Image reading device and image forming device

Abstract

To solve the problem in which: when a document with a torn leading end is conveyed by an ADF, a detected inclination angle may be larger than an actual inclination angle of the document; in this case, if rotation correction is performed based on the detected angle, inclination occurs in an image after the correction.SOLUTION: A document information determination unit 207 determines document information on a surface (hereinafter referred to as surface document information) based on coordinate data with a differential value Δ smaller than a threshold. Consequently, even when the determined amount of inclination of a document is larger than the actual amount of inclination due to a torn leading end of the document, inclination occurring in an image after correction can be prevented.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a correction technique for image data representing an image read by an image reading device.

Background Art

[0002] An image reading device reads an image of a document by irradiating the document with light and detecting the reflected light with a reading unit. As an image reading device, there is one that reads a document conveyed by a document feeder (ADF) with a reading unit.

[0003] In such an image reading device, due to variations in the nip pressure and rotational speed of the rollers that convey the document, skew of the document and variations in the position of the document in a direction perpendicular to the conveyance direction (hereinafter, the main scanning direction) may occur. Patent Document 1 describes a configuration in which a shadow of the leading edge of a document in the conveyance direction is detected from image data representing a reading result, and the image data is rotationally corrected based on the inclination angle of the detected shadow of the leading edge of the document with respect to the main scanning direction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When a document with a torn leading edge is conveyed by an ADF, in the configuration of Patent Document 1, there is a possibility that the detected inclination angle is different from the actual inclination angle of the document. Specifically, the detected inclination angle may be larger than the actual inclination angle of the document. In this case, if rotational correction is performed based on the detected angle, an inclination will occur in the corrected image.

[0006] In view of the above problems, an object of the present invention is to suppress the inclination that occurs in the corrected image.

Means for Solving the Problem

[0007] In order to solve the above problems, the image reading apparatus according to the present invention includes: A loading unit on which a document is loaded; A feeding unit that feeds the document loaded on the loading unit; A conveying unit that conveys the document fed by the feeding unit to a reading position; A light source that emits light; A reading unit that reads an image of the document by receiving reflected light from the document passing through the reading position; A detection unit that detects a side on the leading edge side of the document in the conveyance direction of the document based on first image data representing the image of the document read by the reading unit; First determination means for determining second image data used when determining an inclination amount corresponding to an inclination angle of a side on the leading edge side of the document with respect to a predetermined direction orthogonal to the conveyance direction based on the first image data detected by the detection unit; Second determination means for determining the inclination amount using the second image data determined by the first determination means; Correction means for performing rotation correction on the first image data based on the inclination amount determined by the second determination means; An image reading apparatus having: The first determination means selects, from among the first image data, image data of pixels in which a difference value between a position in the conveyance direction of a pixel representing a side on the leading edge side of the document among pixels at a first position in the predetermined direction and a position in the conveyance direction of a pixel representing a side on the leading edge side of the document among pixels at a second position adjacent to the first position in the predetermined direction is smaller than a predetermined value, and does not select data of pixels in which the difference value is larger than the predetermined value. Image Do not select data; The first determination means determines the second image data by selecting, from among the selected first image data, the image data of pixels in which the number of data continuous in the predetermined direction is greater than a predetermined value, and not selecting the image data of pixels in which the number of data is less than or equal to the predetermined value.

Advantages of the Invention

[0008] According to the present invention, it is possible to suppress the inclination generated in the corrected image.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the shapes of the components described in this embodiment and their relative arrangements, etc. should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions, and the scope of the present invention is not intended to be limited to the following embodiments.

[0011] [First Embodiment] [Image Forming Apparatus] FIG. 1 is a cross-sectional view showing the configuration of a monochrome electrophotographic copying machine (hereinafter referred to as an image forming apparatus) 100 used in the present embodiment. Note that the image forming apparatus is not limited to a copying machine, and may be, for example, a facsimile apparatus, a printing machine, a printer, or the like. Further, the recording method is not limited to the electrophotographic method, and may be, for example, an inkjet method or the like. Furthermore, the image forming apparatus may be in either a monochrome or color format.

