Imaging apparatus, imaging control method, program, and storage medium

Abstract

To provide an imaging apparatus capable of fluctuation correction of preventing moving subject blur that has a harmful effect on smoothing in the time direction.SOLUTION: An imaging apparatus comprises: an acquisition unit that acquires the amount of fluctuation of an image picked up by an imaging unit; an image processing unit that executes correction processing for reducing the fluctuation of the image on the basis of the amount of fluctuation acquired by the acquisition unit; and a determination unit that determines the exposure time of the imaging unit. The determination unit determines the exposure time of the imaging unit on the basis of the amount of fluctuation acquired by the acquisition unit or the correction intensity of the correction processing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In surveillance camera use cases such as port surveillance and infrastructure monitoring, for example, when capturing telephoto images of ships or aircraft, it is known that fluctuations in the subject image caused by uneven changes in the refractive index of the atmosphere (such as heat haze) can reduce the visibility of the subject. A conventional method for reducing such fluctuations involves smoothing images in the time domain. However, this method has the drawback of blurring moving objects when they are included in the image. In particular, surveillance camera use cases require automatic control of the correction strength appropriate for each scene to address phenomena that reduce image visibility, such as fluctuations. Patent Document 1 discloses a technique for correcting fluctuations using an exposure time and frame rate that is not affected by changes in heat haze over time, as a method for correcting fluctuations other than smoothing images in the time domain. Here, the frame rate is set high enough to nearly freeze the changes in the heat haze, and the exposure time is set shorter than the time required for one frame. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-177477 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the conventional method of increasing the frame rate as disclosed in the above-mentioned patent document has drawbacks such as an increase in data volume, a heavy processing load, and an increase in power consumption of the imaging device.

[0005] The problem to be solved by the present invention is to realize fluctuation correction that suppresses blurring of moving objects, which is a drawback of smoothing in the time direction. [Means for solving the problem]

[0006] In order to solve the above problem, an imaging device according to one aspect of the present invention comprises an acquisition unit that acquires the amount of fluctuation in an image captured by an imaging unit, an image processing unit that performs a correction process to reduce the fluctuation in the image based on the amount of fluctuation acquired by the acquisition unit, and a determination unit that determines an exposure time of the imaging unit, wherein the determination unit determines the exposure time of the imaging unit based on the amount of fluctuation acquired by the acquisition unit or the correction strength of the correction process. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an imaging device that enables fluctuation correction that suppresses blurring of a moving object, which is a drawback of smoothing in the time direction. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a device configuration and a functional configuration of an imaging device. [Figure 2] 10A and 10B are diagrams illustrating fluctuation correction by smoothing in the time direction. [Figure 3] FIG. 10 is a diagram showing a comparison of time fluctuations at different shutter speeds. [Figure 4] FIG. 10 is a diagram showing a comparison of in-plane fluctuations at different shutter speeds. [Figure 5] 10 is a diagram showing the relationship between the shutter speed and time fluctuation, in-plane fluctuation, and fluctuation resulting from the combined contribution of time fluctuation and in-plane fluctuation. FIG. [Figure 6] FIG. 10 is a diagram showing the relationship between the time change of high-frequency fluctuations and the shutter speed of the fluctuations. [Figure 7] 10 is a flowchart of a process for determining whether fluctuation correction is performed. [Figure 8]10 is a flowchart of a process for setting a shutter speed for fluctuation correction. [Figure 9] FIG. 10 is a diagram illustrating the relationship between fluctuation and shutter speed. [Figure 10] 10 is a flowchart of a process for setting a shutter speed for fluctuation correction. [Figure 11] FIG. 10 is a diagram illustrating the relationship between fluctuation and shutter speed. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. The embodiment described below is one example of a means for realizing the present invention, and may be appropriately modified or changed depending on the calibration of the device to which the present invention is applied and various conditions (such as the conditions of use and the environment of use). In addition, a configuration may be achieved by appropriately combining parts of each embodiment described below. In each of the following embodiments, the same components are described with the same reference numerals.

