JP2015216519A - Imaging device, and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mechanism for acquiring pixel signals for focus detection over a wide area, without degrading the spatial frequency information, when mixing and decimating the pixel signals for imaging under an environment where the imaging frame speed is limited.SOLUTION: An imaging device includes an imaging element consisting of a plurality of pixels capable of outputting a pair of signals, by performing photoelectric conversion of a light flux passed through different pupil regions of a photographic optical system including a focus lens. The focus lens is driven depending on a defocus amount calculated based on the phase difference information from the pixels arranged in a focus detection region A set by user operation, or the like, and the focus detection region A set for every frame is switched sequentially to other regions B, C and changed.

Description

  The present invention relates to a focus detection technique based on a phase difference detection method using an imaging element in an imaging apparatus such as a digital camera or a digital video camera.

  Imaging devices such as digital cameras and digital video cameras are required to have high resolution, and the number of pixels in the imaging device is increasing. By the way, even in such a high-resolution imaging apparatus, when high-speed readout is required, such as monitoring before moving image capturing or still image capturing, or when low resolution is sufficient, it is common to capture with a low number of pixels. is there.

  In order to draw a subject and obtain a near-ideal subject image, we want to capture the desired number of pixels at the desired frame rate (frame rate), but in reality the relationship between the number of pixels and the frame rate is There is a limit. If the frame rate is not limited, the pixel readout time, which is the time required to read out the image signal from the pixels in the imaging area, can be ignored, so that the signals of all pixels are read out from the effective pixels of the image sensor. Is possible. On the other hand, when the frame rate is limited, since the pixel readout time cannot be ignored, there is a possibility that the signal readout of all the pixels cannot be performed with respect to the effective pixels of the image sensor. This problem is particularly noticeable in an imaging system in which the readout time of pixel signals per frame is closely packed, such as high-speed frame imaging in a high-pixel imaging device.

  For this reason, in imaging that requires a high-speed frame, readout is performed by performing both pixel signal decimation, pixel signal decimation, and mixing (addition, addition averaging, etc.).

  2. Description of the Related Art Conventionally, for example, there has been disclosed an imaging apparatus that performs readout by thinning and mixing the same color in units of 4 × 4 pixels (Patent Document 1). In addition, an imaging apparatus is disclosed in which a plurality of pixel signals are mixed so that the spatial arrangement of each color before mixing and the spatial arrangement of each color after mixing are the same, with 4 × 4 pixels as one group. (Patent Document 2).

  On the other hand, a TTL phase difference detection method is known as an AF (autofocus) method for an imaging apparatus. In the TTL phase difference detection method, a part of a subject light beam from the imaging optical system is divided into two, and a shift amount (phase difference) between two images formed by the divided subject light beam is obtained. Based on this phase difference, the defocus amount indicating the focus state of the imaging optical system is calculated, and the drive amount of the focus lens necessary for obtaining the in-focus state by bringing the calculated defocus amount close to zero is calculated. To do.

  An image pickup apparatus that performs such TTL phase difference detection by arranging focus detection pixels on an image pickup element for acquiring a subject image without providing a dedicated light receiving sensor for photoelectrically converting the two images is proposed. Has been.

  For example, there has been proposed an imaging apparatus configured such that a part of pixels of a photoelectric conversion pixel group receives a light beam that passes through a specific region of a pupil of an imaging lens (Patent Document 3). In this proposal, a part of the photoelectric conversion pixel group is used as a focus detection pixel, and the imaging lens is based on the phase difference between the first image signal and the second image signal obtained from the output of the focus detection pixel. Detect the focus state.

  In addition, a technique has been proposed in which pixel signals are read out precisely in the attention area during AF, and pixels outside the attention area are thinned out to read out pixel signals corresponding to the frame rate (Patent Document 4).

Japanese Patent Application Laid-Open No. 09-247689 JP 2001-036920 A JP 2000-156823 A JP 2007-174149 A

  However, in Patent Documents 1, 2, and 4, the spatial frequency information is lowered due to pixel thinning and mixed readout. In this case, in order to avoid a decrease in spatial frequency information, it is only necessary to read out the focus detection pixel signal finely. However, when the frame speed of a moving image or the like is limited, the pixel readout time is limited. In the case of fine readout, only focus detection pixels in a part of the region can be read out.

  On the other hand, in Patent Document 3, in the thinning readout mode in which low-resolution imaging is performed using a high-resolution imaging device, the pixel signal read from the imaging device does not include a focus detection pixel signal. There is a problem that focus detection cannot be performed during imaging.

  Therefore, the present invention provides a wide range of focus detection pixel signals over a wide area without reducing spatial frequency information when mixing and thinning image pickup pixel signals in an environment where the imaging frame speed is limited. The purpose is to provide a mechanism to acquire the

  In order to achieve the above object, the technical feature of the present invention is that a plurality of light beams that can be photoelectrically converted and output a pair of signals after passing through different pupil regions of a photographing optical system including a focus lens. A control method executed by an imaging device including an imaging device composed of pixels and a driving unit that drives the focus lens, wherein the phase difference calculates a defocus amount based on phase difference information acquired from the pair of signals Obtained from a detection step, a setting step for setting a readout region as a focus detection region for a subject image formed on the image sensor, and a signal read from a pixel arranged in the readout region set in the setting step A control step for controlling the focus lens to be driven according to the defocus amount calculated based on the phase difference information; Characterized in that it comprises a changing step of changing the read area set by said setting step for each chromatography beam sequentially switches to other areas of the subject image, a.

