JP2018066931A - Solid state image pickup element, control method thereof, and imaging apparatus - Google Patents

Abstract

A solid-state imaging device, a control method therefor, and an imaging apparatus capable of realizing quick and highly accurate autofocus using hybrid AF are provided. A pixel array in which a plurality of pixels are arranged in a matrix and a phase difference evaluation value for focus detection by a phase difference detection method are obtained from a phase difference detection pixel included in the plurality of pixels. A defect that occurs in the image signal acquired by the first calculation unit and the pixel array, and that is caused by including a phase difference detection pixel among a plurality of pixels. Interpolation processing unit that generates signals to compensate by interpolation using signals from pixels other than phase difference detection pixels, and contrast evaluation value for focus detection by contrast detection method is generated by interpolation by interpolation processing unit And a second calculation unit that calculates based on the image signal including the processed signal. [Selection] Figure 2-2

Description

  The present invention relates to a solid-state imaging device, a control method thereof, and an imaging apparatus.

  An imaging apparatus such as a digital camera or a video camera is equipped with an auto focus (AF) function that automatically adjusts the focus (lens focus position) of a subject.

  In order to realize quick autofocus, it is necessary to read out a focus detection signal at a high frame rate. However, when the focus detection signal is read out at a high frame rate, the amount of data transferred to the signal processing unit located at the subsequent stage of the solid-state imaging device is increased. In view of this, there has been proposed a solid-state imaging device in which an AF evaluation value detection unit for detecting an AF evaluation value is provided inside the solid-state imaging device, and the AF evaluation value detected by the AF evaluation value detection unit is output to the outside (patent). Reference 1).

Japanese Patent Laying-Open No. 2015-12487

  By the way, as the AF method, there is known a hybrid AF in which AF by a phase difference detection method, that is, phase difference AF, and AF by a contrast detection method, that is, contrast AF are combined. In the hybrid AF, a method of moving the focus lens to the in-focus position by phase difference AF and further moving the focus lens to the in-focus position by contrast AF is common. This shortens the time until focusing and improves focusing accuracy. However, in Patent Document 1, since such a hybrid AF technique is not taken into consideration, it is not always possible to realize a quick and highly accurate autofocus depending on photographing conditions and the like.

  An object of the present invention is to provide a solid-state imaging device, a control method therefor, and an imaging apparatus capable of realizing quick and highly accurate autofocus using hybrid AF.

  According to an aspect of the present invention, a pixel array in which a plurality of pixels are arranged in a matrix and a phase difference evaluation value for focus detection by a phase difference detection method are included in the plurality of pixels. A first calculation unit configured to calculate based on a signal from a phase difference detection pixel; and a defect that occurs in an image signal acquired by the pixel array, and the phase difference detection pixel is included in the plurality of pixels. An interpolation processing unit that generates a signal for compensating for a defect caused by being included by interpolation using signals from the pixels other than the phase difference detection pixel, and a contrast for focus detection by a contrast detection method A solid-state imaging device comprising: a second calculation unit that calculates an evaluation value based on the image signal including the signal generated by the interpolation by the interpolation processing unit. It is subjected.

  According to the present invention, it is possible to provide a solid-state imaging device, a control method therefor, and an imaging apparatus that can realize quick and highly accurate autofocus using hybrid AF.

It is a block diagram which shows the structure of the imaging device by 1st Embodiment. FIG. 2A is a perspective view showing the structure of the solid-state imaging device according to the first embodiment. 2B and 2C are circuit diagrams illustrating the solid-state imaging device according to the first embodiment. It is a figure which shows the pixel and imaging optical system which were distribute | arranged to the normal line. It is a figure which shows the pixel and imaging optical system which were distribute | arranged to phase difference AF line. It is a figure which shows the example of the selection line at the time of the reading in the solid-state image sensor by 1st Embodiment. It is a figure which shows the layout of the pixel in the solid-state image sensor by 1st Embodiment. It is a figure which shows an interpolation process notionally. It is a time chart which shows operation | movement of the imaging device by 1st Embodiment. It is a flowchart which shows operation | movement of the imaging device by 1st Embodiment. It is a time chart which shows operation | movement of the imaging device by 2nd Embodiment. It is a flowchart which shows operation | movement of the imaging device by 2nd Embodiment.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings, but the present invention is not limited to the following embodiments.
[First Embodiment]
A solid-state imaging device, a control method thereof, and an imaging apparatus according to a first embodiment will be described with reference to FIGS. FIG. 1 is a block diagram illustrating the configuration of the imaging apparatus according to the present embodiment. Here, the case where the imaging apparatus 100 according to the present embodiment is an electronic camera that can acquire moving images and still images, that is, a digital camera will be described as an example, but the present invention is not limited thereto.

  As shown in FIG. 1, the imaging apparatus 100 includes an optical barrel 101, a solid-state imaging device 102, a drive unit 103, a signal processing unit 104, a compression / decompression unit 105, a control unit 106, and a light emitting unit 107. , An operation unit 108, an image display unit 109, and an image recording unit 110.

  The optical barrel (lens unit) 101 includes a lens group for condensing light from a subject onto the solid-state image sensor 102. Such a lens group includes a focus lens and a zoom lens. Such a lens group and a microlens ML (see FIGS. 3 and 4) described later constitute an imaging optical system. The optical barrel 101 includes an optical mechanism unit 1011 including an AF mechanism, a zoom drive mechanism, a mechanical shutter mechanism, a diaphragm mechanism, and the like. The optical mechanism unit 1011 is driven by a drive unit (drive circuit) 103 based on a control signal from the control unit 106.

  The solid-state image sensor 102 includes a pixel 201 described later and an A / D converter (not shown). The solid-state image sensor 102 is, for example, an XY readout type CMOS image sensor. The solid-state image sensor 102 is driven by the drive unit 103 based on a control signal from the control unit 106. The solid-state imaging device 102 performs an imaging operation such as exposure / accumulation, signal readout, and reset, and outputs a signal acquired by the imaging operation, that is, an imaging signal (hereinafter also referred to as “image signal” or “image data”). To do. The solid-state image sensor 102 includes an AF evaluation value calculation unit 1021. The AF evaluation value calculation unit 1021 calculates an AF evaluation value, that is, a phase difference evaluation value and a contrast evaluation value, based on a signal acquired by the solid-state imaging device 102, and outputs the calculated AF evaluation value to the control unit 106. To do.

  The signal processing unit 104 performs predetermined signal processing such as white balance adjustment processing, color correction processing, and AE (Auto Exposure) processing on the image signal acquired by the solid-state imaging device 102 under the control of the control unit 106. Apply.

  The compression / decompression unit 105 operates under the control of the control unit 106. The compression / decompression unit 105 generates encoded image data by performing compression encoding processing on the image signal sent from the signal processing unit 104. In the compression encoding process, for example, a predetermined still image data format such as JPEG (Joint Photographic Coding Experts Group) method is used. The compression / decompression unit 105 obtains decoded image data by performing an expansion decoding process on the encoded image data transmitted from the control unit 106. Note that the compression / decompression unit 105 can also perform compression encoding processing and decompression decoding processing on moving image data. In compression encoding processing and decompression decoding processing for moving image data, for example, a moving picture experts group (MPEG) method or the like is used.

  The control unit 106 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). When the CPU executes a program stored in a ROM or the like, the entire imaging apparatus 100 is controlled in an integrated manner by the control unit 106.

  When it is determined in the AE process performed by the signal processing unit 104 that the exposure value of the subject is low, the control unit 106 controls the light emitting unit 107 to emit light to illuminate the subject. . As the light emitting unit 107, for example, a strobe device using a xenon tube, an LED light emitting device, or the like is used.

