Imaging device, flicker frequency calculation method, and program

Abstract

To accurately calculate a flicker frequency.SOLUTION: An imaging apparatus includes a flicker detection unit which calculates a detection value by integrating pixel values in the entire or partial position ranges of each line for one or a plurality of continuous lines of each frame in each of two or more adjacent frames of an image made of a plurality of frames, and calculates a flicker frequency on the basis of a high-pass filter processing result value obtained by performing high-pass filter processing on the plurality of detection values calculated in each of the two or more adjacent frames.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present technology relates to an imaging device, a flicker frequency calculation method, and a program, and in particular to a technology for reducing flicker. [Background technology]

[0002] In imaging devices (cameras), images captured may be affected by flicker. For example, fluorescent lights, which are widely used as indoor light sources, and LEDs (Light Emitting Diodes), which have become increasingly popular in recent years, cause periodic blinking of illumination light, known as flicker. Therefore, images captured under such lighting conditions suffer from degradation in image quality, such as color unevenness, due to the flicker. Patent Documents 1 to 3 disclose techniques for reducing flicker components occurring in an image. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 034076 [Patent Document 2] Japanese Patent Application Publication No. 2019-134257 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-88770 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-described technology has a problem in that when a moving subject is captured, the flicker component cannot be detected with high accuracy due to the influence of the moving subject.

[0005] Therefore, this technology proposes a technology for calculating the flicker frequency with high accuracy. [Means for solving the problem]

[0006] An imaging device according to the present technology calculates a detection value by integrating pixel values ​​in an entire or partial position range of each line for one or more consecutive lines in each of two or more adjacent frames of an image made up of a plurality of frames; For each of three or more adjacent frames, a high-pass filter process is performed to calculate a first difference value, which is a difference value between two or more detection values ​​obtained by integrating pixel values ​​in the same position range for each two adjacent frames, and a second difference value, which is a difference value between the two first difference values ​​obtained by the high-pass filter process, is calculated, and a flicker frequency is calculated based on the second difference value. Equipped with a flicker detection unit. As a result, in the imaging device, the influence of the moving subject is removed from the detected value, and the flicker component remains. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating an external appearance of an imaging device according to an embodiment. [Figure 2] 1 is a diagram illustrating an external appearance of an imaging device according to an embodiment. [Figure 3] FIG. 2 is a diagram illustrating the internal configuration of the imaging device. [Figure 4] FIG. 2 is a diagram illustrating the configuration of a digital signal processing unit. [Figure 5] FIG. 4 is a diagram illustrating a menu screen displayed on an image display unit. [Figure 6] 10A and 10B are diagrams illustrating an image capture standby screen displayed on an image display unit. [Figure 7] FIG. 10 is a diagram illustrating the relationship between shutter speed and flicker. [Figure 8] FIG. 10 is a diagram illustrating the relationship between curtain speed and flicker. [Figure 9] 10 is a flowchart illustrating a procedure for changing settings during flicker scan processing. [Figure 10] 10A and 10B are diagrams illustrating a flicker detection process in the first operation example. [Figure 11] 10A and 10B are diagrams illustrating a method for calculating a flicker frequency in the first operation example. [Figure 12] 10 is a flowchart illustrating the flow of a flicker scan process in the first operation example. [Figure 13] 10 is a flowchart illustrating the flow of a flicker detection process in the first operation example. [Figure 14] 10 is a flowchart illustrating the flow of a flicker correction process in the first operation example. [Figure 15] 10 is a flowchart illustrating the flow of flicker correction processing in a shutter speed correction mode. [Figure 16] 10A and 10B are diagrams illustrating a flicker detection process in an operation example 2. [Figure 17] FIG. 10 is a diagram illustrating the relationship between shutter speed and flicker intensity. [Figure 18] 10 is a flowchart illustrating the flow of a flicker detection process in the second operation example. [Figure 19] 10A and 10B are diagrams illustrating a flicker detection process in an operation example 3. [Figure 20] FIG. 10 is a diagram illustrating an example of an image showing a flicker occurrence state. [Figure 21] 10A and 10B are diagrams illustrating a flicker correction process when a plurality of flicker regions occur. [Figure 22] 10 is a flowchart illustrating the flow of a flicker correction process when a plurality of flicker areas are detected. [Figure 23] FIG. 10 is a diagram illustrating an example of a flicker adjustment UI. [Figure 24] 13 is a flowchart illustrating the flow of a flicker adjustment UI display process in Operation Example 4. [Figure 25] 10 is a flowchart illustrating the flow of a shutter speed change process in response to an operation on a flicker adjustment UI. DETAILED DESCRIPTION OF THE INVENTION

[0008] The embodiments will be described below in the following order. <1. Configuration of imaging device> <2. Example of operation> <3. Modifications> <4. Summary>

[0009] The meanings of some of the terms used in this disclosure will now be explained. "Image" is a term that includes still images and moving images. A "line" refers to a line of pixels arranged horizontally in one frame of a still image or video. A "live view image" or "LV image" refers to an image captured by an image sensor and displayed on an image display unit in a manner that is visible to the user, both when capturing an image without recording the image and when capturing an image with recording the image. In other words, it is an image that shows the scene from the subject side in real time. Generally, a live view image is generated and displayed as a low-resolution image that matches the number of pixels that can be displayed on the image display unit.

[0010] <1. Configuration of imaging device> 1 and 2 are diagrams showing the appearance of an imaging device 1 according to an embodiment. FIG. 2 shows a camera housing 2 with a lens barrel 3 removed. In the following description, the subject side is the front and the photographer (user) side is the rear. The imaging device 1 shown in FIGS. 1 and 2 is an example, and some of its components may be included in an external device connected wirelessly or via a wire, or it may include processing units other than those shown below.

[0011] As shown in Figures 1 and 2, the imaging device 1 comprises a camera housing 2 in which the necessary parts are arranged inside and outside, and a lens barrel 3 that is detachable from the camera housing 2 and attached to the front part 2a. It should be noted that the lens barrel 3 being detachable as a so-called interchangeable lens is just one example, and the lens barrel may be one that cannot be removed from the camera body 2.

[0012] A rear monitor 4 is disposed on the rear surface 2b of the camera housing 2. The rear monitor 4 displays live view images, playback images of recorded images, and the like. The rear monitor 4 is configured by a display device such as a liquid crystal display (LCD) or an organic electroluminescence (EL) display. The rear monitor 4 is rotatable relative to the camera housing 2. For example, the rear monitor 4 is rotatable around the upper end of the rear monitor 4 as a rotation axis so that the lower end of the rear monitor 4 moves rearward. The right or left end of the rear monitor 4 may be the rotation axis. Furthermore, the rear monitor 4 may be rotatable around multiple axes.

[0013] An EVF (Electric Viewfinder) 5 is disposed on the top surface 2c of the camera housing 2. The EVF 5 includes an EVF monitor 5a and a frame-shaped enclosure 5b that protrudes rearward so as to surround the upper and left and right sides of the EVF monitor 5a. The EVF monitor 5a is formed using an LCD, an organic EL display, etc. The EVF monitor 5a displays a live view image, a playback image of a recorded image, etc. Note that an optical view finder (OVF) may be provided instead of the EVF monitor 5a.

[0014] The rear surface 2b and the top surface 2c are provided with various controls 6. The controls 6 include, for example, a shutter button (release button), a menu activation button, a decision button, a cross key, a cancel button, a zoom key, and a slide key. These controls 6 include various types of controls such as buttons, dials, and composite controls that can be pressed and rotated. The various types of controls 6 enable, for example, shutter operation, menu operation, playback operation, mode selection operation, focus operation, zoom operation, parameter change operation, and the like. The controls 6 also include a touch panel provided on the front surface of the rear monitor 4.

[0015] Fig. 3 is a diagram showing the internal configuration of the imaging device 1. As shown in Fig. 3, the imaging device 1 includes a lens system 11, an aperture mechanism 12, an ND (Neutral Density) filter 13, an imaging element 14, an analog signal processing unit 15, an A / D (Analog / Digital) converter 16, a digital signal processing unit 17, an image display unit 18, an image storage unit 19, a lens driver 20, a timing generator 21 (referred to as TG in the drawing), a system controller 22, and a user interface unit 23 (referred to as user I / F unit in the drawing).

[0016] The lens system 11 is provided with various lenses such as a zoom lens, a focus lens, and a condenser lens, as well as a zoom lens drive mechanism and a focus lens drive mechanism, and guides light from a subject to the image sensor 14. The lens system 11 may also be provided with a mechanical shutter (for example, a focal plane shutter).

[0017] The aperture mechanism 12 is configured to be able to mechanically adjust the amount of light from the subject by adjusting the aperture.

[0018] The ND filter 13 is a filter having a predetermined transmittance, and changes the amount of light incident on the image sensor 14 by being inserted into or removed from the optical path of light from the subject.

[0019] The image sensor 14 is configured with, for example, a CMOS (Complementary Metal Oxide Semiconductor) sensor, and light from a subject is incident on the image sensor 14 via the lens system 11. The image sensor 14 obtains an analog image signal by photoelectric conversion. In this embodiment, it is assumed that the image sensor 14 is a CMOS sensor that operates by a so-called rolling shutter method, in which an electronic shutter is used to set the start and end of exposure for a large number of pixels for each line.

