JP2015181221A - Imaging device, defective pixel detection method, program, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an appropriate detection method of a defective pixel, in an imaging element where a plurality of pixels including a pixel memory are arranged.SOLUTION: An imaging device includes an imaging element where a plurality of pixels, each including a photoelectric conversion unit performing photoelectric conversion, a charge holding unit for holding the charges stored in the photoelectric conversion unit, and a floating diffusion unit for converting the charges into a voltage, are arranged, and a defect detector for detecting the defect of the pixel of an imaging element. The defect detector at least detects a first defective pixel due to the defect of the charge holding unit, from a plurality of pixels, and detects the positional information of the first defective pixel.

Description

  The present invention relates to a technique for detecting defective pixels in an imaging apparatus.

  An imaging device such as a CMOS image sensor mounted on an imaging device such as an electronic camera has a pixel array in which a plurality of pixels are arranged in the row and column directions. Many electronic cameras in recent years are equipped with an image pickup device having a pixel array including millions to tens of millions of pixels. It is very difficult to always produce an image sensor in which all the pixels in the pixel array generate an appropriate signal according to the amount of incident light, and each individual image sensor usually does not operate normally. “Defective pixels” are included.

  On the other hand, in the inspection of the manufacturing process of the imaging device, the image signal output at the standard accumulation time is evaluated for each pixel under a predetermined condition, and a pixel exceeding a predetermined output signal level is detected as a defective pixel. ing. Further, for each defective pixel, the data of the type (black scratch, white scratch, etc.), address (horizontal direction coordinate x, vertical direction coordinate y), and output signal level are acquired and stored in the memory unit. According to this method, the imaging apparatus refers to the address stored in the memory unit, and corrects the image signal output from the defective pixel by the interpolation calculation process using the image signal of the surrounding normal pixels. be able to. Image quality degradation can be suppressed by correcting defective pixels.

  In addition, after the imaging device is shipped, when the imaging device receives a shooting instruction from the user, the imaging device is in real time based on the difference between the image signal level output from each pixel and the image signal level of the surrounding pixels. There is a method of detecting defective pixels and storing them in a memory unit. Also by this method, the imaging apparatus can correct the image signal output from the defective pixel by using the image signal of the surrounding normal pixel by referring to the address stored in the memory unit.

  Here, it is conceivable that a defective pixel is generated because a large dark current is generated according to the temperature and accumulation time, or the pixel itself is not formed properly and an appropriate signal is not output. These phenomena occur every time shooting is performed under the same shooting conditions.

  On the other hand, a CMOS image sensor has been proposed in which a global electronic shutter drive is possible by providing a pixel memory inside a pixel of an image sensor as in Patent Document 1, for example. Specifically, a pixel of the image sensor includes a photodiode (hereinafter also referred to as PD), a floating diffusion (hereinafter also referred to as FD), and a pixel memory for temporarily holding electric charges provided therebetween. Including. Further, a reset unit is provided that can collectively reset PDs of all pixels. According to this configuration, it is possible to perform global electronic shutter driving by resetting the PD to all the pixels at once in the image sensor surface and then transferring the signal charges accumulated in the PD to the pixel memory all at once. It becomes. Reading is performed by sequentially transferring the signal charges held in the pixel memory for each row.

JP 2002-064751 A

  By the way, when the PD is defective, the component of the dark current generated during the signal charge accumulation time (PD accumulation time) is added to the appropriate signal charge of the pixel. On the other hand, when the pixel memory has a defect, the dark current component generated in the pixel memory is added to the appropriate signal charge of the pixel during the time for holding the signal charge in the pixel memory (pixel memory holding time). In the image sensor provided with the pixel memory, the normal pixel in which the pixel does not include a defect, the defective pixel due to the PD, the defective pixel due to the pixel memory, and the defective pixel including both the PD and the pixel memory are defective. May occur.

