JP4394470B2 - Imaging device - Google Patents

Description

    The present invention relates to a technique for correcting shading or defective pixels of an image sensor.

  An imaging element such as a MOS type or CCD type area sensor used for a digital still camera or a video movie camera may have a pixel defect due to a defect of a light receiving element. For this reason, image defects called white spots (white scratches) and black spots (black scratches) occur in the image signal generated from the image sensor output. Even if this image defect is small, it is very conspicuous and is one of the factors that degrade the image quality. Pixel defects that occur in the output of the image sensor include a dark current and a non-uniformity of the light receiving surface. Scratches caused by dark current become white scratches that increase in proportion to the charge accumulation time in the image sensor. When the light receiving surface is non-uniform, if the light receiving surface is narrower than a normal light receiving element, black scratches occur, and if it is wide, white scratches occur.

  In order to prevent image quality degradation due to image defects, various methods for detecting the defective pixel position and correcting the defective pixel have been developed. For example, a method is known in which the position of a defective pixel is stored in advance in a ROM table, and the image sensor output signal at the corresponding position is replaced with an adjacent non-scratch signal or an average value thereof (for example, Patent Document 1). reference). Also, a method is known in which a defective pixel position is detected simultaneously with detection of a defective pixel position based on an imaging element output signal as a result of imaging every time imaging is performed (for example, see Patent Document 2). When this method is adopted, even when the number of defective pixels increases, the circuit scale does not increase. Furthermore, a method is known in which test imaging is performed with the image sensor shielded before actual imaging, and defective pixels are detected based on the imaging element output signal of the test imaging result, and the information is acquired (for example, patents). Reference 3).

  Another factor that degrades the image quality is a level difference (shading) of an image sensor output signal having a relatively low frequency that is caused by an equal difference due to a temperature distribution of dark current. This particularly occurs when a long exposure is performed during still image shooting.

As a method for solving the shading, before and after the main shooting, the image sensor output (light-shielded data) read out after the main image capturing is read out after the charge is accumulated for the same time as the main image capturing with the image sensor light-shielded. A method of subtracting from element output (exposure data) is known. According to this method, it is possible to remove part of white scratches caused by dark current. In addition, since there is no need to perform interpolation using surrounding pixels, there are cases where good correction is possible.
JP 61-261974 A Japanese Patent Laid-Open No. 5-41867 JP 2001-36820 A

  In order to prevent the image quality from being deteriorated due to an image defect, if an attempt is made to store flaw coordinates for specifying the position of a flaw due to dark current in a ROM or RAM table, a very large capacity is required, which causes an increase in cost. This is because the damage caused by dark current varies depending on conditions such as deterioration of the device due to changes with time, charge accumulation time in the image pickup device, temperature, and the like. In particular, when exposure is performed for a long time during still image shooting, the charge accumulation time becomes long, so that a large number of white scratches occur.

  In addition, the method of correcting the defective pixel at the same time as detecting the defective pixel position from the exposure data every time the image is taken is based on the premise that the adjacent pixel defect does not occur on the imaging device as a condition for accurately detecting the defective pixel position. Therefore, it is difficult to satisfy this condition during long exposure photography.

  Also, in the method of performing test shooting with the image sensor shielded before the actual shooting and detecting defective pixel information from the image sensor output signal of the test shooting result, until the actual shooting is performed after the user issues a shooting instruction A time lag occurs. Further, it is not possible to detect white scratches caused by the non-uniformity of the light receiving surface. Further, when trying to store the defective pixel information of the test photographing result in the ROM or RAM table as horizontal / vertical coordinate information, a very large capacity is required.

On the other hand, for shading correction, in the method of subtracting the image sensor output that has been charged for the same amount of time as the main shooting in the light-shielded state from the image sensor output during the main shooting, the light receiving element output of the scratched part during the main shooting A problem arises when the signal is saturated, or when the signal processing circuit exceeds the D range of the subsequent signal processing circuit. For example, when the exposure data around the pixel position where the white defect exists is saturated, if the light shielding data is subtracted, the position with the white defect appears as a black defect.
An object of the present invention is to correct defective pixels or shading of an image sensor.

