JP2012075050A - Solid-state imaging element, imaging device, and black level decision method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state imaging element capable of eliminating an OB (optical black) level difference by a configuration entirely different from the conventional art.SOLUTION: A solid-state imaging element has: a plurality of effective pixel pairs arranged two-dimensionally, each consisting of two effective pixels 51 and 52 arranged so as to be adjacent to each other; and at least one OB pixel group including OB pixels 53 and 54 for detecting a black reference level of an imaged image signal, and provided so as to correspond to the plurality of effective pixel pairs aligned in the same row. In the OB pixels 53 and 54 included in the OB pixel group, configuration for element regions 53a and 54a formed at positions corresponding to photoelectric conversion regions 51a and 52a of the effective pixels 51 and 52 included in the effective pixel pair, is different from each other for all the OB pixels 53 and 54.

Description

  The present invention relates to a solid-state imaging device, an imaging apparatus, and a black level determination method.

  In a solid-state imaging device such as a CCD image sensor or a CMOS image sensor, a light shielding film is disposed on a semiconductor substrate provided with a number of effective pixels in a two-dimensional array via an upper film, and this light shielding film corresponds to each effective pixel. The light is incident on the photodiodes (photoelectric conversion elements) of each effective pixel from the openings provided in this manner, so that signal charges corresponding to the amount of incident light are generated in each photodiode, and the captured image signal is obtained by reading this signal charge. To get.

  In such an image sensor, generally, an OB (optical black) pixel for obtaining a black reference level (black level) as a reference for determining a luminance level of a captured image signal is provided separately from an effective pixel. ing.

  In general, an OB pixel provided in a conventional image sensor has a configuration in which a photodiode is formed by a process similar to that of a photodiode of an effective pixel, and a light receiving portion of the photodiode is shielded by a light shielding film shared with the effective pixel. Yes.

  However, when the OB pixel is formed by such a method, the effective pixel and the OB pixel have different effects on the photodiode depending on the presence or absence of the light shielding film (that is, the presence or absence of the opening). In some cases, a characteristic step (OB step) may occur with the photodiode.

  Patent Document 1 describes a method of forming an OB pixel without ion implantation in a region of the OB pixel corresponding to the photodiode of the effective pixel, and Patent Document 2 describes an impurity of the photodiode of the OB pixel. Although a method for changing a profile from an effective pixel is described, even with these methods, there is a possibility that an OB level difference may occur due to manufacturing variation or the like.

  When an OB level difference occurs, an error occurs in the black level that is actually required, resulting in an unnatural image.

  As a method of eliminating the OB step, a method of changing the impurity concentration between the effective pixel and the OB pixel (see Patent Document 3) and a method of changing the photodiode area between the effective pixel and the OB pixel (see Patent Document 4) have been proposed. However, even with these methods, the OB step cannot be completely eliminated because of manufacturing variations.

JP 2009-164295 A JP 2006-344888 A Japanese Patent Laying-Open No. 2005-340338 JP 2005-223133 A

  The present invention provides a solid-state image pickup device capable of preventing image quality deterioration caused by OB steps with a configuration completely different from the above-described conventional technology, an image pickup apparatus including the same, and a black level determination method using the solid-state image pickup device. The purpose is to do.

  The solid-state imaging device of the present invention is an effective pixel pair composed of two effective pixels arranged adjacent to each other, and includes a plurality of effective pixel pairs arranged in a two-dimensional manner, and a black reference level of a captured image signal An OB pixel group including a plurality of OB pixels for detecting a pixel, and includes at least one OB pixel group provided corresponding to the plurality of effective pixel pairs arranged in the same row, and is included in the OB pixel group In the plurality of OB pixels, the configuration of the element region formed at a position corresponding to the photoelectric conversion region of the effective pixel included in the effective pixel pair is not the same in all the OB pixels.

  The imaging apparatus of the present invention uses the solid-state imaging device and a signal output from the OB pixel group of the solid-state imaging device, and a black level of a signal obtained from the effective pixel pair corresponding to the OB pixel group. And a black level determination unit for determining

  The black level determination method of the present invention uses a signal output from the OB pixel group of the solid-state image sensor to determine a black level of a signal obtained from the effective pixel pair corresponding to the OB pixel group. A level determination step is provided.

  According to the present invention, a solid-state imaging device capable of preventing image quality deterioration due to an OB step with a configuration completely different from the above-described prior art, an imaging device including the same, and a black level determination method using the solid-state imaging device Can be provided.

