JP2018148295A - Imaging apparatus and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of acquiring a signal for focus detection with less noise from an imaging element capable of pupil division focus detection.SOLUTION: An imaging apparatus includes an imaging element in which a plurality of pixels each having a plurality of photoelectric conversion elements are two-dimensionally arranged, an autofocus operation unit that performs focus detection processing based on a signal from the imaging device, and a control circuit that drives and controls the imaging element in a first mode when image recording or display is performed and drives and controls the imaging element in a second mode when image recording or display is not performed, and in the first mode, drive control is performed on the imaging element such that a signal obtained by mixing at least signals from the plurality of photoelectric conversion elements are output, and in the second mode, drive control is performed on the imaging element such that respective signals from the photoelectric conversion elements are output to acquire a signal for focus detection with less noise when image recording or display is not performed.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an imaging apparatus and a control method thereof.

  There has been disclosed a technique capable of pupil-focusing focus detection in an image sensor used for a digital camera, a digital video camera, or the like. For example, Patent Document 1 discloses a configuration in which one pixel of an imaging element has two photodiodes, and each photodiode receives light that has passed through different pupil regions of the imaging lens by one microlens. . In this configuration, it is possible to detect the focus by the imaging lens by comparing the output signals from the two photodiodes, and obtain the signal of the photographed image by mixing the output signals from the two photodiodes. it can.

JP 2001-124984 A

  In the above-described imaging device using an imaging element capable of pupil-division focus detection, automatic focus detection (autofocus) is performed by comparing output signals from two photodiodes that receive light that has passed through different pupil regions. Is done. However, in order to obtain a normal image signal, a signal for one photodiode and a signal for a normal image obtained by mixing the signals of two photodiodes are read from the image sensor, and subtraction processing of these signals is performed. In many cases, the signal of the other photodiode is acquired. The subtraction process for acquiring the signal of the other photodiode is a process subsequent to the signal reading from the image sensor, and therefore generally has a larger noise than the signal of the other photodiode directly read from the image sensor. An object of the present invention is to provide an imaging apparatus capable of acquiring a focus detection signal with less noise from an imaging element capable of pupil division type focus detection.

  An image pickup apparatus according to the present invention includes an image pickup element in which a plurality of pixels each having a plurality of photoelectric conversion elements are arranged two-dimensionally, a processing unit that performs a focus detection process based on a signal from the image pickup element, and a recording When recording an image on the display unit or displaying an image on the display unit, the image pickup device is driven and controlled in the first mode, the image is not recorded on the recording unit, and the display unit Control means for driving and controlling the image sensor in a second mode when the image is not displayed, and the control means has the plurality of the pixels included in at least the pixel in the first mode. The image pickup element is driven and controlled so that a signal obtained by mixing signals from the photoelectric conversion element is output from the image pickup element, and in the second mode, the signal from each of the photoelectric conversion elements included in the pixel is Output from the image sensor Wherein the drive control of the sea urchin the imaging device.

  According to the present invention, when image recording or image display is not performed, a signal from each photoelectric conversion element included in the pixel can be acquired from the imaging element, and a focus detection signal with less noise can be acquired. It becomes possible.

It is a figure which shows the structural example of the imaging device in embodiment of this invention. It is a figure which shows the structural example of the image pick-up element in this embodiment. It is a conceptual diagram with which the light beam which came out of the exit pupil of the imaging lens in this embodiment injects into a unit pixel. It is an equivalent circuit diagram of a pixel in the present embodiment. It is a figure explaining the state during the video recording in 1st Embodiment. It is a figure explaining the A and A + B image output state in a 1st embodiment. It is a figure explaining the state in the still image continuous shooting (servo continuous shooting) in 1st Embodiment. It is a figure explaining the A and B image output state in 1st Embodiment. 3 is a flowchart illustrating an operation example of the imaging apparatus according to the first embodiment. It is a figure which shows the structural example of the column A / D conversion circuit in 2nd Embodiment. 10 is a timing chart illustrating an operation example of the column A / D conversion circuit according to the second embodiment. 10 is a timing chart showing another operation example of the column A / D conversion circuit according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 is a block diagram illustrating a configuration example of an imaging apparatus according to an embodiment of the present invention. First, the imaging device 100 will be described. The shutter 12 controls the amount of light entering the image sensor 1400. The image sensor 1400 converts an optical image into an electrical signal. The optical viewfinder 104 forms incident light incident through an optical system such as a photographing lens or a diaphragm when the mirror 130 is on the optical axis by the mirror 131, and confirms the composition of a still image taken by the user. It is possible.

  The analog front-end circuit 1700 includes an analog / digital converter (A / D converter) that converts an analog signal output from the image sensor 1400 into a digital signal. A timing generator (hereinafter referred to as TG) 1800 supplies a clock signal and a control signal to the image sensor and the A / D converter, respectively. The liquid crystal monitor 1200 is an example of a display unit, and can display a live view image or a captured still image. A system control circuit (for example, CPU: Central Processing Unit) 50 controls the entire imaging apparatus 100 including image processing.

  The shutter switch 61 has two stages, and the user presses lightly to the first step is called half-press, and pressing the button deeply to the second step is called full press. When the shutter switch 61 is half-pressed, the system control circuit 50 detects the auto focus detection (auto focus, AF: Auto Focus) processing and the setting of the shutter speed and aperture value by the automatic exposure mechanism in the state before photographing. Done. Further, when the shutter switch 61 is fully pressed, the shutter 12 is operated and the photographing operation is performed.

