JP2009124239A - Imaging apparatus, and flicker detection method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of highly accurately detecting flicker in a short time period regardless of the state of a subject and a photographing scene. <P>SOLUTION: A signal processing circuit 8 reads out an n-th line image of an image subjected to collective reset/collective transfer readout (S2). The signal processing circuit 8 reads out an n-th line image of an image subjected to rolling readout (S3). The signal processing circuit 8 subtracts a pixel output of the rolling readout from the pixel output of the collective reset/collective transfer readout in a specific column, out of both the n-th line images which are read out (S4). As a result of subtraction, the signal processing circuit 8 refers to the differential value of each line, and determines that flicker is generated, if there is a differential value not less than a predetermined threshold value and if there is a periodicity in an image vertical direction (S8). The signal processing circuit 8 determines that flicker is not generated if the differential value has no periodicity in an image vertical direction (S9). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging apparatus that detects flicker in reading a signal from an image sensor during moving image shooting, and a flicker detection method thereof.

  In an imaging apparatus such as a digital camera, a CMOS image sensor is used as a solid-state imaging device in terms of low voltage, low power consumption, and the frequency of use thereof has increased in recent years.

  By the way, when there is a blinking light source such as a fluorescent lamp as the light source in the photographing environment, the photographed image of the imaging device is affected by flicker by the light source. In particular, in the CMOS image sensor, since pixel signals are sequentially read out for each scanning line, it is known that the reading start time is shifted for each scanning line and the exposure time is different.

  Therefore, when the scanning line is line by line, the flicker that occurs is a line flicker whose output changes in the vertical direction of the screen, as in the image shown in FIG. FIG. 8 is a diagram showing the occurrence of line flicker.

In order to remove or reduce the influence of such flicker, the following methods are known as methods for detecting and correcting flicker. For example, there has been proposed one that detects flicker by integrating pixel signal levels for each predetermined line in one frame and using the integration result of lines at the same position in a plurality of past frames (see Patent Document 1). . In addition, there has been proposed one that detects flicker by calculating the line brightness by integrating the pixel level for each line within one frame and detecting the fluctuation period in the vertical direction of the line brightness (see Patent Document 2). ).
Japanese Patent No. 3476400 JP 2004-260574 A

  However, in Patent Document 1, a captured image of at least two frames is necessary to detect flicker, and an integrated value of a plurality of frames is used for flicker detection. I was going to get it.

  In addition, since there is always a time difference between the shooting time of the image used for flicker detection and the actual captured image, if the flicker state changes during that time, the flicker pattern may not be correctly removed.

  Further, in Patent Document 2, when the subject is a “uniform luminance surface” as shown in FIG. 8, it is possible to detect the flicker pattern with high accuracy from the signal amplitude, but in reality, there are various in the shooting screen. It is very rare that there is a uniform subject and a “uniform luminance surface”. Therefore, it is usually difficult to detect the flicker pattern of the captured image.

  The present invention has been made in view of the above problems, and provides an imaging apparatus and a flicker detection method capable of detecting flicker more accurately in a short time regardless of the state of a subject and a shooting scene. With the goal.

  In order to achieve the above object, an imaging apparatus according to the present invention includes two pixel units each including a photoelectric conversion unit that generates and accumulates charges by photoelectric conversion and a floating diffusion unit that accumulates the generated charges. An image pickup apparatus using an image pickup device arranged in a dimension, wherein the batch reset means for collectively resetting the photoelectric conversion unit and the floating diffusion unit of the plurality of pixel units arranged in a two-dimensional manner, Batch transfer means for transferring charges accumulated in the photoelectric conversion unit to the floating diffusion unit in a batch after a predetermined time has elapsed since the batch reset is performed, and the plurality of pixel units arranged in two dimensions A sequential reset unit that sequentially resets the photoelectric conversion unit and the floating diffusion unit for each predetermined unit; and a charge accumulated in the photoelectric conversion unit for each predetermined unit after a predetermined time has elapsed since the sequential reset is performed. Before Difference information is calculated using sequential transfer means for sequentially transferring to the floating diffusion section, the pixel signal of the pixel section obtained by the batch transfer means, and the pixel signal of the pixel section obtained by the sequential transfer means. And detecting means for detecting flicker based on the calculated difference information.

