JP5341566B2 - Image reading apparatus, control method therefor, and image reading system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus preventing output of an image which has become unsuitable due to tilting correction processing that is image processing to be performed for erecting a read image when reading a long document. <P>SOLUTION: The image reading apparatus includes a document feeding means, an image reading means, a document length measuring means, an inclination detecting means for detecting the inclination of a document, and a tilting correcting means for correcting the inclination of a read image. If a document length measured by the document length measuring means is longer than a preset length or a predetermined length, the tilting correction processing is controlled so as not to be performed. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an image reading apparatus that reads image information of a document and a control method for the image reading apparatus.

  A typical scanner with an automatic paper feed function is provided with a paper feed roller 106 and the like for guiding a document from a document table 102 to a conveyance path as illustrated in FIG. Further, the document table 102 is generally provided with a guide plate that can be positioned by a slide type such as 401 and 402 in FIG. 4 so that the documents to be placed can be arranged and placed.

In addition, even if there is a guide plate, the user may not place the document straight, so the document being transported may be tilted, and there is also a device that corrects mechanical skew (see FIG. For example, see Patent Document 1). In this way, the document is often conveyed while being tilted. Therefore, when reading an image with a scanner with an automatic paper feed function, a function of image processing (skew correction processing) that detects the inclination of the original during conveyance and corrects the inclination of the original so that the original image is upright. It is common to have
JP-A-63-82267

FIG. 7 is a diagram illustrating a conveyance path of a general image reading apparatus with an automatic paper feeding function. The document 101 placed on the document table 102 is guided to the conveyance path 108 by the paper feed roller 106 while being sandwiched between the guide plates 401 and 402. A plurality of conveyance rollers 107 are installed on the conveyance path 108, and the original is conveyed by the conveyance rollers 107 and conveyed to the paper discharge tray 103. Image information of the original is read from the conveyed original by the image sensors 104 and 105. Since the guide plates 401 and 402 function to push the original at the position G as the conveyance proceeds even when the original is placed obliquely as shown in FIG. 8, as shown by the arrows in FIG. There is also an effect of skew correction by rotating the document.

However, for a long document, as shown in FIG. 10, when the guide plates 401 and 402 press the document, they may already be applied to a plurality of transport rollers at the position indicated by R. At this time, since the document is sandwiched by the plurality of conveyance rollers 107 at the position R, the force does not attempt to rotate the document in the upright direction, but (the force of the conveyance roller) and (guide) as shown in FIG. The resultant force of the force from the plate will work and be transported diagonally. Accordingly, when a long document having a certain length is not conveyed straight, an image obtained by reading is a document image as illustrated in FIG. If skew correction processing (tilt correction processing) is performed on the image in FIG. 12A based on the inclination of the front end portion or the rear end portion, an image as illustrated in FIG. 12B may be obtained. As can be seen from FIG. 12B, the longer the document length, the greater the horizontal width of the image after skew correction, which is not a preferable output image.

Therefore, in the conventional image reading apparatus, the skew correction result tends to be unfavorable as the length of the document is longer, and the skew correction function does not work when scanning a long document (long document). As the user had to change the setting, it took time and effort.

An object of the present invention is to provide an image reading apparatus capable of preventing a skew correction function (tilt correction function) from operating according to the length of a document when a long document is read.

In order to achieve the above object, an image reading apparatus according to the present invention includes a conveying unit that conveys a document, an image reading unit that reads an image from a document conveyed by the conveying unit, and a front end and a rear side of the conveyed document. Document length measuring means for detecting the edge and measuring the length of the conveyed document from the difference in detection time and the document conveyance speed, and detecting the inclination of the conveyed document from the image read from the image reading means an image reading apparatus comprising: a tilt detection unit, and a tilt correcting means for performing tilt correction on the original image read by said image reading means in accordance with the inclination detected by the inclination detecting means for said inclination correction as the width of the original image by being corrected the tilt is not would provide an increase by means based on the length of the document determined by the document length measuring means, said slope It determines whether to execute the tilt correction by positive means, further comprising a correction execution decision means, characterized in that.

The control method of the image reading apparatus according to the present invention includes a conveying unit that conveys a document, an image reading unit that reads an image from the document conveyed by the conveying unit, and detects a leading edge and a trailing edge of the conveyed document. A document length measuring unit that measures the length of the conveyed document from a difference in detection time and a document conveyance speed, and an inclination detection that detects an inclination of the conveyed document from an image read from the image reading unit. In a control method for controlling an image reading apparatus, comprising: and a tilt correcting unit that performs tilt correction on a document image read by the image reading unit in accordance with the tilt detected by the tilt detecting unit. a measuring step of measuring the length of the document as the lateral width of said original image by being corrected slope does would provide an increased, by the original length measuring means by inclination correction means, Serial based on the length of the measured document by the measuring step, and having a correction process execution determination step of determining whether to execute the tilt correction by the tilt correction means.

