JP6229436B2 - Imaging apparatus and imaging method - Google Patents

Description

  The present invention relates to an imaging apparatus applicable to a digital camera or the like, and more particularly to a pixel signal readout process from an imaging element.

  In a digital camera or the like that captures an image using an image sensor, it is required to image a subject with a wide dynamic range. As a method for expanding the dynamic range of the image pickup device, there is a method in which low-sensitivity and high-sensitivity pixels are mixed and arranged, and a method in which a plurality of pixels are added and output is also known.

  In the case of an image sensor using low-sensitivity pixels and high-sensitivity pixels, the image sensor is arranged corresponding to high-luminance pixels in order to properly correct effective pixel values based on OB pixel signals read from the light-shielding region (OB) pixels. Using the OB pixel signal, an output of the OB pixel signal arranged corresponding to the low luminance pixel is calculated, and black level correction is performed (see Patent Document 1).

  On the other hand, in pixel addition processing, there is known an addition processing method in which a plurality of adjacent pixels are added together and output as one pixel according to the shooting situation (see Patent Document 2). In this case, a photometric (AE) image sensor in which R, G, and B color filter elements are arranged in stripes in the pixel vertical direction is disposed in the optical viewfinder of the camera. Then, R pixels, G pixels, and B pixels that are adjacent to each other along the vertical direction are added and output as one pixel. This increases the sensitivity and improves the sensitivity characteristic on the low luminance side.

Japanese Patent No. 4051674 JP 2012-253462 A

  In the pixel addition process disclosed in Patent Document 2, a uniform pixel addition process is performed on the entire light receiving surface. This improves the sensitivity characteristic on the low luminance side, but the effect of expanding the dynamic range cannot be obtained.

  Therefore, in the pixel signal readout process of the image sensor using pixel addition, a pixel addition process that can realize the expansion of the dynamic range from the low luminance to the entire high luminance is required.

  Further, in the conventional pixel addition process, the output level of the OB pixel signal with respect to the pixel signal output by the pixel addition is not sufficiently considered. Therefore, pixel value correction based on the black level cannot be performed properly, and it is difficult to reliably remove the dark current component.

  Therefore, in the pixel signal reading process of the image sensor using pixel addition, black level correction of the pixel value that appropriately removes the dark current component is required.

  An imaging apparatus according to the present invention includes a plurality of effective pixels arranged in a matrix along the vertical direction and the horizontal direction, and a plurality of OB (optical black) pixels arranged along at least one of a row and a column of the plurality of effective pixels. An image pickup device having an image pickup device, an image pickup device driving unit capable of adding and reading out pixel signals and OB pixel signals of adjacent pixels among a plurality of pixels, and at least one of predetermined columns and rows of the image pickup device A pixel addition setting unit that sets the number of additions of the effective pixel signal and the OB pixel signal, and a pixel signal correction unit that corrects the effective pixel signal based on the corresponding OB pixel signal.

  Then, the pixel addition setting unit sets an addition number of pixel signals different depending on the pixel region for at least one of the predetermined column and row of the effective pixel region, and the pixel signal correction unit sets the OB corresponding to the set addition number. The effective pixel signal is corrected by the pixel signal.

  In the present invention, in the effective pixel signal corresponding to one frame / field or a part of the effective pixel signal, pixel signals are read out by different addition numbers instead of a uniform addition number in at least a part or the entire column / row direction. Is called.

  Thereby, a plurality of output pixel signals having different sensitivities are obtained, and the dynamic range is expanded. However, pixel signal readout without addition is defined as the addition number “1” here.

  Furthermore, in the present invention, a corresponding OB pixel signal is obtained in accordance with the number of effective pixels added. By obtaining an OB pixel signal corresponding to the number of additions, the effective pixel value after the addition is corrected based on the OB pixel signal corresponding to the dark current component for the addition.

  For example, the image sensor driving unit can add and read the OB pixel signal by the number of additions of the corresponding effective pixel signal. In addition, the pixel signal correction unit can multiply the representative value of the read series of OB pixel signals by the number of additions of the corresponding effective pixel signals.

  When the image sensor has a color filter in which color elements of the same color are arranged along the columns or rows, the pixel addition setting unit sets different addition numbers for the columns or rows in which the color elements of the same color are arranged. do it.

  An imaging device may be arranged in a camera, and exposure control of a photographic imaging element in which a subject image is formed during shooting and recording may be performed based on pixel signals read from the imaging element.

