JP2019103030A - Imaging device, control method thereof, and control program - Google Patents

Abstract

Kind Code: A1 An object of the present invention is to reduce the difference in readout noise and suppress deterioration in resolution when performing readout control of an image sensor. Kind Code: A1 An image pickup apparatus has an image pickup element 106 in which a plurality of unit pixels 200 are arranged in a two-dimensional matrix, each unit pixel includes a plurality of photoelectric conversion units 202a and 202b, and an image is formed on the image pickup element 106. To obtain an image corresponding to an optical image. The CPU 109 selectively performs a first readout mode in which pixel signals are collectively read out from a plurality of photoelectric conversion units and a second readout mode in which pixel signals are read out from each of the plurality of photoelectric conversion units. The number of times the pixel signal is read out from the unit pixel is made different between the mode and the second readout mode. [Selection drawing] Fig. 9

Description

  The present invention relates to an imaging apparatus, a control method thereof, and a control program, and more particularly to reduction of noise due to readout control of an imaging device.

  Generally, in an imaging apparatus such as a digital camera, improvement in auto-focus (AF) performance is required as well as improvement in continuous shooting speed at the time of shooting a still image or a frame rate in a moving image is desired. For this reason, there are imaging devices capable of acquiring AF information as well as acquiring an image.

  By the way, there is an imaging device provided in an imaging device, in which a photodiode (PD) provided in a unit pixel is divided into two in correspondence with one microlens (ML) (Patent Document 1) 1). Here, each of the pupil-divided pixels is read out in parallel, subjected to AD conversion, and output. Further, a signal obtained by adding the two AD converted signals is output. With such a configuration, it is possible to simultaneously obtain a signal when the unit pixel is pupil-divided and a signal of the entire unit pixel.

  As described above, in Patent Document 1, AD conversion is separately performed on signals obtained from pupil-divided PDs, and the two signals after AD conversion are added to generate an image (imaging signal). For this reason, in other words, since the two signals after AD conversion are added, the noise resulting from the reading inevitably increases.

  Therefore, in the case of an image pickup element in which unit pixels subjected to pupil division and unit pixels not subjected to pupil division coexist, a difference occurs in readout noise in the unit pixels, and is recognized as pattern noise according to the pixel arrangement. There are times when

  On the other hand, noise reduction processing is performed on a signal (imaging signal) obtained by performing readout control on each of the pupil-divided pixels and digitally adding them (imaging signal) when the level of the signal is lower than a predetermined level. There is a thing (patent document 2).

  If the method described in Patent Document 2 is used, it is possible to reduce the difference in readout noise in an imaging device in which a unit pixel subjected to pupil division and a unit pixel not subjected to pupil division coexist.

JP 2014-72541 A JP, 2016-92792, A

  By the way, it is known that when the image signal is subjected to filter processing, although the noise can be reduced, the sense of resolution is lowered. As described above, if the method described in Patent Document 2 is used, the difference in read noise can be reduced. However, when the method described in Patent Document 2 is used, a difference occurs in the resolution.

  For this reason, in the case of an object having a large amount of high-frequency components, in the image pickup signal obtained by reading and controlling the pupil-divided pixels, the image processing is deteriorated due to the reduction in resolution due to the filtering process. There is.

  Therefore, an object of the present invention is to provide an imaging device capable of reducing a difference in readout noise and suppressing a reduction in resolution, a control method thereof, and a control program.

  In order to achieve the above object, an imaging device according to the present invention includes an imaging device in which a plurality of unit pixels are arranged in a two-dimensional matrix, and obtains an image according to an optical image formed on the imaging device. And each of the unit pixels includes a plurality of photoelectric conversion units, and a first readout mode in which the pixel signals are collectively read out from the plurality of photoelectric conversion units when reading out pixel signals from the unit pixels. Reading means for selectively performing a second reading mode for reading a pixel signal from each of the plurality of photoelectric conversion units; and obtaining the first reading mode and the second reading mode when obtaining the image When used, the number of times the pixel signal is read from the unit pixel in the first read mode and the second read mode is controlled by controlling the read unit. And control means for not, and having a.

  According to the present invention, it is possible to reduce the difference in readout noise and to suppress the reduction in resolution.

It is a block diagram which shows the example about the structure of the imaging device by the 1st Embodiment of this invention. It is a figure for demonstrating an example of a structure of the image pick-up element shown in FIG. It is a figure for demonstrating an example of the unit pixel in the image pick-up element shown in FIG. 2, and a read-out circuit. FIG. 3 is a diagram for explaining an example of the configuration and driving of an ADC shown in FIG. 2; It is a figure which shows the example about the structure of the signal processing circuit shown in FIG. It is a figure for demonstrating the principle of the focus adjustment operation | movement performed with the camera shown in FIG. It is a figure for demonstrating an example of the pixel read-out operation | movement performed in the camera shown in FIG. It is a timing chart for demonstrating an example of the 1st read-out method performed with the camera shown in FIG. It is a timing chart for demonstrating an example of the 2nd read-out method performed with the camera shown in FIG. It is a figure for demonstrating an example of a structure of the image pick-up element used with the camera which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating an example of the pixel read-out operation | movement performed in the camera which concerns on the 2nd Embodiment of this invention. It is a figure which shows an example of the imaging | photography mode selection screen used with the camera which concerns on the 3rd Embodiment of this invention. It is a flowchart for demonstrating the imaging | photography performed with the camera which concerns on the 3rd Embodiment of this invention.

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

First Embodiment
FIG. 1 is a block diagram showing an example of a configuration of an imaging device according to a first embodiment of the present invention.

  The illustrated imaging apparatus is, for example, a digital camera (hereinafter simply referred to as a camera), and has a first lens 100. A diaphragm 101 is disposed downstream of the first lens 100. The diaphragm 101 is driven by a diaphragm actuator 118 to adjust its aperture diameter. That is, the light amount adjustment is performed by the aperture stop 101.

  The second lens 102 and the third lens 103 are sequentially disposed downstream of the diaphragm 101. The second lens 102 and the third lens 103 are driven by the focus actuator 116 to move along the optical axis for focusing.

  A focal plane shutter (hereinafter simply referred to as a shutter) 104 is disposed downstream of the third lens 103. The shutter 104 adjusts the exposure time when shooting a still image. An optical low pass filter (LPF) 105 is disposed downstream of the shutter 104. The LPF 105 is used to reduce false color or moiré in the image. An optical image (object image) that has passed through the LPF 104 forms an image on the image sensor 106. The imaging element 106 generates an electrical signal corresponding to the optical image by photoelectric conversion, and converts the electrical signal into a digital signal by A / D conversion. The image sensor 106 is controlled by a CPU 109 described later.

  A digital signal (image data) which is an output of the image sensor 106 is sent to an image processing unit (Digital Signal Processor: DSP) 107. The DSP 107 performs predetermined processing such as correction processing and compression processing on the image data which is the output of the imaging element 106. The DSP 107 adds A image data and B image data, which will be described later, and performs correlation calculation using the image data.

  The DSP 107 temporarily stores the image data, which is the output of the image sensor 106, in the RAM 108. Furthermore, the DSP 107 stores the image data after image processing in the RAM 108. The RAM 108 is also used as a work memory of the CPU 109.