  The operation unit 108 is, for example, various operation keys such as a shutter release button, a lever, a dial, a touch panel, and the like, and gives an operation signal corresponding to an operation input by the user to the control unit 106.

  The image display unit 109 includes, for example, a display device (not shown) such as an LCD (Liquid Crystal Display) and an interface (not shown) for the display device. The image display unit 109 displays an image corresponding to the image data sent from the control unit 106 on the display screen of the display device.

  As the image recording unit 110, for example, a recording medium such as a portable semiconductor memory, an optical disk, a HDD (Hard Disk Drive), or a magnetic tape is used. The image recording unit 110 records the encoded image data subjected to the compression encoding process by the compression / decompression unit 105 as an image file. The image recording unit 110 reads the image file designated by the control unit 106 from the recording medium, and outputs the image file to the control unit 106. The control unit 106 obtains decoded image data by causing the compression / decompression unit 105 to perform decompression coding processing of the encoded image data read from the image recording unit 110.

  Next, the basic operation of the imaging apparatus 100 according to the present embodiment will be described. For example, when capturing a still image, the solid-state image sensor 102 operates as follows before capturing a still image. That is, the solid-state imaging device 102 sequentially performs CDS processing and AGC processing on an image signal output from the pixel 201 described later, and digitally outputs the image signal subjected to these processing using an A / D converter. Convert to image signal. Note that CDS is an abbreviation for Correlated Double Sampling. AGC is an abbreviation for Automatic Gain Control (automatic gain control). The digital image signal thus obtained is transmitted to the AF evaluation value calculation unit 1021 and the signal processing unit 104.

  The AF evaluation value calculation unit 1021 calculates an AF evaluation value such as a phase difference evaluation value or a contrast evaluation value from the image signal acquired by the solid-state imaging device 102, and outputs the calculated AF evaluation value to the control unit 106. The control unit 106 determines a feedback control amount, that is, a focus lens drive amount based on the AF evaluation value, and outputs the determined feedback control amount to the drive unit 103. The drive unit 103 drives the focus lens using the AF mechanism provided in the optical mechanism unit 1011 based on the feedback control amount given from the control unit 106.

  The signal processing unit 104 generates, for example, a camera-through image signal, that is, a live view image signal, by performing, for example, image quality correction processing on the digital image signal output from the solid-state image sensor 102. The signal processing unit 104 transmits the generated live view image signal to the image display unit 109 via the control unit 106. The image display unit 109 displays a live view image corresponding to the live view image signal. The user can perform angle-of-view alignment (framing) and the like while viewing the live view image displayed on the image display unit 109.

  When the shutter release button provided in the operation unit 108 is pressed by the user while the live view image is displayed on the image display unit 109, the control unit 106 performs the following processing. In other words, the control unit 106 controls the solid-state image sensor 102 via the drive unit 103, whereby an image signal for one frame, that is, a digital image signal for one frame is transmitted from the solid-state image sensor 102 to the signal processing unit 104. To send to. The signal processing unit 104 performs, for example, image quality correction processing on the digital image signal for one frame transmitted from the solid-state imaging device 102, and the digital image signal after the image quality correction processing, that is, image data is sent to the compression / decompression unit 105. Send. The compression / decompression unit 105 obtains encoded image data by performing compression encoding processing on the image data. The encoded image data obtained by the compression / decompression unit 105 is transmitted to the image recording unit 110 via the control unit 106. In this way, an image file of a still image acquired using the solid-state image sensor 102 is recorded in the image recording unit 110.

  When playing back an image file of a still image recorded in the image recording unit 110, the control unit 106 performs the following processing. That is, the control unit 106 reads the image file selected by the user via the operation unit 108 from the image recording unit 110. Then, the control unit 106 transmits the image file read from the image recording unit 110 to the compression / decompression unit 105. The compression / decompression unit 105 obtains decoded image data by performing an expansion decoding process on the image file. The control unit 106 transmits the decoded image data obtained by the compression / decompression unit 105 to the image display unit 109. The image display unit 109 displays a still image corresponding to the decoded image data.

  The control unit 106 performs the following processing when recording moving image data. In other words, the control unit 106 controls the solid-state imaging device 102 via the driving unit 103 to sequentially input digital image signals sequentially output from the solid-state imaging device 102 to the signal processing unit 104. The signal processing unit 104 generates image data, that is, moving image data, by sequentially performing predetermined image processing on sequentially input digital image signals. The compression / decompression unit 105 obtains encoded moving image data by performing compression encoding processing on the moving image data. The encoded moving image data obtained by the compression / decompression unit 105 is sequentially transferred to the image recording unit 110 via the control unit 106 and is recorded in the image recording unit 110 as a moving image file.

  When playing back a moving image file recorded in the image recording unit 110, the control unit 106 performs the following processing. That is, the control unit 106 reads out the moving image file selected by the user via the operation unit 108 from the image recording unit 110. The control unit 106 transmits the moving image file read from the image recording unit 110 to the compression / decompression unit 105. The compression / decompression unit 105 obtains decoded moving image data by performing an expansion decoding process on the moving image file. The control unit 106 transmits the decoded moving image data obtained by the compression / decompression unit 105 to the image display unit 109. The image display unit 109 displays a moving image corresponding to the decoded moving image data.

  FIG. 2A is a perspective view showing the structure of the solid-state imaging device provided in the imaging apparatus according to the present embodiment. As shown in FIG. 2A, the solid-state imaging device 102 according to the present embodiment includes a first semiconductor chip 20 and a second semiconductor chip 21, and the first semiconductor chip 21 is first on the second semiconductor chip 21. This is a stacked image sensor in which the semiconductor chips 20 are stacked. The first semiconductor chip 20 includes a pixel array 206 in which a plurality of pixels (pixel portions) 201 are arranged in a two-dimensional matrix, that is, in a matrix, and the first semiconductor chip 20 includes the second semiconductor chip 20 The semiconductor chip 21 is arranged on the light incident side. That is, the first semiconductor chip 20 is positioned on the light receiving side of the optical image with respect to the second semiconductor chip 21. The second semiconductor chip 21 is formed with a pixel drive circuit (read circuit, read unit) including column scan circuits 213a and 213b, which will be described later, and a row scan circuit 212. The second semiconductor chip 21 is also formed with an AF evaluation value calculation unit 1021 and an interpolation processing unit 219.

  In the present embodiment, since the first semiconductor chip 20 in which the pixel 201 is formed and the second semiconductor chip 21 in which the peripheral circuit is formed are separated, the manufacturing process of the pixel 201 and the manufacturing process of the peripheral circuit And are separated. For this reason, in the present embodiment, thinning and high density of the wiring are realized in the peripheral circuit and the like, and the high speed, miniaturization, high functionality, etc. of the solid-state imaging device 102 are realized.

  2B and 2C are circuit diagrams showing the solid-state imaging device according to the present embodiment. FIG. 2C is a circuit diagram illustrating a configuration of the pixel 201. As shown in FIG. 2B, the first semiconductor chip 20 is formed with a plurality of pixels 201 arranged in a two-dimensional matrix. The pixel 201 is connected to the transfer signal line 203, the reset signal line 204, and the row selection signal line 205 in the horizontal direction, and is connected to the column signal line 202a or the column signal line 202b in the vertical direction. Note that the pixel 201 to which the column signal lines 202a and 202b are connected differs depending on the readout row. That is, the pixels 201SHA and 201SHB (see FIG. 4A) for phase difference detection (focus detection) described later, that is, the pixels 201 located in the phase difference AF row (AF row) are: It is connected to the column signal line 202b. On the other hand, the row not including the phase difference detection pixels 201SHA and 201SHB, that is, the pixel 201 located in the normal row is connected to the column signal line 202a.