  An imaging method according to another aspect of the present invention includes a plurality of effective pixels arranged in a matrix along the vertical direction and the horizontal direction, and a plurality of OBs arranged along at least one of the rows and columns of the plurality of effective pixels ( This is an imaging method of an imaging apparatus including an imaging device having (Optical Black) pixels, and an imaging device driving unit capable of adding and reading out pixel signals and OB pixels of adjacent pixels among a plurality of pixels.

  In an imaging method in which pixel addition setting for setting the number of additions of effective pixel signals and OB pixel signals is performed on at least one of the columns and rows of the imaging elements, and the effective pixel signals are corrected based on the corresponding OB pixel signals. The addition number of pixel signals different depending on the pixel area is set for at least one of the predetermined column and row of the effective pixel area, and the effective pixel signal is corrected by the OB pixel signal corresponding to the set addition number.

  According to the present invention, when a pixel signal is added from an image sensor and read out, a dark current component can be reliably removed.

It is a block diagram of the digital camera which is 1st Embodiment. It is the figure which showed the partial pixel arrangement | sequence and partial circuit structure of AE sensor. It is the figure which showed the pixel signal addition process. It is the figure which showed the timing chart of the drive signal at the time of a pixel signal read-out process. It is the figure which showed the sensitivity characteristic of AE sensor. It is the figure which showed the dynamic range expansion by the pixel signal addition of a different addition number. It is the figure which showed the pixel arrangement | sequence and circuit structure of the AE sensor in 2nd Embodiment. It is the figure which showed the timing chart of the drive signal in 2nd Embodiment. It is the figure which showed one pixel addition process in 3rd Embodiment. It is the figure which showed the pixel signal addition process along a column direction. It is the figure which showed the pixel signal addition process along a row direction. It is the flowchart which showed a series of recording operation processes. This is a sub-routine of photometry processing in step S103 of FIG. It is the figure which showed the pixel addition process at the time of the photometry start. It is the figure which showed the pixel addition process at the time of subject brightness | luminance sudden change. It is the figure which showed the pixel arrangement | sequence of the AE sensor in 5th Embodiment. It is the figure which showed the pixel signal read-out process by the different addition number along a column direction. It is the figure which showed the pixel signal read-out process by the different addition number along a row direction.

  Below, the digital camera which is this embodiment is demonstrated with reference to drawings.

  FIG. 1 is a block diagram of a digital camera according to the first embodiment.

  The digital camera 10 is a single-lens reflex camera in which the photographing lens 20 can be detachably attached to the main body 15, and the photographing mode, the reproduction mode, and the like can be set by operating a mode dial / button (not shown). In the photographing mode, the reflected light from the subject passes through the aperture 22 and the photographing lens 20, and a part thereof is guided toward the optical viewfinder 12 by the quick return mirror 24. Part of the reflected light passes through the quick return mirror 24 and is guided to the AF sensor 32 by the half mirror 26.

  When the light incident on the optical viewfinder 12 is imaged, the user can confirm the subject image through an eyepiece (not shown). A subject image is also formed on the light receiving surface of the AE sensor 34 disposed near the optical viewfinder 12.

  The signal processing device 40 configured by the DSP outputs a control signal to the shutter 27, the image sensor driving unit 28, the LCD 48, a timing generator (not shown), etc., and based on an input operation detected by the button switch 45, etc. Controls the overall camera operation, such as recording of recorded images, playback display, and focusing. A camera operation control program is stored in the nonvolatile memory 44.

  When the release button 19 is pressed halfway, a focusing operation and an exposure calculation process are executed. In the focusing operation, the taking lens 20 is driven by an AF driver (not shown) based on the phase difference detected by the AF sensor 32. In addition, the exposure control unit 50 provided in the signal processing device 40 performs automatic exposure calculation processing based on the brightness (exposure amount) of the subject detected by the AE sensor 34. Here, the AE sensor 34 is configured by a CCD which is a charge transfer type solid-state imaging device.

  When the release button 19 is further fully pressed, a series of recording operation processing is executed. That is, the quick return mirror 24 and the half mirror 26 are retracted from the optical path, and the diaphragm 22 and the shutter 27 are driven based on the set exposure values. Thereby, a subject image is formed on the light receiving surface of the image sensor 30.

  As the image sensor 30, for example, a charge transfer type image pickup device CCD or an XY address type image pickup device CMOS sensor can be applied. A color filter (not shown here) is arranged on the light receiving surface of the image sensor 30. A series of pixel signals generated by the image sensor 30 is sent to the signal processing device 40 by the image sensor driving unit 28.

  The signal processing device 40 performs image signal processing such as white balance adjustment on the pixel signal for one frame output from the image sensor 30 to generate still image data. The generated still image data is temporarily stored in the internal memory 42 and then recorded in an external memory 46 such as a memory card in a compressed / uncompressed state.

