JP2016192678A - Image reading device and image reading method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reading device capable of suppressing the reduction in quality of an output image.SOLUTION: An image reading device includes a tilt angle detection unit 81a, a rotation correction processing unit 82 and a determination unit 83a. The tilt angle detection unit 81a detects a tilt angle of an image read by a reading unit. The rotation correction processing unit 82 executes rotation correction processing on image data corresponding to an image read by the reading unit in accordance with the tilt angle detected by the tilt angle detection unit 81a. The determination unit 83a determines whether the rotation correction processing is approved or not approved on the basis of the tilt angle detected by the tilt angle detection unit 81a.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image reading apparatus and an image reading method.

  An image reading apparatus such as a scanner is known. Also, a scanner (image reading device) provided with a document conveying device is known. The document conveying device automatically conveys the document so as to pass through the document reading area. When the original is conveyed in an inclined state by the original conveying device, the image of the original is read in an inclined state. For this reason, a scanner (image reading device) generally detects an inclination angle of an image from image data of a read image, and performs a rotation correction process (referred to as skew correction or oblique correction) on the image data ( Image processing) is executed (see, for example, Patent Document 1).

  Specifically, the rotation correction process is a process of rotating an image (image data) on the storage area. For the rotation correction process, a rotation process using a nearest neighbor interpolation method or a bilinear interpolation method is typically employed.

JP-A-10-336425

  However, when the rotation process using the nearest neighbor interpolation method or the bilinear interpolation method is executed, the data at the edge portions (particularly, the four corners) of the image may change before and after the rotation process. For this reason, the quality of an output image such as an image displayed (output) on a display or an image printed (output) on a recording medium may deteriorate.

  In view of the above problems, an object of the present invention is to provide an image reading apparatus and an image reading method capable of suppressing deterioration in quality of an output image.

  One aspect of the present invention is an image reading apparatus including a reading unit, an inclination angle detection unit, a rotation correction processing unit, and a determination unit. The reading unit reads an image of a document. The inclination angle detection unit detects an inclination angle of the image read by the reading unit. The rotation correction processing unit performs rotation correction processing on image data corresponding to the image according to the tilt angle detected by the tilt angle detection unit. The determination unit determines permission / non-permission of the rotation correction process based on the tilt angle detected by the tilt angle detection unit.

  According to the present invention, it is possible to suppress a decrease in quality of an output image.

1 is a perspective view illustrating an appearance of a scanner according to an embodiment of the present invention. It is a figure which shows the structure of the scanner which concerns on embodiment of this invention. It is a figure which shows the structure of the control part with which the scanner which concerns on 1st Embodiment-3rd Embodiment of this invention is provided. It is a figure which shows the original image area | region which concerns on embodiment of this invention. It is a figure which shows the flow of the rotation correction process which concerns on 1st Embodiment of this invention. It is a figure which shows the original image area | region which concerns on embodiment of this invention. It is a figure which shows the original image area | region which concerns on embodiment of this invention. It is a figure which shows the flow of the rotation correction process which concerns on 2nd Embodiment of this invention. It is a figure which shows the original image area | region which concerns on embodiment of this invention. It is a figure which shows the structure of the control part with which the scanner which concerns on 4th Embodiment of this invention is provided.

[First Embodiment]
As shown in FIG. 1, a scanner 1 (an example of an image reading device) includes a main body unit 2, a document conveying device 3 that can be opened and closed with respect to the main body unit 2, an operation display unit 4, a main contact glass 5, Sub contact glass 6 is provided. The operation display unit 4 includes an operation unit 41 and a display unit 42. The operation unit 41 includes, for example, a plurality of types of push buttons (keys). The display unit 42 includes, for example, a liquid crystal display.

  As shown in FIG. 2, the document conveying device 3 includes a paper feed tray 31 and a paper discharge tray 32. The document transport device 3 transports the document set on the paper feed tray 31 to the paper discharge tray 32. In this conveyance process, the document passes through the document reading area R. The document reading region R is a region where the sub contact glass 6 (see FIG. 1) is provided.