  According to the flicker detection method of the imaging apparatus of the present invention, a plurality of pixel units each including a photoelectric conversion unit that generates and accumulates charges by photoelectric conversion and a floating diffusion unit that accumulates the generated charges are two-dimensionally arranged. A flicker detection method for an image pickup apparatus using the image pickup device, wherein the photoelectric conversion unit and the floating diffusion unit of the plurality of pixel units arranged in two dimensions are collectively reset; and A batch transfer step of batch transferring the charges accumulated in the photoelectric conversion unit to the floating diffusion unit after a lapse of a predetermined time after the batch reset, and the plurality of pixel units arranged in two dimensions A sequential reset step for sequentially resetting the photoelectric conversion unit and the floating diffusion unit for each predetermined unit, and a predetermined time after the sequential reset is performed, the electric power stored in the photoelectric conversion unit is stored. Sequentially transferred to the floating diffusion unit for each predetermined unit, the pixel signal of the pixel unit obtained in the batch transfer step, and the pixel signal of the pixel unit obtained in the sequential transfer step. And a detection step of detecting flicker based on the calculated difference information.

  According to the imaging device of the first aspect of the present invention, the difference information is calculated using the pixel signal of the pixel unit obtained by the batch transfer unit and the pixel signal of the pixel unit obtained by the sequential transfer unit, Flicker is detected based on the calculated difference information. Thereby, flicker can be detected more accurately in a short time regardless of the state of the subject and the shooting scene.

  According to the imaging apparatus of the second aspect, the difference information can be calculated over a wide range on the shooting screen, and the accuracy of flicker detection can be improved. According to the imaging apparatus of the third aspect, the difference information is calculated for the pixel portion at the same position on the shooting screen, so that accurate difference information can be obtained. According to the imaging apparatus of the fourth aspect, since the difference information is calculated from one photographed image, flicker can be detected in a shorter time.

  According to the imaging device of the fifth aspect, it is possible to detect flicker while ensuring an effective pixel area. According to the imaging device of the sixth aspect, the effective pixel area can be efficiently used, and it is not necessary to provide a pixel area that is reset and transferred in a batch separately from the effective pixel area. According to the imaging device of the seventh aspect, flicker can be easily detected.

  Embodiments of an imaging apparatus and a flicker detection method of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus according to the first embodiment. The image pickup apparatus of the present embodiment is applied to a digital camera that can perform moving image / still image shooting.

  The imaging apparatus includes an optical system 1 including a lens and a diaphragm, a focal plane mechanical shutter (mechanical shutter) 2, and an imaging element 3. When the still image shooting mode is selected by a shooting mode switching SW (not shown) for switching between the moving image / still image shooting mode, the mechanical shutter 2 sets the exposure time to the image sensor due to the difference in travel time between the front curtain and the rear curtain. Control. When the moving image shooting mode is selected, the mechanical shutter 2 is fully opened and light is always guided to the image sensor 3.

  The image sensor 3 is a CMOS image sensor. In the present embodiment, the image sensor 3 has a configuration capable of rolling readout and batch reset batch transfer readout. Note that flicker detection described later can be detected based on pixel information obtained by this different readout method.

  The imaging apparatus also includes a CDS circuit 4 that performs analog signal processing, an A / D converter 5 that converts an analog signal into a digital signal, and a timing signal generation circuit 6. The timing signal generation circuit 6 generates a signal for operating the image sensor 3, the CDS circuit 4 and the A / D converter 5. In addition, the imaging apparatus includes an optical system 1, a mechanical shutter 2, a driving circuit 7 for the imaging device 3, a signal processing circuit 8 that performs signal processing necessary for captured image data, and an image memory that stores the signal processed image data. 9

  In addition, the imaging device includes an image recording medium 10 that is removable from the imaging device, a recording circuit 11 that records signal processed image data on the image recording medium 10, an image display device 12 that displays signal processed image data, and The image display device 12 includes a display circuit 13 that displays an image. The imaging apparatus also includes a system control unit 14 that controls the entire imaging apparatus, a nonvolatile memory (ROM) 15, and a volatile memory (RAM) 16.

  The nonvolatile memory (ROM) 15 stores a program describing a control method executed by the system control unit 14 and control data such as parameters and tables used when the program is executed. In the volatile memory (RAM) 16, the program, control data, and correction data stored in the nonvolatile memory 15 are transferred and stored. The volatile memory (RAM) 16 is used when the system control unit 14 controls the imaging apparatus.

