JP2007006538A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of improving the accuracy of OB clamp, when an image area of an imaging device is split into two or more to the right and to the left and is read and video signal is outputted to the outside. <P>SOLUTION: An imaging device 14 comprises imaging areas 41A and 41B, whose imaging surfaces split into two in the horizontal direction, and OB areas 42A and 42B, which are optical black level detection area, respectively provided at the end of imaging areas 41A and 41B. Level of each line is computed from the mean value of the values obtained, independently, by adding OB level data from each of blocks 43A1 to 43A4 of the imaging area 41A and the OB area 42A and blocks 43B1 to 43B4. The OB clamp is provided, by subtracting the level from the value outputted from each imaging area 41A and 41B to the right and the left. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus that reads a video signal output from a solid-state imaging device by dividing the left and right sides of an imaging area into two or more.

  In recent years, an image pickup apparatus is an electronic still camera capable of performing signal processing on a video signal obtained by using a solid-state image pickup device and transferring data as a still image to a medium such as a personal computer against the background of popularization of a camera-integrated VTR in a general home. Camera-integrated VTRs with added functions have been commercialized and are becoming widespread. In addition, with the advancement of miniaturization processing technology for large-scale semiconductor integrated circuit (LSI) processes, the total number of pixels of a solid-state image sensor tends to increase dramatically.

  In addition, in such a camera-integrated VTR, with respect to a video signal output from a solid-state image sensor, black level detection pixels in advance in the vertical direction are approximately several tens of pixels at the end of the imaging area of the solid-state image sensor. A video signal is obtained by subtracting the level obtained by extracting and averaging a plurality of pixels from the signals output from those pixels, and subtracting the level obtained as a signal level when there is no light from the signal output in the imaging area. The black level is generally defined, and such correction is called an OB clamp.

  By the way, as described above, the number of pixels per line increases as the number of pixels of the solid-state image sensor increases. However, the time for outputting a video signal of one line from the solid-state image sensor is limited to the television. In general, the signal readout clock frequency for outputting a signal from the solid-state imaging device inevitably increases in proportion to the number of pixels.

  However, when the clock frequency for reading signals from the solid-state imaging device increases, the signal processing circuit in the subsequent stage needs to perform processing at the same frequency, which increases circuit design restrictions. In addition, it is necessary to carefully take measures against noise and radiation. Therefore, as a means for avoiding these troubles, the imaging area of the solid-state imaging device is divided into two or more left and right, and each is independently provided with a signal output channel and read, so that it is half that required conventionally. The method of reading out the signal output from the solid-state image sensor at a frequency of.

  However, in an image pickup apparatus mounted on a camera-integrated VTR that reads out a video signal output from a solid-state image pickup device as described above by dividing the image pickup area into two or more left and right, there are a plurality of signal output channels. As a result, variations occur in the characteristics of the output buffer of each channel, and as a result, a step is generated on the output boundary surface between the channels. Further, when output variations due to temperature changes occur in the output buffer of each channel in the solid-state imaging device, the step at the boundary surface further expands with an increase in imaging time.

  In addition, in an imaging apparatus mounted on a camera-integrated VTR that reads an imaging area into two parts on the left and right sides, the OB level of the video signal output from each of the left and right areas is a dispersion variation at the time of manufacturing a solid-state image sensor. As a result, if an average value obtained by averaging the entire OB is used, accurate OB clamping cannot be performed, and a difference occurs in the black level on the left and right sides of the screen.

  In addition, in an imaging device with a large number of pixels, charges are transferred with a high-frequency drive pulse of, for example, 36 MHz, so that a pulse that should be a rectangular wave is dulled and the number of transfer stages is very large. There is an OB level difference between the lines that cannot be ignored and should theoretically be zero.

  Furthermore, in the conventional imaging device, if the average of the signal levels of the black level detection pixels is used as the reference black level for all imaging areas, there will be an offset above and below the imaging area, and black level adjustment will be performed correctly. An area that cannot be created may be created. Furthermore, since a minute modulation component is output from each color filter even when there is no light, an offset from the reference black level obtained by fully adding each color signal occurs.

  The present invention has been made in view of the above points, and aims to improve the accuracy of the OB clamp when the readout image signal is output to the outside by dividing the imaging area of the solid-state imaging device into two or more parts on the left and right. The object is to provide an imaging device.

  Further, another object of the present invention is to perform an OB clamp when reading an imaging area of a solid-state imaging device by dividing it into two left and right or multiple divisions so that there is no correction difference between the left and right sides of the screen. To provide an apparatus.

