JP6272116B2 - Imaging apparatus and control method thereof - Google Patents

Description

  The present invention relates to an imaging apparatus and a control method thereof, and more particularly to an imaging apparatus that performs autofocus control of an imaging plane phase difference detection method and a control method thereof.

  Conventionally, pixels (focus detection pixels) in which the relative positions of a microlens and a plurality of photoelectric conversion units are displaced are two-dimensionally arranged to receive a light beam that has passed through different exit pupils, and a pair of images An image sensor capable of acquiring a signal has been proposed. There is a technique for performing phase difference AF that detects a defocus amount based on a phase difference indicating a relative positional deviation between a pair of acquired image signals (see, for example, Patent Document 1).

  Patent Document 2 discloses an imaging apparatus in which the imaging apparatus has a high resolution mode and a normal mode. In this imaging apparatus, progressive scanning is performed in the high resolution mode to sequentially read out all pixels, and in normal mode, interlace scanning is performed to output a real-time video signal by pixel addition or pixel thinning. However, in the rolling electronic shutter, the accumulation time of one frame at the time of moving image shooting is a signal reading interval, and is fixed regardless of the luminance of the subject.

  Therefore, Patent Document 3 discloses a technique for controlling the drive of a CMOS sensor as follows during moving image shooting. That is, at the time of moving image shooting, at least every other row is scanned a plurality of times to read an image signal, thereby reading out an image signal for one screen from the CMOS sensor, scanning a different row for each scan, and charging for each scan. The drive is controlled so that the accumulation times are different.

  Patent Document 4 discloses the following technique. In other words, in moving image shooting, when a still image shooting instruction is given, still image shooting is performed based on image data obtained by driving the image sensor with a driving method that has the same angle of view and high frame rate as during moving image shooting. The focus adjustment process is performed. By doing so, it is possible to minimize the interruption time of the moving image recording and complete the focus adjustment (AF) operation for still image shooting in a short time.

JP 04-267211 A JP 07-298111 A JP 2006-33381 A JP 2008-141236 A

  However, in Patent Document 3, the CMOS sensor is driven and controlled in order to expand the dynamic range during moving images, and the read image signal is not used for AF. In Patent Document 4, when acquiring image data to be used in focus adjustment processing for still image shooting, the frame rate for acquiring pixel data for focus detection processing is increased by thinning out readout rows. However, since the frames are further thinned out in time series and dropped according to the imaging clock rate, it is difficult to complete the focus detection process in a short time only by reducing the acquired pixel data. Further, the pixel data with dropped frames used in the focus detection process of Patent Document 4 has a problem that the focus detection accuracy is lowered in a low-luminance subject.

  The present invention has been made in view of the above-described problems, and obtains an image signal at a high frame rate, speeds up focus detection, and performs high-precision focus detection even for a low-luminance subject. Objective.

  In order to achieve the above object, an imaging device according to the present invention includes an imaging device including a plurality of pixels that photoelectrically convert subject light that has passed through an imaging optical system that forms an optical image of a subject and output an image signal. , Dividing the plurality of pixels into a plurality of regions, and reading the image signal for each region at a predetermined cycle from a plurality of predetermined regions among the plurality of divided regions. When the focus state is detected based on the control means for controlling and the image signal of the area read out in the cycle, and the luminance of the subject is smaller than a predetermined threshold, it is obtained in a plurality of the cycles. Detecting means for averaging the focus states of the plurality of regions; and when the luminance of the subject is equal to or higher than the threshold, focus adjustment is performed in the cycle based on the focus state obtained in the cycle; When the luminance is smaller than the threshold value, a focus adjustment unit that performs focus adjustment based on the averaged focus state, and an image signal read out in the cycle is converted into a display image and sequentially displayed on the display unit. Display control means.

  According to the present invention, it is possible to acquire an image signal at a high frame rate, increase the speed of focus detection, and perform focus detection with high accuracy even for a low-luminance subject.

