JP2008252785A - Image reading apparatus, image processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve accuracy of detecting the background color of an original in image reading. <P>SOLUTION: An image reading apparatus is equipped with a CCD image sensor for reading an image on the front side of the original 1 to be fed and a line sensor for reading an image on the rear side of the original 1. When feeding and reading the original 1, a front-side background color level LA that is a part of front-side image data read by the CCD image sensor and a rear-side background color level LB that is a part of rear-side image data read by the line sensor, are used to determine a background color level of the original 1, and background color removal is performed on the front-side image data and the rear-side image data. An acquisition area of the front-side background color level LA and an acquisition area of the rear-side background color level LB are deviated on the front and rear sides of the original 1, thereby the influence of punched holes or the like is reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that reads an image of a document.

  In an image reading apparatus such as a copying machine or a facsimile, not only a white document but also a document having various background densities such as a newspaper or colored paper is to be read. For this reason, there is a technique for detecting the ground color (background) of a document based on image data obtained by pre-reading the document, and then removing the ground color from the image data obtained by actually scanning the document for output. (See Patent Document 1). Further, according to this Patent Document 1, in response to a user request, a case where ground color is detected from image data obtained by reading the entire area of the original surface, and an image obtained by reading a partial area of the original surface are disclosed. It describes switching between the case of detecting ground color from data.

Japanese Patent Laying-Open No. 2005-123683

  The present invention has been made against the background of the above-described technique, and an object of the present invention is to improve the accuracy of detecting the background color of an original in image reading.

  For this purpose, an image reading apparatus to which the present invention is applied includes a reading unit that reads a first surface and a second surface of a document, a reading result of the first surface of the document by the reading unit, and a copy of the document. A ground color determining unit that determines a background color of the document using the reading result of the second surface, and the ground color from the first image data obtained by reading the first surface of the document by the reading unit. And ground color removing means for removing the ground color determined by the determining means.

  In such an image reading apparatus, the ground color determination unit is configured to read a result of reading a predetermined first area on the first surface of the document and a back surface side of the first region on the second surface of the document. The background color of the document can be determined using the reading result of the second area. Further, the ground color removing means further removes the ground color determined by the ground color determining means from the second image data obtained by reading the second surface of the document by the reading means. Can be characterized.

  From another point of view, an image reading apparatus to which the present invention is applied includes a first reading unit that reads an image on a first surface of a conveyed document and outputs first image data, and the first reading. A second reading unit that reads an image on the second side of the document and outputs second image data without reversing the document when the image on the first side of the document is read by the unit; and the first reading unit A ground color determining means for determining a ground color of the document based on the first image data input from the second image data and the second image data input from the second reading means; and input from the first reading means. A ground color removal that removes the ground color determined by the ground color determining means from the first image data and removes the ground color from the second image data input from the second reading means. And a stage.

  In such an image reading apparatus, the ground color determination means includes a first data constituting a part of the first image data and a part constituting the second image data, wherein the first data is a document. The background color of the document can be determined using the second data having different reading target areas.

  Further, from another point of view, the image processing apparatus to which the present invention is applied obtains the first data related to the ground color of the first surface from the reading result of the partial region of the first surface of the document. Means, second acquisition means for acquiring second data relating to the ground color of the second surface from the result of reading a partial area of the second surface of the document, and the first data acquired by the first acquisition means. And a ground color determining means for determining a ground color of the document based on the second data acquired by the second acquiring means, and a ground color of the document determined by the ground color determining means, And ground color removal means for performing ground color removal processing on the first image data obtained by reading the first surface of the document.

  In such an image processing apparatus, a partial region of the first surface of the document and a partial region of the second surface of the document do not overlap the first surface and the second surface. can do. Further, the ground color removing means uses the ground color of the original determined by the ground color determining means, and further applies a ground color removing process to the second image data obtained by reading the second surface of the original. It can be characterized by applying.

According to the first aspect of the present invention, it is possible to improve the detection accuracy of the background color of the document in image reading, compared with the case where the configuration of the present invention is not provided.
According to the second aspect of the present invention, even if a punch hole or the like is formed in the document, it is possible to improve the accuracy of detecting the background color of the document in image reading.
According to the third aspect of the invention, the influence of the ground color can be further reduced in each image data obtained by reading both sides of the document.
According to the fourth aspect of the present invention, it is possible to improve the detection accuracy of the background color of the document in the double-sided image reading as compared with the case where the configuration of the present invention is not provided.
According to the fifth aspect of the present invention, even when a punch hole or the like is formed in the document, it is possible to improve the accuracy of detecting the background color of the document in image reading.
According to the sixth aspect of the present invention, it is possible to improve the detection accuracy of the background color of the document in image reading, compared with the case where the configuration of the present invention is not provided.
According to the seventh aspect of the invention, even when a punch hole or the like is formed in the document, for example, the accuracy of detecting the background color of the document in image reading can be improved.
According to the eighth aspect of the invention, the influence of the ground color can be further reduced in each image data obtained by reading both sides of the document.

The best mode for carrying out the present invention (hereinafter referred to as “embodiment”) will be described below with reference to the accompanying drawings.
<Embodiment 1>
FIG. 1 is a diagram showing an overall configuration of an image reading apparatus to which the present embodiment is applied. The image reading apparatus includes a document feeding device 10 that sequentially conveys the document 1 from a stacked document bundle, and a scanner device 70 that reads an image by scanning.

