JP5376907B2 - Image reading apparatus and image processing method - Google Patents

Description

The present invention relates to an image reading apparatus and an image processing method for obtaining a skew amount of a document and correcting an inclination of a read image of the document .

  In the image reading device, a document is transported one page at a time on a platen glass by a document transport device, and an image of the document is read by exposing the document being transported by an exposure device fixed to the transport path. What performs “reading” is known (for example, see Patent Document 1).

  In addition, there is known a technique in which two image reading devices are provided to improve productivity and the front and back of a document are read by one conveyance (for example, see Patent Document 2).

Here, a technique has been proposed for detecting the skew amount of the conveyed document from the read image in the “flow-reading” type image reading apparatus. Specifically, a technique for detecting the boundary line between the background color and the original color (for example, see Patent Document 3) and a technique for detecting a shadow at the leading edge of the original when reading the original (for example, see Patent Document 4) are proposed. Has been.
JP 2001-285595 A JP 2004-187144 A JP 2005-39620 A JP 2003-319160 A

  However, since the technique described in Patent Document 3 detects the boundary between the document color and the background color (or shadow), the skew amount of the document is detected when the leading edge of the document is similar to the background color (or shadow). Cannot be detected.

  In other words, even if the document is white, if the document has a color at the leading edge (documents with borderless printing, document smudges, etc.), the skew amount of the document cannot be detected or an incorrect skew amount is detected. There is a possibility.

  An example in which the skew amount of the document cannot be detected correctly will be described.

  FIG. 5 is a diagram illustrating an image when a document with a gray platen roller and a dirty tip is read.

  For this image, the reading level at a predetermined location in the main scanning direction is sampled for each sub-scanning line. FIG. 6 is a diagram illustrating a result of sampling an image at main scanning positions (1), (2), (3), (4), and (5).

  It is determined that the sub-scanning position where the reading level exceeds a certain value (TH in the drawing) is the document leading edge at each main scanning position. The document leading edge at the main scanning position (1) is A, the document leading edge at the main scanning position (2) is B, the document leading edge at the main scanning position (3) is C, the document leading edge at the main scanning position (4) is D, and main scanning. The leading edge of the document at position (5) is E.

  In a portion where the document leading edge is dirty, the original reading level of the document leading edge is lowered due to the contamination. The correct document leading edge position cannot be detected. Since the skew amount of the document is calculated from the position of the leading edge of the document, the skew amount of the document cannot be detected correctly.

An object of the present invention, by obtaining a suitable amount of skew to assess whether the correctly detect the skew amount of the original conveyed by the conveyance means, it possible to perform an accurate skew correction An image reading apparatus and an image processing method are provided.

In order to achieve the above object, the image reading apparatus according to claim 1 is an image reading apparatus that calculates a skew amount of a document and corrects a tilt of a read image of the document, and includes a transport unit that transports the document. A first image reading unit that reads one side of the document conveyed by the conveying unit, a second image reading unit that reads the other side of the document, and an output from the first image reading unit A plurality of points at the edge of the document corresponding to a plurality of main scanning positions set at equal intervals in the main scanning direction are detected from the read data , and the first detection result of the plurality of points is used to detect the document. From the first skew amount detecting means for detecting the first skew amount and the read data output from the second image reading means, a plurality of main scanning positions set at equal intervals in the main scanning direction are obtained. corresponding, put on an end portion of the document A second skew amount detecting means for detecting a plurality of points and detecting a second skew amount of the document from a second detection result of the plurality of points; and a first calculating a variation of the first detection result. One of the calculation means, the second calculation means for calculating the variation of the second detection result, the variation of the first detection result, and the variation of the second detection result. A skew amount setting means for selecting the first skew amount or the second skew amount as the skew amount for correcting the inclination is provided.

According to the present invention, the first detection result of a plurality of points at the end of one side of the document and the second detection result of a plurality of points at the end of the other side of the document Select the skew amount or the second skew amount. According to the present invention, it is possible to select a skew amount as a measure for evaluating whether or not the skew amount of a document is correctly detected based on variations in detection results detected as a plurality of points at the edge of the document. Therefore, according to the onset bright, it is possible to determine the appropriate amount of skew, it is possible to perform an accurate skew correction.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram of an image reading apparatus according to an embodiment of the present invention.

  In FIG. 1, the image reading apparatus includes a document conveying device 100 and a main body 115.

