Image reading device, control method of the same, program, and memory medium

Abstract

To provide an image reading device capable of surely obtaining a transmission error component caused by an error of a transmission roller, a control method of the same, a program, and a memory medium.SOLUTION: The present invention provides an image reading device that transmits and reads a script. A plurality of line image sensors 106 are arranged in a zigzag shape in a direction crossed to a transmission direction of the script, and two transmission rollers are also arranged on an upstream side and a downstream side of a transmission direction of the script of each line image sensor. In the case where control means detects an error of a transmission speed of the two rollers by reading a script 110 to which a dot pattern 401 is drawn with each image sensor, an image data read by each image sensor positioned on the upstream side of the transmission direction is used for detecting the transmission speed of each transmission roller positioned on the upstream side of the transmission direction, and an image data read by each image sensor positioned on the downstream side of the transmission direction is used for detecting the transmission speed of each transmission roller positioned on the downstream side of the transmission direction.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to an image reading device having a line image sensor. [Background technology]

[0002] In image reading devices capable of reading large-format documents, the use of a long line image sensor for reading the document increases costs, so a configuration using multiple small-sized line image sensors (hereinafter referred to as line sensors) is generally adopted. Since multiple line sensors are used, a process is required to stitch together the data read by each line sensor. In this case, if the document transport roller is eccentric, a transport error occurs, which causes an error in the stitching process.

[0003] Fig. 22 shows a general configuration of an image reading device using multiple line sensors and an example of reading. As shown in Fig. 22(a), an original 110 is transported by upstream rollers 107 and downstream rollers 108, and is read by multiple line sensors 106 arranged in a staggered pattern. Then, a process is performed to join the results read by the multiple line sensors 106 at a joining position 113. At this time, if the upstream rollers 107 and downstream rollers 108 are eccentric, there will be a positional deviation 2001 in the transport direction between the line sensors arranged in a staggered pattern, causing an error in the joining position.

[0004] For example, if the line image sensors 106 are arranged in a straight line, the transport error of the transport roller acts uniformly on all the line image sensors, and an error in the connection position is unlikely to occur. In contrast, if there is a positional deviation 2001 in the transport direction between the line sensors, a difference in the transport amount occurs between the position of the upstream line sensor in the transport direction and the position of the downstream line sensor, and an error occurs in the connection position.

[0005] Specifically, as shown in Fig. 20(b), when reading the straight pattern 2002, due to the eccentricity of the upstream roller 107 and the downstream roller 108, it is read as a line 2003 with different connection position displacements for each straight line.

[0006] To address this problem, a technique is known in which, through a process called calibration, an error component during reading due to the eccentricity of the document conveyance roller is obtained in advance and corrected to achieve accurate splicing.

[0007] In Patent Document 1, in order to perform calibration, a dot pattern formed on a document is read, and based on the position data of the read dot pattern, an error component due to the eccentricity of the document conveyance roller is obtained.

[0008] In Patent Document 1, in addition to the conveyance error component due to the eccentricity of the document conveyance roller, an error component due to the diameter error of the document conveyance roller is also obtained by reading a similar dot pattern. Thus, it is possible to obtain the conveyance error components due to the eccentricity and diameter error of the document conveyance roller.

[0009] Also, in a general sheet feed type image reading apparatus, the document 110 is conveyed by an upstream roller 107 disposed on the upstream side in the conveyance direction of the document 110 and a downstream roller 108 disposed on the downstream side. Therefore, as conveyance forms of the document 110, there are three forms: conveyance by only the upstream roller, conveyance by only the downstream roller, and conveyance by both the upstream and downstream rollers. Since the influence of errors is different for each conveyance form, in order to obtain the error components due to the document conveyance roller with higher precision, it is necessary to obtain the error components for each conveyance form.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] When attempting to obtain error components caused by the conveyance rollers for each conveyance mode as described above, the following problems occur. When conveying on the upstream-side rollers and when conveying on the downstream-side rollers, it is necessary to obtain the error components when conveying using only the conveyance rollers on one side. The conveyance error of the conveyance rollers often results in a conveyance error with a period of one rotation, such as due to eccentricity of the rollers. Therefore, in order to improve the acquisition accuracy of the error components, it is desirable that the distance of conveyance using only the conveyance rollers on one side is at least one full rotation of the conveyance rollers. However, in order to reduce the size of the image reading apparatus, it is necessary to shorten the interval between each conveyance roller, and the section of conveyance using only the rollers on one side becomes shorter than one full rotation of the rollers. As a result, the error pattern cannot be sufficiently read, and it becomes difficult to accurately obtain the error components of conveyance caused by eccentricity and diameter error during upstream-side roller conveyance and downstream-side roller conveyance.

[0012] The present invention has been made in view of the above-described problems, and an object thereof is to provide an image reading apparatus capable of accurately obtaining the conveyance error components caused by the error of the conveyance rollers.

Means for Solving the Problems

[0013] The image reading apparatus according to the present invention is an image reading apparatus that conveys a document and reads the document, and includes a plurality of line image sensors arranged along a direction intersecting the conveyance direction of the document, wherein the line image sensors are arranged in a staggered pattern with a predetermined amount of deviation from each other in the conveyance direction, an upstream roller arranged upstream of the conveyance direction of the document with respect to the plurality of line image sensors, a downstream roller arranged downstream of the conveyance direction of the document, and control means for controlling to detect a conveyance error by reading a document on which a detection pattern for detecting a conveyance error between the upstream roller and the downstream roller is formed by the plurality of line image sensors, and for detecting a conveyance error using the reading data of the line image sensor arranged near the upstream roller among the line image sensors arranged in the staggered pattern for a first region of the document conveyed only by the upstream roller, and for detecting a conveyance error using the reading data of the line image sensor arranged near the downstream roller among the line image sensors arranged in the staggered pattern for a third region of the document conveyed only by the downstream roller.

Effect of the Invention

[0014] According to the present invention, it is possible to accurately acquire a conveyance error component caused by an error of a conveyance roller.

Brief Description of the Drawings

[0015]

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MODE FOR CARRYING OUT THE INVENTION

[0016] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0017] (First Embodiment) In this embodiment, in a sheet feed type image reading apparatus having a plurality of line image sensors, a conveyance form in which a document is conveyed only by an upstream roller disposed on the upstream side in the document conveyance direction, a conveyance form in which a document is conveyed by rollers on both the upstream and downstream sides, and a conveyance form in which a document is conveyed only by a downstream roller disposed on the downstream side in the document conveyance direction will be described with respect to a process of acquiring a conveyance error.

[0018] Note that hereinafter, the conveyance form in which a document is conveyed only by the upstream roller will be referred to as the first conveyance form, the conveyance form in which a document is conveyed by rollers on both the upstream and downstream sides will be referred to as the second conveyance form, and the conveyance form in which a document is conveyed only by the downstream roller will be referred to as the third conveyance form. Further, the process of acquiring a conveyance error refers to a process of calculating a correction value for correcting an error component of document conveyance caused by eccentricity or diameter error of a document conveyance roller.

[0019] Specifically, the conveyance error due to the eccentricity of the document conveyance roller refers to the variation in the amount of document conveyance per unit rotation angle that occurs when the axis of the document conveyance roller is slightly displaced from the center due to manufacturing tolerance. The conveyance amount in a unit interval may be large or small depending on the position, and the conveyance error amount due to the eccentricity of the document conveyance roller changes with one rotation of the roller as one cycle, and becomes zero when added up for one full rotation of the roller.