  Further, as another technical feature, each of the pixel units has a plurality of photoelectric conversion units, an image pickup device that outputs a focus detection signal and an image generation signal from the photoelectric conversion units, and a driving unit that drives the focus lens A phase difference detection step of calculating a defocus amount based on phase difference information acquired from the pair of signals, and a focus on a subject image formed on the image sensor A setting step for setting a readout region as a detection region, and the defocus amount calculated based on phase difference information acquired from a signal read from a pixel arranged in the readout region set by the setting step. The control step for controlling the focus lens to be driven, and the reading set in the setting step for each frame Characterized by comprising a changing step of changing sequentially switching the frequency to other areas of the subject image, a.

  According to the present invention, when mixing and thinning out pixel signals for imaging in an environment where the imaging frame speed is limited, the pixel signals for focus detection are spread over a wide area without reducing spatial frequency information. Can be obtained.

1 is a schematic block diagram of a digital camera that is an example of an embodiment of an imaging apparatus of the present invention. (A) is a top view of a 2 * 2 imaging pixel, (b) is the sectional view on the AA line of (a). (A) is a figure showing the periphery row | line of the pixel for a focus detection for dividing a pupil area | region to the horizontal direction (lateral direction) of an imaging lens, (b) is the sectional view on the AA line of (a). It is a figure which shows the whole arrangement | positioning of 10x12 pixels. It is a figure explaining the thinning-out reading in a perpendicular direction. (A) is a figure explaining the horizontal 3 pixel addition reading of the R / G row in a horizontal direction, (b) is a figure explaining the horizontal 3 pixel addition reading of the G / B row in a horizontal direction. (A) is a schematic diagram of a pixel arrangement at the time of reading all pixels, and (b) is a schematic diagram of a pixel arrangement at the time of moving image capturing operation. It is a schematic diagram of pixel arrangement | positioning at the time of a moving image imaging operation. FIG. 10 is a timing chart showing a focus detection area switching timing when finely reading focus detection pixels in a moving image capturing operation. It is a flowchart figure explaining the operation example at the time of the moving image drive of the digital camera shown in FIG. It is a flowchart figure explaining operation | movement of step S1016 of FIG. It is a pixel arrangement | positioning figure of the image pick-up element which concerns on other embodiment. It is the schematic diagram which showed the relationship between the light beam which emerges from the exit pupil of an imaging optical system, and a pixel. It is a figure which illustrates the whole structure of an image sensor. It is a figure which shows the circuit structural example of 1 pixel of an image pick-up element. It is a figure which shows the read-out circuit structure of each row | line | column of an image pick-up element. It is a timing chart which shows read-out operation of one line of an image sensor.

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

  FIG. 1 is a schematic block diagram of a digital camera which is an example of an embodiment of an imaging apparatus of the present invention.

  The digital camera of this embodiment shown in FIG. 1 includes a lens barrel 101, an image sensor 102, a drive circuit 103, a signal processing unit 104, a compression / decompression unit 105, a phase difference detection unit 106, a control unit 107, a light emitting unit 108, and an operation. Unit 109, image display unit 110, and image recording unit 111.

  The lens barrel 101 includes a photographing optical system for forming an image of a light beam from a subject on the image sensor 102, an AF mechanism, a zoom drive mechanism, a mechanical shutter mechanism, a diaphragm mechanism, and the like constituting the optical mechanism unit 1011. Yes. The optical mechanism unit 1011 is driven by the drive circuit 103 based on a control signal from the control unit 107.

  As the image pickup element 102, an XY readout type CMOS image sensor configured by a pixel unit having an image pickup pixel group and a focus detection pixel group and an AD converter (not shown) is used. The imaging element 102 performs an imaging operation such as exposure, signal readout, and reset by the drive circuit 103 that operates according to an instruction from the control unit 107, and outputs a corresponding imaging signal.

  The signal processing unit 104 performs signal processing such as white balance adjustment processing, color correction processing, and AE processing on the image signal output from the image sensor 102 according to an instruction from the control unit 107.

  The compression / decompression unit 105 performs compression encoding processing on the image signal output from the signal processing unit 104 in a predetermined still image data format such as the JPEG method, according to an instruction from the control unit 107. The compression / decompression unit 105 performs decompression / decoding processing on the encoded data of the still image supplied from the control unit 107. Note that the compression / decompression unit 105 may be configured to be able to execute a compression encoding / decompression decoding process of a moving image by an MPEG method or the like.

  The phase difference detection unit 106 obtains phase difference information from the focus detection pixels arranged in the pixel portion of the image sensor 102 via the signal processing unit 104, and defocuss indicating the focus state of the imaging optical system from the phase difference information. Calculate the amount. Then, from the defocus amount calculated by the phase difference detection unit 106, the control unit 107 calculates the drive amount of the focus lens necessary for obtaining the in-focus state, and sends a control signal to the drive circuit 103. The drive circuit 103 drives the AF mechanism of the optical mechanism unit 1011 according to an instruction from the control unit 107 and moves the focus lens to a desired position.

  The control unit 107 is a microcomputer including, for example, a CPU, a ROM, a RAM, and the like. The control unit 107 controls the entire camera by developing a control program stored in the ROM or the like on the RAM and executing the program on the CPU. .

  The light emitting unit 108 is a device that irradiates light to the subject when the exposure value of the subject is determined to be lower than a predetermined value by the AE processing in the signal processing unit 104, and includes a strobe device using a xenon tube, An LED light emitting device or the like is used.

  The operation unit 109 includes, for example, a lever and a dial in addition to various operation buttons and keys such as a release button, and outputs a control signal corresponding to an input operation by the user to the control unit 107.

  The image display unit 110 includes a display device such as an LCD and an interface circuit of the display device. The image display unit 110 generates an image signal to be displayed on the display device from the image signal supplied from the control unit 107, and generates the generated signal. Supply to a display device to display an image.

