Photoelectric conversion device, photoelectric conversion system, and signal processing method

Abstract

To provide a photoelectric conversion device capable of appropriately performing correction to an image signal.SOLUTION: A photoelectric conversion device according to an embodiment of the present disclosure, includes a pixel array that contains a plurality of pixels arranged in a matrix. The plurality of pixels comprises: a pixel array that contains an effective pixel and a shading member that output a signal corresponded to incident light; a calculation part that calculates a correction value on the basis of a pixel value of the shading pixel; and a correction part that corrects a pixel value of the effective pixel on the basis of the correction value. One pixel row of the pixel array contains: a first shading pixel; a second shading pixel; and the effective pixel. The calculation part calculates the correction value by using a parameter that is different each other in each of the first and second shading pixels of the pixel row.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a photoelectric conversion device, a photoelectric conversion system, and a signal processing method. [Background technology]

[0002] Patent Document 1 discloses a photoelectric conversion device that corrects image values ​​using correction values ​​obtained by multiplying an offset determined for each row based on pixel values ​​in a light-shielded pixel region (horizontal OB region) by a coefficient and attenuating the offset. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-067060 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the photoelectric conversion device described in Patent Document 1, there are cases where image values ​​are not appropriately corrected.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and has an object to provide a photoelectric conversion device and a photoelectric conversion system that can perform more appropriate correction on image values. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, a pixel array includes a plurality of pixels arranged in a matrix, the plurality of pixels including effective pixels that output a signal in response to incident light, and light-shielding pixels having a light-shielding member; a calculation unit that calculates a correction value based on pixel values ​​of the light-shielding pixels; and a correction unit that corrects the pixel values ​​of the effective pixels based on the correction value, wherein a pixel row of the pixel array includes a first light-shielding pixel, a second light-shielding pixel, and the effective pixel, and the calculation unit calculates the correction value using parameters that are different from each other for the first light-shielding pixel and the second light-shielding pixel of the pixel row. Effect of the Invention

[0007] According to the present disclosure, it is possible to provide a photoelectric conversion device and a photoelectric conversion system capable of performing more appropriate correction on an image signal. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram of a photoelectric conversion device according to a first embodiment. [Diagram 2] 1 is a block diagram of a solid-state imaging element according to a first embodiment. [Diagram 3] FIG. 2 is a schematic diagram of a pixel array according to the first embodiment. [Figure 4] 5 is a timing chart showing a read operation in the first embodiment. [Diagram 5] 5 is a flowchart showing the operation of a clamp circuit in the first embodiment. [Figure 6] FIG. 11 is a conceptual diagram of a pixel array according to a second embodiment. [Figure 7] 10 is a flowchart showing the operation of a clamp circuit in the second embodiment. [Figure 8] 13 is a flowchart showing the operation of a clamp circuit in the third embodiment. [Figure 9] 13 is a flowchart showing the operation of a clamp circuit in the fourth embodiment. [Figure 10] FIG. 13 is a block diagram showing an example of the configuration of a device according to a fifth embodiment. [Figure 11] FIG. 13 is a block diagram of devices related to an in-vehicle camera in a sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Elements having common functions throughout the drawings will be designated by the same reference numerals, and duplicated descriptions may be omitted or simplified.

[0010] [First embodiment] 1 is a block diagram of a photoelectric conversion device 1 in the first embodiment. The photoelectric conversion device 1 includes a solid-state imaging element 11, a control unit 12, an instruction unit 13, a timing signal generating unit 14, a photographing lens 15, a lens driving unit 16, a signal processing unit 17, a display unit 18, and a recording unit 19. The photoelectric conversion device 1 can be an imaging device for capturing an image of a subject.

[0011] The solid-state imaging element 11 has a pixel region including a plurality of pixels arranged two-dimensionally in a matrix. The solid-state imaging element 11 can output imaging signal data according to incident light. The detailed configuration of the solid-state imaging element 11 will be described later.

[0012] The instruction unit 13 receives inputs such as instructions from a user for executing photography and settings of the driving mode of the photoelectric conversion device 1. The instruction unit 13 transmits the received inputs to the control unit 12.

[0013] The control unit 12 includes a storage unit that stores driving information and the like for driving the photoelectric conversion device 1. The control unit 12 controls the driving of each functional block of the photoelectric conversion device 1 based on the driving information and instructions via the instruction unit 13. The control unit 12 also performs signal processing such as development processing and compression processing for generating an image for recording or an image for playback on the imaging signal data.

[0014] The timing signal generating unit 14 receives a control signal from the control unit 12. The timing signal generating unit 14 generates a timing signal for driving the solid-state imaging element 11 and the signal processing unit 17 based on the received control signal.

[0015] The photographing lens 15 forms an optical image of a subject on the solid-state imaging element 11. The photographing lens 15 may be configured to be detachable from the photoelectric conversion device 1, or may be configured not to be detachable.

[0016] The lens driving unit 16 drives the photographing lens 15 based on a control signal input from the control unit 2. The lens driving unit 16 also controls the focus, zoom, aperture, etc. based on a control signal input from the control unit 12.

[0017] The signal processing unit 17 performs signal processing such as correction on the imaging signal data output from the solid-state imaging element 11. The display unit 18 displays an image for playback, information on the setting of the driving mode of the photoelectric conversion device 1, and the like. The recording unit 19 is provided with a recording medium (not shown) and records image data for recording on the recording medium. As the recording medium provided in the recording unit 19, for example, a semiconductor memory such as a flash memory is used. The recording medium may be configured to be detachable from the recording unit 19, or may be configured not to be detachable.

[0018] 2 is a block diagram of the solid-state imaging device 11 in the first embodiment. The solid-state imaging device 11 includes a pixel array 100, a vertical scanning circuit 130, a column circuit 140, a horizontal scanning circuit 150, a horizontal output line 160, and a clamp circuit 170.

[0019] As shown in FIG. 2, the pixel array 100 includes a plurality of pixels arranged in a matrix. The pixel array 100 also includes an effective pixel region 110 and a light-shielding pixel region 120. A plurality of effective pixels 111 are arranged in a matrix in the effective pixel region 110. The effective pixels 111 include a photoelectric conversion unit and output an analog signal according to light incident on a light receiving unit of the photoelectric conversion unit. The output signal from the effective pixels 111 is used for generating, displaying, and the like of a captured image. The light-shielding pixel region 120 is provided adjacent to the effective pixel region 110. A plurality of light-shielding pixels 121 including a first light-shielding pixel and a second light-shielding pixel are arranged in the light-shielding pixel region 120. The light-shielding pixels 121 include a photoelectric conversion unit similar to the effective pixels 111. The light receiving unit of the photoelectric conversion unit of the light-shielding pixels 121 is shielded from incident light by a light-shielding member or the like. The pixel signal from the light-shielding pixels 121 is used to correct the pixel signal from the effective pixels 111. The light-shielded pixel region 120 may include a horizontal optical black (HOB) pixel region consisting of multiple columns of light-shielded pixels, and a vertical optical black (VOB) pixel region consisting of multiple rows of light-shielded pixels. However, in this embodiment, the VOB pixel region is not necessarily provided.

[0020] The vertical scanning circuit 130 supplies control signals to multiple pixels in each row of the pixel array 100, and is capable of selecting multiple pixels for each row. That is, the vertical scanning circuit 130 controls the timing of reading out pixel signals output from the effective pixels 111 and the light-shielded pixels 121 on a row-by-row basis, based on the timing signal input from the timing signal generation unit 14.

[0021] The column circuits 140 are provided to correspond to each pixel column of the effective pixels 111 and the light-shielded pixels 121. The column circuits 140 include an AD conversion unit. The AD conversion unit converts an analog signal level corresponding to a pixel signal transmitted from each pixel column into a digital signal value (pixel value). The column circuits 140 also include a storage unit. The column circuits 140 temporarily hold the pixel values ​​converted by the AD conversion unit.

[0022] The horizontal scanning circuit 150 is connected to each of the multiple column circuits 140. The horizontal scanning circuit 150 outputs a selection signal PH to the column circuits 140 based on the timing signal input from the timing signal generating unit 14. The horizontal scanning circuit 150 selects a column circuit 140 by the selection signal PH, and controls the timing of outputting a digital signal value from the memory unit of the column circuit 140. In response to the selection signal PH(x) corresponding to the xth column becoming high level, the column circuit 140 of the xth column is selected. The selected column circuit 140 outputs the digital signal value held in the memory unit to the clamp circuit 170.

[0023] The horizontal output line 160 electrically connects the column circuit 140 and the clamp circuit 170. The digital signal value output from the column circuit 140 is output to the clamp circuit 170 via the horizontal output line 160.

[0024] The clamp circuit 170 includes a calculation unit and a correction unit. The clamp circuit 170 receives pixel values ​​from the column circuit 140 via the horizontal output line 160. The clamp circuit 170 calculates a correction value used to correct the pixel value of the effective pixel 111 based on the received pixel value. The clamp circuit 170 also corrects the pixel value received from the column circuit 140 using the calculated correction value.