  The present invention provides light-shielded data obtained by accumulating charges for the same time as the charge accumulation time of the image sensor at the time of exposure in a state where the image sensor is shielded from exposure data generated by performing charge accumulation with the image sensor exposed. The shading correction data is generated by subtraction. Thereafter, the shading correction data at the defective pixel position detected from the light shielding data is corrected.

Specifically, the imaging apparatus according to the present invention is as follows.
An imaging apparatus according to the present invention outputs an exposure electrical signal by exposure and outputs an electrical shielding signal by light shielding, and the exposure electrical signal and the light shielding electrical signal output from the imaging device are respectively exposed to exposure data and light shielding. A conversion unit for converting into data, wherein the converted data is configured to be able to specify a plurality of pixels each having a pixel value, and pixel values of at least two pixels with respect to the light shielding data Based on the position detection means for specifying the position of the defective pixel corresponding to the output of the image sensor having a defect, the subtracting unit for subtracting the light shielding data from the exposure data and outputting the difference data, and the subtracting unit output Correction means for correcting the pixel value of the pixel corresponding to the position of the defective pixel with respect to the difference data. Thereby, the above object can be achieved.

When the difference between the pixel values of two adjacent pixels is larger than the threshold value, the position detection unit may specify the position of one pixel as a defective pixel.
The position detection unit may specify the position and range where the defective pixel exists using the pixel values of at least three pixels.
The correcting unit may correct the pixel value of the pixel corresponding to the position of the defective pixel with respect to the difference data to a pixel having the same color or a similar color as the pixel value of surrounding pixels.
The imaging device may continuously perform the output of the exposure electrical signal by exposure and the output of the light shielding electrical signal by light shielding.
Comparing the pixel value of each pixel that can be specified by the exposure data with the maximum value that the pixel value can take, it further comprises saturation detection means for judging whether or not each pixel is a saturated pixel, and the correction means The pixel value of the pixel that is the defective pixel and that corresponds to the position of the saturated pixel may be corrected for the difference data.

  Another imaging apparatus according to the present invention is an imaging device that outputs an exposure electrical signal by exposure, and a conversion unit that converts the exposure electrical signal output from the imaging device into exposure data, wherein the exposure data is respectively Stores information on the position of a defective image sensor that has a predetermined positional relationship, and information on the position of a defective imaging device that is configured to be able to identify a plurality of pixels having pixel values. Based on the storage means and the defective pixel position information stored in the storage means, the pixel corresponding to the position of the defective pixel, which can be specified by the exposure data, is corrected and the corrected exposure data is output. Based on the difference between the first correction unit and the corrected exposure data output from the first correction unit, the pixel value of the target pixel, and the pixel values of the pixels around the target pixel, The position detection means for determining the target pixel as a defective pixel and specifying the position of the defective pixel; and the pixel corresponding to the position of the defective pixel specified by the position detection means with respect to the corrected exposure data Second correction means for correcting the pixel value. Thereby, the above object can be achieved.

  The storage means may preferentially store the defective pixel position information for defective pixels in an adjacent positional relationship.

  Still another imaging apparatus according to the present invention is an imaging device that outputs an exposure electrical signal by exposure and can output a light-shielding electrical signal by light shielding, a control means for setting an exposure time, and the exposure time set by the control means. Based on the exposure control means for controlling the exposure to the image sensor, and the conversion unit for converting the exposure electrical signal and the light-shielded electrical signal output from the image sensor into exposure data and light-shielded data, respectively, Is information regarding the position of a defective imaging element having a predetermined positional relationship, and information regarding the position of a defective imaging device and a conversion unit configured to be able to identify a plurality of pixels each having a pixel value A storage means storing pixel position information, and the defect that can be specified by the exposure data based on the defective pixel position information stored in the storage means Correction means for correcting the pixel corresponding to the prime position and outputting the corrected exposure data, and according to the exposure time set by the control means, further for the shading data of the defective pixel Correction means for correcting the pixel corresponding to the position. Thereby, the above object can be achieved.