  As shown in FIG. 2C, the pixel 201 includes a photodiode PD which is a photoelectric conversion element, a transfer transistor M1, a reset transistor M2, an amplification transistor M3, a selection transistor M4, and a floating diffusion FD. doing. As the transistors M1 to M4, for example, n-channel MOSFETs (MOS Field-Effect Transistors) are used.

  A transfer signal line 203 is connected to the gate of the transfer transistor M1. A reset signal line 204 is connected to the gate of the reset transistor M2. A row selection signal line 205 is connected to the gate of the selection transistor M4. These signal lines 203 to 205 extend in the horizontal direction, and the pixels 201 located in the same row are driven simultaneously. As a result, the operation of a line sequential operation type rolling shutter or an all row simultaneous operation type global shutter can be realized. Further, the column signal line 202a or the column signal line 202b is connected to the source of the selection transistor M4.

  The photodiode PD generates charges by photoelectric conversion. The anode side of the photodiode PD is grounded, and the cathode side of the photodiode PD is connected to the source of the transfer transistor M1. When the transfer transistor M1 is turned on, the charge of the photodiode PD is transferred to the floating diffusion FD. Since there is a parasitic capacitance in the floating diffusion FD, charges transferred from the photodiode PD are accumulated in the floating diffusion FD.

  The power supply voltage Vdd is applied to the drain of the amplification transistor M3, and the gate of the amplification transistor M3 is connected to the floating diffusion FD. The potential of the gate of the amplification transistor M3 becomes a potential corresponding to the electric charge accumulated in the floating diffusion FD. The selection transistor M4 is for selecting the pixel 201 from which a signal is read, and the drain of the selection transistor M4 is connected to the source of the amplification transistor M3. The source of the selection transistor M4 is connected to the column signal line 202a or the column signal line 202b. When the selection transistor M4 is turned on, an output signal corresponding to the gate potential of the amplification transistor M3 is output to the column signal line 202a or the column signal line 202b. The power supply voltage Vdd is applied to the drain of the reset transistor M2, and the source of the reset transistor M2 is connected to the floating diffusion FD. When the reset transistor M2 is turned on, the potential of the floating diffusion FD is reset to the power supply voltage Vdd.

  The second semiconductor chip 21 is provided with a column ADC block 211. The column ADC block 211 is connected to the column signal line 202a or the column signal line 202b. Further, the second semiconductor chip 21 is provided with a row scanning circuit 212 that performs scanning of each row and column scanning circuits 213a and 213b that perform scanning of each column. Further, the second semiconductor chip 21 includes a timing control circuit 214 that controls the operation timings of the row scanning circuit 212, the column scanning circuits 213a and 213b, and the column ADC block 211 based on a control signal from the control unit 106, respectively. Is provided. Further, the second semiconductor chip 21 is provided with horizontal signal lines 215a and 215b for transferring signals from the column ADC block 211 in accordance with timing controlled by the column scanning circuits 213a and 213b.

  Further, the second semiconductor chip 21 includes a switch 216 for switching the output destination of the digital image signal output via the horizontal signal line 215b. When the switch 216 is set to the first setting, the output destination of the digital image signal output via the horizontal signal line 215b is set in the phase difference evaluation value calculation unit 217 provided in the AF evaluation value calculation unit 1021. Is done. On the other hand, when the switch 216 is set to the second setting, the output destination of the digital image signal output via the horizontal signal line 215b is set in the interpolation processing unit 219.

  As described above, the row including the phase difference detection pixels 201SHA and 201SHB, that is, the pixel 201 located in the phase difference AF row is connected to the column signal line 202b. For this reason, the signal acquired by the pixel 201 located in the phase difference AF row is transferred via the column signal line 202b and the horizontal signal line 215b. Signals acquired by the phase difference detection pixels 201SHA and 201SHB located in the phase difference AF row are transferred to the phase difference evaluation value calculation unit 217 via the column signal line 202b, the horizontal signal line 215b, and the switch 216. The

  By the way, not only the phase difference detection pixels 201SHA and 201SHB but also the imaging pixel 201G are located in the phase difference AF row (see FIG. 4A). Note that when describing pixels having specific spectral sensitivities such as R (red), G (green), and B (blue), reference numerals 201R, 201G, and 201B are used, respectively. Further, when describing the pixels for phase difference detection, reference numerals 201SHA and 201SHB are used, respectively. In the description of general pixels, reference numeral 201 is used. A signal acquired by the imaging pixel 201G among the pixels 201 located in the phase difference AF row is transmitted to the interpolation processing unit 219 via the column signal line 202b, the horizontal signal line 215b, and the switch 216. The rows that do not include the phase difference detection pixels 201SHA and 201SHB, that is, the pixels 201 located in the normal row are connected to the column signal line 202a as described above. For this reason, a signal acquired by the pixels 201 located in the normal row is output to the interpolation processing unit 219 via the column signal line 202a and the horizontal signal line 215a. As described above, the interpolation processing unit 219 receives the digital image signal output via the horizontal signal line 215a and the digital image signal output via the horizontal signal line 215b. A signal appropriately subjected to interpolation processing by the interpolation processing unit 219, that is, an image signal is output to the contrast evaluation value calculation unit 218 provided in the AF evaluation value calculation unit 1021 and the signal processing unit 104.

The phase difference evaluation value calculated by the phase difference evaluation value calculation unit 217 and the contrast evaluation value calculated by the contrast evaluation value calculation unit 218 are output to the control unit 106, respectively. A signal that is appropriately subjected to the interpolation processing by the interpolation processing unit 219, that is, an image signal is transmitted to the signal processing unit 104, and is used for an image for live view, for example, in live view display.
Note that a signal transferred from the pixel 201 located in the normal row to the horizontal signal line 215a is referred to as a first image signal. A signal transferred from the pixel 201 located in the phase difference AF row to the horizontal signal line 215b is referred to as a second image signal.

  FIG. 5A is a diagram illustrating an example of a selected row at the time of reading in the solid-state imaging device according to the present embodiment. In FIG. 5A, 16 rows × 6 columns of pixels 201 out of a plurality of pixels 201 arranged in a matrix are shown. These pixels 201 are in a Bayer array. In the present embodiment, the selected row and the second image when acquiring the first image signal so that the acquisition of the first image signal and the acquisition of the second image signal can be performed in parallel. A selection line for acquiring a signal is set for each. The first image signal is output to the column signal line 202a. On the other hand, the second image signal is output to the column signal line 202b. Note that the rows with the row numbers 1 and 2 and the rows with the row numbers 9 and 10 are selected rows when the second image signal is acquired, and a pixel group for acquiring the second image signal. (Second pixel group) is arranged. The rows with the row numbers 3 to 8 and the rows with the row numbers 11 to 16 are selected rows when the first image signal is acquired, and the pixel group (first number 1 pixel group).

  FIG. 5B is a diagram illustrating a pixel layout in the solid-state imaging device according to the present embodiment. FIG. 5B shows a part of the pixels 201 extracted from the plurality of pixels 201 arranged in a matrix. The signals R, Gr, Gb, and B output from the pixels 201 located in some of the plurality of normal rows and the pixels 201G located in some of the plurality of phase difference AF rows The signals Gr and Gb to be used are also used when acquiring a contrast evaluation value. The row in which the pixel 201 that outputs a signal used for acquiring the contrast evaluation value is also referred to as a contrast AF row. As shown in FIG. 5B, the contrast AF line includes a phase difference AF line and a normal line. The reason why the contrast AF line is set so as to include not only the normal line but also the phase difference AF line is to acquire a highly accurate contrast evaluation value by setting the contrast AF line in a wide range.