[0010] <Embodiment 1> FIG. 1(a) is a block diagram showing the device configuration of an imaging device according to this embodiment, and FIG. 1(b) is a block diagram showing the functional configuration of the imaging device according to this embodiment.

[0011] (Device configuration) The imaging device according to this embodiment includes an imaging optical system 101, an imaging element 102, a CPU 103, a RAM 104, and a ROM 105, and each part is electrically connected via a bus 106. The imaging optical system 101 is a lens connected to the imaging device, and light incident on the imaging optical system 101 forms an image of a subject, which is then captured by the imaging element 102.

[0012] The imaging optical system 101 is composed of one or more lenses. Lenses include lenses with coatings that change the transmittance of infrared light components, lenses with special processing to reduce the effects of aberration, and lenses that change optical properties such as teleconverters (extenders). It also includes lenses that can be designed to have different functions for different wavelengths, such as metalenses.

[0013] The image sensor 102 is a photoelectric conversion element that captures an image of a subject using the imaging optical system 101 and generates image data or an image signal consisting of multiple pixels. The image data or image signal contains information on multiple colors. The multiple colors are, for example, red, green, and blue. The image data passes through color filters corresponding to each color provided in front of the image sensor, and is converted into electrical signals of red, green, and blue signals by the image sensor and processed. The color filters transmit not only visible light components corresponding to red, green, and blue, but also some infrared light components included in the invisible light range. The image sensor may be a complementary metal oxide semiconductor (CMOS), a charge-coupled device (CCD), a single photon avalanche diode (SPAD), or the like.

[0014] The CPU 103 is a central processing unit that performs overall control of the imaging device. The RAM 104 is a non-volatile memory that provides a work area used by the CPU 103 when executing processing. The RAM 104 also functions as a frame memory and a buffer memory. The ROM 105 stores programs and image data used by the CPU 104 to control the imaging device. The ROM 105 can also store, for example, a threshold value indicating the intensity of fluctuations.

[0015] (Functional configuration) The imaging device according to this embodiment has an acquisition unit 111, a determination unit 112, an exposure control unit 113, and an image processing unit 114. Each function is executed by software, and is realized by reading a program stored in a ROM (storage unit) 105 into a RAM 104 and executing it with a CPU 103.

[0016] The acquisition unit 111 acquires the amount of fluctuation in an image captured by an imaging unit including the imaging optical system 101 and the image sensor 102. Alternatively, the acquisition unit 111 may acquire information about fluctuation from a fluctuation correction value of the image processing unit 114. The information about fluctuation includes not only the amount of fluctuation indicating the magnitude of fluctuation in the image, but also the correction strength when correcting the fluctuation. When acquiring information about fluctuation from an acquired image, the difference in pixel value of a pixel of interest between multiple consecutive images is calculated, and the magnitude of the calculated difference is acquired as the magnitude of fluctuation. More specifically, the edge of a still subject in an image is set as the pixel of interest, and when the pixel of interest is compared between multiple consecutive images, if the difference (amount of change) is large, the amount of fluctuation is large, and if the difference is small, the amount of fluctuation is small. The acquisition unit 111 outputs the acquired amount of fluctuation to the determination unit 112.

[0017] The determination unit 112 determines the shutter speed (exposure time) based on the amount of fluctuation acquired by the acquisition unit 111 and information from the exposure control unit 113, and controls the exposure time at the image sensor 102. The shutter speed is determined so as to reduce fluctuation occurring in the image.

[0018] The exposure control unit 113 controls exposure by performing at least one of aperture drive control, shutter speed control, and gain control based on the subject brightness calculated from the image by the acquisition unit 111 and the shutter speed determined by the determination unit 112.