  An operation when the moving image shooting mode is selected in the imaging apparatus having the above configuration will be described. Here, prior to the shooting operation, when the operation of the system control unit 14 is started, such as when the imaging apparatus is turned on, necessary programs and control data are transferred from the nonvolatile memory 15 to the volatile memory 16 and stored. I shall keep it. These programs and data are used when the system control unit 14 controls the imaging apparatus. Further, the system control unit 14 transfers additional programs and data from the nonvolatile memory 15 to the volatile memory 16 or directly reads and uses data in the nonvolatile memory 15 as necessary.

  First, the drive circuit 7 drives the optical system 1 including a diaphragm and a lens in accordance with a control signal from the system control unit 14 and fully opens the mechanical shutter 2. Then, the optical system 1 forms a subject image set to an appropriate brightness on the image sensor 3.

  The image pickup device 3 is driven by a drive pulse based on an operation pulse generated by the timing signal generation circuit 6 controlled by the system control unit 14, converts the subject image into an electrical signal by photoelectric conversion, and outputs it as an analog image signal. To do. A method for driving the image sensor 3 will be described later.

  The analog image signal output from the image pickup device 3 is subjected to clock synchronization noise removal by the CDS circuit 4 in accordance with an operation pulse generated by the timing signal generation circuit 6 controlled by the system control unit 14, and the A / D converter 5. Is converted into a digital image signal.

  Once the digital image is stored in the image memory 9, the signal processing circuit 8 controlled by the system control unit 14 performs image processing such as color conversion, white balance, gamma correction, and resolution conversion processing on the digital image signal. Then, image compression processing or the like is performed.

  The image memory 9 is used for temporarily storing a digital image signal during signal processing or for storing image data which is a digital image signal subjected to signal processing. The image data signal-processed by the signal processing circuit 8 and the image data stored in the image memory 9 are converted into data suitable for the image recording medium 10 (for example, file system data having a hierarchical structure) in the recording circuit 11. Is recorded on the image recording medium 10. After the resolution conversion process is performed by the signal processing circuit 8, the image data is converted into a signal suitable for the image display device 12 (for example, an NTSC analog signal) by the display circuit 13, and the image display device 12 performs the conversion. Is displayed.

  When requested by the system control unit 14, the signal processing circuit 8 outputs information on digital image signals and image data generated in the signal processing process to the system control unit 14. For example, information such as the spatial frequency of the image, the average value of the designated area, the data amount of the compressed image, or information extracted from the information is output. Further, the signal processing circuit 8 performs an operation from image signals obtained by different reading methods in the CMOS image sensor 3, and also generates flicker information. In addition, the signal processing circuit 8 performs image correction for each line based on the obtained flicker information, and also performs image processing for reducing the influence of flicker. When requested by the system control unit 14, the recording circuit 11 outputs information such as the type and free capacity of the image recording medium 10 to the system control unit 14.

  A reproduction operation when image data is recorded on the image recording medium 10 will be described. The recording circuit 11 reads image data from the image recording medium 10 in accordance with a control signal from the system control unit 14. Similarly, when the image data is a compressed image, the signal processing circuit 8 performs an image expansion process according to a control signal from the system control unit 14 and stores it in the image memory 9. The image data stored in the image memory 9 is subjected to resolution conversion processing in the signal processing circuit 8, converted into a signal suitable for the image display device 12 in the display circuit 13, and displayed on the image display device 12. .

  Next, the CMOS image sensor 3 according to the first embodiment and the driving method thereof will be described in detail. FIG. 2 is a diagram showing a schematic configuration of the CMOS image sensor 3. In FIG. 2, for simplification, a pixel configuration in which unit pixels (pixel portions) 201 are arranged in only 4 rows × 4 columns is shown, but in reality, a large number of pixel portions are two-dimensionally as a shooting screen. Has been placed.

  A photodiode (hereinafter referred to as PD) 202 converts light into electric charge. The transfer switch 203 transfers charges generated in the PD 202 to a storage area (hereinafter referred to as FD) described later in accordance with the transfer pulse φTX. The FD 204 temporarily accumulates charges. The amplification MOS amplifier 205 functions as a source follower. The selection switch 206 selects a pixel according to the selection pulse φSEL. The reset switch 207 removes the charge accumulated in the FD 204 according to the reset pulse φRES.

  The FD 204, the amplification MOS amplifier 205, and the constant current source 209 described later constitute a floating diffusion amplifier. The signal charge of the pixel selected by the selection switch 206 is converted into a voltage and output to the readout circuit 213 through the signal output line 208.