  In order to achieve the above object, an imaging apparatus according to a first aspect of the present invention is a solid state in which an imaging area is divided into a plurality of parts in the horizontal direction and first and second OB areas are provided at both left and right ends of the imaging area. First and second OB signals indicating optical black levels output from the first and second OB areas, respectively, from the imaging element and imaging signals output from the plurality of divided imaging areas of the solid-state imaging element. An OB clamp processing unit that performs OB clamping of an imaging signal by subtracting any OB signal, and the OB clamp processing unit is connected to each line for the first OB area. A first OB correction level calculation means for calculating a first OB correction level for each line, and a second OB correction level calculation for calculating a second OB correction level for each line for the second OB area. And the first OB correction level of all lines from the first OB correction level calculation means are stored, and each line of the divided imaging area closer to the first OB area among the plurality of divided imaging areas is imaged. The first correction means for outputting and subtracting the stored first OB correction level for the signal, and the second OB correction level for all lines from the second OB correction level calculation means are stored. Second correction for outputting and subtracting the stored second OB correction level for the imaging signal of each line in the divided imaging area closer to the second OB area among the plurality of divided imaging areas Means.

  In the present invention, OB due to a difference in the number of charge transfer stages in the OB area (a pixel in the upper part of the OB area has a larger number of transfer stages and a pixel in the lower part of the OB area has a smaller number of transfer stages) like a multi-pixel solid-state imaging device. Even when a difference in signal level appears remarkably, the first and second OB correction levels for each line are calculated for each of the first and second OB areas on the left and right of the imaging area, and the corresponding lines are calculated. Therefore, the correct OB clamping process can be performed.

  In order to achieve the above object, an image pickup apparatus according to a second aspect of the present invention provides a first OB level calculation means according to the first aspect of the present invention from a plurality of pixels in both the vertical and horizontal directions within the first OB area. A plurality of first blocks are provided, an average value of OB signal levels in the plurality of first blocks is calculated for each block, and a correction inclination is given in the vertical direction of the screen based on the plurality of average values. The second OB level calculation means is a means for calculating a first OB correction level for each line, and the second OB level calculation means includes a plurality of second blocks composed of a plurality of pixels in the vertical and horizontal directions in the second OB area. And calculating an average value of the OB signal levels in the plurality of second blocks for each block, and giving a correction gradient in the vertical direction of the screen based on the plurality of average values. A means for calculating the OB correction level And wherein the door.

  In the present invention, a plurality of blocks are provided in each of the first OB area and the second OB area, an average value of the OB signal level is calculated for each block, and a plurality of blocks between the blocks are calculated based on the average value. Since the OB correction level having the correction inclination in the screen vertical direction of the line OB signal level is obtained and subtracted from the imaging signal, correct OB clamping processing can be performed.

  Moreover, the imaging device of 3rd invention is arbitrary from the outside the position in the 1st OB area of said some 1st block, and the position in the 2nd OB area of several 2nd block. It further has a means to move to. As a result, the block can be moved to a portion that is least affected by noise or pixel defects on the solid-state imaging device.

  In the present invention, by having means for arbitrarily moving the position in the first OB area of the plurality of first blocks and the position in the second OB area of the plurality of second blocks from the outside, Since the above block is moved to a portion that is least affected by noise or pixel defects on the solid-state image sensor, a more accurate OB clamping process can be performed.

  According to the present invention, the difference in the number of charge transfer stages in the OB area as in a multi-pixel solid-state imaging device (the number of transfer stages is large in the pixels above the OB area and the number of transfer stages is small in the pixels below the OB area). Even if the difference in the OB signal level due to the difference appears remarkably, the first and second OB correction levels for each line are calculated for each of the first and second OB areas on the left and right of the imaging area. By subtracting from the image signal of the line to be corrected, correct OB clamping processing can be performed, so that the correct black level and achromatic color can be reproduced over the entire screen without causing an offset from the reference black level at the top, bottom, left and right of the imaging area. As a result, it is possible to suppress image shading and low-illumination unnatural coloring due to black level fluctuations.

  According to the present invention, there is provided means for arbitrarily moving the positions of the plurality of first blocks in the first OB area and the positions of the plurality of second blocks in the second OB area from the outside. By having the block, the block is moved to a portion that is least affected by noise, pixel defects on the solid-state imaging device, and the like, so that a more accurate OB clamping process can be performed.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of an embodiment of an imaging apparatus which is a reference example of the present invention. This embodiment is an image pickup apparatus applied to a camera-integrated VTR, and incident light from a subject condensed by an optical lens unit 1 is applied to a solid-state image pickup device 2 and subjected to photoelectric conversion.