[0019] The image processing unit 114 performs image processing using image data and image signals from the image sensor 102 as input. The image processing includes noise reduction processing, saturation and hue correction processing, gamma correction processing, and fluctuation correction processing using time smoothing. The image processing unit 114 executes correction processing to reduce image fluctuation based on the amount of fluctuation acquired by the acquisition unit 111.

[0020] FIG. 2 illustrates jitter correction using time-domain smoothing, such as simple moving average and weighted moving average. Image 201 is a frame from a video, showing jitter in the building subject. Image 202 is a jitter-corrected image obtained by smoothing multiple frames. While jitter in the building is reduced, blurring occurs in the moving bird. Image 203 is a jitter-corrected image obtained when the correction strength of the time-domain smoothing process is weaker than that of image 202. The method for changing the correction strength shown here is to change the number of frames to be smoothed, but other methods, such as changing the weighting of the weighted moving average, are also possible. In this embodiment, shutter speed control is performed according to jitter, as in the case of generating image 203. This reduces the jitter originally present in the captured image, and even if the correction strength of the time-domain smoothing process is weakened, an image with jitter correction and reduced motion blur is obtained. A method for determining the shutter speed to reduce jitter is described below.

[0021] First, the relationship between fluctuation and shutter speed will be explained using Figures 3 and 4. Here, fluctuation will be considered from the perspective of how much the amplitude changes over time (hereafter referred to as time fluctuation) and how much a certain area of ​​interest on the subject changes within one frame (hereafter referred to as in-plane fluctuation).

[0022] Figure 3 compares time fluctuations at different shutter speeds. The dashed lines are random waveforms that mimic fluctuations and show the change in fluctuation over one second. The solid lines in Figures 3(a) and (b) show time fluctuations when capturing images at shutter speeds of 1 / 30 second and 1 / 1000 second, respectively. The plots on the solid lines indicate the time when one frame is generated. Since the frame rate is 60 fps, there are 60 plots per second. Time fluctuations are calculated by averaging the fluctuations (dotted lines) over the accumulation time corresponding to the shutter speed before one frame is generated. The time fluctuations at time t in Figure 3 have a larger amplitude at a shutter speed of 1 / 1000 second than at a shutter speed of 1 / 30 second. This is because the averaging period becomes shorter as the shutter speed increases, resulting in a higher responsiveness to fluctuation changes. Figure 5(a) shows the relationship between shutter speed and time fluctuations. The faster the shutter speed, the larger the time fluctuation, and the slower the shutter speed, the smaller the time fluctuation.

[0023] Figure 4 compares in-plane fluctuations at different shutter speeds. The dashed lines in Figure 4 indicate the time variation of fluctuations, as in Figure 3. The solid lines in Figures 4(a) and (b) indicate in-plane fluctuations when capturing images at shutter speeds of 1 / 30 second and 1 / 1000 second, respectively. In-plane fluctuations are calculated by taking the difference between the minimum and maximum fluctuations (dotted lines) within the accumulation time corresponding to the shutter speed before one frame is generated. The cross marks in Figure 5 indicate the minimum and maximum fluctuations within the accumulation time at time t. The in-plane fluctuations are smaller at a shutter speed of 1 / 1000 second than at 1 / 30 second. This is because the faster the shutter speed, the shorter the accumulation time, and the smaller the amount of change in fluctuation within the accumulation time. Figure 5(b) shows the relationship between shutter speed and in-plane fluctuations. The in-plane fluctuations are smaller at faster shutter speeds and larger at slower shutter speeds.