  The constant current source 209 serves as a load for the amplification MOS amplifier 205. The horizontal selection switch 210 is driven by the horizontal scanning circuit 214 and selects an output signal from the readout circuit 213. The output amplifier 211 outputs an output signal from the readout circuit 213 to the outside of the image sensor 3. The vertical scanning circuit 212 is for selecting the switches 203, 206, and 207.

  In the pulse signals φTX, φRES, and φSEL, the pulse signals applied by, for example, the nth scan line selected by the vertical scanning circuit 212 are described as φTXn, φRESn, and φSELn, respectively.

  Next, the driving operation of the image sensor in the moving image shooting mode will be described. In the present embodiment, when the image sensor 3 is driven, a rolling read operation and a batch reset batch transfer read operation are performed. Then, flicker detection is possible based on the difference in output results obtained from the difference in driving method between the image obtained from the driving for rolling readout and the image obtained from the drive for batch reset batch transfer readout.

  FIG. 3 is a timing chart showing driving of the image sensor 3 in the rolling readout operation. In FIG. 3, description is made with respect to n + 3 lines from n lines scanned and selected by the vertical scanning circuit 112.

  In the n line, first, the vertical scanning circuit 212 applies the reset pulse φRESn and the transfer pulse φTXn to the transfer switch 203 and the reset switch 207 during the period from time t31 to t32, and turns on the transfer switch 203 and the reset switch 207. Thereby, a reset operation for removing unnecessary charges accumulated in the PD 202 and the FD 204 in the nth line is performed.

  At time t32, the transfer switch 203 is turned off, and an accumulation operation for accumulating the photocharge generated in the PD 202 is started.

  Next, the vertical scanning circuit 212 applies the transfer pulse φTXn to the transfer switch 203 at time t34, and turns on the transfer switch 203. As a result, a transfer operation for transferring the photocharge accumulated in the PD 202 to the FD 204 is performed.

  Prior to this transfer operation, it is necessary to turn off the reset switch 207. In FIG. 3, the reset switch 207 is turned off simultaneously with the transfer switch 203 at time t32. Here, the period from time t32 to time t34 is the accumulation time.

  After the transfer operation of the nth line is completed, when the selection pulse φSELn is applied to the selection switch 206 and the selection switch 206 is turned on, the charge held in the FD 204 is converted into a voltage and output to the readout circuit 213. Then, the signals temporarily held by the reading circuit 213 are sequentially output from the time t36 by the horizontal scanning circuit (HSR) 214.

  FIG. 4 is a timing chart showing driving of the image sensor 3 in the batch reset batch transfer read operation. In FIG. 4, all lines are reset simultaneously during a period from time t41 to time t42. The transfer operation is also performed simultaneously during the period from time t43 to time t44.

  In the rolling readout operation of FIG. 3, pixel signals are sequentially read out for each scanning line, and since the exposure time is different for each scanning line, a line flicker whose output changes in the vertical direction of the screen occurs (see FIG. 8). On the other hand, in the batch reset batch transfer readout operation of FIG. 4, since the exposure times of all the pixels are the same, no line flicker occurs. By performing these driving operations on the captured image of two frames, signals of pixels that have been subjected to rolling readout and pixels that have been subjected to batch reset batch transfer readout can be obtained. The signal processing circuit 8 performs arithmetic processing on the pixel signal read out in this way, and detects flicker information.

  FIG. 5 is a flowchart showing a flicker information detection processing procedure in the signal processing circuit 8. First, the signal processing circuit 8 sets a value 1 to the variable n (step S1). Then, the signal processing circuit 8 reads the image on the nth line of the image stored in the image memory 9 and subjected to batch reset batch transfer reading (step S2). Further, the signal processing circuit 8 reads the image on the nth line of the image stored in the image memory 9 and subjected to the rolling reading (step S3).

  Then, the signal processing circuit 8 subtracts the pixel output of the rolling readout from the pixel output of the batch reset batch transfer readout in a specific column among these readout images of the nth line (step S4). As a result of this subtraction, a difference value between both pixel outputs at the same position on the photographing screen is obtained and stored in the image memory 9.

  The signal processing circuit 8 determines whether or not the variable n has exceeded the total number of lines N (step S5). If the total number of lines N is not exceeded, the signal processing circuit 8 adds a value 1 to the variable n (step S6), returns to step S2, and performs the same processing.

