JP2011182321A - Solid-state imaging apparatus, driving method and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a solid-state imaging apparatus capable of acquiring an image signal till timing near an exposure period; a driving method; and an imaging device. <P>SOLUTION: The solid-state imaging apparatus includes: a pixel part configured to two-dimensionally arrange a plurality of pixels having a photoelectric conversion part, a first resetting part for resetting the photoelectric conversion part, a transferring part for transferring signal charge, an amplifying part for amplifying the signal charge, a second resetting part for resetting the amplifying part, and a selecting part for outputting an amplified signal; and a vertical scanning part for selecting and reading pixels by row, wherein the vertical scanning part has a noise signal-reading mode, a simultaneous exposure mode, a first pixel signal-reading mode, and a second pixel signal-reading mode, reads a noise signal in the noise signal-reading mode by group of pixel rows before starting exposure in the simultaneous exposure mode with pixels in a plurality of rows of the pixel part as a group, and reads a pixel signal in the second pixel signal-reading mode by using pixel rows of a group in which reading of the noise signal has not been completed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solid-state imaging device capable of batch resetting and batch-collecting imaging elements, and more particularly to a solid-state imaging device having a plurality of output channels and a driving method. The present invention also relates to an imaging device including a solid-state imaging device.

In recent years, the number of pixels has been increasing in imaging devices such as digital cameras and digital video cameras. Along with the increase in the number of pixels, an increase in the frame rate of an image signal read from the solid-state imaging device has been attempted. In order to achieve both the increase in the number of pixels of the solid-state imaging device and the increase in the frame rate, a MOS (Metal Oxide Semiconductor) type imaging element is often used.
In the MOS type image pickup device, reading by a rolling shutter system in which output signals of unit pixels arranged in two dimensions are sequentially read out in units of rows is generally used. In this rolling shutter readout, the exposure start time and the exposure end time in the unit pixel are different for each line. When the exposure start time and the exposure end time differ for each line, for example, the image quality of the photographed still image deteriorates due to motion blur according to the motion of the subject. Therefore, in order to avoid image quality degradation caused by such subject movement, the exposure start time of all unit pixels can be made the same, and the exposure end time of all unit pixels can be made the same. A MOS type image pickup device having a shutter function is also known.

  An example of the configuration of the unit pixel of such a MOS type image sensor is shown in FIG. The unit pixel shown in FIG. 10 includes a photodiode PD, a signal storage unit FD, a transfer transistor Mtx1, a reset transistor Mtx2, an amplification transistor Ma, a selection transistor Mb, and a reset transistor Mr. In the unit pixel shown in FIG. 10, the global shutter function is enabled by using the signal storage unit FD as a memory within the unit pixel.

  The photodiode PD is a photoelectric conversion unit that photoelectrically converts subject light to generate signal charges. The signal storage unit FD is a signal storage unit that temporarily holds signal charges generated in the photodiode PD. The transfer transistor Mtx1 transfers the signal charge generated in the photodiode PD to the signal storage unit FD in response to the row transfer signal TX1. The reset transistor Mtx2 resets the signal charge generated in the photodiode PD to the level of the voltage source VDD in response to the PD reset signal TX2. The amplification transistor Ma amplifies and outputs the signal charge held in the signal storage unit FD. The amplification transistor Ma constitutes a source follower amplifier with the voltage source VDD. The signal charge amplified by the amplification transistor Ma is a vertical output signal line of the unit pixel via the selection transistor Mb that selects and outputs the signal charge amplified by the amplification transistor Ma according to the row selection signal SEL. It is output to the transfer line VTL. The reset transistor Mr resets the signal storage unit FD and the input unit of the amplification transistor Ma to the level of the voltage source VDD in response to the row reset signal RES.

  Patent Document 1 discloses a technique for suppressing KTC noise (reset noise) generated when the signal storage unit FD is reset using such unit pixels. Here, the drive timing for suppressing the reset noise disclosed in Patent Document 1 will be described. FIG. 11 is a timing chart showing an outline of conventional drive timing for suppressing reset noise in a solid-state imaging device.

  In FIG. 11, a solid-state imaging device in which nine rows of unit pixels shown in FIG. 10 are arranged will be described. In FIG. 11, the number following “L” in “(): parentheses” after the sign of the row selection signal SEL, the row reset signal RES, the row transfer signal TX1, and the PD reset signal TX2 indicates the row of the unit pixel. To express. For example, the row reset signal RES of the unit pixel in the second row is represented as “RES (L02)”.

  In readout of image data at a conventional drive timing in a solid-state imaging device, first, a reset operation of each unit pixel is performed in a reset level readout period from timing t1 to timing t2, and each unit pixel is sequentially scanned for each row. Read the reset signal. In this reset operation, as shown in FIG. 11, the PD reset signal TX2 of all rows is first set to the “H” level, the reset transistors Mtx2 in the unit pixels are turned on, and the photodiodes PD of all rows are reset. To do. Then, the following operations are sequentially performed for each row. First, the row selection signal SEL is set to “H” level, the selection transistor Mb is turned on, and the amplification transistor Ma and the vertical transfer line VTL are connected. At the same time, the “H” level pulse (reset pulse) of the row reset signal RES is applied to the reset transistor Mr. Thereby, the input part of the signal storage part FD and the amplification transistor Ma is reset by the ON state of the reset transistor Mr. And the signal of the reset level of the signal storage part FD output from the amplification transistor Ma is read as a noise signal of the unit pixel. The reset signal of each unit pixel is stored for each unit pixel outside the solid-state imaging device as a noise signal of the solid-state imaging device.

  Subsequently, in the exposure period from timing t3 to timing t4, the photodiodes PD in all rows are exposed at once. In this exposure operation, as shown in FIG. 11, the PD reset signal TX2 of all the rows is simultaneously set to the “L” level, thereby turning off the reset transistor Mtx2 in the unit pixel. As a result, the reset of all the photodiodes PD is released, and the photodiodes PD simultaneously start exposure of subject light. Then, after a predetermined exposure time has elapsed, an “H” level pulse (transfer pulse) of the row transfer signal TX1 is applied to the transfer transistor Mtx1. Thereby, the signal charge generated in the photodiode PD is transferred to the signal storage unit FD at the same time in each row by the ON state of the transfer transistor Mtx1.

  Subsequently, in a signal level reading period from timing t5 to timing t6, each unit pixel is sequentially scanned for each row, and an optical signal corresponding to the signal charge transferred to the signal accumulation unit FD is read. As shown in FIG. 11, the optical signal readout operation is performed by first setting the PD reset signal TX2 of all rows to the “H” level, turning on the reset transistors Mtx2 in the unit pixels, and the photodiodes of all rows. Reset PD. Then, sequentially for each row, the row selection signal SEL is set to the “H” level, the selection transistor Mb is turned on, and the amplification transistor Ma and the vertical transfer line VTL are connected. As a result, a signal charge transferred to the signal storage unit FD output from the amplification transistor Ma, that is, a signal having a signal level corresponding to the subject light exposed by the photodiode PD is read as an optical signal. Then, the difference processing between the noise signal stored in advance in the reset level readout period and the optical signal read out in the signal level readout period is performed for each unit pixel outside the solid-state imaging device, and the signal storage unit FD is reset. An image signal in which reset noise generated when the image is suppressed is obtained.

  As described above, in the solid-state imaging device, the difference between the signal at the reset level when the signal accumulation unit FD in each unit pixel of the solid-state imaging device is reset and the signal at the signal level corresponding to the subject light exposed by the photodiode PD. By performing the processing, it is possible to suppress KTC noise (reset noise) generated when the signal storage unit FD is reset.

JP 2005-65184 A

  However, at the conventional driving timing in the solid-state imaging device as disclosed in Patent Document 1, the noise signal readout operation (reset level readout period in FIG. 11) of the solid-state imaging device and the light after the exposure are performed. In both the signal readout operation (signal level readout period in FIG. 11), readout of unit pixels in the solid-state imaging device is performed. This increases the time required to obtain an image signal in one exposure.

  During a series of operation periods (periods from timing t1 to timing t6) required to obtain the image signal, for example, the image is displayed on the display screen of the imaging device in order to confirm the subject to be photographed. It is impossible to perform an operation such as obtaining a signal such as an image signal for live view or an autofocus (autofocus: AF) for focusing a subject using the image signal for live view.

  For example, the autofocus signal is ideally acquired immediately before the exposure period of the solid-state imaging device in order to suppress a decrease in focusing accuracy due to movement of the subject. However, at the conventional drive timing, in order to suppress the reset noise generated when the signal storage unit FD is reset, the readout operation of the noise signal of all unit pixels is performed before the exposure period. For this reason, the period during which the autofocus signal can be acquired is a timing before the timing t1 shown in FIG. 11, and there is a large divergence from the timing immediately before the ideal exposure period.

  Further, for example, it is desirable that the live view image is always displayed except during the shooting period. However, at the conventional drive timing, the period during which the image signal for live view can be acquired is after the timing t6 shown in FIG. 11 and is after reading of the optical signals of all unit pixels is completed. , Live view image display after shooting is slow. In addition, when autofocus is performed using the image signal of the live view, for example, since the autofocus operation is slow in the second and subsequent shootings when shooting continuously, the shooting interval during continuous shooting is It will also be longer.

  As described above, in the conventional driving timing, by acquiring information on autofocus immediately before the exposure period, consideration for suppressing a decrease in focusing accuracy due to movement of the subject, and an imaging apparatus after the exposure period There is a problem in that sufficient consideration has not been given to the operation of the system.

  The present invention has been made based on the above problem recognition, and in a solid-state imaging device having a global sitter function, a solid-state imaging device capable of acquiring an image signal until a timing close to an exposure period, a driving method, And it aims at providing an imaging device.

  In order to solve the above problems, a solid-state imaging device according to the present invention includes a photoelectric conversion unit that generates a signal charge according to incident light, a first reset unit that resets the photoelectric conversion unit, and the photoelectric conversion unit. A transfer unit that transfers the generated signal charge, an amplification unit that amplifies the signal charge transferred via the transfer unit, a second reset unit that resets the charge input to the amplification unit, A selection unit that outputs the signal charge amplified by the amplification unit as a pixel signal to an output signal line; a pixel unit in which a plurality of pixels are arranged in a two-dimensional matrix; and the pixel is selected for each row. A vertical scanning unit that sequentially reads out pixel signals from the pixel unit, and the vertical scanning unit resets the input of the amplification unit for each row of the pixels, and the signal output from the reset amplification unit The noise signal The noise signal readout mode for sequentially reading out and the photoelectric conversion units of all the pixels are simultaneously reset, and the signal charges generated by the photoelectric conversion units of all the pixels after a predetermined time have passed to the amplification unit. A simultaneous exposure mode in which exposure of the pixel portion is simultaneously performed by transferring simultaneously, and an amplified signal output from the amplifying portion in accordance with the signal charge transferred in the simultaneous exposure mode is sequentially read out as a pixel signal. 1 pixel signal readout mode and the input of the amplifying unit are reset for each row of the pixels, the reset signal output from the amplifying unit, and the photoelectric conversion unit are reset for each row of the pixels, The signal charge generated by the photoelectric conversion unit after a predetermined time has passed is transferred to the amplification unit, and the increase is made according to the transferred signal charge. A second pixel signal readout mode for sequentially reading out the amplified signal output from the unit as a pixel signal, wherein a plurality of rows of pixels in the pixel unit are grouped, and the pixel unit according to the simultaneous exposure mode. Before starting the exposure, the readout of the noise signal in the noise signal readout mode is performed for each set of the pixel rows, and the readout of the noise signal in the noise signal readout mode is not completed. The pixel signal is read out in the second pixel signal reading mode using a row.