  The PD accumulation time and the pixel memory retention time vary depending on the accumulation time set at the time of shooting, the shooting mode, and the like. However, the conventional defective pixel detection method does not consider where the defective portion is in the image sensor provided with the pixel memory. In other words, when the storage time and shooting mode at the time of shooting differ from the conditions for inspection of the manufacturing process of the imaging device, “overcorrection” that corrects pixels that do not require correction, or defective pixels that should be corrected cannot be corrected. There is a risk that the “correction residue” may easily occur. Over-correction and remaining correction cause image quality degradation.

  Therefore, it is not appropriate to simply apply a conventional defective pixel detection method in an image sensor including a pixel memory, and it is desirable to detect a defective pixel after specifying a defective portion of the defective pixel.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an appropriate defective pixel detection method in an image sensor in which a plurality of pixels including a pixel memory are arranged.

  An imaging apparatus according to the present invention includes a plurality of pixels each including a photoelectric conversion unit that performs photoelectric conversion, a charge holding unit that holds charges accumulated in the photoelectric conversion unit, and a floating diffusion unit that converts charges into voltage. And a defect detection means for detecting a defect of a pixel of the image pickup element, wherein the defect detection means includes a first defect caused by a defect of the charge holding unit from at least the plurality of pixels. And detecting position information of the first defective pixel.

  According to the present invention, it is possible to appropriately detect defective pixels in an imaging device in which a plurality of pixels including a pixel memory are arranged.

1 is a block diagram illustrating an overall configuration of an imaging apparatus according to an embodiment of the present invention. The figure which shows typically the structure of the image pick-up element in one Embodiment of this invention. The figure which shows typically the structure of the pixel in one Embodiment of this invention. 1 is an equivalent circuit diagram of an image sensor according to an embodiment of the present invention. The timing chart of the 1st defective pixel detection drive in the 1st example. The flowchart of the 1st defective pixel detection drive in a 1st Example. The timing chart of the 2nd defective pixel detection drive in the 2nd example. The timing chart of the 3rd defective pixel detection drive in the 3rd example. The timing chart of the 4th defective pixel detection drive in the 4th example. Sectional drawing which shows the structure of the pixel in 5th Embodiment typically. FIG. 10 is an equivalent circuit diagram of an image sensor according to the fifth embodiment.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a system block diagram of the entire imaging apparatus according to an embodiment of the present invention. In FIG. 1, a CMOS image sensor 101 receives an optical image formed by an optical system (not shown). An analog front end (hereinafter also referred to as AFE) 102 performs reference level adjustment (clamp processing) and analog-digital conversion processing. A digital front end (hereinafter also referred to as DFE) 103 receives a digital output of each pixel and performs digital processing such as image signal correction and pixel rearrangement. The digital signal processing unit 104 performs development processing and defective pixel interpolation processing on the digital output from the DFE 103. The memory unit 105 is a working memory for the digital signal processing unit 104, and is also used as a buffer memory in continuous shooting or the like. Further, in the present embodiment, the memory unit 105 stores defective pixel data such as a pixel having a defect in the PD, an address of a pixel having a defect in the pixel memory, and an output signal level. The control unit 106 comprehensively controls the entire imaging apparatus and incorporates a known CPU or the like. The operation unit 107 electrically accepts an operation on an operation member in a digital still camera or the like. The display unit 108 displays an image or the like. The recording unit 109 is specifically a recording medium such as a memory card or a hard disk. A timing generation circuit (hereinafter also referred to as TG) 110 generates various timing signals for driving the image sensor 101.

  FIG. 2 is a diagram illustrating a configuration of the imaging element 101 in the imaging apparatus according to the present embodiment. As shown in FIG. 2, the image sensor 101 includes a pixel unit 201, a vertical scanning unit 202, a reading unit 203, and a horizontal scanning unit 204. The pixel unit 201 has a plurality of unit pixels arranged in a matrix and receives an optical image formed by an optical system (not shown). The vertical scanning unit 202 sequentially selects a plurality of rows of the pixel unit 201, and the horizontal scanning unit 204 sequentially selects a plurality of columns of the pixel unit 201. Thereby, a plurality of pixels in the pixel unit 201 are selected in order. The reading unit 203 reads the signal of the pixel selected by the vertical scanning unit 202 and the horizontal scanning unit 204 and outputs the read signal to the AFE 102.

