JP2007214775A - Imaging apparatus having image processor, and camera using the apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a signal level from being deviated from that of an original image caused by that a clamping is performed while a black level is not corrected incorrectly owing to horizontal shading. <P>SOLUTION: The imaging apparatus has a solid-state imaging element which has an effective imaging area formed of light-unshielded pixels and an ineffective imaging area formed of light-shielded pixels and an image processor which inputs an effective pixel signal of the effective imaging area and a light-shielded pixel signal of the ineffective imaging area. The image signal processor has a holding means of holding and updating the light-shielded pixel signal, a comparing means of comparing the light-shielded pixel signal held by the holding means with the light-unshielded pixel signal different from the held light-shielded pixel signal, and a decision means of making a decision based upon a comparison result obtained by the comparing means, the holding means being controlled not to hold the light-shielded pixel signal in response to the decision result of the decision means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image pickup apparatus having an image signal processing apparatus for black level adjustment, and a camera using the apparatus.

  Conventionally, a solid-state imaging device such as a CMOS sensor generally outputs a signal from a light-shielded pixel (hereinafter referred to as an optical black signal or an OB signal) as a reference for an output signal. Then, in a circuit that processes the output signal of the solid-state imaging device, a predetermined black level adjustment value (indicating a value to be subtracted to remove the dark current component from the output signal of the effective pixel) is generated from the OB signal. Then, the output signal of the effective pixel is subjected to OB clamping with the black level adjustment value, that is, source calculation and subsequent signal processing such as conversion to a digital value. As shown in FIG. 16, the light-shielded pixels that normally output an OB signal are provided in a horizontal pixel line arranged above the solid-state imaging device and several pixels at the head portion or the last portion of each horizontal line where effective pixels are arranged. Yes. These are referred to as a vertical OB (Optical Black) pixel 1401 and a horizontal OB pixel 1402, respectively.

  Next, an example of conventional OB clamp signal processing will be described with reference to FIG. FIG. 13 is a block diagram of a conventional OB clamp. Reference numeral 101 denotes a solid-state image sensor, and reference numeral 102 denotes an analog signal processing block that first receives an image signal from the solid-state image sensor 101. It mainly consists of a CDS circuit that performs correlated double sampling of video signals and a variable gain control circuit (PGA circuit) that adjusts the amplitude level of the signals. The output of the analog signal processing block 102 is input to an addition / subtraction circuit 103 for OB clamping by a black level adjustment value, and then input to an A / D converter 104 for conversion to a digital value. The OB signal is converted to a digital value and input to a feedback loop to generate a black level adjustment value. The feedback loop includes an OB signal determination block 106 and a D / A converter 105. The OB signal determination block 106 compares the OB signal converted by the A / D converter 104 with a predetermined arbitrary signal. As a result of the comparison, if the OB signal is within an arbitrary signal range, the D / A converter 105 for black level adjustment is set according to the OB signal. The D / A converter 105 includes a memory that can store the updated black level adjustment value.

  The output of the D / A converter 105 is input to the addition / subtraction circuit 103, and the output of the effective pixel is clamped (subtracted) by the black level adjustment value by adding / subtracting to the output of the analog signal processing block 102. Further, the relationship between the vertical OB pixel 202 and the horizontal OB pixel 203 of the solid-state imaging device and the black level adjustment will be described with reference to FIG. On the vertical OB line, the black level adjustment is performed a plurality of times using the OB output of the vertical OB pixel 202 where the black level adjustment pulse (pulse for defining the timing for taking in the OB signal) becomes Low. Thereby, the black level adjustment value is gradually adjusted. The larger the number of times the black level adjustment is performed in the vertical OB pixel 202, the larger the parameter, so that the black level can be adjusted accurately.

  In the effective pixel line, the black level adjustment is performed again in the horizontal OB pixel 203, and the subsequent output of the effective pixel 201 is clamped, that is, subtracted with the black level adjustment value to ensure the dynamic range of the image.

  Furthermore, as a conventional example, a specific example of a method of discriminating abnormal OB pixels due to defects from their output values and not using them for clamping will be shown. When the resolution of the A / D converter that converts the output of the solid-state imaging device into a digital value is 12 bits, the output full scale of the A / D converter is 4095LSB obtained by subtracting 1 from 2 12 to 0LSB. In this case, a range of about 100 LSB to about 300 LSB is selected as the black level. For example, the OB pixel output is sufficiently drawn by adjusting the black level during the reading period of the vertical OB pixel. After that, in the horizontal OB pixel area, a pixel having an output shifted by, for example, 10 LSB or more from the black level adjustment value is determined as a defective pixel and is not used for black level adjustment. Thereby, it is possible to prevent the malfunction of the clamp due to the defective pixel and to maintain the quality of the output image.