  The vertical scanning unit of the present invention further ends reading of the pixel signal in the second pixel signal reading mode using a set of pixel rows in which reading of the noise signal in the noise signal reading mode is not completed. Then, a noise signal is read out by the noise signal reading mode for a set of pixel rows from which pixel signals are read out by the second pixel signal reading mode.

  The vertical scanning unit of the present invention may further include a pixel signal in the first pixel signal readout mode for each set of pixel rows after the exposure of the pixel unit in the simultaneous exposure mode is completed. And reading out pixel signals in the second pixel signal reading mode using a set of pixel rows for which reading of pixel signals in the first pixel signal reading mode has been completed.

  The vertical scanning unit of the present invention may be configured to read out a pixel signal in the second pixel signal reading mode, read out a noise signal in the noise signal reading mode, or read out a pixel signal in the first pixel signal reading mode. Are performed in time series.

  In addition, the pixel of the present invention further includes a second selection unit that outputs the signal charge amplified by the amplification unit to a second output signal line as a second pixel signal, and performs the vertical scanning. The unit outputs a noise signal in the noise signal readout mode and a pixel signal in the first pixel signal readout mode to the output signal line, and outputs the pixel signal in the second pixel signal readout mode to the second pixel signal. Output to the output signal line and read out the pixel signal in the second pixel signal readout mode is different from readout of the noise signal in the noise signal readout mode or readout of the pixel signal in the first pixel signal readout mode. It is characterized in that it is performed simultaneously in a set of pixel rows.

  The solid-state imaging device driving method according to the present invention includes a photoelectric conversion unit that generates a signal charge according to incident light, a first reset unit that resets the photoelectric conversion unit, and the photoelectric conversion unit that generates the signal charge. A transfer unit that transfers a signal charge; an amplification unit that amplifies the signal charge transferred via the transfer unit; a second reset unit that resets the charge input to the amplification unit; and the amplification unit A selection unit that outputs the signal charges amplified by the output signal line to the output signal line as a pixel signal, a pixel unit in which a plurality of pixels are arranged in a two-dimensional matrix, and the pixel is selected for each row. And a vertical scanning unit that sequentially reads out pixel signals from the unit, wherein the vertical scanning unit resets the input of the amplification unit for each row of the pixels, and the reset Output from amplifier The signal charge generated by the photoelectric conversion units of all the pixels after a predetermined time elapses after the noise signal readout procedure for sequentially reading out signals as noise signals and the photoelectric conversion units of all the pixels are simultaneously reset. Simultaneously exposing the pixel unit by simultaneously transferring the pixel unit to the amplifying unit, and an amplified signal output from the amplifying unit according to the signal charge transferred by the simultaneous exposure procedure, A first pixel signal readout procedure for sequentially reading out signals as signals, resetting the input of the amplification unit for each row of the pixels, and outputting the reset signal output from the amplification unit and the photoelectric conversion unit to the row of pixels; Each time the signal charge generated by the photoelectric conversion unit is transferred to the amplification unit after a predetermined time has passed, and the transferred signal charge And a second pixel signal readout procedure for sequentially reading out the amplified signal output from the amplification unit as a pixel signal, further comprising a plurality of rows of pixels in the pixel unit as a set, and the simultaneous exposure Before starting the exposure of the pixel portion by the procedure, the noise signal is read by the noise signal reading procedure for each set of the pixel rows, and the noise signal reading by the noise signal reading procedure is completed. And a procedure for reading out pixel signals by the second pixel signal readout procedure using a set of pixel rows that are not included.

  The image pickup apparatus of the present invention is read by the solid-state image pickup apparatus of the present invention, a control unit that controls an operation mode of a vertical scanning unit in the solid-state image pickup apparatus, and a noise signal read mode of the solid-state image pickup apparatus. A first image processing unit that performs image processing according to the noise signal and the pixel signal read out in the first pixel signal reading mode, and reading out in the second pixel signal reading mode of the solid-state imaging device. A second image processing unit that performs image processing in accordance with the pixel signal thus obtained, and the control unit starts exposure of the pixel unit in the solid-state imaging device in a simultaneous exposure mode of the solid-state imaging device Before, the noise signal is read by the noise signal reading mode, and the reading of the noise signal is not completed by the noise signal reading mode Using the set of pixel rows so as to perform a reading of the pixel signal by the second pixel signal read mode, characterized in that.

  According to the present invention, in a solid-state imaging device having a global sitter function, an effect that an image signal can be acquired until a timing close to an exposure period is obtained.

1 is a block diagram illustrating a schematic configuration of an imaging apparatus according to a first embodiment of the present invention. 1 is a block diagram illustrating a schematic configuration of an imaging unit in an imaging apparatus according to a first embodiment of the present invention. 5 is a timing chart illustrating an outline of first drive timing of the imaging unit in the imaging apparatus according to the first embodiment of the present invention. 5 is a timing chart illustrating an outline of second drive timing of the imaging unit in the imaging apparatus according to the first embodiment of the present invention. 6 is a timing chart illustrating an outline of a third drive timing of the imaging unit in the imaging apparatus according to the first embodiment of the present invention. It is the block diagram which showed schematic structure of the imaging part in the imaging device by the 2nd Embodiment of this invention. It is the block diagram which showed an example of the structure of the unit pixel of the MOS type image pick-up element with the global shutter function with which the image pick-up part by the 2nd Embodiment of this invention was equipped in the image pick-up part. It is a timing chart which showed the outline of the 1st drive timing of the image pick-up part in the imaging device by a 2nd embodiment of the present invention. It is a timing chart which showed the outline of the 2nd drive timing of the image pick-up part in the imaging device by a 2nd embodiment of the present invention. It is the block diagram which showed an example of the structure of the unit pixel of the MOS type image pick-up element with a global shutter function. It is the timing chart which showed the outline of the conventional drive timing in a solid-state imaging device.

<First Embodiment>
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of the imaging apparatus according to the first embodiment. In FIG. 1, an imaging device 100 includes a lens 1, an imaging unit 2, an image processing unit 3, an AF evaluation value calculation unit 4, a display unit 5, a memory card 6, an exposure control unit 7, and AF control. Unit 8, camera operation unit 9, and camera control unit 10. Note that the memory card 6 that is a component of the imaging device 100 illustrated in FIG. 1 is configured to be detachable, and may not have a configuration unique to the imaging device 100.

The lens 1 is a photographing lens for controlling the driving of a focus lens provided in the lens 1 by the AF control unit 8 and forming an optical image of a subject on the imaging surface of the imaging unit 2.
The imaging unit 2 includes a solid-state imaging device that photoelectrically converts an optical image of a subject formed by the lens 1 and outputs an image signal (digital signal) corresponding to the subject light. Further, the imaging unit 2 has a global shutter function that can make the exposure start time and the exposure end time of all the unit pixels 28 the same, and performs a global shutter operation by drive control by the exposure control unit 7. . The imaging unit 2 also has a rolling shutter function that sequentially performs exposure and pixel signal readout in units of rows of the unit pixels 28, and performs a rolling shutter operation by drive control by the exposure control unit 7. Then, the imaging unit 2 outputs an image signal obtained by the global shutter operation or the rolling shutter operation to the image processing unit 3 and the AF evaluation value calculation unit 4.

The image processing unit 3 performs various digital image processing on the image signal output from the imaging unit 2. Image processing by the image processing unit 3 includes, for example, recording image processing for recording an image signal and display image processing for displaying an image of a subject on the display unit 5. Then, the image signal subjected to the recording image processing is output to the camera control unit 10, and the image signal subjected to the display image processing is output to the display unit 5.
The AF evaluation value calculation unit 4 calculates an AF evaluation value indicating the degree of focus on the subject based on, for example, a luminance signal representing the brightness of the subject in the image signal output from the imaging unit 2. . In addition, the AF evaluation value calculation unit 4 outputs the calculated AF evaluation value to the camera control unit 10.

The display unit 5 includes a display device such as an LCD (Liquid Crystal Display), and displays an image based on the image signal that has been subjected to image processing for display by the image processing unit 3. The display unit 5 can reproduce and display still images captured by the imaging device 100 and images stored in the memory card 6 and also display a live view image that displays an imaging range captured by the imaging device 100 in real time. Can be displayed.
The memory card 6 is a recording medium for storing still images taken by the imaging device 100. The memory card 6 records still image data on which the camera control unit 10 has performed image processing such as compression processing based on the image signal that has been subjected to image processing for recording by the image processing unit 3. .

The exposure control unit 7 drives the imaging unit 2 based on the exposure command input from the camera control unit 10 and performs exposure control of the imaging unit 2.
The AF control unit 8 drives the focus lens included in the lens 1 based on the AF control command input from the camera control unit 10 that has received the AF evaluation value from the AF evaluation value calculation unit 4, and forms an image on the imaging unit 2. The subject image to be focused.

  The camera operation unit 9 is an operation unit for the user of the imaging apparatus 100 to input various operations to the imaging apparatus 100. Constituent elements of the camera operation unit 9 include a power switch for turning on / off the power of the imaging apparatus 100, a release button for capturing a still image by the imaging apparatus 100, and a shooting mode of the imaging apparatus 100 as a single shooting mode. And a shooting mode switch for switching between the continuous shooting mode and an AF mode switch for switching the AF mode between the single AF mode and the continuous AF mode. The camera operation unit 9 outputs camera operation information set in these components to the camera control unit 10.

  The camera control unit 10 controls the entire imaging apparatus 100. The camera control unit 10 is based on the AF evaluation value input from the AF evaluation value calculation unit 4, the operation input from the camera operation unit 9, and the like, and the image processing unit 3, the memory card 6, the exposure control unit 7, and the AF control unit. The control command is output to 8.

  Next, an imaging unit provided in the imaging apparatus of the first embodiment will be described. FIG. 2 is a block diagram illustrating a schematic configuration of the imaging unit 2 in the imaging apparatus 100 according to the first embodiment. In FIG. 2, the imaging unit 2 includes a MOS type solid-state imaging device 21 having a global shutter function, an A / D conversion unit 22, and a KTC noise removal unit 23. The solid-state imaging device 21 includes a pixel unit 24, a CDS unit 25, a vertical control circuit 26, and a horizontal scanning circuit 27.

  In the pixel unit 24, a plurality of unit pixels 28 are arranged in a two-dimensional shape in the row direction and the column direction (9 rows and 9 columns in FIG. 2). The unit pixel 28 includes a photodiode PD, a signal storage unit FD, a transfer transistor Mtx1, a reset transistor Mtx2, an amplification transistor Ma, a selection transistor Mb, and a reset transistor Mr.

  The photodiode PD is a photoelectric conversion unit that photoelectrically converts subject light to generate signal charges. The signal storage unit FD is a signal storage unit that temporarily holds signal charges generated in the photodiode PD. The transfer transistor Mtx1 transfers the signal charge generated in the photodiode PD to the signal storage unit FD in response to the row transfer signal TX1. The reset transistor Mtx2 resets the signal charge generated in the photodiode PD to the level of the voltage source VDD in response to the PD reset signal TX2. The amplification transistor Ma amplifies and outputs the signal charge held in the signal storage unit FD. The amplification transistor Ma constitutes a source follower amplifier with the voltage source VDD. The signal charge amplified by the amplification transistor Ma is a vertical output signal line of the unit pixel via the selection transistor Mb that selects and outputs the signal charge amplified by the amplification transistor Ma according to the row selection signal SEL. It is output to the transfer line VTL. The reset transistor Mr resets the signal storage unit FD and the input unit of the amplification transistor Ma to the level of the voltage source VDD in response to the row reset signal RES. Note that the configuration of the unit pixels 28 arranged in the pixel unit 24 is the same as the configuration of the unit pixels of the MOS type image pickup device having the global shutter function shown in FIG.

