JP2005318337A - Defect detecting and correcting device for solid-state image pickup element and image pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly correct a signal output level from defective pixels in a solid-state image pickup element during photographing. <P>SOLUTION: In a defect detecting circuit 41, a signal output level difference between a pixel part under consideration and a peripheral pixel part is compared with a threshold so that defective pixels can be detected, and the location of the pixel part where the signal output level difference is within a predetermined range from the threshold and the number of times of continuous detection of the pixel part when the signal output level difference is within the predetermined range or beyond the predetermined range are stored as storage information in a storage device 42. A correction object deciding circuit 43 detects the pixel part whose signal output level difference is within the predetermined range from the threshold from the storage information of the storage device 42, and decides whether to correct the pixel part. A defect correcting circuit 44 corrects the pixel part detected as the defective pixels by the defect detecting circuit 41. At that time, the presence/absence of correction is decided according to the decision result of the correction object deciding circuit 43 for the pixels whose signal output level difference is within the predetermined range from the threshold value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a defect detection / correction device for a solid-state image sensor that detects and corrects defective pixels in a solid-state image sensor such as a CMOS image sensor or a CCD (Charge Coupled Device) image sensor, and a digital camera or the like using the same. The present invention relates to an imaging apparatus such as a video camera.

  Conventionally, in a solid-state imaging device such as a CMOS image sensor or a CCD image sensor manufactured on a semiconductor substrate, defective pixels may be generated due to local crystal defects existing on the semiconductor substrate. When such a defective pixel exists, the magnitude of the signal output level output from the defective pixel indicates a specific signal output level without depending on the amount of incident image light. For this reason, there arises a problem that the image quality of the image obtained by imaging the subject is deteriorated by the output image signal output from the defective pixel. It is also known that in a solid-state imaging device, such defective pixels are generated due to various factors such as extremely few when the ambient temperature is normal temperature and exponentially increasing as the ambient temperature becomes high. ing.

  In a conventional imaging device such as a digital camera or a video camera, a defective pixel existing in a solid-state imaging device is detected, and the position of the defective pixel such as address data of the defective pixel is stored in a storage device such as a nonvolatile memory in advance. When photographing, the signal output from the defective pixel is corrected based on the address data of the defective pixel stored in the nonvolatile memory.

  For example, in an imaging apparatus equipped with a CMOS image sensor, detection and correction of defective pixels are performed as follows, for example.

  First, an output signal output from each pixel portion of the CMOS image sensor and a pixel portion to be inspected (target pixel portion) in a state where the lens portion of the imaging device is shielded from light and no light is incident on the CMOS image sensor in the manufacturing stage. Are compared with the output signals output from the respective pixel units in the vicinity of.

  Next, when the difference between the values of the output signal levels of these output signals exceeds a predetermined threshold, the pixel portion (defective pixel) that outputs this specific signal output level is detected. The defective pixel address data (pixel position) is stored in a nonvolatile memory.

  When the detection of the defective pixel is completed, the CMOS image sensor and a nonvolatile memory storing address data of the defective pixel are paired and built in the image pickup apparatus and shipped as a product.

  When a user captures an image of a subject using this imaging device, an output signal (video signal) output from the CMOS image sensor based on address data of a defective pixel of the CMOS image sensor stored in a nonvolatile memory. Among these, the output signal from the defective pixel is corrected by the output signal from the pixel portion in the vicinity of the defective pixel.

  However, in such a defective pixel detection method for a solid-state imaging device, the defective pixel is detected in a state where the lens portion of the imaging device is shielded and no image light is incident on a CMOS image sensor or the like in the manufacturing stage. Since the address data and the like are stored in the non-volatile memory, there is a problem that the number of processes greatly increases in the manufacturing stage.

  Another problem is that defective pixels of a solid-state image sensor that are caused by electrostatic breakdown or the like cannot be corrected after shipping a product of an image pickup apparatus equipped with a solid-state image sensor such as a CMOS image sensor from a factory. .

  In order to solve such a problem, for example, Patent Document 1 discloses a difference in signal output level between a predetermined pixel unit (target pixel unit) and its surrounding pixel unit without using a storage device such as a nonvolatile memory. Of a solid-state imaging device having defect detection means for determining a predetermined pixel portion as a defective pixel when the calculated defective pixel detection value is larger than a preset defect detection threshold value A defect detection and correction apparatus is disclosed. This is shown in FIG.