  Since the second image signal includes signals acquired by the phase difference detection pixels 201SHA and 201SHB, it is important to increase the frame rate in order to realize quick autofocus. For this reason, the second image signal is set to have a relatively high thinning rate. On the other hand, since the first image signal is used for live view display or the like, image quality is important. For this reason, the first image signal is set to have a relatively low thinning rate. When attention is paid to the rows having the row numbers 1 to 8, the first image signal is obtained by thinning out one pixel out of four pixels of the same color arranged in the vertical direction, and the second image signal is obtained in the vertical direction. Is obtained by thinning out three pixels out of four pixels of the same color arranged in. In acquiring the first image signal, the first pixel group is read out at the first frame rate. In acquiring the second image signal, the second pixel group is read out at a second frame rate that is faster than the first frame rate. Here, a case where the second frame rate is set to three times the first frame rate will be described as an example.

  Thus, in the present embodiment, the row from which the first image signal is read out and the row from which the second image signal is read out are set separately. Therefore, according to the present embodiment, the first image signal and the second image signal having different charge accumulation times, different data sizes, and different frame rates can be acquired in parallel. Here, the second pixel group for acquiring the second image signal is located in the row of row numbers 1 and 2, and the first pixel group for acquiring the first image signal is row number. Although the case where it located in the 3-8 line was demonstrated to the example, it is not limited to this. Further, the thinning rate in reading can also be set as appropriate.

  An analog signal output from the pixel 201 to the column signal line 202 a or the column signal line 202 b is converted from analog to digital in the column ADC block 211. The column scanning circuit 213a transmits the digital first image signal output from the column ADC block 211 to the interpolation processing unit 219 via the horizontal signal line 215a. Further, the column scanning circuit 213b transmits the digital second image signal output from the column ADC block 211 to the phase difference evaluation value calculation unit 217 and the interpolation processing unit 219 via the horizontal signal line 215b. The signal subjected to the interpolation processing by the interpolation processing unit 219, that is, the image signal is transmitted to the contrast evaluation value calculation unit 218, and is also transmitted through the output terminal 222 provided in the solid-state imaging device 102. 104 is output.

  The control unit 106 performs autofocus control by the phase difference detection method, that is, phase difference focus control (phase difference AF), using a signal from the phase difference evaluation value calculation unit 217 provided in the solid-state imaging device 102. Furthermore, the control unit 106 also performs autofocus control using a contrast detection method, that is, contrast focus control (contrast AF), using a signal from the contrast evaluation value calculation unit 218 provided in the solid-state imaging device 102.

  The phase difference evaluation value calculation unit 217 calculates a phase difference evaluation value for focus detection by the phase difference detection method based on signals from the phase difference detection pixels 201SHA and 201SHB included in the plurality of pixels 201. Is to be calculated. The phase difference evaluation value calculation unit 217 performs a correlation operation on the pair of image signals generated by the signals SHA and SHB from the plurality of phase difference detection pixels 201SHA and 201SHB, and calculates the relative of the pair of image signals. A phase difference indicating a positional deviation is calculated. Then, based on the phase difference, the phase difference evaluation value calculation unit 217 calculates a defocus amount Df that is an amount indicating how much the focus is off. Based on the defocus amount Df, the control unit 106 indicates an amount indicating how much the focus lens should be moved in order to obtain a state close to focusing, that is, the driving amount of the focus lens up to the in-focus position. calculate. The control unit 106 controls the optical mechanism unit 1011 via the drive unit 103 so that the focus lens moves by the calculated drive amount. The contrast evaluation value calculation unit 218 calculates a contrast evaluation value by extracting a high frequency component in the image signal from the contrast AF row. The control unit 106 appropriately drives the focus lens based on the contrast evaluation value.

  FIG. 3 is a diagram illustrating a pixel and an imaging optical system. FIG. 3A is a plan view showing a pixel. All of the four pixels 201 of 2 rows × 2 columns shown in FIG. 3A are imaging pixels. Among these four pixels 201, two pixels 201G having a spectral sensitivity of G (green) are arranged at two diagonal positions, and R (red) and B ( Pixels 201R and 201B having a spectral sensitivity of (blue) are arranged. Such a pixel array is called a Bayer array. FIG. 3A shows one pixel unit extracted from the Bayer array. FIG. 3B is a cross-sectional view showing the relationship between the imaging optical system and the pixels. FIG. 3B corresponds to a cross section taken along line AA in FIG.

As shown in FIG. 3B, the photodiode PD is formed on the semiconductor substrate 301 of the first semiconductor chip 20 of the solid-state imaging device 102. The photodiode PD is formed so as to correspond to each of the plurality of pixels 201 formed in a matrix. A multilayer wiring structure 302 is formed on the semiconductor substrate 301 on which the photodiode PD is formed. The multilayer wiring structure 302 includes a wiring layer CL and an insulating layer 303. The wiring layer CL constitutes a signal line for transmitting various signals in the solid-state imaging device 102. A color filter layer 304 is formed on the multilayer wiring structure 302. The color filter layer 304 includes a color filter CF _R of R (red), a color filter CF _G of G (green), and a color filter CF _B of B (blue). These color filters CF _R , CF _G , and CF _B are formed so as to correspond to the respective pixels 201. Incidentally, in FIG. 3 (a), R is the portion where the color filter CF _R of R is disposed is conceptually shows, G conceptually a portion where the color filter CF _G of G is arranged B indicates conceptually a portion where the _B color filter CF _B is disposed.

  On the color filter layer 304, a microlens ML, that is, an on-semiconductor chip microlens is arranged. The microlens ML is formed so as to correspond to each pixel 201. The microlens ML and the photodiode PD are configured to capture the light beam 305 passing through the exit pupil EP of the imaging optical system TL as effectively as possible. In other words, the microlens ML is formed so that a conjugate relationship is established between the exit pupil EP of the imaging optical system TL and the photodiode PD. In addition, the effective area of the photodiode PD is set large. In FIG. 3B, the light beam 305 incident on the R pixel 201 is shown as an example, but the same applies to the light beam incident on the G pixel 201 and the light beam incident on the B pixel 201. Thus, the exit pupil EP corresponding to the RGB pixels 201 for imaging has a large diameter, and the light flux from the subject reaches the pixels 201 efficiently. Therefore, an image signal with a high S / N ratio is obtained in each pixel 201.

  FIG. 4 is a diagram illustrating a pixel and an imaging optical system. FIG. 4A is a plan view of a pixel. When obtaining an image signal, the output from the pixel 201G having G spectral sensitivity forms the main component of the luminance information. Since human image recognition characteristics are sensitive to luminance information, if the output from the pixel 201G having G spectral sensitivity is lost, image quality degradation is likely to be recognized. On the other hand, the R pixel 201R (see FIG. 3) and the B pixel 201B (see FIG. 3) are pixels for mainly acquiring color information, and humans are relatively insensitive to color information. For this reason, even if some deficiencies occur in the R and B pixels 201R and 201B for obtaining color information, it is difficult for humans to notice image quality deterioration. Therefore, in the present embodiment, two G pixels 201G out of the four pixels 201 in 2 rows × 2 columns are left as imaging pixels, and the phase difference is set at the position of the R pixel 201R and the B pixel 201B. Detection pixels 201SHA and 201SHB are arranged respectively. In FIG. 4A, SHA conceptually shows the phase difference detection pixel 201SHA arranged at the position of the R pixel 201R, and SHB is the phase difference arranged at the position of the B pixel 201B. A pixel 201SHB for detection is conceptually shown. As described above, not only the phase difference detection pixels 201SHA and 201SHB but also the imaging pixel 201G are located in the phase difference AF row. The plurality of phase difference detection pixels 201SHA constitute a first phase difference detection pixel group. The plurality of phase difference detection pixels 201SHB constitute a second phase difference detection pixel group.