  Further, in Patent Document 1, when a difference in black level occurs between the effective pixel area and the optical black (OB) area, an appropriate offset amount is added to the black level adjustment amount, and a signal in the OB area is obtained. A technique for zeroing is disclosed. The offset amount is determined by referring to the offset table of the offset amount determined from the gain of the gain circuit, the element accumulation time, the time for reading one frame, the ambient environment temperature, and the like. Further, there is disclosed a pedestal adjustment means for averaging the outputs of the digitally converted optical black (OB) area and adjusting the reference level of the effective pixel area based on the result level.

  Patent Document 2 discloses that a solid-state image sensor has unevenness in the horizontal direction (also referred to as horizontal shading) of pixel signals, and is generated depending on imaging conditions such as exposure time and temperature. An example of performing black level adjustment / clamping of a solid-state imaging device in which horizontal shading is present in the prior art will be described with reference to FIG.

  The vertical OBs 301, 302, and 303 correspond to a portion where the output of the vertical OB pixel is small, a portion where the output of the vertical OB pixel is medium, and a portion where the output of the vertical OB pixel is large.

  From this region 301, the black level adjustment is performed a plurality of times using the OB output where the black level adjustment pulse is low, and the black level is gradually adjusted. However, the vertical OB pixel area 303 of the vertical OB line does not reflect an accurate black level due to horizontal shading, and the OB output is large. Therefore, in the vertical OB line, the black level is finally adjusted to the output of the region 303 that does not accurately reflect the black level.

  Thereafter, in the effective pixel line, the black level adjustment is continuously performed in a region where the OB output is small in the horizontal OB pixel region 203 and is not affected by the horizontal shading. However, the black level adjustment value is only slightly smaller than the output of the vertical OB pixel region 303. Therefore, since the clamping is performed with the black level adjustment value as it is, the image signal obtained from the effective pixel region 201 becomes smaller than the correct value.

  As the black level adjustment of the effective pixel line proceeds, the black level adjustment value in the horizontal OB pixel region 203 gradually approaches a value reflecting the horizontal OB pixel output. However, since the output of the upper effective pixel is clamped by then, the upper part of the obtained image becomes dark.

  Also, consider a case where vertical OB lines are arranged in the order of 303, 302, and 301 from the left by horizontal shading in the opposite direction to the above. In this case, the black level is finally adjusted to a small value of the OB output in the vertical OB line. However, like the region 303, the horizontal OB pixel region 203 has a large OB output value.

  Accordingly, as the black level adjustment of the effective pixel line proceeds, the black level adjustment value gradually approaches the value of the horizontal OB pixel region 203. Accordingly, the obtained image is relatively brighter in the upper part and darker in the lower part.

  When a defective pixel is skipped in the vertical OB line, the OBs in the vertical OB pixel region 303 and the vertical OB pixel region 302 are determined to be defective pixels and skipped, and the OB in the vertical OB pixel region 301 having a small OB output is skipped. The black level is adjusted only by the output. In the vertical OB line, the black level is finally adjusted to a small value of the OB output. However, like the region 303, the horizontal OB pixel region 203 has a large OB output value. Therefore, all OB outputs in the horizontal OB pixel area are determined to be defective pixels and skipped. Therefore, the clamping is uniformly performed with the black level adjustment value adjusted from the small value of the OB output in all the effective pixel lines.

In this case, even if vertical shading exists, clamping is performed with a uniform black level adjustment value in all effective pixel lines. Therefore, the obtained image is not corrected for vertical shading.
JP 2004-80168 A ([0011] [0013] [0014], FIGS. 2 to 4) JP 2004-112474 A ([0011] [0012] [0013], FIG. 13)

  In the conventional configuration, when the vertical OB pixel region has an area that does not reflect the accurate black level due to uneven brightness in the horizontal direction of the pixel signal, the OB clamp is applied to the signal of the effective pixel while the black level adjustment value is shifted. Will be done. As a result, there is a problem that the signal level is deviated from the image signal that should originally be obtained.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an imaging apparatus and a camera using an image signal processing apparatus that can prevent a signal level shift of an image due to uneven brightness and obtain a high-quality image signal. To do.