  FIG. 5 is a block diagram illustrating a schematic configuration example of an imaging apparatus equipped with a conventional defect detection / correction apparatus for a solid-state imaging element.

  As shown in FIG. 5, the imaging apparatus 10 includes a lens unit 1 that forms an image of light from a subject at a predetermined position (a solid-state imaging device 2 described later), and a CMOS image sensor or a CCD image that photoelectrically converts incident subject light. A solid-state imaging device 2 such as a sensor, and a defect detection and correction device 3 that detects and corrects defective pixels in the solid-state imaging device 2 are provided.

  The defect detection and correction device 3 includes a defect detection circuit 31 that detects a defective pixel in the solid-state imaging device 2, a defect correction circuit 32 that corrects an output signal from the detected defective pixel, and a digital that performs data processing on the corrected output signal. And a signal processing circuit 33.

  In the defect detection circuit 31, an output signal from the solid-state imaging device 2 is input via a line delay device or the like, and a defective pixel is detected based on a difference in signal output level between the target pixel portion and the surrounding pixel portion.

  The defect correction circuit 32 receives the output signal from the defect detection circuit 31 and corrects the output signal output from the detected defective pixel using the output signals output from the plurality of pixel units in the vicinity thereof.

  The digital signal processing circuit 33 receives the output signal from the defect correction circuit 32, performs various signal processing on the input output signal, and outputs it as a YUV digital signal.

Next, Patent Document 2 compares the signal output levels of a predetermined pixel portion (target pixel portion) and a plurality of surrounding pixel portions, and determines an edge when the level difference is larger than a predetermined value. And a defect detection and correction apparatus for a solid-state imaging device that can reduce erroneous determination of defect detection due to an edge by performing predetermined correction as a flaw defect when there is a further difference in edge determination.
JP 2002-223391 A Japanese Patent Laid-Open No. 7-23297

  As described above, in the method of detecting defective pixels in the solid-state imaging device at the manufacturing stage, the number of processes in the manufacturing stage is greatly increased, and defective pixels in the solid-state imaging element caused by electrostatic breakdown after product shipment are used. However, there was a problem that correction could not be performed.

  In addition, when detecting and correcting a defective pixel of a solid-state imaging device in real time at the time of shooting by the methods disclosed in Patent Document 1 and Patent Document 2, for a pixel portion existing near the defect detection threshold value, There is a problem that the image is flickered because the correction is performed or not performed.

  The present invention solves the above-described conventional problems, and can correct defective pixels generated after product shipment without increasing the number of processes in the manufacturing stage. Defect detection and correction device for solid-state imaging device capable of appropriately correcting the signal output level from defective pixels in the solid-state imaging device during photographing so that image flicker due to the defect detection threshold does not occur when correction is performed And it aims at providing the imaging device using the same.

  The defect detection and correction apparatus for a solid-state imaging device according to the present invention detects whether or not a pixel is a defective pixel according to a level difference between a signal output level of a target pixel portion and a signal output level related to the surrounding pixel portion, and the level difference is predetermined. Defect detection means for detecting whether or not the pixel is within the range, the screen position of the pixel unit in which the level difference is within the predetermined range, and the continuation for each frame of the pixel unit in which the level difference is within or outside the predetermined range Storage means for holding the number of detections as holding information, and a pixel unit in which the level difference is within the predetermined range when the series of level differences is within the predetermined range for each frame based on the holding information Determining means for determining whether or not to correct the series of signal output levels, and defect correcting means for correcting the series of signal output levels based on the determination result by the determining means. The objects can be achieved.

  Preferably, the defect detection means in the defect detection / correction device for a solid-state imaging device according to the present invention calculates a difference between the signal output level of the target pixel unit and the signal output level of the surrounding pixel unit as a level difference detection value. When the calculated level difference detection value is larger than a preset defect detection threshold, the target pixel portion is determined to be a defective pixel, and the calculated level difference detection value includes a predetermined range including the defect detection threshold. Detect if it is inside.

  Still preferably, in a defect detection / correction device for a solid-state imaging device according to the present invention, the determination unit is the same for each frame in which the series of level differences corresponding to the number of consecutive detections held in the storage unit are within the predetermined range. It is determined whether or not the signal output level should be corrected for the pixel portion at the screen position.