FIG. 4B corresponds to a cross section taken along line B-B in FIG. Also in the phase difference detection pixels 201SHA and 201SHB, the photodiode PD is formed on the semiconductor substrate 301 in the same manner as the imaging pixels 201R, 201G, and 201B. Since the signals from the phase difference detection pixels 201SHA and 201SHB are not used in the image, the phase difference detection pixels 201SHA and 201SHB have a transparent film (instead of the color separation filters CF _R and CF _B ). white film) CF _W is disposed. Pixel 201SHA for phase difference detection in the 201SHB, for realizing the pupil division, the wiring layer CL is, the opening _OP HA, constitutes a shielding portion having a _{OP HB.} Since pupil division is performed in the x direction, the openings OP _HA and OP _HB are unevenly distributed in the x direction with respect to the center of the microlens ML. Opening _{OP HA} of the pixel 201SHA for phase difference detection are localized in the -x direction with respect to the center of the microlens ML. For this reason, the photodiode PD of the pixel 201SHA for phase difference detection is the + x-side pupil region of the plurality of pupil regions EP _HA and EP _HB included in the exit pupil of the imaging optical system TL, that is, the first pupil. The light beam that has passed through the region EP _HA is received. The pixel 201SHA acquires a signal corresponding to the light beam passing through the first pupil region EP _HA of the exit pupil of the imaging optical system TL. On the other hand, the opening OP _HB of the phase difference detection pixel 201SHB is unevenly distributed in the + x direction with respect to the center of the microlens. For this reason, the photodiode PD of the phase difference detection pixel 201SHB is a pupil region on the −x side of the plurality of pupil regions EP _HA and EP _HB included in the exit pupil of the imaging optical system TL, that is, the second The light beam that has passed through the pupil region EP _HB is received. The pixel 201SHB acquires a signal corresponding to the light beam passing through the second pupil region EP _HB of the exit pupil of the imaging optical system TL.

  A subject image acquired by a plurality of phase difference detection pixels 201SHA regularly arranged in the x direction, that is, a first phase difference detection pixel group is defined as a first image. A plurality of phase difference detection pixels 201SHB regularly arranged in the x direction, that is, a subject image acquired by the second phase difference detection pixel group is defined as a second image. Then, by detecting the relative positional deviation amount between the first image and the second image, that is, the phase difference, the defocus amount Df of the focus lens with respect to the subject can be calculated based on the phase difference. .

  A signal output from the pixel 201 to the column signal lines 202 a and 202 b is converted from analog to digital by the column ADC block 211. The signals digitally converted by the column ADC block 211 are output from the column ADC block 211 to the horizontal signal lines 215a and 215b by the column scanning circuits 213a and 213b, respectively. The signals R, Gr, Gb, and B output to the horizontal signal line 215a are output to the interpolation processing unit 219. On the other hand, the signal output to the horizontal signal line 215b is output via the switch 216. The signals SHA and SHB from the phase difference detection pixels 201SHA and 201SHB are input to the phase difference evaluation value calculation unit 217 by setting the switch 216 to the first setting. Signals Gr and Gb from the imaging pixel 201G located in the phase difference AF row are input to the interpolation processing unit 219 by setting the switch 216 to the second setting.

  The phase difference evaluation value calculation unit 217 calculates a phase difference evaluation value by correlation calculation based on the signals SHA and SHB transmitted to the phase difference evaluation value calculation unit 217 via the horizontal signal line 215b and the switch 216. That is, the phase difference evaluation value calculation unit 217 calculates a phase difference evaluation value for focus detection by the phase difference detection method based on the signals SHA and SHB from the pixels 201SHA and 201SHB. The phase difference evaluation value calculated by the phase difference evaluation value calculation unit 217 is output to the control unit 106 via the output terminal 223 provided in the solid-state image sensor 102. The phase difference evaluation value calculation unit 217 performs the calculation of the phase difference evaluation value as soon as the calculation of the phase difference evaluation value is completed regardless of whether the output of the image signal acquired by the pixel array 206 to the signal processing unit 104 is completed. Is output to the control unit 106.

  Signals R, Gr, Gb, and B read from the normal row are transmitted to the interpolation processing unit 219 via the horizontal signal line 215a, and signals Gr and Gb read from the phase difference AF row are transmitted to the horizontal signal line 215b and the switch 216. And sent through. The interpolation processing unit 219 performs interpolation processing using these signals as appropriate.

  FIG. 6 is a diagram conceptually illustrating the interpolation processing. FIG. 6A shows a state in which an R signal missing at a location where the phase difference detection pixel 201SHA is located is acquired by interpolation processing. The interpolation processing unit 219 outputs a signal for compensating for a defect that is generated in the image signal acquired by the pixel array 206 and is generated when the phase difference detection pixel is included in the plurality of pixels. It is generated by interpolation using signals from pixels other than the phase difference detection pixels. That is, the interpolation processing unit 219 uses the signal from the pixel 201 other than the phase difference detection pixel 201SHA to interpolate the missing R signal at the location where the phase difference detection pixel 201SHA is located. Generate by processing. More specifically, the interpolation processing unit 219 adds and averages the signals from the six pixels 201R located around the phase difference detection pixel 201SHA so that the phase difference detection pixel 201SHA is positioned. The missing R signal is acquired at the location where the error occurs. FIG. 6B shows a state in which a missing B signal is obtained by interpolation processing at a location where the phase difference detection pixel 201SHB is located. The interpolation processing unit 219 uses a signal from the pixel 201 other than the phase difference detection pixel 201SHB, and performs interpolation processing on the missing B signal at the location where the phase difference detection pixel 201SHB is located. Generate. More specifically, the interpolation processing unit 219 adds and averages signals from six pixels 201B located around the phase difference detection pixel 201SHB, so that the phase difference detection pixel 201SHB is positioned. The missing B signal is obtained at the location where the error occurs. Note that special correction processing is not normally performed on the signals Gr and Gb transmitted via the horizontal signal line 215b. However, it is transmitted via the horizontal signal line 215b based on the difference in characteristics between the signals Gr and Gb transmitted via the horizontal signal line 215b and the signals Gr and Gb transmitted via the horizontal signal line 215a. Correction processing may be appropriately performed on the signals Gr and Gb.

  Signals R and B corresponding to the location where the pixels 201SHA and 201SHB for phase difference detection are located and generated by the interpolation processing by the interpolation processing unit 219 are the contrast evaluation value calculation unit 218 and the signal processing unit. 104. Further, signals Gr and Gb from the imaging pixel 201G located in the phase difference AF row are transmitted to the contrast evaluation value calculation unit 218 and the signal processing unit 104 via the interpolation processing unit 219. Further, signals R, Gr, Gb, and B from the imaging pixels 201 located in the normal row are transmitted to the contrast evaluation value calculation unit 218 via the interpolation processing unit 219. The contrast evaluation value calculation unit 218 calculates a contrast evaluation value for focus detection by the contrast detection method based on an image signal including a signal generated by interpolation by the interpolation processing unit 219. The contrast evaluation value calculation unit 218 calculates a contrast evaluation value based on the image signal subjected to the interpolation processing by performing contrast calculation. The contrast evaluation value calculated by the contrast evaluation value calculation unit 218 is output to the control unit 106 via the output terminal 224 provided in the solid-state image sensor 102. The contrast evaluation value calculation unit 218 controls the contrast evaluation value as soon as the calculation of the contrast evaluation value is completed regardless of whether the output of the image signal acquired by the pixel array 206 to the signal processing unit 104 is completed. It outputs to 106.

