Image capturing apparatus, control method of the same, program, and storage medium

Abstract

To provide an image capturing apparatus capable of suppressing deterioration in a quality of a live view while securing focus detection accuracy.SOLUTION: Included are: imaging means that captures a subject image formed by an optical system; flicker detection means that detects a flicker using an image captured by the imaging means; focus detection means that detects an in-focus state of the subject image by using a light flux that has passed through the optical system; and first determination means that determines, in a case where the focus detection means detects the in-focus state, which of a setting of an exposure time of the imaging means to an exposure time in which a flicker is inconspicuous and an opening of a diaphragm of the optical system to give priority to based on a detection result of a flicker by the flicker detection means, and, based on the determination, determines a combination of an exposure time of the imaging means and a diaphragm value of the optical system.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a focus detection technique in an image pickup apparatus. [Background technology]

[0002] Light sources such as fluorescent lights repeatedly blink at the frequency of an AC power source. Therefore, when an image is captured by an imaging device such as a camera under a fluorescent light source, flicker occurs depending on the shutter speed (accumulation time). Some conventional imaging devices take measures to remove flicker when flicker is detected, even during focus detection.

[0003] Here, as a countermeasure against flicker, it is effective to set the accumulation time of the image sensor to an integer multiple of the blinking cycle of the light source. However, the blinking cycle of the light source is a relatively long time, for example, 1 / 100 sec. If the accumulation time is set to a relatively long time so as to be an integer multiple of this, it becomes necessary to narrow the aperture greatly when the brightness of the subject is high. On the other hand, in focus detection, the focus detection accuracy is higher when the aperture is opened so that the depth of field is shallow. In other words, if the accumulation time is lengthened and the aperture is narrowed to counter flicker, the focus detection accuracy decreases, and conversely, if the aperture is opened to obtain focus detection accuracy, the flicker countermeasure may not be sufficient. In particular, when focus detection is performed while performing live view display, the image quality of the live view display decreases if the countermeasure against flicker is insufficient. On the other hand, if the image quality of the live view is emphasized, the focus detection accuracy decreases. There is a trade-off between the image quality of the live view display and the focus detection accuracy.

[0004] On the other hand, Patent Document 1 discloses the following technique as a countermeasure against flicker that does not control the accumulation time during focus detection: In other words, when focus detection is performed based on phase difference using focus detection pixels, the effect of flicker is reduced by matching the frame rate to the flicker frequency. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-111252 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventional technology disclosed in the above-mentioned Patent Document 1, there is a problem in that fixed-pattern flicker stripes remain, and degradation of the quality of the live view display is unavoidable.

[0007] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide an imaging device that can suppress degradation in live view quality while ensuring focus detection accuracy. [Means for solving the problem]

[0008] The imaging device of the present invention is characterized in comprising an imaging means for capturing an image of a subject formed by an imaging optical system, a flicker detection means for detecting flicker using an image captured by the imaging means, a focus detection means for detecting a focus state of the subject image using a light beam that has passed through the imaging optical system, and a first determination means for, when detecting the focus state by the focus detection means, determining whether to prioritize between setting the exposure time of the imaging means to an exposure time at which flicker is not noticeable or opening the aperture of the imaging optical system based on a result of the flicker detection by the flicker detection means, and determining a combination of the exposure time of the imaging means and the aperture value of the imaging optical system based on the result. Effect of the Invention

[0009] According to the present invention, it is possible to suppress degradation of live view quality while ensuring focus detection accuracy. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing the arrangement of an image capturing apparatus according to an embodiment of the present invention; [Diagram 2]FIG. 2 is a diagram showing a pixel arrangement of an imaging element. [Diagram 3] 11 is a flowchart showing an example of a still image shooting operation. [Figure 4] 4 is a program diagram for calculating exposure control values. [Diagram 5] 6 is a flowchart showing a calculation process of an exposure control value for focus detection. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0012] FIG. 1 is a diagram showing the configuration of an image pickup apparatus according to one embodiment of the present invention.

[0013] 1, the imaging unit 10 has an imaging element 10a that receives light and performs photoelectric conversion, and an A / D conversion unit that converts an analog image signal output from the imaging element 10a into a digital signal. The A / D conversion unit outputs the digitized image data. The imaging element 10a has two photodiodes per pixel to perform imaging surface phase difference AF (autofocus) as shown in FIG.

