Imaging device, control method thereof, program, and storage medium

Abstract

To improve the accuracy of an evaluation value of white balance in an imaging apparatus that can control exposure for every area.SOLUTION: An imaging apparatus 100 has an imaging unit 101, an exposure control unit 104, an extraction unit 102, a calculation unit 105, and a correction unit 106. The imaging unit 101 picks up an image of a subject to create an image, and its exposure is controlled by the exposure control unit 104 for every pixel group composed of one or more pixels. The extraction unit 102 extracts an achromatic color area from the image picked up by the imaging unit 101, and a first calculation unit calculates a first evaluation value for each of the one or more pixel groups included in the extracted area. The first evaluation values are weighted based on the exposure of the pixel groups, and a second calculation unit calculates a second evaluation value in the extracted area. The correction unit 106 corrects the image picked up by the imaging unit 101 based on the second evaluation value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an imaging device, a control method thereof, a program, and a storage medium.

Background Art

[0002] Conventionally, a technique is known in which an area is divided into a plurality of areas, and a correction value for white balance is obtained from an area with the highest luminance, thereby improving the accuracy of an evaluation value for white balance (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem to be solved by the present invention is to improve the accuracy of an evaluation value for white balance in an imaging device capable of controlling exposure for each area.

Means for Solving the Problems

[0005] To solve the above problems, an imaging device according to an aspect of the present invention includes an imaging unit that captures an image of a subject to generate an image, and pixels of the imaging unit or For each pixel group gain is An exposure control unit that controls, an extraction unit that extracts achromatic regions from the image, and a first calculation unit that calculates a first evaluation value for each pixel group included in the extraction unit the evaluation area determined based on the area Included in the pixel or And a first calculation unit that calculates a first evaluation value for each pixel group, the pixel or Based on the pixel groups per Of the gain controlled by the exposure control unit From the first evaluation values weighted respectively, the evaluation areaA second calculation unit that calculates a second evaluation value in the above, and a correction unit that corrects the image based on the second evaluation value calculated by the second calculation unit. and the first evaluation value and the second evaluation value are evaluation values of any one of white balance, hue, and saturation It is characterized by this.

Effect of the Invention

[0006] According to the present invention, the accuracy of the evaluation value of white balance can be further improved.

Brief Description of the Drawings

[0007]

Figure 1

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Figure 8

Figure 9

Mode for Carrying Out the Invention

[0008] Hereinafter, with reference to the accompanying drawings, embodiments for carrying out the present invention will be described in detail. The described embodiments are merely examples of the means for realizing the present invention and should be appropriately modified or changed according to the configuration of the apparatus to which the present invention is applied and various conditions. The present invention is not limited to the following embodiments. Also, a part of each of the embodiments described later may be appropriately combined and configured.

[0009] <Embodiment 1> In this embodiment, an achromatic region is extracted from an image, and an evaluation region for calculating an evaluation value of white balance is determined. A white balance evaluation value 1 is calculated for each pixel group in the evaluation region, and the white balance evaluation value 1 is weighted according to the exposure for each pixel group. A white balance evaluation value 2 is determined by weighted-averaging the weighted white balance evaluation values 1 within the evaluation region. The white balance of the entire image is corrected according to the value of the white balance evaluation value 2. Note that although white balance is described in this embodiment, it may be an evaluation value related to color correction for correcting not only white balance but also chroma or hue.

[0010] (Functional configuration) FIG. 1 is a block diagram showing a configuration example of an imaging device 100 according to the present embodiment. Among the functional blocks shown in FIG. 1, for the functions realized by software, programs for providing the functions of the respective functional blocks are stored in a memory such as a ROM (Read Only Memory). Then, the program is read into a RAM (Random Access Memory) and executed by a CPU (Central Processing Unit) to be realized. For the functions realized by hardware, for example, by using a predetermined compiler, a dedicated circuit may be automatically generated on an FPGA from a program for realizing the functions of the respective functional blocks. FPGA is an abbreviation for Field Programmable Gate Array. Also, a gate array circuit may be formed in the same manner as the FPGA and realized as hardware. Alternatively, it may be realized by an ASIC (Application Specific Integrated Circuit). Note that the configuration of the functional blocks shown in FIG. 1 is an example, and a plurality of functional blocks may constitute one functional block, or any one functional block may be divided into blocks that perform a plurality of functions.