  On the other hand, when the variable n exceeds the total number N of lines, the signal processing circuit 8 determines whether or not there is periodicity in the vertical direction of the image (step S7). That is, the signal processing circuit 8 refers to the difference value of each line stored in the image memory 9, and the difference value is a value equal to or larger than a predetermined threshold value, and is perpendicular to the line of the row to be sequentially transferred. It is determined whether or not there is periodicity in the direction.

  If the difference value has periodicity in the vertical direction of the image, the signal processing circuit 8 determines that flicker has occurred (step S8), and ends this processing. On the other hand, if the difference value does not have periodicity in the vertical direction of the image, the signal processing circuit 8 determines that no flicker has occurred (step S9), and ends this processing.

  Thus, the signal processing circuit 8 performs arithmetic processing on the read pixel signal and detects flicker information. In this arithmetic processing, the signal processing circuit 8 performs, for each line, a subtraction process between the output of the pixel subjected to the batch reset batch transfer readout and the output of the pixel subjected to the rolling readout. As a result of the subtraction process, when there is a difference equal to or greater than a predetermined threshold value and this difference (difference information) has periodicity in the vertical direction with respect to the lines of the row to be sequentially transferred, the signal processing circuit 8 It is determined that there is an influence by.

  Here, regarding the pixel signal in which a difference occurs in the readout time for each line, if flicker exists, the flicker due to the difference in time is applied for each line. On the other hand, no flicker is applied to each line of pixel signals for which there is no difference in readout time for each line. Therefore, flicker is detected by detecting these differences.

  As described above, the imaging apparatus according to the first embodiment performs rolling readout and batch reset batch transfer readout on a captured image of two frames as a pixel readout method in the CMOS image sensor. Of course, it may be performed on a captured image of two fields. Accordingly, flicker information can be detected based on the difference information of the pixel output obtained from the difference in the pixel readout time according to the driving method. Therefore, flicker can be detected more accurately in a short time regardless of the state of the subject and the shooting scene. Furthermore, it is possible to remove the influence of the detected flicker.

  Also, difference information can be calculated over a wide range on the shooting screen, and flicker detection accuracy can be improved. Further, since the difference information is calculated for the pixel portion at the same position on the shooting screen, more accurate difference information can be obtained.

[Second Embodiment]
In the second embodiment, the CMOS image sensor 3 that is an imaging device can make a part of pixels have a different reading method from other pixels. Specifically, in the present embodiment, the imaging device 3 includes a pixel unit that can perform rolling readout and a pixel unit that can perform batch reset batch transfer readout. Note that the configuration of the imaging apparatus in the second embodiment is the same as that in the first embodiment, and a description thereof will be omitted.

  The CMOS image sensor 3 and its driving method in the second embodiment will be described in detail. FIG. 6 is a diagram showing a schematic configuration of the CMOS image sensor 3. For the sake of simplicity, FIG. 6 shows a pixel configuration in which unit pixels (pixel portions) 101 are arranged in only 3 rows × 3 columns, but in reality, a large number of pixels are arranged two-dimensionally as a shooting screen. Has been.

  In the same figure, the pixels located in the left column are different from the other pixels in that the connection destinations of the gates of the transfer switch 103 and the reset switch 107 are the transfer pulse φTX0 and the reset pulse φRES0, respectively. Further, since the pixels in the left one column are not located in the region output as final image data, there is no problem due to the difference in driving method.

  The photodiode (PD) 102 converts light into electric charge as a photoelectric conversion unit. The transfer switch 103 transfers charges generated in the PD 102 to a storage area (floating diffusion: FD) 104 to be described later by a transfer pulse φTX0 for the pixels located in the left column and a transfer pulse φTX for the other pixels. . An accumulation region (FD) 104 that is a floating diffusion portion temporarily accumulates charges. The amplification MOS amplifier 105 functions as a source follower.

  The selection switch 106 selects a pixel by a selection pulse φSEL. The reset switch 107 removes the charge accumulated in the FD 104 by the reset pulse φRES0 for the pixels located in the left column and the reset pulse φRES for the other pixels.

  Here, the FD 104, the amplification MOS amplifier 105, and a constant current source 109, which will be described later, constitute a floating diffusion amplifier. The signal charge of the pixel selected by the selection switch 106 is converted into a voltage, and the readout circuit 113 passes through the signal output line 108. Is output. The constant current source 109 serves as a load for the amplification MOS amplifier 105.

