JP2007150895A - Imaging apparatus, and defect pixel processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct the newly generated flaw of an imaging element by detecting it in real-time during photographing an image from an imaging apparatus by changing a reading pattern by each field. <P>SOLUTION: The imaging apparatus comprises the imaging element (3) composed of a plurality of pixels for outputting an image signal; a timing signal generating circuit (5) for driving the imaging means to perform reading by changing the reading pattern by each field; an optical low-pass filter (2) arranged at the side of a subject from the imaging means; a defect pixel detecting circuit (7) for detecting the defect pixel of the imaging element, based on the image signal; and a defect pixel correcting circuit (9) for correcting the image signal outputted from the detected defect pixel. The defect pixel detecting circuit detects the pixels as the defect pixel, based on the image signal in the field and between the two continuous fields when not less than two pixels, which output the image signal higher than a predetermined first value or lower than a second value, do not continue in the arrangement order of the pixels of the imaging element. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging apparatus using a solid-state imaging device such as an image sensor, and a defective pixel processing method in the imaging apparatus.

  In recent imaging apparatuses, the number of pixels of a solid-state imaging device represented by a CCD or CMOS sensor is increasing. Along with this, the number of defective pixels (scratches) on the image sensor is also increasing.

  Among defective pixels, there are manufacturing scratches that occur during the manufacturing process of the image sensor and growth scratches that occur after being incorporated into the imaging device. Further, among the growth flaws, there is a temperature characteristic dependent flaw that increases or decreases during use depending on the temperature of the imaging device.

  Among these defective pixels, a method of correcting a defect by manufacturing a black image at the time of shipment from the factory and detecting the position of the defective pixel in advance is used. Further, for growth flaws, a black image can be taken by forcibly shielding the image sensor when the power is turned on, and defective pixels can be detected and corrected.

  For example, Patent Document 1 proposes the following method. First, when the power is turned on, the diaphragm is closed and the image sensor is shielded from light, and one screen is imaged. Then, the image data obtained by this imaging is compared with a threshold value, a pixel whose luminance is higher than the threshold value is detected as a defective pixel (white defect), and the position information is stored. Further, in a state where the detection mode of the defective pixel is selected by the mode switch, the camera is pointed at a dedicated subject and an image is captured for one screen. Then, the image data obtained by this imaging is compared with a threshold value, and a pixel whose luminance is lower than the threshold value is detected as a defective pixel (black flaw), and the position information is stored.

  However, the method described in Patent Document 1 cannot detect a temperature characteristic-dependent flaw that occurs due to a temperature change during use of the imaging apparatus.

  On the other hand, Patent Document 2 discloses a method for detecting and correcting defective pixels from an image obtained by imaging. In the method of Patent Document 2, a pixel having a luminance of a certain level difference or more is determined as a white defect by comparing the luminance of each pixel with the luminance of surrounding pixels.

JP-A-10-322603 JP 2004-015191 A JP-A-5-344426

  However, in Patent Document 2, defective pixels are detected using pixel data obtained from all the imaging devices 16, but there is no description about a determination method at the time of field reading (interlace reading) during moving image shooting. When a defective pixel is detected by the method described in Patent Document 2 at the time of field reading, if the defective pixel is not in the read target row, detection cannot be performed, or conversely, erroneous detection occurs. there were.

  On the other hand, Patent Document 3 discloses that when the CCD is driven by field reading (interlace reading) and the mode is switched to a mode for detecting a defective pixel, the mode is forcibly switched to frame reading. . In this way, when detecting defective pixels, since switching to frame readout is forcibly performed, the problem described in Patent Document 2 can be avoided. However, there is no disclosure about a method for detecting a defective pixel while performing field readout. When a defective pixel is detected by the method described in Patent Document 3, a smooth moving image cannot be captured. . In particular, when switching to a mode in which defective pixels are frequently detected in order to detect defective pixels in real time, there is a problem in that the temporal resolution of a moving image decreases.

  The present invention has been made in view of the above problems, and in the middle of taking an image by changing the readout pattern for each field from the imaging device, detects a scratch of the imaging element newly generated in real time, The purpose is to enable correction.

  In order to achieve the above object, an image pickup apparatus of the present invention photoelectrically converts incident subject light and outputs a picture signal, and changes a readout pattern for each field from the image pickup means. The image pickup means based on the drive means for driving the image pickup means so as to output the image signal, the optical low-pass filter disposed on the subject side of the image pickup means, and the image signal output from the image pickup means. Detection means for detecting a defective pixel of the image, and a correction means for correcting an image signal output from the defective pixel detected by the detection means, wherein the detection means changes the readout pattern for each field and changes the image. When the signal is output, based on the image signal in the field and between two consecutive fields, it is higher than the preset first value, or Pixels outputting a low image signal than a second value lower than the value of 1, if the non-contiguous 2 pixels or more in the order of pixels of the image pickup means, for detecting the pixel as a defective pixel of the imaging means.