  Further preferably, the determination means in the defect detection / correction device for a solid-state imaging device according to the present invention detects the continuous detection when the level difference detection value of the target pixel portion continuously changes within the predetermined range for each frame. The presence or absence of correction with respect to the first signal output level during the period is set as a predetermined reference, and the presence or absence of correction is sequentially determined with respect to this continuous signal output level in the same manner as the predetermined reference.

  Further preferably, the storage means in the defect detection / correction device for a solid-state imaging device according to the present invention is configured such that the level difference detection value of the target pixel portion is within a predetermined number of times set in advance for the pixel portion within the predetermined range. The number of times of continuous detection when the level difference detection value is outside the predetermined range and the information on the presence or absence of correction for the pixel portion determined to be outside the predetermined range are stored. When the level difference detection value is held within the predetermined range again, the determination unit determines whether or not the signal output level should be corrected according to the stored information stored in the storage unit. To do.

  Further preferably, the determination means in the defect detection / correction device for a solid-state imaging device according to the present invention is configured such that the level difference detection value is a signal output level of a pixel portion within the predetermined range, and the level difference detection value is outside the predetermined range. Whether or not to correct is determined in the same manner as the presence or absence of correction when

  Further preferably, the level difference in the defect detection / correction device for a solid-state imaging device according to the present invention is a level between a signal output level obtained from a plurality of pixel units around the target pixel unit and a signal output level of the target pixel unit. It is a difference.

  Further preferably, the level difference in the defect detection / correction device for a solid-state imaging device according to the present invention is a level between the largest signal output level in the eight pixel portions around the target pixel portion and the signal output level of the target pixel portion. It is a difference.

  The imaging apparatus according to the present invention receives a solid-state imaging device that receives subject light and converts it into an electrical signal, and an output image signal from the solid-state imaging device, detects a defective pixel based on the signal output level, and detects the defective pixel. The solid-state imaging device defect detection and correction apparatus according to any one of claims 1 to 8, which corrects a signal output level from a defective pixel, thereby achieving the above object.

  The operation of the present invention will be described below with the above configuration.

  In the present invention, the defect detection means calculates the difference between the signal output level of the target pixel portion and the signal output level of the surrounding pixel portion as a level difference detection value, and the calculated level difference detection value is It is compared with a preset defect detection threshold. When the level difference detection value is larger than the defect detection threshold, the target pixel portion is determined as a defective pixel. Further, the defect detection means detects whether the difference in signal output level is within or outside a predetermined range.

  By the storage means, the pixel position where the level difference detection value is within a predetermined range including the defect detection threshold, and the pixel portion where the level difference detection value is within the predetermined range including the defect detection threshold or outside the predetermined range for each frame. The number of times of detection is retained as retained information.

  The determination means detects whether there is a level difference detection value within a predetermined range including the defect detection threshold, using the holding information held in the storage means, for example, the number of continuous detections. In this case, according to a predetermined reference It is determined whether or not the signal output level should be corrected. As the predetermined reference, for example, whether or not a series of pixel portions is corrected during the continuous detection period is determined in the same manner as the correction or not of the first pixel portion during the continuous detection period.

  In the defect correction means, the signal output level of the defective pixel detected by the defect detection means is corrected. At this time, for the pixel portion whose level difference detection value is within a predetermined range including the defect detection threshold, the signal output level from the pixel portion determined as the correction target by the determination means should be corrected and corrected. Correction is not performed for pixel portions that are not determined to be present.

  For example, when the level difference detection value of the target pixel portion continuously shifts within a predetermined range including the defect detection threshold, the first pixel portion correction during the continuous detection period is performed by the defect correction means to eliminate the image flicker. The signal output level may be corrected according to the presence or absence of the signal.

  In addition, the storage unit has detected that the level difference detection value is outside the predetermined range including the defect detection threshold for a predetermined number of times for a pixel portion determined to be within the predetermined range including the defect detection threshold. In this case, the number of continuous detections may be held, and the determination may be performed by the determination unit when the level difference detection value is again within a predetermined range including the defect detection threshold.

