Imaging device and its control method, program

Abstract

To reduce uneven exposure on both ends of an image during capturing an image with strobe light while shortening synchronization seconds.SOLUTION: A system control unit 120 is configured to determine photographing parameters including shutter seconds in strobe flash photography and determine whether to employ front curtain correction control execution (second control) or no front curtain correction control execution (first control) when taking a picture depending on the shutter seconds in the determined photographing parameters. In the first control, the running speed of a front curtain of the shutter is controlled to be the same as the running speed of the rear curtain of the shutter. In the second control, the running speed of the front curtain is controlled to be faster than the running speed of the rear curtain.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to an image pickup apparatus, a control method therefor, and a program.

Background Art

[0002] Conventionally, a focal-plane shutter for an image pickup apparatus includes a front curtain that starts exposure and a rear curtain that ends exposure. There are types of shutters in which both the front curtain and the rear curtain adopt a mechanical shutter system, and types in which both of them adopt an electronic shutter system. In addition, there is also a mixed type (electronic front curtain system) for shutters, in which the front curtain adopts the electronic shutter system and the rear curtain adopts the mechanical shutter system.

[0003] In flash photography using a focal-plane shutter, flash emission is permitted when the shutter fully opens the entire screen with respect to the image sensor, that is, when the traveling of the front curtain of the shutter is completed. After the flash emits light, the rear curtain travels at a timing when the peak value of the signal reaches a predetermined light amount with respect to the maximum value of the emission amount. By this means, the shutter speed that makes the full-open period of the shutter the shortest is obtained. This shutter speed is called flash synchronization speed.

[0004] This operation will be outlined with reference to FIGS. 2 to 5. FIGS. 2 to 5 are conceptual diagrams showing the relationship between the traveling pattern of the front curtain and the traveling pattern of the rear curtain in the electronic front curtain system. In each figure, S1 indicates the scanning pattern (traveling curve) of reset scanning by the electronic front curtain. S2 indicates the traveling curve of the mechanical rear curtain.

[0005] If both the front curtain and the rear curtain are of the mechanical shutter system, the image sensor is exposed by the traveling of the front curtain of the shutter and shielded from light by the rear curtain of the shutter. If both the front curtain and the rear curtain are of the electronic shutter system, the accumulated charges in the horizontal direction of the image sensor are reset by front curtain control, and the accumulated charges in each row of the image sensor are sequentially read out by rear curtain control.

[0006] In each figure, time T1 is the travel time of the shutter's front curtain. In the case of an electronic front curtain system, time T1 is the time required for the front curtain to reset the charge accumulation on the image sensor. In each figure, the flash output curve shows the temporal change in the flash output during strobe firing. The maximum flash output is set to 1, and the amount at which the flash output is halved is set to 1 / 2. Time T2 is the time from the start of strobe firing until the flash output is halved and the rear curtain starts moving. Since the rear curtain starts moving after the light output has decreased to a predetermined level, time T2 is the period when the shutter is fully open, and the time T1 + T2 is the synchronization time in seconds.

[0007] The front curtain's travel speed is the speed at which the accumulated charge of the image sensor is reset by scanning, and corresponds to the tilt of S1. The rear curtain's travel speed is the speed at which the leading edge of the mechanical rear curtain passes over the imaging surface of the image sensor, and corresponds to the tilt of S2.

[0008] Conventionally, in electronic shutter and electronic front curtain systems, the travel curves of the front and rear curtains were made identical. Therefore, the synchronization time was determined by time T1, which is the travel time of the front curtain, and time T2, which is the total light development period. To make the synchronization time faster (shorter), one can either shorten the shutter travel speed (or the reset time and readout time of the accumulated charge in electronic shutters) or shorten the light emission time (by reducing the amount of light emitted or by shortening the time at which the amount of light emitted is halved). These methods will be explained using Figures 3 to 5 in comparison with Figure 2.

[0009] Figure 3 shows an example of control that shortens the synchronization time by increasing the speed of the leading curtain. Increasing the speed of the leading curtain increases the slope of S1 and shortens the time T1. This allows the start timing of the strobe flash to be brought forward, thus shortening the synchronization time.

[0010] Figure 4 shows an example of control that shortens the synchronization time by limiting the strobe flash output. Note that the peak of the flash output waveform in Figures 2 to 5 is represented as a relative quantity, and the flash output in Figures 4 and 5 is smaller than the flash output in Figures 2 and 3. As shown in Figure 4, limiting the strobe flash output shortens the time T2. This allows the start time of the rear curtain to be brought forward, thus shortening the synchronization time.

[0011] Figure 5 shows an example of control that shortens the synchronization time by both increasing the speed of the lead curtain and limiting the amount of strobe light emitted. Since both the effects explained in Figure 3 and the effects explained in Figure 4 are reflected, the synchronization time is shortened.

[0012] Patent Document 1 discloses a technique for an electronic front curtain imaging device in which, during strobe photography, the travel time of the front curtain's electronic shutter is always made shorter than the travel time of the rear curtain's mechanical shutter, thereby shifting the flash timing forward and shortening the synchronization time. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Japanese Patent Publication No. 2008-060640 [Overview of the project] [Problems that the invention aims to solve]

[0014] However, in the technology described in Patent Document 1, when using a strobe, the travel speed of the front curtain and the travel speed of the rear curtain are different, so the accumulation time is always different at the top and bottom of the captured image. As a result, the exposure is always different at the top and bottom of the image, which is the problem of so-called uneven exposure.

