Imaging apparatus

Abstract

To provide an imaging apparatus capable of improving the low light performance of autofocus.SOLUTION: An imaging element includes a first pixel that outputs a signal used for image generation on the basis of an electrically converted charge, a second pixel that outputs a signal used for focus detection on the basis of a photoelectrically converted charge, and a control unit that performs a first control to control the exposure time of the second pixel on the basis of a first period when the exposure time of the first pixel is the first period, and a second control to control the exposure time of the first pixel on the basis of a second period when a predetermined imaging condition is satisfied and the exposure time of the second pixel is the second period longer than the first period.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an imaging element and an imaging device. [Background technology]

[0002] Image sensors that read out a signal for focus detection and a signal for image generation have been known (for example, see Patent Document 1). There has been a demand for improving the accuracy of focus detection. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-34606 A Summary of the Invention

[0004] According to an aspect of the invention, an imaging element includes a first pixel that outputs a signal used for image generation based on an electrically converted charge, a second pixel that outputs a signal used for focus detection based on a photoelectrically converted charge, and a control unit that performs a first control to control the exposure time of the second pixel based on the first period when the exposure time of the first pixel is a first period, and a second control to control the exposure time of the first pixel based on the second period when a predetermined imaging condition is satisfied and the exposure time of the second pixel is a second period longer than the first period. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a camera according to this embodiment. [Figure 2A] FIG. 2A is a schematic diagram of an imaging element as viewed from above. [Figure 2B] FIG. 2B is a schematic diagram showing an example in which a part of FIG. 2A is enlarged. [Diagram 3] FIG. 3 is a block diagram showing an example of the configuration of an imaging element. [Figure 4] FIG. 4 is a block diagram showing an example of the configuration of a pixel of an imaging element. [Diagram 5] FIG. 5 is a flowchart showing the operation of the camera according to this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0007] 1 is a block diagram showing an example of the configuration of a digital camera 1 according to this embodiment. Digital camera 1 (hereinafter simply referred to as camera 1) of this embodiment is made up of a camera body 2 and an interchangeable lens 3. The camera body 2 and the interchangeable lens 3 are configured to be detachable via a mount section 4.

[0008] The camera body 2 is provided with a body side mount section 201 to which the interchangeable lens 3 is attached. The interchangeable lens 3 is provided with a lens side mount section 301 to which it is attached to the camera body 2. The body side mount section 201 and the lens side mount section 301 are provided with a body side connection section 202 and a lens side connection section 302, respectively. The body side connection section 202 and the lens side connection section 302 are each provided with a plurality of terminals, such as a terminal for a clock signal, a terminal for a data signal, and a terminal for power supply.

[0009] When the interchangeable lens 3 is attached to the camera body 2, a terminal provided on the body side connection part 202 is electrically connected to a terminal provided on the lens side connection part 302. This enables power to be supplied from the camera body 2 to the interchangeable lens 3 and communication between the camera body 2 and the interchangeable lens 3.

[0010] The interchangeable lens 3 includes a photographing optical system (imaging optical system) 31 and a lens control unit 32. The photographing optical system 31 includes a plurality of lenses, including a zoom lens (variable magnification lens) 31a that changes the focal length and a focus lens (focus adjustment lens) 31b, and an aperture 31c, and forms a subject image on the imaging surface 22a of the image sensor 22. Note that, although the zoom lens 31a and the focus lens 31b are illustrated in FIG. 1, a normal photographing optical system is generally composed of a large number of optical elements.

[0011] The lens control unit 32 is composed of a processor such as a CPU, FPGA, or ASIC, and a memory such as a ROM or RAM, and controls each unit of the interchangeable lens 3 based on a control program. The lens control unit 32 controls the position of the zoom lens 31a, the position of the focus lens 31b, and the drive of the aperture 31c based on a signal output from the body control unit 21 of the camera body 2. When a signal indicating the movement direction and movement amount of the focus lens 31b is input from the body control unit 21 to the lens control unit 32, the lens control unit 32 moves the focus lens 31b forward and backward in the direction of the optical axis OA1 based on the signal to adjust the focal position of the photographing optical system 31. The lens control unit 32 controls the position of the focus lens 31b via a drive motor (not shown). In addition, the lens control unit 32 controls the position of the zoom lens 31a and the aperture diameter of the aperture 31c based on a signal output from the body control unit 21 of the camera body 2. The lens control unit 32 adjusts the position of the focus lens 31b via a drive motor (not shown). The lens control unit 32 controls the aperture diameter of the aperture 31c via a drive motor (not shown).