  Further, when the level difference detection value is within a predetermined range including the defect detection threshold value in the previous frame and deviates from the predetermined range including the defect detection threshold value in the next frame, the storage unit continuously continues up to a predetermined number of times. The number of detections and the presence or absence of correction when it is determined that the level difference detection value is out of the predetermined range including the defect detection threshold are held as holding information, and then the level difference detection value includes the defect detection threshold. The stored information held in the storage unit may be used when the value again falls within the predetermined range.

  In this way, when the pixel portions within a predetermined range including the defect detection threshold are continuous, it is possible to determine whether or not correction is performed by the determination unit, so that defective pixels of the solid-state image sensor are detected in real time at the time of shooting. When performing the correction, even if pixel portions within a predetermined range including the defect detection threshold are consecutive, it is possible to prevent the image from flickering due to correction being performed or not being performed.

  As described above, according to the present invention, in the case where the level difference detection value within a predetermined range including the defect detection threshold is a pixel portion continuous for each frame, whether or not correction is performed by the determination unit is determined. In order to determine, in an imaging device such as a digital camera or a video camera equipped with a solid-state imaging device such as a CMOS image sensor or a CCD image sensor, a defective pixel in the solid-state imaging device is detected in real time when an object is imaged. When correcting defective pixels, it is possible to perform appropriate correction so that the image does not flicker due to the threshold value.

  In addition, defective pixels generated after product shipment can be corrected without increasing the number of processes as in the prior art in the manufacturing stage.

  Hereinafter, an embodiment of an imaging apparatus including a defect detection and correction apparatus for a solid-state imaging device according to the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram illustrating a schematic configuration example of an imaging apparatus equipped with a solid-state imaging device defect detection and correction apparatus according to an embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member which show | plays the effect similar to the structural member of FIG.

  As shown in FIG. 1, the imaging device 11 includes a lens unit 1 as an optical unit that forms image light from a subject at a predetermined position (solid-state imaging device 2), and image light imaged by the lens unit 1. Is input into a solid-state imaging device 2 such as a CMOS image sensor or a CCD image sensor that is converted into an electrical signal, and a defect detection correction device 4 that detects and corrects defective pixels in the solid-state imaging device 2.

  The defect detection and correction device 4 includes a defect detection circuit 41 as a defect detection unit, a storage device 42 as a storage unit that can store predetermined holding information, and a correction target determination circuit as a determination unit that determines whether or not correction is performed. 43, a defect correction circuit 44 as defect correction means for performing defect correction, and a digital signal processing circuit 45.

  In the defect detection circuit 41, an output signal is input from the solid-state imaging device 2 via a line delay device or the like, and a defective pixel is detected according to a difference in signal output level (level difference detection value) between the target pixel unit and its surrounding pixel unit. Is detected, and whether the level difference detection value is within a predetermined range or outside is detected. More specifically, the defect detection circuit 41 calculates a difference between the signal output level of the target pixel portion and the signal output level of the surrounding pixel portion as a level difference detection value, and the calculated level difference detection value is calculated in advance. When the pixel portion of interest is determined to be a defective pixel when it is larger than the set defect detection threshold, a pixel portion within which the calculated level difference detection value is within or outside the predetermined range including the defect detection threshold is determined. Or a pixel portion outside the predetermined range.

  In the storage device 42, the screen position (address data) of the pixel portion (pixel portion within the predetermined range) whose level difference detection value is within a predetermined range including the defect detection threshold (or within a predetermined range centered on the defect detection threshold) and The number of consecutive detections of each pixel unit (the pixel unit within the predetermined range or the pixel unit outside the predetermined range) whose level difference detection value is within or outside the predetermined range is held as the holding information.

  Based on the information stored in the storage device 42, the determination unit 43 outputs a signal to a pixel unit in which a series of level difference detection values at the same screen position for each frame are within a predetermined range (including a defect detection threshold). It is determined whether or not the output level should be corrected. More specifically, the determination unit 43 receives the holding information from the storage device 42 and uses the holding information of the storage device 42, for example, the number of continuous detections, to detect a series of level difference detection values at the same screen position for each frame as defective. A pixel portion within a predetermined range including the detection threshold is detected as a pixel portion within the predetermined range, and it is determined whether or not the signal output level should be corrected for the detected pixel portion within the predetermined range.

