JP2006166106A - Picture reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a picture reader where a quality of read pictures is high by suppressing picture quality deterioration at the joint of readers. <P>SOLUTION: Regarding reading pixel data about a part where pixels in the main scanning direction of adjacent CISs are overlapped, weighted average processing is carried out to the output value of respective photodetective elements at the same position in the main scanning direction, and a weighted coefficient is not designated to be the same in an overlapped range. Thus, the joint between the readers becomes inconspicuous to improve the quality of the read picture. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image reading apparatus, and more particularly, to reading of a document using a plurality of reading units in which a plurality of light receiving elements are arranged in the main scanning direction, and accurately connecting image data between the reading units. The present invention relates to an image reading apparatus that improves image quality.

  In a conventional image reading apparatus, image data is obtained by irradiating a document with reading light and photoelectrically converting reflected light from the document with a reading unit composed of light receiving elements arranged in a line in the main scanning direction. . As a reading unit, a CIS that is a unity size sensor is used because of its simple structure and easy miniaturization. In CIS, in order to obtain a high quality image, light receiving elements are usually arranged at intervals of 300 dpi to 1200 dpi. The light receiving element combines an optical component such as a Selfoc lens and a photoelectric conversion element such as a phototransistor, and the reflected light from the original surface is imaged on the photoelectric conversion section by passing through the Selfoc lens. Up to A4 and A3 sizes, CIS is relatively easy to manufacture and can be supplied at low cost due to its mass production effect. However, a light receiving element that covers A1 and A0 size documents with a single CIS. It is difficult to manufacture, and the yield is poor, resulting in high costs. Therefore, a large-size reading device such as A1 or A0 can form a sensor unit by reading a plurality of CISs for reading A4 or A3 size originals, and can read a large-size original in one original conveyance. It is possible. When a plurality of CISs are arranged in one row in the main scanning direction, as shown in FIG. 15, the distance Ly between the light receiving elements at one CIS end and the light receiving elements at the other adjacent CIS ends is one. Since it becomes larger than the distance (Lx) between the light receiving elements of the CIS, it is necessary to perform processing such as preventing unnaturalness of joints by interpolating pixels between the CIS after reading. is there. However, this pixel interpolation is not correct because the pixel to be interpolated is estimated from the pixel information read in the vicinity. Therefore, as shown in FIG. 3, adjacent CISs are arranged at different positions in the sub-scanning direction, the ends of adjacent CISs are overlapped, and further, the read image data is delayed on the upstream side by using a delay unit. After the delay, the method of eliminating the blank space at the joint is used by combining with the downstream image data. A specific example of such conventional joining will be described below with reference to FIG. Note that the sub-scanning direction described in this specification is the original transport direction, and the main scanning direction is a row of light receiving elements in the reading unit that is perpendicular to the sub-scanning direction. It ’s a direction.

  Each of CIS (A) 101 and CIS (B) 102 in FIG. 16A is composed of X light receiving elements. The (X-3) th 111th to Xth 116th light receiving elements of CIS (A) 101 and the first 121th to fourth 124th light receiving elements of CIS (B) 102 are overlapped in the main scanning direction. In CIS (A) 101, the (X-2) th to 114th light receiving elements are valid, and (X-1) 115 and the Xth 116th light receiving element are invalid. Similarly, in the CIS (B) 102, the light receiving elements from the third 123 are made valid and the first 121, the second 122 light receiving elements are made invalid, and they are connected as shown below.

..., (X-4) th light receiving element 112 of CIS (A) 101, (X-3) th light receiving element 113 of CIS (A) 101, (X-2) of CIS (A) 101 The first light receiving element 114, the first light receiving element 121 of the CIS (B) 102, the second light receiving element 122 of the CIS (B) 102, the third light receiving element 123 of the CIS (B) 102,.
Such a joining method eliminates the need for pixel interpolation when the reading units are arranged in one row in the main scanning direction, and the original can be reproduced more faithfully with respect to the joints.