[0020] The conveyance error due to the diameter error of the document conveyance roller specifically refers to the variation in the amount of document conveyance that occurs when the diameters of the document conveyance rollers differ due to manufacturing tolerances. Since the conveyance error amount due to the diameter error of the document conveyance roller is equally affected across the entire conveyance area of the document conveyance roller, it causes a change in the magnification in the conveyance direction of the read image. Note that in the process of obtaining the correction value, the correction value is obtained from the result of previously reading a specific pattern (detection pattern).

[0021] <Configuration of the Image Reading Device> First, the basic configuration of the image reading device will be described using an overall view of the image reading device, a diagram showing the image reading form, and the like.

[0022] FIG. 1(a) is a perspective view showing the appearance of a sheet feed type scanner 100, which is an example of the image reading device of the present invention. As shown in FIG. 1(a), the scanner 100 has a document feed slot 101 and a document feed table 102 on the front side of the main body. The user places the leading edge of the document on the document feed table 102 so that the central portion of the document is positioned at the center of the feed slot, and inserts it into the document feed slot 101 by sliding it on the table. The document feed slot 101 is designed to allow a certain degree of misalignment and inclination during insertion with respect to the width of the document in the main scanning direction that can be read by the scanner 100. The configuration of the document feed path will be described later with reference to FIG. 1(b). For ease of explanation, coordinate axes are set as shown in FIG. 1(a), and these coordinate axes shall be similarly applied to other drawings.

[0023] The scanner 100 is provided with an operation unit 103 composed of physical keys, a touch panel, an LCD panel, etc. on the upper surface of the main body, and it is possible to set reading conditions and input the document size. Also, an upper cover 104 is provided on the upper surface of the scanner 100, and access to the reading unit etc. becomes possible when the upper cover 104 opens upward. Thereby, maintenance of the main body can be performed.

[0024] FIG. 1(b) and FIG. 1(c) are schematic diagrams showing the internal configuration of the scanner 100. FIG. 1(b) is a cross-sectional view, and FIG. 1(c) is a top view. In the cross-sectional view of FIG. 1(b), the left side is the upstream side of the document feeding, the right side is the downstream side, and the document is conveyed in the +y direction. The document 110 fed by the user via the document feeder 102 is discharged from the back of the main body through a flat conveyance path.

[0025] The document detection sensor 105 detects the insertion of the document 110. When the insertion of the document 110 is detected, the control unit 202 (see FIG. 2) of the scanner 100 rotates the upstream roller 107 to draw the document 110 into the main body. The end detection sensor 112 is used to detect the leading end of the document 110 drawn into the main body by the rotation of the upstream roller 107. Also, the detection result of the end detection sensor 112 is used to determine the reading start position of the document 110 and to detect the position of the trailing end of the document 110.

[0026] Inside the main body, the document 110 passes between the glass plate 109 and the document pressing plate 111. The document pressing plate 111 functions to press the document 110 against the glass plate 109 with a predetermined pressure. The line image sensor (hereinafter referred to as CIS) 106 is a line image sensor in which light receiving elements are arranged in the main scanning direction (X direction in the figure), which is a direction orthogonal (crossing) to the conveyance direction of the document 110, and is composed of a plurality of chips composed of a plurality of light receiving elements. The reading surface of the CIS 106 faces the glass plate 109 and is designed such that the reading focal position is located at the contact surface between the document 110 and the glass plate 109.

[0027] The downstream roller 108 is configured to be driven by a belt (not shown) following the upstream roller 107, and has the role of discharging the document that has passed through the pressing area against the glass plate 109 by the document pressing plate 111 to the downstream side. The control unit 202 described later is composed of each detection sensor, a motor (not shown) for rotating the upstream roller 107, a circuit board for controlling the CIS 106 and the operation unit 103, etc.

[0028] As shown in the top view of FIG. 1(c), the scanner 100 is configured such that a plurality of CISs 106 are arranged in a staggered manner in the main scanning direction (shifted by a predetermined amount in the sub-scanning direction). In this example, five CISs 106-1 to 106-5 are arranged. In the scanner 100, each CIS 106 reads the document 110, and the control unit 202 performs a process of connecting the data read by each of the CISs 106-1 to 106-5 at the connection position 113.

[0029] FIG. 2 is a block diagram showing the hardware configuration of the scanner 100 in the present embodiment. In the scanner 100, a control unit 202 that controls image reading and the like includes a CPU 204, a memory 208, a motor driver 207, an interface (hereinafter referred to as IF) unit 203, an A / D conversion unit 206, and a power supply unit 205. The operation unit 103 is configured by a touch panel with an LCD (Liquid Crystal Display). On the LCD of the operation unit 103, information regarding the document to be read and the settings of the reading device and the like is displayed according to an instruction from the CPU 204. Further, the user can change inputs to the scanner 100, for example, various settings, by operating the touch panel of the operation unit 103 while checking the information displayed on the LCD of the operation unit 103.

[0030] The conveyance motor 201 is controlled by the CPU 204 via the motor driver 207 to rotate the upstream roller 107 and the downstream roller 108. The outputs of the document detection sensor 105 and the end detection sensor 112 are input to the CPU 204, and the CPU 204 performs control such as determining the driving timing of the plurality of CISs 106-1 to 106-5 based on the changes in the output signals of these sensors and the state of the conveyance motor 201.

[0031] A plurality of CISs 106 output the read images as analog signals to the control unit 202. The analog signals output from the plurality of CISs 106 are converted into digital signals by each A / D conversion unit 206 and input to the CPU 204. The CPU 204 processes the data converted into digital signals in each A / D conversion unit 206 and can transmit the data as image data to an external device connected via USB, LAN, or the like through the IF unit 203. The power supply unit 205 generates the necessary voltages for each unit and supplies power. The memory 208 can store image data for a plurality of lines.

[0032] <Calibration> Hereinafter, the flow of reading a manuscript 110 on which a correction value acquisition processing pattern (also called a calibration chart) is formed using the CIS 106 and acquiring correction values will be described with reference to the flowchart of FIG. 3. Note that the correction value acquisition timing may be to acquire correction values in advance, or correction values may be acquired each time reading is performed.

[0033] When acquiring correction values in advance, correction values are acquired by reading a predetermined manuscript prepared in advance at the time of factory shipment or at the user's site, and then the same correction values are applied each time reading is performed. In this case, since it is not necessary to acquire correction values each time reading is performed, the reading time can be shortened.

[0034] On the other hand, when acquiring correction values each time reading is performed, correction values are acquired by reading a predetermined manuscript before reading or a manuscript with a correction value acquisition pattern printed on the header part of the manuscript. In this case, since the current error components can be sequentially corrected, highly accurate reading can be realized.

[0035] First, in step S301, the CPU 204 receives an input of pressing a calibration start button on the operation unit 103 by the user. As a result, the scanner 100 enters a state of waiting for the insertion of a dedicated manuscript to be used for calibration. Hereinafter, for ease of explanation, "step S~" will be abbreviated as "S~".

[0036] In S302, the CPU 204 determines whether it has detected the insertion of the original document 110 set by the user. If the original document 110 has been inserted, the process proceeds to S303. On the other hand, if the original document 110 has not been inserted, the detection determination of the insertion of the original document 110 is performed again.

[0037] In S303, the CPU 204 controls the conveyance motor 201 to convey the original document 110 to the reading start position.

[0038] In S304, the CPU 204 starts the image reading operation and stores the data (referred to as reading data) acquired by the reading in the memory 208.

[0039] In S305, the CPU 204 determines whether the reading of a predetermined length has been completed. If the reading of the predetermined length has been completed, the process proceeds to S306. On the other hand, if the reading of the predetermined length has not been completed, the reading operation is continued until the reading of the predetermined length is completed.

