JP2011040857A - Document reading apparatus, document reading method, and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve accuracy in preventing show-through of a document. <P>SOLUTION: The document reading apparatus includes: an acquisition unit for acquiring document reading information of the document, with the acquisition unit having document holders with each reflectance located on a back side of the acquisition unit; and a correction unit for correcting the document reading information by using the document reading information acquired by the acquisition unit, and the reflectance of the document holders. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a document reading device, a document reading method, and an image processing method.

2. Description of the Related Art Conventionally, it has been known that in a document reading device such as a scanner, the content read on the back side of the document reading surface, dirt on the document presser (opposite surface of the scanner), etc. show through on the read image of the read document. Yes. In order to solve at least a part of this problem, a technique for reading a document by changing the color of the document press is known (Patent Document 1).

JP-A-56-21163 JP-A-5-14717 JP-A-5-22572 Japanese Patent Laid-Open No. 11-284810 JP 11-298694 A

However, in the above case, there is still room for improvement in the technology for suppressing the show-through of the document, such as the possibility that the difference in the color of the document presser may appear in the read image.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the conventional problems described above, and to improve the accuracy of suppressing the show-through of a document.

  In order to solve at least a part of the above problems, the present invention employs the following aspects.

A first aspect provides a document reading device. The document reading apparatus according to the first aspect of the present invention includes an acquisition unit that acquires document reading information of a document facing a document pressing member (an opposing surface of a reading unit described later) having a plurality of reflectances, and the acquisition unit. And a correction unit that corrects the document reading information using the document reading information acquired by the above and the reflectance of the document presser.

According to the document reading apparatus according to the first aspect, since the document reading information of the document with the document presses having different reflectances on the back and the reflectivity of the document press are corrected, the document reading information of the document is corrected. The document show-through can be suppressed with high accuracy.

In the document reading apparatus according to the first aspect, the acquisition units are arranged side by side in the document conveyance direction, and each of the acquisition units is positioned at a position facing each of the reading units and at least two reading units that read the document. And at least two document pressers having different reflectances on the contact surface on the side in contact with the document, wherein the document reading information includes the document with the contact surface on the back side as the at least two reading units. May be information acquired by reading each of the above. In this case, the acquisition unit can easily acquire the document reading information of the document with the document presses having different reflectivities on the back, and the acquired document reading information and the reflection of each contact surface of at least two document presses. By correcting the document reading information using the rate, the show-through of the document can be accurately suppressed.

In the document reading apparatus according to the first aspect, the acquisition unit may include at least five of the reading unit and the document pressing unit. In this case, the document reading information is corrected using the document reading information of the document read by the reading unit with at least five contact surfaces having different reflectivities on the back and the reflectance of each contact surface. Show-through can be suppressed with high accuracy.

In the document reading apparatus according to the first aspect, the acquisition unit includes: a reading unit that reads a document; and a document pressing unit that is disposed on a back surface of the document and that can change a reflectance of a contact surface that contacts the document. The document reading information may be information obtained by reading each document facing the contact surface set to at least two different reflectances by the reading unit. In this case, the acquisition unit can easily acquire the document reading information of the document with the document presses having different reflectivities on the back, and the acquired document reading information and at least two reflectances set on the contact surface By correcting the document reading information using, the show-through of the document can be accurately suppressed.

In the document reading device according to the first aspect, the correction unit is set on the contact surface and the document reading information of the document read with the contact surface set to at least five different reflectances as the back surface. The document reading information may be corrected using the at least five reflectances. In this case, in order to correct the document reading information using each document reading information and the reflectance of the set contact surface, the document is read with the contact surface set to at least five different reflectances as the back surface. The document show-through can be suppressed with high accuracy.

In the document reading apparatus according to the first aspect, the document reading information may be image data of a document. In this case, since the image data of the document is corrected using the image data of the document with the document presses having different reflectivities on the back and the reflectivity of the document press, the show-through of the document can be accurately suppressed. .

The present invention can be realized in various modes, for example, a scanner, a printer, a digital still camera, a personal computer, a digital video camera, and the like. Also, a document reading method, an image processing method and apparatus, a computer program for realizing the functions of these methods or apparatuses, a recording medium recording the computer program, and data embodied in a carrier wave including the computer program It can be realized in the form of a signal or the like.

