JP2015159438A - Image pick-up device, image reading apparatus, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the correction of reading positions for respective colors relative to a single position of a subject of reading without causing an increase in the circuit scale even when a displacement of the reading position by less than one line has occurred between the colors of a plurality of photoelectric conversion elements, which have been arranged in one direction for the respective colors.SOLUTION: An image pick-up device includes a plurality of photoelectric conversion elements arranged in one direction for respective colors to be photoelectrically converted, and a timing control unit that controls, according to a setting, exposure timings that are dependent for the respective colors in a pixel group constituted for each of the plurality of photoelectric conversion elements outputting signals to a common post-processing circuit.

Description

  The present invention relates to an image sensor, an image reading apparatus, and an image forming apparatus.

  CCD and CMOS image sensors commonly used in scanners have a pixel array in which photodiodes are arranged in one direction for each color such as red (R), green (G), and blue (B). It is a linear sensor. Further, when arranging a plurality of pixel arrays, the image sensor cannot arrange a plurality of photodiodes at the same position. For example, the pixel array for each color is arranged at a position shifted by an integer line interval. Yes. Therefore, if the image read by each pixel array is output as it is, each color is shifted by the interval of the pixel array, so that the position between the lines is corrected. That is, the output timing of each pixel array may be corrected so that each pixel array of a different color reads the same position.

  Further, it is necessary to change the correction value between lines at the time of zooming such as when performing image reading for enlarging the image to a size of 200%. For example, an integer line can be corrected at a magnification of 200%, but a correction for a decimal line is required for correction between lines at a magnification of 60%.

  Since the pixel array of each color does not read the image at the same position in line units, the shift for the decimal line cannot be corrected so that the pixel arrays of different colors read the same position.

  Further, as a conventional technique, Patent Document 1 discloses that an optical system driving unit is controlled at a sub-scanning speed corresponding to a preset magnification, and each color reading sensor is read using a reading control signal corresponding to the magnification. An image reading apparatus that independently controls the image is disclosed.

  However, conventionally, when a shift of less than one line (decimal line) occurs in the reading position of the pixel array for each color, the reading position for each color is corrected to the same position without increasing the circuit scale. There was a problem that I could not.

  The present invention has been made in view of the above, and even when a shift of less than one line occurs in a reading position between colors of a plurality of photoelectric conversion elements arranged in one direction for each color, a circuit is provided. It is an object of the present invention to provide an image pickup device, an image reading apparatus, and an image forming apparatus that can correct the reading position for each color with respect to the same position of the reading target without increasing the scale.

  In order to solve the above-described problems and achieve the object, the present invention provides a plurality of photoelectric conversion elements arranged in one direction for each color to be subjected to photoelectric conversion, and a plurality of the above-described signals that output signals to a common post-processing circuit. And a timing control unit that controls an independent exposure timing for each color in a pixel group configured for each photoelectric conversion element according to the setting.

  According to the present invention, even when a deviation of less than one line occurs in the reading position between colors of a plurality of photoelectric conversion elements arranged in one direction for each color, reading is performed without causing an increase in circuit scale. There is an effect that it is possible to correct the reading position for each color with respect to the same position of the object.

FIG. 1 is a diagram illustrating an outline of the configuration of the image sensor according to the first embodiment. FIG. 2 is a diagram showing the configuration of the pixel group shown in FIG. FIG. 3 is a diagram illustrating the periphery of an AD conversion unit that performs A / D conversion on a signal output from the pixel illustrated in FIG. 1. FIG. 4 is a timing chart showing the drive timing of the image sensor mounted on the image reading apparatus. FIG. 5 is a diagram schematically illustrating a result of correcting the deviation of the reading position of less than one line with respect to the image sensor. FIG. 6 is a diagram illustrating an outline of the configuration of the image sensor according to the second embodiment. FIG. 7 is a diagram illustrating the periphery of an AD conversion unit that performs A / D conversion on a signal output from the pixel illustrated in FIG. 6. FIG. 8 is a timing chart showing drive timing of the image sensor mounted on the image reading apparatus. FIG. 9 is a diagram schematically illustrating a result of correcting the deviation of the reading position of less than one line with respect to the image sensor. FIG. 10 is a diagram illustrating the outline of the configuration of the image sensor according to the third embodiment. FIG. 11 is a timing chart showing the drive timing of the image sensor mounted on the image reading apparatus. FIG. 12 is a timing chart illustrating the timing at which the AD conversion unit of the image sensor performs A / D conversion. FIG. 13 is a diagram illustrating the outline of the configuration of the image sensor according to the fourth embodiment. FIG. 14 is a diagram illustrating the periphery of an AD conversion unit that performs A / D conversion on signals output from the pixels illustrated in FIG. 13. FIG. 15 is a timing chart showing drive timing of the image sensor mounted on the image reading apparatus. FIG. 16 is a timing chart illustrating the timing at which the AD conversion unit of the image sensor performs A / D conversion. FIG. 17 is a flowchart showing drive timings when two RGB pixels are included in the pixel group of the image sensor. FIG. 18 is a diagram schematically illustrating the arrangement of the pixel arrays of the respective colors in the image sensor. FIG. 19 is a timing chart showing an operation at the same magnification reading in the case where the imaging device includes six pixels in the pixel group. FIG. 20 is a diagram illustrating an arrangement of each pixel when the number of pixels included in one pixel group of the image sensor is increased to six. FIG. 21 is a configuration diagram illustrating a configuration example of an image reading apparatus and an automatic document feeder on which, for example, an image sensor is mounted. FIG. 22 is a configuration diagram illustrating a configuration example of an image forming apparatus having an image reading apparatus and an ADF.