[0011] In FIG. 1, the imaging device 100 includes an imaging unit 101, an extraction unit 102, a region determination unit 103, an exposure control unit 104, a calculation unit 105, a correction unit 106, and a communication unit 107.

[0012] The imaging unit 101 includes a lens group 101a, an imaging element 101b, and an amplifier 101c.

[0013] The imaging unit 101 captures an image of a subject based on light from the subject and generates an image. The lens group 101a condenses the light from the subject onto the light-receiving surface of the imaging device 101b. In FIG. 1, only one lens is shown, but it may be provided with a plurality of lenses. For example, it may include a zoom lens, a focus lens, an anti-shake lens, and the like. The imaging device 101b converts the light from the subject into an electrical signal for each pixel and outputs it. The imaging device 101b can change the exposure conditions for each pixel group (i.e., for each of a plurality of divided regions). The imaging device 101b is, for example, a semiconductor device such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor and peripheral circuits. The amplifier 101c amplifies the electrical signal output from the imaging device 101b and outputs an imaging signal. The amplification factor of the amplifier 101c can be changed for each pixel group. An image processing unit (not shown) performs image processing including development processing on the video signal, which is a digital signal. The video signal is converted into image data (such as JPEG format). At this time, the video signal having RGB color information output from the amplification unit 101c is converted into a color difference signal such as YUV format and digitally signal-processed. Finally, the video signal is converted (developed) into image data, and the image data is output via the image output unit 205. The development processing includes white balance correction, saturation correction, color tone correction (hue correction), sharpness correction, gamma correction, gradation correction, and the like, which will be described later. The white balance is not a fixed development parameter, but a white balance evaluation value (development parameter) is calculated from the video signal. White balance correction is performed by applying the calculated development parameter. In addition, the image processing unit (not shown) can calculate luminance information and color difference information by performing YUV conversion. Further, the image processing unit performs brightness correction on the image information corresponding to each pixel group based on the exposure conditions for each pixel group.

[0014] The extraction unit 102 detects an image area determined to be white from the image signal (color signal) A / D converted by an image processing unit (not shown). For example, it detects, as a white area, an image area of a pixel group whose color evaluation value calculated based on the image signal (RGB signal) obtained from each pixel group of the imaging element 101b is included in the evaluation value within a predetermined white range. Hereinafter, the "white area" shall include not only white but also gray, that is, achromatic areas.

[0015] The area determination unit 103 determines an area for calculating an evaluation value for correcting white balance with respect to the image signal output from an image processing unit (not shown). FIG. 2 is an example of an image captured by the imaging device 100 according to the present embodiment. The image 201 is an entire image for correcting white balance. The evaluation area 202 is an area for calculating a white balance evaluation value 2 for correcting the white balance of the image 201. The evaluation area 202 may be the same area as the image 201, or may be determined based on the white area extracted by the extraction unit 102. The minimum exposure area 203 is an image area corresponding to the above-described pixel group, and is the minimum area where the exposure condition can be set for each area. The evaluation area 202 is preferably composed of a plurality of minimum exposure areas 203. In the present embodiment, the case where there is one evaluation area 202 will be described, but two or more evaluation areas may be determined as in Embodiment 3 described later.

[0016] The exposure control unit 104 controls the exposure such as the exposure time and the analog gain for each pixel group. It assigns exposure conditions to each minimum exposure region and controls the imaging device 101a. In order to improve the dynamic range with respect to the brightness of the subject, the exposure control unit 104 sets the exposure conditions so that, for example, the average luminance value within the minimum exposure region 203 becomes the median value of the outputtable data gradation. Note that, in the pixel group corresponding to the evaluation region 202 extracted by the extraction unit 102 or determined by the region determination unit, control is performed so that the exposure time is longer and the analog gain is lower than those of the other pixel groups that have not been extracted or determined. Thereby, in the calculation of the white balance evaluation value described later, it is possible to obtain an evaluation value with a small amount of noise amplification, and it becomes possible to perform more accurate white balance correction.