[0014] 2 shows a configuration in which each of the 4×4 R (red), G (green), and B (blue) pixels in the Bayer array has two photodiodes, RA and RB, BA and BB, and GA and GB (or GC and GD). The light beam from the imaging optical system is separated by a microlens, and the light that has passed through different areas of the exit pupil area is received by two photodiodes, so that two image signals (images A and B, or images C and D) for AF can be generated. The image processing circuit 60, which will be described later, performs correlation calculations on the two image signals, so that the amount of image shift and various other information can be calculated.

[0015] Images A and B are signals from areas divided into the lateral (horizontal) direction, while images C and D are signals from areas divided into the vertical (vertical) direction, making it possible to detect the amount of image shift in different directions. Also, the sum of images A+B or C+D can be used as an imaging signal.

[0016] Returning to the explanation of FIG. 1, light received by imaging unit 10 is light that passes through lens group 15 including a focus lens, aperture 16, and shutter 17, and forms an image at imaging unit 10. Shutter 17 and aperture 16 are controlled by exposure control unit 20, and the focus lens in lens group 15 is controlled by focus control unit 30. Exposure control unit 20 can also control the accumulation time and amplification rate (sensitivity) of pixel signals for imaging unit 10. In addition, a strobe can be emitted by strobe control unit 35, and reflected light from the subject can be captured by imaging unit 10.

[0017] The image sensor 10a is made of a CMOS sensor, and the electronic shutter system used is a rolling electronic shutter that reads out the screen line by line in the horizontal direction. Under a light source whose brightness changes periodically over time, such as a fluorescent lamp, a horizontal (horizontal direction, readout direction) striped flicker occurs in the imaging plane due to the difference in the time of accumulation and readout for each line. Flicker can be eliminated by setting the accumulation time of the image sensor 10a to an integer multiple of the blinking cycle of the light source (an integer multiple of the flicker cycle) and aligning the exposure amount for each horizontal line. For example, a fluorescent lamp connected to a 50 Hz power source generates a 100 Hz flicker, but the occurrence of flicker can be suppressed by setting the accumulation time to an integer multiple of 1 / 100 [second]. However, even if the accumulation time of the image sensor 10a is not set exactly to an integer multiple of the blinking cycle of the light source (the flicker cycle), the flicker can be made less noticeable by setting it to a time close to an integer multiple of the blinking cycle of the light source (the flicker cycle).

[0018] Image data output from the imaging unit 10 is input to the image processing circuit 60 and simultaneously stored in the memory 50. Image data once stored in the memory 50 can be read out again, and the system control unit 40 can refer to the image data or input the read image data to the image processing circuit 60. Furthermore, the system control unit 40 can write image data that has been image-processed by the image processing circuit 60 back to the memory 50, or write any data to the memory 50.

[0019] The image processing circuit 60 has the following functions. Outputs the brightness histogram of the input image. Detect subjects such as faces by extracting features from the input image. -Apply gamma correction to the input image. A plurality of images read from the memory 50 are composited. Outputs a phase difference AF evaluation value from the input phase difference detection signal. Outputs an evaluation value for flicker detection from the input image.

[0020] The display unit 70 can perform D / A conversion on the digital image data that has been image-processed by the image processing circuit 60 and stored in the memory 50, and display it on a display device such as a liquid crystal display. It is also possible to display not only image data but also any other information alone or together with the image, and it is also possible to display exposure information at the time of shooting and to display a frame around a detected face area.

[0021] The recording unit 80 can store the captured image data in a recording medium.

[0022] The operation unit 90 has, in particular, a shutter button for issuing instructions to shoot, and the shutter button includes shutter switches SW1 (92) and SW2 (94). The shutter switch SW1 (92) turns ON during operation of the shutter button, and issues an instruction to start shooting preparation operations such as automatic control of exposure and focus. The shutter switch SW2 (94) turns ON when operation of the shutter button is completed, and issues an instruction to shoot a still image. Other switches include a mode change switch for switching between camera operation modes such as still image shooting mode, video shooting mode, and playback mode, and a parameter selection switch for changing camera settings.

[0023] FIG. 3 is a flowchart showing an example of a still image capturing operation.

[0024] In step S301, the system control unit 40 starts live view display on the display unit 70 using image data captured by the imaging unit 10.

