Exposure control device, exposure control device operation method, exposure control device operation program, and imaging device

Abstract

To provide an exposure control device, an exposure control device operation method, an exposure control device operation program, and an imaging device capable of performing appropriate exposure control.SOLUTION: A CPU of a control unit of an imaging device includes a setting unit and a drive control unit. The drive control unit starts exposure control when an absolute value of a difference between a first target exposure value of a current frame and a second target exposure value of a previous frame becomes larger than a first threshold. The setting unit acquires a second threshold smaller than the first threshold in response to the start of exposure control. When a magnitude relationship between the absolute value of the difference and the second threshold satisfies a preset condition, the drive control unit sets a threshold to be compared with the absolute value of the difference to a third threshold larger than the second threshold, and ends the exposure control.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The technology disclosed herein relates to an exposure control device, an operation method for an exposure control device, an operation program for an exposure control device, and an imaging device.

[0002] Patent Document 1 describes an automatic exposure control device that controls the opening and closing of a lens iris so as to reduce the difference between a target exposure level and brightness information based on information about the opening and closing position of the lens iris and brightness information through a lens. The automatic exposure control device described in Patent Document 1 has a first control means that controls the opening and closing of the lens iris by compensating for the difference between the mechanical hysteresis of the lens iris in the first direction and the mechanical hysteresis in the second direction by setting different control margin amounts for the target exposure level when the lens iris moves in a first direction from the closed side to the open side and when it moves in a second direction from the open side to the closed side. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-041181 A Summary of the Invention

[0004] One embodiment of the technique of the present disclosure provides an exposure control device capable of performing appropriate exposure control, an operation method for an exposure control device, an operation program for an exposure control device, and an imaging device. [Means for solving the problem]

[0005] The exposure control device disclosed herein is an exposure control device that performs exposure control to make the exposure value in an imaging device follow a target exposure value, and is equipped with a processor, wherein the processor starts exposure control when an absolute value of a difference between a first target exposure value of a first frame captured by the imaging device and a second target exposure value of a second frame captured before the first frame becomes greater than a first threshold, obtains a second threshold smaller than the first threshold in response to the start of exposure control, and when a magnitude relationship between the absolute value of the difference and the second threshold meets a preset condition, sets a threshold to be compared with the absolute value of the difference to a third threshold larger than the second threshold, and ends the exposure control.

[0006] Preferably, the processor sets the third threshold to the same value as the first threshold.

[0007] It is preferable that the processor sets the third threshold value to a value different from the first threshold value depending on the condition.

[0008] It is preferable that the processor sets the third threshold value to a value smaller than the first threshold value depending on the condition.

[0009] The condition is preferably based on the result of detection of the subject.

[0010] When the absolute value of the difference becomes equal to or smaller than the second threshold, the processor preferably sets the threshold to be compared with the absolute value of the difference to a third threshold that is greater than the second threshold, and terminates the exposure control.

[0011] It is preferable that the processor stores in the memory unit for each frame whether the absolute value of the difference is greater than the first threshold, the second threshold, or the third threshold, indicating an exposure control state in which exposure control is being performed, or whether the absolute value of the difference is equal to or less than the first threshold, the second threshold, or the third threshold, indicating an exposure control end state in which exposure control has ended.

[0012] It is preferable that, when the state of the second frame is an exposure control end state, the processor sets the threshold to be compared with the absolute value of the difference to the first threshold or the third threshold, and, when the state of the second frame is an exposure control state, sets the threshold to be compared with the absolute value of the difference to the second threshold.

[0013] The processor preferably stores the second target exposure value in the memory for each frame.

[0014] When the absolute value of the difference is less than the first or third threshold but greater than the second threshold, and the sign of the difference is inverted for a predetermined number of frames, it is preferable that the processor sets the threshold to be compared with the absolute value of the difference to a third threshold greater than the second threshold and terminates exposure control.

[0015] The processor preferably stores the difference in a memory unit.

[0016] It is preferable that the processor stores in the memory unit for each frame whether the absolute value of the difference is greater than the first threshold, the second threshold, or the third threshold, indicating an exposure control state in which exposure control is being performed, or whether the absolute value of the difference is equal to or less than the first threshold, the second threshold, or the third threshold, indicating an exposure control end state in which exposure control has ended, and stores the difference in the memory unit only if the state of the first frame is the exposure control state.

[0017] It is preferable that the processor stores in the storage unit a history of the absolute value of the difference when the exposure control ends, and when the maximum value in the history is smaller than the second threshold, subtracts the second threshold from the maximum value.

[0018] It is preferable that the processor performs a process of subtracting the second threshold value from the maximum value when a preset number of histories have been stored in the storage unit.

[0019] It is preferable that, when the processor receives a preset operation instruction, the processor does not carry over the history stored in the storage unit.

[0020] It is preferable that the processor erases the history from the storage unit when a preset operation instruction is received.

[0021] The imaging device of the present disclosure includes the exposure control device described above and an imaging element.

[0022] The operating method of an exposure control device disclosed herein is a method of operating an exposure control device that performs exposure control to make the exposure value in an imaging device follow a target exposure value, and includes starting the exposure control when an absolute value of a difference between a first target exposure value of a first frame captured by the imaging device and a second target exposure value of a second frame captured before the first frame becomes greater than a first threshold, obtaining a second threshold value smaller than the first threshold value in response to the start of exposure control, and setting a threshold value to be compared with the absolute value of the difference to a third threshold value larger than the second threshold value and ending the exposure control when a predetermined condition is satisfied regarding the magnitude relationship between the absolute value of the difference and the second threshold value.

[0023] The operating program of the exposure control device disclosed herein is an operating program of the exposure control device that performs exposure control to make the exposure value in an imaging device follow a target exposure value, and causes a computer to execute processes including starting exposure control when an absolute value of a difference between a first target exposure value of a first frame captured by the imaging device and a second target exposure value of a second frame captured before the first frame becomes greater than a first threshold value, obtaining a second threshold value smaller than the first threshold value in response to the start of exposure control, and setting a threshold value to be compared with the absolute value of the difference to a third threshold value larger than the second threshold value and terminating the exposure control when a predetermined condition is met between the absolute value of the difference and the second threshold value. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an imaging apparatus. [Diagram 2] FIG. 2 is a diagram illustrating a detailed configuration of a control unit. [Diagram 3] FIG. 2 is a block diagram showing a processing unit of a CPU. [Figure 4]13A and 13B are diagrams illustrating the process of the setting unit when the state of the previous frame is the exposure control end state. [Diagram 5] FIG. 13 is a diagram showing the process of the setting unit when the state of the previous frame is the exposure control state. [Figure 6] FIG. 13 is a diagram illustrating a process performed by a determination unit when the threshold is set to a first threshold. [Figure 7] FIG. 13 is a diagram illustrating a process performed by a determination unit when the threshold is set to a first threshold. [Figure 8] FIG. 13 is a diagram illustrating a process performed by the determination unit when the threshold is set to a second threshold. [Figure 9] FIG. 13 is a diagram illustrating a process performed by the determination unit when the threshold is set to a second threshold. [Figure 10] FIG. 1 is a diagram showing an example of a photographic scene requiring exposure control; [Figure 11] 4 is a graph showing changes in a first target exposure value and a second target exposure value. [Figure 12] 13 is a diagram showing the process of the drive control unit when the threshold is set to the first threshold and the state of the current frame is the exposure control end state. FIG. [Figure 13] 13 is a diagram showing the process of the drive control unit when the threshold is set to the first threshold and the state of the current frame is the exposure control state. FIG. [Figure 14] 13 is a diagram showing the process of the drive control unit when the threshold is set to the second threshold and the state of the current frame is the exposure control end state. FIG. [Figure 15] 13 is a diagram showing the process of the drive control unit when the threshold is set to the second threshold and the state of the current frame is the exposure control state. FIG. [Figure 16] 13 is a flowchart showing a processing procedure of a CPU. [Figure 17] 13 is a flowchart showing a processing procedure of a CPU. [Figure 18] 10 is a graph showing changes in a first target exposure value and a second target exposure value in a comparative example. [Figure 19] FIG. 11 is a block diagram showing a processing unit of a CPU according to a second embodiment. [Figure 20] FIG. 13 is a diagram illustrating the process of a counting unit. [Figure 21] FIG. 13 is a diagram illustrating the process of a counting unit. [Figure 22] FIG. 13 is a diagram illustrating the process of a counting unit. [Figure 23] 13A and 13B are diagrams illustrating the process of the determination unit when the number of inversions is equal to or greater than the set number of frames. [Figure 24] 13 is a graph showing the transition of the first target exposure value and the second target exposure value when the number of inversions is equal to or greater than a set number of frames. [Diagram 25] 13A and 13B are diagrams illustrating a process performed by a determination unit when the number of inversions is less than a set number of frames. [Figure 26] 13A and 13B are diagrams illustrating the process of the determination unit when the state of the current frame is an exposure control state. [Figure 27] 10 is a flowchart showing a processing procedure of a CPU according to a second embodiment. [Figure 28] 10 is a flowchart showing a processing procedure of a CPU according to a second embodiment. [Figure 29] 10 is a flowchart showing a processing procedure of a CPU according to a second embodiment. [Diagram 30] FIG. 13 is a block diagram showing a processing unit of a CPU according to a third embodiment. [Diagram 31] FIG. [Diagram 32] FIG. 11 is a diagram illustrating the process of the RW control unit. [Diagram 33] FIG. 13 is a diagram showing the process of the RW control unit when a set number of histories of the absolute values ​​of the differences when the exposure control has ended are stored and the maximum value of the histories is smaller than the second threshold value. [Diagram 34] 13 is a diagram showing a process of the RW control unit when an instruction to turn off the power supply of the imaging device is received. FIG. [Diagram 35] 13 is a flowchart showing a processing procedure of a CPU according to a third embodiment. [Diagram 36] 13 is a flowchart showing a processing procedure of a CPU according to a third embodiment. [Figure 37] 13 is a flowchart showing a processing procedure of a CPU according to a third embodiment. [Figure 38]FIG. 13 is a block diagram showing a processing unit of a CPU according to a fourth embodiment. [Figure 39] FIG. 13 is a diagram illustrating a process of a setting unit in the fourth embodiment. [Diagram 40] FIG. 13 is a diagram illustrating a process of a setting unit in the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] [First embodiment] As an example, as shown in FIG. 1, the imaging device 10 is, for example, a mirrorless single-lens digital camera, and includes an imaging optical system 11 and an imaging element 12. The imaging optical system 11 has a plurality of types of lenses for forming an image of subject light on the imaging element 12. Specifically, the imaging optical system 11 has an objective lens 13, a focus lens 14, and a zoom lens 15. These lenses 13 to 15 are arranged in this order from the object side (subject side) toward the image formation side (image element 12 side). Although simplified in FIG. 1, each of the lenses 13 to 15 is actually a lens group in which a plurality of lenses are combined. The imaging optical system 11 also has an aperture 16. The aperture 16 is arranged on the most image formation side of the imaging optical system 11. The imaging device 10 may be of a type in which a lens barrel in which the imaging optical system 11 and the like are built and a main body in which the image element 12 and the like are built are integrated, or may be of a so-called lens exchange type in which the lens barrel and the main body are separate.