  The document feeder 10 includes a document storage unit 11 on which a bundle of documents composed of a plurality of documents 1 is stacked, and a paper discharge storage unit 12 that is provided below the document storage unit 11 and loads a document 1 that has been read. In the present embodiment, the document 1 is set so that the first surface (hereinafter referred to as the front surface) of the document 1 loaded on the document container 11 faces upward. The document feeder 10 also includes a feeding roll 13 that takes out the document 1 from the document storage unit 11 and conveys it. Further, on the downstream side of the feeding roll 13 in the document transport direction, a mechanism 14 for separating the documents 1 one by one is provided. The separating mechanism 14 includes a feed roll 14a that conveys the document 1 supplied by the feeding roll 13 further downstream, and a retard roll 14b that separates the documents 1 supplied by the feeding roll 13 one by one. A registration roll 16, a conveyance roll 17, a platen roll 18, an out roll 19, and a discharge roll 20 are provided in the conveyance path 15 where the document 1 is conveyed in order from the upstream side in the document conveyance direction. The registration roll 16 rotates and temporarily stops, then restarts at the same timing, and supplies the document 1 while performing registration adjustment on a document reading system described later. The conveyance roll 17 further conveys the conveyed document 1 toward the platen roll 18. The platen roll 18 assists the conveyance of the document being read by the scanner device 70. The out-roll 19 conveys the document 1 read by the scanner device 70 further downstream. The discharge roll 20 further conveys the read original 1 and discharges it to the paper discharge storage unit 12.

Further, as shown in FIG. 1, a CIS (Contact Image Sensor) 50 is provided between the registration roll 16 and the conveyance roll 17 of the document feeder 10. The CIS 50 includes a light source and a lens (not shown) and a line sensor 55 that functions as a second reading unit.
Since the CIS 50 is provided inside the conveyance path 15, an image on the second surface (hereinafter referred to as the back surface) of the document 1 can be read. As the line sensor 55, a CCD, a CMOS sensor, a contact type sensor, or the like can be used, and an image with an actual width (for example, A4 longitudinal width 297 mm) can be read.

  The scanner device 70 supports the document feeding device 10 described above so that it can be opened and closed, supports the document feeding device 10 with a device frame 71, and reads an image on the surface of the document 1 conveyed by the document feeding device 10. ing. Since the scanner device 70 is provided outside the conveyance path 15, it can read the first surface of the document 1. The scanner device 70 also reads a device frame 71 forming a casing, a first platen glass 72A on which a document 1 to be read is placed in a stationary state, and a document 1 conveyed by the document feeder 10. 2nd platen glass 72B which has the opening part of this light.

  Further, the scanner device 70 is stationary under the second platen glass 72B or scans the entire first platen glass 72A to read an image, and the light obtained from the full rate carriage 73 is input to the imaging unit. A half-rate carriage 75 for supplying is provided. The full rate carriage 73 is provided with an illumination lamp 74 for irradiating light on the document 1 and a first mirror 76A for receiving reflected light obtained from the document 1. Further, the half-rate carriage 75 is provided with a second mirror 76B and a third mirror 76C that provide the light obtained from the first mirror 76A to the imaging unit. The scanner device 70 includes a charge coupled device (CCD) image sensor 78 and an imaging lens 77 that function as first reading means. Among these, the imaging lens 77 optically reduces the optical image obtained from the third mirror 76C. The CCD image sensor 78 functioning as first reading means photoelectrically converts the optical image formed by the imaging lens 77. That is, the scanner device 70 forms an image on the CCD image sensor 78 using a so-called reduction optical system.

  The scanner device 70 further includes a control unit 79 and an image processing unit 80. The control unit 79 controls the operation of each unit in the image reading operation. The image processing unit 80 processes the read image data. These functions are realized by a CPU or the like controlled by a program. The control unit 79 controls the operations of the document feeder 10 and the scanner device 70 described above. The control unit 79 controls motor control, various roll operations, feed clutch operations, and the like in the document feeder 10. The control unit 79 controls the image data capturing operation by the line sensor 55 and the image data capturing operation by the CCD image sensor 78. The image processing unit 80 receives the image data of the document 1 read by the CCD image sensor 78 and the line sensor 55 and outputs the image data to a subsequent device that is an output target. Examples of subsequent devices to be output include a host system such as a printer or a personal computer (PC).

  This document reading apparatus operates in a fixed reading mode in which the document 1 is fixed and read on the first platen glass 72A, and a conveyance reading mode in which the document 1 is conveyed while being conveyed using the document feeding device 10. Further, this document reading apparatus is configured to use the single-sided reading mode for reading an image formed on the surface of the document 1 using the CCD image sensor 78 in the conveyance reading mode, and the document 1 using the CCD image sensor 78 and the line sensor 55. It operates in the double-sided simultaneous reading mode for reading the images formed on both sides. Therefore, in this embodiment, the CCD image sensor 78 and the line sensor 55 function as reading means.

First, image reading of a document in the fixed reading mode will be described.
In the fixed reading mode, the document 1 is set on the first platen glass 72A with the surface to be read facing down. When reading is started, the full rate carriage 73 and the half rate carriage 75 move in the scanning direction (arrow direction) at a ratio of 2: 1. At this time, the light of the illumination lamp 74 of the full rate carriage 73 is applied to the surface to be read of the document 1. Then, the reflected light from the document 1 is reflected in the order of the first mirror 76 A, the second mirror 76 B, and the third mirror 76 C and guided to the imaging lens 77. The light guided to the imaging lens 77 forms an image on the light receiving surface of the CCD image sensor 78. The CCD image sensor 78 is a one-dimensional sensor and processes one line at the same time. The full-rate carriage 73 and the half-rate carriage 75 are moved in this line direction (scanning sub-scanning direction), and the next line of the document 1 is read. By executing this over the entire document, reading of one page of the document is completed.

Next, image reading of the document 1 in the conveyance reading mode will be described.
First, image reading of the document 1 in the single-sided reading mode will be described.
When the document 1 transported through the transport path 15 from the document storage unit 11 passes over the second platen glass 72B, the full rate carriage 73 and the half rate carriage 75 are stopped at the solid line positions shown in FIG. I'm left. Then, the reflected light of the first line of the document 1 that has passed through the platen roll 18 of the document feeder 10 is imaged by the imaging lens 77 via the first mirror 76A, the second mirror 76B, and the third mirror 76C. After one line in the main scanning direction is simultaneously processed by the CCD image sensor 78, one line in the next main scanning direction of the document 1 conveyed by the document feeder 10 is read. After the leading edge of the document 1 reaches the reading position of the second platen glass 72B, the trailing edge of the document 1 passes through the reading position of the second platen glass 72B, thereby completing one page of document reading in the sub-scanning direction. To do.

