Imaging device, control method, and program

Abstract

To provide an image sensor control means that allows the user to check the flicker effect on still images in live view display. [Solution] An imaging device comprising: an image sensor for capturing multiple images; a control means for controlling a first drive for capturing a first image for recording using the image sensor and a second drive for capturing a second image for display; a detection means for detecting flicker from the multiple images; a calculation means for calculating exposure time constraints when capturing the first and second images based on the detection results of the detection means; and a determination means for determining whether to switch the second drive based on whether the exposure time constraints that can be taken by the second drive are met, based on the constraints calculated by the calculation means.

Description

Technical Field

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

Background Art

[0002] When shooting under a light source (flicker light source) that periodically repeats lighting and extinguishing, such as a fluorescent lamp or an LED, stripe-like luminance unevenness (flicker stripes) may occur in the captured image.

[0003] Regarding such a problem, in Patent Document 1, a technique is proposed to detect flicker according to changes in the light source and set the exposure time of the imaging element to an integer multiple of the light amount change period of the flicker, thereby improving the influence of the flicker. In addition, in Patent Document 2, a technique is proposed to perform a flicker detection operation at a timing different from the imaging preparation instruction and the imaging instruction during the so-called live view display in which an image obtained using the imaging element is sequentially displayed on the display unit. In the technique described in Patent Document 2, an image for live view display can be obtained with an exposure time that reduces the influence of the detected flicker.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to confirm the influence of flicker that may occur in a still image for recording in live view display, it is necessary to adjust the settings of the exposure times for both the imaging drive for still images and the imaging drive for live view display.

[0006] However, the prior art disclosed in Patent Documents 1 and 2 mentioned above does not mention any adjustment of the exposure time setting.

[0007] Therefore, the object of the present invention is to provide an imaging device and a control method therefor that enables the user to check the effect of flicker during still image capture using a live view display. [Means for solving the problem]

[0008] To achieve the above objective, the present invention provides an imaging device comprising: an image sensor for capturing multiple images; a control means for controlling a first drive for capturing a first image for recording using the image sensor and a second drive for capturing a second image for display; a detection means for detecting flicker from the multiple images; a calculation means for calculating exposure time constraints when capturing the first and second images based on the detection results of the detection means; and a determination means for determining whether to switch the second drive based on whether the exposure time constraints that can be taken by the second drive are satisfied, based on the constraints calculated by the calculation means. [Effects of the Invention]

[0009] According to the present invention, it is possible for users to check the effect of flicker during still image capture using live view display. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram illustrating the schematic of an imaging system according to an embodiment of the present invention. [Figure 2] A block diagram illustrating the details of an imaging system according to an embodiment of the present invention. [Figure 3] A figure showing the charge accumulation timing and readout timing related to an image signal for flicker detection according to an embodiment of the present invention. [Figure 4] A diagram illustrating an exemplary method for determining the period of change in light intensity of flicker according to an embodiment of the present invention. [Figure 5]A flowchart illustrating the process of an embodiment of the present invention. [Figure 6] Conceptual diagram showing the case where an image is captured with an arbitrary exposure time under a flickering environment. [Modes for carrying out the invention]

[0011] The present invention will be described in detail below with reference to the attached drawings, based on exemplary embodiments thereof. Note that the following embodiments do not limit the invention to the claims. Furthermore, while multiple features are described in the embodiments, not all of them are essential to the invention, and the multiple features may be combined arbitrarily. In addition, in the attached drawings, the same or similar configurations are given the same reference numeral, and redundant descriptions are omitted.

[0012] In the following embodiments, the present invention will be described in relation to cases where it is implemented using an imaging device that is a digital camera or a digital video camera. However, the present invention can be implemented with any electronic device having an imaging function. Such electronic devices include computer equipment (personal computers, tablet computers, media players, PDAs, etc.), mobile phones, smartphones, game consoles, robots, drones, dashcams, network cameras, etc. These are examples, and the present invention can be implemented with other electronic devices.

[0013] (First Embodiment) A first embodiment of the imaging device according to the present invention will be described below with reference to Figures 1 to 6.