However, even in such an image reading apparatus in which the ends of the CIS are overlapped, the joints of the read images may become unnatural. This is because the higher the reading resolution, the smaller the CIS mounting accuracy, and the slight expansion and contraction due to the temperature of the plate to which the CIS is mounted. Therefore, a shift of ΔLx occurs in the light receiving elements that should be at the same position in the main scanning direction. This ΔLx makes the image joint between CIS unnatural, and when reading a natural image, the quality of the read image is deteriorated, for example, a line appears to be connected. The variation in the main scanning direction can be adjusted in units of the intervals between the light receiving elements by changing the positions of the pixels on the CIS to be joined, but cannot be adjusted below the interval between the light receiving elements on the CIS. Due to this non-absorbable variation, the joints of the images are displaced, leaving unnaturalness and degrading the image quality.
JP-A-60-31357 (page 8, FIG. 1)

  The conventional image reading apparatus using a plurality of CISs described above has a problem that the quality of the joint image is poor.

  An object of the present invention is to solve the problem of such a conventional configuration, and to eliminate the unnaturalness of the joint image and to realize an image reading apparatus with high quality of the read image. It is what.

  In order to achieve the above object, according to the present invention, read pixel data relating to a portion where pixels in the main scanning direction of adjacent CISs overlap at the time of joining are output values of light receiving elements at the same position in the main scanning direction. An averaging operation by weighting is performed, and the weighting coefficient is not the same in the overlap range. That is, in each of the reading sections to be connected, the gradation values of the pixels around the joint are read, and both read gradation values are included, so that the discontinuity of the gradation of the joint can be made inconspicuous.

Further, according to the present invention, the pixel where the light receiving element of the adjacent reading unit overlaps is calculated from the gradation value obtained from one light receiving element and the gradation value obtained from the other light receiving element using the following arithmetic expression. An image reading apparatus.
Nout (x) = Na (x) × (ga (x) / G) + Nb (x) × (gb (x) / G)
G = ga (x) + gb (x)
x: pixel position Nout (x) in the main scanning direction of the images after stitching: gradation value after calculation of pixels at a position in the main scanning direction x.
Na (x): gradation value of a pixel of one reading unit at a position in the main scanning direction x.
Nb (x): The gradation value of the pixel of the other reading unit at the position in the main scanning direction x.
ga (x): A weighting coefficient for pixels of one reading unit at a position in the main scanning direction x.
gb (x): weighting coefficient of the pixel of the other reading unit at the position in the main scanning direction x.
G: integer greater than or equal to 1 Further, according to the present invention, the weighting coefficient used when calculating the pixels in the overlapping range in the main scanning direction of the adjacent reading units is the gradation value of one reading unit on the side close to one reading unit. This is an image reading apparatus in which the weighting coefficient is increased and the weighting coefficient for the gradation value of the other reading unit is increased on the side closer to the other reading unit.

  Further, according to the present invention, in the overlapping range in the main scanning direction of the reading unit, in the overlapping range closer to the reading unit, the weighting coefficient of the reading value of the CIS is read at the same main scanning position of the adjacent reading unit. In the joint processing of the range that is larger than the weighting of the gradation value and conversely overlaps in the main scanning direction closer to the adjacent reading unit, the weighting coefficient of the reading gradation value of the reading unit is adjacent to the reading unit. Since the weighting coefficient of the reading value at the same position in the main scanning is made smaller, the unnaturalness of the gradation in the range to be joined can be reduced.

  According to the reading apparatus of the present invention, it is possible to provide an image reading apparatus that can eliminate the unnaturalness of the read image that occurs when the reading unit is joined.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
As shown in FIG. 4, the reading unit called CIS 41 has 5000 light receiving elements 42 arranged in one line in the main scanning direction. The light receiving element 42 is composed of a combination of an optical component such as a Selfoc lens (not shown) and a photoelectric conversion element such as a phototransistor (not shown). The reflected light from the original is coupled to the light receiving surface of the photoelectric conversion element by the Selfoc lens. I image. Further, in the CIS 41, three light guides are arranged at positions that are parallel to the arrangement direction of the light receiving elements. The light guides respectively irradiate the original with red light, blue light, and green light by LEDs that emit red, blue, and green light.