The figure which shows schematic structure of the imaging device for describing one Embodiment of this invention 1 is a schematic plan view showing a schematic configuration of the solid-state imaging device 5 in the imaging apparatus 100 shown in FIG. The figure which showed the output level in the dark of the effective pixels 51 and 52 and the output level of the OB pixels 53 and 54 in the solid-state imaging device shown in FIG. The figure which showed the equivalent circuit of the effective pixel pair and OB pixel group corresponding to this in the solid-state image sensor shown in FIG. The figure which shows the dark level output level contained in the effective addition signal among the picked-up image signals output from the solid-state image sensor 5 at the time of addition mode. The figure which shows the output level of the OB addition signal among the picked-up image signals output from the solid-state image sensor 5 at the time of addition mode. FIG. 2 is a schematic plan view showing a schematic configuration of a solid-state image sensor 5 ′ which is a modification of the solid-state image sensor 5 mounted on the image pickup apparatus 100 shown in FIG. 1. FIG. 7 is an equivalent circuit diagram of the OB pixel group of the solid-state imaging device 5 ′ illustrated in FIG. 7. A figure that summarizes the black level obtained for each processing performed by the image processing unit The figure which shows the modification of the equivalent circuit diagram shown in FIG. A figure that summarizes the black level obtained for each processing performed by the image processing unit

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an imaging apparatus for explaining an embodiment of the present invention. Examples of the imaging device include an imaging device such as a digital camera and a digital video camera, an imaging module mounted on an electronic endoscope, a camera-equipped mobile phone, and the like.

  The imaging system of the imaging apparatus 100 shown in FIG. 1 includes a photographic lens system 1, a diaphragm 2, a mechanical shutter 3, a CMOS (Complementary Metal Oxide Semiconductor) type solid-state imaging device 5, and an analog / digital (AD) conversion unit 6. With.

  A diaphragm 2 is disposed on the back of the photographing lens system 1, and the photographing lens system 1 and the diaphragm 2 constitute a photographing optical system.

  A mechanical shutter 3 is disposed on the back of the diaphragm 2, and a CMOS solid-state imaging device 5, which will be described in detail later, is disposed on the back of the mechanical shutter 3. A picked-up image signal corresponding to the subject light image incident on the light-receiving surface of the solid-state image pickup device 5 through the photographing lens system 1 and the diaphragm 2 in this order is output from the solid-state image pickup device 5 and converted into digital data by the AD converter 6. And output to the bus 17.

  The bus 17 includes a central control unit (CPU) 7 that performs overall control of the entire imaging apparatus 100, an operation unit 16 that includes operation buttons including a shutter release button, and a DSP 7 that is instructed by the CPU 7. An image processing unit 9 that performs image processing on the captured image signal based on the captured image signal, a video encoder 15 that converts captured image data obtained by performing image processing on the captured image signal, and conversion by the video encoder 15 A driver 13 that displays the captured image data on the display unit 14, a memory 10 that temporarily stores the captured image signal output from the solid-state imaging device 5, the captured image data generated by the image processing unit 9, and the like, and media control The recording medium (memory card) 11 is detachably attached to the media control unit 12.

  A device control unit 8 is connected to the CPU 7. The device control unit 8 performs drive control of the solid-state imaging device 5 according to an instruction from the CPU 7, performs aperture amount adjustment control of the diaphragm 2, performs opening / closing control of the mechanical shutter 3, and performs focus position control of the photographing lens system 1. Perform zoom position control.

  FIG. 2 is a schematic plan view showing a schematic configuration of the solid-state imaging element 5 in the imaging apparatus 100 shown in FIG.

  The solid-state imaging device 5 includes effective pixels 51 and 52 for detecting subject light arranged in the effective pixel region, and a black level of a captured image signal output from the solid-state imaging device 5 arranged in the OB pixel region. A plurality of pixels including OB pixels 53 and 54, a vertical scanning circuit 55, a horizontal scanning circuit 56, and a control unit 57.

  All the pixels included in the solid-state imaging device 5 are two-dimensionally arranged in the column direction Y on the surface of the semiconductor substrate and the row direction X orthogonal thereto. All the pixels are arranged in such a manner that lines of n pixels (n is a natural number of 2 or more) arranged at a constant pitch in the row direction X are arranged at a constant pitch in the column direction Y.

  Among the plurality of lines, the odd-numbered lines are arranged so as to be shifted in the row direction X by ½ of the row-direction X arrangement pitch of each pixel of each line with respect to the even-numbered lines.

  The odd-numbered line includes an effective pixel 51 and an OB pixel 53, and one OB pixel 53 is arranged at the right end of this line. The even-numbered line includes effective pixels 52 and OB pixels 54, and one OB pixel 54 is arranged at the right end of this line.