1 is a schematic configuration diagram of an imaging system according to an embodiment of the present invention. FIG. 4 is a plan view and a cross-sectional view of focus detection pixels of the image sensor according to the embodiment. 6 is a flowchart showing focus adjustment and image display processing according to subject brightness in the first embodiment. 6 is a timing chart for explaining a normal reading operation and a high frame rate reading operation in the first embodiment. The figure for demonstrating the defocus amount calculated at the time of high-frame-rate reading when it determines with the to-be-photographed object brightness | luminance determination value in 1st Embodiment being more than a brightness | luminance threshold value. The figure for demonstrating the defocus amount calculated at the time of high-frame-rate reading when it determines with the to-be-photographed object brightness | luminance determination value in 1st Embodiment being less than a brightness | luminance threshold value. The figure for demonstrating the image display procedure in 1st Embodiment. The figure for demonstrating the amount of defocus calculated at the time of high frame rate reading in 2nd Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. However, the dimensions, shapes, relative arrangements, and the like of the components exemplified in the present embodiment should be changed as appropriate according to the configuration of the apparatus to which the present invention is applied and various conditions. It is not limited to.

<First Embodiment>
(overall structure)
FIG. 1 is a diagram showing a schematic configuration of a digital still camera which is an example of an imaging system according to an embodiment of the present invention. The imaging system according to the present embodiment mainly includes a camera main body 138 having an image sensor and a separate photographing lens 137, and the photographing lens 137 can be exchanged for the camera main body 138.

  First, the configuration of the taking lens 137 will be described. The first lens group 101 is disposed at the tip of an imaging optical system that forms an optical image of a subject, and is held so as to be able to advance and retract in the optical axis direction. The diaphragm 102 adjusts the light amount at the time of photographing by adjusting the aperture diameter. The second lens group 103 moves forward and backward in the optical axis direction integrally with the stop 102, and can achieve a zooming function (zoom function) in conjunction with the forward and backward movement of the first lens group 101. The third lens group 105 (focus lens) performs focus adjustment by advancing and retreating in the optical axis direction.

  The zoom actuator 111 rotates the cam cylinder (not shown) to drive the first lens group 101 to the third lens group 105 back and forth in the optical axis direction, and performs a zooming operation. The aperture actuator 112 controls the aperture diameter of the aperture 102 to adjust the amount of photographing light. The focus actuator 114 adjusts the focus by driving the third lens group 105 back and forth in the optical axis direction.

  The camera communication circuit 136 passes information about the photographing lens 137 to the camera body 138 and receives information about the camera body 138. Note that the information regarding the photographing lens 137 includes a zoom state, a diaphragm state, a focus state, lens frame information, and the like. The camera communication circuit 136 passes these pieces of information to the lens communication circuit 135 provided on the camera body 138 side.

  Next, the camera body 138 will be described. The optical low-pass filter 106 is an optical element for reducing false colors and moire in the captured image. The image sensor 107 is composed of a CMOS sensor composed of focus detection pixels, at least some of which are described later, and its peripheral circuits. Each pixel constituting the CMOS sensor has a photodiode (PD) that converts light into electric charge. In addition, the peripheral circuit includes a transfer switch that transfers charges generated in the PD to a storage area (floating diffusion: FD), which will be described later, and a storage area (FD) that temporarily stores charges. The image sensor 107 outputs a subject image formed by the photographing lens 137 as an electrical signal. As will be described later, the image sensor 107 in the present embodiment can generate an image signal for the imaging plane phase difference AF. The image sensor 107 of the present embodiment has a configuration for generating an image signal for imaging plane phase difference AF using a pixel provided with a microlens and a plurality of focus detection pixels. However, the imaging plane phase difference AF is used. Any other configuration may be used as long as an image signal can be generated. In addition, signals output from a plurality of focus detection pixels corresponding to one microlens can be added to generate a recording image. As the image sensor 107, a two-dimensional single-plate color sensor in which a Bayer array primary color mosaic filter is formed on-chip on a plurality of pixels of m pixels in the horizontal direction and n pixels in the vertical direction is used.