[0014] Figure 1 is a diagram illustrating a schematic overview of the imaging system according to the first embodiment of the present invention. Figure 2 is a block diagram illustrating the details of the imaging system according to the first embodiment.

[0015] Hereinafter, an imaging system including a camera body 100, a photographing lens 200, and an external strobe 300 according to a first embodiment of the imaging device according to the present invention will be described with reference to FIGS. 1 and 2. Note that one or more of the functional blocks shown in FIGS. 1 and 2 may be realized by hardware such as an ASIC or a programmable logic array (PLA), or may be realized by a programmable processor such as a CPU or MPU executing software. Further, it may be realized by a combination of software and hardware. Therefore, in the following description, even when different functional blocks are described as the operating entity, the same hardware may be realized as the main body.

[0016] The camera body 100 of the digital camera is an imaging device according to this embodiment. The image sensor 101 is a charge accumulation type solid-state image sensor such as a CCD or CMOS including an infrared cut filter, a low-pass filter, etc., and an optical image corresponding to the light beam of the subject guided by the photographing lens 200 is formed.

[0017] By converting the image data obtained by imaging the subject using this image sensor 101 and sequentially displaying it on the display unit 103 described later, the so-called live view function is realized. Note that the image obtained by the image sensor 101 is also used for detecting flicker and as a photographed image for recording, which will be described later.

[0018] The shutter 102 is a light shielding member disposed in front of the image sensor 101 on the optical path of the light beam guided from the lens group 201. The shutter 102 includes blade members, and in the deployed state of these blade members, the light beam from the subject can be blocked, and in the folded state of the blade members, the optical image corresponding to the light beam from the subject that forms an image on the image sensor 101 can be formed on the image sensor 101.

[0019] In the camera body 100, it is possible to adjust the amount of light incident on the imaging element 101 according to the running speed of the shutter 102. Then, by changing the shutter speed, which is an exposure condition based on the running speed of the shutter 102 and the exposure time of the imaging element 101, the brightness of the image signal can be adjusted. Note that a configuration in which a so-called electronic shutter that performs the same configuration as the operation of the shutter 102 in the accumulation control of the imaging element 101 may be adopted.

[0020] The display unit (hereinafter simply referred to as the display) 103 is a display means composed of a TFT-type LCD (thin film transistor drive type liquid crystal display) or the like. The display 103 can display information on shooting parameters such as exposure when imaging a subject, and a display image based on the image acquired using the imaging element 101, and a live view (display) for sequentially displaying this display image is possible. The display on the display unit 103 is controlled by a system control unit 104 described later.

[0021] Note that the display 103 is a so-called touch panel that also serves as an operation means capable of touch operations by the user, and functions as a capacitive touch panel in this embodiment. The configuration of the display 103 that enables touch operations is not limited to one that detects capacitance, and any known method may be adopted.

[0022] The system control unit (CPU) 104 is a control means that comprehensively controls each part of the camera body 100 and the camera accessories attached to the camera body 100. The details of the control content executed by the CPU 104 will be described in detail in the description of various operations described later.

[0023] The photographic lens 200 is an optical device that guides a light beam corresponding to the optical image of the subject into the camera body 100. The lens group 201 of the photographic lens 200 is an optical system equipped with various lenses such as focusing lenses, zoom lenses, and shift lenses. The aperture 202 is a light intensity adjustment member that can adjust the amount of light incident into the camera body 100 by adjusting the aperture diameter. The photographic lens 200 also includes a lens control unit (LPU) 203, which is a control means for the photographic lens. In addition to controlling the lens position of the lens group 201 and the aperture diameter of the aperture 202, the LPU 203 is also a communication control means that controls communication with the CPU 104 of the camera body 100.

[0024] The aperture drive unit 205 is configured to drive the aperture 202 of the photographic lens 200, and can drive the aperture 202 to the aperture position indicated by the LPU 203, and adjust the opening of the aperture 202 to an opening amount corresponding to the aperture value. The lens drive unit 204 is configured to drive the lens group 201 of the photographic lens 200 to a predetermined position, and can drive the lens group 201 to the position indicated by the LPU 203.