  FIG. 2 shows a configuration diagram of an embodiment of the solid-state imaging device 2. As shown in the figure, the solid-state imaging device 2 has imaging areas 21A and 21B whose imaging plane is divided into two in the horizontal direction, and optical black level detection areas provided at the ends of the imaging areas 21A and 21B. OB areas 22A and 22B, and charge from each pixel in the imaging area 21A and the OB area 22A is vertically transferred through a vertical transfer path (not shown) and accumulated, and is horizontally transferred. Charges from the horizontal CCD 24A and the pixels in the imaging area 21B and the OB area 22B are vertically transferred through a vertical transfer path (not shown) and accumulated, and output from the horizontal CCD 24B and the horizontal CCDs 24A and 24B that horizontally transfer the charges. Output amplifiers 25A and 25B for amplifying the received video signal. Independently from the output amplifiers 25A and 25B, video signals captured in the left and right imaging areas 21A and 21B are output for each line.

  By using such a solid-state imaging device 2, the present embodiment can constitute a system at a frequency that is 1/2 times the driving frequency of a solid-state imaging device that is conventionally required. This system can be used to record high-quality video on a recording medium.

  From the output amplifiers 25A and 25B of the solid-state imaging device 2, the left and right two-channel video signals output in parallel based on the driving signal from the solid-state imaging device driving unit 12 in FIG. 1 are sent to the analog signal processing unit 3 in FIG. After being subjected to correlated double sampling, automatic gain control (AGC) and the like, they are supplied to the A / D converter 4 and digitized. The digitized two-channel video signal is subjected to OB clamp processing and gain difference adjustment of the left and right output amplifiers of the solid-state imaging device 2 to be described later based on the control signal from the control unit 11 in the OB clamp processing unit 5. Thereafter, the pixel density conversion unit 6 performs pixel density conversion (such as pixel thinning out within a unit time), thereby converting the image signal into one channel.

  The one-channel video signal output from the pixel density conversion unit 6 is supplied to the digital signal processing unit 7 and subjected to various signal processing, and further converted into predetermined standard television signal data. The analog signal is supplied to the A converter 8 and converted into an analog television signal, and the external image display unit 9 displays the image. At the same time, a video signal having a signal form suitable for recording / reproduction is taken out from the digital signal processing unit 7, supplied to the VTR recording unit 10, and recorded on the magnetic tape by the rotary head.

  Next, the adjustment operation of the output gain difference between the left and right output amplifiers of the solid-state imaging device 2 in the OB clamp processing unit 5 according to this reference example will be described in detail. The output amplifiers 25A and 25B shown in FIG. 2 are designed to have the same fixed amplification factor, but in reality, a gain difference occurs due to variations in manufacturing, and as a result, left and right A step occurs at the boundary surface of the video signal.

  Therefore, the OB clamp processing unit 5 has a block configuration as shown in FIG. 3, for example. The video signal imaged in the imaging area 21A shown in FIG. 2 is digitized by the A / D converter 4 and supplied to the OB clamp circuit 31A in FIG. 3, where a plurality of pixels are obtained for the signal from the OB area 22A. A known clamping process is performed in which the level obtained by extraction and averaging is subtracted from the video signal imaged in the imaging area 21A as a signal level when there is no light. Further, the video signal imaged in the imaging area 21A is supplied to the boundary surface integrating unit 32A.

  On the other hand, at the same time, the video signal imaged in the imaging area 21B shown in FIG. 2 is digitized by the A / D converter 4 and supplied to the OB clamp circuit 31B in FIG. Based on this signal, a known clamping process similar to that of the OB clamp circuit 31A is performed and supplied to the boundary surface accumulating unit 32B.

  The boundary surface accumulating units 32A and 32B extract several pixels, for example, 8 pixels, near the boundary of the imaging areas 21A and 21B from the input video signal before OB clamping, and take the average of each. The change amount calculation unit 33A in FIG. 3 includes four monitoring areas that are in contact with the imaging area 21B of the imaging area 21A indicated by 231, 233, 235, and 237 in FIG. The signals of each pixel are integrated separately. At the same time, the change amount calculation unit 33B in FIG. 3 is in contact with the imaging area 21A of the imaging area 21B indicated by 232, 234, 236, and 238 in FIG. The signals of each pixel in each of the four monitoring areas are integrated separately. The monitoring area 231 is adjacent to the monitoring area 232, the monitoring area 233 is adjacent to the monitoring area 234, the monitoring area 235 is adjacent to the monitoring area 236, and the monitoring area 237 is adjacent to the monitoring area 238.

  Here, each of the monitoring areas 231, 233, 235 and 237 and the monitoring areas 232, 234, 236 and 238 are, for example, areas of 8 pixels × 64 lines as shown in FIG. As for the pixels in this monitoring area, the output from one pixel having the cyan (Cy) color filter and one pixel having the yellow (Ye) color filter alternately appears on the odd lines in a total of 8 pixels. In the even line, the output from one pixel having a magenta (Mg) color filter and one pixel having a green (G) color filter alternately appears in total of eight pixels, and each pixel has 128 pixels for each color filter. The total of 512 pixels.