[0012] Hereinafter, with reference to FIG. 1, the configuration and functions of the image forming apparatus 100 will be described. As shown in FIG. 1, the image forming apparatus 100 includes an image reading apparatus 200 including a document feeding apparatus 201 and a reading apparatus 202, and an image printing apparatus 301. The document feeding apparatus 201 is rotatable with respect to the reading apparatus 202.

[0013] [Image Reading Apparatus] A pickup roller 103 as a feeding unit feeds the document 101 stacked on a tray 102 as a stacking unit into the document feeding apparatus 201. Separation rollers 104 and 105 are provided to prevent a plurality of documents 101 from being fed simultaneously by the pickup roller 103. The document 101 fed into the conveyance path is conveyed toward a reading position A by conveyance rollers 106 and a lead roller 107. Note that the separation rollers 104 and 105, the conveyance rollers 106, and the lead roller 107 are included in the conveyance unit.

[0014] A transparent glass 108 is disposed at the reading position A, and a reading unit 109A is provided on the side opposite to the conveyance path with respect to the glass 108. The reading unit 109A includes an LED 110, an image sensor 111, and an optical component group 112. The image sensor 111 has a plurality of pixels that receive light of R (red), G (green), and B (blue) over the main scanning direction.

[0015] The reading unit 109A reads the image of the front surface (the first surface) of the document 101 as follows. Specifically, the LED 110 as a light source irradiates (emits) light onto the front surface of the document 101 through the glass 108. The optical component group 112 guides the reflected light from the document 101 received through the glass 108 to the image sensor 111. The image sensor 111 outputs analog image data based on the received reflected light. Note that the image sensor 111 simultaneously reads an image for one line across the main scanning direction. Therefore, by reading an image for one line multiple times with the image sensor 111 while transporting the document 101, the image sensor 111 can output image data including the entire document 101. The A / D conversion unit (not shown) of the reading unit 109A converts the analog image data into digital image data and outputs it to the controller 200 (Figure 2).

[0016] On the upstream side of the reading position A in the transport direction of the document 101, a detection sensor 113 for detecting the document 101 is provided. The controller 200 determines the timing at which the reading unit 109A of the document 101 starts reading based on the timing when the detection sensor 113 detects the document 101.

[0017] The pressing rollers 114 and 115 press the document 101 toward the glass 108. Note that a white guide plate 116 as an opposing member is disposed at a position facing the reading unit 109A between the pressing rollers 114 and 115, that is, on the side opposite to the reading unit 109A with respect to the transport path along which the document is transported.

[0018] The document 101 that has passed through the reading position A is transported toward the reading position B by the transport roller 117. A transparent glass 118 is disposed at the reading position B, and a reading unit 109B is provided on the side opposite to the transport path with respect to the glass 118. The reading unit 109B has the same configuration as the reading unit 109A and reads the image of the back surface (the second surface) of the document 101. The timing at which the reading unit 109B starts reading is also determined based on the timing when the detection sensor 113 detects the document. A white guide plate 119 is disposed at a position facing the reading unit 109B.

[0019] The original document 101 that has passed through the reading position B is discharged onto the paper discharge tray 121 by the paper discharge roller 120.

[0020] On the right side of the glass 108, a white reference plate 122, which is a reference reading member when acquiring shading data, is provided.

[0021] <Image printing apparatus> Inside the image printing apparatus 301, sheet storage trays 302 and 304 are provided. Different types of recording media can be stored in the sheet storage trays 302 and 304 respectively. For example, A4 - sized plain paper is stored in the sheet storage tray 302, and A4 - sized thick paper is stored in the sheet storage tray 304. Note that a recording medium is something on which an image is formed by an image forming apparatus, and for example, paper, resin sheet, cloth, OHP sheet, label, etc. are included in the recording media.

[0022] The recording medium stored in the sheet storage tray 302 is fed by the pickup roller 303 and sent to the registration roller 308 by the conveyance roller 306. Also, the recording medium stored in the sheet storage tray 304 is fed by the pickup roller 305 and sent to the registration roller 308 by the conveyance rollers 307 and 306.