[0025] The shutter control unit 105 is configured to control the opening and closing state of the shutter 102, and by controlling the movement of the shutter 102 at a time specified by the CPU 104, it can control the shutter speed when imaging a subject.

[0026] The signal processing unit 106 is configured to perform various processes on the image signal output from the image sensor 101, including predetermined image interpolation, resizing such as reduction, color conversion, and calculation of the number of pixel data such as saturated pixels and blacked-out pixels on the digital image data. The signal processing unit 106 is also a white balance (hereinafter simply referred to as WB) processing means that performs white balance calculation processing on the digital image data.

[0027] The recording unit 112 is a recording medium for recording image signals obtained by imaging, and is capable of recording image signals acquired using the image sensor 101 as still image data or video data. The recording unit 112 is also used as a memory capable of recording data related to the operation of the imaging system centered on the camera body 100 and various data acquired using the camera body 100. The recording unit 112 in this embodiment is equipped with a ROM area that can be used as non-volatile memory and a RAM area that can be used as volatile memory.

[0028] The shooting mode selection unit 109 is a selection means for selecting a shooting mode that can be set on the camera body 100. In this embodiment, a shooting mode refers to a mode in which the method of setting exposure-related elements (exposure control values) differs. For example, it is possible to set an aperture value (Av) priority mode that prioritizes setting the aperture value, or a shutter speed (Tv) priority mode that prioritizes setting the shutter speed. The shooting mode selection unit 109 is electrically connected to the CPU 104, and the CPU 104 controls the camera body 100 according to the shooting mode selected by the shooting mode selection unit 109.

[0029] The imaging instruction unit 110 is, for example, a shutter button. The imaging instruction unit 110 is electrically connected to the CPU 104, and when pressed down by the user's manual operation, the signal becomes active, instructing the camera to prepare for imaging and to start imaging. In all other states, the signal is deactivated. The imaging instruction unit 110 can transition between two pressed states, and the CPU 104 recognizes the half-pressed state of the imaging instruction unit 110 as the imaging standby state and instructs each part of the camera body 100 to perform imaging preparation operations. Then, the CPU 104 recognizes the fully pressed state of the imaging instruction unit 110 as the imaging state and instructs each part of the imaging system to perform imaging operations. In other words, the imaging instruction unit 110 is an operating means that allows the user to manually instruct the camera to prepare for imaging and to initiate imaging.

[0030] The imaging setting input unit 111 is an information input means that can be used to set various imaging settings and functions in the camera body 100. In this embodiment, the imaging setting input unit 111 includes a rotary dial, a cross key, a select button, a reset button, etc., but the mechanism used for information input is not limited to these. Typical settings and functions that can be set using the imaging setting input unit 111 include various settings related to metering mode, continuous shooting function, flickerless shooting function (described later), live view, and flash shooting function. Depending on the operation of the imaging setting input unit 111, a graphical user interface (GUI) and function icons related to the functions of various settings can be displayed on the display 103 by instruction from the CPU 104.

[0031] In addition, metering modes include evaluative metering, which evaluates the entire screen corresponding to the angle of view of the image sensor 101 and performs correction according to the metering point and brightness value, and center-weighted metering, which performs metering by giving greater weight to the central part of the screen than other areas.

[0032] Other metering modes include spot metering, which measures light based on only a portion of the screen, and partial metering, which is wider than spot metering but measures light based on a predetermined area of ​​the screen. Furthermore, the live view display methods (modes) include a normal mode that allows composition confirmation while considering the appearance of the live view, and a simulated mode that simulates the exposure used when actually shooting a subject and obtaining a still image for recording (recorded image) in live view.

[0033] One difference between normal mode and simulate mode is whether or not the user-set exposure compensation amount is reflected in the live view. In normal mode, the exposure compensation amount is not reflected, but in simulate mode, the user's intention is prioritized and the exposure compensation amount is reflected in the live view.