[0017] The calculation unit 105 calculates the white balance evaluation value 2 in the evaluation region 202 determined by the region determination unit 103. More specifically, the white balance evaluation value 1 is calculated for each minimum exposure region 203 within the evaluation region 202, and the white balance evaluation value 2 is calculated according to the weighting based on the exposure conditions assigned to each minimum exposure region 203. Note that the calculation unit 105 may be divided into a first calculation unit and a second calculation unit, which are configured to calculate the white balance evaluation value 1 and the white balance evaluation value 2, respectively.

[0018] The correction unit 106 corrects the white balance of the entire image based on the white balance evaluation value 2 calculated by the calculation unit 105. More specifically, the white balance of the image is corrected by controlling the digital gain of a plurality of color signals in the image 201 according to the white balance evaluation value 2. The color signals referred to here are RGB signals (signals decomposed into three colors of R: red, G: green, and B) and YUV signals (signals represented by one luminance and two color differences of Y: luminance, U: difference of blue color component, and V: difference of red color component), etc. Note that the correction unit 106 is not limited to white balance correction, and may perform saturation correction, color tone correction, sharpness correction, gamma correction, gradation correction, etc.

[0019] The extraction unit 102, the region determination unit 103, the calculation unit 105, and the correction unit 106 may be included in the aforementioned image processing unit (not shown).

[0020] The communication unit 107 transmits the image captured by the imaging device 100 through communication via a network 108 with an external device (not shown) such as a client device or a server. Also, through the same communication, a control signal from the external device may be received by the CPU, and control related to each part of the imaging device 100 may be performed.

[0021] (Operation description) Next, with reference to FIG. 3, the white balance (WB) correction according to the present embodiment will be described. There are various methods for WB correction, but in the present embodiment, a WB correction using a method of detecting a white region from an image and determining a white balance evaluation value so as to make the image region white will be described. FIG. 3 is a flowchart showing the correction process of the white balance in the present embodiment. The flowchart of FIG. 3 illustrates a processing procedure in which each processing block is controlled and executed by a control unit (not shown) in the imaging device 100. It is realized by expanding a program stored in a memory (ROM) of the control unit into a memory (RAM) and executed by the CPU.

[0022] In step S301, the extraction unit 102 extracts an achromatic region with reference to the image signal that has become digital data by an image processing unit (not shown). The region information of the extracted region is output to the region determination unit 103.

[0023] In step S302, the region determination unit 103 determines the evaluation region 202 based on the region information output from the extraction unit 102. The evaluation region 202 may be all of the output region information as the evaluation region 202, or a part of it may be the evaluation region 202. When the region extracted by the extraction unit 102 is used as the evaluation region 202 as it is, it moves to step S303 without passing through step S302. That is, the extraction unit 102 may be configured to be included in the region determination unit 103. Also, the user or designer may specify the evaluation region 202. Note that it is preferable to set the evaluation region 202 outside the moving object region. The moving object region calculates the amount of luminance change between frames for each minimum exposure region, and when the luminance change exceeds the threshold, it is determined as the moving object region. In the moving object region, in order to suppress the motion blur of the moving object, it is preferable to set the exposure time to a short second. Conversely, in the non-moving object region, since there is no moving object, there is no need to suppress blur, and the exposure time can be set to a long second. Therefore, it is possible to set the gain lower by the amount of the long second exposure time set, the SNR of the non-moving object region is improved, and it is possible to appropriately calculate the evaluation value.

[0024] In step S303, the exposure conditions of the pixel group corresponding to the minimum exposure region 203 in the evaluation region 202 determined in step S302 are referred to. When all of the referred exposure conditions are the same exposure condition, since it is not necessary to weight the white balance evaluation value 1 for each exposure condition, it moves to step S306, calculates the white balance evaluation value 2 in the evaluation region 202, and ends. When there is a minimum exposure region 203 having different exposure conditions in the evaluation region 202, it proceeds to step S304.