It is explanatory drawing which illustrated schematic structure of the scanner in a 1st Example. 6 is a flowchart showing a flow of image data generation processing of the scanner in the first embodiment. It is the flowchart which showed the flow of the luminance value correction process. It is explanatory drawing for demonstrating the structure of an original luminance value. It is explanatory drawing for demonstrating the calculation method of a correction | amendment luminance value. It is explanatory drawing which illustrated the external appearance of the scanner in a 2nd Example. It is explanatory drawing which illustrated schematic structure of the scanner in a 2nd Example. It is a flowchart which shows the flow of the image data generation process of the scanner in a 2nd Example. FIG. 10 is an explanatory diagram illustrating a schematic configuration of a scanner according to Modification 1. FIG. 10 is an explanatory diagram illustrating a schematic configuration of a scanner according to Modification 2. 14 is a flowchart showing a flow of image data generation processing of a scanner in Modification 3. FIG. 14 is an explanatory diagram illustrating the appearance of a scanner according to Modification 6. FIG. 10 is an explanatory diagram illustrating a schematic configuration of a scanner in Modification 6.

Hereinafter, a scanner which is an aspect of an original reading apparatus according to the present invention will be described based on an embodiment with reference to the drawings.

A. First embodiment:
A1. Scanner configuration:
FIG. 1 is an explanatory diagram illustrating a schematic configuration of a scanner in the first embodiment. The scanner 10 of this embodiment is a document reading device that optically reads a reading object and outputs image data. The scanner 10 also functions as an image processing device in that it can perform image processing on the generated image data. The scanner 10 of this embodiment takes a document M from a paper feed port (not shown) into the apparatus, reads the document M while being conveyed by a roller, and discharges the read document M from a paper discharge port (not shown). This is a feed type scanner. The scanner 10 includes a light receiving unit 110, a light emitting unit 120, a document press 130, a roller 140, and a control unit 200.

The light receiving unit 110 and the light emitting unit 120 are arranged in a line in the direction along the document transport direction (each five light receiving units 110a, 110b, 110c, 110d, 110e, and light emitting units 120a, 120b, 120c, 120d). 120e) and one light receiving portion 11
One light emitting unit 120 is arranged corresponding to zero. The light receiving unit 110 corresponds to a “reading unit” in claims.

The light receiving unit 110 includes an image sensor such as a charge coupled device (CCD) and a lens that collects light on the image sensor. In this embodiment, a linear CCD (Charge Coupled Devices) having a length equal to the document width in the direction orthogonal to the document conveyance direction,
CIS (Contact Image Se) by combination with rod lens (selfox lens)
nsor). The light emitting unit 120 includes, for example, a light emitting element such as an LED, and irradiates the original M, the original holder 130, and the like with light.

The light receiving unit 110 receives the reflected light of the light emitted from the light emitting unit 120 and outputs a voltage having a magnitude corresponding to the intensity of the received light. The voltage value (analog value) output from the image sensor is converted into a digital value by the control unit 200. The scanner 1 according to this embodiment.
Although 0 is described as a so-called contact type scanner, it may be a reduction optical system scanner that projects an original on a CCD in a reduced size. In addition, the image sensor constituting the light receiving unit 110 is:
For example, it may be constituted by a CMOS image sensor.

There are five document retainers 130 (document retainer 130a) arranged in a line along the document transport direction.
, 130b, 130c, 130d, 130e). Each document retainer 130a,
Reference numerals 130b, 130c, 130d, and 130e face the five light receiving units 110a, 110b, 110c, 110d, and 110e, respectively, in order to bring the document M closer to or in contact with the light receiving unit 110. Each document retainer 130a, 130b, 130c, 130d, 130e has contact surfaces 130at, 130bt, 130ct, 130dt, which are in contact with the document M, respectively.
130et (collectively simply referred to as contact surface 130t). Each contact surface 130a
t, 130bt, 130ct, 130dt, and 130et are set to have different reflectances. The roller 140 is driven by a motor (not shown) so that the original M is received by the light receiving unit 1.
The document M is transported so as to pass between 10 and the document presser 130. The light receiving unit 110, the light emitting unit 120, and even the document holder 130 constitute an “acquiring unit” in the claims.

The control unit 200 includes a general-purpose computer including a ROM, a RAM, and a CPU, and an AFE.
A dedicated processing circuit (not shown) such as (Analog Front End) or an image processing chip is provided, and the entire operation of the scanner 10 is controlled. As shown in FIG. 1, the control unit 200 includes a light receiving control unit 210 that controls the light receiving unit 110, a light source control unit 220 that controls the light emitting unit 120, and a roller as functional blocks realized by a general-purpose computer and a dedicated processing circuit. A movement control unit 230 that controls 140 and an image processing unit 240 are included. The image processing unit 240 includes a correction unit 2
41 is included.