  The image recording unit 111 includes, for example, a portable semiconductor memory, an optical disk, and an HDD, and receives and stores the image data file encoded by the compression / decompression unit 105 from the control unit 107. Further, the image recording unit 111 reads designated data based on an instruction from the control unit 107 and outputs the read data to the control unit 107.

  Next, with reference to FIGS. 2 and 3, the structure of the imaging pixels for image generation in the imaging device 102 and the focus detection pixels for focus detection by the phase difference detection method will be described. In the present embodiment, out of 4 pixels of 2 × 2, pixels having G (green) spectral sensitivity are arranged in two diagonal pixels, and R (red) and B (blue) spectroscopy are arranged in the other two pixels. A Bayer array in which pixels having sensitivity are arranged is employed. Then, focus detection pixels having a structure to be described later are distributed and arranged in a predetermined rule between the Bayer arrays.

  FIG. 2A is a plan view of a 2 × 2 imaging pixel. In the Bayer array, G pixels are arranged in the diagonal direction, R and B pixels are arranged in the other two pixels, and this 2-row × 2-column structure is repeatedly arranged.

  FIG. 2B is a cross-sectional view taken along line AA in FIG. In FIG. 2B, ML is an on-chip microlens disposed on the forefront of each pixel, CFR is an R (red) color filter, and CFG is a G (green) color filter. PD schematically shows the photoelectric conversion unit of the image sensor 102, and CL is a wiring layer for forming signal lines for transmitting various signals of the CMOS sensor. TL schematically shows a photographing optical system.

  Here, the on-chip microlens ML of the imaging pixel and the photoelectric conversion unit PD are configured to capture the subject light flux that has passed through the photographing optical system TL as effectively as possible. In other words, the exit pupil EP of the photographing optical system TL and the photoelectric conversion unit PD are in a conjugate relationship by the on-chip microlens ML, and the effective area of the photoelectric conversion unit PD is designed to be large. In FIG. 2B, the incident light beam of the R pixel has been described, but the G pixel and the B pixel have the same structure. Accordingly, the exit pupil EP corresponding to each of the RGB pixels for imaging has a large diameter, and the S / N of the image signal is improved by efficiently capturing the light flux from the subject.

  FIG. 3A is a diagram illustrating peripheral rows of focus detection pixels for dividing the pupil region in the horizontal direction (lateral direction) of the photographing lens. In FIG. 3A, a part of the R and G pixel rows are arranged as focus detection pixels SHA and SHB.

  FIG.3 (b) is the sectional view on the AA line of Fig.3 (a). In FIG. 3B, the on-chip microlens ML and the photoelectric conversion unit PD have the same structure as the imaging pixel shown in FIG. In the present embodiment, since the signals of the focus detection pixels SHA and SHB are not used for image generation, a transparent film CFW (white) (or CFG) is disposed instead of the color separation color filter. Further, in order to perform pupil division by the image sensor 102, the opening of the wiring layer CL is arranged in one direction with respect to the center line of the on-chip microlens ML.

  Specifically, since the opening OPHA of the pixel SHA is arranged to be biased to the right side of the drawing, the light beam that has passed through the exit pupil EPHA on the left side of the photographing lens TL is received. Similarly, since the opening OPHB of the pixel SHB is arranged so as to be biased to the left side of the drawing, the light beam that has passed through the right exit pupil EPHB of the photographic lens TL is received.

  Then, the pixels SHA are regularly arranged in the horizontal direction, the subject image acquired by these pixel groups is set as an A image, the pixels SHB are also regularly arranged in the horizontal direction, and the subject images acquired by these pixel groups are Let it be B image. Here, by detecting the relative position between the A image and the B image (a pair of signals), it is possible to detect the focus shift amount (defocus amount) of the subject image.

  Further, when it is desired to detect the amount of defocus in the vertical direction (vertical direction), the pixel SHA and its opening OPHA are arranged so as to be biased upward, and the pixel SHB and its opening OPHA are so arranged as to be biased downward. Good. In this case, the opening shapes of the openings OPHA and OPHB are rotated by 90 degrees.

  Next, the relationship between vertical thinning readout and horizontal mixed readout in the pixel arrangement will be described with reference to FIGS.

  FIG. 4 is a diagram showing an overall arrangement of 10 × 12 pixels. In FIG. 4, imaging pixels R, G, and B indicated by hatching, shading, and the like indicate pixels from which signals are read out. The focus detection SHA and SHB are pixels to which signals are output independently.

  FIG. 5 is a diagram for explaining thinning readout in the vertical direction. In FIG. 5, thinning readout is performed at intervals of 3 pixels (rows 0, 3, 6, 9, and 12 in the figure), and other rows are not read, so that data compression and frame rate can be performed in a moving image capturing operation or the like. Speed up.

  6A is a diagram for explaining horizontal three-pixel mixed readout of the R / G row in the horizontal direction, and FIG. 6B is a diagram for explaining horizontal three-pixel mixed readout of the G / B row in the horizontal direction. In FIG. 6, pixel signals are read out in a combination of column numbers 0-2-4, 3-5-7, and 6-8-10, and then mixed (synthesized). In addition, regarding the focus detection pixels SHA and SHB, even if the imaging pixel group is operating in the horizontal mixed readout mode (first readout mode), mixed readout is performed according to the control signal of the control unit 107 or unmixed. It is possible to switch whether to read finely for each pixel by reading.

  7 and 8 schematically show the pixel arrangement after all-pixel reading and horizontal mixing / vertical thinning-out reading described with reference to FIGS.

  FIG. 7A is a schematic diagram of a pixel arrangement at the time of reading all pixels. Since all pixels are read out, the signals of the imaging pixels and focus detection pixels are read out in units of single pixels, and the spatial frequency information does not decrease with respect to the entire angle of view.