  In document feeder 100, document tray 101 stacks documents 102 (hereinafter simply referred to as documents). A paper feed roller 103 is provided above the document tray 101. The paper feed roller 103 is connected to the same drive source as the separation conveyance roller 104 and rotates with the rotation to feed the original.

  The paper feed roller 103 is normally retracted to the upper position, which is the home position, so that the document setting operation is not hindered. When the paper feeding operation is started, the paper feeding roller 103 descends and comes into contact with the upper surface of the document. Since the paper feed roller 103 is pivotally supported by an arm (not shown), it moves up and down as the arm swings.

  The separation conveyance driven roller 105 is disposed on the side opposite to the separation conveyance roller 104 and is pressed toward the separation conveyance roller 104 side. The separation conveyance driven roller 105 is formed of a rubber material or the like that is slightly less frictioned than the separation conveyance roller 104, and cooperates with the separation conveyance roller 104 to feed originals fed by the paper feed roller 103 one by one. Paper is fed.

  The registration roller pair (registration roller 106 and registration driven roller 107) aligns the leading ends of the documents fed by the separation unit, and abuts the leading ends of the separated documents toward the nip portion of the stationary registration roller pair. Then, make a loop in the document and align the tips.

  The lead roller 108 and the lead driven roller 109 convey the original toward the flow reading glass 116 of the main body 115. A platen roller 110 is disposed on the opposite side of the flow reading glass 116.

  At this time, image information on the surface of the document passing on the flow reading glass 116 is read by the CCD line sensor 126.

  Here, the flow-reading glass 116 and the CCD line sensor 126 function as a first image reading unit that reads one side of a document conveyed by the conveyance unit (document conveying apparatus 100).

  When the reading of the surface image of the document by the CCD line sensor 126 is completed, the lead discharge roller 111 and the lead discharge driven roller 112 convey the document to the CIS line sensor 128 side.

  The jump stand 117 is for scooping up the original from the flow reading glass 116. A platen roller 127 is disposed on the opposite side of the CIS line sensor 128.

  At this time, the CIS line sensor 128 reads image information on the back side of the document passing on the flow reading glass 129.

  Here, the flow reading glass 129 and the CIS line sensor 128 function as a second image reading unit that reads the other side of the document.

  When the CIS line sensor 128 finishes reading the back side image of the original, the paper discharge roller 113 discharges the original to the paper discharge tray 114.

  The main body 115 includes a lamp 119 that irradiates light on the surface of the original to be read, and mirrors 120, 121, and 122 that guide reflected light from the original to the lens 125 and the CCD line sensor 126. The lamp 119 and the mirror 120 are attached to the first mirror base 123. The mirrors 121 and 122 are attached to the second mirror base 124.

  The mirror tables 123 and 124 are coupled to a drive motor (not shown) by wires (not shown), and move parallel to the document table glass 118 by the rotation of the drive motor.

  The reflected light from the document is guided to the lens 125 through the mirrors 120, 121, and 122, and is imaged on the light receiving portion of the CCD line sensor 126 by the lens 125. The CCD line sensor 126 photoelectrically converts the formed reflected light with a light receiving element, and outputs an electrical signal corresponding to the amount of incident light.

  Similarly, the CIS line sensor 128 photoelectrically converts the reflected light from the original with a light receiving element and outputs an electrical signal corresponding to the amount of incident light.

  In order to further improve productivity, the registration roller 106 and the registration driven roller 107 are omitted from the above configuration, and the first image reading unit and the second image reading unit do not align the leading edge of the document, and the image information of the document. A configuration for reading is also known.

  At this time, since the image information is read without aligning the leading edge of the document, the document may be skewed in the process of passing through the flow reading glasses 116 and 129, and the document front image and the document back image are inclined. May be read.

  For this reason, as described above, a technique is known in which the skew amount of a conveyed document is detected from a read image and the inclination of the image is corrected using the result.

  A method for detecting the boundary line between the background color and the document color from the read image and detecting the skew amount of the conveyed document will be described.

  FIG. 2 is a diagram showing an image when a platen roller in FIG. 1 is read in a gray and white skewed document.

  For this image, the reading level at a predetermined position in the main scanning direction (in FIG. 2, the main scanning positions (1), (2), (3), (4), and (5)) are set for each sub-scanning line. To sample.

  FIG. 3 is a diagram illustrating image reading levels at main scanning positions (1), (2), (3), (4), and (5).