In order to solve this problem, the present invention provides
A solid-state image sensor having an effective imaging area formed of pixels that are not shielded and an ineffective imaging area formed of shaded pixels, an effective pixel signal of the effective imaging area, and a shaded pixel signal of the ineffective imaging area are input. In an imaging device having an image signal processing device,
The image signal processing apparatus compares a holding unit that holds and updates the light-shielded pixel signal, a light-shielded pixel signal held in the holding unit, and a light-shielded pixel signal different from the held light-shielded pixel signal. A comparison means;
Determination means based on a comparison result obtained from the comparison means,
The holding means is achieved by controlling not to hold the light-shielded pixel signal in response to the determination result of the determination means.

  With the configuration of the above invention, when horizontal shading occurs due to a change in imaging conditions, the black level is automatically applied only to a specific portion of the vertical OB (near the point where the accurate black level is reflected, for example, near the beginning of the line). It can be used for adjustment. Therefore, even if horizontal shading occurs, it is possible to obtain an accurate black level adjustment value and perform clamping. Therefore, it is possible to prevent a partial image signal output shift from the viewpoint of the entire image, and to obtain a high-quality image signal.

  On the other hand, when there is no horizontal shading, stable black level adjustment can be performed using the entire vertical OB pixel region.

[Embodiment 1]
First, a description will be given with reference to FIG. 1 which is a conceptual diagram of the present invention.

  In FIG. 1, a solid line with an arrow at only one end represents an output line of a pixel signal, and an arrow represents the direction of the signal output. A dotted line represents an output line of the control signal.

  The solid-state imaging device 101 includes a non-imaging area 15 having an OB signal including light-shielding pixels that output an optical black (hereinafter also abbreviated as OB) signal, and an effective pixel area 20.

  The image signal processing apparatus 30 includes a correction unit 40 that corrects an effective pixel signal, a second holding unit 80 that holds a value for correcting the effective pixel signal, a comparison unit 60 that compares the magnitude relationships of different OB signals, and a comparison. A determination unit 70 that determines whether a predetermined criterion is satisfied based on the result is a part of the configuration. Further, the image signal processing apparatus 30 includes a first holding unit 50 that holds one OB signal to be compared and outputs the signal to the comparison unit 60, and a control unit 90 that controls the above configuration based on the determination result.

  An example of a specific signal processing method will be described below.

  For example, the OB signal of the light-shielded pixel provided in the uppermost row of the solid-state imaging device 101 is input to the first holding unit 50 and held (may be an average value of a plurality of OB signals). Thereafter, OB signals of different light-shielding pixels in the same row are input to the comparison means 60. The comparison means 60 compares the magnitude relationship between both OB signals. The comparison result obtained from the comparison unit 60 is input to the determination unit 70. The determination unit 70 determines whether or not the comparison result corresponds to a predetermined condition. If not, the control means 90 controls the OB signal held in the first holding means 50 to be input to the second holding means 80 and updated. Then, the above operation is repeated while the comparison result does not correspond to a predetermined condition.

  When this is the case, the control unit 90 controls the OB signal of the new light-shielded pixel so as not to be input to the first holding unit 50. Although not shown in the figure, the above-described operation is restarted with a signal of a light-shielded pixel subsequent to the light-shielded pixel row corresponding to the determined condition.

  As a result of the above operation, the pixel signal output from the effective pixel in the effective imaging region 20 is corrected by the correction unit 40 using the value finally held in the second holding unit 80 and is then sent to the outside of the imaging device 10. Output sequentially.

  Next, Embodiment 1 of the present invention will be described in detail with reference to FIGS. FIG. 2 is a block diagram of the present embodiment. Reference numeral 101 denotes a solid-state image sensor. Reference numeral 102 denotes an analog signal processing block that first receives an image signal from the solid-state imaging device 101. It mainly consists of a CDS circuit that performs correlated double sampling of video signals and a variable gain control circuit (PGA circuit) that adjusts the amplitude level of the signals. The output of the analog signal processing block 102 is input to an adder / subtractor circuit 103 for adjusting the black level, and then input to an A / D converter 104 for conversion into a digital value.

  A timing generator 107 supplies a black level adjustment pulse. A black level adjustment pulse counter 108 counts the number of assertions of the black level adjustment pulse for each line. Reference numeral 109 denotes a horizontal shading determination register that holds a determination result of occurrence of horizontal shading.

  Reference numeral 110 denotes a black level adjustment permission determination unit that outputs a black level adjustment permission signal to the average value register 405 and the comparator 401 with reference to the outputs of 108 and 109.

  The signal obtained by converting the OB signal from the light-shielded pixel into a digital value is input to the feedback loop when the black level adjustment permission determination unit 110 permits the black level adjustment.

  The black level adjustment permission operation is performed by the black level adjustment pulse counter 108, the horizontal shading determination register 109, and the black level adjustment permission determination unit 110.

