JP2008022420A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology of suppressing a show-through caused by an image formed on a backside of a read object face in reading an infrared ray image formed on the read object face of an original. <P>SOLUTION: A backing plate provided to the surface of a backing member 20 for pressing the original on a first platen glass 52A has a characteristic that the reflectance of infrared ray is lower than the reflectance of visible light. In reading a code image (infrared ray image) formed on the original on the first platen glass 52A, when the infrared ray is emitted to the original, the reflection of infrared ray is caused to a read face of the original depending on the presence of the infrared ray image. The infrared ray passing through the read face of the original reaches the backside of the original, the backing plate is provided to the backside, and the infrared ray is absorbed by the image (infrared ray image and black image) formed on the backside of the original or the backing plate. As a result, the reflection amount of the infrared ray from the backside of the original is reduced and the show-through is suppressed as a result of infrared ray reading. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  In recent years, attention has been paid to a technique for distinguishing special manuscripts such as banknotes and securities from ordinary manuscripts in response to increasing security awareness and the trend toward computerization. Specifically, a technique for forming an invisible image that is difficult to visually recognize by using, for example, an image forming material (ink, toner, etc.) that absorbs or reflects infrared rays on a special document is beginning to be adopted. In addition to the special manuscript, for example, a code image (infrared image) in which code information such as ID is embedded is further formed on the manuscript on which confidential information or the like is formed as a visible image using the above-mentioned image forming material. The technology to keep is also being studied.

  For this reason, various image reading apparatuses capable of reading an infrared image in addition to a visible image have been proposed. For example, in addition to a reading filter that transmits visible light and blocks infrared light, an infrared light filter that blocks visible light and transmits infrared light is prepared. A technique that can be selectively inserted into an optical path has been proposed (see Patent Document 1). In this image reading apparatus, when reading an image of a document placed on a platen glass, a reciprocating motion of a carriage mounted with a part of a reading optical system is used, and a reading filter is inserted in the optical path in the forward path. A visible image on the original is read, and an infrared light filter is inserted in the optical path in the return path to read the infrared image on the original.

JP 7-154595 A

  The present invention has been made against the background of the above-described technology, and the purpose of the present invention is to form an infrared image formed on the reading target surface of a document on the back surface of the reading target surface. It is to suppress show-through caused by an image.

  For this purpose, the image reading apparatus to which the present invention is applied has an irradiation part for irradiating the original with infrared light and a characteristic for absorbing the infrared light, and is opposite to the irradiation surface of the original by the irradiation part. A biasing member that biases the document from the side, a light receiving unit that receives infrared light that is irradiated from the irradiation unit and reflected from the document biased by the biasing member, and infrared light reception by the light receiving unit An analysis unit that obtains a code image formed on the document from the result and analyzes code information included in the code image;

  Such an image reading apparatus may further include a binarization processing unit that performs binarization processing on the light reception result by the light receiving unit and outputs the result to the analysis unit. The irradiation unit further irradiates the original with visible light, the light receiving unit further receives visible light reflected from the original, and the urging member is set to have a higher light reflectivity for visible light than for infrared light. It can be characterized by that. The irradiation unit further irradiates the original with visible light, the light receiving unit further receives visible light reflected from the original, and the biasing member further has a characteristic of absorbing the visible light in a specific pattern. In the case where a specific pattern exists in the visible light reception result, a replacement unit that replaces the specific pattern with the background data of the document can be further included.

  From another point of view, an image reading apparatus to which the present invention is applied is provided with an irradiation unit that irradiates a document with infrared light, and an irradiation unit opposite to the irradiation surface of the document. An absorbing member that absorbs infrared light that is irradiated and transmitted through the document, a light receiving unit that receives infrared light that is irradiated from the irradiation unit and reflected from the document, and a document based on the result of receiving infrared light by the light receiving unit And an analysis unit that acquires the code image formed in the first and analyzes the code information included in the code image.

  In such an image reading apparatus, the absorbing member can be arranged in close contact with the surface of the document opposite to the irradiation surface. Further, the absorbing member can be characterized in that the light reflectance for visible light is set higher than the light reflectance for infrared light.

According to the first aspect of the invention, since infrared light transmitted through the document is absorbed, reflection of infrared light from the back side of the document is suppressed, and as a result, it is formed on the back surface of the document. The show-through caused by the image can be suppressed.
According to the second aspect of the present invention, it is possible to more reliably separate the infrared reading result on the front side of the document and the infrared reading result on the back side of the document.
According to the third aspect of the present invention, for example, when a document having a punch hole is read, the influence of the trace of the punch hole on the visible reading result can be reduced.
According to the fourth aspect of the present invention, for example, when a document having a punch hole is read, the influence of the trace of the punch hole on the visible reading result can be reduced.
According to the fifth aspect of the invention, the infrared light transmitted through the document is absorbed, so that the reflection of the infrared light from the back side of the document is suppressed. As a result, the image formed on the back surface of the document The show-through caused by can be suppressed.
According to the sixth aspect of the present invention, the absorbing member can be used as a document backing member.
According to the seventh aspect of the present invention, for example, when a document having a punch hole is read, the influence of the trace of the punch hole on the visible reading result can be reduced.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below in detail with reference to the accompanying drawings.
<Embodiment 1>
FIG. 1 is a diagram illustrating a configuration example of an image reading apparatus to which the exemplary embodiment is applied. With this image reading apparatus, it is possible to read a fixed original image and also to read a conveyed original image. The image reading apparatus includes a document feeding device 10 that sequentially conveys documents from a stacked bundle of documents, and a reading device 50 that reads an image of the document by scanning. Here, the document feeder 10 is attached to the reading device 50 on the back side in the drawing using a hinge or the like. Therefore, the document feeder 10 is attached to the reading device 50 so as to be opened and closed with the back side in the figure as a fulcrum.

The document feeder 10 includes a document tray 11 on which a bundle of documents composed of a plurality of documents is stacked, and a paper discharge tray 12 that is provided below the document tray 11 and stacks documents that have been read. In addition, the document feeder 10 includes a take-out roll 13 that takes out and conveys a document on the document tray 11. Further, on the downstream side of the take-out roll 13 in the document conveyance direction, a mechanism 14 is provided for separating sheets one by one using a pair of roll members. A pre-registration roll 15, a registration roll 16, a backing roll 17, and an out-roll 18 are provided in order from the upstream side in the document conveyance direction in the first conveyance path 31 through which the document is first conveyed. The pre-registration roll 15 conveys the originals that have been rolled up one by one toward the downstream roll and forms a loop of the originals. The registration roll 16 rotates and temporarily stops, then restarts at the same timing, and supplies a document while performing registration adjustment on a document reading unit to be described later. The backing roll 17 functioning as an urging member or an absorbing member assists the conveyance of the original being read by the reading device 50 and presses the original against a second platen glass 52B (described later), thereby allowing the original at the reading position. The height of the is kept almost constant. The out roll 18 conveys the document read by the reading device 50 further downstream.
A second transport path 32 for guiding the document to the paper discharge tray 12 is provided downstream of the out-roll 18 in the document transport direction. A discharge roll 19 is disposed in the second transport path 32.
A backing member 20 is attached to the lower surface of the paper discharge tray 12. The backing member 20 is used to press a document against a first platen glass 52A (described later) provided in the reading device 50 in a fixed reading mode described later.