[0040] In S306, the CPU 204 ends the image reading operation and conveys the calibration original document 110 to the paper discharge position.

[0041] In S307, the CPU 204 performs correction value acquisition processing. The correction value obtained in this step is stored in the memory 208 and read out and applied during the normal reading operation.

[0042] Next, the flow of acquiring the correction value based on the read pattern (details of S307 in FIG. 3) will be described with reference to FIGS. 4 and 5. FIG. 4 is a diagram showing an original document on which a correction value acquisition processing pattern (calibration chart) according to the present embodiment is formed.

[0043] As shown in FIG. 4, a plurality of circular dot patterns 401 each consisting of a plurality of dots (pixel value is 1) are printed in isolation from each other on the calibration chart, and while the document is being conveyed by the document conveyance roller, the circular dot pattern 401 is read.

[0044] In FIG. 4, the upstream roller conveyance area (hereinafter, the first area R1) is the area read by the CIS 106 when the document is conveyed only by the upstream roller 107 (the first conveyance mode). Also, the upstream and downstream roller conveyance area (hereinafter, the second area R2) is the area read by the CIS 106 when the document is conveyed by both the upstream roller 107 and the downstream roller 108 (the second conveyance mode). The downstream roller conveyance area (hereinafter, the third area R3) is the area read by the CIS 106 when the document is conveyed only by the downstream roller 108 (the third conveyance mode).

[0045] A plurality of circular dot patterns 401 are formed over the range of the width Xr of the readable area and the pattern lengths L1 of the first area R1, the pattern length L2 of the second area R2, and the pattern length L3 of the third area R3. Note that, for example, the conveyance error due to the eccentricity of the document conveyance roller causes a change in one cycle per one rotation of the document conveyance roller. Therefore, in order to obtain data for one cycle of the conveyance error, it is desirable that the pattern lengths L1 of the first area R1, the pattern length L2 of the second area R2, and the pattern length L3 of the third area R3 be set to lengths equal to or greater than the circumferential length Yr of one rotation of the document conveyance roller. However, for the purpose of downsizing the apparatus, it is difficult for the pattern lengths L1 to L3 of each area, particularly L1 and L3, to take a length equal to or greater than the circumferential length Yr of one rotation of the document conveyance roller. In the present embodiment, a method for solving this will be described.

[0046] First, in S501, the CPU 204 acquires the center coordinates of the circular dot pattern 401. Specifically, the center coordinates of each circular dot pattern 401 are acquired from the read data obtained by image reading. The center coordinates acquired in this step are used in the acquisition processing of each correction value described later.

[0047] In S502, the CPU 204 performs the process of obtaining the tilt angle of the CIS 106. Specifically, the tilt angle is obtained by utilizing the fact that a plurality of circular dot patterns are arranged concentrically such that the sum of the coordinates from the reference coordinates becomes 0. The process of obtaining the tilt angle in this step is a process for suppressing the deviation of the connection position 113 when the read data is joined together. Based on the information of the tilt angle of the CIS 106 obtained in this step, it becomes possible to perform the joining of the read images with high precision later. In the process of obtaining each correction value described later, the correction value corresponding to the tilt angle of the CIS 106 obtained by S502 is applied in advance and then the process is performed.

[0048] In S503, the CPU 204 performs the process of obtaining the conveyance error due to the eccentricity and diameter error of the document conveyance roller. The detailed obtaining method will be described later.

[0049] In S504, the CPU 204 performs the process of obtaining the main scanning direction magnification due to the step difference between the chips of the CIS 106. The process of obtaining the main scanning direction magnification due to the step difference between the chips is a process for correcting the reading error in the main scanning direction due to the gap between each chip inside the CIS 106.

[0050] In S505, the CPU 204 performs the process of obtaining the connection position. The process of obtaining the connection position is a process for accurately joining the reading results of each CIS 106, and it is a process of applying in advance the correction value obtained from the results of S502 to S504 and obtaining the connection position 113. Thus, the calibration involving the obtaining of each correction value is completed.

[0051] Hereinafter, the processes of the above steps will be described in more detail.

[0052] <Center coordinate acquisition process> Next, the process of obtaining the center coordinates of the circular dot pattern (S501 in FIG. 5) based on the read data will be specifically described using the circular dot pattern 401 shown in FIG. 6 and the flowchart of FIG. 7. As shown in FIG. 6, the circular dot pattern 401 needs to be a pattern that is sufficiently large with respect to the pixel 106a to be read by the scanner.

[0053] First, in S701, the CPU 204 extracts all the pixel data in the main scanning direction MS of the CIS 106 at the target position (the position of the pixel line to be targeted) in the sub-scanning direction SS of the CIS 106 from all the read data.

[0054] In S702, the CPU 204 determines whether there are pixels whose gradation values continuously exceed the threshold Xt in the main scanning direction MS based on the pixel data extracted in S701, and performs binarization for each pixel as shown in FIG. 6. If there are pixels whose gradation values continuously exceed the threshold Xt in the main scanning direction MS, the process proceeds to S703; otherwise, the process proceeds to S705. Note that the threshold Xt used in this step is set in advance, and the data is stored in the memory 208.

[0055] In S703, the CPU 204 determines the position of the central pixel of the continuous pixels whose gradation values exceed the threshold Xt as the central coordinate in the main scanning direction MS.

[0056] In S704, the CPU 204 determines whether the acquisition of the central coordinates in the main scanning direction MS has been completed for all the pixel lines in the sub-scanning direction SS.

[0057] In S705, the CPU 204 advances the target position (the position of the pixel line to be targeted) in the sub-scanning direction SS by one pixel (one line).

[0058] In S706, the CPU 204 takes the average of the obtained central coordinates in the main scanning direction MS, and sets the obtained average value as the center coordinate 601 of the circular dot pattern 401.

[0059] If reading errors due to dust are to be taken into consideration when determining the central coordinate in the main scanning direction MS, this can be accommodated by making the dot pattern larger. Also, if reading errors due to gaps between chips in the CIS 106 are to be taken into consideration, it is necessary to select a point that does not straddle the chips when determining the coordinate in the main scanning direction MS and determine the central coordinate. The dot pattern is preferably substantially circular as shown in Fig. 6. This is because a substantially circular shape is less susceptible to the influence of error components during reading when acquiring the central coordinates 601. For example, if the document is tilted when it is set, it is difficult to determine whether the pixel data in the main scanning direction MS has a gradation value that exceeds the threshold value Xt consecutively in the main scanning direction MS if the dot pattern shape is rectangular. It is easier to determine consecutive pixel data whose gradation values ​​exceed the threshold value Xt consecutively in the main scanning direction MS with a substantially circular shape than with a rectangular shape.

[0060] Furthermore, if the dot pattern is substantially circular, it is not necessary to perform the process of acquiring the center coordinates for all lines in the sub-scanning direction SS as in S704 to S706 in Fig. 7. In other words, assuming that the dot pattern is substantially circular, it is possible to estimate pixel data whose gradation values ​​exceed the threshold value Xt consecutively in the main scanning direction MS and acquire the center coordinates 601 of the dot pattern. This makes it possible to shorten the time required to acquire the center coordinates.

[0061] <Acquisition process of transport error caused by error of document transport roller> Hereinafter, a method for acquiring the transport error caused by the error of the document transport roller in this embodiment will be described with reference to FIGS.

[0062] 8 to 10 are diagrams showing the relationship between the transport form of the document transport rollers and the line image sensor.

[0063] FIG. 8(a) shows a first transfer configuration, FIG. 8(b) shows a second transfer configuration, and FIG. 8(c) shows a third transfer configuration.