  The exposure control unit 50 can output a control signal to the image sensor driving unit 28 and the AE sensor driving unit 29 that drives the AE sensor 34, and can adjust the output timing of the driving signals to the image sensor 30 and the AE sensor 34. . The AE sensor driving unit 29 can output a driving signal so that pixel signals are added and read between adjacent pixels.

  The exposure control unit 50 can perform exposure control so that the exposure amount of the AE sensor 34 becomes an exposure amount appropriate for the brightness of the subject, and can adjust an exposure value (hereinafter referred to as a photometric exposure value). Specifically, in the AE sensor 34, the exposure time by the electronic shutter function is adjusted. Further, the gain value of the pixel signal read from the AE sensor 34 can be adjusted.

  Furthermore, when the face detection mode is set, the exposure control unit 50 can detect the face of the subject by the AE sensor 34 using a conventionally known method during photometry. For example, the user can set the face detection mode while the input setting screen is displayed on the LCD 48.

  In the present embodiment, pixel signals are read with different addition numbers so as to expand the dynamic range. Hereinafter, pixel signal addition processing in the AE sensor 34 will be described with reference to FIGS. For convenience, description will be made using both the terms “pixel signal addition” and “pixel addition”.

  FIG. 2 is a diagram illustrating a partial pixel array and a partial circuit configuration of the AE sensor 34.

  As described above, the AE sensor 34 is composed of a CCD, and a plurality of photodiodes (pixels) PD are arranged in a matrix along the vertical and horizontal directions. Here, 24 pixels PD having 6 rows and 4 columns are illustrated, and the pixels PD are denoted by “A1 to A6”, “B1 to B6”, and “C1 to C6” in the column direction of the matrix arrangement, respectively. ”And“ D1 to D6 ”(hereinafter, the same reference numerals are used for pixel signals generated in the pixels).

  The color filter 35 is a filter array composed of R, G1, G2, and B color elements having different spectral peaks, and is disposed opposite to the pixels A1 to A6, B1 to B6, C1 to C6, and D1 to D6. The color elements R, G1, G2, and B of the same color are arranged along the column direction / vertical direction. The electric charge generated in each photodiode PD by photoelectric conversion is transferred to the horizontal transfer unit HT by the vertical transfer unit VT, and is output from the horizontal transfer unit HT via the amplifier AP.

  FIG. 3 is a diagram illustrating pixel signal addition processing. Here, pixel signal addition in the 24 pixel regions shown in FIG. 2 is shown, and similar processing is performed in the other pixel regions.

  Pixel signal addition is performed along the vertical direction / column direction in which color elements of the same color are arranged. Then, a pixel area where two pixels are added and a pixel area where the pixel signal is read out are defined alternately. In the pixel regions R1 and R3, pixel signals (A1, A2), (B1, B2), (C1, C2), and (D1, D2) adjacent in the vertical direction are read out while being added.

  On the other hand, the pixels (A3, B3, C3, D3) and (A6, B6, C6, D6) are vertically transferred without being added to the adjacent pixels. As a result, the read pixel signals are output as pixel signals for four rows. For example, the pixel signals in the first column are output to the outside as four pixel signals A1 ', A2', A3 ', A4'. Similar pixel addition processing is performed for the other second to fourth columns and other columns.

  The read pixel signal is separated for each addition number, and pixel signal data for one frame is generated for each addition number. As a result, pixel data corresponding to two frames with different sensitivities is formed from the pixel data for one frame. Note that it is also possible to form pixel data without separation for each addition number.

  Note that pixel signal readout that is not added to adjacent pixels is defined herein as “pixel signal readout using the addition number“ 1 ””. The terms “1-pixel addition” and “addition number 1” used below mean no pixel addition.

  FIG. 4 is a diagram showing a timing chart of drive signals at the time of pixel signal readout processing.

  The pixel signal generated in each pixel is transferred to the vertical transfer unit VT by the drive signal F0. Then, after the pixel signals of the sixth row are read by the drive signal F1, the pixel signals of the fourth and fifth rows are read together by the drive signal F2. Similarly, the pixel signals in the third row are read out as they are, while the pixel signals in the first and second rows are read out together. Such control of the drive signal corresponds to setting a different countable number depending on the pixel area, and the addition is performed in accordance with the exposure control unit 50.

  FIG. 5 is a diagram showing sensitivity characteristics of the AE sensor 34. FIG. 6 is a diagram illustrating dynamic range expansion by adding pixel signals having different numbers of additions.

  In FIG. 5, straight lines indicating the input / output relationship of 1-pixel addition (no addition) and 2-pixel addition, that is, the relationship between the amount of incident light and the output voltage value are denoted by P1 and P2, respectively. The graph shown in FIG. 5 is represented on a logarithmic scale.