[0025] In step S304, the calculation unit 105 calculates the white balance evaluation value 1 for each minimum exposure region 203.

[0026] In step S305, for the white balance evaluation value 1 calculated in step S304, weighting is performed with reference to the exposure conditions of the pixel group corresponding to each minimum exposure region 203 in the evaluation region 202. The weighting value for each minimum exposure region 203 may be determined by preparing a table of the weighting value and the exposure conditions, or may be calculated using the set value of the exposure conditions. In that case, the calculation unit 105 calculates the weighting value.

[0027] Figure 4 shows a table for obtaining the weighting value α from the exposure condition G. When the exposure condition G is greater than G1 and less than or equal to G2, the weighting value α is A1, and when the exposure condition G is greater than G2 and less than or equal to G3, the weighting value α is A2. In this way, the weighting value α is set for the range of the exposure conditions to determine the weighting value from the exposure conditions. In the case of Figure 4, up to the nth condition is set so that when the exposure condition G is greater than Gn and less than or equal to G(n + 1), the weighting value α is An.

[0028] The following formula (1) is a formula for obtaining the weighting value α from the exposure condition X. Although a specific example of the following formula (1) will be described later, the following formula (1) is a function that returns the weighting value α when the set value of the exposure condition G is input. α = f(X) Formula (1)

[0029] In step S306, the white balance evaluation value 2 in the evaluation region 202 is calculated by the following formula (2) using the white balance evaluation value 1 in each minimum exposure region 203 calculated in step S304 and the weighting value obtained in S306.

[0030]

Equation

[0031] W is the white balance evaluation value 2 and is the calculation result of a mathematical formula. α is a weighting value determined from the exposure conditions. i is a number indicating the i-th minimum exposure area 203 in the evaluation value calculation area 202, and α_i is a weighting value determined from the exposure conditions of the pixel group corresponding to the i-th minimum exposure area. W_i is the i-th white balance evaluation value 1 calculated in step 302 and corresponds to the i-th minimum exposure area 203 respectively. The white balance evaluation value 2 can be obtained by weighted average using the white balance evaluation value 1 calculated in step S304 and the weighting value obtained in step S305. Note that when all the exposure conditions in the evaluation area 202 are the same in step S303, the white balance evaluation value 1 is not weighted, so the average value of the white balance evaluation value 1 is calculated as the white balance evaluation value 2.

[0032] In step S307, based on the white balance evaluation value 2 calculated in step S306, the white balance of the entire image is corrected by the correction unit 106.

[0033] Using FIG. 5, the white balance correction in this embodiment will be described more specifically. As a premise, it is assumed that there are four minimum exposure areas 203 in the evaluation area 202, and the gain values of the pixel groups corresponding to each are 0, 1, -1, 0 respectively. Also, assume that formula (1) is the following formula (3).

[0034]

Number

[0035] G indicates the gain value. In this case, the weighting values of the white balance evaluation value 1 in each minimum exposure area 203 are calculated as 1, 0.5, 2, 1 respectively by the calculation unit 105.

[0036] Here, the weighting value is determined using the analog gain as the exposure condition, but other exposure conditions (e.g., shutter speed) may also be used. Assuming that the white balance evaluation values 1 of each minimum exposure region 203 are W1, W2, W3, and W4 respectively, the white balance evaluation value 2 is expressed by the following formula (4) according to the weighting value α and formula (3).

[0037] [Number]

[0038] Using the white balance evaluation value 2 calculated as described above, the correction unit 106 corrects the white balance of the entire screen as described above.