Further, in this image reading apparatus, a third transport path 33 is provided between the outlet side of the out roll 18 and the inlet side of the pre-registration roll 15 so that the images formed on both sides of the document can be read in one process. It has been. The discharge roll 19 described above also has a function of reversing and transporting the document carried into the second transport path 32 to the third transport path 33.
Furthermore, this image reading apparatus is provided with a fourth transport path 34 for reversing the original and discharging it to the paper discharge tray 12 when the original is read on both sides. The fourth transport path 34 is provided on the upper side of the second transport path 32. The discharge roll 19 described above also has a function of reversing and conveying the original document carried into the second conveyance path 32 to the fourth conveyance path 34.

  On the other hand, the reading device 50 supports the document feeding device 10 described above so as to be openable and closable, supports the document feeding device 10 by the device frame 51, and reads an image of a document conveyed by the document feeding device 10. Yes. The reading device 50 includes a device frame 51 that forms a casing, a first platen glass 52A on which a document to be read can be placed in a stationary state, and a document that is conveyed by the document feeder 10. A second platen glass 52B having an opening for light is provided.

In addition, the reading device 50 includes a full rate carriage 53 and a half rate carriage 54. The full-rate carriage 53 is stationary under the second platen glass 52B or scans the entire first platen glass 52A to read an image. The half-rate carriage 54 is stationary when the full-rate carriage 53 is stationary, and moves in conjunction with the full-rate carriage 53 so that the light obtained by the full-rate carriage 53 is supplied to the imaging unit. To do. The full rate carriage 53 is provided with an LED light source 55 and a first mirror 57 </ b> A that receives reflected light from a document irradiated with light from the LED light source 55. Further, the half-rate carriage 54 is provided with a second mirror 57B and a third mirror 57C that provide the light obtained from the first mirror 57A to the imaging unit. Furthermore, the reading device 50 includes an imaging lens 58 and a CCD (Charge Coupled Device) image sensor 59. Among these, the imaging lens 58 optically reduces the optical image obtained from the third mirror 57C. The CCD image sensor 59 photoelectrically converts the optical image formed by the imaging lens 58. That is, in the reading device 50, an image is formed on the CCD image sensor 59 using a so-called reduction optical system.
A white reference plate 56 extending along the main scanning direction is attached to the lower part of a member provided between the first platen glass 52A and the second platen glass 52B.

  The reading device 50 further includes a control / image processing unit 60. The control / image processing unit 60 performs predetermined processing on the image data of the document input from the CCD image sensor 59. The control / image processing unit 60 controls the operation of each unit in the reading operation of the image reading apparatus (the document feeder 10 and the reading apparatus 50).

Now, details of each unit constituting the image reading apparatus will be described.
FIG. 2 is a diagram illustrating an example of the configuration of the LED light source 55 provided in the reading device 50. As shown in FIG. 1, the LED light source 55 functioning as an irradiating unit irradiates the original with light from both sides of the first mirror 57A. The LED light source 55 includes a rectangular base 91 having an opening at the center, a plurality of white LEDs 92, and a plurality of infrared LEDs 93. These white LEDs 92 and infrared LEDs 93 are alternately arranged along the longitudinal direction, that is, the main scanning direction of the document. The white LED 92 emits white light including red (R), green (G), and blue (B). The infrared LED 93 emits infrared light including infrared (IR). In the present embodiment, the infrared LED 93 emits infrared light having a central wavelength of 850 nm. The white LED 92 may be configured by combining a red LED, a green LED, and a blue LED, or may be configured by combining an ultraviolet LED and a phosphor.

  FIG. 3 is a diagram showing a schematic configuration of a CCD image sensor 59 provided in the reading device 50. The CCD image sensor 59 functioning as a light receiving unit includes a rectangular sensor substrate 59a and four pixel rows 59R, 59G, 59B, and 59I disposed on the sensor substrate 59a. In the following description, these four pixel columns 59R, 59G, 59B, and 59I are referred to as a red pixel column 59R, a green pixel column 59G, a blue pixel column 59B, and an infrared pixel column 59I, respectively. The red pixel column 59R, the green pixel column 59G, the blue pixel column 59B, and the infrared pixel column 59I are arranged along a direction (main scanning direction) orthogonal to the document transport direction, and the pixel columns are parallel to each other. Has been placed. Each of the red pixel column 59R, the green pixel column 59G, the blue pixel column 59B, and the infrared pixel column 59I is configured by arranging, for example, k photodiodes PD of 10 μm × 10 μm on a straight line. The distance between the blue pixel column 59B and the green pixel column 59G and the interval between the green pixel column 59G and the red pixel column 59R are each two lines in the sub-scanning direction. On the other hand, the distance between the blue pixel row 59B and the infrared pixel row 59I is 10 lines in the sub-scanning direction.

Here, each of the red pixel row 59R, the green pixel row 59G, and the blue pixel row 59B is provided with a color filter for transmitting different wavelength components, and each of them is for red (Red). It functions as a pixel row, a green pixel row, a blue pixel row, that is, a color sensor. The red pixel column 59R, the green pixel column 59G, and the blue pixel column 59B are further equipped with an infrared cutoff filter that blocks near-infrared light (for example, about 800 to 900 nm).
On the other hand, the infrared pixel row 59I is equipped with an infrared transmission filter that blocks light (400 to 800 nm) in the visible region and transmits the near infrared light. As such a CCD image sensor 59, for example, one disclosed in Japanese Patent Application Laid-Open No. 2003-60842 can be used.

FIG. 4 shows a configuration example of the backing member 20 provided in the document feeder 10. The backing member 20 includes a backing plate 20a and a cushion member 20b.
The backing plate 20a that functions as an urging member or an absorbing member is a surface opposite to the surface to be read of the document placed on the first platen glass 52A (light irradiation surface: referred to as the document surface in the following description). (Referred to as the back side of the original in the following description), and the original is pressed against the first platen glass 52A and brought into close contact therewith. The cushion member 20b is made of sponge or the like, and absorbs the height deviation of the backing plate 20a due to the thickness of the document.

Here, the backing plate 20a includes, for example, an infrared absorber having a maximum absorbance in the visible region of, for example, 7% or less and an absorbance in the near infrared region of, for example, 30% or more. The Examples of such infrared absorbers include a frit of Cu-P-containing glass in which copper and phosphorus are contained in silica glass, ytterbium oxide (Yb ₂ O ₃ ), naphthalocyanine such as vanadyl naphthalocyanine, or croconium. Is mentioned.
FIG. 5 shows the light reflection characteristics of naphthalocyanine and croconium among these infrared absorbers. In FIG. 5, the horizontal axis represents the wavelength (nm) of light and the vertical axis represents the reflectance (%). As is clear from the figure, these materials have a low reflectance in the near infrared region relative to the visible region, in other words, a large amount of light absorption in the near infrared region (especially near 850 nm). I understand. That is, in the present embodiment, the emission wavelength of the infrared LED 93 is determined so as to match the absorption wavelength of such an infrared absorbent. And since this backing plate 20a has little light absorption in a visible region, it looks visually gray near white.
In the present embodiment, in addition to the backing plate 20a, the backing roll 17 is also made of a material having similar light reflection characteristics.

