Image forming apparatus, and metho for controlling image forming apparatus

Abstract

To provide an image forming apparatus that creates a document image whose distortion is corrected, and a control method.SOLUTION: An image forming apparatus comprises a control unit, an image input unit that optically reads a document, and a document conveying unit that conveys the document. The control unit causes the image input unit to read the document while causing the document conveying unit to convey the document, and thereby creates a document image obtained by converting the document into an image, and performs conversion related to mapping function for the document image to correct distortion of the document image. The mapping function indicates mapping to the document image created by the image input unit reading the document.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present disclosure relates to scanned image distortions produced by scanners, and more particularly to scanned image distortions that occur in scanners that include document feeders. [Background technology]

[0002] In a scanner equipped with a document feeder, when scanning a document fed by the document feeder, the document feed state may change due to document slippage during the scanning process, which may result in distortion of the scanned image.

[0003] Regarding distortions that occur in scanned images, Patent Document 1 describes a method of extracting a polygon that forms the outline of an image, dividing the extracted polygon into multiple quadrangles, transforming each of the multiple quadrangles into rectangles, and combining the transformed rectangles to generate an image. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-123043 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present disclosure is to provide an image forming apparatus that generates a document image with corrected distortion. [Means for solving the problem]

[0006] The present disclosure provides an image forming device comprising a control unit, an image input unit that optically reads an original document, and an original transport unit that transports the original document, wherein the control unit generates an original image by imaging the original document by reading the original document using the image input unit while transporting the original document using the original transport unit, and corrects distortion of the original document image by performing a conversion on the original document image related to a mapping function that corresponds to changes in the transport state, wherein the mapping function indicates a mapping from the original document to the original document image generated by the image input unit by reading the original document.

[0007] The present disclosure also provides a control method for an image forming device, which generates an original image by imaging the original by reading the original while transporting the original, and corrects distortion of the original image by performing a conversion related to a mapping function on the original image, wherein the mapping function indicates a mapping from the original to the original image generated by the image input unit by reading the original. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide an image forming apparatus that generates a document image with corrected distortion. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a functional block diagram of an image forming apparatus according to a first embodiment of the present disclosure. [Figure 2] 10A and 10B are diagrams for explaining distortions that occur in a scanned image when a document undergoes uniform linear motion and rotational motion simultaneously in a document transport unit, and show a case where the distortion is small. [Figure 3] 10A and 10B are diagrams for explaining distortion that occurs in a scanned image when a document undergoes a constant-velocity linear motion and a rotational motion simultaneously in a document transport unit, and show a case where distortion is moderate. [Figure 4] 10A and 10B are diagrams for explaining distortions that occur in a scanned image when a document undergoes a constant-velocity linear motion and a rotational motion simultaneously in a document transport unit, and show a case where the distortion is large. [Figure 5] 10A and 10B are diagrams for explaining a simulation of occurrence of distortion due to a change in the inclination angle of a document during conveyance. [Figure 6] Figure 6(A) is a diagram showing a business card-sized image used as the original in the simulation of Figure 5, and Figure 6(B) is a diagram showing the image obtained by applying the simulation of Figure 5 to the image of Figure 6(A). [Figure 7] 10A and 10B are diagrams for explaining various numerical values obtained by actual measurement from an original image included in a scanned image. [Figure 8] 10 is a flowchart illustrating a process of detecting an original image from a scanned image. [Figure 9] 10 is a flowchart illustrating a correction processing parameter extraction process. [Figure 10] FIG. 10 is a diagram for explaining the relationship between image transformation and a mapping function. [Figure 11] 10 is a flowchart illustrating a distortion correction process according to the present disclosure. [Figure 12] 1 is an example of a distorted scanned image. [Figure 13] 13 is a diagram for explaining a state in which a rotation process, which is part of a general correction process, is applied to the scanned image of FIG. 12. FIG. [Figure 14] 14 is a diagram for explaining a corrected scanned image obtained by applying a cropping process, which is part of a general correction process, to the scanned image after the rotation process of FIG. 13 has been applied. FIG. [Figure 15] 13 is a diagram for explaining an image obtained by applying the correction process according to the present disclosure to the scanned image of FIG. 12. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] [1. First embodiment] [1.1 Hardware configuration] 1 is a functional block diagram of an image forming apparatus according to a first embodiment of the present disclosure. The image forming apparatus 1 is an MFP (Multi-Function Printer / Peripheral) or a multifunction peripheral, and typically includes a copy function, an image scanner function, a facsimile function, and a printer function. The image forming apparatus 1 includes a display unit 3, an operation unit 5, a document transport unit 7, an image input unit 9, an image forming unit 11, a communication unit 13, a connection unit 15, a control unit 17, and a storage unit 19.