  An image pickup apparatus includes a position detection unit that specifies a position of a defective pixel corresponding to an output of an image sensor having a defect based on pixel values of at least two pixels with respect to the light shielding data corrected by the correction unit; An exposure data correction unit that corrects a pixel value of the pixel of the exposure data corresponding to the position of the defective pixel specified by the detection unit may be further provided.

  The imaging device determines the position of the defective pixel by determining that the target pixel is a defective pixel based on a difference between a pixel value of the target pixel of the exposure data and a pixel value of a pixel around the target pixel. And a correction unit that corrects the pixel value of the pixel corresponding to the position of the defective pixel specified by the position detection unit with respect to the corrected exposure data.

  According to the present invention, not only the exposure data is corrected by subtracting the light shielding data from the exposure data, but also the position of the defective pixel is specified based on the pixel values of at least two pixels with respect to the light shielding data. The exposure data corresponding to is corrected further. As a result, it is possible to obtain an imaging result obtained by removing shading caused by a difference in temperature distribution of the image sensor and white scratches caused by defects in the image sensor without causing black defects due to erroneous correction.

  According to the present invention, the pixel of the exposure data corresponding to the position of the defective pixel is corrected based on the defective pixel position information related to the position of the defective pixel having a predetermined positional relationship, and the corrected data is further corrected. Based on the difference between the pixel value of the target pixel and the pixel values of pixels around the target pixel, the target pixel is determined to be a defective pixel, the position of the defective pixel is specified, and the pixel value is corrected. When there are continuous defective pixels, the first correction is performed, so that it is possible to obtain an imaging result with no defective pixels and no defect remaining.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
(Embodiment 1)
FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus 100 according to the first embodiment. The imaging apparatus 100 includes an imaging element 101, an exposure control unit 102, an A / D converter 103, a memory 104, a defective pixel position detection unit 105, a subtractor 106, a defective pixel correction unit 107, and camera signal processing. Means 108, media I / F 109, recording medium 110, system controller 111 including a microcomputer, image sensor driver 112, operation switch 113, and photometric means 114 are provided.

  The system controller 111 performs overall control of all operations of the imaging apparatus 100. The imaging device 101 is a MOS type or CCD type area sensor that acquires and outputs incident light as an electrical signal. The exposure control unit 102 controls exposure by adjusting a lens and an aperture according to the photometric result. The A / D converter 103 converts an analog electric signal from the image sensor 101 into a digital signal. The memory 104 stores a digitized signal (digital data). The memory 104 is a random access memory (RAM) made of, for example, a semiconductor.

  The defective pixel position detecting means 105 determines a defective pixel based on the pixel value of each pixel and specifies its position. A defective pixel means a pixel corresponding to the output of an image sensor having a defect such as a scratch. The subtractor 106 outputs a difference between two input signals (input data). The defective pixel correction unit 107 corrects the color caused by the defective pixel so as to be the same color as the color of surrounding pixels, for example. A more detailed description of the defective pixel position detection unit 105 and the defective pixel correction unit 107 will be described later. The camera signal processing means 108 receives the signal and performs color separation processing, compression processing, and the like. The media I / F 109 is provided between the recording media 110 and exchanges signals according to a predetermined procedure and specifications. The recording medium 110 is a storage device that can read and write digital data. The recording medium 110 is, for example, a nonvolatile semiconductor memory, an optical disk, a magnetic disk, or the like.

  The image sensor driver 112 is a device that drives the image sensor 101 and operates according to control from the system controller 111. The operation switch 113 is an input device that gives a shooting command to the imaging apparatus 100 by the user. The photometry unit 114 measures light to acquire its intensity and the like, and gives a photometry result to the system controller 111.