  The positions of the monitoring areas 231, 233, 235, and 237 and the monitoring areas 232, 234, 236, and 238 on the imaging areas 21 A and 21 B are arbitrarily set by the control from the control unit 11 in FIG. Can move to a position.

  Here, the change amount calculation unit 33A in FIG. 3 separately integrates the signal of each pixel for each of the four monitoring areas 231, 233, 235, and 237 in the output signal of the boundary surface integration unit 32A. Instead of integrating the data of 512 pixels in each monitoring area at once, the integration is performed separately for each 128 pixels for each color having the above four color filters. That is, the change amount calculation unit 33A has a 128 pixel integrated value C1 having a cyan color filter, a 128 pixel integrated value Y1 having a yellow color filter, and a 128 pixel integrated value having a magenta color filter in the monitoring area 231. The first integration unit integrates M1 and an integrated value G1 of 128 pixels having a green color filter.

  Similarly, the change amount calculation unit 33A includes an integrated value C2 of 128 pixels having a cyan color filter in the monitoring area 232, an integrated value Y2 of 128 pixels having a yellow color filter, and an integrated value of 128 pixels having a magenta color filter. The value M2 and the 128-pixel integrated value G2 having the green color filter are integrated by the second integrating unit, and the 128-pixel integrated value C3 having the cyan color filter in the monitoring area 233 and 128 having the yellow color filter are included. The integrated value Y3 of the pixel, the integrated value M3 of 128 pixels having a magenta color filter, and the integrated value G3 of 128 pixels having a green color filter are integrated by a third integrating unit, and a cyan color filter in the monitoring area 234 is obtained. 128 pixel integrated value C4 having a yellow color filter, 128 pixel integrated value Y4 having a yellow color filter, 128 pixels having a magenta color filter The integrated value G4 of 128 pixels with a color filter of the integrated value M4 and green integrating by the fourth integration unit.

  Similarly, the change amount calculation unit 33B in FIG. 3 does not collectively integrate the data of 512 pixels in each of the four monitoring areas 232, 234, 236, and 238 in the output signal of the boundary surface integration unit 32B. Instead, integration is performed separately for each 128 pixels for each color having the four color filters. Thereby, an error due to a difference in the degree of modulation for each color filter can be absorbed, and more accurate step detection can be performed.

  The interpolation calculation unit 331A in the change amount calculation unit 33A is an integrated value (C1, Y1, M1, G1) for each pixel having the color filters of the four monitoring areas 231, 233, 235, and 237 thus obtained. , (C2, Y2, M2, G2), (C3, Y3, M3, G3) and (C4, Y4, M4, G4), first, a value between integrated values of pixels having the same cyan color filter ( From C1, C2, C3, and C4), correction values in each line as shown in FIG. 5 are calculated. Similarly, the interpolation calculation unit 331A in the change amount calculation unit 33A calculates the integration of pixels having a magenta color filter from the values (Y1, Y2, Y3, Y4) of the integration values of pixels having a yellow color filter. From the values (M1, M2, M3, M4) between the values to the values (G1, G2, G3, G4) between the integrated values of the pixels having the green color filter, corrections in each line as shown in FIG. Calculate the value.

  Similarly to the above-described interpolation calculation unit 331A, the interpolation calculation unit 331B in the change amount calculation unit 33B also has the same color filter among the integrated values for each pixel having the color filters of the four monitoring areas 232, 234, 236, and 238. The correction value for each line is calculated from the values of the integrated values of the pixels having. By repeating this every screen, the signal level converges to a certain level, the effect of instantaneous signal changes on each screen is eliminated, the effect of errors due to noise is reduced, and more accurate step detection is performed. It can be carried out.

  The level comparison unit 34 illustrated in FIG. 3 includes the correction values for the same color filters in the same line in two adjacent monitoring areas among the eight monitoring areas 231 to 238 among the output correction values of the change amount calculation units 33A and 33B. After comparing the levels with each other and taking the difference to obtain a step value, a level correction value is obtained by linear interpolation.

  That is, step values (signal level differences) that are differences between correction values of the same color filter on the same line in two adjacent monitoring areas are as indicated by I to IV in FIG. From these four step values, the step value of each line is obtained by linear interpolation and stored in a buffer in the level comparison unit 34 corresponding to the number of lines prepared in advance, and a value corresponding to each line is obtained. A level correction value corresponding to the level ratio is obtained.

  For example, when the output of the change amount calculation unit 33A in the same line is a and the output of the change amount calculation unit 33B is b, the level comparison unit 34 has a level ratio of (a / b). The level correction value (b / a) is output to the multiplier 35A and multiplied by the output signal of the OB clamp circuit 31A, and the level correction value 1 is output to the multiplier 35B to output the level correction value (b / a). Multiply the output signal.