  The shutter unit 139 performs exposure time control during still image shooting. The shutter actuator 140 moves the shutter unit 139, and the shutter drive circuit 145 drives the shutter actuator 140.

  The in-camera CPU 121 that performs various controls of the camera body 138 includes a calculation unit, a ROM, a RAM, an A / D converter, a D / A converter, a communication interface circuit, and the like. The CPU 121 drives various circuits included in the camera based on a predetermined program stored in the ROM, and executes a series of operations such as AF, photographing, image processing, and recording. Further, the CPU 121 performs arithmetic processing related to subject luminance detection, image display control, focus detection, and various controls.

  The image sensor driving circuit 124 controls the image capturing operation of the image sensor 107, A / D converts the acquired image signal, and transmits it to the CPU 121. The image processing circuit 125 performs processing such as γ conversion, color interpolation, and JPEG compression of the image acquired by the image sensor 107.

  The focus drive circuit 126 controls the focus actuator 114 based on the focus detection result, and adjusts the focus by driving the third lens group 105 back and forth in the optical axis direction. The aperture drive circuit 128 controls the aperture of the aperture 102 by drivingly controlling the aperture actuator 112. The zoom drive circuit 129 drives the zoom actuator 111 according to the zoom operation of the photographer.

  A display 131 such as an LCD displays information on the shooting mode of the camera, a preview image before shooting and a confirmation image after shooting, a focus state display image at the time of focus detection, and the like. The operation switch group 132 includes a power switch, a release (shooting trigger) switch, a zoom operation switch, a shooting mode selection switch, a moving image / LV switch, and the like. The detachable flash memory 133 records captured images.

  The lens communication circuit 135 communicates with the camera communication circuit 136 in the photographing lens 137. The in-camera memory 144 stores various data necessary for calculations performed by the CPU 121.

  The electronic flash 115 for illuminating the subject is preferably a flash illumination device using a xenon tube, but an illumination device including an LED that emits light continuously may be used. The AF auxiliary light emitting unit 116 projects a mask image having a predetermined opening pattern onto the object field via the projection lens, and improves the focus detection capability for a dark subject or a low-contrast subject.

  The electronic flash control circuit 122 controls lighting of the electronic flash 115 in synchronization with the photographing operation. The auxiliary light driving circuit 123 controls the lighting of the AF auxiliary light emitting unit 116 in synchronization with the focus detection operation.

(Configuration of focus detection pixel)
FIG. 2 is a diagram illustrating the configuration of the focus detection pixels constituting the image sensor 107 in the first embodiment. FIG. 2A is a plan view of focus detection pixels of 2 rows × 2 columns. In the present embodiment, out of 4 pixels of 2 rows × 2 columns, pixels having G (green) spectral sensitivity are arranged in 2 diagonal pixels, and R (red) and B (blue) are arranged in the other 2 pixels. A Bayer arrangement in which one pixel each having a spectral sensitivity of 1 is arranged is employed. The focus detection pixels are distributed and arranged in the Bayer array. FIG. 2 shows a case where all the R, G, and B pixels are focus detection pixels.

FIG. 2B shows a cross-sectional view taken along line AA in FIG. 2A and the relationship between the light receiving area of each focus detection pixel and the exit pupil of the photographing lens 137. Focus detection pixel has a color filter CF _G, a contact layer CL of disposed in the top on-chip microlens ML, a color of R (red) filter CF _R or G (green) pixel. The contact layer CL is a wiring layer for forming signal lines for transmitting various signals in the image sensor 107. Although not shown, in the case of the B pixel, a B (blue) color filter CF _B is arranged. The exit pupil of the photographic lens 137 is schematically represented by TL.

In addition, two photoelectric conversion elements included in each focus detection pixel are schematically shown as PDA and PDB. Since the photoelectric conversion element PDA is in the -x side relative to the center of the microlens ML, it receives an object light that has passed through an exit pupil region EP _DA of + x side of the taking lens 137 exit pupil TL. Similarly, the photoelectric conversion element PDB is due to the + x side toward the center of the microlens ML, receives an object light that has passed through an exit pupil region EP _DB of -x side of the exit pupil TL.