[0025] In step S302, the system control unit 40 performs flicker detection using the image processing circuit 60. The image processing circuit 60 acquires an evaluation value for flicker detection using image data captured by the imaging unit 10, and calculates the presence or absence of flicker from the acquired evaluation value, and if flicker is present, its frequency. In calculating the flicker frequency, the frequency may be calculated from the change in signal value within the plane of one piece of image data, or the frequency may be calculated from the change in signal value of multiple images that are consecutive in time.

[0026] In step S303, the system control unit 40 determines whether the shutter switch SW1 is ON. If the shutter switch SW1 is ON, the system control unit 40 advances the process to step S304, and if not, the system control unit 40 waits.

[0027] In step S304, the system control unit 40 performs photometry processing to calculate the luminance value of the subject (hereinafter, subject luminance). The subject luminance is calculated from the luminance signal value of the image data output from the imaging unit 10 and the exposure conditions at the time the image was exposed.

[0028] In step S305, the system control unit 40 determines exposure control values ​​(aperture, accumulation time, and sensitivity) for still images based on the subject brightness calculated in step S304 and a program diagram that differs for each shooting mode of the camera.

[0029] The program diagram specifies a combination of exposure control values ​​as shown in FIG. 4, and a set of exposure control values ​​that will result in a proper exposure value can be found from the program diagram. For example, FIG. 4(a) is a program diagram in which the aperture is changed from F2.8 to F8 with an accumulation time of 1 / 100 [seconds], and FIG. 4(b) is a program diagram in which the accumulation time is changed from 1 / 33 [seconds] to 1 / 4000 [seconds] with the aperture fully open. In the case of the subject brightness that results in an aperture value of F8 and an exposure time of 1 / 100 [seconds] in the program diagram of FIG. 4(a), the aperture value is F2.8 and the exposure time is 1 / 800 [seconds] in the program diagram of FIG. 4(b). When the program diagram of FIG. 4(a) is used, an exposure time of 1 / 100 [seconds] is preferentially selected, and when the program diagram of FIG. 4(b) is used, an aperture value of F2.8 is preferentially selected. In other words, different characteristics can be given to the exposure control values ​​depending on the program diagram.

[0030] In step S306, the system control unit 40 performs exposure control for focus detection. The details will be described later with reference to Fig. 5, but an exposure control value for focus detection is calculated, and exposure is performed so that the calculated exposure control value for focus detection is obtained.

[0031] In step S307, the system control unit 40 transfers the data of the images A and B to detect the amount of focus shift in the horizontal direction (horizontal direction) and the data of the images C and D to detect the amount of focus shift in the vertical direction (vertical direction) to a phase difference detection block in the image processing circuit 60, and calculates a phase difference AF evaluation value. Based on the phase difference AF evaluation value, focus detection of the photographing optical system can be performed. In particular, focus detection can be performed using only the data of the images A and B, or can be performed using the data of the images C and D as well.

[0032] In step S308, the system control unit 40 controls the focus lens based on the focus detection result in step S307, and adjusts the focus of the photographing optical system.

[0033] In step S309, the system control unit 40 changes the exposure control value from the value for focus detection to an exposure control value for live view display. The exposure control value for live view display is an exposure optimized for live view display, and may differ from the exposure optimized for focus detection, so the exposure control value is set here.

[0034] In step S310, the system controller 40 determines whether the shutter switch SW2 is ON. If the shutter switch SW2 is ON, the system controller 40 advances the process to step S312, and if not, the system controller 40 advances the process to step S311.

[0035] In step S311, the system control unit 40 determines whether the shutter switch SW1 is ON. If the shutter switch SW1 is ON, the system control unit 40 returns the process to step S310, and if not, returns the process to step S303.

[0036] In step S312, the system control unit 40 sets the exposure control value to the exposure control value for still images calculated in step S305.

[0037] In step S313, the system control unit 40 performs a main exposure using the exposure control value set in step S312.

[0038] In step S314, the system control unit 40 uses the image processing circuit 60 to perform development processing of the exposure data obtained in step S313.

[0039] In step S315, the system control unit 40 causes the recording unit 80 to record the developed image data on a recording medium.

[0040] FIG. 5 is a flowchart showing an example of the process of calculating an exposure control value for focus detection, which is performed in step S306.

[0041] In step S501, the system control unit 40 determines whether or not to perform focus detection in the focus detection process of step S307 using the vertical defocus amount based on the data of the images C and D. For example, when the data of the images C and D cannot be used, such as when the image sensor 10a thins out data in the vertical direction before reading it out, focus detection is performed without considering the vertical defocus amount.