[0024] Figure 5(c) shows the relationship between shutter speed and fluctuation, which combines the contributions of both temporal fluctuation and in-plane fluctuation. The fluctuation simulated here is greatest at shutter speed 502, and is smaller at slower shutter speeds 501 and 503. Considering the impact of motion blur, motion blur is more likely to occur at slower shutter speeds and less likely to occur at faster shutter speeds. Therefore, given the similar fluctuations at shutter speeds 501 and 503, the faster shutter speed 503 is advantageous in that it can suppress motion blur and reduce motion blur. Furthermore, shutter speed 504 achieves a greater reduction in fluctuation than shutter speed 503. However, since motion blur is a phenomenon dependent on atmospheric temperature, humidity, carbon dioxide concentration, and the like, the amplitude and frequency of the fluctuation vary depending on the environment in which the fluctuation occurs. Figure 6(a) shows the time change over one second of fluctuations that change at a higher frequency than the fluctuations simulated in Figures 3 to 5. Figure 6(b) shows the relationship between the fluctuations and shutter speed, combining the contributions of both the time fluctuation and the in-plane fluctuation in the fluctuations in Figure 6(a). Compared to Figure 5(c), the basic shape of the graph remains the same, but the shutter speed at which the fluctuations are at their maximum has shifted to the higher speed side, and the appropriate shutter speed varies depending on the frequency of the fluctuations. Therefore, it is best to set the shutter speed to reduce the fluctuations according to characteristics such as the amplitude and frequency of the fluctuations.

[0025] There are several methods for setting the shutter speed depending on the characteristics of the fluctuation, but in this embodiment, a method for setting the shutter speed will be described that takes advantage of the characteristics that a high shutter speed results in less blurring of a moving object and less fluctuation. Figure 7 is a flowchart showing the main processing in this embodiment.

[0026] In step S701, it is determined whether or not to perform fluctuation correction. Whether or not to perform fluctuation correction is determined based on user setting information and the amount of fluctuation acquired by the acquisition unit 111. When determining based on user setting information, setting information indicating whether or not to perform fluctuation correction is stored in RAM 104, ROM 105, or an external storage device. The acquisition unit 111 then acquires the setting information to determine whether or not to perform fluctuation correction. When determining based on the acquired amount of fluctuation, it may be determined that fluctuation correction is to be performed if the acquired amount of fluctuation is equal to or greater than a predetermined amount. This predetermined amount can be set arbitrarily by the user or designer, and the user or designer may set an acceptable amount of fluctuation. If the amount of fluctuation indicates that fluctuation correction should be performed, the process proceeds to the next step S702; if not, the process ends.

[0027] In step S702, the shutter speed is determined based on the amount of fluctuation by the determination unit 112. The determination method will be described later.

[0028] In step S703, fluctuation correction is performed by image processing by the image processing unit 114. If fluctuation remains after step S702, fluctuation correction is performed by image processing with a strength according to the remaining fluctuation. Fluctuation correction by image processing is, for example, processing to smooth the image in the time direction.

[0029] The processing of steps S701 to S703 may be re-executed in response to a change in the scene, etc. For example, re-execution may be performed using the following determination conditions: when the amount of change in the fluctuation of the input image is equal to or greater than a predetermined amount, when the amount of change in the exposure of the input image is equal to or greater than a predetermined amount, when a predetermined amount of time has passed since the previous execution, etc. In other words, when the amount of change in the exposure from the appropriate level is equal to or greater than a predetermined amount, the exposure time may be re-determined, or the exposure may be changed by changing a parameter related to brightness that is different from the exposure time.

[0030] Next, the process of setting the shutter speed for fluctuation correction (step S702) will be described with reference to the flowchart in FIG.

[0031] In step S801, the determination unit 112 acquires the current shutter speed vp from the exposure control unit 113.

[0032] In step S802, the determining unit 112 acquires the fluctuation amount q1 of the input image from the acquiring unit 111.

[0033] In step S803, it is determined whether the amount of jitter q1 acquired in step S802 is equal to or greater than a preset jitter tolerance limit qlim (predetermined amount). The jitter tolerance limit qlim is set to a value equal to or greater than the predetermined amount used in determining whether to perform jitter correction in step S701. The user or designer may set a different value for the threshold used in determining whether to perform jitter correction from the threshold used in determining whether to control the shutter speed. As shown in FIG. 9, when capturing an image at a shutter speed of approximately 1 / 64 seconds, the amount of jitter q1 is greater than the jitter tolerance limit qlim. In this case, the process proceeds to the next step S803. If the amount of jitter q1 is smaller than the jitter tolerance limit qlim, the process of setting the shutter speed for jitter correction is terminated.