  Such an arrangement can be obtained by arranging the effective pixels 52 and the OB pixels 54 at positions that are obliquely shifted by 45 ° to the lower left with respect to the effective pixels 51 and the OB pixels 53 arranged in a square lattice pattern.

  All effective pixels included in the solid-state imaging device 5 have substantially the same configuration (design values are the same). With substantially the same configuration, the size of a photoelectric conversion region (for example, a photodiode in a semiconductor substrate) included in an effective pixel is substantially the same, and the opening size of a light shielding film formed above the photoelectric conversion region is also substantially the same. It means that there is.

  As described above, the effective pixel region of the solid-state imaging device 5 includes an effective pixel pair composed of each effective pixel 51 and the effective pixel 52 adjacent to the effective pixel 51 in the same direction (lower left diagonal in the example of FIG. 2). It is arranged in two dimensions.

  In the OB pixel area of the solid-state imaging device 5, an OB pixel group including an OB pixel 53 and an OB pixel 54 that are adjacent to each other corresponds to an effective pixel pair line including a plurality of effective pixel pairs arranged in the row direction X. Is provided.

  In the OB pixel 53, an element region having the same configuration as the photoelectric conversion region is formed at a position corresponding to the photoelectric conversion region of the effective pixels 51 and 52. That is, the OB pixel 54 has a configuration in which no opening is provided in the light shielding film above the photoelectric conversion region in the effective pixels 51 and 52.

  In the OB pixel 53, an element region having a configuration different from that of the photoelectric conversion region is formed at a position corresponding to the photoelectric conversion region of the effective pixels 51 and 52.

  The element region of the OB pixel 53 is formed by not performing ion implantation in the element region when the photoelectric conversion regions of the effective pixels 51 and 52 are formed by ion implantation into the semiconductor substrate. That is, the element region of the OB pixel 53 is a region of the semiconductor substrate in which the same photoelectric conversion region as that of the effective pixel does not exist.

  An opening is not formed in the light shielding film above the element region of the OB pixel 53 like the OB pixel 54. Except for the difference in the configuration of the element region and the presence or absence of the light shielding film opening, the OB pixel 53 and the effective pixel 51, 52 has the same configuration.

  FIG. 3 is a diagram illustrating dark output levels of the effective pixels 51 and 52 and output levels of the OB pixels 53 and 54 in the solid-state imaging device illustrated in FIG.

  As shown in FIG. 3, since the effective pixel 51 and the effective pixel 52 have the same configuration, the dark pixel output levels of the effective pixel 51 and the effective pixel 52 are the same. On the other hand, the OB pixel 54 is different from the effective pixels 51 and 52 in the configuration of the light shielding film. For this reason, the output level of the OB pixel 54 is higher than the dark output level of the effective pixels 51 and 52 (about twice in the example of FIG. 3). Further, since the OB pixel 53 has no photoelectric conversion region, its output level is almost zero.

  All pixels included in the solid-state imaging device 5 are provided with readout circuits configured by MOS circuits (not shown) corresponding to the vicinity thereof.

  FIG. 4 is a diagram showing an equivalent circuit of an effective pixel pair and an OB pixel group corresponding to the effective pixel pair in the solid-state imaging device shown in FIG. In FIG. 4, the photoelectric conversion areas of the effective pixels 51 and 52 are indicated by reference numerals 51a and 52a, and the element areas of the OB pixels 53 and 54 are indicated by reference numerals 53a and 54a.

  As shown in FIG. 4, the effective pixel pair is provided with a floating diffusion FD for accumulating charges, a source follower amplifier 60, and a reset transistor RT. A transfer transistor 51 t is connected to the photoelectric conversion region 51 a of the effective pixel 51, and a transfer transistor 52 t is connected to the photoelectric conversion region 52 a of the effective pixel 52.

  The transfer transistors 51t and 52t transfer the charges accumulated in the photoelectric conversion regions 51a and 52a to the floating diffusion FD.

  The source follower amplifier 60 outputs a signal corresponding to the potential of the floating diffusion FD to the signal output line.

  The reset transistor RT resets the potential of the floating diffusion FD.

  The equivalent circuit diagram of the OB pixel group is the same as the equivalent circuit diagram of the effective pixel pair except that the photoelectric conversion region 51a is changed to the element region 53a and the photoelectric conversion element 52a is changed to the element region 54a.

  The transfer transistor 51t, the floating diffusion FD, the reset transistor RT, and the source follower amplifier 60 constitute a readout circuit for each of the effective pixel 51 and the OB pixel 53.

  The transfer transistor 52t, the floating diffusion FD, the reset transistor RT, and the source follower amplifier 60 constitute a readout circuit for each of the effective pixel 52 and the OB pixel 54.