  As shown in FIG. 3, the sensor unit fixes five reading units 21 to 25 called CIS on the plate 31 so as to form a staggered arrangement. Each of the CISs reads the document by transporting the document 26 in the document transport direction 27 on the sensor unit. FIG. 2 shows the positional relationship between each CIS and the document when FIG. 3 is viewed from above. As can be seen from FIGS. 2 and 3, the CIS (A) 21, CIS (C) 23, and CIS (E) 25 are arranged at the same position in the sub-scanning direction so as not to overlap in the main scanning direction. CIS (B) 22 and CIS (D) 24 are located at the same position in the sub-scanning direction at a position different from the individual CIS in the sub-scanning direction, and CIS (A), (C), (E) They are arranged in a staggered arrangement. In CIS (A) 21 and CIS (B) 22, CIS (B) 22 and CIS (C) 23, CIS (C) 23 and CIS (D) 24, CIS (D) 24 and CIS (E) 25 In this embodiment, the light receiving elements are arranged so that 264 light receiving elements overlap each other in the main scanning direction.

  Next, the flow of CIS output data on the sensor unit will be described with reference to the block diagram of FIG. The outputs of CIS (A) 21, CIS (B) 22, CIS (C) 23, CIS (D) 24, and CIS (E) 25 are input to AD converter 51. The output of the AD converter 51 is input to the data processing unit 52. An image memory 55 and a nonvolatile memory 56 are connected to the data processing unit 52 and can be read / written by the data processing unit 52. The output of the data processing unit 52 is input to the image processing unit 57, and the output of the image processing unit 57 is connected to the outside of the scanner. The CPU 53 is connected to the data processing unit 52, and the CPU 53 controls the data processing unit 52. The CPU 53 is connected to a program memory 54 and stores a program that defines the operation of the CPU 53.

  For each CIS, the data processing unit 52 generates output values from the light receiving elements in order from the first to the 5000th on each CIS starting from the trigger pulse input from the data processing unit 52 for each CIS. An analog signal is output in accordance with the rising edge of the CIS reference clock. The AD converter 51 samples in accordance with the rising edge of the CIS reference clock, performs A / D conversion, and outputs it as 8-bit digital data. The data processing unit 52 includes a gate array, a cell-based ASIC, an FPGA, or the like, receives digital data output from the AD converter, and performs shading correction. A specific method of shading correction will be described later. In addition, when the upstream CIS outputs the read data for the p-th line, the downstream CIS outputs the read data for the p-q line. Therefore, the data processing unit temporarily stores the data after the upstream CIS processing in the image memory 55. After the q lines of originals are conveyed, the downstream CIS reads the p-line, and after AD conversion is performed in the data processing unit, the same line data is read from the memory by the upstream CIS, and the sensor-to-sensor joining process is performed. Do. By the stitching process, the data that has been processed by being divided into five pieces so far becomes one line of data and is sent to the image processing unit.

  The image processing unit is configured by a DSP (Digital Signal Processor) or the like, and performs image processing such as contrast adjustment and gamma correction, clipping processing required in the main scanning direction and sub-scanning direction, enlargement / reduction, and binarization processing. Is executed as necessary, and then sent to the outside of the reading apparatus, and stored as image data, printed out, or transferred to a remote location via a LAN or WAN according to the application.

  The flow of the data processing unit will be described below with reference to FIG. Data input from the AD converter 51 temporarily enters the FIFO 61 in order to absorb the difference between the transfer rate between the AD converter 51 and the data processing unit 52 and the transfer rate in the data processing unit. The reading unit cutout processing unit 62 reads data from the FIFO 61 and discards data for 100 pixels at both ends which are unnecessary for the CIS sensor, as will be described later, and sends the data to the shading correction unit. The shading correction is calculated by the following formula when the number of gradations is 256 in order to widen the dynamic range of the read data.

Data after shading correction = 255 × ((N (x) −Bk (x)) / (Wh (x) −Bk (x)))
N (x): AD converter output read data Bx (x) when the document is read Bk (x): AD converter output read data Wh (x) at the x position with the CIS LED turned off: Bk (x) used for the data shading correction of the AD converter output at the position x when the white reference plate is read is a non-volatile value of the AD conversion value of the light receiving element output with the CIS LED turned off before reading the document. The Wh (x) is also stored in the non-volatile memory 56. The Wh (x) stores the AD conversion value of the output of the light receiving element when the white reference plate provided in the apparatus is read before reading the document. The Bk (x) and Wh (x) are read from the nonvolatile memory 56 at the time of shading correction, and shading correction is performed.