  Thereby, even in an imaging apparatus having output variations caused by gain differences due to manufacturing variations of the output amplifiers 25A and 25B, the OB clamp processing unit 5 shown in FIG. 1 has steps in the divided imaging areas 21A and 21B. Therefore, the video signal subjected to the OB clamping process can be taken out. As a result, it is possible to improve the yield of the image pickup apparatus including the solid-state image pickup device and reduce the cost without breaking the system.

  Next, another embodiment of the OB clamp processing unit 5 of the imaging apparatus having the solid-state imaging device shown in FIG. 2 will be described. FIG. 6 shows a block diagram of another embodiment of the OB clamp processing unit 5 of the imaging apparatus. In the figure, the same components as those in FIG. In the OB clamp processing unit 5 shown in FIG. 3, the signals for obtaining the left and right signal levels are obtained by sampling the video signals before being input to the OB clamp circuits 31A and 31B, but the OB clamp shown in FIG. The processing unit 5 is characterized in that the signal after OB clamping processing by the OB clamping circuits 31A and 31B and level correction by the multipliers 35A and 35B is sampled.

  In FIG. 6, the video signal after the level correction of the imaging area 21A taken out from the multiplier 35A is supplied to the boundary surface integration unit 36A and subjected to the same integration process as the boundary surface integration unit 32A in FIG. The amount is supplied to the amount calculation unit 37A. On the other hand, the video signal after the level correction of the imaging area 21B taken out from the multiplier 35B is supplied to the boundary surface integration unit 36B and is subjected to the integration process similar to the boundary surface integration unit 32B in FIG. To the unit 37B. The change amount calculation units 37A and 37B perform change amount calculation similar to the change amount calculation units 33A and 33B of FIG. 3 to generate level correction values, and supply them to the multipliers 35A and 35B.

  In this embodiment, the level difference between the output amplifiers 25A and 25B of the solid-state imaging device 2 is always zero by correcting the level difference between the left and right imaging areas 21A and 21B in a feedback configuration. Control and build a self-managed system.

  Further, the boundary position between the left and right imaging areas 21A and 21B is detected from the output signal and horizontal / vertical synchronization signal of the digital signal processing unit 7 of FIG. 1, and a step due to the difference in signal level is finally generated. It is possible to further improve the detection accuracy by monitoring whether or not it is detected.

  Each of the embodiments of the OB clamp processing unit 5 shown in FIGS. 3 and 6 is based on the difference in the sampling position of the detection signal for level difference detection. Among these sampling positions, It is also possible to construct a system by combining detection information from one or a plurality of sampling positions.

  Next, an imaging apparatus according to the present invention will be described with reference to examples. FIG. 7 shows a block diagram of an imaging apparatus applied to this embodiment. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. This embodiment is an image pickup apparatus applied to a camera-integrated VTR, and incident light from a subject condensed by the optical lens unit 1 is applied to a solid-state image pickup device 14 and subjected to photoelectric conversion.

  FIG. 8 shows a configuration diagram of an example of the solid-state imaging device 14 in FIG. As shown in the figure, the solid-state imaging device 14 has imaging areas 41A and 41B whose imaging plane is divided into two in the horizontal direction, and optical black level detection areas provided at the ends of the imaging areas 41A and 41B, respectively. OB areas 42A and 42B, and charge from each pixel in the imaging area 41A and the OB area 42A is vertically transferred through a vertical transfer path (not shown) and accumulated, and is horizontally transferred. The charge from each pixel of the horizontal CCD 44A, the imaging area 41B and the OB area 42B is vertically transferred through a vertical transfer path (not shown) and accumulated, and is composed of a horizontal CCD 44B for horizontally transferring the charge and an output amplifier (not shown). ing. Independently of the horizontal CCDs 44A and 44B, video signals captured in the left and right imaging areas 41A and 41B are output for each line.

  By using such a solid-state imaging device 14, this embodiment can constitute a system at a frequency that is 1/2 the driving frequency of a solid-state imaging device that is conventionally required. The system can be used to record high-quality video on a recording medium.

  Based on the drive signal from the solid-state image sensor drive unit 12 in FIG. 7 from the solid-state image sensor 14, the left and right two-channel video signals output in parallel are the analog signal processing unit 3 and the A / D conversion unit 4 in FIG. Is supplied to the OB clamp processing unit 15, where OB clamp processing and OB signal level difference adjustment described later are performed based on a control signal from the control unit 11. The signal processing after the OB clamp processing unit 15 is the same as the signal processing of the imaging apparatus shown in FIG.