  When the timing generator 107 asserts the black level adjustment pulse (for example, Low), the black level adjustment pulse counter 108 counts up. The black level adjustment permission determination unit 110 refers to the count up of the black level adjustment pulse counter 108 and whether or not horizontal shading has occurred from the horizontal shading determination register 109. Then, it is determined whether or not black level adjustment is permitted in the feedback loop.

  If horizontal shading has not occurred, a black level adjustment permission signal is output each time the black level adjustment pulse counter 108 counts up. As a result, a new OB signal is taken into the feedback loop and the black level is adjusted.

  If horizontal shading has occurred, the black level is adjusted only at the beginning of the line. That is, when the black level adjustment pulse counter 108 counts up and the black level adjustment pulse counter value is less than a predetermined value, it is determined that the line is at the head and a black level adjustment permission signal is output.

  If the black level adjustment pulse counter 108 is greater than or equal to a predetermined value, it is determined that the line is not at the head, so that a black level adjustment permission signal is not output, and the feedback loop does not perform black level adjustment.

  The configuration of the feedback loop includes the following plurality of configurations.

  Reference numeral 401 denotes a comparator that compares the captured OB output with the absolute minimum average value, which is the smallest value among the average values of the plurality of OB outputs previously captured. Reference numeral 402 denotes a counter that counts the number of times the comparator 401 determines that the absolute value of the captured OB output is larger than the absolute minimum average value. Reference numeral 403 denotes a horizontal shading determination block for determining the occurrence of horizontal shading from the value of the counter 402. The determination result is output to the horizontal shading determination register 109. Reference numeral 404 denotes a black level adjustment register that outputs a black level adjustment value to the D / A converter 105. Reference numeral 105 denotes a D / A converter that performs analog conversion of the black level adjustment value.

  Every time a black level adjustment permission signal is output from the black level adjustment permission determination unit 110, the comparator 401 compares the absolute minimum average value for an arbitrary number of OB outputs determined in advance. The counter 402 counts the number of times that the absolute value of the OB output is larger than the absolute minimum average value.

  In the horizontal shading determination block 403, the count value of the counter 402 is compared with an arbitrary set value, and if the count value is smaller than the arbitrary set value, it is determined that horizontal shading has not occurred. The black level adjustment value held in the black level adjustment register 404 is updated using the average value of the plurality of OB signals currently taken in, held in the average value register 405. If the count value is larger than an arbitrary set value, it is considered that horizontal shading has occurred, and the black level adjustment value in the black level adjustment register 404 is held without being updated. The horizontal shading determination register 109 holds that horizontal shading has occurred.

  The D / A converter 105 analog-converts the black level adjustment value and supplies the black level adjustment value subjected to analog conversion to the addition / subtraction circuit 103.

  Only when the horizontal shading determination block 403 determines that horizontal shading has not occurred, the updating operation of the absolute minimum average value register 409 is performed as follows.

  The comparator 406 compares the absolute value of the average value of the OB signal held in the average value register 405 with the value held in the absolute minimum average threshold register 410. The larger value is assigned to the absolute minimum average value register 409.

  FIG. 3 is a flowchart illustrating the horizontal shading determination operation in the present embodiment.

  First, in S1, a counter N indicating the number of determinations of the counter 402 is reset to zero.

  Next, in S2, the black level adjustment pulse is used as a trigger, and the magnitude relationship between the individual outputs of an arbitrary number (L in this example) of OB pixels and the absolute minimum average value held in the absolute minimum plain value register 409 is determined. Compare.

  Next, in S3, the number (N) of OB pixels whose OB output is larger than the absolute minimum average value is counted. Then, after the L comparisons are completed, it is compared in S5 whether the number (N) is equal to or larger than an arbitrary set value (M).

  If the number of OB pixels (N) is larger than an arbitrary set value (M), it is determined in S6 that horizontal shading has occurred, and thereafter, black level adjustment is performed only with a black level adjustment pulse near the beginning of the row. . If the number (N) of OB pixels is equal to or less than an arbitrary set value (M), it is determined in S7 that horizontal shading has not occurred.

  Then, the black level adjustment value is changed, and the calculated OB average value is substituted for the held absolute minimum average value. If it is not determined in S6 that horizontal shading has occurred, the above determination operation is repeated until the vertical OB line is completed.

  After the determination operation is completed, while performing black level adjustment in the horizontal OB pixel region 203, the effective pixels in the same row are clamped with the black level adjustment value at that time, and an image signal is output. FIG. 4 is a diagram illustrating an example in which black level adjustment / clamping according to this embodiment is performed when horizontal shading is present.