[0020] The image sensor 14 is formed, for example, on a CMOS substrate, with multiple pixels, each having a photodiode, a transfer transistor, a switching transistor, an amplification transistor, a reset transistor, etc., arranged two-dimensionally, and also with a vertical scanning circuit, a horizontal scanning circuit, and an image signal output circuit formed thereon. The image sensor 14 may be of either a primary color system or a complementary color system, and the analog image signal obtained from the image sensor 14 is a primary color signal of each of the RGB colors or a complementary color signal. Alternatively, the image sensor 14 may be configured without a color filter, and the analog image signal obtained from the image sensor 14 may be a black and white image signal.

[0021] The analog signal processing unit 15 is configured by, for example, an IC (Integrated circuit). The analog signal processing unit 15 performs, for example, CDS (Correlated Double Sampling) processing, AGC (Automatic Gain Control) processing, etc. on the input analog image signal.

[0022] The A / D converter 16 converts the analog signal output from the analog signal processing unit 15 into a digital image signal (for example, an RGB primary color signal).

[0023] The digital signal processing unit 17 is configured as an image processor using an arithmetic processing device such as a DSP (Digital Signal Processor). The digital signal processing unit 17 performs various signal processing on the input digital image signal. The signal processing by the digital signal processing unit 17 will be described in detail later. In addition, the digital signal processing unit 17 performs various signal processing operations on the image data obtained, such as compression encoding for recording or communication, formatting, and generating or adding metadata, to generate files for recording or communication. For example, still image files can be generated in formats such as JPEG (Joint Photographic Experts Group), TIFF (Tagged Image File Format), GIF (Graphics Interchange Format), etc. It is also possible to generate image files in the MP4 format used for recording moving images and audio in accordance with MPEG-4. It is also possible to generate an image file as raw (RAW) image data.

[0024] The image display unit 18 displays various information to the user, and is, for example, the rear monitor 4 or EVF monitor 5a disposed on the housing of the imaging device 1 as shown in FIG. For example, the image display unit 18 displays images based on image files stored in the image storage unit 19. The image display unit 18 also displays live view images when capturing an image without recording the image and when capturing an image with recording the image. The image display unit 18 also displays various operation menus, icons, messages, etc., i.e., a GUI (Graphical User Interface), based on instructions from the system controller 22.

[0025] In this embodiment, the imaging device 1 is provided with an image display unit 18. However, the imaging device 1 may not be provided with the image display unit 18, and images may be displayed on an image display unit of an external device (not shown) connected by wire or wirelessly.

[0026] The image storage unit 19 is, for example, a nonvolatile memory, and stores image files processed by the digital signal processing unit 17. Note that, hereinafter, image data and image files may be simply referred to as images.

[0027] The lens driver 20 includes, for example, a motor driver for a zoom lens drive motor, a motor driver for a focus lens drive motor, a motor driver for a motor of the diaphragm mechanism 12, a motor driver for moving the ND filter 13, and the like. These lens drivers 20 apply drive current or drive voltage to the corresponding drivers in response to instructions from the system controller 22, thereby moving the focus lens or zoom lens, opening and closing the aperture blades of the aperture mechanism 12, moving the ND filter 13, etc.

[0028] The timing generator 21 generates drive pulses required to drive the image sensor 14 in response to instructions from the system controller 22 and supplies them to the image sensor 14. The image sensor 14 is driven by the timing generator 21 to capture an image of the subject (electronic shutter), thereby obtaining an image of the subject. The timing generator 21 also adjusts the speed of the electronic shutter of the image sensor 14, thereby controlling the exposure time when capturing an image. Note that the speed of the electronic shutter will hereinafter be referred to as shutter speed. Although the shutter speed generally indicates the exposure time (s) of each pixel of the image sensor 14, in this embodiment it is defined as the reciprocal (Hz) of the exposure time. For example, if the exposure time is 0.1 s, the shutter speed in this embodiment is 10 Hz.

[0029] The system controller 22 is configured by a microcomputer (arithmetic processing device) equipped with a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The system controller 22 controls the entire imaging device 1 by executing programs stored in the ROM or the like.

[0030] For example, the system controller 22 instructs the analog gain in the analog signal processing unit 15, instructs various signal processing in the digital signal processing unit 17, controls imaging operations and recording operations in response to user operations, and controls playback operations of recorded image files. The system controller 22 also controls the driving of the focus lens and zoom lens in response to autofocus control, manual focus operation, zoom operation, and the like.

[0031] The user interface unit 23 collectively refers to the input devices that allow the user to perform various operational inputs, and is, for example, an operator 6 (keys, dials, touch panel, touch pad, etc.) arranged on the housing of the imaging device 1 as shown in FIG. The user interface unit 23 detects user operations, and sends a signal corresponding to the input operation to the system controller 22 .

[0032] In this embodiment, a still image capturing mode for capturing still images and a video capturing mode for capturing video are provided as normal imaging modes, which are normal settings that do not take into consideration the ease of detecting flicker components. In the imaging device 1, either the still image capturing mode or the video capturing mode is set by a predetermined operation of the control 6, and images are captured in the set mode. Note that the imaging device 1 may have only one of the still image capturing mode and the video capturing mode provided as the normal imaging mode.

[0033] Fig. 4 is a diagram illustrating the configuration of the digital signal processing unit 17. In Fig. 4, an image display unit 18, an image storage unit 19, a timing generator 21, and a system controller 22 are illustrated together with each component of the digital signal processing unit 17.

[0034] As shown in FIG. 4, when performing the flicker scan processing of operation examples 1 to 4 described below, the digital signal processing unit 17 functions as a clamp circuit 31, a gain adjustment circuit 32, a white balance adjustment circuit 33, a flicker detection unit 34, a display switching unit 35, a flicker correction unit 36, a gamma correction circuit 37, a color conversion circuit 38, an image size conversion circuit 39, and a flicker information superimposition unit 40.

[0035] In the digital signal processing unit 17, some or all of the functional units function in the first to fourth operational examples, and some functional units do not function (do nothing) in any of the first to fourth operational examples.

[0036] The clamping circuit 31 clamps the black level of the input RGB primary color signals to a predetermined level. The gain adjustment circuit 32 adjusts the gain of the RGB primary color signals after clamping according to the exposure amount. The white balance adjustment circuit 33 adjusts the white balance of the RGB primary color signals after gain adjustment.

[0037] The flicker detection unit 34 detects flicker components (also simply referred to as flicker) from the RGB primary color signals after white balance adjustment, i.e., from the frame of an image obtained by capturing an image with the image sensor 14, either for the entire frame or for each specified area within the frame.

[0038] Specifically, when the entire frame is the target, the flicker detection unit 34 calculates the frequency of the flicker occurring in the entire frame (hereinafter referred to as the flicker frequency) and sends it to the system controller 22. The flicker detection unit 34 also calculates the intensity of the flicker occurring in the entire frame (hereinafter referred to as the flicker intensity) and sends flicker intensity region information indicating the flicker intensity to the system controller 22.

[0039] When the flicker detection unit 34 targets each specified area within a frame, it calculates the flicker frequency and flicker intensity for each specified area, and detects the area where flicker is occurring (hereinafter referred to as the flicker area) based on the calculation results. Then, the flicker detection unit 34 sends the flicker frequency to the system controller 22 , and sends flicker intensity region information indicating the flicker region and flicker intensity to the flicker information superimposing unit 40 and the system controller 22 .

[0040] The flicker detector 34 may calculate the phase of the flicker occurring in the entire frame or in the flicker region (initial phase of the flicker stripes) and send it to the system controller 22 in addition to the flicker frequency and flicker intensity region information.

[0041] The system controller 22 controls the timing generator 21 based on the flicker frequency input from the flicker detection unit 34 to operate the image sensor 14 so as not to generate flicker, thereby correcting (reducing) the flicker. The system controller 22 also causes the flicker correction unit 36 ​​to correct the flicker in the image captured by the image sensor 14.

[0042] When flicker correction unit 36 ​​corrects flicker, display switching unit 35 switches between displaying an image with no flicker reduction or displaying an image with reduced flicker on image display unit 18. Here, switching can be performed in response to a user operation on control 6, for example. When an image in which flicker occurs is displayed on the image display unit 18, the display switching unit 35 causes an RGB primary color signal that has not been subjected to flicker correction by the flicker correction unit 36 ​​to be input to the gamma correction circuit 37. On the other hand, when the display switching unit 35 displays an image in which flicker has been corrected on the image display unit 18, the display switching unit 35 causes the RGB primary color signal, which has been subjected to flicker correction in the flicker correction unit 36, to be input to the gamma correction circuit 37.

[0043] The flicker correction unit 36 ​​corrects flicker in the RGB primary color signal (image) based on the correction information input from the system controller 22. When the flicker correction unit 36 ​​controls the timing generator 21 to operate the image sensor 14 so as not to cause flicker, thereby correcting flicker, the RGB primary color signal (image) is sent to the gamma correction circuit 37 without correcting the flicker.

[0044] The gamma correction circuit 37 converts the gradation of the RGB primary color signals after flicker correction or before flicker correction.

[0045] The color conversion circuit 38 generates a luminance signal Y and color difference signals RY and BY as image data from the gamma-corrected RGB primary color signals. The image data generated here is stored in the image storage unit 19 as an image file.

[0046] The image size conversion circuit 39 performs a reduction process to reduce the image size (number of pixels) of an image based on image data so that the image can be displayed in its entirety on the image display unit 18.