  The scanner 1 includes a reading unit 7. The reading unit 7 reads an image of a document. The scanner 1 includes a control unit 8. The control unit 8 is a computer having an arithmetic processing device such as a CPU or MPU. The control unit 8 controls the operation of the scanner 1. In addition, the control unit 8 executes various image processing (including correction processing) on the image data of the image read by the reading unit 7.

  The reading unit 7 includes an imaging device 75 including a light source unit 71, two mirrors 72 and 73, a condenser lens 74, and an imaging device such as a charge coupled device. The light source unit 71 includes an LED light source 711 and a mirror 712. The LED light source 711 includes a large number of white LEDs arranged along the main scanning direction (the depth direction in FIG. 2). By selecting the white LED to emit light, the image reading range in the main scanning direction can be adjusted. Further, by controlling the light emission time of the LED light source 711 (white LED), the image reading range in the sub-scanning direction S orthogonal to the main scanning direction can be adjusted. In the first embodiment, the image reading range is set larger than the document size. However, the main scanning direction is set to be larger than the document size, up to the width of the LED light source 711 in the main scanning direction.

  When the reading unit 7 reads an image of a document transported by the document transport device 3, the LED light source 711 irradiates the document being transported through the sub contact glass 6. The light reflected from the document enters the imaging device 75 via the three mirrors 712, 72, 73 and the condenser lens 74. The imaging device 75 inputs an electrical signal corresponding to the amount of incident light received into the control unit 8. The control unit 8 generates image data based on the output of the imaging device 75. The electrical signal output from the imaging device 75 corresponds to the density value or luminance value of each pixel constituting the image data.

  As illustrated in FIG. 3, the control unit 8 includes a storage unit 84. The storage unit 84 can include a ROM, a RAM, an EEPROM, and the like. The control unit 8 causes the storage unit 84 to store the image data of the image read by the reading unit 7. The control unit 8 reads the image data from the storage unit 84 and stores the image data after the image processing in the storage unit 84 every time various image processing is performed on the image data.

  In the first embodiment, the control unit 8 functions as an inclination angle detection unit 81a, a rotation correction processing unit 82, and a determination unit 83a by executing a program stored in the storage unit 84.

  The inclination angle detection unit 81a detects the inclination angle of the image read by the reading unit 7. The rotation correction processing unit 82 executes rotation correction processing on the image data according to the tilt angle detected by the tilt angle detection unit 81a. For the rotation correction process, a general rotation processing technique such as nearest neighbor interpolation or bilinear interpolation can be used.

  The determination unit 83a determines permission / non-permission of the rotation correction process based on the tilt angle detected by the tilt angle detection unit 81a. In the first embodiment, the determination unit 83a compares the inclination angle detected by the inclination angle detection unit 81a with a threshold value. Then, the determination unit 83a determines permission / non-permission of the rotation correction process according to the comparison result between the tilt angle and the threshold value. Specifically, the determination unit 83a determines permission / non-permission of the rotation correction process depending on whether or not the inclination angle is equal to or greater than a threshold value.

  As shown in FIG. 4, the document image area 51 may be inclined with respect to the X direction and the Y direction orthogonal to the X direction. The document image area 51 is an area for storing image data of an image read by the reading unit 7. The X direction corresponds to the main scanning direction or the sub scanning direction. The Y direction corresponds to the sub-scanning direction or the main scanning direction. For example, when the original is conveyed in an inclined state by the original conveying device 3, the original image area 51 is inclined with respect to the X direction and the Y direction according to the inclination.