  Thus, in the solid-state imaging device 5, the effective pixels 51 and the effective pixels 52 of the effective pixel pair share a part of the readout circuit (the floating diffusion FD, the reset transistor RT, and the source follower amplifier 60).

  Further, the OB pixel 53 and the OB pixel 54 of the OB pixel group share a part of the readout circuit (floating diffusion FD, reset transistor RT, and source follower amplifier 60). Thereby, the occupation area per pixel is reduced and miniaturization is achieved.

  Returning to FIG. 2, the vertical scanning circuit 55 performs on / off control of the transfer transistors 51t and 52t, on / off control of the reset transistor RT, control of the source follower amplifier 60, and the like.

  The horizontal scanning circuit 56 performs driving to sequentially select one line of signals output from the source follower amplifier 60 to the signal output line and output the signals to the outside of the solid-state imaging device 5.

  The control unit 57 controls the vertical scanning circuit 55 and the horizontal scanning circuit 56 in accordance with instructions from the device control unit 8.

  The device control unit 8 illustrated in FIG. 1 adds the output signal of the effective pixel 51 of the effective pixel pair and the output signal of the effective pixel 52 and outputs the added signal to the outside of the solid-state imaging device 5, and the OB pixel 53 of the OB pixel group. The output signal and the output signal of the OB pixel 54 are added and output to the outside of the solid-state imaging device 5, and a captured image signal composed of imaging signals corresponding to all effective pixel pairs and all OB pixel groups is output from the solid-state imaging device 5. In addition readout mode to be output and non-addition readout mode in which output signals of all pixels are output without being added to the outside of the solid-state imaging device 5 and a captured image signal composed of imaging signals corresponding to all pixels is output. Then, the solid-state imaging device 5 is driven.

  In the addition mode, the device control unit 8 controls the vertical scanning circuit 55 to perform the following drive.

  That is, the charges stored in the photoelectric conversion regions 51a and 52a of the two lines including the effective pixels 51 and 52 constituting the effective pixel pair are transferred to the floating diffusion FD simultaneously or sequentially, and the element regions 53a and 52a of the two lines are also transferred. The accumulated charges 54a are transferred to the floating diffusion FD simultaneously or sequentially.

  As a result, the accumulated charges in the photoelectric conversion regions 51a and 52a are mixed by the floating diffusion FD, and the accumulated charges in the element regions 53a and 54a are mixed by the floating diffusion FD.

  Thereafter, a signal corresponding to the potential of the floating diffusion FD corresponding to each pixel of the two lines (a signal corresponding to the effective pixel pair is referred to as an effective addition signal, and a signal corresponding to the OB pixel group is referred to as an OB addition signal). The signal is output from the source follower amplifier 60 to the signal output line.

  The vertical scanning circuit 55 performs such driving while shifting the timing for each line including the effective pixels 51 and 52 constituting the effective pixel pair.

  In the non-addition mode, the device control unit 8 controls the vertical scanning circuit 55 to perform the following drive.

  That is, the charges accumulated in the photoelectric conversion region 51a and the element region 53a of each pixel in the odd-numbered line are transferred to the floating diffusion FD, and a signal corresponding to the potential of the floating diffusion FD is output from the source follower amplifier 60 to the signal output line.

  Next, after resetting the floating diffusion FD corresponding to the odd line, the accumulated charge in the photoelectric conversion region 52a and the element region 54a of each pixel of the even line is transferred to the floating diffusion FD, and the potential of the floating diffusion FD is determined. The signal is output from the source follower amplifier 60 to the signal output line.

  The vertical scanning circuit 55 sequentially performs the above driving for the subsequent lines.

  Of the imaging signals output from the solid-state imaging device 5 in the non-addition mode, signals obtained from the effective pixels 51 and 52 are referred to as effective signals, and signals obtained from the OB pixels 53 and 54 are referred to as OB signals.

  The image processing unit 9 illustrated in FIG. 1 performs image processing on a captured image signal output from the solid-state imaging device 5 and subjected to AD conversion, and generates captured image data. This image processing includes processing for correcting the black level of the effective signal or the effective addition signal included in the captured image signal.

  In the addition mode, the image processing unit 9 determines the level of the OB addition signal as the black level as it is, and determines the black level from the effective addition signal obtained from the effective pixel pair corresponding to the OB pixel group that has obtained the OB addition signal. The black level is corrected by subtracting.

  FIG. 5 is a diagram illustrating the dark output level included in the effective addition signal among the captured image signals output from the solid-state imaging device 5 in the addition mode.

