JP2014078925A - Imaging apparatus and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately determine an amount of main emitted light in a constitution for determining an amount of main emitted light by causing a light emitting part to perform preliminary light emission before main light emission.SOLUTION: An imaging apparatus which causes light emitting means to perform preliminary light emission before main light emission comprises: an imaging device for accumulating electric charges corresponding to an incident light amount; generation means for generating a first correction value on the basis of first reference image data read from the imaging device; correction means which uses the first correction value generated by the generation means, to correct image data based on the electric charges accumulated by the imaging device when causing the light emitting means to perform the preliminary light emission; and determination means for determining the amount of the main emitted light emitted by the light emitting means, on the basis of the image data corrected by the correction means.

Description

  The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus that performs pre-emission before main emission of a light emitting unit to determine the main emission amount.

  2. Description of the Related Art Conventionally, in an imaging apparatus using an imaging device such as a digital camera or a video camera, it is well known that image quality is deteriorated by fixed pattern noise caused by readout circuit noise or dark current noise of the imaging device.

  In order to remove this fixed pattern noise, a technique is generally used in which a reference image different from the captured image obtained by exposing the image sensor is obtained and the captured image is corrected based on the obtained reference image. Yes. Patent Document 1 discloses a technique for correcting a captured image based on a dark image obtained by shielding the image sensor separately from a captured image obtained by exposing the image sensor.

  In addition, in an imaging apparatus having a function of flash emission when shooting a dark scene, as in Patent Document 2, light adjustment control is performed to determine the flash emission amount at the time of shooting by performing pre-flash immediately before shooting. It has been known.

JP 2010-118963 A JP 2011-232658 A

  However, in the technique disclosed in Patent Document 1, a good image quality is obtained because the fixed pattern noise is corrected by the reference image for the image at the time of shooting, but no consideration is given to other images. . For example, in the case of the configuration described in Patent Document 2, since appropriate correction is not performed on the pre-emission image for dimming, accurate dimming control is performed when the influence of fixed pattern noise is large. May not be possible.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging apparatus capable of accurately determining the main light emission amount in a configuration in which the pre-light emission is performed before the light emitting unit performs the main light emission and the main light emission amount is determined. .

  In order to achieve the above object, an imaging apparatus according to the present invention is an imaging apparatus that pre-emits light before the main light emission unit emits light, and includes an imaging element that accumulates electric charge according to an incident light amount, and the imaging element. When generating the first correction value based on the read first reference image data and using the first correction value generated by the generating unit to cause the light emitting unit to perform pre-light emission Correction means for correcting image data based on the electric charge accumulated by the imaging device, and determination means for determining the main light emission amount of the light emitting means based on the image data corrected by the correction means. Features.

  According to the present invention, the main light emission amount can be accurately determined in the configuration in which the pre-light emission is performed and the main light emission amount is determined before the light emitting unit performs the main light emission.

1 is an overall configuration diagram of an imaging apparatus 100 according to an embodiment of the present invention. The schematic diagram which shows the structure of DSP109 in embodiment of this invention. FIG. 2 is a schematic diagram illustrating an overall configuration of an image sensor 107 according to an embodiment of the present invention. 2 is a diagram showing a circuit configuration of one pixel of the image sensor 107 according to the embodiment of the present invention. FIG. FIG. 3 is a diagram showing a readout circuit configuration of each column of the image sensor 107 according to the embodiment of the present invention. 5 is a flowchart showing an imaging operation in the first embodiment of the present invention. 6 is a flowchart showing an operation of acquiring the light control image data 1 according to the first embodiment of the present invention. 5 is a flowchart showing an operation of acquiring dimming image data 2 according to the first embodiment of the present invention. 3 is a flowchart showing still image data acquisition operation according to the first embodiment of the present invention. FIG. 5 is a sequence diagram illustrating an imaging operation according to the first embodiment of the present invention. FIG. 6 is a diagram illustrating a reading method of the image sensor 107 according to the embodiment of the present invention. 6 is a timing chart showing a 1H readout operation for still image shooting of the image sensor in the embodiment of the present invention. 6 is a timing chart illustrating a 1H read operation for acquiring a light control image of the image sensor according to the embodiment of the present invention. 9 is a flowchart showing an imaging operation in the second embodiment of the present invention. The sequence diagram which shows the imaging operation in the 2nd Embodiment of this invention. 10 is a flowchart illustrating an imaging operation according to the third embodiment of the present invention. The sequence diagram which shows the imaging operation in the 3rd Embodiment of this invention. FIG. 10 is a diagram illustrating a reading method of the image sensor 107 according to the third embodiment of the present invention. The flowchart which shows the imaging operation in the 4th Embodiment of this invention. The sequence diagram which shows the imaging operation in the 4th Embodiment of this invention. The flowchart which shows the imaging operation in the 5th Embodiment of this invention. The sequence diagram which shows the imaging operation in the 5th Embodiment of this invention. 10 is a flowchart showing an imaging operation in the sixth embodiment of the present invention. 10 is a flowchart showing an imaging operation in the sixth embodiment of the present invention. FIG. 11 is a diagram illustrating a method for reading out an image sensor 107 according to another embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram illustrating an overall configuration of an imaging apparatus 100 according to an embodiment of the present invention.

  The first lens group 101 is a lens group disposed at the tip of the imaging optical system, and is held so as to be able to advance and retract in the optical axis direction. The diaphragm 102 adjusts the light amount at the time of photographing by adjusting the aperture diameter. The second lens group 103 is a lens group that performs a zooming function (zoom function) in conjunction with the advance / retreat operation of the first lens group 101. The third lens group 104 is a lens group that performs focus adjustment by advancing and retreating in the optical axis direction. The first, second, and third lens groups are examples of the imaging optical system, and the number of lens groups is not limited to three. Each lens group may have one lens.

  The mechanical shutter 105 adjusts the amount of light guided to the image sensor 107 in conjunction with an electronic front curtain operation described later.

