JP5313565B2 - Image reading apparatus, image reading method, image reading system, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader having a function of avoiding misoperations in size detection processing and tilt detection processing, when failing to detect the shade of a document. <P>SOLUTION: The image reader switches whether to perform size detection and tilt correction by comparing a length of the document and that of a read image. An image formed on the document is read by a reading unit, and the read image read by the reading unit is scanned in a sub-scanning direction to acquire differential information regarding the sub-scanning direction of the read image in a position of a selected pixel from among all the pixels of the read image, when the length of the read image is larger than the length of the document. Binarized information for each pixel is acquired from differential information, and boundary coordinate values between a background part and a document image part in the read image, from the binarized information. Size detection is performed with the boundary coordinate values, and a rotation angle for tilt correction processing is obtained. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an image reading apparatus for reading image information of a document, an image reading method, and a program for executing the method.

  In general, an image reading apparatus illuminates a document with a light source and reads a document image with a line image sensor or the like. However, since there is unevenness in the light amount of the light source and uneven sensitivity in the line image sensor, the white color reference member is read and corrected. There must be. At this time, after adjusting the amount of light to optimize the amount of light emitted from the light source that irradiates the document and the gain adjustment to optimize the amplification factor of the circuit that amplifies the output signal of the line image sensor, In general, shading correction is performed to correct the sensitivity unevenness of the line image sensor for each photoelectric conversion element of the line image sensor. In the embodiment of the present invention to be described later, the correction for the line image sensor to uniformly read the image information of the document including the above-described “light amount adjustment” and “gain adjustment” is referred to as “shading correction”. I will do it.

In general, when reading a document, the line image sensor is set to a color other than white for the purpose of detecting the boundary between the document and the background, detecting the tilt of the document, and preventing the transparency of the back image of the document. (For example, black) is often used.

19A and 19B are diagrams for explaining a conventional image reading apparatus. FIG. 19A shows a first movement position of the line image sensor, and FIG. 19B shows a second movement position.

As shown in FIG. 19, the image reading apparatus 701 obtains a read image by reading the document 723 by the line image sensor 711 while conveying the document 723. As the timing for reading the image, image reading is started after the leading edge of the document passes through the installation position of the registration sensor 721, and the image reading is finished after the document has passed through the installation position of the registration sensor 721. Since the document detection sensor 721 and the line image sensor 711 are separated from each other, the document reading is started after a predetermined time has elapsed since the leading edge of the document passed over the registration sensor 721. Further, the reading of the document is terminated after a predetermined time has elapsed since the trailing edge of the document passed over the registration sensor 721. In this way, the leading edge resist and trailing edge resist of the read image are adjusted.

The image reading device 701 first reads the color reference member 717 by moving the line image sensor 711 in the direction of arrow S in the figure before reading the document 723. As a result, correction data for shading correction of image data generated based on the output of the line image sensor 711 is generated and stored for each pixel.

The image reading apparatus 701 can detect that the line image sensor 711 has moved to a position where the color reference member 717 is read by the position detection sensor 720.

Thereafter, the image reading device 701 returns the line image sensor 711 to the original position (see FIG. 19B), and reads the document 723 while conveying the document 723. Here, when the original 723 is read, the image data generated based on the output of the line image sensor 711 is subjected to shading correction with reference to correction data stored in advance.

  In this manner, the line image sensor 711 moves between the position for reading the color reference member (see FIG. 19a) and the position for reading the document (see FIG. 19b) in order to acquire correction data for shading correction. In the image reading apparatus, if the position where the image information of the original is read is shifted, registration deviation of the original reading is caused. In order to prevent this registration shift, it is common to position the line image sensor by providing a position detection sensor 720 for detecting the position of the line image sensor.

Conventionally, the size of the original image in the read image and the detection of the inclination of the original image are detected by setting the color of the opposing member of the line image sensor to black, and the boundary between the background image portion and the original image portion in the read image. This is done by detecting the position.

However, when scanning a document with a black border or a document with low light reflectance such as a document with a low brightness margin, the boundary position between the background image (generally black) and the document part is Difficult to detect. In order to solve this problem, in the image reading apparatus disclosed in Patent Document 1, the color of the facing member is set to a color with high reflectance (generally white). In another apparatus, there is a configuration in which a shadow is formed at the trailing edge of the document, and the boundary position is detected using the shadow of the trailing edge of the document in the read image.
JP 2005-57813 A

However, if the document is scanned by specifying an area not including the edge of the document, or if the readable length is shorter than the actual document length, the shadow of the trailing edge of the document cannot be read. An image reading apparatus that uses the shadow of the trailing edge may erroneously detect the document boundary position. For example, assume that an area 2000 surrounded by a dotted line of a document on which a single black horizontal line 2001 is drawn as shown in FIG. In this case, the black horizontal line 2002 appearing in the read image (FIG. 20b) is erroneously recognized as a shadow, and the correct boundary position cannot be detected. Therefore, when the document boundary position detection process is performed, a small image as shown in FIG. 20c is obtained. There is a case to end up.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus that can avoid a malfunction in document boundary position detection processing.

In order to achieve the above object, an image reading apparatus according to an aspect of the present invention includes an image reading unit that reads an image formed on a document, and a leading end of the document in a sub-scanning direction of reading by the image reading unit. and the document longitudinal end detecting means for detecting a rear end, based on the specified scan area, and the document size detection means for detecting the size of the original using the read image of a document obtained by reading by the image reading means, wherein A determination unit that determines whether or not a document size detection process for detecting the size of the document can be performed based on a length of the read image in the sub-scanning direction and a detection result detected by the document front and rear edge detection unit; When the determination unit determines that the document size detection process can be performed, the document size detection unit detects whether the document image in the read image is a background image. Based on the information indicating the position of the field, and detecting the size of the document.
An image reading apparatus according to another aspect of the present invention includes an image reading unit that reads an image formed on a document, and a front end and a rear end of the document in a sub-scanning direction of reading by the image reading unit. Document front and rear edge detection means for detecting, document size detection means for detecting the size of the document using a read image of the document read by the image reading means based on designation of the reading area, and the read image Determination means for determining whether or not document size detection processing for detecting the size of the document can be performed based on a length in the sub-scanning direction and a detection result detected by the document front and rear edge detection unit; The judging means determines the length of the read image along the sub-scanning direction from the leading edge and the trailing edge of the document detected by the document front / rear edge detecting means. Also, when short, it is determined that not be the document size detection processing, if not shorter is characterized in that it is determined that allows the document size detection process.
An image reading apparatus according to another aspect of the present invention includes an image reading unit that reads an image formed on a document, and a front end and a rear end of the document in a sub-scanning direction of reading by the image reading unit. and the document longitudinal end detecting means for detecting, based on the specified scan area, the inclination correction means for performing tilt correction of the original image in the read image of a document obtained by reading by the image reading means, the said read image sub Judging means for judging whether or not inclination correction processing for correcting the inclination of the document image in the read image can be performed based on the length in the scanning direction and the detection result detected by the document front and rear edge detection means; And when the determination means determines that the inclination correction processing can be performed, the inclination correction means is based on information indicating the position of the boundary between the document image and the background image in the read image. , And correcting the inclination of the document image.
An image reading apparatus according to another aspect of the present invention includes an image reading unit that reads an image formed on a document, and a front end and a rear end of the document in a sub-scanning direction of reading by the image reading unit. Document front / rear edge detection means for detecting, inclination correction means for correcting the inclination of the document image in the read image of the document obtained by reading by the image reading means based on the designation of the reading area, and the sub-image of the read image Judging means for judging whether or not inclination correction processing for correcting the inclination of the document image in the read image can be performed based on the length in the scanning direction and the detection result detected by the document front and rear edge detection means; The length of the read image along the sub-scanning direction is determined by the length of the original obtained from the leading edge and the trailing edge of the original detected by the original front and rear edge detecting means. Also, if short, determines not perform the inclination correction processing, if not shorter is characterized in that it is determined that allows the inclination correction processing.