(First embodiment)
FIG. 1 is a diagram illustrating an outline of a configuration of an image sensor 10 according to the first embodiment. For example, the imaging device 10 can read Pix1 to Pix (n), which are pixel positions in a reading target, in three colors of RGB, and has a three pixel array in which n pixels are arranged in one direction for each color. A CMOS color linear sensor.

  That is, the image sensor 10 includes n photodiodes (PD_r) provided with R filters (not shown), n photodiodes (PD_g) provided with G filters (not shown), and B N photodiodes (PD_b) each provided with a filter (not shown) are arranged in one direction. When reading at the same magnification (without enlarging or reducing), the image pickup element 10 is arranged so that the pixel array of each color has an image line in order to prevent a reading position shift for each color less than one line of the image. It is arranged so that the interval is an integral multiple of the width of.

  Each pixel includes a photodiode (photoelectric conversion element) that performs photoelectric conversion, a charge detection unit (Cfd) (not shown) that converts accumulated charge to a voltage, a circuit that drives Cfd, and the like (see FIG. 2). Have Hereinafter, the photodiode may be referred to as PD_ *, and the pixel block may be referred to as pixblk_ *. Note that the subscript * represents one of the colors r, g, and b.

  Further, the image sensor 10 includes n AD converters (ADC) 12, a parallel / serial converter (P / S) 14, and a timing controller (TG: Timing Generator) 16.

  In addition, the image pickup device 10 converts all the color pixels that can be read at the same position in the arrangement direction (main scanning direction) for each pixel color into one pixel group (indicated by a thick black line in FIG. 1). The enclosed range is defined as one pixel group) 18, and a signal is output to one AD converter 12 (common ADC: post-processing circuit) for each pixel group 18. In other words, the image pickup device 10 has a plurality of pixels of all colors (here, three pixels of RGB) that can read the same position of the read target by physically moving the read target or the image pickup device 10 itself as one. The pixel group 18 is used. Further, the image sensor 10 is not limited to three pixels as one image group. For example, the imaging device 10 may have 6 pixels (RGB 3 pixels × 2) as one pixel group.

  The timing control unit 16 generates drive signals and the like which will be described later, and controls the operation timing of each pixel group 18, each AD conversion unit 12, and parallel / serial conversion unit 14. In the image sensor 10, the all AD conversion unit 12 simultaneously performs A / D conversion on the image signals output from all the pixel groups for each pixel in the pixel group 18. Then, the image sensor 10 converts the digital signal image data output from the all AD converters 12 in parallel for each pixel group 18 into serial data (Dout (r), Dout (g), Dout (b) by the parallel-serial converter 14. )) And output to the subsequent stage.

  FIG. 2 is a diagram showing the configuration of the pixel group 18 shown in FIG. The three pixels constituting the pixel group 18 have PD_ * and pixblk_ *, respectively. Vdd is a power supply voltage supplied to the image sensor 10 and serves as a reference potential for the output of the image sensor 10. Each PD_ * accumulates charges according to the intensity of incident light.

  RSr is a signal that resets the charge detection unit (Cdf) that converts the charge accumulated in PD_r into a voltage. RSg is a signal that resets the charge detection unit (Cdf) that converts the charge accumulated in PD_g into a voltage. RSb is a signal that resets the charge detection unit (Cdf) that converts the charge accumulated in PD_b into a voltage.

  TSr transmits the charge to the charge detection unit (Cfd) that converts the charge accumulated in PD_r into a voltage. TSg transmits the charge to the charge detection unit (Cfd) that converts the charge accumulated in PD_g into a voltage. TSb transmits the charge to the charge detection unit (Cfd) that converts the charge accumulated in PD_b into a voltage.

  Analog signals (A_sig_r, A_sig_g, A_sig_b) obtained by converting charges into voltages by pixblk_r, pixblk_g, and pixblk_b are transferred to the AD conversion unit 12 according to transfer signals (ADSTr, ADSTg, ADSTb) having different transfer timings.

  Since the image sensor 10 performs parallel processing with three pixels as one pixel group 18, each signal (RS, TS, ADST) is required. Each of these signals (RS, TS, ADST) is in common with the other pixel group 18.

  FIG. 3 is a diagram illustrating the periphery of the AD conversion unit 12 that performs A / D conversion on the signal output from the pixel illustrated in FIG. 1. In the pixel group 18, the analog signals (A_sig_r, A_sig_g, A_sig_b) output by the respective RGB pixels are transferred to the ADC during the High period of the transfer signals (ADSTr, ADSTg, ADSTb) having different transfer timings.

  The image signal transferred to the AD converter 12 is A / D converted pixel by pixel during a period when the signal ADEN for enabling the AD converter 12 is High, and the transfer signal (ADSTr, ADSTg, ADSTb) is High. Digital signals (D_sig_r, D_sig_g, D_sig_b) are output to the parallel-serial conversion unit 14.

  FIG. 4 is a timing chart showing the drive timing of the image sensor 10 mounted on the image reading apparatus (see FIG. 21). The timing control unit 16 generates each drive signal for driving each part of the image sensor 10 based on the reference clock (CLK). lsync is a line synchronization signal, and indicates the cycle of one line in the main scanning direction of the image data.