  A sub-scanning position where the reading level exceeds a certain value (TH in FIG. 3) is determined to be the leading edge of the document at each main scanning position. The document leading edge at the main scanning position (1) is A, the document leading edge at the main scanning position (2) is B, the document leading edge at the main scanning position (3) is C, the document leading edge at the main scanning position (4) is D, and main scanning. The leading edge of the document at position (5) is E. When the original is tilted as shown in FIG. 2, the position of the front end of the original differs at each main scanning position.

  Using these main scanning positions (1), (2), (3), (4), and (5) at the leading edge of the document and the document leading edges A, B, C, D, and E at the respective main scanning positions, the platen roller 110 is used. And the document boundary line can be calculated to determine the document inclination.

  Next, based on the detection results of the skew amount detecting means on the front surface and the skew amount detecting means on the back surface, which are the features of the present invention, the skew in the reading means (first and second image reading means) on the front surface and back surface of the document. The control of the skew correction amount determining means for determining the correction amount will be described.

  FIG. 4 is a flowchart showing a procedure of skew correction amount determination processing executed by the image reading apparatus of FIG.

  The main body 115 (a control unit not shown) calculates the skew amount (skew correction amount) θ1 of the front surface after conveying the original document through the front surface scanning glass 116 and the back surface scanning glass 129, and similarly. The back surface skew amount (skew correction amount) θ2 is calculated (detected) (step S401). Since the method of calculating the skew amount is the same as the conventional method, a detailed description is omitted.

  Subsequently, the main body 115 calculates the difference between the calculated skew amount θ1 on the front surface and the skew amount θ2 on the back surface. At this time, if the difference between θ1 and θ2 is less than the set value θ (for example, less than 0.1 °), the main body 115 determines that the skew amount of the document can be correctly detected on both the front and back surfaces (step S402). ). Then, the main body 115 sets the average value of the two skew amounts as the skew correction amount for each of the front surface and the back surface (step S409).

  In step S402, if the difference between the skew amounts θ1 and θ2 is equal to or larger than the set value θ, either the front skew amount or the reverse skew amount is not correctly detected.

  A method for determining which is correctly detected will be described below.

  FIG. 3 is a diagram showing the image reading level every sub-scanning line at a predetermined main scanning position as described above.

  Usually, the predetermined main scanning positions are set at equal intervals. That is, if the document end is correctly detected at each main scanning position, the interval between the adjacent main scanning positions is the same. Therefore, considering that the leading end of the document is a straight line, each adjacent main scanning position is The document edge intervals S1, S2, S3, and S4 in FIG.

  S1, S2, S3, and S4 are obtained by the following calculation.

S1 = (B−A), S2 = (C−B), S3 = (D−C), S4 = (E−D)
When a color similar to the background color (or shadow) is attached to the leading edge of the document, the leading edge of the document cannot be detected correctly, and variations in the document edge intervals S1, S2, S3, and S4 at the adjacent main scanning positions are different. It becomes larger (see FIG. 6).

  That is, it is possible to determine whether or not the detected skew feeding amount is correct by calculating the variation in the interval between the document edges at the adjacent main scanning positions.

  A value indicating variation in the distance between the document edges at each adjacent main scanning position is obtained by the following equation.

  Therefore, in the case of this embodiment,

  It becomes.

  The main body 115 sets V1 as the variation in the interval between the document edges at each adjacent main scanning position obtained on the front surface, and V2 as the variation in the interval between the document edges at each adjacent main scanning position obtained on the back surface (step S403). ).

V1, V2 (if not V1 <set value V or V2 <set value V) are both a large variation in which was if the body 115, the surface is determined not to be detected backside together correctly skew amount ( Step S404). Since the main body 115 does not perform the skew correction of the front and back surfaces, the skew correction amount is set to 0 (step S406).

  If at least one of V1 and V2 is less than the set value V (step S404) and V1 <V2 (step S405), the process proceeds to step S407. In step S407, the main body 115 determines that the skew amount calculated on the back surface is not correct, and sets the skew correction amount on the front and back surfaces to θ1 calculated from the front surface.

  If at least one of V1 and V2 is less than the set value V (step S404) and V1 <V2 is not satisfied (step S405), the process proceeds to step S408. In step S408, the main body 115 determines that the skew amount calculated on the front surface is not correct, and sets the skew correction amounts on the front surface and the back surface to θ2 calculated from the back surface.

  Here, step S401 functions as a first skew amount detecting means for detecting the skew amount of the document conveyed from the image read by the first image reading means. Step S401 functions as a second skew amount detection unit that detects the skew amount of the document conveyed from the image read by the second image reading unit.

