JP2013187693A - Image reading device, image forming apparatus, and image reading method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve high-speed reading that exhibits a shorter reading time per line compared to a time required for outputting image information for one line from a line sensor.SOLUTION: An image reading device includes N line sensors (N is two or more) arranged in parallel, and an imaging control unit that controls the N line sensors. The imaging control unit causes the N line sensors to simultaneously take an image of N lines in an image for every sub-scanning time for N lines, and to output an imaging signal for one line for every sub-scanning time for N lines.

Description

  The present invention relates to an apparatus and method for reading an image using a line sensor.

  An image scanner that reads an image from a recording sheet includes a line sensor (one-dimensional image sensor) for main scanning, and a sub-scanning mechanism that relatively moves the recording sheet and the line sensor. The line sensor includes a CCD sensor including a charge coupled device (CCD) and a CMOS sensor constituted by a complementary metal oxide semiconductor (CMOS). The CCD sensor is used in a lens reduction type image scanner that forms an image by a reduction optical system, and the CMOS sensor is used as a contact image sensor (CIS) of a contact type image scanner that brings an imaging lens close to the image. ing.

  Regardless of the CCD sensor or the CMOS sensor, the line sensor performs imaging in parallel with outputting image information obtained by previous imaging. Specifically, the line sensor includes a charge accumulation unit configured by a photodiode array along the main scanning direction, and a charge transfer unit that outputs an analog signal indicating the accumulated charge amount of each photodiode. Usually, while the line sensor is moved by a distance of one line pitch (one pixel) in the sub-scanning direction with respect to the image, charge accumulation by photoelectric conversion in the charge accumulation unit and from the charge accumulation unit to the charge transfer unit The stored charge is transferred. While the charge accumulation before the transfer is being performed, the charge transfer unit completes the output of the image information (imaging signal) for one line corresponding to the amount of charge received at the previous transfer. . The output of the imaging signal is delayed by the sub-scan time for one line from the imaging. However, the output cycle of the imaging signal coincides with the imaging cycle.

  There is prior art related to speeding up reading of a monochrome image. Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique of moving two sensors arranged in parallel in the sub-scanning direction and adding the outputs of two sensors obtained by sequentially reading the same line. This document describes that adding the outputs of two sensors provides an effect equivalent to increasing the charge accumulation time per line without reducing the reading throughput. Patent Document 2 proposes that a monochrome sensor is provided with a plurality of output terminals, and a signal for one line is divided into a plurality of signals and simultaneously output.

Japanese Patent Laid-Open No. 5-284283 JP 2006-54904 A

  Since the output of the line sensor is an analog signal whose amplitude changes so as to sequentially show the information of pixels for one line, the output of information for one line corresponds to the number of pixels of the line sensor (resolution in the main scanning direction). It takes time to do. This is a factor that hinders improvement in reading speed. As described in the above-mentioned Patent Document 1, the prior art for imaging each line of an image twice requires a time required for charge accumulation to simultaneously image pixels for one line and to output image information for one line. Useful if longer than time. However, in the case where a sufficient amount of charge can be accumulated in a shorter time than the required output time by increasing the illumination intensity or using a line sensor having a high light receiving sensitivity, Patent Document 1 Even if the prior art is applied, reading speed cannot be increased. If a plurality of output terminals capable of outputting in parallel are provided as in the prior art of Patent Document 2, the structure of the line sensor becomes complicated and the line sensor becomes expensive.

  In view of such circumstances, an object of the present invention is to realize high-speed reading in which a reading time per line is shorter than a time required for outputting image information for one line from a line sensor. .

  A high-speed device that achieves the above object is an image reading device that reads an image on a recording medium, and includes two or more N line sensors arranged in parallel, the image, and the N line sensors. N lines in the image are converted into the N line sensors every sub-scan time corresponding to N lines, which is a time required to move the distance corresponding to N lines on the image in the sub-scan that relatively moves in one direction. An image pickup control unit that controls the N line sensors so that the N line sensors respectively output an image pickup signal for one line every sub-scan time for the N lines; Is provided.

In a preferred embodiment, the relationship between the arrangement pitch Ps of the N line sensors and the line pitch Pg in the image is expressed by the following equation.
Ps = (A × N + 1) × Pg
However, A in the formula is an arbitrary positive integer including 0 (zero).

