JP2004128653A - Imaging unit, sensitivity correction method, and correction coefficient calculation apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging unit capable of surely correcting dispersion in the sensitivity of each pixel of a solid-state imaging device with a simple configuration. <P>SOLUTION: Calculating a correction coefficient on the basis of an image signal obtained by imaging a uniform imaging object and multiplying the correction coefficient with an image signal obtained by imaging an optional imaging object can accurately correct sensitivity dispersion of each pixel of the solid-state imaging device. Further, calculating correction coefficients by each of a plurality of correction patterns decided by either or a combination of the lens position of an imaging lens and the aperture value of an aperture respectively, selecting the correction coefficient of the correction pattern corresponding to the lens position of the imaging lens and the aperture value of the aperture in imaging, and multiplying the selected correction coefficient with an image signal can more accurately correct the sensitivity dispersion through the use of the correction coefficient in response to the shape of a luminous flux of an imaging light made incident onto the solid-state imaging device. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an imaging apparatus, a sensitivity correction method, and a correction coefficient calculation apparatus and method, and is suitably applied to, for example, a digital still camera.
[0002]
[Prior art]
2. Description of the Related Art In recent years, solid-state imaging devices such as a CCD (Charge Coupled Device) imaging device and a CMOS (Complementary Metal Oxide Semiconductor) imaging device have been widely used as an imaging unit of a video camera and a digital still camera. In such a solid-state imaging device, an image signal is generated by arranging photoelectric conversion elements such as photodiodes in a lattice pattern and sequentially reading signal charges of each photoelectric conversion element obtained by photoelectric conversion. The solid-state imaging device has many advantages such as small size, light weight, no moving parts, and low power consumption (for example, see Patent Documents 1 and 2).
[0003]
[Patent Document 1]
JP-A-5-191644 (pages 2-3)
[0004]
[Patent Document 2]
JP-A-10-284708 (pages 2 to 4)
[0005]
[Problems to be solved by the invention]
Here, the solid-state imaging device has a sensitivity variation for each pixel due to the manufacturing method.
[0006]
FIG. 7 shows a cross section of the CCD image pickup device 100. A substrate 102 on which a plurality of photodiodes 101, transistors (not shown) and the like are arranged, an insulating layer 103 and a light-shielding layer 104 are formed in a layered form. An opening 105 is provided at a position corresponding to 101 through the insulating layer 103 and the light shielding layer 104, and a condenser lens 106 is provided outside each of the openings 105.
[0007]
In the CCD image pickup device 100, the image pickup light coming from an image pickup lens (not shown) is condensed by each condenser lens 106 and made incident on the corresponding photodiode 101, so that the amount of light incident on each photodiode 101 To improve the sensitivity of the CCD imaging device 100.
[0008]
Actually, in the manufacturing process of the CCD image pickup device 100, the resist applied to the light-shielding layer 104 is exposed to a predetermined pattern to form an etching mask and then etched (so-called photolithography processing) to thereby form the light-shielding layer 104 An opening 105 is formed by opening the insulating layer 103.
[0009]
Then, after a glass layer is provided on the upper surface of the light-shielding layer 104, a plurality of glass disks covering each of the openings 105 are formed by subjecting the glass layer to photolithography. Is heated and melted to form a substantially hemispherical condenser lens 106.
[0010]
In these manufacturing steps, the opening shape of the opening 105 and the shape of the condenser lens 106 are controlled to be uniform. However, in actuality, the shape becomes non-uniform due to various factors. The light beam shape incident on the photodiode 101 varies. The variation in the light flux shape causes an increase or decrease in the amount of light incident on each photodiode 101, which causes a sensitivity variation for each pixel. This sensitivity variation for each pixel appears as noise in the image signal, which causes a problem of deteriorating the image quality.
[0011]
The present invention has been made in consideration of the above points, and has an imaging apparatus, a sensitivity correction method, a correction coefficient calculation apparatus and a method capable of reliably correcting a variation in sensitivity of each pixel of a solid-state imaging device with a simple configuration. It is something to propose.