  The tilt angle detection unit 81 a detects the tilt angle of the edge of the image read by the reading unit 7. Specifically, the tilt angle detector 81 a detects the tilt angle of the edge of the document image area 51. For example, the tilt angle detection unit 81a detects the tilt angle θ1 of the front end e1 of the document image area 51. When detecting the inclination angle θ1 of the front edge e1 of the document image area 51, the inclination angle detection unit 81a sets the coordinates in the storage area of a plurality of pixels selected from the pixels constituting the front edge e1 of the document image area 51, respectively. To detect. Then, the tilt angle detection unit 81a detects (calculates) the tilt angle θ1 of the front end e1 with respect to the X direction based on the detected coordinates.

  Note that the tilt angle detection unit 81a may detect the tilt angle of the left end e2 or the right end e3 of the document image region 51 with respect to the Y direction. Alternatively, the tilt angle detection unit 81a may detect the tilt angle of the trailing edge e4 of the document image area 51 with respect to the X direction.

  Next, a rotation correction process (image reading method) in the first embodiment will be described with reference to FIGS. The process shown in FIG. 5 starts when the user sets an original on the paper feed tray 31 and then operates the operation unit 41 to instruct image reading.

  When the control unit 8 receives an image reading instruction from the user, the document conveying device 3 conveys the document, and the reading unit 7 reads the image of the document (step S601). As a result, image data corresponding to the original image is stored in the storage unit 84. When the image data is stored in the storage unit 84, the tilt angle detection unit 81a detects the tilt angle of a specific end of the document image area 51 (step S602a). The target end for detecting the tilt angle is stored (set) in the storage unit 84 in advance.

  Next, the determination unit 83a determines whether or not the tilt angle detected by the tilt angle detection unit 81a is equal to or greater than a threshold value (step S603). The threshold value is stored (set) in the storage unit 84 in advance. The threshold value may be set by the user operating the operation unit 41.

  When the determination unit 83a determines that the tilt angle is equal to or greater than the threshold value, the determination unit 83a determines permission of the rotation correction processing by the rotation correction processing unit 82. As a result, the rotation correction processing unit 82 executes rotation correction processing on the image data to be processed, and the processing shown in FIG. 5 ends. On the other hand, when the determination unit 83a determines that the tilt angle is less than the threshold value, the determination unit 83a determines that the rotation correction processing by the rotation correction processing unit 82 is not permitted. In this case, the process illustrated in FIG. 5 ends without executing the rotation correction process.

  According to the first embodiment described above, the rotation correction process is executed only when the inclination angle of the image read by the reading unit 7 is equal to or larger than the threshold value. In other words, when the inclination angle of the image read by the reading unit 7 is less than the threshold value, the rotation correction process is not executed. Therefore, execution of the rotation correction process can be restricted. As a result, the frequency with which low quality output images are generated is reduced. Therefore, it is possible to suppress a decrease in the quality of the output image.

  The inclination angle stored in advance in the storage unit 84 as the threshold value is preferably an inclination angle that does not bother the user about the inclination of the image. For example, the threshold is 0.2 degrees. In this case, the rotation correction process is not executed for an image tilted at an angle of less than 0.2 degrees. However, if the tilt is less than 0.2 degrees, the user does not notice the tilt of the image, or the image I don't mind the inclination of

  According to the first embodiment, the image reading range of the reading unit 7 is set larger than the document size. Thereby, the inclination angle of the edge of the image (the edge of the document image area 51) can be detected more reliably.

  Further, according to the first embodiment, the inclination angle of the edge of the image (the edge of the document image area 51) is detected. As a result, the amount of calculation by the control unit 8 is reduced as compared with the case where the inclination angle of the entire image (the entire original image area 51) is detected.

[Second Embodiment]
Hereinafter, the second embodiment will be described with reference to FIG. 3 and FIGS. 6 to 8. However, items different from the first embodiment will be described, and descriptions of the same items as the first embodiment will be omitted.

  The control unit 8 in the second embodiment functions as an inclination angle detection unit 81b, a rotation correction processing unit 82, and a determination unit 83b by executing a program stored in the storage unit 84.