[0042] If the system controller 40 performs focus detection using the vertical defocus amount as well, the process proceeds to step S502. If the system controller 40 performs focus detection using only the horizontal defocus amount, the process proceeds to step S503.

[0043] In step S502, the system control unit 40 determines whether or not a flicker has been detected in the flicker detection process in step S302. Here, since focus detection is performed using the vertical focus deviation amount as well, if a flicker has been detected, the system control unit 40 advances the process to step S503. If a flicker has not been detected, the system control unit 40 advances the process to step S504.

[0044] In step S503, the system control unit 40 calculates an exposure control value that prioritizes flicker removal so that the flicker is less likely to affect the calculation of the vertical focus shift amount. Specifically, the exposure control value (aperture, accumulation time, sensitivity) is determined so that the accumulation time of the image sensor 10a becomes an integer multiple (or a value close to that) of the flicker cycle.

[0045] An example of a program diagram when prioritizing flicker elimination is shown in Figure 4(a). Figure 4(a) shows an example when 100Hz flicker is detected. In Figure 4(a), the horizontal axis is accumulation time, the vertical axis is aperture value, and sensitivity is omitted.

[0046] Since the influence of flicker can be cancelled by making the accumulation time an integer multiple of 1 / 100 [second], the diagram shows that accumulation times such as 1 / 100 [second], 1 / 50 [second], and 1 / 33 [second] are used as much as possible. In particular, the aperture is set to F2.8 to F8 at 1 / 100 [second]. The maximum aperture of the aperture is F2.8, and the minimum aperture is F8. In other words, even when the subject brightness is high, the accumulation time is kept not shorter than 1 / 100 [second] by narrowing the aperture to a small aperture. The accumulation time is only made shorter than 1 / 100 [second] when the subject is too bright to obtain proper exposure even with the aperture set to F8. When detecting vertical phase difference, if a signal that changes vertically, such as flicker, is superimposed, different offsets are applied to the signal value depending on the line, which adversely affects focus detection. To avoid this influence, when detecting vertical phase difference, the exposure control value is determined with the highest priority on removing flicker.

[0047] In step S504, the system control unit 40 calculates an exposure control value that prioritizes the open aperture. In this step, since flicker is not detected, the image quality of the live view does not deteriorate even if the aperture is not narrowed to ensure a long accumulation time. Therefore, the aperture is opened as much as possible to prioritize focus detection accuracy.

[0048] An example of a program diagram for the case of open aperture priority is shown in Fig. 4(b). Since focus detection accuracy is improved by opening the aperture and performing focus detection with a shallow depth of field, the diagram uses an accumulation time of up to 1 / 4000 [seconds] with the aperture open (F2.8). With a shallow depth of field, even a slight shift in the focus lens position will cause the image to become significantly blurred, making it easier to detect image shifts and improving focus detection accuracy. Here, 1 / 4000 [seconds] is the shortest accumulation time. In other words, to improve focus detection accuracy, the aperture is kept open until the shortest accumulation time, and the aperture is only narrowed if the subject is too bright and proper exposure cannot be obtained even with an accumulation time of 1 / 4000 [seconds]. If there is no flicker, there is no need to pay attention to the accumulation time, so this diagram is used.

[0049] In step S505, system control unit 40 determines whether or not flicker has been detected in the flicker detection process of step S302, similar to step S502. If flicker has been detected, system control unit 40 advances the process to step S506, and if flicker has not been detected, system control unit 40 advances the process to step S507.

[0050] In step S506, since the amount of focus deviation in the vertical direction is not used in focus detection, the system control unit 40 performs exposure calculation according to the aperture for still image shooting calculated in step S305.

[0051] Figure 4(c) shows an example of a program diagram when 100 Hz flicker is detected. To avoid flicker being superimposed on the image in live view display, an accumulation time of an integer multiple of 1 / 100 seconds (or a value close to it) is used whenever possible, just as in the case of prioritizing flicker elimination in Figure 4(a). However, if the aperture is narrowed down to the minimum aperture (F8) as in Figure 4(a) just because there is flicker, the depth of field becomes deep and focus detection accuracy decreases. With a deep depth of field, the image is less likely to blur even if the focus lens position is slightly shifted, making it difficult to detect image shifts and reducing focus detection accuracy.