  The vertical control circuit 26 receives control signals (a row selection signal SEL, a row reset signal RES, a row transfer signal TX1, and a PD reset signal TX2) for controlling the unit pixels 28 arranged in the pixel unit 24 in units of rows. Output for each line. Further, the vertical scanning circuit 26 includes a reset control unit for resetting the unit pixel 28 and a read control unit for reading a signal from the unit pixel 28. A signal output from the unit pixel 28 in the row selected by the vertical control circuit 26 is output to an output signal line (vertical transfer line VTL) of the unit pixel 28 provided for each column.

The CDS unit 25 performs correlated double sampling processing on the pixel signal transferred through the vertical transfer line VTL when the imaging unit 2 performs a rolling shutter operation by the drive control by the exposure control unit 7.
The horizontal scanning circuit 27 fetches the pixel signals for one row selected by the vertical control circuit 26 and transferred via the vertical transfer line VTL and the CDS unit 25, and fetches them in the arrangement order of the unit pixels 28 in the horizontal direction. Pixel signals (analog image signals) are output to the A / D converter 22 in time series.

The A / D converter 22 converts the analog image signal output from the solid-state imaging device 21 into a digital image signal. Then, the converted digital image signal is output to the KTC noise removing unit 23.
The KTC noise removal unit 23 performs KTC noise removal processing on the digital image signal output from the A / D conversion unit 22 when the imaging unit 2 performs a global shutter operation. Then, the digital image signal subjected to the KTC noise removal process is output to the image processing unit 3 and the AF evaluation value calculation unit 4.

<First drive timing>
Next, the driving timing of the imaging unit of the first embodiment will be described. FIG. 3 is a timing chart showing an outline of the first drive timing of the imaging unit 2 in the imaging apparatus 100 according to the first embodiment. In the first drive timing shown in FIG. 3, when the imaging unit 2 performs the global shutter operation, the AF evaluation value calculation unit 4 calculates the AF evaluation value by acquiring the pixel signal until the timing close to the exposure period. This is a driving method for acquiring an image signal for the purpose.

  As shown in FIG. 1, the driving of the imaging unit 2 is controlled by the exposure control unit 7. At the first drive timing shown in FIG. 3, the imaging unit 2 corresponds to the drive control by the exposure control unit 7. The control signals (row selection signal SEL, row reset signal RES, row transfer signal TX1, PD reset signal TX2) of the pixel unit 24 output from the vertical control circuit 26 are shown. In FIG. 3, the numbers following “L” in “(): parentheses” after the sign of the row selection signal SEL, the row reset signal RES, the row transfer signal TX1, and the PD reset signal TX2 are shown in FIG. Similar to the conventional driving timing, the row of the unit pixels 28 is represented.

  Further, at the first driving timing shown in FIG. 3, the unit pixels 28 from the first row to the ninth row arranged in the pixel unit 24 shown in FIG. The case where it divides and controls to the above three groups is shown. A case where the pixel signal output from one set of unit pixels 28 among the three sets is used as an image signal for the AF evaluation value calculation unit 4 to calculate the AF evaluation value is shown.

  More specifically, the unit pixels 28 arranged in the first row, the fourth row, and the seventh row of the pixel unit 24 are set as one set (hereinafter also referred to as “first field” when collectively expressed), The unit pixels 28 arranged in the second row, the fifth row, and the eighth row of the pixel unit 24 are set as another set (hereinafter, also referred to as “second field” when collectively shown), The unit pixels 28 arranged in the row, the 6th row, and the 9th row are further set as another set (hereinafter also referred to as “third field” when collectively shown). Then, the pixel signal output from the unit pixel 28 in the third field is used as an image signal for the AF evaluation value calculation unit 4 to calculate the AF evaluation value.

  Hereinafter, reading of a noise signal and acquisition of an AF signal performed during reading of the noise signal will be described. First, when the release button is pressed and the imaging apparatus 100 starts capturing a still image, first, in the reset level read period (timing t1 to timing t6), the reset operation of each unit pixel 28 is performed, and each unit pixel 28 is reset. Read the reset signal. However, at the first drive timing shown in FIG. 3, the reset operation is performed for each field.

  In this reset level readout period, first, from the timing t1, the vertical control circuit 26 performs the reset operation of the first field. In the reset operation of the first field, first, the row selection signal SEL (L01) of the first row is set to the “H” level to connect the amplification transistor Ma of the unit pixel 28 of the first row and the vertical transfer line VTL. At this time, the “H” level pulse (reset pulse) of the row reset signal RES (L01) in the first row is applied to the reset transistor Mr of the unit pixel 28 in the first row. With this reset pulse, the reset transistor Mr of the unit pixel 28 in the first row is turned on, and the signal storage unit FD and the input unit of the amplification transistor Ma of the unit pixel 28 in the first row are reset. Then, the reset level signal of the signal storage unit FD of the unit pixel 28 in the first row output from the amplification transistor Ma of the unit pixel 28 in the first row is read as a noise signal of the unit pixel 28 in the first row. Then, the row selection signal SEL (L01) of the first row is returned to the “L” level, and the connection between the amplification transistor Ma of the unit pixel 28 of the first row and the vertical transfer line VTL is disconnected. Similarly, the noise signal of the unit pixel 28 in the fourth row is read by the row selection signal SEL (L04) and the row reset signal RES (L04) of the fourth row in the first field, and the row selection signal SEL ( L07) and the row reset signal RES (L07) are used to read the noise signal of the unit pixel 28 in the seventh row, and the reset operation of the first field is completed.

  In the reset level read period, the row transfer signal TX1 in the first field is at the “L” level, and the PD reset signal TX2 is at the “H” level. Therefore, in the unit pixel 28 in the first field, the photodiode PD is reset by the ON state of the reset transistor Mtx2, and the signal charge reset by the photodiode PD is stored in the signal accumulation by the OFF state of the transfer transistor Mtx1. In this state, the signal is not output to the input part of the part FD and the amplification transistor Ma.

  Subsequently, from timing t2, the vertical control circuit 26 performs a reset operation for the second field. Note that the reset operation of the second field is the same as the reset operation of the first field, and thus description thereof is omitted.

  In the reset level readout period, from timing t3, the vertical control circuit 26 acquires an AF signal for calculating an AF evaluation value using the third field for which the reset operation has not ended. In the acquisition of the AF signal by the third field, the image signal is acquired by the rolling shutter operation in order to suppress the KTC noise.

  In the AF signal acquisition operation in the third field, first, the PD reset signal TX2 (L03) in the third row is set to the “L” level, thereby turning off the reset transistor Mtx2 of the unit pixel 28 in the third row. The reset of the photodiode PD of the unit pixel 28 in the third row is released. Thereby, exposure of the subject light is started so that the exposure time of the photodiode PD becomes a predetermined AF signal level. Then, the row selection signal SEL (L03) in the third row is set to the “H” level, and the amplification transistor Ma of the unit pixel 28 in the third row is connected to the vertical transfer line VTL. At this time, the “H” level pulse (reset pulse) of the row reset signal RES (L03) in the third row is applied to the reset transistor Mr of the unit pixel 28 in the third row. With this reset pulse, the reset transistor Mr of the unit pixel 28 in the third row is turned on, and the signal storage unit FD and the input unit of the amplification transistor Ma of the unit pixel 28 in the third row are reset to 3 from the vertical transfer line VTL. A reset level signal of the signal accumulation unit FD in the row is read as a noise signal of the unit pixel 28 in the third row.

  Thereafter, after a predetermined exposure time has elapsed, an “H” level pulse (transfer pulse) of the row transfer signal TX1 (L03) of the unit pixel 28 in the third row is applied to the transfer transistor Mtx1 of the unit pixel 28 in the third row. Apply. With this transfer pulse, the transfer transistor Mtx1 of the unit pixel 28 in the third row is turned on, and the signal charge generated in the photodiode PD of the unit pixel 28 in the third row becomes the signal storage unit of the unit pixel 28 in the third row. The signal is transferred to the FD, and the signal at the AF signal level of the signal storage unit FD in the third row is read from the vertical transfer line VTL as the AF signal of the unit pixel 28 in the third row. Thereafter, the row selection signal SEL (L03) of the unit pixel 28 in the third row is returned to the “L” level, and the connection between the amplification transistor Ma and the vertical transfer line VTL of the unit pixel 28 in the third row is disconnected. At the same time, the PD reset signal TX2 (L03) of the unit pixel 28 in the third row is returned to the “H” level, and the photodiode PD of the unit pixel 28 in the third row is reset.

  Here, the AF signal and the noise signal read from the unit pixels 28 in the third row are subjected to correlated double sampling processing for removing KTC noise by the CDS unit 25, and then the horizontal scanning circuit. 27 to output to the A / D converter 22. The AF digital image signal output from the A / D conversion unit 22 is output to the AF evaluation value calculation unit 4 via the KTC noise removal unit 23. In the acquisition of the AF signal, the KTC noise removal unit 23 does not perform the KTC noise removal process.

  Similarly, from timing t4, the vertical control circuit 26 controls the control signals (row selection signal SEL, row reset signal RES, row transfer signal TX1, PD reset signal) of the unit pixels 28 in the sixth and ninth rows of the third field. The AF signals are sequentially acquired by TX2), and the AF digital image signals in the 6th and 9th rows are sequentially output to the AF evaluation value calculation unit 4. Then, the AF evaluation value calculation unit 4 calculates an AF evaluation value based on the digital image signal for AF in the third field, and outputs the calculated AF evaluation value to the camera control unit 10. As a result, an AF control command is output from the camera control unit 10 to the AF control unit 8, and the focus lens included in the lens 1 is driven based on the AF control command input by the AF control unit 8, so A focusing operation is performed.

  Thereafter, the AF signal acquisition in the third field and the focusing operation on the subject are repeated once again, and the AF signal acquisition operation in the third field is completed.

  Further, in the reset level readout period, from the timing t5, the vertical control circuit 26 performs the reset operation of the third field by reading out the noise signals of the unit pixels 28 in the third row, the sixth row, and the ninth row. . Then, the noise signal reading operation during the reset level reading period and the AF signal acquisition operation performed during the noise signal reading operation are terminated.

  Here, each noise signal read from the unit pixels 28 in the first field to the third field is output to the A / D conversion unit 22 by the horizontal scanning circuit 27 via the CDS unit 25, and is output from the A / D. After being converted into a digital signal by the conversion unit 22, it is stored in the KTC noise removal unit 23.

  Subsequently, in the exposure period (timing t7 to timing t8), the photodiodes PD of the unit pixels 28 in all rows are exposed together. In this exposure period, first, at the timing t7, the vertical control circuit 26 sets the PD reset signals TX2 (L01 to L09) of the unit pixels 28 of all the rows to the “L” level at the same time. The reset transistor Mtx2 is turned off. As a result, the reset of the photodiodes PD of all the unit pixels 28 is released, and the photodiodes PD start exposure of subject light simultaneously. After a predetermined exposure time has elapsed, at the timing t8, the vertical control circuit 26 generates an “H” level pulse (transfer pulse) in response to the row transfer signal TX1 (L01 to L09) of the unit pixels 28 of all rows. This is applied to the transfer transistors Mtx1 of all the unit pixels 28. With this transfer pulse, the transfer transistors Mtx1 of all the unit pixels 28 are turned on, and the signal charges generated in the photodiodes PD of the unit pixels 28 are transferred to the signal storage units FD of the respective unit pixels 28 at the same time in all rows. The exposure of the unit pixel 28 ends. Thereafter, the PD reset signals TX2 (L01 to L09) of the unit pixels 28 of all the rows are simultaneously set to the “H” level, so that the reset transistors Mtx2 in the unit pixels 28 are turned on, and the photo of all the unit pixels 28 are The diode PD is returned to the reset state.