[0012] Next, the configuration of the camera body 2 will be described. The camera body 2 includes a body control unit 21, an image sensor 22, a recording unit 23, a display unit 24, an operation unit 25, and a gyro sensor 26. The body control unit 21 is configured with a processor such as a CPU, FPGA, or ASIC, and a memory such as a ROM or RAM, and controls each unit of the camera 1 based on a control program. For example, the body control unit 21 controls the exposure time and number of exposures of the image sensor 22. As described later, the body control unit 21 controls the exposure time and number of exposures of the image sensor pixels, and the exposure time and number of exposures of the AF pixels. In addition, the body control unit 21 controls the photographing optical system 31 via the lens control unit 32. Note that the exposure time of the image sensor pixels and the exposure time of the AF pixels correspond to the charge accumulation time of the photoelectric conversion unit described later.

[0013] The body control unit 21 has an image processing unit 211 and a focus detection unit 212. The image processing unit 211 performs various image processing on signals output from imaging pixels of the image sensor 22, which will be described later, to generate image data. Note that the image processing unit 211 may also generate image data using signals output from the AF pixels. The image processing unit 211 performs image processing on signals output from the imaging pixels to generate image data for live view to be displayed on the display unit 24 and image data for still images and / or videos to be recorded in the recording unit 23.

[0014] The focus detection unit 212 performs focus detection processing required for automatic focus adjustment (AF) of the photographing optical system 31. The focus detection unit 212 detects the in-focus position (the amount of movement of the focus lens 31b to the in-focus position) of the focus lens 31b for focusing (forming) an image by the photographing optical system 31 on the imaging surface 22a of the image sensor 22. The focus detection unit 212 calculates the defocus amount by a pupil division type phase difference detection method using a signal output from an AF pixel described later. The focus detection unit 212 calculates the amount of image shift by performing a correlation calculation between a first signal generated by capturing an image by a first light beam passing through a first pupil region of the exit pupil of the photographing optical system 31 and a second signal generated by capturing an image by a second light beam passing through a second pupil region. The focus detection unit 212 converts this amount of image shift into a defocus amount based on a predetermined conversion formula. The focus detection unit 212 calculates the amount of movement of the focus lens 31b to the in-focus position based on the calculated defocus amount.

[0015] The focus detection unit 212 determines whether the defocus amount is within a tolerable value. If the defocus amount is within the tolerable value, the focus detection unit 212 determines that the image is in focus. On the other hand, if the defocus amount exceeds the tolerable value, the focus detection unit 212 determines that the image is not in focus, and transmits a signal to the lens control unit 32 of the interchangeable lens 3 indicating the amount of movement of the focus lens 31b and an instruction to move the lens. The lens control unit 32 moves the focus lens 31b according to the amount of movement, thereby automatically adjusting the focus.

[0016] The focus detection unit 212 can also perform focus detection processing using a contrast detection method in addition to focus detection processing using a phase difference detection method. The body control unit 21 sequentially calculates the contrast evaluation value of the subject image based on the signals output from the imaging pixels while moving the focus lens 31b of the photographing optical system 31 in the direction of the optical axis OA1. The body control unit 21 associates the position of the focus lens 31b with the contrast evaluation value using position information of the focus lens 31b transmitted from the interchangeable lens 3. The body control unit 21 then detects the position of the focus lens 31b at which the contrast evaluation value is at its peak, i.e., at its maximum value, as the in-focus position. The body control unit 21 transmits information on the position of the focus lens 31b corresponding to the detected in-focus position to the lens control unit 32. The lens control unit 32 moves the focus lens 31b to the in-focus position to adjust the focus.

[0017] The imaging element 22 is a CMOS image sensor or a CCD image sensor. The imaging element 22 captures a subject image formed by the photographing optical system 31. The imaging element 22 has a plurality of pixels, each having a photoelectric conversion unit, arranged two-dimensionally (in row and column directions). The photoelectric conversion unit is composed of a photodiode (PD). The imaging element 22 photoelectrically converts received light in the photoelectric conversion unit to generate a signal, and outputs the generated signal to the body control unit 21.

[0018] As described later, the image sensor 22 has imaging pixels that output signals used for image generation and AF pixels that output signals used for focus detection. The imaging pixels include pixels (hereinafter referred to as R pixels) having filters with spectral characteristics that separate light in a first wavelength range (red (R) light) from the incident light, pixels (hereinafter referred to as G pixels) having filters with spectral characteristics that separate light in a second wavelength range (green (G) light) from the incident light, and pixels (hereinafter referred to as B pixels) having filters with spectral characteristics that separate light in a third wavelength range (blue (B) light) from the incident light. The R pixels, G pixels, and B pixels are arranged according to a Bayer array. The AF pixels are arranged by replacing some of the imaging pixels, and are distributed over almost the entire image sensor surface 22a of the image sensor 22.