  Although the RAM 108 is used in the illustrated example, memories other than the RAM may be used if the memory has a sufficiently fast access speed and no problem in operation. Furthermore, in the illustrated example, the RAM 108 is connected to the DSP 107 and the CPU 109, but part or all of the RAM 108 may be incorporated in the DSP 107 or the CPU 109.

  The CPU 109 centrally controls the operation of the camera. For example, the CPU 109 performs drive control of the focus drive circuit 115 according to the correlation calculation result which is the output of the DSP 107 to perform focus adjustment.

  Under the control of the CPU 109, the display unit 110 displays a still image or a moving image obtained by shooting, a menu, and the like. The operation unit 111 is for performing settings such as a shooting command and shooting conditions to the CPU 109. The recording medium 112 records image data such as still image data and moving image data. The recording medium 112 is detachable from the camera. The ROM 113 stores programs executed by the CPU 109 and the like.

  The shutter drive circuit 114 controls driving of the shutter 104 under the control of the CPU 109. The focus drive circuit 115 drives the focus actuator 116 under the control of the CPU 109 to move the second lens 102 and the third lens 103 along the optical axis to perform focus adjustment. The diaphragm drive circuit 117 drives the diaphragm actuator 118 under the control of the CPU 109 to adjust the aperture of the diaphragm 101.

  FIG. 2 is a diagram for explaining an example of the configuration of the imaging device shown in FIG. FIG. 2A is a diagram showing a pixel array, and FIG. 2B is a diagram showing a circuit configuration of an imaging device.

  Referring to FIG. 2A, the imaging device 106 includes a plurality of unit pixels 200 arranged in a two-dimensional matrix, and the pixel arrangement is called a pixel array. A microlens (ML) 201 is disposed in each of the unit pixels 200, and each of the unit pixels 200 has two photodiodes (PD) 202a and 202b for performing photoelectric conversion. And these two PD 202 a and 202 b are arranged under a single ML 201.

  In the pixel array described above, the PDs 202a and 202b are pupil-divided, and an optical image is incident on the PDs 202a and 202b with a phase difference. In the following description, the PDs 202a and 202b may be referred to as an A image photoelectric conversion unit and a B image photoelectric conversion unit, respectively.

  Referring to FIG. 2B, in the illustrated example, a pixel array 300 in which unit pixels 200 are arranged in a two-dimensional matrix is shown. Here, (m + 1) pixels are arranged in the horizontal direction (row direction) , And (n + 1) unit pixels 200 are arranged in the vertical direction (column direction) (m and n are integers of 1 or more).

  The timing generator (TG) 301 generates control pulses as described later, under the control of the CPU 109. Although the TG 301 is built in the imaging device 106 in the illustrated example, the TG 301 may be provided outside the imaging device 106.

  The vertical scanning circuit 302 sends a drive signal to the unit pixel 200 at a predetermined timing according to a control pulse supplied from the TG 301. The drive signal causes each of the unit pixels 200 to output a pixel signal corresponding to the optical image. Note that the pixel signal is output to the vertical output line 303 for each row.

  The constant current source 304 cooperates with the pixel amplifier transistor 403 to constitute a source follower circuit. The readout circuit 305 amplifies the signal output from the vertical output line 303 of each column. An AD converter circuit (ADC) 306 converts the output of the read circuit 305 into a digital signal. The image signal that is the output of the ADC 306 is sequentially selected by the horizontal scanning circuit 307 and sent to the signal processing circuit 308. The signal processing circuit 308 subjects the image signal to predetermined signal processing including black level correction, defect correction, level correction and the like, and the output of the signal processing circuit 308 is output from the output unit 309 to the DSP 107.

  FIG. 3 is a diagram for explaining an example of a unit pixel and a readout circuit in the image sensor shown in FIG. FIG. 3A is a view showing the configuration of a unit pixel, and FIG. 3B is a view showing the configuration of a readout circuit.

  Referring to FIG. 3A, as described above, unit pixel 200 has PDs 202a and 202b. The A image photoelectric conversion unit transfer switch (TxA) 400 a is controlled by the A image transfer signal φtxa supplied from the vertical scanning circuit 302. The B image photoelectric conversion unit transfer switch (TxB) 400b is controlled by the B image transfer signal φtxb. Here, when the transfer signal φtxa for image A is at the high level (H level), the charge accumulated in the PD 202 a is transferred to the floating diffusion (FD) unit 401. Similarly, when the B image transfer signal φtxb is at H level, the charge accumulated in the PD 20 ba is transferred to the FD unit 401. Since these TxA and TxB are independently controlled on and off, the charges accumulated in the PDs 202a and 202b can be independently transferred to the FD unit 401.

  The reset switch 402 is a switch for initializing the FD portion 401, and is controlled by a reset signal φpres supplied from the vertical scanning circuit 302. As illustrated, the FD unit 401 is connected to the amplifier 403, and the amplifier 403 outputs a voltage according to the charge stored in the FD unit 401.

  The select switch 404 outputs a voltage output from the amplifier 403 as a pixel signal to the vertical output line 302 when the select signal (select signal) φpsel sent from the vertical scanning circuit 302 becomes H level.

  Referring to FIG. 3B, readout circuit 305 includes clamp capacitance 500, and the pixel signal output to vertical output line 303 is input to the inverting input terminal of operational amplifier 503 via clamp capacitance 500. . Further, the reference voltage Vref is input to the non-inversion input terminal of the operational amplifier 503.

  The switch 502 and the feedback capacitor 501 are connected in parallel, and the switch 502 and the feedback capacitor 501 are connected to the inverting input terminal and the output terminal of the operational amplifier 503. The switch 502 is a switch for shorting the feedback capacitance 501, and is controlled by a control pulse (control signal φcfs) supplied from the TG 301.

  FIG. 4 is a diagram for explaining an example of the configuration and driving of the ADC shown in FIG.

  The ADC 306 has a plurality of comparators 600, and the output of the readout circuit 305 and the ramp signal from the ramp signal generation circuit (Ramp) 601 are input to the comparator 600. The signal level of the ramp signal increases with the passage of time when the control pulse (control signal φadres) input from the TG 301 via the terminal 602 becomes low level (L level). Then, when the signal level of the ramp signal exceeds the output signal level of the readout circuit 305, the output of the comparator 600 switches from L level to H level.

  The output of comparator 600 is connected to latch select circuit 604. A control pulse (control signal φssel) is input to the latch selection circuit 604 from the TG 301 via the terminal 603. When the control signal φssel is at L level, the latch selection circuit 604 inputs the output of the comparator 600 to the N signal latch (Latch) 605. On the other hand, when the control signal φssel is at H level, the latch selection circuit 604 inputs the output of the comparator 600 to the S signal latch 609.

  When the control signal φssel is at L level, the latch 605 latches the output of the adder 607 at the moment when the output of the comparator 600 switches from L level to H level. The adder 607 adds the output of the latch 605 and the output (count value) of the counter 606. The count value is an output (digital value) of the read circuit 305.

  Due to the presence of the adder 607, even if the counter 806 is reset, the counter 606 can restart counting from the middle if the latch 605 holds the count value. That is, the latch 605 has a function of digitally holding the output of the reading circuit 305.