  In the present embodiment, the loss of R and B signals generated in the phase difference detection pixels 201SHA and 201SHB is eliminated by the interpolation processing by the interpolation processing unit 219. Therefore, in the present embodiment, the contrast evaluation value can be calculated based on signals from a wide range including the phase difference AF row. Since the contrast evaluation value is calculated based on a signal from a wide range including the phase difference AF row, according to the present embodiment, a highly accurate contrast evaluation value can be obtained.

Further, in the present embodiment, since such a defect is eliminated by the interpolation processing unit 219, a high-definition image signal that is not thinned out using the first image signal and the second image signal from which the defect has been eliminated. Can be obtained. Such an image signal is used for an image for live view, for example, at the time of live view display.
Here, a path for outputting the first image signal via the column signal line 202a and the horizontal signal line 215a is referred to as a first channel CH1, and the second channel via the column signal line 202b and the horizontal signal line 215b. A path for outputting an image signal is referred to as a second channel CH2.

  FIG. 7 is a time chart illustrating the operation of the imaging apparatus according to the present embodiment. FIG. 7 shows an operation in a mode in which live view display is performed while performing an autofocus operation, that is, an AF evaluation mode.

  The AF evaluation mode is started when the AF control signal from the control unit 106 is turned on. The timing when the AF control signal is turned on is T0. At timing T0, the vertical synchronization signal VD changes from the High level to the Low level. In synchronization with the vertical synchronization signal VD, the acquisition of the first image signal, that is, the acquisition of the signal from the pixel 201 located in the normal row and the acquisition of the second image signal, that is, the phase difference is located in the AF row. Acquisition of a signal from the pixel 201 is started. As described above, the first image signal is output via the first channel CH1, and the second image signal is output via the second channel CH2.

  During the period from T0 to TF1, signals are read from the pixels 201SHA and 201SHB located in the phase difference AF row. Reading of signals from the pixels 201SHA and 201SHB located in the phase difference AF row is performed in parallel with reading of signals from the pixels 201 located in the normal row. The phase difference evaluation signals SHA and SHB read from the pixels 201SHA and 201SHB located in the phase difference AF row are transmitted to the phase difference evaluation value calculation unit 217 via the horizontal signal line 215b and the switch 216. In the period of TF1 to TF2, the phase difference evaluation value is calculated by the phase difference evaluation value calculation unit 217. In the period from TF <b> 2 to TF <b> 3, the phase difference evaluation value calculated by the phase difference evaluation value calculation unit 217 is output to the control unit 106.

  In the period from T0 to TF1C, an image signal is acquired, that is, a live view signal is acquired. Such an image signal is constituted by the first image signal and the second image signal from which the defect is eliminated. In the period from TF1C to TF2C, the contrast evaluation value calculation unit 218 calculates the contrast evaluation value based on the signal subjected to the interpolation processing by the interpolation processing unit 219. In the period from TF2C to TF3C, the contrast evaluation value calculated by the contrast evaluation value calculation unit 218 is output to the control unit 106.

  The vertical synchronization signal VD changes to the low level at every predetermined time interval ΔT. Note that the vertical synchronization signal that has changed to the Low level returns to the High level after a predetermined time has elapsed. The predetermined time interval ΔT corresponds to the sum of a period required for acquiring a live view signal for one frame, a period during which the contrast evaluation value is calculated, and a period during which the contrast evaluation value is output. That is, the predetermined time interval ΔT corresponds to the sum of the live view signal acquisition period for one frame, the contrast evaluation value calculation period, and the contrast evaluation value output period. In the present embodiment, AF evaluation is performed, for example, three times within a predetermined time interval ΔT. Acquisition of the signal for phase difference evaluation, that is, acquisition of the second image signal is performed independently and in parallel with acquisition of the signal for live view, that is, acquisition of the first image signal.

  The control unit 106 determines whether or not a desired in-focus state is obtained. If the desired in-focus state is obtained, the control unit 106 returns the AF control signal to an OFF state, that is, a low level. In FIG. 7, timing T1 indicates the timing at which the AF control signal is turned off. When the AF control signal is turned off, the AF evaluation is stopped and the live view image is continuously acquired.

FIG. 8 is a flowchart illustrating the operation of the imaging apparatus according to the present embodiment.
When the power of the imaging device 100 is turned on by the operation of the operation unit 108 by the user, the control unit 106 places the imaging device 100 in a standby state. The control unit 106 determines whether or not it is necessary to operate the imaging apparatus 100 in the AF evaluation mode based on the operation of the operation unit 108 by the user (step S801). When it is not necessary to operate the imaging apparatus 100 in the AF evaluation mode (NO in step S801), acquisition of a live view signal is started (step S802). Then, the live view image obtained by acquiring the live view signal is displayed on the image display unit 109 (step S820). On the other hand, when it is necessary to operate the imaging apparatus 100 in the AF evaluation mode (YES in step S801), the control unit 106 turns on the AF control signal (step S803) and acquires a signal for phase difference evaluation. The number of times n is set to 0 (step S804).

  Thereafter, the control unit 106 causes the solid-state image sensor 102 to start acquiring a live view signal (step S812) and causes the solid-state image sensor 102 to start acquiring a phase difference evaluation signal (step S805). The control unit 106 causes the solid-state imaging device 102 to start acquiring a signal for phase difference evaluation, and then increments the number n of acquisition of a signal for phase difference evaluation (step S806). Thereafter, the phase difference evaluation value is calculated by the phase difference evaluation value calculation unit 217 (step S807). In the calculation of the phase difference evaluation value, the phase difference evaluation value calculation unit 217 calculates the phase difference evaluation value based on the phase difference evaluation signals SHA and SHB acquired in step S805. The quantity Df is obtained. The phase difference evaluation value calculation unit 217 outputs the phase difference evaluation value, specifically, the defocus amount Df to the control unit 106 as soon as the calculation of the defocus amount Df is completed. Thereafter, the process proceeds to step S808.

  In parallel with step S807, step S813 is performed. In step S813, the interpolation processing unit 219 performs interpolation processing. Thereafter, the contrast evaluation value calculation unit 218 calculates the contrast evaluation value after waiting for the completion of the reading of the live view signal (step S814). In the calculation of the contrast evaluation value, the contrast evaluation value calculation unit 218 calculates the contrast evaluation value AF_K based on the signal read from the contrast AF row and appropriately subjected to the interpolation process. The contrast evaluation value calculation unit 218 outputs the contrast evaluation value AF_K to the control unit 106 as soon as the calculation of the contrast evaluation value AF_K is completed. The contrast evaluation value AF_K is used in step S815.

In step S808, the control unit 106 determines whether or not the defocus amount Df calculated in step S807 is within a desired defocus amount range based on the following equation (1).
Df_min <Df <Df_max (1)
Here, Df_min and Df_max are a minimum value and a maximum value of the desired defocus amount Df, and are stored in advance in a ROM provided in the control unit 106, for example. Note that these values Df_min and Df_max may be determined at the time of design or may be determined at the time of adjustment.