  Subsequently, finally, in the signal level readout period (timing t9 to timing t13), the unit pixels 28 of each row are sequentially scanned for each field, and the signal charges transferred to the signal storage unit FD of the unit pixels 28 are determined. Read the optical signal.

  In this signal level readout period, first, from the timing t9, the vertical control circuit 26 performs an optical signal readout operation for the first field. In the reading operation of the optical signal of the first field, first, the row selection signal SEL (L01) in the first row is set to the “H” level, and the amplification transistor Ma of the unit pixel 28 in the first row is connected to the vertical transfer line VTL. To do. As a result, an optical signal corresponding to the signal level of the signal charge transferred from the vertical transfer line VTL of the unit pixel 28 in the first row to the signal accumulation unit FD in the first row is read out. Thereafter, the row selection signal SEL (L01) of the unit pixel 28 in the first row is returned to the “L” level, and the connection between the amplification transistor Ma of the unit pixel 28 in the first row and the vertical transfer line VTL is disconnected. Similarly, the optical signal of the unit pixel 28 of the fourth row is read by the row selection signal SEL (L04) of the fourth row of the first field, and the unit pixel of the seventh row is read by the row selection signal SEL (L07) of the seventh row. 28 optical signals are read out, and the first-field optical signal readout operation is completed.

  In the signal level read period, the row transfer signal TX1 in the first field is at the “L” level, and the PD reset signal TX2 is at the “H” level. Therefore, as in the reset level readout period, the photodiode PD is reset by the ON state of the reset transistor Mtx2 in the unit pixel 28 of the first field, and the photodiode PD is reset by the OFF state of the transfer transistor Mtx1. This is a state in which the signal charge that has been output is not output to the signal storage unit FD and the input unit of the amplification transistor Ma. In the signal level read period, the row reset signal RES in the first field is at the “L” level. Therefore, in the unit pixel 28 of the first field, the input unit of the signal storage unit FD and the amplification transistor Ma is not reset due to the OFF state of the reset transistor Mr.

  Subsequently, from timing t10, the vertical control circuit 26 performs a read operation of the optical signal of the second field. Note that the reading operation of the optical signal in the second field is the same as the reading operation of the optical signal in the first field, and thus description thereof is omitted.

  Subsequently, from timing t12, the vertical control circuit 26 performs the reading operation of the optical signal of the third field, and ends the signal level reading of all the fields. Note that the reading operation of the optical signal of the third field is the same as the reading operation of the optical signal of the first field and the second field, and thus description thereof is omitted. Note that during the period from the timing t11 when the second-field optical signal readout operation is completed to the timing t12 when the third-field optical signal readout operation is started, the reset operation in the reset level readout period and the light in the signal level readout period. This is an interval period for making the period (interval) with the signal reading operation the same time in each field.

  Here, the respective optical signals read from the unit pixels 28 in the first field to the third field are output to the A / D conversion unit 22 by the horizontal scanning circuit 27 via the CDS unit 25, and A / D After being converted into a digital signal by the conversion unit 22, it is output to the KTC noise removal unit 23. Then, the KTC noise removal unit 23 performs a difference process between the noise signal stored in the reset level readout period and the optical signal read out in the signal level readout period, and captures the digital image signal from which the KTC noise has been removed. The image signal output from the unit 2 is output to the image processing unit 3 and the AF evaluation value calculation unit 4.

  Thereafter, each process in the imaging apparatus 100 is performed based on the image signal output from the imaging unit 2.

  As described above, at the first drive timing of the imaging unit 2 in the imaging apparatus 100 according to the first embodiment, the pixel unit 24 is divided into a plurality of fields when the imaging unit 2 performs the global shutter operation. To obtain a noise signal. Finally, after the AF signal is acquired using the unit pixel 28 of the field from which the noise signal is acquired, it can be driven to acquire the noise signal of that field. Thereby, the acquisition of the AF signal and the focusing operation can be performed until the timing close to the exposure period of the imaging apparatus 100, and a decrease in focusing accuracy due to movement of the subject can be suppressed.

  In the first drive timing, the case where the acquisition of the AF signal by the third field and the reset operation of the third field are performed following the reset operation of the first field and the second field has been described. Can also be changed. For example, the AF signal using the third field can be acquired at both the timing after the reset operation (noise signal readout) in the first field and after the reset operation (noise signal readout) in the second field. . Further, in the first driving timing, the case where the AF signal acquisition operation by the third field is performed twice has been described, but the number of AF signal acquisition operations may be set to another number.

<Second drive timing>
Next, another drive timing of the imaging unit of the first embodiment will be described. FIG. 4 is a timing chart showing an outline of the second drive timing of the imaging unit 2 in the imaging apparatus 100 according to the first embodiment. In the second drive timing shown in FIG. 4, when the imaging unit 2 performs the global shutter operation, the pixel signal is acquired until the timing close to the exposure period, and the acquisition of the pixel signal is started from the timing close to the exposure period. Thus, the AF evaluation value calculation unit 4 is a driving method for acquiring an image signal for calculating the AF evaluation value.

  Note that the numbers following “L” in “(): brackets” after the sign of the row selection signal SEL, the row reset signal RES, the row transfer signal TX1, and the PD reset signal TX2 at the second drive timing shown in FIG. Represents a row of the unit pixels 28 as in the first drive timing shown in FIG. Also in the second drive timing shown in FIG. 4, the drive is divided into three fields in the same manner as the first drive timing shown in FIG.

  In the reset level readout period, the pixel signal output from the unit pixel 28 in the third field is used as an image signal for the AF evaluation value calculation unit 4 to calculate the AF evaluation value. In the signal level readout period, the pixel signal output from the unit pixel 28 in the first field is used as an image signal for the AF evaluation value calculation unit 4 to calculate the AF evaluation value.

  Note that the reset operation in the reset level readout period, the AF signal acquisition operation, and the exposure operation in the exposure period are the same as the first drive timing shown in FIG.

  Hereinafter, reading of an optical signal in the signal level reading period and acquisition of an AF signal performed during reading of the optical signal will be described. In the signal level readout period (timing t9 to timing t14), as in the signal level readout period (timing t9 to timing t13) at the first drive timing shown in FIG. Scanning is performed to read an optical signal corresponding to the signal charge transferred to the signal storage unit FD of the unit pixel 28.

  In this signal level readout period, first, from the timing t9, the vertical control circuit 26 performs an optical signal readout operation for the first field. Then, from the timing t10, the vertical control circuit 26 performs the reading operation of the optical signal of the second field. The first field optical signal read operation and the second field optical signal read operation are the same as the first drive timing shown in FIG.

  Subsequently, from timing t11, the vertical control circuit 26 acquires an AF signal for calculating an AF evaluation value by using the first field in which the optical signal read operation is completed in the signal level read period. In the acquisition of the AF signal by the first field, the image signal is acquired by the rolling shutter operation in order to suppress the KTC noise.

  In the AF signal acquisition operation in the first field, first, the PD reset signal TX2 (L01) in the first row is set to the “L” level, thereby turning off the reset transistor Mtx2 of the unit pixel 28 in the first row. The reset of the photodiode PD of the unit pixel 28 in the first row is released. Thereby, exposure of the subject light is started so that the exposure time of the photodiode PD becomes a predetermined AF signal level. Then, the row selection signal SEL (L01) of the first row is set to the “H” level, and the amplification transistor Ma of the unit pixel 28 of the first row is connected to the vertical transfer line VTL. At this time, the “H” level pulse (reset pulse) of the row reset signal RES (L01) in the first row is applied to the reset transistor Mr of the unit pixel 28 in the first row. With this reset pulse, the reset transistor Mr of the unit pixel 28 in the first row is turned on, the signal storage unit FD and the input unit of the amplification transistor Ma of the unit pixel 28 in the first row are reset, and 1 from the vertical transfer line VTL. A reset level signal of the signal accumulation unit FD in the row is read as a noise signal of the unit pixel 28 in the first row.

  Thereafter, after a predetermined exposure time elapses, an “H” level pulse (transfer pulse) of the row transfer signal TX1 (L01) of the unit pixel 28 in the first row is applied to the transfer transistor Mtx1 of the unit pixel 28 in the first row. Apply. With this transfer pulse, the transfer transistor Mtx1 of the unit pixel 28 in the first row is turned on, and the signal charge generated in the photodiode PD of the unit pixel 28 in the first row becomes the signal storage unit of the unit pixel 28 in the first row. The signal is transferred to the FD, and the signal of the AF signal level of the signal accumulation unit FD in the first row is read from the vertical transfer line VTL as the AF signal of the unit pixel 28 in the first row. Thereafter, the row selection signal SEL (L01) of the unit pixel 28 in the first row is returned to the “L” level, and the connection between the amplification transistor Ma of the unit pixel 28 in the first row and the vertical transfer line VTL is disconnected. At the same time, the PD reset signal TX2 (L01) of the unit pixel 28 in the first row is returned to the “H” level, and the photodiode PD of the unit pixel 28 in the first row is reset.

  Here, the AF signal and noise signal read from the unit pixel 28 in the first row are subjected to correlated double sampling processing for removing KTC noise by the CDS unit 25, and then the horizontal scanning circuit. 27 to output to the A / D converter 22. The AF digital image signal output from the A / D conversion unit 22 is output to the AF evaluation value calculation unit 4 via the KTC noise removal unit 23. In the acquisition of the AF signal, the KTC noise removal unit 23 does not perform the KTC noise removal process.

  Similarly, from timing t12, the vertical control circuit 26 controls the control signals (row selection signal SEL, row reset signal RES, row transfer signal TX1, PD reset signal) of the unit pixels 28 in the fourth and seventh rows of the first field. The AF signals are sequentially acquired by TX 2), and the digital image signals for AF in the fourth and seventh rows are sequentially output to the AF evaluation value calculation unit 4. The AF evaluation value calculation unit 4 calculates an AF evaluation value based on the digital image signal for AF in the first field, and outputs the calculated AF evaluation value to the camera control unit 10. As a result, an AF control command is output from the camera control unit 10 to the AF control unit 8, and the focus lens included in the lens 1 is driven based on the AF control command input by the AF control unit 8, so A focusing operation is performed.

  Thereafter, the AF signal acquisition in the first field and the focusing operation on the subject are repeated once again, and the AF signal acquisition operation in the first field is completed.

  Further, in the signal level readout period, from timing t13, the vertical control circuit 26 performs the readout operation of the optical signal of the third field in the same manner as the readout operation of the optical signal of the first field and the second field. Then, the reading operation of the optical signal in the signal level reading period and the AF signal acquisition operation performed during the reading of the optical signal are ended.

  Here, the respective optical signals read from the unit pixels 28 in the first field to the third field are output to the A / D conversion unit 22 by the horizontal scanning circuit 27 via the CDS unit 25, and A / D After being converted into a digital signal by the conversion unit 22, it is output to the KTC noise removal unit 23. Then, the KTC noise removal unit 23 performs a difference process between the noise signal stored in the reset level readout period and the optical signal read out in the signal level readout period, and captures the digital image signal from which the KTC noise has been removed. The image signal output from the unit 2 is output to the image processing unit 3 and the AF evaluation value calculation unit 4.