  The data after shading correction is written into the image memory 55 for delay processing by the memory controller 64. The delay processing unit 65 reads the data corresponding to the same line on the document via the memory controller 64 in consideration of the shift of the transport time in the sub-scanning direction of the CIS arranged in a staggered arrangement, and puts it in the inter-sensor connection processing unit 66. . The operation of the inter-sensor connection processing unit 66 will be described later.

  The data after the linking process is sent to the main scanning direction data cutout processing unit 67, and only the range in the main scanning direction designated by the CPU is extracted and sent to the output FIFO 68. The output FIFO 68 reads data from the output FIFO 68 and transfers it to the outside of the data processing unit 52 so as to meet the transfer rate between the data processing unit 52 and the image processing unit, and the image processing unit 57 performs the above-described processing.

A detailed embodiment of the inter-sensor connection process will be described below.
In each CIS, 100 pixels at both ends are used for adjustment when the deviation in the main scanning direction between adjacent CISs is larger than the interval between the light receiving elements. The output for pixels is invalid.
Therefore, 4800 light receiving elements are effective from the 101st light receiving element to the 4900th light receiving element. When there are adjacent CISs, the light receiving elements for 64 pixels at the end of 4800, that is, the 101st to 164th and 4737th to 4800th light receiving elements in the CIS are the calculation target of the joining. In the joining calculation, weighting calculation is performed on the 101st received light data of one CIS and the 4737th received light data of the other CIS, and the data of the pixel is calculated. Thereafter, similarly, the weighting operation is performed on the 102nd and 4738th of the other CIS,... 164th and the other 4800th of the other CIS.

  Therefore, in CIS (A) and CIS (E), 4800 light receiving elements are effective. Of these, 64 are used for connection with adjacent CIS, and 4736 light receiving elements are not subjected to the connecting process. is there. In CIS (B), CIS (C), and CIS (D), which require joint processing at both ends, 4800 light receiving elements are effective, of which 128 are used for joining with adjacent CIS. There are 4672 light receiving elements not subjected to the joining process. Therefore, the number of pixels in one line after joining is 4736 + 64 + 4672 + 64 + 4672 + 64 + 4672 + 64 + 4736 = 23744.

In the weighting calculation in the joining process, when the gradation of one light receiving element is Na and the gradation of the other light receiving element is Nb, calculation is performed using the following equation.
Nout = ((ga / G) × Na) + (((G−ga) / G) × Nb)
Nout: Gradation after stitching G: integer greater than or equal to 1: ga: weighting factor, which is an integer greater than or equal to 1 and less than or equal to G. In this embodiment, G is 9 and 8 stitches in the range of 64 pixels. The same weighting coefficient is used in each small area. Here, G is not limited to 9, and if the subdivision area is subdivided, the number of subdivision areas will be equal to or greater than that. For example, if the connection range of 64 pixels is divided into 64 small areas, the G is a number of 64 or more, and if the connection range is 64 pixels or more, the G is a large number. As the subdivision area and G are subdivided into smaller subdivision areas, natural image joints can be realized, but the amount of data that needs to be processed increases accordingly.

  Further, the weighting coefficient ga is an integer of 1 or more and G or less, and becomes G when added to the weighting coefficient gb of the other CIS at the same position in the main scanning direction.

  Also, the weighting coefficient ga (x) at the position x in the main scanning direction within one reading unit and the weighting coefficient ga (y) at the position y adjacent to the position x and close to the other reading unit within the same reading unit. , Ga (x) ≧ ga (y) is satisfied. That is, as the light receiving element is closer to the end of the CIS, the weighting coefficient becomes smaller, and a more natural read image can be obtained.

  FIG. 7 (a) shows the positional relationship between the joining portions of CIS (A) and CIS (B). In the figure, a10 to a18 indicate the positions of the light receiving elements of CIS (A). b1 to b9 indicate the positions of the light receiving elements of the CIS (B). Similarly, FIG. 7 (b) shows CIS (B) and CIS (C), FIG. 7 (c) shows CIS (C) and CIS (D), and FIG. 7 (d) shows CIS (D) and CIS (D). CIS (E) is shown.

Which light receiving element on each CIS is identified by the symbols (a10 to a18, b1 to b9, b10 to b18, c1 to c9, c10 to c18, d1 to d9, d10 to d18, e1 to e9) in FIG. Is shown in FIG.
FIG. 9 shows the weighting coefficients for the small areas that require the weighting operations shown in FIGS.