[0039] In this embodiment, the case where the evaluation region 202 is composed of a plurality of minimum exposure regions 203 has been described. However, a supplementary explanation will be given for the case where the regions of the evaluation region 202 and the minimum exposure region 203 do not match. At this time, it is preferable to change the size of the evaluation region 202 or the size of the minimum exposure region 203 for the pixels where the regions of the evaluation region 202 and the minimum exposure region 203 do not match. As a result, since the evaluation region 202 is composed of a plurality of minimum exposure regions 203, it is possible to appropriately calculate the evaluation value. Also, when the size cannot be changed, it is desirable to exclude the pixels not included in the evaluation region 202 within the minimum exposure region 203 during the calculation of the evaluation value. Further, for the minimum exposure region 203 that is only partially included in the evaluation region 202, the ratio of the number of pixels included in the evaluation region 202 is multiplied by the number of pixels in the minimum exposure region 203 to change the weighting for each minimum exposure region 203. By these processes, it is possible to appropriately calculate the evaluation value even when the regions of the evaluation region 202 and the minimum exposure region 203 do not match.

[0040] It is preferable that the minimum exposure area 203 included in the evaluation area 202 does not exceed the range where the RGB luminance in the image is below the minimum value or above the maximum value. When it is below the minimum value, change the exposure condition to increase the exposure amount. When it is above the maximum value, decrease the exposure amount. By changing the exposure amount in this way, video data that is not saturated in the RGB pixels can be used, so that the evaluation value can be calculated appropriately. After calculating the evaluation value, perform brightness correction to correct the changed exposure amount.

[0041] According to the present embodiment, even when a plurality of pixel groups with different exposure conditions are mixed in the evaluation area for white balance, a suitable white balance evaluation value can be calculated. Therefore, the accuracy of white balance correction is improved.

[0042] <Embodiment 2> In this embodiment, a method for calculating a white balance evaluation value different from that in Embodiment 1 will be described. In this embodiment, a plurality of minimum exposure areas in the evaluation area are classified according to the exposure conditions, and a weighting value is determined for each classification. Note that the functional configuration of the imaging device 100 according to this embodiment is the same as that in Embodiment 1 described above, so the description thereof will be omitted.

[0043] Hereinafter, with reference to FIGS. 6, 7, and 8, a method for obtaining a white balance evaluation value of an image in this embodiment will be described.

[0044] FIG. 6 is an example of an image captured by the imaging device 100 according to this embodiment. In the image 601, the evaluation area 602 is determined in the same manner as in Embodiment 1. There are a plurality of minimum exposure areas 603 in the evaluation area 602, and in this embodiment, a case where the exposure conditions in each area of the minimum exposure area 603 are different will be described. The low gain area 604 and the high gain area 605 are determined by classifying the minimum exposure area 603 in the white balance correction process described later.

[0045] FIG. 7 is a flowchart showing white balance correction processing in the present embodiment. In the present embodiment, step S701, step S702, step S703, step S707, and step S708 are the same as those in the first embodiment, and thus the description thereof is omitted.

[0046] In step S704, the minimum exposure region 603 within the evaluation region 602 is classified according to the exposure conditions of the pixel group corresponding to the minimum exposure region 603. In the present embodiment, classification is performed using gain as the exposure condition, but classification may also be performed using the exposure time. FIG. 6 shows the evaluation region 602 after classification. The low gain region 604 indicates the minimum exposure region 603 having a gain lower than a predetermined threshold, and the high gain region 605 indicates the minimum exposure region 603 having a gain higher than the predetermined threshold. This predetermined threshold can be set to an average value, a median value, etc. among the analog gains set in the image 601, so that the region can be roughly divided into two. Also, instead of the set value in the image 601, the average value or median value may be used for the analog gain that can be set by the imaging device 100, or may be arbitrarily set by the designer or user. In the present embodiment, classification is performed into two regions with one predetermined threshold, but the threshold may be two or more. In that case, the minimum exposure region 603 is classified into three or more regions. The regions classified in the present embodiment are referred to as gain regions.

[0047] In step S705, the calculation unit 106 calculates the white balance evaluation value 1 for each of the classified gain regions.

[0048] In step S706, weighting is performed on the white balance evaluation value 1 for each gain region calculated in step S705. As the weighting value, the weighting value determined for each gain region as shown in FIG. 8 may be used, or it may be determined from the average value of the exposure conditions of each minimum exposure region 603 in each gain region.

[0049] According to this embodiment, since the number of arithmetic operations required for calculating the white balance evaluation value 1 and its weighting value is smaller than that in Embodiment 1, the memory usage and CPU load due to calculation can be reduced.