  The focus detection pixels having the above-described configuration are regularly arranged in the x direction, the subject image acquired from the photoelectric conversion element PDA of these pixel groups is an A image, and the subject image acquired from the photoelectric conversion element PDB is B It is an image. Then, by detecting the phase difference between the acquired A image and B image, it is possible to detect a defocus amount (defocus amount) indicating a focus state of a subject image having a luminance distribution in the x direction. Based on this, the lens position of the taking lens 137 is adjusted. A technique for discretely arranging focus detection pixels between imaging pixels and a technique for performing focus detection using the focus detection pixels are disclosed in Japanese Patent Laid-Open No. 2000-20961. Since this is a known technique, the description thereof is omitted.

  In the pixel shown in FIG. 2, focus detection is possible for an object having a luminance distribution in the x direction on the shooting screen, for example, a line (vertical line) in the y direction, but in an x direction having a luminance distribution in the y direction. The line (horizontal line) cannot detect the focus. Therefore, a pixel that performs pupil division may also be provided in the y direction of the photographic lens so that the latter can be detected in focus.

(AF control flow)
Next, an operation for increasing the frame rate (cycle) during live view and switching the defocus amount and the display image according to the subject luminance in the first embodiment will be described with reference to the flowchart of FIG.

  The processing shown in FIG. 3 starts when the imaging system is turned on. In S1, lens communication is performed with the camera communication circuit 136 in the photographing lens 137 via the lens communication circuit 135. The operation of the photographic lens 137 is confirmed through lens communication, the memory contents in the photographic lens 137 and the execution program are initialized, and a preparatory operation is executed. Further, lens characteristic data necessary for focus detection and imaging is acquired and stored in the in-camera memory 144. When the operation is completed, the process proceeds to S2.

  In S2, it is determined whether or not the video / LV (live view) switch is pressed by the photographer in the operation switch group 132. If not, the shooting standby state is maintained in S2. When the moving image / LV switch is pressed in S2, the process proceeds to S3.

  In S3, the main subject brightness is detected by detecting the main subject in the shooting screen, and is held as a subject brightness determination value. Here, as a method for detecting the main subject in the shooting screen, for example, there is face detection. There are various face detection processes including a face detection technique described in, for example, Japanese Patent Laid-Open No. 6-259534, but the description thereof is omitted because it is a known technique.

  In S4, the image sensor 107 is exposed, thinned and read. Here, in the first embodiment, the row to be read by thinning is changed for each frame. Here, high frame rate readout by the slit rolling shutter system in the first embodiment will be described with reference to FIG.

  FIG. 4 shows the operation for each row of the image sensor 107 in the first embodiment on the time axis. FIG. 4A shows a normal reading operation, and FIG. 4B shows a high frame rate reading operation in the first embodiment.

  In the normal reading operation shown in FIG. 4A, when a shooting start instruction is given at the Start timing, the shooting operation is started after the PD and FD are collectively reset. Then, the diagonal lines from the upper part of the screen to the lower part of the screen in FIG. t is the charge accumulation time.

  On the other hand, in the high frame rate read operation shown in FIG. 4B, the frame rate is doubled (the charge accumulation time is halved) and the read row is compared with the normal read operation shown in FIG. And the line to skip are different for each frame. Hereinafter, a signal read out by thinning out an odd frame is called a first image signal I1, and a signal read out by thinning out an even frame is called a second image signal I2. That is, the first image signal I1 and the second image signal I2 are alternately read for each frame. At this time, PD and FD reset operations are performed on the thinned-out rows at the start timing shown in FIG. 4B as in the normal read operation, but the read operation is not performed. In FIG. 4B, the first image signal I1 read in the (fn) th frame is represented as I1 (fn). Further, the second image signal I2 read in the (fn + 1) frame is I2 (fn + 1), the first image signal I1 read in the (tn + 2) frame is I1 (tn + 2), and so on. Represents. In addition, pixels included in a row read in an odd frame are called a first pixel group, and pixels included in a row read in an even frame are called a second pixel group.