[0052] Therefore, in the example of Fig. 4(c), the aperture value used to remove flicker is set to F5.6 in order to maintain the image quality of the live view display. If the subject is too bright and proper exposure cannot be obtained even with the aperture set to F5.6, flicker removal is abandoned and an accumulation time shorter than 1 / 100 [second] is used. F5.6 is the aperture value in the exposure control value for still images calculated in step S305.

[0053] If you adjust the focus when the aperture is narrower than the exposure control value for still images, the depth of field may become shallow and the image may become blurred when the aperture is opened during shooting. Therefore, the aperture for still images is set as the smallest aperture limit (limit value), and within that range, the accumulation time is maintained as much as possible at 1 / 100 [seconds].

[0054] If the phase difference is detected in the horizontal direction instead of the vertical direction, even if a signal that changes in the vertical direction, such as flicker, is superimposed, the offset on the signal value of the horizontal pixels is the same, so there is little adverse effect on focus detection accuracy. In other words, from the perspective of focus detection, there is no need to perform flicker removal by narrowing the aperture to the minimum. Therefore, by giving up on flicker removal and shortening the accumulation time to less than 1 / 100 [second], focus detection accuracy can be ensured by avoiding over-narrowing the aperture.

[0055] By calculating the exposure control value during focus detection from the program diagram in Figure 4(c), it is possible to eliminate flicker in live view images as much as possible without causing focus shifts in still images.

[0056] Furthermore, if the focus detection accuracy allows, the threshold value may be determined based on the shooting aperture, for example, by setting the limit on the small aperture side at an accumulation time of 1 / 100 seconds to the shooting aperture -1 stop (one stop narrower than the shooting aperture), rather than being set to the aperture itself when shooting a still image.

[0057] In step S507, since flicker is not detected, the system control unit 40 calculates an exposure control value that prioritizes the open aperture in order to prioritize focus detection accuracy. The method of calculating the exposure control value that prioritizes the open aperture is the same as in step S504.

[0058] As described above, in this embodiment, if flicker is not detected, the aperture is opened in order to prioritize focus detection accuracy. On the other hand, if flicker is detected, the accumulation time that allows flicker removal is maintained and the aperture is narrowed in order to remove the flicker. Furthermore, since the degree of influence of flicker on focus detection varies depending on the direction in which the phase difference is detected, the limit value on the small aperture side when narrowing the aperture to remove the flicker is changed. In particular, focus detection processing is performed as much as possible with an aperture value that is wider than the shooting aperture, thereby ensuring focus detection accuracy. By determining the aperture value during focus detection in this way, it is possible to remove flicker and maintain the quality of the live view display while ensuring focus detection accuracy.

[0059] The disclosure of this specification includes the following display device, control method thereof, program, and storage medium.

[0060] (Item 1) an imaging means for capturing an object image formed by an imaging optical system; a flicker detection means for detecting flicker using an image captured by the imaging means; a focus detection unit that detects a focus state of the subject image by using a light beam that has passed through the photographing optical system; a first determination means for determining whether to give priority to setting the exposure time of the image capture means to an exposure time at which flicker is not noticeable or to opening the aperture of the photographic optical system based on a result of the flicker detection by the focus detection means when the in-focus state is detected by the focus detection means, and determining a combination of the exposure time of the image capture means and the aperture value of the photographic optical system based on the result of the determination; An imaging device comprising:

[0061] (Item 2) 2. The imaging device according to item 1, further comprising a display unit that displays an image captured by the imaging unit as a live view image while the focus state is being detected.

[0062] (Item 3) The imaging device described in item 1 or 2, characterized in that when flicker is detected by the flicker detection means, the first determination means determines a combination of the exposure time of the imaging means and the aperture value of the imaging optical system by giving priority to setting the exposure time to an exposure time at which flicker is not noticeable over opening the aperture of the imaging optical system.

[0063] (Item 4) The imaging device described in item 3, characterized in that, when flicker is detected by the flicker detection means, the first determination means determines a combination of the exposure time of the imaging means and the aperture value of the photographing optical system so as to open the aperture of the photographing optical system within a range where the exposure time can be maintained at an exposure time at which flicker is not noticeable.

[0064] (Item 5) 5. The imaging device according to any one of items 1 to 4, wherein the first determination means, when no flicker is detected by the flicker detection means, determines a combination of the exposure time of the imaging means and the aperture value of the imaging optical system by giving priority to opening the aperture of the imaging optical system.