[0015] The present invention aims to reduce exposure unevenness at both edges of an image during strobe photography while shortening the synchronization time. [Means for solving the problem]

[0016] To achieve the above object, the present invention imaging device comprises: determining means that, when performing flash emission photography, determines shooting parameters including shutter speed and tentatively determines a flash emission amount; and control means that selectively executes a first control for controlling such that the running speed of a front curtain of a shutter and the running speed of a rear curtain of the shutter are equal to each other, and a second control for controlling such that the running speed of the front curtain is higher than the running speed of the rear curtain, wherein when performing flash emission photography, the control means determines which one of the first control and the second control is to be adopted during shooting in accordance with the shutter speed in the shooting parameters determined by the determining means, and controls the flash emission amount during shooting based on the shutter speed and the tentatively determined flash emission amount Furthermore, if the length of the shutter time is longer than the first time, the first control is adopted; if the length of the shutter time is less than or equal to the first time, the second control is adopted; and if the length of the shutter time is less than or equal to the second time (which is shorter than the first time) and the provisionally determined strobe flash amount is greater than or equal to a predetermined flash amount, the strobe flash amount during shooting is limited to a value lower than the provisionally determined strobe flash amount. . Advantageous Effects of Invention

[0017] According to the present invention, exposure unevenness at both ends of an image in flash emission photography can be reduced while shortening the synchronizing speed. Brief Description of Drawings

[0018] [Figure 1] It is a block diagram of an imaging apparatus. [Figure 2] It is a conceptual diagram showing the relationship between a running pattern of a front curtain and a running pattern of a rear curtain. [Figure 3] It is a conceptual diagram showing the relationship between a running pattern of a front curtain and a running pattern of a rear curtain. [Figure 4] It is a conceptual diagram showing the relationship between a running pattern of a front curtain and a running pattern of a rear curtain. [Figure 5] It is a conceptual diagram showing the relationship between a running pattern of a front curtain and a running pattern of a rear curtain. [Figure 6] It is a flowchart showing still image shooting processing. [Figure 7] It is a flowchart showing synchronizing speed increasing calculation processing. [Figure 8] It is a diagram explaining the range imaged by an image sensor. [Figure 9]It is a conceptual diagram showing the relationship between the traveling pattern of the front curtain and the traveling pattern of the rear curtain. [Figure 10] It is a flowchart showing the arithmetic processing for speeding up the synchronized shutter speed.

Mode for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0020] (First Embodiment) Figure 1 is a block diagram of an image pickup apparatus according to the first embodiment of the present invention. As an example, this image pickup apparatus is a digital camera 1 (hereinafter simply referred to as camera 1). Note that one or more of the functional blocks shown in Figure 1 may be implemented by hardware such as an ASIC or a programmable logic array (PLA), or may be implemented by a programmable processor such as a CPU or MPU executing software. Alternatively, one or more of the functional blocks described above may be implemented by a combination of software and hardware. Therefore, in the following description, even when different functional blocks are described as the operating主体, the same hardware can be implemented as the主体.

[0021] Note that the camera 1 is a so-called interchangeable-lens image pickup apparatus including a camera unit 100, an external recording medium 200, a lens unit 300, and a strobe unit 400, but is not limited thereto. For example, the camera unit 100 and at least one of the lens unit 300 or the strobe unit 400 may be configured as an integrated structure.

[0022] In the camera unit 100, the front and rear curtain systems of the shutter 102 can be either mechanical or electronic, as long as the control, including the travel speed, can be changed. If both the front and rear curtains are mechanical, the shutter 102 is a light-shielding member for opening and closing the optical path between the lens unit 300 and the image sensor 103. If the front curtain is an electronic shutter, the horizontal accumulated charge of the image sensor 103 is reset by front curtain control. If the rear curtain is an electronic shutter, the accumulated charge of each row of the image sensor 103 is read out sequentially by rear curtain control.

[0023] In this embodiment, the shutter 102 is assumed to have an electronic shutter for the front curtain and a mechanical or electronic shutter for the rear curtain, but is not limited to this.

[0024] The image sensor 103 is a charge-accumulating solid-state image sensor such as a CCD or CMOS, which converts the light beam of the subject incident via the lens unit 300 into photoelectric form (imaging) to generate analog image data. The electronic viewfinder 105 is an electronic viewfinder that uses a TFT-type LCD (thin-film transistor-driven liquid crystal display) or an organic EL element (organic electroluminescent element), allowing the user to confirm the image of the subject.

[0025] The A / D conversion unit 106 converts analog image data output from the image sensor 103 into digital image data. The image processing unit 107 performs various processes on the digital image data output from the A / D conversion unit 106, such as white balance adjustment and gradation processing. The timing generation unit 108 generates signals (control signals such as clock signals) to operate the image sensor 103, the A / D conversion unit 106, and the D / A conversion unit 109. In addition, the timing generation unit 108 can control the accumulation and reading of charge in the image sensor 103 by controlling the reset timing and readout timing of the accumulated charge in the image sensor 103. The timing generation unit 108 is controlled by the system control unit 120.

[0026] The memory control unit 110 controls the A / D conversion unit 106, the image processing unit 107, the D / A conversion unit 109, and the compression / decompression unit 111 to execute the process of writing the acquired image data to the display memory 112 or the recording memory 113.

[0027] The image display unit 114 employs a TFT LCD or organic EL element, similar to the electronic viewfinder 105. Digital image data for display written to the display memory 112 is converted into analog image data for display by the D / A conversion unit 109, and then displayed in the electronic viewfinder 105 or the image display unit 114.

[0028] The recording memory 113 has sufficient storage capacity to store a predetermined number of still image data and moving image data, and stores image data acquired by imaging a subject. It is also possible to use the recording memory 113 as a workspace for the system control unit 120.