The image processing unit 240 receives an electrical signal output from the image sensor. The image processing unit 240 performs noise removal, amplification, A / D conversion, digital image processing, and the like on the received electrical signal to generate digital image data. The correction unit 241 corrects the luminance value of each pixel constituting the image data in a luminance value correction process described later. The brightness value correction process is a process for suppressing document show-through in the image data, and will be described in detail later.

The control unit 200 stores the generated image data and the like in a storage device such as a ROM or a RAM. In addition, the control unit 200 includes various functions such as an input unit that receives an operation from the user.

A2. Scanner behavior:
With reference to FIG. 2, the image data generation processing by the scanner 10 will be described. FIG. 2 is a flowchart showing the flow of image data generation processing of the scanner in the first embodiment. The image data generation process is a process of reading the document M and generating image data. The image data generation process is started when the control unit 200 receives an image data generation instruction via the operation panel or a connected computer.

The control unit 200 reads the contact surface 130t (step S100). Specifically, the light source control unit 220 controls the light emitting unit 120 to turn on the LED, and the contact surface 130t.
Project light. The light receiving control unit 210 controls the light receiving unit 110 to receive the reflected light of the light projected on the contact surface 130t, and each contact surface 130at, 130bt, 130ct, 130dt.
, 130et, the respective contact luminance values (Vta, Vtb, Vtc, V
td, Vte). In the present embodiment, the luminance value refers to a digital value obtained by A / D converting a voltage value (analog value) output from an image sensor that receives light. The control unit 200 stores the acquired contact surface luminance values Vta, Vtb, Vtc, Vtd, and Vte in the RAM.

After reading the contact surface 130t, the control unit 200 reads the document M (step S110). Specifically, the movement control unit 230 controls the roller 140 to control the document M.
Is conveyed between the light receiving unit 110 and the document holder 130. The light source control unit 220 includes the light emitting unit 12.
The LED is turned on by controlling 0, and light is projected onto the original M. The light receiving control unit 210 includes the light receiving unit 1
10, the reflected light of the light projected on the original M is received, and the reflection luminance value of the original M is acquired. The light reception control unit 210 acquires a reflection luminance value for each area corresponding to each pixel constituting the image data in the document M. In step S110, the reflection luminance value of each region corresponding to one line in the direction orthogonal to the conveyance direction of the document M is acquired from the regions corresponding to the pixels constituting the image data.

The reading of the document M is performed by five light receiving units 110a, 110b, 110c, 110d, and 110.
Since each of the contact surfaces 130at, 130bt, 130ct, 130dt, and 130et is the back surface, five reflection luminance values (hereinafter referred to as the original luminance value Vma, Vmb, Vmc, Vmd, and Vme) are acquired. In this embodiment, the reflection luminance value of the document corresponds to “document reading information” in the claims. Since the reflection luminance value of the document corresponds to the pixel value of each pixel constituting the image data of the entire document, it can be said to be image data in a broad sense.

Since the five light receiving portions 110a, 110b, 110c, 110d, and 110e have different mounting positions, the five light receiving portions can be obtained by using the conveyance speed of the original M during reading and the distance between the light receiving portions. Each of the sections 110a, 110b, 110c, 110d, and 110e associates each original luminance value with respect to the same area (pixel) of the original M read. The controller 200 controls the document luminance values Vma, Vmb, Vmc for each area corresponding to each pixel of the document M.
Vmd and Vme are stored in the RAM.

The correction unit 241 performs luminance value correction processing. FIG. 3 is a flowchart showing the flow of luminance value correction processing. In the brightness value correction process, the document brightness values Vma, Vmb, Vmc, Vmd, and Vme and the contact surface brightness values Vta, Vtb, and Vt are determined for each area corresponding to each pixel of the document M.
c, Vtd, and Vte are used to calculate a document brightness value in a state where there is no show-through, and correct the read document brightness value.

First, the correction unit 241 calculates a corrected luminance value V′m. (Step S200). The corrected luminance value V′m is a value that becomes the original luminance value after being corrected by the correcting unit 241, and is acquired in an ideal state where there is no show-through in each pixel constituting the image data of the original M. This is the original brightness value. The calculation method of the corrected luminance value V′m and the calculation basis will be described below.