  FIG. 3 is a diagram illustrating a configuration of the pixel unit 201 in the image sensor 101. In order to make the explanation easy to understand, only the unit pixel 301 is shown, but actually, a plurality of such pixels 301 are arranged to constitute the pixel unit 201. As shown in FIG. 3, the pixel 301 in the pixel unit 201 includes a PD 303, a first transfer switch 304, a pixel memory (charge holding unit) 305, a second transfer switch 306, an FD 307, an output unit 308, a selection switch 309, and a reset switch. 310 is comprised. FD is a floating diffusion part. The layout of each component in the pixel 301 is not limited to the arrangement shown in FIG. 3 and may be arranged at an appropriate position within a range where the function is exhibited.

  FIG. 4 is an equivalent circuit diagram of the image sensor 101. For easy understanding, only the pixel 301, its signal output path, and the readout unit 203 are shown.

  The PD 303 functions as a photoelectric conversion unit that receives incident light and generates and accumulates signal charges corresponding to the amount of received light. The first transfer switch 304 is driven by the transfer pulse signal φTX1 and transfers the charge generated in the PD 303 to the pixel memory 305. The pixel memory 305 is configured to hold the charge transferred from the PD 303. The second transfer switch 306 is driven by the transfer pulse signal φTX2 and transfers the charge held in the pixel memory 305 to the FD 307. The FD 307 is configured to hold the charge transferred from the pixel memory 305.

  The reset switch 310 is driven by a reset pulse signal φRES and has a configuration capable of supplying the reference potential SVDD to the FD 307. The FD 307 functions as a charge-voltage converter that holds the transferred charge and converts the held charge into a voltage signal. The output unit 308 amplifies the voltage signal based on the electric charge held in the FD 307 and outputs it as a pixel signal. Here, as an example, a source follower circuit using a MOS transistor and a constant current source 401 is shown. The selection switch 309 is driven by the vertical selection pulse signal φSEL, and the signal output from the output unit 308 is output to the vertical signal line 402. The signal output to the vertical signal line 402 is sampled by the readout unit 203 for each column, and further output to the AFE 102.

  The read unit 203 includes read switches 403, 404, and 405, signal holding units 406, 407, and 408, and signal transfer switches 409, 410, and 411. The read switches 403, 404, and 405 are driven by read pulse signals φS 2, φS 1, and φN, respectively, and the signals output to the vertical signal lines 402 are sampled by the signal holding units 406, 407, and 408, respectively. The signal transfer switches 409, 410, and 411 are driven by the horizontal selection pulse signal φH, and sequentially output the signals sampled in the signal holding units 406, 407, and 408 to the AFE as N signals, S1 signals, and S2 signals, respectively. . In addition to the above configuration, the reading unit 203 may include a buffer amplifier for amplifying a signal.

  Next, four types of embodiments of the defective pixel detection (defect detection) driving method applied to the above-described imaging apparatus will be described with reference to FIGS.

(First embodiment)
In the first defective pixel detection drive in the first embodiment, it is possible to detect a defective pixel caused by the PD and a defective pixel caused by the pixel memory in one scan. The defective pixel is detected by accumulating charges in each pixel in a state where the pixel is shielded from light.

  FIG. 5 is a timing chart of the first defective pixel detection drive. In order to make the explanation easy to understand, signal pulses from the nth row to the (n + 2) th row are shown.

  A period 501 is a reset period, and signal pulses φTX1, φTX2, φRES, and φSEL are applied to all the rows in the pixel portion 201. In the reset period 501, the charges of the PD 303 and the pixel memory 305 are discharged, and the potential of the FD 307 is reset to the reference potential SVDD. A period 502 is an accumulation period of the nth row. At the time of defective pixel detection driving, in order to detect the charge amplified by the dark current, the image sensor is put in a light shielding state at least in the accumulation period of each row. The light shielding state may be shielded by a light shielding member such as a shutter (not shown), or an imaging device may be arranged in a dark room or a light shielded box. In addition, it is desirable that the accumulation period 502 is set to a long time of 1 second or more as a condition that a dark current is likely to be generated. In the accumulation period 502, charges generated by dark current continue to be accumulated in the PD 303 and the pixel memory 305.