[0019] The recording unit 23 is composed of, for example, a non-volatile storage medium. Image data, control programs, and the like are recorded in the recording unit 23. Writing data to the recording unit 23 and reading data from the recording unit 23 are controlled by the body control unit 21. The recording unit 23 may be either a removable card-type memory or a built-in memory.

[0020] The display unit 24 displays images based on image data generated by the image processing unit 211, for example images for live view, at a predetermined frame rate. The display unit 24 also displays images showing focus detection areas (AF areas) such as AF frames, information related to shooting such as shutter speed and F-number, and menu screens, etc. The operation unit 25 includes various setting switches such as a release button, a power switch, and switches for switching between various modes, and outputs operation signals to the body control unit 21 according to the respective operations.

[0021] The gyro sensor 26 detects shaking of the camera 1, such as camera shake. The gyro sensor detects an angle component around a predetermined axis, and outputs a detection signal to the body control unit 21.

[0022] Next, referring to FIG. 2, an example of the configuration of the imaging element 22 will be described. FIG. 2A is a schematic diagram of the imaging element 22 according to this embodiment as viewed from above. FIG. 2B is a schematic diagram showing an example of pixel arrangement by enlarging a part of FIG. 2A. In FIG. 2A, in a pixel section (pixel region) 100, a plurality of pixels 10 are arranged two-dimensionally in row and column directions. Note that the number and arrangement of pixels arranged in the imaging element 22 (pixel section 100) are not limited to the example shown in the figure. For example, several million to several hundred million pixels 10 are provided in number, or more. In FIG. 2B, a first pixel group 101 in which R pixels 10 and G pixels 10 are arranged alternately in the row direction, and a second pixel group 102 in which G pixels 10 and B pixels 10 are arranged alternately in the row direction are arranged alternately in the column direction. The R pixels 10, G pixels 10, and B pixels 10 are imaging pixels and arranged according to a Bayer array.

[0023] Some of the second pixel groups 102 among the multiple second pixel groups 102 include the first or second AF pixel 11, 12. The first and second AF pixels 11, 12 each have a light-shielding portion 13. In FIG. 2B, the second pixel group 102 including the first AF pixel 11 is indicated as second pixel group 102a, and the second pixel group 102 including the second AF pixel 12 is indicated as second pixel group 102b. The second pixel group 102a including the first AF pixel 11 and the second pixel group 102b including the second AF pixel 12 will be described below.

[0024] In the second pixel group 102a, the B pixel 10 is replaced with the first AF pixel 11. In the second pixel group 102a, the first AF pixel 11 and the G pixel 10 are alternately arranged. The photoelectric conversion unit of the first AF pixel 11 receives a light beam that has passed through one of the first and second pupil regions of the exit pupil of the photographing optical system 31. The light shielding unit of the first AF pixel 11 shields a light beam that has passed through the other of the first and second pupil regions of the exit pupil of the photographing optical system 31. The photoelectric conversion unit of the first AF pixel 11 receives a light beam that has passed through the first pupil region of the exit pupil of the photographing optical system 31. The light shielding unit of the first AF pixel 11 shields a light beam that has passed through the second pupil region of the exit pupil of the photographing optical system 31.

[0025] In the second pixel group 102b, which is a predetermined row away from the second pixel group 102a, the B pixels 10 are replaced with second AF pixels 12. In the second pixel group 102b, the second AF pixels 12 and the G pixels 10 are arranged alternately. The photoelectric conversion unit of the second AF pixel 12 receives a light beam that has passed through a pupil region of an exit pupil different from that of the first AF pixel 11. The light shielding unit of the second AF pixel 12 shields the light beam that has passed through a pupil region of an exit pupil different from that of the first AF pixel 11. The photoelectric conversion unit of the second AF pixel 12 receives a light beam that has passed through a second pupil region of the exit pupil of the photographing optical system 31. The light shielding unit of the second AF pixel 12 shields the light beam that has passed through a first pupil region of the exit pupil of the photographing optical system 31.

[0026] The arrangement position of the first AF pixel 11 in the second pixel group 102a and the arrangement position of the second AF pixel 12 in the second pixel group 102b are the same as each other. That is, the first AF pixel 11 and the second AF pixel 12 are arranged in the same column. The first AF pixel 11 of the second pixel group 102a and the second AF pixel 12 of the second pixel group 102b configure a first AF pixel pair. The second pixel group 102a and the second pixel group 102b may be arranged in multiple rows, and multiple first AF pixel pairs may be arranged.