[0023] The image data output from the image reading apparatus 200 is input into an optical scanning device 311 including a semiconductor laser and a polygon mirror. Also, the photosensitive drum 309 has its outer peripheral surface charged by the charger 310. After the outer peripheral surface of the photosensitive drum 309 is charged, laser light corresponding to the image signal input from the original document reading apparatus 200 to the optical scanning device 311 is irradiated onto the outer peripheral surface of the photosensitive drum 309 via the polygon mirror and mirrors 312 and 313 from the optical scanning device 311. As a result, an electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 309.

[0024] Subsequently, the electrostatic latent image is developed by toner in the developing unit 314 as the image forming unit, and a toner image is formed on the outer peripheral surface of the photosensitive drum 309. The toner image formed on the photosensitive drum 309 is transferred to the recording medium by a transfer charger 315 provided at a position (transfer position) facing the photosensitive drum 309. The registration roller 308 feeds the recording medium to the transfer position in accordance with the transfer timing at which the image is transferred to the recording medium by the transfer charger 315.

[0025] As described above, the recording medium onto which the toner image has been transferred is fed to the fixing unit 318 by the conveyance belt 317, and is heated and pressed by the fixing unit 318 so that the toner image is fixed to the recording medium. In this way, an image is formed on the recording medium by the image forming apparatus 100.

[0026] When image formation is performed in the single-sided printing mode, the recording medium that has passed through the fixing unit 318 is discharged to a discharge tray (not shown) by the discharge rollers 319 and 324. When image formation is performed in the double-sided printing mode, after the fixing process is performed on the first surface of the recording medium by the fixing unit 318, the recording medium is conveyed to the reverse path 325 by the discharge rollers 319, the conveyance rollers 320, and the reverse roller 321. Thereafter, the recording medium is conveyed again to the registration roller 308 by the conveyance rollers 322 and 323, and an image is formed on the second surface of the recording medium by the method described above. Thereafter, the recording medium is discharged to a discharge tray (not shown) by the discharge rollers 319 and 324.

[0027] When the recording medium on which the image has been formed on the first surface is discharged face-down to the outside of the image forming apparatus 100, the recording medium that has passed through the fixing unit 318 is conveyed in the direction toward the conveyance roller 320 through the discharge roller 319. Then, immediately before the rear end of the recording medium passes through the nip portion of the conveyance roller 320, the rotation of the conveyance roller 320 is reversed, so that the recording medium is discharged to the outside of the image forming apparatus 100 via the discharge roller 324 with the first surface facing downward.

[0028] The above is the description of the configuration and functions of the image forming apparatus 100.

[0029] <Control Configuration> FIG. 2 is a block diagram showing an example of the control configuration of the image forming apparatus 100. First, the control configuration of the image printing apparatus 301 will be described.

[0030] As shown in FIG. 2, the system controller 151 includes a CPU 151a, a ROM 151b, and a RAM 151c. Further, the system controller 151 is connected to an analog-digital (A / D) converter 153, a high voltage control unit 155, a motor control device 600, sensors 159, and an AC driver 160. The system controller 151 can transmit and receive data and commands to and from each connected unit.

[0031] The CPU 151a reads and executes various programs stored in the ROM 151b, thereby executing various sequences related to a predetermined image forming sequence.

[0032] The RAM 151c is a storage device. Various data such as set values for the high voltage control unit 155 and command values for the motor control device 600 are stored in the RAM 151c.

[0033] The system controller 151 receives a signal from the sensors 159 and sets a set value of the high voltage control unit 155 based on the received signal.

[0034] The high voltage control unit 155 supplies a voltage required for the high voltage unit 156 (charger 310, developing device 314, transfer charger 315, etc.) according to the set value set by the system controller 151.

[0035] The motor control device 600 controls a motor 509 that drives a load provided in the image printing apparatus 301 according to a command output from the CPU 151a.

[0036] The A / D converter 153 receives the detection signal detected by the thermistor 154 for detecting the temperature of the fixing heater 161, converts the detection signal from an analog signal to a digital signal, and transmits it to the system controller 151. The system controller 151 controls the AC driver 160 based on the digital signal received from the A / D converter 153. The AC driver 160 controls the fixing heater 161 so that the temperature of the fixing heater 161 becomes the temperature required for performing the fixing process. Note that the fixing heater 161 is a heater used for the fixing process and is included in the fixing unit 318.