  As is apparent from the straight lines P1 and P2, the exposure amount by the addition of two pixels is doubled as compared to one pixel. Therefore, when light of the input value IN1 is input to the AE sensor 34, an output value OUT1 and an output value OUT2 that is twice the output value OUT1 are obtained from the AE sensor 34.

  If the ratio between the input value IN1 and the input value IN2 when the same output value OUT2 is obtained is twice, the dynamic range is different by twice that ratio. This input difference is the dynamic range expansion width.

  FIG. 6 shows a dynamic range without pixel addition (addition number 1) and a dynamic range with pixel addition. The sensitivity with pixel addition increases in accordance with the number of additions compared to without pixel addition. Therefore, by having both the sensitivity without pixel addition and the sensitivity with pixel addition, it is possible to obtain a dynamic range that covers both the dark portion and the high luminance portion of the subject.

  As described above, according to the first embodiment, the color filter 35 in which the color elements of the same color are arranged in the column direction is disposed in the AE sensor 34 constituted by the CCD. Then, when reading out the pixel signal, the image sensor driving unit 28 adds the adjacent pixel signal in each column direction (addition number 2) and reads the pixel signal without adding it as it is (addition number 1). The reading process is alternately executed in adjacent pixel regions.

  By alternately switching the number of additions and performing pixel signal readout, a sensitivity difference occurs between adjacent pixels. This sensitivity difference leads to an expansion of the dynamic range. As a result, it is possible to obtain a dynamic range that covers a low-brightness to high-brightness subject.

  Also, by setting pixel regions with different addition numbers next to each other, pixel data equivalent to one frame with different sensitivity is obtained for a subject with the same composition, and the entire subject captured by the photographic lens is expanded with an expanded dynamic range. Can be covered. Since the two pieces of pixel data are obtained at the same timing, the brightness can be appropriately detected even if the subject is a moving object. This brings about an effect that cannot be obtained with a configuration in which shooting is performed while changing the exposure in time series. Furthermore, the dynamic range can be expanded with respect to the entire imaging region by setting pixel regions having different addition numbers uniformly over the entire AE sensor light receiving surface.

  Further, by setting different countable numbers only in the column direction, an output having two sensitivity characteristics can be obtained, and the luminance calculation processing after pixel signal readout becomes easy. In particular, by setting different addition numbers in the column or row direction in which color elements of the same color of the color filter are arranged, the dynamic range can be expanded for the brightness of each color.

  Next, a digital camera according to the second embodiment will be described with reference to FIGS. In the second embodiment, the AE sensor is constituted by a CMOS sensor. About another structure, it is substantially the same as 1st Embodiment.

  FIG. 7 is a diagram illustrating a pixel array and a circuit configuration of the AE sensor according to the second embodiment. FIG. 8 is a timing chart of drive signals in the second embodiment.

  The AE sensor 134 is configured by a CMOS sensor that is an XY address type image sensor, and in FIG. 7, 4 rows × 4 columns (pixels A1 to A4, B1 to B4, C1 to C4, and a part thereof) are formed. A pixel array 134R of D1-D4) is shown. Similar to the first embodiment, color filters (not shown) in which color elements of the same color are arranged are arranged along each column.

  A pixel signal generation / output circuit S1 including a photodiode is configured as each pixel. Further, a switch circuit S2 for connecting pixel signal outputs between adjacent pixels is provided in the column direction. When the switch circuit S2 is turned on, pixel signals are added between adjacent pixels along the column direction.

  In the case of pixel signal reading with the addition number 1 (no pixel addition), the pixel signals are sequentially read out along the lines (rows) as they are, and the pixel signals are read out sequentially for each line (row). On the other hand, when the pixel signal is read out with the addition number 2, the pixel signals for two lines are read out while being added.

  In the second embodiment, pixel signal readout of addition number 2 and pixel signal readout of addition number 1 (without pixel addition) are not performed alternately, but pixel signal readout of addition number 2 and pixel of addition number 1 are performed. Signal reading is performed twice in succession. This is repeated along the column direction.

  As shown in FIG. 8, after reading out the pixel signals of the first row, the pixel signals of the second and third rows are added and read out, and the pixel signals are read out as they are in the fourth row. Thus, the dynamic range is expanded by performing pixel signal readout in which a sensitivity difference occurs along each column.

  Next, a third embodiment will be described with reference to FIGS. In the third embodiment, pixel regions having different addition numbers are provided not only in the column direction but also in the row direction or both the column and row directions. As in the second embodiment, a CMOS sensor is applied to the image sensor. A CCD may be used.