  When control signal φssel is at H level, latch selection circuit 604 inputs the output of comparator 600 to latch 609. Then, the latch 609 performs the same operation as the latch 605 to convert the output of the read circuit 305 into a digital signal.

  The outputs of latches 605 and 609 are sent to column select circuit 608. The column selection circuit 608 outputs an image signal (digital signal) to the signal processing circuit 308 as will be described later according to a control signal φhsr_i (i indicates column numbers 1 to m) input from the horizontal scanning circuit 307.

  In column selection circuit 608, the i-th column is off when control signal φhsr_i is at L level, and is disconnected from signal processing circuit 308. On the other hand, when the control signal φhsr_i is at the H level, the i-th column is turned on, and the outputs of the N signal latch 605 and the S signal latch 609 of the corresponding column are output to the signal processing circuit 308.

  The horizontal scanning circuit 307 sets the control signal φhsr_0 to the H level when detecting the rising edge of the control signal φhsr input from the TG 301 via the terminal 610 when all the control signals φhsr_i are at the L level. Thereafter, when the rising edge of φhsr is detected when control signal φhsr_i is at H level, horizontal scanning circuit 307 sets control signal φhsr_i to L level. Furthermore, the horizontal scanning circuit 307 sets the control signal φhsr_ (i + 1) to the H level. When the rising edge of the control signal φhsr is detected when the control signal φhsr_m is at the H level, the horizontal scanning circuit 307 sets all the control signals φhsr_i to the L level.

  In this manner, the horizontal scanning circuit 307 performs horizontal scanning in which the outputs of the first to m-th latches are sequentially output to the signal processing circuit 308.

  FIG. 5 is a diagram showing an example of the configuration of the signal processing circuit shown in FIG.

  The signal processing circuit 308 includes normalization operators 700a and 700b. Here, the normalization operator 700 a receives the latch signal for S signal (that is, S signal) from the ADC 306 and performs normalization processing. Similarly, the normalization operator 700b receives an N signal latch signal (that is, N signal) and performs normalization processing. The subtractor 701 subtracts the normalized N signal from the normalized S signal and outputs the result as image data.

  Each of normalization operators 700a and 700b normalizes the level of the signal output based on the setting according to the number of times of reading. For example, when two readings are performed, the level of the digital signal output from the latch is approximately doubled as compared to the case where one reading is performed. In such a case, the output level is normalized as setting of dividing the setting of the normalization operator 700 by two.

  FIG. 6 is a diagram for explaining the principle of the focusing operation performed by the camera shown in FIG. 6 (a) is a diagram showing a state in which the subject is not in focus, and FIG. 6 (b) is a diagram showing an output level in the state shown in FIG. 6 (a). Further, FIG. 6 (c) is a diagram showing a state in which the camera is in focus, and FIG. 6 (d) is a diagram showing an output level in the state shown in FIG. 6 (c).

  First, referring to FIGS. 6A and 6B, as described above, the PDs 202a and 202b share the ML 201 and are pupil-divided in the horizontal direction. The rays from the main subject 800 can then be split into rays 801 and 802 passing through different pupil planes in the horizontal direction of the lens 803.

  After passing through the lens 803, these light rays 801 and 802 are collected at the focal point 804. Since the position of the focal point 804 is different from the imaging plane, the light is incident on the PDs 202 a and 202 b of pixels at different positions in the imaging device. Therefore, the output levels of the A image 805 obtained from the PD 202a and the B image 806 obtained from the PD 202b do not match in the horizontal direction (see FIG. 6B).

  Subsequently, referring to FIGS. 6C and 6D, two light rays 801 and 802 from the main subject 800 are condensed at the focal point 807 after passing through the lens 803. Since the position of the focal point 807 is a position on the imaging plane, the light rays 801 and 802 are incident on the PDs 202a and 202b in the same pixel. Therefore, as shown in FIG. 6D, the output levels of the A image 805 and the B image 806 match in the horizontal direction.

  Thus, the A image 805 and the B image 806 can be acquired separately, and it can be determined how much the focus position is shifted with respect to the imaging surface based on the image shift information in the horizontal direction.

  In FIG. 6B, the shift amount (image shift amount) 808 is a shift amount between the A image 805 and the B image 806. The calculation of the shift amount 808 by the DSP 107 is called correlation calculation. Then, based on the displacement amount 808 calculated by the correlation calculation, the CPU 109 obtains the drive direction and the drive amount of the focusing lens (the second lens 102 and the third lens 103). The CPU 109 controls the focus drive circuit 115 based on the obtained drive direction and drive amount, and drives the focusing lens by the focus actuator 116 to perform focusing.

  In the illustrated example, the DSP 107 performs correlation calculation and the CPU 109 obtains the lens drive direction and the drive amount. However, the present invention is not limited to such a configuration. For example, the correlation operation may be performed by the CPU 109, the lens driving direction and the driving amount may be obtained by the DSP 107, or a special IC may be provided in each of them.

  As described above, in order to perform focusing, it is necessary to separately acquire the A-image 805 and the B-image 806. Now, it is assumed that a readout method of combining at the pixel signal level obtained by readout of the PDs 202 a and 202 b is a first readout method (first readout mode). Further, a method of reading out the A image signal and the B image signal independently is referred to as a second reading method (second reading mode). The second read method takes longer to read one row than the first read method.

  In the second readout method, the readout time per row increases, and thus the frame rate at the time of readout decreases if the second readout method is performed for all the pixels. Therefore, in the present embodiment, in order to perform focus detection while maintaining the read frame rate, as described later, the second read method is performed for only a part of the pixels. That is, when obtaining an image of one frame, the first read mode and the second read mode are selectively performed.

  FIG. 7 is a diagram for explaining an example of the pixel readout operation performed in the camera shown in FIG. FIG. 7A is a timing chart in the reading operation, and FIG. 7B is a diagram showing the reading in the entire imaging device.

  In FIG. 7A, in the illustrated example, the read method (read mode) is selected in row units. In the n-th row, pixel readout is performed collectively by the first readout method 900. In the first reading method, the charges transferred from the PDs 202 a and 202 b are combined by the FD unit 401 and read as an (A + B image) signal.

  In the (n + 1) th row, pixel readout is performed by the second readout method 901. In the second read method, charges are separately transferred from the PDs 202a and 202b. In the illustrated example, first, the charge is transferred from the PD 202a to the FD unit 401, and a pixel signal corresponding to the charge is read. Subsequently, after resetting the FD unit 401, the charge is transferred from the PD 202b to the FD unit 401, and a pixel signal corresponding to the charge is read.

  As described above, by limiting the pixels from which the image signal is obtained by the second readout method to a part of pixels of the imaging device, an increase in readout time can be suppressed. Then, if the second readout method is performed for only a part of the pixels, the image signal and the AF information can be performed without reducing the frame rate.

  In the example shown in FIG. 7B, in the row in which the distance measurement frame 903 is present with respect to the image sensor 902, pixel readout is performed by the second readout method only in a part of the rows. For the other rows in which the distance measurement frame 903 exists, pixel readout is performed by the first readout method.