[0011] The display unit 3 displays images and characters. For example, it is configured with a liquid crystal display (LCD), an organic electroluminescence (EL) panel, etc. The display unit 3 may be a standalone display device, or may further include an externally connected display device.

[0012] The operation unit 5 accepts operation inputs from a user. For example, the operation unit 5 is configured with hardware keys and / or software keys. The operation unit 5 also includes operation keys such as task keys for issuing instructions to execute tasks such as sending a fax or scanning an image, and a stop key for issuing an instruction to cancel an operation.

[0013] The document transport unit 7 includes a document setting table 7a and a transport mechanism 7b. The document setting table 7a is a table for setting paper on which an image to be read by the image input unit 9 is drawn, i.e., one or more documents. The document setting table 7a includes a document guide 7a1 that serves as a reference for the position at which the document is set. The transport mechanism 7b transports the document set on the document setting table 7a to the image input unit 9 and ejects the document with the image input by the image input unit 9.

[0014] The image input unit 9 reads the image formed on the surface of the document and outputs it as image data (scanned image). The image input unit 9 is composed of a color scanner (image input device). The image input unit 9 has a reading surface on which the document is placed. The reading surface is made of a transparent plate-like member such as a glass plate. The image input unit 9 has image sensors such as CCDs (Charge Coupled Devices) below the reading surface that correspond to the colors red (R), green (G), and blue (B).

[0015] These three color image sensors are arranged along the direction in which the document transport unit 7 transports the document (document feed direction). That is, along the document feed direction, from rear to front in the document feed direction, they are arranged in the order of B sensor, G sensor, and R sensor. Therefore, when the document transport unit 7 transports the document, these three color sensors read the document in the order of B sensor, G sensor, and R sensor. A gap of a predetermined length is provided between the B sensor and the G sensor. Similarly, a gap of the same length is provided between the G sensor and the R sensor.

[0016] The image forming unit 11 forms (prints) an image on a medium such as copy paper based on image data. The printing method of the image forming unit is arbitrary, and may be, for example, an inkjet printer, a laser printer, a thermal transfer printer, etc. The image forming unit may be a monochrome printer or a color printer.

[0017] The communication unit 13 is connected to a network. The communication unit 13 is configured with an interface that can be connected to, for example, a wired LAN (Local Area Network), a wireless LAN, or an LTE (Long Term Evolution) network. When the communication unit 13 is connected to a network, it is connected to other devices and an external network. Note that the communication unit 13 may be an interface that performs short-range wireless communication, such as NFC (Near Field Communication) or Bluetooth (registered trademark).

[0018] The connection unit 15 connects the image forming apparatus 1 to other devices. For example, the connection unit 15 is a USB interface to which a USB memory or the like is connected. Furthermore, the connection unit 15 may be an interface other than a USB interface, such as HDMI (registered trademark).

[0019] The control unit 17 controls the entire image forming apparatus 1. The control unit 17 is made up of one or more control devices and control circuits, and is made up of, for example, a CPU (Central Processing Unit) which is a processor that executes various types of arithmetic processing, an SoC (System on a Chip), etc. The control unit 17 can realize each function by reading out programs stored in the storage unit 19 and executing the processing.

[0020] The storage unit 19 stores various programs and various data necessary for the operation of the image forming apparatus 1. The storage unit 19 includes one or more recording devices capable of temporary storage, such as a dynamic random access memory (DRAM), and non-temporary recording devices, such as a solid state drive (SSD) configured with semiconductor memory or a hard disk drive (HDD) configured with a magnetic disk. For convenience of explanation, the storage unit 19 is shown as a single unit, but it may also be configured as separate units for different purposes, such as an area used for executing programs (main storage area), an area for saving programs and data (auxiliary storage area), an area used for caching, etc.