[0034] The subject brightness determination unit 107 is a brightness detection means that determines (detects) the brightness (brightness value) of a subject based on the image signal output from the signal processing unit 106. Specifically, the subject brightness determination unit 107 divides a single screen corresponding to the acquired image signal into multiple blocks and calculates the average brightness value of each block. Then, it integrates the average brightness value of each block to obtain a representative brightness value. In the following description, this representative brightness value will be used as the brightness value (photometric value) of the subject, and this brightness value will be used for various processes and controls such as exposure control. Note that the method for detecting the brightness value is not limited to this, and various methods for calculating the brightness value can be adopted.

[0035] The CPU 104 calculates exposure control amounts for various exposure control values ​​(shutter speed, aperture value, ISO sensitivity, etc.) based on the brightness value detected by the subject brightness determination unit 107 and the shooting mode selected by the shooting mode selection unit 109. The focal length determination unit 108 calculates information to determine whether the lens position of the focus lens included in the shooting lens 200 is in focus, based on the image signal output from the signal processing unit 106. If the current lens position is out of focus based on the calculated information, the CPU 104 controls the shooting lens 200 through the LPU 203. The position of the focus lens can be adjusted by the CPU 104 in response to user input, regardless of the focus state.

[0036] The strobe control unit 113 controls the emission of the light-emitting means when it is determined by the CPU 104 to require illumination of the subject based on the brightness value, or based on manual operation by the user. In this embodiment, the light-emitting means is either a built-in strobe 114 built into the camera body 100, or an external strobe 300 that can be attached to or detached from the camera body 100 via a connection part (not shown). The external strobe 300 is an external light-emitting device that can be attached to or detached from the camera body 100, and includes an external strobe control unit (SPU) 301 for controlling the operation of the external strobe 300. The SPU 301 is a control means that controls the emission control of the external strobe 300 and communication with the camera body 100.

[0037] (Flicker detection and flicker-free shooting function) Next, the flicker detection operation will be described in detail. The flicker detection operation in this embodiment may use known techniques, and will be explained with reference to Figure 3 as an example. Figure 3 is a diagram showing the charge accumulation timing and readout timing related to the image signal for flicker detection according to the first embodiment of the present invention, in which accumulation and readout are performed 12 times consecutively at 600 fps with a period of approximately 1,667 ms.

[0038] This 600fps is equal to the least common multiple of the predetermined flicker light intensity change periods (100Hz and 120Hz). Furthermore, by performing 12 accumulations at 600fps, the accumulation is performed over a period of 20ms in total, and regardless of whether the commercial power frequency is 50Hz or 60Hz, two periods of light intensity change of the flicker light source are included. All 12 accumulations are performed under the same exposure conditions, which are determined based on the results of the photometering operation. Note that the 600fps accumulation and readout may not use a configuration that uses all pixels of the image sensor 101, but rather a configuration that adjusts the frame rate to 600fps (1,667ms period) by so-called pixel addition readout or decimation readout. When determining the exposure during 600fps driving, it is preferable to use the luminance value output from the area of ​​the image sensor 101 used for flicker detection operation as the reference value.

[0039] Figure 3(a) is a diagram illustrating the transition of storage control and image signal output when flicker (flicker illumination period of 100Hz) is present at a commercial power supply of 50Hz. As shown in Figure 3(a), the nth storage is described as "storage n", the readout of storage n is described as "readout n", and the image signal output (photometric value) obtained from the result of readout n is described as "AE(n)". In this embodiment, a total of 12 storage operations are performed in a series of flicker detection operations, so outputs AE(1) to AE(12) are obtained. Regarding the acquisition time of each output, since storage is performed over a finite period, the median value during the storage period is used to represent it. From these AE(1) to AE(12), an evaluation value used to determine the flicker light intensity change period (frequency) is calculated. In this embodiment, the evaluation value used to determine the flicker light intensity change period is defined by the following equation (1).

[0040]

number

[0041] SAD stands for Sum of Absolute Difference and is a similarity index used in fields such as pattern matching. m is a number that indicates how many outputs ahead the nth output AE(n) out of 12 accumulations should be compared to in order to calculate the similarity. Therefore, SAD(m) is a formula that calculates the similarity with the output after (1.667 × m) ms.