  As shown in FIG. 5, in the addition mode, since the dark output level of the effective pixel 51 and the dark output level of the effective pixel 52 are added, the dark output level included in the effective addition signal is the non-addition mode. This is twice the dark output level included in the time effective signal.

  FIG. 6 is a diagram illustrating the output level of the OB addition signal among the captured image signals output from the solid-state imaging device 5 in the addition mode.

  In the addition mode, the output level of the OB pixel 53 and the output level of the OB pixel 54 are added. As shown in FIG. 6, the output level of the OB pixel 53 is zero, and the output level of the OB pixel 54 is twice the dark output level of the effective pixels 51 and 52. For this reason, the output level of the OB addition signal is the same as the dark output level included in the effective addition signal.

  Therefore, in the addition mode, the image processing unit 9 can accurately correct the black level of the effective addition signal by subtracting the OB addition signal from the effective addition signal.

  On the other hand, in the non-addition mode, the image processing unit 9 calculates the average of the levels of the two OB signals respectively obtained from the OB pixels 53 and 54 of the OB pixel group, and determines the calculated average value as the black level.

  As can be seen from FIGS. 5 and 6, the level of the OB signal obtained from the OB pixel 54 is twice the dark output level included in the effective signal. For this reason, if the OB signal is set to the black level, the black level correction of the effective signal cannot be performed accurately.

  Further, since the level of the OB signal obtained from the OB pixel 53 is zero, the black level of the effective signal cannot be accurately corrected even if the OB signal is set to the black level.

  The average value of the OB signal obtained from the OB pixel 53 and the OB signal obtained from the OB pixel 54 (the value obtained by adding both together and divided by 2) is the same as the dark output level included in the effective signal.

  Therefore, in the non-addition mode, the black level correction can be performed accurately by determining the average value of the two OB signals obtained from the OB pixel group as the black level.

  As described above, the level difference between the dark output levels of the effective pixels 51 and 52 included in the effective pixel pair and the output level of the OB pixel 54 included in the OB pixel group (here, the dark pixel output of the effective pixels). In the addition mode, the dark output level and the OB addition signal included in the effective addition signal are set so that the output level of the OB pixel 53 is substantially zero. The difference from the output level can be eliminated, and image quality deterioration can be prevented.

  Further, in the non-addition mode, it is possible to obtain almost the same level as the dark output level included in the effective signal only by calculating the average of the output level of the OB pixel 54 and the output level of the OB pixel 53, and the image quality deterioration is reduced. Can be prevented.

  According to the solid-state imaging device 5, since the OB pixel 53 and the OB pixel 54 are configured differently and the output levels of the OB pixels 53 and 54 are different from each other, for example, The output levels that can be acquired from the OB pixel group are 0, (0 + 2) / 2 = 1, and 0 + 2 = 2, and three types of OB levels can be obtained.

  On the other hand, when the OB pixel 53 and the OB pixel 54 have the same configuration and both output levels are the same, for example, when the output level of each of the OB pixels 53 and 54 is 2, the output that can be acquired from the OB pixel group The level is 2, (2 + 2) / 2 = 2, 2 + 2 = 4, and only two types of OB levels can be obtained.

  Therefore, when the OB level of the effective pixel pair does not match these two types of OB levels, the OB level difference cannot be eliminated, and the probability that the OB level difference can be eliminated decreases, leading to a decrease in yield. According to the imaging apparatus of the present embodiment, since three types of OB levels can be created, the possibility that an OB level that matches the OB level of an effective pixel pair can be increased, and a decrease in yield can be prevented. Become.

  In the above description, a configuration for obtaining three types of OB levels has been described, but a configuration for obtaining four or more types of OB levels can correspond to more OB steps. Below, the modification of the solid-state image sensor 5 is demonstrated.

  FIG. 7 is a schematic plan view illustrating a schematic configuration of a solid-state imaging element 5 ′ that is a modification of the solid-state imaging element 5 mounted on the imaging apparatus 100 illustrated in FIG. 1.

  In the solid-state imaging device 5 ′ shown in FIG. 7, two OB pixels 61 and 63 are arranged on the right end of each odd-numbered line and on the left side thereof, and two OB pixels on the right end of each even-numbered line and on the left side thereof. Except for the arrangement of 62 and 64, the configuration is the same as that shown in FIG.

  The solid-state imaging device 5 ′ has a configuration in which an OB pixel group including the OB pixels 61 to 64 is provided corresponding to one effective pixel pair line.

  The OB pixel 61 has the same configuration as the OB pixel 53 shown in FIG. The OB pixels 62 to 64 have the same configuration as the OB pixel 54 shown in FIG.