  According to the present invention, since N images (N is a natural number of 2 or more: 2, 3, 4...) On the image are simultaneously imaged, output of image information for one line from each line sensor is performed for N lines. It may be performed within the sub-scanning time. Therefore, when using a line sensor capable of outputting image information for one line within the sub-scan time for one line when the sub-scan speed is V, the sub-scan speed is increased to approximately N × V. Can do.

It is a figure which shows the structure of the image scanner which concerns on 1st Embodiment of this invention. It is a figure which shows the structure of the imaging device of 1st Embodiment. It is a figure which shows the arrangement | sequence pitch of the some line sensor in the imaging device of 1st Embodiment. It is a figure which shows the spectral sensitivity of the some line sensor which concerns on 1st Embodiment, and the light emission distribution of a green light source. It is a figure which shows typically the arrangement | sequence of the line in the monochrome reading mode which concerns on 1st Embodiment. It is a figure which shows the reading operation of 1st Embodiment. It is a figure which shows the structure of the signal processing circuit of 1st Embodiment. It is a figure which shows the function of the rearrangement process part in 1st Embodiment. It is a figure which shows the structure of the imaging device of 2nd Embodiment. It is a figure which shows the structure of the signal processing circuit of 2nd Embodiment. It is a timing chart which shows operation of a line sensor and a light source concerning a 2nd embodiment. It is a figure which shows a response | compatibility with the line sensor and line in 2nd Embodiment. It is a figure which shows a response | compatibility with the line sensor and line in 2nd Embodiment. It is a figure which shows the function of the rearrangement process part in 2nd Embodiment.

[First Embodiment]
An image scanner 1 illustrated in FIG. 1 is an image reading device provided in a copying machine 100 capable of monochrome and color copying. The image scanner 1 includes a carriage 10, an imaging control unit 30, a signal control circuit 40, and a sub scanning mechanism (not shown) that moves the carriage 10. The carriage 10 moves in the sub-scanning direction below the platen glass 8 on which the document sheet 5 as an image recording medium is placed. The carriage 10 of this example is assembled with a line light source 12 that illuminates a part of the original sheet 5 in a strip shape along the main scanning direction, a reduction optical system composed of a lens 15 and a plurality of mirrors, and an imaging device 16 described later. It has been. However, the configuration is not limited to moving a single carriage. For example, the imaging device 16 or a part of the mirror is fixedly arranged, and the two carriages having other optical components are arranged so that the optical path length is kept constant. It may be configured to be moved. The line light source 12 includes a light emitting diode array (hereinafter referred to as R-LED) that emits red light, a light emitting diode array (hereinafter referred to as G-LED) that emits green light, and a light emitting diode array (hereinafter referred to as G-LED) that emits blue light. And B-LED). The imaging control unit 30 is responsible for controlling the lighting / non-lighting of the line light source 12 and the operation of the imaging device 16. The signal processing circuit 40 generates image data for printing based on the signal output from the imaging device 16. The generated image data is sent to the printer engine 2 as a printing unit, and is printed on a sheet by, for example, electrophotography.

  As shown in FIG. 2, the imaging device 16 has four line sensors 16BW, 16R, 16G, and 16B. The line sensors 16BW, 16R, 16G, and 16B are all CCD sensors. The color reading line sensors 16R, 16G, and 16B are provided with optical filters (not shown) for separating the incident light into R (red), G (green), and B (blue). The monochrome (B / W) read-only line sensor 16BW is sensitive to light of any of the three colors RGB. The relative sensitivity distribution of the line sensors 16BW, 16R, 16G, and 16B depending on the transmittance of the optical filter is shown in FIG. The distributions of BW-CCD, R-CCD, G-CCD, and B-CCD in FIG. 5 correspond to the line sensors 16BW, 16R, 16G, and 16B in order. The imaging device 16 in which these four line sensors 16BW, 16R, 16G, and 16B are housed in one package is useful for downsizing a scanner that performs color and monochrome reading and reducing the number of parts.

  The image scanner 1 performs a color reading mode operation when a color copy is designated by a user of the copying machine 100, and performs a monochrome reading mode operation when a monochrome copy is designated.