  A period 503 is a vertical readout period of the n-th row, the vertical selection pulse signal φSEL is applied, and the selected n-th row signal is read out to the reading unit 203. In the period 504, the reset pulse signal φRES is applied, and the potential of the FD 307 is reset to the reference potential SVDD. In the period 505, the readout pulse signal φN is applied and a noise signal corresponding to the voltage of the FD 307 after being reset is sampled in the readout unit 203 as an N signal.

  In the period 506, the transfer pulse signal φTX2 is applied, and the charge generated in the pixel memory 305 in the accumulation period 502 is transferred to the FD 307 (transfer state). At the same time, the readout pulse signal φS1 is applied to the readout unit 203. At this time, a signal obtained by adding the generated charge in the pixel memory 305 to the N signal is sampled as the S1 signal. In the period 506, the transfer pulse signal φTX1 is set to a low level (the first transfer switch 304 is in an off state: a non-transfer state), so that the charge generated in the PD 303 is not transferred and remains accumulated in the PD 303.

  In the period 507, transfer pulse signals φTX1 and φTX2 are applied at the same time, and charges generated in the PD 303 in the accumulation period 502 are transferred to the FD 307 all at once. At the same time, the readout pulse signal φS2 is applied to the readout unit 203. At this time, a signal obtained by adding the charge generated in the PD 303 to the S1 signal is sampled as the S2 signal.

  A period 508 is a horizontal readout period of the n-th row, a horizontal selection pulse φH is applied, and each signal sampled by the readout unit 203 is sequentially output to the AFE.

  Here, a difference (S1-N) signal between the N signal sampled in the period 505 and the S1 signal sampled in the period 506 is a signal corresponding to the charge of the dark current generated in the pixel memory 305 during the accumulation period. It is. Therefore, whether or not the pixel is a defective pixel caused by the pixel memory 305 is determined based on the output signal level of the (S1-N) signal. A difference (S2-S1) signal between the S1 signal sampled in the period 506 and the S2 signal sampled in the period 507 is a signal corresponding to the dark current charge generated in the PD 303 during the accumulation period. Therefore, whether or not the pixel is a defective pixel due to the PD is determined based on the output signal level of the (S2-S1) signal.

  This difference processing may be performed by the AFE 102, the DFE 103, the digital signal processing unit 104, or the like, for example. Alternatively, the difference processing may be performed inside the reading unit 203 and output to the AFE 102.

  When the horizontal reading period 508 of the n-th row ends, the (n + 1) -th and (n + 2) -th rows are scanned, and reading is sequentially performed in the same manner as the n-th row.

  By the way, in the period 501, the reset operation is performed on all the rows in the pixel portion 201. However, since the scanning for reading is performed in the row order, the n + 1-th row is compared with the n-th accumulation period 502. The accumulation period 509 is longer. Further, the time required to read one row becomes longer (vertical reading period 503 + horizontal reading period 508) as the accumulation period 510 of the (n + 2) th row is longer than the accumulation period 510 of the (n + 1) th row. The accumulation period is longer by that amount.

  The difference in the accumulation period for each row may be ignored by setting the length of the entire accumulation period to be sufficiently longer than the time required for reading one row. Or when determining whether it is a defective pixel from an output signal level, you may correct | amend an output signal level for every line, for example. Alternatively, a different threshold value may be set for each row as a determination threshold value to be compared with the output signal level. FIG. 6 is a flowchart showing the flow of the first defective pixel detection driving process.