  The optical low-pass filter 106 is an optical element for reducing false colors and moire in the captured image. The image sensor 107 photoelectrically converts the subject image formed by the lens group described above. Here, a Bayer array CMOS image sensor is used for the image sensor 107.

  The AFE 108 converts an analog image signal output from the image sensor 107 into a digital signal. A DSP (Digital Signal Processor) 109 performs various types of image processing including image correction on the digital image signal output from the AFE 108.

  The recording medium 110 is a recording medium that records image data that has been subjected to image processing by a DSP. The display unit 111 is a display unit for displaying captured images and various menu screens, and a liquid crystal display (LCD) or the like is used. During a live view operation to be described later, images based on image data acquired by continuously capturing images are sequentially displayed on the display unit 111.

  The RAM 112 is a RAM that temporarily stores image data and the like, and is connected to the DSP 109. A timing generator (TG) 113 supplies a drive signal to the image sensor 107.

  The CPU 114 controls each unit such as the AFE 108, the DSP 109, the TG 113, the aperture driving circuit 116, the focus driving circuit 118, and the like. When the shutter switch (SW) 115 is turned on by a photographer's operation, it transmits a photographing instruction to the CPU 114.

  The aperture driving circuit 116 drives the aperture 102 by drivingly controlling the aperture actuator 117. The focus drive circuit 118 performs focus adjustment by driving and controlling the focus actuator 119 to advance and retract the third lens group 104 in the optical axis direction.

  The shutter drive circuit 120 drives the mechanical shutter 105 according to the control of the CPU 114. The light emitting unit 121 uses a xenon lamp, an LED, or the like as a light source, and emits light according to control from the CPU 114.

  FIG. 2 is a diagram showing a main block configuration inside the DSP 109. The “black” level of each pixel of the image sensor is not uniform for each pixel due to the characteristics of the image sensor, wiring, and the like, and shading may occur. This is called dark shading. The dark shading correction value generation unit 901 calculates a dark shading correction value based on reference image data described later. The dark shading correction unit 902 corrects the dark shading in the horizontal direction by subtracting a correction value that is one-dimensional data in the horizontal direction from the target image data.

  The optical shading correction unit 903 corrects optical shading by performing gain correction on the image data according to the position (coordinates) in the horizontal direction or the vertical direction on the corresponding shooting screen.

  A WB (white balance) processing unit 904 performs white balance processing by multiplying each of the R, G, and B pixels in the Bayer array by a gain. A development processing unit 905 performs development processing such as color matrix processing and gamma processing on the image data.

  The memory control unit 906 performs control to read / write image data and correction values used in each correction block from / to the RAM 112. The recording unit 907 performs a process of writing the image data after the development process to the recording medium 110.

  FIG. 3 is a diagram illustrating the overall configuration of the image sensor 107. In the pixel area PA, the pixels 200 are arranged on a matrix like p11 to pkn.

  Here, the configuration of each pixel of the pixel 200 will be described with reference to FIG. A photodiode (hereinafter referred to as PD) 301 photoelectrically converts an incident optical signal and accumulates charges corresponding to the incident light amount.

  The transfer gate 302 transfers the charge accumulated in the PD 301 to the FD (floating diffusion) unit 303 by setting the signal tx to a high level.

  The FD unit 303 is connected to the gate of a floating diffusion amplifier 304 (hereinafter referred to as an FD amplifier), and the amount of charge transferred from the PD 301 by the FD amplifier 304 is converted into a voltage value.

  The FD reset switch 305 is a switch for resetting the FD unit 303 and resets the FD unit 303 by setting the signal res to a high level. Further, the signal tx and the signal res are simultaneously set to the high level to turn on both the transfer gate 302 and the FD reset switch 305, whereby the PD 301 is reset via the FD unit 303.

  The pixel selection switch 306 outputs the pixel signal converted into a voltage by the FD amplifier 304 to the output vout of the pixel 200 by setting the signal sel to a high level.

  Returning to FIG. 3, the vertical scanning circuit 201 supplies drive signals such as res_1, tx_1, and sel_1 to each pixel 200. These drive signals are connected to the FD reset switch 305 (res), the transfer gate 302 (tx), and the pixel selection switch 306 (sel) of each pixel 200, respectively.

  The output vout of each pixel 200 is connected to the column common readout circuit 203 via the vertical output line 202 for each column.

  Here, the configuration of the column common readout circuit 203 will be described with reference to FIG.

  The vertical output line 202 is provided for each column, and the output vout of the pixel 200 for one column is connected thereto. A current source 204 is connected to the vertical output line 202, and a source follower circuit is configured by the current source 204 and the FD amplifier 304 of the pixel 200 connected to the vertical output line 202.

  401 is a clamp capacitor C1, 402 is a feedback capacitor C2, and the operational amplifier 403 has a non-inverting input terminal connected to a reference voltage Vref. The switch 404 is a switch for short-circuiting both ends of the feedback capacitor C2, and is controlled by a signal cfs.

  The S signal transfer switch 405 is a switch for transferring the pixel signal S read from the pixel 200 to the S signal holding capacitor 407. By setting the signal ts to a high level, the pixel signal S amplified by the operational amplifier 403 is stored in the S signal holding capacitor 407 via the S signal transfer switch 405.

  The N signal transfer switch 406 is a switch for transferring the noise signal N read from the pixel 200 to the N signal holding capacitor 408. By setting the signal tn to High level, the pixel signal N amplified by the operational amplifier 403 is stored in the N signal holding capacitor 408 via the N signal transfer switch 406.

  The S signal holding capacitor 407 and the N signal holding capacitor 408 are connected to the outputs vs and vn of the column common readout circuit 203, respectively.