  FIG. 6 is a block diagram of the control / image processing unit 60 shown in FIG. The control / image processing unit 60 includes a signal processing unit 70 and a control unit 80. The signal processing unit 70 receives each color input from the CCD image sensor 59 (specifically, a red pixel column 59R, a green pixel column 59G, a blue pixel column 59B, and an infrared pixel column 59I: see FIG. 3). Process the read data. On the other hand, the control unit 80 controls the operations of the document feeder 10 and the reading device 50.

The signal processing unit 70 includes a visible image processing unit 100, an infrared image processing unit 200, and a synthesis unit 300.
The visible image processing unit 100 performs various processes on the read data of each RGB color sent from the red pixel row 59R, the green pixel row 59G, and the blue pixel row 59B of the CCD image sensor 59, and outputs it as image information. To do.
The infrared image processing unit 200 performs various processes on the infrared read data sent from the infrared pixel row 59I of the CCD image sensor 59, and then extracts the identification information contained in the read data. Is output. The identification information is, for example, information given for each document, each image, or each file, and is used to uniquely identify the origin of the document. Details of the identification information will be described later.
The synthesizing unit 300 synthesizes (associates) the image information input from the visible image processing unit 100 and the identification information input from the infrared image processing unit 200, and uses a device (printer or PC) provided in the subsequent stage. Output to (Personal Computer)).

On the other hand, the control unit 80 includes a reading controller 81, a CCD driver 82, an LED driver 83, a scan driver 84, and a transport mechanism driver 85.
The reading controller 81 controls the entire document feeder 10 and the reading device 50 shown in FIG.
The CCD driver 82 controls the image data capturing operation by the CCD image sensor 59 (specifically, the red pixel column 59R, the green pixel column 59G, the blue pixel column 59B, and the infrared pixel column 59I: see FIG. 3). .
The LED driver 83 outputs an LED lighting switching signal, and controls turning on / off of the white LED 92 and the infrared LED 93 of the LED light source 55 in accordance with the reading timing of the document.
The scan driver 84 controls the scanning operation by the full rate carriage 53 and the half rate carriage 54 by turning on / off the motor in the reading device 50.
The transport mechanism driver 85 controls motor control, various rolls, clutches, and gate switching operations in the document feeder 10.

  From these various drivers, control signals are output to the document feeder 10 and the reading device 50, and these operations can be controlled based on the control signals. The reading controller 81 sets a reading mode and controls the document feeder 10 and the reading device 50 based on a control signal from the host system, a sensor output detected in the automatic selection reading function, a selection from the user, and the like. is doing. Examples of the reading mode include a fixed reading mode for reading a document placed on the first platen glass 52A, a transport reading mode for reading a document transported on the second platen glass 52B, and the like. Further, in the conveyance reading mode, there are a single-side mode for reading an image on one side of a document, a double-side mode for reading images on both sides of a document, and the like.

  FIG. 7 is a functional block diagram showing the configuration of the visible image processing unit 100 shown in FIG. The visible image processing unit 100 further includes an analog processing unit 110, an A / D conversion unit 120, a visible shading data storage unit 130, a visible shading correction unit 140, a delay processing unit 150, and an image processing unit 160. The analog processing unit 110 includes blue data Br from the blue pixel row 59B, green data Gr from the green pixel row 59G, and red data Rr from the red pixel row 59R that constitute the CCD image sensor 59. Each is input independently. The blue data Br, green data Gr, and red data Rr input from the CCD image sensor 59 are analog data.

The analog processing unit 110 performs analog correction such as gain / offset adjustment for each of the blue data Br, the green data Gr, and the red data Rr.
The A / D conversion unit 120 converts the blue data Br, the green data Gr, and the red data Rr that have been subjected to analog correction into digital data.
The visible shading data storage unit 130 stores visible shading data SHD (VIS) acquired in advance. The visible shading data SHD (VIS) is set for each of the blue pixel column 59B, the green pixel column 59G, and the red pixel column 59R.
The visible shading correction unit 140 performs shading correction on the input blue data Br, green data Gr, and red data Rr using each visible shading data SHD (VIS) read from the visible shading data storage unit 130. . Here, for each visible shading data SHD (VIS), for example, the white reference plate 56 is irradiated with white light by the white LED 92 before the document reading operation is started, and the blue pixel row 59B, the green pixel row 59G, and the red Obtained based on each read data obtained in the pixel row 59R.
In the visible shading correction, for the input blue data Br, green data Gr, and red data Rr, the photodiode PD in each of the corresponding blue pixel row 59B, green pixel row 59G, and red pixel row 59R is provided. Correction is performed in accordance with variations in sensitivity and light quantity distribution characteristics of the LED light source 55 (in this case, the white LED 92).

  The delay processing unit 150 corrects a gap due to a difference in attachment positions of the blue pixel row 59B, the green pixel row 59G, and the red pixel row 59R (see FIG. 3). That is, as shown in FIG. 3, the green pixel row 59G is arranged so as to be shifted by two lines in the sub-scanning direction with respect to the red pixel row 59R, and the blue pixel row 59B is subordinate to the green pixel row 59G. They are shifted by two lines in the scanning direction. Therefore, in this image reading apparatus, when a document reading operation is performed, a specific part (main scanning direction line) of the original is first read by the blue pixel row 59B, and then this specific part is read by the green pixel row. This is read at 59G, and finally this specific part is read by the pixel row for red 59R. In other words, at the same timing, the blue pixel row 59B, the green pixel row 59G, and the red pixel row 59R each read an image of a portion shifted by two lines in the sub-scanning direction. Become. Therefore, the delay processing unit 150 uses the red data Rr from the red pixel row 59R to be read last as a reference, and the green data Gr from the green pixel row 59G is equivalent to two lines in the sub-scanning direction with respect to the red data Rr. The blue data Br by the blue pixel row 59B is delayed by four lines in the sub-scanning direction with respect to the red data Rr (by two lines in the sub-scanning direction with respect to the green data Gr). Accordingly, the delay processing unit 150 outputs the blue data Br, the green data Gr, and the red data Rr obtained by reading the same part (the same main scanning direction line) of the document in synchronization. Become.

  The image processing unit 160 performs various types of image processing on the input blue data Br, green data Gr, and red data Rr, and blue image data B, green image data G, and red image data R as image information. Is output to the combining unit 300 (see FIG. 6). Examples of processing performed by the image processing unit 160 include γ / gray balance correction, color space conversion, enlargement / reduction, filtering processing, contrast adjustment, and background removal.

  FIG. 8 is a functional block diagram showing the configuration of the infrared image processing unit 200 shown in FIG. The infrared image processing unit 200 includes an analog processing unit 210, an A / D conversion unit 220, an infrared shading data storage unit 230, an infrared shading correction unit 240, a binarization processing unit 250, and an identification information analysis unit 260. Prepare. The analog processing unit 210 receives infrared data Ir from the infrared pixel row 59I that constitutes the CCD image sensor 59. The infrared data Ir input from the CCD image sensor 59 is analog data.