[0064] As already described with reference to FIG. 4, the first conveyance mode is a mode in which the document is conveyed only by the upstream roller 107, and the second conveyance mode is a mode in which the document is conveyed by both the upstream roller 107 and the downstream roller 108. Further, the third conveyance mode is a mode in which the document is conveyed only by the downstream roller 108.

[0065] In each conveyance mode, the influence of eccentricity and diameter error of the document conveyance roller on the conveyance error is different. The right diagram in FIG. 8 is a diagram showing the change in the conveyance amount according to the rotational position of the roller, with the rotational position of the document conveyance roller on the horizontal axis and the conveyance amount on the vertical axis.

[0066] In FIGS. 8(a) to 8(c), as shown by the amplitudes a1 to a3, the amplitude of the change in the conveyance amount differs depending on the conveyance mode. When obtaining the conveyance error in the first conveyance mode as shown in FIG. 8(a) and correcting the reading error based on the conveyance error, a correction error occurs because the conveyance errors are different in the cases of the second and third conveyance modes. Therefore, by obtaining the conveyance error due to eccentricity and diameter error of the document conveyance roller in each conveyance mode, the reading error can be corrected with higher accuracy.

[0067] Here, when obtaining the conveyance error for each conveyance mode, it is desirable that the length conveyed in each conveyance mode is longer than one circumference of the document conveyance roller. However, in order to reduce the size of the image reading apparatus, it is necessary to shorten the interval in the conveyance direction between the upstream roller 107 and the downstream roller 108. Therefore, this is good for the second conveyance mode, but for the first and third conveyance modes, it is difficult to make the conveyed length longer than one circumference of the document conveyance roller.

[0068] Hereinafter, the configuration of the present embodiment for solving this problem will be described.

[0069] FIGS. 9 and 10 are diagrams showing the relationship between the upstream CIS and the downstream CIS arranged in a staggered pattern and the conveyance length.

[0070] As already described with reference to FIG. 4, in FIG. 9 as well, the first region R1 is the region read by the CIS 106 when the document is conveyed only by the upstream roller 107 (first conveyance mode). The second region R2 is the region read by the CIS 106 when the document is conveyed by both the upstream roller 107 and the downstream roller 108 (second conveyance mode). The third region R3 is the region read by the CIS 106 when the document is conveyed only by the downstream roller 108 (third conveyance mode).

[0071] In this case, as shown in FIG. 9(d), for the first region R1, both the upstream CISs 106-1, 106-3, 106-5 and the downstream CISs 106-2, 106-4 are in a state of reading a document conveyed only by the upstream roller (in the first conveyance mode).

[0072] On the other hand, for the overlapping portion R12 of the first and second regions, the upstream CISs 106-1, 106-3, 106-5 read a document conveyed only by the upstream roller, while the downstream CISs 106-2, 106-4 read a document conveyed by both the upstream roller and the downstream roller. Thus, for the overlapping portion R12, the conveyance mode is different between the case of reading by the upstream CISs 106-1, 106-3, 106-5 and the case of reading by the downstream CISs 106-2, 106-4.

[0073] In other words, for the upstream CISs 106-1, 106-3, 106-5, the region combining the first region R1 and the overlapping portion R12 (the region of length Ygu in FIGS. 9 and 10) can be conveyed and read in the first conveyance mode. That is, the length of the region conveyed in the first conveyance mode can be made longer than that of the downstream CISs 106-2, 106-4 which can read only the first region R1 (the region of length Ygd in FIGS. 9 and 10) in the first conveyance mode. As a result, it becomes easier to make the length of the region conveyed in the first conveyance mode longer than one circumference of the document conveyance roller.

[0074] Therefore, in this embodiment, when reading the area conveyed in the first conveyance mode, by using the data of the upstream CISs 106-1, 106-3, and 106-5, it is possible to obtain the data of the first conveyance mode for a longer range. In this case, the data of the downstream CISs 106-2 and 106-4 for the first conveyance mode is not used.

[0075] Similarly, for the third area R3 in FIG. 9(d), both the upstream CISs 106-1, 106-3, and 106-5 and the downstream CISs 106-2 and 106-4 are in a state of reading the document (in the third conveyance mode) conveyed only by the downstream roller.

[0076] On the other hand, for the overlapping portion R23 of the second and third areas, the downstream CISs 106-2 and 106-4 read the document conveyed only by the downstream roller, while the upstream CISs 106-1, 106-3, and 106-5 read the document conveyed by both the upstream roller and the downstream roller. Thus, for the overlapping portion R23, the conveyance modes are different when reading with the upstream CISs 106-1, 106-3, and 106-5 and when reading with the downstream CISs 106-2 and 106-4.

[0077] In other words, for the downstream CISs 106-2 and 106-4, the area combining the third area R3 and the overlapping portion R23 (the area with a length of Ygd in FIGS. 9 and 10) can be conveyed and read in the third conveyance mode. That is, the length of the area conveyed in the third conveyance mode can be made longer than that of the upstream CISs 106-1, 106-5, and 106-5 which can only read the third area R3 (the area with a length of Ygu in FIGS. 9 and 10) in the third conveyance mode. As a result, it becomes easier to make the length of the area conveyed in the third conveyance mode longer than one circumference of the document conveyance roller.

[0078] Therefore, in this embodiment, when reading the area conveyed in the third conveyance mode, by using the data of the downstream CISs 106-2 and 106-4, the data in the third conveyance mode can be obtained for a longer range. In this case, the data of the upstream CISs 106-1, 106-3, and 106-5 for the third conveyance mode is not used.

[0079] As described above, instead of switching the data to be used after reading all the CISs 106, it is also possible to adopt a configuration in which the CIS 106 for performing the reading operation is switched for each conveyance mode when performing the image reading operation in S304 to S306. For example, during the conveyance of the upstream roller conveyance area (the first conveyance mode), the reading operation is performed only by the upstream CIS, and during the conveyance of the downstream roller conveyance area (the third conveyance mode), the reading operation is performed only by the downstream CIS. As described above, it is possible to accurately acquire the conveyance error of the document conveyance roller for each conveyance mode.

[0080] Next, with reference to the flowcharts of FIGS. 11 and 12, the process for accurately acquiring the conveyance error of the document conveyance roller for each conveyance mode will be described.

[0081] FIG. 11 is a diagram showing the acquisition process of the conveyance error by the document conveyance roller, and is a flowchart showing the details of the conveyance error acquisition process in S503 of FIG. 5.

[0082] In S901, the CPU 204 discriminates the target CIS 106 and the target reading area for each conveyance mode. In this step, the upstream roller conveyance area (the first area), the upstream and downstream roller conveyance areas (the second area), and the downstream roller conveyance area (the third area) are discriminated, and data extraction for each conveyance mode is performed. The detailed process will be described later.

[0083] In S902, the CPU 204 performs magnification acquisition processing in the sub-scanning direction by the document conveyance roller for the target CIS 106 and the target data. The magnification acquisition processing in the sub-scanning direction by the document conveyance roller is processing for acquiring the sub-scanning direction magnification resulting from the diameter error of the document conveyance roller that affects the entire reading result of the scanner 100. The detailed acquisition processing will be described later.

[0084] In S903, the CPU 204 performs processing to suppress the influence of the eccentricity of the document conveyance roller for the target CIS 106 and the target data. This step is processing for correcting the reading error in the sub-scanning direction resulting from the eccentricity of the document conveyance roller that affects the entire reading result of the scanner 100, for example, by obtaining the eccentricity rate of the document conveyance roller. The detailed acquisition processing will be described later.