  As described above, by setting the number of rows read in each frame to half that in the normal read operation, an image signal can be acquired at a high frame rate. Therefore, the charge accumulation time is shortened to t / 2 which is half of the charge accumulation time t in normal reading.

  When one of the first image signal I1 and the second image signal I2 is read in S4 as described above, in S5, the phase difference detection method is used using the read first image signal I1 or second image signal I2. Perform AF. Since the image sensor 107 of the present embodiment includes focus detection pixels, the first image signal I1 or the second image signal read from the focus detection pixels included in the first pixel group or the second pixel group. An A image and a B image are generated from I2, and a phase difference between the A image and the B image can be obtained. Then, the defocus amount is detected based on the obtained phase difference.

  When the process of S5 is completed, the process proceeds to S6, where the subject brightness determination value detected in S3 is compared with the brightness threshold. If it is determined that the subject brightness determination value is equal to or greater than the brightness threshold value, it is determined that the subject brightness in the shooting screen is sufficient, and the process proceeds to S7. If it is determined that the subject brightness determination value is smaller than the brightness threshold value, it is determined that the subject brightness is not sufficient in the shooting screen and the process proceeds to S8.

  Here, the focus adjustment process performed in S7 when the subject brightness is determined to be equal to or greater than the brightness threshold value in S6 will be described with reference to FIG. Hereinafter, the defocus amount detected based on the first image signal I1 (fn) read in the (fn) th frame is represented as a first defocus amount Def1 (fn). Further, the defocus amount detected based on the second image signal I2 (fn + 1) read in the (fn + 1) th frame is represented as a second defocus amount Def2 (fn + 1). In the same manner, after the defocus amount Def, the detection based on the first image signal I1 or the second image signal I2 and the number of the first frame are described.

  First, the CPU 121 calculates the focus lens drive amount from the first defocus amount Def1 or the second defocus amount Def2 detected in S5, using the lens characteristic data acquired in S1. Then, the CPU 121 performs focus adjustment by driving the third lens group 105 via the focus actuator 114 based on the calculated focus lens drive amount. Accordingly, the focus adjustment based on the first defocus amount Def1 and the focus adjustment based on the second defocus amount Def2 are alternately performed in time series. When the operation is completed, the process proceeds to S9.

  On the other hand, the focus adjustment process performed in S8 when it is determined in S6 that the subject brightness is smaller than the brightness threshold will be described with reference to FIG. In FIG. 6, the average defocus amount of the first defocus amount Def1 (fn) and the second defocus amount Def2 (fn + 1) is expressed as an average defocus amount Def ′ (fn + 1). . First, an average defocus amount Def ′ (fn + 1) is calculated from the first defocus amount Def1 (fn) and the second defocus amount Def2 (fn + 1) in FIG.

  In the example illustrated in FIG. 6, focus adjustment is performed using the first defocus amount Def1 and the second defocus amount Def2 for two frames every two frames. However, the present invention is not limited to this. An average for each frame from the first defocus amount Def1 or the second defocus amount Def2 obtained in each frame and the second defocus amount Def2 or the first defocus amount Def1 obtained one frame before. The defocus amount Def ′ (fn + 1) may be calculated. In this case, it is possible to adjust the focus for each frame.

  Next, the focus lens drive amount is calculated from the calculated average defocus amount Def ′ using the lens characteristic data acquired in S1. Then, the CPU 121 performs focus adjustment by driving the third lens group 105 via the focus actuator 114 based on the calculated focus lens drive amount. When the operation is completed, the process proceeds to S9.