[0029] The compression / decompression unit 111 reads the image data stored in the recording memory 113 and compresses and decompresses the image data according to predetermined image compression and image decompression methods to accommodate various applications. The shutter control unit 115 controls the operation of the shutter 102 based on the photometric results of the subject calculated by the system control unit 120. The shutter 102 can be controlled in conjunction with the aperture 302.

[0030] The system control unit 120 comprehensively controls the operation of camera 1. Based on the image data captured by the image sensor 103, the system control unit 120 performs exposure control and focus control based on the focus detection result. For example, the system control unit 120 uses the image data captured by the image sensor 103 to control the lens position (focus control) based on the contrast information of the acquired image data while shifting the position of the focus lens. Alternatively, as another focus control method, the system control unit 120 detects the focus state of the optical image from the phase difference between two images of the subject based on the captured image data, and controls the lens position (focus control) based on the result of this focus detection.

[0031] The system control unit 120 can also perform flicker detection, which uses the captured image data to detect whether or not there is flicker in the shooting environment. Furthermore, the system control unit 120 can perform photometric calculations, which use the captured image data to calculate the brightness value of the subject. As exposure control when capturing an image of a subject and acquiring image data, the system control unit 120 adjusts exposure parameters such as aperture value, shutter speed, and shooting sensitivity (ISO sensitivity).

[0032] Note that the aperture value is a parameter related to the opening of the aperture 302. The shutter speed is a parameter related to the charge accumulation time in the image sensor 103. The shooting sensitivity is a parameter related to the amount of analog gain and digital gain.

[0033] The system control unit 120 controls the strobe unit 400 to control the amount and timing of light emission of the strobe unit 400, according to the results of the photometric calculation, camera settings, and the state of the strobe unit 400. Furthermore, the system control unit 120 can switch the imaging range of the image sensor 103 based on user settings based on the operation of the operation unit 133, enabling shooting using the pixel output of the entire image sensor or shooting a cropped portion of it.

[0034] In this way, the system control unit 120 can perform appropriate exposure and strobe control according to the brightness value, and change the range captured by the image sensor 103, based on various information such as the brightness of the subject, exposure control, and settings.

[0035] The main memory 121 stores data related to the operation of the camera 1, such as information on exposure (correct exposure) in relation to brightness values ​​(program diagrams using table data, etc.), constants for operations performed by the camera 1, various exposure conditions, and calculation formulas. The non-volatile memory 123 is an EEPROM, such as flash memory, and allows for the electrical erasure and storage of data.

[0036] The following describes the operating components for inputting various operation instructions to the system control unit 120. Each operating component consists of a button, switch, dial, touch panel, eye-tracking device, voice recognition device, or a combination thereof.

[0037] First, the mode dial 130 is used to select a shooting mode from among the multiple shooting modes that the camera unit 100 can set. The selectable shooting modes include a still image mode for capturing still images and a video mode for recording videos. In both still image and video shooting modes, various modes are available that allow you to set exposure parameters automatically or manually, such as automatic, program, aperture priority, shutter speed priority, and manual. In addition, in still image mode, it is possible to set whether or not to fire the flash when taking still images.

[0038] For still image shooting, a live view display function can be implemented to display an image (live view image) on the electronic viewfinder 105 or image display unit 114 in order to confirm the subject. The live view display function is a function that sequentially displays multiple image data acquired by continuously accumulating charge (imaging) using the image sensor 103.

[0039] The shutter switch 131 is used to instruct the camera to prepare the subject for imaging and to start the imaging operation. SW1 is turned on by the first stroke of the shutter switch 131 (for example, half-press). When SW1 is turned on, the imaging preparation operation starts, and the system control unit 120 starts focus control, exposure control, auto white balance (AWB) processing, etc. SW2 is turned on by the second stroke of the shutter switch 131 (for example, fully press). When SW2 is turned on, the imaging operation starts, and the system control unit 120 starts exposure processing and recording processing related to charge accumulation (imaging) using the image sensor 103.

[0040] In the exposure process, in response to instructions from the system control unit 120, the signal read from the image sensor 103 is written to the recording memory 113 as image data via the A / D conversion unit 106 and the memory control unit 110. Then, in response to instructions from the system control unit 120, development processing is performed on this image data based on various calculations in the image processing unit 107 and the memory control unit 110, and the developed image data is written to the recording memory 113.

[0041] During the recording process, the image data after development processing, read from the recording memory 113, is compressed by the compression / decompression unit 111 in response to instructions from the system control unit 120. Subsequently, in response to instructions from the system control unit 120, the compressed image data is written to the recording unit 201 of the external recording medium 200 via the first camera I / F 140, first camera connector 141, media connector 203, and media I / F 202.

[0042] The playback switch 132 is used to instruct the start of the playback process. When the playback switch 132 is pressed, the acquired image data is read from the recording memory 113 or the external recording medium 200 and displayed on the image display unit 114.

[0043] The control unit 133 is used for menu display, various settings related to image capture, and various settings related to playback. For example, the user can set various settings for flash photography, shutter time, aperture, ISO, etc., as well as the imaging range on the image sensor 103, as will be described later in Figure 8. In this embodiment, it is also possible to set whether or not to fire the flash when taking still images, and the shutter time when shooting with flash.

[0044] The power switch 134 is used to switch the power supply from the power supply unit (battery) (not shown) to each part of the camera 1 on or off. Furthermore, by operating the power switch 134, it is possible to switch the power supply not only to the camera unit 100, but also to various accessories connected to the camera unit 100, such as the lens unit 300 and the external recording medium 200.