The analog processing unit 210 performs analog correction such as gain / offset adjustment on the infrared data Ir.
The A / D converter 220 converts the infrared data Ir subjected to analog correction into digital data.
The infrared shading data storage unit 230 stores infrared shading data SHD (IR) acquired in advance.
The infrared shading correction unit 240 performs shading correction on the input infrared data Ir using the infrared shading data SHD (IR) read from the infrared shading data storage unit 230. Here, the infrared shading data SHD (IR) is, for example, read data obtained by the infrared pixel array 59I by irradiating the white reference plate 56 with infrared light by the infrared LED 93 before starting the document reading operation. Get based on.
In the infrared shading correction, correction according to variation in sensitivity of the photodiode PD in the infrared pixel row 59I and light quantity distribution characteristics of the LED light source 55 (in this case, the infrared LED 93) is performed on the input infrared data Ir. Apply.

The binarization processing unit 250 binarizes the infrared data Ir input from the infrared shading correction unit 240 based on a predetermined threshold. That is, when the density at a certain pixel is equal to or higher than the threshold, the density at this pixel is set to the maximum value (for example, 255 for 8-bit gradation), and when the density at a certain pixel is less than the threshold, this pixel is set. The density is set to a minimum value (for example, 0) and output is performed.
The identification information analysis unit 260 analyzes the identification information from the code pattern image included in the binarized infrared data Ir, and outputs the obtained identification information to the synthesis unit 300 (see FIG. 6).

By the way, the image reading apparatus according to the present embodiment can read a document in which a visible image is formed on a medium such as paper, and can also read a document in which a visible image and an infrared image are formed on a medium. . In the latter, a document in which a visible image (document image) and a code pattern image as an infrared image are formed on a medium is used. A code pattern image (code image) is an image of an identification code and a position code obtained by encoding identification information and position information on a medium such as paper.
Here, as the identification information, either identification information for uniquely identifying a medium or identification information for uniquely identifying a visible image (document image) printed on the medium is employed. In the case where the former identification information is adopted, when a plurality of copies of the same document image are printed, different identification information is given to different media. On the other hand, when the latter identification information is employed, when a plurality of copies of the same document image are printed, the same identification information is given even on different media.
The position information is information indicating the coordinate position on the medium.

Now, a code pattern that is the basis of a code pattern image formed on a document will be described.
FIG. 9 is a diagram for explaining a code pattern.
First, the bit pattern constituting the code pattern will be described.
FIG. 9A shows an example of bit pattern arrangement.
A bit pattern is the minimum unit of information embedding. Here, as shown in FIG. 9A, bits are arranged at two locations selected from nine locations. In the figure, black squares indicate positions where bits are arranged, and hatched squares indicate positions where bits are not arranged. There are 36 (= ₉ C ₂ ) combinations for selecting 2 locations out of 9 locations. Therefore, 36 kinds of information (about 5.2 bits) can be expressed by such an arrangement method. However, the identification information and the position information are expressed using 32 (5 bits) of the 36.

Incidentally, the minimum square shown in FIG. 9A has a size of 2 dots × 2 dots at a resolution of 600 dpi (dot per inch). Since the size of one dot at 600 dpi is 0.0423 mm, one side of this minimum square is 84.6 μm (= 0.0423 mm × 2). Since the dots that make up the code pattern become more noticeable as the size of the dots increases, it is preferable that the dots be as small as possible. However, if it is too small, it becomes difficult to print with an image forming apparatus such as a printer, and reading with an image reading apparatus becomes difficult. Therefore, the above value is adopted as the dot size, which is larger than 50 μm and smaller than 100 μm. As a result, it is possible to make dots that can be printed relatively easily in the image forming apparatus, and that the size can be read relatively easily in the image reading apparatus. That is, 84.6 μm × 84.6 μm is the minimum size that can be stably formed and read by the current image forming apparatus and image reading apparatus.
By setting the dots to such a size, one side of one bit pattern is about 0.5 (0.0423 × 2 × 6) mm.

A code pattern composed of such bit patterns will be described.
FIG. 9B shows an example of the arrangement of code patterns.
Here, the minimum square shown in FIG. 9B corresponds to the bit pattern shown in FIG. That is, the identification code obtained by encoding the identification information is embedded using 16 (= 4 × 4) bit patterns. Also, the X position code obtained by encoding the position information in the X direction and the Y position code obtained by encoding the position information in the Y direction are each embedded using four bit patterns. Further, a synchronization code for detecting the position and rotation of the code pattern is embedded in the upper left corner using one bit pattern.
Since the size of one code pattern is equal to the width of five bit patterns, it is about 2.5 mm. In the present embodiment, a code pattern image obtained by imaging the code pattern generated in this way is arranged on the entire surface of a document to be read.
The code pattern image is recorded on the sheet with an image forming material (for example, toner or ink) containing an infrared absorber such as naphthalocyanine or croconium. Therefore, the light reflection characteristics of the code pattern image formed on the document to be read are as shown in FIG.

  Now, an original reading operation using the image reading apparatus will be described with reference to FIGS. In this image reading apparatus, as described above, reading of a document placed on the first platen glass 52A (fixed reading mode) and reading of a document conveyed by the document feeder 10 (conveyance reading mode) are performed. It is feasible.

First, the fixed reading mode will be described. In the fixed reading mode, the document feeder 10 is opened with respect to the reading device 50, and after the document is set on the first platen glass 52A, the document feeder 10 is closed. As a result, the document on the first platen glass 52A is pressed against the first platen glass 52A by the backing member 20 provided in the document feeder 10.
When reading an image of a document placed on the first platen glass 52A, the full rate carriage 53 and the half rate carriage 54 move in the scanning direction (arrow direction) at a ratio of 2: 1. At this time, both the white LED 92 and the infrared LED 93 constituting the LED light source 55 of the full-rate carriage 53 are turned on, and light from these is irradiated on the surface to be read of the document. Then, the reflected light from the document is reflected in the order of the first mirror 57A, the second mirror 57B, and the third mirror 57C and guided to the imaging lens 58. The light guided to the imaging lens 58 is imaged on the light receiving surface of the CCD image sensor 59. That is, of the reflected light, visible light is received by the blue pixel row 59B, green pixel row 59G, and red pixel row 59R, and infrared light is received by the infrared pixel row 59I. Each pixel column constituting the CCD image sensor 59 is constituted by a one-dimensional sensor as described above, and one line is processed simultaneously. The full-rate carriage 53 and the half-rate carriage 54 are moved in this line direction (scanning sub-scanning direction) to read the next line of the document. By executing this over the entire document, reading of one page of the document is completed. That is, blue data Br, green data Gr, red data Rr, which is read data of a visible image on a document, and infrared data Ir, which is read data of an infrared image, are obtained.