According to the present invention, since it is determined whether or not to execute the inclination correction process according to the length of the document measured during image reading, it is preferable that the user does not care about the length of the document. An image can be obtained.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 3 shows a preferred embodiment of an image reading system to which the present invention is applied, in which the image reading apparatus 1 and the host computer 2 are connected by a general-purpose communication cable 3.

FIG. 1 is a cross-sectional view illustrating the schematic configuration of a conveyance path of an image reading apparatus according to the present invention. The documents 101 on the document table 102 are separated one by one by a paper feed roller 106 and the like, sent to the conveyance path 108, and pass through the front of the image sensors 104 and 105 while being conveyed along the conveyance path by the conveyance rollers 107. The paper is discharged to the paper portion 103.

FIG. 4 is a perspective view of the paper feeding unit 102 of the image reading apparatus 1. The sheet feeding unit 102 of the image reading apparatus 1 is provided with guide plates 401 and 402 for aligning documents. The guide plates 401 and 402 can be slid according to the size of the document to change their positions. By pressing the document from the left and right, there is also an effect of suppressing the oblique conveyance of the document so that the document is fed straight.

FIG. 2 is a circuit block diagram of a control system provided in the image reading apparatus 1 according to the present invention. The image reading apparatus 1 includes a circuit board 200, a CPU 202, a RAM 203, a ROM 204, a reading unit 206, a motor driver 207, a stepping motor 208, and an external I / F 205. The CPU 202, RAM 203, ROM 204, reading unit 206, motor driver 207, and external I / F 205 are connected to each other via a system bus 201.

The CPU 202 controls the entire image reading apparatus. A RAM 203 provides a work area to the CPU 202 and functions as a buffer memory that temporarily stores image data obtained from the reading unit 206 during image scanning. The ROM 204 stores various programs and initial setting values.

The reading unit 206 includes an A / D converter and a shading correction processing unit that are not shown. Control is performed so that the image sensor 209 reads the reflected light from the read original surface irradiated with light by the illumination LED 210. Analog data output from the image sensor 209 corresponding to the image sensors 104 and 105 in FIG. 1 is A / D converted, and image data generated by performing shading correction is written into the RAM 203.

The sheet feeding roller 106 receives driving force from a sheet feeding motor (not shown) driven by a motor driver (not shown) via a gear, a belt, etc. (not shown), and is controlled by the CPU 202. The conveyance roller 107 is connected to a stepping motor 208 by a gear and a belt (not shown), and the stepping motor 208 is controlled by the CPU 202 through a motor driver 207.

When image reading is started by the user operating the host computer 2, after the paper feed roller is driven, the registration sensor 109 detects that the document has reached the image sensor, and the illumination LED 210 is turned on after a certain time. At the same time, the image sensor 209 and the like are operated to read an image. The read image is sent to the host computer 2 after image processing for making the image suitable, such as shading correction, gamma correction, and edge enhancement processing. The above is the scan operation generally performed.

Further, the image reading apparatus has a function of measuring the length of the conveyed document based on the output change of the registration sensor. As will be described later, it is determined whether or not skew correction (tilt correction) is performed in accordance with the measured length of the document.

Further, the color of the member on the opposite side of the reading sensors 104 and 105 of the image reading apparatus is black. As a result, a high-brightness original image surrounded by a black background image as shown in FIG. 5 can be acquired, and by detecting the boundary from the difference in lightness, the contour can be detected as shown in FIG. There are the following methods for calculating the inclination from the contour. First, as shown in FIG. 6, the contour is vectorized by tracing the contour at predetermined intervals. From the individual vectors (X, Y) acquired by vectorization of the contour, the average value of all vectors is calculated by the method illustrated in Equation 1.
Average value = Σ {POSI_VECTOR (X, Y)} / (number of vectors)
However,
POSI_VECTOR (X, Y) is a function that changes the vector (X, Y) to a positive direction.
(X, Y) when (X ≧ 0 and Y ≧ 0)
When (X <0 and Y ≧ 0), (Y, -X)
(-Y, X) when X ≧ 0 and Y <0)
(When X <0 and Y <0), (−X, −Y)
It is represented by

The calculated average value is a vector representing the inclination of the document, and an upright document image can be obtained by rotating the image according to the angle. A known image rotation process is used for image rotation. Note that any method other than the above method may be used as a method of calculating the inclination from the contour.