Steps S 4 06 to S 4 09 function as skew correction amount determination means for determining the document skew correction amount based on the detection results of the first skew amount detection means and the second skew amount detection means. To do.

  As described above, the skew amount detection is always performed on the front surface and the back surface, and the skew amount correction amount for the front surface and the back surface is determined using the skew amount detection results of both, so that the leading edge of the original on one side is the background color ( Even if the color is similar to that of the shadow, it is possible to correctly detect the skew amount of the document.

  The skew correction amount determining means for determining the skew correction amount may be controlled by software using a CPU or the like, or may be performed by hardware using an ASIC or the like.

1 is a configuration diagram of an image reading apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing an image when a platen roller in FIG. 1 reads a gray and white skewed original. It is a figure showing the image reading level in main scanning position (1) of FIG. 2, (2), (3), (4), (5). 3 is a flowchart showing a procedure of skew correction amount determination processing executed by the image reading apparatus of FIG. 1. FIG. 5 is a diagram illustrating an image when a document with a gray platen roller and a dirty end is read. FIG. 6 is a diagram illustrating image reading levels at main scanning positions (1), (2), (3), (4), and (5) in FIG. 5.

Explanation of symbols

100 Document Conveying Device 101 Document Tray 103 Paper Feeding Roller 104 Separation Conveying Roller 106 Registration Roller 108 Lead Roller 110 Platen Roller 111 Lead Discharge Roller 113 Paper Discharge Roller 114 Paper Discharge Tray 115 Main Body 116 Flowing Reading Glass 118 Document Plate Glass 119 Lamp 120 Mirror 121 Mirror 122 Mirror 123 First Mirror Stand 124 Second Mirror Stand 125 Lens 126 CCD Line Sensor 127 Platen Roller 128 CIS Line Sensor 129 Flow Reading Glass

Claims (5)

An image reading apparatus for obtaining a skew amount of a document and correcting the inclination of a read image of the document,
Conveying means for conveying the document;
First image reading means for reading one side of the document conveyed by the conveying means;
Second image reading means for reading the other side of the document;
A plurality of points at the edge of the document corresponding to a plurality of main scanning positions set at equal intervals in the main scanning direction are detected from the read data output from the first image reading unit, First skew amount detecting means for detecting a first skew amount of the document from a first detection result;
A plurality of points at the edge of the document corresponding to a plurality of main scanning positions set at equal intervals in the main scanning direction are detected from the read data output from the second image reading unit, Second skew amount detecting means for detecting a second skew amount of the document from a second detection result;
First calculating means for calculating variation in the first detection result;
Second calculating means for calculating variation in the second detection result;
From the variation in the first detection result and the variation in the second detection result, the first skew amount or the second skew amount is used as the skew amount for correcting the inclination of the read image of the document. An image reading apparatus comprising skew amount setting means for selecting a line amount. Before SL variation is a variation in the spacing position adjacent in the main scanning direction,
The skew amount setting means selects one having a small variation from the variation of the first detection result and the variation of the second detection result, and the first skew amount and the second skew 2. The image reading apparatus according to claim 1, wherein a skew amount corresponding to the selected small variation is selected from the amount.   The skew amount setting means does not correct the inclination of the read image of the original when both the variation of the first detection result and the variation of the second detection result exceed a set value. The image reading apparatus according to claim 1 or 2.   The skew amount setting means, when the difference between the first skew amount and the second skew amount is less than a set value, as the skew amount for correcting the inclination of the read image of the document. The image reading apparatus according to claim 1, wherein an average value of the first skew amount and the second skew amount is obtained. An image processing method for obtaining a skew amount of an original and correcting an inclination of a read image of the original,
Obtaining first read data obtained by the first image reading means reading one side of the document conveyed by the conveying means;
Obtaining second read data obtained by reading the other side of the conveyed document by a second image reading means;
A plurality of points at the edge of the document corresponding to a plurality of main scanning positions set at equal intervals in the main scanning direction are detected from the read data output from the first image reading unit, A first skew amount of the document is detected from the first detection result;
A plurality of points at the edge of the document corresponding to a plurality of main scanning positions set at equal intervals in the main scanning direction are detected from the read data output from the second image reading unit, A second skew amount of the document is detected from a second detection result;
Calculating a variation in the first detection result;
Calculating a variation in the second detection result;
From the first detection result variation and the second detection result variation, the skew amount for correcting the inclination of the read image of the document is obtained from the first detection results of the plurality of points. An image processing method comprising: selecting a second skew amount of the document from a first skew amount of the document or a second detection result of the plurality of points.

Images