Next, the conveyance reading mode will be described. In the conveyance reading mode, after the document feeding device 10 is closed with respect to the reading device 50, a document or a document bundle is set on the document tray 11, and then the document feeding device 10 starts conveying the document.
When reading an image of a document transported by the document feeder 10, the transported document passes over the second platen glass 52B while being pressed against the second platen glass 52B by the backing roll 17. At this time, the full rate carriage 53 and the half rate carriage 54 are stopped at the position indicated by the solid line in FIG. Then, the light of the white LED 92 and the infrared LED 93 constituting the LED light source 55 of the full rate carriage 53 is irradiated onto the surface to be read of the document. At this time, the backing roll 17 faces the original reading position by the full rate carriage 53 with the original interposed therebetween. Then, the reflected light of the first line of the original is imaged by the imaging lens 58 via the first mirror 57A, the second mirror 57B, and the third mirror 57C. The light guided to the imaging lens 58 is imaged on the light receiving surface of the CCD image sensor 59. That is, of the reflected light, visible light is received by the blue pixel row 59B, green pixel row 59G, and red pixel row 59R, and infrared light is received by the infrared pixel row 59I. Then, after one line in the main scanning direction is simultaneously processed in each pixel row constituting the CCD image sensor 59, the next line in the main scanning direction of the document conveyed by the document feeder 10 is read. Then, after the leading edge of the document reaches the reading position of the second platen glass 52B, the trailing edge of the document passes through the reading position of the second platen glass 52B, thereby reading one page of the document in the sub-scanning direction. Is completed. That is, blue data Br, green data Gr, red data Rr, which is read data of a visible image on a document, and infrared data Ir, which is read data of an infrared image, are obtained.

  Further, when reading images formed on both sides of the original, the discharge roll 19 is immediately before the rear end of the original, which has been read on the front side, passes through the discharge roll 19 provided in the second conveyance path 32. The driving direction is switched to the reverse direction. At this time, the document is guided to the third conveyance path 33 by switching the direction of the gate (not shown). At this time, the trailing edge side of the document is now the leading edge side. Then, the original passes again over the second platen glass 52B with the front and back sides reversed, and the back side is read in the same manner as the above-described process. As a result, blue data Br, green data Gr, red data Rr, which is read data of a visible image on a document, and infrared data Ir, which is read data of an infrared image, are obtained. Thereafter, the drive direction of the discharge roll 19 is switched to the reverse direction again immediately before the rear end of the document that has been read on the back side passes through the discharge roll 19 provided in the second conveyance path 32. At this time, the document is guided to the fourth conveyance path 34 by switching the direction of the gate (not shown). At this time, the leading and trailing edges of the document are replaced again, and the document is discharged onto the paper discharge tray 12 in a state where the front and back of the document are reversed. By doing so, the arrangement order of a plurality of document bundles can be made the same when placed on the document tray 11 and when ejected onto the paper discharge tray 12.

The blue data Br, the green data Gr, and the red data Rr obtained by reading the document in the fixed reading mode and the conveyance reading mode are subjected to predetermined processing in the visible image processing unit 100, and are then processed into image information, Output as blue image data B, green image data G, and red image data R.
On the other hand, infrared data Ir obtained by reading a document is subjected to a predetermined process by the infrared image processing unit 200 and then output as identification information.
These image information and identification information are associated with each other by the synthesis unit 300 and then output to an external device.

  Here, in the present embodiment, an infrared LED 93 that emits light having a central wavelength of 850 nm is used, and the infrared pixel row 59I receives infrared light in the vicinity of 850 nm. The wavelength of 850 nm substantially coincides with the absorption wavelength of the infrared absorbent that constitutes the identification information on the document as described above. For this reason, the infrared pixel row 59I can more accurately detect the presence or absence of identification information on the document, and can further improve the accuracy of identification information acquired based on the obtained infrared data Ir. Can do.

  By the way, in the image reading apparatus according to the present embodiment, for example, a document having punched holes for files may be read. In addition, this image reading apparatus sometimes reads a document in which images are formed on both sides of a medium (referred to as a double-sided document). In this case, infrared images may be formed on the surface to be read (front surface) of the original and the surface opposite to the surface to be read (back surface), respectively.

  FIG. 10A is a diagram for explaining the visible image reading of the document M in which the punch hole H is opened in the fixed reading mode. Here, FIG. 10A-1 schematically shows the relationship between the original M and the backing plate 20a, and the irradiation light and reflected light. 10A-2 shows a CCD image sensor 59 (specifically, a blue pixel row 59B, a green pixel row 59G, and a red pixel when the original M shown in FIG. 10A-1 is read). The relationship between the reading position and the sensor output by any one of the columns 59R) is shown.

  As shown in FIG. 10A-1, the document M is pressed against the first platen glass 52A (see FIG. 1) (not shown) by the backing plate 20a. Further, it is assumed that the document M has punch holes H penetrating the front surface (read surface) and the back surface. Further, in this example, it is assumed that images (visible images and infrared images) are not formed on the front and back surfaces of the document M within the range shown in the drawing. Note that the arrow shown in the figure indicates white light that is irradiated on or reflected from the original M, and the larger the thickness of the line, the larger the amount of light.

When reading the document M, white light (visible light) emitted from the white LED 92 of the LED light source 55 is sequentially irradiated onto the surface of the document M as the full-rate carriage 53 moves.
Part of the white light applied to the document M passes through the surface of the document and enters the document M, and the others are reflected from the document surface and output as reflected light. Here, if the background of the medium constituting the document M is white, much of the irradiated white light is reflected by the document surface. The reflected light from the document surface thus output is received by the blue pixel row 59B, the green pixel row 59G, and the red pixel row 59R provided in the CCD image sensor 59.

  The white light that has passed through the document surface and entered the document M then reaches the document back surface. At this time, the backing plate 20a is in close contact with the back side of the document, and the backing plate 20a has a characteristic of reflecting white light (visible light) as shown in FIG. The reached white light is reflected by the backing plate 20a. Therefore, most of the white light transmitted through the document surface is reflected by the backing plate 20a. The white light reflected by the backing plate 20a in this way passes through the document surface in the direction opposite to the previous time and is output as reflected light. The reflected light from the backing plate 20a thus output is also received by the blue pixel row 59B, the green pixel row 59G, and the red pixel row 59R.

  On the other hand, since the original M does not exist, the white light irradiated to the formation site of the punch hole H reaches the backing plate 20a as it is. The backing plate 20a has the property of reflecting white light as described above, and the irradiated white light is reflected by the backing plate 20a and output as reflected light. The reflected light from the backing plate 20a thus output is also received by the blue pixel row 59B, the green pixel row 59G, and the red pixel row 59R.

  Then, as shown in FIG. 10A-2, the sensor output from the CCD image sensor 59 (here, the blue pixel row 59B, the green pixel row 59G, and the red pixel row 59R) is the presence of the document M. The area where the punch hole H is formed (the area where the document M is not present) and the area where the punch hole H is formed (the area where the document M does not exist) are both large, and both are almost unchanged. Therefore, by using the backing plate 20a having the light reflection characteristics shown in FIG. 5, the influence of the punch hole H is greatly reduced when the visible image of the original M is read.

  On the other hand, FIG. 10B is a diagram for explaining infrared image reading of a double-sided document in which infrared images are formed on both sides of the medium in the fixed reading mode. Here, FIG. 10 (b-1) schematically shows the relationship between the original M and the backing plate 20a, and the irradiated light and reflected light. FIG. 10B-2 shows the relationship between the reading position by the CCD image sensor 59 (specifically, the infrared pixel row 59I) and the sensor output when the original shown in FIG. 10B-1 is read. Show.