[0042] As can be seen from equation (1), the higher the similarity, the smaller the value of SAD(m). For example, under a 100Hz flicker light source, the period of change in the light intensity of the flicker is approximately 10ms, and the relationship with the flicker detection period of 1.667ms is 10÷1.667≈6. Therefore, as shown in Figure 3(a), the same output is obtained in 6 cycles regardless of the timing of accumulation, and the relationship AE(n)≈AE(n+6) holds. From this property, when SAD(6) is calculated under a 100Hz flicker light source, SAD(6)≈0. Furthermore, in order to detect the presence of the 100Hz flicker, SAD(3) is calculated additionally. SAD(3) is the value obtained by calculating the similarity with the output after 1.667×3=5ms has elapsed. Under a 100Hz flicker light source, the photometric values ​​at timings shifted by 5ms are in opposite phase, so SAD(3) is a much larger value than SAD(6). In other words, if SAD(3) is large and SAD(6) is small, it is thought that flicker corresponding to a 100Hz light intensity change period may occur (may exist).

[0043] Figure 3(b) illustrates the transition of storage control and image signal output when flicker (flicker on / off cycle is 120Hz) is present under a commercial power supply of 60Hz. Similar to the case where the flicker light intensity change cycle is 100Hz, SAD(5) and SAD(3) are calculated for flicker (flicker on / off cycle is 120Hz) under a commercial power supply of 60Hz. Under a 120Hz flicker light source, the flicker light intensity change cycle is approximately 8.333ms, so AE(n) ≈ AE(n+5) and SAD(5) ≈ 0. Also, with a 120Hz flicker, the phase inversion occurs after 4.16ms, and ideally, the similarity to the waveform after 4.16ms should be determined. However, since 4.16ms is not an integer multiple of the frame period of 1.667ms, the value of SAD(3), which shows the similarity to the waveform after 5ms, is used as a substitute, as it is a value that is relatively close to this. In other words, even under a 120Hz flicker light source, SAD(3) shows the similarity of photometric value changes at intervals close to opposite phase, so SAD(3) is a much larger value than SAD(5). Based on the above, SAD(6), SAD(5), and SAD(3) are calculated, and these evaluation values ​​are used to perform the final determination of the flicker light intensity change period. Figure 4 is a diagram illustrating an exemplary method for determining the flicker light intensity change period according to the first embodiment of the present invention.

[0044] Figure 4(a) shows the data used to determine flicker with a light intensity change period of 100 Hz, Figure 4(b) shows the data used to determine flicker with a light intensity change period of 120 Hz, and Figure 4(c) shows the data used to detect the presence or absence of flicker and the light intensity change period. As mentioned above, under a 100 Hz flicker light source, SAD(3) becomes a much larger value than SAD(6). Therefore, considering a plane like the one shown in Figure 4(a) with SAD(3) on the horizontal axis and SAD(6) on the vertical axis, under a 100 Hz flicker light source, the plot will be obtained in the relatively lower right region of this plane. In other words, by dividing the region as shown in Figure 4(a) into regions to determine 100 Hz flicker and regions to determine that it is not 100 Hz flicker, 100 Hz flicker can be accurately determined from the position of the plot relative to these regions. Similarly, by dividing the plane into regions as shown in Figure 4(b), with SAD(3) on the horizontal axis and SAD(5) on the vertical axis, it is possible to determine whether it is a 120Hz flicker.

[0045] Note that the region division lines shown in Figures 4(a) and (b) are merely examples, and the slope and inflection points of these division lines are not limited to those shown. The results of the determination of whether or not flicker occurs for each light intensity change period described above are integrated to perform the final flicker detection. In this embodiment, the correspondence table shown in Figure 4(c) is used to perform the final flicker detection related to the detection of whether or not flicker occurs and the light intensity change period.