  The S signal addition switch 409 and the N signal addition switch 410 are switches for averaging the S signal and N signal in the corresponding columns, respectively. One end of the S signal addition switch 409 is connected to the node A in the figure, and the other end is connected to the same node A in another column to be added. Further, the N signal addition switch 410 is connected to a node B in the figure, and the other end is connected to a node B in another column to be added. That is, by setting the signal add to the high level, the S signal holding capacitors 407 and the N signal holding capacitors of the column to be added are connected to each other. The signal add is once set to the high level and then set to the low level, whereby the signals of the columns to be added are averaged. The combination of columns to be added will be described later. Drive signals such as cfs, ts, tn, and add are supplied by the TG 113 under the control of the CPU 114.

  Returning to FIG. 3, horizontal transfer switches 205 and 206 are connected to the outputs vs and vn of the column common readout circuit 203, respectively.

  The horizontal transfer switches 205 and 206 are controlled by the output signal hsr * (* is a column number) of the horizontal scanning circuit 207. By setting the signal hsr * to a high level, the signals of the S signal holding capacitor 407 and the N signal holding capacitor 408 are displayed. Are transferred to the horizontal output lines 208 and 209, respectively.

  The horizontal output lines 208 and 209 are connected to the input of the differential amplifier 210. In the differential amplifier 210, the difference between the S signal and the N signal is obtained and at the same time a predetermined gain is applied, and the final image signal is sent to the output terminal 211. Output to.

  The horizontal output line reset switches 212 and 213 are turned on by setting the signal chres to High, and reset the horizontal output lines 208 and 209 to the reset voltage Vchres.

(First embodiment)
Next, an imaging operation flow of the imaging apparatus 100 according to the first embodiment of the present invention will be described using the flowcharts of FIGS. Please refer to the sequence diagram of the imaging operation shown in FIG.

  First, in step S501 of FIG. 6, the CPU 114 starts live view shooting. In live view shooting, images based on image data continuously acquired by a live view shooting operation of the image sensor 107 described later are sequentially displayed on the display unit 111.

  Thereafter, the CPU 114 continues the live view shooting until the shutter switch (SW) 115 is pressed and turned on by the photographer in step S502.

  When the shutter switch 115 is pressed (shooting instruction) by the photographer (time Ta in FIG. 10), the CPU 114 ends the live view shooting operation of the image sensor 107 in step S503, and the dimming reference image data (first reference). Image data) is acquired (time Tb in FIG. 10). Details of the reference image data acquisition operation will be described later.

  In subsequent step S504, the dark shading correction value generation unit 901 obtains the dark shading correction value (first correction value) for correcting the dimming image data 1 and 2 acquired in steps S505 and S506 in step S503. Generated based on the reference image data. In the generation of the correction value, the average value of each pixel column of the reference image data is calculated as the correction value. The generated dimming correction value is set in the dark shading correction unit 902, and the dark shading of each image data is corrected by subtracting from the dimming image data 1 and 2 acquired in steps S505 and S506.

  In step S505, the CPU 114 acquires the light control image data 1 (time Tc in FIG. 10). In order to acquire the dimming image data 1 in a short time, the horizontal direction is averaged for every three pixels of the same color, and the vertical direction is thinned and read out every nine rows. In the acquisition of the light control image data 1, the light emitting unit 121 does not emit light.

  Next, in step S506, the CPU 114 acquires the light control image data 2 (time Td in FIG. 10). Similarly to the dimming image data 1, the dimming image data 2 is averaged for every three pixels of the same color in the horizontal direction, and is read out with a cycle of 9 rows in the vertical direction. In acquiring the dimming image data 2, the CPU 114 controls the light emitting unit 121 to perform pre-light emission with a predetermined light amount.

  As shown in FIG. 10, the reading scan for acquiring the dimming image data 1 and the reset scanning for acquiring the dimming image data 2 are performed in parallel, so that the dimming image data 1 is actually acquired. It is also possible to overlap the operation and the acquisition operation of the dimming image data 2 by overlapping them.

  In step S <b> 507, the CPU 114 performs a dimming operation for calculating the light emission amount of the light emitting unit 121 during still image shooting (hereinafter referred to as the main light emission amount), and determines the calculated light emission amount as the main light emission amount.

  In this dimming calculation, the corrected dimming image data 1 corrected by the dark shading correction unit 902 using the dark shading correction value generated in step S504 is compared with the corrected dimming image data 2 to perform pre-compensation. The reflected light component of the light emission is extracted. Then, the main light emission amount is calculated based on the extracted reflected light component of the pre-light emission.

  In step S508, the CPU 114 obtains still image reference image data (second reference image data) in preparation for still image shooting (time Te in FIG. 10). In subsequent step S509, the dark shading correction value generation unit 901 generates a still image dark shading correction value (second correction value) based on the reference image data acquired in step S508. At this time, as in S504, the average value of each pixel column of the reference image data is calculated as a correction value. The generated still image correction value is set in the dark shading correction unit 902, and the dark shading of the still image data is corrected by subtracting this correction value from the still image data acquired in step S510.

  In step S510, the CPU 114 causes the light emitting unit 121 to perform main light emission and acquires still image data (time Tf in FIG. 10). Then, the dark shading correction unit 902 corrects still image data using the dark shading correction value generated in step S508, and the series of imaging operations ends.

  Here, the operation of acquiring the light control image data 1 in step S505 will be described with reference to FIG.

  First, the CPU 114 starts reset scanning in which each pixel row of the image sensor 107 is sequentially reset in step S601. Each pixel is reset by setting both the signal res and the signal tx to the high level via the vertical scanning circuit 201 in FIG.

  After completing the reset scanning of the last pixel row in step S602, the CPU 114 waits until a predetermined accumulation time elapses (step S603). When the predetermined accumulation time has elapsed, the CPU 114 starts reading scanning of the image sensor 107 in step S604. When the readout scanning is completed in step S605, acquisition of the light control image data 1 is completed.

  When the predetermined accumulation time is short, it is also conceivable that the accumulation time of the first pixel row elapses before the reset scanning of the last pixel row is completed. In that case, even before the reset scanning of the last pixel row is completed, the readout scanning may be started in order from the pixel row for which a predetermined accumulation time has elapsed.

