JP2012191400A - Imaging device and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously provide pixel signals for image display and pixel signals for focus detection in a pixel signal read operation of one frame of pixels including a pair of photoelectric conversion parts.SOLUTION: An imaging device includes control means for controlling first processing in which a first transfer switch transfers electric charges stored by a first photoelectric conversion part to a charge holding part, a signal output part outputs first signals based on electric signals corresponding to a first charge amount held by the charge holding part, a second transfer switch transfers electric charges stored by a second photoelectric conversion part to the charge holding part holding the first charge amount, and the signal output part outputs second signals based on the electric signals corresponding to a third charge amount equal to an addition value of the second charge amount corresponding to the electric charges stored by the second photoelectric conversion part and the first charge amount.

Description

  The present invention relates to an imaging element and an imaging apparatus having pixels that receive a pair of light beams.

  A pixel including a microlens and a pair of photoelectric conversion units disposed behind the microlens is integrally formed on the image sensor, and the image sensor is disposed on a predetermined focal plane of the optical system. Thus, a pair of image signals corresponding to a pair of images formed by a pair of light beams passing through the optical system is output from the pixel, and an image shift amount (spatial phase difference) between the pair of image signals is detected. An imaging device that detects the focus adjustment state of an optical system is known. Further, there is known an imaging apparatus that adds a pair of image signals in a signal output unit provided in common to the pair of photoelectric conversion units, and uses the added pixel signal as an imaging signal.

JP 2001-83407 A

  In the above-described conventional technology, a first mode in which signals from the pair of photoelectric conversion units are read independently and a second mode in which signals from the pair of photoelectric conversion units are added and read in each pixel are provided. ing. When performing focus detection, it operates in the first mode, and when performing image capture, it is necessary to operate in the second mode. Therefore, there is a problem in that focus detection and image capture cannot be performed simultaneously.

(1) The image pickup device according to claim 1 receives the incident light, generates and accumulates charges according to the amount of incident light of the incident light, and stores the charges. A charge holding unit that temporarily holds, a signal output unit that outputs an electric signal corresponding to the amount of charge held in the charge holding unit, and a charge accumulated by the first photoelectric conversion unit is transferred to the charge holding unit. A pixel including a first transfer switch and a second transfer switch for transferring the charge accumulated by the second photoelectric conversion unit to the charge holding unit, and the first transfer switch accumulated by the first photoelectric conversion unit And the signal output unit outputs a first signal based on an electrical signal corresponding to the first charge amount held by the charge holding unit, and the second transfer switch The charge accumulated by the two photoelectric conversion units is changed to the first charge. The second signal based on the electric signal corresponding to the third charge amount equal to the added value of the second charge amount corresponding to the charge and the first charge amount is And a control means for controlling the first process output by the output unit.
(2) The imaging device according to claim 5 receives the incident light, generates a charge corresponding to the incident light quantity of the incident light, and accumulates the first photoelectric conversion unit and the second photoelectric conversion unit. A charge holding unit that temporarily holds, a signal output unit that outputs an electric signal corresponding to the amount of charge held in the charge holding unit, and a charge accumulated by the first photoelectric conversion unit is transferred to the charge holding unit. A first transfer switch, a second transfer switch that transfers the charge accumulated by the second photoelectric conversion unit to the charge holding unit, and a charge that the first transfer switch accumulates by the first photoelectric conversion unit. The signal is transferred to the charge holding unit, the signal output unit outputs a first signal based on the electric signal corresponding to the first charge amount held by the charge holding unit, and the second transfer switch performs the second photoelectric conversion. The charge accumulated by the unit holds the first charge amount The signal output unit transfers the second signal based on the electric signal corresponding to the third charge amount that is transferred to the load holding unit and is equal to the sum of the second charge amount corresponding to the charge and the first charge amount. And a control means for controlling the first process to be output.
(3) An image pickup apparatus according to claim 6 is an image pickup device according to claim 2 arranged on a predetermined focal plane of the photographing optical system, and reading means for reading out the third signal and the fourth signal from the image pickup device. Output means for outputting an image based on the fourth signal; signal generation means for generating a fifth signal by subtracting the third signal from the fourth signal; and the third signal and the fifth signal And a focus detection means for detecting the focus adjustment state of the photographic optical system by calculating the phase difference between and.

  According to the present invention, an image display pixel signal and a focus detection pixel signal can be simultaneously obtained in a pixel signal readout operation for one frame of a pixel including a pair of photoelectric conversion units.