[0085] In S904, the CPU 204 determines whether the acquisition processing of the data for all the target CISs 106 has been completed. If the acquisition of the data for all the target CISs 106 has not been completed, it returns to S902 and performs the processing for the remaining CISs 106.

[0086] In S905, the CPU 204 holds, as the conveyance error of the target area, the results acquired for each target CIS 106 by averaging them. Note that the results acquired for each target CIS 106 may be either the case of averaging the correction values acquired in S1107 of FIG. 13 and S1403 of FIG. 16 described later, or the case of averaging based on the conversion coordinate data of S1105 of FIG. 13. When averaging based on the conversion coordinate data of S1105 of FIG. 13, correction values are acquired by the same processing as S1107 of FIG. 13 and S1401 - S1403 of FIG. 16 after averaging.

[0087] In S906, the CPU 204 determines whether the data acquisition for all the target sections in the upstream roller conveyance area (the first area), the upstream and downstream roller conveyance area (the second area), and the downstream roller conveyance area (the third area) has been completed. If the acquisition for all the target sections has not been completed, it returns to S901 and performs the processing for the remaining target sections.

[0088] FIG. 12 is a diagram showing the data discrimination process of the target CIS and the target area in S901 of FIG. 11.

[0089] In S1001, the CPU 204 determines whether the target roller is an upstream roller. As for the determination order of the target roller, it is desirable that the upstream roller, the upstream and downstream rollers, and the downstream roller are in this order from the data flow, but it does not have to be in this order. If the CPU 204 determines that it is an upstream roller, the process proceeds to S1002; otherwise, the process proceeds to S1004.

[0090] In S1002, the CPU 204 sets the upstream CISs 106-1, 106-3, 106-5 as the target CIS 106.

[0091] In S1003, the CPU 204 extracts the data of the upstream roller conveyance area (the first area) from all the read data of the target CIS 106. As the extraction method, extraction is performed based on the number of read lines of the data obtained by reading the document 110 on which the dot pattern 401 is drawn. Based on the end data of the document 110, data is extracted from the number of lines corresponding to the section conveyed by the upstream roller 107. Note that the method is not limited to this, and for example, extraction may be performed based on the timing when the end detection sensor 112 detects the document 110.

[0092] In S1004, the CPU 204 determines whether the target roller is a downstream roller. If the CPU 204 determines that it is a downstream roller, the process proceeds to S1005; otherwise, the process proceeds to S1007. By passing through S1001 and S1004, the discrimination of the upstream roller conveyance area (the first area), the upstream and downstream roller conveyance area (the second area), and the downstream roller conveyance area (the third area) is completed.

[0093] In S1005, the CPU 204 sets the downstream CISs 106-2, 106-4 as the target CIS 106.

[0094] In S1006, the CPU 204 extracts data in the downstream roller conveyance area (the third area) from all the read data of the target CIS 106. As an extraction method, similar to S1003, extraction is performed based on the number of read lines of the data obtained by reading the document 110 on which the dot pattern 401 is drawn.

[0095] In S1007, the CPU 204 sets all the CISs 106-1 to 106-5 as the target CIS 106.

[0096] In S1008, the CPU 204 extracts data in the upstream and downstream roller conveyance areas (the second area) from all the read data of the target CIS 106. As an extraction method, similar to S1003, extraction is performed based on the number of read lines of the data obtained by reading the document 110 on which the dot pattern 401 is drawn.

[0097] Thus, the acquisition process of the conveyance error caused by the document conveyance roller is completed.

[0098] <Acquisition Process of Magnification in Sub-scanning Direction> Hereinafter, the magnification acquisition method in the sub-scanning direction in the present embodiment will be described with reference to FIG. 13. FIG. 13 is a flowchart showing details of the magnification acquisition process in the sub-scanning direction in S902 of FIG. 11.

[0099] In S1101, the CPU 204 determines the main scanning section that is the acquisition target of the magnification in the sub-scanning direction. The main scanning section determined in this step is the main scanning area read by one chip out of the plurality of CIS internal chips constituting one CIS 106.

[0100] In S1102, the CPU 204 searches for the center coordinates of the circular dot patterns included in the main scanning section determined in S1101 in the sub-scanning direction. Then, first, a reference point and a main scanning distance measurement point are selected from among the center coordinates detected by the search. The reference point and the main scanning distance measurement point are the center coordinates of circular dot patterns having the same coordinates in the sub-scanning direction on the chart. As the reference point and the main scanning distance measurement point, points in a positional relationship sandwiching the pixel located at the center in the main scanning section of the sensor chip that reads a predetermined main scanning section are selected. Here, among the two selected center coordinates, the center coordinate on the main scanning direction reference side (the leading pixel side) is selected as the reference point, and the other center coordinate is selected as the main scanning distance measurement point.

[0101] After selecting the reference point and the main scanning distance measurement point, a sub-scanning distance measurement point is selected. The sub-scanning distance measurement point is the center coordinate of a circular dot pattern having the same coordinates in the main scanning direction on the chart, and the coordinate point at a position where the distance between the reference point and the main scanning distance measurement point and the distance between the reference point and the sub-scanning distance measurement point are the same on the chart is selected.

[0102] FIG. 14(a) shows the positional relationship between the chart printed with the circular dot pattern and the chip 1201 in the CIS 106 that performs reading. FIG. 14(b) represents the positional relationship of the center coordinates of the circular dot pattern obtained based on the data obtained as a result of reading the pattern shown in FIG. 14(a).

[0103] Here, it represents a state in which the center coordinates of the circular dot pattern are shifted and read in each of the main scanning direction and the sub-scanning direction due to the inclination of the CIS 106 and the inclination of the chart in the set original document. For such data, when A11(x11, y11) is selected as the reference point, A12(x12, y12) is selected as the main scanning distance measurement point, and A21(x21, y21) is selected as the sub-scanning distance measurement point.

[0104] In S1103, the CPU 204 converts the coordinates of each ranging point centered on the reference point A11 into relative coordinates. When the coordinates of A11 after conversion are A11’(0,0), A12 is converted to A12’(x12’,y12’), and A21 is converted to A21’(x21’,y21’). At this time, x12’ = x12 - x11, y12’ = y12 - y11, x21’ = x21 - x11, and y21’ = y21 - y11. Hereinafter, specific explanations will be made using these coordinates. FIG. 15 shows the concept of the coordinate data after conversion.

[0105] In S1104, the CPU 204 corrects the coordinates (in this example, the converted coordinates A12’ and A21’) converted in S1103 based on the inclination information of the CIS 106 obtained in the immediately preceding correction value acquisition. When the inclination angle of the corresponding chip is obtained as φ by the inclination detection of the CIS 106 performed immediately before, A12’ and A21’ are respectively converted to A12”(x12”,y12”) and A21”(x21”,y21”) with the coordinate A11’ as the reference point. Here, when the inclination of the CIS 106 or the chip 1201 is mechanically limited and the tolerance does not affect the reading result, it is also possible to omit the correction process. By S1104, the distance (referred to as the main scanning direction distance) x21” between the reference point and the converted main scanning ranging point A12”, and the distance (referred to as the sub-scanning direction distance) y12” between the reference point and the converted sub-scanning ranging point A21” can be obtained.

[0106] In S1105, the CPU 204 stores the main scanning direction distance x21” and the sub-scanning direction distance y12” obtained in S1104 in the memory as distance data at the reference point A11.

[0107] The above is the flow of the process for acquiring the conveyance data information at one reference point. The same process is also performed for other center coordinates arranged in the sub-scanning direction.