  Next, the operation of acquiring the light control image data 2 in step S506 will be described with reference to FIG. The operation for acquiring the light control image data 2 is different from the operation for acquiring the light control image data 1 only in that pre-emission is performed.

  After completing the reset scanning in step S602, in step S701, the CPU 114 outputs a light emission pulse for pre-light emission to the light emitting unit 121 to cause the light emitting unit 121 to emit light. After the light emission, readout scanning is started in step S604.

  In the present embodiment, a pre-emission light emission pulse is output after the end of reset scanning. However, when it takes time from the light emission pulse output to the actual light emission of the light emitting unit 121, the light emission pulse is output before the completion of the reset scanning in consideration of the time lag, and the actual pre-light emission is performed immediately after the completion of the reset scanning. It may be made to become. In that case, a light emission pulse may be output when a predetermined time has elapsed from the start of reset scanning in step S601.

  Similarly to the operation of acquiring the dimming image data 1, even before the reset scanning of all the pixels is completed, the reading scanning may be started in order from the pixels for which a predetermined accumulation time has elapsed. In this case, it is preferable that the pre-emission is continuously performed from the start of the reset scanning of the pixel to be reset-scanned first until the reading scan of the pixel to be reset-scanned is completed.

  Next, the still image data acquisition operation in step S509 will be described with reference to FIG.

  First, in step S801, the CPU 114 starts reset scanning for still images (time Tf in FIG. 10). Thereby, the charge of each pixel of the image sensor 107 is sequentially cleared for each pixel row. The reset scan for the still image is performed so as to draw a curve similar to that of the mechanical shutter travel for shielding the image sensor 107 in step S804.

  The actual configuration is not limited to this, and the charges in all the pixel rows may be cleared simultaneously. However, in this case, since the time from clearing the charge to being shielded by the mechanical shutter is different for each pixel row, the exposure amount varies depending on the row.

  After completing the reset scan for still images in step S802, in step S803, the CPU 114 outputs a light emission pulse for main light emission that prompts light emission for still image shooting (hereinafter referred to as main light emission), and the light emitting unit 121 is turned on. Make it emit light.

  In step S804, the CPU 114 waits for the accumulation time corresponding to the set shutter speed to elapse. In step S805, the CPU 114 causes the mechanical shutter 105 to travel via the shutter driving circuit 120 to shield the image sensor 107 from light. Thereafter, in step S806, reading scanning of the image sensor 107 is started (time Th in FIG. 10). When the reading scanning is ended in step S807, the still image data acquisition operation is ended.

  Next, a method for reading out pixels of the image sensor 107 according to the mode will be described with reference to FIG. FIG. 11 is a diagram illustrating a method of reading pixels of the image sensor 107 in each operation mode during still image shooting, live view shooting, and dimming image data acquisition.

  FIG. 11A shows a reading method at the time of still image shooting. The image sensor 107 is a Bayer-arranged CMOS sensor. The shaded portion is a reference pixel for obtaining a correction value, and the white portion is a normal aperture pixel. The reference pixel in this embodiment is a pixel in which the photodiode 301 is not provided. However, the configuration of the reference pixel is not limited to this, and a light-shielded optical black pixel may be used as the reference pixel. In the still image, all the pixels of the image sensor 107 are read out independently.

  FIG. 11B shows a reading method at the time of live view shooting. In order to secure a frame rate, the number of read pixels is limited by performing pixel signal addition or thinning-out reading. Here, the averaging is performed for every three pixels of the same color in the horizontal direction, and thinning-out reading is performed at a cycle of one row for every three rows in the vertical direction. The combination of horizontal addition is shown in the upper part of FIG. Also, black pixels indicate pixels that are not read out due to thinning or the like.

  FIG. 11C shows a method of reading out the dimming image data 1 and the dimming image data 2. In the dimming control, it is desirable to read out the signal from the image sensor 107 at high speed in order to shorten the release time lag as much as possible. In this embodiment, the number of pixels to be read out is further limited than during live view shooting. Here, as in the live view, the horizontal direction is averaged for every three pixels of the same color, and the vertical direction is thinned and read out at a rate of one row for every nine rows.

  FIG. 11D shows a reading method when acquiring the still image reference image data. The horizontal direction is the same as that in the still image shooting of FIG. 11A in that all pixels are read out without adding. In the vertical direction, since only the reference pixel is read out, the reference pixel region (1st to 4th rows in the figure) is repeatedly read out.

  FIG. 11E shows a reading method when acquiring the dimming reference image data. Here again, the row of reference pixels is repeatedly read as in FIG. 11 (d), but the horizontal direction is the same as the dimming image data 1 and 2 in FIG. Read out. That is, the reading method at the time of obtaining the light control reference image data corresponds to the reading method related to the light control image data 1 and the light control image data 2. Further, the reading method when acquiring the reference image data for dimming is different from the reading method when acquiring the reference image data for still image.

  In this way, an appropriate dark shading correction value can be generated by associating the reading method at the time of acquiring reference image data with the reading method at the time of acquiring image data to be corrected.

  Note that in the acquisition of the still image reference image data and the dimming reference image data acquisition, the number of rows to be read, that is, the number of repetitions of repeatedly reading the reference pixels, may be different. When the correction accuracy of the light control image data may be coarser than that of the still image data, the release time lag (time Ta To the time Tf) can be further shortened.

  Next, the reading operation of the image sensor 107 will be described with reference to FIGS.

  FIG. 12 is a timing chart showing the read operation of each row of the image sensor 107 in acquiring still image data. Here, it is assumed that the i-th row signal is read.

  First, the CPU 114 sets the signal cfs to the high level via the TG 113 to turn on the switch 404, thereby short-circuiting both ends of the feedback capacitor C2 (402). Next, the CPU 114 sets the signal sel_i to the high level via the TG 113 to turn on the pixel selection switch 306 for the pixel in the i-th row, and then sets the signal res_i to the low level to turn off the FD reset switch 305 to turn off the FD unit 303. Release the reset. Thereafter, the CPU 114 sets the signal cfs to the low level via the TG 113 and turns off the switch 404, thereby clamping the voltage of the vertical output line 202 after the reset release of the FD unit 303 to the clamp capacitor C1.