[0025] The clamp circuit 170 receives the pixel value from the light-shielded pixel 121 and updates the correction value based on the received pixel value. The detailed operation of the clamp circuit 170 will be described later.

[0026] A signal read operation from the solid-state imaging element 11 according to the present embodiment will be described with reference to Figures 3 and 4. Figure 3 is a schematic diagram of a pixel array 100 according to the first embodiment.

[0027] 3, the light-shielded pixel region 120 is disposed adjacent to the effective pixel region 110. The light-shielded pixel region 120 includes pixel columns of light-shielded pixels 121 from the 1st column to the Cth column. The effective pixel region 110 includes pixel columns of effective pixels 111 from the jth column to the kth column. That is, the pixel array 100 in this embodiment includes a total of k pixel columns.

[0028] The light-shielded pixel region 120 includes a first light-shielded pixel region 120-1, a second light-shielded pixel region 120-2, and a third light-shielded pixel region 120-3. The first light-shielded pixel region 120-1 includes a pixel row of light-shielded pixels 121 (plurality of first light-shielded pixels) from the x11th column to the x12th column, and is adjacent to the second light-shielded pixel region 120-2. The second light-shielded pixel region 120-2 includes a pixel row of light-shielded pixels 121 (plurality of second light-shielded pixels) from the x21th column to the x22th column, and is adjacent to the third light-shielded pixel region 120-3. The third light-shielded pixel region 120-3 includes a pixel row of light-shielded pixels 121 from the x31st column to the x32nd column. In the example shown in FIG. 3, each of the first light-shielded pixel region 120-1, the second light-shielded pixel region 120-2, and the third light-shielded pixel region 120-3 includes a plurality of pixel columns, but each of the light-shielded pixel regions 120-1, 120-2, and 120-3 may include only one pixel column. The x11th column may be the first column, and the x32th column may be the Cth column. The ranges occupied by the effective pixel region 110 and the light-shielded pixel region 120 in the pixel array 100 shown in FIG. 3 are schematic. The effective pixel region 110 and the light-shielded pixel region 120 are not limited to the number of each region shown in FIG. 3, and may be two or four or more. Furthermore, the number of pixel columns included in each of the first to third light-shielded pixel regions 120-1 to 120-3 may be different from each other, or may be the same as each other.

[0029] Each of the pixel columns from the 1st column to the kth column included in the pixel array 100 is associated with a column address. The x11th column to the x12th column are associated with the first light-shielded pixel region 120-1, and the x21th column to the x22th column are associated with the second light-shielded pixel region 120-2. The x31th column to the x32nd column are associated with the third light-shielded pixel region 120-3, and the jth column to the kth column are associated with the effective pixel region 110. Information indicating the correspondence between the pixel column numbers and the column addresses is stored in, for example, a storage unit provided in the control unit 12. Furthermore, the column addresses of the pixel columns used to update the correction value Sc are stored in the storage unit. For example, the address corresponding to the x11th column may be stored as the column address that is read out first when the process of updating the correction value Sc starts. The address corresponding to the x32nd column may be stored as the column address that is read out last when the process of updating the correction value Sc starts. When driving the solid-state imaging element 11, the photoelectric conversion device 1 controls the solid-state imaging element 11 based on drive information including stored column address information. Note that a further pixel column may be arranged between the x12th column and the x21st column, and a further pixel column may be arranged between the x22th column and the x31st column. Also, the column number of a pixel column included in the pixel array 100 may be used as a column address.

[0030] 4 is a timing chart showing a read operation in the first embodiment. That is, FIG. 4 shows a read operation of pixel signals of each column in an arbitrary scanning row (one pixel row) of the pixel array 100.

[0031] At a time (not shown) before time t1, the column circuit 140 reads out pixel signals from each of the effective pixels 111 and the light-shielded pixels 121. The column circuit 140 performs analog-to-digital (AD) conversion on each of the read-out pixel signals. The column circuit 140 stores the AD-converted pixel values ​​D(1) to D(k) in the memory of the column circuit 140.

[0032] At time t1, the selection signal PH(1) transitions from low level to high level. Based on PH(1) that has transitioned to high level, the column circuit 140 corresponding to the first column is selected. The selected column circuit 140 holds the pixel value D(1) of the light-shielded pixel 121 in the first column. Based on the selection signal PH(1), the selected column circuit 140 outputs the pixel value D(1) to the clamp circuit 170.

[0033] At time t2, the selection signal PH(1) transitions from high level to low level, and the selection signal PH(2) transitions from low level to high level. Based on PH(2) that has transitioned to high level, the column circuit 140 corresponding to the second column is selected. The selected column circuit 140 holds the pixel value D(2) of the light-shielded pixel 121 in the second column. The selected column circuit 140 sequentially outputs the pixel value D(2) to the clamp circuit 170 based on the selection signal PH(2). At time t3, the selection signal PH(2) transitions from high level to low level, and the selection signal PH(3) transitions from low level to high level. At times t4 to t9 after t3, the selection signal PH similarly transitions from low level to high level sequentially, and the corresponding column circuit 140 outputs the held pixel value D to the clamp circuit 170. Specifically, from time t4 to t5, the column circuit 140 sequentially outputs pixel values ​​D(x11) to D(x12) of the light-shielded pixels 121 in the x11th to x12th columns to the clamp circuit 170. From time t5 to t6, the column circuit 140 sequentially outputs pixel values ​​D(x21) to D(x22) of the light-shielded pixels 121 in the x21th to x22nd columns to the clamp circuit 170. From time t6 to t7, the column circuit 140 sequentially outputs pixel values ​​D(x31) to D(x32) of the light-shielded pixels 121 in the x31st to x32nd columns to the clamp circuit 170. From time t8 to t9, the column circuit 140 sequentially outputs pixel values ​​D(j) to D(k) of the effective pixels 111 in the jth to kth columns to the clamp circuit 170. The vertical scanning circuit 130 outputs a signal to each corresponding pixel to select the next row. In the selected pixel row, pixel values ​​D from the first column to the kth column are sequentially read out to the clamp circuit 170 in the same procedure as the readout operation for the previously scanned pixel row.

[0034] As shown in FIG. 4, the horizontal scanning circuit 150 transitions the selection signals PH(1) to PH(k) from low level to high level to sequentially select the column circuits 140 corresponding to the first to k-th columns. The selected column circuits 140 sequentially output the held pixel values ​​D(1) to D(k) to the clamp circuit 170 based on the selection signals PH(1) to PH(k). That is, pixel signals are scanned while sequentially switching the selected columns from the first to k-th columns of the pixel array 100. In a pixel row including an effective pixel 111, the first light-shielded pixel region 120-1 is scanned, and then the second light-shielded pixel region 120-2 is scanned. After the second light-shielded pixel region 120-2 is scanned, the third light-shielded pixel region 120-3 is scanned. After the pixel values ​​are read from the first to third light-shielded pixel regions 120-1 to 120-3, the pixel value of the effective pixel 111 is read.

[0035] 5 is a flowchart showing the operation of the clamp circuit 170 in the first embodiment. The clamp circuit 170 calculates a correction value Sc for correcting the pixel value of the effective pixel 111 based on the pixel values ​​D(x11) to D(x32). The clamp circuit 170 also corrects the pixel values ​​D(j) to D(k) of the effective pixels 111 using the calculated correction value Sc. The calculation process of the correction value Sc in a scanning row (one pixel row) and the correction process of the pixel value D(x) will be described below.

[0036] 4, the clamp circuit 170 reads out pixel values ​​D(1) to D(k) from the column circuit 140. That is, the pixel values ​​D(1) to D(k) held in the column circuit 140 are input to the clamp circuit 170 sequentially from the first column to the k-th column of the pixel area 110. A clamping operation is performed in the clamp circuit 170 while a signal is being input to the clamp circuit 170. The operation of reading out the pixel values ​​D(1) to D(k) from the column circuit 140 is executed in step S505 or S515 of FIG. 5, which will be described later.

[0037] In step S501, the clamp circuit 170 adds 1 to the count value x of the column address. In step S502, the clamp circuit 170 determines whether the count value x indicates a pixel column in the pixel array 100. Specifically, if the count value x is equal to or less than the total number of pixels included in the scanning row (total number of pixels k) (YES in step S502), the clamp circuit 170 determines that there is a pixel signal to be read from the column circuit 140, and proceeds to step S503. On the other hand, if the count value x exceeds the total number of pixels k (NO in step S502), the clamp circuit 170 determines that the input of pixel signals from the scanning row to the clamp circuit 170 has been completed, and proceeds to step S516.

[0038] In step S503, the clamp circuit 170 determines whether the count value x corresponds to a pixel column in the effective pixel area 110. Specifically, the clamp circuit 170 compares the count value x with a column address j indicating the first pixel column of the effective pixel area 110. If the count value x is less than j (NO in step S503), the clamp circuit 170 determines that the pixel signal can be used to update the correction value Sc, and proceeds to step S504. On the other hand, if the count value x is equal to or greater than j (YES in step S503), the clamp circuit 170 determines that the count value x indicates a column address in the effective pixel area 110. In other words, the clamp circuit 170 determines that the pixel signal is not used to update the correction value Sc, and proceeds to step S515.