[0047] The flicker information superimposing unit 40 displays the flicker area and flicker intensity for the image whose image size has been changed by the image size conversion circuit 39, based on the flicker intensity area information detected by the flicker detection unit 34, so that the flicker area and flicker intensity can be recognized by the user. At this time, flicker intensity region information may be input to the flicker information superimposing unit 40 from either the flicker detection unit 34 or the system controller 22, depending on the processing load of the system controller 22. When the processing load of the system controller 22 is low, the flicker intensity region information corresponding to the image size changed by the system controller 22 in the reduction process is input to the flicker information superimposing unit 40. On the other hand, when the processing load of the system controller 22 is high, the flicker intensity region information is input directly to the flicker information superimposing unit 40 from the flicker detection unit 34. Alternatively, the flicker intensity region information may be input from only one of the flicker detection unit 34 and the system controller 22 .

[0048] <2. Example of operation> The following mainly describes the flicker scanning process performed by the flicker detection unit 34, the flicker correction unit 36, the flicker information superimposition unit 40, and the system controller 22.

[0049] As described above, the image sensor 14 is a CMOS sensor that operates using the rolling shutter method, and therefore the exposure timing differs for each horizontal line. Therefore, when a light source such as a fluorescent lamp or LED is turned on (blinking) at a predetermined frequency, the amount of light received by the image sensor 14 changes for each horizontal line. Therefore, in-plane flicker, which is a phenomenon in which lines where the signal levels (pixel values) of the RGB primary color signals are higher than the average value and lines where the signal levels of the RGB primary color signals are lower than the average value, may occur in the image output from the image sensor 14. Note that in-plane flicker can be approximated by a sine wave having a frequency, amplitude, and phase.

[0050] Therefore, the digital signal processing unit 17 and the system controller 22 perform a flicker scan process to detect and correct flicker from the image obtained by capturing an image with the image sensor 14, and display the flicker-corrected image on the image display unit 18.

[0051] Fig. 5 is a diagram illustrating a menu screen displayed on the image display unit 18. Fig. 6 is a diagram illustrating an image capture standby screen displayed on the image display unit 18.

[0052] 5(a), a menu screen corresponding to the flicker scan processing is provided in the imaging device 1. When display of the menu screen corresponding to the flicker scan processing is selected in response to a user operation, the system controller 22 displays the menu screen corresponding to the flicker scan processing on the image display unit 18.

[0053] The menu screen corresponding to the flicker scan process includes, for example, a flicker scan enable / disable button for switching between enabling and disabling the flicker scan process, a flicker scan setting button for displaying a screen for making various settings for the flicker scan process, and an auto scan execution button for immediately executing the flicker scan process.

[0054] When the auto scan execution button is operated via the menu screen, the digital signal processor 17 and the system controller 22 execute the flicker scan process.

[0055] In the flicker scan process, the normal imaging mode is switched to the flicker detection mode, which will be described in detail later, and the imaging element 14 is set to a flicker detection adaptive setting that makes it easier for the flicker detection unit 34 to detect flicker, and an image is output in the flicker detection adaptive setting.

[0056] During the execution of the flicker scan process, the system controller 22 displays, for example, an icon saying "Flicker detection in progress" to notify the user that the flicker scan process is being executed, as shown in FIG. 5(b).

[0057] Furthermore, when flicker is corrected in the flicker scan process, the digital signal processing unit 17 and the system controller 22 display the image after flicker correction on the image display unit 18, as shown in FIG. 5(c), and also display the shutter speed below the image display unit 18 ("155.6 Hz" in the lower part of FIG. 5). Furthermore, when the shutter speed is changed in the flicker scan process, the digital signal processor 17 and the system controller 22 update and display the changed shutter speed below the image display unit 18 .

[0058] When a user operation is performed to change the shutter speed during execution of the flicker scan process, when a user operation is performed to stop the flicker scan process, or when a user operation is performed to close the flicker scan screen, the flicker scan process is terminated.

[0059] 6(a), while waiting to capture an image, the system controller 22 displays a live view image together with various icons on the image display unit 18. Then, the digital signal processing unit 17 and the system controller 22 execute flicker scan processing when the operator 6 to which the operation for executing flicker scan processing is assigned is operated. During the execution of the flicker scan process, the system controller 22 notifies the user that the flicker scan process is being executed by, for example, flashing an icon labeled "Flicker Scan," as shown in Fig. 6(b). The system controller 22 also displays the shutter speed below the image display unit 18 ("248.6 Hz" in Fig. 6(b)).

[0060] Furthermore, when the shutter speed is changed during the flicker scan process, the digital signal processing unit 17 and the system controller 22 update and display the changed shutter speed at the bottom of the image display unit 18, as shown in FIG. 6(c) (in the figure, it is changed from "248.6 Hz" to "155.6 Hz").

[0061] The digital signal processing unit 17 and the system controller 22 then terminate the flicker scan process when a user operation is performed to change the shutter speed, when a user operation is performed to stop the flicker scan process, when an operation is performed to lock imaging parameters (e.g., F-number, shutter speed, ISO sensitivity, etc.) (e.g., pressing the AEL (Auto Exposure Lock) button or half-pressing the release button), or when an operation is performed to close the flicker scan screen.

[0062] Fig. 7 is a diagram illustrating the relationship between shutter speed and flicker. Fig. 8 is a diagram illustrating the relationship between curtain speed and flicker. Fig. 9 is a flowchart illustrating the flow of setting changes during flicker scan processing. In Fig. 8, the light source waveform is shown as a sine wave, and the curtain speed, which is the time from the first pixel (upper left) on the first line of the image sensor 14 to the last pixel (lower right) on the last line, (hereinafter referred to as pixel readout time), is shown schematically as a parallelogram.

[0063] 7, when the shutter speed is relatively slow (low shutter speed), the exposure time for each pixel in the image sensor 14 is longer than when the shutter speed is relatively fast (high shutter speed), resulting in higher overall brightness and smaller contrast in flicker. Therefore, when the shutter speed is relatively slow, flicker is more difficult to detect than when the shutter speed is relatively fast.

[0064] 8, when the pixel readout time is short and the curtain speed is relatively fast (high curtain speed), the number of overlaps with the flicker cycle is reduced and the number of flicker stripes is reduced compared to when the pixel readout time is long and the curtain speed is relatively slow (low curtain speed). Therefore, when the curtain speed is relatively fast, flicker is more difficult to detect than when the curtain speed is relatively slow.

[0065] Furthermore, for example, if flicker is detected and corrected based on an image with a certain number of pixels displayed on image display unit 18, the number of flicker stripes will be smaller because the number of pixels is smaller than in an image captured using all of the pixels of image sensor 14. Therefore, when processing an image with a small number of pixels, it is more difficult to detect flicker than when processing an image with a large number of pixels.

[0066] 9, in step S1, the system controller 22 transitions from the normal imaging mode to the flicker detection mode before executing the flicker scan process. The flicker detection mode is a mode that makes it easier for the flicker detector 34 to detect flicker than in the normal imaging mode, and sets the imaging element 14 to a flicker detection adaptive setting. As the flicker detection adaptive settings, the system controller 22 sets a shutter speed, a curtain speed (pixel readout time) and a number of pixels suitable for detecting flicker in the flicker detection unit 34.

[0067] For example, the system controller 22 instructs the timing generator 21 to set the shutter speed to a speed higher than a predetermined speed. Setting the shutter speed to a high speed means setting the shutter speed to a speed equal to or higher than a predetermined speed that is previously set to a high speed within the range of settable shutter speeds. Here, for example, the frequency of dynamic blinking of the LED (e.g., 1000 Hz) is set to the predetermined speed.

[0068] Furthermore, the system controller 22 instructs the timing generator 21 to set the curtain speed slower than a predetermined speed. That is, the system controller 22 instructs the timing generator 21 to set the pixel readout time longer than a predetermined time. Note that slowing the curtain speed refers to setting the curtain speed to a predetermined speed or lower that is previously set as a low speed within the settable curtain speed range. In this example, the curtain speed is set to a predetermined speed so that, for example, when an LED is turned on (dynamic blinking), multiple flicker stripes appear in the captured image.

[0069] Therefore, the shutter speed is not necessarily set to a higher speed than the shutter speed set before the flicker scan process is executed, but is set to a preset high speed.Similarly, the shutter speed is not necessarily set to a lower speed than the shutter speed set before the flicker detection and correction process is executed, but is set to a preset low speed.

[0070] Furthermore, the system controller 22 issues instructions to the timing generator 21 to control the number of pixels to be added in the additive readout of the image sensor 14 via the timing generator 21. This allows the system controller 22 to control the number of pixels output from the image sensor 14 to be a number of pixels suitable for flicker detection. Note that the number of pixels suitable for flicker detection is a number of pixels that makes it easy to detect flicker, such as the total number of pixels of the image sensor 14, which is greater than in normal imaging mode. Note that in the case of the total number of pixels, additive readout of pixels is not performed in the image sensor 14.

[0071] In this way, by setting the shutter speed, curtain speed, and number of pixels of the image used for flicker detection as the flicker detection adaptive settings as described above, it becomes possible to perform flicker scanning processing (flicker detection processing) based on an image in which flicker is relatively easy to detect. Note that the flicker detection adaptive settings can be set by setting any one of the shutter speed, curtain speed, and number of pixels of the image used for flicker detection.

[0072] Thereafter, in step S2, the system controller 22 determines whether the flicker scan process has ended, and repeats step S4 until the flicker scan process has ended. On the other hand, if the flicker scan process has ended (Yes in step S2), the system controller 22 transitions from the flicker detection mode to the normal imaging mode in step S3. Here, the system controller 22 transitions to the normal imaging mode in response to the detection of a flicker component by the flicker detection unit 34 in the flicker detection mode or the completion of flicker correction. Specifically, if flicker correction has not been performed in the shutter speed correction mode (described later), the system controller 22 instructs the timing generator 21 to restore the shutter speed, curtain speed, and number of pixels to those before the flicker scan process was executed.