[0065] (Item 6) 6. The imaging device according to any one of items 1 to 5, further comprising a second determination means for determining a shooting aperture value, which is an aperture value when a still image is captured by the imaging means, wherein when flicker is detected by the flicker detection means, the first determination means determines a combination of the exposure time of the imaging means and the aperture value of the imaging optical system when detecting the in-focus state, with the shooting aperture value as the limit on the small aperture side.

[0066] (Item 7) 3. The imaging device according to item 1 or 2, characterized in that the imaging means has a plurality of pixels each having a plurality of photoelectric conversion units that receive light beams passing through different pupil regions of the photographing optical system, and the focus detection means detects the focus state based on an amount of deviation of image signals from the plurality of photoelectric conversion units of the pixels.

[0067] (Item 8) The imaging device described in item 7, characterized in that the focus detection means detects the focus state using at least one of the amount of shift of the image signal in a first direction, which is the readout row direction of the pixels, and the amount of shift of the image signal in a second direction different from the first direction.

[0068] (Item 9) 9. The imaging device according to item 8, wherein the second direction is perpendicular to the first direction.

[0069] (Item 10) 10. The imaging device according to item 8 or 9, wherein when the focus detection means detects the focus state using the amount of shift of the image signal in the second direction and when flicker is detected by the flicker detection means, the first determination means determines a combination of the exposure time of the imaging means and the aperture value of the imaging optical system by giving priority to setting the exposure time to an exposure time at which flicker is not noticeable over opening the aperture of the imaging optical system.

[0070] (Item 11) 10. The imaging device according to item 8 or 9, further comprising a second determination means for determining a photographing aperture value, which is an aperture value when a still image is photographed by the imaging means, wherein the first determination means determines a combination of the exposure time of the imaging means and the aperture value of the photographing optical system when the focus detection means detects the in-focus state without using the shift amount of the image signal in the second direction and when flicker is detected by the flicker detection means, with the photographing aperture value as the limit on the small aperture side.

[0071] (Item 12) 12. The imaging device according to item 10 or 11, characterized in that, when no flicker is detected by the flicker detection means, the first determination means determines a combination of the exposure time of the imaging means and the aperture value of the imaging optical system by giving priority to opening the aperture of the imaging optical system.

[0072] (Item 13) 13. The imaging device according to any one of items 1 to 12, wherein the first determination unit determines the exposure time of the imaging unit to be an integer multiple of a flicker period as the exposure time at which the flicker is not noticeable.

[0073] (Item 14) A method for controlling an image capturing apparatus including an image capturing unit that captures a subject image formed by an image capturing optical system, comprising the steps of: a flicker detection step of detecting flicker using an image captured by the imaging means; a focus detection step of detecting a focus state of the subject image by using a light beam that has passed through the photographing optical system; a determination step of determining whether to give priority to setting the exposure time of the image capture means to an exposure time at which flicker is not noticeable or to opening the aperture of the photographing optical system based on a result of the flicker detection in the focus detection step when detecting the in-focus state in the focus detection step, and determining a combination of the exposure time of the image capture means and the aperture value of the photographing optical system based on the result of the determination; 13. A method for controlling an imaging apparatus comprising:

[0074] (Item 15) Item 15. A program for causing a computer to execute each step of the control method according to item 14.

[0075] (Item 16) A computer-readable storage medium storing a program for causing a computer to execute each step of the control method described in item 14.

[0076] (Other embodiments) The present invention can also be realized by a process in which a program for realizing one or more functions of the above-mentioned embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) for realizing one or more functions.

[0077] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0078] 10: imaging section, 10a: imaging element, 15: lens group, 16: aperture, 17: shutter, 20: exposure control section, 30: focus control section, 35: flash control section, 40: system control section, 50: memory, 60: image processing section, 70: display section, 80: recording section, 90: operation section

Claims

1. An imaging means for capturing an image of a subject formed by an imaging optical system, A flicker detection means for detecting flicker using an image captured by the imaging means, A focus detection means that uses the light beam that has passed through the aforementioned imaging optical system to detect the focus state of the subject image, When the focus detection means detects the focus state, a first determination means determines, based on the flicker detection result by the flicker detection means, whether to prioritize setting the exposure time of the imaging means to an exposure time that minimizes flicker, or opening the aperture of the imaging optical system, and then determines a combination of the exposure time of the imaging means and the aperture value of the imaging optical system based on that determination. The system includes a second determination means for determining the shooting aperture value, which is the aperture value when capturing a still image with the aforementioned imaging means, The imaging apparatus is characterized in that, when flicker is detected by the flicker detection means, the first determination means determines the exposure time of the imaging means and the aperture value of the imaging optical system when detecting the focus state, using the aperture value determined by the second determination means as the limit on the small aperture side.