[0027] 3 is a block diagram showing an example of the configuration of the image sensor 22 according to this embodiment. The image sensor 22 has a pixel section (pixel region) 100, a vertical control section 30, a plurality of readout sections 40 (a first readout section 40a and a second readout section 40b) arranged above and below the pixel section 100, a first vertical signal line VoutA, and a second vertical signal line VoutB.

[0028] As described above, the pixel section has a plurality of pixels (imaging pixels) 10, a first AF pixel 11, and a second AF pixel 12 arranged therein. Note that the 128 pixels of 8 pixels in the row direction × 16 pixels in the column direction shown in Fig. 3 represent a pixel group arranged in an arbitrary region of the imaging surface of the image sensor 22, and pixels may exist not only to the right of the pixel in the 8th column and below the pixel in the 16th row in Fig. 3, but also to the left of the pixel in the 1st column and above the pixel in the 1st row.

[0029] The vertical control unit 30 is controlled by the body control unit 21 of the camera 1, and supplies a control signal to each pixel to control the operation of each pixel. The first readout unit 40a and the second readout unit 40b each include a signal processing circuit such as an analog / digital conversion unit (AD conversion unit). The first vertical signal line VoutA and the second vertical signal line VoutB are signal lines electrically connected to each pixel and for outputting a signal of the pixel selected by the vertical control unit 30. The pixel signal output to the first vertical signal line VoutA is converted into a digital signal by the first readout unit 40a and then output to the body control unit 21 (image processing unit 211). The pixel signal output to the second vertical signal line VoutB is converted into a digital signal by the second readout unit 40b and then output to the body control unit 21 (image processing unit 211).

[0030] 4 is a block diagram showing an example of the configuration of a pixel of the image sensor 22 according to this embodiment. Each pixel includes a photoelectric conversion unit 11a and a transfer unit 12a. The pixel 10g has a photoelectric conversion unit 11a and a transfer unit 12a, and the pixel 10b has a photoelectric conversion unit 11b and a transfer unit 12b. The photoelectric conversion unit 11a is a photodiode PD that converts incident light into an electric charge and accumulates the photoelectrically converted electric charge.

[0031] In addition, the imaging element 22 of this embodiment is configured such that two adjacent pixels share a floating diffusion (FD) 15, a reset section 16, an amplifier section 17, a first selection section 18, and a second selection section 19, as indicated by the dashed line 20.

[0032] The transfer unit 12a of the pixel 10g is composed of a transistor M1 controlled by a signal TX1, and transfers the charge photoelectrically converted by the photoelectric conversion unit 11a to the FD15. That is, the transfer unit 12a forms a charge transfer path between the photoelectric conversion unit 11a and the FD15. The transfer unit 12b of the pixel 10b is composed of a transistor M2 controlled by a signal TX2, and transfers the charge photoelectrically converted by the photoelectric conversion unit 11b to the FD15. That is, the transfer unit 12b forms a charge transfer path between the photoelectric conversion unit 11b and the FD15. The transistors M1 and M2 are each a transfer transistor. The capacitance C of the FD15 accumulates (holds) the charge transferred to the FD15 and converts it into a voltage divided by the capacitance value.

[0033] The amplifier 17 amplifies and outputs a signal due to the charge accumulated in the capacitance C of the FD 15. The amplifier 17 is configured with a transistor M5 having a drain (terminal) and a gate (terminal) connected to a power supply VDD and the FD 15, respectively. The source (terminal) of the transistor M5 is connected to a first vertical signal line VoutA via a first selection unit 18, and is connected to a second vertical signal line VoutB via a second selection unit 19.

[0034] The reset unit 16 is composed of a transistor M4 controlled by a signal RST, and resets the charge of the FD 15 and resets the voltage of the FD 15. The transistor M4 is a reset transistor.

[0035] The first selection unit 18 is composed of a transistor M6 controlled by a signal SELA, and electrically connects or disconnects the amplifier unit 17 and the first vertical signal line VoutA. When the transistor M6 of the first selection unit 18 is in an on state, it outputs a signal from the amplifier unit 17 to the first vertical signal line VoutA. The second selection unit 19 is composed of a transistor M7 controlled by a signal SELB, and electrically connects or disconnects the amplifier unit 17 and the second vertical signal line VoutB. When the transistor M7 of the second selection unit 19 is in an on state, it outputs a signal from the amplifier unit 17 to the second vertical signal line VoutB. The transistor M6 is a first selection transistor, and the transistor M7 is a second selection transistor.