  In addition, the defective pixel of the present invention in an imaging device having an imaging unit composed of a plurality of pixels that photoelectrically convert incident subject light and output an image signal, and an optical low-pass filter disposed on the subject side of the imaging unit The processing method includes: an imaging step of outputting an image signal by changing a readout pattern for each field from the imaging unit; and an image signal in the field and between two consecutive fields output from the imaging unit in the imaging step. Based on the pixel arrangement order of the pixels of the image pickup means, pixels that output an image signal that is higher than the preset first value or lower than the second value lower than the first value. A detection step of detecting the pixel as a defective pixel of the imaging means when the pixel is not continuous, and an image signal output from the defective pixel determined in the determination step. Correcting the and a correction step.

  According to the present invention, it is possible to detect and correct a newly generated flaw in the image sensor in real time while taking an image while changing the readout pattern for each field from the image pickup apparatus.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

<Embodiment of FIG. 1>
An imaging apparatus according to a first embodiment of the present invention will be described with reference to FIG. In the first embodiment, a digital camera capable of shooting moving images and still images will be described as an example of the imaging device.

  In the imaging apparatus shown in FIG. 1, a subject image that has passed through a lens 1 and an optical low-pass filter (optical LPF) 2 is an imaging device 3 (here, a CCD) represented by a charge coupled device (CCD) or a CMOS sensor. In this case, photoelectric conversion is performed and an electric signal is output. Note that the CCD 3 is covered with a color filter (not shown) such as a primary color Bayer array, and can capture a color image. As will be described later, the CCD 3 can perform readout control by frame readout for sequentially reading all pixels and field readout (interlaced readout) for reading out the CCD 3 every predetermined line. Next, the analog front end (AFE) circuit 4 performs reset noise removal, gain adjustment, analog-digital (A / D) conversion, and the like on the electrical signal output from the CCD 3 to output digital image data. The

  Digital image data output from the AFE circuit 4 is sent to the memory 8 and the defective pixel detection circuit 7. The memory 8 has a capacity capable of storing data for one frame, and stores image data for two fields in field reading. Then, the image data of the previous field is output to the defective pixel detection circuit 7 described later, and the image data of the current field is output to the defective pixel correction circuit 9. The defective pixel detection circuit 7 detects defective pixels using the image data output from the AFE circuit 4 at the time of frame reading, and further using image data output from the memory 8 at the time of field reading. The defective pixel detection process performed by the defective pixel detection circuit 7 will be described later in detail.

  The defective pixel correction circuit 9 receives the current field or current frame image data output from the memory 8 and the defective pixel detection result of the defective pixel detection circuit 7. When the image data from the memory 8 includes image data resulting from defective pixels of the CCD 3 (hereinafter referred to as “defective pixel data”), correction for removing the defective pixel data is performed. The center-of-gravity shift correction circuit 10 performs center-of-gravity shift correction, which will be described later, on the image data that has been corrected for defective pixel data by the defective pixel correction circuit 9. Next, the camera signal processing circuit 11 performs image pickup system camera signal processing such as aperture correction, gamma correction, and white balance on the image data that has been corrected for center of gravity deviation.

  The output of the camera signal processing circuit 11 is displayed on the monitor 13 after being converted into an analog signal by a digital-analog (D / A) converter 12. Thereby, the user can monitor the captured image.

  On the other hand, the output of the camera signal processing circuit 11 is also sent to the encoding circuit 14. When the recording of an image is instructed by the input key 16, the encoding circuit 14 is driven via the microcomputer 17 and the data bus 18 to compress the data and record it on a recording medium 15 such as a tape, a card, or a disk. Note that the type of the recording medium 15 to be used is not particularly limited, and a recording medium suitable for the imaging device may be used as appropriate.

  Next, the defective pixel detection process in the first embodiment performed by the defective pixel detection circuit 7 will be described in detail.

  If the subject has an isolated point such as a star floating in the night sky, the high band is optically removed due to the influence of the optical LPF 2, so that the output of the AFE circuit 4 becomes slightly gentle as shown in FIG. It is an isolated region that spans the pixels. On the other hand, when there is a defective pixel (white flaw) on the CCD 3, it is not affected by the optical LPF 2, so that the output of the AFE circuit 4 becomes an isolated point where the signal level of only one pixel protrudes as shown in FIG. Therefore, in the first embodiment, the defective pixel detection circuit 7 detects defective pixel data by detecting an isolated point as shown in FIG.

  FIG. 4 shows a part of the primary color Bayer array CCD 3. In recent years, the number of pixels in the image sensor has increased, but since there is no time restriction when shooting a still image, even if the CCD 3 has a large number of pixels, all the pixels can be read out over an arbitrary time. . On the other hand, when displaying or recording a moving image, it is difficult to read out all the pixels in a predetermined time (for example, 1/60 second in the NTSC standard) due to restrictions on the operation speed of the CCD 3. Therefore, the control signal is generated by the timing signal generating circuit (TG) 5 based on the field index (FI), the vertical synchronizing signal (VD), and the horizontal synchronizing signal (HD) from the synchronizing signal generating circuit (SSG) 6, The CCD 3 is driven as follows. That is, as shown in FIG. 6, for example, when FI is at a high level, as shown in FIG. 5 (a), pixels are placed every two lines, such as 0, 1, 4, 5, 8, 9. read out. For example, when the FI is at the low level, as shown in FIG. 5B, the pixels that are not read out when the FI is at the high level, such as 2, 3, 6, 7, 10, 11,. Read every other line. By controlling in this way, it is only necessary to read out half of the pixels within a predetermined time (1/60 seconds in the NTSC standard), so that it is possible to satisfy the restriction on the operation speed of the CCD 3.