[0012]
[Means for Solving the Problems]
In order to solve such a problem, in the present invention, a solid-state imaging device that photoelectrically converts imaging light incident through an imaging lens and an aperture to generate an image signal, and an image of a predetermined uniform imaging target is captured by the solid-state imaging device. Correction coefficient storage means for storing a correction coefficient obtained by dividing the average value of each pixel value of the obtained image signal by each pixel value, and an image signal obtained by imaging an arbitrary imaging target. There is provided a sensitivity correction means for correcting a variation in sensitivity of each pixel of the solid-state imaging device by multiplying the correction coefficient read from the correction coefficient storage means.
[0013]
Then, a plurality of correction coefficients respectively corresponding to a plurality of correction patterns determined by one or a combination of the lens position of the imaging lens and the aperture value of the aperture are stored in the correction coefficient storage means, and the lens position of the imaging lens at the time of imaging is stored. The image signal is multiplied by a correction coefficient of a correction pattern corresponding to the aperture value of the aperture.
[0014]
In addition, the sensitivity variation of each pixel of the solid-state imaging device is corrected by dividing the average value of each pixel value of an image signal obtained by imaging a predetermined uniform imaging target with the solid-state imaging device by the pixel value. And a correction coefficient storage unit for storing the calculated correction coefficient in a correction coefficient storage unit provided in an imaging apparatus having a solid-state imaging device.
[0015]
Optical system control means for sequentially setting the lens position of the imaging lens and the aperture value of the aperture of the imaging device to representative values respectively set for a plurality of correction patterns determined by one or a combination of the lens position and the aperture value. The coefficient calculating means calculates a correction coefficient for each of the plurality of correction patterns, and the correction coefficient storing means stores the correction coefficients in the correction coefficient storing means for each of the plurality of correction patterns.
[0016]
By calculating a correction coefficient based on an image signal obtained by imaging a uniform imaging target, and multiplying the correction coefficient by an image signal obtained by imaging an arbitrary imaging target, each pixel of the solid-state imaging device Can be precisely corrected.
[0017]
Further, a correction coefficient for each of a plurality of correction patterns determined by one or a combination of the lens position of the imaging lens and the aperture value of the aperture is calculated, and a correction pattern corresponding to the lens position of the imaging lens and the aperture value of the aperture at the time of imaging. By multiplying the image signal by the correction coefficient, the sensitivity variation can be more precisely corrected using a correction coefficient corresponding to the shape of the light beam of the imaging light incident on the solid-state imaging device.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0019]
(1) Principle of Sensitivity Correcting Method According to the Present Invention First, the principle of the sensitivity correcting method for a solid-state imaging device according to the present invention will be described. As described above, since the variation in sensitivity of each pixel of the solid-state imaging device is caused by the variation of the light beam shape caused by the non-uniform aperture shape, the signal value of each pixel has a linear characteristic with respect to the amount of incident light. Have. For this reason, the sensitivity correction can also be performed by a linear operation (multiplication of the signal value of each pixel by the reciprocal (correction coefficient) of the sensitivity variation of each pixel).
[0020]
In order to calculate such a correction coefficient for each pixel, a subject having a uniform light amount is photographed in advance (hereinafter, this is referred to as calibration), and a signal value for each pixel of the solid-state image sensor (hereinafter, referred to as calibration) is obtained. , This is referred to as a calibration signal value) by dividing the average value by the calibration signal value of each pixel.
[0021]
(1-1) Correction of Monochrome Solid-State Image Sensor First, correction in a monochrome solid-state image sensor will be described. Assuming that the number of pixels of the solid-state imaging device is n and the calibration signal value of each pixel pi (i = 0, 1,..., N−1) is ai, the average calibration signal value A is obtained by the following equation.
[0022]
A = (a0 + a1 +... + An-1) / n (1)
[0023]
Further, the correction coefficient ki for each pixel pi is obtained by the following equation.
[0024]
ki = A / ai (i = 0, 1,..., n−1) (2)
[0025]
Assuming that the signal value of each pixel at the time of actual photographing is Si, as shown in the following equation, the corrected signal value Sci is obtained by multiplying the signal value Si of each pixel by a correction coefficient ki. Can be.
[0026]
Sci = Si * ki (i = 0, 1,..., N−1) (3)
[0027]
(1-2) Correction of Color Solid-State Image Sensor Next, correction of the color solid-state image sensor will be described. A color solid-state imaging device is configured by arranging color filters such as R (red), G (green), and B (blue) in a dot shape on the front surface of the solid-state imaging device. In this case, the average calibration signal value of each pixel of RGB varies depending on the spectrum of the light source, the spectral transmission characteristics of each color filter, and the spectral sensitivity characteristics of the solid-state imaging device.
