output amplifier. It is a block diagram which shows the example of the CCD image sensor with which several output amplifier was connected to HCCD. It is a block diagram which shows the example of the CCD image sensor provided with the some HCCD. It is a block diagram which shows the example of the CCD image sensor provided with the optical black area | region. It is a block diagram which shows the example of a multi-plate CCD structure. It is a flowchart which shows the recording process of RAW data.

Explanation of symbols

10 Digital camera 14a LUT for gamma correction
14b Correction data calculation program 14c Linearity correction LUT
16 CCD image sensor 26 Correlated double sampling circuit 27 Auto gain control amplifier 28 A / D converter 29 Analog signal processing unit 31 Digital signal processing circuit 34 Compression / decompression processing circuit 36 Memory card 37 Linearity correction processing circuit 40 Output amplifier 50 Light receiving portion 50a Photo diode 51 Horizontal transfer path 70 Optical black region 80 Prism 81 CCD image sensor

Claims (8)

Imaging means for converting signal charges generated by a plurality of two-dimensionally arranged photoelectric conversion elements into imaging signals by an output amplifier;
Digital data conversion means for performing a predetermined process on the imaging signal output from the imaging means and converting it to digital data;
A received light amount control means for changing the received light amount of the imaging means in a plurality of stages so as to include a light shielding state;
An ideal straight line determined based on a predetermined pixel data included in the digital data generated in each received light amount set by the received light amount control means and a difference between the pixel data in the light shielding state and a predetermined exposure state Correction data calculating means for calculating linearity correction data that relates the difference amount and the pixel data;
An image pickup apparatus comprising: correction processing means for correcting the digital data based on the linearity correction data.   The imaging apparatus according to claim 1, wherein the correction data calculation unit calculates the pixel data for a received light amount not set by the received light amount control unit by linear interpolation.   Digital signal processing means for performing digital signal processing including gamma correction on the digital data, the linearity correction data calculated by the correction data calculation means, and gamma correction data used for the gamma correction; The imaging apparatus according to claim 1, wherein the imaging device is integrated.   The imaging means is a CCD image sensor including a plurality of output amplifiers, the correction data calculation means calculates the linearity correction data for each output amplifier, and the correction processing means 4. The imaging apparatus according to claim 1, wherein the digital data corresponding to an amplifier is corrected using the linearity correction data calculated for each output amplifier.   The imaging means is provided with a plurality of output amplifiers for each horizontal transfer path, and when the linearity correction data is calculated by the correction data calculation means, the horizontal transfer path is connected to the same photoelectric conversion element from the same photoelectric conversion element. 5. The image pickup apparatus according to claim 4, wherein the signal charge transferred through the horizontal transfer path is distributed to each of the output amplifiers in time series.   The imaging means is provided with a plurality of horizontal transfer paths to which the output amplifier is connected and a distribution means for distributing signal charges from the same photoelectric conversion element to the horizontal transfer paths. 5. The calculation unit according to claim 4, wherein when calculating the linearity correction data, the distribution unit distributes the signal charges output from the same photoelectric conversion element to the horizontal transfer paths in time series. Imaging device.   A prism for splitting incident light into a plurality of colors is provided, and the imaging unit is provided for each of the dispersed colors, and the correction data calculation unit calculates the linearity correction data for each color, 4. The imaging apparatus according to claim 1, wherein the correction processing unit corrects the digital data corresponding to each color using the linearity correction data calculated for each color. . 8. The imaging apparatus according to claim 1, further comprising recording means for recording the digital data together with the linearity correction data.

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