  FIG. 8 is a timing chart for explaining an example of a first reading method performed by the camera shown in FIG.

  When the horizontal synchronization signal (HD) becomes L level at time T = t1000, reset is performed. In particular, in ADC 306, latches 605 and 609 are reset to a value of zero.

  From time T = t1000 to t1001, the reset signal φpres becomes H level, and the FD unit 401 is reset. Subsequently, at time T = t1001, the A-image transfer signal φtxa and the B-image transfer signal φtxb become H level, and the PDs 202a and 202b are reset.

  At time T = t1002, the transfer signal for image A φtxa and the transfer signal for image B φtxb become L level, and charge accumulation is started in the PDs 202a and 202b. At time T = t1003, the selection signal φpsel becomes H level, and the amplifier 403 is in the operating state. Then, at T = t1004, the reset signal φpres becomes L level, and the reset of the FD section 401 is released. When the reset is released, the charge stored in the FD unit 401 is read as a noise signal (hereinafter referred to as an N signal) and output to the read circuit 305.

  In the read circuit 305, the control signal φcfs is set to L level at time T = t1005, and the operational amplifier 503 cancels the output buffer state of the reference voltage Vref. Then, the N signal which is the output of the readout circuit 305 is output from the operational amplifier 503. At this time, the input from the readout circuit 305 to the comparator 600 starts rising as indicated by reference numeral 1000 in the figure.

  At time T = t1006, the control signal φadres becomes L level, the reset of the ramp signal generation circuit 601 and the counter 606 is released, and the AD conversion operation is started. The ramp signal input from the ramp signal generation circuit 601 to the comparator 600 is indicated by reference numeral 1001 in the drawing, and the count value of the counter 606 is indicated by reference numeral 1002.

  At time T = t1007, the ramp signal becomes larger than the input 1000 from the readout circuit, and at this time, the output of the comparator 600 rises from the L level to the H level. At time T = t1007, since the control signal φssel is at L level, the latch selection circuit 604 selects the N signal latch 605. As a result, the output of the comparator 600 is input to the latch 605.

  The latch 605 latches the output of the adder 607 at time T = t1007, but since the latch 605 has output 0 until now, the output of the adder 607 has the same value as the output of the counter 606. Here, the value is N (N is an integer of 0 or more) as indicated by reference numeral 1003 in the drawing. That is, the output of the latch 605 is N at time T = t1007.

  At time T = t1008, both the ramp signal 1001 and the count value 1002 become maximum values, and at this timing, the control signal φadres is set to H level, and the AD conversion operation of the N signal ends.

  At time T = t1009, transfer signals φtxa and φtxb attain the H level, and the charges accumulated in PDs 202a and 202b are transferred to FD portion 401. A voltage corresponding to the charge stored in the FD unit 401 is sent to the reading circuit 305 through the vertical output line 302 and the operational amplifier 503. Then, the readout circuit 305 sends a signal of signal component + noise component (hereinafter referred to as S + N signal) to the comparator 600.

  The illustrated input 1000 starts to increase at time T = t1009. At time T = t1010, control signal φssel attains the H level, and latch selection circuit 604 selects S signal latch 609. At time T = t1011, transfer signals .phi.txa and .phi.txb attain L level, and transfer of charges is completed. After that, until the time T = t1012, stabilization of the output of the reading circuit 305 is awaited.

  At time T = t1012, the control signal φadres becomes L level, and the AD conversion operation of the S + N signal is started. The S + N signal includes a pixel signal corresponding to the charge stored in the PDs 202 a and 202 b, an offset signal caused by the variation of each column of the readout circuit 305, and the like. The circuit noise component included in the S signal can be canceled by subtracting the N signal from the S + N signal, and only the S signal which is a pixel signal component can be obtained.

  The operation of AD conversion of the S + N signal is performed in the same manner as AD conversion of the N signal, and the output S of the counter 606 is latched at the output S of the counter 606 at time T = t1013. The output of the latch 609 is an AD conversion value of the S + N signal. At time T = t1014, the control signal φadres becomes H level, and the AD conversion operation is completed.

  At time T = t1015, the rising edge of control signal φhsr is input to horizontal scanning circuit 307. As a result, only the control signal φhsr_0 becomes H level from the state where all the outputs of the horizontal scanning circuit 307 are L level. Thereby, the switches of the horizontal selection circuit 608 in the first column are connected to the latches 605 and 609, and the values latched in the latches 605 and 609 are input to the signal processing circuit 308.

  In signal processing circuit 308, the values of latches 605 and 609 are processed by normalization operator 700. Here, since the values of the latches 605 and 609 are counted only once, there is no need to perform a normalization operation. For this reason, the normalization operator 700 is programmed to perform a process of 1 ×.

  Using the signal processed by the normalization operator 700, the subtractor 701 subtracts the N signal from the S + N signal to obtain only the S signal. Then, the S signal is output from the output unit 309.

  In this way, when the control signal φhsr is input after the S signal is output from the first column, only the control signal φhsr_1 becomes H level. Thus, the S signal is sequentially read in the row direction, and the S signal is read from the first column to the m-th column. Then, the horizontal scanning ends at time T = t1016.

  At time T = t1017, initialization is performed to initialize the state of the pixel. Here, the reset signal φpres becomes H level, and the FD unit 401 is initialized. Further, the control signal φcfs becomes H level, and the output of the operational amplifier 503 is put in the output buffer state of the reference voltage Vref. Further, the control signal .phi.ssel is set to the L level, and the latch selection circuit 604 selects the N signal latch 605.

  At time T = t1018, select signal φpsel attains L level, and the selected state of the row is released. Then, at time T = t1019, the falling edge of HD is input, and the latches 605 and 609 are reset.

  Thus, after the read operation of one row is completed, the read operation of the next row is started. The time T = t1019 is T = t1000 in the reading of the next row.

  FIG. 9 is a timing chart for explaining an example of a second reading method performed by the camera shown in FIG.

  At time T = t1100, HD becomes L level and reset is performed. In particular, in ADC 306, latches 605 and 609 are reset to a value of zero.

  From time T = t1100 to t1101, the reset signal φpres becomes H level, and the FD unit 401 is reset. Subsequently, at time T = t1101, the A image transfer signal φtxa and the B image transfer signal φtxb become H level, and the PDs 202a and 202b are reset.

  At time T = t1102, the A-image transfer signal φtxa and the B-image transfer signal φtxb become L level, and charge accumulation is started in the PDs 202a and 202b. At time T = t1103, the selection signal φpsel becomes H level, and the amplifier 403 is in the operating state. Then, at T = t 1104, the reset signal φpres becomes L level, and the reset of the FD section 401 is released. When the reset is released, the charge stored in the FD unit 401 is read as an N signal and is output to the reading circuit 305.

  In read circuit 305, control signal φcfs is set to L level at time T = t1105, and in operational amplifier 503, the output buffer state of reference voltage Vref is released. Then, the N signal which is the output of the readout circuit 305 is output from the operational amplifier 503. At this time, the input from the readout circuit 305 to the comparator 600 starts rising as indicated by reference numeral 1100 in the figure.