10 to 14 show arithmetic expressions for pixel data of one line after joining, using the weighting coefficient of FIG.
Due to these splicing processes, the peripheral pixels between the reading units contain both reading data at the same position in the main scanning direction, which is caused by variations in CIS manufacturing and accuracy in mounting the CIS to the sensor unit. Therefore, it is possible to eliminate the unnaturalness of the read image that occurs when the reading unit is connected.

FIG. 1 shows the configuration of a reading apparatus according to an embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a sensor unit that irradiates an original with reading light and reads the reflected light. Reference numeral 3 denotes an original table and an original table 3, and a white reference plate 2 is placed at a position facing the sensor unit 1. Fix it. A document transport path 4 is between the document table 3 and the white reference plate 2. Reference numerals 5a and 5b denote transmission sensors for detecting the insertion of a document when the document is inserted from the document carry-in entrance (not shown) from the outside. There are a carry-in driving roller 6a and a carry-in driven roller 6b for conveying the document to the document table 3 by sensing the insertion of the document. Reference numerals 8a and 8b denote sensors for detecting the conveyance of the original to the original table 3. Reference numeral 7a denotes a driving roller for conveying the original. Reference numeral 7b denotes a driven roller for conveying the original. Reference numeral 9a denotes a discharge driving roller for discharging the original after reading out of the apparatus, and 9b denotes a discharge driven roller.

  Next, the operation of the embodiment shown in FIG. 1 will be described. Before reading the document, the sensor unit 1 reads the black reference value with the light turned off, and the LED on the sensor unit 1 is turned on to read the white reference plate 2, and the parameters for shading correction are stored. A document inserted from a document carry-in entrance (not shown) is sensed by the transmission sensors 5a and 5b, and the document table 3 until the transmission sensors 8a and 8b sense the leading edge of the document by the carry-in driving roller 6a and the carry-in driven roller 6b. Sent to. The original is read by the sensor unit 1 while the original is being conveyed by the original feeding driving roller 7a and the original feeding driven roller 7b. When the reading of the predetermined line is completed or when the transmission sensors 5a and 5b detect the trailing edge of the document, the sensor unit 1 finishes reading, and the discharge driving roller 9a and the discharge driven roller 9b It is discharged outside.

Configuration diagram of a reader according to the present invention The figure which shows the positional relationship of the zigzag arrangement | sequence of the reading part based on this invention, and a document. The figure which shows the structure of the sensor unit which concerns on this invention The figure which shows the structure of the reading part which concerns on this invention The block diagram which shows the electric constitution of the reading part which concerns on this invention The figure which shows the flow of the data processing part shown in FIG. The figure which shows the overlap of the light receiving element of an adjacent reading part The figure which shows the specific place of the symbol which shows the position of each reading part shown in FIG. The figure which shows the correspondence of the position of the light receiving element and the weighting coefficient in the joining process between sensors The figure which shows the weighting calculating formula between CIS (A) and CIS (B) in an Example. The figure which shows the weighting arithmetic expression between CIS (B) and CIS (C) in an Example. The figure which shows the weighting arithmetic expression between CIS (C) and CIS (D) in an Example. The figure which shows the weighting arithmetic expression between CIS (D) and CIS (E) in an Example. The figure which shows the computing equation which calculates the read data of the range which is not contained in FIG.10, FIG.11, FIG.12 and FIG. The figure which shows arrangement of the conventional reading part The figure explaining the joining of the conventional reading part