  That is, when the captured image is displayed on the monitor 13 in real time as a preview image at the time of moving image recording or still image recording, half of the pixels of the CCD 3 that are different for each field are read out. When an instruction to record a still image is input by the input key 16, the control of the CCD 3 by the TG 5 is changed, and all the pixels are sequentially read out as shown in FIG. Record.

  In the case of still image shooting, since all the pixels of the CCD 3 are read out, the defective pixel correction circuit 7 detects defective pixels data by detecting isolated points as shown in FIG. 3 from the obtained image data. Can be detected. On the other hand, in the case of moving image shooting, for example, in the readout method compliant with the NTCS standard described above, pixels are read every two lines for each field. Will be invited. This point will be described in detail below.

  FIG. 7 is a diagram illustrating an example of signal levels in some pixels of the CCD 3. In FIG. 7, A to H indicate pixel positions in the horizontal direction, and 0 to 7 indicate pixel positions in the vertical direction.

  For example, when shooting a star in the night sky, a white pattern appears on a black background. A schematic diagram of the image data obtained at this time is shown in FIG. Assuming that the pixel 1-B is a defective pixel (here, white scratches), the image data output from the pixel 1-B becomes an isolated point for the reason described above. On the other hand, other white portions (referred to as stars in this example) are spread in at least one of the horizontal and vertical directions due to the influence of the optical LPF 2 and thus have a certain area across a plurality of pixels. At this time, when lines different from each other every other field are read every two lines as shown in FIG. 5, when FI is at a high level (hereinafter, the field when FI is at a high level is referred to as an “even field”). .) Becomes as shown in FIG. Further, when FI is at a low level (hereinafter referred to as “odd field”), it becomes as shown in FIG.

  In FIG. 7B, not only the pixel 1-B but also the pixel 1-E appears to be an isolated point. However, as shown in FIG. 7A, the pixel 1-E is not actually an isolated point and is not a defective pixel. As described above, in the case of field reading, it is necessary to detect an isolated point using image data of two consecutive fields in order to accurately detect an isolated point. In FIG. 7C, the isolated point cannot be detected because the pixel 1-B is not read out. Therefore, isolated regions and isolated points are identified as described below.

  FIGS. 8A to 8D show four patterns of white pixels (pixels whose luminance value is higher than a preset luminance value) that are two consecutive pixels in the vertical direction, and for each pattern, between successive fields. It is a figure which shows how it appears as a signal value. Note that when two or more white pixels continue in the horizontal direction, it can be determined that the pixel is not an isolated point without examining the continuity in the vertical direction, so here, the white pixels continue only in the vertical direction. The case where it is confirmed whether it is doing is demonstrated.

  First, when the white region is located at the position shown in the pattern I in FIG. 8A, when half of the pixels are read for each field, the signal level pattern in three consecutive fields is as shown in FIG. 8B. . At this time, first, in the even field (even), the white pixel appears on the even line (here, the 0th line), so the white pixel continues between two consecutive lines with the line one line below in the field. Find out if it is. When a white pixel appears on an odd line (here, the first line), it is checked whether the white pixel continues between two consecutive lines with a line on one line in the field. If white pixels continue, it can be seen that the white pixels on lines 0 and 1 are not isolated points and not defective pixels. Here, when a white pixel appears on an even line (for example, the fourth line), a line on one line in the field (here, the first line) is examined, or when a white pixel appears on an odd line (for example, the first line). The line below the line in the field (here, the fourth line) is not examined. This is to avoid misrecognizing that it is not a defective pixel when there are defective pixels on the first line and the fourth line, for example.

  Further, when the white region is at the position shown in the pattern III of FIG. 8A, when half of the pixels are read for each field, the signal level pattern in the three consecutive fields is as shown in FIG. 8D. . At this time, first, in the odd field (even), the white pixel appears on the even line (here, the second line), so the white pixel continues between two consecutive lines with the line below the first line in the field. Find out if it is. When a white pixel appears on an odd line (here, the third line), it is checked whether the white pixel continues between two consecutive lines with a line on one line in the field. If white pixels continue, it can be seen that the white pixels on lines 2 and 3 are not isolated points and not defective pixels. Here, when a white pixel appears on an even line (for example, the sixth line), when a line on one line in the field (here, the third line) is examined, or when a white pixel appears on an odd line (for example, the third line) The line below the line in the field (here, the sixth line) is not examined. This is to avoid misrecognizing that it is not a defective pixel when there are defective pixels on the third line and the sixth line, for example.

  In the case of the pattern I and the pattern III, it is possible to determine whether the white pixel is an isolated point by examining the continuity of the white pixel in the field. Hereinafter, this search method is referred to as “in-field search”.