  As shown in FIG. 10 (b-1), the document M is pressed against the first platen glass 52A (see FIG. 1) (not shown) by the backing plate 20a as in the case of reading the visible image. Further, it is assumed that a front infrared image FI is formed on the front surface (read surface) of the document M, and a back infrared image RI is formed on the back surface of the document M. Note that the arrows shown in the figure indicate infrared light that is irradiated on or reflected from the original M, and the larger the thickness of the line, the larger the amount of light. Moreover, what represented the line with the broken line means that the light quantity is very small.

When reading the document, the infrared light emitted from the infrared LED 93 of the LED light source 55 is sequentially irradiated onto the surface of the document M as the full-rate carriage 53 moves.
Of the infrared light irradiated to the document M, a part of the infrared light irradiated to the portion where the surface infrared image FI is not formed passes through the document surface and enters the document M. Is reflected on the document surface and output as reflected light. Here, if the background of the medium constituting the document M is white (high reflectivity even in the near infrared region), much of the irradiated infrared light is reflected on the document surface. The reflected light from the document surface output in this way is received by the infrared pixel row 59I.

  The infrared light that has passed through the document surface and entered the document M then reaches the document back surface. At this time, the backing plate 20a is in close contact with the back side of the document, and the backing plate 20a has a characteristic of absorbing infrared light as shown in FIG. External light is absorbed by the backing plate 20a. Further, the infrared light that has reached the portion of the back side of the document where the back side infrared image RI is formed has a characteristic that the back side infrared image RI itself absorbs infrared light as shown in FIG. Therefore, it is absorbed by the back infrared image RI. Therefore, most of the infrared light that has entered the document M is absorbed by the backing plate 20a or the back infrared image RI, and as a result, almost no reflected light from the document back side.

  Then, as shown in FIG. 10 (b-2), the sensor output from the CCD image sensor 59 (here, the infrared pixel row 59I) is large for the region where the surface infrared image FI does not exist, and the surface red It becomes smaller for the area where the outer image FI exists. Further, in the present embodiment, since the backing plate 20a is configured using a material having absorption in the infrared region, the reflected light from the back side of the document includes the region where the back side infrared image RI exists and the presence of the back side infrared image RI. Both areas are almost the same (actually little reflection). Therefore, by using the backing plate 20a according to the present embodiment, when the infrared image of the front infrared image FI of the document M is read, the influence of the back infrared image RI of the same document M is reduced. The occurrence of so-called show-through is suppressed. In this example, the sensor output corresponding to the back infrared image RI is substantially the same as that of the background portion, but may be slightly smaller than the background portion. However, also in this case, a large gap portion is formed between the sensor output corresponding to the front surface infrared image FI and the sensor output corresponding to the back surface infrared image RI.

  Next, for comparison, a case where a white backing plate (hereinafter referred to as white backing plate 20W) is used will be described. Note that, unlike the backing plate 20a in the present embodiment, the white backing plate 20W has a high light reflectance (low light absorption rate) in the visible region and the near infrared region.

  FIG. 11A is a diagram for explaining the visible image reading of the document M in which the punch holes H are opened in the fixed reading mode. Here, FIG. 11 (a-1) schematically shows the relationship between the original M and the white backing plate 20W and the irradiated light and reflected light. 11A-2 shows a CCD image sensor 59 (specifically, a blue pixel row 59B, a green pixel row 59G, and a red pixel row when the original shown in FIG. 11A-1 is read). 59R) shows the relationship between the reading position and the sensor output.

  In the visible region, the white backing plate 20W has the same light reflection characteristics as the backing plate 20a according to the present embodiment. Therefore, in the visible image reading, as shown in FIG. 11A-1, the white light irradiated on the original M is reflected on the surface of the original, and the white light irradiated on the formation site of the punch hole H is reflected. Reflected by the white backing plate 20W. Thus, as in the case of using the backing plate 20a, as shown in FIG. 11 (a-2), the influence of the punch hole H on the sensor output is greatly reduced.

  On the other hand, FIG. 11B is a diagram for explaining infrared image reading of a double-sided document in which infrared images are formed on both sides of the medium in the fixed reading mode. Here, FIG. 11 (b-1) schematically shows the relationship between the original M and the white backing plate 20W, and the irradiated light and reflected light. FIG. 11B-2 shows the relationship between the reading position by the CCD image sensor 59 (specifically, the infrared pixel row 59I) and the sensor output when the original shown in FIG. 11B-1 is read. Show.

  As shown in FIG. 11 (b-1), among the infrared light irradiated on the document M, a part of the infrared light irradiated on the portion where the surface infrared image FI is not formed is the surface of the document. , And enters the original M, and the others are reflected by the original surface and output as reflected light. Here, if the background of the medium constituting the document M is white (high reflectivity even in the near infrared region), much of the irradiated infrared light is reflected on the document surface. The reflected light from the document surface output in this way is received by the infrared pixel row 59I.

  Of the infrared light that has entered the document M without being reflected on the surface of the document, the infrared light that has reached a portion where the back-side infrared image RI does not exist is reflected by the white backing plate 20W. On the other hand, of the infrared light that has entered the document M, the infrared light that reaches the portion where the back infrared image RI is present is absorbed by the back infrared image RI. For this reason, the amount of light reflected from the back side of the document increases in a region where the back infrared image RI does not exist and decreases in a region where it does not exist. The reflected light from the back side of the document output in this way is received by the infrared pixel row 59I.

  Then, as shown in FIG. 11B-2, the sensor output from the CCD image sensor 59 (here, the infrared pixel row 59I) is large in the region where the surface infrared image FI does not exist, and the surface infrared image FI. It becomes smaller in the area where there is. Further, the sensor output is large in a region where the back infrared image RI does not exist, and is small in a region where the back infrared image RI exists. Here, the sensor output corresponding to the back-side infrared image RI is larger than the sensor output corresponding to the front-side infrared image FI (light as an image), but an overlapping portion where the output values overlap is formed. Therefore, when the white backing plate 20W is used, the influence of the back-side infrared image RI formed on the same document M cannot be eliminated when reading the infrared image of the front-side infrared image FI of the document M. In this case, an overlapping portion occurs between the sensor output corresponding to the front infrared image FI and the sensor output corresponding to the back infrared image RI.

  For comparison, document reading when a black backing plate (hereinafter referred to as black backing plate 20K) is used will be described. The black backing plate 20K has a low light reflectance (high light absorption rate) in the visible region and the near infrared region.

  FIG. 12A is a diagram for explaining the visible image reading of the document M in which the punch hole H is opened in the fixed reading mode. Here, FIG. 12 (a-1) schematically shows the relationship between the original M and the black backing plate 20K, and the irradiated light and reflected light. 12A-2 shows a CCD image sensor 59 (specifically, a blue pixel row 59B, a green pixel row 59G, and a red pixel row when the original shown in FIG. 12A-1 is read). 59R) shows the relationship between the reading position and the sensor output.

  As shown in FIG. 12 (a-1), in the visible image reading, the white light irradiated on the original M is reflected on the surface of the original, while the white light irradiated on the formation site of the punch hole H is black. It is absorbed by the backing plate 20K. Then, as shown in FIG. 12 (a-2), the sensor output becomes high at the portion where the document M exists, while it becomes extremely low at the portion where the punch hole H is formed (the portion where the document M does not exist). Therefore, when the black backing plate 20K is used, when the visible image of the original M is read, the influence of the punch holes H cannot be reduced, and the marks of the punch holes H remain black.