[0045] The power control unit 124 includes a battery detection circuit, a DC-DC converter, and a switch circuit used for switching the power supply block. Based on instructions from the system control unit 120 in response to the operation of the power switch 134, the power control unit 124 detects whether a battery is installed, the type of battery, and the remaining battery level, and supplies the necessary voltage to each part of the camera 1 for the required period of time.

[0046] The second camera interface 150 is provided on the camera mount section 160 and is an interface for connecting the camera unit 100 and the lens unit 300. The second camera connector 151 electrically connects the camera unit 100 and the lens unit 300 via the lens connector 311 and the lens interface 310.

[0047] The third camera interface 170 is an interface for connecting the camera unit 100 and the strobe unit 400. The third camera connector 171 electrically connects the camera unit 100 and the strobe unit 400 via the strobe connector 411 and the strobe interface 410.

[0048] The second camera connector 151 and the third camera connector 171 transmit control signals, status signals, data signals, etc., between the camera unit 100 and the lens unit 300 and the strobe unit 400. Furthermore, various voltages of current can be supplied to the lens unit 300 and the strobe unit 400 via the second camera connector 151 and the third camera connector 171. Note that the second camera connector 151 and the third camera connector 171 may be configured to transmit not only electrical communications but also optical communications, voice communications, etc.

[0049] The external recording medium 200 is an external recording device such as a memory card or a hard disk. The external recording medium 200 includes a recording unit 201 made of semiconductor memory or a magnetic disk, and a media I / F 202 for the camera unit 100. The external recording medium 200 also includes a media connector 203 for connecting to the camera unit 100.

[0050] The lens unit 300 is an optical device that can be attached to and detached from the camera unit 100. The lens mount portion 320 engages with the camera mount portion 160, enabling the lens unit 300 to be mechanically attached to the camera unit 100.

[0051] The lens mount section 320 is equipped with a lens connector 311 that electrically connects the lens unit 300 and the camera unit 100. The lens connector 311 transmits control signals, status signals, data signals, etc., between the lens unit 300 and the camera unit 100. In addition, it is possible to receive and supply current of various voltages via the lens connector 311. The lens connector 311 may be configured to transmit not only electrical communications but also optical communications, voice communications, etc.

[0052] The imaging lens group 301 is an optical component that includes a focus lens, a zoom lens, a shift lens, and the like. The aperture 302 adjusts the amount of light from the subject that passes through the imaging lens group 301 and enters the image sensor 103. The aperture control unit 303 controls the aperture opening of the aperture 302 based on instructions from the system control unit 120. The system control unit 120 instructs the aperture control unit 303 to change the aperture diameter of the aperture 302 so that the opening corresponds to a target aperture value.

[0053] The changing aperture diameter of the aperture 302 is detected sequentially through communication between the lens unit 300 and the camera unit 100. The system control unit 120 then terminates the change in the aperture diameter of the aperture 302 when the aperture diameter of the aperture 302 reaches the aperture diameter corresponding to the target aperture value.

[0054] The lens control unit 304 controls the operation (driving) of the imaging lens group 301. The lens control unit 304 can detect the lens position (focal position) of the focus lens, and the detected lens position information is transmitted to the camera unit 100.

[0055] The lens system control unit 305 comprehensively controls the lens unit 300. The lens system control unit 305 incorporates a CPU (not shown), volatile memory, and non-volatile memory. The volatile memory stores constants, variables, and programs for operation, while the non-volatile memory stores identification information such as a unique number related to the lens unit 300, management information, and functional information such as the maximum aperture value, minimum aperture value, and focal length.

[0056] The strobe unit 400 is a detachable accessory (strobe device) for the camera unit 100. The strobe connector 411 transmits control signals, status signals, data signals, etc., between the strobe unit 400 and the camera unit 100. It is also possible to receive and supply current of various voltages via the strobe connector 411. The strobe connector 411 may be configured to transmit not only electrical communications but also optical communications, voice communications, etc. The strobe control unit 402 performs light emission control according to the amount of light emitted from the strobe light emitter 401 and various settings of the strobe unit 400.

[0057] Figures 2 to 5 are conceptual diagrams showing the relationship between the travel pattern of the front curtain and the travel pattern of the rear curtain in the electronic front curtain system, as described above.

[0058] As shown in Figure 2, in the electronic front curtain method, time T1 is the time required for the front curtain to perform a charge accumulation reset scan of the image sensor 103. Time T2 is the time from the start of strobe emission until the rear curtain starts moving. Time T1 + Time T2 is the synchronization time.

[0059] As shown in Figure 3, increasing the speed of the lead curtain shortens time T1, thus shortening the synchronization time. Also, as shown in Figure 4, limiting the strobe flash output shortens time T2, thus shortening the synchronization time. Furthermore, as shown in Figure 5, increasing the speed of the lead curtain and limiting the strobe flash output shortens both time T1 and time T2, thus shortening the synchronization time.

[0060] Figure 6 is a flowchart showing the still image capture process. This process is implemented, for example, by the CPU loading a program stored in the ROM of the system control unit 120 into RAM and executing it. This process starts when the power to camera 1 is turned on. This process ends when the power to camera 1 is turned off.

[0061] In step S101, the system control unit 120 transitions to a shooting standby state and displays the live view. In step S102, the system control unit 120 determines whether SW1 of the shutter switch 131 is turned on or not. If SW1 is not turned on, the system control unit 120 returns to step S101; if SW1 is turned on, it proceeds to step S103.

[0062] In step S103, the system control unit 120 performs a distance measurement calculation based on the image captured by the image sensor 103, and controls the imaging lens group 301 to adjust the focus based on the result of the distance measurement calculation. In step S104, the system control unit 120 performs a photometric calculation based on the image captured by the image sensor 103. This photometric calculation can be performed by any method, including well-known methods.