  Next, the operation of the OB clamp processing unit 15 according to the present embodiment will be described in detail with reference to the drawings. As described above, the solid-state imaging device 14 used in this embodiment has a bilaterally symmetric configuration as shown in FIG. 8, and the video signals read from the imaging area 41A and the OB area 42A are In parallel with this, video signals read out from the imaging area 41B and the OB area 42B are output to the outside via the horizontal CCD 44A and an output amplifier (not shown) for each line, and the horizontal CCD 44B and not shown for each line. It is output to the outside through an output amplifier.

  Here, the pixels in the left and right OB areas 42A and 42B have photodiodes, color filters, on-chip lenses, and vertical CCDs (vertical transfer paths), and have the same structure as the imaging areas 41A and 41B in the center. Unlike the imaging areas 41A and 41B, the pixels in the OB areas 42A and 42B are shielded from light, and incident light from the outside does not reach the photodiodes in the OB areas 42A and 42B. Accordingly, the signals output from the OB areas 42A and 42B always output an optical black level (OB level) signal.

  The OB level signals output from the OB areas 42A and 42B are also output to the outside via the horizontal CCDs 44A and 44B in FIG. 8 and an output amplifier (not shown) for each line, while the OB clamp in FIG. In the processing unit 15, among the OB level data output from the input OB areas 42A and 42B, each of arbitrary four blocks (as shown in FIG. 8, in the OB area 42A, blocks 43A1 to 43A4 and in the OB area 42B, The OB level data of the blocks 43B1 to 43B4) are added independently for each block.

  Each of the blocks 43A1 to 43A4 and the blocks 43B1 to 43B4 is, for example, an area of 1024 pixels in total of 16 pixels in the horizontal direction and 64 pixels in the vertical direction as shown in FIG. Within one block, in odd lines, the output from one pixel having a cyan (Cy) color filter and one pixel having a yellow (Ye) color filter alternately appears in total of 16 pixels of 8 pixels, In the even line, the output from one pixel having a magenta (Mg) color filter and one pixel having a green (G) color filter alternately appears in total of 16 pixels of 8 pixels. It consists of 1024 pixels.

  The OB clamp processing unit 15 calculates the level of each line from the average value obtained by independently adding the OB level data from each of the blocks 43A1 to 43A4 and the blocks 43B1 to 43B4, By subtracting this from the values output from the left and right imaging areas 41A and 41B, OB clamping is realized.

  The positions of the blocks 43A1 to 43A4 and the blocks 43B1 to 43B4 on the OB areas 42A and 42B can be moved to arbitrary positions by the control from the control unit 11 in FIG. It is possible to integrate the parts that are least affected by pixel defects or the like on the image sensor.

  Next, the configuration and operation of the OB clamp processing unit 15 will be described in more detail. FIG. 10 is a block diagram showing a main part of an embodiment of the OB clamp processing unit 15 described above. FIG. 10 shows an OB clamp processing unit for one imaging area of the left and right imaging areas of the OB clamp processing unit 15 as a representative, and actually two circuit configurations shown in FIG. 10 are provided in parallel.

  A two-channel video signal digitized by the A / D conversion unit 4 shown in FIG. 7 is supplied to the OB clamp processing unit 15, and one of the video signals (here, the imaging area 41A and the OB area 42A) is supplied. Are supplied to the OB BLK integrating unit 51 and the subtractor 54 shown in FIG. The OB BLK integrating unit 51 receives the digital video signals from the imaging area 41A and the OB area 42A as input signals, and the four blocks 43A1 to 43A4 from the control unit 11 shown in FIG. Based on the position information, the OB level data of the four blocks 43A1 to 43A4 are gated out using the horizontal synchronizing signal and the vertical synchronizing signal, supplied to the adder 512 of FIG. 10, and added to the output of the adder 512. Accumulate.

  The integrated value of the OB level data for each of the four blocks 43A1 to 43A4 obtained by the OB BLK integrating unit 51 is supplied to the averaging unit 521 in the change amount calculating unit 52 and averaged independently of each other. Then, the OB correction level for each line is obtained by the calculation unit 522 in the change amount calculation unit 52. That is, the arithmetic unit 522 determines that the average value input from the averaging unit 521 is AV1 in the block 43A1 from the line La to the line Lb, AV2 in the block 43A2 from the line Lc to the line Ld, and from the line Le to the line Lf. If the block 43A3 is AV3 and the block 43A4 from the line g to the line Lh is AV4, the following calculation is performed.

The center position in the vertical direction in the block 43A1 is (La + Lb) / 2, the center position in the vertical direction in the block 43A2 is (Lc + Ld) / 2, the center position in the vertical direction in the block 43A3 is (Le + Lf) / 2, and the block 43A4 Since the center position in the vertical direction at (Lg + Lh) / 2 is, the distance D (A12) between the center pixel of the block 43A1 and the center pixel of the block 43A2 is
D (A12) = {(Lc + Ld) / 2}-{(La + Lb) / 2}
The change amount X (A12) of the OB level at that time is
X (A12) = AV2-AV1
It is.