  On the other hand, FIG. 12B is a diagram for explaining infrared image reading of a double-sided document in which infrared images are formed on both sides of the medium in the fixed reading mode. Here, FIG. 12B-1 schematically shows the relationship between the original M and the black backing plate 20K, and the irradiated light and reflected light. FIG. 12B-2 shows the relationship between the reading position by the CCD image sensor 59 (specifically, the infrared pixel row 59I) and the sensor output when the original shown in FIG. 12B-1 is read. Show.

  In the near-infrared region, the black backing plate 20K has light reflection characteristics similar to those of the backing plate 20a according to the present embodiment. Therefore, in the infrared image reading, as shown in FIG. 12 (b-1), almost no reflected light from the back side of the document is lost. As a result, as in the case of using the backing plate 20a, as shown in FIG. 12 (b-2), the influence (back show) of the back infrared image RI on the sensor output is greatly reduced. Become.

  Thus, by using the backing plate 20a in the present embodiment, the influence of the punch hole H in reading the visible image is remarkably reduced. Further, by using the backing plate 20a, the influence of the back surface infrared image RI in the infrared image reading is remarkably reduced. Here, the case where an infrared image is formed on the back surface of the document M has been described as an example. However, for example, a black image containing carbon black on the back surface of the document M (similarly absorbs infrared light). ) Is also formed, the influence of the back black image is similarly reduced.

Here, the show-through of the back infrared image RI when the front infrared image FI is read will be described in detail.
FIG. 13A is a diagram for explaining the reflected light amount distribution from the front surface infrared image FI and the back surface infrared image RI when the white backing plate 20W is used. FIG. 13B is a diagram for explaining the distribution of the amount of reflected light from the front surface infrared image FI and the back surface infrared image RI when the backing plate 20a and the black backing plate 20K in the present embodiment are used. It is.

  As shown in FIG. 13 (a), when the white backing plate 20W is used, the surface reflection intensity distribution D (FI) of the front surface infrared image FI and the back surface reflection intensity distribution D (RI) of the back surface infrared image RI. There is an overlapping part (see also FIG. 11 (b-2)). That is, the influence of the show-through of the back infrared image RI on the front infrared image FI increases. For this reason, even if the binarization processing unit 250 performs binarization processing on the infrared data Ir obtained by reading, the two cannot be separated.

  On the other hand, as shown in FIG. 13B, when the backing plate 20a or the black backing plate 20K according to the present embodiment is used, the surface reflection intensity distribution D (FI) and the back surface of the surface infrared image FI are used. A gap portion is generated in the back surface reflection intensity distribution D (RI) of the infrared image RI (see also FIG. 10 (b-2) and FIG. 12 (b-2)). That is, the influence of the show-through of the back infrared image RI on the front infrared image FI is reduced. For this reason, if the binarization processing unit 250 performs binarization processing on the infrared data Ir obtained by reading, for example, with the threshold shown in the figure, the influence of show-through by the back infrared image RI is easily eliminated. Infrared data relating to the surface infrared image FI is obtained. That is, the identification information analysis unit 260 can easily analyze the identification information. However, when the black backing plate 20K is used, there is a problem that the marks of the punch holes H become black. Therefore, the usefulness of the backing plate 20a in the present embodiment is understood.

  Here, the fixed reading mode has been described as an example. However, for example, also in the conveyance reading mode, the backing roll 17 is made of the same material as the backing plate 20a, and therefore, the influence of the show-through of the back image of the document M can be reduced for the same reason. .

  In this example, the case where infrared images are formed on both sides of the document M has been described. However, when a black toner image containing carbon black is formed on the back side of the reading surface of the original M, for example, infrared absorption occurs in the black toner image formation region as in the case of the infrared image. Therefore, even in such a case, it is effective to use the backing plate 20a.

<Embodiment 2>
The present embodiment is substantially the same as the first embodiment, but uses a backing plate 20a that is slightly different from the first embodiment. 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. 14 illustrates the configuration of the backing plate 20a used in the present embodiment. The backing plate 20a includes a base portion 20X and a lattice portion 20Y formed on the base portion 20X. The lattice portion 20Y is formed over almost the entire surface of the base portion 20X.
Similarly to the backing plate 20a in the first embodiment, the base portion 20X includes an infrared absorber such as naphthalocyanine or croconium in the base material. Therefore, the base 20X has a relatively high reflection characteristic (low absorption characteristic) for visible light, and has a reflection characteristic (high absorption characteristic) lower than that for the visible region for infrared light.
The lattice portion 20Y is formed of, for example, carbon black. Therefore, the grating portion 20Y has low reflection characteristics (high absorption characteristics) with respect to visible light and infrared light. Furthermore, it is preferable to set the interval between the lines constituting the grid portion 20Y in correspondence with the number of screen lines that are not often used when printing a document to be read, for example.

FIG. 15 is a functional block diagram showing the configuration of the visible image processing unit 100 used in the present embodiment. The configuration of the visible image processing unit 100 is substantially the same as that described in the first embodiment, except that a data replacement unit 170 is further provided. The data replacement unit 170 is provided between the delay processing unit 150 and the image processing unit 160.
The data replacement unit 170 detects whether the blue data Br, the green data Gr, and the red data Rr input from the delay processing unit 150 include data obtained by reading the backing plate 20a instead of the original. Yes. When the data replacement unit 170 determines that the data read from the backing plate 20a exists, all the corresponding blue data Br, green data Gr, and red data Rr are set to the maximum values (in the case of 8 bits). Is replaced with 255) and output.

  FIG. 16A is a diagram for explaining the visible image reading of the document M in which the punch holes H are opened in the fixed reading mode. Here, FIG. 16 (a-1) schematically shows the relationship between the document M and the backing plate 20a, the irradiation light and the reflected light. 16A-2 shows a CCD image sensor 59 (specifically, a blue pixel row 59B, a green pixel row 59G, and a red pixel row when the original shown in FIG. 16A-1 is read). 59R) shows the relationship between the reading position and the sensor output.

  As shown in FIG. 16 (a-1), the document M is pressed against the first platen glass 52A (see FIG. 1) (not shown) by the backing plate 20a. Further, it is assumed that the document M has punch holes H penetrating the front surface (read surface) and the back surface. Further, in this example, it is assumed that images (visible images and infrared images) are not formed on the front and back surfaces of the document within the range shown in the drawing. Note that the arrow shown in the figure indicates white light that is irradiated on or reflected from the original M, and the larger the thickness of the line, the larger the amount of light.

  In the visible image reading, the white light irradiated to the site where the punch hole H is formed reaches the backing plate 20a as it is because the original M does not exist. As described above, the backing plate 20a includes the base portion 20X that reflects white light and the lattice portion 20Y that absorbs white light, and the irradiated white light is partially absorbed by the backing plate 20a and The remaining majority is output as reflected light. The output reflected light from the backing plate 20a is received by the blue pixel row 59B, the green pixel row 59G, and the red pixel row 59R.