[0034] In step S804, the acquisition unit 111 acquires the range of exposure times that can be set in the image capture unit, and the determination unit 112 sets the fastest shutter speed vmax (shortest exposure time) within the acquired range of exposure times as the shutter speed for jitter correction in the image capture unit. In this embodiment, the shortest exposure time that can be set in the image capture unit is set, but it does not necessarily have to be the fastest shutter speed. It is sufficient to determine a shutter speed that is faster than the current shutter speed to the extent that the amount of jitter can be reduced.

[0035] Here, the range of exposure times that can be set in the image capture unit refers to a range of exposure times that does not result in an image becoming too dark or an increase in noise due to an increase in gain to maintain image brightness. Therefore, the range of exposure times that can be set in the image capture unit can be calculated by comprehensively considering parameters related to image brightness, including image brightness, noise level, shutter speed, gain value, aperture value, and the presence or absence of an ND filter. For example, an acceptable image brightness or noise level is set in advance, and the shutter speed that does not exceed the acceptable brightness or noise level when the shutter speed is reduced is the lower limit of the range of exposure times that can be set. In this way, it is sufficient to determine the shutter speed within a range that maintains proper exposure.

[0036] In step S805, the exposure control unit 113 controls the shutter speed to vmax.

[0037] In step S806, the determination unit 112 acquires the fluctuation amount q2 at the shutter speed vmax from the acquisition unit 111.

[0038] In step S907, the determination unit 112 compares the amount of fluctuation before and after setting the shutter speed for fluctuation correction. In Fig. 9, the amount of fluctuation q2 is smaller than the amount of fluctuation q1, and the fluctuation is reduced by setting the shutter speed for fluctuation correction. In this way, if the amount of fluctuation after setting the shutter speed for fluctuation correction is smaller than the amount of fluctuation before setting, the process of setting the shutter speed for fluctuation correction amount ends.

[0039] In step S908, if the fluctuation becomes large after the determination unit 112 sets the shutter speed for fluctuation correction, the determination unit 112 returns the setting to the original shutter speed vp. The exposure control unit 113 controls the shutter speed based on the shutter speed set by the determination unit 112.

[0040] According to the first embodiment described above, it is possible to easily set a shutter speed that reduces fluctuations, and to perform fluctuation correction while suppressing blurring of moving objects, which is a drawback of fluctuation correction using image processing.

[0041] In the present embodiment, the image capturing unit including the imaging optical system 101 and the image sensor 102 and the image processing unit 114 (corresponding to the CPU 103, RAM 104, and ROM 105) that performs jitter correction are integrated into one unit. However, the image capturing unit and the image processing unit 114 may be separate units. That is, an external information processing device may receive and acquire images captured by the image capturing device via a network, and may calculate the amount of jitter, calculate the amount of jitter correction, and determine the shutter speed of the image capturing device based on the acquired images. In this case, the image capturing device may receive the determined shutter speed from the external information processing device, and the exposure control unit 113 may perform overall exposure control including gain based on the received shutter speed.

[0042] <Embodiment 2> In this embodiment, the relationship between shutter speed and fluctuation is not a simple one with a single peak as in the first embodiment, but rather, when the fluctuation has periodicity, a relationship is considered in which fluctuation is smallest at a certain shutter speed. In this case, rather than simply increasing the shutter speed, the shutter speed can be set to an optimum value by setting it using the method described below. The process of setting the shutter speed for fluctuation correction (step S702) in this embodiment will be described using the flowchart in FIG. 10. Note that the device configuration and functional configuration of the imaging device according to this embodiment are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0043] In step S1001, the determination unit 112 receives the current shutter speed from the exposure control unit 203, and initializes the shutter speed at which the amount of fluctuation is smallest (hereinafter, optimal shutter speed vb) to the current shutter speed vp.