[0021] [1.2 Relationship between document transport and scanned image distortion] 2 to 4 are diagrams illustrating distortions that occur in scanned images due to the document undergoing uniform linear motion and simultaneous rotational motion in document transport unit 7. Scanned images 21, 31, and 41 are shown in FIGS. 2, 3, and 4, respectively. Scanned images 21, 31, and 41 are all images generated by placing the same business card as a document on document set table 7a and reading it with image input unit 9. Scanned image 21 includes document image 23, scanned image 31 includes document image 33, and scanned image 41 includes document image 43. The document business card is a typical business card, the page of which is rectangular, and the characters of text written on the card are arranged in a straight line.

[0022] Although they were generated by scanning the same document, there are differences between scanned images 21, 31, and 41. Looking at scanned images 21, 31, and 41, we can see that the distortion increases in that order.

[0023] Depending on the document transport conditions, there may be no distortion, slight distortion, or significant distortion. The ideal transport condition is for the document to be transported with only uniform linear motion, but distortion occurs when the document not only moves at a uniform speed but also rotates. The greater the rotation angle, the greater the distortion.

[0024] Distortion will be described with reference to FIG. 4. Original image 43 has original edges 42, 45, 47, and 49. Dotted lines 51 and 57 are parallel to original edge 42, and dotted line 55 represents a straight line connecting the left ends of original edges 42 and 47 (note that dotted line 25 corresponds to dotted line 55 in original image 23, and dotted line 35 corresponds to dotted line 55 in original image 33). Since dotted lines 51 and 57, which are parallel to original edge 42, angle 59 between dotted lines 53 and 57 is equal to the angle between dotted lines 51 and 53. In other words, there is an angle 59 between original edge 42, which is the front edge of original image 43 in the transport direction, and original edge 47, which is the rear edge in the transport direction. Angle 59 is called the tilt difference.

[0025] This tilt difference varies depending on various conditions related to document transport, such as the size and thickness of the document, the number and size variations of the documents placed, and the adjustment level of the document guide 7a1 width. In experiments conducted by the inventors, for example, when scanning ten A4-sized documents, the tilt difference was approximately 0.3 to 0.5 degrees. Meanwhile, when scanning ten business cards of various sizes, the tilt difference was approximately 0.5 to 0.6 degrees. Furthermore, compared with A4-sized documents, business-card-sized documents tend to have a larger curvature due to the tilt difference because the distance (travel length) traveled by the image input unit 9 during scanning is shorter. For these reasons, when comparing scanned images generated by transporting documents by the document transport unit 7 when the document size is A4 and when the document size is business card, the scanned image generated from the business-card-sized document tends to have more noticeable distortion.

[0026] [1.3 Simulation of distortion generation] Figure 5 is a diagram for explaining a simulation of distortion caused by a change in the inclination angle of a document during transport. The state in which a document is transported along a transport path by document transport unit 7 is illustrated by showing the transport path developed on a plane. When a document is transported to image input unit 9 by document transport unit 7, it is assumed that the document is transported under the following conditions: The center of the document is C, and the x-coordinate of the center C of the document is c x Let the y coordinate be c y The initial value of the y coordinate of the center of the document C is c y0 Let's say. The document moves at a uniform speed in a straight line in the direction indicated by the arrow in the document feed direction T. At this time, the document center C moves at a uniform speed on a straight line expressed by the following equation 1. X=c x …(Formula 1) If the time is t, the y-coordinate of the document is c y is expressed as follows in Equation 2: c y =t+c y0 …(Formula 2) First, the document is conveyed to the document set table 7a at an inclination of the initial angle φ. As shown by the dotted line S, the document rotates at a constant angular velocity ω around the document center C. At this time, the angle θ of the U axis with respect to the X axis is expressed by the following equation 3. θ=ωt+φ ...(Equation 3) When the transport mechanism 7b transports the document, the document center C undergoes a constant linear motion according to Equation 2 along the document feed direction (the straight line according to Equation 1), while also undergoing a rotational motion according to Equation 3. The line sensor (image sensor) of the image input unit 9 is located on the X axis, and the line sensor stores the portion of the document that overlaps on the X axis as image data (scanned image). The manuscript is rectangular, with the length (width) in the short direction being 2a and the length (height) in the long direction being 2b. The position on the original is expressed by the UV coordinate axis with the original center C as the origin. Point P on the manuscript lies in the range of -a≦u≦a, -b≦v≦b. Point P on the document is calculated based on the UV coordinate system (P u ,P v ) Point P on the document is calculated based on the XY coordinate system (P x ,P y )

[0027] In the above cases, (P u ,P v ) is calculated by the following equation 4 (P x ,P y ) can be converted to

number

[0028] Fig. 6(B) is a diagram showing a simulated original image 63 obtained by executing the simulation of Fig. 5 using the above-mentioned parameters on the original 61 of Fig. 6(A). In a typical image forming apparatus, the inventors have confirmed that, when compared with a distorted scanned image generated by an image input unit after an original is actually conveyed by an original conveying unit, the simulated original image 63 can adequately reproduce the distortion in the actual scanned image.