  Then, as shown in FIG. 16A-2, the sensor output from the CCD image sensor 59 (here, the blue pixel row 59B, the green pixel row 59G, and the red pixel row 59R) is the presence of the document M. It becomes uniformly large in the part to be performed (however, the background part without an image). Further, the sensor output has a saw-tooth shape corresponding to the pattern of the lattice at the portion where the punch hole H is formed (the portion where the document M does not exist). That is, the sensor output is large because the amount of reflected light is large at the portion corresponding to the base portion 20X, and the sensor output is small because the amount of reflected light is small at the portion corresponding to the grating portion 20Y.

  Then, if the sawtooth pattern is detected in the input blue data Br, green data Gr, and red data Rr, the data replacement unit 170 of the visible image processing unit 100 forcibly sets this region to the maximum value (that is, Replace with (white) and output. Therefore, the trace of the punch hole H is erased from the blue image data B, the green image data G, and the red image data R that are finally output.

  On the other hand, FIG. 16B is a diagram for explaining infrared image reading of a double-sided document in which infrared images are formed on both sides of the medium in the fixed reading mode. Here, FIG. 16 (b-1) schematically shows the relationship between the original M and the backing plate 20a, the irradiation light and the reflected light. FIG. 16B-2 shows the relationship between the reading position by the CCD image sensor 59 (specifically, the infrared pixel row 59I) and the sensor output when the original shown in FIG. 16B-1 is read. Show.

  As shown in FIG. 16 (b-1), the document M is pressed against the first platen glass 52A (see FIG. 1) (not shown) by the backing plate 20a as in the case of reading the visible image. Further, it is assumed that a front infrared image FI is formed on the front surface (read surface) of the document M, and a back infrared image RI is formed on the back surface of the document M. Note that the arrows shown in the figure indicate infrared light that is irradiated on or reflected from the original M, and the larger the thickness of the line, the larger the amount of light. Moreover, what represented the line with the broken line means that the light quantity is very small.

  In the present embodiment, the base 20X constituting the backing plate 20a is made of a material in which both visible light and the grating portion 20Y have infrared absorption characteristics. From the infrared point of view, this is synonymous with the fact that the backing plate 20a is entirely black (absorber). Therefore, as in the first embodiment, as shown in FIG. 16 (b-1), there is almost no reflected light from the back side of the document. Thereby, as shown in FIG. 16 (b-2), the influence of the back infrared image RI on the sensor output is greatly reduced.

It is a figure which shows the structural example of an image reading apparatus. It is a figure which shows an example of a structure of a LED light source. It is a figure which shows schematic structure of a CCD image sensor. FIG. 4 is a diagram showing a configuration of a backing member in the first embodiment. It is the figure which showed the light reflection characteristic of the naphthalocyanine and croconium used for a backing member and a backing roll. It is a block diagram of a control and image processing unit. 2 is a functional block diagram of a visible image processing unit in Embodiment 1. FIG. 4 is a functional block diagram of an infrared image processing unit in Embodiment 1. FIG. It is a figure for demonstrating the code pattern formed on a manuscript with a visible image. FIG. 4 is a diagram for explaining light reflection from a document when the backing plate of the first embodiment is used. (A) illustrates a case where a document having a punch hole is read and a visible image is read. This is a case where an infrared image is read from an original on which an infrared image is formed. It is a figure for demonstrating the light reflection from the original in the case of using a white backing plate, (a) is a case where a document with a punch hole is read, and (b) is infrared on both sides. This is a case of reading an infrared image of a document on which an image is formed. It is a figure for demonstrating the light reflection from the original at the time of using a black backing board, (a) is a case where a visible image is read on the original with a punched hole, and (b) is infrared on both sides. This is a case of reading an infrared image of a document on which an image is formed. (a) is a figure for demonstrating the reflected light quantity distribution from the surface infrared image and back surface infrared image at the time of using a white backing plate, (b) is a backing plate and black in this Embodiment. It is a figure for demonstrating the reflected light quantity distribution from the surface infrared image and back surface infrared image at the time of using a backing plate. 6 is a diagram showing a schematic configuration of a backing plate in Embodiment 2. FIG. 10 is a functional block diagram of a visible image processing unit according to Embodiment 2. FIG. FIG. 6 is a diagram for explaining light reflection from a document when the backing plate of the second embodiment is used. (A) shows a case where a document with a punch hole is read, and (b) shows both sides. This is a case where an infrared image is read from an original on which an infrared image is formed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Document feeder, 17 ... Backing roll, 20 ... Backing member, 20a ... Backing plate, 20b ... Cushion member, 50 ... Reading device, 52A ... First platen glass, 52B ... Second platen glass, 55 ... LED light source, 59 ... CCD image sensor, 59R ... red pixel row, 59G ... green pixel row, 59B ... blue pixel row, 59I ... infrared pixel row, 60 ... control / image processing unit, 70 ... signal processing unit , 80 ... control unit, 92 ... white LED, 93 ... infrared LED, 100 ... visible image processing unit, 200 ... infrared image processing unit, 240 ... infrared shading correction unit, 250 ... binarization processing unit, 260 ... Identification information analysis unit, 300 ... compositing unit, FI ... front infrared image, RI ... back infrared image, Br ... blue data, Gr ... green data, Rr ... red data, Ir ... infrared data, B ... blue image data , G ... green image data, R ... red image data

Claims (7)

An irradiation unit for irradiating the document with infrared light;
A biasing member having a characteristic of absorbing infrared light, and biasing the document from a side opposite to the irradiation surface of the document by the irradiation unit;
A light receiving unit that receives infrared light reflected from the document irradiated by the irradiation unit and biased by the biasing member;
An image reading apparatus comprising: an analysis unit that acquires a code image formed on the document from a result of receiving infrared light by the light receiving unit and analyzes code information included in the code image.   The image reading apparatus according to claim 1, further comprising: a binarization processing unit that performs binarization processing on a light reception result by the light receiving unit and outputs the result to the analysis unit. The irradiation unit further irradiates the original with visible light,
The light receiving unit further receives visible light reflected from the document,
The image reading apparatus according to claim 1, wherein the biasing member is set to have a higher light reflectivity for visible light than a light reflectivity for infrared light. The irradiation unit further irradiates the original with visible light,
The light receiving unit further receives visible light reflected from the document,
The biasing member further has a property of absorbing visible light in a specific pattern,
The image reading apparatus according to claim 1, further comprising: a replacement unit that replaces the specific pattern with background data of the document when the specific pattern is present in the visible light reception result of the light receiving unit. . An irradiation unit for irradiating the document with infrared light;
An absorption member that is provided on the opposite side of the irradiation surface of the document by the irradiation unit and that absorbs infrared light that is irradiated by the irradiation unit and transmitted through the document;
A light receiving unit that receives infrared light irradiated from the irradiation unit and reflected from the document;
An image reading apparatus comprising: an analysis unit that acquires a code image formed on the document from a result of receiving infrared light by the light receiving unit and analyzes code information included in the code image.   6. The image reading apparatus according to claim 5, wherein the absorbing member is disposed in close contact with the surface of the document opposite to the irradiation surface.   6. The image reading apparatus according to claim 5, wherein the absorbing member is set to have a higher light reflectivity for visible light than a light reflectivity for infrared light.

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