[0039] In step S504, the clamp circuit 170 determines whether the count value x corresponds to a pixel column included in the first to third light-shielded pixel regions 120-1 to 120-3. Specifically, the clamp circuit 170 compares the count value x with column addresses x11 and x32. If the count value x corresponds to a column address between column addresses x11 and x32 (YES in step S504), the clamp circuit 170 determines that the pixel signal is used to update the correction value Sc, and proceeds to step S505. On the other hand, if the count value x does not correspond to a column address between column addresses x11 and x32 (NO in step S504), the clamp circuit 170 determines that the pixel signal is not used to update the correction value Sc, and returns the process to step S501.

[0040] In step S505, the clamp circuit 170 obtains the pixel value D(x) of the pixel column corresponding to the count value x from the column circuit 140. In step S506, the clamp circuit 170 determines whether the count value x corresponds to a pixel column in the first light-shielded pixel region 120-1. Specifically, the clamp circuit 170 compares the count value x with the column address x12. If the count value x is equal to or smaller than the column address x12 (YES in step S506), the clamp circuit 170 determines that the pixel signal corresponds to a light-shielded pixel in the first light-shielded pixel region 120-1, and proceeds to step S508. On the other hand, if the count value x is greater than the column address x12 (NO in step S506), the clamp circuit 170 determines that the pixel signal corresponds to a light-shielded pixel other than the first light-shielded pixel region 120-1, and proceeds to step S507.

[0041] In step S507, the clamp circuit 170 determines whether the count value x corresponds to a pixel column in the second shaded pixel region 120-2. Specifically, the clamp circuit 170 compares the count value x with the column address x22. If the count value x is equal to or less than the column address x22 (YES in step S507), the clamp circuit 170 determines that the pixel signal corresponds to a shaded pixel in the second shaded pixel region 120-2, and proceeds to step S509. On the other hand, if the count value x is greater than the column address x22 (NO in step S507), the clamp circuit 170 determines that the pixel signal corresponds to a shaded pixel other than the second shaded pixel region 120-2, and proceeds to step S510.

[0042] In step S508, the clamp circuit 170 sets a parameter used to calculate the correction value. In this embodiment, the parameter that is set is an attenuation coefficient A that determines the attenuation rate for attenuating the difference between the updated correction value Sc and the correction value before the update. That is, the attenuation rate in this disclosure changes depending on the attenuation coefficient A. In this embodiment, when the attenuation coefficient A is set low, the attenuation rate becomes large, and when the attenuation coefficient A is set high, the attenuation rate becomes small. The clamp circuit 170 sets the attenuation coefficient A to the attenuation coefficient A1 corresponding to the first light-shielded pixel region 120-1, and proceeds to step S511.

[0043] In step S509, the clamp circuit 170 sets the attenuation coefficient A to the attenuation coefficient A2 corresponding to the second light-shielded pixel region 120-2, and proceeds to step S511. In step S510, the clamp circuit 170 sets the attenuation coefficient A to the attenuation coefficient A3 corresponding to the third light-shielded pixel region 120-3, and proceeds to step S511. In this embodiment, a separate attenuation coefficient A is set for each of the first to third light-shielded pixel regions 120-1 to 120-3. Specifically, the attenuation coefficients are set so that A1>A2>A3. As an example, the attenuation coefficients can be set to A1=0.8, A2=0.4, and A3=0.2.

[0044] In step S511, the clamp circuit 170 calculates the difference value Sd using the pixel value D(x). Specifically, the clamp circuit 170 subtracts the target pixel value Dt from the pixel value D(x). Furthermore, the clamp circuit 170 further subtracts the correction value Sc(x-1) calculated for the light-shielded pixel in the (x-1)th column from the pixel value D(x). That is, the difference value Sd according to this embodiment can be calculated by the following arithmetic formula (1). Sd = D(x) - Dt - Sc(x - 1) (1)

[0045] If the xth column is the first pixel row scanned in the light-shielded pixel region 120 and the scanned row is the first pixel row scanned in the calculation of the correction value, the correction value Sc(x-1) is set to 0. If the xth column is the first pixel row scanned in the light-shielded pixel region 120 but a correction value has already been calculated before the scanning of the scanned row, the correction value immediately before the scanning of the scanned row is set as Sc(x-1).

[0046] In step S512, the clamp circuit 170 sequentially updates the correction value Sc(x) of the xth column based on the correction value Sc(x-1) of the (x-1)th column. Specifically, the clamp circuit 170 adds a value obtained by multiplying the difference value Sd by the attenuation coefficient A to the correction value Sc(x-1). That is, according to this embodiment, the correction value Sc(x) for the light-shielded pixel in the xth column can be calculated by the following arithmetic expression (2). Sc(x)=Sc(x-1)+Sd×A (2) The correction value Sc(x) according to the arithmetic expression (2) is set as the correction value Sc(x) based on the pixel values ​​of the light-shielded pixels 121 in the xth column.

[0047] In step S513, the clamp circuit 170 sets the correction value Sc(x) calculated in step S512 as the updated correction value Sc. In step S514, the clamp circuit 170 corrects the pixel value D(x) based on the correction value Sc updated in step S513. The clamp circuit 170 subtracts the updated correction value Sc from the pixel value D(x) and outputs the pixel value Do(x). Thereafter, the clamp circuit 170 repeats the processes of steps S501 to S514 and starts processing for the next input pixel value. After the update of the correction value based on the pixel signal from the light-shielded pixel 121 is completed, the clamp circuit 170 holds the correction value Sc last updated in step S512. Note that after the correction value is updated in step S513, the process may return to step S501 without executing step S514.

[0048] If the count value x indicates a pixel column in the effective pixel area 110 in step S503 (YES in step S503), the clamp circuit 170 acquires the pixel value D(x) of the effective pixel 111 from the column circuit 140 (step S515). Next, the clamp circuit 170 subtracts the correction value Sc from the pixel value D(x) of the effective pixel 111 (step S514). That is, the clamp circuit 170 corrects the offset of the pixel value D(x) of the effective pixel 111. After correcting the pixel value D(x), the clamp circuit 170 executes the process of step S501 again and starts processing the next input pixel value.

[0049] If the count value x exceeds the total number of pixels k in step S502 (NO in step S502), the clamp circuit 170 determines that the input of pixel signals for the scanning row is complete. In step S516, the clamp circuit 170 resets the count value x and ends the process of this flowchart. If there is a pixel row to be scanned next, the clamp circuit 170 executes the process of this flowchart again and corrects the pixel values ​​based on the correction value Sc.

[0050] According to this embodiment, a different attenuation coefficient is set for each of a plurality of light-shielded pixel regions arranged in the horizontal direction. The correction value is updated based on the pixel signals of the light-shielded pixels and the attenuation coefficient. Here, a relatively low attenuation rate is applied to the light-shielded pixel region scanned first, and a relatively high attenuation rate is applied to the light-shielded pixel region scanned later.

[0051] For example, white spot noise is known as one of the noises that appear in an image captured by a photoelectric conversion device. White spot noise is generated due to defects contained in a semiconductor substrate used in the imaging device, cosmic rays present in the atmosphere, and the like. Therefore, white spot noise appears in the captured image regardless of the spatial arrangement of pixels and the order of signal readout. If white spot noise is present in a light-shielded pixel region, a relatively large correction value may be calculated to cancel out this noise. As a result, the captured pixel value is overcorrected. This overcorrection may appear as horizontal stripe-like noise in the captured image. On the other hand, if the correction value is set taking white spot noise into consideration, the correction value may be calculated too low, and noise such as dark shading components may not be sufficiently removed. As a result, a problem may occur in which noise due to dark shading components remains in the captured image.

[0052] According to the photoelectric conversion device of the present disclosure, when white spot noise is present in a light-shielded pixel region to which a relatively low attenuation rate is applied, the correction value that is set too large is updated by the light-shielded pixels scanned thereafter. Thus, the correction value is gradually updated to an appropriate correction value. That is, even if a correction value that deviates from the ideal correction value is temporarily calculated due to the occurrence of white spot noise, the correction value is updated again to the ideal correction value by repeatedly updating the correction value thereafter. Thus, the problem of horizontal stripe noise being generated due to the occurrence of white spot noise is suppressed. That is, the photoelectric conversion device of the present disclosure can perform just the right amount of correction for various noises that may occur on a solid-state imaging element using light-shielded pixels arranged in the light-shielded pixel region.

[0053] On the other hand, when white spot noise or the like is present in a light-shielded pixel region to which a relatively high attenuation rate is applied, a relatively small attenuation coefficient is applied to the pixel signal of the light-shielded pixel in the calculation of the correction value. That is, the influence of white spot noise or the like on the correction value is reduced. Thus, the problem of an excessive correction value being set due to the occurrence of white spot noise or the like is suppressed. Therefore, the photoelectric conversion device according to the present disclosure can suppress the occurrence of horizontal stripe noise due to an inappropriate correction value.