  In the color reading mode, the line sensors 16R, 16G, and 16B are used. The R-LED, G-LED, and B-LED of the line light source 12 are turned on to perform sub-scanning while illuminating the original sheet 5 with white light, and three lines on the original sheet 5 are line sensors 16R, 16G, and 16B. The main scanning for simultaneous imaging is repeated at a constant cycle. At this time, the sub-scanning speed is a speed at which each line sensor 16R, 16G, 16B can complete the output of the imaging signal for one line within the sub-scanning time for one line. Since the imaging signals simultaneously output from the line sensors 16R, 16G, and 16B are signals of different lines, the signal processing unit 40 performs a process of synthesizing the three color data of the same line after converting the imaging signals into digital data. Done.

  On the other hand, in the monochrome reading mode, the line sensor 16BW dedicated for monochrome reading and the G line sensor 16G among the line sensors 16R, 16G, and 16B for color reading are used. As a result, it is possible to read almost twice as fast as when only a single line sensor is used, and a high-speed monochrome copy is realized. Hereinafter, the operation in the monochrome reading mode will be described in detail.

As shown in FIG. 3, the four line sensors 16BW, 16R, 16G, and 16B are arranged in parallel at a constant pitch P1 along the sub-scanning direction on the imaging device 16 with the pixel positions in the main scanning direction aligned. Has been. In the example, since the line sensor 16R exists between the two line sensors 16BW and 16G used for monochrome reading, the center-to-center distance (Ps) of the line sensors 16BW and 16G in the sub-scanning direction is twice the pitch P1. . In other words, the line sensor 16BW and the line sensor 16G are arranged with a pitch Ps. The pitch Ps is selected so that the relationship with the line pitch (Pg) in the image (original image) on the original sheet 5 to be read is expressed by the equation (1).
Ps = (A × N + 1) × Pg (1)
However, A in the formula is an arbitrary integer of 0 or more, and N is the number of line sensors used for monochrome reading. In the first embodiment, N is 2. Since it is a requirement to use a plurality of line sensors, N may be a natural number of 2 or more, but a practical value in consideration of cost and arrangement space is preferably about 2 to 4.

  The line pitch (Pg) in the image is determined by the reading resolution in the sub-scanning direction in the specification.

  In the monochrome reading mode, only the LED emitting green light, that is, the G-LED among the three color LEDs in the line light source 12 is turned on. There are two reasons for this. One of the reasons is that the color of the image is not limited to an achromatic color, and a plurality of colors may be mixed. Therefore, in performing data correction to compensate for the difference in spectral sensitivity between the line sensor 16BW and the line sensor 16G. This is because monochromatic light is preferable as the illumination light. Another reason is that green is a color with a high relative visibility and an intermediate color between red and blue, so even if the image to be read is a multicolor image, the red or blue portion This is because color dropouts that cannot be read are unlikely to occur.

  As shown in FIG. 5, two lines on the document sheet 5 are simultaneously read (captured) by the line sensors 16BW and 16G while moving the imaging device 16 relative to the document sheet 5 in the sub-scanning direction. Here, regarding the arrangement of the line sensors 16BW and 16G, it is assumed that the line sensor 16G is positioned downstream of the line sensor 16BW in the sub-scanning direction. That is, when one line on the original sheet 5 is noticed, the line sensor 16G passes through the position corresponding to the noticed line on the relative movement path first, and then the line sensor 16BW passes. However, the line sensor 16G or the line sensor 16BW reads this noticed line. Any line on the document sheet 5 is read by only one of the line sensor 16G and the line sensor 16BW. A line is a portion of an image that is read as a pixel row in one main scan.

  As described above, the line sensors 16BW and 16G are separated by a distance satisfying the expression (1). Therefore, in order to read the image of the original sheet 5 at a constant pitch, it is necessary to set the start position and the end position of the sub-scan so that dummy lines are provided at both ends of the original sheet 5 in the sub-scan direction. In FIG. 5, line [1] to line [2], line [3], line [4],... Line [Z-3], line [Z-2], and line [Z-1] indicated by solid lines are changed. The group of lines up to the line [Z] that passes through corresponds to the effective reading range 5A in the sub-scanning direction on the document sheet 5. Then, a line [0], a line [−1], a line [−2] indicated by broken lines on the start side of the sub-scan, and a line [Z + 1], a line [Z + 2] indicated by broken lines on the end side of the sub-scan, Line [Z + 3] is a dummy line group. The leading line [1] in the effective reading range 5A is read by the line sensor 16G located on the downstream side in the sub-scanning direction of the two line sensors 16BW and 16G. The last line [Z] in the effective reading range 5A is read by the line sensor 16BW located upstream in the sub-scanning direction.