In addition, an image reading method according to an aspect of the present invention detects an image reading unit that reads an image formed on a document, and a leading edge and a trailing edge of the document in a sub-scanning direction of reading by the image reading unit. An image reading apparatus comprising: a document front / rear edge detection unit; and a document size detection unit configured to detect a document size using a read image of a document read by the image reading unit based on designation of a reading area. an image reading method when reading an image of a document, and a length in the sub-scanning direction of the read image based on the detection result detected by the document longitudinal end detecting means, for detecting the size of the document A determination step for determining whether or not document size detection processing can be performed, and if it is determined in the determination step that the document size detection processing can be performed, the document size detection processing is performed. It means by, based on the information indicating the position of the boundary between the original image and the background image of the read in image, characterized in that it comprises a and a document size detection process for detecting the size of the document.
An image reading method according to another aspect of the present invention includes an image reading unit that reads an image formed on a document, and a front end and a rear end of the document in a sub-scanning direction of reading by the image reading unit. An image reading apparatus comprising: a document front and rear edge detection unit to detect; and a tilt correction unit that performs tilt correction of a document image in a read image of a document obtained by reading by the image reading unit based on designation of a reading area . an image reading method when reading an image of the document, a length in the sub-scanning direction of the read image based on the detection result detected by the document longitudinal end detecting means, the document of the reading in the image A determination step for determining whether or not tilt correction processing for correcting the tilt of an image can be performed, and if it is determined in the determination step that the tilt correction processing can be performed, the tilt correction means It, on the basis of information indicating the position of the boundary between the original image and the background image of the read in image, characterized in that it comprises a and a tilt correction step of correcting the inclination of the document image.
An image reading system according to an aspect of the present invention is an image reading system including an image reading device that reads an image of a document and a computer connected to the image reading device, and is provided in the image reading device. An image reading unit that reads an image formed on the original, and a front and rear of the original that are provided in the image reading device and detect the leading end and the rear end of the original in the sub-scanning direction of reading by the image reading unit An original detection image obtained from the edge detection unit and the image reading apparatus, and based on the designation of the reading area, the size of the original is detected using the read image of the original read by the image reading unit. Based on the document size detection means, the length of the read image in the sub-scanning direction, and the detection result detected by the document front and rear edge detection means, the document size is detected. Determination means for determining whether or not document size detection processing can be performed, and when the determination means determines that the document size detection processing can be performed, the document size detection means detects the read image. The size of the original is detected based on information indicating the position of the boundary between the original original image and the background image.
An image reading system according to another aspect of the present invention is an image reading system including an image reading device that reads an image of a document and a computer connected to the image reading device. An image reading means for reading an image formed on the original, and an image reading means provided in the image reading device for detecting the leading edge and the trailing edge of the original in the sub-scanning direction of reading by the image reading means. Document front and rear edge detection means, inclination correction means for correcting the inclination of the document image in the read image of the document read by the image reading means based on the designation of the reading area, and the sub-scanning direction of the read image Whether or not tilt correction processing for correcting the tilt of the document image in the read image can be performed based on the length of the document and the detection result detected by the document front and rear edge detection means Determining means for determining whether the inclination correction processing can be performed by the determining means, the inclination correcting means uses information indicating a position of a boundary between the document image and the background image in the read image. Based on this, the inclination of the original image is corrected.

According to the present invention, in document boundary position detection processing using a shadow or the like of the document edge, when the document is read in a state in which an area inside the document edge is specified, or the document length is equal to the readable length. In this case, it is possible to avoid a malfunction in the document boundary position detection process.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view showing a configuration of an image reading apparatus according to an embodiment of the present invention. The configuration of the image reading apparatus shown in FIG. 1 is schematic and is not limited to this configuration.

As shown in FIG. 1, the image reading apparatus 100 includes an upper frame 181 and a lower frame 182. The upper frame 181 is pivotable about a pivot shaft 181a. In order to remove a document staying in the image reading apparatus 100 when a jam of the conveyed document occurs, the upper frame 181 is manually moved. It can be opened and closed.

The image reading apparatus 100 also includes a pickup roller 102 that picks up the document 123, a feed roller 103 that feeds the document bundle 123 picked up by the pickup roller 102, and one sheet of the picked document bundle 123. A separation roller 104 that separates the documents one by one, a reading unit 108 that reads image information on the upper surface of the document (sheet) separated from the document bundle 123, and a pair that is arranged upstream of the reading unit 108 to convey the document. The registration roller pair 105, the conveyance roller pair 107 disposed in the downstream of the reading unit 108 and provided in pairs to convey the original, and the registration roller pair 105 are disposed and conveyed in the vicinity of the downstream side of the registration roller pair 105. And a registration sensor 110 for detecting a document.

A reading unit 108 (image reading means) is fixed to the upper frame 181. The reading unit 108 includes a line image sensor 120 that reads a document or an image of an opposing member described later, and a light source 121 that irradiates light to the conveyed document or the like. The lower frame 182 is provided with a facing member 109 disposed at a position facing the reading unit 108 and a plate-like glass 106 disposed between the facing member 109 and the reading unit 108. The color of the facing member 109 is white, and shading correction is performed using this facing member. As described above, since the facing member 109 is white, unlike the above-described conventional example, there is no need to move the reading unit 108 when acquiring correction data used for shading correction and when reading an image, and the image reading mechanism is not necessary. It has been simplified.

Next, an operation when the image reading apparatus 100 reads an image formed on a document will be described. First, the reading unit 108 reads the white facing member 109 with the line image sensor 120, generates correction data for shading correction, and stores it for each pixel.

Thereafter, the document bundle 123 is taken into the image reading apparatus 100 by the pickup roller 102 and the feeding roller 103 and separated one by one by the separation roller 104. The separated original is transported in the sub-scanning direction while being sandwiched between the registration roller pair 105 and the transport roller pair 107, and the image formed on the upper surface (front side) is read by the reading unit 108 in the main scanning direction (original transport direction). In a direction perpendicular to the direction). Further, the image data generated from the output signal of the line image sensor 120 is subjected to shading correction with reference to the correction data described above. After the image is read, the document is conveyed while being held by the conveyance roller pair 107, and is discharged to the outside of the apparatus.