  Hereinafter, the imaging operation of the imaging apparatus 100 (FIG. 1) will be described with reference to FIG. FIG. 6 is a flowchart showing processing for correcting defective pixels. First, a shooting command from the user is given to the system controller 111 via the operation switch 113. The system controller 111 controls the exposure control unit 102 including a lens and a diaphragm and the image sensor driver 112 according to the photometry result in the photometry unit 114, and controls the incident light amount and the charge accumulation time to the image sensor 101. Take a picture of the subject (main exposure). When the charge accumulation is completed, a signal is read from the image sensor 101, converted into digital data (exposure data) by the A / D converter 103, and then recorded in the memory 104 (step 601). The exposure data includes noise components such as shading caused by a white defect caused by a defect of the image sensor 101 and a difference in temperature distribution of the image sensor 101, in addition to a signal caused by incident light from the subject. Note that the exposure data includes information on the pixels constituting the image, and the pixels in the exposure data can be specified, and information (pixel values, etc.) on the pixels can be read and processed.

  When all the signals on the image sensor 101 are read, the exposure control means 102 blocks incident light on the image sensor 101. In this state, based on the control of the image sensor driver 112, the image sensor 101 accumulates electric charges for the same period as during the main exposure. When the charge accumulation is completed, a signal is read from the image sensor 101 and converted into digital data (light-shielded data) by the A / D converter 103 (step 602).

  Since the light shielding data is obtained from the charges accumulated in a state where the incident light is blocked, the light shielding data includes only noise components that should not be included in the original photographing. That is, the light shielding data includes a noise component that is substantially equal to white scratches and shading included in the exposure data. The light-shielding data also includes information on pixels constituting an image captured with light shielding, and it is possible to specify a pixel in the light-shielding data and read and process information (pixel value and the like) regarding the pixel.

  The shading data is output to the memory 104, the defective pixel position detecting means 105, and the subtractor 106. Along with the output of the light shielding data, the exposure data is read from the memory 104 and both data are given to the subtractor 106. The subtractor 106 subtracts the light shielding data from the exposure data, and outputs the difference data as a result to the defective pixel correction means 107.

  The output (difference data) of the subtracter 106 is a signal from which shading and some white scratches included in the exposure data are removed. However, the white defect portion at the position corresponding to the portion where the exposure data is saturated is erroneously corrected and output as a black defect.

  Therefore, it is necessary to identify such white scratches. FIG. 2 is a block diagram showing the configuration of the defective pixel position detecting means 105. As shown in FIG. The defective pixel position detection unit 105 receives the A / D converted light shielding data, and identifies the defective pixel based on the pixel values of two adjacent pixels. Furthermore, using the pixel values of at least three pixels, the position and range of the flaw (defective pixel range) can be specified. Here, the pixel value is represented, for example, as a set of gradation values for each color of red (R), green (G), and blue (B), and it is assumed that the larger the gradation value, the closer to white. The comparison of pixel values is a comparison of gradation values for each color.

  Specifically, the defective pixel position detection unit 105 compares the pixel values of the target pixel and the pixel immediately before the target pixel (previous pixel), and the pixel value of the target pixel is the pixel value of the previous pixel. It is determined whether it is larger than the threshold value TH (step 604). The threshold value TH is determined for each color constituting the pixel value. If it is larger than the threshold value TH, it is determined that the target pixel is a defective pixel and is a scratch start position (step 605). If not, the target pixel is shifted to the next pixel (step 606).