  When correcting the signal output level of the defective pixel, the defect correction circuit 44 corrects the signal output level of the pixel portion within the predetermined range based on the determination result by the correction target determination unit 43. Thus, in the defect correction circuit 44, each output signal is input from the defect detection circuit 41 and the correction target determination circuit 43, and an output signal output from the defective pixel is output from a plurality of pixel units in the vicinity thereof. It is corrected using the signal. At this time, for the pixel portion whose level difference detection value is within a predetermined range including the defect detection threshold, only the output signal level output from the pixel portion determined to be the correction target by the correction target determination circuit 43 is corrected. The

  In the digital signal processing circuit 45, an output signal is input from the defect correction circuit 44, and various signal processings are performed on the input output signal and output as a YUV digital signal.

  With reference to the above configuration, a schematic operation example of the defect detection and correction apparatus of the present embodiment will be described below with reference to the flowchart of FIG.

  As shown in FIG. 2, first, in step S1, it is determined whether or not a defective pixel is detected by the defect detection circuit 41. That is, the defect detection circuit 41 calculates a difference in signal output level between the target pixel portion to be corrected and its surrounding pixel portion as a level difference detection value and compares it with a preset defect detection threshold value. At this time, when the level difference detection value is larger than the defect detection threshold, the target pixel is determined to be a defective pixel and is set as a correction target. Further, it is determined whether or not the level difference detection value is within a predetermined range including a defect detection threshold. In this way, even when the detection data is outside the predetermined range of the threshold value, there is a possibility that the storage means may store the number of continuous times. Therefore, all the cases (YES, NO) are detected in the defect detection in step S1. )), The process proceeds to step S2.

  In step S2, the position of the pixel portion where the level difference detection value, which is the output signal level difference, is within a predetermined range including the defect detection threshold, and the level difference detection value is within or outside the predetermined range including the defect detection threshold. The number of continuous detections for each frame of the pixel unit is stored and held in the storage device 42 as holding information.

  In step S <b> 3, the level difference detection value of the target pixel portion includes a defect detection threshold based on the defective pixel detected by the defect detection circuit 41 by the correction target determination circuit 43 and the retained information retained in the storage device 42. It is determined whether or not to perform correction on a pixel portion (pixel portion within a predetermined range) that is within a predetermined range.

  In step S4, when the target pixel portion is a correction target in step S3 (when defect correction is performed in the correction determination; YES), the target pixel portion is corrected by the defect correction circuit 44, and the target attention is also given. When the pixel portion is not determined as a correction target (when defect correction is not performed in the correction determination; NO), the target pixel portion is not corrected, and the process proceeds to the next step S5.

  In step S5, it is determined whether or not all the target pixel portions have finished processing. If all the target pixel portions have been processed in step S5 (YES), this defective pixel detection correction processing is ended. If all the target pixel portions have not been processed (NO), step S5 is performed. The process returns to S1.

  Hereinafter, further specific operations of the defect detection and correction apparatus 4 of the present embodiment will be described with reference to FIGS. 3 and 4.

  FIG. 3 is a graph showing an example of a change in signal output level difference between a target pixel portion and its peripheral pixel portion for each frame for one pixel (target pixel portion) in the solid-state imaging device 2 shown in FIG. . In FIG. 3, the vertical axis indicates the signal output level difference (level difference detection value) between the target pixel portion and the surrounding pixel portion, and the horizontal axis indicates the number of frames. Here, the threshold value (defect detection threshold value) of the signal output level difference between the target pixel portion and the plurality of peripheral pixel portions is set to “30”. Further, the predetermined range centered on the defect detection threshold is 10% above and below the threshold, and the range from “27” to “33” (defect detection threshold) is set within the predetermined range centered on the defect detection threshold.

  In the normal defect detection and correction method, as shown in FIG. 3, the level difference detection value (signal output level difference between the target pixel portion and the surrounding pixel portion) of a certain pixel portion is near the defect detection threshold “30”. In the case of transition, correction is performed when the level difference detection value is larger than the defect detection threshold “30”, and correction is not performed when the defect detection threshold is “30” or less.

  Therefore, in the case of FIG. 3, in the normal defect detection and correction method, the case where correction is performed and the case where correction is not performed are alternately repeated. However, since the defect detection threshold is normally set so as to be conspicuous when observed with the human eye, the level difference detection value (signal output level difference between the target pixel portion and its surrounding pixel portion) is the defect detection threshold. If correction is performed or no correction is performed in a nearby pixel portion (pixel portion within a predetermined range), the image may flicker during photographing.