  The inclination angle detection unit 81b detects the inclination angles of the left end e2 and right end e3 (the left end and right end of the image) of the document image area 51. The determination unit 83b compares the inclination angles θ2 and θ3 of the left end e2 and the right end e3 (the left end and the right end of the image) of the document image area 51. In addition, the determination unit 83b determines whether the rotation correction process is permitted or not according to the comparison result between the inclination angle θ2 and the inclination angle θ3 and the comparison result between the inclination angle θ2 or the inclination angle θ3 and the threshold value. Specifically, the determination unit 83b determines whether or not the inclination angle θ2 and the inclination angle θ3 match. Further, the determination unit 83b permits the execution of the rotation correction process when the inclination angle θ2 and the inclination angle θ3 match and the inclination angle θ2 or the inclination angle θ3 is equal to or greater than a threshold value. In other words, when the inclination angles θ2 and θ3 of the left end e2 and the right end e3 of the document image area 51 do not match, the rotation correction process is not executed.

  That is, as shown in FIG. 6, when the shape of the document image is a shape other than a rectangle, the inclination angles θ2 and θ3 of the left end e2 and the right end e3 of the document image area 51 do not match. The rotation correction process for the image data of the image having such a shape may cause a reduction in the quality of the output image. On the other hand, as shown in FIG. 7, when the shape of the document image is a rectangle, the inclination angles θ1, θ2, and θ3 of the front end e1, the left end e2, and the right end e3 of the document image area 51 are equal or substantially the same. Match. When rotation correction processing is performed on image data of an image having a rectangular shape, the possibility that the quality of the output image will be lower is lower than when rotation correction processing is performed on image data of an image having a shape other than a rectangle. . Therefore, by executing the rotation correction process on the condition that the inclination angles θ2 and θ3 of the left end e2 and the right end e3 of the document image area 51 coincide with each other, it is possible to suppress a decrease in the quality of the output image.

  Next, the rotation correction process (image reading method) in the second embodiment will be described with reference to FIGS. 3 and 6 to 8. As shown in FIG. 8, in the second embodiment, when the reading unit 7 reads an image of a document (step S601), the tilt angle detection unit 81b detects the tilt angles θ2 of the left end e2 and the right end e3 of the document image region 51, and θ3 is detected (step S602b).

  Next, the determination unit 83b compares the inclination angle θ2 and the inclination angle θ3, and determines whether or not the inclination angle θ2 and the inclination angle θ3 match (step S701). If the determination unit 83b determines that the inclination angle θ2 and the inclination angle θ3 coincide with each other, the determination unit 83b determines whether the inclination angle θ2 or the inclination angle θ3 is equal to or greater than a threshold value (step S603). On the other hand, when the determination unit 83b determines that the inclination angle θ2 and the inclination angle θ3 do not match, the determination unit 83b determines that the rotation correction processing by the rotation correction processing unit 82 is not permitted. In this case, the process illustrated in FIG. 8 ends without executing the rotation correction process. Note that the order of step S701 and step S603 can be interchanged.

  According to the second embodiment described above, the rotation correction process is executed on condition that the inclination angles θ2 and θ3 of the left end e2 and the right end e3 of the document image area 51 are the same. As a result, deterioration of the quality of the output image is suppressed.

  In the second embodiment, it is determined whether or not the inclination angles θ2 and θ3 of the left end e2 and the right end e3 (the left end and the right end of the image) of the document image area 51 match, but the inclination angle θ2 and the inclination angle θ3 are determined. It may be determined whether or not the difference is within the allowable range. Specifically, the determination unit 83b compares the inclination angle θ2 and the inclination angle θ3, calculates the difference between the inclination angle θ2 and the inclination angle θ3, and the difference between the inclination angle θ2 and the inclination angle θ3 is an allowable value. It may be determined whether it is within the range. In this case, one of the conditions for executing the rotation correction process is that the difference between the tilt angle θ2 and the tilt angle θ3 is within the allowable value range.