  First, the timing control unit 16 turns on RSr and resets Cfd for the pixel group 18 prior to the start of line reading. Next, the timing control unit 16 turns on RSg at a timing different from RSr, further turns on RSb at a timing different from RSr and RSg, and resets three Cfd of the pixel group 18 once.

  After resetting Cfd, the timing control unit 16 sequentially turns on TSr / TSg / TSb at different timings, and transfers the charge accumulated in PD_ * to Cfd. Then, the timing control unit 16 sequentially turns on ADSTr / ADSTg / ADSTb at different timings, and inputs an analog signal obtained by charge-voltage conversion of Cfd to the AD conversion unit 12. The image sensor 10 performs the operation shown in FIG.

  Note that, when ADEN is High, the AD converter 12 repeats A / D conversion, for example, about 10 times according to the required number of bits and outputs it as 10-bit data. The image signal converted into the digital signal is subjected to parallel-serial conversion by the parallel-serial conversion unit 14 and output to the subsequent image processing unit.

  FIG. 5 is a diagram schematically illustrating a result of correcting the reading position shift of less than one line (decimal line) with respect to the image sensor 10. When the image sensor 10 is mounted on an image reading apparatus and performs variable magnification reading that is enlarged or reduced, if correction is performed in units of line intervals (integer lines), a shift of less than one line (decimal lines) may occur. is there. In this case, the output result of the image sensor 10 is corrected by a decimal line correction circuit (not shown).

  In this method, a decimal line shift occurs in the reading position for each color. When attention is paid to R and G, the original reading position after the interline correction of the integer lines in FIG. The gap remains. Thereafter, even if the deviation of the reading position is corrected by the decimal line correction circuit, there is a concern that the color deviation occurs.

(Second Embodiment)
FIG. 6 is a diagram illustrating an outline of the configuration of the image sensor 10a according to the second embodiment. The image sensor 10a can change the exposure timing by independent drive signals for RGB, and a positional shift of less than one line can be corrected by adjusting the exposure timing. In addition, the same code | symbol is attached | subjected to the component substantially the same as the component of the image pick-up element 10 mentioned above.

  The imaging device 10a includes three timing control units 16a (TG_r, TG_g, TG_b) that control the drive timing independently for each color, and generates three independent line synchronization signals (lsync_r, lsync_g, lsync_b). ing. Further, the image sensor 10a is provided with an AD conversion unit 12 for each pixel in order to change the drive timing for each color. The imaging element 10a is provided with three parallel / serial conversion units 14 (P / S_r, P / S_g, and P / S_b) because the AD conversion timing differs for each color.

  FIG. 7 is a diagram illustrating the periphery of the AD conversion unit 12 that performs A / D conversion on signals output from the pixels illustrated in FIG. 6. The analog signals output from the RGB pixels are transferred to the AD converter 12 (ADC_r, ADC_g, ADC_b), respectively, in a period in which ADSTr, ADSTg, ADSTb having different transfer timings are High.

  The image signal transferred to the AD converter 12 (ADC_r, ADC_g, ADC_b) is subjected to analog-to-digital conversion for each pixel when ADENr, ADENg, and ADENb are High, and digital signals (ADSTr, ADSTg, and ADSTb are High). D_sig_r, D_sig_g, D_sig_b) are output to the parallel-serial conversion unit 14 (P / S_r, P / S_g, P / S_b), respectively. Each parallel-serial conversion unit 14 converts a parallel signal output from each pixel into a serial signal by driving signals PSENr, PSENg, and PSENb.

  FIG. 8 is a timing chart showing the drive timing of the image sensor 10a mounted on the image reading apparatus (see FIG. 21). The image sensor 10a generates a drive signal based on the reference clock (CLK). lsync_r, lsync_g, and lsync_b are line synchronization signals of the pixel arrays of the respective colors, and indicate the reading cycle of one line in the main scanning direction of the image data.

  First, the timing control unit 16a (TG_r) turns on RSr and resets Cfd prior to the start of reading the drive timing line of the first color R pixel. After resetting Cfd, the timing controller 16a (TG_r) turns on TSr and transfers the charge accumulated in PD_r to Cfd. The analog signal subjected to charge-voltage conversion by Cfd is input to the AD conversion unit 12 when ADSTr is turned on.

  Next, the timing control unit 16a (TG_g) makes it possible to correct a shift of less than one line (decimal line) that occurs at the time of reading for scaling without using a correction circuit or the like in the subsequent stage. The lsync_g of the pixel of the first color G is delayed from the lsync_r. Here, the time Tg delayed by the timing control unit 16a (TG_g) is a delay time of the exposure timing corresponding to the shift amount less than one line (decimal line).

  The relationship between the deviation of the reading position and the delay time (Tg) of the exposure timing is determined according to the line period (one period) that is the time for reading one line. For example, when the G reading position is shifted by 0.2 lines from the R reading position, the imaging device 10a delays the G exposure timing by 0.2 cycles. That is, the timing control unit 16a (TG_g) delays lsync_g by time Tg (= 0.2 cycles) from lsync_r. Further, the timing control unit 16a (TG_g) drives the second color G pixel with a delay of time Tg (= 0.2 period).

  Similarly, the timing control unit 16a (TG_b) delays the B exposure timing by 0.4 cycles when the B reading position deviates by 0.4 lines from the R reading position. That is, the timing control unit 16a (TG_b) delays lsync_b by time Tb (= 0.4 period) from lsync_r. Further, the timing controller 16a (TG_b) drives the pixel of the third color B with a delay of time Tb (= 0.4 period), similarly to the second color G.