Next, image reading of the document 1 in the double-sided simultaneous reading mode will be described.
In the double-sided simultaneous reading mode, the full-rate carriage 73 and the half-rate carriage 75 are stopped at the solid line positions shown in FIG. 1, and the surface of the document 1 is read by the CCD image sensor 78 through the second platen glass 72B. The back side (second side) of the document 1 is read by the sensor 55. At this time, the surface (first surface) of the document 1 is read by the CCD image sensor 78 in the same process as in the single-sided reading mode described above. On the other hand, the back side of the document 1 is read by the CIS 50 as follows. In the CIS 50, first, a light source irradiates the back surface of the document 1 with light. The lens collects reflected light of the light irradiated on the back surface of the document 1. The line sensor 55 reads the light collected by the lens. As described above, after one line in the main scanning direction is simultaneously processed by the line sensor 55, one line in the next main scanning direction of the document 1 conveyed by the document feeder 10 is read. After the leading edge of the document 1 reaches the reading position of the CIS 50, the trailing edge of the document 1 passes through the reading position of the CIS 50, thereby completing one page of document reading in the sub-scanning direction. Note that “simultaneous” in double-sided simultaneous reading does not completely coincide with time, but is defined here as meaning about the same time of document conveyance.

  In the present embodiment, as shown in FIG. 1, the reading position of the back surface of the document 1 by the line sensor 55 is set upstream of the reading position of the document 1 by the CCD image sensor 78 in the document transport direction (sub-scanning direction). It is shifted to the side. Therefore, in the double-sided simultaneous reading mode, the document 1 supplied one by one from the document storage unit 11 at a predetermined timing is read first by the line sensor 55 and then read by the CCD image sensor 78. become. In this manner, the images of the plurality of documents 1 stacked on the document storage unit 11 are read in the order of the back surface and the front surface of the document 1. When only one document is set in the document storage unit 11, the image is read once for each of the front and back surfaces.

  This image reading apparatus is configured to remove the background color component of the document from the image data obtained by reading the document when the background color of the document, that is, the background color is other than white. In the image reading apparatus, when the operation is performed in the conveyance reading mode, the image data on one side of the document to be read and the image data on the other side of the document on the back side of the one side are used. The background color of this manuscript is determined. Hereinafter, this process will be described in detail.

FIG. 2 shows a part of the configuration of the image processing unit 80 that functions as an image processing apparatus. The image processing unit 80 includes a storage unit 81, a first background color level detection unit 82, a second background color level detection unit 83, a background color removal level determination unit 84, a selection unit 85, and a background color removal unit 86. Yes.
Among these, the storage unit 81 temporarily stores image data on the back side of the document 1 (second image data: hereinafter referred to as back image data) read by the line sensor 55.
The first ground color level detection unit 82 functioning as a first acquisition unit is based on image data of the surface of the document 1 (first image data: hereinafter referred to as surface image data) read by the CCD image sensor 78. The ground color level of the surface of 1 (hereinafter referred to as the surface ground color level) is detected.
The second background color level detection unit 83 functioning as a second acquisition unit is based on the back surface image data read by the line sensor 55 and stored in the storage unit 81, and the background color level (hereinafter referred to as the back surface background) of the document 1. Called color level).
The ground color removal level determination unit 84 that functions as a ground color determination unit has a front ground color level detected by the first ground color level detection unit 82 and a back ground color level detected by the second ground color level detection unit 83. Based on both, the ground color level of the document 1 is determined.
The selection unit 85 selectively outputs the front surface image data input from the CCD image sensor 78 or the back surface image data stored in the storage unit 81 toward the ground color removal unit 86.
The ground color removing unit 86 functioning as a ground color removing unit uses the ground color level of the document 1 determined by the ground color removal level determining unit 84 for the front surface image data or the back surface image data input from the selection unit 85. The background color is then removed and output to the subsequent stage as output image data.

FIG. 3 shows a detailed block diagram of the ground color removal level determination unit 84 shown in FIG.
The ground color removal level determining unit 84 includes a first holding unit 91, a second holding unit 92, a ground color level comparing unit 93, a maximum value selecting unit 94, a comparison line setting unit 95, an offset value setting unit 96, an adding unit 97, And an output value selection unit 98.
The first holding unit 91 holds the surface background color levels LA (L1A to L5A) for five lines in the sub-scanning direction detected by the first background color level detection unit 82. In the following description, these are respectively the first surface ground color level L1A, the second surface ground color level L2A, the third surface ground color level L3A, the fourth surface ground color level L4A, and the fifth surface ground color level. Called L5A. In the present embodiment, the surface ground color level LA functions as a reading result or first data of the first surface.
The second holding unit 92 holds the back side ground color level LB (L1B to L5B) for five lines in the sub-scanning direction detected by the second ground color level detecting unit 83. In the following description, these are the first back ground color level L1B, the second back ground color level L2B, the third back ground color level L3B, the fourth back ground color level L4B, and the fifth back ground color level, respectively. Called L5B. In the present embodiment, this back surface background color level LB functions as a reading result or second data of the second surface.
The ground color level comparison unit 93 compares the front ground color level LA read from the first holding unit 91 with the back ground color level LB read from the second holding unit 92 for each line.
The maximum value selection unit 94 refers to the comparison result by the ground color level comparison unit 93, and each of the front ground color levels L1A to L5A read from the first holding unit 91 and each back ground color read from the second holding unit 92. From the levels L1B to L5B, the maximum value is selected and output.
The comparison line setting unit 95 sets a comparison start line and a comparison end line to be compared by the maximum value selection unit 94 and an output value selection unit 98 described later.
The offset value setting unit 96 sets the offset value of the background color of the document that is different for each image reading apparatus.
The adding unit 97 outputs an added value obtained by adding the maximum value input from the maximum value selecting unit 94 and the offset value read from the offset value setting unit 96.
The output value selection unit 98 refers to the comparison start line and the comparison end line input from the comparison line setting unit 95, and reads the surface background color levels L1A to L5A and the second holding unit 92 read from the first holding unit 91. The background color levels L1B to L5B read from the above, or the addition value input from the adding unit 97 is output to the ground color removing unit 86 as a ground color removal level.