[0063] For example, the system control unit 120 calculates the average brightness of each block obtained by dividing the entire captured image into multiple regions. Then, with a predetermined weight applied to the average brightness of each block, the system control unit 120 uses the average brightness of all blocks as the photometric result to perform calculations, including whether or not to fire the strobe unit 400 during still image capture, and to calculate control values ​​for shooting.

[0064] Next, in step S105, the system control unit 120 waits until SW2 of the shutter switch 131 is turned on, and then proceeds to step S106. In step S106, the system control unit 120 determines whether or not to perform flash photography based on the metering results in step S104 and the settings of the camera unit 100. Flash photography is the process of firing the flash unit 400 when taking still images. If forced flash is set, it is determined that flash photography will be performed. If automatic flash is set, it is determined whether or not to perform flash photography based on the metering results.

[0065] If the system control unit 120 determines that flash photography will not be performed, it proceeds to step S111. If it determines that flash photography will be performed, it proceeds to step S107. In step S107, the system control unit 120 calculates the shooting parameters (Tv value, Av value, ISO) for flash photography based on the metering result in step S104 and the condition that the photography will be performed with flash. That is, the system control unit 120 calculates the shooting parameters such as shutter speed (or Tv value), aperture value, and ISO that correspond to when taking still images with flash.

[0066] In step S108, the system control unit 120 performs a dimming calculation to determine the amount of strobe light emitted when taking a still image. The amount of strobe light emitted calculated here is called the "provisionally determined strobe light emission amount".

[0067] In step S109, the system control unit 120 executes the synchronization time acceleration calculation process (Figure 7), which will be described later. The system control unit 120 fires a strobe in step S110 and takes a still image in step S112. The amount of light emitted in step S110 may be different from the provisionally determined strobe light amount (a limited value) due to the synchronization time acceleration calculation process (Figure 7).

[0068] In step S111, the system control unit 120 calculates the shooting parameters for non-flash mode based on the photometering results from step S104. Specifically, the system control unit 120 calculates the shooting parameters such as shutter speed (or Tv value), aperture value, and ISO, which are appropriate for still image shooting without flash. The system control unit 120 then proceeds to step S112.

[0069] In step S113, the system waits until the shutter switch 131 is released (SW1 turns off) after still image capture. If the shutter switch 131 is released, the process shown in Figure 6 is terminated. Alternatively, after determining "Yes" in step S113, the system may return to step S101.

[0070] Figure 7 is a flowchart showing the synchronization time acceleration calculation process performed in step S109 of Figure 6.

[0071] In step S201, the system control unit 120 obtains the shooting parameters (Tv value, Av value, ISO) for strobe flash photography calculated in step S107. In step S202, the system control unit 120 checks whether the shutter speed is short (fast), intermediate (medium speed), or long (slow). Then, depending on the result of this check, it branches the process to one of steps S206, S205, or S203.

[0072] Here, when checking the shutter speed, TV0 and TV1 are used as thresholds to compare with the Tv value indicated by the shooting parameters. TV0 corresponds to the first shutter speed, and TV1 corresponds to the second shutter speed. The relationship is TV1 > TV0, and the relationship is first shutter speed > second shutter speed (the second shutter speed is shorter).

[0073] If TV0 > Tv value is true, it is determined that the shutter duration is longer than the first duration and the shutter speed is slow. In this case, the system control unit 120 proceeds to step S206.

[0074] If TV1 > Tv value ≥ TV0 is true, it is determined that the shutter duration is less than or equal to the first duration and longer than the second duration, and the shutter speed is medium. In this case, the system control unit 120 proceeds to step S205.

[0075] If the Tv value ≥ TV1 is true, it is determined that the shutter duration is less than or equal to the second duration, and the shutter speed is high. In this case, the system control unit 120 proceeds to step S203.

[0076] In this embodiment, the system control unit 120 determines whether or not to perform front curtain correction control (second control) to correct the travel speed of the front curtain, depending on the branch destination in step S202. Here, front curtain correction control is a control that makes the travel speed of the shutter's front curtain faster than the travel speed of the shutter's rear curtain. If front curtain correction control is to be performed, the front curtain correction implementation flag is set to "1".

[0077] On the other hand, if front curtain correction control is not performed (front curtain correction control not performed), the shutter is controlled so that the travel speed of the front curtain and the travel speed of the rear curtain are the same (first control). In this case, the front curtain correction execution flag is reset to "0". The system control unit 120 selectively executes the first control and the second control.

[0078] In step S203, the system control unit 120 determines whether the provisionally determined strobe flash output is equal to or greater than a predetermined flash output (flash output check). If the provisionally determined strobe flash output is equal to or greater than a predetermined flash output, the system control unit 120 determines that, given the current shutter speed, the duration of the strobe flash will not fit within the fully open shutter interval, and proceeds to step S204. In step S204, the system control unit 120 limits the strobe flash output during shooting to a value lower than the provisionally determined strobe flash output (flash output clipping).

[0079] On the other hand, if the provisionally determined strobe flash amount is less than a predetermined flash amount, the system control unit 120 proceeds to step S205. In step S205, which is a transition from step S203 or step S204, the determined shutter time is fast, so it is not appropriate to slow down the actual synchronization time. Therefore, in step S205, the system control unit 120 sets the front curtain correction implementation flag (to 1). As a result, in the processing from step S210 onward, the shutter front curtain travel speed is controlled to be faster than the shutter rear curtain travel speed according to the determined shutter time.