[0026] The focus lens 14 is provided with a focus lens driving mechanism 17, the zoom lens 15 is provided with a zoom lens driving mechanism 18, and the aperture 16 is provided with an aperture opening adjustment mechanism 19. The focus lens driving mechanism 17 includes, for example, a focus cam ring that holds the focus lens 14 and has a cam groove formed on its outer periphery, a focus motor that rotates the focus cam ring around the optical axis OA to move the focus cam ring along the optical axis OA, and a driver for the focus motor. Similarly, the zoom lens driving mechanism 18 includes a zoom cam ring that holds the zoom lens 15 and has a cam groove formed on its outer periphery, a zoom motor that rotates the zoom cam ring around the optical axis OA to move the zoom cam ring along the optical axis OA, and a driver for the zoom motor. The focus cam ring and the zoom cam ring can also be rotated manually by a user from outside the lens barrel. That is, the imaging device 10 can adjust the focus and change the focal length electrically by the focus motor and the zoom motor, or manually by the user.

[0027] The aperture 16 is, for example, an iris aperture, and is configured by combining a plurality of aperture blades. The aperture 16 adjusts the amount of light passing through by simultaneously moving the aperture blades with a cam mechanism to open and close a central opening formed by the inner edges of the aperture blades, that is, by changing the opening degree of the opening (hereinafter referred to as the aperture degree of the aperture 16). The aperture opening adjustment mechanism 19 includes an aperture motor that opens and closes the aperture blades, and a driver for the aperture motor. The aperture 16 can also be opened and closed manually by the user. In other words, the imaging device 10 can adjust the opening degree of the aperture 16 electrically using the aperture motor, or manually by the user.

[0028] The focus motor, zoom motor, and aperture motor are, for example, stepping motors. In this case, the positions of focus lens 14 and zoom lens 15 on the optical axis OA and the opening degree of aperture 16 can be derived from the drive amounts of the focus motor, zoom motor, and aperture motor. Note that instead of the drive amounts of the focus motor and zoom motor, position sensors may be provided to detect the positions of focus lens 14 and zoom lens 15.

[0029] The motors (focus motor, zoom motor, and aperture motor) or electric components such as drivers of the drive mechanisms 17-19 are connected to the control unit 20. The electric components of the drive mechanisms 17-19 are driven under the control of the control unit 20. More specifically, the control unit 20 issues a drive signal according to an instruction from a user input via the operation unit 21 to drive the electric components of the drive mechanisms 17-19. For example, when an instruction to change the angle of view to the telephoto side is input via the angle of view change switch of the operation unit 21, the control unit 20 issues a drive signal to a driver of the zoom motor of the zoom lens drive mechanism 18 to move the zoom lens 15 to the telephoto side.

[0030] The focus motor, zoom motor, and diaphragm motor output their drive amounts to the control unit 20. The control unit 20 derives the positions of the focus lens 14 and zoom lens 15 on the optical axis OA and the opening degree of the diaphragm 16 from the drive amounts.

[0031] The imaging element 12 is, for example, a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor, and has an imaging surface 22 that captures subject light. The imaging surface 22 is formed of a plurality of pixels arranged two-dimensionally. The pixels accumulate signal charges corresponding to the subject light, and output an image signal (voltage signal) corresponding to the signal charges. The imaging element 12 is arranged so that the center of the imaging surface 22 coincides with the optical axis OA, and the imaging surface 22 is perpendicular to the optical axis OA. Note that "coincidence" and "orthogonality" here refer to perfect coincidence and orthogonality, as well as coincidence and orthogonality that include errors generally permitted in the technical field to which the technology of the present disclosure belongs.

[0032] An imaging element driver 23 is connected to the imaging element 12. The imaging element driver 23 is connected to the control unit 20. Under the control of the control unit 20, the imaging element driver 23 controls the timing of imaging of subject light by the imaging element 12 by, for example, supplying a vertical scanning signal and a horizontal scanning signal to the imaging element 12. The imaging element driver 23 also sets a gain to be given to an image signal output from a pixel, which gain corresponds to ISO (International Organization for Standardization) sensitivity.

[0033] A shutter 24 is provided between the imaging optical system 11 and the imaging element 12. The shutter 24 is, for example, a focal plane shutter having a front curtain and a rear curtain. A shutter drive mechanism 25 is connected to the shutter 24. The shutter drive mechanism 25 includes an electromagnet that holds the front curtain and the rear curtain and releases the hold to cause the front curtain and the rear curtain to run, and a driver for the electromagnet. The shutter drive mechanism 25 is driven under the control of the control unit 20 to open and close the shutter 24.

[0034] The control unit 20 is connected to each unit, such as an image input controller 30, an image memory 31, and an image processing unit 32, through a bus line 33. In addition, a VRAM (Video Random Access Memory) 34, a display control unit 35, a media controller 36, an instruction receiving unit 37, etc. are connected to the bus line 33. Although not shown in the figure, the bus line 33 is also connected to a strobe drive control unit that controls the drive of a strobe device, an external communication I / F (Interface) that communicates with an external device via a connection terminal such as a USB (Universal Serial Bus) terminal, a wireless communication I / F, etc.

[0035] Image data 75 (see FIG. 3) obtained by capturing an image of the subject light is input to the image input controller 30 from the imaging element 12. The image input controller 30 outputs the image data 75 to the image memory 31. The image memory 31 is, for example, a Synchronous Dynamic Random Access Memory (SDRAM), and temporarily stores the image data 75.

[0036] The image processing unit 32 reads unprocessed image data 75 from the image memory 31. The image processing unit 32 performs various image processing on the image data 75. The various image processing includes, for example, offset correction processing, sensitivity correction processing, pixel interpolation processing, white balance correction processing, gamma correction processing, demosaic processing, luminance signal and color difference signal generation processing, contour enhancement processing, color correction processing, etc. The image processing unit 32 writes the image data 75 after the various image processing back to the image memory 31.

[0037] The VRAM 34 receives image data 75 after various image processes, which is to be displayed as a live view image (also called a through image), from the image memory 31. The VRAM 34 has an area for storing image data 75 for two consecutive frames. The image data 75 stored in the VRAM 34 is sequentially rewritten with new image data 75. The VRAM 34 sequentially outputs the newer image data 75 of the two consecutive frames of image data 75 to the display control unit 35.

[0038] The display control unit 35 functions as a so-called video encoder, converting image data 75 from the VRAM 34 into video data and outputting it to either the viewfinder monitor 38 or the rear monitor 39. This allows the user to view a live view image through either the viewfinder monitor 38 or the rear monitor 39. The display frame rate of the live view image is, for example, 60 fps (frames per second).

[0039] Whether the video data is output to the viewfinder monitor 38 or the rear monitor 39 is determined, for example, as follows. That is, an pupil detection sensor is provided in the viewfinder. If the pupil detection sensor detects that the user is looking through the viewfinder, the video data is output to the viewfinder monitor 38. On the other hand, if the pupil detection sensor detects that the user is not looking through the viewfinder, the video data is output to the rear monitor 39.

[0040] When an instruction to start shooting a still image or a moving image is issued by fully pressing the release button on the operation unit 21, the image processing unit 32 performs a compression process on the image data 75 in the image memory 31. In the case of a still image, the image processing unit 32 performs a compression process, for example, in the Joint Photographic Experts Group (JPEG) format on the image data 75. In the case of a moving image, the image processing unit 32 performs a compression process, for example, in the Moving Picture Experts Group (MPEG) format on the image data 75. The image processing unit 32 outputs the image data 75 after the compression process to the media controller 36.

[0041] The media controller 36 records the compressed image data 75 from the image processing unit 32 on the memory card 40. The memory card 40 is detachably attached to a memory card slot (not shown).

[0042] When the image playback mode is selected via the mode changeover switch of the operation unit 21, the media controller 36 reads out the image data 75 from the memory card 40 and outputs it to the image processing unit 32. The image processing unit 32 performs decompression processing on the image data 75 from the memory card 40. The decompressed image data 75 is output to the display control unit 35. The display control unit 35 converts the image data 75 into video data and outputs it to the rear monitor 39. This allows the user to view the played back image through the rear monitor 39.

[0043] The instruction receiving unit 37 receives various operation instructions input by the user via the operation unit 21 and a touch panel 41 provided integrally with the rear monitor 39. The instruction receiving unit 37 outputs the received various operation instructions to the control unit 20 via the bus line 33.

[0044] As described above, the operation unit 21 includes a field angle change switch, a release button, and a mode change switch. The release button is a two-stage push button that can be pressed halfway or fully. Pressing the release button halfway issues an instruction to prepare for shooting a still image or a video, and pressing it fully issues an instruction to start shooting a still image or a video. In addition to these, the operation unit 21 includes a menu button for displaying various setting menus on the rear monitor 39, a cross key used for setting numerical values ​​and switching between options, and a confirmation button operated when confirming settings. The touch panel 41 is superimposed on the display surface of the rear monitor 39. The touch panel 41 recognizes various operation instructions from the user by detecting contact with a dedicated indicator such as a user's finger or a stylus pen.