  The column selection switch 110 is driven by the horizontal scanning circuit 114 and selects an output signal from the readout circuit 113. The output amplifier 111 outputs an output signal from the readout circuit 113 to the outside of the image sensor 3. The vertical scanning circuit (shift register) 112 is for selecting the switches 103, 106, and 107. The read circuit 113 temporarily holds the output signal generated on the signal output line 108. The horizontal scanning circuit 114 sequentially outputs pixel outputs that are output for each column of the readout circuit 113 to the output amplifier 111.

  For the pulse signals φTX, φRES, and φSEL, the pulse signals applied by, for example, the nth scan line selected by the vertical scanning circuit 112 are described as φTXn, φRESn, and φSELn, respectively. For the pulse signals φTX0 and φRES0, the same pulse signal is applied to each scan line regardless of the nth scan line.

  Next, the driving operation of the image sensor in the moving image shooting mode will be described. FIG. 7 is a timing chart showing the driving operation of the image sensor 3. In the present embodiment, the pixels in the CMOS image sensor 3 are driven to be divided into pixels for performing rolling readout and pixels for performing batch reset batch transfer readout in one frame, thereby obtaining an output obtained from a difference in driving method. Based on the result, flicker can be detected.

  First, driving of pixels other than the left one column in which rolling readout is performed will be described. The vertical scanning circuit 112 applies the reset pulse φRESn and the transfer pulse φTXn and turns on the transfer switch 103 and the reset switch 107 during the period from time t11 to t12 on the n line. Then, the vertical scanning circuit 112 performs a reset operation for sequentially removing unnecessary charges accumulated in the PD 102 and the FD 104 other than the first column on the left of the n line by every predetermined unit (for each line).

  When the transfer switch 103 is turned off at time t12, an accumulation operation for accumulating the photoelectric charge generated in the PD 102 for a predetermined time Tint1 is started. Here, the PD 102 for which the accumulation operation is started is located in a position other than the left one column, and the accumulation of the PD 102 located in the left one column is started at a timing described later.

  Next, the vertical scanning circuit 112 applies a transfer pulse φTXn at time t17 after a predetermined time, which is the predetermined time Tint1, turns on the transfer switch 103, and transfers the photocharge accumulated in the PD 102 to the FD 104. Perform the action.

  Prior to this transfer operation, the reset switch 107 needs to be turned off, and is turned off simultaneously with the transfer switch 103 at time t12. Here, for pixels other than the left one column, a predetermined time Tint1 from the reset operation end time t12 to the transfer end time t17 is the accumulation time.

  After completion of the n-line transfer operation, the vertical scanning circuit 112 applies the selection pulse φSELn at time t18 to turn on the selection switch 106, whereby the n-line charge held in the FD 104 is converted into a voltage and read. It is output to the circuit 113. The signals temporarily held in the readout circuit 113 are sequentially output from the time t19 by the horizontal scanning circuit (HSR) 114.

  After the reset pulse φTXn is applied to the n line, the same operation is performed on the n + 1 line which is the next row of the n line. That is, for the n + 1 line, at time t13 after a predetermined time, as with the n line, application of a pulse signal corresponding to each line is started, and charges are accumulated at a predetermined time Tint1 that is the same accumulation time as the n line. Thereafter, the signals are sequentially output and read. Further, for the n + 2 line which is the next row, the same operation as the n line and the n + 1 line is performed at time t15.

  On the other hand, the pixels in the left first column are read by batch reset batch transfer. The driving of pixels within a predetermined range located in the left column will be described. First, the reset operation is performed not only on a specific line but also on all lines at the same time.

  The vertical scanning circuit 112 applies the reset pulse φRES0 and the transfer pulse φTX0 during the period from time t15 to t16, and turns on the transfer switch 103 and the reset switch 107 of the pixels located in the left column. The vertical scanning circuit 112 performs a reset operation for removing unnecessary charges accumulated in the PD 102 and the FD 104. This reset operation is performed on all lines at the same time.

  When the transfer switch 103 is turned off at time t16, an accumulation operation for accumulating the photoelectric charge generated in the PD 102 for a predetermined time Tint0 is started.

  Next, the vertical scanning circuit 112 applies a transfer pulse φTX0 at time t17 after a predetermined time, which is a predetermined time Tint0, turns on the transfer switch 103, and transfers the photocharge accumulated in the PD 102 to the FD 104. Perform the action. This transfer operation is also performed on all lines at the same time.