  Next, when the white region is at the position shown in the pattern II of FIG. 8A, when half of the pixels are read for each field, the signal level pattern in three consecutive fields is as shown in FIG. 8C. Become. At this time, first, white pixels appear on the odd lines in the even field (even), and then appear on the even lines in the odd field. At this time, if the continuity of the white pixels is merely confirmed by the intra-field search as described with reference to FIGS. 8B and 8D, an isolated point is erroneously recognized. That is, when white pixels are examined only between two consecutive lines of even lines (for example, the 0th and 2nd lines) and one line below (in this case, the 1st and 3rd lines) in the field, 2 are mistakenly recognized as being isolated points. Similarly, when a white pixel is examined only between two consecutive lines of an odd line (for example, the first and third lines) and one line in the field (here, the zeroth and second lines), the line 1, 2 are mistakenly detected as being isolated points. Therefore, in the case of the pattern II, the data of the line 1 (here, the first line) on one line of the even line (for example, the second line) in which the white pixel is detected in the immediately preceding field is checked. 2, it can be determined that two lines of white pixels are continuous. Alternatively, by examining data of a line (second line) one line below an odd line (for example, the first line) in which white pixels are detected, it is determined that two lines of white pixels in lines 1 and 2 are continuous. can do.

  Further, when the white region is at the position shown in the pattern IV of FIG. 8A, when half of the pixels are read for each field, the signal level pattern in three consecutive fields becomes as shown in FIG. . Therefore, as in the case of pattern II, in this case as well, the in-field search alone causes erroneous recognition of isolated points. Therefore, similarly to the pattern II, also in the pattern IV, in the immediately preceding field, a line (here, the third line) one line above the even line (for example, the fourth line) in which the white pixel is detected in the immediately preceding field. By examining the data, it can be determined that two lines of white pixels on lines 1 and 2 are continuous. Alternatively, by examining data of a line (fourth line) one line below an odd line (for example, the third line) in which a white pixel is detected, it is determined that two white pixels in lines 3 and 4 are continuous. can do.

  In the case of the pattern II and the pattern IV, it is possible to determine whether the white pixel is an isolated point by examining the continuity of the white pixel between the fields. This search method is hereinafter referred to as “inter-field search”.

In other words, if the line where the white pixel appears is an even line,
(1) Search data in the field and field below one line.
(2) Search between the data on one line before one field and the field.

Need to do.
If the line where the white pixel appears is an odd line,
(1) Line data on one line and field search.
(2) Search between the data one field before one field and between fields.

Need to do.
Thus, in each case, if it is determined that the search results of (1) and (2) do not continue for two pixels, it is determined that the point is an “isolated point”, that is, a defective pixel. Can do.

  FIG. 9 shows the operation of the defective pixel correction circuit 7 capable of realizing the above isolated point detection operation, and FIG. 10 shows the configuration thereof. First, the operation will be described.

  In step S <b> 11, the defective pixel detection circuit 7 inputs the image data taken from the AFE 4 and the image data of the previous field from the memory 8. Using the image data input in step S11, in-line search, in-field search, and inter-field search for image data (white pixels) exceeding a predetermined luminance is performed in steps S12 to S14. In the in-line search in step S12, when a white pixel is detected, it is determined whether or not two or more pixels continue in the horizontal direction. In step S13, when a white pixel is detected, in the same field, if the detected line is an even line, it is checked whether the pixel on the lower line is one line, and if it is an odd line, the pixel on the first line is a white pixel. In step S14, when a white pixel is detected, if the detected line is an even line, the pixel one line before the previous field is one line, and if it is an odd line, the pixel one line before the one field is Check if it is a white pixel.

  Next, in step S15, it is determined whether white continuation is continuous in the line. If it is continuous, the process proceeds to step S19 to determine that the examined white pixel is not an isolated point. If it is determined in step S15 that the lines are not continuous in the line, the process proceeds to step S16 to determine whether white pixels are continuous in the field. If it is continuous, the process proceeds to step S19 to determine that the examined white pixel is not an isolated point. If it is determined in step S16 that the field is not continuous, the process proceeds to step S17 to determine whether white pixels are continuous between the fields. If it is continuous, the process proceeds to step S19 to determine that the examined white pixel is not an isolated point. If it is determined in step S17 that the fields are not continuous, the process proceeds to step S18 to determine that the white pixel is an isolated point. That is, as a result of examining the image data in steps S12 to S14, if it is determined that all the determinations in steps S15 to S17 are not continuous, it is determined that the white pixel is an isolated point. Note that the determinations in steps S15 to S17 are not limited to the order described above, and all or some of them may be performed simultaneously.

  After determining whether or not the white pixel is an isolated point in step S18 or S19, it is determined whether or not there is image data to be searched in step S20. If there is, the process returns to step S11 to read the image data. The isolated point search process is terminated.

  FIG. 10 is a block diagram illustrating a detailed configuration example of the defective pixel detection circuit 7 for realizing the above processing. The configuration shown in FIG. 10 shows a configuration in which the determinations in steps S15 to S17 can be performed simultaneously.