  Therefore, in the present embodiment, as in the case of FIG. 3, the level difference detection value (signal output level difference between the target pixel portion and the peripheral pixel portion) of a certain pixel portion is within a predetermined range centered on the defect detection threshold. In order to prevent image flickering, it is determined whether or not to correct the signal output level according to the presence or absence of the first correction during the continuous period.

  Specifically, in FIG. 3, since the signal output level difference is equal to or smaller than the defect detection threshold “30” in the first frame, the target pixel portion is not corrected, but the signal output level difference is detected as a defect detection. Since it is within a predetermined range including the threshold, at this time, the pixel position, being within 10 percent below the defect detection threshold, and the number of times within 10 percent below the defect detection threshold (number of consecutive detections) Is stored and retained in the storage device 42 as retained information.

  In the second frame, the signal output level difference is larger than the defect detection threshold “30”, and the defect detection circuit 41 determines that the pixel is a defective pixel. Here, the signal output level difference is 10 above the defect detection threshold. Since it is within the percentage, the pixel-of-interest portion is not corrected as in the first frame.

  The subsequent frame is processed in the same manner. In the example of FIG. 3, the signal output level difference is within 10% up and down centered on the defect detection threshold until the 10th frame, so that the pixel of interest is not corrected.

  As described above, by detecting and correcting a defective pixel, correction is performed or not performed on a pixel portion (a pixel portion within a predetermined range) in which a level difference detection value exists near the defect detection threshold. This can prevent the image from flickering.

  Here, a defect detection threshold value to be compared with a difference in signal output level between the target pixel portion and a plurality of surrounding pixel portions, and a predetermined range centered on the defect detection threshold value can be set as appropriate.

  FIG. 4 shows another example of a change in signal output level difference between a target pixel unit and a plurality of surrounding pixel units for each frame for a certain pixel (target pixel unit) in the solid-state imaging device 2 shown in FIG. It is a graph to show. In FIG. 3, the vertical axis represents the signal output level difference (defective pixel detection value) between the target pixel portion and the peripheral pixel portion, and the horizontal axis represents the number of frames. Here again, the threshold value (defect detection threshold value) of the signal output level difference between the target pixel portion and the plurality of peripheral pixel portions is set to “30”. Further, the predetermined range from the defect detection threshold is 10% above and below the threshold, and the range from “27” to “33” is within a range of ± 3 (within the predetermined range) centering on the defect detection threshold “30”. .

  In FIG. 4, after a level difference detection value (signal output level difference between a target pixel portion and its surrounding pixel portion) in a certain pixel portion transitions within a predetermined range centering on the defect detection threshold, it exceeds the defect detection threshold. This is a case where the transition is outside the predetermined range and the transition is again within the predetermined range.

  In such a case, in the present embodiment, the level difference detection value is up to a predetermined number of times set in advance by the storage device 42 with respect to the pixel portion determined to be within a predetermined range centered on the defect detection threshold. The number of continuous detections outside the predetermined range equal to or greater than the defect detection threshold and the presence / absence of correction at that time are retained as retained information.

  Next, when the level difference detection value returns within a predetermined range centered on the defect detection threshold, whether or not to correct the signal output level according to the presence or absence of correction held in the storage device 42. It is determined.

  Explaining in detail using the example of FIG. 4, in the first frame and the second frame, as in the case of FIG. 3, the target pixel portion is not corrected. At this time, the pixel position, the number within 10% below and above the defect detection threshold in the first frame, and the number of times within 10% above and below the defect detection threshold (continuous detection number) are stored in the storage device 42. It is stored and held as holding information.

  Next, in the third and fourth frames, the signal output level difference is larger than the defect detection threshold “30”, and the signal output level difference is further outside the predetermined range outside the upper 10% of the defect detection threshold. For this reason, the target pixel portion is corrected. At this time, the pixel position, the number of times of being out of the predetermined range from the defect detection threshold (the number of continuous detections), and the presence / absence of correction at that time are stored and retained in the storage device 42 as retained information.