  The vertical OB pixel areas 301, 302, and 303 correspond to a portion where the vertical OB pixel output is small, a portion where the vertical OB pixel output is medium, and a portion where the vertical OB pixel output is large.

  The black level adjustment permission determination unit 110 permits black level adjustment at a position where the black level adjustment pulse 701 becomes Low, and holds an average value of an arbitrary number of OB pixel outputs as a minimum average value. As a result of performing the determination operation described with reference to FIG. 3, it is assumed that the number of OB pixels whose output is larger than the absolute minimum average value of a plurality of OB pixels exceeds an arbitrary set value at a position 702.

  Since the set value is exceeded, it is determined that horizontal shading has occurred, and the black level adjustment register is not updated, and the horizontal shading determination register 109 holds that horizontal shading has occurred. Thereafter, the black level adjustment permission determination unit 110 does not output a black level adjustment permission signal even when the black level adjustment pulse indicated by the dotted line in the drawing becomes Low. Therefore, only the black level adjustment pulse at the head of the line indicated by the solid line in the drawing is used as a trigger, and the black level adjustment is performed only from the output of the OB pixel in that portion.

  Therefore, the black level adjustment is performed only in the portion 301 where the output of the vertical OB pixel is small, so that the black level adjustment value is stable and accurate. As a result, a black image is then adjusted in the horizontal OB pixel region 203, and a stable image can be obtained from the effective pixel 201 when clamping is performed.

  FIG. 5 is an example showing a case where horizontal shading occurs at a position 702 as in FIG. However, after it is determined that horizontal shading has occurred, black level adjustment is performed from the OB output using a plurality of black level adjustment pulses near the beginning of the row as shown by the solid line in the figure (two lines in this figure) as a trigger. Yes. In FIG. 5, compared to FIG. 4, the black level adjustment can be performed more accurately because the number of times of black level adjustment in a portion where horizontal shading is considered not to occur is increased.

  FIG. 6 is a case where the direction of occurrence of horizontal shading is opposite to that in FIG. The vertical OB pixel areas 301, 302, and 303 are examples corresponding to a portion where the vertical OB pixel output is large, a middle portion of the vertical OB pixel output, and a portion where the vertical OB pixel output is small.

  At a portion where the black level adjustment pulse 701 is low (including a plurality of OB pixels), the average value of the plurality of OB pixel outputs is held as the minimum average value. Therefore, the number of OB pixels whose output of the OB pixel is larger than the absolute minimum average value of the OB exceeds the arbitrary set value at the position 702, and it is determined that horizontal shading occurs.

  Therefore, only the black level adjustment pulse at the head of the line indicated by the solid line in the figure is used as a trigger, and black level adjustment is performed only from the output of the OB pixel in that portion.

  Therefore, after the second row, the black level adjustment is performed only in the portion 702 where the output of the vertical OB pixel is large. Therefore, a stable black level adjustment value is obtained, and then a black image is adjusted in the horizontal OB pixel region 203, and a stable image can be obtained from the effective pixel 201 when clamping is performed.

[Embodiment 2]
Embodiment 2 of the present invention will be described in detail with reference to FIG. FIG. 7 is a block diagram of the present embodiment.

  The present embodiment is characterized in that the average value of the OB pixel output, which is the detection target for occurrence of horizontal shading, is compared with the absolute minimum average value held in advance.

  Differences from the first embodiment will be described below.

  The comparator 401 compares the absolute value of the average value of the OB pixel output held in the average value register 405 and the value held in the absolute minimum average value register 409. If the absolute value of the average value of the OB pixel output is larger than the value held in the absolute minimum average value register 409, it is determined that horizontal shading has occurred. Conversely, when it is small, it is determined that horizontal shading has not occurred.

  Next, the horizontal shading determination operation in this embodiment will be described.

  First, a counter N indicating the number of determinations is reset to zero.

  Next, the magnitude relationship between the average value of an arbitrary number (L in this example) of OB pixel outputs, which are targets for horizontal shading determination, and the absolute minimum average value of the OB pixel outputs held so far Compare

  If the average value of the OB pixel output is larger than the absolute minimum average value of the OB pixel output held so far, it is determined that horizontal shading has occurred. In that case, the black level adjustment is performed only with the black level adjustment pulse near the head of the line.

  If the average value of the OB pixel output is equal to or less than the absolute minimum average value of the held OB pixel output, it is determined that horizontal shading has not occurred. In that case, the black level adjustment value is changed, and the average value of the OB pixels is replaced with the held absolute minimum average value of the OB.

  If it is not determined that horizontal shading has occurred, the above determination operation is repeated until the vertical OB line ends.