It is a cross-sectional view which shows the structure of the digital still camera of 1st Embodiment. It is a front view which shows the detailed structure of an image pick-up element. It is a figure which shows the relationship of a pair of focus detection light beam which arrives at each focus detection area from a pair of ranging pupil. It is a figure which shows the relationship of a pair of focus detection light beam which arrives at each focus detection area from a pair of ranging pupil. It is a circuit structure conceptual diagram of an image sensor. It is a detailed circuit diagram of each pixel. It is a figure which shows the detailed circuit structure for every row | line | column of a CDS circuit. It is an operation | movement timing chart of an image pick-up element. It is an operation | movement timing chart of an image pick-up element. It is a flowchart which shows the imaging operation of a digital still camera. It is a figure which shows the focus detection area on the imaging | photography screen set to the scheduled image formation surface of an interchangeable lens. It is a front view which shows the detailed structure of an image pick-up element.

--- First embodiment ---
As an image pickup apparatus including the image pickup device of the first embodiment, a lens interchangeable digital still camera will be described as an example. FIG. 1 is a cross-sectional view illustrating a configuration of a digital still camera 201 according to the first embodiment. A digital still camera 201 according to the present embodiment includes an interchangeable lens 202 and a camera body 203, and the interchangeable lens 202 is attached to the camera body 203 via a mount unit 204. An interchangeable lens 202 having various photographing optical systems can be attached to the camera body 203 via a mount unit 204.

  The interchangeable lens 202 includes a lens 209, a zooming lens 208, a focusing lens 210, a diaphragm 211, a lens drive control device 206, and the like. The lens drive control device 206 includes a microcomputer (not shown), a memory, a drive control circuit, and the like. The lens drive control device 206 performs focus control of the focusing lens 210, drive control for adjusting the aperture diameter of the aperture 211, state detection of the zooming lens 208, the focusing lens 210, and the aperture 211, and the like. Further, lens information is transmitted and camera information (defocus amount, aperture value, etc.) is received by communication with a body drive control device 214 described later. The aperture 211 forms an aperture having a variable aperture diameter at the center of the optical axis in order to adjust the amount of light and the amount of blur.

  The camera body 203 includes an image sensor 212, a body drive control device 214, a liquid crystal display element drive circuit 215, a liquid crystal display element 216, an eyepiece lens 217, a memory card 219, and the like. Pixels are arranged two-dimensionally on the image sensor 212. Details of the image sensor 212 will be described later.

  The body drive control device 214 includes a microcomputer, a memory, a drive control circuit, and the like. The body drive control device 214 repeatedly performs drive control of the image sensor 212, readout of pixel signals, focus detection calculation based on the pixel signals, and focus adjustment of the interchangeable lens 202, and generation processing of image data based on the pixel signals, and Performs recording and camera operation control. The body drive control device 214 communicates with the lens drive control device 206 via the electrical contact 213 to receive lens information and send camera information.

  The liquid crystal display element 216 functions as an electric view finder (EVF). The liquid crystal display element driving circuit 215 displays a through image on the liquid crystal display element 216 based on the image data read from the image sensor 212, and the photographer can observe the through image through the eyepiece 217. The memory card 219 is an image storage that stores image data captured by the image sensor 212.

  A subject image is formed on the imaging surface of the imaging element 212 by the light beam that has passed through the interchangeable lens 202. This subject image is photoelectrically converted by the image sensor 212, and the pixel output signal is sent to the body drive control device 214.

  The body drive control device 214 has an imaging control function and a focus detection control function, as will be described later with reference to FIG. The body drive control device 214 calculates the defocus amount based on the output signal (focus detection signal) of the pixel of the image sensor 212 and sends this defocus amount to the lens drive control device 206. In addition, the body drive control device 214 processes the output signal (image pickup signal) of the pixel of the image pickup device 212 to generate image data, stores the image data in the memory card 219, and sends it to the liquid crystal display device drive circuit 215 to send through images. Is displayed on the liquid crystal display element 216. Further, the body drive control device 214 sends aperture control information to the lens drive control device 206 to control the aperture of the aperture 211.

  The lens drive controller 206 updates the lens information according to the focusing state, zooming state, aperture setting state, aperture opening F value, and the like. Specifically, the positions of the zooming lens 208 and the focusing lens 210 and the aperture value of the aperture 211 are detected, and lens information is calculated according to these lens positions and aperture values, or prepared in advance. Lens information (F value, exit pupil distance information, etc.) corresponding to the lens position and aperture value is selected from the look-up table.

  The lens drive control device 206 calculates a lens drive amount based on the received defocus amount, and drives the focusing lens 210 to the in-focus position according to the lens drive amount. Further, the lens drive control device 206 drives the diaphragm 211 in accordance with the received diaphragm value.

  FIG. 2 is a front view showing a detailed configuration of the image sensor 212, and shows a detail of the pixel arrangement by enlarging a part of the image sensor 212. As shown in FIG. 2, pixels 311 are densely arranged on the image sensor 212 in a two-dimensional square lattice pattern. A pixel 311 indicated by a rectangle includes a rectangular microlens 10 and a pair of photoelectric conversion units 15 and 16 in which a light receiving region is separated in the horizontal direction. The focus detection pixel 311 has a color filter. The color filters include three types of color filters having different spectral sensitivity characteristics of a red filter (R), a green filter (G), and a blue filter (B), and three types having these three types of color filters. Pixels are arranged according to the arrangement rule of the Bayer array.