  In this example, when the signal output level difference in the previous frame is within a predetermined range from “30” of the defect detection threshold, and in the next frame, the signal output level difference is not less than the defect detection threshold and outside the predetermined range, It is set so that the position of the pixel portion, the number of times of continuous detection outside a predetermined range, and information on the presence or absence of correction can be held as retained information in the storage device 42 up to twice (continuous detection times; 2 times). Yes.

  In the fifth frame, since the signal output level difference is within the predetermined range at “30” or less of the defect detection threshold value, correction is not normally performed. In this case, however, the signal output level difference is the defect detection threshold value. Even if it is within the lower 10%, it is within the predetermined range, and since it was held in the storage device 42 that it was corrected in the previous frame, the pixel portion of interest is corrected.

  From the sixth frame to the tenth frame, the signal output level difference is within a predetermined range within 10 percent above and below the defect detection threshold, so that these target pixels are corrected as in the fifth frame.

  As described above, according to the present embodiment, the defect detection circuit 41 detects the defective pixel by comparing the signal output level difference between the target pixel portion and the peripheral pixel portion with the threshold value, and the signal output level difference includes the threshold value. It is determined whether it is within range. Further, the position of the pixel portion where the signal output level difference is within a predetermined range from the threshold and the number of times of continuous detection when the pixel portion is within the predetermined range or outside the predetermined range are held in the storage device 42 as retained information. The In the correction target determination circuit 43, a pixel portion whose signal output level difference is within a predetermined range from the threshold value is detected from the information held in the storage device 42, and it is determined whether or not correction is to be performed on the pixel portion. The defect correction circuit 44 corrects the pixel portion detected as a defective pixel by the defect detection circuit 41. At this time, for pixels whose signal output level difference is within a predetermined range from the threshold, whether or not to correct is determined according to the determination result of the correction target determination circuit 43. In this way, by performing defect detection correction, flickering occurs in the image when the level difference detection value is corrected or not performed on the pixel portion in the vicinity of the defect detection threshold. Can be prevented.

  In the above embodiment, when the level difference between the signal output level of the target pixel unit and the signal output levels obtained from the plurality of peripheral pixel units is equal to or greater than the defect detection threshold and outside the predetermined range, the information on the pixel unit is displayed. The number of times the data can be stored in the storage device 42 is 2. However, the number is not limited to this, and may be 3 times, 4 times, or more, and this number can be set as appropriate.

  Although not specifically described in the above embodiment, when the level difference between the signal output level of the target pixel unit and the signal output level related to the surrounding pixel unit is calculated, it is obtained from a plurality of pixel units around the target pixel unit. It may be calculated as a level difference between the signal output level and the signal output level of the target pixel portion. Specifically, the level difference between the signal output level of the target pixel unit and the signal output level related to the surrounding pixel unit is the highest signal output level in the eight pixel units around the target pixel unit and the signal output of the target pixel unit. It may be calculated as a level difference from the level, or may be calculated as a difference between the signal output level of the average value of the eight pixel portions around the target pixel portion and the signal output level of the target pixel portion. The level difference can be calculated as appropriate.

  As mentioned above, although this invention has been illustrated using preferable embodiment of this invention, this invention should not be limited and limited to this embodiment. It is understood that the scope of the present invention should be construed only by the claims. It is understood that those skilled in the art can implement an equivalent range based on the description of the present invention and the common general technical knowledge from the description of specific preferred embodiments of the present invention. Patents, patent applications, and documents cited herein should be incorporated by reference in their entirety, as if the contents themselves were specifically described herein. Understood.

  The present invention relates to a defect detection / correction device for a solid-state image sensor that detects and corrects defective pixels in a solid-state image sensor such as a CMOS image sensor or a CCD (Charge Coupled Device) image sensor, and a digital camera or the like using the same. In the field of imaging devices such as video cameras, when detecting defective pixels in the solid-state image sensor in real time during imaging and correcting the detected defective pixels, appropriate correction is made so that the image does not flicker due to the threshold value. Is possible. Further, it is possible to correct defective pixels generated after product shipment without increasing the number of processes in the manufacturing stage.

  INDUSTRIAL APPLICABILITY The present invention can be used for various electronic information devices such as a camera-equipped mobile phone equipped with an imaging device and a camera-equipped portable information terminal, and can obtain a good captured image without flicker.