[0045] Modes that can be switched by the mode switch include a still image shooting mode, a video shooting mode, an image playback mode, and a setting mode. The still image shooting modes include not only a normal shooting mode in which one still image is shot, but also a continuous shooting mode in which still images are shot continuously at a predetermined shooting interval (for example, a frame rate of 5 fps to 10 fps). The continuous shooting mode is activated, for example, when the release button is pressed all the way down for a predetermined time or more (for example, one second or more). The continuous shooting mode ends when the release button is released from the fully pressed state.

[0046] 2, the control unit 20 includes a storage 50, a CPU (Central Processing Unit) 51, and a memory 52. ​​The storage 50, the CPU 51, and the memory 52 are interconnected via a bus line 53. The control unit 20 is an example of an "exposure control device" and a "computer" according to the technology of the present disclosure.

[0047] The storage 50 is a non-volatile storage device such as an EEPROM (Electrically Erasable Programmable Read-Only Memory). The storage 50 stores various programs and various data associated with the programs. The storage 50 is an example of a "storage unit" according to the technology of the present disclosure. Instead of the EEPROM, a FeRAM (Ferroelectric Random Access Memory) or an MRAM (Magnetoresistive Random Access Memory) may be used as the storage 50.

[0048] The memory 52 is a work memory for the CPU 51 to execute processing. The CPU 51 loads a program stored in the storage 50 into the memory 52 and executes processing according to the program. In this way, the CPU 51 comprehensively controls each unit of the imaging device 10. The CPU 51 is an example of a "processor" according to the technology of the present disclosure. The memory 52 may be built into the CPU 51.

[0049] 3, an operation program 60 is stored in the storage 50. The operation program 60 is a program for causing the CPU 51 to perform exposure control. In other words, the operation program 60 is an example of an "operation program for an exposure control device" according to the technology of the present disclosure.

[0050] In addition to the operating program 60, the storage 50 also stores a second target exposure value EV2, a first threshold value TH1, a second threshold value TH2, status information 61, and the like. The second target exposure value EV2 is the exposure value targeted for exposure control in a past frame, in this case, the previous frame, which is the frame immediately before the current frame. The status information 61 is information indicating whether the state of the previous frame is an exposure control state in which exposure control is being performed, or an exposure control end state in which exposure control has ended. The current frame is an example of a "first frame" according to the technology of the present disclosure. Moreover, the past frame and the previous frame are examples of a "second frame" according to the technology of the present disclosure.

[0051] When the operating program 60 is started, the CPU 51, in cooperation with the memory 52, etc., functions as a photometry unit 65, a calculation unit 66, a setting unit 67, a read / write (hereinafter referred to as RW (Read Write)) control unit 68, a judgment unit 69, and a drive control unit 70.

[0052] Unprocessed image data 75 of the current frame is input to the photometry unit 65 from the image memory 31. The photometry unit 65 derives a photometry value 76 indicating the overall brightness of the image represented by the image data 75 from each pixel value of the image data 75. The photometry unit 65 outputs the photometry value 76 to the calculation unit 66. Note that, when a partial area of ​​the imaging surface 22 of the image sensor 12 is set as the imaging area of ​​the image by the electronic zoom function or electronic blur correction function, the photometry value 76 may be derived by limiting it to the set imaging area.

[0053] The calculation unit 66 calculates a first target exposure value EV1 based on the photometric value 76. The first target exposure value EV1 is an exposure value that is a target of exposure control in the current frame. More specifically, the first target exposure value EV1 is an exposure value for making the image represented by the image data 75 have appropriate brightness. The calculation unit 66 outputs the first target exposure value EV1 to the determination unit 69.

[0054] The setting unit 67 sets a threshold value based on the state information 61. More specifically, the setting unit 67 sets a threshold value for comparing the absolute value |ΔEV| of the difference ΔEV (=EV2-EV1) between the first target exposure value EV1 and the second target exposure value EV2 (hereinafter simply referred to as the absolute value of the difference |ΔEV|) to either the first threshold value TH1 or the second threshold value TH2. The setting unit 67 outputs threshold value setting information 77 to the determination unit 69 and the drive control unit 70.

[0055] The RW control unit 68 controls the storage of various data in the storage 50 and the reading of various data stored in the storage 50. For example, the RW control unit 68 reads the second target exposure value EV2 from the storage 50, and outputs the read second target exposure value EV2 to the determination unit 69. The RW control unit 68 also reads the first threshold value TH1 and the second threshold value TH2 from the storage 50, and outputs the read first threshold value TH1 and second threshold value TH2 to the determination unit 69. Furthermore, the RW control unit 68 reads the status information 61 from the storage 50, and outputs the read status information 61 to the setting unit 67.

[0056] The determination unit 69 calculates the difference ΔEV from the first target exposure value EV1 and the second target exposure value EV2. The determination unit 69 compares the absolute value of the difference |ΔEV| with the first threshold value TH1 or the second threshold value TH2. Then, depending on the result, the determination unit 69 determines whether or not to perform exposure control to make the exposure value of the current frame follow the first target exposure value EV1, that is, whether or not to perform exposure control. The determination unit 69 outputs determination information 78 indicating whether or not to perform exposure control to the drive control unit 70.

[0057] Furthermore, the determination unit 69 outputs the state information 61 to the RW control unit 68. The RW control unit 68 stores the state information 61 in the storage 50. The state information 61 is output from the determination unit 69 to the RW control unit 68 for each frame, and is stored for each frame by the RW control unit 68 while being updated in the storage 50. Although not shown in the figure, the determination unit 69 also outputs the state information 61 to the drive control unit 70.

[0058] The drive control unit 70 controls the driving of the aperture opening adjustment mechanism 19, the image sensor driver 23, and the shutter drive mechanism 25. The drive control unit 70 operates when the determination information 78 indicates that exposure control is to be performed. The drive control unit 70 adjusts the opening of the aperture 16, a gain according to the ISO sensitivity of the image sensor 12, and the shutter speed of the shutter 24 so that the difference ΔEV between the first target exposure value EV1 and the second target exposure value EV2 becomes zero.

[0059] The drive control unit 70 outputs the second target exposure value EV2 to the RW control unit 68. The RW control unit 68 stores the second target exposure value EV2 in the storage 50. The second target exposure value EV2 is output from the drive control unit 70 to the RW control unit 68 for each frame, and is stored in the storage 50 for each frame while being updated by the RW control unit 68.

[0060] The photometry unit 65, calculation unit 66, setting unit 67, determination unit 69, and drive control unit 70 repeatedly perform the above-described processes for each frame during live view image display and / or video shooting.

[0061] 4, when the state of the previous frame indicated by the state information 61 was an exposure control end state, the setting unit 67 sets the threshold to a first threshold TH1. The setting unit 67 outputs setting information 77 indicating that the threshold has been set to the first threshold TH1 to the determination unit 69. In this case, the determination unit 69 determines whether or not to implement exposure control by comparing the absolute value of the difference |ΔEV| with the first threshold TH1.

[0062] On the other hand, as an example, as shown in FIG. 5, when the state of the previous frame indicated by the state information 61 is the exposure control state, the setting unit 67 sets the threshold value to the second threshold value TH2. The setting unit 67 outputs setting information 77 indicating that the threshold value has been set to the second threshold value TH2 to the determination unit 69. In this case, the determination unit 69 determines whether to perform exposure control by comparing the absolute value |ΔEV| of the difference with the second threshold value TH2.

[0063] Since the first threshold value TH1 and the second threshold value TH2 are set such that exposure control is not performed unless the absolute value |ΔEV| of the difference is greater than that value, they are set as a so-called dead zone for exposure control. Here, the second threshold value TH2 is a value smaller than the first threshold value TH1 (TH2 < TH1). For example, the first threshold value TH1 is 20 and the second threshold value TH2 is 5.

[0064] As an example, as shown in FIG. 6, when the threshold value is set to the first threshold value TH1 and the absolute value |ΔEV| of the difference is less than or equal to the first threshold value TH1 (|ΔEV| ≦ TH1), the determination unit 69 determines not to perform exposure control and outputs determination information 78 indicating that exposure control is not performed to the drive control unit 70. In this case, the determination unit 69 outputs state information 61 indicating that the state of the current frame is the exposure control end state to the RW control unit 68.

[0065] On the other hand, as an example, as shown in FIG. 7, when the threshold value is set to the first threshold value TH1 and the absolute value |ΔEV| of the difference is greater than the first threshold value TH1 (|ΔEV| > TH1), the determination unit 69 determines to perform exposure control and outputs determination information 78 indicating that exposure control is to be performed to the drive control unit 70. The determination unit 69 includes the difference ΔEV in the determination information 78. The threshold value is set to the first threshold value TH1 when the state of the previous frame is the exposure control end state as shown in FIG. 4. Therefore, "performing exposure control" means starting exposure control. In this case, the determination unit 69 outputs state information 61 indicating that the state of the current frame is the exposure control state to the RW control unit 68.

[0066] As an example, as shown in FIG. 8, when the threshold is set to the second threshold TH2 and the absolute value of the difference |ΔEV| is equal to or less than the second threshold TH2 (|ΔEV|≦TH2), the determination unit 69 determines that exposure control is not to be performed and outputs determination information 78 indicating that exposure control is not to be performed to the drive control unit 70. The threshold is set to the second threshold TH2 when the state of the previous frame was the exposure control state as shown in FIG. 5. Therefore, "exposure control is not performed" means that exposure control is to be ended. In this case, the determination unit 69 outputs state information 61 indicating that the state of the current frame is the exposure control end state to the RW control unit 68. When the absolute value of the difference |ΔEV| is equal to or less than the second threshold TH2, this is an example of "when the magnitude relationship between the absolute value of the difference and the second threshold meets a preset condition" according to the technology of the present disclosure. Note that the case where the absolute value of the difference |ΔEV| becomes smaller than the second threshold TH2 may be determined as the case where the magnitude relationship between the absolute value of the difference and the second threshold meets a preset condition.

[0067] In the frame following the frame shown in FIG. 8, since the state indicated by the state information 61 is the exposure control end state, the setting unit 67 sets the threshold to the first threshold TH1 as shown in FIG. 4. The first threshold TH1 is a value greater than the second threshold TH2. Therefore, when the absolute value of the difference |ΔEV| becomes equal to or smaller than the second threshold TH2, the setting unit 67 sets a threshold greater than the second threshold TH2. That is, in the first embodiment, the first threshold TH1 is an example of a "third threshold greater than the second threshold" according to the technology of the present disclosure.