[0044] In step S1002, the determination unit 112 acquires the current fluctuation amount qp from the acquisition unit 111, and initializes the minimum value of the fluctuation amount that varies as the shutter speed is changed (hereinafter, minimum fluctuation amount qmin) to the current fluctuation amount qp.

[0045] In step S1003, the determination unit 112 acquires the amount of fluctuation while changing the shutter speed by a predetermined amount Δv, and determines the optimal shutter speed vb that minimizes the amount of fluctuation (hereinafter referred to as shutter scan). At this time, a range within which the shutter speed is changed (hereinafter referred to as shutter scan range) is set. The shutter scan range is set based on the shutter speed range within which proper exposure is maintained, calculated by the exposure control unit 113, and the current shutter speed vp. Specifically, a range equal to or greater than the shutter speed before the shutter scan and equal to or less than the fastest shutter speed within the proper exposure range is set. The shaded area in FIG. 12 is the shutter scan range. Shutter scan is not performed on the side slower than the shutter speed before the shutter scan to avoid blurring of moving objects caused by the shutter speed for fluctuation correction being slower than the originally set shutter speed. Furthermore, when calculating the shutter speed range within which proper exposure is maintained, attempting to maintain exposure by gain control may increase noise in the image. Therefore, in order to prevent an increase in noise, it is desirable to calculate a range in which the correct exposure is maintained while keeping the gain fixed.

[0046] In step S1004, the determination unit 112 sets a value that is faster than the current shutter speed vp by a predetermined amount Δv as the control target for the shutter speed, and outputs the value to the exposure control unit 113. The exposure control unit 113 performs shutter speed control based on the shutter speed received from the determination unit 112.

[0047] In step S1005, the determination unit 112 acquires from the acquisition unit 111 the current fluctuation amount qp at the shutter speed set in step S1004.

[0048] In step S1006, the determination unit 112 determines whether the current fluctuation amount vp is smaller than the minimum fluctuation amount vmin. If the current fluctuation amount vp is smaller than the minimum fluctuation amount vmin, the process proceeds to the next step S1007. If the current fluctuation amount vp is equal to or greater than the minimum fluctuation amount vmin, the subsequent steps S1007 and S1008 are skipped and shutter scanning continues.

[0049] In step S1007, the determination unit 112 updates the minimum fluctuation amount vmin with the current fluctuation amount vp.

[0050] In step S1008, the determination unit 112 updates the optimum shutter speed vb with the current shutter speed vp.

[0051] The process from step S1004 to S1008 is repeated until the current shutter speed vp + predetermined amount Δv falls outside the shutter scan range, thereby determining the shutter speed at which fluctuation within the shutter scan range is minimized. In Figure 12, the shutter speed at which fluctuation within the shutter scan range is minimized qmin is the optimal shutter speed vb.

[0052] In step S1009, the determination unit 112 sets the optimum shutter speed vb as the control target for the shutter speed, and outputs it to the exposure control unit 113. The exposure control unit 113 performs shutter speed control based on the shutter speed received from the determination unit 112. As described above, since the shutter speed at which the amount of fluctuation is minimized is determined by scanning, it is possible to control the shutter speed to one at which the amount of fluctuation is small with higher accuracy than in the first embodiment, and a greater fluctuation reduction effect can be obtained.

[0053] (Variation) As a modification of this embodiment, in S1006, it may be determined whether the acquired current fluctuation amount qp is equal to or less than a predetermined amount, and if it is equal to or less than the predetermined amount, shutter scanning may be terminated. This makes it possible to terminate the processing of this flowchart when the fluctuation amount becomes equal to or less than the desired fluctuation amount without performing shutter scanning until the fluctuation amount becomes the minimum, thereby achieving advantageous effects in terms of processing speed and processing efficiency compared to this embodiment.