[0029] [1.4 Overview of correction process] Assuming that distortion of the original image occurs as in the above simulation, the outline of the original is calculated as follows based on the original image contained in the scanned image.

[0030] FIG. 7 is a diagram for explaining various numerical values that can be acquired from the original image 173 included in the scanned image 171. F0, F1, F2, and F3 are the vertices of the four corners of the original image. The coordinates of F0, F1, F2, and F3 are respectively expressed as (x f0 ,y f0 ), (x f1 ,y f1 ), (x f2 ,y f2 ), (x f3 ,y f3 ) M1 is the midpoint of line segment F0F3, and the coordinates of M1 are (x1, t1). M2 is the midpoint of line segment F1F2, and the coordinates of M2 are (x2, t2). θ1 is the angle that line segment F0F3 makes with the X-axis. θ2 is the angle that line segment F1F2 makes with the X-axis.

[0031] Based on these values, the following parameters are calculated: cx: x-coordinate of the center of the original C cy0: Initial value of the y coordinate of the center of the document C ω: angular velocity of tilt angle φ: Initial value of tilt angle a: 1 / 2 the width of the original size b: 1 / 2 the height of the original size The parameters are calculated as follows:

[0032] (1) Find the coordinates of four points F0 to F3. (2) Find the coordinates of the midpoints M1 and M2. (3) Calculate θ1 and θ2. (4) Substitute t1, t2, θ1, and θ2 into equation 3 to find ω and φ. ω=(θ2-θ1)÷(t2-t1) …Equation 5 φ=θ1-ω×t1…Equation 6 (5) The coordinate value of the midpoint M1 on the original before distortion (p u ,p v ) is expressed as (0, b). Also, the coordinate value of the midpoint M2 on the original before distortion (p u ,p v ) is expressed as (0, -b). x and p y By substituting into the equation to find b and c, we can solve the simultaneous equations x is calculated as follows: b=(x2-x1)÷(sinθ1+sinθ2) …Equation 7 c x =x1+(x2-x1)sinθ1÷(sinθ1+sinθ2) …Equation 8 (6) The coordinate value of point F3 on the original before distortion (p u ,p v ) is (a, b). These are p in Eq. x By substituting into the equation, a is found. u ,p v The time when the point on the document of (a, b) reaches the line sensor position is defined as t3, and the inclination of the document at this time t3 is defined as θ3. a=(x f3 +b·sinθ3-c x )÷cosθ3...Equation 9

[0033] At this time, (a, b) is located on the line sensor, so p y =0 and t=y f3 Therefore, from equation 2 and equation 4, c y0 is calculated as follows: c y0 =-a sinθ3-b cosθ3-y f3…Formula 10

[0034] [1.5 Extraction of Correction Processing Parameters for Operation of Image Forming Device 1] The control unit 17 uses the transport mechanism 7b to transport the document set on the document set table 7a to the image input unit 9. The control unit 17 generates a scanner image including the transported document using the image input unit 9. After the scanner image is generated, the control unit 17 uses the transport mechanism 7b to transport the document to the paper output tray 7d.

[0035] 8 is a flowchart for explaining the process of detecting an original image from scanned image data. The control unit 17 executes the process of FIG.

[0036] The control unit 17 grays the scanner image (step S1). Next, the control unit 17 performs gradation correction on the graysed scanner image (step S3). Next, the control unit 17 scales the gradation-corrected scanner image (step S5). Next, the control unit 17 performs filtering on the scaled scanner image (step S7). Next, the control unit 17 performs edge detection on the filtered scanner image (step S9). Next, the control unit 17 removes noise from the detected edges (step S11). Next, the control unit 17 extracts outline edge information based on the edges from which the noise has been removed (step S13). The processes from step S1 to step S13 are performed on image data. The processes from step S7 to step S13 are performed separately for extracting vertical edges and extracting horizontal edges.