  If the defocus amount Df does not satisfy Expression (1) (NO in step S808), the process proceeds to step S809. In step S809, based on the defocus amount Df, the control unit 106 determines a feedback control amount, that is, a focus lens drive amount. Then, the control unit 106 controls the optical mechanism unit 1011 via the driving unit 103 to drive the focus lens in the optical barrel 101 (phase difference AF control). In step S810, the control unit 106 determines whether or not the number n of acquisitions of the phase difference evaluation signal is three. If the number n of acquisition of the signal for phase difference evaluation is not 3, the process returns to step S805. On the other hand, when the number n of acquisitions of signals for phase difference evaluation is 3, live view display is performed (step S817), and the process returns to step S804.

  If the defocus amount Df satisfies Expression (1) (YES in step S808), the process proceeds to step S811. In step S811, the control unit 106 determines whether or not the number n of acquisitions of the phase difference evaluation signal is three. If the number n of acquisition of the signal for phase difference evaluation is not 3 (NO in step S811), the process returns to step S805. On the other hand, when the number n of acquisition of the signal for phase difference evaluation is 3 (YES in step S811), the process proceeds to step S815.

In step S815, it is determined based on the following formula (2) whether the contrast evaluation value AF_K acquired in step S814 is within a desired contrast amount range.
K_min <AF_K <K_max (2)
Here, K_min and K_max are the minimum value and the maximum value of the desired contrast evaluation value AF_K, and are stored in, for example, a ROM provided in the control unit 106. Note that these values K_min and K_max may be determined at the time of design or may be determined at the time of adjustment.

  When contrast evaluation value AF_K does not satisfy Expression (2) (NO in step S815), the process proceeds to step S816. In step S816, based on the contrast evaluation value AF_K, the control unit 106 determines a feedback control amount, that is, a focus lens drive amount. Then, the control unit 106 drives the focus lens in the optical barrel 101 by controlling the optical mechanism unit 1011 via the drive unit 103 (contrast AF control). Thereafter, the process proceeds to step S817. When the contrast evaluation value AF_K satisfies Expression (2) (YES in step S815), the control unit 106 turns off the AF control signal (step S818). Thereafter, the control unit 106 ends the acquisition of the phase difference evaluation signal (step S819), and displays the live view signal acquired in step S812 on the image display unit 109 (step S820).

  As described above, according to the present embodiment, the pixel array 206 includes the phase difference detection pixels 201SHA and 201SHB, and defects that occur in the image signal are detected as pixels other than the phase difference detection pixels 201SHA and 201SHB. Interpolation is performed using the signal from 201. Based on the interpolated image signal, a contrast evaluation value for focus detection by the contrast detection method is calculated. Since the contrast evaluation value can be calculated based on a wide range of image signals including rows including the pixels 201SHA and 201SHB for phase difference detection, according to the present embodiment, a highly accurate contrast evaluation value can be obtained. That is, according to the present embodiment, it is possible to obtain a highly accurate contrast evaluation value even though the plurality of pixels 201 constituting the pixel array 206 include the pixels 201SHA and 201SHB for detecting the phase difference. Can do. Since rapid autofocus is possible with the phase difference detection pixels 201SHA and 201SHB, according to the present embodiment, an imaging apparatus capable of performing autofocus quickly and with high accuracy can be provided.

[Second Embodiment]
A solid-state imaging device, a control method thereof, and an imaging apparatus according to the second embodiment will be described with reference to FIGS. 9 and 10. The same components as those of the solid-state imaging device, the control method thereof, and the imaging device according to the first embodiment shown in FIGS. 1 to 8 are denoted by the same reference numerals, and description thereof is omitted or simplified.
The imaging apparatus 100 according to the present embodiment performs continuous acquisition of still images, that is, continuous shooting of still images.

  FIG. 9 is a time chart illustrating the operation of the imaging apparatus according to the present embodiment. A still image continuous shooting mode, which is a mode for continuously acquiring still images, is started when a still image continuous shooting control signal from the control unit 106 is turned on. The control unit 106 controls the solid-state imaging device 102 through the drive unit 103 while controlling the mechanical shutter mechanism, the diaphragm mechanism, and the like provided in the optical mechanism unit 1011 through the drive unit 103. Specifically, a reset operation is performed on the pixel 201, and exposure to the pixel 201 is started by opening a mechanical shutter (shutter). When exposure to the pixel 201 is started, photoelectric conversion is started by the photodiode PD. After a predetermined exposure time that satisfies a preset exposure condition has elapsed, the control unit 106 closes the shutter via the drive unit 103. By closing the shutter, the exposure to the pixel 201 is completed. When the exposure to the pixel 201 is completed, acquisition of a first image signal, that is, acquisition of a signal for a still image and acquisition of a second image signal, that is, acquisition of a signal for phase difference evaluation are started. The The timing at which the acquisition of the first image signal and the acquisition of the second image signal is started is TF0. The first image signal is output via the first channel CH1, and the second image signal is output via the second channel CH2. The selected row for acquiring the first image signal and the selected row for acquiring the second image signal can be the same as those in the first embodiment described above with reference to FIG. 5, for example. .

  During the period from TF0 to TF1, phase difference evaluation signals SHA and SHB are transmitted to the phase difference evaluation value calculation unit 217 via the horizontal signal line 215b and the switch 216. In the period of TF1 to TF2, the phase difference evaluation value is calculated by the phase difference evaluation value calculation unit 217. In the period from TF <b> 2 to TF <b> 3, the phase difference evaluation value calculated by the phase difference evaluation value calculation unit 217 is output to the control unit 106. The control unit 106 drives the focus lens provided in the optical barrel 101 via the drive unit 103 based on the phase difference evaluation value.

  In the period from TF0 to TF1C, acquisition of a still image signal is performed. In the period from TF1C to TF2C, the contrast evaluation value calculation unit 218 calculates the contrast evaluation value. In the period from TF2C to TF3C, the contrast evaluation value calculated by the contrast evaluation value calculation unit 218 is output to the control unit 106. The control unit 106 drives the focus lens provided in the optical barrel 101 via the drive unit 103 based on the contrast evaluation value. When the driving of the focus lens is completed and the still image continuous shooting mode is not ended, the process proceeds to acquisition of the next still image.

  FIG. 10 is a flowchart illustrating the operation of the imaging apparatus according to the present embodiment. First, in response to an operation input to the operation unit 108 by the user, the control unit 106 shifts the imaging device 100 from the standby state to the still image continuous shooting mode. In step S <b> 1001, the control unit 106 opens a mechanical shutter provided in the optical mechanism unit 1011 via the drive unit 103. Thereby, exposure to the pixel 201 is started, photoelectric conversion is started by the photodiode PD, and charge accumulation is started (step S1002). After a predetermined exposure time has elapsed, the control unit 106 closes the mechanical shutter provided in the optical mechanism unit 1011 via the drive unit 103 (step S1003).

  Next, the control unit 106 causes the solid-state image sensor 102 to start acquiring a still image signal (step S1007), and causes the solid-state image sensor 102 to start acquiring a phase difference evaluation signal (step S1004). Thereafter, the phase difference evaluation value is calculated by the phase difference evaluation value calculation unit 217 (step S1005). In the calculation of the phase difference evaluation value (step S1005), the phase difference evaluation value calculation unit 217 calculates the phase difference evaluation value based on the phase difference evaluation signals SHA and SHB acquired in step S1004. Thus, the defocus amount Df is obtained. The phase difference evaluation value calculation unit 217 outputs the phase difference evaluation value, specifically, the defocus amount Df to the control unit 106 as soon as the calculation of the phase difference evaluation value is completed. Thereafter, the process proceeds to step S1006.