[0108] In S1106, the CPU 204 determines whether there are any remaining center coordinates that can be selected as reference points based on the stored center coordinate data. If the CPU 204 determines that there are no remaining selectable center coordinates, the process proceeds to S1107. On the other hand, if there are remaining selectable center coordinates, the CPU 204 selects the center coordinates of a circular dot pattern shifted by one in the sub-scanning direction from the center coordinates previously selected as the reference point.

[0109] In this way, the center coordinates from A11 to A(N - 1)1 are selected as reference points, and the distances to each ranging point are obtained with the selected reference points as the centers and recorded in the memory. When A(N - 1)1 is selected as the reference point, AN1 becomes the sub-scanning ranging point with respect to A(N - 1)1, and since there is no subsequent data, the process ends. When the distance data for all intervals is complete, in S1107, the CPU 204 reads out that data from the memory and calculates the sub-scanning direction magnification. The sub-scanning magnification can be obtained by the following formula (1). a = (y21” + y31” + … + yN1”) / (x12” + x22” + … + x(N - 1)2”) … Formula (1) The sub-scanning magnification obtained by the above calculation can be reflected in the line read start trigger generation timing, magnification correction in image processing, etc.

[0110] <Suppression of errors due to eccentricity of the document conveyance roller> Hereinafter, the process of suppressing the error due to the eccentricity of the document conveyance roller will be described with reference to FIG. 16. FIG. 16 is a flowchart showing the details of the eccentricity error suppression process in S903 of FIG. 11.

[0111] To obtain the error due to eccentricity, the sub-scanning direction distances (y21”, y31”, …, yN1”) in the converted coordinate data used when obtaining the sub-scanning direction magnification described above can be used. If the sub-scanning direction magnification is not obtained in advance, the sub-scanning direction distance after conversion is obtained by the processes of S1101 to S1106 in FIG. 13 before the flow of FIG. 16. The sub-scanning direction distance obtained here also includes the variation due to the sub-scanning direction magnification.

[0112] Therefore, in S1401, the CPU 204 divides all the sub-scanning direction distances by the sub-scanning direction magnification a. When the sub-scanning direction distances divided by the sub-scanning direction magnification a are Δy2, Δy3, …, ΔyN, ΔyN is expressed as ΔyN = yN1” / a.

[0113] In S1402, the CPU 204 obtains an approximate curve with the vertical axis being the conveyance amount Δy per unit interval and the horizontal axis being the cumulative addition value y of Δy, using this ΔyN as the conveyance amount per unit interval. When cumulative addition is performed for all the sub-scanning direction distances between dots included in a region where the conveyance amount for one rotation of the document conveyance roller is F or more, and the obtained values are plotted, an approximate curve as shown by the broken line in FIG. 17, for example, is obtained.

[0114] In S1403, the CPU 204 stores the timing correction value. By using the equation of the approximate curve obtained in S1402, it becomes possible to obtain a correction value for correcting the generation timing of the read start trigger of the line sensor at an arbitrary rotation angle of the document conveyance roller. In the memory of the scanner 100, a table for holding the timing correction value with respect to the conveyance amount per unit interval is stored, and the timing correction value obtained in S1403 is held in this table.

[0115] The timing correction data held in the timing correction table is read out during normal reading operations and used to finely adjust the generation timing of the line read start trigger. As a result of this fine adjustment, for a section where the conveyance amount per unit interval is larger than the theoretical value, the generation timing of the line read start trigger becomes earlier than the initial value, and for a section where the conveyance amount per unit interval is smaller than the theoretical value, the generation timing becomes later than the initial value. Thereby, even when there is a variation in the conveyance amount due to the eccentricity of the document conveyance roller, the line reading cycle becomes constant, and the reading quality can be improved.

[0116] <Effects of the Present Embodiment, etc.> In this embodiment, in a sheet feed type image reading apparatus composed of a plurality of CISs, in a first conveyance mode in which a document is conveyed only by an upstream roller, a second conveyance mode in which a document is conveyed by both an upstream roller and a downstream roller, and a third conveyance mode in which a document is conveyed only by a downstream roller, by switching the target CIS, it is possible to obtain the conveyance error of the document conveyance roller with high accuracy.

[0117] As described in this embodiment, when a configuration for switching the CIS 106 that performs the reading operation for each conveyance mode is used, since the reading of the CIS that is not used is not performed, the time required for data transfer can be shortened, and the reading time of the image reading apparatus can be shortened.

[0118] Also, in this embodiment, a method of obtaining a conveyance error using a dot pattern as a document pattern has been described. However, any pattern can be used as long as it can obtain a conveyance error in each conveyance mode, not limited to the dot pattern. For example, it is also possible to obtain a conveyance error for each conveyance mode using a pattern in which horizontal lines are continuously drawn at regular intervals.

[0119] (Second Embodiment) In the second embodiment, a process of obtaining the conveyance error of the document conveyance roller in each conveyance mode will be described even when the pattern length of the document cannot be sufficiently ensured. In the following, the differences from the first embodiment will be mainly described, and the description of the same content as the first embodiment will be omitted as appropriate.

[0120] Hereinafter, a method of obtaining a conveyance error caused by an error of the document conveyance roller in this embodiment will be described with reference to FIGS. 18 to 21.

[0121] FIG. 18 is a diagram showing problems in obtaining a conveyance error when the pattern length of a document cannot be sufficiently ensured in each of the first to third conveyance modes.

[0122] FIG. 18(a) is a diagram showing the pattern arrangement of a document when the pattern length of the document cannot be sufficiently ensured.

[0123] As described in the first embodiment, it is desirable that the pattern length of the document can ensure the circumferential length of one rotation of the document conveyance roller in each conveyance mode. However, if the pattern length used in each conveyance mode can be reduced, other patterns can be arranged in the available space.

[0124] Since the size of the document affects the cost, if the available space can be effectively utilized, the conveyance direction length of the document can be reduced, and the cost of the document can be reduced. When the pattern length used in each conveyance mode is reduced, for example, as shown in FIG. 18(a), the upstream and downstream roller conveyance areas (the second area) can ensure a pattern length L2 of the circumferential length Yr or more. On the other hand, the upstream roller conveyance area (the first area) and the downstream roller conveyance area (the third area) will have pattern lengths L1 and L3 less than the circumferential length Yr.

[0125] FIG. 18(b) is a diagram showing the change in conveyance error when the pattern length of the document cannot be sufficiently ensured in each conveyance mode. When the conveyance error is acquired in the state as shown in FIG. 18(a), the conveyance error can be acquired only within the range of the pattern length. Therefore, in the upstream roller conveyance area (the first area) and the downstream roller conveyance area (the third area), the conveyance error corresponding to the circumferential length of the document conveyance roller cannot be acquired. Therefore, the conveyance errors in the first area and the third area cannot be acquired accurately.

[0126] Next, with reference to the flowcharts of FIGS. 19 and 20 and FIG. 21, the process for accurately acquiring the conveyance error of the document conveyance roller for each conveyance mode even when the pattern length of the document cannot be sufficiently ensured will be described.

[0127] FIG. 19 is a diagram showing the acquisition process of the conveyance error by the document conveyance roller in a state where the pattern length of the document cannot be sufficiently ensured, and is a flowchart showing the details of the conveyance error acquisition process in S503 of FIG. 5.

[0128] S1701 to S1706 are the same as S901 to S906 in FIG. 11, and thus the description thereof will be omitted.

[0129] In S1707, the CPU 204 determines whether there is a timing correction value (eccentricity correction data) of the upstream roller conveyance area (first area) stored in S1403 of FIG. 16 that is equal to or greater than the circumferential length Yr. If the CPU 204 determines that there is a value equal to or greater than the circumferential length Yr, the process proceeds to S179; otherwise, the process proceeds to S1708.