  FIG. 7B, FIG. 8A, and FIG. 8B are schematic diagrams of pixel arrangement during the moving image capturing operation. As described above, the amount of data per frame can be compressed by performing the horizontal mixing and vertical thinning readout operation, so that the data amount is smaller than the data amount for all pixel readout. At this time, three pixels of the same color are mixed in the horizontal direction by the mixing operation.

  As for the focus detection pixel, as a result of selecting either horizontal mixed readout or single pixel readout by the control unit 107, three focus detection pixels SHA or SHB are mixed, or single pixel readout is performed Is output as one of If the focus detection pixels are output in a horizontally mixed state, phase difference information can be obtained at all angles of view in the horizontal direction, but the signal is read out in a horizontally mixed state, so the filter effect As a result, the spatial frequency information is lowered.

  On the other hand, when the signal from the focus detection pixel is read out in units of pixels during the moving image capturing operation, the number of pixels that can be read out per frame is determined by the restriction of the frame rate. That is, the number of pixels is determined by the time that can be read in one frame. For this reason, the range in which the focus detection pixels are read out is determined in the range of the region A, the region B, and the region C in the entire pixel arrangement in FIG.

  Therefore, when it is necessary to read out the focus detection pixels precisely during the moving image capturing operation, as shown in FIGS. 7B, 8A, and 8B, the row of the focus detection pixels is The focus detection pixels in the area A to C in all the pixels in FIG. 7A are read out. In the present embodiment, the horizontal division region of the focus detection pixels is described as three regions, and the reading end position and the reading start position are adjacent to each other. However, the present invention is not limited to this. For example, it is also possible to increase the number of AF detection frames by changing the reading start position and the reading end position of adjacent areas alternately to cope with an increase in the number of AF detection frames.

  FIG. 9 is a timing chart showing the switching timing of the focus detection area when the focus detection pixels are read out finely in the moving image capturing operation.

  In the example of FIG. 9, a case will be described in which the AF detection frame is set in the area A in the entire pixel arrangement of the subject image by a user operation on the control unit 107 or the operation unit 109.

  First, the imaging operation is started in synchronization with the imaging synchronization signal, and readout of the imaging pixels and focus detection pixels starts (period T60). At this time, the focus detection pixels read out only the area A and do not read out the areas B and C of other areas.

  Next, when reading of one frame is completed and reading of the next frame is started, the reading area of the focus detection pixels is switched to the area B (period T61). In the period T61, the phase difference detection unit 106 calculates the defocus amount from the signal of the focus detection pixel in the region A obtained by the previous frame imaging operation at the same time.

  After the defocus amount in the area A is calculated, the obtained defocus amount is sent to the control unit 107. The control unit 107 sends a control signal of the focus lens movement amount according to the defocus amount to the drive circuit 103, and drives the optical mechanism unit 1011 by the drive circuit 103 (period T62).

  In a period T63 in which reading of frames is started one after another, the reading area of the focus detection pixels is switched to the area C. In the period T63, as in the case of the period T61, the phase difference detection unit 106 calculates the defocus amount from the focus detection pixel signal of the region B obtained in the previous frame. From the calculated defocus amount, A control signal for driving the optical mechanism unit 1011 is not generated. However, the defocus amount obtained from the region B is stored in the memory or the like in the control unit 107 as the defocus amount of the region B.

  Similarly, in the period T64, the phase difference detection unit 106 calculates the defocus amount from the signal of the focus detection pixel in the focus detection area C acquired in the period T63 to T64 which is the previous frame. The control unit 107 stores the calculated defocus amount in the memory as the defocus amount of the region C, and does not generate a control signal to the optical mechanism unit 1011. In the imaging operation starting from the period T64, the focus detection pixel readout area is returned to the area A.

  Next, in the period T65 to the period T66, similarly to the period T61 to the period T62, the defocus amount is obtained through the phase difference detection unit 106 from the focus detection pixel signal in the focus detection area A obtained in the period T64 to the period T65. calculate. The control unit 107 sends a control signal for the focus lens movement amount according to the calculated defocus amount to the drive circuit 103, and causes the optical mechanism unit 1011 to be driven by the drive circuit 103.

  By controlling in this way, the focus detection pixel readout area for each frame as an imaging operation is repeated in order of A → B → C → A → B. Can be obtained in

  Next, an example of operation of the digital camera shown in FIG. 1 when driving a moving image will be described with reference to FIGS. Each process in FIGS. 10 and 11 is executed by a CPU or the like by developing a control program stored in the ROM or the like of the control unit 107 in the RAM.

  In FIG. 10, in step S1001, the control unit 107 sets an AF detection frame according to the user operation on the operation unit 109 or the processing of subject recognition information such as face recognition after the power is turned on and in the standby state. The process proceeds to step S1002.

  In step S1002, the control unit 107 switches and sets the drive mode of the image sensor 102 to a fine readout mode (second readout mode) in which readout of focus detection pixels is read out pixel by pixel, and the process proceeds to step S1003.

  In step S1003, the control unit 107 selects a focus detection pixel (region A in FIG. 7A) corresponding to the same region as the AF detection frame set in step S1001, and starts reading pixel by pixel. The process proceeds to step S1004.

  In step S1004, when the control unit 107 finishes reading the focus detection pixels in the area A of the AF detection frame selected in step S1003 and completes imaging for one frame, the control unit 107 proceeds to step S1005.

  In step S1005, the control unit 107 starts the imaging operation for the next frame, and the focus detection pixels (FIG. 7A) in the AF detection frame outside region 1 different from the AF detection frame region read out in the previous frame. Reading of the area B, the period T61 in FIG. 9 is started.