  The light beam incident on the pixel 311 is collected on the pair of photoelectric conversion units 15 and 16 by the microlens 10.

  3 and 4 are schematic diagrams for explaining the state of light beams received by the photoelectric conversion units 15 and 16 of the pixel 311 shown in FIG. 2, and are shown in the horizontal direction (a pair of photoelectric conversion units 15 and 16 in FIG. 2). The cross-section of the optical system and the pixel array is shown by a straight line in the direction in which the optical system is arranged. Note that the pixel structure is simplified in the figure.

  3 and 4, the photoelectric conversion units 15 and 16 of the pixels arranged on the image sensor 212 respectively receive the light beams that have passed through the openings provided by the light shielding mask (not shown) arranged in the vicinity thereof. The shape of the region through which the light beam received by the photoelectric conversion unit 16 passes through the opening of the light shielding mask is such that all the photoelectric conversion units 16 of all pixels on the distance measurement pupil plane 90 separated from the micro lens 10 by the distance measurement pupil distance d by the micro lens 10. Are projected onto a common area 96. Similarly, the shape of the region through which the light beam received by the photoelectric conversion unit 15 passes through the light shielding mask opening is the photoelectric conversion unit 15 of all pixels on the distance measurement pupil plane 90 separated from the micro lens 10 by the distance measurement pupil distance d by the micro lens 10. It is projected onto the area 95 common to all. The pair of regions 95 and 96 is called a distance measuring pupil, and this corresponds to a divided pupil in so-called pupil division type focus detection.

  Therefore, the photoelectric conversion unit 15 of each pixel receives the light beam 85 passing through the distance measuring pupil 95 and the microlens 10 of each pixel, and corresponds to the intensity of the image formed on each microlens 10 by the light beam 85. Output a signal. The photoelectric conversion unit 16 of each pixel receives a light beam 86 passing through the distance measuring pupil 96 and the microlens 10 of each pixel, and corresponds to the intensity of an image formed on the microlens 10 by the light beam 86. Output a signal.

  Actually, on the distance measuring pupil plane 90, the luminous flux is limited by the aperture of the interchangeable lens. Even in the case of the brightest aperture diameter, the aperture diameter is smaller than the area where the distance measuring pupils 95 and 96 are added. Is set to be 3 and 4, an axis 91 is a normal line to the imaging screen passing through the center of the imaging screen, and coincides with the optical axis of the imaging optical system.

  By combining the outputs of the pair of photoelectric conversion units 15 and 16 into a pair of output groups corresponding to the distance measurement pupils 95 and 96, a pair of light beams passing through the distance measurement pupils 95 and 96 respectively on the pixel array (horizontal Information on the intensity distribution of a pair of images formed in (direction) is obtained. By performing image shift detection calculation processing (correlation calculation processing, phase difference detection processing) on this information, the image shift amount of a pair of images by a so-called pupil division type phase difference detection method is detected. Furthermore, by performing a conversion operation according to the proportional relationship between the distance between the center of gravity of the pair of distance measurement pupils and the distance measurement pupil distance with respect to the image displacement amount, the current imaging plane at the focus detection position (vertical direction) and the current A deviation (defocus amount) from the image plane is calculated.

  In addition, by adding the outputs of the pair of photoelectric conversion units 15 and 16 of each pixel, the entire imaging light flux can be obtained in the same manner as a normal imaging pixel having one photoelectric conversion unit instead of the pair of photoelectric conversion units 15 and 16. An output equivalent to the case of receiving light can be obtained, whereby an image can be obtained.

  FIG. 5 is a conceptual diagram of a circuit configuration of the image sensor 212. The image sensor 212 is configured as a CMOS image sensor. The circuit configuration of the image sensor 212 will be described in a simplified manner with a layout of 4 pixels in the horizontal direction and 4 pixels in the vertical direction.

  In FIG. 5, common control signals φSn, φRn, φPn, and φQn are supplied from the vertical scanning circuit 503 to the pixels 311 belonging to the same row, for example, the nth row, in order to control the operation of each pixel 311. The output of the pixel 311 in each column is connected to a common vertical signal line 501 for each column. Each vertical signal line 501 is input to a correlated double sampling circuit (CDS circuit) 502, and sample hold and difference processing are performed for each column. The operation of the CDS circuit 502 is controlled by control signals φC1 and φC2 output from the vertical scanning circuit 503.