  After the determination operation is completed, the black level is adjusted in the horizontal OB pixel area from the horizontal OB line, the effective pixels are clamped, and an image signal is output. The advantage of this embodiment is that the number of comparisons of signal magnitudes can be reduced, and the occurrence of horizontal pudging can be determined in a short time. Other than the above, the description is omitted because it is common to the first embodiment.

[Embodiment 3]
A third embodiment of the present invention will be described with reference to FIG.

  FIG. 8 is a block diagram showing the configuration of the present embodiment.

  The present embodiment is an example in which an OB scratch detection unit 1001 is added before the average value register unit 405 of the first embodiment.

  An OB scratch is an OB pixel that is abnormal due to a problem in the manufacturing process, and an OB level that is an output of an OB pixel having an OB scratch is different from an OB level of a normal OB pixel. Therefore, if the OB level of an OB pixel having an OB defect is used for calculating the average value of the average value register unit 405, a deviation occurs in the average value.

  Therefore, the OB scratch is detected by the OB scratch detection 1001 and is not used for the average value calculation. The means for detecting OB scratches is not specified, but it is conceivable to perform comparison with the previous OB value or comparison with the previous OB average value.

  Therefore, the OB flaw detection unit 1001 can remove the output of the flawed OB pixel before calculating the average value of the OB pixels, and more accurately detect the occurrence of horizontal shading. Other than the above, the description is omitted because it is common to the first embodiment.

[Embodiment 4]
Embodiment 4 of the present invention will be described with reference to FIG.

  FIG. 9 is a block diagram showing the configuration of the present embodiment.

  Unlike the first embodiment, the present embodiment is an example in which an adder / subtracter circuit 103 for adjusting the black level is provided in the subsequent stage of the A / D converter 104. Therefore, black level adjustment is performed on the digital signal. The advantage of adjusting the black level on the digital signal is that the feedback loop is all processed with digital values, so that it is difficult to be affected by external noise and power supply voltage fluctuations.

  Other than the above, the description is omitted because it is common to the first embodiment.

[Embodiment 5]
Embodiment 5 of the present invention will be described with reference to FIG.

  FIG. 10 is a block diagram showing the configuration of the present embodiment.

  The present embodiment compares the magnitude relationship between an individual output of an arbitrary number of OB pixels that are targets of horizontal shading determination, and an added value of an absolute minimum average value and an allowable value considering random noise. It is an example.

  The output of the absolute minimum average value register 409 and the output of the tolerance value register 1201 holding the tolerance value in consideration of random noise are added by the adder 1202, and the added value is input to the comparator 401.

  The advantages of adding the allowable values are as follows. When the random noise of the solid-state imaging device 101 or the A / D converter 104 is large, the OB pixel output level and the average value of the OB pixel output level may be affected by the random noise. In this case, the horizontal shading determination 403 may erroneously determine that horizontal shading has occurred even though horizontal shading has not occurred.

  However, according to the present embodiment, since an allowable value is set and added in consideration of random noise, an erroneous determination of horizontal shading due to random noise can be prevented.

  Other than the above, the description is omitted because it is common to the first embodiment.

[Embodiment 6]
A sixth embodiment of the present invention will be described with reference to FIGS. Embodiment 6 in which the solid-state imaging device and the image signal processing device of the present invention are applied to a still camera 1300 or a solid-state imaging system will be described in detail. The solid-state imaging system is an imaging system using a solid-state imaging device, and is an embodiment equivalent to the following still camera 1300.

  FIG. 14 is a block diagram illustrating a case where the solid-state imaging device and the image signal processing device according to the fourth embodiment of the present invention are applied to a still video camera 1300.

  Reference numeral 1301 denotes a barrier that serves as a lens switch and a main switch, 1302 denotes a lens that forms an optical image of a subject on the solid-state imaging device 1304, and 1303 denotes an aperture for changing the amount of light passing through the lens 1302. Reference numeral 1304 denotes a solid-state image sensor for taking in the subject imaged by the lens 1302 as an image signal, and 1305 denotes an image signal processing circuit for performing analog signal processing.

  Reference numeral 1306 denotes an A / D converter that performs analog-digital conversion of an image signal output from the solid-state imaging device 1304. A signal processing unit 1307 performs various corrections on the image data output from the A / D converter 1306 and compresses the data. The signal processing unit 1307 includes a configuration corresponding to an image signal processing device such as the addition / subtraction circuit 103 and the black level adjustment register 404 according to the fourth embodiment of the present invention. Therefore, the clamp correction of the fourth embodiment for the OB floating is performed as it is. A timing generator 1309 outputs various timing signals to the solid-state imaging device 104, the imaging signal processing circuit 105, the A / D converter 106, and the signal processing unit 107. Reference numeral 1310 denotes an overall control / arithmetic unit for controlling various calculations and the entire still video camera. Reference numeral 1311 denotes a recording medium control I / F unit for performing recording or reading on the recording medium. Reference numeral 1312 denotes a removable recording medium such as a semiconductor memory for recording or reading image data. Reference numeral 1308 denotes an external I / F unit for communicating with an external computer or the like.