[Third Embodiment]
Hereinafter, the third embodiment will be described with reference to FIGS. 3 and 9. However, matters different from the first embodiment and the second embodiment will be described, and descriptions of the same matters as the first embodiment and the second embodiment will be omitted.

  The control unit 8 in the third embodiment functions as an inclination angle detection unit 81c, a rotation correction processing unit 82, and a determination unit 83c by executing a program stored in the storage unit 84.

  The inclination angle detection unit 81c detects the inclination angles of the front edge e1, the left edge e2, and the right edge e3 (the front edge, the left edge, and the right edge of the image) of the document image area 51. The determination unit 83c compares the inclination angles θ1, θ2, and θ3 of the front end e1, the left end e2, and the right end e3 (the front end, the left end, and the right end of the image) of the document image area 51. Further, the determination unit 83c determines whether the rotation correction process is permitted or not according to the comparison result of the inclination angles θ1, θ2, and θ3 and the comparison result of the inclination angles θ1, θ2, or θ3 and the threshold value. . Specifically, the determination unit 83c determines whether the inclination angles θ1, θ2, and θ3 match. The determination unit 83c permits the rotation correction process to be executed when the tilt angles θ1, θ2, and θ3 match and the tilt angles θ1, θ2, or θ3 are equal to or greater than the threshold value. In other words, when the tilt angles θ1, θ2, and θ3 of the front end e1, the left end e2, and the right end e3 of the document image area 51 do not match, the rotation correction process is not executed.

  That is, as shown in FIG. 9, the left end e2 and the right end e3 of the document image area 51 may not be inclined with respect to the Y direction, while the front end e1 of the document image area 51 may be inclined with respect to the X direction. If rotation correction processing is executed in such a case, the quality of the output image may be degraded. On the other hand, as described with reference to FIG. 7, when the shape of the document image region 51 is a rectangle, the inclination angles θ1, θ2, and θ3 of the front end e1, the left end e2, and the right end e3 of the document image region 51 coincide. Or approximately match. Therefore, by performing the rotation correction process on the condition that the inclination angles θ1, θ2, and θ3 of the front end e1, the left end e2, and the right end e3 of the document image area 51 coincide with each other, a reduction in the quality of the output image is suppressed. be able to.

  According to the third embodiment described above, the rotation correction process is executed on the condition that the inclination angles θ1, θ2, and θ3 of the front end e1, the left end e2, and the right end e3 of the document image area 51 coincide with each other. . As a result, deterioration of the quality of the output image is suppressed.

  In the third embodiment, it is determined whether or not the inclination angles θ1, θ2, and θ3 of the front end e1, the left end e2, and the right end e3 (the front end, the left end, and the right end of the image) of the document image area 51 match. However, it may be determined whether or not the difference between the tilt angles θ1, θ2, and θ3 is within the allowable value range. For example, the determination unit 83c compares the tilt angle θ1 and the tilt angle θ2, calculates the difference between the tilt angle θ1 and the tilt angle θ2, and the difference between the tilt angle θ1 and the tilt angle θ2 is within the allowable range. It is determined whether or not. Further, the determination unit 83c compares the tilt angle θ1 and the tilt angle θ3 to calculate the difference between the tilt angle θ1 and the tilt angle θ3, and the difference between the tilt angle θ1 and the tilt angle θ3 is within the allowable range. It is determined whether or not. In this case, one of the conditions for executing the rotation correction process is that the difference between the inclination angle θ1 and the inclination angle θ2 and the difference between the inclination angle θ1 and the inclination angle θ3 are both within the allowable range.

[Fourth Embodiment]
Hereinafter, the fourth embodiment will be described with reference to FIG. However, matters different from the first embodiment to the third embodiment will be described, and description of the same matters as the first embodiment to the third embodiment will be omitted.

  The control unit 8 in the fourth embodiment functions as an inclination angle detection unit 81c, a rotation correction processing unit 82, a determination unit 83c, and a warning processing unit 85 by executing a program stored in the storage unit 84.