  The start / stop switch 62 of the live view operation performs a live view operation for continuously displaying images obtained by the image sensor 1400 when a start instruction is given by the user. When the shutter switch 61 is pressed halfway during live view display, autofocus processing using the focus detection output signal of the image sensor 1400 is performed.

  In the ISO sensitivity setting switch 63, the system control circuit 50 sets the sensitivity of the imaging apparatus 100 with respect to the amount of light according to a user instruction. In the power switch 64, the system control circuit 50 switches the power of the imaging apparatus 100 on and off according to a user instruction. In addition, the power on and power off settings of various accessory devices such as the lens unit 300, the external strobe, and the recording medium 200 connected to the imaging device 100 can be switched. The continuous shooting switch 65 can be set to a mode in which still images are continuously taken while the shutter switch 61 is fully pressed.

  A volatile memory (for example, RAM: Random Access Memory) 70 temporarily records image data. The volatile memory 70 also has a function as a work memory of the system control circuit 50. A nonvolatile memory (for example, ROM: Read Only Memory) 71 stores a program used when the system control circuit 50 operates.

  The image processing unit 72 performs processing such as still image correction / compression. The autofocus calculation unit 73 calculates a position change amount of the photographing lens 310 described later from a focal length detection signal for automatic focus detection processing. The read mode control unit 74 changes the control of the drive circuit that drives the image sensor 1400 according to the read mode.

  The power control unit 80 includes a battery detection circuit, a DC-DC converter, a switch circuit that switches blocks to be energized, and the like. The power supply control unit 80 detects the presence / absence of a battery, the type of battery, and the remaining battery level, and controls the DC-DC converter based on the detection result and an instruction from the system control circuit 50, and requires a necessary voltage. It is supplied to each part including the recording medium for a long period. The power supply unit 86 includes a primary battery such as an alkaline battery or a lithium battery, a secondary battery such as a lithium ion battery, an AC adapter, or the like, and is connected to the power supply control unit 80 via connectors 82 and 84.

  The interface 90 with the recording medium 200 is connected to the recording medium 200 such as a memory card or a hard disk via a connector 92. The recording medium 200 includes a recording unit 201 configured with a semiconductor memory, a magnetic disk, and the like, and an interface 202 with the imaging apparatus 100.

  The lens unit 300 includes a photographing lens 310, a diaphragm 312, and a lens mount 316. The lens mount 316 is connected to the lens mount 106 of the imaging device 100. The lens control unit 320 is electrically connected to the connector 122 on the imaging device 100 side via the connector 322. The lens control unit 320 receives a signal from the imaging apparatus 100 via the connectors 322 and 122. The position on the optical axis of the photographic lens 310 is changed by a signal from the imaging device 100 to control the focus. Similarly, the lens control unit 320 receives a signal from the imaging device 100 and controls the size of the aperture of the diaphragm 312. The interface 120 is an interface for communicating with the lens unit 300 using an electrical signal.

  FIG. 2 is a diagram illustrating a configuration example of the image sensor 1400. In the pixel unit 208, a plurality of pixels (unit pixels) 205 are arranged in a matrix (two-dimensional), and the arrangement in the vertical direction (column direction) is referred to as a “column”, and the horizontal direction (row direction). The line is called a “line”. The vertical scanning circuit 204 outputs a signal necessary for row selection for reading a selected row and reading of electric charges to each pixel circuit for each row.

  Each pixel 205 of the pixel unit 208 is connected to a vertical output line (column output line) 410 of a corresponding column. The signal output to the vertical output line 410 is output to the horizontal scanning circuit 203 via the column gain amplifier 206 and the column circuit 207 connected to each vertical output line 410. The horizontal scanning circuit 203 sequentially outputs the signal output for one row in the horizontal direction.

  FIG. 3 is a conceptual diagram in which the light beam emitted from the exit pupil 307 of the photographing lens enters the unit pixel. The unit pixel 205 includes a microlens 304, a color filter 305, a first photodiode 306A, and a second photodiode 306B. That is, each of the plurality of pixels 205 arranged two-dimensionally in the pixel portion 208 includes a plurality of photodiodes (photoelectric conversion elements) 306A and 306B included in one microlens.

  For the pixel having the microlens 304, the optical axis 303 is the center of the light beam emitted from the exit pupil. The light that has passed through the exit pupil enters the unit pixel 205 around the optical axis 303. As shown in FIG. 3, the light beam passing through the pupil region 301 that is a partial region of the exit pupil of the photographing lens is received by the first photodiode 306A through the microlens 304. The light beam passing through the pupil region 302 that is a partial region of the exit pupil of the photographing lens is received by the second photodiode 306B through the microlens 304. As described above, the photodiodes 306A and 306B receive light from different areas of the exit pupil of the photographing lens. Therefore, the phase difference can be detected by comparing the signals of the photodiodes 306A and 306B.

  Here, a signal obtained from the first photodiode 306A is defined as an A image signal, and a signal obtained from the second photodiode 306B is defined as a B image signal. A signal obtained by mixing the A image signal and the B image signal is an A + B image signal, and the A + B image signal can be used for a captured image.

  FIG. 4 shows an equivalent circuit diagram of the pixel (unit pixel) 205. The charge generated and accumulated in the first photodiode 306A is transferred to the floating diffusion portion (hereinafter referred to as FD) 407 by controlling the transfer switch 405A by the transfer control signal 401. Further, the charge generated and accumulated in the second photodiode 306B is transferred to the FD 407 by controlling the transfer switch 405B with the transfer control signal 402. That is, transfer switches 405A and 405B are provided for each photodiode (for each photoelectric conversion element) in the photodiodes 306A and 306B included in the pixel 205.