[0036] As described above, the charge photoelectrically converted by the photoelectric conversion unit 11a is transferred to the FD 15 by the transfer unit 12a. Then, a signal (pixel signal) corresponding to the charge transferred to the FD 15 is output to the first vertical signal line VoutA or the second vertical signal line VoutB. The pixel signal is an analog signal generated based on the charge photoelectrically converted by the photoelectric conversion unit 11a. The pixel signal output from the pixel 10 is subjected to signal processing by the readout unit 40 and then output as an imaging signal to the body control unit 21 (image processing unit 211).

[0037] In this embodiment, the circuit configurations of the first AF pixel 11 and the second AF pixel 12 are the same as the circuit configuration of the pixel 10. The signals output from the first AF pixel 11 and the second AF pixel 12 are subjected to signal processing by the readout unit 40 and then output to the body control unit 21 (focus detection unit 212) as a pair of focus detection signals. The first AF pixel 11 and the second AF pixel 12 can control an exposure time different from that of the pixel 10. The body control unit 21 can set an optimal exposure time for each of the imaging pixel and the AF pixel via the vertical control unit 30. In other words, the body control unit 21 can set an optimal charge accumulation time for each of the photoelectric conversion unit of the imaging pixel and the photoelectric conversion unit of the AF pixel via the vertical control unit 30.

[0038] Next, an example of the sequence of live view image processing and autofocus (AF) processing by the body control unit 21 will be described. First, live view image processing will be described. The body control unit 21 sets an exposure time for generating image data for live view based on shooting conditions such as the movement of the subject, the shooting environment (brightness of the subject or background), and the shooting mode. The vertical control unit 30 of the image sensor 22 performs continuous shooting at the exposure time set by the body control unit 21 using multiple imaging pixels. The image sensor 22 outputs signals read from the multiple imaging pixels as image data to the body control unit 21 (image processing unit 211). The image processing unit 211 performs image processing on the image data output from the image sensor 22 to generate image data for live view. The display unit 24 displays an image based on the image data for live view generated by the image processing unit 211.

[0039] Similar to the processing of live view images, the body control unit 21 performs autofocus (AF) processing. The body control unit 21 sets an optimal exposure time for calculating the defocus amount based on the shooting environment. The vertical control unit 30 of the image sensor 22 uses multiple AF pixels to capture an image at the exposure time set by the body control unit 21. The image sensor 22 outputs signals read out from the multiple AF pixels to the body control unit 21 (focus detection unit 212) as detection data for calculating the defocus amount. The focus detection unit 212 performs focus detection processing such as the calculation of the above-mentioned defocus amount based on the detection data output from the image sensor 22.

[0040] As described above, the optimal exposure time can be set for each of the imaging pixels and the AF pixels. Therefore, the exposure time and the number of exposures for the imaging pixels and the AF pixels may be different from each other. However, if a specific shooting condition described later is not satisfied, the exposure time and the number of exposures for the AF pixels are limited by the exposure time and the number of exposures for the imaging pixels.

[0041] The body control unit 21 sets the exposure time of the imaging pixels based on the shooting conditions in order to process the live view image. The body control unit 21 sets the frame rate of the imaging element 22 based on the exposure time of the imaging pixels. Then, the vertical control unit 30 appropriately changes the exposure time of the imaging pixels according to the shooting environment so as to satisfy the frame rate of the imaging element 22. Furthermore, the vertical control unit 30 sets the exposure time of the AF pixels so as to satisfy the frame rate of the imaging element 22. That is, the exposure time of the AF pixels is limited by the longest exposure time of the imaging pixels set based on the frame rate of the imaging element 22. For example, when the frame rate of the imaging element 22 is set to 30 fps by the body control unit 21, the longest exposure time of the imaging pixels is set to 1 / 30 sec and varies within a time range of 30 sec depending on the shooting environment. If the longest exposure time of the imaging pixels is 1 / 30 sec, the longest exposure time of the AF pixels is also set to 1 / 30 sec.

[0042] Incidentally, in order to improve the accuracy of autofocus when shooting a low-luminance subject or in a dark shooting environment such as at night or in a dark room, there is a demand for making the exposure time of the AF pixel longer than the exposure time of the imaging pixel. In other words, in order to improve the accuracy of autofocus when shooting a low-luminance subject or in a dark shooting environment such as at night or in a dark room, there is a demand for lowering the frame rate of the imaging element 22. However, if the frame rate is lowered to improve the accuracy of AF, a problem occurs in that the live view image cannot be displayed smoothly on the display unit 24. In particular, when shooting a moving subject, the photographer cannot track the subject in the live view image, which causes problems in shooting.

[0043] In this embodiment, when a predetermined shooting condition is satisfied, the frame rate is lowered to improve the accuracy of autofocus. For example, when lowering the frame rate has little effect on the shooting of the subject or the display of the live view image, the frame rate is lowered to improve the accuracy of autofocus.