  At time T = t1106, the control signal φadres becomes L level, the reset of the ramp signal generation circuit 601 and the counter 606 is released, and the AD conversion operation is started. At time T = t1107, the output of the comparator changes from the L level to the H level, and the output of the latch 605 changes to the count value. Then, at time T = t1108, the control signal φadres becomes H level, and the AD conversion operation ends.

  At time T = t1109, control signal φadres attains the L level again. As a result, AD conversion is performed again for the same N signal. Here, the readout noise superimposed on the signal converted by the second AD conversion is different from the readout noise of the signal converted by the first AD conversion as described above. The counter 606 performs the same operation as in the first AD conversion, but the input from the latch to the adder 607 is the value of the first AD conversion.

  The output of comparator 600 changes from L level to H level at time T = t 1110, and the output of adder 607 at this time is latched by the latch. The output of the adder 607 at this time is the sum of the first AD conversion value of the N signal and the second AD conversion value.

  At time T = t1111, the AD conversion operation of the N signal ends, and the control signal φadres becomes H level. In this manner, the same N signal on which different read noises are superimposed is read twice and added.

  At time T = t 1112, the transfer signal φtxa becomes H level, and the charge stored in the PD 202 a is transferred to the FD unit 401. A voltage corresponding to the charge stored in the FD unit 401 is sent to the reading circuit 305 through the vertical output line 302 and the operational amplifier 503. Then, the readout circuit 305 inputs the signal of the S + N signal to the comparator 600.

  The input 1100 of the readout circuit 305 starts to increase at time T = t1112. At time T = t1113, the control signal φssel becomes H level, and the latch selection circuit 604 selects the S signal latch 609. At time T = t1114, transfer signal φtxa becomes L level, and transfer of charges from PD 202a is completed. After that, it waits for the output of the reading circuit 305 to be stabilized until time T = t1115.

  At time T = t1115, the control signal φadres becomes L level, and the AD conversion operation of the S + N signal is started. The operation of this A / D conversion is performed in the same manner as the A / D conversion of the N signal, and the output S of the counter 606 is latched at the time T = t1116. Then, the output of the latch 609 becomes an AD conversion value of the S + N signal.

  At time T = t1114, the control signal φadres becomes H level, and the AD conversion operation ends. Subsequently, at time T = t1118, the control signal φadres becomes L level again to start AD conversion. Then, at T = t1119, the output of the latch is the sum of the count value and the first AD conversion result.

  At time T = t1120, the control signal φadres becomes H level, and the second AD conversion operation ends. In this way, the same S + N signal on which different read noises are superimposed is read twice and addition is performed.

  At time T = t1121, the rising edge of the control signal φhsr is input to the horizontal scanning circuit 307. When the horizontal scanning circuit 307 detects the rising edge, all the outputs from the horizontal scanning circuit 307 are at L level, and only the control signal φhsr_0 becomes H level. Thereby, the switches of the horizontal selection circuit 608 of the first column are connected to the latches 605 and 609. Then, the values latched in the latches 605 and 609 are sent to the signal processing circuit 308.

  In signal processing circuit 308, the values of latches 605 and 609 are processed by normalization operator 700. Here, since the values of the latches 605 and 609 are counted twice in the read operation, the output is doubled as compared to the case where one read operation is performed. Thus, the normalization operator 700 is programmed to perform processing to halve the digital value. Using the signal processed by the normalization operator 700, the subtractor 701 subtracts the N signal from the S + N signal to obtain the S signal. Then, the S signal is output from the output unit 309.

  Thus, after the S signal is output from the first column, the control signal φhsr is input again. As a result, only the control signal φhsr_1 is at H level. In this manner, the S signal is sequentially read in the row direction, and the S signals in the first to m-th columns are read. Then, the horizontal scanning ends at time T = t1122.

  At time T = t1123, initialization is performed to initialize the state of the pixel. Here, the reset signal φpres becomes H level, and the FD unit 401 is initialized. Further, control signal φcfs attains the H level, and the output of operational amplifier 503 is brought into the output buffer state of reference voltage Vref. Further, the control signal φssel is set to the L level, and the circuit for latch selection 604 selects the latch for N signal 605.

  At time T = t 1124, select signal φpsel attains the L level, and the selected state of the row is cancelled. Then, at time T = t1125, the falling edge of HD is input, and the latches 605 and 609 are reset. Thus, the operation of reading out the A image of one row is completed, and then the operation of reading the B image is started.

  During the reading operation of the B image, the photodiode is not reset to read out the signal accumulated simultaneously with the A image.

  At time T = t1126, the selection signal φpsel becomes H level, and the amplifier 403 is put into operation. At time T = t1127, the reset signal φpres becomes L level, and the reset of the FD unit 401 is released. When the reset is released, a voltage corresponding to the charge stored in the FD unit 401 is read out as a noise component on the vertical output line 302 and output to the read out circuit 305.

  At time T = t1128, control signal φcfs attains the L level, and read circuit 305 cancels the output buffer state of reference voltage Vref in operational amplifier 503. Then, the N signal is output from the operational amplifier 503.

  At time T = t1129, the control signal φadres becomes L level, the reset of the ramp signal generation circuit 601 and the counter 606 is released, and the AD conversion operation is started. At time T = t1130, the output of the comparator changes from the L level to the H level, and the output of the latch 605 changes to the count value N1103 at this time. Then, at time T = t1131, the control signal φadres becomes H level, and the first AD conversion operation of the N signal ends.

  Subsequently, at time T = t1132, the control signal φadres becomes L level, and the second AD conversion operation of the N signal starts. At time T = t1133, the output of the comparator changes from the L level to the H level, and the output of the latch 605 is added by the adder 607 with the value of the latch 605 determined by the first AD conversion and the count value N1103. It changes to the added value. Then, at time T = t1134, the control signal φadres becomes H level, and the AD conversion operation of the N signal ends.

  In this way, the same N signal on which different read noises are superimposed is read twice to perform addition.

  At time T = t1135, the transfer signal φtxb becomes H level, and the charge stored in the PD 202b is transferred to the FD unit 401. A voltage corresponding to the charge stored in the FD unit 401 is sent to the readout circuit 305 via the vertical output line 302 and the operational amplifier 503. By this, the readout circuit 305 inputs the S + N signal to the comparator 600.

  The input 1100 from the readout circuit 305 starts to increase at time T = t1135. At time T = t1136, control signal φssel attains the H level, and latch selection circuit 604 selects S signal latch 609. At time T = t1137, the transfer signal φtxb becomes L level, and the transfer of charge from the PD 202b is completed. After that, it waits for stabilization of the output of the reading circuit 305 until time T = t1138. Then, at time T = t1138, the control signal φadres becomes L level, and the AD conversion operation of the S + N signal starts.

  The AD conversion operation is performed in the same manner as the AD conversion of the N signal, and at time T = t1139, the AD conversion value of the S + N signal is determined as the output S of the counter 606 and latched in the latch 609. At time T = t1140, the control signal φadres becomes H level, and the first AD conversion operation ends.

  Subsequently, at time T = t1141, the control signal φadres becomes L level again to start AD conversion. Then, at time T = t1142, the output of the latch is the sum of the count value and the first AD conversion result. At time T = t1143, the control signal φadres becomes L level, and the second AD conversion operation ends.