Next, image reading and image processing of the document 1 in the conveyance reading mode will be specifically described with reference to a timing chart. Here, a case where four originals 1 are read while being conveyed will be described as an example.
FIG. 4 shows a timing chart in the single-sided reading mode.
When the first document 1 is transported into the transport path 15, first, the leading end in the transport direction reaches a reading position by the line sensor 55. Then, the line sensor 55 starts reading the back image of the first document 1. The obtained back side image data of the first original 1 is sequentially stored in the storage unit 81. Subsequently, the leading end of the first original 1 in the conveyance direction reaches a reading position by the CCD image sensor 78. Then, the CCD image sensor 78 starts reading the surface image of the first document 1. The obtained surface image data of the first document 1 is output to the first ground color level detection unit 82 and the selection unit 85. When the rear end of the first document 1 in the transport direction passes the reading position by the line sensor 55, the reading of the back image of the first document 1 is completed. When the rear end of the second document 1 in the transport direction passes the reading position by the CCD image sensor 78, the reading of the surface image of the first document 1 is completed.

In addition, when the CCD image sensor 78 starts reading the surface image of the first document 1, the first ground color level detection unit 82 detects the surface ground color level LA (5 lines in the sub-scanning direction). L1A to L5A). On the other hand, the second ground color level detection unit 83 also has the back ground color level LB (L1B to 5L) corresponding to five lines in the sub-scanning direction that is read at almost the same timing as the start of reading the front image of the first document 1. L5B). Then, the ground color removal level determination unit 84 determines a ground color removal level based on the front surface ground color level LA and the back surface ground color level LB and outputs the ground color removal level to the ground color removal unit 86.
The ground color removal unit 86 performs ground color removal on the surface image data input from the CCD image sensor 78 using the ground color removal level determined by the ground color removal level determination unit 84, and outputs it as output image data. Output.
Thereafter, image reading and ground color removal are performed in the same manner for the second document 1, the third document 1, and the fourth document 1.
In the single-sided reading mode, there is no need to output the back surface image data, so the selection unit 85 is always set to the side that outputs the front surface image data. Further, the entire back surface image data is not output from the storage unit 81.

On the other hand, FIG. 5 shows a timing chart in the double-sided simultaneous reading mode.
When the first document 1 is transported into the transport path 15, first, the leading end in the transport direction reaches a reading position by the line sensor 55. Then, the line sensor 55 starts reading the back surface image of the first document 1. Subsequently, the leading end of the first original 1 in the conveyance direction reaches a reading position by the CCD image sensor 78. Then, the CCD image sensor 78 starts reading the surface image of the first document 1. The obtained surface image data of the first document 1 is output to the first ground color level detection unit 82 and the selection unit 85. When the rear end of the first document 1 in the transport direction passes the reading position by the line sensor 55, the reading of the back image of the first document 1 is completed. When the rear end of the second document 1 in the transport direction passes the reading position by the CCD image sensor 78, the reading of the surface image of the first document 1 is completed.

  In addition, when the CCD image sensor 78 starts reading the surface image of the first document 1, the first ground color level detection unit 82 detects the surface ground color level LA (5 lines in the sub-scanning direction). L1A to L5A). On the other hand, the second ground color level detection unit 83 also has the back ground color level LB (L1B to 5L) corresponding to five lines in the sub-scanning direction that is read at almost the same timing as the start of reading the front image of the first document 1. L5B). Then, the ground color removal level determination unit 84 determines a ground color removal level based on the front surface ground color level LA and the back surface ground color level LB and outputs the ground color removal level to the ground color removal unit 86.

The selection unit 85 is first connected to the side that outputs the surface image data. The surface image data input from the CCD image sensor 78 is input to the ground color removal unit 86 via the selection unit 85. The ground color removal unit 86 performs ground color removal on the input surface image data using the ground color removal level determined by the ground color removal level determination unit 84 and outputs the result as output image data.
When the background color removal unit 86 completes the processing for the front surface image data of the first document 1, the selection unit 85 is connected to the side that outputs the back surface image data. Then, the back surface image data is output from the storage unit 81 and input to the ground color removal unit 86 via the selection unit 85. The ground color removal unit 86 performs ground color removal on the input back surface image data using the ground color removal level determined by the ground color removal level determination unit 84, and outputs it as output image data.
Thereafter, image reading and ground color removal are performed in the same manner for the second document 1, the third document 1, and the fourth document 1.

Here, the background color level determination process of the document 1 executed by the background color removal level determination unit 84 will be described with a specific example.
FIG. 6 shows an example of the document 1 to be read. It is assumed that the letter “A” is drawn on the front side of the document 1 and the letter “B” is drawn on the back side. Further, it is assumed that a plurality of filing punch holes P are formed at one end of the document 1 (the leading end side in the transport direction). Further, it is assumed that the background color of the document 1 is not gray but light gray, for example.

  In the present embodiment, as described above, the front ground color level LA and the back ground color level LB are acquired when the CCD image sensor 78 starts reading the front surface image of the document 1. For this reason, the acquisition area (corresponding to the first area or a partial area of the first surface) of the surface background color level LA on the front side of the document 1 is the front end side in the conveyance direction of the document 1. Further, the acquisition area (corresponding to the second area or a part of the second surface) of the back ground color level LB on the back side of the document 1 is between the front end side and the rear end side in the transport direction of the document 1. That is, the acquisition area of the front surface background color level LA and the acquisition area of the back surface background color level LB are shifted (not matched) in the sub-scanning direction. In this example, punch holes P are formed in the acquisition area of the front surface background color level LA, whereas no punch holes P are formed in the acquisition area of the back surface background color level LB. The distance between the two acquisition regions corresponds to the distance between the reading position of the front surface of the document 1 by the CCD image sensor 78 and the reading position of the back surface of the document 1 by the line sensor 55.

  In the ground color removal level determination unit 84, the first holding unit 91 reads the first surface ground color level L1A, the second surface ground color level L2A, and the third surface obtained by reading the acquisition region of the surface ground color level LA. The ground color level L3A, the fourth surface ground color level L4A, and the fifth surface ground color level L5A are held. Further, the second holding unit 92 reads the first back ground color level L1B, the second back ground color level L2B, the third back ground color level L3B, the fourth back ground color level LB obtained by reading the acquisition region of the back ground color level LB. The back side ground color level L4B and the fifth back side ground color level L5B are held.