[0130] In S1708, the CPU 204 performs conveyance error compensation processing in the first conveyance mode using only the upstream rollers. Compensation is performed by comparing the conveyance errors between the upstream roller conveyance area (first area) and the upstream and downstream roller conveyance area (second area). The detailed processing flow will be described with reference to FIG. 20.

[0131] In S1709, the CPU 204 determines whether there is a timing correction value (eccentricity correction data) of the downstream roller conveyance area (third area) stored in S1403 of FIG. 16 that is equal to or greater than the circumferential length Yr. If the CPU 204 determines that there is a value equal to or greater than the circumferential length Yr, this flow ends; otherwise, the process proceeds to S1710.

[0132] In S1710, the CPU 204 performs conveyance error compensation processing in the third conveyance mode using only the downstream rollers. Compensation is performed by comparing the conveyance errors between the downstream roller conveyance area (third area) and the upstream and downstream roller conveyance area (second area). The detailed processing flow will be described with reference to FIG. 20.

[0133] FIG. 20 is a diagram showing conveyance error compensation processing in a state where the pattern length of the document cannot be sufficiently ensured, and is a flowchart showing the details of the conveyance error compensation processing in S1708 and S1710 of FIG. 19. Further, FIG. 21 is a diagram explaining a method of comparing the conveyance errors between the upstream and downstream roller conveyance area (second area) and the upstream or downstream roller conveyance area (first or third area).

[0134] In S1801, the CPU 204 extracts the conveyance error for one rotation of the rollers in the upstream and downstream roller conveyance area (second area). The conveyance error may be either when using the timing correction value stored in S1403 of FIG. 16 or when using the conversion coordinate data of S1105 of FIG. 13. When using the timing correction value stored in S1403 of FIG. 16, it is converted to a conveyance error including the sub-scanning direction magnification by multiplying by the sub-scanning direction magnification obtained in S1108 of FIG. 13. Also, although the data extraction in the upstream and downstream roller conveyance area (second area) is described as being for one rotation of the rollers, it may be any number of rotations as long as it is one rotation or more.

[0135] In S1802, the CPU 204 extracts the conveyance error within the acquisition range of the upstream or downstream roller conveyance area (first or third area). Similar to S1801, the conveyance error may be either when using the timing correction value stored in S1403 of FIG. 16 or when using the conversion coordinate data of S1105 of FIG. 13.

[0136] In S1803, as shown in FIG. 21, the CPU 204 compares the conveyance errors between the upstream and downstream roller conveyance area (second area) and the upstream or downstream roller conveyance area (first or third area). Regarding the comparison method, as shown in FIG. 21, when the pattern length L is about half the circumference of the document conveyance roller, the amplitude a of the change curve of the conveyance error is compared. Other methods such as comparing the rise and fall of the change curve of the conveyance error may also be used if the pattern length L is about 1 / 4 of the circumference of the document conveyance roller.

[0137] In S1804, the CPU 204 complements the conveyance error in the upstream or downstream roller conveyance area (the first or third area) and obtains it as the conveyance error for one rotation of the roller. As a complementing method, for example, based on the ratio of the amplitude a of the upstream or downstream roller conveyance area (the first or third area) to the amplitude a of the upstream and downstream roller conveyance area (the second area) from the result compared in S1803. Then, the obtained ratio is multiplied by the conveyance error in the upstream and downstream roller conveyance area (the second area) to obtain a change curve of the conveyance error in the upstream or downstream roller conveyance area (the first or third area). Alternatively, it is also possible to estimate the amplitude a of the change curve of the conveyance error from the rise and fall of the change curve of the conveyance error, and perform complementation based on the ratio of the amplitude a between the upstream and downstream roller conveyance area (the second area) and the upstream or downstream roller conveyance area (the first or third area).

[0138] Based on the data for one rotation of the roller obtained by complementing the change curve of the conveyance error in the upstream or downstream roller conveyance area (the first or third area) shown in FIG. 21, correction values can be obtained by performing the same processing as S1107 in FIG. 13 and S1401 - S1403 in FIG. 16. Thereby, the conveyance error for one rotation of the roller in the upstream roller conveyance area (the first area) and the downstream roller conveyance area (the third area) can be obtained.

[0139] <Effects of the present embodiment, etc.> In this embodiment, even when the pattern length of the document cannot be sufficiently ensured, the conveyance errors of the document conveyance roller can be obtained with high precision in the upstream roller conveyance area, the downstream roller conveyance area, and the upstream and downstream roller conveyance area.

[0140] In addition, this embodiment can also be applied to a configuration in which the CIS described in the first embodiment is switched, and when the conveyance lengths of the upstream roller conveyance area and the downstream roller conveyance area are less than the circumferential length Yr of the document conveyance roller. For example, it can also be applied when the conveyance direction interval between each document conveyance roller is made shorter for further miniaturization of the image reading apparatus. Similar to the case where the pattern length of the document cannot be sufficiently secured, by comparing the conveyance error between the upstream roller conveyance area and the downstream roller conveyance area with the conveyance error of the upstream and downstream roller conveyance areas, the conveyance error of the document conveyance roller can be obtained with high accuracy in each conveyance mode.

[0141] The disclosure of this specification includes the following image reading apparatus, its control method, program, and storage medium.

[0142] (Item 1) An image reading apparatus that conveys a document and reads the document, A plurality of line image sensors arranged along a direction intersecting the conveyance direction of the document, the line image sensors being arranged in a staggered pattern with a predetermined amount of shift from each other in the conveyance direction, An upstream roller arranged upstream of the document conveyance direction with respect to the plurality of line image sensors, A downstream roller arranged downstream of the document conveyance direction, When reading a document on which a detection pattern for detecting the conveyance error between the upstream roller and the downstream roller is formed by the plurality of line image sensors to detect the conveyance error, for the first area of the document conveyed only by the upstream roller, the conveyance error is detected using the reading data of the line image sensor arranged near the upstream roller among the line image sensors arranged in the staggered pattern, and for the third area of the document conveyed only by the downstream roller, the conveyance error is detected using the reading data of the line image sensor arranged near the downstream roller among the line image sensors arranged in the staggered pattern. Control means for controlling as follows. An image reading apparatus characterized by comprising the above.

[0143] (Item 2) For the first region, the control means selects data read by the line image sensor disposed near the upstream roller from the read data of the detection pattern read by the plurality of line image sensors, detects a conveyance error, and for the third region, the control means selects data read by the line image sensor disposed near the downstream roller from the read data of the detection pattern read by the plurality of line image sensors, and controls to detect a conveyance error. The image reading apparatus according to claim 1, characterized in that.

[0144] (Item 3) When reading the detection pattern of the first region, the control means selects and reads the line image sensor disposed near the upstream roller among the line image sensors arranged in a staggered pattern, and when reading the detection pattern of the third region, the control means selects and reads the line image sensor disposed near the downstream roller among the line image sensors arranged in a staggered pattern. The image reading apparatus according to claim 1, characterized in that.

[0145] (Item 4) For the second region of the document conveyed by both the upstream roller and the downstream roller, the line image sensor reads the detection pattern of a region of one or more circumferences of the circumference of the upstream roller or the downstream roller. The image reading apparatus according to any one of claims 1 to 3, characterized in that.

[0146] (Item 5) For the first region and the third region, the line image sensor reads the detection pattern of a region shorter than the circumference of the upstream roller or the downstream roller. The image reading apparatus according to claim 4, characterized in that.