FIG. 2 is a block diagram showing a schematic configuration of an electric circuit of the image reading apparatus 100 of FIG. In FIG. 2, 120 is a line image sensor in the reading unit 108, and 121 is a light source. Reference numeral 400 denotes an A / D converter that converts the output signal of the line image sensor 120 into digital data after performing analog processing such as amplification and black level clamping.

Reference numeral 401 denotes image processing for controlling the line image sensor 120, the light source 121, the A / D converter 400, and the like, and performing various image processing (shading correction, etc.) on the image data generated by digitizing the output signal of the line image sensor 120. Part.

Reference numeral 402 denotes an image memory serving as an image storage unit that stores image data. Reference numeral 403 denotes an interface unit with an external host device, which is connected to an external host device such as a PC by a signal cable 409. Reference numeral 404 denotes a CPU serving as a control unit that controls the image reading apparatus. Reference numeral 405 denotes a work memory serving as a storage unit used for the CPU 404 to operate. The image processing unit 401, the CPU 404, and the work memory 405 are connected via a bus 408. The CPU 404 is configured to be able to access the image memory 402 via the image processing unit 401. Reference numeral 412 denotes a driving means (conveyance motor) that conveys the original, and operates when the motor driver 407 receives an instruction from the CPU 404 and passes an excitation current.

3A and 3B are diagrams showing the reading unit 108 and the vicinity thereof. FIG. 3A shows the reading unit 108, and FIG. 3B shows a state in which the rear end of the document 123 is read by the reading unit 108.

In FIGS. 3 a and 3 b, a glass 106 is disposed between the line image sensor 120 and the facing member 109. The glass 106 serves to prevent the opposing member 109 from being scratched or soiled. In addition, the gap between the original 123 and the facing member 109 is equal to or greater than the thickness of the glass 106. The light source 121 is provided along one side surface of the line image sensor 120, and a shadow 124 of the document appears by irradiating light from above on the document 123 obliquely from one side. Such single-sided irradiation tends to cause shadows in the read image as compared with double-sided irradiation. Note that double-sided irradiation refers to a method in which a pair of light sources arranged at symmetrical positions with respect to the line image sensor is provided, and light is applied to the document using the pair of light sources. At this time, the line image sensor and the pair of light sources are arranged in the order of the light source, the line image sensor, and the light source in the sub-scanning direction as shown in FIG. Thus, it can be seen that the shadow 124 in FIG. On the other hand, by using one-sided irradiation as in this embodiment and further providing an opposing member with the glass 106 interposed, the shadow of the document edge can be emphasized, and the boundary of the document image can be easily detected.

Next, processing for obtaining the size and inclination of the original image and a rectangle circumscribing the original image based on the original image in the read image read by the reading unit 108 and inclination correction will be described. In this embodiment, the size detection, the inclination detection, and the detection of the rectangle circumscribing the document image are performed by the above-described shading correction on the read image temporarily stored in the image memory 402 after the document is read by the document reading process described above. The tilt correction is performed before the process, and the tilt correction is performed after the shading correction process. However, it is not limited to the order of the above processing.

First, a differential information generation process for acquiring differential information used in the present invention will be described with reference to FIG. This differential information generation process is executed by the image processing unit 401 and the CPU 404.

FIG. 4 is a diagram showing an xy coordinate system with the upper left corner of the read image being read as the origin. In the present embodiment, the density value (pixel value) of each pixel in the xy coordinate system is set to f (x, y), and the density value f (x, y) is set to a larger value as it becomes brighter. In the present embodiment, the y-axis direction is the sub-scanning direction. The absolute value of the value obtained by differentiating the read image of the document in the sub-scanning direction is used as the differential information value. Further, in the image actually read by the image reading apparatus, a shadow is formed on the boundary between the background portion and the document portion. However, in the description using FIG. Is omitted.

First, the differential information value Δ (x, y) of the read image at the position of each pixel is expressed by the following equation (1). Note that the method of obtaining the differential information value of the equation (1) is an example.

Δ (x, y) = abs (f (x, y + m) −f (x, y)) (1)
f (x, y): density value of pixel at each coordinate f (x, y + m): density value of pixel m lines ahead from each coordinate (in this embodiment, m = 1)

Here, the phrases shown in FIG. 4 are defined as follows.
Width: the width of the image (for example, (the width of the image whose x coordinate is from 0 to 23) = 24)
Height: the length of the image (for example, (the length of the image where the y coordinate is 0 to 25) = 26)
・ N line: attention line ・ n + m line: line ahead of m line from attention line

  First, a process of applying the density value of each pixel from the upper left end (x, y) = (0, 0) to (Width-1, 0) of the image in FIG. 4 to the expression (1) is performed. When the process proceeds to (Width-1, 0), the process moves to the next line, and the process is performed from the left end (x, y) = (0, 1) to (Width-1, 1). Similarly, the line is continuously moved, and the same processing as described above is performed up to (Width-1, Height-1-m). Thereby, the differential information value of the image at the position of each pixel in the sub-scanning direction is obtained (FIG. 5). Further, the line of y = Height-1 in FIG. 5 is blank because it cannot be calculated. Further, in this embodiment, scanning is performed while increasing x by 1 and shifted by one line. However, by shifting x by several lines while increasing x by 1 or more, differential information is acquired at the position of the selected pixel. Also good.

Next, the differential information binarization process will be described. The differential information binarization process is executed by the image processing unit 401 and the CPU 404.

In the differential information binarization process, the differential information value Δ (x, y) described above is binarized with a certain threshold value s.
In this embodiment, 1 is set when the differential information value exceeds the threshold s (= 50), and 0 is set otherwise. The binarized information T (x, y) is acquired by the following equation (2). Note that setting s to 50 is an example.
T (x, y) = 1 (Δ (x, y)> s) (2)
0 (Δ (x, y) ≦ s) (s = 50)

Next, boundary coordinate information acquisition means will be described with reference to FIG. The coordinate information acquisition process is executed by the image processing unit 401 and the CPU 404.

FIG. 6 is a diagram illustrating the binarization information T (x, y) acquired by the differential information binarization processing.

  In FIG. 6, 604 is an overall view of the binarized information, and 601 is the x coordinate value of the pixel having the smallest x coordinate value among the pixels where T (x, y) = 1 in each horizontal line. The buffer to store. Reference numeral 602 denotes a buffer that stores the x coordinate value of the pixel having the largest x coordinate value among the pixels having T (x, y) = 1 in each horizontal line. Reference numeral 603 denotes a buffer for storing the y coordinate value of the pixel having the largest y coordinate value among the pixels having T (x, y) = 1 in each vertical line. Reference numeral 605 denotes a buffer for storing the y coordinate value of the pixel having the smallest y coordinate value among the pixels having T (x, y) = 1 in each vertical line. When a pixel having T (x, y) = 1 is not found in each horizontal line or each vertical line, −1 is set in each buffer. Note that −1 is set in the last column (value corresponding to y = 25) of the buffers 601 and 602. This is because the calculation of the formula (1) is performed only up to the Height-1-m line.