  FIG. 9 is a diagram showing one pixel addition process in the third embodiment.

  FIG. 9 shows a partial pixel array 134′R (6 rows × 4 columns) of the AE sensor, and a color filter 135 ′ in which color elements of the same color are arranged in the horizontal direction, that is, the row direction. Be placed. Then, pixel addition processing is performed with different addition numbers in the row direction.

  Specifically, two pixel regions R2 and R3 with the addition number 1 are provided between the pixel regions R1 and R4 along the adjacent column direction with the addition number 2. As a result, the read pixel signals become four pixel signals A1 'to A4' along the row direction. As shown in FIG. 8, the AE sensor 134 is provided with a switch circuit that allows pixel signals to be added between adjacent pixels in the row direction. Signal reading is performed. When a CCD is applied, pixel signals can be added by using a horizontal transfer unit.

  10A and 10B are diagrams illustrating pixel signal addition processing along the column and row directions, respectively. Here, pixel signal addition is performed with different numbers of additions in both the row and column directions. For the column direction, pixel signal readout with the addition number 1 and the addition number 2 is alternately performed as in the first embodiment. In addition, pixel signal readout with addition number 1 and addition number 2 is alternately performed in the row direction. As a result, pixel signals based on three different addition numbers 1, 2, and 4 are output as a whole.

  Alternatively, as shown in FIG. 10B, pixel signal addition of countable number 1 and addition number 2 is performed in the column direction, while pixel signal addition of countable number 1 and countable number 3 is possible in the row direction. It is. As a result, pixel signals based on four different addition numbers 1, 2, 3, and 6 are output as a whole.

  When the pixel areas are alternately set so that the countable number is 1: k in the column direction and the addition number is 1: l (k, l is an integer of 2 or more) in the row direction, the ratio of the addition numbers Becomes a 1: k: k × l pixel signal. In addition, when performing pixel addition like FIG. 10A and 10B, it is good to comprise by the image pick-up element which does not provide a color filter.

  It is possible to set an arbitrary number of additions along such row and column directions by controlling the image sensor driving unit 28 by the exposure control unit 50. Regarding the setting of the addition number, it may be automatically switched and set by a program relating to photographing in advance. For example, it is possible to adopt a configuration in which the addition number is set by a user input operation.

  In addition to setting pixel areas without pixel addition and with pixel addition, even if different addition numbers such as pixel addition number 2 and pixel addition number 4 are set, the dynamic range is expanded. Generally speaking, in the first to third embodiments, pixel signal addition in which the addition number m is different from the addition number n may be performed in the column direction and / or the row direction. However, m and n are integers satisfying m ≧ 1 and m <n.

  In the first to third embodiments, pixel signal readout processing with different addition numbers is performed on the entire light receiving surface of the AE sensor, but it is also possible to perform the processing on a part of the light receiving surface.

  In the first embodiment using a CCD as the AE sensor, the pixel signal is added when the pixel signal is transferred to the horizontal transfer unit. However, it is also possible to add the pixel signal in the vertical transfer unit or the horizontal transfer unit. Alternatively, the pixel signal may be added at the output unit.

  When the XY address type image sensor is used as in the second and third embodiments, it is possible to set pixel regions having different addition numbers in the diagonal direction instead of the column direction and the row direction. In this case, a color filter in which color elements are arranged in a checkered pattern can be used. However, even if the addition number is set along the diagonal direction, a different addition number is set along the column and row directions. You may apply the image pick-up element which does not arrange | position a color filter.

  Next, a digital camera according to a fourth embodiment will be described with reference to FIGS. In the fourth embodiment, the pixel addition setting is switched and changed according to the shooting situation, the exposure amount of the subject, and the like. Other configurations are substantially the same as those in the first to third embodiments.

  The circuit configuration of the digital camera according to the fourth embodiment is substantially the same as the circuit configuration of the digital camera according to the first embodiment shown in FIG. Photometry processing is executed by the AE sensor 34. A subject image captured by the photographic lens 20 is formed on the image sensor 30 by an operation on the release button 19, and still image data is recorded. Then, the exposure value for the image sensor 30 during recording is set based on the brightness of the subject image detected by the AE sensor 34.

  FIG. 11 is a flowchart showing a series of recording operation processing. FIG. 12 is a photometric processing subroutine in step S103 of FIG.

  When the release button 19 is pressed halfway, the brightness of the subject image is detected together with the AF operation process. (S101 to S103). Then, exposure values for the image sensor 30 such as a shutter speed and an aperture value are determined (S104). When the power is turned on, the brightness of the subject image is detected as in the process of step S103.