[0073] This allows the imaging device 1 to output an image with a shutter speed, curtain speed, and number of pixels suitable for flicker detection that were set before the flicker scan process was executed.

[0074] Next, the flicker scan process will be described using examples of operation 1 to operation 4. The imaging device 1 may be configured to perform processing based on one of the multiple operation examples described below, or may be configured to be able to perform processing based on all of the operation examples, or may be configured to perform processing by combining several operation examples.

[0075] [2-1. Example of operation 1] [2-1-1. Flicker detection processing] In the first operational example, the flicker detection unit 34 executes a flicker detection process to calculate a flicker frequency, and the flicker correction unit 36 ​​performs a flicker correction process by setting a shutter speed via the timing generator 21 or by performing flicker correction.

[0076] Fig. 10 is a diagram illustrating the flicker detection process of Operation Example 1. As shown in Fig. 10, the flicker detection unit 34 calculates a detection value Fn(y) by integrating the signal levels of the input RGB primary color signals for one line. The calculated detection value Fn(y) is stored and held for flicker detection in subsequent frames. Note that y indicates the line position from the top of the image.

[0077] The flicker detection unit 34 calculates the difference value Sn(y) between the detection value Fn(y) and the detection value Fn-1(y) by subtracting the detection value Fn-1(y) at the same line position one frame before from the calculated detection value Fn(y).

[0078] The flicker detection unit 34 also calculates a difference value Sn+1(y) between the detected value Fn+1(y) and the detected value Fn(y) by subtracting the detected value Fn+1(y) at the same line position one frame later from the calculated detected value Fn(y). The process of calculating the difference values ​​Sn(y) and Sn+1(y) functions as a high-pass filter because the influence of a moving subject has been sufficiently removed from the difference values ​​Sn(y) and Sn+1(y), leaving only flicker components. The difference values ​​Sn(y) and Sn+1(y) correspond to high-pass filter processing result values ​​obtained by performing high-pass filter processing.

[0079] Next, the system controller 22 calculates the difference value SSn(y) between the difference value Sn+1(y) and the difference value Sn(y) by subtracting the difference value Sn(y) between the detection value Fn(y) and the detection value Fn-1(y) from the difference value Sn+1(y) between the detection value Fn(y) and the detection value Fn+1(y).

[0080] 11 is a diagram illustrating a method for calculating the flicker frequency in Operation Example 1. The difference value SSn(y) between the difference value Sn+1(y) and the difference value Sn(y) indicates the rate of change of the detection value Fn(y). Therefore, the flicker frequency can be calculated based on the difference between the line positions at which the difference value SSn(y) changes from a negative value to a positive value or the line positions at which the difference value SSn(y) changes from a positive value to a negative value.

[0081] Therefore, as shown in FIG. 11, the system controller 22 calculates the number of lines L between the zero cross position y0 where the difference value SSn(y) changes from a negative value to a positive value and the next zero cross position y1 where the difference value SSn(y) changes from a negative value to a positive value.

[0082] The system controller 22 then calculates the flicker frequency by calculating the reciprocal of the product of the calculated number of lines L and the readout time of pixel values ​​for one line (1 / (Z×M)). Here, the readout time of pixel values ​​for one line can be expressed as the reciprocal of the product of the readout time Z (fps) of pixel values ​​for the entire image and the total number of lines M of the image.

[0083] [2-1-2. Flicker correction processing] Once the flicker frequency is calculated, a flicker correction process is performed to correct and reduce flicker based on the calculated flicker frequency in the imaging device 1. The flicker correction process includes a shutter speed correction mode that reduces flicker by changing the shutter speed, and an image correction mode that reduces flicker by adding a flicker correction signal to an RGB primary color signal.

[0084] If the mode selected in advance by the user is the shutter speed correction mode and is not the moving image capturing mode (if it is the still image capturing mode), the system controller 22 executes the shutter speed correction mode. On the other hand, if the mode selected by the user is the image correction mode, or if the modes previously selected by the user are the shutter speed correction mode and the video shooting mode, the system controller 22 executes the image correction mode.

[0085] In the shutter speed correction mode, the shutter speed is changed, which may result in an excessively fast shutter speed when capturing a moving image, resulting in a jerky, unnatural moving image. Therefore, even if the mode selected by the user is the shutter speed mode, the image correction mode is executed when the moving image capture mode is selected.

[0086] In the shutter speed correction mode, the system controller 22 instructs the timing generator 21 to operate at a shutter speed that is 1 / N (N is a positive number) times the calculated flicker frequency.

[0087] Specifically, the system controller 22 determines whether A>B holds, where A is the calculated flicker frequency and B is the shutter speed, and if A>B holds, determines whether the absolute value of (AB)>(A / 2-B). If the absolute value of (AB)>(A / 2-B) holds, the system controller 22 updates A to A / 2 and determines again whether A>B holds.

[0088] A is updated to A / 2 until A>B is no longer true or the absolute value of (AB)>(A / 2-B) is no longer true. When A>B is no longer true or the absolute value of (AB)>(A / 2-B) is no longer true, the system controller 22 sets the current value of A as the shutter speed and instructs the timing generator 21 to the set shutter speed.

[0089] In this way, if the shutter speed is set to 1 / N times the flicker frequency, even if the light source is blinking at the flicker frequency, the exposure time for all lines will be the same, so no flicker will occur in the image output from the image sensor 14.

[0090] In the image correction mode, flicker correction is performed by adding a flicker correction signal generated based on correction waveform data that approximates flicker with a sine wave to the RGB primary color signal. Note that in the image correction mode, a known method such as that described in JP-A-2004-222228 can be used.

[0091] Specifically, the flicker detection unit 34 calculates the flicker intensity and phase (initial phase of the flicker stripes) by performing a discrete Fourier transform on the difference value S(y) corresponding to one wavelength (L lines) of the flicker. Then, the system controller 22 sends correction waveform data according to the flicker frequency and correction information indicating the flicker intensity and phase to the flicker correction unit 36. The flicker correction unit 36 ​​generates a flicker correction signal from the correction waveform data indicated in the correction information, with an amplitude according to the flicker intensity and that cancels out the phase of the flicker, and performs flicker correction by adding the generated flicker correction signal to the RGB primary color signal. The flicker correction in the image correction mode is not limited to this method, and other methods may be used.

[0092] The RGB primary color signals that have been subjected to the flicker correction process in this manner are converted in gradation by a gamma correction circuit 37, and an output luminance signal Y and color difference signals RY and BY are generated by a color conversion circuit 38. The image size is then reduced by an image size conversion circuit 39. The reduced image is then displayed on the image display unit 18 by a flicker information superimposing unit 40. The image size conversion circuit 39 is provided because the number of display pixels of the image display unit 18 is smaller than the number of pixels of the luminance signal Y and the color difference signals RY and BY, but is not necessary if the number of pixels of both is the same.

[0093] Therefore, flicker is reduced in the image displayed on image display unit 18. Therefore, the user can see the image with reduced flicker.

[0094] [2-1-3. Processing flow] FIG. 12 is a flowchart illustrating the flow of the flicker scan process in the first operation example.

[0095] As shown in FIG. 12, when the flicker scan process is executed, the system controller 22 checks the flicker correction process mode set by the user in step S11.

[0096] Then, in step S12, the flicker detection unit 34 executes a flicker detection process, which will be described later.

[0097] In step S13, the system controller 22 determines whether flicker has been detected, and if flicker has not been detected (No in step S13), the flicker scan process ends. Note that if flicker has not been detected, the user may be notified that flicker has not been detected.

[0098] On the other hand, if flicker is detected (Yes in step S13), in step S14 the system controller 22 notifies the user that flicker has been detected, for example, via the image display unit 18. Thereafter, in step S15, the system controller 22 and the flicker correction unit 36 ​​execute a flicker correction process to correct the flicker. The flicker correction process will be described later.

[0099] When the flicker correction process is completed, in step S16, the system controller 22 determines whether a user operation to stop the flicker scan process as described above has been performed. If a user operation to stop the flicker scan process has been performed (Yes in step S16), the system controller 22 ends the flicker scan process.

[0100] On the other hand, if a user operation to stop the flicker scan process has not been performed (No in step S16), the system controller 22 determines in step S17 whether the flicker intensity of the flicker component contained in the RGB primary color signal after flicker correction is equal to or less than a predetermined threshold value. Note that the flicker intensity may be calculated by frequency analysis as described below, or may be calculated based on the difference value Sn(y).

[0101] If the flicker intensity is not equal to or less than the predetermined threshold (No in step S17), the process returns to step S 15. On the other hand, if the flicker intensity is equal to or less than the predetermined threshold (Yes in step S17), in step S18, the system controller 22 notifies the image display unit 18 that the flicker scan process has ended, and ends the flicker scan process.

[0102] Fig. 13 is a flowchart illustrating the flow of flicker detection processing in Operation Example 1. As shown in Fig. 13, in step S21, when RGB primary color signals for one frame are input, the flicker detection unit 34 calculates a detection value Fn(y) by integrating the input RGB primary color signals for each line.

[0103] Then, in step S22, the flicker detection unit 34 determines whether the detection values ​​Fn-1(y), Fn(y), and Fn+1(y) for three adjacent frames have been acquired, and repeats steps S21 and S22 until the detection values ​​for three adjacent frames have been acquired (No in step S22).