  The upper half of FIG. 6 shows the operation timing of the line sensors 16BW and 16G and the line light source 12, and the lower half shows the lines read by the line sensors 16BW and 16G. In sub-scanning in which the line sensors 16BW and 16G move at a substantially constant speed, N times the sub-scanning time T1 for one line, which is the time required to move the distance of one line on the image (N in this example) Therefore, the imaging operation and the image transfer operation for outputting the imaging signal for one line are repeated at a cycle of 2). That is, the line sensors 16BW and 16G alternately perform charge accumulation and transfer of accumulated charge from the charge accumulation unit to the charge transfer unit in accordance with a control signal from the imaging control unit 30 (see FIG. 1). In parallel with this, image transfer to the signal processing circuit 40 is performed. In each of the imaging period T2 in which the period for reading the entire image in the effective reading range 5A is divided every two lines of sub-scanning time, from the start to the end of the imaging period T2, except when the accumulated charge is transferred. The line sensors 16BW and 16G accumulate electric charges. That is, the charge accumulation operation time corresponding to one line is longer than the sub-scan time T1 for one line. However, in each imaging cycle period T2, the G-LED is lit only during the imaging period Ts from the start of the imaging cycle period T2 until the sub-scanning time T1 for one line or a little shorter time elapses. In the monochrome reading mode, the R-LED and the B-LED are always unlit, so that no light enters the line sensors 16BW and 16G when the G-LED is not lit. Therefore, the period during which charges are substantially accumulated in each imaging period T2 is only the imaging period Ts during which the G-LED is lit. That is, in the first embodiment, the line position and width are determined by the lighting control of the G-LED.

  As shown in the lower half of FIG. 6, at the time point t1 during sub-scanning, the line sensor 16G reads the first line [1] of the effective reading range 5A. The diagonal line in the figure indicates that the line with the hatched line is being read or has already been read. When the line sensor 16G reads the first line [1], the other line sensor 16BW reads the dummy line [-2] on the upstream side (upper side in the drawing) with respect to the line [1].

  At time t2 when two lines of sub-scanning time (2 × T1) have elapsed from time t1, the line sensor 16G reads the third line [3], and the line sensor 16BW reads the dummy line [0]. In parallel with this, the line sensor 16G performs image transfer of the line [1] read in the previous imaging operation, and the line sensor 16BW performs image transfer of the line [-2]. At this stage, the line [2] between the line [1] and the line [3] is not read.

  At time t3, line [5] and line [2] are read, and in parallel, image transfer of line [3] and line [0] is performed. Further, at time t4 when the sub-scan time for two lines has elapsed, line [7] and line [4] are read, and image transfer of line [5] and line [2] is performed. Thereafter, similarly, the line sensor 16G reads odd-numbered lines and transfers images, and the line sensor 16BW reads even-numbered lines and transfers images.

  As shown in the figure, if one line is read every N lines of sub-scanning time by the N line sensors 16G and 16BW satisfying the relationship of the above-described expression (1), the effective reading range does not occur. The entire 5A can be read. However, the reading order of the line group from the line [1] to the line [Z] is different from the arrangement order. For this reason, it is necessary to rearrange the image information output from the line sensors 16G and 16BW in the order of arrangement of the lines on the document sheet 5. This rearrangement is performed by the signal processing circuit 40.

  As illustrated in FIG. 7, the signal processing circuit 40 includes an A / D conversion unit 43, a sensitivity correction unit 44, a rearrangement processing unit (data processing unit) 45, and an image processing unit 47.

  The A / D converter 43 converts the imaging signals output from the total of four line sensors 16BW, 16R, 16G, and 16B into imaging data having a predetermined number of bits. In the monochrome reading mode, imaging data obtained by quantizing imaging signals from the line sensors 16BW and 16G used for reading is input to the sensitivity correction unit 44.

  The sensitivity correction unit 44 performs data correction to compensate for the sensitivity difference between line sensors and the output difference between pixels in each line sensor. In the color reading mode, data correction is performed based on correction data DC for correcting the outputs of the line sensors 16R, 16G, and 16B with respect to white illumination light. In the monochrome reading mode, data correction is performed based on the correction data DM for correcting the outputs of the line sensors 16BW and 16G with respect to the green illumination light. The correction data DM is composed of correction data DMbw applied to the output of the line sensor 16BW and correction data DMg applied to the output of the line sensor 16G. For example, the correction data DC and the correction data DM are generated based on the read image data at the time of sub-scanning the first original sheet in each copying operation. The white reference plate is provided on the end of the platen glass 8 on the upstream side in the sub-scanning direction.