[0068] On the other hand, as shown in FIG. 9 as an example, when the threshold is set to the second threshold TH2 and the absolute value of the difference |ΔEV| is greater than the second threshold TH2 (|ΔEV|>TH2), the determination unit 69 determines to perform exposure control and outputs determination information 78 indicating that exposure control is to be performed to the drive control unit 70. The determination unit 69 includes the difference ΔEV in the determination information 78. As described above, the threshold is set to the second threshold TH2 when the state of the previous frame was the exposure control state as shown in FIG. 5. Therefore, "performing exposure control" means that exposure control is to be continued. In this case, the determination unit 69 outputs state information 61 indicating that the state of the current frame is the exposure control state to the RW control unit 68.

[0069] A specific example will be described below. As an example, as shown in Fig. 10, consider a shooting scene capturing a parent and child playing on the grass in a park, where the sun is hidden by clouds, but then the clouds move and the sun emerges. In this case, the photometric value 76 indicating the brightness of the image gradually increases. For this reason, as shown by the black circles in the graph of Fig. 11 as an example, the first target exposure value EV1 gradually decreases in order to maintain the image represented by image data 75 at an appropriate brightness.

[0070] When exposure control is performed appropriately while the sun is hidden by clouds as shown by the arrow above in Figure 10, and exposure control has ended, the threshold is set to the first threshold TH1. Then, as the clouds move and the sun gradually emerges, the first target exposure value EV1 begins to drop, and the difference ΔEV between the first target exposure value EV1 and the second target exposure value EV2 begins to increase. As the difference ΔEV increases, the absolute value of the difference |ΔEV| also increases, and finally the absolute value of the difference |ΔEV| exceeds the first threshold TH1.

[0071] When the absolute value of the difference |ΔEV| becomes larger than the first threshold value TH1, the determination unit 69 determines that exposure control is to be performed, and the drive control unit 70 starts exposure control. This results in an exposure control state, and the setting unit 67 sets the threshold value to the second threshold value TH2.

[0072] When the sun comes out as indicated by the arrow below in Figure 10, the photometric value 76 indicating the brightness of the image becomes almost constant, and the first target exposure value EV1 becomes almost constant at a relatively low value. As a result, the difference ΔEV narrows, and the absolute value of the difference |ΔEV| also becomes smaller, and finally the absolute value of the difference |ΔEV| becomes equal to or smaller than the second threshold value TH2.

[0073] When the absolute value of the difference |ΔEV| becomes equal to or smaller than the second threshold value TH2, the determination unit 69 determines that exposure control is not to be performed, and the drive control unit 70 ends the exposure control. This results in an exposure control end state, and the setting unit 67 sets the threshold value to the first threshold value TH1 again.

[0074] As an example, as shown in FIG. 12, when the setting information 77 from the setting unit 67 indicates that the first threshold value TH1 has been set and the state of the current frame indicated by the state information 61 from the judgment unit 69 is an exposure control stopped state, the drive control unit 70 outputs the first target exposure value EV1 calculated by the calculation unit 66 in the previous frame to the RW control unit 68 as the second target exposure value EV2.

[0075] As an example, as shown in FIG. 13, when the setting information 77 from the setting unit 67 indicates that the first threshold value TH1 has been set and the state of the current frame indicated by the state information 61 from the judgment unit 69 is an exposure control state, the drive control unit 70 outputs the first target exposure value EV1 calculated by the calculation unit 66 for the current frame to the RW control unit 68 as the second target exposure value EV2.

[0076] As an example, as shown in FIG. 14, when the setting information 77 from the setting unit 67 indicates that the second threshold value TH2 has been set and the state of the current frame indicated by the state information 61 from the judgment unit 69 is the exposure control end state, the drive control unit 70 outputs the first target exposure value EV1 calculated by the calculation unit 66 for the current frame to the RW control unit 68 as the second target exposure value EV2, as in the case of FIG. 13.

[0077] As an example, as shown in FIG. 15, when the setting information 77 from the setting unit 67 indicates that the second threshold value TH2 has been set and the state of the current frame indicated by the state information 61 from the judgment unit 69 is an exposure control state, the drive control unit 70 outputs the first target exposure value EV1 calculated by the calculation unit 66 for the current frame to the RW control unit 68 as the second target exposure value EV2, as in the cases of FIGS. 13 and 14.

[0078] Next, the operation of the above configuration will be described with reference to the flowcharts shown in Figures 16 and 17. As shown in Figure 3, the CPU 51 of the control unit 20 functions as a photometry unit 65, a calculation unit 66, a setting unit 67, a RW control unit 68, a determination unit 69, and a drive control unit 70 by starting the operating program 60.

[0079] Unprocessed image data 75 of the current frame is input from the image memory 31 to the photometry unit 65. Then, as shown in Fig. 16, a photometry value 76 is derived in the photometry unit 65 (step ST100). The photometry value 76 is output from the photometry unit 65 to the calculation unit 66.

[0080] The calculation unit 66 calculates a first target exposure value EV1 based on the photometric value 76 (step ST105). The first target exposure value EV1 is output from the calculation unit 66 to the determination unit 69.

[0081] 17. If the calculation of the first target exposure value EV1 by the calculation unit 66 is the first time (YES in step ST110), the process proceeds to step ST195 in Fig. 17. On the other hand, if the calculation of the first target exposure value EV1 by the calculation unit 66 is not the first time (NO in step ST110), the state information 61 is read from the storage 50 under the control of the RW control unit 68, and the read state information 61 is output to the setting unit 67. In addition, under the control of the RW control unit 68, the second target exposure value EV2, the first threshold value TH1, and the second threshold value TH2 are read from the storage 50, and the read second target exposure value EV2, the first threshold value TH1, and the second threshold value TH2 are output to the determination unit 69.

[0082] In the setting unit 67, the threshold is set based on the state information 61. That is, when the state of the previous frame indicated by the state information 61 is the exposure control end state (YES in step ST115), the threshold is set to the first threshold TH1 (step ST120) as shown in FIG.

[0083] The determination unit 69 calculates the difference ΔEV between the first target exposure value EV1 and the second target exposure value EV2 (step ST125), and then compares the absolute value |ΔEV| of the difference with the first threshold value TH1 (step ST130).

[0084] When the absolute value of the difference |ΔEV| is equal to or smaller than the first threshold value TH1 (|ΔEV|≦TH1 YES in step ST130), the determination unit 69 determines not to perform exposure control as shown in FIG. 6 (step ST135). The determination unit 69 outputs determination information 78 indicating that exposure control is not performed to the drive control unit 70. In this case, the determination unit 69 outputs state information 61 indicating that exposure control is in an end state to the RW control unit 68, and the state information 61 is stored in the storage 50 under the control of the RW control unit 68 (step ST140). Furthermore, as shown in FIG. 12, the drive control unit 70 outputs the first target exposure value EV1 of the previous frame as the second target exposure value EV2 to the RW control unit 68, and the second target exposure value EV2 is stored in the storage 50 under the control of the RW control unit 68 (step ST145). Thereafter, the process proceeds to the next frame.

[0085] On the other hand, when the absolute value of the difference |ΔEV| is greater than the first threshold value TH1 (|ΔEV|>TH1, NO in step ST130), the determination unit 69 determines to perform exposure control as shown in FIG. 7 (step ST150). The determination unit 69 outputs determination information 78 including the difference ΔEV, indicating that exposure control is to be performed, to the drive control unit 70. This starts exposure control under the control of the drive control unit 70 (step ST155). In this case, the determination unit 69 outputs state information 61 indicating that the exposure control is in progress to the RW control unit 68, and the state information 61 is stored in the storage 50 under the control of the RW control unit 68 (step ST160). Furthermore, as shown in FIG. 13, the drive control unit 70 outputs the first target exposure value EV1 of the current frame as the second target exposure value EV2 to the RW control unit 68, and the second target exposure value EV2 is stored in the storage 50 under the control of the RW control unit 68 (step ST165). After that, the process moves to the next frame.

[0086] If the state of the previous frame indicated by the state information 61 was the exposure control state (NO in step ST115), the process proceeds to step ST170 in Fig. 17. That is, as shown in Fig. 5, the threshold is set to the second threshold TH2.

[0087] In the determination unit 69, the difference ΔEV between the first target exposure value EV1 and the second target exposure value EV2 is calculated (step ST175) as in step ST125. Then, the absolute value |ΔEV| of the difference is compared with the second threshold value TH2 (step ST180).

[0088] When the absolute value of the difference |ΔEV| is equal to or smaller than the second threshold value TH2 (|ΔEV|≦TH2 YES in step ST180), the determination unit 69 determines not to perform exposure control as shown in FIG. 8 (step ST185). The determination unit 69 outputs determination information 78 indicating that exposure control will not be performed to the drive control unit 70. This causes the exposure control by the drive control unit 70 to end (step ST190). In this case, the determination unit 69 outputs state information 61 indicating that the exposure control is in an end state to the RW control unit 68, and the state information 61 is stored in the storage 50 under the control of the RW control unit 68 (step ST195). Furthermore, as shown in FIG. 14, the drive control unit 70 outputs the first target exposure value EV1 of the current frame as the second target exposure value EV2 to the RW control unit 68, and the second target exposure value EV2 is stored in the storage 50 under the control of the RW control unit 68 (step ST200). Thereafter, the process proceeds to the next frame.

[0089] Similarly, when the calculation unit 66 has calculated the first target exposure value EV1 for the first time (YES in step ST110), the determination unit 69 outputs state information 61 indicating that exposure control is in an end state to the RW control unit 68, and under the control of the RW control unit 68, the state information 61 is stored in the storage 50 (step ST195). Furthermore, the drive control unit 70 outputs the first target exposure value EV1 of the current frame to the RW control unit 68 as a second target exposure value EV2, and under the control of the RW control unit 68, the second target exposure value EV2 is stored in the storage 50 (step ST200).