  When determining that the defective pixel detection process should be started, the control unit 106 first sets detection conditions for detecting defective pixels such as ISO sensitivity and accumulation time (S601). In the defective pixel detection drive, the purpose is mainly to detect a defective pixel amplified by a dark current. For this reason, the detection conditions set here are such that the dark current is more likely to occur, the accumulation time is set to a long time of 1 second or longer, and the ambient temperature is set to a high temperature such as 40 ° C. to 60 ° C. It is desirable that

  Next, the control unit 106 controls each unit to drive the image sensor as described in FIG. 5 under the detection condition set in step 601 to obtain each signal of the N signal, the S1 signal, and the S2 signal. (S602).

  Subsequently, the digital signal processing unit 104 determines whether each pixel includes a defect in the PD 303 or the pixel memory 305 based on the signals (S1-N) and (S2-S1). (S603). The difference processing for acquiring the (S1-N) signal and the (S2-S1) signal can be performed by the AFE 102, the DFE 103, or the digital signal processing unit 104. The defective pixel determination method calculates, for example, a difference in signal level between the target pixel and the surrounding pixels, and determines that the target pixel is a defective pixel when the difference is equal to or greater than a predetermined value. Further, for example, the determination may be made by comparing a threshold value set in advance according to the detection condition and the output signal level.

  The control unit 106 records the defective pixel data such as the PD 303, the pixel memory 305, each address (position information), and the output signal level detected in S603 in the memory unit 105 (S604), and ends the defective pixel detection process. To do. By recording not only the address of the defective pixel but also the output signal level as the defective pixel data, it is possible to correct the defective pixel more appropriately according to the photographing conditions.

  As described above, in the first defective pixel detection drive, the defective pixel caused by the PD 303 and the defective pixel caused by the pixel memory 305 are detected by one scan of the image sensor 101, and these defective pixel data are detected. Can be saved. In the imaging apparatus, by referring to the address stored in the memory unit at the time of shooting, the image signal output from the defective pixel can be corrected appropriately according to the accumulation time and shooting mode at the time of shooting.

(Second embodiment)
In the second defective pixel detection driving in the second embodiment, it is possible to detect defective pixels caused by the pixel memory in one scan. In the following description, only the differences from the first defective pixel detection drive will be described.

  FIG. 7 is a timing chart of second defective pixel detection driving. For ease of explanation, only the signal pulse in the nth row is shown. Further, the same period as that in FIG. 5 is indicated by the same symbol, and detailed description is omitted.

  In FIG. 7, in the readout period 503 of the n-th row, the transfer pulse signal φTX1 is at a low level, and the first transfer switch 304 is always in an off state. In the period 701, the reset pulse signal φRES is applied, and the potential of the FD 307 is reset to the reference potential SVDD.

  In the period 702, the readout pulse signal φN is applied and a noise signal corresponding to the voltage of the FD 307 after being reset is sampled in the readout unit 203 as an N signal.

  In the period 703, the transfer pulse signal φTX2 is applied, and the charge generated in the pixel memory 305 in the accumulation period 502 is transferred to the FD 307. At the same time, the readout pulse signal φS1 is applied to the readout unit 203. At this time, a signal obtained by adding the generated charge in the pixel memory 305 to the N signal is sampled as the S1 signal. By setting the transfer pulse signal φTX1 to a low level (the first transfer switch 304 is in an off state), the charge generated in the PD 303 is not transferred and remains accumulated in the PD 303.

  Here, a difference (S1-N) signal between the N signal sampled in the period 702 and the S1 signal sampled in the period 703 is a signal corresponding to the charge of the dark current generated in the pixel memory 305 during the accumulation period. It is. Therefore, whether or not the pixel is a defective pixel due to the pixel memory can be determined based on the output signal level of the (S1-N) signal.

(Third embodiment)
In the third defective pixel detection drive in the third embodiment, defective pixels caused by the PD can be detected by one scan. In the following description, only the differences from the first defective pixel detection drive will be described.

  FIG. 8 is a timing chart of the third defective pixel detection drive. For ease of explanation, only the signal pulse in the nth row is shown. Further, the same period as that in FIG. 5 is indicated by the same symbol, and detailed description is omitted.