  FIG. 9 is a diagram schematically illustrating a result of correcting the reading position shift of less than one line (decimal line) with respect to the image sensor 10a. Due to the timing control performed by the timing control unit 16a, the image sensor 10a has a reading position shift for each color that is only an integral multiple (integer line) of the line interval during reading. Therefore, the image sensor 10a can correct the deviation of the reading position without providing a decimal line correction circuit or the like in the subsequent stage, and can read at the same position for each color. However, since the image pickup device 10a is provided with the timing control unit 16a, the AD conversion unit 12, and the parallel serial conversion unit 14 for each color, the circuit scale is increased.

(Third embodiment)
FIG. 10 is a diagram illustrating an outline of the configuration of the image sensor 20 according to the third embodiment. For example, the imaging element 20 is configured to be able to read Pix1 to Pix (n), which are pixel positions in a reading target, with three colors of RGB, and each of three pixel arrays in which n pixels are arranged in one direction for each color. A CMOS color linear sensor.

  In other words, the imaging device 20 includes n photodiodes (PD_r) provided with R filters (not shown), n photodiodes (PD_g) provided with G filters (not shown), and B N photodiodes (PD_b) each provided with a filter (not shown) are arranged in one direction. In order to prevent the reading position from being shifted for each color less than one line of the image when the image pickup device 20 performs the reading at the same magnification (without enlarging or reducing), the pixel array of each color has the line of the image. It is arranged so that the interval is an integral multiple of the width of.

  Each pixel includes a pixel block (see FIG. 2) including a photodiode and a charge detection unit (Cfd) (not shown) that converts the accumulated charge to a voltage, a circuit that drives Cfd, and the like.

  Furthermore, the imaging device 20 includes n AD converters (ADC) 12, a parallel / serial converter (P / S) 14, and a timing controller (TG: Timing Generator) 16b.

  In addition, the image sensor 20 displays all the color pixels that can be read at the same position in the arrangement direction (main scanning direction) for each pixel color as one pixel group (indicated by a thick black line in FIG. 10). An enclosed range is defined as one pixel group) 22, and one AD conversion unit 12 (common ADC) is used for each pixel group 22. That is, the image pickup device 20 has a plurality of pixels of all colors (three pixels of RGB in this case) that can read the same position of the read target by physically moving the read target or the image pickup device 20 itself. The pixel group 22 is used. Further, the image sensor 20 is not limited to three pixels as one image group. For example, the image sensor 20 may have 6 pixels (RGB 3 pixels × 2) as one pixel group.

  The timing control unit 16b generates drive signals and the like which will be described later, and controls the operation timing of each pixel group 22, each AD conversion unit 12, and parallel / serial conversion unit 14. In the image sensor 20, the all AD conversion unit 12 simultaneously performs A / D conversion on the image signals output from all the pixel groups for each pixel in the pixel group 22. The image pickup device 20 converts the digital signal image data output from the all AD converters 12 in parallel for each pixel group 22 into serial data (Dout (r), Dout (g), Dout (b) by the parallel-serial converter 14. )) And output to the subsequent stage.

  In addition, the image sensor 20 has different timings when RS *, TS *, and ADST * are turned on for each color in the pixel group 22. In addition, in the image sensor 20, the timing control unit 16b controls the exposure timing and driving of PD_g and PD_b according to the amount of deviation of the reading position for each color less than one line (decimal line) that occurs at the time of reading for scaling. By controlling the timing independently, the deviation of the reading position for each color of the decimal line is corrected.

  Specifically, the timing control unit 16b includes three registers EXPstr_ * that hold setting values for controlling the exposure start timing of each PD_ *. That is, the image sensor 20 holds the setting value according to the amount of shift of the decimal line in EXPstr_ *, and changes the timing for turning on RS *, TS *, and ADST * according to the setting of EXPstr_ *. The exposure timing for PD_ * of each color is adjusted, and the deviation of the reading position for each color of the decimal line is corrected. The exposure start timing may be set from an external CPU (not shown).

  FIG. 11 is a timing chart showing drive timing of the image sensor 20 mounted on the image reading apparatus (see FIG. 21). The image sensor 20 sequentially exposes each pixel of RGB for each color and transfers an image signal. As described above, in the image sensor 20, the drive start timing of each pixel is set by EXPstr_ *, and the setting value held by EXPstr_ * is set to a value corresponding to the decimal line shift amount, thereby exposing the exposure timing. Is delayed by the shift of the decimal line.

  The relationship between the deviation of the reading position and the delay time (Tg) of the exposure timing is determined according to the line period (one period) that is the time for reading one line. For example, when the G reading position is shifted by 0.2 lines from the R reading position, the imaging device 20 delays the G exposure timing by 0.2 cycles. That is, the timing control unit 16b delays TSg by time Tg (= 0.2 cycle) from TSr.

  Similarly, when the B reading position is shifted by 0.4 lines from the R reading position, the timing control unit 16b delays the B exposure timing by 0.4 cycles. That is, the timing control unit 16b delays TSb by time Tb (= 0.4 period) from TSr. Therefore, the image sensor 20 does not cause a decimal line shift at the time of image reading, and can prevent a color shift caused by a decimal line shift at the reading position.