  Image data after correction corresponding to a plurality of line sensors used in each of the color reading mode and the monochrome reading mode is input from the sensitivity correction unit 44 to the rearrangement processing unit 45 in parallel. The rearrangement processing unit 45 temporarily stores the imaging data, rearranges them in the order of line arrangement, and sends them to the image processing unit 47 as one page of image data. The rearrangement in the monochrome reading mode deeply related to the present invention is shown in FIG.

  The image processing unit 47 is responsible for various image processing related to the image quality of the print output. For example, processing such as density adjustment, contrast adjustment, edge enhancement, smoothing, halftone reproduction, and the like is performed according to user operation settings. In the color reading mode, the image processing unit 47 also performs processing for converting RGB additive color data into CMYK subtractive color data.

As shown in FIG. 8, in the monochrome reading mode, imaging data corresponding to the line sensors 16G and 16BW is input to the rearrangement processing unit 45 in parallel. That is, odd-numbered line data and even-numbered line data in the effective reading range are input simultaneously. However, the data input at the same time is not data between adjacent lines, but data between lines separated from each other across the other two lines. For example, the data on the line [5] and the data on the line [2] are input simultaneously, and the data on the line [7] and the data on the line [4] are input simultaneously. That is, with respect to each odd line data, the data of the even line adjacent to the odd line is input with a delay of two image transfer cycles. For this reason, the rearrangement processing unit 45 stores the odd-numbered line data previously input corresponding to the line sensor 16G in the primary memory for at least a period of two image transfer periods. Then, the rearrangement processing unit 45 arranges even line data adjacent to the odd line next to the odd line data. The odd line [2m + 1] of the rearranged image data output from the rearrangement processing unit 45 is a line read by the line sensor 16G and input to the rearrangement processing unit 45 in the kth (m = 0, 1, 2, 3 ..., k = m + 1). The even line [2m + 2] is a line read by the line sensor 16BW and inputted to the rearrangement processing unit 45 in the (k + 2) th.
[Second Embodiment]
In the second embodiment, an image is read by the imaging device 17 in which three line sensors 17U, 17V, and 17W are arranged in parallel as shown in FIG. The line sensors 17U, 17V, and 17W are CCD sensors having substantially the same spectral sensitivity characteristics. The pitch Ps of the arrangement of the line sensors 17U, 17V, and 17W is selected so as to satisfy the relationship of the above-described expression (1). However, the value of N in the second embodiment is 3. The imaging device 17 is mounted on the carriage 10 as in the example of FIG. 1, for example, and moves relative to the image to be read in the sub-scanning direction. At this time, it is assumed that the line sensor 17W is located on the most downstream side in the sub-scanning direction among the line sensors 17U, 17V, and 17W. Since the spectral sensitivity characteristics of the line sensors 17U, 17V, and 17W are the same, the line light source that illuminates the original sheet may be a monochromatic light source (preferably green) or a mixed color light source (preferably white).

  As shown in FIG. 10, the imaging signals output from the line sensors 17U, 17V, and 17W are input to the signal processing circuit 40b. In the signal processing circuit 40b, the A / D converter 43b quantizes the imaging signal into imaging data, and the sensitivity correction unit 44b is based on the shading correction data DMu, DMv, DMw corresponding to the line sensors 17U, 17V, 17W, respectively. Correct the imaging data. The corrected imaging data is rearranged so that the rearrangement processing unit 45b matches the line arrangement, and the image processing unit 47b performs predetermined processing on the image data obtained thereby. The processed image data becomes the output of the signal processing circuit 40b.