[0046] Furthermore, if no flicker is present (indicated as "DC" in Figure 4(c)), the output from 12 accumulations does not change significantly over time. Therefore, comparing each output, AE(1)≒AE(2)≒AE(3)≒·····≒AE(12), resulting in each evaluation value SAD(6)≒SAD(5)≒SAD(3)≒0. In this case, since the plots are obtained near the origin of both planes in Figures 4(a) and (b), it is determined that 100Hz flicker and 120Hz flicker are absent (not occurring), corresponding to "DC" in the lower right box of the table in Figure 4(c). Also, the upper left box of the table in Figure 4(c) indicates a state where 100Hz flicker and 120Hz flicker are detected. Normally, such a result would not be obtained, but this is not the case if, for example, the subject changes during the 12 accumulations due to movement or panning of the subject. In this case, since the flicker detection result is an error, it is determined that no flicker exists (is not detected). The above is an explanation of one example of the flicker detection operation.

[0047] (Exposure simulation) Next, with reference to Figure 5, a flowchart of the processing in the simulated mode in this embodiment will be described.

[0048] Figure 5 is a flowchart showing the control during the simulation from live view display to shooting of the camera 100 in this embodiment. First, the user sets the metering mode to a mode that simulates exposure on the live view display via the imaging setting input unit 111, etc., and this flow begins when the acquisition of the live view display image starts.

[0049] First, in step S501, the system control unit 104 determines the method for capturing an image for live view display on the display unit 103 and controls the driving of the image sensor 101.

[0050] In step S502, flicker detection is performed by executing the process shown in Figure 4 based on instructions from the system control unit 104. Here, the flicker frequency (flicker frequency) is mainly detected. The result of the flicker detection is temporarily stored, for example, in the ROM area of ​​the recording unit 112.

[0051] Next, in step S503, the system control unit 104 calculates constraints on the exposure time for still image driving and the exposure time for display driving in order to reduce the effect of flicker. Details of the method for calculating the constraints will be described later. Once the calculation of the constraints is complete, the process proceeds to step S504.

[0052] In step S504, the system control unit 104 makes a decision on switching the imaging drive, as described later, based on the exposure time constraint calculated in step S503. If it determines that a switch should be performed, it proceeds to step S505; otherwise, it proceeds to step S506. Details will be described later.

[0053] In step S505, the system control unit 104 performs control to switch the image sensor 101, which is controlled by the image capture drive for live view display, to the same image capture drive as for still image capture, and then proceeds to step S501. Note that the switching of the image capture drive in step S505 is not limited to the image capture drive for still image capture, but may be any other image capture drive.

[0054] In step S506, the system control unit 104 displays an image on the display unit 103 in live view mode that simulates the effect of reducing the flicker effect in the image capture drive for still image capture. After that, if an image preparation instruction and an image capture instruction are given through operations on the image capture instruction unit 110, the process proceeds to step S507.

[0055] In step S507, still image capture is started based on operations on the imaging instruction unit 110. In step S506, the effect of reducing flicker is simulated in the live view display. Therefore, it is possible to confirm the effect of reducing flicker in the live view display and reflect it in still image capture. The above is the flow up to the start of still image capture.

[0056] Next, the method for calculating the exposure time constraint in S503 will be explained. Depending on the method of driving the image sensor 101, the HD resolution (HD resolution), which is the time required to read out a horizontal unit row of the image sensor 101, may differ, and the settable exposure time may also differ. An example of this embodiment will be explained with reference to Figure 6.

[0057] In Figure 6, 601 is a conceptual diagram of an image being captured with an arbitrary exposure time, where the horizontal axis is time and the vertical axis is the pixel position on the screen. The striped pattern represents the occurrence of flicker due to fluctuations in the light intensity of the light source along the time axis. 602 shows the effect of flicker on the captured image. In this embodiment, a drive with coarse HD resolution is used for display, and the unit exposure time is shown as period 603. A drive with fine HD resolution is used for still images, and the unit exposure time is shown as period 604. 605 shows the flicker period, and 606 is the period exceeding an integer multiple of the flicker period when imaging is performed with the unit exposure time of the display drive, representing the correspondence with the effect of flicker in 602.

[0058] At this time, in order to obtain the effect of reducing the effect of flicker, it is preferable to set the exposure time constraint for the still image drive in increments of the least common multiple of 604 and 605. For example, if 604 is 1 [us] and 605 is 2 [us], the exposure time constraint will be in increments of 2 [us]. The exposure time constraint is determined under these conditions. Hereafter, the exposure time constraint will be referred to as T. Note that the exposure time constraint is characterized by being calculated from the resolution of the imaging drive for live view display, the resolution of the imaging drive for still image capture, and the flicker period, and the calculation formula is not limited.