  The source follower amplifier 408 amplifies a voltage signal based on the electric charge accumulated in the FD 407 and outputs it as a pixel signal. The output of the source follower amplifier 408 is connected to the vertical output line 410 by controlling the row selection switch 409 with the row selection control signal 404. When resetting unnecessary charges accumulated in the FD 407, the reset switch 406 is controlled by a reset control signal 403. Further, when resetting the photodiodes 306A and 306B, the transfer switches 405A and 405B are controlled by the transfer control signals 401 and 402 together with the reset switch 406 to execute the reset.

  The transfer control signals 401 and 402, the reset control signal 403, and the row selection control signal 404 are connected to the vertical scanning circuit 204, and each control signal is supplied to each row. The transfer control signals 401 and 402, the reset control signal 403, and the row selection control signal 404 are output by the system control circuit 50 controlling the vertical scanning circuit 204 via the TG 1800.

  Here, both the A image signal and the B image signal are necessary for the correlation calculation in the focus detection process. The system control circuit 50 controls the autofocus calculation unit 73 and controls the lens control unit 320 based on the result calculated by the autofocus calculation unit 73 to control the focus.

  FIG. 5 is a diagram illustrating a state during moving image shooting by the imaging device according to the first embodiment. In FIG. 5, the direction of the horizontal axis indicates the course of time. The system control circuit 50 shifts the imaging state in the imaging apparatus 100 from the standby 501 to the moving image readout state 502 via the readout mode control unit 74. When shifting the imaging state from the standby 501 to the moving image readout state 502, the system control circuit 50 shifts the imaging element 1400 from the standby state 503 to the A, A + B image output state 504 via the TG 1800. Here, the standby state is a state in which the image sensor 1400 does not output a signal, and the A and A + B image output states are states in which the image sensor 1400 outputs an A image signal and an A + B image signal.

  Thereafter, the system control circuit 50 shifts to the standby state 505 when reading of the display signal is completed, and shifts to the A, A + B image output state 506 again when the timing of the next frame comes. Then, the system control circuit 50 shifts to the standby state 507 again when reading of the display signal is completed. Thereafter, the above-described operation is repeated. During moving image shooting, for example, the imaging apparatus obtains a B image signal by subtracting an A image signal from an A + B image signal output from the imaging element 1400 in an A, A + B image output state, and obtains an A image signal. Focus detection processing is performed using the B image signal.

  FIG. 6A is a timing chart showing an example of driving the image sensor 1400 in the A, A + B image output state. FIG. 6B to FIG. 6D are diagrams illustrating signal states (potentials) of the FD 407 at each timing. In this embodiment, when a signal is accumulated in the FD 407 of the pixel 205, negative charge increases. However, in FIGS. 6B to 6D, the lower direction is set to a high potential in order to easily understand that the signal has accumulated. (The same applies to FIGS. 8B to 8E).

  In FIG. 6A, 406_i indicates the state of the reset switch of the pixel 205 in the i-th row. 405A_i indicates the state of the transfer switch connected to the first photodiode 306A of the pixel 205 in the i-th row, and 405B_i indicates the transfer connected to the second photodiode 306B of the pixel 205 in the i-th row. Indicates the switch status. 409_i indicates the state of the row selection switch of the pixel 205 in the i-th row. Here, the reset switch 406 — i is in an on state (conducting state) when it is at a low level, and is in an off state (non-conducting state) when it is at a high level. In addition, the transfer switches 405A_i and 405B_i and the row selection switch 409_i are turned on (conductive state) when at a high level, and turned off (non-conductive state) when at a low level. The same applies to FIG. 8A.

  At timing T600, the system control circuit 50 turns on the reset switch 406_1 via the TG 1800 to reset the FD 407 of the pixels 205 in the first row. At timing T601, the system control circuit 50 selects (turns on) the row selection switch 409_1 via the TG 1800 in order to read the signal of the FD 407 after reset. As a result, as shown in FIG. 6B, the potential of the FD 407 of the pixel 205 in the first row is read as a reset signal (N signal) and stored in the column circuit 207.

  At timing T602, the system control circuit 50 turns on the transfer switch 405A_1 via the TG 1800, and the A image signal is transferred to the FD 407 in the pixels 205 in the first row. As shown in FIG. 6C, the signal accumulated in the first photodiode 306A is transferred to the FD 407 of the pixel 205 in the first row. At this time, since the row selection switch 409_1 is kept in the selected state (ON state), the A image signal (A image S signal) related to the pixel 205 in the first row is sent to the column circuit 207. The read A image signal is output from the image sensor 1400 by subtracting the reset signal read at the timing T601 and stored in the column circuit 207.

  At timing T603, the system control circuit 50 turns on the transfer switches 405A_1 and 405B_1 via the TG 1800, and the A image signal and the B image signal are transferred to the FD 407 in the pixels 205 in the first row. As shown in FIG. 6D, signals accumulated in the first photodiode 306A and the second photodiode 306B are transferred to the FD 407 of the pixel 205 in the first row. At this time, since the row selection switch 409_1 is kept in the selected state (ON state), the A + B image signal (A + B image S signal) related to the pixel 205 in the first row obtained by mixing the A image signal and the B image signal. ) Is sent to the column circuit 207. The read A + B image signal is output from the image sensor 1400 by subtracting the reset signal read at the timing T601 and stored in the column circuit 207.

  At timing T604, the system control circuit 50 turns on the reset switch 406_2 via the TG 1800 to reset the FD 407 of the pixels 205 in the second row. At timing T605, the system control circuit 50 selects (turns on) the row selection switch 409_2 via the TG 1800 in order to read the signal of the FD 407 after reset. As a result, as shown in FIG. 6B, the potential of the FD 407 of the pixel 205 in the second row is read as a reset signal (N signal) and stored in the column circuit 207.