[0104] On the other hand, if detection values ​​for three adjacent frames have been acquired (Yes in step S22), the flicker detection unit 34 calculates the flicker frequency in step S23. Here, a high-pass filter is applied to the detection values ​​for the three frames to calculate difference values ​​Sn(y) and Sn+1(y). The flicker detection unit 34 also calculates a difference value SSn(y) of the calculated difference values, and calculates the flicker frequency based on the number of lines L between the zero-cross positions of the difference value SSn(y). Then, in step S24, the flicker detection unit 34 sends the calculated flicker frequency to the system controller 22.

[0105] 14 is a flowchart illustrating the flow of flicker correction processing in Operation Example 1. In step S31, the system controller 22 determines whether the shutter speed correction mode is selected. If the shutter speed correction mode is selected (Yes in step S31), in step S32, the system controller 22 determines whether the moving image shooting mode is selected.

[0106] If the shutter speed correction mode is not selected (No in step S31), or if the shutter speed correction mode is selected and the video shooting mode is selected (Yes in step S31, Yes in step S32), the system controller 22 selects the image correction mode in step S33.

[0107] Then, in step S34, the system controller 22 calculates correction waveform data, flicker intensity, and phase for flicker correction based on the calculated flicker frequency. Thereafter, in step S35, the system controller 22 sends correction information indicating the calculated correction waveform data, flicker intensity, and phase to the flicker correction unit 36. The flicker correction unit 36 ​​generates a flicker correction signal from the correction waveform data indicated in the correction information, which has an amplitude according to the flicker intensity and which cancels out the phase of the flicker, and performs flicker correction by adding the generated flicker correction signal to the RGB primary color signals.

[0108] On the other hand, if the shutter speed correction mode is selected and the video imaging mode is not selected (Yes in step S31, No in step S32), that is, if the still image imaging mode is selected, the system controller 22 selects the shutter speed correction mode in step S36.

[0109] Then, in step S37, the system controller 22 performs flicker correction processing in the shutter speed correction mode.

[0110] FIG. 15 is a flowchart illustrating the flow of the flicker correction process in the shutter speed correction mode. As shown in FIG. 15, when flicker correction processing in the shutter speed correction mode is started, the system controller 22 sets the flicker frequency to A and the shutter speed to B in step S41, and determines whether A>B holds in step S42.

[0111] If A>B is true (Yes in step S42), then in step S43 the system controller 22 determines whether the absolute value of (AB)>the absolute value of (A / 2-B) is true.

[0112] If the absolute value of (AB)>the absolute value of (A / 2-B) is true (Yes in step S43), the system controller 22 updates A to A / 2 in step S44 and returns the process to step S42.

[0113] On the other hand, if A>B is not true (No in step S42), or if the absolute value of (AB)>(A / 2-B) is not true (No in step S43), then in step S45 the system controller 22 sets the current value of A as the shutter speed and instructs the timing generator 21 to achieve the set shutter speed.

[0114] In the flicker correction process of operation example 1 (FIG. 14), when the shutter speed correction mode is selected and the video imaging mode is selected, the image correction mode is set, and when the shutter speed correction mode is selected and the still image imaging mode is selected, the shutter speed correction mode is set. However, regardless of whether the shutter speed correction mode is selected, when the video imaging mode is selected, the image correction mode may be set, and when the still image imaging mode is selected, the shutter speed correction mode may be set.

[0115] [2-2. Flicker detection process in operation example 2] 16 is a diagram illustrating the flicker detection process of Operation Example 2. In Operation Example 2, the flicker detection process is different from that of Operation Example 1, but the other processes are the same, so only the flicker detection process will be described here.

[0116] 16, the flicker detection unit 34 calculates a detection value Fn(y) by integrating the signal levels of the input RGB primary color signals for one line. The calculated detection value Fn(y) is stored and held for use in flicker detection in subsequent frames.

[0117] The flicker detection unit 34 calculates a difference value Sn(y) between the detection value Fn+1(y) and the detection value Fn(y) by subtracting the detection value Fn-1(y) of the same line from the detection value Fn+1(y) one frame later. Calculating the difference value Sn(y) sufficiently removes the influence of a moving subject, leaving the flicker component, and therefore functions as a so-called high-pass filter. The difference value Sn+1(y) corresponds to a high-pass filter processing result value obtained by performing high-pass filtering. Note that, although high-pass filtering is performed on detection values ​​of two adjacent frames here, high-pass filtering may also be performed on detection values ​​of multiple adjacent frames.

[0118] The flicker detection unit 34 performs frequency analysis on the difference value Sn(y). Possible frequency analysis methods include a discrete Fourier transform (DFT) and a fast Fourier transform (FFT). However, when the number of lines is 2 to the power of N, performing a fast Fourier transform can reduce the processing load and increase the processing speed.

[0119] Then, based on the result of the frequency analysis, the flicker detection unit 34 estimates (calculates) the frequency at which the flicker intensity (power spectrum) is maximum as the flicker frequency. Then, the flicker detection unit 34 sends the estimated flicker frequency to the system controller 22.

[0120] Here, the flicker frequency estimated based on the results of frequency analysis may have low estimation accuracy due to low frequency resolution.

[0121] Fig. 17 is a diagram illustrating the relationship between shutter speed and flicker intensity. As shown in Fig. 17, when flicker occurs, the maximum value of flicker intensity becomes minimum when the shutter speed is the same as the flicker frequency.

[0122] Therefore, the system controller 22 gradually changes the shutter speed within a predetermined range, using as a reference a shutter speed corresponding to the flicker frequency estimated by frequency analysis (shown as the estimated result in the figure.) Then, the flicker detection unit 34 performs high-pass filtering and frequency analysis on the image (RGB primary color signals) output from the image sensor 14 for each changed shutter speed, and calculates the maximum value of the flicker intensity.

[0123] Then, the flicker detection unit 34 determines, as the flicker frequency, the frequency corresponding to the shutter speed at which the maximum value of the flicker intensity is the smallest, from the maximum values ​​of the flicker intensity for each changed shutter speed.

[0124] Fig. 18 is a flowchart illustrating the flow of flicker detection processing in Operation Example 2. As shown in Fig. 18, in step S51, when RGB primary color signals for one frame are input, the flicker detection unit 34 calculates a detection value Fn(y) by integrating the input RGB primary color signals for each line.

[0125] Then, in step S52, the flicker detection unit 34 determines whether the detection values ​​Fn(y) and Fn+1(y) for two adjacent frames have been acquired, and repeats steps S51 and S52 until the detection values ​​for two adjacent frames have been acquired (No in step S52).

[0126] On the other hand, if detection values ​​for two adjacent frames have been obtained (Yes in step S52), in step S53 the flicker detection unit 34 calculates the difference value Sn(y) between the detection values ​​for the two adjacent frames using a high-pass filter, and estimates the flicker frequency by frequency-analyzing the difference value.

[0127] In step S54, the system controller 22 gradually changes the shutter speed within a predetermined range, using as a reference a shutter speed corresponding to the flicker frequency estimated by frequency analysis. Then, the flicker detection unit 34 performs high-pass filtering and frequency analysis on the image (RGB primary color signals) output from the image sensor 14 for each changed shutter speed, and calculates the maximum value of the flicker intensity.

[0128] In step S55, the flicker detection unit 34 determines, from the maximum values ​​of the flicker intensity for each changed shutter speed, the frequency corresponding to the shutter speed at which the maximum value of the flicker intensity is minimum, as the flicker frequency. Then, in step S56, the flicker detection unit 34 sends the determined flicker frequency to the system controller 22.

[0129] [2-3. Example of operation 3] In the third operation example, a flicker scan process is performed to notify the user of the flicker area and flicker intensity based on the flicker intensity area information calculated by the flicker detection unit 34.

[0130] [2-3-1. Flicker detection process in operation example 3] Fig. 19 is a diagram illustrating the flicker detection process of Operation Example 3. As shown in Fig. 19(a), for example, assume that flicker occurs in a part of an image. In the flicker detection process of Operation Example 3, as shown by the dashed lines in Fig. 19(b), the flicker detection unit 34 divides an image based on the input RGB primary color signal into a plurality of regions in the horizontal and vertical directions. Here, for example, the flicker detection unit 34 divides one line of adjacent pixels into one region.

[0131] The flicker detection unit 34 then calculates the detection value Fn(y) by integrating the signal levels of the RGB primary color signals for each divided area. The flicker detection unit 34 then treats vertically continuous areas (areas continuous in the up and down direction in FIG. 19(b)) as one block, and performs flicker detection processing for each block similar to that in Operation Example 1 or Operation Example 2. As a result, the flicker detection unit 34 calculates the flicker frequency for each block.

[0132] The flicker detection unit 34 calculates the flicker intensity by performing a discrete Fourier transform on the detection value Fn(y) for each region. Here, the flicker intensity may be calculated from, for example, a temporal change in the average value of the detection value Fn(y) for each region, or may be calculated by other methods.

[0133] 19(c), the flicker detector 34 calculates the flicker intensity for all regions and determines that the region where the flicker intensity is equal to or greater than the threshold is a region where flicker is occurring. Furthermore, the flicker detector 34 determines that the same flicker is occurring in adjacent flicker regions on the left, right, and above if the flicker frequency and flicker intensity are within a predetermined error range.

[0134] In this way, when the flicker detection unit 34 extracts the area where flicker is occurring as a flicker area, as surrounded by a thick line in Figure 19(c), it sends information about the flicker area (position information) and information about the flicker intensity of that flicker area to the flicker information superposition unit 40 or the system controller 22 as flicker intensity area information.