[0054] <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 first embodiment. This program is supplied to a system or device via a network or a computer-readable storage medium, and is read and executed by one or more processors in the computer of the system or device. The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0055] 101 Imaging optical system 102 Image sensor 103 CPU 104 RAM 105 ROM Bus 106 111 Acquisition Department 112 Decision Section 113 Exposure control unit 114 Image processing section

Claims

1. an acquisition unit that acquires the amount of fluctuation in an image captured by the imaging unit; an image processing unit that executes a correction process to reduce fluctuations in the image based on the fluctuation amount acquired by the acquisition unit; a determination unit that determines an exposure time of the imaging unit, The imaging device, wherein the determination unit determines an exposure time of the imaging unit based on the amount of fluctuation acquired by the acquisition unit or the correction strength of the correction process.

2. The imaging device according to claim 1 , wherein the determination unit determines the exposure time based on the amount of fluctuation acquired by the acquisition unit or the correction strength of the correction process so as to reduce fluctuation occurring in the image.

3. the acquisition unit acquires a range of exposure times that can be set to the imaging unit; The imaging device according to claim 1, characterized in that, when the amount of fluctuation acquired by the acquisition unit is determined to be equal to or greater than a predetermined amount, the determination unit determines an exposure time shorter than the current exposure time of the imaging unit as the exposure time of the imaging unit.

4. The imaging device according to claim 3, characterized in that, when it is determined that the amount of fluctuation acquired by the acquisition unit is equal to or greater than a predetermined amount, the determination unit determines the shortest exposure time within a range of exposure times that can be set for the imaging unit as the exposure time for the imaging unit.

5. the acquisition unit acquires a plurality of fluctuation amounts while changing the exposure time of the imaging unit by a predetermined amount, The imaging device according to claim 1, characterized in that the determination unit determines, based on the multiple fluctuation amounts acquired by the acquisition unit, an exposure time at which fluctuations occurring in the image captured by the imaging unit are smaller than a predetermined amount as the exposure time of the imaging unit.

6. 6. The imaging device according to claim 1, wherein the determination unit determines the exposure time to be the same as or shorter than the original exposure time.

7. 6. The imaging device according to claim 1, wherein the determination unit determines the exposure time within a range in which appropriate exposure is maintained.

8. 6. The imaging device according to claim 1, wherein the determination unit determines the exposure time within a range in which a gain of the imaging element is maintained.

9. The imaging device described in any one of claims 1 to 5, characterized in that the determination unit acquires the amount of fluctuation from the acquisition unit at predetermined time intervals, and based on the acquired amount of fluctuation, re-determines the exposure time if the change in the current amount of fluctuation is greater than or equal to a predetermined amount compared to the amount of fluctuation when the previous exposure time was determined.

10. The imaging device described in any one of claims 1 to 5, characterized in that the determination unit re-determines the exposure time when the amount of change from the appropriate exposure is greater than or equal to a predetermined amount, or changes the exposure by changing a parameter related to brightness that is different from the exposure time.

11. 6. The imaging device according to claim 1, wherein the fluctuation determination unit re-determines the exposure time when a predetermined time has elapsed.

12. 2. The imaging device according to claim 1, wherein the amount of fluctuation is calculated based on a difference in pixel values ​​between a plurality of images captured by the imaging unit.

13. The imaging device according to claim 1 , wherein the image processing unit executes a fluctuation correction process based on the fluctuation amount acquired by the acquisition unit.

14. an acquisition step of acquiring a fluctuation amount of an image captured by the imaging unit; an image processing step of executing a correction process to reduce fluctuations in the image based on the fluctuation amount acquired in the acquisition step; a determining step of determining an exposure time of the imaging unit, The control method is characterized in that, in the determining step, an exposure time of the imaging unit is determined based on the amount of fluctuation acquired in the acquiring step or the correction strength of the correction process.

15. A program for causing a computer to execute the control method according to claim 14.

16. A computer-readable storage medium storing the program according to claim 15.

Images