[0037] Next, the control unit 17 detects the tilt based on the extracted outer edge information (step S15). Next, the control unit 17 corrects the detected tilt (step S17). Next, the control unit 17 detects the document range based on the tilt-corrected edges (step S19). The image within the document range is the document image. In step S19, the coordinates of points F0 to F3, which are the four vertices of the document image, are found. Next, the control unit 17 executes a process of extracting correction process parameters (step S21).

[0038] 9 is a flowchart for explaining the extraction process of the correction process parameters in step S21. As described above, in step S19, the control unit 17 extracts the coordinates (x f0 ,y f0 ), the coordinates of point F1 (x f1 ,y f1 ), the coordinates of point F2 (x f2 ,y f2 ), and the coordinates of point F3 (x f3 ,y f3 ) is calculated. The control unit 17 calculates midpoints M1 and M2 from these coordinates (step S31). Next, the control unit 17 calculates θ1 from the slope of the line segment F0F3, and calculates θ2 from the slope of the line segment F1F2 (step S33). Next, the control unit 17 calculates ω and φ (step S35). ω is calculated from equation 5. φ is calculated from equation 6.

[0039] Next, the control unit 17 applies x1, x2, θ1, and θ2 to equations 7 and 8 to obtain b and c x (Step S37). Next, the control unit 17 calculates x f3 , b, θ3, c x is applied to Equation 9 to obtain a (step S39). Next, the control unit 17 calculates a, b, θ3, y f3 Substituting this into equation 10, we get c y0 is calculated (step S41).

[0040] [1.6 Image transformation and mapping functions] Figure 10 is a diagram for explaining the relationship between image transformation and mapping functions. As shown in Figure 10, image transformation can be performed using a mapping function. At this time, by changing the mapping function, various image transformations such as rotation, translation, enlargement, reduction, etc. can be performed.

[0041] Here, image A is the image before image conversion, and image B is the image after image conversion. The coordinates of image A are (x a ,y a ), and the coordinates of image B are (x b ,y b ) Generally, image conversion processing using a mapping function can be performed in the following procedure. Transformed coordinates (x b ,y b ) before transformation (x a ,y a ) is found. - Coordinates before transformation (x a ,y a ) is generally not an integer value, so the neighboring pixels are found. -Appropriate interpolation is performed based on the pixel values of the neighboring pixels, and the converted coordinates (x b ,y b The interpolation process may be, for example, nearest neighbor, bilinear, or bicubic. ·The above process is performed for all coordinates of the transformed image to obtain pixel values.

[0042] The correction process according to the present disclosure is also a type of image transformation using a mapping function. The mapping function for distortion caused by a change in the tilt angle of a document during transport described above is formulated as Equation 2, Equation 3, and Equation 4. Therefore, based on Equation 2, Equation 3, and Equation 4, it is possible to generate a post-transformation image, that is, a distortion-corrected image, from a scanned image that has distortion before conversion.

[0043] [1.7 Image forming device operation correction processing] The image forming apparatus 1 performs a correction process based on this idea on the document image detected in step S19 of Fig. 8. At this time, the correction process is performed based on the parameters extracted in the correction process parameter extraction process shown in step S21 of Fig. 8 and Fig. 9.

[0044] FIG. 11 is a flowchart for explaining the distortion correction process according to the present disclosure. In this flowchart, "correction" refers to calculating pixel values of an ideal, distortion-free original image from pixel values of a distorted original image. The distorted original image is an image generated immediately after scanning the original. "Pre-correction coordinate values" are the coordinate values of pixels in the distorted image obtained immediately after scanning the original. "Post-correction coordinate values" are the coordinate values of pixels in the ideal, distortion-free original image.