[0044] The predetermined shooting conditions under which the frame rate may be lowered are determined by factors such as brightness, camera settings, gyro information (camera movement), motion vector (subject movement), etc. An example of the predetermined shooting conditions is as follows.

[0045] (Specified shooting conditions) (1) The brightness of the subject and / or within the angle of view (entire screen) is below a predetermined brightness threshold. (2) The subject's moving speed is below a predetermined speed. (3) The frame rate before autofocus (focus detection) is equal to or lower than a predetermined value. (4) The exposure time when taking a photograph is equal to or longer than a predetermined value (the shutter speed is equal to or longer than a predetermined value). (5) The movement of the camera body is below a certain value.

[0046] The predetermined imaging condition may include at least one of the above conditions (1) to (5), and may include a plurality of conditions. For example, the predetermined imaging condition may be a composite condition such as satisfying the above conditions (1), (2), and (3) and also satisfying either condition (4) or (5). The method of determining each condition will be described below.

[0047] The body control unit 21 determines whether or not condition (1) is met based on image data output from the image sensor 22. When a specific subject is not included, such as when photographing a night scene or a dark indoors, the body control unit 21 determines that condition (1) is met when the overall luminance of the shooting screen is equal to or lower than a predetermined luminance. When a specific subject is recognized, the body control unit 21 determines that condition (1) is met when the luminance of an area of ​​the shooting screen that includes the recognized subject is equal to or lower than a predetermined luminance.

[0048] The body control unit 21 detects contrast information from the output of multiple pixels and recognizes a subject based on the detected contrast information. The body control unit 21 calculates a motion vector of the recognized subject based on the contrast information. The body control unit 21 compares a moving speed corresponding to the magnitude of the calculated vector with a predetermined speed (speed threshold), and determines that condition (2) is satisfied if the moving speed is equal to or less than the predetermined speed.

[0049] For example, when a live view image is being displayed and the shooting environment is dark, the body control unit 21 sets the frame rate to a low rate before focus detection. The body control unit 21 sets exposure conditions according to the shooting conditions before focus detection. The exposure conditions are indicated by charge accumulation time, gain, ISO sensitivity, frame rate, shutter speed, etc. The body control unit 21 compares the frame rate included in the exposure conditions with a predetermined value, and determines that condition (3) is satisfied if the frame rate is equal to or lower than the predetermined value.

[0050] The body control unit 21 identifies the shutter speed from the exposure conditions, and determines that condition (4) is met if the shutter speed at the time of shooting is equal to or greater than a predetermined value (the shutter time is longer than a predetermined length).

[0051] The body control unit 21 determines whether or not condition (5) is met based on the detection value of the gyro sensor 26. For example, when the camera body is fixed to a tripod, or when the camera is stable without camera shake and the subject movement is small, the condition (5) is met. The body control unit 21 calculates the movement of the camera body from the detection value of the gyro sensor 26, and determines that condition (5) is met when the calculated value is equal to or less than a predetermined value.

[0052] The body control unit 21 may determine whether or not condition (5) is met based on the presence or absence of a motion vector of the recognized subject. When the camera body is not fixed to a tripod and is held by hand, the detection value of the gyro sensor 26 is a small value other than zero. In such a case, the body control unit 21 adds a motion vector condition to determine whether or not condition (5) is met. When the subject is not moving or the movement of the subject is small, the motion vector of the subject is not calculated. For example, the body control unit 21 may determine that condition (5) is met when the detection value of the gyro sensor 26 is equal to or less than a predetermined value and the motion vector of the subject is not calculated.

[0053] The body control unit 21 determines whether or not a predetermined photographing condition, which is at least one of the above conditions (1) to (5), is satisfied based on the detection value of the sensor of the gyro sensor 26 and / or the camera settings. If it is determined that the predetermined photographing condition is satisfied, the body control unit 21 reduces the frame rate of the image sensor 22 from the first frame rate to the second frame rate. In other words, if it is determined that the predetermined photographing condition is satisfied, the vertical control unit 30 lengthens the exposure time of the image sensing pixels and the AF pixels from the previous time. On the other hand, if it is determined that the predetermined photographing condition is not satisfied, the body control unit 21 maintains the frame rate at the first frame rate. The first frame rate is a rate that is set under a normal photographing environment, and the body control unit 21 sets a frame rate that is suitable for the brightness of the photographing environment, the movement of the subject, and the like, as the first frame rate. In other words, if the predetermined photographing condition is satisfied, the body control unit 21 reduces the frame rate from the current frame rate of the image sensor 22 in order to improve the accuracy of autofocus.