[0054] [Second embodiment] The photoelectric conversion device 1 according to the present embodiment will be described with reference to Fig. 6 and Fig. 7. This embodiment differs from the first embodiment in that the attenuation coefficient A is changed for each column address of the column pixels to be scanned. The following describes the photoelectric conversion device 1 according to this embodiment, focusing on the differences from the first embodiment.

[0055] Fig. 6 is a schematic diagram of a pixel array 100 according to the second embodiment. Note that the description of the same items as those in the configuration of Fig. 3 according to the first embodiment may be simplified or omitted.

[0056] 6, the light-shielded pixel region 120 is disposed adjacent to the effective pixel region 110. The light-shielded pixel region 120 includes pixel columns of light-shielded pixels 121 from column 1 to column C. The effective pixel region 110 includes pixel columns of effective pixels 111 from column j to column k. That is, the pixel array 100 in this embodiment includes a total of k pixel columns.

[0057] The light-shielded pixel region 120 according to the present embodiment includes a fourth light-shielded pixel region 120-4. The fourth light-shielded pixel region 120-4 includes pixel columns of light-shielded pixels 121 from the x11th column to the x32nd column. The light-shielded pixels 121 in the fourth light-shielded pixel region 120-4 are used to update the correction value. The x11th column may be the first column, and the x32nd column may be the Cth column.

[0058] Each of the pixel columns from the 1st column to the kth column included in the pixel array 100 is associated with a column address. The x11th column to the x32th column are associated with the fourth light-shielded pixel region 120-4, and the jth column to the kth column are associated with the effective pixel region 110. The column address of the pixel column used to update the correction value Sc is stored in the storage unit of the control unit 12. For example, the column address corresponding to the x11th column may be recorded as the address that is read out first when the update process of the correction value Sc is started. Also, the address corresponding to the x32nd column may be recorded as the column address that is read out last when the update process of the correction value Sc is started. When driving the solid-state imaging element 11, the photoelectric conversion device 1 controls the solid-state imaging element 11 based on the drive information including the stored column address information. Note that the read operation of the pixel signal by the solid-state imaging element 11 in this embodiment is similar to the read operation in the first embodiment shown in FIG. 4, and therefore a description thereof will be omitted.

[0059] 7 is a flowchart showing the operation of the clamp circuit 170 in the second embodiment. The clamp circuit 170 calculates a correction value Sc based on the pixel values ​​D(x11) to D(x32). The clamp circuit 170 also corrects the pixel values ​​D(j) to D(k) of the effective pixels using the correction value Sc. The calculation process of the correction value Sc in a scanning row (one pixel row) and the correction process of the pixel value D(x) will be described below.

[0060] In step S701, the clamp circuit 170 adds 1 to the count value x of the column address. In step S702, the clamp circuit 170 determines whether the count value x indicates a pixel column in the pixel array 100. Specifically, if the count value x is equal to or less than the total number of pixels k (YES in step S702), the clamp circuit 170 determines that there is a pixel signal to be read from the column circuit 140, and proceeds to step S703. On the other hand, if the count value x exceeds the total number of pixels k (NO in step S702), the clamp circuit 170 determines that the input of pixel signals from the scanning row to the clamp circuit 170 has been completed, and proceeds to step S712.

[0061] In step S703, the clamp circuit 170 determines whether the count value x corresponds to a pixel column in the effective pixel area 110. Specifically, the clamp circuit 170 compares the count value x with a column address j of the effective pixel area 110. If the count value x is less than j (NO in step S703), the clamp circuit 170 determines that the pixel signal can be used to update the correction value Sc, and proceeds to step S704. On the other hand, if the count value x is equal to or greater than j (YES in step S703), the clamp circuit 170 determines that the count value x indicates a column address in the effective pixel area 110. In other words, the clamp circuit 170 determines that the pixel signal is not used to update the correction value Sc, and proceeds to step S711.

[0062] In step S704, the clamp circuit 170 determines whether the count value x corresponds to a pixel column in the fourth light-shielded pixel region 120-4. Specifically, the clamp circuit 170 compares the count value x with column addresses x11 and x32. If the count value x corresponds to a column address between column addresses x11 and x32 (YES in step S704), the clamp circuit 170 determines that the pixel signal is used to update the correction value Sc, and proceeds to step S705. On the other hand, if the count value x does not correspond to a column address between column addresses x11 and x32 (NO in step S704), the clamp circuit 170 determines that the pixel signal is not used to update the correction value Sc, and returns to step S701.

[0063] In step S705, the clamp circuit 170 acquires the pixel value D(x) from the column circuit 140. In step S706, the clamp circuit 170 sets a parameter used to calculate the correction value. The parameter that is set is the attenuation coefficient A, as in the first embodiment. In this embodiment, the clamp circuit 170 calculates the attenuation coefficient A using the count value x as a variable. For example, the attenuation coefficient A can be calculated by the following equation (3) including column addresses x11 (x1th column) and x32 (x2th column). A = (x32-x) / (x32-x11) (3) That is, the attenuation coefficient A can be set to a different value for each pixel column using equation (3).

[0064] In step S707, the clamp circuit 170 calculates the difference value Sd using the pixel value D(x). Specifically, the clamp circuit 170 can calculate the difference value Sd based on the arithmetic expression (1) as in the first embodiment. That is, the clamp circuit 170 subtracts the target pixel value Dt and the correction value Sc(x-1) from the pixel value D(x) to obtain the difference value Sd.

[0065] In step S708, the clamp circuit 170 sequentially updates the correction value Sc(x) of the xth column based on the correction value Sc(x-1) of the (x-1)th column. Specifically, the correction value Sc(x) can be calculated based on the arithmetic expression (2) as in the first embodiment. That is, the clamp circuit 170 adds a value obtained by multiplying the difference value Sd by the attenuation coefficient A to the correction value Sc(x-1). The correction value Sc(x) calculated by the arithmetic expression (2) is set as the correction value Sc(x) based on the pixel values ​​of the light-shielded pixels 121 in the xth column.

[0066] In step S709, the clamp circuit 170 sets the correction value Sc(x) calculated in step S708 as the updated correction value Sc. In step S710, the clamp circuit 170 corrects the pixel value D(x) based on the correction value Sc updated in step S709. The clamp circuit 170 subtracts the updated correction value Sc from the pixel value D(x) and outputs the pixel value Do(x). Thereafter, the clamp circuit 170 repeats the processes of steps S701 to S710 and starts processing for the next input pixel value. After the update of the correction value based on the pixel signal from the light-shielded pixel 121 is completed, the clamp circuit 170 holds the correction value Sc last updated in step S710. Note that after the correction value is updated in step S709, the process may return to step S701 without executing step S710.

[0067] If the count value x indicates a pixel column in the effective pixel area 110 in step S703 (YES in step S703), the clamp circuit 170 acquires the pixel value D(x) of the effective pixel 111 from the column circuit 140 (step S711). Next, the clamp circuit 170 subtracts the correction value Sc from the pixel value D(x) of the effective pixel 111 (step S710). That is, the clamp circuit 170 corrects the offset of the pixel value D(x) of the effective pixel 111. After correcting the pixel value D(x), the clamp circuit 170 executes the process of step S701 again and starts processing the next input pixel value.

[0068] In step S702, if the count value x exceeds the total number of pixels k (NO in step S702), the clamp circuit 170 determines that the input of pixel signals of the scanning row is complete. In step S712, the clamp circuit 170 resets the count value x and ends the process of this flowchart. If there is a pixel row to be scanned next, the clamp circuit 170 executes the process of this flowchart again and corrects the pixel values ​​based on the correction value Sc.

[0069] According to this embodiment, different attenuation coefficients are assigned to each pixel column of light-shielded pixels. Therefore, the correction values ​​are updated with higher accuracy, and the pixel values ​​of the effective pixels can be corrected with ideal correction values. Therefore, the photoelectric conversion device according to this embodiment can more effectively suppress the problem of horizontal stripe noise caused by white spot noise and the like.

[0070] [Third embodiment] The photoelectric conversion device 1 according to the present embodiment will be described with reference to Figs. 3 and 8. This embodiment differs from the first embodiment in that a threshold value B is applied to each pixel signal from a light-shielded pixel region. The following describes the photoelectric conversion device 1 according to this embodiment, focusing on the differences from the first embodiment. The configuration of the light-shielded pixel region 120 and the signal readout operation by the solid-state imaging element 11 in this embodiment are similar to those in the first embodiment, and therefore description thereof will be omitted.

[0071] 8 is a flowchart showing the operation of the clamp circuit 170 in the third embodiment. The clamp circuit 170 calculates a correction value Sc based on the pixel values ​​D(x11) to D(x32). The clamp circuit 170 also uses the correction value Sc to correct the pixel values ​​D(j) to D(k) of the effective pixels 111. The calculation process of the correction value Sc in a scanning row (one pixel row) and the correction process of the pixel value D(x) will be described below.

[0072] In step S801, the clamp circuit 170 adds 1 to the count value x of the column address. In step S802, the clamp circuit 170 determines whether the count value x indicates a pixel column in the pixel array 100. Specifically, if the count value x is equal to or less than the total number of pixels k (YES in step S802), the clamp circuit 170 determines that there is a pixel signal to be read from the column circuit 140, and proceeds to step S803. On the other hand, if the count value x exceeds the total number of pixels k (NO in step S802), the clamp circuit 170 determines that the input of pixel signals from the scanning row to the clamp circuit 170 has been completed, and proceeds to step S817.