Next, characteristics related to the present embodiment of the read image actually read by the image reading apparatus will be described. In the read image to be described below, there is a shadow at the boundary between the document portion and the background portion.

  FIG. 7 is a diagram illustrating a correspondence relationship between the line image sensor 120, a document conveyed into the image reading apparatus 100, and a read image of the document.

  In FIG. 7, an arrow 1109 indicates the document conveyance direction, 1102 is a document conveyed into the image reading apparatus 100, and 1104 is a line image sensor 120 that reads the document 1102 conveyed in the sub-scanning direction. 1103 is a document image corresponding to the document 1102 in the scanned image 1104, 1105 is a background image in the scanned image 1104, and 1106 is a document image and a background image at the rear end of the document image 1103. It is a shadow part formed at the boundary.

  FIG. 8 is a graph showing the change in density in the sub-scanning direction when the original 1102 is read by the line image sensor 120 of FIG. 7, and FIG. 8a is the density of the vertical line read at the reading position 1107 of the line image sensor 120. 8b shows the density change of the vertical line read at the reading position 1108 of the line image sensor 120, FIG. 8c shows the differential value of the density change at the reading position 1107, and FIG. 8d shows the reading position 1108. The differential value of the density | concentration change in is shown. The density of the margin of the document image 1103 is illustrated as being substantially equal to the density of the background image 1105.

  As shown in FIG. 8a, since the reading position 1107 of the line image sensor 120 reads a place where the original 1102 does not pass, the density of the read image becomes a substantially constant value (for example, 200). On the other hand, as shown in FIG. 8B, the reading position 1108 of the line image sensor 120 reads the position through which the document 1102 passes. At this time, since a shadow portion 1106 is formed at the boundary between the rear end portion of the document image and the background image 1105, the density of the read image changes rapidly at the position of the shadow portion 1106. At the position where the density changes rapidly, the absolute value of the value differentiated in the sub-scanning direction (vertical direction in FIG. 8) increases (FIG. 8d). In the present embodiment, the density change at the boundary between the document image and the background image at the shadow portion 1106 formed at the boundary between the document image and the background image by obtaining the differential in the vertical direction, that is, the sub-scanning direction, or the document leading edge. Is detected. Accordingly, the values stored in the buffers 601, 602, and 603 indicate boundary coordinate values (coordinate data) indicating the position of the boundary of the document image.

  Here, dust adhering to the line image sensor 120 and the facing member 109 will be described. As shown in FIG. 22, when dust adheres to the line image sensor 120 or the opposing surface of the line image sensor 120 (for example, the upper surface of the glass 106), vertical stripes (black lines) 2204 are generated in the document image. However, when the differentiation process of the present invention is executed, there is no sudden density change in the sub-scanning direction even if differentiation is performed on the vertical stripe in the sub-scanning direction generated due to the influence of dust. As shown in the graph of 8c, the value is low. Therefore, the process of detecting the shadow 1106 at the trailing edge of the document 1102 is not affected by the occurrence of vertical stripes due to dust. In addition, when dust is attached to the reading position 1108, the position of the original and the background cannot be specified from the differential value on the vertical streak line generated by the dust, but data of adjacent lines to which dust is not attached should be used. Thus, it is possible to perform size detection and inclination detection described later.

  Next, processing for storing the boundary coordinate values of the document image and the background image in the buffers 601 to 603 will be described.

  FIG. 9 is a flowchart showing processing for storing boundary coordinate values in the buffer 601. Here, the array variable for the buffer 601 is buff [y], and the coordinate of the pixel of interest is (x, y).

  In FIG. 9, first, the upper left end A of the entire binarized information diagram 604 shown in FIG. 6 is set as the start point (x = 0, y = 0) (steps S91, S91a), and the target pixel is parallel to the x-axis. Scanning is performed while sequentially shifting the pixels in the direction from the smallest x coordinate value. Next, it is determined whether or not the binarization information T (x, y) of the target pixel is 1 (step S92). If the binarization information T (x, y) of the target pixel is not 1, x is incremented (x = x + 1) (step S93), and the process proceeds to step S95. When the binarization information T (x, y) of the target pixel is 1, the x coordinate value of the target pixel is stored in the buffer 601 (buff [y] = x) (step S94), and the process proceeds to step S98. . In step S95, it is determined whether or not the target pixel exceeds the right end of the read image (x ≧ Width?). If the target pixel does not exceed the right end, the process returns to step S92. If the target pixel exceeds the right end, -1 is stored in the buffer (buff [y] =-1) (step S97). It is determined whether or not the horizontal line to be included is the last line (y ≧ Height−1?) (Step S98). If the horizontal line including the pixel of interest is not the final line, y is incremented to move to the next horizontal line (y = y + 1) (step S99), and the process returns to step S91a. The process ends.

  FIG. 10 is a flowchart showing processing for storing boundary coordinate values in the buffer 602. In the process of FIG. 10, the upper right end B of the entire binarized information diagram 604 shown in FIG. 6 is used as the start point of the pixel of interest, and scanning is performed in order from the pixel having the largest x coordinate value in the direction parallel to the x axis. Except for this, it is basically the same as the data storage process of FIG.

FIG. 11 is a flowchart showing processing for storing boundary coordinate values in the buffer 603. In the process of FIG. 11, the lower left C of the binarization information overall diagram 604 shown in FIG. Except for setting buff [x] as an array variable for 603 (that is, corresponding to buff [y]), it is basically the same as the data storage process of FIG. According to the boundary coordinate value storing process, the boundary coordinate values of the document image and the background image are stored in the buffers 601 to 603 and 605, and the boundary coordinate value of the document image and the background image can be acquired.

  FIG. 23 is a flowchart showing processing for storing boundary coordinate values in the buffer 605. In the processing of FIG. 23, the upper left end A of the binarization information overall diagram 604 shown in FIG. 9 is basically the same as the data storage process of FIG. 9 except that the array variable for 605 (that is, corresponding to buff [y]) is buff [x], and the description thereof is omitted.

  According to the boundary coordinate value storing process, the boundary coordinate values of the document image and the background image are stored in the buffers 601 to 603 and 605, and the boundary coordinate value of the document image and the background image can be acquired.

Next, the document front and rear edge detection means will be described. The document front / rear edge detection means is the registration sensor 110 in FIG. 1 and the CPU 404 that recognizes the change in its output signal and detects the front / rear edge of the document. A hardware circuit (not shown) may be used for detection. The CPU 404 measures the time from when the leading edge of the document passes through the registration sensor 110 to when the trailing edge of the document passes. Further, the speed at which the document is conveyed is determined in advance by the resolution or the like and is recorded on the memory. The length of the document is acquired from the document conveyance speed and the time from when the document starts to pass through the registration sensor 110 to when it finishes passing.