[0135] 19(d), when the flicker intensity region information is input, the flicker information superimposing unit 40 superimposes an image indicating the flicker occurrence state on the image sized by the image size conversion circuit 39, i.e., the image after flicker correction in the shutter speed correction mode or the image correction mode. The image indicating the flicker occurrence state is displayed at a position corresponding to the flicker region indicated in the flicker intensity region information, in a display mode according to the flicker intensity of that flicker region. This makes it possible to notify the user of the region where flicker is occurring and the flicker intensity in that region.

[0136] Fig. 20 is a diagram illustrating an example of an image showing a flicker occurrence state. As shown in Fig. 20, the image showing a flicker occurrence state is displayed with hatching of a thickness corresponding to the flicker intensity of the flicker region. More specifically, the image showing a flicker occurrence state is displayed so that the thickness of the lines becomes thicker as the flicker intensity increases.

[0137] In this way, by superimposing an image showing the flicker occurrence status on the image after flicker correction, the user can check the areas where flicker is occurring and the intensity of the flicker even in an image in which flicker has been corrected and reduced.

[0138] The image showing the flicker occurrence status may be displayed in a manner that corresponds to the flicker intensity, for example, in a color that corresponds to the flicker intensity, or may be displayed as lines of a density that corresponds to the flicker intensity.

[0139] Fig. 21 is a diagram illustrating a flicker correction process when multiple flicker areas occur. As shown in Fig. 21, for example, suppose that flicker areas occur in two places. Also, suppose that flicker occurs in each flicker area with a different flicker frequency and flicker intensity.

[0140] In such a case, if flicker correction is performed in the above-described flicker correction mode in accordance with the flicker frequency in one of the flicker regions, there is a risk that flicker in the other flicker region cannot be reduced.

[0141] Therefore, first, the flicker information superimposing unit 40 superimposes an image showing the flicker occurrence status for a plurality of flicker regions, as shown in Fig. 21. Then, the system controller 22 allows the user to select a flicker region from the plurality of flicker regions in which flicker is to be reduced by the shutter speed correction mode. Here, for example, one of the flicker regions may be selected by touching the touch panel.

[0142] When any one of the flicker areas is selected via the touch panel, the system controller 22 performs flicker correction processing in the shutter speed correction mode based on the flicker frequency of the selected flicker area.

[0143] As a result, the shutter speed is set to 1 / N times the flicker frequency of the selected flicker region, and as shown in the lower part of FIG. 21, the flicker in the selected flicker region is reduced.

[0144] After performing flicker correction processing in the shutter speed correction mode based on the flicker frequency of the flicker area selected by the user, flicker detection unit 34 performs flicker detection processing on the image output from image sensor 14. If a flicker area is detected in the flicker detection processing, system controller 22 performs flicker correction processing on the detected flicker area in the same image correction mode as in Operation Example 1 or Operation Example 2.

[0145] The system controller 22 corrects the flicker in the detected flicker area by performing flicker correction processing in the image correction mode on the detected flicker area.

[0146] In this way, even if multiple flicker areas occur, the system controller 22 and the flicker correction unit 36 ​​correct the flicker for the selected flicker area using the shutter speed correction mode, and correct the flicker for any subsequently detected flicker area using the image correction mode.

[0147] This makes it possible to reduce flicker in all flicker regions even when a plurality of flicker regions with different flicker frequencies occur in an image.

[0148] Although the flicker correction process in the shutter speed correction mode is performed on the flicker area selected by the user, the flicker correction process in the image correction mode may also be performed on the flicker area. In other words, if a plurality of different flicker areas occur in an image, the flicker correction process in the image correction mode may be performed on all of the flicker areas.

[0149] However, by performing flicker correction processing in the shutter speed correction mode based on the flicker frequency of the flicker region selected by the user, it is possible that flicker outside the flicker region selected by the user will also be reduced. In such a case, it may not be necessary to perform flicker correction processing in the image correction mode for the flicker region where flicker has been reduced, thereby reducing the processing load and enabling efficient flicker correction.

[0150] Fig. 22 is a flowchart illustrating the flow of flicker correction processing when multiple flicker areas are detected. As shown in Fig. 22, when multiple flicker areas are detected, the system controller 22 determines in step S61 whether any of the flicker areas has been selected by the user. Step S61 is repeated until a flicker area is selected by the user, and when any of the flicker areas has been selected by the user (Yes in step S61), in step S62 the system controller 22 performs flicker correction processing in a shutter speed correction mode based on the flicker frequency of the selected flicker area.

[0151] After the flicker correction process in the shutter speed correction mode has been performed, the flicker detection unit 34 performs flicker detection process on the image newly output from the image sensor 14 in step S63.

[0152] In step S64, the system controller 22 determines whether a flicker area was detected in step S63, and if a flicker area was not detected (No in step S64), the flicker correction process ends.

[0153] On the other hand, if a flicker area is detected (Yes in step S64), the system controller 22 performs flicker correction processing in the image correction mode on the detected flicker area in step S65, and ends the flicker correction processing.

[0154] [2-4. Example 4] In Operation Example 4, the shutter speed is changed in response to a user operation while the flicker scan process is being performed. Here, when the flicker correction process such as that in Operation Examples 1 to 3 described above is performed, ideally no flicker occurs in the image captured thereafter. However, if there is an error between the flicker frequency calculated in the flicker detection process and the frequency of the flicker that actually occurs, the flicker may not be sufficiently reduced by the flicker correction process.

[0155] Fig. 23 is a diagram illustrating an example of a flicker adjustment UI (user interface) 50. If the flicker intensity of the image (RGB primary color signal) after the flicker correction process is greater than a predetermined threshold, that is, if the flicker has not completely disappeared, the system controller 22 causes the image display unit 18 to display the flicker adjustment UI 50 shown in Fig. 23. Furthermore, even if the flicker intensity is equal to or less than a predetermined threshold, if the video shooting mode is set, the video may stutter, so the system controller 22 displays the flicker adjustment UI 50 on the image display unit 18. Note that the system controller 22 may also display the flicker adjustment UI 50 on the image display unit 18 if the video shooting mode is set, regardless of the flicker intensity. Furthermore, when the user has made a setting to display the flicker adjustment UI 50 on the image display unit 18, the system controller 22 causes the image display unit 18 to display the flicker adjustment UI 50.

[0156] The flicker adjustment UI 50 is an interface for changing the shutter speed in response to user operation, and includes a plus magnification adjustment button 51, a minus magnification adjustment button 52, a plus fine adjustment button 53, a minus fine adjustment button 54, and an end button 55.

[0157] The plus magnification adjustment button 51 and the minus magnification adjustment button 52 are controls for roughly adjusting the shutter speed, and more specifically, are controls that can change the shutter speed to either 1 / N (N is a positive number) times the detected flicker frequency. The plus magnification adjustment button 51 is a control for setting the shutter speed to 1 / (N-1) times. The minus magnification adjustment button 52 is a control for setting the shutter speed to 1 / (N+1) times. Here, when N=1, the shutter speed is set to match the flicker frequency.

[0158] Therefore, the shutter speed increases each time the plus magnification adjustment button 51 is pressed, and decreases each time the minus magnification adjustment button 52 is pressed. However, the upper limit of the shutter speed is set to 1x the flicker frequency. When the shutter speed is at the upper limit, the shutter speed will not increase even if the plus magnification adjustment button 51 is operated.

[0159] The plus fine adjustment button 53 and the minus fine adjustment button 54 are controls for finely adjusting the shutter speed. The plus fine adjustment button 53 is a control for making the shutter speed faster by, for example, several Hz. The minus adjustment button 52 is a control for making the shutter speed slower by several Hz. Therefore, each time the plus fine adjustment button 53 is pressed, the shutter speed becomes faster, and each time the minus fine adjustment button 54 is pressed, the shutter speed becomes slower. In this way, by having the user operate the plus fine adjustment button 53 and the minus fine adjustment button 54, it is possible to manually fine-tune the shutter speed and reduce flicker.

[0160] The end button 55 is an operator for hiding the flicker adjustment UI 50. When the end button 55 is operated, the flicker adjustment UI 50 is hidden.

[0161] Fig. 24 is a flowchart illustrating the flow of the flicker adjustment UI display process of operation example 4. As shown in Fig. 24, in step S71, the system controller 22 determines whether the user has made a setting to display the flicker adjustment UI 50 on the image display unit 18. If the setting to display the flicker adjustment UI 50 on the image display unit 18 has not been made (No in step S71), in step S72 the flicker detection unit 34 detects the flicker intensity of the image output from the image sensor 14 after the flicker correction process.

[0162] In step S73, the system controller 22 determines whether the flicker intensity is equal to or less than the threshold value, and if the flicker intensity is less than the threshold value (Yes in step S73), in step S74, determines whether the moving image shooting mode is set.

[0163] If the setting for displaying the flicker adjustment UI 50 on the image display unit 18 has been made (Yes in step S71), and if the flicker intensity is greater than the threshold value (No in step S73), in step S75 the system controller 22 causes the image display unit 18 to display the flicker adjustment UI 50. Also, if the flicker intensity is equal to or less than the threshold value (Yes in step S73) and the video shooting mode is set (Yes in step S74), the system controller 22 also causes the image display unit 18 to display the flicker adjustment UI 50 in step S75.

[0164] On the other hand, if the flicker intensity is below the threshold (Yes in step S73) and the video capture mode is not set (No in step S74), that is, if the still image capture mode is set, the system controller 22 terminates the flicker adjustment UI display process without displaying the flicker adjustment UI 50 on the image display unit 18.