[0073] In step S803, the clamp circuit 170 determines whether the count value x corresponds to a pixel column in the effective pixel region 110. Specifically, the clamp circuit 170 compares the count value x with a column address j of the effective pixel region 110. If the count value x is less than j (NO in step S803), the clamp circuit 170 determines that the pixel signal can be used to update the correction value Sc, and proceeds to step S804. On the other hand, if the count value x is equal to or greater than j (YES in step S803), the clamp circuit 170 determines that the count value x indicates a column address in the effective pixel region 110. In other words, the clamp circuit 170 determines that the pixel signal is not used to update the correction value Sc, and proceeds to step S816.

[0074] In step S804, the clamp circuit 170 determines whether the count value x corresponds to a pixel column included in the first to third light-shielded pixel regions 120-1 to 120-3. Specifically, the clamp circuit 170 compares the count value x with column addresses x11 and x32. If the count value x corresponds to a column address between column addresses x11 and x32 (YES in step S804), the clamp circuit 170 determines that the pixel signal is used to update the correction value Sc, and proceeds to step S805. On the other hand, if the count value x does not correspond to a column address between column addresses x11 and x32 (NO in step S804), the clamp circuit 170 determines that the pixel signal is not used to update the correction value Sc, and returns the process to step S801.

[0075] In step S805, the clamp circuit 170 obtains the pixel value D(x) from the column circuit 140. In step S806, the clamp circuit 170 determines whether the count value x corresponds to a pixel column in the first light-shielded pixel region 120-1. Specifically, the clamp circuit 170 compares the count value x with the column address x12. If the count value x is equal to or smaller than the column address x12 (YES in step S806), the clamp circuit 170 determines that the pixel signal corresponds to a light-shielded pixel in the first light-shielded pixel region 120-1, and proceeds to step S808. On the other hand, if the count value x is greater than the column address x12 (NO in step S806), the clamp circuit 170 determines that the pixel signal corresponds to a light-shielded pixel other than the first light-shielded pixel region 120-1, and proceeds to step S807.

[0076] In step S807, the clamp circuit 170 determines whether the count value x corresponds to a pixel column in the second shaded pixel region 120-2. Specifically, the clamp circuit 170 compares the count value x with the column address x22. If the count value x is equal to or less than the column address x22 (YES in step S807), the clamp circuit 170 determines that the pixel signal corresponds to a shaded pixel in the second shaded pixel region 120-2, and proceeds to step S809. On the other hand, if the count value x is greater than the column address x22 (NO in step S807), the clamp circuit 170 determines that the pixel signal corresponds to a shaded pixel other than the second shaded pixel region 120-2, and proceeds to step S810.

[0077] In step S808, the clamp circuit 170 sets a parameter used to calculate the correction value. In this embodiment, the parameter that is set is a threshold B that is used to determine whether or not to update the correction value. For example, the clamp circuit 170 may be configured not to update the correction value of a shaded pixel when the pixel value of the shaded pixel exceeds the absolute value of the set threshold. The clamp circuit 170 may also be configured not to update the correction value of the shaded pixel when the absolute value of the difference value exceeds the set threshold. In this embodiment, the threshold B for the difference value is set. The clamp circuit 170 sets a threshold B1 corresponding to the first shaded pixel region 120-1, and the process proceeds to step S811.

[0078] In step S809, the clamp circuit 170 sets the threshold B2 corresponding to the second light-shielded pixel region 120-2 as the threshold B, and proceeds to step S811. In step S810, the clamp circuit 170 sets the threshold B3 corresponding to the third light-shielded pixel region 120-3 as the threshold B, and proceeds to step S811. In this embodiment, a separate threshold B is set for each of the first to third light-shielded pixel regions 120-1 to 120-3. Specifically, the thresholds are set so that B1>B2>B3. As an example, the thresholds can be set to B1=128 [LSB], B2=64 [LSB], and B3=32 [LSB].

[0079] In step S811, the clamp circuit 170 calculates the difference value Sd using the pixel value D(x). Specifically, the clamp circuit 170 may calculate the difference value Sd based on the arithmetic expression (1) as in the first embodiment. That is, the clamp circuit 170 subtracts the target pixel value Dt and the correction value Sc(x-1) from the pixel value D(x) to obtain the difference value Sd.

[0080] In step S812, the clamp circuit 170 compares the difference value Sd with a threshold value B. If the absolute value of the difference value Sd is less than the threshold value B (YES in S812), the clamp circuit 170 determines that the pixel value D(x) is used to update the correction value Sc, and proceeds to step S813. On the other hand, if the absolute value of the difference value Sd is equal to or greater than the threshold value B (NO in S812), the clamp circuit 170 determines that the pixel value D(x) is not used to update the correction value Sc, and proceeds to step S815.

[0081] In step S813, the clamp circuit 170 sequentially updates the correction value Sc(x) of the xth column based on the correction value Sc(x-1) of the (x-1)th column. Specifically, the clamp circuit 170 adds the difference value Sd to the correction value Sc(x-1). That is, according to this embodiment, the correction value Sc(x) for the light-shielded pixel in the xth column can be calculated by the following arithmetic expression (4). Sc(x)=Sc(x-1)+Sd (4) The correction value Sc(x) according to the arithmetic expression (4) is set as the correction value Sc(x) based on the pixel values ​​of the light-shielded pixels 121 in the xth column.

[0082] In step S814, the clamp circuit 170 sets the correction value Sc(x) calculated in step S813 as the updated correction value Sc. In step S815, the clamp circuit 170 corrects the pixel value D(x) based on the correction value Sc updated in step S814. The clamp circuit 170 subtracts the updated correction value Sc from the pixel value D(x) and outputs the pixel value Do(x). After that, the clamp circuit 170 repeats the processes of steps S801 to S815 and starts processing for the next input pixel value. After the update of the correction value based on the pixel signal from the light-shielded pixel 121 is completed, the clamp circuit 170 holds the correction value Sc last updated in step S814. Note that after the correction value is updated in step S814, the process may return to step S801 without executing step S815. Also, if the absolute value of the difference value Sd is equal to or greater than the threshold value B (NO in S812), the process may return to step S801 without executing step S815.

[0083] If the count value x indicates a pixel column in the effective pixel area 110 in step S803 (YES in step S803), the clamp circuit 170 acquires the pixel value D(x) of the effective pixel 111 from the column circuit 140 (step S816). Next, the clamp circuit 170 subtracts the correction value Sc from the pixel value D(x) of the effective pixel 111 (step S815). That is, the clamp circuit 170 corrects the offset of the pixel value D(x) of the effective pixel 111. After correcting the pixel value D(x), the clamp circuit 170 executes the process of step S801 again and starts processing the next input pixel value.

[0084] If the count value x exceeds the total number of pixels k in step S802 (NO in step S802), the clamp circuit 170 determines that the input of pixel signals for the scanning row is complete. In step S817, the clamp circuit 170 resets the count value x and ends the process of this flowchart. If there is a pixel row to be scanned next, the clamp circuit 170 executes the process of this flowchart again and corrects the pixel values ​​based on the correction value Sc.

[0085] According to this embodiment, a different threshold value is set for each of a plurality of light-shielding pixel regions arranged in the horizontal direction. If the difference value is less than the set threshold value, the correction value is updated based on the pixel signals of the light-shielding pixels. Here, a relatively high threshold value is applied to the light-shielding pixel region scanned first, and a relatively low threshold value is applied to the light-shielding pixel region scanned later. If a pixel value exceeding the threshold value is input, the pixel value is not used to update the correction value.

[0086] By setting a relatively large threshold value in a part of the light-shielded pixel region, even if the pixel value has a large change amount due to random noise or the like, the correction value is updated based on the pixel value. Therefore, the correction using the light-shielded pixel region against random noise or the like is effectively performed. Furthermore, if there is white spot noise or the like in the light-shielded pixel region in which a relatively large threshold value is set, the correction value may be set excessively. According to the present embodiment, the correction value set excessively is gradually updated to an appropriate correction value by the update of the correction value using the light-shielded pixel region that is executed thereafter. Furthermore, pixel signals having prominent values ​​due to white spots or the like are excluded in the process of updating the correction value by the set threshold value. Therefore, peculiar pixel signals due to white spot noise or the like, pixel values ​​that are prominent compared to pixel values ​​from surrounding pixels, etc. are not reflected in the correction value. Therefore, the influence of random noise or the like can be effectively corrected, and the generation of horizontal stripe noise due to white spot noise or the like can be suppressed.

[0087] [Fourth embodiment] The photoelectric conversion device 1 according to this embodiment will be described with reference to Figs. 6 and 9. This embodiment differs from the third embodiment in that the threshold value B is changed for each column address of the column pixels to be scanned. The following describes the photoelectric conversion device 1 according to this embodiment, focusing on the differences from the third embodiment. The configuration of the light-shielded pixel region 120 in this embodiment is similar to that of the second embodiment, and therefore a description thereof will be omitted. In addition, the signal readout operation by the solid-state imaging element 11 is similar to that of the first embodiment, and therefore a description thereof will be omitted.