  At timing T606, the system control circuit 50 turns on the transfer switch 405A_2 via the TG 1800, and the A image signal is transferred to the FD 407 in the pixels 205 in the second row as shown in FIG. At this time, since the row selection switch 409_2 is kept in the selected state (ON state), the A image signal (A image S signal) related to the pixel 205 in the second row is sent to the column circuit 207. The read A image signal is output from the image sensor 1400 by subtracting the reset signal read at the timing T605 and stored in the column circuit 207.

  At timing T607, the system control circuit 50 turns on the transfer switches 405A_2 and 405B_2 via the TG 1800, and the A image signal and the B image signal are output from the pixel 205 in the second row as shown in FIG. It is transferred to the FD 407. At this time, since the row selection switch 409_2 is kept in the selected state (ON state), the A + B image signal (A + B image S signal) related to the pixel 205 in the second row obtained by mixing the A image signal and the B image signal. ) Is sent to the column circuit 207. The read A + B image signal is output from the image sensor 1400 by subtracting the reset signal read at timing T605 and stored in the column circuit 207.

  At timing T608, the system control circuit 50 turns on the reset switch 406_3 via the TG 1800 to reset the FD 407 of the pixels 205 in the third row. At timing T609, the system control circuit 50 selects (turns on) the row selection switch 409_3 via the TG 1800 in order to read the signal of the FD 407 after reset. As a result, as shown in FIG. 6B, the potential of the FD 407 of the pixel 205 in the third row is read as a reset signal (N signal) and stored in the column circuit 207.

  At timing T610, the system control circuit 50 turns on the transfer switch 405A_3 via the TG 1800, and the A image signal is transferred to the FD 407 in the pixels 205 in the third row as shown in FIG. At this time, since the row selection switch 409_3 is kept in the selected state (ON state), the A image signal (A image S signal) related to the pixel 205 in the third row is sent to the column circuit 207. The read A image signal is output from the image sensor 1400 by subtracting the reset signal read at the timing T609 and stored in the column circuit 207.

At timing T611, the system control circuit 50 turns on the transfer switches 405A_3 and 405B_3 via the TG 1800, and the A image signal and the B image signal are output from the pixels 205 in the third row as shown in FIG. It is transferred to the FD 407. At this time, since the row selection switch 409_3 is maintained in the selected state (ON state), the A + B image signal (A + B image S signal) related to the pixel 205 in the third row obtained by mixing the A image signal and the B image signal. ) Is sent to the column circuit 207. The read A + B image signal is output from the image sensor 1400 by subtracting the reset signal read at time T609 and stored in the column circuit 207.
Thereafter, the same driving is repeated for the pixels 205 in the fourth and subsequent rows.

  FIG. 7 is a diagram for explaining a state when an AF signal is read for servo AF during still image continuous shooting by the imaging apparatus according to the first embodiment. In the servo AF, the autofocus operation is continuously performed while the shutter switch 61 is being pressed. The system control circuit 50 controls the imaging state in the imaging device 100 via the readout mode control unit 74. The system control circuit 50 further controls the output state of the image sensor 1400 via the TG 1800.

  When the imaging state is the standby 700, the output state of the imaging element 1400 is a standby state 706 in which no signal is output. When the imaging state becomes a still image reading state 701 for reading a still image, the output state of the imaging element 1400 becomes an A + B image output state 707 for outputting an A + B image signal. After the still image is read, the imaging state returns to the standby 702 again, and the output state of the imaging element 1400 also becomes the standby state 708.

  Thereafter, when the imaging state becomes the AF readout state 703 in which the focus detection signal is read out, the output state of the imaging element 1400 becomes the A and B image output states 709 in which the A image signal and the B image signal are output, respectively. After the AF signal is read, the imaging state returns to the standby 704 again, and the output state of the imaging element 1400 also becomes the standby state 710. Thereafter, when continuous shooting of still images is continued, the imaging state becomes the still image readout state 705, the output state of the image sensor 1400 becomes the A + B image output state 711, and then standby and AF readout are performed as necessary. Continues to.

  In this way, when the image sensor 1400 is driven and controlled to output an A + B image signal related to a still image repeatedly a plurality of times, the A related to focus detection until the next drive control to output the A + B image signal. The image sensor 1400 is driven and controlled so as to output an image signal and a B image signal. That is, when the drive control of the image sensor 1400 is performed a plurality of times so as to output the A + B image signal, the A image signal and B related to focus detection are performed during the drive control of the image sensor 1400 so as to output the A + B image signal. Drive control of the image sensor 1400 is performed so as to output an image signal. In servo AF during still image continuous shooting, the imaging apparatus performs focus detection processing using the A image signal and the B image signal output from the imaging element 1400, respectively.

  FIG. 8A is a timing chart showing a driving example of the image sensor 1400 in the A and B image output states. FIG. 8B to FIG. 8E are diagrams illustrating signal states (potentials) of the FD 407 at each timing.

  At timing T800, the system control circuit 50 turns on the reset switch 406_1 via the TG 1800 to reset the FD 407 of the pixels 205 in the first row. At timing T801, the system control circuit 50 selects (turns on) the row selection switch 409_1 via the TG 1800 in order to read the signal of the FD 407 after reset. As a result, as shown in FIG. 8B, the potential of the FD 407 of the pixels 205 in the first row is read as a reset signal (N signal) and stored in the column circuit 207.