  The output signal for each column of the CDS circuit 502 is sequentially transferred to the output circuit 330 by the control signals (φH1 to φH4) output from the horizontal scanning circuit 504, and is amplified with the amplification degree set by the output circuit 330. Output to the outside.

  FIG. 6 is a detailed circuit diagram of each pixel 311. A pair of photoelectric conversion units included in each pixel 311 includes a pair of photodiodes PD1 and PD2. The pair of photodiodes PD1 and PD2 are connected to a floating diffusion layer (floating diffusion) FD via transfer MOS transistors 513 and 514, respectively. The transfer MOS transistors 513 and 514 are turned on by the control signals φPn and φQn, respectively, so that the charges generated and stored in the pair of photodiodes PD1 and PD2 are transferred to the floating diffusion layer FD. The floating diffusion layer FD is connected to the gate of the amplification MOS transistor AMP, and the amplification MOS transistor AMP generates a signal corresponding to the amount of charge accumulated in the floating diffusion layer FD.

  The floating diffusion layer FD is connected to the power supply voltage Vdd via the reset MOS transistor 510. When the reset MOS transistor 510 is turned on by the control signal φRn, the charge accumulated in the floating diffusion layer FD is cleared and the reset state is set.

  The output of the amplification MOS transistor AMP is connected to the vertical output line 501 via the row selection MOS transistor 512. When the row selection MOS transistor 512 is turned on by the control signal φSn, the output of the amplification MOS transistor AMP is output to the vertical output line 501.

  In FIG. 6, when the transfer MOS transistor 513 is turned on by the control signal φPn, a signal corresponding to the amount of charge accumulated in the photodiode PD1 is output from the amplification MOS transistor AMP. Next, the transfer MOS transistor 514 is turned on by the control signal φQn in this state, whereby the charge amount accumulated in the photodiodes PD1 and PD2 in the floating diffusion layer FD is added, and a signal corresponding to the added charge amount is output. Output from the amplification MOS transistor AMP.

  FIG. 7 shows a detailed circuit configuration for each column of the CDS circuit 502 of FIG. The vertical output line 501 is input to the sample & hold circuit 521 (for holding the pixel reset level) and the sample & hold circuit 522 (for holding the pixel signal level). The signal on the vertical output line 501 is sampled and held in the sample and hold circuits 521 and 522 when the control signals φC1 and φC2 are turned ON. The difference circuit 523 subtracts the signal sampled and held by the sample and hold circuit 521 from the signal sampled and held by the sample and hold circuit 522 and outputs the result.

  There are two operation modes for the operation of the image sensor, that is, a first readout mode and a second readout mode. In the first readout mode, a normal pixel signal output operation for recording an image generated by imaging, that is, an operation of reading out the added output signals of the photodiodes PD1 and PD2 from all the pixels is performed. In the second readout mode, the addition output signals of the photodiodes PD1 and PD2 are read from all the pixels in order to display an image on the liquid crystal display element 216, and the single output signal of the photodiode PD1 is read in order to perform focus detection. Perform the action. The imaging device switches between the first readout mode and the second readout mode in accordance with a control signal from the body drive control device 214, and the vertical scanning circuit 503 and the horizontal scanning circuit 504 have various control signals described above in accordance with the readout mode. Change the timing.

  FIG. 8 is an operation timing chart of the image sensor shown in FIG. 5 in the first readout mode. At time t0, the pixels 311 in the first row are selected by the control signal φS1 generated by the vertical scanning circuit 503. The control signal φR1 is turned ON at time t0, and the floating diffusion layer FD of the pixels 311 in the first row is reset to the reset level. At time t1, the control signal φR1 is turned OFF and the control signal φC1 is turned ON, and the reset level of the pixel 311 in each column is sampled and held by the CDS circuit 502 for each column. After the control signal φC1 is turned off, the control signals φP1 and φQ1 are turned on at the same time at time t2, and the charges accumulated in the photodiodes PD1 and PD2 are added in the floating diffusion layer FD, and according to the added charge amount An electric signal is output to the vertical signal line 501. At time t3, the control signals φP1 and φQ1 are simultaneously turned OFF, the control signal φC2 is turned ON, and the added signal level of the pixel 311 in each column is sampled and held by the CDS circuit 502 for each column. At this time, the CDS circuit 502 outputs a signal obtained by subtracting the reset level from the added signal level. After the control signal φC2 is turned OFF, the control signal φS1 is turned OFF at time t4, and the addition signal for each column of the CDS circuit is transferred to the output circuit 330 according to the scanning signals φH1 to φH4 sequentially issued from the horizontal scanning circuit 504. The signal is amplified with the amplification degree set by the output circuit 330 and output to the outside of the image sensor 212.