  In FIG. 10, reference numerals 701 to 704 denote line memories for delaying image data by one horizontal line. The line memories 701 and 703 output the image data output from the AFE 4 and the memory 8 with a delay of one horizontal line period. The line memories 702 and 704 output the image data output from the line memories 701 and 703 with a delay of one horizontal line period. As a result, the line memories 702 and 704 output image data delayed by two horizontal line periods. A selector 705 selects either image data delayed by two horizontal line periods or non-delayed image data output from the AFE 4. Reference numeral 706 denotes a selector that selects either a signal read from the memory 8 or image data delayed by two horizontal line periods.

  The selectors 705 and 706 are controlled by a control signal generation circuit 707. The control signal generation circuit 707 receives the FI, VD, and HD signals from the SSG 6 and generates a control signal for switching the output of the AFE 4 and the output of the line memory 702 for each horizontal line by the selector 705. Specifically, when an odd line signal is output from the AFE 4, the selector 705 selects the 0 side (AFE 4), and when an even line signal is output from the AFE 4, the 1 side (line memory 702). Is controlled to select. The control signal generation circuit 707 also generates a control signal for switching which one of the memory 8 and the line memory 704 the output is selected by the selector 706 for each field. Specifically, the selector 706 selects the 0 side when the even field signal is output from the AFE 4, and the selector 706 selects the 1 side when the odd field signal is output from the AFE 4. Be controlled.

  The concept of image data output from the AFE 4, the line memories 701 to 704, and the selectors 706 and 706 by the above control is shown in the time chart of FIG. 11 in units of lines. The numbers in the chart of FIG. 11 indicate line numbers. FIG. 11A shows the case of an even field, and FIG. 11B shows the case of an odd field.

  Reference numeral 708 denotes an in-line isolated pattern detection circuit that detects white pixels from image data delayed by one horizontal line period by the line memory 701 and determines whether white pixels are not continuous with pixels before and after the same line. . Only when it is not continuous, a logic “high” is output (corresponding to step S12).

  An intra-field isolated pattern detection circuit 709 operates as follows. First, white pixels are detected from image data delayed from one horizontal line period output from the line memory 701. When a white pixel is detected, it is determined whether the image data selected by the selector 705 is a white pixel. As a result of the determination, the logic “high” is output only when the white pixels are not continuous (corresponding to step S13).

  Specifically, for example, as shown in FIG. 11A, when the fourth line is output from the AFE 4 in the even field, the selector 705 selects one side. Therefore, the first line that is the output of the line memory 701 and the 0th line that is the output of the line memory 702 are input to the isolated field detection circuit 709. Thereby, it can be determined whether the white pixel is an isolated point between the first line and the 0th line. For example, as shown in FIG. 11B, when the seventh line is output from the AFE 4 in the odd field, the selector 705 selects the 0 side. Accordingly, the sixth line which is the output of the line memory 701 and the seventh line which is the output of the AFE 4 are input to the intra-field isolated pattern detection circuit 709. Thereby, it can be determined whether the white pixel is an isolated point between the sixth line and the seventh line.

  Reference numeral 710 denotes an inter-field isolated pattern detection circuit which operates as follows. First, white pixels are detected from image data delayed from one horizontal line period output from the line memory 701. When a white pixel is detected, it is determined whether the image data selected by the selector 706 is a white pixel. As a result of the determination, the logic “high” is output only when the white pixels are not continuous (corresponding to step S14).

  Specifically, for example, as shown in FIG. 11A, when even-field image data is output from the AFE 4, the selector 706 selects the 0 side. Therefore, for example, when the image data of the fourth line is output from the AFE 4, the inter-field isolated pattern detection circuit 710 outputs the first line as the output of the line memory 701 and the output of the line memory 704. The second line one field before is input. Thereby, it can be determined whether the white pixel is an isolated point between the first line and the second line. For example, as shown in FIG. 11B, when the image data of the odd field is output from the AFE 4, the selector 706 selects one side. Therefore, for example, when the image data of the seventh line is output from the AFE 4, the sixth line as the output of the line memory 701 and the output of the memory 8 as 1 are sent to the inter-field isolated pattern detection circuit 710. The fifth line before the field is input. Thereby, it can be determined whether the white pixel is an isolated point between the fifth line and the sixth line.

  The intra-field isolated pattern detection circuit 709 and the inter-field isolated pattern detection circuit 710 output the detection result after being delayed by one pixel. This is because the in-line isolated pattern detection circuit 708 needs to determine the image data after one pixel, and the output timing of the detection result is delayed by one pixel compared with the other detection results.

  An AND gate 711 outputs a logic “high” when all the outputs from the intra-line isolated pattern detection circuit 708, the intra-field isolated pattern detection circuit 709, and the inter-field isolated pattern detection circuit 710 are logic “high”. (Corresponding to steps S15 to S18). Thus, when the detected white pixel is an isolated point, a signal indicating that fact is output and output to the defective pixel correction circuit 9.