[0050] <Embodiment 3> In this embodiment, the case where there are a plurality of evaluation regions will be described. In this embodiment, when there are a plurality of evaluation regions determined by the extraction unit 102 and the region determination unit 103, the white balance evaluation value 2 is calculated for each evaluation region. Next, the white balance evaluation value 2 in each evaluation region is weighted again to calculate and correct the white balance evaluation value of the entire image. Note that since the functional configuration of the imaging apparatus 100 according to this embodiment is the same as that in Embodiment 1 and Embodiment 2, the description thereof will be omitted.

[0051] Hereinafter, the white balance correction process in this embodiment will be described with reference to FIG. 9.

[0052] FIG. 9 is an example of an image captured by the imaging apparatus 100 according to this embodiment. The image 901 is an entire image for correcting the white balance. The evaluation region 902 is one of the regions for calculating an evaluation value for correcting the white balance of the image 901. The minimum exposure region 903 is the minimum region that can be set by the imaging element capable of setting the exposure condition for each region. The evaluation region 904 is a different evaluation region from 902 and is one of the regions for calculating an evaluation value for correcting the white balance of the image 901. The minimum exposure region 905 is the minimum region that can be set by the imaging element capable of setting the exposure condition for each region. Note that in this embodiment, the case where there are two evaluation regions will be described, but there may be three or more. In this embodiment, the calculation of the white balance evaluation value is performed in each of the evaluation region 902 and the evaluation region 904. Since the calculation of the white balance evaluation value in each evaluation region is performed in the same manner as in Embodiment 1 or Embodiment 2, the description of the calculation process of the white balance evaluation value in each region will be omitted.

[0053] In each evaluation area, a white balance evaluation value 2 is calculated. When the calculated white balance evaluation values are the same, similar to Embodiment 1 or Embodiment 2, it is possible to suitably correct the white balance of the entire image according to the white balance evaluation value 2. However, it is rare for the two evaluation areas to have the same white balance evaluation value, and generally they are different.

[0054] In this embodiment, the case where the white balance evaluation values 2 in the calculated respective evaluation areas are not the same will be described. In this case, weighting is performed again for each of the white balance evaluation values 2 in the respective evaluation areas, and the white balance evaluation value of the entire image is calculated. Specifically, for the evaluation area 902 and the evaluation area 904, the weighting value is determined such that the smaller the standard deviation of the RGB luminance in the evaluation area, the greater the weighting. The method for calculating the white balance evaluation value of the entire image after weighting is the same as the calculation of the white balance evaluation value 2 in Embodiment 1 and Embodiment 2, so it is omitted.

[0055] According to this embodiment, when there are two or more evaluation areas, by increasing the weighting of the evaluation area with more uniform luminance, it is possible to calculate a highly accurate white balance evaluation value.

[0056] <Other Embodiments> The present invention can be realized by a process of reading and executing a program that realizes one or more functions of the above-described Embodiment 1, Embodiment 2, and Embodiment 3. This program is supplied to a system or device via a network or a storage medium, and is read and executed by one or more processors in a computer of the system or device. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

Description of Reference Numerals

[0057] 100 Imaging device 101 Imaging unit 101a Lens group 101b imaging element 101c amplifier 102 extraction unit 103 region determination unit 104 exposure control unit 105 calculation unit 106 correction unit 107 communication unit

Claims

1. An imaging unit that captures an image of a subject to generate an image, An exposure control unit that controls gain for each pixel or pixel group on the imaging surface of the imaging unit, An extraction unit that extracts an achromatic region from the image, A first calculation unit that calculates a first evaluation value for each pixel or pixel group included in an evaluation region determined based on the region extracted by the extraction unit, A second calculation unit that calculates a second evaluation value in the evaluation region from the first evaluation values weighted respectively based on the gain controlled by the exposure control unit for each pixel or pixel group, A correction unit that corrects the image based on the second evaluation value calculated by the second calculation unit, and has, The imaging device, wherein the first evaluation value and the second evaluation value are evaluation values of any one of white balance, hue, and saturation.