  Therefore, the OB correction level OBA12 (n) in each line between the block 43A1 and the block 43A2 is given by the following equation, where n is the number of lines from the central pixel of the block 43A1 to the central pixel of the block 43A2.

OBA12 (n) = n · X (A12) / D (A12) + AV1
Similarly, the OB correction level in each line between the block 43A2 and the block 43A3 and the OB correction level in each line between the block 43A3 and the block 43A4 are also obtained.

  If the number of lines in the vertical direction of the solid-state imaging device 14 is 480, the OB correction level OBA01 (n) from the first line to the center line of the block 43A1 and the OB correction from the center line of the block 43A4 to the 480th line. The level OBA45 (n) is calculated by the following equation using the slope between the blocks 43A1 and 43A2 and the slope between the blocks 43A3 and 43A4, respectively.

OBA01 (n) = AV1- (La-n) .X (A12) / D (A12)
OBA45 (n) = n · X (A34) / D (A34) + AV4

  FIG. 11 shows the OB correction level of each line obtained in the change amount calculation unit 52 in this way. The OB correction level of each line is temporarily stored in a register assigned to the corresponding line among 480 registers 531 provided in parallel in the correction value storage unit 53. Thereafter, at the time of video signal correction, the number of lines of the input video signal is detected from the horizontal synchronization signal and the vertical synchronization signal, and the OB correction level of the line corresponding to the detected line is stored in the correction value storage unit 53 from the corresponding register 531. The OB clamp is realized by selecting by the switch circuit 532 and supplying to the subtractor 54 and subtracting it from the input video signal.

  Thus, by detecting a change in the OB level for each line and changing the OB correction level, it is possible to perform OB clamping with higher accuracy, and even with the multi-pixel solid-state imaging device 14, the OB clamp level is stable. Correct black level and achromatic color. As a result, it is possible to suppress image shading due to black level fluctuations and unnatural coloring at low illuminance.

  The present invention is not limited to the above embodiments. For example, in the embodiment of the reference example shown in FIG. 1 and FIG. 3, the gain difference due to the manufacturing variations of the left and right output amplifiers 25A and 25B. As sampling signals for detection, video signals in any of the four monitoring areas on the left and right are extracted, integrated, and gain values in each line are calculated by calculation using the values obtained from them, and corrected. However, instead of this, all the level values are calculated for each line, the correction level in each line is calculated individually, and the obtained correction level is the same as that of the embodiment shown in FIG. 1 and FIG. Similarly, the correction of the video signal may be performed by temporarily storing the correction value storage unit provided in the control unit 11 in a buffer prepared for each line.

  In this case, for example, video signals for 16 pixels on the left and right are extracted for each line, and an average of these is taken to obtain a level difference in that line. In addition, in each line, output from pixels having two different types of color filters is output every clock. Therefore, by accumulating 8 pixels for each color filter and subtracting each, more accurate results can be obtained. High gain difference correction can be realized.

  In the above embodiment, the solid-state imaging device that reads the signal output by dividing the imaging area into two in the horizontal direction is used. However, when the image is divided into three or more in the horizontal direction and output. Alternatively, the signal level difference at each boundary surface may be corrected by the same method as the above-described reference example, or a plurality of blocks are provided in each of the two left and right OB areas to extract the OB signal. Then, integration may be performed, an OB correction level in each line may be calculated using a value obtained therefrom, and OB clamping processing may be performed.

  Further, when the OB level data is integrated in each of the blocks 43A1 to 43A4 and the blocks 43B1 to 43B4 shown in FIG. 8, as shown in FIG. 9, in an odd line, cyan (Cy) is included in one block. Output from one pixel having a color filter and one pixel having a yellow (Ye) color filter alternately appears in total of 16 pixels of 8 pixels, and one pixel having a magenta (Mg) color filter in even lines. Then, the output from one pixel having the green (G) color filter alternately appears in total of 16 pixels of 8 pixels each, and the total of 256 pixels of each color filter is composed of 1024 pixels.

  Therefore, instead of integrating the data of 1024 pixels output from one block as in the embodiment shown in FIGS. 7 and 8, the integration from each color filter is performed separately. May be. Specifically, two OB BLK integration units 51 shown in FIG. 10 are prepared, and when integration is performed for each line, signals are alternately input to the integration circuit pixel by pixel, and integration is performed for each color. Further, the buffer for storing the integrated value of the change amount calculation unit 52 is set to a total of 16 buffers of 4 blocks × 4 colors. That is, for the change amount calculation unit 52 and the correction value storage unit 53 in FIG. 10, four channels are prepared for each color filter. As a result, it is possible to absorb errors due to clock jumps, noise, etc., and perform more accurate OB clamping.