  At time t5 when the output of the addition signal of the pixel 311 in the first row from the output circuit 330 is completed, the pixel 311 in the second row is selected by the control signal φS2 generated by the vertical scanning circuit 503, and the same operation as described above. Then, the output signal 330 of the addition signal of the pixels 311 in the second row is output. Subsequently, the addition signal in the third and fourth rows is output from the output circuit 330. When the output of the addition signal of all the pixels 311 is completed, the operation returns to the first row again and the above operation is repeated periodically.

  FIG. 9 is an operation timing chart of the image sensor 212 shown in FIG. 5 in the second readout mode. A case will be described in which only the pixel 311 in the third row outputs a single signal of the photodiode PD1 for focus detection in addition to the addition signal output.

  Output of the addition signal of the pixels 311 in the first row and the second row is performed in the same manner as in the timing chart of FIG. At the time t10 when the output of the addition signal of the pixel 311 in the second row from the output circuit 330 is completed, the pixel 311 in the third row is selected by the control signal φS3 generated by the vertical scanning circuit 503. The control signal φR3 is turned ON at time t10, and the floating diffusion layer FD of the pixels 311 in the third row is reset to the reset level. At time t11, the control signal φR3 is turned OFF and the control signal φC1 is turned ON, and the reset level of the pixel 311 in each column is sampled and held by the CDS circuit 502 for each column. After the control signal φC1 is turned off, the control signal φP3 is turned on at time t12, the charge accumulated in the photodiode PD1 is transferred in the floating diffusion layer FD, and the electrical signal corresponding to the transferred charge amount is a vertical signal. Output to line 501. At time t13, the control signal φP3 is turned OFF and the control signal φC2 is turned ON, and the signal level corresponding to the amount of charge accumulated in the photodiode PD1 of the pixel 311 in each column is sampled and held by the CDS circuit 502 for each column. Is done. At this point, the CDS circuit 502 outputs a signal obtained by subtracting the reset level from the signal level corresponding to the amount of charge accumulated in the photodiode PD1. After the control signal φC2 is turned off, the output for each column of the CDS circuit 502 is transferred to the output circuit 330 according to the scanning signals φH1 to φH4 sequentially issued from the horizontal scanning circuit 504 and set by the output circuit 330 after time t14. Amplified with the amplification degree and output to the outside of the image sensor 212.

  At time t15 when the output of the single signal from the output circuit 330 according to the amount of charge accumulated in the photodiode PD1 of the pixel 311 in the third row is completed, the control signal φQ3 is turned on, and the floating diffusion layer FD performs photo The charge accumulated in the diode PD1 and the charge accumulated in the photodiode PD2 are added, and an electric signal corresponding to the added charge amount is output to the vertical signal line 501. At time t16, the control signal φQ3 is turned OFF, the control signal φC2 is turned ON, and the added signal level of the pixel 311 in each column is sampled and held by the CDS circuit 502 for each column. At this time, the CDS circuit 502 outputs a signal obtained by subtracting the reset level from the added signal level. After the control signal φC2 is turned off, the output of each column of the CDS circuit 502 is transferred to the output circuit 330 according to the scanning signals φH1 to φH4 sequentially issued from the horizontal scanning circuit 504 after time t17 and set by the output circuit 330. Amplified with the amplification degree and output to the outside of the image sensor 212.

  When the output of the addition signal of the pixel 311 in the third row is completed, the output of the addition signal of the pixel 311 in the fourth row is performed in the same manner as in the timing chart of FIG. When the output of the addition output signal of all the pixels 311 and the single signal of the third row is completed, the operation is periodically repeated by returning to the first row.

  In the timing chart of FIG. 9, it has been described that only the pixel 311 in the third row outputs a single signal of the photodiode PD1 for focus detection in addition to the addition signal output. However, a pixel row that outputs a single signal can be changed according to a selection signal from the body drive control device 214, and the vertical scanning circuit 503 and the horizontal scanning circuit 504 can perform the above-described various controls according to the selected pixel row. The timing of the signal can be changed.

  FIG. 10 is a flowchart showing an imaging operation of the digital still camera 201 of the present embodiment. Each processing step shown in FIG. 10 is executed by the body drive control device 214. When the power of the digital still camera 201 is turned on in step S100 by the body drive control device 214, the image sensor 212 starts an operation of repeating an imaging operation at a constant cycle (for example, outputting 60 frames per second). In step S110, data for one frame is read in the second read mode. Note that the single signal readout row in the second readout mode is a row corresponding to the vertical position in the shooting screen of a part of the region (focus detection area) in the shooting screen selected by the user using an operation member (not shown). is there. A single signal is read from the pixels 311 arranged in the row corresponding to the selected focus detection area, and an addition signal is read from all the pixels 311. The read single signal and addition signal are stored in the body drive control unit 214.