[0088] 9 is a flowchart showing the operation of the clamp circuit 170 in the fourth embodiment. The clamp circuit 170 calculates a correction value Sc based on the pixel values ​​D(x11) to D(x32). The clamp circuit 170 also corrects the pixel values ​​D(j) to D(k) of the effective pixels using the correction value Sc. The calculation process of the correction value Sc in a scanning row and the correction process of the pixel value D(x) will be described below.

[0089] In step S901, the clamp circuit 170 adds 1 to the count value x of the column address. In step S902, the clamp circuit 170 determines whether the count value x indicates a pixel column in the pixel array 100. Specifically, if the count value x is equal to or less than the total number of pixels k (YES in step S902), the clamp circuit 170 determines that there is a pixel signal to be read from the column circuit 140, and proceeds to step S903. On the other hand, if the count value x exceeds the total number of pixels k (NO in step S902), the clamp circuit 170 determines that the input of pixel signals from the scanning row to the clamp circuit 170 has been completed, and proceeds to step S913.

[0090] In step S903, the clamp circuit 170 determines whether the count value x corresponds to a pixel column in the effective pixel region 110. Specifically, the clamp circuit 170 compares the count value x with a column address j of the effective pixel region 110. If the count value x is less than j (NO in step S903), the clamp circuit 170 determines that the pixel signal can be used to update the correction value Sc, and proceeds to step S904. On the other hand, if the count value x is equal to or greater than j (YES in step S903), the clamp circuit 170 determines that the count value x indicates a column address in the effective pixel region 110. In other words, the clamp circuit 170 determines that the pixel signal is not used to update the correction value Sc, and proceeds to step S912.

[0091] In step S904, the clamp circuit 170 determines whether the count value x corresponds to a pixel column in the fourth light-shielded pixel region 120-4. Specifically, the clamp circuit 170 compares the count value x with column addresses x11 and x32. If the count value x corresponds to a column address between column addresses x11 and x32 (YES in step S904), the clamp circuit 170 determines that the pixel signal is used to update the correction value Sc, and proceeds to step S905. On the other hand, if the count value x does not correspond to a column address between column addresses x11 and x32 (NO in step S904), the clamp circuit 170 determines that the pixel signal is not used to update the correction value Sc, and returns to step S901.

[0092] In step S905, the clamp circuit 170 acquires the pixel value D(x) from the column circuit 140. In step S906, the clamp circuit 170 sets a parameter used to calculate the correction value. In this embodiment, the parameter that is set is the threshold B, similar to the third embodiment. The clamp circuit 170 calculates the threshold B using the count value x as a variable. For example, the threshold B can be calculated by the following arithmetic expression (5) including the maximum allowable value b and column addresses x11 and x32. B = b × (x32-x) / (x32-x11) (5) That is, the threshold B can be set to a different value for each pixel column using equation (5).

[0093] In step S907, the clamp circuit 170 calculates the difference value Sd using the pixel value D(x). Specifically, the clamp circuit 170 can calculate the difference value Sd based on the above-mentioned arithmetic expression (1) in the same manner as in the first embodiment. That is, the clamp circuit 170 subtracts the target pixel value Dt and the correction value Sc(x-1) from the pixel value D(x) to obtain the difference value Sd.

[0094] In step S908, the clamp circuit 170 compares the difference value Sd with a threshold value B. If the absolute value of the difference value Sd is less than the threshold value B (YES in S908), the clamp circuit 170 determines that the pixel value D(x) is used to update the correction value Sc, and proceeds to step S909. On the other hand, if the absolute value of the difference value Sd is equal to or greater than the threshold value B (NO in S908), the clamp circuit 170 determines that the pixel value D(x) is not used to update the correction value Sc, and proceeds to step S911.

[0095] In step S909, the clamp circuit 170 sequentially updates the correction value Sc(x) of the xth column based on the correction value Sc(x-1) of the (x-1)th column. Specifically, the clamp circuit 170 may calculate the correction value Sc(x) based on the above-mentioned arithmetic expression (4) similarly to the third embodiment. That is, the clamp circuit 170 may calculate the correction value Sc(x) by adding the difference value Sd calculated in step S907 to the correction value Sc(x-1). The correction value Sc(x) based on the arithmetic expression (4) is set as the correction value Sc(x) based on the pixel value of the light-shielded pixel 121 of the xth column.

[0096] In step S910, the clamp circuit 170 sets the correction value Sc(x) calculated in step S909 as the updated correction value Sc. In step S911, the clamp circuit 170 corrects the pixel value D(x) based on the correction value Sc updated in step S910. The clamp circuit 170 subtracts the correction value Sc from the pixel value D(x) and outputs the pixel value Do(x). After that, the clamp circuit 170 repeats the processes of steps S901 to S911 and starts the process for the next input pixel value. After the update of the correction value based on the pixel signal from the light-shielded pixel 121 is completed, the clamp circuit 170 holds the correction value Sc last updated in step S909. Note that after the correction value is updated in step S910, the process may return to step S901 without executing step S911. Also, if the absolute value of the difference value Sd is equal to or greater than the threshold value B (NO in S908), the process may return to step S901 without executing step S911.

[0097] If the count value x indicates a pixel column in the effective pixel area 110 in step S903 (YES in step S903), the clamp circuit 170 acquires the pixel value D(x) of the effective pixel 111 from the column circuit 140 (step S912). Next, the clamp circuit 170 subtracts the correction value Sc from the pixel value D(x) of the effective pixel 111 (step S911). That is, the clamp circuit 170 corrects the offset of the pixel value D(x) of the effective pixel 111. After correcting the pixel value D(x), the clamp circuit 170 executes the process of step S901 again and starts processing the next input pixel value.

[0098] In step S902, if the count value x exceeds the total number of pixels k (NO in step S902), the clamp circuit 170 determines that the input of pixel signals of the scanning row is complete. In step S913, the clamp circuit 170 resets the count value x and ends the process of this flowchart. If there is a pixel row to be scanned next, the clamp circuit 170 executes the process of this flowchart again and corrects the pixel values ​​based on the correction value Sc.

[0099] According to this embodiment, different threshold values ​​are assigned to each pixel column of light-shielded pixels. Therefore, the pixel values ​​of the light-shielded pixels are selected for updating the correction value with higher accuracy, and the pixel values ​​of the effective pixels are corrected by the ideal correction value. Therefore, the photoelectric conversion device according to this embodiment can more effectively suppress the problem of horizontal stripe noise caused by white spot noise and the like.

[0100] [Fifth embodiment] A device according to a fifth embodiment of the present disclosure will be described with reference to Fig. 10. Fig. 10 is a block diagram showing an example of the configuration of a device according to the fifth embodiment.

[0101] The photoelectric conversion device in the above-described embodiment can be applied to various devices. Examples of the devices include digital still cameras, digital camcorders, camera heads, copiers, fax machines, mobile phones, vehicle-mounted cameras, observation satellites, and surveillance cameras. Fig. 10 shows a block diagram of a digital still camera as an example of the device.

[0102] The device shown in FIG. 10 includes a barrier 706, a lens 702, an aperture 704, an imaging device (an example of a photoelectric conversion device) 700, a signal processing unit 708, a timing generating unit 720, an overall control / calculation unit (control device) 718, a memory unit (storage device) 710, a recording medium control I / F unit 716, a recording medium 714, and an external I / F unit 712. At least one of the barrier 706, the lens 702, and the aperture 704 is an optical device corresponding to the device. The barrier 706 protects the lens 702, and the lens 702 forms an optical image of a subject on the imaging device 700. The aperture 704 varies the amount of light that passes through the lens 702. The imaging device 700 is configured as in the above-mentioned embodiment, and converts the optical image formed by the lens 702 into image data (image signal). Here, it is assumed that an AD (analog-digital) conversion unit is formed on a semiconductor substrate of the imaging device 700. The signal processing unit 708 performs various corrections and compresses the data on the imaging data output from the imaging device 700. That is, the signal processing unit 708 can be a signal processing device that processes the image signal output from the photoelectric conversion device.

[0103] The timing generating unit 720 outputs various timing signals to the imaging device 700 and the signal processing unit 708. The overall control and calculation unit 718 controls the entire digital still camera, and the memory unit 710 temporarily stores image data. The recording medium control I / F unit 716 is an interface for recording or reading image data to or from the recording medium 714, which is a removable recording medium such as a semiconductor memory for recording or reading imaging data. The external I / F unit 712 is an interface for communicating with an external computer or the like. Timing signals and the like may be input from outside the device. The photoelectric conversion system 7 may further include a display device (monitor, electronic viewfinder, etc.) that displays information obtained by the photoelectric conversion device. The device includes at least a photoelectric conversion device. Furthermore, the device includes at least one of an optical device, a control device, a processing device, a display device, a storage device, and a mechanical device that operates based on information obtained by the photoelectric conversion device. The mechanical device is a movable part (for example, a robot arm) that operates by receiving a signal from the photoelectric conversion device.