[0037] As described above, the system controller 151 controls the operation sequence of the image forming apparatus 100.

[0038] Next, the control configuration of the image reading apparatus 200 will be described. The CPU 203 controls the image reading apparatus 100 by executing a program stored in the non-volatile memory 209.

[0039] The conveyance motor 201 is a drive source for each roller provided in the document feeder 201 and is rotationally driven under the control of the controller 200.

[0040] The operation unit 202 provides a user interface. The CPU 203 controls the operation unit 202 so as to display an operation screen for the user to set the type of recording medium to be used (hereinafter referred to as the paper type) and the like on the display unit provided in the operation unit 202. The CPU 203 receives the information set by the user from the operation unit 202 and outputs the information set by the user to the system controller 151.

[0041] The system controller 151 transmits information indicating the state of the image forming apparatus to the operation unit 202. Note that the information indicating the state of the image forming apparatus is, for example, information regarding the number of image formations, the progress of the image forming operation, paper jams and double feeding in the image printing apparatus 301 and the document feeder 201, and the like. The operation unit 202 displays the information received from the system controller 151 on the display unit.

[0042] The reading units 109A and 109B output digital image data to the controller 200. This image data has higher numerical values as the intensity of the reflected light is greater. This numerical level is hereinafter expressed as the luminance level. Also, hereinafter, the image data output by the reading unit 109A is referred to as surface image data, and the image data output by the reading unit 109B is referred to as back surface image data.

[0043] The surface image data output by the reading unit 109A is input to the shading circuit 204A, and the back surface image data output by the reading unit 109B is input to the shading circuit 204B. The shading circuits 204A and 204B correct (shading correction) the influence of the non-uniformity of the light amount of the LED 110 and the sensitivity unevenness of each pixel of the image sensor 111 by performing addition, subtraction, multiplication, and division on the image data, and generate image data that is uniform in the main scanning direction.

[0044] The surface image data after shading correction by the shading circuit 204A is stored in the image memory 205. On the other hand, the back surface image data after shading correction by the shading circuit 204B is input to the image inversion circuit 210.

[0045] The image inversion circuit 210 inverts the main scanning direction of the back surface image data. This is because in the present embodiment, the reading units 109A and 109B have the same configuration, and the image read by the reading unit 109B has the main scanning direction inverted with respect to the image read by the reading unit 109A. The back surface image data after the processing by the image inversion circuit 210 is stored in the image memory 205. That is, the image scale 205 functions as the first storage unit.

[0046] FIG. 3 is an explanatory diagram of the acquisition timing of the front surface image data and the back surface image data stored in the image memory 205. After starting the conveyance of the document 101 at time t0, the detection sensor 113 detects the leading edge of the document 101 at time t1. Based on time t1, the CPU 203 determines, for example, time t2 before the document 101 reaches the reading position A, based on the conveyance speed at which the document 101 is conveyed. Then, the CPU 203 stores the front surface image data output from the reading unit 109A in the image memory 205 for a predetermined period from time t2. Note that the predetermined period is at least the period until the trailing edge of the document 101 passes through the reading position A. This predetermined period is obtained based on the conveyance speed of the document 101. Similarly, the CPU 203 determines time t3 before the document 101 reaches the reading position B based on time t1. Then, the CPU 203 stores the back surface image data output from the reading unit 109B in the image memory 205 for a predetermined period from time t3. Note that the CPU 203 may start reading by the reading unit 109A at time t2 and store the front surface image data in the image memory 205, or may store the front surface image data of the reading unit 109A that has been reading before time t2 in the image memory 205. Also, the CPU 203 may start reading by the reading unit 109B at time t3 and store the back surface image data in the image memory 205, or may store the back surface image data of the reading unit 109B that has been reading before time t3 in the image memory 205. In the following description, the image indicated by the front surface image data is also referred to as the front surface image, and the image indicated by the back surface image data is also referred to as the back surface image.

[0047] As shown in FIG. 2, the front surface image data output from the shading circuit 204A is also input to the edge detection unit 206. Further, the back surface image data output from the image inversion circuit 210 is also input to the edge detection unit 206. Hereinafter, the correction of the front surface image data will be described, but the back surface image data is corrected in the same manner.