  The defective pixel correction circuit 9 inputs signals from the memory 8 and the defective pixel detection circuit 7 respectively, and uses a known technique such as replacement with peripheral pixels when the output of the defective pixel detection circuit 7 is at a high level. Defective pixel correction is performed on the read image data of the current field. If necessary, the phase of the output of the memory 8 and the output of the defective pixel detection circuit 7 are matched.

  Next, the operation of correcting the center of gravity deviation performed by the center of gravity deviation correction circuit 10 will be described. As shown in FIG. 5, in the field reading, the image signal is read from the CCD 3 every two lines every field. For this reason, when the read image signal is displayed on the monitor 13 in an interlaced manner, as shown in the left half of FIG. Therefore, as shown in FIG. 12, by switching the interpolation field by adding the lines having the same color filter array by 1: 3 or using the read data as it is depending on the readout field and line, each field is switched. Are arranged every other line. This reduces the resolution unevenness.

  The operations of the pixel readout of the CCD 3, the defective pixel detection circuit 7, and the gravity center shift correction circuit 10 described above are controlled in conjunction with each other.

  As described above, according to the first embodiment, even when field reading is performed as a preview image during moving image recording or still image recording, an isolated point is determined within and between fields. It becomes possible to detect defective pixels in real time. Therefore, it is possible to detect defective pixels that increase due to a change in internal temperature during use of the imaging apparatus.

  In the description of the operation for detecting an isolated point, in FIGS. 7 to 12, an example in which a white isolated point is detected from a black background image is described. However, the present invention is not limited to this. It can also be applied when detecting a black isolated point from an image. In that case, pixels below a preset luminance value are detected, and the continuity of black pixels is examined instead of white pixels. In addition, although white pixels and black pixels are given as examples, isolated point detection is not limited to binarized data. Even if isolated points are searched after binarizing multi-value data with a threshold value. Good. Alternatively, a difference between multi-value data may be taken and an isolated point search may be performed using the absolute value.

  In the first embodiment, the primary color filter is shown as an example of the color filter of the CCD. However, the present invention is not limited to this, and a complementary color filter or the like may be used.

  In the first embodiment, the digital camera capable of shooting moving images and still images has been described as an example of the imaging device. However, the present invention is not limited to this, and can be applied to a digital camera capable of shooting only moving images or still images. In addition, the present invention is applied to the case where an incident optical image is acquired as an electrical image by photoelectric conversion using a two-dimensionally arranged solid-state imaging device such as an area sensor and is read out in a field. be able to.

<Second Embodiment>
Next, a second embodiment of the present invention will be described.

  FIG. 14 is a block diagram illustrating a configuration of the imaging apparatus according to the second embodiment. The configuration of the imaging apparatus described with reference to FIG. 1 in the first embodiment is different in that a motion vector detection circuit 19 is provided. In addition, the same reference number is attached | subjected to the structure which has the function similar to FIG. 1, and description is abbreviate | omitted.

  The motion vector detection circuit 19 obtains a motion vector between fields or frames from the output data of the AFE circuit 4, and sends the obtained motion vector value to the microcomputer 17 via the data bus 18.

  Next, the control operation of the defective pixel detection and correction processing in the second embodiment will be described with reference to the flowchart of FIG. When the operation is started, the microcomputer 17 acquires a motion vector value from the motion vector detection circuit 19 (step S21) and compares it with a predetermined value set in advance (step S22). If the motion vector value is equal to or smaller than the predetermined value, the defective pixel detection circuit 7 is operated to perform the defective pixel detection operation described with reference to FIG. 9 in the first embodiment, that is, detection of an isolated point ( Step S23). Next, based on the isolated point detection result in step S23, the isolated pixel is removed by the defective pixel correction circuit 9, and the defective pixel data is corrected (step S24).

  On the other hand, if the motion vector value is greater than or equal to the predetermined amount (NO in step S22), the operation of the defective pixel detection circuit 7 is stopped and the isolated point detection operation is not performed.

  Next, in step S25, it is determined whether or not to end the control operation. If the control operation is to be continued, the process returns to step S21 to acquire the next motion vector.

  As described above, according to the second embodiment, defective pixel detection is performed only when the motion between fields of image data is small. Thereby, when performing the inter-field isolated point determination described in the first embodiment, it is possible to prevent a change in pattern caused by the movement of image data from being erroneously determined as an isolated point. As a result, it is possible to improve the accuracy of defective pixel correction.

<Third Embodiment>
Next, a third embodiment of the present invention will be described.

  FIG. 15 is a block diagram illustrating a configuration of the imaging apparatus according to the third embodiment. The configuration shown in FIG. 15 differs from the second embodiment in that a gyro sensor 20 is provided instead of the motion vector detection circuit 19 of FIG. In the second embodiment, the movement of the subject is detected by the motion vector detection circuit 19 based on the image obtained by imaging, and the defective pixel detection circuit 7 is controlled based on the detected magnitude. On the other hand, in the third embodiment, the gyro sensor 20 detects the movement amount of the entire imaging apparatus shown in FIG. Then, the motion amount data acquired by the gyro sensor 20 is sent to the microcomputer 15 via the data bus 18. Other operations are performed based on the flowchart of FIG. 14 as in the second embodiment, but in the third embodiment, the amount of motion is compared with a predetermined value instead of the motion vector value in step S22.