  FIG. 8 is an equivalent circuit diagram of the OB pixel group of the solid-state imaging device 5 ′ illustrated in FIG. 7. In FIG. 8, element regions of the OB pixels 61 to 64 are indicated by reference signs A to D, respectively.

  The configuration of the readout circuit for each pixel of the solid-state imaging device 5 'is the same as that shown in FIG.

  That is, the equivalent circuit diagram of the pair of the OB pixel 61 and the OB pixel 62 is obtained by changing the element region 53a of the equivalent circuit diagram of the OB pixel group in FIG. The element region 54a is changed to the element region B.

  Further, the equivalent circuit diagram of the pair of the OB pixel 63 and the OB pixel 64 is obtained by changing the element region 53a of the equivalent circuit diagram of the OB pixel group in FIG. 4 to the element region C, and replacing the equivalent circuit diagram of the OB pixel group in FIG. The element region 54a is changed to the element region D.

  The image processing unit 9 of the imaging device 100 equipped with the solid-state imaging device 5 'determines a black level using a signal output from the OB pixel group, and performs black level correction using the black level.

  Specifically, the image processing unit 9 calculates the average of the first process of determining the output signal of the element region A as it is as the black level, the average of the output signal of the element region A and the output signal of the element region C. A second process for determining the value as a black level, a third process for determining the sum signal of the output signal of the element region A and the output signal of the element region B as a black level, the output signal of the element region A and the element region B Fourth process for calculating the average of the addition signal of the output signal, the output signal of the element region C and the addition signal of the output signal of the element region D, and determining this average value as the black level, the output signal of the element region C And a fifth process of determining the sum signal of the output signals of the element region D as a black level.

  At the time of shipment of the imaging apparatus 100, a setting is made by the manufacturer so as to perform any two of these processes.

  FIG. 9 shows black level values determined in the above-described processes when the output level of the element region A is 0 and the output levels of the element regions B to D are 2.

  In the first process, the black level is “0”. In the second process, the black level is “1” as a result of the calculation of (0 + 2) ÷ 2. In the third process, the black level is “2” as a result of the calculation of (0 + 2). In the fourth process, the black level is “3” as a result of the calculation of {(0 + 2) + (2 + 2)} / 2. In the fifth process, the black level is “4” as a result of the calculation of (2 + 2).

  When performing the first process and the second process, the device control unit 8 drives the solid-state imaging device 5 ′ in the non-addition mode. When performing the third to fifth processes, the device control unit 8 drives the solid-state imaging device 5 ′ in the non-addition mode or the addition mode.

  As described above, in the imaging device 100 including the solid-state imaging device 5 ′, the black level determination method can be changed depending on the content of the processing performed by the image processing unit 9. For this reason, even when there is an individual difference in the solid-state image pickup device 5 ′, an appropriate black level can be determined by changing the content of processing in accordance with the individual solid-state image pickup device 5 ′. 100 can be manufactured efficiently.

  For example, when the imaging apparatus 100 is manufactured, dark imaging is performed in the addition mode and the non-addition mode using the solid-state imaging device 5 ′, and the dark output level and the effective addition included in the effective signal obtained by the dark imaging. Get the dark output level included in the signal.

  Then, among the processes performed by the image processing unit 9, a process that obtains the black level closest to the acquired dark output level is selected. For example, the processing that can determine the black level close to the dark output level included in the effective signal acquired in the non-addition mode is the second processing, and is close to the dark output level included in the effective addition signal acquired in the addition mode. It is assumed that the process that can determine the black level is the third process.

  In this case, the manufacturer performs setting so that the image processing unit 9 performs the second process in the non-addition mode and performs the third process in the addition mode.

  Thus, by manufacturing the imaging device 100 using the solid-state imaging device 5 ′, the dark output level included in the effective signal and the effective addition signal output from the solid-state imaging device 5 ′ is unknown, Even when there is an individual difference in the image sensor 5 ′, an appropriate black level can be determined.

  Note that the configuration of the element regions of the OB pixels included in the OB pixel group of the solid-state imaging device 5 ′ need not be the same in all the element regions as described in the description of the solid-state imaging device 5. This is because if all the element regions are the same, the black level cannot be determined with a fine step size even if the first to fifth processes are performed. Since the black level can be determined with a small step size, it is possible to deal with so many OB steps, leading to an improvement in yield.

  As shown in FIG. 10, by providing three or more types of OB pixels having different element region configurations in the OB pixel group, a finer black level can be determined.

  FIG. 10 is a diagram showing a modification of the equivalent circuit diagram shown in FIG. The equivalent circuit diagram shown in FIG. 10 is the same as that shown in FIG. 8 except that the element region C is changed to the element region C ′. In the element region C ′, ion implantation is performed, but the concentration is lower than the impurity concentration of the element regions B and D.