[0090] On the other hand, when the absolute value of the difference |ΔEV| is greater than the second threshold value TH2 (|ΔEV|>TH2, NO in step ST180), the determination unit 69 determines to perform exposure control as shown in FIG. 9 (step ST205). The determination unit 69 outputs determination information 78 including the difference ΔEV, indicating that exposure control is to be performed, to the drive control unit 70. As a result, exposure control is continued under the control of the drive control unit 70 (step ST210). In this case, the determination unit 69 outputs state information 61 indicating that the exposure control is in progress to the RW control unit 68, and the state information 61 is stored in the storage 50 under the control of the RW control unit 68 (step ST215). Furthermore, as shown in FIG. 15, the drive control unit 70 outputs the first target exposure value EV1 of the current frame as the second target exposure value EV2 to the RW control unit 68, and the second target exposure value EV2 is stored in the storage 50 under the control of the RW control unit 68 (step ST200). After that, the process moves to the next frame.

[0091] As described above, the CPU 51 of the control unit 20 of the imaging device 10 includes the setting unit 67 and the drive control unit 70. The drive control unit 70 starts exposure control when the absolute value |ΔEV| of the difference between the first target exposure value EV1 of the current frame and the second target exposure value EV2 of the previous frame becomes larger than the first threshold value TH1. The setting unit 67 acquires a second threshold value TH2 smaller than the first threshold value TH1 in response to the start of exposure control. When the magnitude relationship between the absolute value |ΔEV| of the difference and the second threshold value TH2 meets a preset condition, the drive control unit 70 sets the threshold value to be compared with the absolute value |ΔEV| of the difference to a third threshold value larger than the second threshold value TH2, here the first threshold value TH1, and ends the exposure control.

[0092] 18 shows a comparative example in which exposure control is performed without changing the threshold value to the first threshold value TH1. In this case, because the first threshold value TH1 is relatively large and the dead band of exposure control is wide, the exposure control ends with the difference ΔEV between the first target exposure value EV1 and the second target exposure value EV2 remaining large (up to the first threshold value TH1), and there is a risk that an image with appropriate brightness cannot be provided.

[0093] In contrast, in the imaging device 10 of the present disclosure, the threshold is changed to a second threshold TH2 smaller than the first threshold TH1 in response to the start of exposure control. This reduces the risk of the exposure control ending with a large difference ΔEV between the first target exposure value EV1 and the second target exposure value EV2, resulting in a state in which an image with appropriate brightness cannot be provided. This makes it possible to perform appropriate exposure control.

[0094] The setting unit 67 sets the first threshold TH1 as the third threshold, which simplifies the setting of the threshold.

[0095] The drive control unit 70 ends the exposure control when the absolute value of the difference |ΔEV| becomes equal to or less than the second threshold value TH2. Therefore, the difference ΔEV between the first target exposure value EV1 and the second target exposure value EV2 in the exposure control end state is always equal to or less than the second threshold value TH2. By setting the second threshold value TH2 to an appropriate value, it is possible to provide an image that maintains appropriate brightness.

[0096] The determination unit 69 outputs state information 61 to the RW control unit 68, which indicates whether the absolute value of the difference |ΔEV| is greater than the first threshold value TH1 or the second threshold value TH2, indicating an exposure control state in which exposure control is being performed, or the absolute value of the difference |ΔEV| is equal to or smaller than the first threshold value TH1 or the second threshold value TH2, indicating an exposure control end state in which exposure control has ended. The RW control unit 68 stores the state information 61 in the storage 50 for each frame. This makes it possible to reliably grasp whether the state of the previous frame was the exposure control state or the exposure control end state. The setting unit 67 can set the threshold value based on the state information 61 without error.

[0097] When the state of the previous frame was the exposure control end state, the setting unit 67 sets the threshold to the first threshold TH1. On the other hand, when the state of the previous frame was the exposure control state, the setting unit 67 sets the threshold to the second threshold TH2. In the exposure control end state, the threshold is set to the first threshold TH1 to widen the dead band of the exposure control, thereby making it possible to avoid hunting, in which exposure control is frequently performed in response to every small change in the difference ΔEV between the first target exposure value EV1 and the second target exposure value EV2. On the other hand, in the exposure control state, the threshold is set to the second threshold TH2 to narrow the dead band of the exposure control, thereby reducing the risk of the exposure control end state being reached with the difference ΔEV between the first target exposure value EV1 and the second target exposure value EV2 remaining large.

[0098] The drive control unit 70 outputs the second target exposure value EV2 to the RW control unit 68. The RW control unit 68 stores the second target exposure value EV2 for each frame in the storage 50. This makes it possible to reliably calculate the difference ΔEV between the first target exposure value EV1 and the second target exposure value EV2.

[0099] [Second embodiment] 19, in the second embodiment, the CPU 51 functions as a counting unit 85 in addition to the processing units 65-70 (not shown except for the RW control unit 68 and the determination unit 69) of the first embodiment. The counting unit 85 receives an input of a first target exposure value EV1 from the calculation unit 66.

[0100] The RW control unit 68 reads out the second target exposure value EV2, the first threshold TH1, and the second threshold TH2 from the storage 50, and outputs the read out second target exposure value EV2, the first threshold TH1, and the second threshold TH2 to the counting unit 85 and the determination unit 69. The RW control unit 68 also reads out the difference ΔEV between the first target exposure value EV1 and the second target exposure value EV2 from the storage 50, and outputs the read out difference ΔEV to the counting unit 85. This difference ΔEV was calculated by the determination unit 69 in the previous frame. Hereinafter, this difference ΔEV will be referred to as a difference ΔEVX in order to distinguish it from the difference ΔEV of the current frame.

[0101] The storage 50 also stores an inversion count NR and a set frame number SF. The inversion count NR is the number of times that the positive and negative of the difference ΔEV are consecutively inverted. The set frame number SF is a threshold for comparing the inversion count NR with the set frame number SF, and is, for example, 5 to 10. The set frame number SF is an example of a "preset frame number" according to the technology of the present disclosure. The RW control unit 68 reads out the inversion count NR and the set frame number SF from the storage 50, and outputs the read inversion count NR and set frame number SF to the determination unit 69.

[0102] The counter 85 calculates the difference ΔEV between the first target exposure value EV1 and the second target exposure value EV2. The counter 85 generates an update instruction signal 86 for the number of inversions NR based on the difference ΔEV of the current frame, the difference ΔEVX of the previous frame, the first threshold value TH1, and the second threshold value TH2. The counter 85 outputs the update instruction signal 86 to the RW control unit 68. The RW control unit 68 updates the number of inversions NR in response to the update instruction signal 86.

[0103] 20, when the absolute value of the difference |ΔEV| of the current frame is equal to or smaller than the first threshold value TH1 and is larger than the second threshold value TH2 (TH2<|ΔEV|≦TH1), and when the positive and negative signs of the difference ΔEV of the current frame and the difference ΔEVX of the previous frame are inverted, the counting unit 85 outputs an update instruction signal 86 to the RW control unit 68 to increment the inversion number NR. The RW control unit 68 increments the inversion number NR in response to this update instruction signal 86.

[0104] 21, when the absolute value of the difference |ΔEV| of the current frame is equal to or smaller than the first threshold value TH1 and larger than the second threshold value TH2, but the difference ΔEV of the current frame and the difference ΔEVX of the previous frame are the same in sign, the counter 85 outputs an update instruction signal 86 to the RW control unit 68 to clear the inversion number NR to 0. The RW control unit 68 clears the inversion number NR to 0 in response to this update instruction signal 86. Clearing the inversion number NR to 0 means setting the inversion number NR to 0.

[0105] Also, as shown in FIG. 22 as an example, when the absolute value of the difference |ΔEV| of the current frame is greater than the first threshold value TH1 (|ΔEV|>TH1), the counting unit 85 also outputs an update instruction signal 86 for clearing the inversion count NR to 0 to the RW control unit 68. The RW control unit 68 clears the inversion count NR to 0 in response to this update instruction signal 86.

[0106] As shown in FIG. 23 as an example, when the inversion count NR is equal to or greater than the set frame number SF (NR≧SF), the determination unit 69 determines that exposure control is not performed, and outputs determination information 78 indicating that exposure control is not performed to the drive control unit 70.

[0107] As shown in FIG. 24 as an example, the reason why the inversion count NR becomes equal to or greater than the set frame number SF is that, at the end of the exposure control state, the first target exposure value EV1 and the second target exposure value EV2 continue to change slightly, and exposure control is frequently performed in response to each change, resulting in hunting. In such a case, the determination unit 69 determines that further exposure control is unnecessary because hunting has occurred, and determines that exposure control is not performed. Therefore, "not performing exposure control" shown in FIG. 24 means forcibly ending exposure control.

[0108] On the other hand, as shown in FIG. 25 as an example, when the inversion count NR is less than the set frame number SF (NR<SF), the determination unit 69 determines that exposure control is performed, and outputs determination information 78 indicating that exposure control is performed to the drive control unit 70. The determination unit 69 includes the difference ΔEV in the determination information 78. "Performing exposure control" in this case means continuing exposure control.

[0109] As shown in FIG. 26 as an example, the determination unit 69 outputs the difference ΔEVX to the RW control unit 68 only when the state of the current frame indicated by the state information 61 is the exposure control state. The RW control unit 68 stores the difference ΔEVX in the storage 50.

[0110] The operation of the second embodiment will be described with reference to the flowcharts shown in Figures 27 to 29 as an example. Descriptions of processes that are the same as those in the first embodiment will be omitted as much as possible, and mainly processes unique to the second embodiment will be described.

[0111] First, as shown in FIG. 27, when the absolute value of the difference |ΔEV| is greater than the first threshold value TH1 (NO in step ST130), exposure control is started under the control of the drive control unit 70 (step ST155), and state information 61 indicating that the exposure control state is being output from the determination unit 69 to the RW control unit 68 (step ST160), then, as shown in FIG. 26, the difference ΔEVX is output from the determination unit 69 to the RW control unit 68, and under the control of the RW control unit 68, the difference ΔEVX is stored in the storage 50 (step ST300).

[0112] Under the control of the RW control unit 68, the second target exposure value EV2, the first threshold value TH1, and the second threshold value TH2 are read from the storage 50, and the read second target exposure value EV2, the first threshold value TH1, and the second threshold value TH2 are output to the counting unit 85 and the determination unit 69. In addition, under the control of the RW control unit 68, the difference ΔEVX of the previous frame is read from the storage 50, and the read difference ΔEVX is output to the counting unit 85.