[0080] In particular, if the system proceeds to step S205 without going through step S204, the front curtain correction control is performed, but the light emission clipping is not applied, so the running patterns of the front and rear curtains will be as illustrated in Figure 3.

[0081] On the other hand, if the system proceeds to step S205 via step S204, the front curtain correction control is performed and light emission clipping is also applied, so the running patterns of the front and rear curtains will be as illustrated in Figure 5.

[0082] When moving from step S202 to step S205, the determined shutter timing is at a medium speed, so it is not appropriate to slow down the actual synchronization timing. On the other hand, full-power flash is possible based on the provisionally determined strobe flash amount. Therefore, in step S205, the system control unit 120 sets the front curtain correction implementation flag (to 1). As a result, in the processing from step S210 onward, the shutter's front curtain travel speed is controlled to be faster than the shutter's rear curtain travel speed, according to the determined shutter timing.

[0083] When transitioning from step S202 to step S205, front curtain correction control is performed, but light emission clipping is not applied, so the running patterns of the front and rear curtains will be as illustrated in Figure 3.

[0084] In step S206, since the determined shutter speed is slow, there is little need to speed up the actual synchronization speed. Therefore, the system control unit 120 resets the front curtain correction flag (to 0). Consequently, in the processing from step S210 onward, the front curtain and rear curtain are controlled at the same speed. This reduces uneven exposure (exposure deviation) between the top and bottom of the image. Since front curtain correction control is not performed and flash amount clipping is not applied, the travel patterns of the front and rear curtains are as illustrated in Figure 2.

[0085] After steps S205 and S206, the system control unit 120 terminates the process shown in Figure 7.

[0086] Thus, in strobe photography, when the shutter duration is long enough that TV0 > Tv value, the front and rear curtains of the shutter are controlled at the same speed, which reduces exposure unevenness at the top and bottom of the screen (S206). On the other hand, even when the shutter duration is short enough that Tv value ≥ TV0, and the front and rear curtains are controlled at different speeds, if the provisionally determined strobe flash output is greater than or equal to a predetermined flash output, flash output clipping is applied, making it less likely for exposure unevenness at the top and bottom of the screen to occur.

[0087] According to this embodiment, the system control unit 120, acting as a determination means, determines shooting parameters, including the shutter speed, when performing strobe flash photography (S107). The system control unit 120, acting as a control means, determines whether to implement front curtain correction control (second control) or not implement front curtain correction control (first control) during shooting, according to the shutter speed in the determined shooting parameters (S202).

[0088] In other words, the system control unit 120 adopts the first control (S206) if the determined shutter duration is longer than the first duration (TV0 > Tv value), and adopts the second control (S205) if the shutter duration is less than or equal to the first duration (TV ≥ TV0).

[0089] This reduces uneven exposure at both edges of the image when using a flash. It also allows for a shorter sync time when a high shutter speed is required.

[0090] Furthermore, the system control unit 120 controls the amount of flash emitted during shooting based on the shutter time and the provisionally determined flash amount. Specifically, if the shutter time is less than or equal to the second time (Tv value ≥ TV1) and the provisionally determined flash amount is greater than or equal to a predetermined flash amount, the system control unit 120 limits the amount of flash emitted during shooting to a value lower than the provisionally determined flash amount (S204). A second control (S205) is also employed. This makes it possible to more effectively shorten the synchronization time when there is a high need for a fast shutter speed.

[0091] In this embodiment, the change in the positions of the front and rear curtains from the start to the end of shutter movement may be linear or nonlinear.

[0092] The threshold values ​​TV0, TV1, and predetermined light emission amount were all set to fixed values. However, this is not limited to fixed values; they may be made variable, or multiple values ​​may be stored and the appropriate value selected may be chosen.

[0093] Although the first and second seconds are said to be different values, they may be the same value. Alternatively, in order to control them to be substantially the same, steps S203 and S204 in Figures 7 and 10 may be omitted.

[0094] Furthermore, the first and second time intervals (or thresholds TV0 and TV1) and predetermined flash output may be variably controlled based on the photometric information. For example, when photometric information is acquired and the shooting brightness is dark, the strobe light becomes dominant in shooting, so exposure unevenness due to the speed difference between the front and rear curtains of the shutter is less noticeable. However, when the shooting brightness is bright, the exposure of ambient light also becomes important. Therefore, at least one of the thresholds TV0 and TV1 or the predetermined flash output may be switched depending on the shooting brightness. For example, when the shooting brightness is dark, the thresholds TV0 and TV1 may be changed to smaller values ​​(the first time interval, etc., may be changed to a longer value).

[0095] Furthermore, the thresholds TV0 and TV1 may also be changed when the imaging range of the image sensor 103 changes. This will be explained using Figures 8 and 9.

[0096] Figures 8(a) to 8(d) illustrate the area captured by the image sensor 103. Regarding the imaging area of ​​the image sensor 103, the original imaging area when the entire effective area of ​​the image sensor 103 is used is shown in Figure 8(a). The vertical length (vertical length) in the original imaging area is h1.

[0097] The imaging area when the aspect ratio is set to 16:9 relative to the original imaging area is shown by a solid line in Figure 8(b), and its vertical length is h2. The imaging area of ​​APS-C relative to the original imaging area is shown by a solid line in Figure 8(c), and its vertical length is h3. The imaging area when the aspect ratio is set to 16:9 relative to the APS-C imaging area is shown by a solid line in Figure 8(d), and its vertical length is h4. The relationship of vertical lengths is h1 > h2 > h3 > h4. Note that the imaging area may be automatically switched based on information from the lens unit 300.