[0054] Next, the frame rate and the exposure time will be described. For example, assume that the frame rate for displaying a live view image is set to 30 fps under normal circumstances. When the frame rate is set to 30 fps, the exposure time determined from the frame rate is 1 / 30 sec, and the exposure time for generating a live view image (exposure time of the imaging pixels: equivalent to the first exposure time) is set to 1 / 30 sec (equivalent to the first period).

[0055] Normally, the exposure time for focus detection (exposure time of the AF pixel: equivalent to the second exposure time) is set to be equal to or shorter than the first period. For example, when the exposure time of the imaging pixel is set to 1 / 30 sec, the exposure time of the AF pixel can be set to 1 / 30 sec or shorter.

[0056] When the above-mentioned predetermined shooting conditions are satisfied, the frame rate of the imaging pixel can be reduced to 30 fps or less, for example, 15 fps. It is set. The exposure time determined from the frame rate (15 fps) is 1 / 15 sec. When the above-mentioned predetermined shooting conditions are satisfied, the exposure time of the AF pixel is set to a long period in order to increase the amount of light. The exposure time of the AF pixel can be set to 1 / 15 sec (corresponding to the second period). In other words, the exposure time of the AF pixel is a period longer than the exposure time of the imaging pixel in normal times. Note that when the above-mentioned predetermined shooting conditions are satisfied, the exposure time of the AF pixel may be set to a period shorter than the exposure time determined from the frame rate, as long as it is a period longer than the exposure time determined from the frame rate in normal times.

[0057] Next, an example of the operation of the camera 1 according to this embodiment will be described. Fig. 5 is a flow chart showing the operation of the camera 1. Note that the operation shown in Fig. 5 is carried out when capturing an image after the camera body 2 is switched on.

[0058] First, in step S1, the body control unit 21 acquires output data including the detection value of the gyro sensor 26. In step S2, the body control unit 21 determines whether or not a predetermined shooting condition is satisfied. If the predetermined condition is not satisfied, the process proceeds to step S3, and if the predetermined condition is satisfied, the process proceeds to step S5.

[0059] In step S3, the body control unit 21 sets the frame rate to a first frame rate. In step S4, the body control unit 21 sets the exposure time of the imaging pixels to a first period. The body control unit 21 also sets the exposure time of the AF pixels to the first period. Note that the first period is the longest exposure time determined from the first frame rate, and the body control unit 21 may change the exposure time within the range of the first period depending on the shooting environment.

[0060] In step S5, the body control unit 21 sets the frame rate to a second frame rate. In step S6, the body control unit 21 sets the exposure time of the AF pixels to a second period longer than the first period, and sets the exposure time of the imaging pixels to the second period. Note that the second period is the longest exposure time determined from the second frame rate, and the body control unit 21 may change the exposure time within the range of the second period depending on the shooting environment.

[0061] In step S7, the body control unit 21 performs autofocus processing. The body control unit 21 determines control parameters that determine exposure conditions such as gain, in addition to the frame rate and exposure time set in steps S3 to S6. The body control unit 21 also determines an AF area in the pixel array. The body control unit 21 transmits a command including the control parameters to the lens control unit 32, and calculates a defocus amount by performing phase difference detection calculation based on output signals from AF pixels included in the AF area.

[0062] In step S8, the body control unit 21 generates a live view image based on the output signals of the imaging pixels, and displays the live view image on the display unit 24. In step S9, the drive amount of the focus lens 31b is calculated and the focus lens 31b is driven based on the defocus amount.

[0063] As described above, the body control unit 21 in this embodiment As described above, the body control unit 21 performs a first control in which the exposure time of the second pixel that outputs a signal used for focus detection is controlled based on the first period when the exposure time of the first pixel that outputs a signal used for image generation is a first period, and a second control in which the exposure time of the first pixel is controlled based on the second period when a predetermined imaging condition is satisfied and the exposure time of the second pixel is a second period longer than the first period. This makes it possible to improve the low brightness performance of the autofocus.

[0064] A modified example of this embodiment will be described below. In the following description, the same components as those in the above embodiment will be given the same reference numerals and the description above will be used as appropriate. In the modified example, when a mode for extending the low luminance limit of focus detection is on, the image capture device reduces the frame rate at which signals are read from a plurality of pixels to a second frame rate lower than the first frame rate, and when the mode is off and a predetermined image capture condition is satisfied, the image capture device reduces the frame rate to the second frame rate or lower.