As described above, according to the present embodiment, the image formed on the original is read by the reading unit 108, the read image read by the reading unit 108 is scanned in the sub-scanning direction, and all of the pixels of the read image are scanned. Differential information regarding the sub-scanning direction of the read image at the position of the selected pixel is acquired (differential information generation processing), and binarization information of each pixel is acquired from the differential information (differential information binarization processing). Since the boundary coordinate value between the original image and the background image in the read image is acquired from the binarized information (coordinate information acquisition process), the vertical length extending in the sub-scanning direction in the read image due to dust adhering to the reading unit 108 and the opposing member 109 Even when streaks occur, the boundary position between the document image and the background image can be accurately detected. In addition, since the opposing member 109 of the line image sensor 120 is white, it is not necessary to move the line image sensor 120 during shading correction and image reading. This can be omitted, and the configuration of the reading unit can be simplified.

Next, the document size detection process will be described. FIG. 12 is a diagram for explaining the document size detection process. In the document size detection process, the boundary coordinate value obtained by the coordinate information acquisition process is used. The document size detection process is executed by the image processing unit 401 and the CPU 404.

As shown in FIG. 12, the size detected by the document size detection process is a minimum rectangular size including all parts of the document image in the read image 1303. Reference numeral 1301 denotes a document image in the read image 1303, and reference numeral 1302 denotes a minimum rectangle obtained as a size detection result. The boundary lines 1304 to 1307 are derived from boundary data stored in the buffers 601 to 603, respectively. Specifically, first, in order to obtain the coordinate values x _1, utilizing a buffer 601. The coordinate value _xl is set to the smallest value in the boundary data stored in the buffer 601 (however, -1 is excluded). Similarly, the coordinate values x _r is set to 1 number larger value among the boundary data stored in the buffer 602, the coordinate value y _t is set to a largest value among the boundary data stored in the buffer 603 The The position to start reading the line image sensor is the same as the position of the leading edge of the document, the coordinate value y _b is always set to 0.

Next, the inclination correction process will be described. The inclination correction process includes a document inclination angle detection process, a circumscribed rectangle calculation process, and a rotation process, which will be described later.

First, document inclination angle detection processing will be described. In the document inclination angle detection process, boundary coordinate values stored in the buffer 603 are used. This document inclination angle detection process is executed by the CPU 404.

FIG. 13 is a diagram showing line segments obtained from the boundary coordinate values of the buffer 603. In FIG. 13, the section A in the x-axis direction is a portion where the boundary coordinate value is set to −1 because there is no change in density. In the section B, the y coordinate is stored in the array. The value stored in the buffer 603 corresponds to the shadow position on the lower side of the document. First, the maximum value (P ₂ ), the left end (P ₁ ), and the right end (P ₃ ) are obtained from the boundary coordinate values of the buffer 603. Next, line segment P ₁ -P ₂
And the line segments P ₂ -P ₃ are separated, and the inclination angles of the line segments P ₁ -P ₂ and the line segments P ₂ -P ₃ are detected.

FIG. 14 is a diagram for explaining the detection of the inclination angles of the line segments P ₁ -P ₂ and the line segments P ₂ -P ₃ , FIG. 14 a shows the line segments P ₁ -P ₂ , and FIG. The minutes P ₂ -P ₃ are shown.

As shown in FIG. 14a, with respect to line segment P ₁ -P ₂ , a constant interval a from P ₁ toward P ₂
In will promote sequence _{(p 1n;} n is a natural number), calculates the difference value _b 1 ~b _n y coordinate to over _{P 2,} the total value sum1 (sum1 difference value _b 1 ~b _n the illustrated example Then, a positive value) is calculated. Similarly, with respect to the line segment P ₂ -P ₃ , the arrangement is advanced from P ₂ toward P ₃ at a constant interval a (p _2m ; m is a natural number), and the difference value c _{1 of the} y coordinate until P ₃ is exceeded. seek to c _m, the total value sum2 of difference values _c 1 to c _m (sum2 in the illustrated example a negative value) is calculated (Fig. 14b).

  Next, the larger one of the natural number n and the natural number m is adopted (the longer one of the sections C and D is adopted), and the gradient vector (g, h) is obtained using the following equation (3). The inclination angle of the document image is detected from the inclination vector.

(G, h) = (a, sum1 / n) n ≧ m (3)
(a, sum2 / m) n <m
According to the original document inclination angle detection process, the inclination angle of the original image in the read image can be detected using the boundary coordinate values stored in the buffer 603.

Next, circumscribed rectangle calculation processing will be described. In the circumscribed rectangle calculation process, the inclination vector (g, h) obtained by the inclination angle detection process and the boundary coordinate values (values stored in the buffer 601 and the buffer 602) are used. Note that this circumscribed rectangle calculation process is executed by the image processing unit 401 and the CPU 404.

  FIG. 15 is a view showing a tilted original image 1602 in the read image 1601. In FIG. 15, reference numerals 1604 and 1605 are boundary lines obtained from boundary coordinate values stored in the buffer 601. Reference numerals 1606 and 1607 denote boundary lines obtained from the boundary coordinate values stored in the buffer 602. 1612a and 1614a indicate straight lines having an inclination h / g when n ≧ m, and 1613a and 1615a indicate straight lines having an inclination −g / h. Reference numerals 1612 to 1615 denote straight lines in contact with the boundary lines 1604 to 1607 among 1612a to 1615a, respectively. Points 1608 to 1611 indicate intersections of two straight lines that intersect perpendicularly to each other among the straight lines 1612 to 1615.

First, a method for obtaining an equation of a straight line 1612 having an inclination h / g in contact with the boundary line 1605 will be described. Here, a case where n ≧ m and (g, h) = (a, sum1 / n) is described as an example. First, deform y = (h / g) x + b,
b =-(h / g) x + y (4)
And Then, the boundary coordinate values stored in the buffer 601 are substituted into x and y in the above equation (4) to obtain b. The largest value among the y-intercepts b obtained by substituting all the boundary coordinate values of the buffer 601 into the above equation (4) is selected, and a straight line in contact with the boundary line 1605 is obtained by this maximum value.

Similarly, when calculating the equation of the straight line 1614 that touches the boundary line 1607,
c =-(h / g) x + y (5a)
The smallest value is selected from the y-intercepts c obtained by substituting all the boundary coordinate values of the buffer 602 into the formula.

When calculating the equation of the straight line 1615 that is in contact with the boundary line 1604,
e = (g / h) x + y (5b)
The smallest value is selected from the y-intercepts e obtained by substituting all the boundary coordinate values of the buffer 601 into the formula.

Similarly, when calculating the equation of the straight line 1613 that is in contact with the boundary line 1606,
d = (g / h) x + y (5c)
The largest value among the y-intercepts d obtained by substituting all the boundary coordinate values of the buffer 602 into the formula is selected.

  Next, the coordinates of the intersection points 1608 to 1611 of the four straight lines 1612 to 1615 obtained in the above procedure are obtained. The coordinates of the intersection points 1608 to 1611 are obtained by solving two simultaneous equations that intersect perpendicularly to each other. Note that the calculation method when n <m is omitted.