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor unit 2 White reference board 3 Document stand 4 Document conveyance path 5a Transmission sensor light-receiving part 5b Transmission sensor light emission part 6a Document loading drive roller 6b Document loading driven roller 7a Document feeding drive roller 7b Document feeding driven roller 8a Transmission Sensor light receiving portion 8b Transmission sensor light emitting portion 9a Document discharge driving roller 9b Document discharge driven roller 21 CIS (A)
22 CIS (B)
23 CIS (C)
24 CIS (D)
25 CIS (E)
26 Document 27 Document transport direction 41 CIS
42 Light-receiving element 43 Light guide for red LED 44 Light guide for green LED 45 Light guide for blue LED 51 AD converter 52 Data processing unit 53 CPU
54 Program memory 55 Image memory 56 Non-volatile memory 57 Image processing unit 58 Reading device 61 Input FIFO
62 Intra-reading cutout processing unit 63 Shading correction unit 64 Memory controller 65 Delay processing unit 66 Inter-sensor connection processing unit 67 Main scanning direction data cutout processing unit 68 Output FIFO
69 Output processor 91 Light receiving element 92 on CIS (A) Light receiving element 93 on CIS (B) Light receiving element 94 on CIS (C) Light receiving element 95 on CIS (D) Light receiving element 101 on CIS (E) One reading unit 102 The other reading unit 103 The light receiving element 104 The distance 105 between adjacent light receiving elements on the CIS 111 The distance 111 between the light receiving elements at the ends of adjacent CISs The x-5th light receiving element 112 of one CIS One CIS X-4th light receiving element 113 of one CIS x-3th light receiving element 114 of one CIS x-2th light receiving element 115 of one CIS x-1th light receiving element 116 of one CIS x The first light receiving element 121 of the other CIS The first light receiving element 122 of the other CIS The second light receiving element 123 of the other CIS The third light receiving element 124 of the other CIS The other C S 4th light receiving element 125 5th light receiving element 126 of the other CIS 6th light receiving element 131 of the other CIS x-5th light receiving element 132 of one CIS x-4th light receiving element of one CIS Element 133 One CIS x-3 light receiving element 134 One CIS x-2 light receiving element 135 One CIS x-1 light receiving element 136 One CIS x light receiving element 141 The other CIS x-2 light receiving element 141 CIS first light receiving element 142 The other CIS second light receiving element 143 The other CIS third light receiving element 144 The other CIS fourth light receiving element 145 The other CIS fifth light receiving element 146 The other CIS fifth light receiving element 146 CIS 6th photo detector

Claims (6)

  By irradiating the original with the reading light and photoelectrically converting the reflected light by the light receiving element, the reading part for reading the image of the original is arranged in such a manner that a part of the light receiving element of the adjacent reading part overlaps in the main scanning direction. At least two or more are arranged at different positions in the scanning direction, and the reading unit moves the sensor unit composed of the plurality of reading units or the document in the sub-scanning direction using a moving unit, thereby the document. An image reading apparatus that combines image data read by the reading unit positioned upstream and image data read by the downstream reading unit using a combining unit to generate one line of image data The synthesizing unit obtains gradation values in a range in which the light receiving elements overlap in the main scanning direction of the adjacent reading units from the reading unit located on the upstream side. And a joint image processing means for calculating by means of weighted averaging processing of gradation values obtained from a reading unit located on the downstream side, and the weighting coefficient used for the averaging processing calculation depends on the position in the main scanning direction The image reading apparatus is characterized by being different in the overlapping range.   The image reading apparatus according to claim 1, wherein the image reading apparatus fixes the sensor unit and moves the document using document moving means.   The image reading apparatus according to claim 1, wherein the image reading apparatus fixes a document and moves the sensor unit using a sensor unit moving unit.   The image reading apparatus according to claim 1, wherein the reading units are odd-numbered and even-numbered in the main scanning direction, and are arranged at the same position in each of the sub-scanning directions. The image reading apparatus according to claim 1, wherein the weighted averaging processing calculation is calculated by the following equation.
Nout (x) = Na (x) × (ga (x) / G) + Nb (x) × (gb (x) / G)
G = ga (x) + gb (x)
x: pixel position Nout (x) in the main scanning direction of the images after stitching: gradation value after calculation of pixels at a position in the main scanning direction x.
Na (x): gradation value of a pixel of one reading unit at a position in the main scanning direction x.
Nb (x): The gradation value of the pixel of the other reading unit at the position in the main scanning direction x.
ga (x): A weighting coefficient for pixels of one reading unit at a position in the main scanning direction x.
gb (x): weighting coefficient of the pixel of the other reading unit at the position in the main scanning direction x.
G: integer greater than or equal to 1 The weighting coefficient used for the averaging is the weighting coefficient ga (x) of the pixel located at the position x close to the center of one reading section and the other weighting coefficients adjacent to x in the adjacent pixels in the main scanning direction in one reading section. 6. The image reading apparatus according to claim 1, wherein ga (x) ≧ ga (y) is satisfied in a weighting coefficient ga (y) of a pixel located at a position y close to the reading unit.

Images