[0059] Next, we will explain the determination of switching the imaging drive in step S504. In order to satisfy the constraint of obtaining the effect of reducing flicker in the imaging drive for still image capture based on the result calculated in step S503, and to obtain the effect of reducing flicker in the imaging drive for live view display, it is necessary to set the least common multiple step of 603 and T.

[0060] Therefore, in order to prevent the difference in exposure time between capturing still images and images for live view display from increasing, the system control unit 104 may determine to perform a drive switch (drive switching) if 603 and T are not divisible. For example, if 603 is 7 [us] and T is 2 [us], the imaging drive for the live view display image will be switched. Note that the determination of whether to switch the imaging drive is calculated from the resolution of the imaging drive for live view display, the resolution of the imaging drive for still image capture, the flicker period, and T, and the calculation formula is not limited. Also, if the difference is less than or equal to a predetermined value, the system control unit 104 will determine not to perform a drive switch.

[0061] In addition, due to the specifications of the camera body 100, it may not be possible to set an exposure time that satisfies the above constraints or to switch the drive mode. In such cases, it becomes difficult to perform an appropriate simulation on the live view display. In such cases, the system control unit 104 may, for example, control the system to display a predetermined message superimposed on the live view display to inform the user that the exposure time constraints cannot be met. The predetermined message could be an icon or text superimposed on the display. Alternatively, the camera body 100 may be equipped with a sound or light notification means to inform the user by sound or light.

[0062] (Second Embodiment) Next, a second embodiment of the present invention will be described.

[0063] In this embodiment, the basic configuration is the same as in the first embodiment, so the explanation will be omitted. In the first embodiment, the drive with coarse HD resolution was mainly described as the imaging drive for live view display, and the drive with fine HD resolution was mainly described as the imaging drive for still images. On the other hand, in this embodiment, the exposure time constraint calculation means in S503 and the supplement and differences in the drive switching determination in S504 will be explained when the drive with coarse HD resolution is used for still images and the drive with fine HD resolution is used for display.

[0064] At this time, it is possible to set an exposure time to eliminate flicker with the HD resolution display drive, but this may not be possible with the still image drive, which has a coarser resolution. In that case, the exposure time of the image drive for live view display may be matched to the exposure time of the image drive for still image shooting, thereby reflecting the effect of flicker during still image shooting in the live view display.

[0065] For example, suppose the unit exposure time for the imaging drive used for still image capture is 3 [us], the unit exposure time for the imaging drive used for live view display is 1 [us], and the flicker period is 2 [us]. In this case, by setting the exposure time constraint for the imaging drive used for live view display to 3 [us] increments, the drive switching can be avoided, and the exposure times for the still image drive and the display drive can be matched.

[0066] When the exposure time for still image drive is 3 [us], flicker will appear in the still image, but this can be confirmed from the displayed image. Note that while an example of calculating exposure time constraints and drive switching criteria from the resolution of the display drive, the resolution of the still image drive, and the flicker period is given, this does not limit the calculation method.

[0067] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its gist.

[0068] The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0069] This embodiment includes the following imaging device, a control method for the imaging device, and a program.

[0070] (Item 1) An image sensor that captures multiple images, Control means for controlling a first drive that captures a first image for recording using the image sensor, and a second drive that captures a second image for display, A detection means for detecting flicker from the aforementioned multiple images, A calculation means that calculates the exposure time constraints when capturing the first image and the second image based on the detection results of the detection means, A determination means that determines whether to switch the second drive based on the constraints calculated by the calculation means, and whether the constraints on the exposure time that can be taken by the second drive are met. An imaging device characterized by having the following features.

[0071] (Item 2) The imaging apparatus according to item 1, characterized in that the first drive and the second drive are drives with different HD resolutions.

[0072] (Item 3) The imaging apparatus according to item 2, characterized in that the second drive has a coarser HD resolution than the first drive.