1 is a block diagram illustrating a schematic configuration example of an imaging apparatus equipped with a solid-state imaging element defect detection and correction apparatus according to an embodiment of the present invention. 3 is a flowchart for explaining a schematic operation example in the defect detection / correction device for a solid-state imaging device in FIG. 2 is a graph showing an example of a change in signal output level difference between a target pixel and a plurality of pixels around it for each pixel in a certain pixel (target pixel) in the solid-state imaging device shown in FIG. 1. 6 is a graph showing another example of a change in signal output level difference between a target pixel for each frame and a plurality of surrounding pixels for one pixel (target pixel) in the solid-state imaging device shown in FIG. 1. It is a block diagram which shows the example of schematic structure of the imaging device by which the defect detection correction apparatus of the conventional solid-state image sensor described in patent document 1 was mounted.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens part 2 Solid-state image sensor 4 Defect detection correction apparatus 11 Imaging apparatus 41 Defect detection circuit 42 Memory | storage device 43 Correction object determination circuit 44 Defect correction circuit
45 Digital signal processing

Claims (9)

Defect detecting means for detecting whether or not the pixel is a defective pixel according to a level difference between a signal output level of the target pixel portion and a signal output level relating to the surrounding pixel portion, and detecting whether or not the level difference is within a predetermined range; ,
Storage means for holding the screen position of the pixel portion in which the level difference is within the predetermined range and the continuous detection count for each frame of the pixel portion in which the level difference is within or outside the predetermined range as holding information;
Whether or not to correct the series of signal output levels of the pixel units in which the level difference is within the predetermined range when the series of the level difference is within the predetermined range based on the holding information Determination means for determining any one of
A defect detection / correction device for a solid-state imaging device, comprising: defect correction means for correcting the series of signal output levels based on a determination result by the determination means.   The defect detection means calculates a difference between a signal output level of the target pixel portion and a signal output level related to the surrounding pixel portion as a level difference detection value, and the calculated level difference detection value is a preset defect detection threshold value. 2. The solid-state imaging according to claim 1, wherein the pixel portion of interest is determined to be a defective pixel when larger than the threshold value, and whether or not the calculated level difference detection value is within a predetermined range including the defect detection threshold value is detected. Device defect detection and correction device.   Whether the determination means should correct the signal output level for the pixel portion at the same screen position for each frame in which the series of level differences corresponding to the number of consecutive detections held in the storage means are within the predetermined range. The defect detection correction apparatus of the solid-state image sensor of Claim 1 or 2 which determines whether or not.   In the case where the level difference detection value of the target pixel portion continuously shifts within the predetermined range for each frame, the determination unit uses the presence or absence of correction for the first signal output level during the continuous detection period as a predetermined reference. The defect detection / correction device for a solid-state imaging device according to claim 1, wherein the presence / absence of correction is sequentially determined for the continuous signal output levels, similarly to the predetermined reference.   The storage means has the level difference detection value out of the predetermined range for a pixel portion in which the level difference detection value of the target pixel portion is within the predetermined range by a number within a predetermined number of times set in advance. The number of times of continuous detection and information on whether or not the pixel portion for which the level difference detection value is determined to be outside the predetermined range are held as holding information, and the level difference detection value falls within the predetermined range again. 5. The solid-state imaging according to claim 1, wherein the determination unit determines whether or not the signal output level should be corrected according to the stored information stored in the storage unit. Device defect detection and correction device.   Whether the determination means should sequentially correct the signal output level of the pixel portion whose level difference detection value is within the predetermined range, as well as whether or not correction is performed when the level difference detection value is outside the predetermined range. The defect detection and correction apparatus for a solid-state imaging device according to claim 5, which determines whether or not.   2. The defect detection correction of the solid-state imaging device according to claim 1, wherein the level difference is a level difference between a signal output level obtained from a plurality of pixel units around the target pixel unit and a signal output level of the target pixel unit. apparatus.   The defect detection correction of the solid-state image pickup device according to claim 7, wherein the level difference is a level difference between the largest signal output level in the eight pixel portions around the target pixel portion and the signal output level of the target pixel portion. apparatus. A solid-state imaging device that receives subject light and converts it into an electrical signal;
The solid-state imaging according to any one of claims 1 to 8, wherein a signal output level from the solid-state imaging device is input, a defective pixel is detected based on the signal output level, and a signal output level from the defective pixel is corrected. An imaging device comprising an element defect detection and correction device.

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