  Note that the image sensor 20 also delays the timing of A / D conversion by delaying the exposure timing, so the ADEN intervals shown in FIG. 11 are not equal in RGB.

  FIG. 12 is a timing chart illustrating the timing at which the AD conversion unit 12 of the image sensor 20 performs A / D conversion. Since the image sensor 20 A / D converts each analog signal output from one pixel group 22 by one AD converter 12, only one pixel can be A / D converted.

  Therefore, the image pickup device 20 can secure a time (ADEN ON period) during which A / D conversion can be performed for each color analog signal with respect to the timing of transferring the signal photoelectrically converted by each color PD_ * to the AD conversion unit 12. The timing is shifted. As shown in FIG. 12, for example, if the image sensor 20 turns ADSTr and ADSTb on at the same time, R and B signals are simultaneously input to the AD conversion unit 12, and normal A / D conversion cannot be performed.

  In other words, the image sensor 20 must secure time for A / D conversion of analog signals from pixels for each color, so that the exposure timing can be changed within a limited range, and the correction can be limited to decimal line deviations. There is. In addition, the image pickup device 20 cannot perform simultaneous exposure because there is a limit to the range in which the exposure timing can be changed even when a decimal line shift does not occur, such as when reading at the same magnification (without enlarging / reducing), and the simultaneous exposure cannot be performed. In some cases, line deviation occurs and correction is required.

(Fourth embodiment)
FIG. 13 is a diagram illustrating an outline of the configuration of the image sensor 20a according to the fourth embodiment. The image sensor 20a illustrated in FIG. 13 includes a memory group 24 in addition to the configuration of the image sensor 20 illustrated in FIG. The memory group 24 includes an analog memory (storage unit) 240 (Memory_r, Memory_g, Memory_b) for each color pixel.

  In other words, the imaging device 20a is arranged in front of the AD conversion unit 12 in order to avoid that the range in which the exposure timing can be changed is limited due to restrictions on the AD conversion unit 12 and all decimal line deviations cannot be corrected. An analog memory 240 that temporarily holds signals photoelectrically converted by PD_ * is provided. As described above, since the image pickup device 20a temporarily stores the signals photoelectrically converted by the PD_ *, there is no restriction on the control for changing the exposure timing for each color.

  FIG. 14 is a diagram illustrating the periphery of the AD conversion unit 12 that performs A / D conversion on the signals output from the pixels illustrated in FIG. 13. The image sensor 20a holds the analog signals output from the respective PD_ * in the corresponding capacitors Cr, Cg, and Cb. Note that the capacitors Cr, Cg, and Cb correspond to the Memory_r, Memory_g, and Memory_b shown in FIG. 13, respectively.

  That is, the image sensor 20a can arbitrarily adjust the timing of transferring the analog signal to the AD converter 12 by temporarily holding the analog signal in the capacitor. The signals held in the capacitors Cr, Cg, and Cb are sequentially transferred while ADSTr, ADSTg, and ADSTb are High. The image signal transferred to the AD conversion unit 12 is subjected to analog-to-digital conversion for each pixel during a period when ADEN is High. Thereafter, the digital signals (D_sig_r, D_sig_g, D_sig_b) output from the AD conversion unit 12 during the High period of ADSTr, ADSTg, and ADSTb are input to the parallel-serial conversion unit 14.

  The image sensor 20a includes the capacitors Cr, Cg, and Cb, but the circuit scale is sufficiently smaller than the AD converter 12 for each pixel included in the image sensor 10a (FIG. 6).

  FIG. 15 is a timing chart showing drive timing of the image sensor 20a mounted on the image reading apparatus (see FIG. 21). The image sensor 20a has the same drive timing as the image sensor 20 (FIG. 10) until the charge accumulated in PD_ * is transferred by TSr, TSb, TSg. In the imaging device 20a, the analog memory 240 temporarily holds the signal for each pixel before transferring the analog signal to the AD conversion unit 12.

  Then, the image sensor 20a sequentially transfers the analog signals held by the analog memories 240 to the AD conversion unit 12 using ADSTr, ADSTg, and ADSTb. As described above, the image sensor 20a temporarily holds analog signals for each pixel group 22 by each analog memory 240, so that the range in which the exposure timing can be changed is not limited, and the reading deviation of the decimal lines is reduced. It is possible to eliminate the limit that can be corrected.

  FIG. 16 is a timing chart showing the timing at which the AD conversion unit 12 of the image sensor 20a performs A / D conversion. Since the image sensor 20a temporarily holds the analog memory 240 before A / D converting the signal output from the PD_ *, it can be sequentially transferred to the AD conversion unit 12 even if the exposure timing of each color is simultaneously set. . Therefore, the image sensor 20a can perform simultaneous exposure of all colors even at a reading speed that is shifted by an integer number of lines, and by correcting only the shift of the integer lines, it is possible to prevent a color shift.

(First modification)
Next, a case where the pixel group 22 of the image sensor 20a includes 2 pixels each of RGB (6 pixels in total) will be described. FIG. 17 is a flowchart showing the drive timing when the pixel group 22 of the image sensor 20a includes 2 RGB pixels (6 pixels in total).

  In the pixel group 22 in the first modification, each pixel is classified into two, Even and Odd. For example, an R even pixel is denoted by Re and an R odd pixel is denoted by Ro.