  As described above, according to the third embodiment, defective pixel detection is performed only when the movement of the imaging apparatus is small. Thereby, when the inter-field isolated point determination described in the first embodiment is performed, it is possible to prevent a change in pattern caused by the movement of the imaging apparatus from being erroneously determined as an isolated point. As a result, it is possible to improve the accuracy of defective pixel correction.

<Fourth Embodiment>
Next, a fourth embodiment of the present invention will be described.

  FIG. 16 is a block diagram illustrating a configuration of an imaging apparatus according to the fourth embodiment. The configuration shown in FIG. 16 is different in that a tripod attachment terminal 21 is provided instead of the motion vector detection circuit 19 of FIG. 13 and the gyro sensor 20 of FIG. In the fourth embodiment, the state of the tripod mounting terminal 21 is detected from, for example, the state of impedance, and is sent to the microcomputer 15 via the data bus 18. Only when a tripod (not shown) is attached to the tripod mounting terminal 21, an isolated point is detected by an instruction from the microcomputer 15.

  FIG. 17 is a flowchart illustrating a control operation of defective pixel detection and correction processing in the imaging apparatus according to the fourth embodiment. 14 differs from the operation shown in the flowchart of FIG. 14 in that instead of obtaining a motion vector value in steps S21 and S22 and comparing it with a predetermined value, the state of the tripod mounting terminal is acquired in step S31. Other operations are the same as the operations shown in FIG. 14, and thus the same reference numerals are given and description thereof is omitted.

  As described above, according to the fourth embodiment, when a tripod is attached, the influence of camera shake is eliminated, so that it is possible to prevent the image pattern change caused by the movement of the imaging apparatus from being misidentified as an isolated point. it can. As a result, it is possible to improve the accuracy of defective pixel correction.

  In the first to fourth embodiments, the case where all the pixels of the CCD 3 are read in two fields at the time of field reading has been described. However, the present invention is not limited to this. For example, read out 2 lines and skip 4 lines, read all pixels over 3 fields, read 2 lines and skip 6 lines, read out all pixels over 4 fields, etc. The present invention is also applicable when reading out pixels.

<Other embodiments>
In the above embodiment, the case where the detection of the defective pixel is realized by hardware has been described. However, all or part of the detection can be realized by software.

  In that case, first, a storage medium (or recording medium) in which a program code of software for realizing the functions of the above-described embodiments is recorded is supplied to the system or apparatus. Then, the computer (or CPU or MPU) of the system or apparatus reads and executes the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also the following can be achieved. That is, when the operating system (OS) running on the computer performs part or all of the actual processing based on the instruction of the read program code, the functions of the above-described embodiments are realized by the processing. It is. Examples of the storage medium for storing the program code include a flexible disk, hard disk, ROM, RAM, magnetic tape, nonvolatile memory card, CD-ROM, CD-R, DVD, optical disk, magneto-optical disk, MO, and the like. Can be considered. Also, a computer network such as a LAN (Local Area Network) or a WAN (Wide Area Network) can be used to supply the program code.

1 is a block diagram illustrating a configuration of an imaging apparatus according to a first embodiment of the present invention. It is a figure which shows the concept of the signal level with respect to the pixel position when there exists an isolated point in a to-be-photographed object. It is a figure which shows the concept of the signal level with respect to a pixel position when there exists a defective pixel in an image pick-up element. It is a figure showing the concept of CCD all pixel readout. It is a figure showing the concept of the field reading of CCD. It is a timing chart showing the timing of field reading of CCD. It is a figure showing an example of an isolated area | region and an isolated point, and the isolated area | region and isolated point which were thinned-out read. It is a figure which shows an example of the shape of the isolated area | region continuous in the orthogonal | vertical direction, and the isolated area | region in the continuous 3 field by which thinning-out reading was carried out. It is a flowchart which shows the isolated point determination operation | movement in embodiment of this invention. It is a block diagram showing an example of the internal configuration of the defective pixel detection circuit in the embodiment of the present invention. It is a time chart showing the output of each structure of the defective pixel detection circuit in embodiment of this invention. It is a figure showing the principle of gravity center deviation correction in an embodiment of the invention. It is a block diagram which shows the structure of the imaging device in the 2nd Embodiment of this invention. It is a flowchart which shows the control operation | movement of the detection and correction process of a defective pixel in the 2nd and 3rd embodiment of this invention. It is a block diagram which shows the structure of the imaging device in the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the imaging device in the 4th Embodiment of this invention. It is a flowchart which shows the control operation | movement of the detection and correction process of a defective pixel in the 4th Embodiment of this invention.