  Next, the CPU 114 sets the signal tn to the high level via the TG 113 and stores the N signal in the N signal holding capacitor 408. Subsequently, the CPU 114 sets the signal tn to LOW via the TG 113, turns off the N signal transfer switch 406, turns the signal ts to high level, turns on the S signal transfer switch 405, and transfers signal tx_i to the high level. The gate 302 is turned on.

  By this operation, the signal accumulated in the PD 301 in the selected i-th row is output to the vertical output line 202 via the FD amplifier 304 and the pixel selection switch 306, and further, the S signal is transferred via the S signal transfer switch 405. It is stored in the signal holding capacitor 407.

  Next, the CPU 114 sets the signals tx_i and ts to the low level via the TG 113 to turn off the transfer gate 302 and the S signal transfer switch 405, and then sets the signal res_i to the high level to turn on the FD reset switch 305 to turn on the FD unit. 303 is reset.

  With the operations so far, the operation of storing the S signal and N signal in the i-th row in the S signal holding capacitor 407 and the N signal holding capacitor 408 is completed.

  Subsequently, an operation of outputting the S signal and the N signal stored in the S signal holding capacitor 407 and the N signal holding capacitor 408 from the image sensor 107 is performed.

  First, when the CPU 114 sets the output hsr1 of the horizontal scanning circuit 207 to a high level, the horizontal transfer switches 205 and 206 are turned on. Then, the signals of the S signal holding capacitor 407 and the N signal holding capacitor 408 are output to the output terminal 211 via the horizontal output lines 208 and 209 and the differential amplifier 210.

  The CPU 114 sequentially sets the selection signals hsr1, hsr2,..., Hsrk of each column of the horizontal scanning circuit 207 to High so that all signals in the i-th row are output. Note that the horizontal output line reset switches 212 and 213 are turned on by setting the signal chres to the high level while the signals of each column are read by the signals hsr1 to hsrk, and the levels of the horizontal output lines 208 and 209 are set to the reset voltage Vchres. To reset.

  This completes the reading operation for one row. By sequentially performing this operation in each row to be read, the signal reading operation of the image sensor 107 is performed.

  FIG. 13 is a timing chart showing the reading operation of the image sensor 107 when live view shooting and dimming image data 1 and 2 are acquired. Description will be made by paying attention to the difference from FIG.

  After the S signal is stored in the S signal holding capacitor 407, before the operation of the horizontal scanning circuit 207 starts, the CPU 114 temporarily sets the signal add to the high level via the TG 113, so that the S signal addition switch 409 and the N signal The addition switch 410 is turned on. Thereafter, the CPU 114 returns the signal add to the low level via the TG 113, whereby the S signal addition switch 409 and the N signal addition switch 410 are turned off. By this operation, the signals of the S signal holding capacitor 407 and the N signal holding capacitor 408 of each column are added and averaged with the signal of the column to be added.

  Thereafter, the horizontal scanning circuit 207 is driven. At this time, for example, the number of pixels in the horizontal direction is limited by turning on the selection signals with a cycle of one column in three columns, such as hsr1, hsr4, hsr7. And read out.

  As described above, the dimming reference image data used for correcting the dimming image data is obtained before obtaining the dimming image data, and the fixed pattern noise (dark shading) of the dimming image data is obtained. It is possible to determine the main light emission amount with high accuracy by appropriately correcting.

(Second Embodiment)
In the first embodiment, after the acquisition operation of the dimming image data 2 accompanied by the pre-emission, the reference image data for the still image is acquired and then the process proceeds to the still image shooting. For this reason, there is a problem that the time difference between the acquisition timing of the dimming image data 2 and the still image shooting becomes large and the dimming accuracy is lowered when the subject is moving. In addition, due to the time difference from pre-flash to still image shooting, a so-called eye-meditation phenomenon is likely to occur in which a person who is a subject closes his eyes during still image shooting due to the effect of pre-flash.

  Therefore, in the second embodiment, a configuration for shortening the time from the operation of acquiring the light control image data 2 accompanied by the pre-light emission to the still image shooting will be described.

  FIG. 14 is a flowchart illustrating an imaging operation of the imaging apparatus 100 according to the present embodiment. Please refer to the sequence diagram of the imaging operation shown in FIG.

  FIG. 14 differs from the flowchart of FIG. 6 only in the processing order, and steps having the same processing contents are given the same step numbers in FIGS. 6 and 14. First, the process from the start of live view shooting in step S501 to the generation of the light adjustment correction value in step S504 is exactly the same as the flowchart in FIG.

  In the present embodiment, after step S504, the still image reference image data is acquired in step S508 (time T'c in FIG. 15). In step S509, a still image correction value is generated. At this time, since it is necessary to hold the correction value for dimming generated in step S504, more memory for storing correction values is required than in the first embodiment.

  Next, dimming image data 1 and dimming image data 2 are acquired in steps S505 and S506 (time T'd and T'e in FIG. 15). Then, the obtained dimming image data 1 and dimming image data 2 are corrected, and the dimming calculation is performed in step S507 based on the corrected dimming image data 1 and the corrected dimming image data 2, and the main light emission amount. Is calculated.

  Thereafter, in step S510, the light emitting unit 121 performs main light emission to acquire still image data (time T′f in FIG. 15), and still image data is corrected.

  As described above, in the present embodiment, the still image reference image data used for correcting the still image data is acquired before the dimming image data is acquired. It is possible to suppress an increase in the time difference between image shootings. Therefore, it is possible to accurately determine the main light emission amount even for a moving subject while appropriately correcting the fixed pattern noise (dark shading) of the still image data, and it is possible to prevent the eye-meditation phenomenon from occurring.