  According to the circumscribed rectangle calculation process, a rectangle circumscribing the document image in the read image can be detected.

  Next, an image rotation process performed in the inclination correction process will be described. In this inclination correction process, the coordinates of the intersection points 1608 to 1611 of the four vertices of the document detected by the inclination vector (g, h) obtained by the inclination angle detection process and the circumscribed rectangle calculation process are used.

  FIG. 16 is a diagram showing the relationship between the value of the inclination vector (g, h) and the inclination direction of the document. FIG. 16a shows a case where h is a positive value and g <h, and FIG. FIG. 16c shows the case where h is positive and g> h, FIG. 16c shows the case where h is negative and g <| h |, FIG. 16d shows that h is negative and The case of g> | h | is shown.

  16a to 16d, when h is a positive value and g <h, the original image is rotated clockwise by an angle θ with the rotation axis as the upper left vertex of the original image (FIG. 16a), h Is a positive value and g> h, the original image is rotated counterclockwise by an angle θ (FIG. 16b). In this embodiment, when g = h, the document image is rotated clockwise. If h is a negative value and g <| h |, the original image is rotated counterclockwise by an angle θ (FIG. 16c), h is a negative value, and g> | h | In this case, it is rotated clockwise by an angle θ (FIG. 16d). When g = | h |, the document image is rotated clockwise. Normally, since the document to be read does not frequently tilt, the rotation of one of FIGS. 16b and 16d is often performed. Further, correction is performed so that the upper left vertex of the rotated original image is aligned with the origin of the xy coordinate system.

  FIGS. 17A and 17B are diagrams for explaining a method for rotating a document image. FIG. 17A shows an image A before rotation, and FIG. 17B shows an image B after rotation.

In FIG. 17, the width and height of the image B are set to 3 points (x ₁ , y ₁ ), ( ₄ ) of the 4 vertices of the document calculated by the circumscribed rectangle calculation process using the following equation (6). x ₂ , y ₂ ), (x ₄ , y ₄ ) is obtained by the following equation.
w = √ ((x ₁ −x ₄ ) ² + (y ₁ −y ₄ ) ² )
...... (6)
h = √ ((x ₁ −x ₂ ) ² + (y ₁ −y ₂ ) ² )

  Next, a method for determining the density value of each pixel of the image B will be described. The density value of each pixel of the image B is determined by referring to the density value of each pixel of the image A using the following equation (7).

x = X cos θ−Y sin θ + x ₁ (7)
y = Xsinθ + Ycosθ + y ₁
(X, y): pixel position before rotation
(X, Y): Pixel position after rotation However, here, the angle θ is an angle measured clockwise.

  FIG. 18 is a flowchart showing the inclination correction process. This inclination correction process is executed by the image processing unit 401 and the CPU 404.

18, first, scanning is sequentially performed for each pixel from the upper left end to the lower right end of the image B shown in FIG. 17 (step S181), and the target pixel (X, Y) is calculated using the above equation (7). The coordinates (x, y) before rotation are calculated (step S182). Next, it is determined whether or not the coordinates (x, y) before rotation protrude from the image A (step S183). When the coordinates (x, y) before the rotation are out of the image A, the density value of the target pixel (X, Y) is set to a value corresponding to white (step S184), and the coordinates (x, y) before the rotation are set. If it does not protrude from the image A, the pixel density value at the coordinates (x, y) is set to the density value of the target pixel (X, Y) (step S185). Next, it is checked whether or not the target pixel (X, Y) is positioned at the lower right end of the image B (step S186). If the target pixel (X, Y) is not located at the lower right end of the image B, the process returns to step S181. If the target pixel (X, Y) is located at the lower right end of the image B, this process is terminated. To do. According to the tilt correction process, the tilt of the rotated document image can be corrected.

Next, a process for determining whether or not to perform a size detection process by the size detection unit and a process for determining whether or not to perform a process for correcting the inclination of the document (hereinafter referred to as an inclination correction process) will be described. The condition for selecting not to perform the size detection process and the inclination correction process is that the length of the read original image (hereinafter referred to as the original image length) is based on the actual original length acquired by the original front and rear edge detection means. Is also a short time. At this time, size detection or tilt correction processing is not performed. At this time, the size detection process is actually performed, but the same value as the width and height of the read image is output. Further, at this time, the inclination correction process is executed, and the correction process is performed assuming that the inclination angle detected by the inclination angle detection process described above is 0 degrees. As a result, it is equivalent to the fact that correction is not actually performed. Note that the size detection process and the inclination correction process may be skipped.

Next, the reason why it is inappropriate to perform the size detection process and the inclination correction process when the document image length is shorter than the actual document length.

FIG. 21 b shows a case where the length of the read image 904 is shorter than the length of the document 902. In FIG. 21 b, a black straight line 903 is drawn in the document 902. In the case of FIG. 21b, since the document has not been read up to the trailing edge, the shadow of the trailing edge of the document is not known. For this reason, when the size detection process is performed, the black straight line 903 in the original is erroneously recognized as the trailing edge of the original, and boundary coordinate information is acquired from the black straight line 903, which is inappropriate. When the length of the read image is shorter than the actual document length, it can be distinguished whether the boundary coordinate information acquired by the boundary coordinate information acquisition unit is obtained from the trailing edge of the document or from a picture in the document. Not stick. In addition, the boundary between the document and the background is not known when an area in the document is designated and read. Also at this time, the document image length is shorter than the actual document length. Even when scanning is performed without designating an area, if the actual document is longer than the readable length of the image reading apparatus, the document image length cannot be read by the image reading apparatus because the end of the document cannot be read. Shorter than. Even in these cases, it is inappropriate to perform the size detection process.

FIG. 21 a shows a case where the length of the read image 905 is longer than the length of the original 901. In this case, since the two document edges 907 are all on the document image, it can be understood that the size detection process and the inclination correction process can be performed by using the document edge 907.

  In the present embodiment, the differential information generation processing performs primary differentiation in order to find the change point of concentration, but may perform secondary differentiation. Moreover, you may perform both a primary differentiation and a secondary differentiation.

In the present embodiment, size detection processing, tilt detection, detection of a rectangle circumscribing a document, and tilt correction processing are executed by the image processing unit 401 and the CPU 404, but a host device such as a PC connected to the signal cable 409. It may be executed by the image processing means and the CPU provided in.

  Further, in the process of detecting a rectangle circumscribing the document, the registration sensor 110 is used to detect the timing at which the leading edge and the trailing edge of the document pass, and the leading edge position and the trailing edge position of the document image in the read image are estimated. Information may be used to correct the detection result of one side of the leading edge and one side of the trailing edge of the document image. Specifically, one side of the leading edge of the document is a straight line passing through a position corresponding to the timing at which the leading edge of the document detected by the registration sensor 110 passes, and one side of the trailing edge of the document is detected by the registration sensor 110. A straight line passing through a position corresponding to the timing at which the rear end passes is set.