  Since it is necessary to match the exposure timing for the same color, Re and Ro, Ge and Go, and Be and Bo are exposed at the same timing. In the variable magnification reading, if the G reading position is shifted by 0.2 lines from the R reading position, Tg = 0.2 period, and the B reading position is 0.4 with respect to the R reading position. When the line is shifted, if a delay is given with Tg = 0.4 period, the decimal line shift can be prevented. That is, each PD_ * is arranged so that the arrangement interval of PD_ * in the direction orthogonal to the direction in which PD_ * is arranged for each color and the setting of the exposure timing have a predetermined relationship. Thus, since the number of pixels that can be included in one pixel group 22 can be increased, the number of AD conversion units 12 can be reduced, and the circuit scale can be reduced.

  In the first modification, the case where a total of 6 pixels are included in one pixel group 22 has been described as an example. However, if the number of pixels of each color is the same, all A / D conversions are completed in one line. It is possible to increase the number of pixels included in one pixel group 22 up to the possible number of pixels.

(Second modification)
FIG. 18 is a diagram schematically illustrating the arrangement of the pixel array of each color in the image sensor 20. When image reading is performed using a linear sensor such as the image sensor 20, the pixel arrays of the respective colors cannot be arranged at the same position. Generally, pixel arrays of different colors are arranged at positions shifted by integer lines in the sub-scanning direction. To do.

  In FIG. 18, Lr, Lg, and Lb represent RGB pixel arrays, respectively. Wg represents the deviation width of Lg in the sub-scanning direction based on Lr, and Wb represents the deviation width of Lb in the sub-scanning direction based on Lr. Since Lg and Lb are arranged at positions shifted by an integer number of lines from Lr, the RGB color is shifted by the lines of Wg and Wb when image reading is performed at the same magnification. In this case, the image data output from the linear sensor is subjected to an inter-line correction process for correcting a positional shift of an integer line shifted in the subsequent stage.

  On the other hand, the image sensor 20 sequentially performs exposure for each color and cannot perform simultaneous exposure. For this reason, when Wg and Wb are arranged shifted by an integral number of lines and image reading is performed at the same magnification, a reading shift for a few lines occurs due to a shift in exposure timing. Therefore, in the second modification of the image sensor 20, Lg and Lb are arranged so that Wg and Wb correspond to the exposure timing shift for each color.

  For example, when Wg = 0.2 lines and Wb = 0.4 lines, at the same magnification (magnification: 100%), the G exposure timing is 0.2 line cycles, and the B exposure timing is 0.4 lines. By delaying by the period, it is possible to eliminate reading deviation for a fractional line.

  When the magnification is changed from 100% to 50%, the G exposure timing is changed from the delay of 0.2 line period to 0.1 line period, and the B exposure timing is set to 0.4 line period. By changing from the delay to the period of 0.2 lines, it is possible to eliminate reading deviations for decimal lines without overlapping A / D conversion timing.

  Further, even when the magnification is changed from 100% to 200%, the G exposure timing is changed from the delay of 0.2 line period to 0.4 line period, and the B exposure timing is set to 0.4 line period. By changing from the delay to the 0.8 line period, it is possible to eliminate the reading deviation of the decimal line without overlapping the A / D conversion timing.

  In this way, by setting the line interval of the image sensor 20 so that the exposure start timing can be adjusted within a range not subject to the limitation of the AD converter 12, any timing can be set for each color similarly to the image sensor 20a. Thus, the exposure can be started, and even if the analog memory 240 is not provided, the decimal line reading deviation can be eliminated.

(Third Modification)
FIG. 19 is a timing chart illustrating an operation at the same magnification reading in the case where the pixel group 22 includes six pixels (two pixels of Reven, G, and B, each of Even and Odd) in the image sensor 20. The difference between Re and Ro exposure timing is Tro, the difference between Re and Ge exposure timing is Tge, the difference between Re and Go exposure timing is Tgo, the difference between Re and Be exposure timing is Tbe, and the exposure timing between Re and Bo. The deviation is Tbo.

  Since the image sensor 20 sequentially exposes each pixel in the pixel group 22, simultaneous exposure cannot be performed. That is, Tro, Tge, Tgo, Tbe, and Tbo must be set to delay times that secure the time required for A / D conversion of the AD converter 12. Therefore, as in FIG. 18, even when the arrangement interval of each pixel in the sub-scanning direction is an integer line, the exposure timing shift occurs in each pixel. Deviation occurs.

(Fourth modification)
FIG. 20 is a diagram illustrating an arrangement of each pixel when the number of pixels included in one pixel group 22 of the image sensor 20 is increased to six. In FIG. 20, a region surrounded by a thick frame is defined as one pixel group, and one pixel group 22 includes two pixels of RGB, Even and Odd (6 pixels in total). Wro is the width between Re and Ro, Wge is the width between Re and Ge, Wgo is the width between Re and Go, Wbe is the width between Re and Be, and Wbo is the width between Re and Bo. .

  Similarly to the second modified example shown in FIG. 18, the image sensor 20 sequentially performs exposure for each pixel, so that simultaneous exposure cannot be performed. Therefore, even when Wro, Wge, Wgo, Wbe, and Wbo are each shifted by an integral number of lines and the image is read at the same magnification, the exposure timing in the image sensor 20 shifts to a fractional number of lines. Misreading occurs. In the fourth modification of the image sensor 20, Wro, Wge, Wgo, Wbe, and Wbo are set at intervals corresponding to the deviation of the exposure timing for each pixel.