Explanation of symbols

1 Lens 2 Optical LPF
DESCRIPTION OF SYMBOLS 3 Image pick-up element 4 Analog front end 5 Timing signal generation circuit 6 Synchronization signal generation circuit 7 Defective pixel detection circuit 8 Memory 9 Defective pixel correction circuit 10 Center-of-gravity shift correction circuit 11 Camera signal processing circuit 12 D / A converter 13 Monitor 14 Encoding Circuit 15 Recording medium 16 Input key 17 Microcomputer 18 Data bus 701 to 704 Line memory 705, 706 Selector 708 In-line isolated pattern detection circuit 709 In-field isolated pattern detection circuit 710 Inter-field isolated pattern detection circuit 711 AND gate

Claims (10)

Imaging means comprising a plurality of pixels for photoelectrically converting incident subject light and outputting an image signal;
Driving means for driving the imaging means so as to output an image signal by changing a readout pattern for each field from the imaging means;
An optical low-pass filter disposed closer to the subject than the imaging means;
Detection means for detecting defective pixels of the imaging means based on an image signal output from the imaging means;
Correction means for correcting the image signal output from the defective pixel detected by the detection means,
When the image signal is output by changing the readout pattern for each field, the detection means is higher than a first preset value based on the image signal in the field and between two consecutive fields, or When a pixel that outputs an image signal lower than the second value lower than the first value is not continuous in two or more pixels in the order of the pixels of the imaging unit, the pixel is regarded as a defective pixel of the imaging unit. An imaging apparatus characterized by detecting. The detection means includes
Whether pixels that output an image signal higher than the preset first value or lower than the second value lower than the first value are continuous in the horizontal direction within the field. An in-line detection means for judging;
Whether pixels that output an image signal higher than the preset first value or lower than the second value lower than the first value are continuous in the vertical direction within the field. In-field detection means to judge,
Whether pixels that output image signals that are higher than the preset first value or lower than the second value lower than the first value are continuous in the vertical direction between fields. An inter-field detection means for judging;
And determining means for determining the pixel as a defective pixel when it is determined that none of the in-line detection means, the in-field detection means, and the inter-field detection means is continuous. The imaging apparatus according to claim 1. Motion detection means for detecting the amount of movement of the subject based on the image signal of the latest field obtained by changing the readout pattern for each field from the imaging means, and then the image signal of the new field;
3. A control means for driving the detection means when the detected motion amount is smaller than a preset motion amount and stopping the detection means when the detected motion amount is larger. The imaging device described in 1. Shake detecting means for detecting the shake of the imaging device;
2. The apparatus according to claim 1, further comprising: a control unit that drives the detection unit when the detected shaking of the imaging apparatus is smaller than a preset shaking, and stops the detection unit when the shaking is large. The imaging device according to any one of 1 to 3. Tripod attachment means for attaching a tripod to the imaging device;
Tripod detection means for detecting whether a tripod is attached to the tripod attachment means;
2. The control unit according to claim 1, further comprising a control unit that drives the detection unit when the tripod detection unit detects a state where the tripod is attached and stops the detection unit when the tripod detection unit does not detect the tripod. The imaging device according to any one of 1 to 4. A defective pixel processing method in an imaging apparatus, comprising: an imaging unit comprising a plurality of pixels for photoelectrically converting incident subject light and outputting an image signal; and an optical low-pass filter disposed on the subject side of the imaging unit. ,
An imaging step of changing the readout pattern for each field and outputting an image signal from the imaging unit;
Based on image signals output from the imaging means in the imaging step and between two consecutive fields, a first value that is higher than a preset first value or lower than the first value. A detection step of detecting a pixel that outputs an image signal lower than a value of 2 as a defective pixel of the imaging unit when two or more pixels are not consecutive in the pixel arrangement order of the imaging unit;
And a correction step of correcting an image signal output from the defective pixel determined in the determination step. In the detection step,
Whether pixels that output an image signal higher than the preset first value or lower than the second value lower than the first value are continuous in the horizontal direction within the field. In-line detection process to judge,
Whether pixels that output an image signal higher than the preset first value or lower than the second value lower than the first value are continuous in the vertical direction within the field. In-field detection process to judge,
Whether pixels that output image signals that are higher than the preset first value or lower than the second value lower than the first value are continuous in the vertical direction between fields. A field-to-field detection process to determine;
A determination step of determining the pixel as a defective pixel when it is determined that the detection is not continuous in any of the in-line detection step, the in-field detection step, and the inter-field detection step. The defective pixel processing method according to claim 6. A motion detection step of detecting the amount of motion of the subject based on the image signal of the latest field output from the imaging means in the imaging step and the image signal of the next new field;
And a control step of executing the detection step when the detected amount of motion is smaller than a preset amount of motion, and stopping execution of the detection step when the amount of motion is large. Or the defective pixel processing method according to 7; A shaking detection step of detecting shaking of the imaging device;
And a control step for executing the detection step when the detected shaking of the imaging device is smaller than a preset shaking, and for stopping the detection step when the shaking is large. Item 9. The defective pixel processing method according to any one of Items 6 to 8. The imaging device has a tripod attachment means for attaching a tripod to the imaging device,
A tripod detection step for detecting whether a tripod is attached to the tripod attachment means;
A control step of executing the detection step when the tripod detection state is detected in the tripod detection step, and stopping the execution of the detection step when the tripod is not detected. The defective pixel processing method according to claim 6.

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