(Third embodiment)
In the above two embodiments, the still image reference image data and the dimming reference image data are acquired before acquiring the dimming image data, but the release time lag is long because the reference data is acquired twice. There is a problem of becoming.

  Therefore, in the third embodiment, a description will be given of a configuration in which the time from when the shutter switch 115 is pressed by the photographer until the still image shooting is shortened by acquiring the dimming reference image data in advance.

  FIG. 16 is a flowchart illustrating an imaging operation of the imaging apparatus 100 according to the present embodiment. Please refer to the sequence diagram of the imaging operation shown in FIG.

  In FIG. 16, steps having the same processing contents as those in FIG. 6 are given the same step numbers in FIG. 6 and FIG.

  In this embodiment, first, in step S901, the CPU 114 acquires live view reference image data for correcting a live view image. As shown in FIG. 11B, the live view image is read by addition in the horizontal direction. Therefore, in step S901, addition is performed in the horizontal direction as in FIG. That is, the method for reading the reference image data for live view corresponds to the method for reading the live view image. Next, in step S902, the dark shading correction value generation unit 901 sets dark shading correction values for correcting the image data continuously acquired in step S501 based on the live view reference image data obtained in step S901. Generate. At this time, as in step S504 of FIG. 6, the average value of each pixel column of the reference image data is calculated as a correction value. The generated live view correction value (third correction value) is set in the dark shading correction unit 902. Then, the dark shading of the live view image data (moving image data) is corrected by subtracting this correction value from the live view image data acquired in the subsequent step S501.

  When the process of step S902 is completed, live view shooting is started in step S501. At this time, in step S501, the CPU 114 corrects each frame of the live view image using the dark shading correction value generated in step S902, generates a live view image, and sequentially displays the live view image on the display unit 111.

  When the shutter switch is pressed in step S502 (time T3a in FIG. 17), in step S903, the dark shading correction value generation unit 901 uses the correction value for correcting the light control image data 1 and 2 as the reference image data for live view. Generate based on At this time, in the present embodiment, the dimming image data 1 and 2 are read out by partially cutting out a partial area on the pixel area PA in order to shorten the readout time, and the horizontal direction is addition. Reading is performed (FIG. 18B). On the other hand, the live view reference image data is added in the horizontal direction in the same manner as in FIG. 18A to read out all pixel regions. That is, the reading method of the live view reference image data corresponds to the reading method of the dimming image data 1 and 2 in that they are read in the horizontal direction, but the pixel area PA to be read is different. Therefore, in step S903, the CPU 114 cuts out the live view correction value so as to correspond to a partial area of the pixel area PA from which the dimming images 1 and 2 are read out, thereby adjusting the dimming from the live view reference image data. A correction value is generated.

  Then, the light control image data 1 and the light control image data 2 are acquired by step S505, S506 (FIG. 17 time T3b, T3c). Then, the obtained dimming image data 1 and dimming image data 2 are corrected, and the dimming calculation is performed in step S507 based on the corrected dimming image data 1 and the corrected dimming image data 2, and the main light emission amount. Is calculated.

  Thereafter, reference image data for still images is acquired in step S508 (time T3d in FIG. 17). In step S509, a still image correction value is generated. In step S510, the light emitting unit 121 is caused to perform main light emission to acquire still image data (time T3f in FIG. 17), and still image data is corrected.

  In the present embodiment, live view shooting has been described as an example, but moving image shooting may be performed instead of live view shooting.

  In addition, although the dimming correction value is generated from the live view correction value, the dimming reference image data is generated from the live view reference image data, and the dimming correction value is generated from the generated dimming image data. It may be generated. In this case, an extra memory for storing the dimming image data is required.

  As described above, in the present embodiment, the light adjustment value is generated by calculating the live view correction value without acquiring the light adjustment reference image data, and the light adjustment image data is corrected. For this reason, it is possible to suppress an increase in the time difference of the still image data acquisition after the shutter switch is pressed.

(Fourth embodiment)
In the above three embodiments, still image reference image data and dimming reference image data are acquired, but in this embodiment, only one of the reference image data is acquired and acquired. A configuration for generating the other reference image data based on the reference image data will be described. In this embodiment, in order to use the acquired reference image data for correction of the light control image data, the reference image data is acquired before the light control image data is acquired. According to such a configuration, the number of acquisitions of the reference image data can be reduced, and the release time lag can be further shortened.

  In the following, a description will be given of a configuration that shortens the time from when the shutter switch 115 is pressed by the photographer until the still image is captured without acquiring the dimming reference image data.

  FIG. 19 is a flowchart illustrating an imaging operation of the imaging apparatus 100 according to the present embodiment. Please refer to the sequence diagram of the imaging operation shown in FIG.

  19, steps having the same processing contents as those in FIG. 6 are denoted by the same step numbers in FIG. 6 and FIG.

  First, from the start of live view shooting in step S501 until the shutter switch (SW) 115 is pressed and turned on by the photographer in step S502, it is exactly the same as the flowchart in FIG.

  In this embodiment, after the shutter switch is pressed in step S502 (FIG. 20, time T4a), in step S508, the CPU 114 acquires still image reference image data (FIG. 20, time T4b). In step S509, a still image correction value is generated. At this time, since it is necessary to hold the still image correction value generated in step S509, more memory for storing correction values is required than in the first embodiment.

  In step S1001, the CPU 114 uses the dark shading correction value generation unit 901 to calculate the correction value for correcting the light control image data 1 and 2 acquired in steps S505 and S506, based on the still image correction value obtained in step S509. To generate. At this time, since the reading method of the still image reference image data and the reading method of the light control image data are different, the CPU 114 adds the predetermined number of pixels in the horizontal direction by adding the still image correction value generated in step S509. A correction value for dimming is generated. The generated dimming correction value is set in the dark shading correction unit 902, and the dark shading of each image data is corrected by subtracting from the dimming image data 1 and 2 acquired in steps S505 and S506.

