JP2010118911A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader capable of accurately detecting the skew amount of a document conveyed from a document conveyance device and performing skew correction. <P>SOLUTION: In a step S401, one surface of the document conveyed by the document conveyance device is read and the other surface is also read. The skew amount of the conveyed document is detected from the read images. In steps S406 and S409, an skew correction amount for the document is determined on the basis of the skew amount detection result. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that is mounted on a digital copying machine, a scanner or the like and reads image information recorded on a 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) 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 is to provide an image reading apparatus capable of accurately detecting a skew amount of a document transported from a document transport device and performing skew correction.

  In order to achieve the above object, the image reading apparatus according to claim 1 includes a conveying unit that conveys a document, a first image reading unit that reads one surface of the document conveyed by the conveying unit, A second image reading means for reading the other side of the document, 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, A second skew amount detecting means for detecting the skew amount of the document conveyed from the image read by the second image reading means; the first skew amount detecting means; and the second skew amount. And a skew correction amount determining means for determining a skew correction amount of the original document based on a detection result of the detection means.

  According to the image reading apparatus of the present invention, it is possible to accurately detect the skew amount of the document transported from the document transport device and perform 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 transport roller 104 and rotates with the rotation to feed a document.

  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 has slightly less friction than the separation conveyance roller 104, and in cooperation with the separation conveyance roller 104, the documents fed by the sheet feeding roller 103 are fed one by one. Paper is fed.

  The registration roller pair (registration roller 106 and registration driven roller 107) aligns the leading edge of the document fed by the separation unit, and abuts the leading edge of the separated document 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 the productivity, the registration roller 106 and the registration driven roller 107 are omitted from the above configuration, and the image information of the original is read by the first image reading means and the second image reading means without aligning the front end of the original. 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 is different 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.

  After the main body 115 (the control unit (not shown)) conveys the original document through the front surface reading glass 116 and the back surface reading glass 129, the main body 115 calculates the front surface skew amount (skew correction amount) θ1, 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 the leading edge of the document has a color similar to the background color (or shadow), 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). ).

  When V1 and V2 are both greatly varied (when V1 <setting value V or V2 <setting value V), the main body 115 has not correctly detected the skew amount on both the front surface and the back surface. Judgment is made (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. Further, step S401 functions as a second skew amount detecting means for detecting the skew amount of the document conveyed from the image read by the second image reading means.

  Steps S606 to S609 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.

  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 (3)

Conveying means for conveying an original;
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;
First skew amount detecting means for detecting the skew amount of the document conveyed from the image read by the first image reading means;
Second skew amount detection means for detecting the skew amount of the document conveyed from the image read by the second image reading means;
A skew correction amount determining means for determining a skew correction amount of the document from detection results of the first skew amount detecting means and the second skew amount detecting means;
An image reading apparatus comprising: The skew correction amount determining means includes
When the first skew amount detecting unit and the second skew amount detecting unit can correctly detect the skew amount of the document, the first skew amount detecting unit obtains the skew amount by the first skew amount detecting unit. An average value of the skew feeding correction amount obtained from the skew feeding correction amount and the skew feeding amount by the second skew feeding amount detecting means is used as the skew in the first image reading means and the second image reading means. Line correction amount,
When the first skew amount detecting means and the second skew amount detecting means cannot correctly detect the skew amount of the document, the skew in the first image reading means and the second image reading means. The image reading apparatus according to claim 1, wherein the correction amount is a value that does not perform skew correction. The skew correction amount determining means includes
If the skew amount of the original cannot be detected correctly by the first skew amount detection means, the skew correction amount obtained from the skew amount by the second skew amount detection means is the first skew amount. The skew correction amount in the image reading means and the second image reading means,
If the skew amount of the document cannot be detected correctly by the second skew amount detection means, the skew correction amount obtained from the skew amount by the first skew amount detection means is the first skew amount. The image reading apparatus according to claim 1, wherein the skew feeding correction amount in the image reading unit and the second image reading unit is used.

Images