  In S9, an image for display is generated from the first image signal I1 or the second image signal I2 acquired in S4 and sequentially displayed. This display method will be described with reference to FIG. As described above, the focus detection pixels in the present embodiment each include two photoelectric conversion elements PDA and PDB, and independently output signals. Therefore, in order to obtain a captured image, in the (fn) th frame, two signals output from the two photoelectric conversion elements PDA and PDB of each focus detection pixel in the first image signal I1 (fn) are converted into pixels. A signal for display is generated by adding in units. In this way, a display signal generated from the first image signal I1 in the (fn) th frame is represented as a captured image P1 (fn). Similarly, a display signal generated from the second image signal I2 in the (fn + 1) th frame is represented as a captured image P2 (fn + 1).

  The first image signal I1 and the second image signal I2 are image signals obtained alternately at a high frame rate in time series. Captured images P1 (fn), P2 (tn + 1), P1 (fn + 2), P2 (fn + 3). . . Are alternately displayed at a high frame rate, so that there is no flickering on the screen and smooth video display is possible. When the operation is completed, the process proceeds to S10.

  In S10, it is determined whether or not the video / LV switch has been pressed again by the photographer after a series of focus detection, focus adjustment, and image recording / display, or whether a live view (LV) shooting instruction has been issued. . If not instructed, the process proceeds to S3 to continue moving image / LV shooting. On the other hand, when the moving image / LV switch is pressed in S11, the moving image / LV shooting ends. As described above, a series of focus detection flows is completed.

  As described above, according to the first embodiment, it is possible to change the thinning-out readout line for each frame, acquire an image signal at a high frame rate, and speed up focus detection. In addition, the defocus amount calculation method can be switched according to the main subject luminance in the shooting screen.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. The second embodiment is different from the first embodiment described above in terms of control relating to charge accumulation time and readout. FIG. 8 is a diagram illustrating charge accumulation and readout control in the second embodiment. Also in the second embodiment, as in the first embodiment described above, the first pixel group and the second pixel group are alternately read for each frame. However, in the second embodiment, when scanning the first pixel group and the second pixel group, reading is performed with the charge accumulation time overlapping by a predetermined time interval Δt.

  The focus adjustment and live view display processing in the second embodiment is basically the same as the procedure shown in the flowchart of FIG. 3, but the details of the processing in S7 and S8 are different. To do.

  In FIG. 8, signals similar to those in FIG. 6 are denoted by the same reference numerals. In FIG. 8, in the second embodiment, the image signal read in the (fn) frame is the first image signal I1 ′ (fn), and the image signal read in the (fn + 1) frame is the second image signal I2 ′. It is expressed as (fn + 1). Δt is a predetermined time interval. In the second embodiment, when the CPU 121 acquires the first image signal I1 ′ and the second image signal I2 ′, the CPU 121 performs reading by partially overlapping the charge accumulation time by a predetermined time interval Δt. From the first image signal I1 ′ (fn) and the second image signal I2 ′ (fn + 1) obtained in this way, the first defocus amount Def1 (fn) and the second defocus amount Def2 (fn). +1) is detected. Then, in response to the result determined in S6, the defocus amount is determined in S7 and S8, and the focus is adjusted. The defocus amount determination method is the same as in the first embodiment described above.

  As described above, according to the second embodiment, it is possible to speed up focus detection by changing the thinning-out readout row for each frame to acquire an image signal at a high frame rate.

  Further, it is possible to calculate and switch the defocus amount according to the main subject brightness in the shooting screen.

  Furthermore, by performing readout so as to overlap only a predetermined time interval, highly accurate focus detection can be performed even when the main subject luminance is lower than the luminance threshold.

  In the first and second embodiments described above, the phase difference method is used for the correlation calculation. However, similar results can be obtained even if other methods are used.