  Further, in the present embodiment, the irradiation direction is such that a shadow is easily formed at the rear end portion of the document image, and the boundary of the document image is detected using the shadow at the rear end portion. However, the present invention is not limited to this. Alternatively, detection and correction may be performed using a shadow formed on the leading edge of the original image.

Next, a method for stopping image reading and notifying the user as an error when the size detection process and the inclination correction process cannot be performed will be described. The configuration of the image reading apparatus, the image reading process, the size detection process, and the content of the inclination correction process are as described above.

FIG. 25 is a flowchart until an error is displayed on the PC as an error when it is determined that the size detection process cannot be performed. First, initialization and other processes for starting image reading are performed (step S200), and then it is confirmed whether there is a document (step S201). If there is no document, the reading process is terminated (step S206). If there is a document, image reading is performed (step S202), and it is determined whether the length of the document is longer than the length of the read image and size detection processing can be performed (step S203). If it is determined that the size detection process can be performed, the size detection process is performed (step S204), the image is stored (step S205), and the process returns to step S201 to continue the process. If it is determined in step S203 that the size detection process cannot be performed, the image reading is stopped, and an image of the document in which an error is detected is displayed and an error is displayed (step S207). Here, as an example of how to display an error, an error dialog is displayed on the PC to notify the user of an error. Thereafter, the user is allowed to select whether or not to continue the image reading process (step S208). Will you continue on your PC as a means of selection? A dialog including a Yes button and a No button that display a character string with the content of is displayed. If the user presses the Yes button in step S208 and chooses to continue, the process returns to step S201 and continues. If it is selected that the process is interrupted by pressing the No button, the image reading process is terminated (step S209). The error display flowchart in FIG. 25 exemplifies a case in which a determination related to the size detection process is performed. However, in a case where a determination regarding the inclination correction process is performed, a determination as to whether or not the size detection process in the flowchart in FIG. 25 can be performed. The step S203 for performing the step S204 and the step S204 for performing the size detection process may be replaced with a step for determining whether the tilt correction process can be performed and a step for performing the tilt correction process.

In this embodiment, an error dialog is displayed on the PC. However, an error may be recorded as a log in a file without displaying the error dialog on the PC.

In addition to displaying an error dialog, an input unit that allows the user to input document tilt information may be provided, and tilt correction processing may be performed using the input tilt information.

Another object of the present invention is to supply a storage medium storing a software program for realizing the functions of the above-described embodiments to an image processing reading apparatus, and the computer (or CPU, MPU, etc.) of the image processing apparatus stores the storage medium. It is also achieved by reading and executing the program code stored on the medium.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the program code and the storage medium storing the program code constitute the present invention.

  Examples of the storage medium for supplying the program code include a floppy (registered trademark) disk, a hard disk, a magneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a DVD-ROM, a DVD-RAM, and a DVD. An optical disc such as RW or DVD + RW, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used. Alternatively, the program code may be downloaded via a network.

  By executing the program code read from the computer, not only the functions of the above-described embodiments are realized, but an OS (operating system) operating on the computer based on an instruction of the program code is actually used. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the processing and the processing is included.

  Further, after the program code read from the storage medium is written to a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. This includes a case where the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

Sectional drawing which shows the structure of the image reading apparatus which concerns on embodiment of this invention Block diagram showing schematic configuration of electric circuit of image reading apparatus The figure of a reading unit and the figure which shows the state in which the rear end of the original is read by the reading unit The figure which shows xy coordinate system which made the origin the upper left end of the read original image The figure which shows the differential information value of each pixel regarding a subscanning direction The figure which shows the binarization information T (x, y) acquired by the differential information binarization process The figure which shows the correspondence of a line image sensor, a manuscript, and a read image A graph showing the density change of the read vertical line and a graph showing the differential value of the density change The flowchart which shows the process which stores a boundary coordinate value in the buffer 601 The flowchart which shows the process which stores a boundary coordinate value in the buffer 602 The flowchart which shows the process which stores a boundary coordinate value in the buffer 603 Diagram explaining the document size detection process The figure which shows the boundary line obtained from the boundary coordinate value of the buffer 603 Diagram illustrating the line segment _P 1 -P _2, the detection of the inclination angle of the line segment _P 2 -P ₃ The figure which shows the manuscript image which is inclined due to the skew when reading The figure which shows the relationship between inclination vector (g, h) and the inclination direction of a document. Diagram showing image A before rotation and image B after rotation Flow chart showing tilt correction processing FIG. 2 is a diagram illustrating a conventional image reading apparatus The figure when a document is read by area designation using a conventional image reading device The figure which illustrates the case where the document image length is longer than the document length and the case where the document image length is shorter than the document length Illustration for explaining the effect of vertical streaks due to dust The flowchart which shows the process which stores a boundary coordinate value in the buffer 605 Illustration for explaining double-sided irradiation Flow chart showing error display processing

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image reading apparatus 106 Glass 109 Opposing member 110 Registration sensor 120 Line image sensor 121 Light source 123 Original 124 Shadow 401 Image processing part 402 Image memory 403 Interface part 404 CPU
405 Work memory 601 Edge position storage buffer 602 Edge position storage buffer 603 Edge position storage buffer 604 Document trailing edge line 605 Edge position storage buffer 701 Image reading device 711 Reading unit 717 Opposing member 720 Position detection sensor 723 Document 901 Document 902 Document 903 Black straight line 904 Document image 905 Document image 906 Document edge 907 Document edge 1102 Document 1103 Document document 1104 Read image 1105 Image background 1106 Shadow 1107 Scan position 1108 Scan position 1109 Transport direction 1602 Document Image 1612a Outer tangent line expression 1613a Outer tangent line expression 1614a Outer tangent line expression 1615a Outer tangent line expression 2000 Reading area 2001 Black line 2002 Black line 2201 in reading image Reading image 2202 Original Manuscript image 2203 Background image 2204 Vertical stripe

Claims (16)