[0113] As shown in FIG. 28, the threshold is set to the second threshold TH2 by the setting unit 67 (step ST170), and if the absolute value of the difference |ΔEV| is greater than the second threshold TH2 (NO in step ST180), the counting unit 85 compares the absolute value of the difference |ΔEV| with the first threshold TH1 (step ST305).

[0114] If the absolute value of the difference |ΔEV| is less than or equal to the first threshold value TH1 (|ΔEV|≦TH1, YES in step ST305), the counter 85 further determines whether the sign of the difference ΔEV of the current frame and the difference ΔEVX of the previous frame is inverted (step ST310).

[0115] When the positive and negative of the difference ΔEV of the current frame and the difference ΔEVX of the previous frame are inverted (YES in step ST310), the counting unit 85 outputs an update instruction signal 86 to the RW control unit 68 to increment the inversion number NR (step ST315), as shown in Fig. 20. In response to this update instruction signal 86, the RW control unit 68 increments the inversion number NR of the storage 50.

[0116] Under the control of the RW control unit 68 , the number of transitions NR and the set number of frames SF are read from the storage 50 , and the read number of transitions NR and the set number of frames SF are output to the determination unit 69 .

[0117] The determination unit 69 compares the number of inversions NR with the set number of frames SF (step ST320). If the number of inversions NR is equal to or greater than the set number of frames SF (YES in step ST320), the determination unit 69 determines not to perform exposure control (step ST325), as shown in FIG. 23. The determination unit 69 outputs determination information 78 indicating that exposure control will not be performed to the drive control unit 70. This causes the exposure control by the drive control unit 70 to be forcibly ended (step ST330).

[0118] When the absolute value of the difference |ΔEV| is greater than the first threshold value TH1 (|ΔEV|>TH1, NO in step ST305), and when the difference ΔEV of the current frame and the difference ΔEVX of the previous frame are the same in sign (NO in step ST310), the process proceeds to step ST335 in Fig. 29. That is, as shown in Figs. 21 and 22, the counter 85 outputs an update instruction signal 86 to the RW control unit 68 to clear the inversion count NR to 0. In response to this update instruction signal 86, the RW control unit 68 clears the inversion count NR of the storage 50 to 0.

[0119] Thereafter, exposure control continues under the control of the drive control unit 70 (step ST340). Even when the number of inversion times NR is less than the set number of frames SF (NO in step ST320, NR < SF), exposure control continues under the control of the drive control unit 70 (step ST340).

[0120] In this case, state information 61 indicating that it is in the exposure control state is output from the determination unit 69 to the RW control unit 68, and under the control of the RW control unit 68, the state information 61 is stored in the storage 50 (step ST345). Further, the first target exposure value EV1 of the current frame is output from the drive control unit 70 to the RW control unit 68 as the second target exposure value EV2, and under the control of the RW control unit 68, the second target exposure value EV2 is stored in the storage 50 (step ST350).

[0121] Then, similar to step ST300 in FIG. 27, the difference ΔEVX is output from the determination unit 69 to the RW control unit 68, and under the control of the RW control unit 68, the difference ΔEVX is stored in the storage 50 (step ST355). Thereafter, the process proceeds to the next frame.

[0122] In this way, in the second embodiment, when the absolute value of the difference |ΔEV| is less than or equal to the first threshold TH1 and greater than the second threshold TH2, and the positive / negative of the difference ΔEV has been inverted for the set number of frames SF, the drive control unit 70 ends the exposure control.

[0123] By setting the second threshold TH2 to be relatively small, hunting as shown in FIG. 24 is more likely to occur compared to the case where the threshold is set to the first threshold TH1. Therefore, in the second embodiment, when the state where the positive / negative of the difference ΔEV has been inverted continues for the set number of frames SF, it is determined that hunting has occurred, and the exposure control is forcibly ended. Thus, it is possible to reduce the risk of unnecessary exposure control continuing indefinitely.

[0124] The determination unit 69 outputs the difference ΔEVX of the previous frame to the RW control unit 68. The RW control unit 68 stores the difference ΔEVX in the storage 50. For this reason, it is possible to reliably grasp whether or not the positive and negative of the difference ΔEV of the current frame and the difference ΔEVX of the previous frame are inverted, and further whether or not hunting is occurring.

[0125] Only when the state of the current frame indicated by the state information 61 is the exposure control state, the determination unit 69 stores the difference ΔEVX in the storage 50. For this reason, it is possible to store in the storage 50 only the difference ΔEVX relating to whether or not hunting is occurring, and it is not necessary to store unnecessary information in the storage 50.

[0126] [Third embodiment] As shown in Fig. 30 as an example, in the third embodiment, history information 90 is stored in the storage 50. As shown in Fig. 31 as an example, the history information 90 is a collection of histories of absolute values ​​of differences |ΔEV| when the exposure control ends. The determination unit 69 outputs the absolute value of the difference |ΔEV| to the RW control unit 68. The RW control unit 68 registers the absolute value of the difference |ΔEV| in the history information 90.

[0127] The RW control unit 68 outputs the maximum value |ΔEV|max of the history of the absolute values ​​of the differences |ΔEV| registered in the history information 90 to the determination unit 69 as the second threshold value TH2. The determination unit 69 determines whether or not to implement exposure control by comparing the absolute value of the difference |ΔEV| calculated from the first target exposure value EV1 and the second target exposure value EV2 with the second threshold value TH2 based on this maximum value |ΔEV|max. Hereinafter, the second threshold value TH2 based on this maximum value |ΔEV|max will be referred to as TH2max to distinguish it from the default second threshold value TH2.

[0128] As an example, as shown in FIG. 32, when it is determined that the absolute value of the difference |ΔEV| is equal to or less than the second threshold TH2 and exposure control is not performed, and when the state of the current frame becomes the exposure control end state, the determination unit 69 outputs the absolute value of the difference |ΔEV| to the RW control unit 68. The RW control unit 68 stores the absolute value of the difference |ΔEV| in the storage 50 by registering the absolute value of the difference |ΔEV| in the history information 90.

[0129] Also, as an example, as shown in FIG. 33, when the history of the absolute value of the difference |ΔEV| when the exposure control ends is stored in the storage 50 for the set number SN, and the maximum value |ΔEV|max of the history of the absolute value of the difference |ΔEV| when the exposure control ends is smaller than the second threshold TH2 (|ΔEV|max < TH2), the RW control unit 68 subtracts the second threshold TH2 from the maximum value |ΔEV|max to obtain a second threshold TH2max. The RW control unit 68 outputs the second threshold TH2max to the determination unit 69. The set number SN is, for example, 10 to 15.

[0130] When the power button of the operation unit 21 is operated by the user to give an instruction to turn off the power of the imaging device 10, the power-off signal 95 is received by the instruction reception unit 37. As an example, as shown in FIG. 34, the power-off signal 95 is input from the instruction reception unit 37 to the RW control unit 68. Upon receiving the power-off signal 95, the RW control unit 68 outputs a history deletion signal 96 for deleting the history of the absolute value of the difference |ΔEV| when the exposure control ends, which has been registered in the history information 90 until then. The instruction to turn off the power of the imaging device 10 is an example of the "predetermined operation instruction" according to the technology of the present disclosure. Note that the RW control unit 68 newly starts storing the history of the absolute value of the difference |ΔEV| when the exposure control ends when the power of the imaging device 10 is turned on.

[0131] The operation of the third embodiment will be described with reference to the flowcharts shown in FIGS. 35 to 37 as an example. For the same processes as those in the first embodiment, the description will be omitted as much as possible, and mainly the processes specific to the third embodiment will be described.

[0132] First, as shown in FIG. 35, when the absolute value of the difference |ΔEV| is equal to or less than the second threshold TH2 (YES in step ST180), and it is determined by the determination unit 69 that exposure control is not to be performed (step ST185), and when the exposure control by the drive control unit 70 is completed (step ST190), as shown in FIG. 32, the absolute value of the difference |ΔEV| is output from the determination unit 69 to the RW control unit 68, and under the control of the RW control unit 68, the absolute value of the difference |ΔEV| is stored in the storage 50 (step ST400).

[0133] As shown in FIG. 36, when the state of the previous frame indicated by the state information 61 is the exposure control state (NO in step ST115), the RW control unit 68 searches whether the absolute value of the difference |ΔEV| history at the time of the exposure control end state is stored in the storage 50 for the set number SN (step ST405).

[0134] When the absolute value of the difference |ΔEV| history is stored in the storage 50 for the set number SN (YES in step ST405), the RW control unit 68 compares the maximum value |ΔEV|max among the histories with the second threshold TH2 (step ST410).

[0135] When the maximum value |ΔEV|max is smaller than the second threshold TH2 (|ΔEV|max < TH2, YES in step ST410), as shown in FIG. 33, the second threshold TH2 is subtracted from the maximum value |ΔEV|max by the RW control unit 68 to obtain the second threshold TH2max (step ST415). Then, the threshold is set to the second threshold TH2max by the setting unit 67 (step ST420).

[0136] On the other hand, when the absolute value of the difference |ΔEV| history is not stored in the storage 50 for the set number SN (NO in step ST405), and when the maximum value |ΔEV|max is the same as the second threshold TH2 (|ΔEV|max = TH2, NO in step ST410), the threshold is set to the second threshold TH2 by the setting unit 67 without subtracting the second threshold TH2 from the maximum value |ΔEV|max (step ST420).

[0137] 37, when the user operates the power button of the operation unit 21 to instruct to power off the imaging device 10, and a power-off signal 95 is input to the RW control unit 68 as shown in Fig. 34 (YES in step ST425), a history erasure signal 96 is output from the RW control unit 68. This causes the history of the absolute value of the difference |ΔEV| when the exposure control ended state was reached, which had been registered in the history information 90 up until that point (step ST430).

[0138] Thus, in the third embodiment, the RW control unit 68 stores in the storage 50 a history of the absolute value |ΔEV| of the difference when the exposure control ends. Then, when the maximum value |ΔEV|max in the history is smaller than the second threshold value TH2, the second threshold value TH2 is subtracted from the maximum value |ΔEV|max. This makes it possible to set the second threshold value TH2 to a value suitable for the shooting scene. In addition, it is possible to further reduce the risk of the exposure control ending state occurring when the difference ΔEV between the first target exposure value EV1 and the second target exposure value EV2 remains large, resulting in a state in which an image with appropriate brightness cannot be provided.