  On the other hand, the defective pixel position detecting means 105 similarly calculates the difference between the pixel values of the pixel of interest and the pixel immediately after the pixel of interest (rear pixel) (step 607). Then, it is determined whether or not the pixel value of the target pixel is larger than the threshold value TH compared with the pixel value of the subsequent pixel (step 608). When it is larger than the threshold value TH, the target pixel is a defective pixel and becomes a scratch end position. The defective pixel position detection unit 105 determines that the pixel from the pixel detected as the scratch start position to the pixel detected as the scratch end position is a defective pixel group (scratch) (step 609). If it is not larger than the threshold value TH, the target pixel is shifted to the next pixel (step 610), and the processing from step 607 is repeated. This process is continued until the pixel value of the target pixel becomes larger than the threshold value TH as compared with the pixel value of the subsequent pixel. As a result of the above processing, the defective pixel position detecting unit 105 identifies the end position of the scratch, and determines from the pixel detected as the scratch start position to the pixel detected as the scratch end position as a defective pixel group (scratch). .

  The above-described processing is processing for each scanning line, and this processing is performed for all scanning lines constituting one captured screen. With this operation, the position of the flaw can be accurately detected even if the signal is a signal with shading superimposed or there is a continuous white flaw. The position of the flaw detected by the defective pixel position detection unit 105 is output to the defective pixel correction unit 107.

  The defective pixel correction unit 107 determines whether white defects have occurred in the output of the subtractor 106 (difference data of the difference between the exposure data and the light shielding data) based on the position of the defective pixel determined as a white defect by the defective pixel position detection unit 105. The pixel corresponding to the position is replaced with a pixel having the same color or a similar color as the surrounding (step 611). More specifically, the signal corresponding to the defective pixel in the output signal of the subtractor 106 is replaced with the signal of the pixel having the same color as the surroundings by, for example, the previous value hold. The pixel signal of “same color as surrounding” is a pixel output signal corresponding to a filter of the same color at the nearest position among adjacent pixels when a color filter is provided on the image sensor for colorization. In the case of a monochrome imaging device, this is an output signal of an adjacent pixel. A similar color is a color determined by pixel values within a range close to a reference pixel value. Thereby, it is possible to obtain a signal in which black flaws due to erroneous correction of a portion where exposure data is saturated are corrected. The defective pixel correcting unit 107 outputs the signal to the camera signal processing unit 108.

The camera signal processing unit 108 performs signal processing such as color separation and compression processing on the signal output from the defective pixel correction unit 107 and records the signal on the recording medium 110 via the media I / F 109.
With the above operation, it is possible to obtain an imaging result obtained by removing shading caused by a difference in temperature distribution of the image sensor and white scratches caused by defects in the image sensor without causing black defects due to erroneous correction.

  The “front pixel” and the “rear pixel” may mean pixels before and after the target pixel when scanning in the horizontal direction, or pixels before and after the target pixel when scanning in the vertical direction. It may be. It only means before and after the scanning direction, and the direction is arbitrary.

(Embodiment 2)
FIG. 3 is a block diagram illustrating a configuration of the imaging apparatus 300 according to the second embodiment. The image pickup apparatus 300 is different from the image pickup apparatus 100 (FIG. 1) in the first embodiment in that a saturation detection unit 301 detects whether or not the image obtained by the main exposure read from the memory 104 is saturated. And the defective pixel correction means 107 further performs correction by the previous value hold based on the detection result of the saturation detection means 301. Since the configuration and operation of other elements are common to the imaging apparatus 300 and the imaging apparatus 100 (FIG. 1), description thereof is omitted. Hereinafter, operations of the saturation detection unit 301 and the defective pixel correction unit 107 will be described. Here, it is assumed that each pixel value of the exposure data read from the memory 104 is expressed by an 8-bit value (0 to 255).

  The saturation detection unit 301 compares each pixel value of the exposure data read from the memory 104 with 255, which is the maximum value that can be taken by 8 bits, and determines that the value is saturated if it is 255. The saturation detection unit 301 performs this comparison / determination for each pixel. The defective pixel correcting unit 107 corrects only the output signal of the subtractor 106 corresponding to the pixel position determined to be a flaw by the defective pixel position detecting unit 105 and determined to be saturated by the saturation detecting unit 301. To do. With the above operation, the defective pixel correction unit 107 can correct only black defects due to erroneous correction that occur when subtracting light-shielding data from exposure data, so that side effects due to correction can be minimized.