  At timing T802, the system control circuit 50 turns on the transfer switch 405A_1 via the TG 1800, and the A image signal is transferred to the FD 407 in the pixels 205 in the first row. As shown in FIG. 8C, the signal accumulated in the first photodiode 306A is transferred to the FD 407 of the pixel 205 in the first row. At this time, since the row selection switch 409_1 is kept in the selected state (ON state), the A image signal (A image S signal) related to the pixel 205 in the first row is sent to the column circuit 207. The read A image signal is output from the image sensor 1400 by subtracting the reset signal read and stored in the column circuit 207 at timing T801.

  At timing T803, the system control circuit 50 turns on the reset switch 406_1 via the TG 1800 to reset the FD 407 of the pixels 205 in the first row again. At timing T804, the system control circuit 50 selects (turns on) the row selection switch 409_1 via the TG 1800 in order to read the signal of the FD 407 after reset. As a result, as shown in FIG. 8D, the potential of the FD 407 of the pixel 205 in the first row is read again as a reset signal (N signal) and stored in the column circuit 207.

  At timing T805, the system control circuit 50 turns on the transfer switch 405B_1 via the TG 1800, and the B image signal is transferred to the FD 407 in the pixels 205 in the first row. As shown in FIG. 8E, the signal accumulated in the second photodiode 306A is transferred to the FD 407 of the pixel 205 in the first row. At this time, since the row selection switch 409_1 is maintained in the selected state (ON state), the B image signal (B image S signal) related to the pixel 205 in the first row is sent to the column circuit 207. The read B image signal is output from the image sensor 1400 by subtracting the reset signal read at timing T804 and stored in the column circuit 207.

  At timing T806, the system control circuit 50 turns on the reset switch 406_2 via the TG 1800 to reset the FD 407 of the pixels 205 in the second row. At timing T807, the system control circuit 50 selects (turns on) the row selection switch 409_2 via the TG 1800 in order to read out the signal of the FD 407 after reset. As a result, as shown in FIG. 8B, the potential of the FD 407 of the pixel 205 in the second row is read as a reset signal (N signal) and stored in the column circuit 207.

  At timing T808, the system control circuit 50 turns on the transfer switch 405A_2 via the TG 1800, and the A image signal is transferred to the FD 407 in the pixels 205 in the second row as shown in FIG. At this time, since the row selection switch 409_2 is kept in the selected state (ON state), the A image signal (A image S signal) related to the pixel 205 in the second row is sent to the column circuit 207. The read A image signal is output from the image sensor 1400 by subtracting the reset signal read and stored in the column circuit 207 at timing T807.

  At timing T809, the system control circuit 50 turns on the reset switch 406_2 via the TG 1800 to reset the FD 407 of the pixels 205 in the second row again. At timing T810, the system control circuit 50 selects (turns on) the row selection switch 409_2 via the TG 1800 in order to read the signal of the FD 407 after reset. As a result, the potential of the FD 407 of the pixel 205 in the second row is read again as a reset signal (N signal) and stored in the column circuit 207 as shown in FIG.

  At timing T811, the system control circuit 50 turns on the transfer switch 405B_2 via the TG 1800, and the B image signal is transferred to the FD 407 at the pixels 205 in the second row as shown in FIG. At this time, since the row selection switch 409_2 is kept in the selected state (ON state), the B image signal (B image S signal) related to the pixel 205 in the second row is sent to the column circuit 207. The read B image signal is output from the image sensor 1400 by subtracting the reset signal read at the timing T810 and stored in the column circuit 207.

  At timing T812, the system control circuit 50 turns on the reset switch 406_3 via the TG 1800 to reset the FD 407 of the pixels 205 in the third row. At timing T813, the system control circuit 50 selects (turns on) the row selection switch 409_3 via the TG 1800 in order to read the signal of the FD 407 after reset. As a result, as shown in FIG. 8B, the potential of the FD 407 of the pixel 205 in the third row is read as a reset signal (N signal) and stored in the column circuit 207.

  At timing T814, the system control circuit 50 turns on the transfer switch 405A_3 via the TG 1800, and the A image signal is transferred to the FD 407 in the pixels 205 in the third row as shown in FIG. 8C. At this time, since the row selection switch 409_3 is kept in the selected state (ON state), the A image signal (A image S signal) related to the pixel 205 in the third row is sent to the column circuit 207. The read A image signal is output from the image sensor 1400 by subtracting the reset signal read at the timing T813 and stored in the column circuit 207.

  At timing T815, the system control circuit 50 turns on the reset switch 406_3 via the TG 1800 to reset the FD 407 of the pixels 205 in the third row again. At timing T816, the system control circuit 50 selects (turns on) the row selection switch 409_3 via the TG 1800 in order to read out the signal of the FD 407 after reset. Thereby, as shown in FIG. 8D, the potential of the FD 407 of the pixel 205 in the third row is read again as a reset signal (N signal) and stored in the column circuit 207.

  At timing T817, the system control circuit 50 turns on the transfer switch 405B_3 via the TG 1800, and the B image signal is transferred to the FD 407 in the pixels 205 in the third row as shown in FIG. At this time, since the row selection switch 409_3 is kept in the selected state (ON state), the B image signal (B image S signal) related to the pixel 205 in the third row is sent to the column circuit 207. The read B image signal is output from the image sensor 1400 by subtracting the reset signal read at the timing T816 and stored in the column circuit 207.

  Thereafter, the same driving is repeated for the pixels 205 in the fourth and subsequent rows. Note that the area of the image sensor 1400 from which signals are read out in the A and B image output states is only an area necessary for autofocus processing, for example, an area corresponding to a distance measuring point. For this reason, the area of the image sensor 1400 that reads signals when in the A and B image output states may be read out only in a region that is narrower than the area where the signals are read when in the A and A + B image output states. Speeding up is possible.