  In the case of the configuration shown in FIG. 10, the image processing unit 9 performs first processing for determining the output signal of the element region A as a black level as it is, the average of the output signal of the element region A and the output signal of the element region C ′. The second process of calculating and determining this average value as the black level, the third process of determining the output signal of the element region C ′ as the black level as it is, the output signal of the element region A and the output signal of the element region B A fourth process for determining the addition signal as a black level; an addition signal of the output signal of the element region A and the output signal of the element region B; and an addition signal of the output signal of the element region C ′ and the output signal of the element region D A fifth process for calculating the average and determining this average value as the black level, and a sixth process for determining the sum signal of the output signal of the element region C ′ and the output signal of the element region D as the black level can be performed. is there.

  Here, assuming that the output level of the element region C ′ is 1, the value of the black level determined by the above-described processes is as shown in FIG.

  In the first process, the black level is “0”. In the second process, the black level is “0.5” as a result of the calculation of (0 + 1) ÷ 2. In the third process, the black level is “1”. In the fourth process, the black level is “2” as a result of the calculation of (0 + 2). In the fifth process, the black level is “2.5” as a result of the calculation of {(0 + 2) + (1 + 2)} / 2. In the sixth process, the black level is “3” as a result of the calculation (2 + 1).

  As described above, by including three or more element regions having different configurations in the OB pixel group, a finer black level can be determined.

  In the solid-state imaging device shown in FIGS. 2 and 7, the number of OB pixel groups provided for the effective pixel pair line is not limited to one and may be two or more. When two or more OB pixel groups are provided, the average of the black level determined using the OB signal or the OB addition signal obtained from each OB pixel group is calculated, and this average is used as the final black level. That's fine.

  In the solid-state imaging device shown in FIGS. 2 and 7, one readout circuit may be provided for every pixel. In this case, in the non-addition mode, the valid signal and the OB signal are read out from all the pixels by shifting the timing for each line, and in the addition mode, the effective signal and the OB signal are read out from all the pixels by shifting the timing for each line. Thereafter, the image processing unit 9 may generate an effective addition signal by adding two effective signals obtained from the effective pixel pair.

  Further, the solid-state imaging device shown in FIGS. 2 and 7 is not limited to the MOS type, but may be a CCD type.

  Even in the case of the CCD type, it is possible to add the charges of the effective pixels 51 and 52 of the effective pixel pair in the solid-state imaging device by using the line memory and the horizontal charge transfer path. For this reason, in the addition mode, either a method of directly outputting an effective addition signal from the solid-state imaging device or a method of obtaining an effective addition signal by adding the effective signal output from the solid-state imaging device by the image processing unit 9 is adopted. Can do.

  The black level is determined by the image processing unit based on the digital signal. However, the black level may be determined using a captured image signal before AD conversion. Further, a block for determining the black level may be provided inside the solid-state imaging device.

  As described above, the following items are disclosed in this specification.

  The disclosed solid-state imaging device includes an effective pixel pair including two effective pixels arranged adjacent to each other, and a plurality of effective pixel pairs arranged in a two-dimensional manner, and a black reference level of a captured image signal An OB pixel group including a plurality of OB pixels for detecting a pixel, and includes at least one OB pixel group provided corresponding to the plurality of effective pixel pairs arranged in the same row, and is included in the OB pixel group In the plurality of OB pixels, the configuration of the element region formed at a position corresponding to the photoelectric conversion region of the effective pixel included in the effective pixel pair is not the same in all the OB pixels.

  In the disclosed solid-state imaging device, the plurality of OB pixels included in the OB pixel group outputs a level lower than the dark output level of the effective pixel, and the dark output level of the effective pixel. Including those that output at a high level.

  The disclosed solid-state imaging device is an OB pixel that does not have the photoelectric conversion region at a position corresponding to the photoelectric conversion region of the effective pixel, and outputs a level lower than the dark output level of the effective pixel. What outputs a higher level than the dark output level of the effective pixel is an OB pixel in which the photoelectric conversion region exists at a position corresponding to the photoelectric conversion region of the effective pixel.

  In the disclosed solid-state imaging device, the difference in configuration of the element regions of the plurality of OB pixels included in the OB pixel group is obtained by a difference in impurity concentration in the element regions.

  In the disclosed solid-state imaging device, the OB pixel group includes three or more types of OB pixels having different element region configurations.