  In the above-described example, the case where the image signal is alternately read every other row in the odd-numbered frame and the even-numbered frame has been described, but the present invention is not limited to this. For example, the image sensor 107 may be thinned and read over three frames or more. In that case, if the subject luminance is smaller than the luminance threshold, focus adjustment may be performed every necessary number of frames. Further, depending on the number of pixels of the display 131, the number of thinned rows may be increased. For example, every four rows, two rows may be alternately read in odd frames and even frames. Further, when the pixels of the image sensor 107 are all composed of focus detection pixels divided in the horizontal direction, a plurality of rows of image signals different in odd frames and even frames may be added and read out. Also, for example, every 8 rows, the first and second rows are added and read in odd frames, the third and fourth rows are added and read in even frames, and the fifth to eighth rows are not read. Both addition and addition reading and thinning-out reading may be performed.

  107: Image sensor, 114: Focus actuator, 121: CPU, 124: Image sensor drive circuit, 125: Image processing circuit, 126: Focus drive circuit, 131: Display, 132: Operation switch group, 307: Shooting lens

Claims (9)

An imaging device including a plurality of pixels that photoelectrically convert subject light that has passed through an imaging optical system that forms an optical image of the subject and output an image signal;
The plurality of pixels are divided into a plurality of regions, and the image sensor is controlled so as to read image signals for each region at a predetermined cycle from a plurality of predetermined regions among the plurality of divided regions. Control means to
When the focus state is detected based on the image signal of the area read out in the period and the luminance of the subject is smaller than a predetermined threshold value, the plurality of areas obtained in the plurality of periods are detected. Detecting means for averaging the focus state;
When the luminance of the subject is equal to or higher than the threshold, focus adjustment is performed in the cycle based on the focus state obtained in the cycle. When the luminance of the subject is lower than the threshold, the focus is adjusted based on the average focus state. Focus adjusting means for adjusting the focus,
An image pickup apparatus comprising: a display control unit that converts the image signal read at the cycle into a display image and sequentially displays the image signal on a display unit. The imaging device includes focus detection pixels that photoelectrically convert subject light that has passed through different pupil regions of the imaging optical system and output a plurality of image signals,
The imaging apparatus according to claim 1, wherein the detection unit detects a focus state based on an image signal of a focus detection pixel included in the region read out in the cycle.   The imaging apparatus according to claim 1, wherein the control unit controls the charge accumulation time of each of the plurality of regions to be the cycle.   3. The imaging apparatus according to claim 1, wherein the control unit performs control so that a charge accumulation time of a region where reading is performed and a charge accumulation time of a region where reading is performed next partially overlap. .   5. The imaging apparatus according to claim 1, wherein the plurality of regions include pixels in a plurality of different rows.   The plurality of regions include a first region composed of every other row of pixels and a second region composed of every other row of pixels not included in the first region. The focus state obtained from the image signal of the first region and the focus state obtained from the image signal of the second region are averaged when the luminance of the subject is smaller than the threshold value. Item 6. The imaging device according to Item 5.   The imaging apparatus according to claim 1, wherein control and processing are performed by the control unit, the detection unit, and the focus adjustment unit when shooting live view or a moving image.   The imaging apparatus according to claim 1, wherein the imaging device is a CMOS sensor, and the control unit drives and controls the CMOS sensor by a slit rolling shutter system. A method for controlling an imaging apparatus including a plurality of pixels each having an imaging element that photoelectrically converts subject light that has passed through an imaging optical system that forms an optical image of a subject and outputs an image signal,
A reading step in which the reading unit divides the plurality of pixels into a plurality of regions, and reads an image signal for each region at a predetermined cycle from a plurality of predetermined regions among the plurality of divided regions; ,
The detection means detects the focus state based on the image signal of the area read out in the cycle, and the luminance obtained in the plurality of cycles when the luminance of the subject is smaller than a predetermined threshold value. A detection step of averaging the focus states of a plurality of regions;
The focus adjustment unit performs focus adjustment in the cycle based on the focus state obtained in the cycle when the luminance of the subject is equal to or higher than the threshold value, and the average when the luminance of the subject is smaller than the threshold value. A focus adjustment step for performing focus adjustment based on the focused state,
And a display control step in which the display control means converts the image signal read out in the cycle into a display image and sequentially displays it on the display means.

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