  In FIG. 8, in a period 801, the reset pulse signal φRES and the transfer pulse signal φTX2 are applied, the charge of the pixel memory 305 is discharged, and the FD 307 is reset to the reference potential SVDD.

  In the period 802, the readout pulse signal φN is applied and a noise signal corresponding to the voltage of the FD 307 after being reset is sampled in the readout unit 203 as an N signal.

  In the period 803, φTX1 and φTX2 are applied, and charges generated in the PD 303 in the accumulation period 502 are transferred to the FD 307. At the same time, the readout pulse signal φS2 is applied to the readout unit 203. A signal obtained by adding the charge generated in the PD 303 to the N signal is sampled as the S2 signal.

  Here, the difference (S2-N) signal between the N signal sampled in the period 802 and the S2 signal sampled in the period 803 is a signal corresponding to the charge of the dark current generated in the PD 303 during the accumulation period. . Therefore, whether or not the pixel is a defective pixel due to the PD can be determined based on the output signal level of the (S2-N) signal.

  According to the second defective pixel detection drive and the third defective pixel detection drive described above, it is possible to detect a defective pixel caused by PD and a defective pixel caused by pixel memory, respectively.

(Fourth embodiment)
FIG. 9 is a timing chart of fourth defective pixel detection driving in the fourth embodiment. The same period as that of FIG. 5 is indicated by the same symbol, and detailed description is omitted. The defective pixel detection drive of this embodiment is driven by a so-called rolling shutter system.

  In FIG. 9, a period 901 is an accumulation period of the (n + 1) th row, and a period 902 is an accumulation period of the (n + 2) th row. As shown in FIG. 9, in the fourth defective pixel detection driving, the length of the accumulation period of each row is equal by driving by the rolling shutter system. That is, in all the pixels 301 of the pixel unit 201, the time for accumulating the generated charge in the PD 303 is equal to the time for accumulating the generated charge in the pixel memory 305. Thus, when determining whether a pixel is a defective pixel from the output signal level, it is not necessary to correct the output signal level for each row. Further, it is not necessary to set a different threshold value for each row as a determination threshold value to be compared with the output signal level.

(Fifth embodiment)
Next, an example of a defective pixel detection (defect detection) driving method applied to an imaging apparatus having a configuration of the pixel unit 201 different from that of the first to fourth examples will be described with reference to FIGS. . The fifth embodiment described below is different from the first to fourth embodiments in that the photoelectric conversion unit of the pixel is formed of an organic photoelectric conversion film.

  FIG. 10 is a cross-sectional view showing a part of the configuration of the pixel portion 201 of the image sensor 101 in the fifth embodiment. In FIG. 10, the unit pixel 1001 constitutes a pixel portion 201. FIG. 10 shows a cross-sectional view of three pixels, but actually, a plurality of such pixels 1001 are arranged to constitute the pixel portion 201. The microlens 1002 further collects the light that passes through an optical system (not shown) and is imaged on the image sensor 101 for each pixel. A color filter 1003, a power supply wiring 1004, an upper electrode 1005, and an organic photoelectric conversion film 1006 are disposed below the microlens 1002. The lower electrode 1007 is provided to face the upper electrode 1005.

  In the pixel unit 201 configured in this manner, only light having a specific wavelength that is condensed by the microlens 1001 and transmitted through the color filter 1003 is photoelectrically converted by the organic photoelectric conversion film 1006 to generate a signal charge. Then, by applying a bias voltage Vbias between the upper electrode 1005 and the lower electrode 1007 and applying an electric field in the organic photoelectric conversion film 1006, the signal charge moved to the lower electrode 1007 can be extracted to the outside. It has become.

  The first pixel memory 1008 is formed on a semiconductor substrate and has a configuration capable of holding signal charges generated and taken out by the organic photoelectric conversion film 1006. Further, on the semiconductor substrate, a first transfer switch 1009, a second pixel memory 1010, a second transfer switch 1011 and a floating diffusion portion (hereinafter referred to as FD) 1012 are arranged.