  In step S1006, the control unit 106 determines whether or not the defocus amount Df calculated in step S1005 is within a desired defocus amount range based on the equation (1) described above in the first embodiment. Judgment. If the defocus amount Df does not satisfy Expression (1) (NO in step S1006), the process proceeds to step S1010. In step S1010, based on the defocus amount Df, the control unit 106 determines a feedback control amount, that is, a focus lens drive amount. In step S1010, the control unit 106 drives the focus lens in the optical barrel 101 by controlling the optical mechanism unit 1011 via the drive unit 103 (phase difference AF control). Thereafter, the process proceeds to step S1013. When the defocus amount Df satisfies Expression (1) (YES in step S1006), the process proceeds to step S1011.

  In parallel with step S1005, step S1008 is performed. In step S1008, interpolation processing is performed by the interpolation processing unit 219. Thereafter, the contrast evaluation value calculation unit 218 calculates the contrast evaluation value after waiting for the completion of the reading of the live view signal (step S1009). In the calculation of the contrast evaluation value, the contrast evaluation value calculation unit 218 calculates the contrast evaluation value AF_K based on the signal read from the contrast AF row and appropriately subjected to the interpolation process. The contrast evaluation value calculation unit 218 outputs the contrast evaluation value AF_K to the control unit 106 as soon as the calculation of the contrast evaluation value AF_K is completed. The contrast evaluation value AF_K is used in step S1011.

  In step S1011, whether or not the contrast evaluation value AF_K acquired in step S1009 is within a desired contrast amount range is determined based on Expression (2) described above in the first embodiment. If the contrast evaluation value AF_K does not satisfy Expression (2) (NO in step S1011), the process proceeds to step S1012. In step S1012, based on the contrast evaluation value AF_K, the control unit 106 determines a feedback control amount, that is, a focus lens drive amount. The control unit 106 drives the focus lens in the optical barrel 101 by controlling the optical mechanism unit 1011 via the drive unit 103 (contrast AF control). Thereafter, the process proceeds to step S1013. When contrast evaluation value AF_K satisfies Expression (2) (YES in step S1011), the process proceeds to step S1013.

In step S <b> 1013, the control unit 106 determines whether to end the still image continuous shooting mode in response to an operation input of the operation unit 108 by the user. If the still image continuous shooting mode is not terminated (NO in step S1013), the process returns to step S1001, and acquisition of the next still image is started. On the other hand, when the still image continuous shooting mode is to be ended (YES in step S1013), the next still image is not acquired and the process shifts to a standby state.
As described above, the present invention can also be applied to continuous shooting of still images. Also in the present embodiment, it is possible to provide an imaging apparatus that can perform autofocus quickly and with high accuracy.

[Modified Embodiment]
As mentioned above, although this invention was explained in full detail based on suitable embodiment, this invention is not limited to these embodiment, Various forms in the range which does not deviate from a summary are also contained in this invention. Moreover, you may combine suitably a part of above-mentioned embodiment.

  For example, in the above embodiment, the case where the imaging apparatus 100 is a digital camera has been described as an example, but the imaging apparatus 100 is not limited to a digital camera. For example, the imaging apparatus 100 may be a digital video camera, or may be a smartphone that is an electronic device having both the functions of a portable information terminal and a mobile phone. Further, the imaging device 100 may be, for example, a tablet terminal, a personal digital assistant (PDA), or the like.

  In the first embodiment, the case where the autofocus operation is performed while performing live view display has been described as an example, but the present invention is not limited to this. For example, the present invention can be applied to the case where an autofocus operation is performed while capturing a moving image.

  In the above embodiment, the AF evaluation value is output from the solid-state imaging device 102 to the control unit 106, and the control unit 106 controls the optical mechanism unit 1011 via the drive unit 103 as an example. It is not limited. For example, the AF evaluation value may be directly output from the solid-state imaging device 102 to the functional block that controls the autofocus operation.

  The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

DESCRIPTION OF SYMBOLS 100 ... Imaging device 101 ... Optical barrel 102 ... Solid-state image sensor 1021 ... AF evaluation value calculation part 103 ... Drive part 106 ... Control part 201 ... Pixel 217 ... Phase difference evaluation value calculation unit 218... Contrast evaluation value calculation unit 219... Interpolation processing unit

Claims (9)

A pixel array in which a plurality of pixels are arranged in a matrix;
A first calculation unit that calculates a phase difference evaluation value for focus detection by a phase difference detection method based on a signal from a phase difference detection pixel included in the plurality of pixels;
A signal for compensating for a defect that occurs in an image signal acquired by the pixel array and is generated when the phase difference detection pixel is included in the plurality of pixels. An interpolation processing unit that generates by interpolation using signals from the pixels other than the pixels;
A second calculation unit that calculates a contrast evaluation value for focus detection by a contrast detection method based on the image signal including the signal generated by the interpolation by the interpolation processing unit. Solid-state image sensor.   When the calculation of the phase difference evaluation value is completed by the first calculation unit, the phase difference evaluation value is output regardless of whether the output of the image signal acquired by the pixel array is completed. The solid-state imaging device according to claim 1. The pixel array is formed on a first semiconductor chip;
The first calculation unit, the interpolation processing unit, and the second calculation unit are formed on a second semiconductor chip different from the first semiconductor chip,
The solid-state imaging device according to claim 1, wherein the first semiconductor chip and the second semiconductor chip are stacked.   The solid-state imaging device according to claim 1, wherein the image signal interpolated by the interpolation processing unit is output.   5. The phase difference evaluation value and the contrast evaluation value are output via an output terminal different from an output terminal from which the image signal interpolated by the interpolation processing unit is output. The solid-state image sensor of any one of these.   6. The signal readout from the row including the phase difference detection pixel is performed in parallel with the readout of the signal from the row not including the phase difference detection pixel. The solid-state imaging device according to item 1. The pixel array includes a plurality of the phase difference detection pixels,
The plurality of phase difference detection pixels include a first phase difference detection pixel that acquires a signal according to a light beam that passes through a first pupil region of an exit pupil of the imaging optical system, and the first phase difference detection pixel. A second phase difference detection pixel that acquires a signal according to a light flux that passes through a second pupil region different from the pupil region of
The first calculation unit calculates the phase difference evaluation value based on signals from the first phase difference detection pixel and the second phase difference detection pixel. The solid-state image sensor of any one of thru | or 6. A phase difference evaluation value for focus detection by a phase difference detection method based on a signal from a phase difference detection pixel included in the plurality of pixels of a pixel array in which a plurality of pixels are arranged in a matrix. Calculating steps,
A signal for compensating for a defect that occurs in an image signal acquired by the pixel array and is generated when the phase difference detection pixel is included in the plurality of pixels. Generating by interpolation using signals from said pixels other than pixels;
A method for controlling a solid-state imaging device, comprising: calculating a contrast evaluation value for focus detection by a contrast detection method based on the image signal including the signal generated by the interpolation. A pixel array in which a plurality of pixels are arranged in a matrix and a phase difference evaluation value for focus detection by a phase difference detection method are used as signals from the phase difference detection pixels included in the plurality of pixels. A defect that occurs in the image signal acquired by the first calculation unit calculated based on the pixel array, and the defect that occurs when the phase difference detection pixel is included in the plurality of pixels. An interpolation processing unit that generates a signal for compensation by interpolation using a signal from the pixel other than the phase difference detection pixel, and a contrast evaluation value for focus detection by a contrast detection method is determined by the interpolation processing unit. A solid-state imaging device having a second calculation unit for calculating based on the image signal including the signal generated by the interpolation;
An imaging apparatus comprising: a control unit that performs control for driving a focus lens based on the phase difference evaluation value and the contrast evaluation value.

Images