  Next, FIG. 12 is a block diagram showing a case where the solid-state imaging device and the image signal processing apparatus of Embodiment 1 are applied to a still video camera 1300. The difference from FIG. 11 when carrying out the invention of Embodiment 1 is that a D / A converter 1313 and an addition / subtraction circuit 1314 are added. At this time, the signal processing unit 1307 includes a configuration corresponding to the image signal processing apparatus of the present invention, such as the black level adjustment register 404. Thereby, the OB clamping operation of the first embodiment for the OB floating is performed as it is.

  Next, the operation of the still video camera 1300 at the time of shooting in the above configuration will be described.

  When the barrier 1301 is opened, a main power supply (not shown) is turned on, a power supply for a control system (not shown) is turned on, and a power supply for an imaging system circuit such as the A / D converter 1306 is turned on.

  Subsequently, in order to control the exposure amount, the overall control / calculation unit 1310 opens the aperture 1303, and the signal output from the solid-state imaging device 1304 is converted by the A / D converter 1306, and then the signal processing unit 1307. Is input. Here, the processing of Embodiment 1 or Embodiment 4 and other processing are performed.

  Based on this data, exposure calculation is performed by the overall control / calculation unit 1310. Brightness is determined based on the result of this photometry, and the overall control / calculation unit 1310 controls the aperture according to the result.

  Next, based on the signal output from the solid-state imaging device 1304, the high-frequency component is extracted and the distance to the subject is calculated by the overall control / calculation unit 1310. Thereafter, the lens 1302 is driven to determine whether or not it is in focus. When it is determined that the lens is not in focus, the lens 1302 is driven again to perform distance measurement. Then, after the in-focus state is confirmed, the main exposure is started.

  When the exposure is completed, the image signal output from the solid-state imaging device 1304 is A / D converted by the A / D converter 1306, and the signal processing unit 1307 performs the correction processing of Embodiment 1 or Embodiment 4 and other processing. The The data is written into the memory unit 1315 by the overall control / calculation unit 1310.

Thereafter, the data stored in the memory unit 1315 is recorded on a removable recording medium 1312 such as a semiconductor memory through the recording medium control I / F unit 1311 under the control of the overall control / arithmetic unit 1310.
Further, the image processing may be performed by directly inputting to a computer or the like through the external I / F unit 1311.

  The present invention may be used in an apparatus and an industry that use an image by a solid-state imaging device.

It is a conceptual diagram of this invention. It is a block diagram of Embodiment 1 of this invention. It is a flowchart explaining the horizontal shading determination operation | movement of Embodiment 1 of this invention. It is a figure explaining the example (the 1) of black level adjustment of the solid-state image sensor in which the horizontal shading of Embodiment 1 of this invention exists. It is a figure explaining the example (the 2) of black level adjustment of the solid-state image sensor in which the horizontal shading of Embodiment 1 of this invention exists. It is a figure explaining the example (the 3) of black level adjustment of the solid-state image sensor in which the horizontal shading of Embodiment 1 of this invention exists. It is a block diagram of Embodiment 2 of this invention. It is a block diagram of Embodiment 3 of this invention. It is a block diagram of Embodiment 4 of this invention. It is a block diagram of Embodiment 5 of this invention. It is a block diagram of Embodiment 6 (the 1) of this invention. It is a block diagram of Embodiment 6 (the 2) of this invention. It is a block diagram of the conventional OB clamp circuit. It is a figure explaining the arrangement | positioning of the effective pixel of the conventional solid-state image sensor, OB pixel, and the relationship of black level adjustment. It is a figure explaining the example of the black level adjustment of the solid-state image sensor in which the conventional horizontal shading exists. It is a figure explaining arrangement | positioning of the effective pixel and OB pixel of a solid-state image sensor.