[0045] The control unit 17 selects an unprocessed corrected pixel whose corrected pixel value has not yet been determined (step S51). Next, the control unit 17 calculates, from the coordinate value (corrected coordinate value) of the selected pixel, the coordinate value (pre-correction coordinate value) indicating the corresponding position on the scanned image where distortion has occurred (step S53). This calculation is performed based on the mapping functions of Equations 2, 3, and 4 formulated above. Next, the control unit 17 acquires neighboring pixels at the position indicated by the pre-correction coordinate values (step S55). Next, the control unit 17 performs interpolation calculations using the neighboring pixels to obtain post-correction pixel values (step S57). Generally, the pre-correction coordinate values obtained in step S53 are not integer values, so there is usually no pixel with coordinate values that exactly match the pre-correction coordinate values. For this reason, interpolation calculations are performed using neighboring pixels located in positions surrounding the pre-correction coordinate values obtained in step S53. Next, the control unit 17 sets the obtained post-correction pixel values (step S59). If there are still unprocessed post-correction pixels for which post-correction pixel values have not been determined for which steps S51 to S59 have not been performed (step S61, No), the control unit 17 returns to step S51. If steps S61 to S59 have been performed for all pixels (step S61, Yes), the control unit 17 ends the process.

[0046] [1.8 Effects] FIG. 12 is an example of a scanned image with distortion. Scanned image 71 includes original image 73. Arrow T indicates the transport direction in which the transport mechanism 7b of document transport unit 7 transported the document when image input unit 9 generated scanned image 71. Original image 73 has original edge 75 in front of transport direction T, which is approximately perpendicular to transport direction T. Original image 73 also has original edge 77 behind transport direction T. Due to distortion caused by transport of the document, original edge 77 is not perpendicular to transport direction T, as shown in FIG. 12.

[0047] More specifically, the direction indicated by arrow T is the positive direction of the Y-axis, the right side of the figure perpendicular to arrow T is the positive direction of the X-axis, and the angle rotated counterclockwise is a positive angle. The angle between document edge 75 and the X-axis and the angle between document edge 77 and the X-axis are both referred to as the skew angle. In this case, the skew angle of document edge 75 is approximately -0.68 degrees. The skew angle of document edge 77 is approximately -6.53 degrees. Document image 73 has four vertices F0, F1, F2, and F3, listed counterclockwise from the upper left. The coordinates of vertex F0 are (334, 207), the coordinates of vertex F1 are (209, 2273), the coordinates of vertex F2 are (1484, 2420), and the coordinates of vertex F3 are (1626, 221). For ease of explanation, scanned image 71 has larger distortion than normal.

[0048] A typical correction process consists of a rotation process and a cropping process. FIG. 13 is a diagram illustrating a scanned image 80 obtained by applying a rotation process, one of the typical correction processes, to the scanned image 71 of FIG. 12. In the rotation process of the typical correction process, correction is performed by rotating the original image 73 based on the average of the tilt angles of the original side 75 and the original side 77. That is, the average (approximately -3.605 degrees) of the tilt angle of the original side 75 (approximately -0.68 degrees) and the tilt angle of the original side 77 (approximately -6.53 degrees) is calculated, and the original image 73 is rotated so that the tilt angles of both the original sides 75 and 77 become the average (approximately -3.605 degrees). Therefore, in the corrected scanned image 80, the tilt angles 93 and 97 of the original sides 83 and 87 corresponding to the original sides 75 and 77, respectively, are both the average (approximately -3.605 degrees). In the subsequent cropping process, a rectangular area 99 indicated by a dashed line is cropped from the rotated scanned image 80.

[0049] Fig. 14 is a diagram for explaining a scanned image obtained by applying a cropping process to the scanned image after applying the rotation process of Fig. 13. By the above-described rotation and cropping processes, the shape of the business card in the corrected original image 101 is adjusted to a rectangular shape without distortion.

[0050] However, due to this cropping process, the area of original image 81 sandwiched between original side 83 and rectangular area 99 is lost from corrected original image 101. Similarly, the area of original image 81 sandwiched between original side 87 and rectangular area 99 is lost from corrected original image 101.

[0051] 13, document edge 85 curves to the right in the figure, so by cutting out rectangular area 99, a portion of the document image 81 on the right side in the figure is removed. On the other hand, document edge 89 also curves to the right in the figure, so rectangular area 99 includes an area on the left side in the figure that does not correspond to the document image. Therefore, an area that does not correspond to the document has been added to corrected document image 101. Also, corrected document image 101 has lost a portion of the area that corresponds to the document.

[0052] Furthermore, distortions of various images and character strings printed on the business card have not been corrected in the corrected original image 101. For example, as indicated by the dotted curve 103, the arrangement of character strings on the business card remains distorted.