[0098] When the imaging range setting changes, the vertical length of the imaging range changes, which in turn changes the start and end positions of the shutter's movement. In other words, the shutter's travel distance changes, and the synchronization time also changes. For example, using the movement pattern shown in Figure 5 as a reference, if the vertical length is shortened, times T1 and T2 become shorter, as shown in Figure 9. As a result, the synchronization time becomes shorter.

[0099] Therefore, the system control unit 120 may variably control the thresholds TV0 and TV1 based on the imaging range. For example, the system control unit 120 sets the thresholds TV0 and TV1 to larger values ​​(shorter time intervals) as the vertical length decreases. In this case, the thresholds TV0 and TV1 may be changed according to the ratio of the vertical length before the change to the vertical length after the change.

[0100] (Second Embodiment) When shooting in a flickering environment, depending on the shutter speed in the shooting parameters, flicker-induced banding may appear in the captured image. To suppress this banding, one method is to set the shutter speed to an integer multiple of the flicker period or to set it to be sufficiently longer than the flicker period. On the other hand, in a flickering environment, if the travel speed of the front curtain and the travel speed of the rear curtain are different, in addition to uneven exposure at the top and bottom of the screen, the way flicker-induced banding appears will change, which may degrade the quality of the captured image.

[0101] Therefore, in the second embodiment of the present invention, the implementation of front curtain correction control (second control) is adopted on the condition that there is no flicker in the shooting environment. In this embodiment, the synchronization time acceleration calculation process differs from that of the first embodiment, but the other configurations are the same.

[0102] Figure 10 is a flowchart showing the synchronization time acceleration calculation process performed in step S109 of Figure 6.

[0103] In step S301, the system control unit 120 determines, using a known method, whether or not there is flicker in the shooting environment. If there is no flicker, the system control unit 120 proceeds to step S201; if there is flicker, it proceeds to step S206. Steps S201 to S206 are the same as those explained in Figure 7.

[0104] Therefore, if flicker is present, regardless of the shutter speed, front curtain correction control is not performed during shooting (first control) (S206).

[0105] According to this embodiment, the same effects as in the first embodiment can be achieved in reducing exposure unevenness at both edges of the image during strobe flash photography while shortening the synchronization time. Furthermore, since front curtain correction control is not performed when flicker is present, a decrease in the quality of the captured image can be suppressed.

[0106] In this embodiment, even if flicker is present, the predetermined light emission amount may be changed to a smaller value. That is, if flicker is present, in addition to step SS206, the process corresponding to step S204 may be executed.

[0107] It should be noted that the imaging device to which the present invention is applied is not limited to digital cameras. For example, the present invention can also be applied to imaging devices that are not called digital cameras, such as portable devices like smartphones, wearable devices, in-vehicle cameras, and security cameras.

[0108] The camera 1 is configured such that its operation is controlled by the coordinated operation of its constituent parts, such as the image processing unit 107, memory control unit 110, and system control unit 120, but it is not limited to this configuration. For example, a program that implements the processing shown in Figure 6 above may be stored in the main memory 121 in advance. Then, the system control unit 120, including a microcomputer, may execute this program to control the operation of the camera 1. Furthermore, the form of the program is not limited as long as it has the functionality of a program, including object code, programs executed by an interpreter, and script data supplied to the OS. In addition, the recording medium for supplying the program may be, for example, a hard disk, a magnetic recording medium such as magnetic tape, or an optical / magneto-optical recording medium.

[0109] Although the present invention has been described in detail above based on its preferred embodiments, the present invention is not limited to these specific embodiments, and various forms that do not depart from the spirit of the invention are also included in the present invention. Some of the above embodiments may be combined as appropriate.