[0165] Fig. 25 is a flowchart illustrating the flow of the shutter speed change process in response to an operation on the flicker adjustment UI 50. As shown in Fig. 25, in step S81, the system controller 22 determines whether an operation to double the shutter speed has been performed. Here, it is detected whether the plus-times adjustment button 51 or the minus-times adjustment button 52 has been operated.

[0166] If an operation to double the shutter speed has been performed (Yes in step S81), the system controller 22 determines in step S82 whether an operation to slow the shutter speed has been performed. Here, it detects whether the minus double adjustment button 52 has been operated.

[0167] If an operation to slow the shutter speed has been performed (Yes in step S82), then in step S83 the system controller 22 sets the shutter speed to 1 / (N+1) times and instructs the timing generator 21 to that shutter speed. Also, in step S84 the system controller 22 updates N to N+1.

[0168] If an operation to slow the shutter speed has not been performed (No in step S82), that is, if the plus magnification adjustment button 51 has been operated, then in step S85 the system controller 22 determines whether N is greater than 1. If N is greater than 1 (Yes in step S85), then in step S86 the system controller 22 sets the shutter speed to 1 / (N-1) times and instructs the timing generator 21 of that shutter speed. Also, in step S87 the system controller 22 updates N to N-1.

[0169] If the operation to double the shutter speed has not been performed (No in step S81), the system controller 22 determines in step S88 whether an operation to finely adjust the shutter speed has been performed. Here, it detects whether the plus fine adjustment button 53 or the minus fine adjustment button 54 has been operated.

[0170] If an operation to fine-adjust the shutter speed has been performed (Yes in step S88), the system controller 22 determines in step S89 whether an operation to slow down the shutter speed has been performed. Here, it detects whether the minus fine-adjustment button 54 has been operated.

[0171] If an operation to slow the shutter speed has been performed (Yes in step S89), the system controller 22 slows the shutter speed by several Hz in step S90 and instructs the timing generator 21 to set the shutter speed.

[0172] If no operation to slow the shutter speed has been performed (No in step S89), that is, if the plus fine adjustment button 53 has been operated, in step S91 the system controller 22 sets the shutter speed to be several Hz faster and instructs the timing generator 21 to that shutter speed.

[0173] When these processes are completed, in step S92, the system controller 22 determines whether an operation has been performed to hide the flicker adjustment UI 50. Here, it is detected whether the end button 55 has been operated.

[0174] If an operation to hide the flicker adjustment UI 50 has not been performed (No in step S92), the process returns to step S81. On the other hand, if an operation to hide the flicker adjustment UI 50 has been performed (Yes in step S92), the system controller 22 hides the flicker adjustment UI 50 and ends the shutter speed change process.

[0175] <3. Modifications> The embodiment is not limited to the specific example described above, and various modified configurations can be adopted. For example, the digital signal processing unit 17 is configured to function as a clamp circuit 31, a gain adjustment circuit 32, a white balance adjustment circuit 33, a flicker detection unit 34, a display switching unit 35, a flicker correction unit 36, a gamma correction circuit 37, a color conversion circuit 38, an image size conversion circuit 39, and a flicker information superimposition unit 40, but some or all of these functional units may be provided in the system controller 22.

[0176] Furthermore, although the imaging device 1 has been described as a camera, the imaging device 1 may also be a PC (personal computer), a smartphone, etc. For example, if the imaging device 1 is a smartphone, since smartphones have few controls 6, various GUIs may be used in place of the controls 6. For example, when a zoom icon for changing the zoom and a focus icon for changing the focus are displayed on the image display unit, an icon for executing flicker scan processing may also be displayed alongside these icons. Furthermore, a menu icon for displaying a menu screen and an icon for executing flicker scan processing may be displayed alongside these icons. Additionally, an icon for executing flicker scan processing may be displayed next to the shutter speed display area. When a pop-up for changing the shutter speed is displayed, an icon for executing flicker scan processing may be displayed next to the shutter speed display area within the pop-up.

[0177] In the embodiment, in the flicker scan process, the flicker detection unit 34 calculates the detection value by integrating the signal levels (pixel values) of the RGB primary color signals. However, the flicker detection unit 34 may calculate the detection value based on the pixel values ​​of the image output from the image sensor 14, and may calculate the detection value by, for example, converting the RGB primary color signals into luminance / color difference signals and integrating the luminance values, which are the signal levels of each pixel value of the luminance signal.

[0178] In the embodiment, in the flicker scan process, the flicker detection unit 34 calculates the detection value by integrating the signal levels (pixel values) of the RGB primary color signals for each line. However, the flicker detection unit 34 may calculate the detection value by integrating the signal levels (pixel values) for each of a plurality of consecutive lines.

[0179] In the embodiment, in the flicker scan process, the flicker detection unit 34 calculates the detection value by integrating the signal levels (pixel values) of all pixels in one line. However, the flicker detection unit 34 may calculate the detection value by integrating the pixel values ​​of a partial range (position range) of pixels in one line. That is, the flicker detection unit 34 may calculate the detection value by integrating pixel values ​​in the entire or partial positional range of each of multiple consecutive lines of each image. Note that when partial positional ranges are set for multiple consecutive lines, it is desirable to set the same positional ranges for each line, i.e., to form rectangular areas.

[0180] Furthermore, in the embodiment, when detecting flicker for the entire frame as in Operation Example 1, the flicker detection unit 34 calculates the detection value by integrating the pixel values ​​for the entire line. However, when detecting flicker for the entire frame as in Operation Example 3, the detection value may be calculated for each region and the calculation results for each region may be combined to calculate the detection value.

[0181] <4. Summary> According to the above embodiment, the following effects can be obtained. The imaging device 1 of the embodiment is equipped with a flicker detection unit 34 that calculates a detection value by accumulating pixel values ​​over the entire or partial positional range of each line for one or more consecutive lines in each of two or more adjacent frames of an image consisting of multiple frames, and calculates a flicker frequency based on the high-pass filter processing result values ​​(difference values ​​Sn(y), Sn+1(y)) obtained by performing high-pass filter processing on the multiple detection values ​​calculated for each of the two or more adjacent frames. As a result, the imaging device 1 calculates difference values ​​Sn(y) and Sn+1(y) in which the influence of the moving subject is removed from the detection value and the flicker component remains, thereby enabling the imaging device 1 to accurately calculate the flicker frequency.

[0182] In addition, the flicker detection unit 34 calculates the flicker frequency based on the difference between the line positions at which the high-pass filter processing result value changes from a negative value to a positive value or the line positions at which the high-pass filter processing result value changes from a positive value to a negative value. As a result, the imaging device 1 can accurately calculate the flicker frequency based on the difference in line position based on the difference values ​​Sn(y) and Sn+1(y) where the flicker component remains.

[0183] Also, some position ranges are the same for each line. This enables the imaging device 1 to calculate the high-pass filter processing result values ​​(difference values ​​Sn(y), Sn+1(y)) based on pixel values ​​in the same position range in each frame, thereby improving the detection accuracy of flicker components.

[0184] The imaging device 1 also includes a correction unit (a timing generator 21, a system controller 22, and a flicker correction unit 36) that corrects flicker in each frame based on the flicker frequency. As a result, the imaging device 1 can efficiently reduce flicker by performing flicker correction processing in the shutter speed correction mode or the image correction mode.

[0185] The flicker detection unit 34 also performs high-pass filtering to calculate the difference between two or more detection values ​​obtained by integrating pixel values ​​in the same position range for each of two or more adjacent frames. As a result, even if a moving subject is captured on each line, the flicker detection unit 34 removes the detection value component based on the moving subject by calculating the difference value. In other words, the detection value component based on the moving subject is not included in the difference value. This allows the flicker detection unit 34 to efficiently detect flicker.

[0186] Furthermore, the flicker detection unit 34 performs high-pass filter processing for each of three or more adjacent frames to calculate a first difference value, which is the difference value between two or more detection values ​​obtained by accumulating pixel values ​​in the same position range for each two adjacent frames, calculates a second difference value, which is the difference value between the two first difference values ​​obtained by the high-pass filter processing, and calculates the flicker frequency based on the second difference value. Here, the first difference value corresponds to the difference values ​​Sn(y) and Sn+1(y) in the first operational example, and the second difference value corresponds to the difference value SSn(y) in the first operational example. This allows the flicker detection section 34 to determine the flicker frequency based on the rate of change of the detection value, thereby enabling the flicker frequency to be calculated with high accuracy.

[0187] Furthermore, the flicker detection unit 34 calculates the flicker frequency by performing frequency analysis on the high-pass filter processing result value (difference value Sn(y)). This allows the flicker detection unit 34 to perform frequency analysis on the flicker component with the influence of the moving subject removed, and to estimate the flicker frequency.

[0188] In addition, the flicker detection unit 34 calculates the flicker intensity from the image obtained after changing the shutter speed within a predetermined range based on the shutter speed corresponding to the calculated flicker frequency, and determines the frequency corresponding to the shutter speed at which the lowest flicker intensity is calculated as the flicker frequency. This allows the flicker detection unit 34 to determine the flicker frequency with higher accuracy based on the flicker frequency estimated by frequency analysis.

[0189] The imaging device 1 also has a shutter speed correction mode that corrects flicker components by changing the shutter speed, and an image correction mode that corrects flicker occurring in the image signal based on the flicker correction signal, and the correction unit corrects the flicker components using the shutter speed correction mode and the image correction mode. This allows the correction unit to efficiently correct flicker in accordance with the imaging conditions and the like using two different modes.