  After generating the light adjustment correction value in step S1001, the light adjustment image data 1 and the light adjustment image data 2 are acquired in steps S505 and S506 (time T4c and T4d in FIG. 20). Then, the obtained dimming image data 1 and dimming image data 2 are corrected, and the dimming calculation is performed in step S507 based on the corrected dimming image data 1 and the corrected dimming image data 2, and the main light emission amount. Is calculated.

  Thereafter, in step S510, the light emitting unit 121 is caused to perform main light emission to acquire still image data (time T4f in FIG. 20), and still image data is corrected.

  In this embodiment, the dimming correction value is generated by adding the still image correction value in the horizontal direction by a predetermined number of pixels. However, the method of generating the dimming correction value is not limited to this. When the dimming image data 1 and 2 are read out in the horizontal direction, the correction values for the dimming image data 1 and 2 are generated by thinning out the still image correction values in the horizontal direction in step S1001. I do not care. Alternatively, the dimming correction value may be generated by digitally processing the still image correction value.

  In the present embodiment, the light adjustment correction value is generated from the still image correction value. However, the still image correction value may be generated after the light adjustment correction value is generated. In this case, the order of step S1001 and step S509 is reversed, and a light adjustment correction value is generated first in step S1001, and then a still image correction value is generated in step S509.

  As described above, in this embodiment, the reference image data for dimming is obtained by calculating the reference image data for still image used for correcting the still image data without acquiring the reference image data for dimming. Generate. For this reason, an increase in the release time lag due to the acquisition of the dimming reference image data can be suppressed.

(Fifth embodiment)
In the fourth embodiment, the reference image data is acquired before acquiring the dimming image data. However, the time difference between the acquisition timing of the reference image data and the still image shooting is larger than that in the first embodiment. Thus, there is a problem that the correction accuracy of still image data is lowered.

  Therefore, in the fifth embodiment, a configuration will be described in which the correction accuracy of still image data is maintained while shortening the time from when the shutter switch 115 is pressed by the photographer until the still image shooting.

  FIG. 21 is a flowchart illustrating the imaging operation of the imaging apparatus 100 according to the present embodiment. Please refer to the sequence diagram of the imaging operation shown in FIG.

  FIG. 21 differs from the flowchart of FIG. 19 only in the processing order, and steps having the same processing contents are denoted by the same step numbers in FIG. 19 and FIG.

  First, from the start of live view shooting in step S501 until the shutter switch (SW) 115 is pressed and turned on by the photographer in step S502, it is exactly the same as the flowchart of FIG.

  In the present embodiment, after the shutter switch is pressed in step S502 (FIG. 22, time T5a), dimming image data 1 and dimming image data 2 are acquired in steps S505 and S506 (time T5b and T5c in FIG. 22). Subsequently, the still image reference image data is acquired in step S508 (time T5d in FIG. 22).

  Next, after the light adjustment correction value is generated in step S1001, the light adjustment image data 1 and the light adjustment image data 2 acquired in steps S505 and S506 are corrected. Thereafter, a still image correction value is generated in step S509.

  In step S507, the light emission calculation is performed based on the corrected light control image data 1 and the corrected light control image data 2 to calculate the main light emission amount.

  Thereafter, in step S510, the light emitting unit 121 is caused to perform main light emission to acquire still image data (time T5f in FIG. 22), and still image data is corrected.

  As described above, in the present embodiment, since the still image reference image data is acquired before the still image acquisition, there is no time difference between the acquisition timing of the reference image data and the still image shooting, and the correction accuracy of the still image data is eliminated. Can be maintained. In addition, an increase in the release time lag due to the acquisition of the dimming reference image data can be suppressed.

(Sixth embodiment)
In the fourth and fifth embodiments, in order to shorten the release time lag, the reference image data for dimming is generated by calculating the reference image data for still image. Here, the release time lag can be further shortened by moving the acquisition timing of the still image reference image data forward.

  In the sixth embodiment, a configuration will be described in which the time from when the shutter switch 115 is pressed by the photographer until still image shooting is further shortened.

  FIG. 23 is a flowchart illustrating the imaging operation of the imaging apparatus 100 according to the present embodiment. Please refer to the sequence diagram of the imaging operation shown in FIG.

  In FIG. 23, steps having the same processing contents as those in the flowchart of FIG. 19 are given the same step numbers in FIG. 19 and FIG. In the present embodiment, the shutter switch 115 will be described separately for the shutter switch 1 (SW1) and the shutter switch 2 (SW2) in the pressed state and function. A portion where the shutter switch 115 is pressed and the CPU 114 starts photographing preparation operations such as photometry processing and distance measurement processing is referred to as a shutter switch SW1. That is, the shutter switch 115 performs a shooting preparation operation start instruction and a shooting operation start instruction by different operations. When the shutter switch 115 is pressed, the CPU 114 drives the mechanical shutter 105 and starts a series of imaging operations in which a signal read from the imaging element 107 is written to the recording medium 110 via the AFE 108 and DSP 109 is referred to as a shutter switch SW2. .

  In the present embodiment, the CPU 114 continues the live view shooting from the start of the live view shooting in step S501 until the shutter switch 1 (SW1) is pressed and turned on by the photographer in step S1101. After the shutter switch 1 is pressed by the photographer, the CPU 114 obtains still image reference image data in step S508.

  Next, in step S1102, when the shutter switch 1 is turned off, the CPU 114 starts live view shooting again. If the shutter switch 2 (SW2) is pressed in step S1103 without turning the shutter switch 1 OFF (time T6a in FIG. 24), a still image correction value is generated in step S509. Thereafter, in step S1001, light adjustment correction values are generated.

  Thereafter, the dimming image data 1 and the dimming image data 2 are acquired in steps S505 and S506 (time T6b and T6c in FIG. 24), and the dimming image data 1 and the dimming image data 1 are adjusted using the dimming correction values generated in step S1001. The optical image data 2 is corrected.

  In step S507, after the light emission calculation is performed based on the corrected light control image data 1 and the corrected light control image data 2 to calculate the main light emission amount, the light emitting unit 121 is caused to perform main light emission in step S510. (Time T6e in FIG. 24), and still image data is corrected.