  In step S1006, the control unit 107 calculates the defocus amount in the phase difference detection unit 106 from the focus detection pixel signal in the AF detection frame area read up to step S1004 simultaneously with the start of imaging in step S1005. Then, the process proceeds to step S1007.

  In step S1007, the control unit 107 controls the drive circuit 103 according to the defocus amount calculated in step S1006 to drive the focus lens of the optical mechanism unit 1011. The process proceeds to step S1008.

  In step S1008, when the imaging frame for reading the focus detection pixels in the AF detection frame outside region 1 is finished (period T63 in FIG. 9), the control unit 107 proceeds to step S1009.

  In step S1009, the control unit 107 starts reading the focus detection pixels in the AF detection frame outside region 2 different from the focus detection pixel readout regions started in steps S1003 and S1005 (region in FIG. 7A). C, period T63 in FIG. 9).

  In step S1010, the control unit 107 calculates the defocus amount in the phase difference detection unit 106 from the focus detection pixel signal in the AF detection frame outside region 1 read out until step S1008 simultaneously with the start of imaging in step S1009. Then, the process proceeds to step S1011.

  In step S1011, the control unit 107 records the defocus amount calculated in step S1010 in the memory, and proceeds to step S1012. That is, here, the control unit 107 does not control the optical mechanism unit 1011 based on the defocus amount.

  In step S1012, the control unit 107 proceeds to step S1013 when the imaging frame for reading the focus detection pixels in the AF detection frame outside region 2 is completed (period T64 in FIG. 9).

  In step S1013, the control unit 107 calculates the defocus amount in the phase difference detection unit 106 from the focus detection pixel signal in the AF detection frame outside area 2 read up to step S1012, and the process proceeds to step S1014.

  In step S1014, the control unit 107 records the defocus amount calculated in step S1013 in the memory, and proceeds to step S1015. Here, as in step S1011, the control unit 107 does not control the optical mechanism unit 1011.

  In step S1015, the control unit 107 determines whether or not to continue reading the focus detection pixels. If the reading is to be ended, the control unit 107 sets the camera in a standby state. If the reading is to be continued, the control unit 107 proceeds to step S1016.

  In step S1016, the control unit 107 determines whether or not to change the AF detection frame area setting. If it is necessary to switch the AF detection frame region setting, the control unit 107 returns to step S1001. If the AF detection frame region setting in this state is acceptable, the control unit 107 returns to step S1002 and reads out the focus detection pixels. And the focus operation is continued.

  Next, the operation in step S1016 in FIG. 10 will be described in detail with reference to FIG.

  In step S1101, if it is determined in step S1015 in FIG. 10 that the readout of the focus detection pixels is continued, the control unit 107 determines whether or not the AF detection frame area setting has been changed by a user operation on the operation unit 109. Determine.

  If the AF detection frame region setting is changed by a user operation, the control unit 107 returns to step S1001 in FIG. 10 and changes the AF detection frame region setting. Although the case where the AF detection frame region setting is changed by a user operation is illustrated here, the AF detection frame region setting may be changed by subject recognition information such as face detection. On the other hand, if the AF detection frame area setting has not been changed by a user operation on the operation unit 109, the control unit 107 proceeds to step S1102.

  In step S1102, the control unit 107 acquires the image contrast information Ca of the AF detection frame from the image data obtained at the current time, and proceeds to step S1103. Here, the current focus state in the AF detection frame is confirmed by obtaining contrast information. However, the current focus state may be confirmed based on phase difference information by focus detection pixels.

  In step S1103, the control unit 107 determines whether or not the contrast information Ca obtained in step S1102 is less than or equal to the contrast threshold D set to be less than or equal to the focus error threshold.

  If the contrast information Ca is equal to or less than the contrast threshold D, the control unit 107 returns to step S1002 in FIG. 10 to continue the fine readout mode in the current AF detection frame area and exceed the contrast threshold D. Advances to step S1104.

  In step S1104, the control unit 107 determines whether or not the defocus amount information Def_AF1 of the AF detection frame outside area 1 recorded in the memory in step S1011 in FIG. 10 is equal to or less than a threshold P set to be equal to or less than the focus error threshold. judge.

  The control unit 107 proceeds to step S1105 when the defocus amount information Def_AF1 of the AF detection frame outside region 1 exceeds the threshold P, and proceeds to step S1108 when the defocus amount information Def_AF1 is less than or equal to the threshold P.

  In step S1105, the control unit 107 determines whether or not the defocus amount information Def_AF2 of the AF detection out-of-frame area 2 recorded in the memory in step S1014 is equal to or less than a threshold P set to be equal to or less than the focus error threshold.

  Then, when the defocus amount information Def_AF2 of the AF detection frame outside region 2 exceeds the threshold value P, the control unit 107 proceeds to step S1106 and enters a standby state because defocus information cannot be obtained in all regions. . In the present embodiment, the case where the defocus information is not obtained in all the regions is exemplified as a standby state. However, the focus operation may be continued until the defocus information is obtained. On the other hand, when the defocus amount information Def_AF2 of the AF detection frame outside region 2 is equal to or less than the threshold value P, the control unit 107 proceeds to step S1107.

  In step S1107, the control unit 107 resets the AF detection frame area setting to the area outside the AF detection frame area 2 and returns to step S1001 in FIG.

  On the other hand, in step S1108, as in step S1105, the control unit 107 sets the threshold value P set so that the defocus amount information Def_AF2 of the AF detection frame outside area 2 recorded in the memory in step S1014 is equal to or less than the focus error threshold value. It is determined whether or not.

  Then, the control unit 107 proceeds to step S1109 when the defocus amount information Def_AF2 of the AF detection out-of-frame area 2 exceeds the threshold P, and proceeds to step S1110 when the defocus amount information Def_AF2 is less than or equal to the threshold P.