  The aforementioned horizontal transfer operation is performed from time T = t1144 to T = t1145. Also in this case, since the N signal and the S + N signal are the sum of the values obtained by the two AD conversions, they are normalized to a half value in the normalization operator 700. Thereafter, the subtractor 701 subtracts the N signal from the S + N signal to obtain the S signal related to the B image.

  At time T = t1146, initialization is performed to initialize the state of the pixel. Here, the reset signal φpres becomes H level, and the FD unit 401 is initialized. Further, control signal φcfs attains the H level, and the output of operational amplifier 503 is brought into the output buffer state of reference voltage Vref. Further, the control signal φssel is set to the L level, and the circuit for latch selection 604 selects the latch for N signal 605.

  At time T = t1147, select signal φpsel attains the L level, and the selected state of the row is cancelled. Then, at time T = t1148, the falling edge of HD is input, and the latches 605 and 609 are reset.

  In this way, the read operation of one row is completed and the read operation of the next row is started. The time T = t1148 is T = t1100 at the time of reading of the next row.

  In the examples shown in FIGS. 8 and 9, although the output from the reading circuit 305 has been described as being constant in time, the output is actually changed due to fluctuation of various signals such as a power supply. Do. Also, the quality of the ramp signal is similarly affected by fluctuations in the power supply and the like. Therefore, when the count value is always correctly counted, the result of AD conversion differs every time even if the same read operation is performed on the same signal. This variation causes read noise.

  Here, the noise amount of the image signal obtained by each of the first and second readout methods will be described. The amount of noise superimposed on the signal by one read operation is denoted by σ. This noise is known to be Gaussian noise.

In the first readout method described with reference to FIG. 8, two signals of the N signal and the S + N signal are read out and subjected to subtraction processing by the subtractor 701 to obtain the S signal. If uncorrelated Gaussian noises are added to each other, the amount of noise is (2) ^1/2 times, so the amount of readout noise present in the final S signal is σ × (2) ^1/2 .

On the other hand, in the second readout method described with reference to FIG. 9, the N signal is read twice, the S + N signal is read twice, these are normalized, and then subtraction processing is performed by the subtractor 701. The readout noise amount becomes σ × (2) ^1/2 by addition of the signals read out twice. However, since the signal strength is doubled, when it is averaged by the normalization operator 700, it is divided by 2 and the read noise amount becomes σ / (2) ^1/2 . Then, if the S + N signal and the N signal having the noise are subtracted by the subtractor 701, the amount of noise finally present in the S signal becomes σ.

Since the signals obtained by the second readout method are the signals of the A image 805 and the B image 806, when used as an image signal, it is necessary to add them by the DSP 107. Since the readout noise amounts of the A and B image signals are respectively σ as described above, the readout noise amount of the image signal obtained by adding these is σ × (2) ^1/2 Become. This noise amount is the same as the readout noise amount of the image signal obtained by the first readout method.

  Using the A image 805 and the B image 806 obtained as described above, the DSP 107 performs correlation calculation to determine the amount of shift 808 between the A image 805 and the B image 806. Then, the deviation amount 808 is sent to the CPU 109. The CPU 109 obtains the drive amount and drive direction of the focusing lenses 102 and 103 based on the shift amount. The CPU 109 controls the focus drive circuit 115 according to the drive amount and the drive direction to drive the focus adjustment lenses 102 and 103 by the focus actuator 116 to perform focus adjustment.

  Further, the DSP 107 adds the A + B signal obtained by the first reading method and the A image 805 and the B image 806 obtained by the second reading method to generate an image of one frame. Then, the CPU 109 compresses and processes the image of one frame and writes the image on the recording medium 112.

  As described above, in the first embodiment of the present invention, the number of signal readouts is made different in the first readout method and the second readout method. By this, it is possible to obtain a signal for focus detection and an image signal of one frame at high speed while suppressing the deterioration of the image quality.

  Furthermore, since the noise in the signal read by the second read method is reduced, the accuracy of the correlation calculation in the DSP 107 is improved, and the AF performance is improved.

[Modification]
In the first embodiment described above, in the second readout method, both the A image signal and the B image signal are separately read out, but the present invention is not limited to this. For example, after the A image signal is read alone, the B image signal may be transferred to the FD unit 401, and may be combined with the previously transferred A image signal and read out as an A + B image signal. In this case, the DSP 107 subtracts the A image from the A + B image to obtain the B image and performs the correlation operation.

  In the above readout method, since the image signal is read out only once, the readout noise amount is the same as the readout noise amount of the signal obtained by the first readout method. On the other hand, after reading out the N signal from the FD unit 401, it is necessary to read out the A image signal and then read out the A + B image signal without resetting the FD unit 401. Therefore, it takes time from reading out the N signal to reading out the image signal. For this reason, it is known that 1 / f noise increases, and furthermore, the state of the N signal changes to increase pixel noise. The present invention can also be applied to reduce the increase in the noise.

  That is, by reading the A image signal alone, the B image signal is transferred to the FD unit 401, and the present invention is applied to a method of combining with the A image signal transferred earlier and reading out as the A + B image signal. , Degradation of the image can be reduced.

  Furthermore, in the above-described reading method, the A image signal is not output as an image signal, so the noise amount of the A image signal does not affect the image quality. For this reason, when acquiring the A image signal, the readout operation for each signal may be performed once, and AD conversion may be performed a plurality of times when acquiring the A + B image signal.

  In the case of such a configuration, an image signal can be obtained at high speed as compared to the case where a plurality of reading operations are performed at the time of obtaining the A image signal.

  Further, in the first embodiment, after the read operation of the N signal is completed, the signal + noise component is transferred to the vertical line 303 to perform the read operation of the S + N signal, but the present invention is limited thereto. It is not a thing. For example, even if an analog memory (sample and hold circuit: not shown) is disposed immediately after the operational amplifier 503, the vertical transfer of the S + N signal and the AD conversion of the second N signal are performed in parallel in time. Good.

  In the case of such a configuration, the signal can be read out at higher speed because the readout of the signal to the vertical line 303 and the AD conversion operation are performed in parallel in time.

  Furthermore, when the main factor of the noise superimposed on the read signal is noise generated by AD conversion, only the AD conversion is performed multiple times without performing the operation of transferring the same signal to the vertical line 303 multiple times. You may In this case, vertical transfer of the S + N signal can be started immediately after sample and hold of the N signal.

  In such a configuration, the time for transferring the same signal to the vertical line 303 can be omitted, so that the signal can be read faster.

  Further, a plurality of AD conversion circuits corresponding to one column of vertical output lines 303 may be provided in the ADC 306 so that AD conversion may be performed a plurality of times in parallel in time.

  In such a configuration, two read operations of the same signal are performed in parallel, so that the signal can be read at higher speed.

  In addition, any configuration that can reduce read noise can be applied to the present invention by reading the same signal multiple times.

Second Embodiment
Subsequently, an example of a camera according to a second embodiment of the present invention will be described. The configuration of the camera according to the second embodiment is similar to that of the camera shown in FIG.

  FIG. 10 is a diagram for explaining an example of the configuration of an imaging device used in the camera according to the second embodiment of the present invention. 10 (a) is a diagram showing a pixel array, and FIG. 10 (b) is a diagram showing a configuration of a unit pixel.