  The end of the transfer operation performed on all the lines simultaneously and the timing of reading from each line are the same as those of the pixels on which the above-described rolling reading has been performed. That is, in each line, a pixel for which batch reset batch transfer is performed is once held in the FD 104 and then read from the FD 104 as a pixel signal on one line at the same timing as a pixel on which rolling reading is performed on the same line. Read out to the circuit 113. The pixel signal obtained in this way is a pixel signal that has the same accumulation time and the same time for all lines without different readout times for each line.

  By such a driving operation, a pixel signal that has been subjected to rolling readout from one photographed image and a pixel signal that has been subjected to batch reset batch transfer readout can be obtained.

  The signal processing circuit 8 performs arithmetic processing on the pixel signal read out in this way, and detects flicker information. That is, the signal processing circuit 8 outputs, in the above arithmetic processing, the output (pixel signal) of the pixel that has been subjected to batch reset batch transfer readout that is positioned in the left column and the pixel that has undergone rolling readout adjacent to that pixel. A subtraction process with the output (pixel signal) is performed for each line. As a result of the subtraction process, when there is a difference equal to or greater than a predetermined threshold value and this difference (difference information) has periodicity in the vertical direction with respect to the lines of the row to be sequentially transferred, the signal processing circuit 8 causes the flicker. It is determined that there is an influence by.

  In the case where there is flicker, in a pixel signal in which a difference occurs in readout time for each line, flicker due to the difference in the time is applied for each line. On the other hand, flicker is not applied to each line for pixel signals that have no difference in readout time for each line. Therefore, flicker can be detected by performing the above subtraction process and calculating the difference information. In this way, flicker can be easily detected. Further, the influence of flicker can be removed by subtracting the detected amount of flicker from the pixel signal for each line.

  In this way, by reading out the CMOS image sensor 3 with different pixel driving methods, the difference information of the pixel output obtained from the difference in the reading time of the pixels by the driving method can be obtained for one photographed image. Based on this, flicker information can be detected.

  In the above-described embodiment, the pixel column within a predetermined range in which batch reset batch transfer readout is performed is the left one column. However, the present invention is not limited to this. That is, it is only necessary to have a column of pixels other than the effective pixel region where light is guided, and the position and the number of columns of the pixel outside the effective pixel region are not particularly limited. Thereby, flicker can be detected with high accuracy while ensuring an effective pixel area.

  In addition, in the case of an imaging apparatus that performs image shooting by column thinning, a column to be thinned is a column of pixels that are subjected to batch reset batch transfer readout, and a column that is not to be thinned is a column of pixels that is subjected to rolling readout Similarly, flicker can be detected in the same manner. Accordingly, the effective pixel area can be efficiently used, and it is not necessary to provide a pixel area where batch reset batch transfer reading is performed separately from the effective pixel area.

  Further, in the case of an imaging apparatus that performs image shooting by thinning out rows, a configuration in which thinned rows are rows of pixels that are subjected to batch reset batch transfer readout, and rows that are not thinned out are rows of pixels that are subjected to rolling readout Similarly, flicker can be detected in the same manner. In this case, the rows to be thinned out by the vertical scanning circuit can be realized by selecting them at the same timing at a time. Further, the reset pulse φRES0 and the transfer pulse φTX0 for reading the batch reset batch transfer are not necessary.

  The imaging apparatus according to the second embodiment performs rolling readout and batch reset batch transfer readout on a single photographed image as a pixel readout method in the CMOS image sensor 3. Thus, flicker information can be detected based on the difference information of the pixel output obtained from the difference in the pixel readout time according to the driving method. Therefore, flicker can be detected more accurately in a shorter time regardless of the state of the subject and the shooting scene. Furthermore, it is possible to remove the influence of the detected flicker.

  The present invention is not limited to the configuration of the above-described embodiment, and any configuration can be used as long as the functions shown in the claims or the functions of the configuration of the present embodiment can be achieved. Is also applicable.

It is a block diagram which shows the structure of the imaging device in 1st Embodiment. 2 is a diagram showing a schematic configuration of a CMOS image sensor 3. FIG. 6 is a timing chart showing driving of the image sensor 3 in a rolling readout operation. 6 is a timing chart illustrating driving of the image sensor 3 in a batch reset batch transfer read operation. 6 is a flowchart showing a flicker information detection processing procedure in the signal processing circuit 8; 2 is a diagram showing a schematic configuration of a CMOS image sensor 3. FIG. 3 is a timing chart illustrating a driving operation of the image sensor 3. It is a figure which shows generation | occurrence | production of a line flicker.