[0104] In this embodiment, the imaging device 700 and the AD conversion unit are provided on different semiconductor substrates, but the imaging device 700 and the AD conversion unit may be formed on the same semiconductor substrate. Also, the imaging device 700 and the signal processing unit 708 may be formed on the same semiconductor substrate.

[0105] Moreover, each pixel may include a plurality of photoelectric conversion units. The signal processing unit 708 may be configured to process a pixel signal based on the charge generated in the first photoelectric conversion unit and a pixel signal based on the charge generated in the second photoelectric conversion unit, and to acquire distance information from the imaging device 700 to the subject.

[0106] [Sixth embodiment] FIG. 11(a) and FIG. 11(b) are block diagrams of devices related to a vehicle-mounted camera in the sixth embodiment. The device 8 is one aspect of the photoelectric conversion system in this embodiment, and has an imaging device (an example of a photoelectric conversion device) 800 of the above-mentioned embodiment. The device 8 has an image processing unit 801 that performs image processing on a plurality of image data acquired by the imaging device 800, and a parallax calculation unit 802 that calculates parallax (phase difference of parallax images) from a plurality of image data acquired by the device 8. The device 8 also has a distance measurement unit 803 that calculates a distance to an object based on the calculated parallax, and a collision determination unit 804 that determines whether or not there is a possibility of collision based on the calculated distance. Here, the image processing unit 801 can be a signal processing device that processes an image signal output from the photoelectric conversion device. The parallax calculation unit 802 and the distance measurement unit 803 are examples of distance information acquisition means that acquire distance information to an object. That is, the distance information is information on the parallax, the defocus amount, the distance to the object, and the like. The collision determination unit 804 may determine the possibility of a collision using any of these pieces of distance information. The distance information acquisition means may be realized by dedicated hardware, or may be realized by a software module. In addition, it may be realized by an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or a combination of these.

[0107] The device 8 is connected to a vehicle information acquisition device 810, and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. In addition, the device 8 is connected to a control ECU 820, which is a control device that outputs a control signal to generate a braking force for the vehicle based on the judgment result of the collision judgment unit 804. In addition, the device 8 is also connected to an alarm device 830 that issues an alarm to the driver based on the judgment result of the collision judgment unit 804. For example, when the judgment result of the collision judgment unit 804 indicates that there is a high possibility of a collision, the control ECU 820 performs vehicle control to avoid a collision and reduce damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 830 warns the user by sounding an alarm such as a sound, displaying alarm information on a screen of a car navigation system, etc., and applying vibrations to a seat belt or steering wheel. The device 8 functions as a control means that controls the operation of controlling the vehicle as described above.

[0108] In this embodiment, the surroundings of the vehicle, for example the front or rear, are imaged by the device 8. FIG. 11(b) shows the device when imaging the area in front of the vehicle (imaging range 850). A vehicle information acquisition device 810 as an imaging control means sends instructions to the device 8 or the imaging device 800 to perform the operations described in the first to fifth embodiments. With this configuration, the accuracy of distance measurement can be further improved.

[0109] Although the above describes an example of control to prevent collision with other vehicles, the present invention can also be applied to control of automatic driving by following other vehicles, control of automatic driving to prevent deviation from lanes, etc. Furthermore, the device is not limited to vehicles such as automobiles, but can be applied to moving bodies (moving devices) such as ships, aircraft, artificial satellites, industrial robots, and consumer robots. In addition, the present invention can be applied to devices that use object recognition or biometric recognition, such as intelligent transport systems (ITS) and surveillance systems, in addition to moving bodies.

[0110] [Other embodiments] The present disclosure is not limited to the above-mentioned embodiments, and various modifications are possible. For example, an example in which a part of the configuration of any of the embodiments is added to another embodiment, or an example in which a part of the configuration of another embodiment is replaced with another embodiment is also an embodiment of the present disclosure. For example, the first embodiment and the third embodiment may be combined, and the attenuation coefficient A and the threshold value B may be set for each of the multiple light-shielded pixel regions 120. Also, the second embodiment and the fourth embodiment may be combined, and the attenuation coefficient A and the threshold value B may be set for each pixel column (column address). Also, instead of the difference value Sd, the pixel value of the light-shielded pixel may be compared with the absolute value of a predetermined threshold value, and if the pixel value exceeds the absolute value of the predetermined threshold value, the correction value in the light-shielded pixel may not be updated.

[0111] The disclosure of this specification includes the following configurations. (Configuration 1) a pixel array including a plurality of pixels arranged in a matrix, the plurality of pixels including effective pixels that output signals in response to incident light, and light-shielding pixels having a light-shielding member; a calculation unit that calculates a correction value based on the pixel values ​​of the light-shielded pixels; a correction unit that corrects pixel values ​​of the effective pixels based on the correction value; Equipped with a pixel row of the pixel array includes a first light-shielding pixel, a second light-shielding pixel, and the effective pixel; the calculation unit calculates the correction value using parameters different from each other for the first light-shielding pixel and the second light-shielding pixel in the pixel row, Photoelectric conversion device. (Configuration 2) 2. The photoelectric conversion device according to configuration 1, wherein the pixel row includes a pixel region having a plurality of the first light-shielding pixels and a pixel region having a plurality of the second light-shielding pixels. (Configuration 3) 3. The photoelectric conversion device according to configuration 1 or 2, wherein the correction unit corrects an offset of the pixel value of the effective pixel based on the correction value. (Configuration 4) 4. The photoelectric conversion device according to any one of configurations 1 to 3, wherein the calculation unit sequentially receives the pixel values ​​of the light-shielded pixels in the pixel row, and updates the correction value for each light-shielded pixel. (Configuration 5) the calculation unit updates the correction value calculated based on the pixel value of the first light-shielding pixel based on the pixel value of the second light-shielding pixel; the correction unit corrects the pixel values ​​of the valid pixels included in the pixel row using the updated correction values. 5. The photoelectric conversion device according to configuration 4. (Configuration 6) the pixel value of the second light-shielding pixel is input to the calculation unit after the pixel value of the first light-shielding pixel; the pixel value of the effective pixel is input to the correction unit after the pixel value of the second light-shielded pixel is input to the calculation unit; The photoelectric conversion device according to configuration 4 or 5. (Configuration 7) the parameter is a damping rate for damping a difference between the correction value before and after the update, the attenuation rate for updating the correction value at the second light-shielded pixel is greater than the attenuation rate for updating the correction value at the first light-shielded pixel; 7. The photoelectric conversion device according to configuration 6. (Configuration 8) 8. The photoelectric conversion device according to configuration 6 or 7, wherein when the pixel value of the light-shielded pixel exceeds an absolute value of a predetermined threshold, the calculation unit does not update the correction value for the light-shielded pixel. (Configuration 9) the parameter is the threshold, 9. The photoelectric conversion device according to configuration 8, wherein an absolute value of the threshold in the second light-shielded pixel is smaller than an absolute value of the threshold in the first light-shielded pixel. (Configuration 10) When the pixel value of the light-shielding pixel in the xth column of the pixel row is D(x), the correction value of the light-shielding pixel in the xth column is Sc(x), the correction value of the light-shielding pixel in the (x-1)th column is Sc(x-1), the target pixel value is Dt, the parameter is a coefficient A, and the difference value is Sd, the correction value Sc(x) is Sd = D(x) - Dt - Sc(x-1) Sc(x)=Sc(x-1)+Sd×A It is calculated based on the formula: 10. The photoelectric conversion device according to claim 6. (Configuration 11) The parameter is a coefficient A, the coefficient A when the light shielding pixel in the xth column is the first light shielding pixel is greater than the coefficient A when the light shielding pixel in the xth column is the second light shielding pixel; 11. The photoelectric conversion device according to configuration 10. (Configuration 12) 12. The photoelectric conversion device according to configuration 10 or 11, wherein when the absolute value of the difference value exceeds a predetermined threshold, the calculation unit does not update the correction value for the light-shielded pixel. (Configuration 13) the parameter is the threshold, the threshold value in the second light-shielded pixel is smaller than the threshold value in the first light-shielded pixel; 13. The photoelectric conversion device according to configuration 12. (Configuration 14) When the light-shielding pixels are arranged in the x1-th column to the x2-th column in the pixel row, the coefficient A of the light-shielding pixel in the x-th column is expressed as follows: A=(x2-x) / (x2-x1) It is calculated based on the formula: 14. The photoelectric conversion device according to any one of configurations 11 to 13. (Configuration 15) In the pixel row, the light-shielding pixels are arranged from the x1-th column to the x2-th column, and the maximum value of the threshold is represented by b. The threshold B of the light-shielding pixel in the x-th column is expressed as follows: B = b × (x2-x) / (x2-x1) It is calculated based on the formula: 14. The photoelectric conversion device according to claim 13. (Configuration 16) a pixel array including a plurality of pixels arranged in a matrix, the plurality of pixels including effective pixels that output signals in response to incident light, and light-shielding pixels having a light-shielding member; a calculation unit that calculates a correction value based on the pixel values ​​of the light-shielded pixels; a correction unit that corrects pixel values ​​of the effective pixels based on the correction value; Equipped with a pixel row of the pixel array includes a pixel region having a plurality of the effective pixels, a pixel region having a plurality of first light-shielding pixels, and a pixel region having a plurality of second light-shielding pixels; the calculation unit calculates the correction value using parameters different from each other for the first light-shielding pixel and the second light-shielding pixel in the pixel row, Photoelectric conversion device. (Configuration 17) The photoelectric conversion device according to any one of configurations 1 to 16, a signal processing device that processes an image signal output from the photoelectric conversion device; A photoelectric conversion system comprising: (Configuration 18) The photoelectric conversion system according to configuration 17, wherein the signal processing device processes the image signals generated by the plurality of photoelectric conversion devices, respectively, and obtains distance information from the photoelectric conversion devices to a subject. (Method 1) A signal processing method for a signal output from a pixel array including a plurality of pixels arranged in a matrix, the plurality of pixels including effective pixels that output a signal corresponding to incident light, and light-shielding pixels having a light-shielding member, one pixel row of the pixel array including a first light-shielding pixel, a second light-shielding pixel, and the effective pixel, the method comprising: A calculation process of a correction value based on the pixel values ​​of the light-shielded pixels; a correction process for correcting the pixel values ​​of the effective pixels based on the correction value; having The calculation process is a process of calculating the correction value using parameters different from each other for the first light-shielded pixel and the second light-shielded pixel in the pixel row. Signal processing methods.