[0048] FIG. 4 is an explanatory diagram of the processing by the edge detection unit 206. FIG. 4 shows an image in which columns of pixels in the main scanning direction obtained by the reading unit 109A at every predetermined time from time t2 are combined in the sub-scanning direction orthogonal to the main scanning direction. As described above, the surface image data input to the edge detection unit 206 is from time t2 before the leading end of the document 101 in the conveyance direction reaches the reading position A. That is, when the reading of the image by the reading unit 109A is started, first, the guide plate 116 is read. Thereafter, as the document 101 is conveyed, the image of the document 101 is read. That is, the surface image data input to the edge detection unit 206 includes image data indicating the guide plate 116 and image data indicating the side on the leading end side of the document 101.

[0049] The edge detection unit 206 performs binarization processing on the surface image data with a region of a total of 9 pixels, 3 pixels in the main scanning direction and 3 pixels in the sub-scanning direction, as one block. Hereinafter, the number of pixels in the main scanning direction of the reading units 109A and 109B is assumed to be 7488, and the reading units 109A and 109B perform reading 12000 times during the predetermined period. The pixel position in the main scanning direction is denoted as n (0 ≦ n ≦ 7487), and the pixel position in the sub-scanning direction is denoted as m (0 ≦ m ≦ 11999). Also, the luminance values of the 9 pixels of one block are denoted as px (x = 0 to 8), and the maximum value and the minimum value thereof are denoted as pmax and pmin.

[0050] At a point like point A in FIG. 4(A), since all 9 pixels are in the area of the guide plate 116 (white), all 9 pixels become white pixels, so the difference between pmax and pmin is a small value. On the other hand, at a boundary like point B in FIG. 4(A) between the guide plate 116 (white) and the shadow (gray) of the leading edge side of the original 101, since white pixels and gray pixels are mixed among the 9 pixels, the difference between pmax and pmin becomes large. Therefore, when the difference between pmax and pmin is larger than a predetermined threshold value pth, it can be determined that there are pixels (hereinafter referred to as candidate pixels) that are candidates for the shadow caused by the leading edge side of the original 101 within the block. In the present embodiment, when the difference between pmax and pmin within the block is larger than a predetermined threshold value pth, the central pixel (the pixel at coordinates (n, m)) of the block is determined as a candidate pixel. The edge detection unit 206 performs this determination process for each n and m except n = 0, n = 7487, m = 0, and m = 11999. Note that one scale on the x-axis and y-axis in the present embodiment corresponds to the distance between the central positions of two adjacent pixels.

[0051] FIG. 4(A) is an image shown by 8-bit (luminance level: 0 to 255) image data, and FIG. 4(B) is an image shown by image data obtained by binarizing the image data of FIG. 4(A) with a threshold value pth = 14. The white in FIG. 4(B) indicates the pixels determined as candidates for the shadow caused by the leading edge side of the original 101 by the above processing. Among the plurality of candidate pixels shown in FIG. 4(B), the column of candidate pixels in the main scanning direction that is the most leading in the sub-scanning direction (the pixel column in the main scanning direction that is first determined as a candidate pixel in the sub-scanning direction) is determined to be the shadow caused by the leading edge side of the original 101.

[0052] As shown in FIG. 2, the binarized data output by the edge detection unit 206 is input to the original information determination unit 207. The original information determination unit 207 calculates the difference value of the sub-scanning direction coordinate data of the data adjacent in the main scanning direction.

[0053] FIG. 5 is a diagram showing a document having a V-shaped scratch near the center of the side on the leading edge side. When the edge detection unit 206 detects an edge with respect to an image obtained when a document having a V-shaped scratch near the center of the side on the leading edge side is read, data as shown in FIG. 5(b) is obtained. The document information determination unit 207 calculates a difference value Δ (=|Y(m) - Y(m + 1)|) between the sub-scanning position Y(m) at the coordinate (n,m) and the sub-scanning position Y(m + 1) at the coordinate (n + 1,m + 1).