  Next, the ground color level comparison unit 93 reads the local color levels from the first holding unit 91 and the second holding unit 92. Then, the ground color level comparison unit 93 first compares whether or not the first line, that is, the first front ground color level L1A and the first back ground color level L1B are within a predetermined range. The predetermined range here is, for example, that the difference between the two is not more than a predetermined value, or that the first back surface ground color level L1B is within ± 10% with respect to the first ground surface ground color level L1A. Etc. Based on the comparison result, the ground color level comparison unit 93 sets 1 as a flag when the predetermined range is satisfied, that is, when the first front ground color level L1A can be regarded as the first back ground color level L1B. If not, 0 is set as a flag. The ground color level comparison unit 93 compares the second line, that is, the second surface ground color level L2A with the second back surface ground color level L2B, and the third line, that is, the third surface ground color level L3A and the third back surface ground color. Comparison with level L3B Comparison between the fourth line, that is, the fourth surface background color level L4A, and the fourth back surface background color level L4B, and the fifth line, that is, the fifth surface background color level L5A and the fifth back surface background color level L5B Are sequentially compared, and a flag of 1 or 0 is set for each. In this example, it is assumed that the flag for the first and second lines is set to 0, and the flag for the third to fifth lines is set to 1. The obtained five flags are stored in a memory (not shown).

  Subsequently, the maximum value selection unit 94 includes a first surface background color level L1A, a second surface background color level L2A, a third surface background color level L3A, a fourth surface background color level L4A, a fifth surface background color level L5A, The maximum value is selected from the first back ground color level L1B, the second back ground color level L2B, the third back ground color level L3B, the fourth back ground color level L4B, and the fifth back ground color level L5B. However, at this time, the maximum value selection unit 94 selects the maximum value while referring to the set value by the comparison line setting unit 95. For example, when the comparison line setting unit 93 sets the comparison start line = 3 and the comparison end line = 5, the maximum value selection unit 94 sets the ground color level of the third to fifth lines, that is, the third surface ground color level L3A, The maximum value is selected from the fourth surface background color level L4A, the fifth surface background color level L5A, the third back surface background color level L3B, the fourth back surface background color level L4B, and the fifth back surface background color level L5B. . If the comparison is always set from the first line, it is not necessary to set the comparison start line. Further, the maximum value selection unit 94 selects a maximum value based on the comparison result in the ground color level comparison unit 93, excluding the line whose flag is 0. In this example, since the flags of the first and second lines are 0 as described above, the ground color levels of the third to fifth lines, that is, the third surface ground color level L3A, the fourth surface ground color level L4A, the first The maximum value is selected from among the five front surface background color levels L5A, the third back surface background color level L3B, the fourth back surface background color level L4B, and the fifth back surface background color level L5B. In this example, it is assumed that the fifth back ground color level L5B is selected as the maximum value.

  Further, the adding unit 97 adds the offset value read from the offset value setting unit 96 to the maximum value selected by the maximum value selecting unit 94, that is, the fifth back ground color level L5B. Then, the adding unit 97 outputs the added value obtained in this way.

  The output value selection unit 98 outputs the ground color level of the line as it is until the comparison start line set in the comparison line setting unit 95 is reached. For example, when the comparison start line = 2 and the comparison end line = 5 are set by the comparison line setting unit 95, the first surface background color level L1A is kept as it is for the first line at the start time of the background color removal processing for the surface image data. Output. Further, after reaching the comparison start line set in the comparison line setting unit 95, the output value selection unit 98 outputs the ground color level of the line as it is for the line whose flag is 0. For example, the second surface ground color level L2A is output as it is to the second line whose flag is 0 at the start of the ground color removal processing for the surface image data. On the other hand, since the flag is 1 for the third line, the output value selection unit 98 selects the maximum value from the third surface background color level L3A and the third back surface background color level L3B of the third line. Output. Further, since the flag is also 1 in the fourth line, the output value selection unit 98 has the third surface ground color level L3A and the third back ground color level L3B of the third line and the fourth surface ground of the fourth line. The maximum value is selected from the color level L4A and the fourth back ground color level L4B and output is performed. Further, since the flag for the fifth run is also 1, the output value selection unit 98 has the third surface ground color level L3A and the third back ground color level L3B for the third line and the fourth surface ground for the fourth line. The maximum value is selected from the color level L4A and the fourth back ground color level L4B, the fifth surface ground color level L5A and the fifth back ground color level L5B of the fifth line, and output is performed. Then, after the sixth line exceeding the comparison end line set in the comparison line setting unit 95, the output is performed while holding the maximum value of the fifth line. Further, output is also performed on the back side image data of the original 1 while maintaining the maximum value of the fifth line.

  In this embodiment, the background color of the front surface of the document 1 and the background color of the back surface are detected, and the background color of the document 1 is obtained based on both detection results. For this reason, the detection accuracy of the ground color is improved. Further, in the present embodiment, the acquisition area of the front ground color level LA and the acquisition area of the back ground color level LB, which are areas for detecting the ground color of the surface of the document 1, are shifted on the front and back surfaces of the document 1. I tried not to overlap the front and back. Thereby, for example, even when a punch hole or the like is formed in the document 1, the accuracy of detecting the background color of the document 1 is improved.

  In the present embodiment, the acquisition area of the front ground color level LA is the leading end side in the conveyance direction of the document 1, and the acquisition area of the back ground color level LB is between the leading edge side and the trailing edge side of the document 1 in the conveyance direction. However, it is not limited to this.