(Embodiment 3)
FIG. 4 is a block diagram illustrating a configuration of the imaging apparatus 400 according to the third embodiment. The imaging apparatus 400 differs from the imaging apparatus 100 (FIG. 1) in the first embodiment in the configuration and processing from the A / D converter 103 to the camera signal processing means 108. Specifically, the imaging apparatus 400 newly includes a first defective pixel correction unit A401, a defective pixel address storage unit 402, and a second defective pixel correction unit B404, and the memory 104 and the subtractor 106 (FIG. 1) are provided. Not. The imaging apparatus 400 handles only exposure data and does not use light shielding data. In the following, the configuration and operation of these different parts, and processing different from the imaging apparatus 100 (FIG. 1) will be described.

  Exposure data is output from the A / D converter 103 by photographing the subject with the image sensor 101. This exposure data is input to the first defective pixel correction means A401. Prior to this, the defective pixel address storage unit 402 preferentially stores the positions of defective pixels occurring at adjacent positions in the information related to the position of the defective image sensor 101 (defective pixel position information). . This defective pixel is, for example, a pixel that has been damaged due to non-uniformity of the light receiving surface. The position of the defective pixel is described by coordinates indicating the position of the pixel in the photographed image. The defective pixel correction unit A401 corrects a continuous defective pixel preferentially by correcting the signal corresponding to the position stored in the defective pixel address storage unit 402 by, for example, the previous value hold. Therefore, the output of the first defective pixel correction unit A401 becomes exposure data after correcting the defective pixel.

The defective pixel position detection unit 403 compares, for example, the size of the pixel value (signal level) of the target pixel and the size of the pixel values (signal level) of the surrounding pixels, and determines all the surrounding pixel values. If the pixel is larger than a predetermined threshold value, the pixel of interest is judged to be white, and if the pixel value is smaller than the pixel value of all surrounding pixels, the pixel of interest is judged to be black. To do.
However, in this case, if there are continuous flaws, the defective pixel position detecting unit 403 cannot determine that the flaws are present, and there is a possibility that a detection failure may occur. However, since the consecutive scratches have already been removed by the defective pixel correction means A401, no detection omission occurs. In the second defective pixel correction unit B404, the output signal of the defective pixel correction unit A401 corresponding to the position of the defective pixel determined to be white or black by the defective pixel position detection unit 403 is corrected by, for example, previous value hold. . Thereafter, the processing from the camera signal processing means 108 is the same as that of the imaging device 100 (FIG. 1).

  With the above operation, even when there are continuous defective pixels, it is possible to obtain an imaging result with no scratches remaining. In addition, since the defective pixel address storage unit 402 only needs to store the coordinates of at least consecutive defective pixels, it can be realized with a small-capacity memory as compared with the case where all the defective pixel coordinates are stored. become.

(Embodiment 4)
FIG. 5 is a block diagram illustrating a configuration of an imaging apparatus 500 according to the fourth embodiment. The imaging apparatus 500 is different from the imaging apparatus 400 (FIG. 4) in the third embodiment in that the imaging apparatus 500 newly has a memory 504, a defective pixel correction unit 505, a defective pixel position detection unit A506, and a defective pixel. The position detecting means B507 is provided. However, the defective pixel position detecting means B507 is provided in place of the defective pixel position detecting means 403 (FIG. 4). The imaging apparatus 500 can handle both exposure data and light shielding data according to the exposure time. In the following, the configuration and operation of these different parts, and the processing different from that of the imaging apparatus 400 (FIG. 4) will be described.