  FIG. 9 is a flowchart illustrating an operation example of the imaging apparatus according to the first embodiment. FIG. 9 shows an operation example in which servo AF is performed during still image continuous shooting in the imaging apparatus. When continuous shooting by servo AF is started, the system control circuit 50 controls the image sensor 1400 via the TG 1800 and controls to read out an A + B image signal for outputting a normal image as a still image ( S901). When the reading of the A + B image signal is completed, the system control circuit 50 checks whether or not the continuous shooting is finished (S902). When the system control circuit 50 determines that the continuous shooting is completed, the imaging apparatus ends the continuous shooting operation in the servo AF and shifts to the live view operation.

  On the other hand, when the continuous shooting is not completed, that is, when the system control circuit 50 determines that continuous shooting is to be continued, the system control circuit 50 controls the image sensor 1400 via the TG 1800 and the A image signal and the B image signal are used for AF. Drive control is performed to perform reading (S903). Subsequently, based on the read A image signal and B image signal, the autofocus calculation unit 73 performs a calculation for focusing on the subject (S904). Next, the system control circuit 50 controls the lens control unit 320 based on the calculation result in the autofocus calculation unit 73 to appropriately change the position of the photographing lens 310 and focus (S905). Thereafter, drive control is performed so that the A + B image signal is read again for outputting a normal image that is a still image.

  As described above, in the first embodiment, when recording or displaying an image, the image sensor 1400 is driven and controlled so that at least an A + B image signal is output from the image sensor 1400. In addition, when focus detection is performed and no image recording or display is performed, the image sensor 1400 is driven and controlled so that an A image signal and a B image signal are output from the image sensor 1400. Thus, according to the first embodiment, when recording or display of an image is not performed, a signal from each photoelectric conversion element can be directly acquired from the imaging element 1400, and a focus detection signal with less noise is acquired. It becomes possible to do.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. The second embodiment is an image pickup apparatus having a digital image pickup device having a function (column A / D conversion circuit) for performing analog-to-digital conversion for each column, and the A and A + B image signals shown in the first embodiment. Reading and reading of A and B images are applied. Hereinafter, only points of the second embodiment that are different from the first embodiment will be described.

  FIG. 10 shows an equivalent circuit diagram of the column A / D conversion circuit in the second embodiment. The column A / D conversion circuit illustrated in FIG. 10 is provided in the column circuit 207 of the imaging element 1400. In the column A / D conversion circuit, the signal output to the vertical output line (column output line) 410 by the system control circuit 50 driving and controlling the image sensor 1400 via the TG 1800 is input to one input terminal of the comparator 1001. Entered. The signal line 1000 from the reference signal generator 1003 controlled by the timing control unit 1004 is input to the other input terminal of the comparator 1001.

  The output of the comparator 1001, which is a comparison result between the ramp signal (reference signal) supplied via the signal line 1000 and the signal input via the vertical output line 410, is output to the counter 1002. The ramp signal (reference signal) is a signal whose potential (signal level) changes in one direction as time passes during scanning. The counter 1002 performs a count operation using the clock signal 1005 supplied from the timing control unit 1004. The counter 1002 counts the time from the start of scanning of the ramp signal until the comparison result output from the comparator 1001 is inverted, and outputs the count value, which is the counting result, as a digital signal.

  FIG. 11 is a timing chart showing an operation example of the column A / D conversion circuit in the second embodiment, and shows an operation example in the case of reading out the A and A + B image signals.

  The reset level is output from the pixel 205 to the vertical output line 410 at timing T1100. At timing T1100, the system control circuit 50 controls the timing control unit 1004 and the reference signal generator 1003 starts scanning the ramp signal (reference signal) from the initial level. The system control circuit 50 controls the timing control unit 1004 to output a clock signal having a predetermined cycle to the counter 1002 while the reference signal generator 1003 scans the ramp signal. The counter 1002 counts clock signals. Here, the predetermined period is a period determined by the scanning period of the ramp signal and the bit accuracy of the digital output. For example, when the ramp signal scanning period is 256 μs and an 8-bit output value is acquired, 256 counts are necessary, and the period of the clock signal is 1 μs.

  At timing T1101, since the reset level and the level of the ramp signal match, the output of the comparator 1001 changes from the high level to the low level. Since the output of the comparator 1001 works as an enable of the counter 1002, the count operation of the counter 1002 is stopped when the output of the comparator 1001 becomes low level. When the ramp signal is scanned to the pixel saturation level at timing T1102, the system control circuit 50 controls the timing control unit 1004 to set the level of the ramp signal output from the reference signal generator 1003 to an initial value. At timing T1103, the system control circuit 50 controls the timing control unit 1004 to store the count value of the reset level in the reset value memory in the counter 1002, and reset the counter 1002 to the initial value. Thereafter, the signal level of the A image signal is read from the pixel 205 to the vertical output line 410.

  At timing T1104, the system control circuit 50 controls the timing control unit 1004 to AD convert the signal level of the A image signal read to the vertical output line 410, and the reference signal generator 1003 scans the ramp signal from the initial level. To start. The system control circuit 50 controls the timing control unit 1004 to output a clock signal having a predetermined cycle to the counter 1002 while the reference signal generator 1003 scans the ramp signal. The counter 1002 counts clock signals.