  In the disclosed solid-state imaging device, the solid-state imaging device is a MOS type, and the two effective pixels included in the effective pixel pair read out a signal corresponding to the charge generated in the photoelectric conversion region of the effective pixel A part of the circuit is shared, and the OB pixel group includes at least one pair of the two OB pixels having the same arrangement as the two effective pixels. In the two OB pixels included, a part of the readout circuit that reads a signal corresponding to the electric charge generated in the element region of the OB pixel is shared.

  The disclosed imaging apparatus uses the solid-state imaging device and a signal output from the OB pixel group of the solid-state imaging device, and a black level of a signal obtained from the effective pixel pair corresponding to the OB pixel group. And a black level determination unit for determining

  In the disclosed imaging device, the black level determination unit adds an output signal of the two effective pixels of the effective pixel pair to generate a captured image signal, and the two effective pixels of the effective pixel pair. The black level determination method is changed in a non-addition mode in which a captured image signal is generated without adding pixel output signals.

  The disclosed black level determination method uses a signal output from the OB pixel group of the solid-state imaging device to determine a black level of a signal obtained from the effective pixel pair corresponding to the OB pixel group. A level determination step is provided.

  In the disclosed black level determination method, in the black level determination step, an addition mode in which output signals of the two effective pixels of the effective pixel pair are added to generate a captured image signal; The black level determination method is changed in the non-addition mode in which the captured image signal is generated without adding the output signals of the two effective pixels.

5 Solid-state image sensor 51, 52 Effective pixel 53, 54 OB pixel 51a, 52a Photoelectric conversion area 53a, 54a Element area

Claims (10)

An effective pixel pair composed of two effective pixels arranged adjacent to each other, and a plurality of effective pixel pairs arranged two-dimensionally;
An OB pixel group including a plurality of OB pixels for detecting a black reference level of a captured image signal, and at least one OB pixel group provided corresponding to the plurality of effective pixel pairs arranged in the same row. Prepared,
The plurality of OB pixels included in the OB pixel group have the same configuration of element regions formed in positions corresponding to the photoelectric conversion regions of the effective pixels included in the effective pixel pair in all the OB pixels. Not a solid-state image sensor. The solid-state imaging device according to claim 1,
The plurality of OB pixels included in the OB pixel group output a level lower than the dark output level of the effective pixel and output a level higher than the dark output level of the effective pixel And a solid-state imaging device. The solid-state imaging device according to claim 2,
What outputs a level lower than the dark output level of the effective pixel is an OB pixel in which the photoelectric conversion region does not exist at a position corresponding to the photoelectric conversion region of the effective pixel,
A solid-state imaging device that outputs a level higher than the dark output level of the effective pixel is an OB pixel in which the photoelectric conversion region exists at a position corresponding to the photoelectric conversion region of the effective pixel. The solid-state image sensor according to any one of claims 1 to 3,
The solid-state imaging device in which a difference in configuration of the element regions of the plurality of OB pixels included in the OB pixel group is obtained by a difference in impurity concentration of the element regions. The solid-state image sensor according to any one of claims 1 to 4,
The OB pixel group is a solid-state imaging device including three or more types of OB pixels having different element region configurations. The solid-state imaging device according to any one of claims 1 to 5,
The solid-state image sensor is a MOS type;
The two effective pixels included in the effective pixel pair share a part of a readout circuit that reads a signal corresponding to the charge generated in the photoelectric conversion region of the effective pixel,
The OB pixel group includes at least one pair of the two OB pixels that are arranged in the same arrangement as the two effective pixels.
In the pair, a solid-state imaging device in which a part of a readout circuit that reads a signal corresponding to the electric charge generated in the element region of the OB pixel is shared by the two OB pixels included in the pair. A solid-state imaging device according to any one of claims 1 to 6,
An imaging apparatus comprising: a black level determination unit that determines a black level of a signal obtained from the effective pixel pair corresponding to the OB pixel group using a signal output from the OB pixel group of the solid-state imaging element. The imaging apparatus according to claim 7,
The black level determining unit adds the output signal of the two effective pixels of the effective pixel pair and the addition mode of generating the captured image signal by adding the output signals of the two effective pixels of the effective pixel pair. An image pickup apparatus that changes the determination method of the black level in a non-addition mode that generates a picked-up image signal.   A black level of a signal obtained from the effective pixel pair corresponding to the OB pixel group is determined using a signal output from the OB pixel group of the solid-state imaging device according to claim 1. A black level determination method comprising a black level determination step. The black level determination method according to claim 9,
In the black level determination step, an addition mode in which output signals of the two effective pixels of the effective pixel pair are added to generate a captured image signal, and output signals of the two effective pixels of the effective pixel pair are added. A black level determination method that changes the determination method of the black level in a non-addition mode in which a captured image signal is generated.

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