[0053] FIG. 15 is a diagram illustrating a corrected original image 111 obtained by applying the correction process according to the present disclosure to the scanned image of FIG. 12. As described above with reference to FIG. 10, in the correction process according to the present disclosure, the generation of a distorted original image by scanning an original is considered to be the generation of an original image as a mapping of the original. In other words, the original is understood as an inverse mapping of the original image. Therefore, the four original sides of image 111 correspond to the four original sides of the original, respectively, so that areas that do not exist in the original are not added to the original image, and areas that exist in the original are not lost from the original image, as in conventional correction processes.

[0054] Furthermore, distortions of various images and character strings printed on the business card are also corrected in the corrected original image 111. For example, in the corrected original image 111, the character strings on the business card are arranged in a substantially straight line, as indicated by the dotted curve 113.

[0055] [2. Modifications] The present disclosure is not limited to the above-described embodiments and variations, and various modifications are possible. In other words, embodiments obtained by combining appropriately modified technical means within the scope of the gist of the present disclosure are also included in the technical scope of the present disclosure.

[0056] The distortion correction of the present disclosure is effective when the document is small, particularly when it is business card sized. Therefore, the control unit 17 may perform the distortion correction of the present disclosure when the document size is business card sized. In this case, a sensor for acquiring the document size may be provided on the document setting table 7a, and the control unit 17 may acquire the document size from the document setting table 7a, or may acquire the document size based on the document size setting input via the operation unit 5.

[0057] The programs that run on each device in the embodiments are programs that control the CPU, etc. (programs that make a computer function) so as to realize the functions of the above-described embodiments. Information handled by these devices is temporarily stored in a temporary storage device (e.g., RAM) during processing, and then stored in various storage devices such as ROMs (Read Only Memories) and HDDs, and is read, modified, and written by the CPU as needed.

[0058] Here, the recording medium for storing the program may be any of semiconductor media (e.g., ROM, non-volatile memory card, etc.), optical recording media / magneto-optical recording media (e.g., DVD (Digital Versatile Disc), MO (Magneto Optical Disc), MD (Mini Disc), CD (Compact Disc), BD (Blu-ray (registered trademark) Disc), etc.), magnetic recording media (e.g., magnetic tape, flexible disk, etc.), etc. Furthermore, not only are the functions of the above-described embodiments realized by executing the loaded program, but the functions of the present disclosure may also be realized by processing in cooperation with an operating system or other application programs, etc., based on instructions from the program.

[0059] Furthermore, when distributing the program on the market, the program can be stored in a portable recording medium and distributed, or transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer is also included in the present disclosure. [Explanation of symbols]

[0060] 1. Image forming device 3 Display section 5 Control section 7 Document transport section 7a Document tray 7a1 Manuscript Guide 7b Transport mechanism 9 Image input section 11 Image forming unit 13 Communications Department 15 Connection 17 Control Unit 19 Memory section 21, 31, 41, 71, 80, 171 scanned images 23, 33, 73, 81 Original images 25, 35, 51, 53, 55, 57, 91, 95, 161, 163 dotted lines 42, 45, 47, 49, 75, 77, 83, 85, 87, 89 manuscript side 59 angle 61 Manuscript (business card size) 63 Simulated original image 99 Rectangular area 101, 111 Corrected original image 103, 113 curve

Claims

1. The image reading apparatus includes a control unit, an image input unit that optically reads an original, and an original transport unit that transports the original, The control unit a document image obtained by imaging the document by reading the document using the image input unit while the document transport unit is transporting the document; correcting distortion of the original image by performing a transformation related to a mapping function on the original image; the mapping function indicates a mapping from the original to an original image generated by the image input unit reading the original; Image forming device.

2. The mapping function indicates a mapping from the original to the original image generated by reading the original, which rotates while linearly moving at a constant speed along the conveyance direction. The image forming apparatus according to claim 1 .

3. The image forming apparatus according to claim 1 , wherein the correction is performed when the document is of a business card size.

4. 2. The image forming apparatus according to claim 1, wherein the correction parameters are calculated based on midpoints of two opposing sides of the document image and inclinations of the two opposing sides.

5. generating an original image by imaging the original while reading the original while conveying the original; correcting distortion of the original image by performing a transformation related to a mapping function on the original image; the mapping function indicates a mapping from the original to an original image generated by the image input unit reading the original; A control method for an image forming apparatus.

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