  For example, when the line intervals of Wro, Wge, Wgo, Wbe, and Wbo are 0.05, 0.1, 0.15, 0.2, and 0.25, Ro is set at the same magnification (magnification 100%). The exposure timing is 0.05 line cycle, Ge exposure timing is 0.1 line cycle, Go exposure timing is 0.15 line cycle, Be exposure timing is 0.2 line cycle, Bo exposure timing Is delayed by a period of 0.25 lines, so that it is possible to eliminate a reading deviation of a few lines.

  When the magnification is changed from 100% to 50%, the Ro exposure timing is changed from a delay of 0.05 line period to 0.025 line period, and the Ge exposure timing is set to 0.1 line period. From delay to 0.05 line period, Go exposure timing from 0.15 line period delay to 0.075 line period, Be exposure timing from 0.2 line period delay to 0.1 line By changing the Bo exposure timing from a delay of 0.25 line period to a period of 0.125 line period, the A / D conversion timing is not duplicated, and the reading deviation of the decimal line is eliminated. It becomes possible.

  Further, even when the magnification is changed from 100% to 200%, the exposure timing of Ro is changed from a delay of 0.05 line cycle to 0.1 line cycle, and the exposure timing of Ge is set to 0.1 line cycle. From delay to 0.2 line period, Go exposure timing from 0.15 line period to 0.3 line period, Be exposure timing from 0.2 line period to 0.4 line period By changing the Bo exposure timing from the delay of 0.25 line period to 0.5 line period, the A / D conversion timing does not overlap and the reading deviation of the decimal line is eliminated. It becomes possible.

  As described above, even when the number of pixels included in one pixel group 22 is six, the interval between the pixel arrays is set so that the exposure start timing can be changed within a range not limited by the AD conversion unit 12. As a result, exposure can be started for each pixel at an arbitrary timing as in the case of the image sensor 20a. Further, even if the analog memory 240 is not provided, it is possible to eliminate the decimal line reading deviation. Therefore, the number of pixels that can be included in one pixel group 22 can be increased, and the number of AD conversion units 12 can be reduced, so that an increase in circuit scale can be prevented. The case where there are a total of 6 pixels in one pixel group 22 has been described as an example. However, the present invention is not limited to this, and if the number of pixels of each color is the same, all A / D conversions are performed in one line. It is possible to increase the number of pixels included in one pixel group 22 up to the number of pixels that can be completed.

  Next, an image reading apparatus on which the above-described image sensor is mounted will be described. FIG. 21 is a configuration diagram illustrating a configuration example of the image reading apparatus 100 and the automatic document feeder (ADF) 200 in which, for example, the image sensor 20 (or the image sensor 20a) is mounted. The image reading apparatus 100 is a scanner device mounted on an image forming apparatus such as a digital copying machine, a digital multifunction peripheral, or a facsimile machine. Further, the image reading apparatus 100 may be a single scanner apparatus. Then, the image reading apparatus 100 illuminates a document that is a subject (reading object) with irradiation light from a light source, performs processing on a signal received by the image sensor 20 from reflected light from the document, and converts image data of the document. Read.

  Specifically, as shown in FIG. 21, the image reading apparatus 100 includes a contact glass 101 on which a document is placed, a first carriage 106 including a light source 102 for document exposure and a first reflection mirror 103, and a first carriage 106. And a second carriage 107 having a second reflecting mirror 104 and a third reflecting mirror 105. In addition, the image reading apparatus 100 includes an imaging element 20, a lens unit 108 for forming an image on the imaging element 20, and a reference white plate (white reference plate) 110 used for correcting various distortions caused by a reading optical system and the like. And a sheet-through reading slit 111.

  The image reading apparatus 100 has an ADF 200 mounted thereon, and is connected via a hinge (not shown) or the like so that the ADF 200 can be opened and closed with respect to the contact glass 101.

  The ADF 200 includes a document tray 221 as a document placement table on which a document bundle composed of a plurality of documents can be placed. The ADF 200 also includes separation / feeding means including a feeding roller 222 that separates documents one by one from a bundle of documents placed on the document tray 221 and automatically feeds them toward the sheet-through reading slit 111. ing.

  The image reading apparatus 100 scans the image surface of the document to scan the image of the document and scans the image of the document by the first carriage 106 and the second carriage 107 by a stepping motor (not shown) in the arrow A direction (sub-scan). Scan the document in the direction). At this time, the second carriage 107 moves at a speed half that of the first carriage 106 in order to keep the optical path length from the contact glass 101 to the imaging device 20 constant.

  At the same time, the image surface which is the lower surface of the document set on the contact glass 101 is illuminated (exposed) by the light source 102 of the first carriage 106. Then, the reflected light image from the image plane is sequentially transmitted to the image sensor 20 via the first reflecting mirror 103 of the first carriage 106, the second reflecting mirror 104 and the third reflecting mirror 105 of the second carriage 107, and the lens unit 108. Sent and imaged.

  And a signal is output by photoelectric conversion of the image sensor 20, and the output signal is converted into a digital signal. In this way, the image of the document is read, and digital image data is obtained.

  On the other hand, in the sheet-through mode in which the document is automatically fed and the image of the document is read, the first carriage 106 and the second carriage 107 move below the sheet-through reading slit 111. Thereafter, the document placed on the document tray 221 is automatically fed in the arrow B direction (sub-scanning direction) by the feeding roller 222, and the document is scanned at the position of the sheet through reading slit 111.