[0190] Furthermore, when the video imaging mode is set, the correction section corrects the flicker component in the image correction mode. As a result, the imaging device 1 can reduce jerky motion pictures caused by changing the shutter speed.

[0191] The image processing unit also includes a flicker area detection unit (flicker detection unit 34) that detects flicker areas where flicker components occur in each frame, and when multiple flicker areas are detected, the correction unit corrects the flicker components for each detected flicker area. As a result, the imaging device 1 can reduce flicker for each region even when multiple flickers with different flicker frequencies occur.

[0192] The image processing unit also includes a flicker area detection unit (flicker detection unit 34) that detects flicker areas where flicker components occur in each frame. When multiple flicker areas are detected, the correction unit corrects the flicker components in one of the areas using the shutter speed correction mode, and then corrects the flicker components in the other flicker areas using the image correction mode. As a result, the imaging device 1 may not need to perform flicker correction using the image correction mode for other areas where flicker has been reduced using the shutter speed correction mode, thereby reducing the processing load and enabling efficient flicker correction.

[0193] In addition, the flicker frequency calculation method involves the imaging device 1 calculating a detection value for each of two or more adjacent frames of an image consisting of multiple frames by accumulating pixel values ​​within the entire or partial positional range of each line for one or more consecutive lines in each frame, and calculating the flicker frequency based on the high-pass filter processing result value obtained by performing high-pass filter processing on the multiple detection values ​​calculated for each of the two or more adjacent frames. Furthermore, the program causes the imaging device to calculate a detection value by accumulating pixel values ​​in the entire or partial positional range of each line for one or more consecutive lines in each of two or more adjacent frames of an image consisting of multiple frames, and to calculate a flicker frequency based on the high-pass filter processing result value obtained by performing high-pass filter processing on the multiple detection values ​​calculated for each of the two or more adjacent frames.

[0194] These programs can be pre-recorded on a hard disk drive (HDD) as a recording medium built into a computer or other device, or on a ROM within a microcomputer having a CPU. Alternatively, the programs can be temporarily or permanently stored (recorded) on removable recording media such as a flexible disk, a CD-ROM (Compact Disc Read Only Memory), an MO (Magneto Optical) disc, a DVD (Digital Versatile Disc), a Blu-ray Disc (registered trademark), a magnetic disk, a semiconductor memory, or a memory card. Such removable recording media can be provided as so-called packaged software. Such a program can be installed onto a personal computer or the like from a removable recording medium, or can be downloaded from a download site via a network such as a LAN (Local Area Network) or the Internet.

[0195] The effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0196] The present technology can also be configured as follows. (1) In each of two or more adjacent frames of an image consisting of a plurality of frames, a detection value is calculated by integrating pixel values ​​in a position range of the entirety or a part of each line for one or more consecutive lines of each frame; a flicker detection unit that calculates a flicker frequency based on a high-pass filter processing result value obtained by performing high-pass filter processing on the plurality of detection values ​​calculated for each of the two or more adjacent frames; An imaging device comprising: (2) The flicker detection unit Calculating a flicker frequency based on the difference between the line positions at which the high-pass filter processing result value changes from a negative value to a positive value or the line positions at which the high-pass filter processing result value changes from a positive value to a negative value The imaging device described in (1). (3) The partial position range is Each line has the same position range An imaging device according to (1) or (2). (4) a correction unit that corrects the flicker component in a frame based on the flicker frequency; An imaging device according to any one of (1) to (3). (5) The flicker detection unit A high-pass filter process is performed to calculate a difference value between two or more detection values ​​obtained by integrating pixel values ​​in the same position range for each of the two or more adjacent frames. An imaging device according to any one of (1) to (4). (6) The flicker detection unit For each of the three or more adjacent frames, a high-pass filter process is performed to calculate a first difference value, which is a difference value between two or more detection values ​​obtained by integrating pixel values ​​in the same position range for each two adjacent frames, and a second difference value, which is a difference value between the two first difference values ​​obtained by the high-pass filter process, is calculated, and a flicker frequency is calculated based on the second difference value. An imaging device according to any one of (1) to (5). (7) The flicker detection unit The flicker frequency is calculated by performing a frequency analysis on the high-pass filter processing result value. An imaging device according to any one of (1) to (6). (8) The flicker detection unit The shutter speed is changed within a predetermined range based on the shutter speed corresponding to the calculated flicker frequency, and the flicker intensity is calculated from the image obtained, and the frequency corresponding to the shutter speed at which the lowest flicker intensity is calculated is determined as the flicker frequency. The imaging device according to (7). (9) a shutter speed correction mode for correcting the flicker component by changing the shutter speed, and an image correction mode for correcting the flicker component occurring in the image signal based on the flicker correction signal; The correction unit corrects flicker in at least one of the shutter speed correction mode and the image correction mode. The imaging device according to (4). (10) The correction unit When the video shooting mode is set, flicker is corrected by the image correction mode. The imaging device according to (9). (11) a flicker area detection unit that detects a flicker area in each frame where a flicker component occurs, The correction unit If multiple flicker areas are detected, the flicker component is corrected for each detected area. The imaging device according to (4). (12) a flicker area detection unit that detects a flicker area in each frame where a flicker component occurs, The correction unit When a plurality of flicker areas are detected, the flicker component of one of the flicker areas is corrected by the shutter speed correction mode, and then the flicker of the other flicker areas is corrected by the image correction mode. The imaging device according to (9). (13) In each of two or more adjacent frames of an image consisting of a plurality of frames, a detection value is calculated by integrating pixel values ​​in a position range of the entirety or a part of each line for one or more consecutive lines of each frame; A flicker frequency is calculated based on a high-pass filter processing result value obtained by performing high-pass filter processing on the plurality of detection values ​​calculated for each of the two or more adjacent frames. Flicker frequency calculation method. (14) In each of two or more adjacent frames of an image consisting of a plurality of frames, a detection value is calculated by integrating pixel values ​​in a position range of the entirety or a part of each line for one or more consecutive lines of each frame; A flicker frequency is calculated based on a high-pass filter processing result value obtained by performing high-pass filter processing on the plurality of detection values ​​calculated for each of the two or more adjacent frames. A program that causes a computer to perform a process. [Explanation of symbols]

[0197] 1. Imaging device 17 Digital Signal Processing Unit 21 Timing Generator 22 System Controller 34 Flicker detection unit 37 Flicker correction section 40 Image size conversion circuit 41 Flicker information superimposition unit

Claims

1. In each of two or more adjacent frames of an image consisting of a plurality of frames, a detection value is calculated by integrating pixel values ​​in a position range of the entirety or a part of each line for one or more consecutive lines of each frame; a flicker detection unit that performs high-pass filtering for each of three or more adjacent frames to calculate a first difference value, which is a difference value between two or more detection values ​​obtained by integrating pixel values ​​in the same position range for each two adjacent frames, calculates a second difference value, which is a difference value between the two first difference values ​​obtained by the high-pass filtering, and calculates a flicker frequency based on the second difference value; An imaging device comprising:

2. The flicker detection unit Calculating a flicker frequency based on the difference between the line positions at which the second difference value changes from a negative value to a positive value or from a positive value to a negative value. The imaging device according to claim 1 .

3. The partial position range is Each line has the same position range The imaging device according to claim 1 .

4. a correction unit that corrects the flicker component of the frame based on the flicker frequency; The imaging device according to claim 1 .

5. a shutter speed correction mode for correcting the flicker component by changing the shutter speed, and an image correction mode for correcting the flicker component occurring in the image signal based on the flicker correction signal; The correction unit corrects flicker in at least one of the shutter speed correction mode and the image correction mode. The imaging device according to claim 4 .

6. The correction unit When the video shooting mode is set, the flicker component is corrected by the image correction mode. The imaging device according to claim 5 .

7. a flicker area detection unit that detects a flicker area in each frame where a flicker component occurs, The correction unit If multiple flicker areas are detected, the flicker component is corrected for each detected area. The imaging device according to claim 4 .

8. a flicker area detection unit that detects a flicker area in each frame where a flicker component occurs, The correction unit When a plurality of flicker areas are detected, the flicker components of one of the flicker areas are corrected in the shutter speed correction mode, and then the flicker components of the other flicker areas are corrected in the image correction mode. The imaging device according to claim 5 .

9. In each of two or more adjacent frames of an image consisting of a plurality of frames, a detection value is calculated by integrating pixel values ​​in a position range of the entirety or a part of each line for one or more consecutive lines of each frame; For each of three or more adjacent frames, a high-pass filter process is performed to calculate a first difference value, which is a difference value between two or more detection values ​​obtained by integrating pixel values ​​in the same position range for each two adjacent frames, and a second difference value, which is a difference value between the two first difference values ​​obtained by the high-pass filter process, is calculated, and a flicker frequency is calculated based on the second difference value. Flicker frequency calculation method.

10. In each of two or more adjacent frames of an image consisting of a plurality of frames, a detection value is calculated by integrating pixel values ​​in a position range of the entirety or a part of each line for one or more consecutive lines of each frame; For each of three or more adjacent frames, a high-pass filter process is performed to calculate a first difference value, which is a difference value between two or more detection values ​​obtained by integrating pixel values ​​in the same position range for each two adjacent frames, and a second difference value, which is a difference value between the two first difference values ​​obtained by the high-pass filter process, is calculated, and a flicker frequency is calculated based on the second difference value. A program that causes a computer to perform a process.

Images