  In step S1109, the control unit 107 sets the AF detection frame to the same area as the AF detection frame outside region 1 because the AF detection frame outside region 1 is closer to the in-focus state than the current AF detection frame and the AF detection frame outside region 2. The setting is reset, and the process returns to step S1001 in FIG.

  On the other hand, in step S1110, the current AF detection frame is out of focus, and the AF detection frame area 1 and the AF detection frame area 2 are in focus to some extent. Therefore, the control unit 107 determines whether or not the defocus amount Def_AF1 of the AF detection frame outside region 1 exceeds the defocus amount Def_AF2 of the AF detection frame outside region 2. The control unit 107 proceeds to step S1111 when Def_AF1 exceeds Def_AF2, and proceeds to step S1112 when Def_AF1 is equal to or less than Def_AF2.

  In step S1111, the control unit 107 resets the AF detection frame to the area outside the AF detection frame 2 and returns to step S1001 in FIG.

  In step S1112, the control unit 107 resets the AF detection frame to the area outside the AF detection frame 1 and returns to step S1001 in FIG.

  As described above, in the present embodiment, in the environment where the imaging frame speed is limited such as when driving a moving image, the fine readout area for readout of the focus detection pixels is sequentially switched for each imaging frame, so that the fineness of the entire area is determined. Defocus amount information can be obtained. This enables focus detection pixel signals to be acquired over the entire area without degrading spatial frequency information when mixing and thinning out pixel signals for imaging in an environment where imaging frame speed is limited. can do.

  In addition, this invention is not limited to what was illustrated to the said embodiment, In the range which does not deviate from the summary of this invention, it can change suitably.

  For example, in the above embodiment, the case where the focus detection pixel readout region is sequentially switched from the left to the right is illustrated, but the present invention is not limited to this, and the region readout order may be arbitrarily switched.

  In the above embodiment, the phase difference AF method has been described in which the phase difference of the image signal is detected using the output signal of the focus detection pixel, and the focus adjustment is performed. However, for example, there may be a case where an imaging element having a pixel composed of a plurality of photoelectric conversion units for dividing one microlens and an exit pupil is used. For example, FIG. 12 shows a schematic diagram showing a pixel array of the image sensor 102 in this case.

  The unit pixel units 300 are arranged in a matrix, and R (Red) / G (Green) / B (Blue) color filters are arranged in a Bayer array. In each unit pixel unit 300, a sub pixel a and a sub pixel b are arranged. In the drawing, PD 401a is a first photoelectric conversion unit constituting subpixel a, and PD 401b is a second photoelectric conversion unit constituting subpixel b. Each signal of the sub-pixel a and the sub-pixel b is used for focus detection (focus detection signal). Further, an a / b mixed signal (hereinafter simply referred to as a mixed signal) obtained by mixing the signal of the sub-pixel a and the signal of the sub-pixel b is used as an image generation signal for generating image data.

  FIG. 13 is a schematic diagram for explaining the relationship between the light beam emitted from the exit pupil 203 of the photographing optical system and the unit pixel unit 300. The unit pixel unit 300 includes a PD 401a and a PD 401b. The color filter 201 and the micro lens 202 are each formed on the unit pixel unit 300.

  The center of the light beam emitted from the exit pupil 203 is indicated by the optical axis 204 for the pixel portion having the microlens 202. The light that has passed through the exit pupil 203 enters the unit pixel unit 300 with the optical axis 204 as the center. Regions 205 and 206 represent partial regions of the exit pupil 203 of the photographing optical system, respectively. As shown in FIG. 13, the light beam passing through the region 205 is received by the PD 401 a (subpixel a) through the microlens 202. The light beam passing through the pupil region 206 is received by the PD 401b (subpixel b) through the microlens 202. Accordingly, each of the sub-pixel a and the sub-pixel b receives light that passes through different areas of the exit pupil 203 of the photographing optical system. Therefore, the phase difference type focus detection can be performed by comparing the output signals of the sub-pixel a and the sub-pixel b.

  Next, the configuration of the image sensor 102 will be described with reference to FIGS. FIG. 14 is a diagram illustrating an example of the overall configuration of the image sensor 102. FIG. 15 is a circuit diagram showing a configuration of the unit pixel unit 300. FIG. 16 is a circuit diagram showing a configuration of the column common readout circuit 303.

  In the pixel area PA shown in FIG. 14, a large number of unit pixel portions 300 (see p11 to pkn) are arranged in a matrix. The configuration of the unit pixel unit 300 will be described with reference to FIG.

  The PDs 401a and 401b photoelectrically convert incident light and accumulate charges corresponding to the exposure amount. The transfer gates 402a and 402b are turned on by setting the signals txa and txb to the high level, respectively. As a result, the charges accumulated in the PDs 401 a and 401 b are transferred to the FD (floating diffusion) unit 403. The FD unit 403 is connected to the gate of a floating diffusion amplifier 404 (hereinafter referred to as FD amplifier). The charge amount transferred from the PDs 401a and 401b by the FD amplifier 404 is converted into a voltage amount. The FD reset switch 405 resets the FD unit 403 by setting the signal res to a high level. When resetting the charges of the PDs 401a and 401b, the signal res and the signals txa and txb are simultaneously set to the high level. When the transfer gates 402 a and 402 b and the FD reset switch 405 are turned on, the PDs 401 a and 401 b are reset via the FD unit 403. In the pixel selection switch 406, the signal sel is set to a high level, so that the pixel signal converted into a voltage by the FD amplifier 404 is output from the output terminal vout of the unit pixel unit 300.