  Referring to FIG. 10A, the imaging device 106 has a plurality of unit pixels 200 arranged in a two-dimensional matrix. An ML 201 is disposed in each of the unit pixels 200, and each of the unit pixels 200 has four PDs 1200a, 1200b, 1200c, and 1200d for performing photoelectric conversion. And, these four PDs 1200a, 1200b, 1200c, and 1200d are disposed under a single ML 201.

  By independently performing read control on these PDs 1200a, 1200b, 1200c, and 1200d, it is possible to obtain a phase difference in the vertical direction in addition to the phase difference in the horizontal direction.

  Thus, when the unit pixel includes more than two PDs, it is not necessary to read out all the pixels independently in order to obtain the phase difference. For example, if it is sufficient to obtain a phase difference in the horizontal direction as focus adjustment information, it is sufficient to combine and read the charges of the PDs adjacent in the vertical direction in the unit pixel. Specifically, the charges of the PDs 1200a and 1200c are combined and read out, and the charges of the PDs 1200b and PD 1200d are combined and read out.

  Referring to FIG. 10B, as described above, unit pixel 200 includes PDs 1200a, 1200b, 1200c, and 1200d. The A image photoelectric conversion unit transfer switch (TxA) 1300 a is controlled by the A image transfer signal φtxa supplied from the vertical scanning circuit 302. The B image photoelectric conversion unit transfer switch (TxB) 1300 b is controlled by the B image transfer signal φtxb. The C image photoelectric conversion unit transfer switch (TxC) 1300 c is controlled by the C image transfer signal φtxc. Further, the D image photoelectric conversion unit transfer switch (TxB) 1300d is controlled by the D image transfer signal φtxd.

  Here, when the transfer signal φtxa for the image A is at the H level, the charge accumulated in the PD 1200 a is transferred to the floating diffusion (FD) unit 401. Similarly, when the B image transfer signal φtxb is at H level, the charges accumulated in the PD 1200 b are transferred to the FD unit 401. When the C image transfer signal φtxc is at H level, the charge accumulated in the PD 1200 c is transferred to the FD unit 401. When the D image transfer signal φtxd is at H level, the charge accumulated in the PD 1200 d is transferred to the FD unit 401.

  Since the transfer switches TxA, TxB, TxC, and TxD are independently controlled on and off, the charges accumulated in the PDs 1200a, 1200b, 1200c, and 1200d can be independently transferred to the FD unit 401. If at least two of the transfer switches TxA, TxB, TxC, and TxD are simultaneously set to the H level, charges accumulated in the corresponding PD can be combined and read out by the FD unit 401.

  FIG. 11 is a diagram for explaining an example of the pixel readout operation performed in the camera according to the second embodiment of the present invention. FIG. 11A is a timing chart in the reading operation, and FIG. 11B is a diagram showing the reading in the entire imaging device.

  In FIG. 11A, in the n-th row, pixel readout is performed by the first readout method 1400. In the first readout method 1400, the charges transferred from the PDs 1200a, 1200b, 1200c, and 1200d are combined by the FD unit 401 and read out as an (A + B + C + D image) signal.

  In the (n + 1) th row, pixel readout is performed by the second readout method 1401 (third readout mode). In the second reading method 1401, charges are transferred from the PDs 1200a and 1200c (groups) to the FD unit 301 (that is, charges are read out for each group). Then, they are combined by the FD unit 401 and read out as an A + B image signal. When the second readout method 1402 is performed, a phase difference in the horizontal direction can be obtained.

  In the (n + 2) th row, the first read method 1401 is performed again. In the (n + 3) -th row, pixel readout is performed by the second readout method 1403 (fourth readout mode). Here, the image A is read from the PD 1200 a, the image B is read from the PD 1200 b, the image C is read from the PD 1200 c, and the image D is read from the PD 1200 d. Then, these readouts are performed independently for each PD (each photoelectric conversion unit). By performing such a reading method, it is possible to obtain phase differences in the horizontal direction and the vertical direction.

  In the example shown in FIG. 7B, in the row in which the distance measurement frame 903 exists with respect to the image sensor 902, pixel readout is performed on a part of the rows by the first readout method 1400, and the second The pixel readout is performed by the readout method of

  When performing the second readout method, there are a row in which the second readout method 1401 for combining signals of adjacent PDs in the vertical direction is performed, and a row in which the second readout method 1402 is performed. In addition, for the other rows in which the distance measurement frame 903 exists, the pixel readout is performed by the first readout method.

  When pixel readout is performed using the plurality of readout methods to generate an image signal, the number of signals required to generate the image signal is different. For example, since the signal obtained by the first readout method 1400 is an image signal, it is counted as one signal. In the case of the second readout method 1401, the number of signals required to generate an image signal is two. Further, in the case of the second readout method 1402, the number of signals required to generate an image signal is four.

  When a unit pixel includes a plurality of PDs divided into pupils, the PDs are independently read out and controlled to generate an image signal by adding the signals. In this case, as described in the first embodiment, the noise amount of the image signal differs according to the number of signals required to generate the image signal. In such a case, the number of readouts is determined according to the number of signals used for the combining process without determining the number of readouts according to the first readout method or the second readout method.

  For example, in the case of the first reading method 1401, as described in FIG. 8, an image signal is obtained by one reading. On the other hand, in the case of the second readout method 1401, as described in FIG. 9, an image signal is obtained by two readouts. Then, in the case of the second reading method 1402, an image signal is obtained by four readings.

  Although the case where the division number of PD in the unit pixel is four has been described here, the present invention is not limited to this, and the number of divisions of PD in the unit pixel may be plural. Further, the type of reading method is not limited.

  As described above, in the second embodiment of the present invention, since the number of times of sampling is determined according to the number of signals used to generate an image signal, in an imaging element divided into pupils in various patterns, The present invention can also be applied.

Third Embodiment
Subsequently, an example of a camera according to a third embodiment of the present invention will be described. The configuration of the camera according to the third embodiment is the same as that of the camera shown in FIG.

  When the same signal is read a plurality of times to reduce the read noise, the same signal may be read a plurality of times even when the first read method is used to obtain an image with less noise.

  For example, as shown in FIG. 2A, when the unit pixel has two PDs, two readings are performed using the first reading method, and four readings are performed using the second reading method. As a result, it is possible to obtain an image with lower noise while obtaining the same effect as the effect obtained in the first embodiment.

  However, in this case, since the number of times the signal is read in one frame is doubled, the frame rate is lowered. In order to prevent the reduction of the frame rate, for example, the number of rows using the second readout method may be reduced to reduce the number of readouts as a whole. Therefore, the number of times of sampling is set in accordance with the imaging mode selected by the user.

  FIG. 12 is a view showing an example of a shooting mode selection screen used in the camera according to the third embodiment of the present invention.

  The illustrated shooting mode selection screen 1500 is displayed on the display unit 110. The user can use the operation unit 111 to select one of the “image quality priority mode” and the “AF priority mode”.

  FIG. 13 is a flowchart for explaining shooting performed by the camera according to the third embodiment of the present invention.