[0112] The present disclosure can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) for implementing one or more of the functions.

[0113] It should be noted that the above-mentioned embodiments are merely examples of the implementation of the present disclosure, and the technical scope of the present disclosure should not be interpreted as being limited by these embodiments. In other words, the present disclosure can be implemented in various forms without departing from its technical concept or main features. [Explanation of symbols]

[0114] 1...Photoelectric conversion device 11...Solid-state image sensor 110...effective pixel area 111...effective pixels 120...Light-shielding pixel area 121…Light-shielding pixel 170...Clamp circuit

Claims

1. a pixel array including a plurality of pixels arranged in a matrix, the plurality of pixels including effective pixels that output signals in response to incident light and light-shielding pixels having a light-shielding member; a calculation unit that calculates a correction value based on the pixel values ​​of the light-shielded pixels; a correction unit that corrects pixel values ​​of the effective pixels based on the correction value; Equipped with a pixel row of the pixel array includes a first light-shielding pixel, a second light-shielding pixel, and the effective pixel; the calculation unit calculates the correction value using parameters different from each other for the first light-shielded pixel and the second light-shielded pixel in the pixel row; the correction unit corrects an offset of the pixel value of the effective pixel based on the correction value. Photoelectric conversion device.

2. The photoelectric conversion device according to claim 1 , wherein the pixel row includes a pixel region having a plurality of the first light-shielding pixels and a pixel region having a plurality of the second light-shielding pixels.

3. A pixel array including a plurality of pixels arranged in a matrix, the plurality of pixels including effective pixels that output signals in response to incident light and light-shielding pixels having a light-shielding member; a calculation unit that calculates a correction value based on the pixel values ​​of the light-shielded pixels; a correction unit that corrects pixel values ​​of the effective pixels based on the correction value; Equipped with a pixel row of the pixel array includes a first light-shielding pixel, a second light-shielding pixel, and the effective pixel; the calculation unit calculates the correction value using parameters different from each other for the first light-shielded pixel and the second light-shielded pixel in the pixel row; the calculation unit sequentially inputs the pixel values ​​of the light-shielded pixels in the pixel row and updates the correction value for each light-shielded pixel. Photoelectric conversion device.

4. the calculation unit updates the correction value calculated based on the pixel value of the first light-shielding pixel based on the pixel value of the second light-shielding pixel; the correction unit corrects the pixel values ​​of the valid pixels included in the pixel row using the updated correction values. The photoelectric conversion device according to claim 3 .

5. the pixel value of the second light-shielded pixel is input to the calculation unit after the pixel value of the first light-shielded pixel; the pixel values ​​of the effective pixels are input to the correction unit after the pixel values ​​of the second light-shielded pixels are input to the calculation unit. The photoelectric conversion device according to claim 3 .

6. the parameter is an attenuation rate for attenuating a difference between the correction value before updating and the correction value after updating, the attenuation rate for updating the correction value in the second light-shielded pixel is greater than the attenuation rate for updating the correction value in the first light-shielded pixel; The photoelectric conversion device according to claim 5 .

7. The photoelectric conversion device according to claim 5 , wherein when the pixel value of the light-shielded pixel exceeds an absolute value of a predetermined threshold, the calculation unit does not update the correction value for the light-shielded pixel.

8. the parameter is the threshold, The photoelectric conversion device according to claim 7 , wherein the absolute value of the threshold value in the second light-shielded pixel is smaller than the absolute value of the threshold value in the first light-shielded pixel.

9. When the pixel value of the light-shielded pixel in the x-th column of the pixel row is represented by D(x), the correction value of the light-shielded pixel in the x-th column is represented by Sc(x), the correction value of the light-shielded pixel in the (x-1)-th column is represented by Sc(x-1), the target pixel value is represented by Dt, the parameter is represented by a coefficient A, and the difference value is represented by Sd, the correction value Sc(x) is Sd=D(x)-Dt-Sc(x-1) Sc(x)=Sc(x-1)+Sd×A It is calculated based on the formula The photoelectric conversion device according to claim 5 .

10. The parameter is a coefficient A, the coefficient A when the light-shielding pixel in the xth column is the first light-shielding pixel is greater than the coefficient A when the light-shielding pixel in the xth column is the second light-shielding pixel; The photoelectric conversion device according to claim 9 .

11. The photoelectric conversion device according to claim 9 , wherein when the absolute value of the difference value exceeds a predetermined threshold, the calculation unit does not update the correction value for the light-shielded pixel.

12. the parameter is the threshold, the threshold value of the second light-shielded pixel is smaller than the threshold value of the first light-shielded pixel; The photoelectric conversion device according to claim 11 .

13. When the plurality of light-shielding pixels are arranged from the x1-th column to the x2-th column in the pixel row, the coefficient A for the light-shielding pixel in the x-th column is expressed as follows: A=(x2-x) / (x2-x1) It is calculated based on the formula The photoelectric conversion device according to claim 10.

14. In the pixel row, when the plurality of light-shielding pixels are arranged from the x1-th column to the x2-th column and the maximum value of the threshold is represented by b, the threshold B for the light-shielding pixel in the x-th column is B=b×(x2-x) / (x2-x1) It is calculated based on the formula The photoelectric conversion device according to claim 12 .

15. The photoelectric conversion device according to any one of claims 1 to 14, a signal processing device that processes an image signal output from the photoelectric conversion device; A photoelectric conversion system comprising:

16. A photoelectric conversion device; a signal processing device that processes an image signal output from the photoelectric conversion device; and The photoelectric conversion device is a pixel array including a plurality of pixels arranged in a matrix, the plurality of pixels including effective pixels that output signals in response to incident light and light-shielding pixels having a light-shielding member; a calculation unit that calculates a correction value based on the pixel values ​​of the light-shielded pixels; a correction unit that corrects pixel values ​​of the effective pixels based on the correction value; Equipped with a pixel row of the pixel array includes a first light-shielding pixel, a second light-shielding pixel, and the effective pixel; the calculation unit calculates the correction value using parameters different from each other for the first light-shielded pixel and the second light-shielded pixel in the pixel row; The signal processing device processes the image signals generated by the plurality of photoelectric conversion devices, and acquires distance information from the photoelectric conversion devices to a subject. A photoelectric conversion system comprising:

17. A signal processing method for a signal output from a pixel array including a plurality of pixels arranged in a matrix, the plurality of pixels including effective pixels that output a signal in response to incident light, and light-shielding pixels having a light-shielding member, wherein one pixel row of the pixel array includes a first light-shielding pixel, a second light-shielding pixel, and the effective pixel, the method comprising: A calculation process of a correction value based on the pixel values ​​of the light-shielded pixels; a correction process for correcting the pixel values ​​of the effective pixels based on the correction value; and the calculation process is a process of calculating the correction value using parameters different from each other for the first light-shielded pixel and the second light-shielded pixel in the pixel row, the correction process is a process of correcting an offset of the pixel value of the effective pixel based on the correction value. Signal processing methods.

18. A signal processing method for a signal output from a pixel array including a plurality of pixels arranged in a matrix, the plurality of pixels including effective pixels that output a signal according to incident light and light-shielding pixels having a light-shielding member, one pixel row of the pixel array including a first light-shielding pixel, a second light-shielding pixel, and the effective pixel, comprising: A calculation process of a correction value based on the pixel values ​​of the light-shielded pixels; a correction process for correcting the pixel values ​​of the effective pixels based on the correction value; and The arithmetic processing calculating the correction value using parameters different from each other for the first light-shielded pixel and the second light-shielded pixel in the pixel row; The pixel values ​​of the light-shielded pixels in the pixel row are input in order, and the correction value is updated for each light-shielded pixel. A signal processing method.

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