  In subsequent step S120, a display image is generated using the addition signal read in the second read mode as display data, and the liquid crystal display element 216 outputs the live view display. In step S130, a single signal (photodiode PD1 signal) read in the second read mode is subtracted from the addition signal (photodiode PD1 signal + photodiode PD2 signal) read and stored in the second read mode. A single signal (a signal of the photodiode PD2) corresponding to the amount of charge accumulated in the photodiode PD2 is generated.

  In step S140, out of a pair of pixel signals formed from the single signal (signal of photodiode PD1) read and stored in step S110 and the single signal generated in step S130 (signal of photodiode PD2). The phase difference between the pair of pixel signals (the signal of the photodiode PD1 and the signal of the photodiode PD2) of the pixel 311 arranged in the column corresponding to the horizontal position in the screen of the selected focus detection area is calculated. Thus, the focus adjustment state of the photographing optical system is detected. That is, focus detection is performed and a defocus amount is calculated. When the reliability of the defocus amount is low or when the defocus amount cannot be calculated, focus detection is impossible.

  In step S150, it is checked whether or not the focus is close, that is, whether or not the calculated absolute value of the defocus amount is within a predetermined value. If it is determined that the lens is not in focus, the process proceeds to step S160, where the defocus amount is transmitted to the lens drive controller 206, and the focusing lens 210 of the interchangeable lens 202 is driven to the focus position. Then, it returns to step S110 and repeats the operation | movement mentioned above.

  Even when focus detection is impossible, the process branches to this step, a scan drive command is transmitted to the lens drive control device 206, and the focusing lens 210 of the interchangeable lens 202 is scan-driven from infinity to the nearest. Then, it returns to step S110 and repeats the operation | movement mentioned above.

  If it is determined in step S150 that the focus is close to the focus, the process proceeds to step S170, and it is determined whether or not a shutter release has been performed by operating a shutter button (not shown). If it is determined that the shutter release has not been performed, the process returns to step S110 and the above-described operation is repeated. On the other hand, if it is determined that the shutter release has been performed, the process proceeds to step S180, where an aperture adjustment command is transmitted to the lens drive control unit 206, and the aperture value of the interchangeable lens 202 is set to the control F value (the F value set by the photographer or F value set automatically). When the aperture control is completed, the image pickup device 212 is caused to perform an image pickup operation with an exposure time corresponding to the subject luminance, and an addition signal is read from all the pixels 311 of the image pickup device 212 in the first read mode, and a predetermined value is added to the addition signal. The image processing is performed to generate image data.

  In subsequent step S190, the generated image data is output and stored in the memory card 219, and the process returns to step S110 to repeat the above-described operation.

  Details of calculation of the defocus amount in step S140 of FIG. 10 and general image shift detection calculation processing (correlation calculation processing) used for the calculation are disclosed in Japanese Patent Application Laid-Open No. 2010-129783. The defocus amount is calculated by multiplying the shift amount by the conversion coefficient. If, for example, a green pixel and a red pixel are arranged in the row read in the second readout mode, the defocus amounts are calculated from the green pixel data and the red pixel data, respectively. The conversion coefficient changes according to the aperture diameter (F value) because the center-of-gravity distance of the distance measurement pupil changes according to the aperture diameter.

  Since the defocus amount is calculated based on the output signal of the green pixel and similarly the defocus amount is calculated based on the output signal of the red pixel, both are averaged to obtain the final defocus amount of the selected focus detection area. Focus amount.

  In the present embodiment, in the second readout mode, signals from a pair of photoelectric conversion units are added and read out by one frame of pixel signal readout operation, and one signal of the pair of photoelectric conversion units is independently read. Can be read. Therefore, it is possible to display an image using the added signal as it is, and to perform focus detection based on a signal read out independently of the added signal. Therefore, it is not necessary to separately perform read operations for focus detection and image display as in the prior art, and the update period of image display and focus detection can be increased.

  If an image for display or recording is generated by adding signals from the pair of photoelectric conversion units read out in the first mode in a later process, considerable processing is required to perform addition processing for all pixels. A quantity is required. Since there is a time lag between signal reading from the image sensor and image generation, there is a risk that display delay is conspicuous at the time of composition change or the like, and high-speed continuous shooting recording cannot be performed. In this embodiment, since it is not necessary to add signals from the pair of photoelectric conversion units outside the imaging device, it is possible to perform quick display and recording without delay with a simple configuration.

  When signals from the pair of photoelectric conversion units are read independently, it is necessary to reset the signal output unit provided in common to the pair of photoelectric conversion units each time. However, in the present embodiment, only one signal of the pair of photoelectric conversion units is read out independently, and then the addition signal is read out. Therefore, high-speed reading can be performed.

---- Modified example ---
(1) In the above-described embodiment, in the second readout mode, one row is selected according to the position of the selected focus detection area, and single signal readout is additionally performed in that row. However, a plurality of rows may be selected and a single signal may be read out in the plurality of rows.