  As described above, at the second drive timing of the imaging unit 2 in the imaging apparatus 100 according to the first embodiment, the pixel unit 24 is divided into a plurality of fields when the imaging unit 2 performs the global shutter operation. To obtain a noise signal. Finally, after the AF signal is acquired using the unit pixel 28 of the field from which the noise signal is acquired, it can be driven to acquire the noise signal of that field. Thereby, the acquisition of the AF signal and the focusing operation can be performed until the timing close to the exposure period of the imaging apparatus 100, and a decrease in focusing accuracy due to movement of the subject can be suppressed.

  Further, at the second drive timing, the pixel portion 24 is divided into a plurality of fields to obtain an optical signal. Then, after the operation of reading the optical signal in the field from which the optical signal is read out first, the AF signal can be obtained using the unit pixel 28 in the field. Thereby, AF signal acquisition and focusing operation can be performed periodically from a timing close to the exposure period of the image capturing apparatus 100. For example, during continuous shooting in which continuous shooting is performed, the second and subsequent times. The focusing operation in shooting can be resumed at an early timing. As a result, it is possible to solve the problem in the conventional driving timing that the focusing operation at the time of continuous shooting is delayed and the shooting interval of continuous shooting becomes long, and the focusing accuracy at the time of continuous shooting can be improved.

  In the second drive timing, the case where the acquisition of the AF signal by the third field and the reset operation of the third field are performed following the reset operation of the first field and the second field has been described. Can also be changed. For example, the AF signal using the third field can be acquired at both the timing after the reset operation (noise signal readout) in the first field and after the reset operation (noise signal readout) in the second field. . Further, in the second drive timing, the case where the AF signal acquisition operation in the third field is performed twice has been described, but the number of AF signal acquisition operations may be set to another number.

  Further, at the second drive timing, after the first field and second field optical signal read operations, the AF signal acquisition by the first field and the third field optical signal read operation are performed. As described above, the driving conditions can be changed. For example, the acquisition of the AF signal using the first field can be performed at both the timing after the reading operation of the optical signal of the first field and the reading operation of the optical signal of the second field. Further, in the second drive timing, the case where the AF signal acquisition operation by the first field is performed twice has been described, but the number of AF signal acquisition operations may be set to another number.

<Third drive timing>
Next, another drive timing of the imaging unit of the first embodiment will be described. FIG. 5 is a timing chart showing an outline of the third drive timing of the imaging unit 2 in the imaging apparatus 100 according to the first embodiment. The third drive timing shown in FIG. 5 includes an AF signal acquisition operation in the reset level readout period and an AF signal acquisition operation in the signal level readout period in the second drive timing shown in FIG. This is a driving method performed between the reset operation of each field and the read operation of the optical signal.

  Note that the numbers following “L” in “(): brackets” after the sign of the row selection signal SEL, row reset signal RES, row transfer signal TX1, and PD reset signal TX2 at the third drive timing shown in FIG. Represents a row of the unit pixels 28 as in the first drive timing shown in FIG. 3 and the second drive timing shown in FIG. In the third drive timing shown in FIG. 5 as well, the drive is divided into three fields, similarly to the first drive timing shown in FIG. 3 and the second drive timing shown in FIG.

  In the reset level readout period, the pixel signal output from the unit pixel 28 in the third field is used as an image signal for the AF evaluation value calculation unit 4 to calculate the AF evaluation value. In the signal level readout period, the pixel signal output from the unit pixel 28 in the first field is used as an image signal for the AF evaluation value calculation unit 4 to calculate the AF evaluation value.

  Note that the reset operation and AF signal acquisition operation in the reset level readout period, the exposure operation in the exposure period, and the optical signal readout operation and AF signal acquisition operation in the signal level readout period are the second shown in FIG. Since this is the same as the drive timing, detailed description is omitted. Therefore, in the third drive timing shown in FIG. 5, only the order of performing each operation will be described.

  First, the reading of the noise signal and the acquisition of the AF signal performed during the reading of the noise signal will be described. When the release button is pressed and the imaging apparatus 100 starts capturing a still image, first, in the reset level read period (timing t1 to timing t9), the reset operation for each field and the AF signal acquisition operation by the third field. And done.

  In this reset level read period, first, the vertical control circuit 26 performs the first field reset operation from the timing t1. Then, from timing t2, an AF signal acquisition operation is performed in the third field. Subsequently, the reset operation of the second field is performed from timing t4. Then, from timing t5, an AF signal acquisition operation is performed in the third field. Finally, the reset operation of the third field is performed from timing t7.

  Subsequently, reading of an optical signal in a signal level reading period and acquisition of an AF signal performed during reading of the optical signal will be described. In the signal level readout period (timing t11 to timing t18), the optical signal readout operation for each field and the AF signal acquisition operation in the first field are performed.

  In this signal level readout period, first, the vertical control circuit 26 performs the first field optical signal readout operation from timing t11. Then, from timing t12, an AF signal acquisition operation is performed in the first field. Subsequently, the read operation of the optical signal of the second field is performed from timing t14. Then, from timing t15, an AF signal acquisition operation is performed in the first field. Finally, the read operation of the optical signal in the third field is performed from timing t17.

  As described above, at the third drive timing of the imaging unit 2 in the imaging apparatus 100 according to the first embodiment, the acquisition of the AF signal using the third field is performed in the reset level readout period. This can be performed at both the timing after the field reset operation and after the second field reset operation. In the signal level readout period, the acquisition of the AF signal using the first field is performed both at the timing after the first field optical signal readout operation and after the second field optical signal readout operation. Can do. Thereby, the AF signal acquisition and focusing operation can be performed until the timing close to the exposure period of the imaging apparatus 100, and the AF signal acquisition and focusing operation is started from the timing close to the exposure period of the imaging apparatus 100. And can be resumed. As a result, it is possible to suppress a decrease in focusing accuracy due to movement of the subject and to improve the focusing accuracy during continuous shooting.

  In the third drive timing, the case where the AF signal acquisition operation by the third field and the AF signal acquisition operation by the first field are each performed twice has been described. However, each AF signal acquisition operation is described above. The number of times can also be other times.

  As described above, according to the first embodiment, the AF evaluation is performed using the field (the third field in the first embodiment) in which the reset operation is not completed in the reset level reading period. An AF signal for calculating the value can be acquired. Thereby, the acquisition of the AF signal and the focusing operation can be performed until the timing close to the exposure period of the imaging apparatus, and a decrease in focusing accuracy due to movement of the subject can be suppressed.

  In addition, according to the first embodiment, the AF evaluation value is calculated using the field (the first field in the first embodiment) in which the optical signal read operation is completed in the signal level read period. For this purpose, an AF signal is acquired. As a result, the AF signal acquisition and the focusing operation can be restarted from the timing close to the exposure period of the imaging apparatus, and the focusing accuracy during continuous shooting can be improved.

<Second Embodiment>
Next, another embodiment of the present invention will be described. FIG. 6 is a block diagram illustrating a schematic configuration of an imaging unit in the imaging apparatus according to the second embodiment. FIG. 7 is a block diagram showing an example of the configuration of a unit pixel of a MOS type image pickup device having a global shutter function provided in the image pickup unit in the image pickup apparatus according to the second embodiment. The imaging unit 20 illustrated in FIG. 6 is an imaging unit provided in the imaging device instead of the imaging unit 2 provided in the imaging device 100 illustrated in FIG. Further, the unit pixel 208 shown in FIG. 7 is a MOS type imaging device that replaces the unit pixel 28 in the pixel unit 24 provided in the imaging unit 2 shown in FIG. Therefore, in the following description, it is assumed that the imaging unit 20 shown in FIG. 6 is provided in the imaging device 100 shown in FIG. 1, and the imaging device 100 shown in FIG. 1, the imaging unit 2 shown in FIG. Components similar to those in the unit pixel 28 shown in FIG. 10 are assigned the same reference numerals, and descriptions thereof are omitted.

  In FIG. 6, the imaging unit 20 includes a pixel unit 204, which is a MOS solid-state imaging device having a global shutter function, a vertical control circuit 206, a still image output circuit 201, and an AF output circuit 202. ing.

  The imaging unit 20 photoelectrically converts the optical image of the subject formed by the lens 1 and outputs an image signal (digital signal) corresponding to the subject light. In addition, the imaging unit 20 has a global shutter function that allows the exposure start time and the exposure end time of all the unit pixels 208 to be the same as in the imaging unit 2 shown in FIG. The global shutter operation is performed by the drive control by the unit 7. The imaging unit 20 also has a rolling shutter function that sequentially performs exposure and readout of pixel signals in units of rows of the unit pixels 208, and performs a rolling shutter operation by drive control by the exposure control unit 7. Then, the imaging unit 20 outputs an image signal obtained by the global shutter operation or the rolling shutter operation to the image processing unit 3 and the AF evaluation value calculation unit 4. The imaging unit 20 has a multi-line readout configuration in which an optical signal and a noise signal read from the pixel unit 204 are output from two output circuits (a still image output circuit 201 and an AF output circuit 202), respectively. .

  In the pixel unit 204, a plurality of unit pixels 208 are two-dimensionally arranged in a row direction and a column direction (9 rows and 9 columns in FIG. 6). As shown in FIG. 7, the unit pixel 208 includes a photodiode PD, a signal accumulation unit FD, a transfer transistor Mtx1, a reset transistor Mtx2, an amplification transistor Ma, a selection transistor Mb1, a selection transistor Mb2, and a reset transistor Mr. The configuration of the unit pixel shown in FIG. 7 is different from the configuration of the unit pixel shown in FIG. 10 in that the selection transistor Mb has two configurations of a selection transistor Mb1 and a selection transistor Mb2. . In addition, with this configuration, the row selection signal SEL input from the vertical control circuit 206 becomes the row selection signal SEL1 and the row selection signal SEL2, and the vertical transfer line VTL of the unit pixel 208 becomes the vertical transfer line VTL1. This is a vertical transfer line VTL2. With this configuration, the pixel unit 204 can simultaneously output pixel signals from the unit pixels 208 in two different rows to the vertical transfer line VTL1 and the vertical transfer line VTL2.

  The photodiode PD, the signal storage unit FD, the transfer transistor Mtx1, the reset transistor Mtx2, the amplification transistor Ma, and the reset transistor Mr have functions similar to those of the components of the MOS type image pickup device illustrated in FIG. The selection transistor Mb1 selects the signal charge of the photodiode PD amplified by the amplification transistor Ma according to the row selection signal SEL1, and outputs the signal charge to the vertical transfer line VTL1 that is an output signal line of the unit pixel 208. The selection transistor Mb2 selects the signal charge of the photodiode PD amplified by the amplification transistor Ma according to the row selection signal SEL2, and outputs it to the vertical transfer line VTL2 that is an output signal line of the unit pixel 208.

  The vertical control circuit 206 is a control signal (row selection signal SEL1, row selection signal SEL2, row reset signal RES, row transfer signal TX1, PD reset signal) for controlling the unit pixels 208 arranged in the pixel unit 204 in units of rows. TX2) is output for each row of the pixel portion 204. In addition, the vertical scanning circuit 206 includes a reset control unit for resetting the unit pixel 208 and a read control unit for reading a signal from the unit pixel 208. The vertical control circuit 206 also has an AF signal readout control unit and a noise signal / optical signal readout control unit. The signal output from the unit pixel 208 in the row selected by the vertical control circuit 206 selects either the vertical transfer line VTL1 or the vertical transfer line VTL2 that is an output signal line of the unit pixel 208 provided for each column. To the output signal line.