[0073] (Item 4) The imaging apparatus according to item 2 or 3, characterized in that the calculation means calculates the exposure time constraint from the HD resolution of the first drive, the HD resolution of the second drive, and the flicker frequency.

[0074] (Item 5) The imaging apparatus according to any one of items 1 to 4, characterized in that the calculation means calculates the constraint on the exposure time so that the exposure time reduces the effect of flicker.

[0075] (Item 6) The imaging apparatus according to item 2 or 3, characterized in that the determination means makes a determination based on the HD resolution of the first drive, the HD resolution of the second drive, and the flicker frequency.

[0076] (Item 7) The imaging apparatus according to any one of items 1 to 6, characterized in that the determination means determines not to switch the drive when the difference between the exposure time of the first drive and the exposure time that can be set by the second drive is less than or equal to a predetermined value.

[0077] (Item 8) It further includes a display control means for controlling a display unit that displays an image, The imaging apparatus according to any one of items 1 to 7, characterized in that the display control means displays a predetermined message on the live view display when it is not possible to set an exposure time that satisfies the constraints or when it is not possible to switch the drive.

[0078] (Item 9) The imaging step involves capturing multiple images, A control step that controls a first drive for capturing a first image for recording and a second drive for capturing a second image for display, A detection step for detecting flicker from the aforementioned multiple images, A calculation step to calculate the exposure time constraints when capturing the first image and the second image based on the detection results, A determination step to determine whether to switch the second drive based on the constraints mentioned above, and whether the constraints on the exposure time that can be taken with the second drive are met, A control method for an imaging device, characterized by having the following features.

[0079] (Item 10) A program for causing a computer to function as each of the means of the imaging apparatus described in claim 1. [Explanation of Symbols]

[0080] 100 Camera Body 101 Image sensor 102 Shutter 103 Display Unit 104 System Control Unit (CPU) 112 Records Section 200 shooting lens 203 Lens Control Unit (LPU) 300 External flash 301 External Strobe Unit (SPU)

Claims

1. An image sensor that captures multiple images, Control means for controlling a first drive that captures a first image for recording using the image sensor, and a second drive that captures a second image for display, A detection means for detecting flicker from the aforementioned multiple images, A calculation means that calculates the exposure time constraints when capturing the first image and the second image based on the detection results of the detection means, A determination means that determines whether to switch the second drive based on the constraints calculated by the calculation means, and whether the constraints on the exposure time that can be taken by the second drive are met. An imaging device characterized by having the following features.

2. The imaging apparatus according to claim 1, characterized in that the first drive and the second drive are drives with different HD resolutions.

3. The imaging apparatus according to claim 2, characterized in that the second drive has a coarser HD resolution than the first drive.

4. The imaging apparatus according to claim 1, characterized in that the calculation means calculates the exposure time constraint from the HD resolution of the first drive, the HD resolution of the second drive, and the flicker frequency.

5. The imaging apparatus according to claim 1, characterized in that the calculation means calculates the constraint on the exposure time so that the exposure time becomes one that reduces the effect of flicker.

6. The imaging apparatus according to claim 1, characterized in that the determination means makes a determination based on the HD resolution of the first drive, the HD resolution of the second drive, and the flicker frequency.

7. The imaging apparatus according to claim 1, characterized in that the determination means determines not to switch the drive when the difference between the exposure time of the first drive and the exposure time that can be set by the second drive is less than or equal to a predetermined value.

8. It further includes a display control means for controlling a display unit that displays an image, The imaging apparatus according to claim 1, characterized in that the display control means displays a predetermined message on the live view display when it is not possible to set an exposure time that satisfies the constraints or when it is not possible to switch the drive.

9. The imaging step involves capturing multiple images, A control step that controls a first drive for capturing a first image for recording and a second drive for capturing a second image for display, A detection step for detecting flicker from the aforementioned multiple images, A calculation step to calculate the exposure time constraints when capturing the first image and the second image based on the detection results, A determination step to determine whether to switch the second drive based on the constraints mentioned above, and whether the constraints on the exposure time that can be taken with the second drive are met, A control method for an imaging device, characterized by having the following features.

10. A program for causing a computer to function as each of the means of the imaging apparatus described in claim 1.

Images