[0028]
Therefore, in the correction of the color solid-state imaging device, the average calibration signal values Ar, Ag, and Ab of each of the RGB colors are obtained from the calibration signal values ari, agi, and abi of the pixels of each of the RGB colors using the following equation.
[0029]
Ar = (ar0 + ar1 +... + Arn-1) / n
Ag = (ag0 + ag1 +... + Agn-1) / n
Ab = (ab0 + ab1 +... + Abn-1) / n (4)
[0030]
The correction coefficients kri, kgi, and kbi for the pixels pri, pgi, and pbi of each of the RGB colors are obtained by the following equations.
[0031]
kri = Ar / ari
kgi = Ag / agi
kbi = Ab / abi (i = 0, 1,..., n−1) (5)
[0032]
Further, assuming that the signal values of the pixels of each of the RGB colors at the time of actual shooting are Sri, Sgi, and Sbi, respectively, the correction coefficients kri, which correspond to the signal values of the pixels of each color, Sri, Sgi, and Sbi, respectively, as shown in the following equations: By multiplying kgi and kbi, corrected signal values Scri, Scgi, and Scbi can be obtained.
[0033]
Scri = Sri * kri
Scgi = Sgi * kgi
Scgi = Sri * kri (i = 0, 1,..., N−1) (6)
[0034]
(2) Overall Configuration of Digital Still Camera Next, the configuration of a digital still camera using the present invention will be described. In FIG. 1, reference numeral 1 denotes a digital still camera as an imaging apparatus as a whole, and guides imaging light L incident from a subject to a color CCD 4 via an imaging lens 2 including lenses 2A, 2B, and 2C.
[0035]
At this time, an MCU (Micro Control Unit) 7 of the digital still camera 1 controls the aperture value of the aperture 3 in accordance with an operation by a user or an automatic exposure control process, thereby adjusting the light amount of the imaging light L incident on the color CCD 4. The focal length and the focus position of the imaging lens 2 are controlled by controlling the positions of the lenses 2A, 2B and 2C according to the zoom operation and the auto focus control process by the user.
[0036]
The color CCD 4 generates an image signal S1 by sequentially reading out signal charges for each pixel obtained by photoelectrically converting the imaging light L in accordance with a readout clock supplied from the clock generator 8, and generates an image signal S1. 5 The analog / digital converter 5 converts the image signal S1 into a digital signal to generate a digital video signal D1 and supplies the digital video signal D1 to the coefficient multiplier 6.
[0037]
Here, a correction coefficient EEPROM 10 as a correction coefficient storage means stores correction coefficients kri, pri, pgi, and pbi for each pixel pri, pgi, and pbi of the color CCD 4 calculated by a correction coefficient calculation device (described later) in a manufacturing process of the digital still camera 1. A correction coefficient table storing kgi and kbi is stored.
[0038]
In practice, in the digital still camera 1, the shape of the light flux of the imaging light L incident on each pixel of the color CCD 4 includes the incident angle of the imaging light L, the focal length of the imaging lens 2, and the aperture value of the aperture 3 as shown in FIG. It changes variously according to.
[0039]
For this reason, in the digital still camera 1, as shown in FIG. 3, a plurality of correction patterns each consisting of a combination of the focal length of the imaging lens 2 and the aperture value of the aperture 3 are set (that is, correction patterns a to i). A correction coefficient table for each is stored in the correction coefficient ROM 10.
[0040]
The ROM address generator 9 acquires the focal length of the imaging lens 2 and the aperture value of the aperture 3 from the MCU 7, and based on the focal length and the aperture value, a correction coefficient corresponding to the current state of the imaging lens 2 and the aperture 3. A table is selected from the correction coefficient ROM 10. The ROM address generator 9 serving as the sensitivity correction unit sequentially supplies the ROM addresses corresponding to the pixels pri, pgi, and pbi from which the signal charge is being read to the sensitivity coefficient EEPROM 10, thereby obtaining the correction coefficient for the pixel Pi during the read. kri, kgi, and kbi are sequentially read from the correction coefficient EEPROM 10 and supplied to the coefficient multiplying unit 6. The coefficient multiplying unit 6 serving as a sensitivity correction unit multiplies the image signal S1 by the sensitivity correction coefficients kri, kgi, and kbi sequentially supplied from the correction coefficient EEPROM 10, corrects the image signal S1, and outputs the corrected signal to the outside. The sensitivity variation of each pixel of the CCD 4 is corrected.