  At this time, the lower surface (image surface) of the automatically fed document is illuminated by the light source 102 of the first carriage 106. Therefore, the reflected light image from the image plane is sequentially transmitted to the image sensor 20 via the first reflecting mirror 103 of the first carriage 106, the second reflecting mirror 104 and the third reflecting mirror 105 of the second carriage 107, and the lens unit 108. Sent and imaged. And a signal is output by photoelectric conversion of the image sensor 20, and the output signal is converted into a digital signal. In this way, the image of the document is read, and digital image data is obtained. The document whose image has been read is discharged to a discharge port (not shown).

  Note that the reflected light from the reference white plate 110 is converted into an analog signal by the image sensor 20 by the illumination by the light source 102 started before reading an image in the scan mode or the sheet through mode, and then converted into a digital signal. In this way, the reference white plate 110 is read, and shading correction at the time of reading the image of the document is performed based on the reading result (digital signal).

  Further, when the ADF 200 is provided with a conveyance belt, the document can be automatically fed to the reading position on the contact glass 101 by the ADF 200 and the image of the document can be read even in the scan mode.

  The image reading apparatus 100 is provided with a control unit (not shown) that changes the reading speed in accordance with the document reading magnification designated by the user. At the same magnification reading, the reading speed is a speed at which each color PD_ * of the image sensor 20 can read the same position of the document. That is, the reading speed is a speed at which only an integer line shift occurs.

  On the other hand, at the time of variable magnification reading that performs enlargement or reduction, a control unit (not shown) changes the reading speed according to the variable magnification. For example, when the zoom ratio is 90%, the reading speed is about 110% with respect to the reading speed at the same magnification reading. Further, when the arrangement interval of the pixel array of the image sensor 20 is 2 lines between RGs and 4 lines between RBs, the deviation of G with respect to R is 2 × 0.9 = 1.8 lines. A decimal line deviation of the reading position for 0.8 lines occurs. Similarly, the deviation of B with respect to R is 4 × 0.9 = 3.6 lines, and a decimal line deviation of the reading position for 0.6 lines occurs. The deviation of the reading position is calculated in advance by a control unit (not shown) including the CPU or the timing control unit 16.

  The image reading apparatus 100 corrects the decimal line deviation by changing the exposure timing of the imaging element 20 or the imaging element 20a (including the modification) to G and B with respect to the decimal line deviation calculated in advance. Prevent misalignment.

  FIG. 22 is a configuration diagram illustrating a configuration example of the image forming apparatus 300 including the image reading apparatus 100 and the ADF 200. The image forming apparatus 300 is a digital copying machine having a paper feeding unit 303 and an image forming apparatus main body 304 and having the above-described image reading apparatus 100 and ADF 200 mounted thereon.

  In the image forming apparatus main body 304, a tandem image forming unit (image forming unit) 305 and a registration roller 308 that transports recording paper supplied from the paper supply unit 303 via the transport path 307 to the image forming unit 305. An optical writing device 309, a fixing conveyance unit 310, and a double-sided tray 311.

  In the image forming unit 305, four photosensitive drums 312 are arranged side by side corresponding to toners of four colors Y, M, C, and K. Around each photosensitive drum 312, image forming elements including a charger, a developing unit 306, a transfer unit, a cleaner, and a static eliminator are arranged.

  In addition, an intermediate transfer belt 313 stretched between the driving roller and the driven roller is disposed between the transfer unit and the photosensitive drum 312 while being sandwiched between the two nips.

  The tandem image forming apparatus 300 configured as described above performs optical writing on the photosensitive drum 312 corresponding to each color for each of Y, M, C, and K colors, and develops each toner of each color by the developing unit 306. Then, primary transfer is performed on the intermediate transfer belt 313 in the order of, for example, Y, M, C, and K.

  Then, the image forming apparatus 300 forms a full-color image on the recording paper by secondarily transferring the full-color image superimposed on the four colors by the primary transfer onto the recording paper, and then fixing and discharging. The image forming apparatus 300 forms an image read by the image reading apparatus 100 on a recording sheet.

12 AD conversion unit 14 Parallel serial conversion unit 16, 16a, 16b Timing control unit 18, 22 Pixel group 20, 20a Image sensor 24 Memory group 100 Image reading device 240 Analog memory 300 Image forming device PD_ * Photodiode (photoelectric conversion device)
Lr, Lg, Lb Pixel array

JP 20065592 A

Claims (6)

A plurality of photoelectric conversion elements arranged in one direction for each color to be photoelectrically converted;
A timing control unit that controls an independent exposure timing for each color in a pixel group configured for each of the plurality of photoelectric conversion elements that outputs a signal to a common post-processing circuit; and
An image pickup device comprising: 2. The imaging according to claim 1, further comprising a plurality of storage units that respectively store signals output from the plurality of photoelectric conversion elements between the plurality of photoelectric conversion elements and the post-processing circuit. element. The plurality of photoelectric conversion elements are:
The imaging device according to claim 1, wherein the arrangement interval in a direction orthogonal to the one direction and the setting are arranged so as to have a predetermined relationship. An image reading apparatus comprising the image pickup device according to claim 1. The timing controller is
5. The exposure timing is controlled according to the setting so that a deviation of the reading position in a direction orthogonal to the one direction with respect to a line interval corresponds to a delay with respect to a cycle of the exposure timing. Image reading device. An image reading apparatus according to claim 4 or 5,
An image forming apparatus comprising: an image forming unit that forms an image read by the image reading apparatus.

Images