[0110] (Other examples) The present invention can also be realized by supplying a program that implements one or more of the functions of the above embodiments to a system or device via a network or a non-transient storage medium, and by having one or more processors in the computer of that system or device read and execute the program. The above program and the storage medium that stores the above program constitute the present invention. Furthermore, the present invention can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0111] This embodiment includes the following configurations (methods, programs). (Composition 1) When performing strobe photography, a means for determining shooting parameters, including shutter speed, is required. The system includes a control means that selectively performs a first control that controls the travel speed of the front curtain of the shutter to be the same as the travel speed of the rear curtain of the shutter, and a second control that controls the travel speed of the front curtain to be faster than the travel speed of the rear curtain. The imaging device is characterized in that the control means determines, when performing strobe flash photography, whether to adopt the first control or the second control at the time of shooting, according to the shutter time in the shooting parameters determined by the determination means. (Configuration 2) The imaging apparatus according to configuration 1, characterized in that the control means adopts the first control when the length of the shutter time is longer than the first time, and adopts the second control when the length of the shutter time is less than or equal to the first time. (Composition 3) The imaging apparatus according to configuration 1 or 2, characterized in that the control means controls the amount of strobe light emitted during shooting based on the shutter time. (Composition 4) The aforementioned determination means further provisionally determines the amount of flash when performing strobe flash photography, The imaging apparatus according to configuration 3, characterized in that the control means controls the amount of strobe light emitted during shooting based on the shutter time and the provisionally determined amount of strobe light emitted. (Composition 5) The imaging apparatus according to configuration 4, characterized in that the control means limits the amount of strobe light emitted during shooting to a value lower than the provisionally determined amount of strobe light emitted when the length of the shutter time is less than or equal to a second time and the provisionally determined amount of strobe light emitted is greater than or equal to a predetermined amount of strobe light emitted. (Composition 6) The aforementioned determination means further provisionally determines the amount of flash when performing strobe flash photography, The imaging apparatus according to configuration 2, characterized in that the control means limits the amount of strobe light emitted during shooting to a value lower than the provisionally determined amount of strobe light emitted when the length of the shutter time is less than or equal to a second time shorter than the first time and the provisionally determined amount of strobe light emitted is greater than or equal to a predetermined amount of strobe light emitted. (Composition 7) The imaging apparatus according to any one of configurations 1 to 6, characterized in that the front curtain is realized by an electronic shutter, and the travel speed of the front curtain is the speed at which the accumulated charge of the image sensor by the front curtain is reset by scanning. (Composition 8) The imaging apparatus according to configuration 7, characterized in that the rear curtain is realized by an electronic shutter, and the travel speed of the rear curtain is the speed at which the rear curtain reads and scans the accumulated charge of the image sensor. (Composition 9) The imaging device according to any one of configurations 1 to 8, characterized in that the control means determines whether or not there is flicker in the shooting environment when performing strobe flash photography, and if there is flicker, the first control is adopted at the time of shooting regardless of the shutter time. (Composition 10) The imaging apparatus according to configuration 2, characterized in that the control means variably controls the first time interval based on photometric information. (Composition 11) The imaging apparatus according to configuration 5 or 6, characterized in that the control means variably controls the second time interval based on photometric information. (Composition 12) The imaging apparatus according to configuration 5 or 6, characterized in that the control means variably controls the predetermined amount of light emission based on photometric information. (Composition 13) The imaging apparatus according to configuration 2, characterized in that the control means variably controls the first time interval based on the imaging range. (Composition 14) The imaging apparatus according to configuration 5 or 6, characterized in that the control means variably controls the second time interval based on the imaging range. (Method 1) When performing strobe photography, there is a decision step to determine the shooting parameters, including the shutter speed, and The control step includes selectively executing a first control that controls the travel speed of the front curtain of the shutter to be the same as the travel speed of the rear curtain of the shutter, and a second control that controls the travel speed of the front curtain to be faster than the travel speed of the rear curtain. The control step is a method for controlling an imaging device, characterized in that, when performing strobe flash photography, it is determined which of the first control and the second control to adopt at the time of shooting, according to the shutter time in the shooting parameters determined by the determination step. (Program 1) A program for causing a computer to function as one of the means of an imaging apparatus described in any one of items 1 to 14. [Explanation of symbols]

[0112] 1 Digital camera 100 Camera Units 102 Shutter 120 System Control Unit

Claims

1. When performing strobe photography, a means for determining shooting parameters, including shutter speed, and for making a preliminary determination of the strobe flash output is required. The system includes a control means that selectively performs a first control that controls the travel speed of the front curtain of the shutter to be the same as the travel speed of the rear curtain of the shutter, and a second control that controls the travel speed of the front curtain to be faster than the travel speed of the rear curtain. The control means is When performing strobe flash photography, the determination means determines which of the first control and the second control to adopt during shooting, according to the shutter time in the shooting parameters. Based on the shutter time and the provisionally determined strobe flash amount, the amount of strobe flash during shooting is controlled. If the length of the shutter time is longer than the first time, the first control is adopted; if the length of the shutter time is less than or equal to the first time, the second control is adopted. If the length of the shutter time is less than or equal to a second time shorter than the first time, and the provisionally determined strobe flash amount is equal to or greater than a predetermined flash amount, the strobe flash amount during shooting is limited to a value lower than the provisionally determined strobe flash amount. An imaging device characterized by the following features.

2. The imaging apparatus according to claim 1, characterized in that the front curtain is realized by an electronic shutter, and the travel speed of the front curtain is the speed at which the accumulated charge of the image sensor by the front curtain is reset by scanning.

3. The imaging apparatus according to claim 2, characterized in that the rear curtain is realized by an electronic shutter, and the traveling speed of the rear curtain is the speed at which the rear curtain reads and scans the accumulated charge of the image sensor.

4. It further includes a detection means for detecting flicker in the shooting environment, The imaging apparatus according to claim 1, characterized in that, if flicker is detected, the control means employs the first control during shooting, regardless of the shutter time.

5. The imaging apparatus according to claim 1, characterized in that the control means variably controls the first time interval based on photometric information.

6. The imaging apparatus according to claim 1, characterized in that the control means variably controls the second time interval based on photometric information.

7. The imaging apparatus according to claim 1, characterized in that the control means variably controls the predetermined amount of light emission based on photometric information.

8. The imaging apparatus according to claim 1, characterized in that the control means variably controls the first time interval based on the imaging range.

9. The imaging apparatus according to claim 1, characterized in that the control means variably controls the second time interval based on the imaging range.

10. When performing strobe photography, there is a decision step that involves determining the shooting parameters, including the shutter speed, and making a preliminary determination of the strobe flash output. The control step includes selectively executing a first control that controls the travel speed of the front curtain of the shutter to be the same as the travel speed of the rear curtain of the shutter, and a second control that controls the travel speed of the front curtain to be faster than the travel speed of the rear curtain. The control step is, When performing strobe flash photography, it is determined which of the first control and the second control to adopt at the time of shooting, according to the shutter time in the shooting parameters determined in the determination step. Based on the shutter time and the provisionally determined strobe flash amount, the amount of strobe flash during shooting is controlled. If the length of the shutter time is longer than the first time, the first control is adopted; if the length of the shutter time is less than or equal to the first time, the second control is adopted. If the length of the shutter time is less than or equal to a second time shorter than the first time, and the provisionally determined strobe flash amount is equal to or greater than a predetermined flash amount, the strobe flash amount during shooting is limited to a value lower than the provisionally determined strobe flash amount. A control method for an imaging device, characterized by the following:

11. A program for causing a computer to function as one of the means of an imaging apparatus described in any one of claims 1 to 9.

Images