  For example, as indicated by (1) in FIG. 6B, it is also possible to acquire the back surface background color level LB from the front end side in the document transport direction, similarly to the front surface background color level LA. In this case, as indicated by (1) in FIG. 4 and FIG. 5, the second ground color level detection unit 83 is synchronized with the start of reading of the back side image of the document 1 by the line sensor 55. However, what is necessary is just to acquire the back surface background color level LB for 5 lines in the sub-scanning direction. In this example, the acquisition area of the front surface background color level LA and the acquisition area of the back surface background color level LB overlap each other. However, if there are lines that are read avoiding punch holes in the obtained front ground color level LA (L1A to L5A) and back ground color level LB (L1B to L5B), the ground color level of the line is It is close to the actual value. For this reason, even in this case, the ground color detection accuracy of the document 1 is improved to some extent.

  On the other hand, for example, as shown by (2) in FIG. 6B, it is also possible to acquire the back surface background color level LB from the rear end side in the document conveying direction, contrary to the front surface background color level LA. In this case, as indicated by (2) in FIG. 4 and FIG. 5, the second ground color level detection unit 83 is at a timing immediately before the reading of the back image of the document 1 by the line sensor 55 is completed. The back side ground color level LB for 5 lines in the sub-scanning direction may be acquired. Then, in this case, the acquisition region of the front surface background color level LA and the acquisition region of the back surface background color level LB are greatly shifted in the sub-scanning direction. When the back side ground color level LB is acquired between the leading end side and the trailing end side of the document 1 in the conveyance direction, for example, if a high density image such as a photographic image is formed in this area, the high density image There is a risk of misdetecting the level. On the other hand, when the back surface background color level LB is acquired on the rear end side in the conveyance direction of the document 1, there are many cases in which no image is formed in this area. Is possible.

<Embodiment 2>
In the first embodiment, the image reading apparatus configured to be able to read the images formed on both sides of the original document by one conveyance of the original document 1 has been described. On the other hand, in the present embodiment, the image formed on both sides of the document 1 is read by reversing and transporting the document 1. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 7 is a diagram showing an overall configuration of an image reading apparatus to which the present embodiment is applied. The image reading apparatus includes a document feeding device 110 that sequentially conveys the document 1 from a stacked document bundle, and a scanner device 150 that reads an image by scanning.

The document feeder 110 includes a document storage unit 111 for stacking a bundle of documents composed of a plurality of documents 1, and a paper discharge storage unit 112 provided below the document storage unit 111 for stacking the document 1 that has been read. . In addition, the document feeder 110 includes a feeding roll 113 that takes out and transports the document 1 in the document container 111. Further, on the downstream side of the feeding roll 113 in the document transport direction, a mechanism 114 for separating the documents 1 one by one by a feed roll and a retard roll is provided. A pre-registration roll 115, a registration roll 116, a conveyance roll 117, and an out-roll 118 are provided in order from the upstream side in the document conveyance direction in the first conveyance path 131 through which the document 1 is conveyed. The pre-registration roll 115 conveys the original 1 that has been wound one by one toward the downstream roll and also forms a loop of the original 1. The registration roll 116 rotates and temporarily stops, then restarts at the same time, and supplies the document 1 while performing registration adjustment on a document reading unit described later. A conveyance roll 117 assists conveyance of a document being read by the scanner device 150. The out-roll 118 conveys the document 1 read by the scanner device 150 further downstream.
Further, a second transport path 132 for guiding the document 1 to the paper discharge tray 112 is provided downstream of the out-roll 118 in the document transport direction. A discharge roll 119 is disposed in the second transport path 132.

Further, in this image reading apparatus, a third transport path 133 is provided between the outlet side of the out roll 118 and the inlet side of the pre-registration roll 115 so that the images formed on both sides of the document 1 can be read in one process. Is provided. The discharge roll 119 described above also has a function of reversing and conveying the document 1 to the third conveyance path 133.
Furthermore, the image reading apparatus is provided with a fourth transport path 134 for reversing the original 1 and discharging it to the paper discharge accommodating portion 112 when the original 1 is read on both sides. Yes. The fourth transport path 134 is provided on the upper side of the second transport path 132. The discharge roll 119 described above also has a function of conveying the document 1 in the reverse direction to the fourth conveyance path 134.

  On the other hand, the scanner device 150 supports the document feeding device 110 described above so as to be openable and closable, supports the document feeding device 110 by the device frame 151, and reads an image of the document 1 conveyed by the document feeding device 110. ing. The scanner device 150 includes a device frame 151 that forms a casing, a first platen glass 152A on which a document 1 to be read is placed stationary, and a document 1 conveyed by the document feeder 110. A second platen glass 152B having an opening for light is provided.

  Further, the scanner device 150 is stationary under the second platen glass 152B, or scans the entire first platen glass 152A to read an image, and the light obtained from the full rate carriage 153 is input to the imaging unit. A half-rate carriage 154 is provided. The full rate carriage 153 includes an illumination lamp 155 that irradiates light on the document, a reflection mirror 156 that reflects the light emitted from the illumination lamp 155 toward the document surface, and a first mirror 157A that receives the reflected light obtained from the document 1. Is provided. Further, the half-rate carriage 154 is provided with a second mirror 157B and a third mirror 157C that provide the light obtained from the first mirror 157A to the imaging unit. Furthermore, the scanner device 150 includes an imaging lens 158 and a CCD (Charge Coupled Device) image sensor 159. Among these, the imaging lens 158 optically reduces the optical image obtained from the third mirror 157C. The CCD image sensor 159 photoelectrically converts the optical image formed by the imaging lens 158. That is, the scanner device 150 forms an image on the CCD image sensor 159 using a so-called reduction optical system.

  The scanner device 150 further includes a control unit 160 and an image processing unit 170. The control unit 160 controls the operation of each unit in the image reading operation. The image processing unit 170 processes the read image data. These functions are realized by a CPU or the like controlled by a program. The control unit 160 controls operations of the document feeder 110 and the scanner device 150 described above. The control unit 160 controls motor control, various roll operations, feed clutch operations, and the like in the document feeder 110. The control unit 160 also controls an image data capturing operation by the line sensor 55, an image data capturing operation by the CCD image sensor 78, and the like. The image processing unit 170 receives the image data of the document 1 read by the CCD image sensor 78 and the line sensor 55, and outputs the image data to a subsequent device to be output.

  Now, a document reading operation using the image reading apparatus will be described. This image reading apparatus operates in a fixed reading mode for reading the document 1 placed on the first platen glass 152A and a conveyance reading mode for reading the document 1 conveyed by the document feeding device 110.