  The vertical scanning circuit 301 in FIG. 14 supplies gate control signals (res, txa, txb, sel) to the transistors of the unit pixel unit 300. These signals are common to each row. The output terminal vout of each unit pixel unit 300 is connected to the column common readout circuit 303 via the vertical output line 302 for each column. The configuration of the column common readout circuit 303 will be described with reference to FIG.

  The vertical output line 302 is provided for each column, and the output terminal vout of the unit pixel unit 300 for one column is connected thereto. A current source 304 is connected to the vertical output line 302. This current source 304 and the FD amplifier 404 of the unit pixel unit 300 connected to the vertical output line 302 constitute a source follower circuit.

  The clamp capacitor (C1) 501 is connected to the inverting input terminal of the operational amplifier 503. The feedback capacitor (C2) 502 is connected to the output terminal and the inverting input terminal of the operational amplifier 503. A reference power supply Vref is connected to the non-inverting input terminal of the operational amplifier 503. The switch 504 is a transistor for short-circuiting both ends of the feedback capacitor C2, and is controlled by a signal cfs. The transfer switches 505 to 508 are transistors for transferring signals read from the unit pixel unit 300 to the signal holding capacitors 509 to 512, respectively. The pixel signal Sa of the sub-pixel a is stored in the first S signal holding capacitor 509 and the signal of the sub-pixel a and the signal of the sub-pixel b are added to the second S signal holding capacitor 511 by a read operation described later. The added signal Sab is stored. In addition, the noise signal N of the unit pixel unit 300 is stored in the first N signal holding capacitor 510 and the second N signal holding capacitor 512, respectively. Each of the signal holding capacitors 509 to 512 is connected to output terminals vsa, vna, vsb, and vnb of the column common readout circuit 303, respectively.

  Horizontal transfer switches 305 and 306 are connected to the output terminals vsa and vna of the column common readout circuit 303 in FIG. The horizontal transfer switches 305 and 306 are controlled by an output signal ha * (* represents an arbitrary column number) of the horizontal scanning circuit 311. When the signal ha * becomes the high level, the signals of the first S signal holding capacitor 509 and the first N signal holding capacitor 510 are transferred to the horizontal output lines 309 and 310, respectively.

  Further, horizontal transfer switches 307 and 308 are connected to the output terminals vsb and vnb of the column common readout circuit 303, respectively. The horizontal transfer switches 307 and 308 are controlled by an output signal hb * (* represents an arbitrary column number) of the horizontal scanning circuit 311. When the signal hb * becomes the high level, the signals of the second S signal holding capacitor 511 and the second N signal holding capacitor 512 are transferred to the horizontal output lines 309 and 310, respectively.

  The horizontal output lines 309 and 310 are connected to the input terminals of the differential amplifier 314. The differential amplifier 314 calculates the difference between the S signal and the N signal, simultaneously applies a predetermined gain, and outputs the final output signal to the output terminal 315. The horizontal output line reset switches 312 and 313 are turned on when the signal chres becomes High level, and the horizontal output lines 309 and 310 are set to the reset voltage Vchres (reset).

  Next, the reading operation of the image sensor 102 will be described with reference to FIG. FIG. 17 is a timing chart showing the read operation of each row of the image sensor 102.

  First, by setting the signal cfs to a high level, the switch 504 in FIG. 16 is turned on, and the operational amplifier 503 is placed in a buffer state. Next, when the signal sel is set to the High level, the pixel selection switch 406 in FIG. 15 is turned ON. Thereafter, by setting the signal res to the low level, the FD reset switch 405 is turned off, and the reset of the FD unit 403 is released. Subsequently, the signal cfs is returned to the Low level, and after the switch 504 is turned OFF, the signals tna and tnb are set to the High level. As a result, the N signal is stored in the first N signal holding capacitor 510 and the second N signal holding capacitor 512 via the transfer switches 506 and 508.

  Next, when the signals tna and tnb are set to the low level, the transfer switches 506 and 508 are turned off. Thereafter, the signal tsa is set to the high level to turn on the transfer switch 505, and the signal txa is set to the high level to control the transfer gate 402a to be turned on. By this operation, the signal accumulated in the PD 401 a of the subpixel “a” is output to the vertical output line 302 via the FD amplifier 404 and the pixel selection switch 406. The signal of the vertical output line 302 is amplified by the operational amplifier 503 with a gain corresponding to the capacitance ratio between the clamp capacitor C1 and the feedback capacitor C2, and stored in the first S signal holding capacitor 509 via the transfer switch 505 (pixel). Signal Sa).

  Next, the signal txa and the signal tsa are sequentially set to a low level. Thereafter, the signal tsb is set to high level to turn on the transfer switch 507, and the signals txa and txb are set to high level to turn on the transfer gates 402a and 402b. By this operation, the signal accumulated in the PD 401b of the subpixel b is added to the signal of the subpixel a by the FD unit 403. The signal after addition is output to the vertical output line 302 via the FD amplifier 404 and the pixel selection switch 406. The signal of the vertical output line 302 is amplified by the operational amplifier 503 with a gain corresponding to the capacitance ratio between the clamp capacitor C1 and the feedback capacitor C2, and stored in the second S signal holding capacitor 511 via the transfer switch 507 (addition). Signal Sab).

  After the transfer gates 402a and 402b and the transfer switch 507 are sequentially turned OFF, when the signal res is set to the High level, the FD reset switch 405 is turned ON and the FD unit 403 is reset.

  Next, when the output ha1 of the horizontal scanning circuit 311 becomes High level, the horizontal transfer switches 305 and 306 are turned on. Each signal of the first S signal holding capacitor 509 and the first N signal holding capacitor 510 is output to the output terminal 315 via the horizontal output lines 309 and 310 and the differential amplifier 314. The horizontal scanning circuit 311 sequentially outputs the signals (image signal A) of the sub-pixels a for one row by sequentially setting the selection signals ha1, ha2,.