  FIG. 11 is an equivalent circuit diagram of the image sensor 101 in the fifth embodiment. For easy understanding, only the pixel 1001, the signal output path, and the readout unit 203 are shown. Note that the internal configurations of the output unit 308, the selection switch 309, the reset switch 310, the constant current source 401, the vertical signal line 402, and the reading unit 203 are the same as those in FIG. To do. As described above, the fifth embodiment is different from the first to fourth embodiments in that an organic photoelectric conversion film is used as the photoelectric conversion portion.

  The organic photoelectric conversion film 1006 functions as a photoelectric conversion unit that receives incident light and generates and accumulates signal charges corresponding to the amount of received light. The first transfer switch 1009 is driven by the transfer pulse signal φTX1, and transfers the signal charge generated in the organic photoelectric conversion film 1006 and held in the first pixel memory 1008 to the second pixel memory 1010 via the lower electrode 1007. . The second pixel memory 1010 has a configuration capable of holding the charge transferred from the first pixel memory 1008. The second transfer switch 1011 is driven by the transfer pulse signal φTX2, and transfers the charge held in the second pixel memory 1010 to the FD 1012. The FD 1012 is configured to hold the charge transferred from the second pixel memory 1010.

  Here, also in the image sensor 101 of the fifth embodiment, the first to fourth defective pixel detection driving described above can be performed in the same manner as the first to fourth embodiments. For example, in the first defective pixel detection driving shown in FIG. 5, the defective pixel caused by either the organic photoelectric conversion film 1006 or the first pixel memory 1008 and the second pixel memory 1010 in one scan. Defective pixels can be detected.

  The operation when the first defective pixel detection drive shown in FIG. 5 is applied to the image sensor 101 of the fifth embodiment will be described below. Note that the imaging device is in a light-shielding state during the defective pixel detection drive. Further, during the defective pixel detection driving, the bias voltage Vbias is applied so that the charge in the organic photoelectric conversion film 1006 is transferred to the first pixel memory 1008.

  In the period 505, the readout pulse signal φN is applied, and a noise signal corresponding to the voltage of the FD 1012 after being reset in the period 504 is sampled in the readout unit 203 as an N signal.

  In the period 506, the transfer pulse signal φTX2 is applied, and a signal obtained by adding the charge generated in the second pixel memory 1010 to the N signal is sampled as the S1 signal.

  In the period 507, transfer pulse signals φTX1 and φTX2 are applied at the same time, and charges generated in the first pixel memory 1008 in the accumulation period 502 are transferred to the FD 1012 at a time. At the same time, the readout pulse signal φS2 is applied to the readout unit 203. At this time, a signal obtained by adding the charge generated in the first pixel memory 1008 to the S1 signal is sampled as the S2 signal.

  Here, the difference (S1-N) signal between the N signal sampled in the period 505 and the S1 signal sampled in the period 506 is a signal corresponding to the charge generated in the second pixel memory 1010 during the accumulation period. is there. Therefore, whether or not the pixel is a defective pixel caused by the second pixel memory 1010 is determined based on the output signal level of the (S1-N) signal. Further, the difference (S2-S1) signal between the S1 signal sampled in the period 506 and the S2 signal sampled in the period 507 corresponds to the charge generated in the light-shielded state in the accumulation period in the first pixel memory 1008. Signal. Therefore, whether the pixel is a defective pixel due to either the organic photoelectric conversion film 1006 or the first pixel memory 1008 is determined based on the output signal level of the (S2-S1) signal.

  That is, according to the defective pixel detection driving method of the present invention, even in an image sensor using an organic photoelectric conversion film as a photoelectric conversion unit of a pixel, each defective pixel caused by a plurality of pixel memories is detected, and these defective pixel data are detected. Can be saved. In the imaging apparatus, by referring to the address of the defective pixel stored in the memory unit at the time of shooting, the image signal output from the defective pixel is appropriately corrected according to the accumulation time and shooting mode at the time of shooting. Can do.