[0065] For example, when shooting in a dark place, the body control unit 21 can set a mode (hereinafter referred to as the extension mode) that extends the low luminance limit for focus detection. The extension mode is set by operating the touch panel of the display unit 24, and when the extension mode is turned on, the frame rate is reduced to brighten the shooting screen. On the other hand, when the extension mode is turned off, the frame rate can only be reduced to a predetermined frame rate lower limit value. And, the frame rate lower limit value when the extension mode is off is higher than the frame rate when the extension mode is on. In a modified example, when the extension mode is off and a predetermined imaging condition is satisfied, the body control unit 21 reduces the frame rate to a value equal to or lower than the frame rate when the extension mode is on (corresponding to a third frame rate).

[0066] That is, in the modified example, when the extended mode is on, the body control unit 21 reduces the frame rate at which signals are read out from multiple pixels to a predetermined frame rate, and when the extended mode is off and the above-mentioned specified imaging conditions are satisfied, reduces the frame rate to below the predetermined frame rate.This makes it possible to improve the accuracy of autofocus by reducing the frame rate in an imaging environment where the extended mode is off and reducing the frame rate has little effect.

[0067] In a modified example of this embodiment, the body control unit 21 may set the frame rate so that the lower limit of the frame rate when the extended mode is on is higher than the lower limit of the frame rate when the extended mode is off, and may set the frame rate so that the frame rate when the above-mentioned specified imaging conditions are satisfied is lower than the lower limit of the frame rate when the extended mode is on. [Explanation of symbols]

[0068] 1 Camera 2 Camera body 3 Interchangeable lenses 4 Mounting section 10, 10b, 10g pixels (R pixel, G pixel, B pixel) 11 First AF pixel 11a, 11b Photoelectric conversion unit 12 Second AF pixel 12a, 12b Transfer section 13 Light shielding section 15 Floating Diffusion (FD) 16 Reset section 17 Amplification section 18 First Selection Section 19 Second Selection Section 20 Dashed Line 21 Body control unit 22 Image sensor 22a Imaging surface 23 Recording Department 24 Display section 25 Control section 26 Gyro sensor 30 Vertical control section 31 Photographing optical system 31a Zoom lens 31b Focus lens 32 Lens control unit 40, 40a, 40b Readout section 100 pixels 101 First pixel group 102, 102a, 102b second pixel group 201 Body side mount 202 Body side connection part 211 Image processing section 212 Focus detection unit 301 Lens mount 302 Lens side connection part

Claims

1. a first pixel that outputs a signal used for image generation based on the photoelectrically converted charge; a second pixel that outputs a signal used for focus detection based on the photoelectrically converted charge; an imaging element comprising: a control unit that performs a first control to control an exposure time of the second pixel based on the first period when an exposure time of the first pixel is a first period; and a second control to control the exposure time of the first pixel based on the second period when a predetermined imaging condition is satisfied and the exposure time of the second pixel is a second period longer than the first period.

2. 2. The imaging device according to claim 1, The control unit controls the exposure time of the second pixel to be equal to or shorter than the first period in the first control, and controls the exposure time of the first pixel to be the second period in the second control.

3. 3. The image sensor according to claim 1, an output unit that outputs image data based on a signal output from the first pixel; When the predetermined imaging condition is satisfied, the control unit controls a frame rate at which image data is output from the output unit to a second frame rate lower than a first frame rate.

4. Another word for lowering the frame rate. The imaging device according to any one of claims 1 to 3, When the predetermined imaging condition is satisfied, the control unit makes the exposure time of the second pixel in the second control longer than the exposure time of the second pixel in the first control.

5. The imaging device according to any one of claims 1 to 4, The predetermined imaging condition includes that the luminance of the subject and / or within the angle of view is equal to or lower than a predetermined luminance value.

6. The imaging device according to any one of claims 1 to 5, The predetermined imaging condition includes that the moving speed of the subject is equal to or lower than a predetermined speed.

7. The imaging device according to any one of claims 1 to 6, The predetermined imaging condition includes a frame rate being equal to or lower than a predetermined value.

8. The imaging device according to any one of claims 1 to 7, The predetermined imaging condition includes a shutter speed being equal to or greater than a predetermined value.

9. The imaging element according to any one of claims 1 to 8, a generation unit that generates image data based on the data output from the imaging element.

10. 10. The imaging device according to claim 9, The predetermined imaging condition includes that the imaging device motion is equal to or less than a predetermined value.

11. The imaging device according to any one of claims 1 to 8, The control unit is When a mode for extending the low luminance limit of focus detection is on, a frame rate for reading out signals from the plurality of pixels is reduced to a third frame rate; an imaging element that reduces the frame rate to the third frame rate or lower when the mode is off and the predetermined imaging condition is satisfied;

Images