  Since the signal level of the A image signal and the signal level of the ramp signal match at timing T1105, the output of the comparator 1001 changes from the high level to the low level, and the count operation of the counter 1002 is performed when this output becomes the low level. Will stop. When the ramp signal is scanned to the pixel saturation level at timing T1106, the system control circuit 50 controls the timing control unit 1004 to set the ramp signal level to the initial value. At timing T1107, the system control circuit 50 controls the timing control unit 1004 to store the count value of the signal level of the A image signal in the A image signal value memory in the counter 1002, and reset the counter 1002 to an initial value. Thereafter, the signal level of the A + B image signal is read from the pixel 205 to the vertical output line 410.

  At timing T1108, the system control circuit 50 controls the timing control unit 1004 to perform AD conversion on the signal level of the A + B image signal read to the vertical output line 410, and the reference signal generator 1003 scans the ramp signal from the initial level. To start. The system control circuit 50 controls the timing control unit 1004 to output a clock signal having a predetermined cycle to the counter 1002 while the reference signal generator 1003 scans the ramp signal. The counter 1002 counts clock signals.

  At timing T1109, the signal level of the A + B image signal matches the signal level of the ramp signal, so that the output of the comparator 1001 changes from the high level to the low level, and the count operation of the counter 1002 is performed when this output becomes the low level. Will stop. When the ramp signal is scanned to the pixel saturation level at timing T1110, the system control circuit 50 controls the timing control unit 1004 to set the ramp signal level to the initial value. At timing T1111, the system control circuit 50 controls the timing controller 1004 to store the count value of the signal level of the A + B image signal in the A + B image signal value memory in the counter 1002, and reset the counter 1002 to the initial value.

  FIG. 12 is a timing chart showing an operation example of the column A / D conversion circuit according to the second embodiment, and shows an operation example in the case of reading out the A and B image signals.

  At timing T1201, the reset level is output from the pixel 205 to the vertical output line 410. At timing T1201, the system control circuit 50 controls the timing control unit 1004, and the reference signal generator 1003 starts scanning the ramp signal from the initial level. The system control circuit 50 controls the timing control unit 1004 to output a clock signal having a predetermined cycle to the counter 1002 while the reference signal generator 1003 scans the ramp signal. The counter 1002 counts clock signals.

  Here, in the present embodiment, compared with the reading operation of the A and A + B image signals, the scanning time of the ramp signal is shortened in the reading operation of the A and B image signals due to the signal amount. That is, the processing time for one analog-digital conversion in the reading operation for the A and B image signals is made shorter than the processing time for one analog-digital conversion in the reading operation for the A, A + B image signals. For example, it is assumed that the scanning period of the ramp signal is 256 μs in order to output an 8-bit precision in the read operation of the A and A + B image signals while the period of the clock signal remains 1 μs. In the reading operation of the A and B image signals, the scanning period of the ramp signal is driven at 128 μs in order to output 7-bit precision.

  At timing T1202, since the reset level and the level of the ramp signal coincide with each other, the output of the comparator 1001 changes from the high level to the low level, and the count operation of the counter 1002 is stopped when the output becomes the low level. Become. When the ramp signal is scanned to the pixel saturation level at timing T1203, the system control circuit 50 controls the timing control unit 1004 to set the ramp signal level to the initial value. At timing T1204, the system control circuit 50 controls the timing control unit 1004 to store the count value of the reset level in the reset value memory in the counter 1002, and reset the counter 1002 to the initial value. Thereafter, the signal level of the A image signal is read from the pixel 205 to the vertical output line 410.

  At timing T1205, the system control circuit 50 controls the timing control unit 1004 to perform AD conversion on the signal level of the A image signal read to the vertical output line 410, and the reference signal generator 1003 scans the ramp signal from the initial level. To start. The system control circuit 50 controls the timing control unit 1004 to output a clock signal having a predetermined cycle to the counter 1002 while the reference signal generator 1003 scans the ramp signal. The counter 1002 counts clock signals.

  At timing T1206, the signal level of the A image signal matches the signal level of the ramp signal, so that the output of the comparator 1001 changes from the high level to the low level, and the count operation of the counter 1002 is performed when this output becomes the low level. Will stop. When the ramp signal is scanned to the pixel saturation level at timing T1207, the system control circuit 50 controls the timing control unit 1004 to set the level of the ramp signal to the initial value. At timing T1208, the system control circuit 50 controls the timing control unit 1004 to store the count value of the signal level of the A image signal in the A image signal value memory in the counter 1002, and reset the counter 1002 to an initial value. Thereafter, the reset signal level is read out from the pixel 205 to the vertical output line 410 again.

  At timing T1209, the system control circuit 50 controls the timing control unit 1004 to AD-convert the reset level read to the vertical output line 410, and the reference signal generator 1003 starts scanning the ramp signal from the initial level. The system control circuit 50 controls the timing control unit 1004 to output a clock signal having a predetermined cycle to the counter 1002 while the reference signal generator 1003 scans the ramp signal. The counter 1002 counts clock signals.

  Since the reset level and the signal level of the ramp signal match at timing T1210, the output of the comparator 1001 changes from the high level to the low level, and the count operation of the counter 1002 is stopped when this output becomes the low level. become. When the ramp signal is scanned to the pixel saturation level at timing T1211, the system control circuit 50 controls the timing control unit 1004 to set the ramp signal level to the initial value. At timing T <b> 1212, the system control circuit 50 controls the timing control unit 1004 to store the reset level count value in the reset value memory in the counter 1002 and reset the counter 1002 to the initial value. Thereafter, the signal level of the B image signal is read out to the vertical output line 410.

  At timing T1213, the system control circuit 50 controls the timing control unit 1004 to perform AD conversion on the signal level of the B image signal read to the vertical output line 410, and the reference signal generator 1003 scans the ramp signal from the initial level. To start. The system control circuit 50 controls the timing control unit 1004 to output a clock signal having a predetermined cycle to the counter 1002 while the reference signal generator 1003 scans the ramp signal. The counter 1002 counts clock signals.