  When the reading of the image signal A is completed, the output hb1 of the horizontal scanning circuit 311 subsequently becomes High level. As a result, the horizontal transfer switches 307 and 308 are turned on, and the signals of the second S signal holding capacitor 511 and the second N signal holding capacitor 512 are output via the horizontal output lines 309 and 310 and the differential amplifier 314. It is output to 315. The horizontal scanning circuit 311 outputs the addition signal (image signal AB) for one row by sequentially setting the selection signals hb1, hb2,..., Hbk of each column to the high level.

  Note that the horizontal output line reset switches 312 and 313 are temporarily turned on by setting the signal chres to the high level during the period in which the signals of the respective columns are read by the signals ha1 to hak and the signals hb1 to hbk. At this time, the horizontal output lines 309 and 310 are reset to the level of the reset voltage Vchres.

  When reading a signal from such an image sensor, the signal of the image sensor 102 is sequentially read from the top line in the focus detection region. At this time, both the image signal A and the image signal AB are read from each line. Outside the focus detection area, signals from the image sensor 102 are read in order from the first line. At this time, only the image signal AB is read from each line. This is because the control of the control unit 107 stops the output of the image signal A that is unnecessary for the arithmetic processing in the image sensor 102. Power and readout time can be saved accordingly.

  Similar to the above-described embodiment, by switching the focus detection region, even in an imaging device having a plurality of photoelectric conversion units for one microlens, in an environment where the imaging frame speed is limited, such as when driving a moving image. Thus, fine defocus amount information of the entire region can be obtained.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed. It can also be realized by executing software (program) acquired via a network or various storage media on a personal computer (CPU, processor).

DESCRIPTION OF SYMBOLS 101 Lens barrel 102 Image pick-up element 103 Drive circuit 104 Signal processing part 105 Compression / decompression part 106 Phase difference detection part 107 Control part 108 Light emission part 109 Operation part 110 Image display part 111 Image recording part 1011 Optical mechanism part

Claims (8)

An imaging apparatus including an imaging device having a plurality of pixels capable of photoelectrically converting light beams that have passed through different pupil regions of a photographing optical system including a focus lens and outputting a pair of signals,
Phase difference detection means for calculating a defocus amount based on the phase difference information acquired from the pair of signals;
Setting means for setting a readout region as a focus detection region for a subject image formed on the image sensor;
Drive means for driving the focus lens in accordance with a defocus amount calculated based on phase difference information acquired from a signal read from a pixel arranged in the readout region set by the setting means;
An imaging apparatus comprising: a changing unit that sequentially switches and changes the readout area set by the setting unit for each frame to another area of the subject image.   The imaging apparatus according to claim 1, wherein the number of pixels when reading the pair of signals is determined by a time that can be read in one frame.   2. A memory for recording defocus amount information calculated by the phase difference detection unit based on phase difference information acquired from a signal of a pixel arranged in the changed other region. 2. The imaging device according to 2.   The said setting means sets the said read-out area | region based on the input operation by a user, the recognition information by a to-be-recognized means, or the said phase difference information acquired by the said phase difference detection means. The imaging device according to any one of the above. The imaging device includes a first readout mode in which an imaging pixel group for image generation and a focus detection pixel group for focus detection by a phase difference detection method are arranged, and a signal is read from the imaging pixel group. Driven in a second readout mode for reading out signals in pixel units from the focus detection pixel group;
The changing unit reads out signals of the focus detection pixels arranged in the readout area in the second readout mode in an imaging operation for each frame that reads out signals of the imaging pixel group in the first readout mode. 5. The imaging apparatus according to claim 1, wherein the readout area set by the setting unit is sequentially switched and changed to another area of the subject image for each frame. . Each of the pixel units includes a plurality of photoelectric conversion units, and includes an imaging device that outputs a focus detection signal and an image generation signal from the photoelectric conversion units,
Phase difference detection means for calculating a defocus amount based on the phase difference information acquired from the focus detection signal;
Setting means for setting a readout region as a focus detection region for a subject image formed on the image sensor;
Drive means for driving the focus lens according to the defocus amount calculated based on the phase difference information acquired from the signal read from the pixel arranged in the readout region set by the setting means;
An imaging apparatus comprising: a changing unit that sequentially switches and changes the readout area set by the setting unit for each frame to another area of the subject image. An imaging device having a plurality of pixels capable of photoelectrically converting a light beam that has passed through different pupil regions of a photographing optical system including a focus lens and outputting a pair of signals, and a drive unit that drives the focus lens A control method executed by an imaging apparatus,
A phase difference detection step of calculating a defocus amount based on the phase difference information acquired from the pair of signals;
A setting step for setting a readout region as a focus detection region for a subject image formed on the image sensor;
A control step for controlling the focus lens to be driven according to a defocus amount calculated based on phase difference information acquired from a signal read from a pixel arranged in the readout region set in the setting step;
And a changing step of sequentially switching and changing the readout area set in the setting step for each frame to another area of the subject image. Each of the pixel units includes a plurality of photoelectric conversion units, and is executed by an imaging device that includes an imaging element that outputs a focus detection signal and an image generation signal from the photoelectric conversion units, and a driving unit that drives a focus lens. A control method,
A phase difference detection step of calculating a defocus amount based on phase difference information acquired from the focus detection signal;
A setting step for setting a readout region as a focus detection region for a subject image formed on the image sensor;
A control step for controlling the focus lens to be driven according to a defocus amount calculated based on phase difference information acquired from a signal read from a pixel arranged in the readout region set in the setting step;
And a changing step of sequentially switching and changing the readout area set in the setting step for each frame to another area of the subject image.