  FIG. 11 shows the operation timing of the line sensors 17U, 17V, 17W and the line light source. In the sub-scanning in which the line sensors 17U, 17V, and 17W are moved at a substantially constant speed, imaging is performed at a cycle of N times the sub-scanning time T1 for one line (in this example, N is 3, so 3 times). The operation and the image transfer operation are repeated. That is, the line sensors 17U, 17V, and 17W alternately perform charge accumulation and transfer of accumulated charge from the charge accumulation unit to the charge transfer unit, and perform image transfer to the signal processing circuit 40b in parallel with charge accumulation. Do. In each of the imaging cycle period T3 in which the period for reading the entire image is divided every sub-scan time for three lines, each line sensor 17U, from the start to the end of the imaging cycle period T2, except when the accumulated charge is transferred. 17V and 17W accumulate electric charges. That is, the charge accumulation operation time corresponding to one line is longer than the sub-scan time T1 for one line. However, in each imaging cycle period T3, the electronic shutter function of the imaging device 17 is used except for the imaging period Ts from the start of the imaging cycle period T3 until the sub-scanning time T1 for one line or slightly shorter time elapses. The charge storage unit is shielded. Therefore, the period during which charges are substantially accumulated in each imaging cycle period T3 is only the imaging period Ts in which the charge accumulation unit is not shielded. In the second embodiment, the position and width of the line are determined by controlling the electronic shutter. The line light source may be turned on over the entire sub-scanning period as in the illustrated example, or at least during the imaging period Ts.

  12 and 13 show the correspondence between line sensors and lines in the second embodiment. In the example, the value of A in the formula (1) is 2, and the pitch Ps of the array of the line sensors 17U, 17V, 17W is 7 times the line pitch Pg of reading.

  As shown in FIG. 12, at the time point t1 during the sub-scanning, the line sensor 17W reads the first line [1] in the effective reading range 5A. At this time, the line sensor 17V reads the upstream dummy line [−6] with respect to the line [1], and the line sensor 17U further reads the upstream dummy line [−13]. Each time three lines of sub-scanning time elapse from time t1 to time t2, time t3, time t4, and time t5, the lines read by the line sensors 17W, 17V, and 17U are shifted to the downstream line every two lines. change.

  As shown in FIG. 13, at the time t6 when the sub-scan time for three lines has elapsed from the time t5, the line sensor 17U reads the second line [2] in the effective reading range 5A. That is, at this stage, the lines read by the three line sensors 17W, 17V, and 17U become lines within the effective reading range 5A. Thereafter, every time the sub-scanning time for 3 lines elapses from time t7 to time t8,..., The effective reading range 5A is read line by line. If one line is read every three sub-scanning times for three lines by the three line sensors 17W, 17V, and 17U that satisfy the relationship of the above-described equation (1), the effective reading range 5A can be reduced without causing line loss. The whole can be read.

  As shown in FIG. 14, the rearrangement processing unit 45b arranges the imaging data corresponding to each of the line sensors 17U, 17V, and 17W so as to match the line arrangement. The (3m + 1) th line [3m + 1] counted in order from the first line in the image data output from the rearrangement processing unit 45b is a line that is read by the line sensor 17W and input to the rearrangement processing unit 45b kth. (M = 0, 1, 2, 3,..., K = m + 1). Similarly, the (3m + 2) th line [3m + 2] is a line read by the line sensor 17U and input to the rearrangement processing unit 45b as the (k + 5) th line. Similarly, the (3m + 3) th line [3m + 3] is a line read by the line sensor 17V and input to the rearrangement processing unit 45b as the (k + 3) th line.

  According to the first embodiment and the second embodiment described above, since N images (N is a natural number of 2 or more: 2, 3, 4...) On the image are simultaneously imaged, each line sensor 16BW, 16G, 17U, The output of image information for one line from 17V and 17W may be performed within the sub-scanning time for N lines (that is, the imaging cycle periods T2 and T3). Therefore, when using a line sensor capable of outputting image information for one line within the sub-scan time for one line when the sub-scan speed is V, the sub-scan speed is increased to approximately N × V. Can do.

  According to the first embodiment, using a general-purpose imaging device 16 for a color scanner having a monochrome line sensor 16BW and three line sensors 16R, 16G, and 16B for color, reading using only the line sensor 16BW Compared to, it is possible to realize a reading that is about twice as fast. There is no need to prepare a special imaging device for high-speed reading.

  In the first embodiment, an example in which A in formula (1) is 1 and N is 2 is given, and in the second embodiment, an example in which A is 2 and N is 3 is given. However, the value of A and the value of N are not limited to the examples.

  By arranging the line sensor so as to satisfy the expression (1) in the CIS type image scanner as well as the lens reduction type capable of adjusting the relationship between the sensor arrangement pitch Ps and the line pitch Pg by the reduction optical system. Therefore, the reading speed can be increased several times as many as the line sensor.