Explanation of symbols

3 CMOS image sensor (image sensor)
7 Driving Circuit 8 Signal Processing Circuit 101, 201 Pixel Unit 102, 202 Photodiode (PD)
103, 203 Transfer switch 104, 204 Storage area (FD)
107, 207 Reset switch

Claims (8)

An imaging apparatus using an imaging device in which a plurality of pixel units each having a photoelectric conversion unit that generates and accumulates charges by photoelectric conversion and a floating diffusion unit that accumulates the generated charges are two-dimensionally arranged ,
Batch reset means for collectively resetting the photoelectric conversion unit and the floating diffusion unit of the plurality of pixel units arranged two-dimensionally;
A batch transfer means for collectively transferring charges accumulated in the photoelectric conversion unit to the floating diffusion unit after a predetermined time has elapsed since the batch reset was performed;
Sequential resetting means for sequentially resetting the photoelectric conversion units and the floating diffusion units of the plurality of pixel units arranged two-dimensionally for each predetermined unit;
Sequential transfer means for sequentially transferring the charge accumulated in the photoelectric conversion unit to the floating diffusion unit for each predetermined unit after a predetermined time has elapsed since the sequential reset was performed;
The difference information is calculated using the pixel signal of the pixel unit obtained by the batch transfer unit and the pixel signal of the pixel unit obtained by the sequential transfer unit, and flicker is calculated based on the calculated difference information. An imaging apparatus comprising: a detecting means for detecting. The batch reset means collectively resets the photoelectric conversion units and floating diffusion units of all the pixel units in the shooting screen as the plurality of pixel units,
The imaging apparatus according to claim 1, wherein the sequential reset unit sequentially resets the photoelectric conversion units and floating diffusion units of all the pixel units in the imaging screen.   The detection unit uses the pixel signal of the pixel unit obtained by the batch transfer unit and the pixel signal of the pixel unit obtained by the sequential transfer unit for the pixel unit at the same position on the shooting screen. The imaging apparatus according to claim 2, wherein the difference information is calculated. The collective resetting unit collectively resets the photoelectric conversion unit and the floating diffusion unit of the pixel unit within a predetermined range including some columns or rows among the plurality of pixel units arranged in two dimensions. The sequential reset means is configured to apply a predetermined unit to the photoelectric conversion unit and the floating diffusion unit of the plurality of pixel units arranged in two dimensions, excluding the pixel unit within a predetermined range including the partial columns or rows. The imaging apparatus according to claim 1, wherein the resetting is sequentially performed every time.   5. The imaging according to claim 4, wherein a pixel portion within a predetermined range composed of the partial columns or rows from which a pixel signal is obtained by the batch transfer means is located outside an effective pixel region of the imaging device. apparatus.   When an image is captured by performing a thinning operation on columns or rows, a pixel portion within a predetermined range consisting of the partial columns or rows is a pixel portion of a column or row thinned out by the thinning operation. The imaging apparatus according to claim 4, characterized in that:   The detection means detects flicker when the difference information is equal to or greater than a predetermined threshold and has periodicity in a vertical direction with respect to a row or column line to be sequentially transferred. Item 7. The imaging device according to any one of Items 1 to 6. Flicker detection of an image pickup apparatus using an image pickup element in which a plurality of pixel portions each having a photoelectric conversion portion that generates and accumulates electric charges by photoelectric conversion and a floating diffusion portion that accumulates the generated electric charges is two-dimensionally arranged A method,
A batch reset step for collectively resetting the photoelectric conversion unit and the floating diffusion unit of the plurality of pixel units arranged two-dimensionally;
A batch transfer step of collectively transferring charges accumulated in the photoelectric conversion unit to the floating diffusion unit after a predetermined time has elapsed since the batch reset was performed;
A sequential reset step of sequentially resetting the photoelectric conversion units and floating diffusion units of the plurality of pixel units arranged in two dimensions for each predetermined unit;
A sequential transfer step of sequentially transferring the charge accumulated in the photoelectric conversion unit to the floating diffusion unit for each predetermined unit after a predetermined time has elapsed since the sequential reset was performed;
Difference information is calculated using the pixel signal of the pixel unit obtained in the batch transfer step and the pixel signal of the pixel unit obtained in the sequential transfer step, and flicker is calculated based on the calculated difference information. A flicker detection method for an image pickup apparatus, comprising: a detection step for detecting.