  The warning processing unit 85 causes the display unit 42 to display warning information based on the tilt angles θ1, θ2, and θ3 detected by the tilt angle detection unit 81c. In the fourth embodiment, the warning processing unit 85 determines whether only the front end e1 of the document image area 51 is tilted based on the tilt angles θ1, θ2, and θ3 detected by the tilt angle detecting unit 81c. . For example, the warning processing unit 85 determines whether only the front end e1 of the document image area 51 is tilted based on whether the tilt angles θ1, θ2, and θ3 are within the allowable range. Further, the warning processing unit 85 counts the number of consecutive times when it is determined that only the front end e1 of the document image area 51 is tilted. The warning processing unit 85 displays warning information on the display unit 42 when the count value exceeds a predetermined value. Specifically, the warning processing unit 85 causes the display unit 42 to display information that teaches that the document conveying device 3 is installed in an inclined state with respect to the main body unit 2.

  That is, in the case where the left end e2 and the right end e3 are not tilted as in the document image area 51 (image) described with reference to FIG. It may be installed in a tilted state. For this reason, in such a case, a tilted image is always output. On the other hand, according to the fourth embodiment, information indicating that the document conveying device 3 is installed in a tilted state with respect to the main body unit 2 is displayed on the display unit 42, whereby the tilted state is displayed. It is possible to eliminate the problem that images are always output.

  In the second to fourth embodiments, the inclination angle θ1 of the front end e1 (the leading end of the image) of the document image area 51 is detected. However, the present invention is not limited to this. In the second to fourth embodiments, instead of the tilt angle θ1, the tilt angle of the trailing edge e4 (the trailing edge of the image) of the document image area 51 may be detected.

  In the above-described embodiment, the embodiment in which the present invention is applied to the scanner 1 has been described. However, the present invention is not applied only to the scanner. The present invention may include an image forming apparatus having an image reading function such as a multifunction peripheral (MFP).

  The present invention is useful for an electronic apparatus having an image reading function.

DESCRIPTION OF SYMBOLS 1 Scanner 3 Document conveying apparatus 7 Reading part 8 Control part 81a-81c Inclination angle detection part 82 Rotation correction process part 83a-83c Determination part 84 Memory | storage part

Claims (8)

A reading unit for reading an image of a document;
An inclination angle detection unit for detecting an inclination angle of the image read by the reading unit;
A rotation correction processing unit that executes rotation correction processing on image data corresponding to the image according to the tilt angle detected by the tilt angle detection unit;
An image reading apparatus comprising: a determination unit that determines permission / non-permission of the rotation correction process based on the tilt angle detected by the tilt angle detection unit.   The image reading apparatus according to claim 1, wherein the determination unit determines whether the rotation correction process is permitted or not according to a comparison result between the tilt angle detected by the tilt angle detection unit and a threshold value.   The image reading apparatus according to claim 1, wherein the inclination angle detection unit detects an inclination angle of an edge of the image read by the reading unit. The inclination angle detection unit detects an inclination angle of at least two of the edges of the image;
The determination unit performs the rotation correction process according to the comparison result of the tilt angle detected by the tilt angle detection unit and the comparison result of the tilt angle detected by the tilt angle detection unit and a threshold value. The image reading apparatus according to claim 3, wherein permission / denial is determined. A display unit;
The image reading apparatus according to claim 1, further comprising: a warning processing unit that displays warning information on the display unit based on the tilt angle detected by the tilt angle detection unit. .   The image reading apparatus according to claim 1, wherein a reading range larger than the image of the original is set when the reading unit reads the image of the original. A document conveying device for conveying the document;
The image reading apparatus according to claim 1, wherein the reading unit reads an image of the document conveyed by the document conveying device. Scanning the image of the document;
Detecting a tilt angle of the image;
Determining permission / denial of rotation correction processing based on the tilt angle;
And a step of executing rotation correction processing on image data corresponding to the image in accordance with the tilt angle when the rotation correction processing is permitted.

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