2. The imaging apparatus according to claim 1, further comprising a display means for displaying the image captured by the imaging means as a live view image while the state of focus detection is being performed.

3. The imaging apparatus according to claim 1, characterized in that, when flicker is detected by the flicker detection means, the first determination means determines a combination of the exposure time of the imaging means and the aperture value of the imaging optical system, prioritizing setting the exposure time to an exposure time at which flicker is not noticeable over opening the aperture of the imaging optical system.

4. The imaging apparatus according to claim 3, characterized in that, when the first determination means detects flicker, it determines a combination of the exposure time of the imaging means and the aperture value of the imaging optical system so as to open the aperture of the imaging optical system within a range that can maintain the exposure time for an exposure time in which flicker is not noticeable.

5. The imaging apparatus according to claim 1, characterized in that the first determination means, if no flicker is detected by the flicker detection means, prioritizes opening the aperture of the imaging optical system to determine a combination of the exposure time of the imaging means and the aperture value of the imaging optical system.

6. The imaging apparatus according to claim 1, wherein the imaging means has a plurality of pixels, each having a plurality of photoelectric conversion units that receive light beams passing through different pupil regions of the imaging optical system, and the focus detection means detects the focus state based on the amount of shift of image signals from the plurality of photoelectric conversion units of the pixels.

7. The imaging apparatus according to claim 6, characterized in that the focus detection means detects the focus state using at least one of the amount of shift of the image signal in a first direction which is the readout row direction of the pixels, and the amount of shift of the image signal in a second direction different from the first direction.

8. The imaging apparatus according to claim 7, characterized in that the second direction is perpendicular to the first direction.

9. The imaging apparatus according to claim 7, wherein the first determination means determines a combination of the exposure time of the imaging means and the aperture value of the imaging optical system, prioritizing setting the exposure time to an exposure time at which flicker is not noticeable over opening the aperture of the imaging optical system, when the focus detection means detects the focus state using the amount of shift of the image signal in the second direction and flicker is detected by the flicker detection means.

10. The imaging apparatus according to claim 7, further comprising a second determination means for determining a shooting aperture value, which is the aperture value when capturing a still image with the imaging means, wherein the first determination means determines a combination of the exposure time of the imaging means and the aperture value of the imaging optical system when detecting the focus state, using the shooting aperture value as the limit on the small aperture side, when the focus detection means detects the focus state without using the amount of shift of the image signal in the second direction and when flicker is detected by the flicker detection means.

11. The imaging apparatus according to claim 9, characterized in that the first determination means, if no flicker is detected by the flicker detection means, prioritizes opening the aperture of the imaging optical system to determine a combination of the exposure time of the imaging means and the aperture value of the imaging optical system.

12. The imaging apparatus according to claim 1, characterized in that the first determination means sets the exposure time of the imaging means to an integer multiple of the period of the flicker as an exposure time in which the flicker is not noticeable.

13. A method for controlling an imaging device that includes imaging means for capturing an image of a subject formed by an imaging optical system, A flicker detection step involves detecting flicker using an image captured by the imaging means, A focus detection step is performed using the light beam that has passed through the aforementioned imaging optical system to detect the focus state of the subject image, In the focus detection step, when detecting the focus state, a first determination step is made to determine, based on the flicker detection result from the flicker detection step, whether to prioritize setting the exposure time of the imaging means to an exposure time that minimizes flicker, or opening the aperture of the imaging optical system, and then determine a combination of the exposure time of the imaging means and the aperture value of the imaging optical system based on that determination. The system includes a second determination step for determining the shooting aperture value, which is the aperture value when capturing a still image using the aforementioned imaging means. The first determination step is a method for controlling an imaging device, characterized in that, if flicker is detected in the flicker detection step, the shooting aperture value determined in the second determination step is used as the limit on the small aperture side to determine the combination of the exposure time of the imaging means and the aperture value of the imaging optical system when detecting the focus state.

14. A program for causing a computer to execute each step of the control method described in claim 13.

15. A computer-readable storage medium storing a program for causing a computer to execute each step of the control method described in claim 13.

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