  Further, in the embodiment shown in FIGS. 7 and 8, any four blocks are extracted from the signals of the OB areas 42A and 42B output from the solid-state imaging device 14, are integrated, and values obtained therefrom are obtained. The OB correction level in each line is calculated and the OB clamping process is performed. Instead, all OB values are calculated for each line, and the OB correction level in each line is calculated. The OB correction level may be temporarily stored in a buffer prepared for each line in a correction value storage unit similar to the correction value storage unit 53 to correct the video signal.

  In this case, for example, an OB area for 16 pixels is extracted for each line, and these are integrated and averaged to obtain a correction value for that line. In addition, since the output of OB pixels having two different types of color filters is output every clock in each line, as in the above example, 8 pixels are integrated for each color filter, and each is subtracted. By doing so, a more accurate OB clamp can be realized.

It is a block diagram of an embodiment of an imaging device serving as a reference example of the present invention. It is a block diagram of one Embodiment of the solid-state image sensor in FIG. It is a block diagram of an example of the OB clamp process part in FIG. It is a block diagram of an example of each monitoring area in FIG. It is a figure which shows the signal level difference in each line calculated by the OB clamp process part of FIG. It is a block diagram of the other example of the OB clamp process part in FIG. It is a block diagram of the imaging device applied to a present Example. It is a block diagram of one Embodiment of the solid-state image sensor in FIG. It is a block diagram of an example of each block in the OB area in FIG. It is a block diagram of an example of the principal part of the OB clamp process part in FIG. It is a figure which shows the OB correction level in each line calculated by the OB clamp process part of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical lens part 2, 14 Solid-state image sensor 3 Analog signal processing part 4 A / D conversion part 5, 15 OB clamp processing part 6 Pixel density conversion part 7 Digital signal processing part 8 D / A conversion part 9 External image display part 10 VTR recording unit 11 control unit 12 solid-state imaging device driving unit 21A, 21B, 41A, 41B imaging area 22A, 22B, 42A, 42B OB area 231 to 238 monitoring area 24A, 24B, 44A, 44B horizontal CCD
25A, 25B Output amplifier 31A, 31B OB clamp circuit 32A, 32B, 36A, 36B Boundary surface accumulating unit 33A, 33B, 37A, 37B, 52 Change amount calculating unit 34, 38 Level comparing unit 35A, 35B Multiplier 43A1, 43A2, 43A3, 43A4, 43B1, 43B2, 43B3,
43B4 Block in OB area 51 OB BLK integration unit 53 Correction value storage unit 54 Subtractor

Claims (3)

An imaging area is divided into a plurality in the horizontal direction, and a solid-state imaging device in which first and second OB areas are respectively provided at the left and right ends of the imaging area, and the plurality of divided imaging areas of the solid-state imaging device By subtracting one of the OB signals from the first and second OB signals indicating the optical black levels output from the first and second OB areas, respectively, from the output imaging signals. An OB clamp processing unit that performs OB clamping of the imaging signal,
The OB clamp processing unit
First OB correction level calculating means for calculating a first OB correction level for each line for the first OB area;
Second OB correction level calculating means for calculating a second OB correction level for each line for the second OB area;
The first OB correction level of all lines from the first OB correction level calculation means is stored, and the image of each line in the divided imaging area closer to the first OB area among the plurality of divided imaging areas is captured. First correction means for outputting and subtracting the stored first OB correction level from the signal;
The second OB correction level of all lines from the second OB correction level calculation means is stored, and the image of each line in the divided imaging area closer to the second OB area among the plurality of divided imaging areas is captured. An image pickup apparatus comprising: a second correction unit that outputs and subtracts the stored second OB correction level for a signal.   The first OB level calculation means includes a plurality of first blocks each including a plurality of pixels in the vertical direction and the horizontal direction in the first OB area, and the OB signal level in the plurality of first blocks is determined. Means for calculating a first OB correction level for each line by calculating an average value for each block and giving a correction inclination in a vertical direction of the screen based on the plurality of average values; The OB level calculation means includes a plurality of second blocks each including a plurality of pixels in the vertical direction and the horizontal direction in the second OB area, and calculates an average value of the OB signal levels in the plurality of second blocks. 5. A means for calculating a second OB correction level for each line by calculating for each block and giving a correction inclination in the vertical direction of the screen based on the plurality of average values. The imaging device according to 1 .   The apparatus further comprises means for arbitrarily moving the positions of the plurality of first blocks in the first OB area and the positions of the plurality of second blocks in the second OB area from the outside. The imaging apparatus according to claim 1, wherein the imaging apparatus is characterized.

Images