  The still image output circuit 201 outputs the pixel signal from the pixel unit 204 transferred via the vertical transfer line VTL1 to the image processing unit 3 as a still image signal. The still image output circuit 201 includes, for example, a CDS unit 25, a horizontal scanning circuit 27, an A / D conversion unit 22, and a KTC noise removal unit 23 among the components of the imaging unit 2 shown in FIG. It is. In the configuration of the still image output circuit 201, a digital image signal subjected to KTC noise removal processing from the pixel signal read from the pixel unit 204 is output to the image processing unit 3.

  The AF output circuit 202 outputs the pixel signal from the pixel unit 204 transferred via the vertical transfer line VTL2 to the AF evaluation value calculation unit 4 as an image signal for AF. The AF output circuit 202 includes, for example, the CDS unit 25, the horizontal scanning circuit 27, and the A / D conversion unit 22 among the components of the imaging unit 2 illustrated in FIG. 2. In the configuration of the AF output circuit 202, a digital image signal subjected to correlated double sampling processing from the pixel signal read from the pixel unit 204 is output to the AF evaluation value calculation unit 4.

<First drive timing>
Next, the drive timing of the imaging unit of the second embodiment will be described. FIG. 8 is a timing chart showing an outline of the first drive timing of the imaging unit 20 in the imaging apparatus 100 according to the second embodiment. In the first drive timing shown in FIG. 8, when the imaging unit 20 performs the global shutter operation, the AF evaluation value calculation unit 4 calculates the AF evaluation value by acquiring the pixel signal until the timing close to the exposure period. This is a driving method for acquiring an image signal for the purpose.

  As shown in FIG. 1, the driving of the imaging unit 20 is controlled by the exposure control unit 7. At the first drive timing shown in FIG. 8, the imaging unit 20 corresponds to the drive control by the exposure control unit 7. The control signals (row selection signal SEL1, row selection signal SEL2, row reset signal RES, row transfer signal TX1, and PD reset signal TX2) output from the vertical control circuit 206 are shown. In FIG. 8, the numbers following “L” in “(): parentheses” after the sign of the row selection signal SEL1, the row selection signal SEL2, the row reset signal RES, the row transfer signal TX1, and the PD reset signal TX2 are: Similar to the drive timing of the first embodiment shown in FIGS. 3 to 5, a row of unit pixels 208 is represented.

  Further, at the first drive timing shown in FIG. 8, the unit pixels 208 in the first to ninth rows arranged in the pixel portion 204 shown in FIG. Similarly to the driving timing of the first embodiment, a case is shown in which control is performed by dividing into three fields from one set (first field) to three sets (third field) sequentially for each row. A case where the pixel signal output from the unit pixel 208 in one field among the three fields is used as an image signal for the AF evaluation value calculation unit 4 to calculate the AF evaluation value is shown.

  The three fields are the unit pixels 208 arranged in the first row, the fourth row, and the seventh row of the pixel unit 204, similarly to the drive timing of the first embodiment shown in FIGS. Is the first field, unit pixels 208 arranged in the second, fifth, and eighth rows of the pixel portion 204 are the second field, and the third, sixth, and ninth rows of the pixel portion 204 are The unit pixels 208 arranged in the third field are defined as a third field. The pixel signal output from the unit pixel 208 in the third field is used as an image signal for the AF evaluation value calculation unit 4 to calculate the AF evaluation value.

  Hereinafter, reading of a noise signal and acquisition of an AF signal performed simultaneously with reading of the noise signal will be described. First, when the release button is pressed and the imaging apparatus 100 starts capturing a still image, first, in the reset level readout period (timing t1 to timing t4), the reset operation of each unit pixel 208 is performed, and each unit pixel 208 is reset. Read the reset signal. However, at the first drive timing shown in FIG. 8, a reset operation is performed for each field.

  In this reset level read period, first, from the timing t1, the vertical control circuit 206 performs the reset operation of the first field. In the reset operation of the first field, first, the row selection signal SEL1 (L01) of the first row is set to the “H” level, and the amplification transistor Ma of the unit pixel 208 of the first row is connected to the vertical transfer line VTL1. At this time, the “H” level pulse (reset pulse) of the row reset signal RES (L01) of the first row is applied to the reset transistor Mr of the unit pixel 208 of the first row. With this reset pulse, the reset transistor Mr of the unit pixel 208 in the first row is turned on, and the signal storage unit FD and the input unit of the amplification transistor Ma of the unit pixel 208 in the first row are reset. Then, the reset level signal of the signal accumulation unit FD of the unit pixel 208 in the first row output from the amplification transistor Ma of the unit pixel 208 in the first row is read as a noise signal of the unit pixel 208 in the first row. Then, the row selection signal SEL1 (L01) of the first row is returned to the “L” level, and the connection between the amplification transistor Ma and the vertical transfer line VTL1 of the unit pixel 208 of the first row is disconnected.

  In the reset level read period, the row transfer signal TX1 in the first field is at the “L” level, and the PD reset signal TX2 is at the “H” level. Accordingly, in the unit pixel 208 of the first field, the photodiode PD is reset by the ON state of the reset transistor Mtx2, and the reset signal charge of the photodiode PD is stored in the signal accumulation by the OFF state of the transfer transistor Mtx1. In this state, the signal is not output to the input part of the part FD and the amplification transistor Ma.

  In the reset level readout period, simultaneously with the readout of the noise signal of the unit pixel 208 in the first row, from the timing t1, the vertical control circuit 206 uses the third field for which the reset operation has not been completed to use the AF evaluation value. An AF signal for calculating is acquired. In the acquisition of the AF signal by the third field, the image signal is acquired by the rolling shutter operation in order to suppress the KTC noise.

  In the AF signal acquisition operation in the third field, first, the PD reset signal TX2 (L03) in the third row is set to the “L” level in advance to turn off the reset transistor Mtx2 of the unit pixel 208 in the third row. As a result, the reset of the photodiode PD of the unit pixel 208 in the third row is released. Thereby, the exposure of the subject light is started so that the exposure time of the photodiode PD becomes a predetermined AF signal level. Then, the row selection signal SEL2 (L03) in the third row is set to the “H” level, and the amplification transistor Ma of the unit pixel 208 in the third row is connected to the vertical transfer line VTL2. At this time, the “H” level pulse (reset pulse) of the row reset signal RES (L03) in the third row is applied to the reset transistor Mr of the unit pixel 208 in the third row. With this reset pulse, the reset transistor Mr of the unit pixel 208 in the third row is turned on, the signal storage unit FD and the input unit of the amplification transistor Ma of the unit pixel 208 in the third row are reset, and the vertical transfer lines VTL2 to 3 The reset level signal of the signal accumulation unit FD in the row is read as a noise signal of the unit pixel 208 in the third row.

  Thereafter, after a predetermined exposure time has elapsed, an “H” level pulse (transfer pulse) of the row transfer signal TX1 (L03) of the third row unit pixel 208 is applied to the transfer transistor Mtx1 of the third row unit pixel 208. Apply. With this transfer pulse, the transfer transistor Mtx1 of the unit pixel 208 in the third row is turned on, and the signal charge generated in the photodiode PD of the unit pixel 208 in the third row becomes the signal storage unit of the unit pixel 208 in the third row. The signal is transferred to the FD, and the signal of the AF signal level of the signal accumulation unit FD in the third row is read from the vertical transfer line VTL2 as the AF signal of the unit pixel 208 in the third row. Thereafter, the row selection signal SEL2 (L03) of the unit pixel 208 in the third row is returned to the “L” level, and the connection between the amplification transistor Ma and the vertical transfer line VTL2 in the unit pixel 208 of the third row is disconnected. At the same time, the PD reset signal TX2 (L03) of the unit pixel 208 in the third row is returned to the “H” level, and the photodiode PD of the unit pixel 208 in the third row is reset.

  Here, the AF signal and noise signal read from the unit pixel 208 in the third row are subjected to correlated double sampling processing for removing KTC noise in the AF output circuit 202, and then AF. A digital image signal is output to the AF evaluation value calculation unit 4.

  Similarly, simultaneously with the readout of the noise signal of the unit pixel 208 of the fourth row by the row selection signal SEL1 (L04) and the row reset signal RES (L04) of the fourth row of the first field, the sixth row of the third field is read. The AF signal of the unit pixel 208 in the sixth row is read by the row selection signal SEL2 (L06), the row reset signal RES (L06), the row transfer signal TX1 (L06), and the PD reset signal TX2 (L06). . Similarly, simultaneously with the readout of the noise signal of the unit pixel 208 in the seventh row by the row selection signal SEL1 (L07) and the row reset signal RES (L07) in the seventh row of the first field, 9 in the third field. The AF signal of the unit pixel 208 in the ninth row is read by the row selection signal SEL2 (L09), the row reset signal RES (L09), the row transfer signal TX1 (L09), and the PD reset signal TX2 (L09) in the row. Done. In this way, simultaneously with the reset operation of the first field, the digital image signal for AF acquired using the third field is output to the AF evaluation value calculation unit 4.

  Then, the AF evaluation value calculation unit 4 calculates an AF evaluation value based on the digital image signal for AF in the third field, and outputs the calculated AF evaluation value to the camera control unit 10. As a result, an AF control command is output from the camera control unit 10 to the AF control unit 8, and the focus lens included in the lens 1 is driven based on the AF control command input by the AF control unit 8, so A focusing operation is performed.

  Thereafter, from timing t2, the vertical control circuit 206 performs the second field reset operation by reading out noise signals of the unit pixels 208 in the second row, the fifth row, and the eighth row. At the same time, an AF signal acquisition operation is performed using the third field, and the acquired AF digital image signal is output to the AF evaluation value calculation unit 4. Thereby, the focusing operation on the subject is repeated.

  Further, in the reset level readout period, from the timing t3, the vertical control circuit 206 causes the noise of the unit pixels 208 in the third row, the sixth row, and the ninth row as in the reset operation of the first field and the second field. By reading the signal, the reset operation of the third field is performed. Then, the noise signal reading operation during the reset level reading period and the AF signal acquisition operation performed simultaneously with the noise signal reading operation are terminated.

  Here, each noise signal read from the unit pixels 208 in the first field to the third field is stored in the KTC noise removing unit 23 in the still image output circuit 201.

  Subsequently, in the exposure period (timing t5 to timing t6), the photodiodes PD of the unit pixels 208 in all rows are exposed together. In this exposure period, first, at the timing t5, the vertical control circuit 206 simultaneously sets the PD reset signals TX2 (L01 to L09) of the unit pixels 208 of all the rows to the “L” level to thereby store the unit pixels 208 in the unit pixels 208. The reset transistor Mtx2 is turned off. As a result, the reset of the photodiodes PD of all the unit pixels 208 is canceled, and the photodiodes PD simultaneously start exposure of subject light. After a predetermined exposure time has elapsed, at the timing t6, the vertical control circuit 206 generates an “H” level pulse (transfer pulse) in response to the row transfer signal TX1 (L01 to L09) of the unit pixels 208 of all rows. This is applied to the transfer transistors Mtx1 of all the unit pixels 208. By this transfer pulse, the transfer transistors Mtx1 of all the unit pixels 208 are turned on, and the signal charges generated in the photodiodes PD of the unit pixels 208 are simultaneously transferred to the signal storage units FD of the respective unit pixels 208. The exposure of the unit pixel 208 is completed. Thereafter, the PD reset signals TX2 (L01 to L09) of the unit pixels 208 in all the rows are simultaneously set to the “H” level, so that the reset transistors Mtx2 in the unit pixels 208 are turned on, and the photo of all the unit pixels 208 are turned on. The diode PD is returned to the reset state.