  When a photographing command from the user is given to the system controller 111 via the operation switch 113, the system controller 111 determines the lens aperture value and the charge accumulation time Tr in the image sensor according to the photometric result in the photometric means 114. Thereafter, based on an instruction from the system controller 111, the exposure control unit 102 controls the exposure, and the subject is photographed according to the determined aperture value of the lens and the charge accumulation time Tr. An electric signal obtained as a result of photographing is sent to the A / D converter 103, and the A / D converter 103 outputs exposure data. This exposure data is input to the defective pixel correction means A401. In the defective pixel correction unit A401, the input signal corresponding to the defective pixel position stored in the defective pixel address storage unit 402 is corrected by, for example, previous value hold. The corrected signal is output to the memory 504 and stored. The system controller 111 determines which of the following operations (1) to (3) is to be adopted according to the charge accumulation time Tr, and executes the operation.

  (1) When the charge accumulation time Tr is very long (that is, in the case of long exposure), for example, when Tr> 1 second, exposure data is written in the memory 504, and then the exposure control means 102 sends it to the image sensor 101. In the state where the incident light is blocked, charge accumulation is performed in the image sensor 101 for the same period as in the main exposure. When the charge accumulation is completed, a signal is read from the image sensor, and the light shielding data is generated by the A / D converter 103. The defective pixel correction unit A401 performs the same correction as the exposure data on the light shielding data, and outputs it to the defective pixel position detection unit A506. The configuration of the defective pixel position detection unit A506 is the same as the configuration and operation of the defective pixel position detection unit 105 (FIG. 2). The defective pixel position detecting unit A506 detects a flaw including a continuous flaw from the corrected light shielding data.

  The exposure data is read out from the memory 504 in parallel with the subsequent processing that is performed after the incident light is blocked. The defective pixel correcting unit 505 corrects a signal corresponding to the defective pixel position detected by the defective pixel position detecting unit A506. The output of the defective pixel correction unit 505 is input to the defective pixel correction unit B404 corresponding to the defective pixel position detection unit B507, but is not corrected here. The subsequent processing is as described in the first embodiment.

  With the above operation, it is possible to correct a large number of scratches including continuous scratches that occur in the case of long-time exposure. Further, by storing in the defective pixel address storage unit 402 the coordinates of scratches due to non-uniformity of the light receiving surface that cannot be detected by the light shielding data, it is possible to obtain an imaging result with no correction omission.

  (2) When the charge accumulation time Tr is very short, for example, when Tr <1/30 seconds, the exposure data is read from the memory 504 immediately after the writing of the exposure data to the memory 504 is completed. At this time, the imaging apparatus 500 does not perform imaging while blocking incident light. That is, no light shielding data is generated.

  The exposure data is input to the defective pixel correction unit 505 corresponding to the defective pixel position detection unit A506. However, the position of the defective pixel is not corrected. After that, the exposure data is input to the defective pixel correcting unit B404 corresponding to the defective pixel position detecting unit B507, but no correction is performed here. The signal is input to the camera signal processing means 108 and the subsequent processing is performed.

  By the above operation, unnecessary shading data is not captured when the charge accumulation time is very short, so that unnecessary power consumption is eliminated and an operation with a short photographing interval can be realized. In addition, when the charge accumulation time Tr is very short, the number of defective pixel signals appearing in the output of the image sensor is limited, so that necessary defective pixel correction is performed only by storing a small number of defective pixel addresses. An imaging result can be obtained.

  (3) When the charge accumulation time Tr is 1/30 sec <Tr <1 sec, the exposure data is read from the memory 104 immediately after the exposure data is written to the memory 140. In this case, the defective pixel correction unit 505 corresponding to the defective pixel position detection unit A506 does not perform correction, but directly inputs the defective pixel position detection unit B507 and the defective pixel correction unit B404. For example, the defective pixel position detection unit B507 compares the level of the target pixel signal and the surrounding pixel signals, and determines that the target pixel is white scratch if the level is higher than all the peripheral pixel signal levels. On the other hand, when the pixel signal level is lower than all the peripheral pixel signal levels, the defective pixel position detection unit B507 determines that the target pixel is a black flaw. In the defective pixel correction unit B404, the defective pixel is corrected by, for example, previous value hold according to the detection result in the defective pixel position detection unit B507. The correction result output by the defective pixel correction unit B404 is input to the camera signal processing unit 108, and the subsequent processing is performed.