The determination of whether or not to perform the skew correction, which is a feature of the image reading apparatus embodying the present invention, is performed according to the following determination criteria.
When (the length of the conveyed document)> a, skew correction is not executed.
When (the length of the conveyed document) ≦ a, skew correction is executed.
However, a is a preset threshold value (correction possibility threshold value).

As described above, according to the present invention, since skew correction is not performed when it is determined that the document is a long document, it is possible to prevent an undesired image of a long document that is difficult to be conveyed straight from being output. I can do it. Note that a is a threshold value (correction enable / disable threshold value) set in advance by the user on the setting screen or the like, but may be a fixed value stored in the ROM or the like of the image reading apparatus.

FIG. 13 is a flowchart showing a process of preventing the skew correction from being executed when the length of the document is greater than or equal to a threshold value (correctability threshold) in the image reading apparatus. The CPU 202 determines whether an image reading instruction is input from the operation unit (not shown) by the user (step S101). When an image reading instruction is input, the CPU 202 rotates the paper feed roller 106 to feed the original 101 (step S102). The document 101 is transported by the transport roller 107, and the CPU 202 checks whether or not the leading edge of the document 101 is detected by the registration sensor 109 (step S103). When CPU 202 determines that the leading edge of the document has been detected by registration sensor 109 (YES in step 103), CPU 202 starts measuring time while document 101 passes registration sensor 109 (step S104).

Next, the CPU 202 checks whether or not the trailing edge of the document 101 has been detected by the registration sensor 109 (step S105). When the trailing edge of the document 101 is detected by the registration sensor 109 (YES in step 105), the CPU 202 ends the time measurement (step 106). As a result, the time required for the document 101 to pass through the registration sensor 109 is measured. The CPU 202 calculates the length of the original by multiplying the previously measured paper conveyance speed by the measurement time (step S107). In this way, an example of the document length measuring means is realized. The document length may be measured using an existing sensor other than the registration sensor 109 or a dedicated sensor. The document length may be calculated from the read image. If the calculated document length is less than the threshold (NO in step S108), the CPU 202 executes an inclination correction process (step S109), and if it is equal to or greater than the threshold (YES in step S108), the inclination correction is performed. Exit without executing any processing. In this way, an example of correction processing execution determination means is realized.

In this embodiment, the inclination of the document is calculated from the read image. However, a sensor for detecting the inclination of the document may be provided at an arbitrary position on the conveyance path. For example, a method is conceivable in which a plurality of sensors arranged in a direction orthogonal to the conveyance direction are provided on the conveyance path, and the inclination of the document is calculated from the difference in time at which the document leading edge passes through each sensor. The skew correction processing of the image according to the present embodiment may be executed by the CPU 202 based on the processing program stored in the ROM 204. The present invention also includes a case where processing is executed by the host computer 2. In addition, on the setting parameter input screen of the image reading apparatus, a check box or the like that enables setting whether skew correction is executed / not executed in the case of a long document is provided. The present invention may be applied only when “do not execute skew correction”.

In addition, a check box or the like that enables the setting of whether or not to flow a long document is provided on the input screen for setting parameters of the image reading apparatus, and only when the user sets the “flow a long document” setting. The invention may be applied.

Also, instead of the setting of “flowing / not flowing a long document”, document maximum length setting means such as a parameter input screen that enables setting of the maximum length that can be conveyed by the image reading apparatus is provided, and the setting value is When it is larger than a predetermined threshold (judgment threshold), the long mode may be set. “Maximum length that can be transported by the image reading apparatus” means that when it is determined that the actually transported document is longer than that, it is determined in the normal mode that the status during transport is, for example, “JAM” The value to use. That is, when making the above determination, if the user sets the maximum length that can be conveyed by the image reading apparatus to a value larger than, for example, the JAM determination threshold (determination threshold), the image reading apparatus is interpreted as being in the long mode. Then, it is determined whether or not to perform skew correction based on the document length and a predetermined threshold (correction propriety threshold). On the contrary, if the maximum length that can be conveyed by the image reading apparatus is set to a value that is equal to or less than a threshold (judgment threshold) for JAM determination, for example, it is interpreted that the long mode is not set, and the skew according to the document length It is not determined whether or not to execute correction.

In addition to the above determination, the determination whether to perform the skew correction based on the determination criterion such as the amount of skew (gradient) may be used in combination. For example, when the skew amount is small, the effect of skew correction is small, so that the skew correction may not be performed regardless of the length of the document. Conversely, if it is determined that the skew amount is too large and the reliability of the skew amount calculation is low, skew correction may not be performed regardless of the length of the document.