  For example, when the range of the focus detection area is relatively wide, a plurality of rows in the focus detection area in the vertical direction in the shooting screen are selected, and single signals are read out in the plurality of rows.

(2) In the above-described embodiment, in the second readout mode, one row is selected according to the position of the selected focus detection area, and single signals are read out in all the pixels belonging to the row. Yes. However, by limiting the control signal from the horizontal scanning circuit, the single signal may be read out only in some of the pixels belonging to the row.

  For example, when a single signal is read out, only a part of the pixels is obtained by applying a control signal from the horizontal scanning circuit only to the pixels arranged in the column corresponding to the horizontal position in the screen of the selected focus detection area. The single signal can be read out in, and the reading time as a whole can be shortened.

(3) In the above-described embodiment, in the second readout mode, single signals are read out from a row in which pixels including a pair of photoelectric conversion units arranged in the horizontal direction are arranged in the horizontal direction. However, a single signal may be read out from a column in which pixels including a pair of photoelectric conversion units arranged in the vertical direction are arranged in the vertical direction.

  For example, the timing of the control signals output from the vertical scanning circuit and the horizontal scanning circuit can be changed so that the single signal is read out only for pixels in a specific column in all rows. This makes it possible to detect the focus even when the contrast of the image changes only in the vertical direction.

(4) In the above-described embodiment, description has been made assuming that all the pixels of the image sensor have a pair of photoelectric conversion units. However, the present invention is not limited to this, and some pixels of the image sensor are The present invention can also be applied to a configuration having a pair of photoelectric conversion units.

  FIG. 11 is a diagram showing the arrangement of focus detection areas on the shooting screen set on the scheduled image plane of the interchangeable lens 202. FIG. 11 shows regions (focus detection area, focus detection position) where an image is sampled on the shooting screen in focus detection using an array of focus detection pixels including a pair of photoelectric conversion units on the image sensor 212. It is an example. In this example, focus detection areas 101 to 105 are arranged at the center (on the optical axis) on the rectangular shooting screen 100 and at five locations on the top, bottom, left, and right. Focus detection pixels are linearly arranged in the longitudinal direction of the focus detection area indicated by a rectangle. In the focus detection areas 101, 102, 103, 104, and 105, focus detection pixels are arranged in the horizontal direction.

  FIG. 12 is a front view showing a detailed configuration of the image sensor 212. Details of the pixel arrangement in which the vicinity of an arbitrary focus detection area in the focus detection areas 101, 102, 103, 104, and 105 in FIG. Show. In the imaging element 212, known imaging pixels 310 are densely arranged in a two-dimensional square lattice. Each imaging pixel 310 has one photoelectric conversion unit 11. The imaging pixel 310 includes a red pixel (R), a green pixel (G), and a blue pixel (B), and is arranged according to a Bayer arrangement rule. In FIG. 12, for focus detection, a focus detection pixel 341 having the same pixel size as the image pickup pixel and having a pair of photoelectric conversion units is essentially continuously green and blue pixels in the horizontal direction. They are arranged linearly and continuously in the horizontal direction to be arranged. The focus detection pixel 341 is provided with a color filter of the same color as that of the imaging pixel that should be originally arranged at that position.

  In the imaging device having the above-described configuration, in the second readout mode, the row corresponding to the position of the selected focus detection area has a pair of photoelectric conversion units arranged in a column corresponding to the position of the focus detection area. A single signal is read from the pixel. In such a configuration, normal imaging pixels other than the pixels corresponding to the focus detection area can be used, so that the structure of the imaging element can be simplified.

(5) In the above-described embodiment, the description has been made assuming that one pixel has a pair of photoelectric conversion units. However, the present invention is not limited to this, and includes pixels having three or more photoelectric conversion units. It can be applied to an image sensor. For example, the present invention can also be applied to an image sensor having a photoelectric conversion unit divided into four pixels as disclosed in FIG. 2 of Japanese Patent Laid-Open No. 58-24105. The photoelectric conversion units divided into four are respectively referred to as photodiodes PD1 to PD4. When reading from the pixels in one row in the second reading mode, the PD1 signal is read first, then the (PD1 + PD2) signal is read, then the (PD1 + PD2 + PD3) signal is read, and finally the (PD1 + PD2 + PD3 + PD4) signal is read. . By calculating the signal difference in post-processing, it is possible to obtain a single signal of PD2, a single signal of PD3, and a single signal of PD4.

(6) The imaging apparatus is not limited to a digital still camera having a configuration in which an interchangeable lens is attached to the camera body as described above. For example, the present invention can also be applied to a lens-integrated digital still camera or a video camera. Furthermore, the present invention can be applied to a small camera module built in a mobile phone, a surveillance camera, a visual recognition device for a robot, an in-vehicle camera, and the like.