  With the above operation, even when a relatively large number of scratches are generated, correction can be performed without increasing the shooting interval due to the capture of light shielding data. In addition, if at least the coordinates of the defective pixels are stored in the defective pixel address storage unit 402, it is possible to correct the continuous scratches.

As described above, the operations (1), (2), and (3) enable sufficient flaw correction with the minimum necessary side effects according to the charge accumulation time.
In the first, second, and fourth embodiments, the camera signal processing unit 108 usually requires a memory for scan conversion during compression processing, recording rate conversion to a recording medium, and the like. Therefore, as the memory, the memories 104 and 504 that only temporarily hold the exposure data in the above description may be shared. As a result, the circuit scale can be reduced. For example, sharing is possible by providing a memory having a sufficiently large read / write bit rate and a memory arbitration circuit that performs read / write of the memory at the same time in a time division manner.

  The processing operation of the imaging apparatus according to the first embodiment described with reference to the flowchart illustrated in FIG. 6 and the operation of the imaging apparatus according to the other embodiments are based on a computer program described to operate as described above. Can be realized. Such a computer program can be recorded on an appropriate storage medium such as a nonvolatile semiconductor storage medium such as a flash ROM, a volatile semiconductor storage medium such as a DRAM, or a magnetic storage medium such as an optical disk or a floppy disk.

1 is a block diagram illustrating a configuration of an imaging apparatus according to Embodiment 1. FIG. It is a block diagram which shows the structure of a defective pixel position detection means. 4 is a block diagram illustrating a configuration of an imaging apparatus according to Embodiment 2. FIG. 6 is a block diagram illustrating a configuration of an imaging apparatus according to Embodiment 3. FIG. FIG. 10 is a block diagram illustrating a configuration of an imaging apparatus according to a fourth embodiment. It is a flowchart which shows the process which correct | amends a defective pixel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image pick-up device 101 Image pick-up element 102 Exposure control means 103 A / D converter 104 Memory 105 Defective pixel position detection means 106 Subtractor 107 Defective pixel correction means 108 Camera signal processing means 109 Media I / F
DESCRIPTION OF SYMBOLS 110 Recording medium 111 System controller 112 Image sensor driver 113 Operation switch 114 Photometry means

Claims (5)

An image sensor that outputs an exposure electrical signal by exposure and outputs a light-shielding electrical signal by light shielding;
A conversion unit that converts the exposure electrical signal and the shading electrical signal output from the image sensor into exposure data and shading data, respectively, and the converted data can specify a plurality of pixels each having a pixel value. A conversion unit configured in
Saturation detection means for judging whether or not the pixel value is saturated for each pixel by comparing each pixel value of the exposure data with the maximum value that the exposure data can take,
Position detecting means for identifying the position of a defective pixel corresponding to the output of an image sensor having a defect based on pixel values of at least two pixels with respect to the light shielding data;
A subtraction unit that subtracts the light-shielding data from the exposure data and outputs difference data;
An image pickup apparatus comprising: a correction unit that corrects a pixel value of a pixel detected by the saturation detection unit, the pixel corresponding to the position of the defective pixel among the pixels included in the difference data output by the subtraction unit .   The imaging apparatus according to claim 1, wherein the position detection unit specifies the position of one pixel as a defective pixel when a difference between pixel values of two adjacent pixels is larger than a threshold value.   The imaging apparatus according to claim 1, wherein the position detection unit specifies a position and a range where the defective pixel exists using pixel values of at least three pixels.   The correction unit corrects the pixel value of the pixel corresponding to the position of the defective pixel to the pixel having the same color as the pixel value of the surrounding pixels or a similar color to the difference data. The imaging device described in 1.   The imaging device according to claim 1, wherein the imaging element continuously outputs the exposure electrical signal by exposure and the output of the light shielding electrical signal by light shielding.

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