  In the brightness detection of the subject image, that is, the photometric processing, pixel signal addition processing for expanding the dynamic range is executed as necessary. Then, the exposure of the AE sensor 34 is adjusted, the exposure value (photometric exposure value) of the AE sensor 34 is corrected and corrected, and the brightness of the subject image is finally measured. At this time, pixel signal addition is not performed.

  When the release button 19 is fully pressed, a series of recording operation processes such as exposure control such as shutter opening / closing and image data generation are executed (S105 to S107). At this time, a recording operation is performed based on the set exposure value for the image sensor 30.

  A photometric process using the AE sensor 34 will be described in detail with reference to FIG. In the present embodiment, the different addition numbers are not set, and “1: 1 pixel signal readout processing” of the addition number 1 (no pixel addition) and the pixel areas of the addition number 1 and the addition number 3 are arranged in all pixel regions. “1: 3 pixel signal readout processing” that is alternately set along the direction, and “1:19 pixel signal readout processing” that is alternately set along the column direction for the pixel areas of the addition number 1 and the addition number 19 Either is selectively executed according to the shooting situation.

  When the photometric process is started, the flag IF and the exposure amount difference ΔEv representing the difference from the previous exposure amount are initialized and set to IF = 1 and ΔEv = 0 (S201). If the metering is not finished, it is determined whether or not the initial flag IF = 1 (S202, S203).

  The initial flag IF is a flag for determining whether or not the first photometric process is performed in a series of photographing operations. When the initial flag IF = 1, after setting IF = 0, the dynamic range is set. In order to enlarge greatly, it progresses to step S208 which performs a 1:19 pixel signal read-out process.

  In step S208, a predetermined initial value is set as the exposure value of the AE sensor. In steps S209 and S210, a 1:19 pixel signal reading process is executed. Here, the exposure time by the electronic shutter function is adjusted as the exposure. The pixel signal of the entire pixel region output from the AE sensor 34 is converted into detection data corresponding to the exposure calculation, and a representative value (such as an average value) is calculated from the detection data (S211 and S212). Then, ΔEv representing the difference between the representative value and the target value is calculated (S223).

  In a state where there is no sudden change in subject brightness, which will be described later, the process proceeds to a step of performing a 1: 1 pixel signal reading process without pixel addition at the second photometry (S203, S206). Then, after the exposure value of the AE sensor 34 is corrected based on the calculated ΔEv (S218), a 1: 1 pixel signal readout process is executed (S219, S220). As a result, a representative value that accurately represents the brightness of the subject image is detected (S221, S222).

  FIG. 13 is a diagram showing pixel addition processing at the start of photometry.

  At the start of AE sensor photometry, the actual brightness of the subject cannot be determined until it is measured. Therefore, by executing the 1:19 pixel signal reading process, two pieces of pixel data corresponding to one frame having different sensitivities can be obtained. As a result, the dynamic range is covered from low luminance to high luminance.

  Then, the photometric exposure values such as the exposure time and gain of the AE sensor 34 that are initially set as initial values are corrected according to the obtained exposure amount difference ΔEv. At the next photometry, a 1: 1 pixel signal readout process is executed. Thereby, the pixel signal is read from the AE sensor 34 under the exposure condition suitable for the brightness of the subject image, and the luminance value can be detected with high accuracy.

  On the other hand, if the brightness of the subject image changes suddenly during photometry, the detection data may become saturated, and the brightness of the subject image cannot be measured appropriately. Therefore, if the luminance of the subject exceeds a predetermined range, it is determined that there is a sudden luminance change in the subject image, and the dynamic range is expanded by performing a 1:19 pixel signal readout process.

  Specifically, when the absolute value of the exposure amount difference ΔEv is greater than or equal to the threshold value TE, the process proceeds to steps S208 to S212 in a situation where the face detection mode is not set. Thereby, the exposure amount difference ΔEv is obtained in the same manner as at the start of photometry. When the exposure amount difference ΔEv becomes smaller than the threshold value TE, the process proceeds to steps S218 to S222 in which a 1: 1 pixel signal reading process without pixel addition is performed. Thereby, the brightness of the subject image is detected with high accuracy.

  FIG. 14 is a diagram showing a pixel addition process at the time of sudden change in subject brightness. If the subject brightness changes abruptly while the 1; 1 pixel signal readout process is performed by normal photometry, the dynamic range is expanded by the 1:19 pixel signal output process. Then, after correcting and correcting the exposure conditions of the AE sensor 34, the luminance of the subject image is measured by a 1: 1 pixel signal readout process.