[0041]
(3) Calculation of Correction Coefficient Next, calculation of the correction coefficient by the correction coefficient calculation device will be described. As shown in FIG. 4, in the manufacturing process of the digital still camera 1, first, the correction coefficient calculating device 20 is connected to the digital still camera 1, and the light diffusing plate 21 is arranged at a predetermined distance in front of the imaging lens 2. . In FIG. 4, the ROM address generator 9 is omitted.
[0042]
Subsequently, the back surface of the light diffusing plate 21 is illuminated by the illumination device 22 to irradiate the imaging lens 2 with uniform diffused light. In this state, the CPU (not shown) of the correction coefficient calculation device 20 executes the correction coefficient calculation processing shown in FIG.
[0043]
That is, the CPU of the correction coefficient calculation device 20 as the coefficient calculation means enters the start step of the routine RT1, moves to step SP1, selects one of the correction patterns a to i shown in FIG. Move on to
[0044]
Here, as shown in FIG. 3, representative values of the focal length and the aperture value are set in each correction table. In step SP2, the CPU of the correction coefficient calculation device 20 controls the MCU 7 of the digital still camera 1, sets the focal length of the imaging lens 2 and the aperture value of the aperture 3 to the representative value of the selected correction pattern, and sets the next step SP3 Move on to
[0045]
In step SP3, the CPU of the correction coefficient calculation device 20 controls the clock generator 8 of the digital still camera 1 to start photographing the light diffusing plate 21, and thereby the digital video signal D1 output from the analog / digital converter 5 Are stored in a RAM (not shown) as calibration signal values ari, agi, and abi, and the flow advances to next step SP4.
[0046]
In step SP4, the CPU of the correction coefficient calculation device 20 reads the calibration signal values ari, agi, and abi stored in the RAM, and calculates the average calibration signal values Ar, Ag, and Ab using Expression (4). Move to the next step SP5.
[0047]
In step SP5, the CPU of the correction coefficient calculation device 20 uses the equation (5) to calculate the correction coefficient kr for the color CCD 4 from the calibration signal values ari, agi, and abi and the calculated average calibration signal values Ar, Ag, and Ab. , Kgi and kbi are calculated. Then, the CPU of the correction coefficient calculation device 20 writes the calculated correction coefficients kri, kgi, and kbi into the correction coefficient EEPROM 10 of the digital still camera 1 via an EEPROM interface (not shown) as a correction coefficient storage unit. Move to step SP6.
[0048]
In step SP6, the CPU of the correction coefficient calculation device 20 determines whether the correction coefficients kri, kgi, and kbi have been calculated for all the correction patterns. If it is determined in step SP6 that the correction coefficients kri, kgi, and kbi have not been calculated for all the correction patterns, the CPU of the correction coefficient calculation device 20 returns to step SP1, selects the next correction pattern, and selects step SP2. Execute the following.
[0049]
On the other hand, if it is determined in step SP6 that the correction coefficients kri, kgi, and kbi have been calculated for all the correction patterns, the CPU of the correction coefficient calculation device 20 proceeds to step SP7 and ends the correction coefficient calculation processing.
[0050]
(4) Operation and Effect In the configuration described above, the correction coefficient calculation device 20 sequentially sets the focal length of the imaging lens 2 of the digital still camera 1 and the aperture value of the aperture 3 to the representative values of the correction patterns a to i. The uniform light is photographed, and correction coefficients kri, kgi, and kbi, which are the reciprocals of the sensitivity variation of each pixel of the color CCD 4, are determined for each of the correction patterns a to i based on the calibration signal values ari, agi, and abi obtained at this time. And writes this in the correction coefficient EEPROM 10 of the digital still camera 1.
[0051]
Then, at the time of shooting, the MCU 7 of the digital still camera 1 selects a correction pattern corresponding to the focal length of the imaging lens 2 and the aperture value of the aperture 3, and sets correction coefficients kri, kgi, and kbi corresponding to the selected correction pattern. By reading from the correction coefficient table in the correction coefficient EEPROM 10 and multiplying it by the image signal S1, it is possible to correct the sensitivity variation of each pixel of the color CCD 4.