[0054] In a region on the side of the leading edge of the document where there are no irregularities, the difference value Δ is small, but in a region with steep irregularities such as a V-shaped scratch, the difference value Δ becomes large. If the difference value Δ is equal to or greater than the threshold value, the document information determination unit 207 does not use the data at the coordinate (n + 1,m + 1) for calculating the inclination angle of the document.

[0055] FIG. 6 is an image shown by the binarized data input to the document information determination unit 207. The image shown by the binarized data input to the document information determination unit 207 is an image in the range indicated by the dotted line in FIG. 6 and includes the document 101. The range of this dotted line is n = 0 to 7487, m = 0 to 11999. Note that FIG. 6 shows an image when there is no indentation on the side of the leading edge of the document.

[0056] The original document information determination unit 207 determines the original document information on the surface (hereinafter referred to as the surface original document information) based on the coordinate data where the difference value Δ is smaller than the threshold value. Also, the original document information determination unit 207 determines the distance (width) W in the main scanning direction of two corner portions on the leading end side of the original document 101. Then, the original document information determination unit 207 outputs the surface original document information and the width W to the CPU 203. Here, the surface original document information is information including the position and angle of the original document in the surface image. Note that the position of the original document 101 is the position (x1, y1) in the surface image of the first position of the original document 101. In the present embodiment, this first position is one of the two corner portions on the leading end side of the shadow generated by the original document 101 (the left side in FIG. 5). Also, the angle of the original document 101 is the angle with respect to the reference direction of the surface image of a predetermined side of the original document 101 in the surface image. In the present embodiment, the predetermined side is the shadow generated by the leading end side of the original document 101, and the reference direction is the main scanning direction (predetermined direction). That is, the angle of the original document 101 is θ1 in FIG. 5. Note that when the shadow generated by the leading end side of the original document 101 in the conveyance direction is inclined upstream from the position (x1, y1), the angle θ1 takes a negative value, and when the shadow generated by the leading end side of the original document 101 is inclined downstream from the position (x1, y1), the angle θ1 takes a positive value.

[0057] The CPU 203 outputs the surface original document information, that is, the position (x1, y1) and the angle θ1, to the correction unit 208.

[0058] Based on the position (x1, y1) and the angle θ1, the correction unit 208 reads out the surface image data stored in the image memory and outputs it to the system controller 151. Specifically, the correction unit 208 reads out the image data along the direction parallel to the shadow generated by the leading end side of the position original document 101 starting from the read start position (x1, y1).

[0059] The correction unit 208 reads the surface image data stored in the image memory up to the trailing end side of the original document as described above. That is, the correction unit 208 functions as a reading unit.

[0060] FIG. 7 is a diagram showing an image read by the correction unit 208. As shown in FIG. 7, by reading out image data by an amount corresponding to the width W along the direction parallel to the shadow, the side on the leading edge side of the document becomes parallel to the main scanning direction. Note that the same processing is also performed on the backside image data.

[0061] The system controller 151 cuts out an image area to be printed from the image data output from the correction unit 208. Specifically, for example, the system controller 151 cuts out the image data with reference to the position (0, 0) of the image data shown in FIG. 7 output from the correction unit 208 according to the size of the recording medium set by the user using the operation unit 202. More specifically, for example, when the document shown in FIG. 7 is A4 size and the size of the recording medium set by the user using the operation unit 202 is A4 size, the system controller 151 can cut out the image of the document excluding the shadow at the right end and the shadow at the trailing end of the document. The system controller 151 controls the image printing apparatus 301 to perform printing based on the cut-out image data. That is, the system controller 151 functions as an external device. Note that the external devices include not only the system controller 151 provided in the image forming apparatus 100 but also smartphones, tablets, PCs, and the like.

[0062] FIG. 8 is a flowchart of the image reading process according to the present embodiment. The process of the flowchart shown in FIG. 8 is executed by the controller 200.

[0063] When an instruction to start reading of a document is input, the controller 200 starts feeding and conveying the document 101 on the tray 102 in S10.

[0064] The controller 200 waits in S11 until the detection sensor 113 detects the document. When the detection sensor 113 detects the document, the controller 200 determines the times t2 and t3 described with reference to FIG. 3.