10 microlens, 11, 15, 16 photoelectric conversion unit,
85, 86 luminous flux, 90 distance pupil plane, 91 axis, 95, 96 area,
100 shooting screen, 101-105 focus detection area,
201 digital still camera, 202 interchangeable lens, 203 camera body,
204 mount unit, 206 lens drive control device,
208 zooming lens, 209 lens, 210 focusing lens,
211 Aperture, 212 Image sensor, 213 Electrical contact,
214 body drive control device, 215 liquid crystal display element drive circuit, 216 liquid crystal display element,
217 eyepiece, 219 memory card,
310 imaging pixels, 311 pixels, 330 output circuit, 341 focus detection pixels,
501 vertical signal line, 502 CDS circuit,
503 vertical scanning circuit, 504 horizontal scanning circuit,
510 reset MOS transistor, 512 row selection MOS transistor,
513, 514 transfer MOS transistor,
521, 522 Sample and hold circuit, 523 Difference circuit

Claims (6)

A first photoelectric conversion unit and a second photoelectric conversion unit configured to receive incident light and generate and store a charge according to an incident light amount of the incident light; a charge holding unit that temporarily holds the charge; A signal output unit that outputs an electrical signal corresponding to the amount of charge held in the charge holding unit; a first transfer switch that transfers the charge accumulated by the first photoelectric conversion unit to the charge holding unit; A pixel including a second transfer switch that transfers the charge accumulated by the second photoelectric conversion unit to the charge holding unit;
The first transfer switch transfers the charge accumulated by the first photoelectric conversion unit to the charge holding unit, and the signal output unit according to a first charge amount held by the charge holding unit. And outputting a first signal based on the electrical signal, and transferring the charge accumulated by the second photoelectric conversion unit to the charge holding unit holding the first charge amount by the second transfer switch. Then, the signal output unit outputs a second signal based on the electric signal corresponding to the third charge amount equal to the added value of the second charge amount corresponding to the charge and the first charge amount. An image pickup device comprising: control means for controlling the first processing. The imaging device according to claim 1,
A reset level holding unit;
An output signal holding unit;
A differential output unit,
The pixel further includes a reset unit that resets the charge holding unit to a reset level,
The control means includes a reset level signal based on the electrical signal at the reset level according to the charge amount of the charge held by the charge holding unit and the signal output unit resets the charge holding unit by the reset unit. Controlling the first process after controlling the second process to output
The reset level holding unit holds the reset level signal output by the signal output unit,
The output signal holding unit holds the first signal and the second signal,
The differential output unit includes a third signal corresponding to a difference between the first signal held by the output signal holding unit and the reset level signal held by the reset level holding unit, and the output signal An image sensor that outputs a fourth signal corresponding to a difference between the second signal held by the holding unit and the reset level signal held by the reset level holding unit. The image sensor according to claim 1 or 2,
The first photoelectric conversion unit and the second photoelectric conversion unit have a first region and a second region that are paired on a specific surface separated from the pixel by a predetermined distance in the incident direction of the incident light. An image pickup device that receives a first light beam and a second light beam formed by passing incident light, respectively. The imaging device according to claim 3,
The pixel further comprises a microlens;
The first photoelectric conversion unit and the first region are optically conjugate by the microlens, and the second photoelectric conversion unit and the second region are optically conjugate by the microlens. An image sensor characterized by being. A first photoelectric conversion unit and a second photoelectric conversion unit that receive incident light and generate and store electric charges according to the amount of incident light of the incident light;
A charge holding unit for temporarily holding the charge;
A signal output unit that outputs an electrical signal corresponding to the amount of charge held in the charge holding unit;
A first transfer switch for transferring the charge accumulated by the first photoelectric conversion unit to the charge holding unit;
A second transfer switch for transferring the charge accumulated by the second photoelectric conversion unit to the charge holding unit;
The first transfer switch transfers the charge accumulated by the first photoelectric conversion unit to the charge holding unit, and the signal output unit according to a first charge amount held by the charge holding unit. And outputting a first signal based on the electrical signal, and transferring the charge accumulated by the second photoelectric conversion unit to the charge holding unit holding the first charge amount by the second transfer switch. Then, the signal output unit outputs a second signal based on the electric signal corresponding to the third charge amount equal to the added value of the second charge amount corresponding to the charge and the first charge amount. An image pickup device comprising: control means for controlling the first processing. The image sensor according to claim 2 or 5, which is disposed on a planned focal plane of the photographing optical system;
Reading means for reading out the third signal and the fourth signal from the imaging device;
Output means for outputting an image based on the fourth signal;
Signal generating means for generating a fifth signal by subtracting the third signal from the fourth signal;
An imaging apparatus comprising: a focus detection unit that detects a focus adjustment state of the photographing optical system by calculating a phase difference between the third signal and the fifth signal.

Images