  On the other hand, when the face detection mode is set, the light receiving surface of the AE sensor 34 is divided into a plurality of regions. If the number of added pixels is large, the resolution may be reduced and the face may not be detected. Therefore, when the subject brightness changes suddenly in the state where the face detection mode is set, a 1: 3 pixel signal readout process with a relatively small number of additions is performed.

  Specifically, when it is determined in step S207 that the face detection mode is set, a 1: 3 pixel signal reading process with an addition number of 3 is executed (S213 to S217). By setting such a relatively small number of additions, the dynamic range is expanded while maintaining the situation where face recognition is possible.

  As described above, according to the fourth embodiment, when the photometry process is started, the pixel signal readout process of the addition number 1:19 is executed to calculate the subject luminance. Then, after obtaining the exposure amount difference ΔEv and adjusting the exposure time of the AE sensor 34, a 1: 1 pixel signal readout process without pixel addition is executed. Based on the subject brightness obtained at this time, an exposure value for the image sensor 30 is calculated.

  Further, even when the subject brightness changes abruptly, the pixel signal readout process with the addition number of 1:19 is executed, the exposure value of the AE sensor 34 is adjusted, and then the 1: 1 pixel signal readout process without pixel addition is performed. Run. Further, when the face detection mode is set, a 1: 3 pixel signal reading process with a relatively small addition number is executed.

  As described above, the brightness of the subject can be instantaneously measured by switching the number of additions according to the shooting state, subject change, photometry mode, and the like. In particular, the dynamic range expansion width can be finely set by switching and setting different addition numbers for two or more addition numbers. When the power is turned on, a 1:19 pixel signal readout process is executed in accordance with the power on. Thereby, it is possible to quickly move to the photographing operation from the power ON.

  Here, at the start of photometry, the 1:19 pixel signal readout process is performed only once in the rapid change in subject brightness, but the feedback control may be performed repeatedly twice or three times. In particular, the exposure may be adjusted so that the exposure amount difference ΔEv falls within an allowable value.

  For pixel addition readout, different addition numbers can be set along the row direction or the column direction as in the third embodiment.

  Regarding the addition number, a numerical value other than 3 and 19 can be set. In addition, the entire light receiving surface of the AE sensor may be configured to be switched and set to include a process of reading pixel signals with the same addition number (not limited to 1). For example, any of the addition numbers 3, 5, and 9 may be set for the entire light-receiving surface according to the shooting situation, and further to pixel signal readout processing in which different addition numbers are provided along the column / row direction. Including (1: 3, 1:19, etc.), it is possible to selectively set the number of additions. Even when uniform addition numbers are set for columns and rows, depending on the subject, there is an effect of expanding the dynamic range, so two or more uniform addition numbers and different addition numbers can be set depending on the pixel area. Various dynamic range expansions can be realized by using properly according to the shooting situation.

  Next, the digital camera which is 5th Embodiment is demonstrated using FIGS. In the fifth embodiment, pixel value correction is performed in consideration of the number of additions in dark current removal processing by OB pixels. About another structure, it is substantially the same as 1st Embodiment.

  FIG. 15 is a diagram illustrating a pixel array of the AE sensor according to the fifth embodiment.

  The AE sensor 234 is provided with an effective pixel region 234A and a light-shielded OB (optical black) pixel region 234B. Luminance data of the subject image is calculated based on pixel signals read from the pixels constituting the effective pixel region 234A. On the other hand, the dark current component included in the effective pixel signal is removed based on the pixel signal read from the pixel in the OB pixel region. FIG. 15 illustrates a part of OB pixels OB1 to OB6 and OB7 to OB10 arranged on the right side and the lower side of the effective pixel region 234A.

  FIG. 16 is a diagram illustrating pixel signal readout processing with different addition numbers along the column direction. FIG. 17 is a diagram illustrating pixel signal readout processing with different addition numbers along the row direction. Similar to the first embodiment, pixel regions of addition number 1 and addition number 2 are alternately set along the column direction or the row direction.

  In the present embodiment, an OB pixel signal is also added and output according to the number of additions. Specifically, the OB1 pixel signal and the OB2 pixel signal are added to the output pixel signals A1 + A2, B1 + B2,. On the other hand, the OB3 pixel signal is output as it is for the output pixel signals A3, B3,.

  Then, the OB1 + OB2 pixel signal is divided from the output pixel signals A1 + A2, B1 + B2,. On the other hand, for the output pixel signals of A3, B3,. Similar correction and correction of OB pixel values are performed in other pixel arrays.

  As described above, in the fifth embodiment, pixel signals of addition number 1 and addition number 2 are alternately read out from the effective pixels along the column or row direction. On the other hand, pixel signals are read out for OB pixels according to the number of corresponding effective pixels added. Then, the dark current component is removed by subtracting the OB pixel signal from the effective pixel signal.