[0065] Then, from S12 which is time t2, the controller 200 starts storing the surface image data into the image memory 205. In addition, in S12, the output to the edge detection unit 206 of the surface image data is also started. The edge detection unit 206 performs a detection process of detecting a shadow generated by the side on the leading edge side of the document.

[0066] Next, in S13, the document information determination unit 207 calculates the difference value Δ by the above method and determines the data to be used for determining the surface document information.

[0067] Then, in S14, the document information determination unit 207 determines the surface document information based on the data determined in S13.

[0068] In S15, the correction unit 208 starts reading the surface image data stored in the image memory 205 based on the detected inclination amount.

[0069] The controller 200 waits in S16 until the correction unit 208 outputs the surface image data stored in the image memory 205.

[0070] When the correction unit 208 outputs the corrected image data, the controller 200 determines in S17 whether the next document to read the image is in the tray 102. If there is a next document, the controller 200 repeats the process from S10. On the other hand, if there is no next document, the controller 200 ends the process of FIG. 8.

[0071] As described above, in the present embodiment, the document information determination unit 207 determines the surface document information (hereinafter, surface document information) based on the coordinate data in which the difference value Δ is smaller than the threshold value. As a result, even when the inclination amount determined due to the leading edge of the document being torn is larger than the actual inclination amount of the document, it is possible to suppress the inclination generated in the corrected image.

[0072] 〔Second Embodiment〕 The description of the parts of the image forming apparatus 100 having the same configuration as that of the first embodiment will be omitted.

[0073] Figure 9 shows a document with a semi-circular scratch on the edge of the leading end of the document. Such scratches occur when a hole is accidentally punched only halfway through the leading end of the document when punching a hole in the document, or in the case of a loose-leaf document. When such a document is read, only the method described in the first embodiment will leave data unnecessary for determining the surface document information. Therefore, in this embodiment, when the difference value Δ is equal to or less than the threshold value and the number of consecutive data in the main scanning direction is equal to or less than a predetermined value, the reliability of the data used for determining the surface document information is low, so the corresponding data is not used for determining the surface document information. With the above configuration, even when the inclination amount determined due to the leading end of the document being torn is larger than the actual inclination amount of the document, it is possible to suppress the inclination that occurs in the corrected image.

Explanation of Signs

[0074] 102 Tray 103 Pickup Roller 104, 105 Separation Rollers 106 Conveyor Roller 107 Feed Roller 110 LED 111 Image Sensor 200 Controller 203 CPU 206 Edge Detection Unit 207 Document Information Determination Unit 208 Correction Unit

Claims

1. A loading section on which a document is loaded, A feeding section that feeds the document loaded on the loading section, A conveying section that conveys the document fed by the feeding section to a reading position, A light source that emits light, A reading section that reads an image of the document by receiving reflected light from the document passing through the reading position, A detection section that detects a side on the leading edge side of the document in the conveyance direction of the document based on first image data representing the image of the document read by the reading section, First determination means for determining second image data used when determining an inclination amount corresponding to an inclination angle of a side on the leading edge side of the document with respect to a predetermined direction orthogonal to the conveyance direction based on the first image data detected by the detection section, Second determination means for determining the inclination amount using the second image data determined by the first determination means, Correction means for performing rotation correction on the first image data based on the inclination amount determined by the second determination means, An image reading apparatus having: The first determination means selects image data of pixels whose difference value between the position in the conveyance direction of pixels representing the side on the leading edge side of the document among the pixels at a first position in the predetermined direction in the first image data and the position in the conveyance direction of pixels representing the side on the leading edge side of the document among the pixels at a second position adjacent to the first position in the predetermined direction is smaller than a predetermined value, and does not select image data of pixels whose difference value is larger than the predetermined value. The first determination means determines the second image data by selecting image data of pixels having a data number continuous in the predetermined direction larger than a predetermined value among the selected first image data and not selecting image data of pixels whose data number is less than or equal to the predetermined value. The image reading apparatus is characterized by this.

2. The image reading apparatus according to claim 1, and An image forming unit that forms an image on a recording medium based on the image read by the image reading device, An image forming apparatus, characterized by having the above.

Images