  Subsequently, finally, in the signal level readout period (timing t7 to timing t10), the unit pixels 208 in each row are sequentially scanned for each field, and the signal charges transferred to the signal storage unit FD of the unit pixels 208 are determined. Read the optical signal.

  In this signal level readout period, first, from timing t7, the vertical control circuit 206 performs the first field optical signal readout operation. In the reading operation of the optical signal of the first field, first, the row selection signal SEL1 (L01) of the first row is set to the “H” level, and the amplification transistor Ma of the unit pixel 208 of the first row is connected to the vertical transfer line VTL1. To do. As a result, an optical signal corresponding to the signal level of the signal charge transferred from the vertical transfer line VTL1 of the unit pixel 208 of the first row to the signal storage unit FD of the first row is read out. Thereafter, the row selection signal SEL1 (L01) of the unit pixel 208 in the first row is returned to the “L” level, and the connection between the amplification transistor Ma of the unit pixel 208 in the first row and the vertical transfer line VTL1 is disconnected. Similarly, the optical signal of the unit pixel 208 of the fourth row is read by the row selection signal SEL1 (L04) of the fourth row of the first field, and the unit pixel of the seventh row is read by the row selection signal SEL1 (L07) of the seventh row. The optical signal 208 is read, and the optical signal reading operation for the first field is completed.

  In the signal level read period, the row transfer signal TX1 in the first field is at the “L” level, and the PD reset signal TX2 is at the “H” level. Accordingly, as in the reset level readout period, the photodiode PD is reset by the ON state of the reset transistor Mtx2 in the unit pixel 208 of the first field, and the photodiode PD is reset by the OFF state of the transfer transistor Mtx1. This is a state in which the signal charge thus output is not output to the signal storage unit FD and the input unit of the amplification transistor Ma. In the signal level read period, the row reset signal RES in the first field is at the “L” level. Therefore, in the unit pixel 208 of the first field, the signal storage unit FD and the input unit of the amplification transistor Ma are not reset due to the OFF state of the reset transistor Mr.

  Subsequently, the vertical control circuit 206 performs a second field optical signal read operation from timing t8, and performs a third field optical signal read operation from timing t9. Note that the second field optical signal read operation and the third field optical signal read operation are the same as the first field optical signal read operation, and thus description thereof is omitted.

  Here, each optical signal read from the unit pixel 208 in the first field to the third field is the noise signal stored in the reset level reading period in the KTC noise removing unit 23 in the still image output circuit 201. Then, a difference process with the optical signal read during the signal level reading period is performed, and the digital image signal from which the KTC noise has been removed is output to the image processing unit 3 as an image signal output from the imaging unit 20.

  Thereafter, each process in the imaging apparatus 100 is performed based on the image signal output from the imaging unit 20.

  As described above, at the first drive timing of the imaging unit 20 in the imaging apparatus 100 according to the second embodiment, the pixel unit 204 is divided into a plurality of fields when the imaging unit 20 performs the global shutter operation. To obtain a noise signal. Finally, after the AF signal is acquired using the unit pixel 208 of the field from which the noise signal is acquired, it can be driven to acquire the noise signal of that field. Thereby, the acquisition of the AF signal and the focusing operation can be performed until the timing close to the exposure period of the imaging apparatus 100, and a decrease in focusing accuracy due to movement of the subject can be suppressed.

  Further, at the first drive timing, the noise signal reading and the AF signal acquisition can be performed simultaneously by performing the AF signal acquisition operation using a field different from the field in which the reset operation is being performed. it can. Thereby, it is possible to reduce the time of the reset level readout period for acquiring the noise signal even when the focusing operation is performed. As a result, when the release button is pressed and the imaging apparatus 100 starts capturing a still image, it can perform the focusing operation on the subject, and the time until the subject to be actually captured is exposed. And the delay time of the shutter (shutter time lag) can be reduced. In addition, this makes it possible to increase the number of shots during continuous shooting, for example.

<Second drive timing>
Next, another drive timing of the imaging unit of the second embodiment will be described. FIG. 9 is a timing chart showing an outline of the second drive timing of the imaging unit 20 in the imaging apparatus 100 according to the second embodiment. In the second drive timing shown in FIG. 9, when the imaging unit 20 performs the global shutter operation, the pixel signal is acquired until the timing close to the exposure period, and the acquisition of the pixel signal is started from the timing close to the exposure period. Thus, the AF evaluation value calculation unit 4 is a driving method for acquiring an image signal for calculating the AF evaluation value.

  Note that “():“ in parentheses ”after the sign of the row selection signal SEL1, the row selection signal SEL2, the row reset signal RES, the row transfer signal TX1, and the PD reset signal TX2 at the second drive timing shown in FIG. The numbers following L ″ represent the row of unit pixels 208 as in the first drive timing shown in FIG. In the second drive timing shown in FIG. 9 as well, the drive is divided into three fields as in the first drive timing shown in FIG.

  In the reset level readout period, the pixel signal output from the unit pixel 208 in the third field is used as an image signal for the AF evaluation value calculation unit 4 to calculate the AF evaluation value. In the signal level readout period, the pixel signal output from the unit pixel 208 in the first field is used as an image signal for the AF evaluation value calculation unit 4 to calculate the AF evaluation value.

  Note that the reset operation, the AF signal acquisition operation in the reset level readout period, and the exposure operation in the exposure period are the same as the first drive timing shown in FIG.

  Hereinafter, reading of an optical signal in a signal level reading period and acquisition of an AF signal performed simultaneously with reading of the optical signal will be described. In the signal level readout period (timing t7 to timing t10), as in the signal level readout period (timing t7 to timing t10) at the first drive timing shown in FIG. Scanning is performed to read out an optical signal corresponding to the signal charge transferred to the signal storage unit FD of the unit pixel 208.

  In this signal level readout period, first, from timing t7, the vertical control circuit 206 performs the first field optical signal readout operation. Subsequently, from timing t8, the vertical control circuit 206 performs a read operation of the optical signal in the second field. Note that the first field optical signal read operation and the second field optical signal read operation are the same as the first drive timing shown in FIG.

  In this signal level readout period, simultaneously with the readout of the optical signal of the unit pixel 208 in the second row, from timing t8, the vertical control circuit 206 performs AF evaluation using the first field for which the optical signal readout operation has been completed. An AF signal for calculating a value is acquired. In the acquisition of the AF signal by the first field, the image signal is acquired by the rolling shutter operation in order to suppress the KTC noise.

  In the AF signal acquisition operation in the first field, first, the PD reset signal TX2 (L01) in the first row is set to the “L” level in advance to turn off the reset transistor Mtx2 of the unit pixel 208 in the first row. As a result, the reset of the photodiode PD of the unit pixel 208 in the first row is released. Thereby, the exposure of the subject light is started so that the exposure time of the photodiode PD becomes a predetermined AF signal level. Then, the row selection signal SEL2 (L01) in the first row is set to the “H” level, and the amplification transistor Ma of the unit pixel 208 in the first row is connected to the vertical transfer line VTL2. At this time, the “H” level pulse (reset pulse) of the row reset signal RES (L01) of the first row is applied to the reset transistor Mr of the unit pixel 208 of the first row. With this reset pulse, the reset transistor Mr of the unit pixel 208 in the first row is turned on, the signal storage unit FD and the input unit of the amplification transistor Ma of the unit pixel 208 in the first row are reset, and the vertical transfer line VTL2 A reset level signal of the signal accumulation unit FD in the row is read as a noise signal of the unit pixel 208 in the first row.

  Thereafter, after a predetermined exposure time elapses, an “H” level pulse (transfer pulse) of the row transfer signal TX1 (L01) of the unit pixel 208 in the first row is applied to the transfer transistor Mtx1 of the unit pixel 208 in the first row. Apply. With this transfer pulse, the transfer transistor Mtx1 of the unit pixel 208 in the first row is turned on, and the signal charge generated in the photodiode PD of the unit pixel 208 in the first row becomes the signal storage unit of the unit pixel 208 in the first row. The signal is transferred to the FD, and the signal of the AF signal level of the signal accumulation unit FD in the first row is read from the vertical transfer line VTL2 as the AF signal of the unit pixel 208 in the first row. Thereafter, the row selection signal SEL2 (L01) of the unit pixel 208 in the first row is returned to the “L” level, and the connection between the amplification transistor Ma and the vertical transfer line VTL2 of the unit pixel 208 in the first row is disconnected. At the same time, the PD reset signal TX2 (L01) of the unit pixel 208 in the first row is returned to the “H” level, and the photodiode PD of the unit pixel 208 in the first row is reset.

  Here, the AF signal and the noise signal read from the unit pixel 208 in the first row are subjected to correlated double sampling processing for removing KTC noise in the AF output circuit 202, and then AF. A digital image signal is output to the AF evaluation value calculation unit 4.

  Similarly, simultaneously with the reading of the optical signal of the unit pixel 208 in the fifth row by the row selection signal SEL1 (L05) in the fifth row in the second field, the row selection signal SEL2 (L04) in the fourth row in the first field The AF signal of the unit pixels 208 in the fourth row is read by the row reset signal RES (L04), the row transfer signal TX1 (L04), and the PD reset signal TX2 (L04). Similarly, simultaneously with the reading of the optical signal of the unit pixel 208 of the eighth row by the row selection signal SEL1 (L08) of the eighth row of the second field, the row selection signal SEL2 (L07 of the seventh row of the first field). ), The row reset signal RES (L07), the row transfer signal TX1 (L07), and the PD reset signal TX2 (L07), the AF signals of the unit pixels 208 in the seventh row are read. In this way, simultaneously with the reading operation of the optical signal of the second field, the digital image signal for AF acquired using the first field is output to the AF evaluation value calculation unit 4.

  The AF evaluation value calculation unit 4 calculates an AF evaluation value based on the digital image signal for AF in the first field, and outputs the calculated AF evaluation value to the camera control unit 10. As a result, an AF control command is output from the camera control unit 10 to the AF control unit 8, and the focus lens included in the lens 1 is driven based on the AF control command input by the AF control unit 8, so A focusing operation is performed.

  Thereafter, from timing t9, the vertical control circuit 206 reads out the optical signals of the unit pixels 208 in the third row, the sixth row, and the ninth row, thereby performing the reading operation of the optical signal in the third field. The third field optical signal readout operation is the same as the first field optical signal readout operation and the second field optical signal readout operation, and thus description thereof is omitted.

  Here, each optical signal read from the unit pixel 208 in the first field to the third field is the noise signal stored in the reset level reading period in the KTC noise removing unit 23 in the still image output circuit 201. Difference processing with the optical signal read during the signal level reading period is performed. The still image output circuit 201 outputs the digital image signal from which the KTC noise has been removed to the image processing unit 3 as an image signal output from the imaging unit 20.

  At the same time as the optical signal readout operation for the third field, an AF signal acquisition operation is performed using the first field for which the optical signal readout operation has been completed, and the acquired digital image signal for AF becomes AF It is output to the evaluation value calculation unit 4. Thereby, the focusing operation on the subject is repeated.