  As described above, in the present embodiment, since the still image reference image data is acquired after the SW1 is pressed, the time difference between the SW2 pressing timing and the still image shooting is shortened, and the release time lag can be shortened.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  The above six embodiments have been described on the assumption that one-dimensional dark shading is corrected as fixed pattern noise. However, the present invention is not limited to this, and two-dimensional dark shading correction may be performed. You may comprise so that correction | amendment may be performed.

  Further, although the configuration has been described in which the output of a reference pixel without a photodiode is acquired as reference image data, the present invention is not limited to this. For example, a configuration in which the signal of the optical black pixel is used as the reference image data, or a configuration in which only the circuit noise is read out without opening the transfer gate 302 of the aperture pixel and used as the reference image data is also conceivable. A configuration is also conceivable in which a reference voltage is input to any part of the vertical output line 202 or the column readout circuit 203 and a signal read out is used as reference image data.

  Furthermore, although it has been described on the assumption that the gain of the operational amplifier 403 is the same when the dimming image data is acquired and when the still image data is acquired, the present invention is not limited to this. The capacitance value of the feedback capacitor C2 (402) may be selected from a plurality of types, and the dimming image data and the still image data may be configured to be different. Further, for example, the capacitance value of the feedback capacitor C2 (402) may be switched for each row in one frame of the dimming image data, and a plurality of types of gain signals may be acquired in the same frame. In this case, the dark shading correction value generation unit 901 generates a correction value for each gain, and the dark shading correction unit 902 is also configured to perform dark shading correction using a correction value corresponding to the gain. preferable.

  In addition, the dimming image data and the live view image data are described so as to limit the number of pixels to be read by adding and averaging in the horizontal direction and by thinning out in the vertical direction. The means may be any combination of decimation / addition. For example, the dimming image data may be read out by thinning out three pixels in the horizontal direction and thinning out nine pixels in the vertical direction as shown in FIG. Further, a method of partially cutting out and reading out a partial area on the pixel area PA may be used. If it is not necessary to acquire the light control image data or the live view image data in a short time, all the pixels may be read out without limiting the number of read pixels.

  In the above six embodiments, the dimming image data 1 and the dimming image data 2 are acquired. However, when the influence of external light is small, the dimming image data 1 is not acquired. The main light emission amount may be determined based only on the light control image data 2 subjected to the pre-light emission.

  In the above six embodiments, an example of an imaging device that performs pre-light emission with a built-in light emitting unit has been described. However, a removable light-emitting device is attached to the imaging device, and pre-light emission is performed with the attached light-emitting device. You may apply to the imaging device to perform.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

DESCRIPTION OF SYMBOLS 100 Imaging device 107 Imaging element 109 DSP
114 CPU
121 Light Emitting Unit 901 Dark Shading Correction Value Generation Unit 902 Dark Shading Correction Unit

Claims (15)

An imaging device that pre-emits light before the main light emitting means emits light,
An image sensor that accumulates charges according to the amount of incident light;
Generating means for generating a first correction value based on first reference image data read from the image sensor;
Correction means for correcting image data based on charges accumulated by the imaging device when the light emitting means is pre-lit using the first correction value generated by the generating means;
An imaging apparatus comprising: a determining unit that determines a main light emission amount of the light emitting unit based on the image data corrected by the correcting unit. The generating unit generates a second correction value based on second reference image data read from the image sensor before the light emitting unit performs main light emission,
2. The correction unit according to claim 1, wherein the correction unit corrects image data based on charges accumulated by the image pickup device when the light emitting unit is caused to perform main light emission by using the second correction value. Imaging device.   The image pickup apparatus according to claim 2, wherein the second reference image data is image data read from the image pickup element before the light emitting unit performs pre-light emission.   4. The image pickup apparatus according to claim 1, wherein the first reference image data and the second reference image data have different reading methods when reading from the image pickup device. 5.   The first reference image data is read from the image pickup device by a reading method corresponding to a reading method related to image data based on charges accumulated by the image pickup device when the light emitting unit is caused to perform pre-light emission. The imaging device according to any one of claims 1 to 4. The generating means generates a third correction value based on the first reference image data,
6. The imaging according to claim 1, wherein the correction unit corrects moving image data based on the electric charge accumulated by the imaging element, using the third correction value. 7. apparatus. The generating means generates a second correction value based on the first reference image data,
2. The correction unit according to claim 1, wherein the correction unit corrects image data based on charges accumulated by the image pickup device when the light emitting unit is caused to perform main light emission by using the second correction value. Imaging device.   The method for reading out the first reference image data corresponds to a method for reading out image data based on charges accumulated by the image pickup device when the light emitting unit is caused to perform main light emission. Imaging device.   9. The method for reading out the first reference image data is different from a method for reading out image data based on charges accumulated by the imaging device when the light emitting means is pre-lit. The imaging device described in 1.   The imaging apparatus according to claim 9, wherein the generation unit generates the third correction value by performing digital arithmetic processing on the first correction value.   The imaging apparatus according to claim 9, wherein the generation unit generates the third correction value by adding the first correction value by a predetermined number of pixels.   The imaging apparatus according to claim 9, wherein the generation unit generates the third correction value using a part of the first correction value.   The imaging apparatus according to claim 1, wherein the correction unit corrects dark shading of image data.   The image pickup apparatus according to claim 1, wherein the first reference image data is read from the image pickup element after an instruction to start a shooting preparation operation is given. A control method for an image pickup apparatus that has an image pickup element that accumulates electric charge according to the amount of incident light and performs pre-light emission before the light emitting means performs main light emission,
Generating a first correction value based on first reference image data read from the image sensor;
Using the first correction value generated in the generating step, a correction step of correcting image data based on charges accumulated by the imaging device when the light emitting unit is pre-lit;
And a determining step of determining a main light emission amount of the light emitting means based on the image data corrected in the correcting step.

Images