First, image reading of the document 1 in the fixed reading mode will be described.
When reading the image of the document 1 placed on the first platen glass 152A, the full rate carriage 153 and the half rate carriage 154 move in the scanning direction (arrow direction) at a ratio of 2: 1. At this time, the light of the illumination lamp 155 of the full rate carriage 153 is irradiated on the surface to be read of the document 1. Then, the reflected light from the document 1 is reflected in the order of the first mirror 157A, the second mirror 157B, and the third mirror 157C and guided to the imaging lens 158. The light guided to the imaging lens 158 is imaged on the CCD image sensor 159. The CCD image center 159 is a one-dimensional sensor and simultaneously processes one line. The full-rate carriage 153 and the half-rate carriage 154 are moved in this line direction (scanning sub-scanning direction), and the next line of the document 1 is read. By executing this over the entire document, reading of one page of the document is completed.

Next, image reading of the document 1 in the conveyance reading mode will be described.
For example, in the single-sided reading mode, the conveyed document 1 passes over the second platen glass 152B. At this time, the full rate carriage 153 and the half rate carriage 154 are stopped at the positions indicated by solid lines in FIG. Then, the reflected light of the first line of the document that has passed through the transport roll 117 of the document feeder 110 is imaged by the imaging lens 158 via the first mirror 157A, the second mirror 157B, and the third mirror 157C. An image is read by the CCD image sensor 159. Then, after one line in the main scanning direction is simultaneously processed by the CCD image sensor 159 which is a one-dimensional sensor, the next line in the main scanning direction of the document conveyed by the document feeder 110 is read. After the leading edge of the document reaches the reading position of the second platen glass 152B, the trailing edge of the document passes through the reading position of the second platen glass 152B, thereby completing one page of document reading in the sub-scanning direction. To do.
In the double-sided reading mode, the original 1 that has completed the reading of one side (front surface) of the original 1 is reversely conveyed via the second conveying path 132 and the third conveying path 133 in the first time. Passes over the platen glass 152B again with the front and back reversed. Then, the image on the back side of the document 1 is read by the CCD image sensor 159 in the same procedure. The document 1 for which the image reading on the back side has been completed is reversed again through the second conveyance path 132 and the fourth conveyance path 134 and is discharged to the paper discharge storage portion 112.

  Similarly to the first embodiment, the image reading apparatus according to the present embodiment also uses the background color component of the document from the image data obtained by reading the document when the background color of the document, that is, the background color is other than white. The structure which removes is provided. In the image reading apparatus, when the operation is performed in the conveyance reading mode, the image data on one side of the document to be read and the image data on the other side of the document on the back side of the one side are used. The background color of this manuscript is determined. Hereinafter, this process will be described in detail.

FIG. 8 shows a part of the configuration of the image processing unit 170. The image processing unit 170 includes a first storage unit 171, a second storage unit 172, a first background color level detection unit 173, a second background color level detection unit 174, a background color removal level determination unit 175, a selection unit 176, and A ground color removing unit 177 is provided.
The first storage unit 171 temporarily stores the surface image data of the document 1 read by the CCD image sensor 159.
The second storage unit 172 temporarily stores the back side image data of the document 1 read by the CCD image sensor 159.
The first background color level detection unit 173 detects the surface background color level of the document 1 based on the surface image data of the document 1 read from the first storage unit 171.
The second ground color level detection unit 174 detects the back ground color level of the document 1 based on the back image data of the document 1 read from the second storage unit 172.
The ground color removal level determination unit 175 is based on both the front ground color level detected by the first ground color level detection unit 173 and the back ground color level detected by the second ground color level detection unit 174. Determine the ground color level.
The selection unit 176 selectively outputs the front surface image data stored in the first storage unit 171 or the back surface image data stored in the second storage unit 172 toward the ground color removal unit 177.
The ground color removal unit 177 performs ground color removal processing on the front surface image data or back surface image data input from the selection unit 176 using the ground color level of the document 1 determined by the ground color removal level determination unit 175. The output image data is output to the subsequent stage. Note that the configuration of the ground color removal level determination unit 175 is the same as that of the ground color removal level determination unit 84 (see FIG. 3) in the first embodiment, and a description thereof will be omitted.

Next, image reading and image processing of the document 1 in the duplex reading mode will be specifically described with reference to a timing chart shown in FIG. Here, a case where two originals 1 are read while being conveyed will be described as an example.
When the first document 1 is transported into the first transport path 131, first, the leading end in the transport direction reaches a reading position by the CCD image sensor 159. Then, the CCD image sensor 159 starts reading the surface image of the first document 1. The obtained surface image data of the first document 1 is sequentially stored in the first storage unit 171. Subsequently, at the timing when the central portion in the conveyance direction of the first document 1 reaches the reading position, the first ground color level detection unit 173 detects the surface ground color level LA (L1A to L5A) for five lines in the sub-scanning direction. To get. When the rear end of the first document 1 in the transport direction passes through the reading position, the reading of the surface image of the first document 1 is completed. Next, the first document 1 is turned upside down via the second conveyance path 132 and the third conveyance path 133 and is conveyed again into the first conveyance path.

  When the first document 1 is re-conveyed into the first conveyance path 131, the leading end in the conveyance direction reaches the reading position by the CCD image sensor 159. Then, the CCD image sensor 159 starts reading the back side image of the first document 1. The obtained back side image data of the first original 1 is sequentially stored in the second storage unit 172. In addition, as the CCD image sensor 159 starts reading the back surface image of the first document 1, the second ground color level detection unit 174 causes the back ground color level LB (L1B to L5B) for five lines in the sub-scanning direction. ) To get. When the rear end of the first document 1 in the transport direction passes the reading position, the reading of the first back image is completed. Then, the first document 1 is discharged through the second conveyance path 132 and the fourth conveyance path 134.

  On the other hand, as the back ground color level LB is acquired by the second ground color level detection unit 174, the ground color removal level determination unit 175 obtains the surface ground color level LA already acquired and the back surface background acquired here. A ground color removal level is determined based on the color level LB, and is output to the ground color removal unit 177.