  In the second embodiment, the imaging device 17 can be replaced with a device without an electronic shutter function. In that case, the imaging period Ts, which is a substantial charge accumulation period for one line, may be determined by lighting control of the light source as in the first embodiment.

  The image scanner 1 may be assembled as an image reading unit in an image forming apparatus such as an MFP (Multi-functional Peripheral) or a facsimile machine, or may be configured as a separate device from other devices.

1 Image scanner (image reader)
5 Document sheet (recording medium)
5A Effective reading range 16BW, 16G Line sensor 17U, 17U, 17W Line sensor 16R, 16B Line sensor 30 Imaging control unit Ps Pitch (arrangement pitch)
Pg Line pitch 43, 43b AD conversion unit 45, 45b Rearrangement processing unit (data processing unit)
12 line light source T1 sub-scan time for one line T2, T3 imaging cycle period Ts imaging period 44, 44b sensitivity correction unit 100 copier (image forming apparatus)
2 Printer engine (printing section)

Claims (8)

An image reading device for reading an image on a recording medium,
Two or more N line sensors arranged in parallel;
For each sub-scanning time of N lines, which is the time required to move the distance of N lines on the image in sub-scanning in which the image and the N line sensors are relatively moved in one direction, N in the image The N line sensors are simultaneously imaged by the N line sensors, and the N line sensors output the image signals for one line every sub-scan time for the N lines. And an image pickup control unit for controlling the line sensor. The relationship between the arrangement pitch Ps of the N line sensors and the line pitch Pg in the image is expressed by the following formula: Ps = (A × N + 1) × Pg
The image reading apparatus according to claim 1, wherein A in the formula is an arbitrary integer of 0 or more. An AD conversion unit that quantizes an imaging signal output from each of the N line sensors;
A data processing unit that arranges imaging data corresponding to the imaging signals from each of the N line sensors obtained by the AD conversion unit so as to match the line arrangement order of the images. 2. The image reading apparatus according to 2. A light source that emits green light to illuminate the recording medium;
The N line sensors include three line sensors for color reading in an imaging device in which three line sensors for RGB color reading and one line sensor for monochrome reading are arranged in parallel. Two line sensors, a line sensor corresponding to G and the line sensor for monochrome reading,
In the monochrome reading mode, the imaging control unit causes the two line sensors and the light source to move the light source for each sub-scanning time of two lines, which is a time required to move the distance of two lines on the image. The two lines in the image illuminated by the two images are simultaneously imaged by the two line sensors, and an image signal for one line is taken for each of the two lines for the sub-scanning time. The image reading device according to any one of claims 1 to 3, wherein the image reading device is controlled to output each of the image reading devices. The imaging control unit turns on the light source only for a period of time equal to or less than the sub-scanning time for one line in each of the imaging cycle periods in which the period for reading the entire image is divided into sub-scanning times for the N lines. The image reading apparatus according to claim 4. The apparatus further includes a sensitivity correction unit that corrects imaging data corresponding to the imaging signal from each of the two line sensors in accordance with the sensitivity of each of the two line sensors with respect to the light emitted from the light source. Item 6. The image reading device according to Item 4 or 5. An image forming apparatus for copying an image on a recording medium,
Two or more N line sensors arranged in parallel;
For each sub-scanning time of N lines, which is the time required to move the distance of N lines on the image in sub-scanning in which the image and the N line sensors are relatively moved in one direction, N in the image The N line sensors are simultaneously imaged by the N line sensors, and the N line sensors output the image signals for one line every sub-scan time for the N lines. An imaging control unit for controlling the line sensor;
An AD conversion unit that quantizes an imaging signal output from each of the N line sensors;
A data processing unit that arranges imaging data corresponding to the imaging signals from each of the N line sensors obtained by the AD conversion unit so as to match the line arrangement order of the images;
An image forming apparatus comprising: a printing unit that prints the image based on imaging data for one page arranged by the data processing unit. An image reading method for reading an image on a recording medium,
Using two or more N line sensors arranged in parallel, it is necessary to move a distance corresponding to N lines on the image in the sub-scan in which the image and the N line sensors are relatively moved in one direction. N lines in the image are simultaneously captured every sub-scan time for N lines as time,
An image reading method comprising: outputting an imaging signal for one line from each of the N line sensors every sub-scan time for the N lines.

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