[0052]
Here, a correction coefficient is obtained for each of the correction patterns a to i, which is a combination of the focal length of the imaging lens 2 and the aperture value of the aperture 3, and an image is formed using the correction coefficients corresponding to the focal length and the aperture value at the time of shooting. By correcting the signal S1, sensitivity variations can be precisely corrected using a correction coefficient adapted to the actual light beam shape incident on the color CCD 4.
[0053]
(5) Other Embodiments In the above-described embodiment, the correction coefficient is obtained by forming a correction pattern by combining the focal length of the imaging lens 2 and the aperture value of the aperture 3. However, the present invention However, the present invention is not limited to this, and a correction coefficient may be obtained by forming a correction pattern using a combination of the focal length of the imaging lens 2 in addition to the focal length and the aperture value. In this case, a correction coefficient further adapted to the actual light beam shape can be obtained, and sensitivity variations can be corrected more precisely.
[0054]
Further, a correction pattern may be configured by a combination of the focal length and the focus position of the imaging lens 2 or a combination of the focus position and the aperture value of the aperture 3. Further, any one of the focal length, the focus position, and the aperture value may be used. May be formed based on the correction pattern. In short, the sensitivity variation can be precisely corrected by using a correction coefficient according to the shape of the light beam incident on the CCD.
[0055]
In the above-described embodiment, the correction coefficient is calculated in the manufacturing process of the digital still camera 1 and written in the correction coefficient EEPROM 10. However, the present invention is not limited to this. You may make it calculate.
[0056]
That is, in FIG. 6 in which the same parts as in FIG. 1 are denoted by the same reference numerals, reference numeral 30 denotes a digital still camera of another embodiment as a whole, which has a correction coefficient calculation unit 31 and is replaced with a correction coefficient EEPROM 10. It has the same configuration as the digital still camera 1 shown in FIG.
[0057]
In this case, immediately before photographing using the digital still camera 30, the light diffusing plate 21 is arranged at a predetermined distance in front of the imaging lens 2, and the back surface of the light diffusing plate 21 is illuminated by the illumination device 22, so that the imaging lens 2 Is irradiated with uniform diffused light.
[0058]
In this state, the correction coefficient calculation unit 31 sequentially selects the correction patterns shown in FIG. 3, and sets the focal length of the imaging lens 2 and the aperture value of the aperture 3 to the representative values of the selected correction patterns. Then, the correction coefficient calculation unit 31 controls the clock generator 8 to start photographing the light diffusing plate 21, and converts the digital video signal D1 output from the analog / digital conversion unit 5 into calibration signal values ari, agi, and abi. , Correction coefficients kri, kgi and kbi are calculated.
[0059]
However, in this case, since it is difficult to obtain the average calibration signal values Ar, Ag, and Ab in real time, the expected minimum signal strengths Armin, Agmin, and Abmin are set in advance instead. The correction coefficient calculation unit 31 calculates the correction coefficients kri, kgi, and kbi by dividing the minimum signal strengths Armin, Agmin, and Abmin by the calibration signal values ari, agi, and abi, respectively, and stores them in the correction coefficient RAM 32. .
[0060]
Then, at the time of actual photographing, the digital still camera 30 can correct the sensitivity variation of each pixel of the color CCD 4 by multiplying the image signal S1 by the correction coefficients kri, kgi, and kbi read from the correction coefficient RAM 32.
[0061]
Furthermore, in the above-described embodiment, the sensitivity variation for each pixel of the CCD is corrected inside the digital still camera. However, the present invention is not limited to this. The sensitivity variation for each pixel may be corrected by the processing device.
[0062]
In this case, first, a digital still camera is used to photograph a subject having a uniform light amount, and the obtained image data is processed on a personal computer to calculate a correction coefficient. Then, if the image data obtained by actual photographing is corrected on the personal computer using the correction coefficient, the sensitivity variation for each pixel of the CCD can be corrected in the same manner as in the above-described embodiment. In this case, the image data output from the digital still camera needs to be in a data format in which data for each pixel such as RAW data or a lossless compression method is recorded as it is, such as JPEG (Joint Picture Coding Experts Group). The data format of the lossy compression method is inappropriate.
[0063]
Further, in the above-described embodiment, a case has been described in which the present invention is applied to a digital still camera. However, the present invention is not limited to this, and is applicable to various imaging devices using solid-state imaging devices, such as digital video cameras and scanners. can do.