2. The imaging device according to claim 1, further comprising a region determination unit that determines the evaluation region so as to include pixels or pixel groups within the region extracted by the extraction unit.

3. The imaging device according to claim 1 or 2, wherein the evaluation region does not include a moving subject.

4. The exposure control unit according to any one of claims 1 to 3, wherein the exposure control unit controls such that the exposure time of pixels or pixel groups in the evaluation region is longer than the exposure time of pixels or pixel groups in a region outside the evaluation region.

5. The exposure control unit according to any one of claims 1 to 4, wherein the exposure control unit controls such that the analog gain of pixel groups in the evaluation region is lower than the analog gain of pixels or pixel groups in a region outside the evaluation region.

6. The imaging device according to any one of claims 1 to 5, wherein the correction unit corrects the white balance of the image by controlling the digital gain of a plurality of color signals included in the image.

7. The imaging device according to any one of claims 1 to 6, wherein the second calculation unit calculates by weighted-averaging a plurality of the first evaluation values.

8. The imaging device according to any one of claims 1 to 7, wherein the pixels or pixel groups in the evaluation region are classified into a plurality of regions based on a threshold value of the gain, and weighting is performed on the first evaluation value for each of the classified regions.

9. When there are a plurality of the evaluation regions, the second calculation unit calculates second evaluation values for the respective evaluation regions, and calculates the second evaluation values weighted based on the standard deviation of luminance in the evaluation regions by weighted-averaging the second evaluation values. The imaging device according to any one of claims 1 to 8, characterized in that.

10. An imaging step of imaging an image of a subject to generate an image; An exposure control step of controlling the gain for each pixel or pixel group in the imaging step; An extraction step of extracting an achromatic region from the image; A first calculation step of calculating a first evaluation value for each of the pixels or pixel groups included in an evaluation region determined based on the region extracted in the extraction step; A second calculation step of calculating a second evaluation value in the evaluation region from the first evaluation values weighted based on the gain for each of the pixels or pixel groups controlled in the exposure control step; A correction step of correcting the image based on the second evaluation value calculated in the second calculation step, and having The first evaluation value and the second evaluation value are evaluation values of any one of white balance, hue, and chroma. A control method for an imaging device, characterized in that.

11. The control method for an imaging device according to claim 10, further comprising a region determination step of determining the evaluation region so as to include pixels or pixel groups within the region extracted in the extraction step.

12. The control method for an imaging device according to claim 10 or 11, characterized in that the evaluation region does not include a moving subject.

13. In the exposure control step, the exposure time of the pixels or pixel groups in the evaluation region is controlled to be longer than the exposure time of the pixels or pixel groups outside the evaluation region. The control method for an imaging device according to any one of claims 10 to 12, characterized in that.

14. In the exposure control step, the analog gain of the pixels or pixel groups in the evaluation region is controlled to be lower than the analog gain of the pixels or pixel groups in the region outside the evaluation region. The control method for an imaging device according to any one of claims 10 to 13, characterized in that.

15. The control method of an imaging device according to any one of claims 10 to 14, wherein in the correction step, the white balance of the image is corrected by controlling the digital gain of a plurality of color signals included in the image.

16. The control method of an imaging device according to any one of claims 10 to 15, wherein in the second calculation step, it is calculated by weighted-averaging a plurality of the first evaluation values.

17. The control method of an imaging device according to any one of claims 10 to 16, wherein the pixel or the pixel group in the evaluation region is classified into a plurality of regions based on the gain threshold value, and the first evaluation value is weighted for each of the classified regions.

18. The control method of an imaging device according to any one of claims 10 to 17, wherein in the second calculation step, when there are a plurality of the evaluation regions, the second evaluation value in each evaluation region is calculated, and a weighted average of the second evaluation values weighted based on the standard deviation of the luminance in the evaluation region is calculated.

19. A program for causing a computer to execute the control method of an imaging device according to any one of claims 10 to 18.

20. A computer-readable storage medium storing a program for causing a computer to execute the control method of an imaging device according to any one of claims 10 to 18.

Images