Sectional view of conveyance path of image reading device Circuit block diagram of control system provided in image reading apparatus Schematic diagram of connecting image reading device and host computer Perspective view of document table and guide plate of image reading apparatus Scanning results when scanning a tilted document The figure which represented the vector acquired from the detected outline and outline from the reading result of FIG. A diagram showing the positional relationship between the document table, guide plate, transport path, and rollers of the image reader A drawing depicting a manuscript placed diagonally hitting a guide plate A drawing depicting a document hitting a guide plate, rotating, and fed straight Illustration depicting a long manuscript placed diagonally hitting the guide plate A diagram showing the force applied to a long document hitting the guide plate Diagram showing scanned image of long original that was not correctly conveyed and skew correction result A flowchart showing processing for preventing skew correction according to the length of the document.

DESCRIPTION OF SYMBOLS 1 Image reader 2 Host computer 3 Communication cable 101 Original 102 Original stand 103 Discharge stand 104 Image sensor 105 Image sensor 106 Paper feed roller 107 Conveyance roller 108 Conveyance path 109 Registration sensor 200 Circuit board 201 System bus 202 CPU
203 RAM
204 ROM
205 External interface unit 206 Reading unit 207 Motor driver 208 Stepping motor 209 Image sensor 210 Light source (illumination LED)
401 Guide plate 402 Guide plate

Claims (5)

Conveying means for conveying an original;
Image reading means for reading an image from a document conveyed by the conveying means;
A document length measuring means for detecting the leading edge and the trailing edge of the conveyed document and measuring the length of the conveyed document from a difference in detection time and a document conveying speed;
An inclination detecting means for detecting an inclination of the conveyed original document from an original image read from the image reading means ;
A tilt correction unit that performs tilt correction on the document image read by the image reading unit in accordance with the tilt detected by the tilt detection unit;
In an image reading apparatus having
Based on the length of the original measured by the original length measuring means, the inclination by the inclination correcting means is set so that the horizontal width of the original image is not increased by correcting the inclination by the inclination correcting means. A correction processing execution determining means for determining whether to execute correction;
An image reading apparatus. Conveying means for conveying an original;
Image reading means for reading an image from a document conveyed by the conveying means;
A document length measuring means for detecting the leading edge and the trailing edge of the conveyed document and measuring the length of the conveyed document from a difference in detection time and a document conveying speed;
An inclination detecting means for detecting an inclination of the conveyed document;
A tilt correction unit that performs tilt correction on the document image read by the image reading unit in accordance with the tilt detected by the tilt detection unit;
In an image reading apparatus having
A correction processing execution determination unit that determines whether or not to execute the inclination correction by the inclination correction unit based on the length of the original measured by the original length measurement unit;
Further comprising a <br/> the original maximum length setting means allowing setting the maximum length of conveyable originals,
When the maximum length set by the document maximum length setting unit exceeds a determination threshold, the correction processing execution determination unit determines whether to perform the inclination correction by the inclination correction unit;
When the maximum length set by the document maximum length setting unit is equal to or less than the determination threshold value, the inclination is not determined by the correction processing execution determination unit without determining whether the inclination correction unit performs the inclination correction. Executing the inclination correction by the correction means;
Images reader, characterized in that. The correction process execution determination means includes
3. The image reading according to claim 1, wherein when the document length measured by the document length measurement unit exceeds a correction availability threshold, it is determined that the tilt correction by the tilt correction unit is not executed. 4. apparatus. Conveying means for conveying an original;
Image reading means for reading an image from a document conveyed by the conveying means;
A document length measuring means for detecting the leading edge and the trailing edge of the conveyed document and measuring the length of the conveyed document from a difference in detection time and a document conveying speed;
An inclination detecting means for detecting an inclination of the conveyed original document from an original image read from the image reading means ;
A tilt correction unit that performs tilt correction on the document image read by the image reading unit in accordance with the tilt detected by the tilt detection unit;
In a control method for controlling an image reading apparatus having:
A measuring step of measuring the length of the original by the original length measuring means;
The tilt correction by the tilt correction unit is performed based on the length of the document measured in the measurement step so that the width of the document image does not increase by correcting the tilt by the tilt correction unit. A correction process execution determination step for determining whether or not to execute, and
An image reading apparatus control method comprising: Conveying means for conveying an original;
Image reading means for reading an image from a document conveyed by the conveying means;
A document length measuring means for detecting the leading edge and the trailing edge of the conveyed document and measuring the length of the conveyed document from a difference in detection time and a document conveying speed;
An inclination detecting means for detecting an inclination of the conveyed original document from an original image read from the image reading means ;
A tilt correction unit that performs tilt correction on the document image read by the image reading unit in accordance with the tilt detected by the tilt detection unit;
Based on the length of the original measured by the original length measuring means, the inclination by the inclination correcting means is set so that the horizontal width of the original image is not increased by correcting the inclination by the inclination correcting means. Correction processing execution determining means for determining whether or not to execute correction;
An image reading system.

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