[0139] The RW control unit 68 performs a process of subtracting the second threshold value TH2 from the maximum value |ΔEV|max when the history of the absolute value |ΔEV| of the difference when the exposure control is ended is stored for the set number SN in the storage 50. This ensures the validity of the process of subtracting the second threshold value TH2 from the maximum value |ΔEV|max.

[0140] When the RW control unit 68 receives an instruction to turn off the power of the imaging device 10, the RW control unit 68 does not inherit the history of the absolute value of the difference |ΔEV| stored in the storage 50 when the exposure control ends. More specifically, the RW control unit 68 erases the history of the absolute value of the difference |ΔEV| when the exposure control ends from the storage 50. Turning off the power of the imaging device 10 indicates that the shooting of the image in the shooting scene has ended. Therefore, when the power of the imaging device 10 is turned off, the history of the absolute value of the difference |ΔEV| is erased without being inherited in order to newly store the history of the absolute value of the difference |ΔEV| in the next shooting scene. This makes it possible to always set the second threshold value TH2 to a value suitable for the shooting scene.

[0141] The preset operation instruction is not limited to an instruction to turn off the power of the exemplified imaging device 10. It may be an instruction to perform a zoom operation, an instruction to switch from a video shooting mode to an image playback mode, etc. As a method for not carrying over the history, in addition to erasing the history, a method of not treating the data stored in the storage 50 as history can also be considered.

[0142] The process of reducing the second threshold TH2 may be performed any number of times, not limited to once. If the default second threshold TH2 is 5, for example, the second threshold TH2 may be reduced in multiple stages such as 5, 4, 3, . . .

[0143] The second frame is not limited to the frame immediately preceding the current frame. A set of frames from the current frame to a predetermined number of frames before may be the second frame. In this case, the second target exposure value EV2 is a representative value such as the average value of the second target exposure values ​​EV2 of the set of frames.

[0144] [Fourth embodiment] As an example, as shown in FIG. 38, in the fourth embodiment, the CPU 51 of the control unit 20 functions as the subject detection unit 100 in addition to the processing units 65 to 70 (only the setting unit 67 and the determination unit 69 are shown in FIG. 38) of the first embodiment. Image data 75 is input to the subject detection unit 100. The subject detection unit 100 detects a person as a subject appearing in the image represented by the image data 75. The subject detection unit 100 outputs the detection result 101 of the person to the setting unit 67.

[0145] The state information 61 from the RW control unit 68 and the detection result 101 from the subject detection unit 100 are input to the setting unit 67. Further, a condition 102 based on the detection result 101 is input to the setting unit 67. The condition 102 is stored in the storage 50, read from the storage 50 under the control of the RW control unit 68, and output to the setting unit 67.

[0146] In the present fourth embodiment, in addition to the first threshold TH1 and the second threshold TH2, a third_1 threshold TH3_1 and a third_2 threshold TH3_2 can be set as thresholds. Both the third_1 threshold TH3_1 and the third_2 threshold TH3_2 are larger than the second threshold TH2 (TH2 < TH3_1, TH3_2). Also, the third_1 threshold TH3_1 is smaller than the first threshold TH1 (TH3_1 < TH1). And the third_2 threshold TH3_2 is larger than the first threshold TH1 (TH1 < TH3_2). For example, the first threshold TH1 is 20, the second threshold TH2 is 5, the third_1 threshold TH3_1 is 18, and the third_2 threshold TH3_2 is 22.

[0147] 39, when the state of the previous frame indicated by the state information 61 is the exposure control end state and the detection result 101 indicates that one person has been detected, the setting unit 67 sets the threshold to the 3_1 threshold TH3_1 according to a condition 102 that indicates that if there is one person, the threshold is set to the 3_1 threshold TH3_1. The setting unit 67 outputs setting information 77 indicating that the threshold has been set to the 3_1 threshold TH3_1 to the determination unit 69. In this case, the determination unit 69 determines whether or not to implement exposure control by comparing the absolute value of the difference |ΔEV| with the 3_1 threshold TH3_1.

[0148] As an example, as shown in FIG. 40, when the state of the previous frame indicated by the state information 61 is the exposure control end state and the detection result 101 indicates that multiple people are detected, the setting unit 67 sets the threshold to the 3_2 threshold TH3_2 according to the condition 102 that the threshold is set to the 3_2 threshold TH3_2 when multiple people are detected. The setting unit 67 outputs setting information 77 indicating that the threshold has been set to the 3_2 threshold TH3_2 to the determination unit 69. In this case, the determination unit 69 determines whether or not to perform exposure control by comparing the absolute value of the difference |ΔEV| with the 3_2 threshold TH3_2. Note that when the detection result 101 does not satisfy the condition 102, such as when no people are captured in the image represented by the image data 75, the setting unit 67 sets the threshold to the first threshold TH1.

[0149] In this manner, in the fourth embodiment, the setting unit 67 sets the third threshold different from the first threshold TH1, that is, the 3_1 threshold TH3_1 or the 3_2 threshold TH3_2, in accordance with the condition 102. Therefore, it is possible to set a threshold in accordance with the condition 102.

[0150] The setting unit 67 sets the third_1st threshold TH3_1 which is smaller than the first threshold TH1, so that the exposure control can be made to follow the change in the photographing scene more quickly than in the case where the first threshold TH1 is set.

[0151] As shown in Fig. 39, when the image represented by the image data 75 contains one person, the threshold is set to a 3_1 threshold TH3_1 smaller than the first threshold TH1 in order to allow exposure control to quickly follow changes in the shooting scene according to the movement of the one person. On the other hand, as shown in Fig. 40, when the image represented by the image data 75 contains multiple people, the threshold is set to a 3_2 threshold TH3_2 larger than the first threshold TH1 in order not to overreact to changes in the shooting scene according to the movements of the multiple people. By setting the threshold in this way according to the condition 102 based on the detection result 101 of the subject detection unit 100, more appropriate exposure control can be performed.

[0152] The fourth embodiment may be implemented in combination with the second embodiment and / or the third embodiment.

[0153] The imaging device according to the technique of the present disclosure may be a compact digital camera, a smartphone, or a tablet terminal.

[0154] In each of the above embodiments, the following various processors can be used as the hardware structure of the processing unit that executes various processes, such as the image processing unit 32, the display control unit 35, the instruction receiving unit 37, the photometry unit 65, the calculation unit 66, the setting unit 67, the RW control unit 68, the determination unit 69, the drive control unit 70, the counting unit 85, and the subject detection unit 100. The various processors include the CPU 51, which is a general-purpose processor that executes software (operation program 60) and functions as various processing units, as well as a programmable logic device (PLD), which is a processor whose circuit configuration can be changed after manufacture, such as an FPGA (Field Programmable Gate Array), and / or a dedicated electric circuit, which is a processor having a circuit configuration designed specifically for executing specific processes, such as an ASIC (Application Specific Integrated Circuit), and the like.

[0155] A single processing unit may be composed of one of these various processors, or may be composed of a combination of two or more processors of the same or different types (e.g., a combination of multiple FPGAs and / or a combination of a CPU and an FPGA). Also, multiple processing units may be composed of a single processor.

[0156] As an example of configuring multiple processing units with one processor, first, there is a form in which one processor is configured with a combination of one or more CPUs and software, as typified by computers such as client and server, and this processor functions as multiple processing units. Second, there is a form in which a processor is used that realizes the functions of the entire system including multiple processing units with one IC (Integrated Circuit) chip, as typified by System On Chip (SoC), etc. In this way, the various processing units are configured using one or more of the above various processors as a hardware structure.

[0157] Furthermore, more specifically, the hardware structure of these various processors can be an electric circuit that combines circuit elements such as semiconductor elements.

[0158] From the above description, the technology described in the following supplementary paragraphs can be understood.

[0159] [Additional note 1] An exposure control device that performs exposure control to make an exposure value in an imaging device follow a target exposure value, A processor is provided. The processor, starting the exposure control when an absolute value of a difference between a first target exposure value of a first frame captured by the imaging device and a second target exposure value of a second frame captured prior to the first frame becomes greater than the first threshold value; obtaining a second threshold value that is smaller than the first threshold value in response to the start of the exposure control; when the magnitude relationship between the absolute value of the difference and the second threshold value satisfies a preset condition, a threshold value to be compared with the absolute value of the difference is set to a third threshold value that is greater than the second threshold value, and the exposure control is terminated. Exposure control device. [Additional note 2] The processor, 2. The exposure control device according to claim 1, wherein the third threshold value is set to the same value as the first threshold value. [Additional note 3] The processor, 3. The exposure control device according to claim 1 or 2, wherein the third threshold value is set to a value different from the first threshold value depending on a condition. [Additional note 4] The processor, The exposure control device according to claim 3, further comprising: setting the third threshold value to a value smaller than the first threshold value depending on the condition. [Additional note 5] 5. The exposure control device according to claim 3, wherein the condition is based on a result of detection of a subject. [Additional note 6] The processor, An exposure control device as described in any one of appendix 1 to appendix 5, which, when the absolute value of the difference becomes equal to or less than the second threshold, sets a threshold to be compared with the absolute value of the difference to a third threshold that is greater than the second threshold, and terminates the exposure control. [Additional note 7] The processor, An exposure control device according to any one of appendix 1 to appendix 6, in which a memory unit stores, for each frame, whether the absolute value of the difference is greater than the first threshold, the second threshold, or the third threshold, and the exposure control is being performed, or whether the absolute value of the difference is equal to or less than the first threshold, the second threshold, or the third threshold, and the exposure control has been terminated. [Additional note 8] The processor, If the second frame is in the exposure control end state, a threshold value to be compared with the absolute value of the difference is set to the first threshold value or the third threshold value; 8. The exposure control device according to claim 7, wherein, when the second frame is in the exposure control state, a threshold value to be compared with an absolute value of the difference is set to the second threshold value. [Additional note 9] The processor, 9. The exposure control device according to claim 7 or 8, wherein the second target exposure value is stored in the storage unit for each frame. [Additional Note 10] The processor, An exposure control device as described in any one of appendix 1 to appendix 9, wherein, when the absolute value of the difference is equal to or less than the first threshold or the third threshold and greater than the second threshold, and the positive and negative of the difference are inverted for a predetermined number of frames, a threshold to be compared with the absolute value of the difference is set to the third threshold which is greater than the second threshold, and the exposure control is terminated. [Additional Note 11] The processor, The exposure control device according to claim 10, wherein the difference is stored in a storage unit. [Additional Note 12] The processor, storing, for each frame, in the storage unit, whether the absolute value of the difference is greater than the first threshold, the second threshold, or the third threshold and the exposure control is being performed, or whether the absolute value of the difference is equal to or less than the first threshold, the second threshold, or the third threshold and the exposure control has been terminated; The exposure control device according to claim 11, wherein the difference is stored in the storage unit only when the first frame is in the exposure control state. [Additional Note 13] The processor, a history of the absolute value of the difference when the exposure control is ended is stored in the storage unit; The exposure control device according to any one of appended claims 7 to 12, wherein, when a maximum value in the history is smaller than the second threshold, the second threshold is subtracted from the maximum value. [Additional Note 14] The processor, The exposure control device according to claim 13, further comprising a process of subtracting the second threshold value from the maximum value when a preset number of the histories have been stored in the storage unit. [Additional Note 15] The processor, 15. The exposure control device according to claim 13 or 14, wherein, when a preset operation instruction is received, the history stored in the storage unit is not carried over. [Additional Note 16] The processor, 16. The exposure control device according to claim 15, wherein the history is erased from the storage unit when a preset operation instruction is received. [Additional Note 17] An exposure control device according to any one of claims 1 to 16, An imaging element; An imaging device comprising:

[0160] The technology of the present disclosure can be appropriately combined with the above-mentioned various embodiments and / or various modified examples. In addition, it is not limited to the above-mentioned embodiments, and various configurations can be adopted without departing from the gist of the technology. Furthermore, the technology of the present disclosure extends to a storage medium that non-temporarily stores a program, in addition to a program.

[0161] The above description and illustrations are detailed descriptions of the parts related to the technology of the present disclosure, and are merely an example of the technology of the present disclosure. For example, the above description of the configuration, function, action, and effect is an example of the configuration, function, action, and effect of the parts related to the technology of the present disclosure. Therefore, it goes without saying that unnecessary parts may be deleted, new elements may be added, or replaced with respect to the description and illustrations shown above, within the scope of the gist of the technology of the present disclosure. In addition, in order to avoid confusion and to facilitate understanding of the parts related to the technology of the present disclosure, the description and illustrations shown above omit explanations of technical common sense that do not require explanation in order to enable the implementation of the technology of the present disclosure.

[0162] In this specification, "A and / or B" is synonymous with "at least one of A and B." In other words, "A and / or B" means that it may be only A, only B, or a combination of A and B. In addition, in this specification, the same idea as "A and / or B" is also applied when three or more things are expressed by connecting them with "and / or."

[0163] All publications, patent applications, and standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, and standard was specifically and individually indicated to be incorporated by reference. [Explanation of symbols]

[0164] 10. Imaging device 11 Imaging optical system 12 Image sensor 13 Objective Lens 14 Focus Lens 15 Zoom Lens 16 Aperture 17 Focus lens drive mechanism 18 Zoom lens drive mechanism 19 Aperture opening adjustment mechanism 20 Control section 21 Control section 22 Imaging surface 23 Image sensor driver 24 Shutter 25 Shutter drive mechanism 30 Image Input Controller 31 Image Memory 32 Image processing section 33, 53 bus lines 34 VRAM 35 Display control section 36 Media Controller 37 Instruction Reception Department 38 Finder Monitor 39 Rear Monitor 40 Memory Card 41 Touch Panel 50 Storage 51 CPU 52 Memory 60 Operating Program 61 Status Information 65 Photometry section 66 Calculation section 67 Setting section 68 Read / write control unit (RW control unit) 69 Judgment section 70 Drive control unit 75 Image data 76 Photometric value 77 Setting information 78 Judgment information 85 Counting Department 86 Update instruction signal 90 Historical Information 95 Power off signal 96 History Clearing Signal 100 Object detection unit 101 Detection Results 102 Conditions ΔEV Difference between the first and second target exposure values ΔEVX The difference between the first and second target exposure values ​​in the previous frame |ΔEV| Absolute value of the difference |ΔEV|max Maximum absolute difference EV1 First target exposure value EV2 Second target exposure value NR Reversal Number OA optical axis SF Set frame number SN setting number ST100, ST105, ST110, ST115, ST120, ST125, ST130, ST135, ST140, ST145, ST150, ST155, ST160, ST165, ST170, ST175, ST180, ST185, ST190, ST195, ST200, ST205, ST210, ST215, ST300, ST305, ST310, ST315, ST320, ST325, ST330, ST335, ST340, ST345, ST350, ST355, ST400, ST405, ST410, ST415, ST420, ST425, ST430 STEP TH1 First Threshold TH2 Second Threshold TH2max Second Threshold TH3_1 3rd_1 threshold TH3_2 3rd_2nd threshold

Claims

1. An exposure control device that performs exposure control to make an exposure value in an imaging device follow a target exposure value, A processor is provided. The processor, starting the exposure control when an absolute value of a difference between a first target exposure value of a first frame captured by the imaging device and a second target exposure value of a second frame captured prior to the first frame becomes greater than a first threshold value; obtaining a second threshold value that is smaller than the first threshold value in response to a start of the exposure control; when the magnitude relationship between the absolute value of the difference and the second threshold value satisfies a preset condition, a threshold value to be compared with the absolute value of the difference is set to a third threshold value that is greater than the second threshold value, and the exposure control is terminated. Exposure control device.

2. The processor, The exposure control device according to claim 1 , wherein the third threshold value is set to the same value as the first threshold value.

3. The processor, The exposure control device according to claim 1 , wherein the third threshold value is set to a value different from the first threshold value depending on conditions.

4. The processor, The exposure control device according to claim 3 , wherein the third threshold value is set to a value smaller than the first threshold value depending on the condition.

5. 4. The exposure control device according to claim 3, wherein the condition is based on a result of detection of a subject.

6. The processor, 2 . The exposure control device according to claim 1 , wherein, when the absolute value of the difference becomes equal to or smaller than the second threshold, a threshold to be compared with the absolute value of the difference is set to the third threshold which is greater than the second threshold, and the exposure control is terminated.

7. The processor, 2. An exposure control device as described in claim 1, wherein a memory unit stores for each frame whether the absolute value of the difference is greater than the first threshold, the second threshold, or the third threshold, indicating an exposure control state in which the exposure control is being performed, or whether the absolute value of the difference is less than or equal to the first threshold, the second threshold, or the third threshold, indicating an exposure control end state in which the exposure control has ended.

8. The processor, If the second frame is in the exposure control end state, a threshold value to be compared with the absolute value of the difference is set to the first threshold value or the third threshold value; The exposure control device according to claim 7 , wherein a threshold value to be compared with the absolute value of the difference is set to the second threshold value when the second frame is in the exposure control state.

9. The processor, 8. The exposure control device according to claim 7, wherein the second target exposure value is stored in the storage unit for each frame.

10. The processor, 2. The exposure control device according to claim 1, wherein, when the absolute value of the difference is equal to or less than the first threshold or the third threshold and greater than the second threshold, and the state in which the positive and negative of the difference is inverted continues for a predetermined number of frames, the threshold to be compared with the absolute value of the difference is set to the third threshold which is greater than the second threshold, and the exposure control is terminated.

11. The processor, The exposure control device according to claim 10, wherein the difference is stored in a storage unit.

12. The processor, storing, for each frame, in the storage unit, whether the absolute value of the difference is greater than the first threshold, the second threshold, or the third threshold, indicating an exposure control state in which the exposure control is being performed, or whether the absolute value of the difference is equal to or less than the first threshold, the second threshold, or the third threshold, indicating an exposure control end state in which the exposure control has been ended; The exposure control device according to claim 11 , wherein the difference is stored in the storage unit only if the first frame is in the exposure control state.

13. The processor, a history of the absolute value of the difference when the exposure control is ended is stored in the storage unit; The exposure control device according to claim 7 , wherein, when a maximum value in the history is smaller than the second threshold value, the maximum value is reduced by the second threshold value.

14. The processor, The exposure control device according to claim 13 , wherein a process of subtracting the second threshold value from the maximum value is executed when a preset number of the histories have been stored in the storage section.

15. The processor, The exposure control device according to claim 13, wherein when a preset operation instruction is received, the history stored in the storage unit is not carried over.

16. The processor, The exposure control device according to claim 15, wherein the history is erased from the storage unit when a preset operation instruction is received.

17. An exposure control device according to any one of claims 1 to 16, An imaging element; An imaging device comprising:

18. 1. A method for operating an exposure control device that performs exposure control to make an exposure value in an imaging device follow a target exposure value, comprising: starting the exposure control when an absolute value of a difference between a first target exposure value of a first frame captured by the imaging device and a second target exposure value of a second frame captured prior to the first frame becomes greater than a first threshold value; obtaining a second threshold value that is smaller than the first threshold value in response to the start of the exposure control; and when a magnitude relationship between the absolute value of the difference and the second threshold value satisfies a preset condition, a threshold value to be compared with the absolute value of the difference is set to a third threshold value that is greater than the second threshold value, and the exposure control is terminated; A method for operating an exposure control device comprising:

19. An operation program for an exposure control device that performs exposure control to make an exposure value in an imaging device follow a target exposure value, starting the exposure control when an absolute value of a difference between a first target exposure value of a first frame captured by the imaging device and a second target exposure value of a second frame captured prior to the first frame becomes greater than a first threshold value; obtaining a second threshold value that is smaller than the first threshold value in response to the start of the exposure control; and when a magnitude relationship between the absolute value of the difference and the second threshold value satisfies a preset condition, a threshold value to be compared with the absolute value of the difference is set to a third threshold value that is greater than the second threshold value, and the exposure control is terminated; An operating program for an exposure control device that causes a computer to execute a process including the steps of:

Images