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

(Other embodiments)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

Claims (14)

An image sensor in which a plurality of pixels each including a photoelectric conversion unit that performs photoelectric conversion, a charge holding unit that holds charges accumulated in the photoelectric conversion unit, and a floating diffusion unit that converts charges into voltage are arranged;
A defect detection means for detecting a defect of a pixel of the image sensor;
The defect detection means detects at least a first defective pixel caused by a defect in the charge holding unit and detects position information of the first defective pixel from at least the plurality of pixels. Imaging device. Each of the plurality of pixels includes a first transfer unit that controls transfer of charge from the photoelectric conversion unit to the charge holding unit, and a second transfer unit that controls transfer of charge from the charge holding unit to the floating diffusion unit. Transfer means,
The defect detection unit controls the first transfer unit to a non-transfer state and controls the second transfer unit to a transfer state in accordance with the charge transferred from the charge holding unit to the floating diffusion unit. The imaging apparatus according to claim 1, wherein the first defective pixel is detected.   The said defect detection means detects the positional information on this 2nd defective pixel while further detecting the 2nd defective pixel resulting from the defect of the said photoelectric conversion part, The Claim 1 or 2 characterized by the above-mentioned. Imaging device. Each of the plurality of pixels includes a first transfer unit that controls transfer of charge from the photoelectric conversion unit to the charge holding unit, and a second transfer unit that controls transfer of charge from the charge holding unit to the floating diffusion unit. Transfer means,
The defect detection means controls the first transfer means to a transfer state and controls the second transfer means to a transfer state, and controls the second transfer means to a transfer state according to the charge transferred from the photoelectric conversion unit to the floating diffusion unit. The imaging apparatus according to claim 3, wherein a second defective pixel is detected.   5. The imaging apparatus according to claim 1, wherein the defect detection unit further detects information related to an output signal level of the first defective pixel. 6.   The imaging apparatus according to claim 3, wherein the defect detection unit further detects information related to an output signal level of the second defective pixel. Defect in imaging device in which a plurality of pixels each including a photoelectric conversion unit that performs photoelectric conversion, a charge holding unit that holds charges accumulated in the photoelectric conversion unit, and a floating diffusion unit that converts charges into voltage are arranged A pixel detection method comprising:
A defect detection step of detecting a defect of a pixel of the image sensor;
In the defect detection step, at least a first defective pixel caused by a defect in the charge holding unit is detected from at least the plurality of pixels, and position information of the first defective pixel is detected. Defective pixel detection method. Each of the plurality of pixels includes a first transfer unit that controls transfer of charge from the photoelectric conversion unit to the charge holding unit, and a second transfer unit that controls transfer of charge from the charge holding unit to the floating diffusion unit. Transfer means,
In the defect detection step, the first transfer unit is controlled to be in a non-transfer state, and the second transfer unit is controlled to be in a transfer state, according to the charge transferred from the charge holding unit to the floating diffusion unit. The defective pixel detection method according to claim 7, wherein the first defective pixel is detected.   9. The defect detection step further comprises detecting a second defective pixel due to a defect in the photoelectric conversion unit and detecting position information of the second defective pixel. Defective pixel detection method. Each of the plurality of pixels includes a first transfer unit that controls transfer of charge from the photoelectric conversion unit to the charge holding unit, and a second transfer unit that controls transfer of charge from the charge holding unit to the floating diffusion unit. Transfer means,
In the defect detection step, the first transfer unit is controlled to be in a transfer state, and the second transfer unit is controlled to be in a transfer state so that the charge is transferred from the photoelectric conversion unit to the floating diffusion unit. The defective pixel detection method according to claim 9, wherein the second defective pixel is detected.   11. The defective pixel detection method according to claim 7, wherein in the defect detection step, information related to an output signal level of the first defective pixel is further detected.   11. The defective pixel detection method according to claim 9, wherein in the defect detection step, information relating to an output signal level of the second defective pixel is further detected.   The program for making a computer perform each process of the defective pixel detection method of any one of Claims 7 thru | or 12.   A computer-readable storage medium storing a program for causing a computer to execute each step of the defective pixel detection method according to claim 7.

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