  At timing T1214, since the signal level of the B image signal matches the ramp signal level, the output of the comparator 1001 changes from the high level to the low level, and the count operation of the counter 1002 stops when the output changes to the low level. It will be in the state. When the ramp signal is scanned to the saturation level of the pixel at timing T1215, the system control circuit 50 controls the timing control unit 1004 to set the level of the ramp signal to an initial value. At timing T1216, the system control circuit 50 controls the timing controller 1004 to store the count value of the signal level of the B image signal in the B image signal value memory in the counter 1002, and reset the counter 1002 to the initial value.

  According to the second embodiment, as in the first embodiment, when recording or display of an image is not performed, a signal from each photoelectric conversion element can be directly acquired from the image sensor 1400, and the focus is low in noise. It is possible to acquire a detection signal. In the above-described example, when the A image signal and the B image signal are read, a processing time of 128 × 4 = 512 μs is required for AD conversion with 7-bit accuracy, for example. When reading out the A image signal and the A + B image signal, a processing time of 256 × 3 = 768 μs is required with 8-bit accuracy. Therefore, it is possible to shorten the processing time required for AD conversion.

(Other embodiments of the present invention)
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 the 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.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

DESCRIPTION OF SYMBOLS 100: Imaging device 200: Recording medium 300: Lens unit 50: System control circuit 61: Shutter switch 62: Switch 65: Continuous shooting switch 73: Auto focus calculating part 310: Shooting lens 1200: Liquid crystal monitor 1400: Image sensor 1800: Timing Generator 204: Vertical scanning circuit 205: Pixel 207: Column circuit 304: Microlens 306A, 306B: Photodiode 405A, 405B: Transfer switch 406: Reset switch 407: Floating diffusion section (FD) 408: Source follower amplifier 409: Row selection Switch 410: Vertical output line (column output line)

Claims (11)

An image sensor in which a plurality of pixels each having a plurality of photoelectric conversion elements are arranged two-dimensionally;
Processing means for performing focus detection processing based on a signal from the image sensor;
When recording an image on the recording unit or displaying an image on the display unit, the image pickup device is driven and controlled in the first mode, and no image is recorded on the recording unit, and the display unit Control means for driving and controlling the image sensor in the second mode when not displaying an image at
In the first mode, the control unit drives and controls the image sensor so that a signal obtained by mixing at least signals from the plurality of photoelectric conversion elements included in the pixel is output from the image sensor. In the second mode, the image pickup device is driven and controlled so that a signal from each of the photoelectric conversion elements of the pixel is output from the image pickup device.   The imaging apparatus according to claim 1, wherein an area of the imaging element from which a signal is read out in the second mode is narrower than an area of the imaging element from which a signal is read out in the first mode.   The imaging apparatus according to claim 2, wherein an area of the imaging element from which a signal is read out in the second mode is an area corresponding to a distance measuring point. The image sensor has conversion means for analog-digital conversion of signals from the pixels for each column,
The imaging apparatus according to any one of claims 1 to 3, wherein a processing time of one analog-digital conversion in the conversion unit is different between the first mode and the second mode.   The imaging apparatus according to claim 4, wherein the processing time for one analog-digital conversion in the second mode is shorter than the processing time for one analog-digital conversion in the first mode.   In the first mode, the control unit drives the image sensor so that a signal from one of the plurality of photoelectric conversion elements of the pixel is output from the image sensor. The imaging apparatus according to claim 1, wherein the imaging apparatus is controlled.   In the first mode, the control means includes a signal from the first photoelectric conversion element included in the pixel, a signal from the first photoelectric conversion element, and a second photoelectric conversion element included in the pixel. The image pickup device is driven and controlled so that a signal obtained by mixing the signal is output from the image pickup device, and in the second mode, the signal from the first photoelectric conversion device and the second photoelectric conversion device The image pickup device according to claim 1, wherein the image pickup device is driven and controlled so that signals from the image pickup device are respectively output from the image pickup device.   The processing means performs the focus detection process using a signal from the first photoelectric conversion element and a signal from the second photoelectric conversion element, and is output from the imaging element in the first mode. 8. The imaging apparatus according to claim 7, wherein a signal from the first photoelectric conversion element is obtained by subtracting a signal from the first photoelectric conversion element from the mixed signal.   The control means drives the image pickup device in the first mode and then controls to drive the image pickup device in the first mode until the image pickup device is driven in the second mode. The image pickup apparatus according to claim 1, wherein the image pickup apparatus is driven and controlled.   When performing the drive control of the image sensor in the first mode a plurality of times, the control unit performs the drive control in the second mode while performing the drive control of the image sensor in the first mode. The image pickup apparatus according to any one of claims 1 to 8, wherein drive control of the image pickup element is performed. A control method for an image pickup apparatus including an image pickup element in which a plurality of pixels each having a plurality of photoelectric conversion elements are two-dimensionally arranged,
A processing step of performing focus detection processing based on a signal from the image sensor;
When recording an image on the recording unit or displaying an image on the display unit, the image pickup device is driven and controlled in the first mode, and no image is recorded on the recording unit, and the display unit A control step of driving and controlling the image sensor in the second mode when not displaying an image at
In the control step, in the first mode, the imaging element is driven and controlled so that a signal obtained by mixing at least signals from the plurality of photoelectric conversion elements included in the pixel is output from the imaging element, A control method for an image pickup apparatus, wherein in the second mode, the image pickup element is driven and controlled so that a signal from each of the photoelectric conversion elements of the pixel is output from the image pickup element.

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