Explanation of symbols

10 Imaging device 15 Non-imaging area (light-shielding pixel)
20 Effective imaging area (non-shading pixels)
DESCRIPTION OF SYMBOLS 30 Image signal processor 40 Correction | amendment means 50 1st holding means 60 Comparison means 70 Determination means 80 2nd holding means 90 Control means 101 Solid-state image sensor 102 Analog signal processing block 103 Addition / subtraction circuit 104 A / D converter 105 D / A conversion Device 106 OB level determination block 107 timing generator 108 black level adjustment pulse counter 109 black level adjustment permission determination unit 110 horizontal shading determination register 201 effective pixel region 202 vertical OB pixel region 203 horizontal OB pixel region 301 vertical OB pixel region (small signal) )
302 Vertical OB pixel area (during signal)
303 Vertical OB pixel area (large signal)
401, 406 Comparator 402 Counter 403 Horizontal shading determination block 404 Black level adjustment register 405 Average value register 407, 408 Switch 409 Absolute minimum average value register 410 Absolute minimum average threshold register 701, 702 Black level adjustment pulse 1001 OB scratch detection block 1201 Allowable value register 1202 Adder 1300 Still camera, Still video camera 1301 Barrier 1302 Lens 1303 Aperture 1304 Solid-state imaging device 1305 Imaging signal processing circuit 1306 A / D converter 1307 Signal processing unit 1308 External 1 / F unit 1309 Timing generation unit 1310 Overall Control / Calculation Unit 1311 Recording Medium Control 1 / F Unit 1312 Recording Medium 1313 D / A Converter 1314 Addition / Subtraction Circuit 1315 Memory Unit 1401 Straight OB pixel 1402 horizontal OB pixels 1403 effective pixels

Claims (10)

A solid-state image sensor having an effective imaging area formed of pixels that are not shielded and an ineffective imaging area formed of shaded pixels, an effective pixel signal of the effective imaging area, and a shaded pixel signal of the ineffective imaging area are input. In an imaging device having an image signal processing device,
The image signal processing apparatus includes:
Holding means for holding and updating the shading pixel signal;
Comparison means for comparing the light-shielded pixel signal held in the holding means with a light-shielded pixel signal different from the held light-shielded pixel signal;
Determination means based on a comparison result obtained from the comparison means,
The image pickup apparatus, wherein the holding unit is controlled not to hold the light-shielded pixel signal in response to a determination result of the determination unit.   The imaging apparatus according to claim 1, wherein the image signal processing apparatus includes a correction unit that corrects an effective pixel signal of the effective pixel region based on a value held in the holding unit.   The imaging apparatus according to claim 1, wherein the holding unit holds an average value obtained by averaging a plurality of light-shielded pixel signals.   A plurality of rows of the light-shielded pixels are arranged in the light-shielding region, receive a light-shielded pixel signal from the light-shielded pixels for one row of the plurality of rows, and the holding unit outputs a light-shielded pixel signal in response to a determination result of the determination unit. The imaging apparatus according to claim 1, wherein after being controlled not to hold, the holding unit is controlled to receive a shading pixel signal from the next row onward. The comparison means compares an average value of a plurality of light-shielded pixel signals held in the holding means with a light-shielded pixel signal not passing through the holding means,
2. The determination unit according to claim 1, wherein the determination unit determines whether or not the number of light-shielded pixel signals not passing through the holding unit having an absolute value larger than the average value exceeds a predetermined number. The imaging device described in 1. The comparing means compares an average value of a plurality of light-shielded pixel signals held in the holding means with an average value of a plurality of light-shielded pixel signals not passing through the holding means,
The determination unit determines whether an average value of a plurality of light-shielded pixel signals not passing through the holding unit is larger than an average value of a plurality of light-shielded pixel signals held in the holding unit. The imaging device according to claim 1. The comparison unit compares a value obtained by adjusting a comparison result with an average value of a plurality of light-shielded pixel signals held in the holding unit and a light-shielded pixel signal that does not pass through the holding unit. And
The determination means determines whether the number of light-shielded pixel signals not passing through the holding means having a larger absolute value than the value obtained by correcting the average value for adjusting the comparison result exceeds a predetermined number. The imaging apparatus according to claim 1, wherein it is determined whether or not. The comparison means includes a value obtained by performing correction for adjusting a comparison result on an average value of a plurality of light-shielded pixel signals held in the holding means, and an average of a plurality of light-shielded pixel signals not passing through the holding means. Compare values,
The determination unit determines whether an average value of a plurality of light-shielded pixel signals not passing through the holding unit is larger than a value obtained by correcting the average value held in the holding unit to adjust a comparison result. The image pickup apparatus according to claim 1, wherein the image pickup device is determined.   The imaging apparatus according to claim 6, wherein the determination unit includes a unit capable of changing the predetermined number.   10. The image pickup apparatus according to claim 1, an optical system that forms an image of light on the solid-state image pickup device, and a signal processing circuit that processes an output signal from the pixel signal processing device. A camera characterized by that.

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