[0147] (Item 6) The control means complements data of the detection pattern in a region less than the circumferential length of the upstream roller or the downstream roller in the first region and the third region, with data read by the line image sensor for the second region. The image reading apparatus according to item 5, characterized in that.

[0148] (Item 7) The control means, based on the ratio between the change in conveyance error based on the detection pattern read for the first region or the third region and the change in conveyance error based on the detection pattern read for the second region, complements data of the detection pattern in a region less than the circumferential length of the upstream roller or the downstream roller in the first region and the third region. The image reading apparatus according to item 6, characterized in that.

[0149] (Item 8) The control means multiplies the ratio by the detection pattern read for the second region to complement data of the detection pattern in a region less than the circumferential length of the upstream roller or the downstream roller in the first region and the third region. The image reading apparatus according to item 7, characterized in that.

[0150] (Item 9) The control means detects a conveyance error due to eccentricity between the upstream roller and the downstream roller. The image reading apparatus according to any one of items 1 to 8, characterized in that.

[0151] (Item 10) The control means detects a conveyance error due to an error in the diameters of the upstream roller and the downstream roller. The image reading apparatus according to any one of items 1 to 9, characterized in that.

[0152] (Item 11) The detection pattern is a pattern in which dots are arranged side by side in the conveyance direction and in a direction orthogonal to the conveyance direction. The image reading apparatus according to any one of items 1 to 10, characterized in that.

[0153] (Item 12) A control method for an image reading apparatus that conveys a document and reads the document, wherein the image reading apparatus includes a plurality of line image sensors arranged in a plurality along a direction intersecting the conveyance direction of the document, the line image sensors being arranged in a staggered pattern with a predetermined amount of shift from each other in the conveyance direction, an upstream roller arranged upstream of the plurality of line image sensors in the conveyance direction of the document, and a downstream roller arranged downstream of the plurality of line image sensors in the conveyance direction of the document; The control method includes: When reading a document on which a detection pattern for detecting a conveyance error between the upstream roller and the downstream roller is formed by the plurality of line image sensors to detect the conveyance error, for a first region of the document conveyed only by the upstream roller, detecting the conveyance error using the reading data of the line image sensor arranged near the upstream roller among the line image sensors arranged in the staggered pattern, and for a third region of the document conveyed only by the downstream roller, controlling to detect the conveyance error using the reading data of the line image sensor arranged near the downstream roller among the line image sensors arranged in the staggered pattern. A control method for an image reading apparatus, characterized by having a control step.

[0154] (Item 13) A program for causing a computer to execute the control method according to Item 12.

[0155] (Item 14) A computer-readable storage medium storing a program for causing a computer to execute the control method according to Item 12.

[0156] (Other Embodiments) Further, the present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and causing one or more processors in a computer of the system or device to read and execute the program. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

[0157] The invention is not limited to the above-described embodiments, and various changes and modifications are possible without departing from the spirit and scope of the invention. Therefore, the claims are attached to disclose the scope of the invention.

Description of Reference Numerals

[0158] 100: Scanner, 106: Line Image Sensor (CIS), 107: Upstream Roller, 108: Downstream Roller, 110: Document, 204: CPU, 401: Circular Dot Pattern

Claims

1. An image reading apparatus that conveys an original document and reads the original document, A plurality of line image sensors arranged along a direction intersecting the conveyance direction of the original document, the line image sensors being arranged in a staggered pattern with a predetermined amount of displacement from each other in the conveyance direction, An upstream roller arranged upstream in the conveyance direction of the original document with respect to the plurality of line image sensors, A downstream roller arranged downstream in the conveyance direction of the original document, When detecting a conveyance error by reading, with the plurality of line image sensors, an original document on which a detection pattern for detecting a conveyance error between the upstream roller and the downstream roller is formed, for a first region of the original document conveyed only by the upstream roller, a conveyance error is detected using the reading data of the line image sensor arranged near the upstream roller among the line image sensors arranged in the staggered pattern, and for a third region of the original document conveyed only by the downstream roller, a conveyance error is detected using the reading data of the line image sensor arranged near the downstream roller among the line image sensors arranged in the staggered pattern, and control means for controlling as such, An image reading apparatus characterized by comprising the above.

2. The control means selects, from the reading data of the detection pattern read by the plurality of line image sensors, the data read by the line image sensor arranged near the upstream roller for the first region and detects a conveyance error, and for the third region, selects the data read by the line image sensor arranged near the downstream roller and detects a conveyance error, and controls as such. The image reading apparatus according to Claim 1.

3. When the control means reads the detection pattern of the first region, it selects and reads the line image sensor arranged near the upstream roller among the line image sensors arranged in a staggered pattern. When reading the detection pattern of the third region, it is characterized in that the control means controls to select and read the line image sensor arranged near the downstream roller among the line image sensors arranged in a staggered pattern. The image reading apparatus according to claim 1.

4. Regarding the second region of the document conveyed by both the upstream roller and the downstream roller, the line image sensor reads the detection pattern of a region that is more than one circumference of the upstream roller or the downstream roller. The image reading apparatus according to claim 1.

5. Regarding the first region and the third region, the line image sensor reads the detection pattern of a region shorter than the circumference of the upstream roller or the downstream roller. The image reading apparatus according to claim 4.

6. The control means complements the data of the detection pattern of the region of the first region and the third region that is less than the circumference of the upstream roller or the downstream roller with the data read by the line image sensor for the second region. The image reading apparatus according to claim 5.

7. The control means, based on the ratio between the change in the conveyance error based on the detection pattern read for the first region or the third region and the change in the conveyance error based on the detection pattern read for the second region, complements the data of the detection pattern of the region of the first region and the third region that is less than the circumference of the upstream roller or the downstream roller. The image reading apparatus according to claim 6.

8. The control means multiplies the detection pattern read for the second region by the ratio to complement the data of the detection pattern of the regions of the upstream roller or the downstream roller that are less than the circumferential length of the first region and the third region. The image reading apparatus according to claim 7, characterized in that.

9. The control means detects a conveyance error due to eccentricity between the upstream roller and the downstream roller. The image reading apparatus according to claim 1, characterized in that.

10. The control means detects a conveyance error due to an error in the diameters of the upstream roller and the downstream roller. The image reading apparatus according to claim 1, characterized in that.

11. The detection pattern is a pattern in which dots are arranged side by side in the conveyance direction and in a direction orthogonal to the conveyance direction. The image reading apparatus according to claim 1, characterized in that.

12. A control method for an image reading apparatus that conveys and reads a document, The image reading apparatus includes a plurality of line image sensors arranged along a direction intersecting the conveyance direction of the document, the line image sensors being arranged in a staggered pattern with a predetermined amount of displacement from each other in the conveyance direction, an upstream roller arranged upstream of the conveyance direction of the document with respect to the plurality of line image sensors, and a downstream roller arranged downstream of the conveyance direction of the document with respect to the plurality of line image sensors. The control method is, When reading a document on which a detection pattern for detecting a conveyance error between the upstream roller and the downstream roller is formed by the plurality of line image sensors to detect the conveyance error, for a first area of the document conveyed only by the upstream roller, the conveyance error is detected using the read data of the line image sensor arranged near the upstream roller among the line image sensors arranged in a staggered pattern, and for a third area of the document conveyed only by the downstream roller, the conveyance error is detected using the read data of the line image sensor arranged near the downstream roller among the line image sensors arranged in a staggered pattern. A control method for an image reading apparatus, characterized by having a control step for controlling as described above.

13. A program for causing a computer to execute the control method according to claim 12.

14. A computer-readable storage medium storing a program for causing a computer to execute the control method according to claim 12.

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