  In addition, instead of adding adjacent OB pixel signals, a configuration may be used in which one OB pixel signal is multiplied by the number of additions. For example, the pixel value of the OB pixel signal may be doubled to remove the dark current component.

  Further, the average value OBA of the OB pixel signals of all the columns is calculated, the pixel value is corrected by multiplying the output pixel signal of the addition number 2 by OBA twice, and the output pixel signal of the addition number 1 is left as it is. The average value OBA may be used.

  FIG. 17 shows reading of an OB pixel signal at the time of pixel signal reading processing with different addition numbers along the row direction. For the pixel signals in the columns A1 + B1, A2 + B2,..., The OB7 pixel signal and the OB8 pixel signal are added to correct the pixel value. For the pixel signals of C1, C2,..., The pixel values are corrected as they are using the OB9 pixel signal.

  In the first to fifth embodiments, pixel addition processing is performed using a photometric sensor in a single-lens reflex camera, but it can also be applied to an external AE sensor that is not provided in an optical viewfinder such as a compact camera. In addition, the pixel addition process can be applied to the imaging element for a camera that detects the brightness of the subject using the imaging element for imaging.

DESCRIPTION OF SYMBOLS 10 Digital camera 29 AE sensor drive part 30 Image sensor (imaging image sensor for imaging | photography)
40 Signal Processing Device 50 Exposure Control Unit 34, 134, 134 ', 234 AE Sensor (Image Sensor, Photometric Image Sensor)

Claims (6)

An imaging device having a plurality of effective pixels arranged in a matrix along the vertical direction and the horizontal direction, and a plurality of OB (optical black) pixels arranged along at least one of a row and a column of the plurality of effective pixels; ,
A plurality of the OB pixel signal OB pixels adjacent in the effective pixel signal and the plurality of OB pixels in the effective pixel adjacent in the effective pixel, and readable image sensor driving unit adds,
To at least one of the predetermined column and row of the imaging device, a pixel addition setting unit for setting the addition number of the effective pixel No. signal to be read by adding,
A pixel signal correction unit that corrects an effective pixel signal based on a corresponding OB pixel signal;
The pixel addition setting unit sets the number of additions of effective pixel signals that differ depending on the pixel region, for at least one of a predetermined column and row of the effective pixel region,
The image sensor driving unit reads out an effective pixel signal according to the number of additions set by the pixel addition setting unit and varies depending on the image area, and reads out an OB pixel signal according to the number of additions of the corresponding effective pixel signal. ,
The image pickup apparatus, wherein the pixel signal correction unit corrects a corresponding effective pixel signal based on an OB pixel signal read according to a set addition number. The imaging apparatus according to claim 1, wherein the pixel addition setting unit can switch and set different addition numbers depending on image areas . Instead of reading out an OB pixel signal according to the number of corresponding effective pixel signals added, the image sensor driving unit reads out the OB pixel signal as it is without pixel addition,
The imaging apparatus according to claim 1, wherein the pixel signal correction unit multiplies the representative value of the read series of OB pixel signals by the number of additions of the corresponding effective pixel signals. The image sensor is provided with a color filter in which color elements of the same color are arranged along columns or rows,
4. The camera according to claim 1, wherein the pixel addition setting unit sets different addition numbers for columns or rows in which color elements of the same color are arranged. A camera comprising the imaging device according to claim 1,
A camera in which exposure control of an image pickup device for photographing on which a subject image is formed at the time of photographing is performed based on a pixel signal read from the image pickup device. An imaging device having a plurality of effective pixels arranged in a matrix along the vertical direction and the horizontal direction, and a plurality of OB (optical black) pixels arranged along at least one of a row and a column of the plurality of effective pixels; , image pickup apparatus having an OB pixel signal OB pixels adjacent in the effective pixel signal and the plurality of OB pixels in the effective pixel adjacent in the plurality of effective pixels and readable image sensor driving unit adds An imaging method of
To at least one of the columns and rows of the imaging element, and a pixel addition setting sets the addition number of the effective pixel No. signal to be read by adding,
In an imaging method for correcting an effective pixel signal based on a corresponding OB pixel signal,
For at least one of the predetermined columns and rows of the effective pixel area, set the number of additions of effective pixel signals that differ depending on the pixel area,
The effective pixel signal is read according to the number of additions that differ depending on the image area set by the pixel addition setting unit, and the OB pixel signal is read according to the addition number of the corresponding effective pixel signal,
An imaging method, wherein an effective pixel signal is corrected by an OB pixel signal read according to a set addition number.

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