Image reading means for reading an image formed on a document;
Document front and rear edge detection means for detecting the leading edge and the trailing edge of the document in the sub-scanning direction of reading by the image reading means;
A document size detecting means for detecting the size of the document using a read image of the document read by the image reading means based on the designation of the reading area ;
A length in the sub-scanning direction of the read image, the document on the basis of a detection result detected by the front and rear end detecting means, determining means for determining whether perform a document size detection process for detecting the size of the document And
When the determination unit determines that the document size detection process can be performed, the document size detection unit determines the size of the document based on information indicating the position of the boundary between the document image and the background image in the read image. An image reading apparatus characterized by detecting the above. Image reading means for reading an image formed on a document;
Document front and rear edge detection means for detecting the leading edge and the trailing edge of the document in the sub-scanning direction of reading by the image reading means;
A document size detecting means for detecting the size of the document using a read image of the document read by the image reading means based on the designation of the reading area ;
A length in the sub-scanning direction of the read image, the document on the basis of a detection result detected by the front and rear end detecting means, determining means for determining whether perform a document size detection process for detecting the size of the document And
In the case where the length of the read image along the sub-scanning direction is shorter than the length of the original obtained from the leading edge and the trailing edge of the original detected by the original front and rear edge detecting means, An image reading apparatus that determines that the document size detection process cannot be performed and determines that the document size detection process can be performed when the document size detection process is not short. Differential information acquisition means for differentiating the pixel value of each pixel included in the read image in the sub-scanning direction to acquire differential information;
Boundary coordinate information acquisition means for acquiring boundary coordinate information indicating the position of the boundary between the document image and the background image in the read image based on the differential information,
The image reading apparatus according to claim 1, wherein the document size detection unit detects the size of the document based on boundary coordinate information acquired by the boundary coordinate information acquisition unit. Further comprising an inclination correction means for correcting the inclination of the document image in the read image based on the boundary coordinate information acquired by the boundary coordinate information acquisition means;
Whether the determination unit further performs an inclination correction process of the document image based on the length of the read image along the sub-scanning direction and the detection result detected by the document front and rear edge detection unit. Judging
The image reading apparatus according to claim 3, wherein the inclination correction unit corrects the inclination of the document image based on the boundary coordinate information when the determination unit determines that the inclination correction process is performed. apparatus.   The tilt correction unit includes a document tilt angle detection unit that detects a tilt angle of the document image in the read image based on the boundary coordinate information, and the tilt of the document image is based on the detected tilt angle. The image reading apparatus according to claim 4, wherein:   The inclination correction means further comprises circumscribed rectangle calculation means for calculating a rectangle circumscribing the document image in the read image based on the boundary coordinate information and the inclination angle, and based on the calculated rectangle, The image reading apparatus according to claim 5, wherein the inclination of the document image is corrected.   6. The apparatus according to claim 1, further comprising an error notifying unit that displays the read image and notifies an error when the size detecting process is not performed by the document size detecting unit. The image reading apparatus described in 1.   7. The apparatus according to claim 4, further comprising an error notification unit that displays the read image and notifies an error when the tilt correction unit has not performed the tilt correction process. 8. The image reading apparatus described. Image reading means for reading an image formed on a document;
Document front and rear edge detection means for detecting the leading edge and the trailing edge of the document in the sub-scanning direction of reading by the image reading means;
A tilt correction unit that performs tilt correction of a document image in a read image of a document obtained by reading by the image reading unit based on a designation of a reading area ;
A length in the sub-scanning direction of the read image, the document on the basis of a detection result detected by the front and rear end detecting means, whether or not perform the inclination correction processing for correcting the inclination of the document image of the read in image A judging means for judging,
When the determination unit determines that the inclination correction process can be performed, the inclination correction unit calculates the inclination of the document image based on information indicating the position of the boundary between the document image and the background image in the read image. An image reading apparatus which performs correction. Image reading means for reading an image formed on a document;
Document front and rear edge detection means for detecting the leading edge and the trailing edge of the document in the sub-scanning direction of reading by the image reading means;
A tilt correction unit that performs tilt correction of a document image in a read image of a document obtained by reading by the image reading unit based on a designation of a reading area ;
A length in the sub-scanning direction of the read image, the document on the basis of a detection result detected by the front and rear end detecting means, whether or not perform the inclination correction processing for correcting the inclination of the document image of the read in image A judging means for judging,
In the case where the length of the read image along the sub-scanning direction is shorter than the length of the original obtained from the leading edge and the trailing edge of the original detected by the original front and rear edge detecting means, An image reading apparatus that determines that the tilt correction processing cannot be performed and determines that the tilt correction processing can be performed if the tilt correction processing is not short. Differential information acquisition means for differentiating the pixel value of each pixel included in the read image in the sub-scanning direction to acquire differential information;
Boundary coordinate information acquisition means for acquiring boundary coordinate information indicating the position of the boundary between the document image and the background image in the read image based on the differential information,
The image reading apparatus according to claim 9, wherein the inclination correction unit corrects an inclination of the document image based on the boundary coordinate information. Based on an image reading unit that reads an image formed on a document, a document front and rear edge detection unit that detects a leading edge and a trailing edge of the document in a sub-scanning direction of reading by the image reading unit, and a reading area designation An image reading apparatus comprising an original size detecting means for detecting the size of an original using a read image of the original obtained by reading by the image reading means, wherein the image reading method reads an image of the original,
Wherein the length in the sub-scanning direction of the read image, based on a detection result detected by the document longitudinal end detecting means, step determination of determining whether perform a document size detection process for detecting the size of the document When,
When it is determined in the determination step that the document size detection process can be performed, the document size detection unit determines the size of the document based on information indicating the position of the boundary between the document image and the background image in the read image. A document size detection process for detecting
An image reading method comprising: Based on an image reading unit that reads an image formed on a document, a document front and rear edge detection unit that detects a leading edge and a trailing edge of the document in a sub-scanning direction of reading by the image reading unit, and a reading area designation An image reading apparatus comprising an inclination correction unit that performs inclination correction of an original image in a read image of an original obtained by reading by the image reading unit, the image reading method when reading an image of the original,
A length in the sub-scanning direction of the read image, the document on the basis of a detection result detected by the front and rear end detecting means, whether or not perform the inclination correction processing for correcting the inclination of the document image of the read in image A judging process for judging;
If it is determined in the determining step that the tilt correction process can be performed, the tilt correction unit determines the tilt of the document image based on information indicating the position of the boundary between the document image and the background image in the read image. An inclination correction process to be corrected;
An image reading method comprising:   The program for making a computer perform each process in the image reading method of Claim 12 or 13. An image reading system comprising an image reading device for reading an image of a document and a computer connected to the image reading device,
An image reading means provided in the image reading device for reading an image formed on a document;
A document front / rear edge detection unit that is provided in the image reading device and detects a leading edge and a trailing edge of the document in a sub-scanning direction of reading by the image reading unit;
A document size detection unit that detects a size of a document using a read image of the document obtained by reading by the image reading unit based on a designation of a reading region, the document being a read image obtained from the image reading device. ,
A length in the sub-scanning direction of the read image, the document on the basis of a detection result detected by the front and rear end detecting means, determining means for determining whether perform a document size detection process for detecting the size of the document And
When the determination unit determines that the document size detection process can be performed, the document size detection unit determines the size of the document based on information indicating the position of the boundary between the document image and the background image in the read image. An image reading system characterized by detecting the above. An image reading system comprising an image reading device for reading an image of a document and a computer connected to the image reading device,
An image reading means provided in the image reading device for reading an image formed on a document;
A document front / rear edge detection unit that is provided in the image reading device and detects a leading edge and a trailing edge of the document in a sub-scanning direction of reading by the image reading unit;
A tilt correction unit that performs tilt correction of a document image in a read image of a document obtained by reading by the image reading unit based on a designation of a reading area ;
A length in the sub-scanning direction of the read image, the document on the basis of a detection result detected by the front and rear end detecting means, whether or not perform the inclination correction processing for correcting the inclination of the document image of the read in image A judging means for judging,
When the determination unit determines that the inclination correction process can be performed, the inclination correction unit calculates the inclination of the document image based on information indicating the position of the boundary between the document image and the background image in the read image. An image reading system characterized by correcting.

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