[0064]
【The invention's effect】
As described above, according to the present invention, a correction coefficient is calculated based on an image signal obtained by imaging a uniform imaging target, and the correction coefficient is multiplied by an image signal obtained by imaging an arbitrary imaging target. By doing so, it is possible to precisely correct the sensitivity variation of each pixel of the solid-state imaging device.
[0065]
Further, a correction coefficient for each of a plurality of correction patterns determined by one or a combination of the lens position of the imaging lens and the aperture value of the aperture is calculated, and a correction pattern corresponding to the lens position of the imaging lens and the aperture value of the aperture at the time of imaging. By multiplying the image signal by the correction coefficient, the sensitivity variation can be more precisely corrected using a correction coefficient corresponding to the shape of the light beam of the imaging light incident on the solid-state imaging device.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the overall configuration of a digital still camera according to the present invention.
FIG. 2 is a schematic diagram used to describe a change in the shape of a light beam incident on a CCD.
FIG. 3 is a graph used for explaining a correction table selection according to a focal length and an aperture value.
FIG. 4 is a block diagram used for explaining calculation of a correction coefficient.
FIG. 5 is a flowchart illustrating a correction coefficient calculation process.
FIG. 6 is a block diagram illustrating an overall configuration of a digital still camera according to another embodiment.
FIG. 7 is a schematic diagram illustrating a structure of a CCD.
[Explanation of symbols]
1, 30 digital still camera, 2 imaging lens, 3 aperture, 4 CCD, 5 analog / digital conversion unit, 6 coefficient multiplication unit, 7 MCU, 8 clock Generator 9 ROM address generator 10 Correction coefficient EEPROM 20 Correction coefficient calculator 31 Correction coefficient calculator 32 Correction coefficient RAM

Claims (6)

A solid-state imaging device that photoelectrically converts imaging light incident through an imaging lens and an aperture to generate an image signal;
Correction coefficient storage means for storing a correction coefficient obtained by dividing an average value of each pixel value of an image signal obtained by imaging a predetermined uniform imaging target with the solid-state imaging device by each of the pixel values,
A sensitivity correction unit configured to correct a sensitivity variation of each pixel of the solid-state imaging device by multiplying the image signal obtained by imaging an arbitrary imaging target by a correction coefficient read from the correction coefficient storage unit. An imaging device, comprising: The correction coefficient storage means stores a plurality of correction coefficients respectively corresponding to a plurality of correction patterns determined by one or a combination of the lens position of the imaging lens and the aperture value of the aperture,
The sensitivity correction means multiplies the image signal by the correction coefficient of the correction pattern corresponding to the lens position of the imaging lens and the aperture value of the aperture when the arbitrary imaging target is photographed. 2. The imaging device according to 1. For an image signal obtained by imaging an arbitrary imaging target with a solid-state imaging device, an average value of pixel values of an image signal obtained by imaging a predetermined uniform imaging target with the solid-state imaging device is calculated for each of the image signals. A sensitivity correction method, wherein a sensitivity variation of each pixel of the solid-state imaging device is corrected by multiplying a correction coefficient obtained by dividing each pixel value. In order to correct the sensitivity variation of each pixel of the solid-state imaging device, the average value of each pixel value of an image signal obtained by imaging a predetermined uniform imaging target with the solid-state imaging device is divided by the pixel value. Coefficient calculating means for calculating a correction coefficient of
A correction coefficient storage unit configured to store the calculated correction coefficient in a correction coefficient storage unit provided in an imaging device having the solid-state imaging device. Optical system control means for sequentially setting the lens position of the imaging lens and the aperture value of the aperture of the imaging device to representative values respectively set for a plurality of correction patterns determined by one or a combination of the lens position and the aperture value. With
The coefficient calculating means calculates the correction coefficient for each of the plurality of correction patterns,
5. The correction coefficient calculation device according to claim 4, wherein said correction coefficient storage means stores said correction coefficient for each of said plurality of correction patterns in said correction coefficient storage means. An average value calculation step of calculating an average value of each pixel value of an image signal obtained by imaging a predetermined uniform imaging target with a solid-state imaging device,
A coefficient calculating step of calculating a correction coefficient for correcting a sensitivity variation of each pixel of the solid-state imaging device by dividing the calculated average value by each of the pixel values. Calculation method.

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