  Further, as the ground color removal level determination unit 175 determines the ground color removal level, the selection unit 176 first reads the surface image data stored in the first storage unit 171 and stores it in the ground color removal unit 177. Output toward. The ground color removal unit 177 performs ground color removal on the input surface image data using the ground color removal level determined by the ground color removal level determination unit 175, and outputs the result as output image data. Thereafter, when the processing for the front surface image data is completed in the ground color removal unit 177, the selection unit 176 next reads out the back surface image data stored in the second storage unit 172 and outputs it to the ground color removal unit 177. . The ground color removing unit 177 performs ground color removal processing on the input back surface image data using the ground color removal level determined by the ground color removal level determining unit 175, and outputs the result as output image data. . Thereafter, the image reading and the ground color removal are similarly performed for the second document 1. The background color removal level is determined by the same process as in the first embodiment.

  In this embodiment, the background color of the front surface of the document 1 and the background color of the back surface are detected, and the background color of the document 1 is obtained based on both detection results. For this reason, the detection accuracy of the ground color is improved. Further, in the present embodiment, the front ground color level LA is acquired from the central portion in the transport direction for the front surface of the document 1, and the back ground color level LB is acquired from the front end portion in the transport direction for the back surface of the same document 1. did. That is, as in the first embodiment, the acquisition area of the front ground color level LA and the acquisition area of the back ground color level LB are shifted in the sub-scanning direction. For this reason, the detection accuracy of the background color of the document 1 is further improved.

  In the present embodiment, the acquisition area of the front ground color level LA is between the front end side and the rear end side of the document 1 and the acquisition area of the back ground color level LB is the front end side of the document 1 in the transport direction. However, it is not limited to this.

  For example, the acquisition area of the surface background color level LA can be the leading end side in the conveyance direction of the document 1. In this case, as indicated by (1) in FIG. 9, the first ground color level detection unit 173 starts as the CCD image sensor 159 starts reading the surface image of the document 1. What is necessary is just to acquire the surface ground color level LA for 5 lines in the sub-scanning direction.

  On the other hand, the acquisition area of the surface background color level LA may be the rear end side in the conveyance direction of the document 1. In this case, as shown by (2) in FIG. 9, the first ground color level detection unit 173 performs sub-scanning immediately before the reading of the surface image of the document 1 by the CCD image sensor 159 is completed. What is necessary is just to acquire the surface ground color level LA for 5 lines of scanning directions.

1 is a diagram illustrating an overall configuration of an image reading apparatus to which Embodiment 1 is applied. 4 is a diagram for explaining a part of the configuration of an image processing unit according to Embodiment 1. FIG. It is a detailed block diagram of a ground color removal level determination part. It is a timing chart in single-sided reading mode. It is a timing chart in the double-sided simultaneous reading mode. 3 is a diagram illustrating an example of a document to be read. FIG. It is a figure which shows the whole structure of the image reading apparatus with which Embodiment 2 is applied. 10 is a diagram for explaining a part of the configuration of an image processing unit in Embodiment 2. FIG. It is a timing chart in double-sided reading mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Document, 10 ... Document feeder, 50 ... CIS (Contact Image Sensor), 55 ... Line sensor, 70 ... Scanner device, 78 ... CCD (Charge Coupled Device) image sensor, 79 ... Control part, 80 ... Image processing part , 81, storage unit, 82, first ground color level detection unit, 83, second ground color level detection unit, 84, ground color removal level determination unit, 85, selection unit, 86, ground color removal unit, 110, original document 150, scanner device, 159, CCD image sensor, 160, control unit, 170, image processing unit, 171, first storage unit, 172, second storage unit, 173, first ground color level detection unit, 174 ... second ground color level detection unit, 175 ... ground color removal level determination unit, 176 ... selection unit, 177 ... ground color removal unit

Claims (8)

Reading means for reading the first side and the second side of the document;
Ground color determination means for determining a ground color of the document using a reading result of the first surface of the document and a reading result of the second surface of the document by the reading unit;
An image reading apparatus comprising: ground color removing means for removing the ground color determined by the ground color determining means from first image data obtained by reading the first surface of the document by the reading means.   The ground color determining means obtains a reading result of a predetermined first area on the first surface of the document and a reading result of a second area other than the back side of the first area on the second surface of the document. The image reading apparatus according to claim 1, wherein the background color of the document is determined.   The ground color removing unit further removes the ground color determined by the ground color determining unit from second image data obtained by reading the second surface of the document by the reading unit. The image reading apparatus according to claim 1. First reading means for reading an image on the first surface of the conveyed document and outputting first image data;
A second reading unit that reads an image of the second side of the original without outputting the original when the image of the first side of the original is read by the first reading unit, and outputs second image data;
Ground color determination means for determining the ground color of the document based on the first image data input from the first reading means and the second image data input from the second reading means;
The ground color determined by the ground color determining means is removed from the first image data input from the first reading means, and the background is determined from the second image data input from the second reading means. An image reading apparatus including a removing unit that removes a color.   The ground color determining means includes a first data constituting a part of the first image data and a part constituting the second image data, and the first data is different in a reading target area on the document. The image reading apparatus according to claim 4, wherein the background color of the document is determined using the second data. First acquisition means for acquiring first data relating to the ground color of the first surface from a reading result of a partial region of the first surface of the document;
Second acquisition means for acquiring second data relating to the ground color of the second surface from the result of reading a partial area of the second surface of the document;
Ground color determination means for determining the ground color of the document based on the first data acquired by the first acquisition means and the second data acquired by the second acquisition means;
Image processing including ground color removal means for performing ground color removal processing on first image data obtained by reading the first surface of the document using the ground color of the document determined by the ground color determination means apparatus.   7. The image processing according to claim 6, wherein a partial area of the first surface of the document and a partial region of the second surface of the document do not overlap with the first surface and the second surface. apparatus.   The ground color removing unit uses the ground color of the document determined by the ground color determining unit to further perform ground color removal processing on the second image data obtained by reading the second surface of the document. The image processing apparatus according to claim 6.

Images