  As described above, at the second drive timing of the imaging unit 20 in the imaging apparatus 100 according to the second embodiment, the pixel unit 204 is divided into a plurality of fields when the imaging unit 20 performs the global shutter operation. To obtain a noise signal. Finally, after the AF signal is acquired using the unit pixel 208 of the field from which the noise signal is acquired, it can be driven to acquire the noise signal of that field. Thereby, the acquisition of the AF signal and the focusing operation can be performed until the timing close to the exposure period of the imaging apparatus 100, and a decrease in focusing accuracy due to movement of the subject can be suppressed.

  In the second drive timing, the noise signal reading and the AF signal acquisition can be performed simultaneously by performing the AF signal acquisition operation using a field different from the field in which the reset operation is being performed. it can. Thereby, it is possible to reduce the time of the reset level readout period for acquiring the noise signal even when the focusing operation is performed. As a result, when the release button is pressed and the imaging apparatus 100 starts capturing a still image, it can perform the focusing operation on the subject, and the time until the subject to be actually captured is exposed. And the delay time of the shutter (shutter time lag) can be reduced. In addition, this makes it possible to increase the number of shots during continuous shooting, for example.

  Further, at the second drive timing, the pixel portion 204 is divided into a plurality of fields to obtain an optical signal. Then, after the operation of reading the optical signal in the field from which the optical signal is first read is completed, it is possible to drive to acquire the AF signal using the unit pixel 208 of the field. Thereby, AF signal acquisition and focusing operation can be performed periodically from the timing close to the exposure period of the imaging apparatus 100. For example, during continuous shooting, the focusing operation in the second and subsequent shootings can be performed. It can be resumed at an early timing. As a result, it is possible to solve the problem in the conventional driving timing that the focusing operation at the time of continuous shooting is delayed and the shooting interval of continuous shooting becomes long, and the focusing accuracy at the time of continuous shooting can be improved.

  As described above, according to the embodiment for carrying out the present invention, when the pixel portion of the solid-state imaging device having the global sitter function is divided into a plurality of fields and the noise signal before exposure is acquired, In addition, the image signal can be acquired using the unit pixel of the field from which the noise signal is acquired. Thereby, an image signal can be acquired until the timing close to the exposure period of the solid-state imaging device, and the function of the imaging device can be improved. For example, it is possible to perform a focusing operation on a subject by using a live view image displayed on a display screen of the imaging device in order to confirm the subject to be photographed by the imaging device.

  According to the embodiment for carrying out the present invention, when an optical signal after exposure is acquired, an image signal can be acquired using a unit pixel of a field from which the optical signal is first read. Thereby, an image signal can be acquired from a timing close to the exposure period of the solid-state imaging device, and the function of the imaging device can be improved. For example, a live view image can be displayed on the display screen of the imaging apparatus at an early timing after the imaging by the imaging apparatus is completed.

  Moreover, according to the form for implementing this invention, an image signal can be acquired using the unit pixel of the field from which the field which acquires the noise signal, or the field which reads the optical signal is different. Thereby, acquisition of a noise signal or an optical signal and acquisition of an image signal can be performed at the same time, and the function of the imaging apparatus can be improved. For example, it is possible to perform a focusing operation on the subject at the same time while confirming the subject with a live view image displayed on the display screen of the imaging apparatus.

  In addition, the specific configuration of the circuit configuration and the driving method in the present invention is not limited to the mode for carrying out the present invention, and various modifications can be made without departing from the spirit of the present invention. . For example, the number of fields to be divided can be increased. Also, the number of lines in each field can be set to a different value. In addition, even when the constituent elements of the unit pixel and the driving method are changed, the circuit configuration of the vertical scanning circuit and the output circuit and the driving method thereof can be changed.

  Further, in the present embodiment, an example of 9 rows and 9 columns with respect to the arrangement of the unit pixels in the row direction and the column direction has been shown. The number of row and column directions in which unit pixels are arranged can be changed without departing from the scope of the present invention.

  The embodiment of the present invention has been described above with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes various modifications within the scope of the present invention. It is.

DESCRIPTION OF SYMBOLS 100 ... Imaging device 1 ... Lens 2 ... Imaging part 21 ... Solid-state imaging device 22 ... A / D conversion part 23 ... KTC noise removal part 24 ... Pixel part 25 ... CDS section 26 ... vertical control circuit (vertical scanning section)
27: Horizontal scanning circuit 28: Unit pixel (pixel)
PD ・ ・ ・ Photodiode (photoelectric conversion part)
FD ... Signal storage unit Mtx1 ... Transfer transistor (transfer unit)
Mtx2... Reset transistor (first reset unit)
Ma: Amplifying transistor (amplifying unit)
Mb ... selection transistor (selection unit)
Mr: reset transistor (second reset unit)
3. Image processing unit (first image processing unit)
4... AF evaluation value calculation unit (second image processing unit)
5 ... Display unit 6 ... Memory card 7 ... Exposure control unit (control unit)
8 ... AF control unit 9 ... camera operation unit 10 ... camera control unit (control unit)
20: Imaging unit 204 ... Pixel unit 206 ... Vertical control circuit (vertical scanning unit)
208 ... Unit pixel (pixel)
201 ... still image output circuit 202 ... AF output circuit Mb1 ... selection transistor (selection unit)
Mb2... Selection transistor (second selection unit)

Claims (7)

A photoelectric conversion unit that generates a signal charge according to incident light, a first reset unit that resets the photoelectric conversion unit, a transfer unit that transfers the signal charge generated by the photoelectric conversion unit, and the transfer unit An amplifying unit for amplifying the signal charge transferred via the second signal, a second reset unit for resetting the charge input to the amplifying unit, and an output signal using the signal charge amplified by the amplifying unit as a pixel signal A selection unit that outputs to a line, a pixel unit that includes a plurality of pixels arranged in a two-dimensional matrix,
A vertical scanning unit that selects the pixels for each row and sequentially reads out pixel signals from the pixel unit;
With
The vertical scanning unit includes:
A noise signal readout mode in which the input of the amplification unit is reset for each row of the pixels, and a signal output from the reset amplification unit is sequentially read as a noise signal;
By simultaneously resetting the photoelectric conversion units of all the pixels and simultaneously transferring the signal charges generated by the photoelectric conversion units of all the pixels to the amplification units after a predetermined time has elapsed, exposure of the pixel units is performed. Simultaneous exposure mode to be performed at the same time,
A first pixel signal reading mode for sequentially reading out amplified signals output from the amplifying unit according to the signal charges transferred in the simultaneous exposure mode as pixel signals;
The input of the amplifying unit is reset for each row of the pixels, the reset signal output from the amplifying unit, and the photoelectric conversion unit are reset for each row of the pixels, and after a predetermined time has elapsed, Second pixel signal readout that sequentially transfers the signal charges generated by the conversion unit to the amplification unit and sequentially reads out the amplified signals output from the amplification unit according to the transferred signal charges as pixel signals Mode,
Have
A set of pixels in a plurality of rows in the pixel portion,
Before starting the exposure of the pixel portion by the simultaneous exposure mode,
For each set of pixel rows in the set, read out the noise signal in the noise signal read mode,
Reading out the pixel signal in the second pixel signal reading mode using a set of pixel rows in which the reading of the noise signal in the noise signal reading mode is not completed;
A solid-state imaging device. The vertical scanning unit further includes:
After the readout of the pixel signal by the second pixel signal readout mode using the set of pixel rows in which the readout of the noise signal by the noise signal readout mode is not finished,
Reading out a noise signal in the noise signal readout mode for a set of pixel rows from which pixel signals have been read out in the second pixel signal readout mode;
The solid-state imaging device according to claim 1. The vertical scanning unit further includes:
After the exposure of the pixel portion in the simultaneous exposure mode is completed,
For each set of pixel rows, the pixel signal is read out in the first pixel signal readout mode,
Reading out pixel signals in the second pixel signal reading mode using a set of pixel rows for which reading of pixel signals in the first pixel signal reading mode has been completed;
The solid-state imaging device according to claim 2. The vertical scanning unit includes:
The readout of the pixel signal in the second pixel signal readout mode and the readout of the noise signal in the noise signal readout mode or the readout of the pixel signal in the first pixel signal readout mode are performed in time series.
The solid-state imaging device according to claim 2, wherein the solid-state imaging device is provided. The pixel further comprises:
A second selection unit that outputs the signal charge amplified by the amplification unit to a second output signal line as a second pixel signal;
Have
The vertical scanning unit includes:
The noise signal by the noise signal readout mode and the pixel signal by the pixel signal readout mode of 1 are output to the output signal line,
Outputting a pixel signal in the second pixel signal readout mode to the second output signal line;
The pixel signal readout in the second pixel signal readout mode and the noise signal readout in the noise signal readout mode or the pixel signal readout in the first pixel signal readout mode are simultaneously performed in different sets of pixel rows. ,
The solid-state imaging device according to claim 2, wherein the solid-state imaging device is provided. A photoelectric conversion unit that generates a signal charge according to incident light, a first reset unit that resets the photoelectric conversion unit, a transfer unit that transfers the signal charge generated by the photoelectric conversion unit, and the transfer unit An amplifying unit for amplifying the signal charge transferred via the second signal, a second reset unit for resetting the charge input to the amplifying unit, and an output signal using the signal charge amplified by the amplifying unit as a pixel signal A selection unit that outputs to a line, a pixel unit that includes a plurality of pixels arranged in a two-dimensional matrix,
A vertical scanning unit that selects the pixels for each row and sequentially reads out pixel signals from the pixel unit;
A method for driving a solid-state imaging device comprising:
The vertical scanning unit includes:
A noise signal reading procedure for resetting the input of the amplification unit for each row of the pixels and sequentially reading out the signal output from the reset amplification unit as a noise signal;
By simultaneously resetting the photoelectric conversion units of all the pixels and simultaneously transferring the signal charges generated by the photoelectric conversion units of all the pixels to the amplification units after a predetermined time has elapsed, exposure of the pixel units is performed. A simultaneous exposure procedure to be performed simultaneously;
A first pixel signal readout procedure for sequentially reading out amplified signals output from the amplifying unit in accordance with the signal charges transferred by the simultaneous exposure procedure as pixel signals;
The input of the amplifying unit is reset for each row of the pixels, the reset signal output from the amplifying unit, and the photoelectric conversion unit are reset for each row of the pixels, and after a predetermined time has elapsed, Second pixel signal readout that sequentially transfers the signal charges generated by the conversion unit to the amplification unit and sequentially reads out the amplified signals output from the amplification unit according to the transferred signal charges as pixel signals Procedure and
Including,
A set of pixels in a plurality of rows in the pixel portion,
Before starting the exposure of the pixel portion by the simultaneous exposure procedure,
For each set of pixel rows as the set, read the noise signal by the noise signal read procedure,
A procedure for reading a pixel signal by the second pixel signal readout procedure using a set of pixel rows for which the readout of the noise signal by the noise signal readout procedure has not been completed;
The solid-state imaging device drive method characterized by including. The solid-state imaging device according to any one of claims 1 to 5,
A control unit for controlling an operation mode of a vertical scanning unit in the solid-state imaging device;
A first image processing unit that performs image processing according to the noise signal read out in the noise signal reading mode of the solid-state imaging device and the pixel signal read out in the first pixel signal reading mode;
A second image processing unit that performs image processing according to the pixel signal read out in the second pixel signal reading mode of the solid-state imaging device;
With
The controller is
Before the pixel unit in the solid-state imaging device starts exposure by the simultaneous exposure mode of the solid-state imaging device,
Pixels in the second pixel signal read mode using the pixel rows of the set of the pixel units that read the noise signal in the noise signal read mode and have not finished reading the noise signal in the noise signal read mode. To read out the signal,
An imaging apparatus characterized by that.

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