  Referring to FIGS. 12 and 13, when photographing is started, CPU 109 determines whether the mode set by the user operation is the "image quality priority mode" (step S1601).

  If the user setting is “image quality priority mode” (YES in step S1601), the CPU 109 sets a first setting (setting 1) (step S1602). In this setting 1, the number of readings in the first reading method is set to two, and the number of readings in the second reading method is set to four. At this time, j is the number of rows read by the second reading method (j is an integer of 1 or more).

  If the user setting is not the “image quality priority mode” (NO in step S1601), the CPU 109 sets a second setting (setting 2). In this setting 2, the number of readings in the first reading method is set to one, and the number of readings in the second reading method is set to two. In this case, the number of rows read by the second read method is k (k is an integer of 1 or more). Note that k is a number larger than j.

  After the process of step S1602 or S1603, the CPU 109 performs photographing based on the determined setting (step S1604). Here, at the time of pixel readout, the same signal is read out according to the set number of times. For example, when the readout by the first readout method is performed twice, the operations from time T = t1006 to T = t1008 and the operations from time T = t1012 to T = t1014 shown in FIG. 8 are repeated twice each.

  When reading by the second read method is four times, the operation from time T = t1106 to T = t1111 and the operation from time T = t1115 to T = t1120 shown in FIG. 9 are repeated twice each. Furthermore, the operation from time T = t1129 to T = t1134 and the operation from time T = t1138 to T = t1143 are repeated twice each.

  In this manner, the number of times of reading the same signal is changed according to the setting even if the reading method is the same.

  Subsequently, the CPU 109 performs correlation calculation by the DSP 107 based on the image signal (image data) obtained in step S1604. Then, the CPU 109 obtains the drive direction and drive amount of the focus adjustment lenses 102 and 103 based on the correlation calculation result (step S1605: calculation for AF).

  Next, the CPU 109 drives the lens as described above based on the AF calculation result (step S1606). Then, the CPU 109 performs image processing (including compression processing) on the image signal obtained in step S1604 (step S1607). Thereafter, the CPU 109 stores the image-processed image data in a recording medium or the like (step S1608), and ends the shooting.

  By performing pixel readout as described above, an image with lower noise can be obtained in the “image quality priority mode” as compared to the “AF priority mode”. On the other hand, in the "AF priority mode", the AF accuracy can be enhanced because there are many signals that can be used for correlation calculation as compared with the "image quality priority mode".

  In the illustrated example, the “image quality priority mode” and the “AF priority mode” are displayed on the shooting mode selection screen, but the present invention is not limited to this example. For example, the number of times of sampling may be selected, or the number of times of sampling may be changed based on the change of other imaging condition settings without explicitly selecting it by the user.

  As described above, in the third embodiment of the present invention, the number of times of sampling is determined according to the setting of the imaging mode, so that imaging suitable for the imaging situation, that is, pixel readout can be performed.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, The various form of the range which does not deviate from the summary of this invention is also included in this invention .

  For example, the control method may be performed by the imaging apparatus as the control method of the above-described embodiment. In addition, a program having the functions of the above-described embodiments may be used as a control program to cause a computer included in the imaging apparatus to execute the control program. The control program is recorded, for example, on a computer readable recording medium.

Other Embodiments
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. Can also be realized. It can also be implemented by a circuit (eg, an ASIC) that implements one or more functions.

106 image sensor 109 CPU
200 unit pixel 201 micro lens 202a, 202b photoelectric conversion part (PD)
302 Vertical scan circuit 305 Readout circuit 306 AD converter 307 Horizontal scan circuit 308 Signal processing circuit

Claims (11)

An imaging device including an imaging device in which a plurality of unit pixels are arranged in a two-dimensional matrix, and obtaining an image according to an optical image formed on the imaging device,
Each of the unit pixels includes a plurality of photoelectric conversion units,
When reading out pixel signals from the unit pixels, a first readout mode in which the pixel signals are read out collectively from the plurality of photoelectric conversion units, and a second readout mode in which the pixel signals are read out from each of the plurality of photoelectric conversion units Reading means for selectively
When the first readout mode and the second readout mode are used when obtaining the image, the readout unit is controlled to control the readout unit from the unit pixel in the first readout mode and the second readout mode. Control means for changing the number of times the pixel signal is read out;
An imaging apparatus characterized by having:   When the control means controls the reading means to read the pixel signal from the unit pixel, the control means selects one of the first reading mode and the second reading mode on a row basis of the image sensor. The imaging device according to claim 1, characterized in that   3. The image pickup apparatus according to claim 1, further comprising focusing means for performing focusing in accordance with a plurality of images obtained in the second readout mode. An image processing unit configured to obtain an image by combining a plurality of images obtained in the second readout mode;
The image pickup apparatus according to any one of claims 1 to 3, wherein the control means determines the number of times of reading in accordance with the number of images used for combining in the image processing means.   5. The image pickup apparatus according to claim 4, wherein the control means sets the number of readouts in the second readout mode to be larger than the number of readouts in the first readout mode. It has selection means for selecting one shooting mode from a plurality of shooting modes at the time of shooting,
The image pickup apparatus according to claim 4, wherein the control unit determines the number of times of reading in accordance with the photographing mode selected by the selection unit. The plurality of shooting modes include at least an image quality priority mode and an AF priority mode.
7. The image pickup apparatus according to claim 6, wherein the control means sets the number of readouts in the image quality priority mode to be larger than the number of readouts in the AF priority mode.   The image pickup apparatus according to any one of claims 1 to 7, wherein the unit pixel includes two photoelectric conversion units.   In the second readout mode, a third readout mode in which the two photoelectric conversion units are grouped and the pixel signal is read collectively for each group as a group, and a fourth readout mode in which the pixel signal is read out for each photoelectric conversion unit The imaging apparatus according to any one of claims 1 to 7, further comprising: a readout mode. An imaging device having an imaging device in which a plurality of unit pixels are arranged in a two-dimensional matrix, and each of the unit pixels includes a plurality of photoelectric conversion units, and obtaining an image according to an optical image formed on the imaging device. Control method, and
When reading out pixel signals from the unit pixels, a first readout mode in which the pixel signals are read out collectively from the plurality of photoelectric conversion units, and a second readout mode in which the pixel signals are read out from each of the plurality of photoelectric conversion units And a read-out step to selectively
When the first readout mode and the second readout mode are used to obtain the image, the pixel signal from the unit pixel in the readout step in the first readout mode and the second readout mode Control step of changing the number of times of reading out
A control method characterized by comprising: An imaging apparatus comprising: an imaging element in which a plurality of unit pixels are arranged in a two-dimensional matrix, and each of the unit pixels includes a plurality of photoelectric conversion units, and obtaining an image corresponding to an optical image formed on the imaging element. The control program used,
In a computer provided in the imaging device,
When reading out pixel signals from the unit pixels, a first readout mode in which the pixel signals are read out collectively from the plurality of photoelectric conversion units, and a second readout mode in which the pixel signals are read out from each of the plurality of photoelectric conversion units And a read-out step to selectively
When the first readout mode and the second readout mode are used to obtain the image, the pixel signal from the unit pixel in the readout step in the first readout mode and the second readout mode Control step of changing the number of times of reading out
A control program characterized by causing

Images