FIG. 4 is an explanatory diagram for explaining the configuration of the document luminance value. As shown in FIG. 4, a document M on which characters, figures, and the like are printed on both sides of the paper surface is a surface formed by a mount layer Mm of paper or the like and a pigment for displaying characters or the like on the surface of the mount layer Mm. The printing layer Mf and a back printing layer Mb formed of a pigment on the back of the mount layer Mm are provided. At this time, the reflected light detected by the light receiving unit 110 includes the front surface print layer reflected light L1 reflected by the front surface print layer Mf, and the back surface transmitted through the front surface print layer Mf and the mount layer Mm and reflected by the back surface print layer Mb. Components such as the print layer reflected light L2 and the contact surface reflected light L3 transmitted through the document M and reflected by the contact surface 130t are included. As a result, the image of the read original M includes the back print layer Mb, the pattern of the contact surface 130t, and the like. For this reason, by eliminating the influence of reflected light other than the surface print layer reflected light L1 from the acquired document brightness value, it is possible to acquire a document brightness value without show-through.

FIG. 5 is an explanatory diagram for explaining a method of calculating a corrected luminance value. In FIG. 5, for the sake of explanation, the mount layer Mm, the front print layer Mf, and the back print layer Mb of the document M are shown separately. As shown in FIG. 5, the reflectance of the surface printing layer Mf is a ₁ , the transmittance is b ₁ , and the surface side (upper side in FIG. 5).
The incident light amount from 1 is 1 (one), and the incident light amount from the back side (the lower side in FIG. 5) is l. Further, the reflectance of the mount layer Mm is a ₂ , the transmittance is b ₂ , the amount of incident light from the front side is m, and the amount of incident light from the back side is n. Further, the reflectance of the back print layer Mb is a ₃ , the transmittance is b ₃ , the incident light quantity from the front side is o, and the incident light quantity from the back side is p. The reflectance of the contact surface 130t is a ₄ ,
The transmittance is 0 (zero), the amount of incident light from the front side is q, and the amount of incident light from the back side is 0 (zero). At this time, if the original luminance value read by the image sensor is x, the following simultaneous equation (1) is established.

At this time, when it is assumed that the original brightness is x ₀ when the original mount is sufficiently thick and the transmittance b ₂ of the mount layer Mm is 0, the following equation (2) is established.

If there is no show-through component and the mount is uniform, x ₀ is proportional to the reflectance on the front side, that is, the reflectance a ₁ of the surface printing layer Mf and the reflectance a ₂ of the mount layer Mm. Further, when x is obtained using x ₀ , the following equation (3) is obtained.

  However, C, D, E, and F satisfy the following formula (4).

Since this equation is an equation having five unknowns (x ₀ , C, D, E, F), if five pairs of x and a ₄ are obtained for a certain region of the original, x ₀ can be obtained. That is, the original luminance value Vm read the x, when the x ₀ and the correction luminance value V 'm, 5 single original luminance value Vma, Vmb, Vmc, Vmd, and Vme, contact surface luminance value Vta
, Vtb, Vtc, Vtd, Vte, the corrected luminance value V′m can be calculated. Note that the reflectance a ₄ of the contact surface 130 t can be calculated by dividing the contact surface luminance value by the projection luminance value of the light emitting unit 120.

Returning to FIG. 3, the correction unit 241 corrects the document brightness value (step S <b> 210). Specifically, the document brightness value Vm obtained by reading the document M is calculated as the corrected brightness value V′m.
Correct so that As a result, for each area corresponding to each pixel of the document M, the document brightness value in the state where there is no show-through is corrected. Note that shading correction and γ correction may be performed before and after this correction. Thus, the brightness value correction process ends.

Returning to FIG. 2, if the reading of the entire document has not been completed (step S <b> 130: NO), the control unit 200 obtains the reflection luminance value of the area for one line of the document M (step S <b> 110).
And the luminance value correction process are repeated (step S120). When the reading of the entire document M is completed (step S130: YES), image data in a state where there is no show-through of the document M is generated (step S140). The image processing unit 240 may perform image processing such as edge enhancement and saturation adjustment on the generated image data of the document M.

According to the scanner 10 according to the first embodiment described above, the document reading information of the document is corrected using the document reading information of the document with the document pressing having different reflectances on the back and the reflectance of the document pressing. Therefore, the show-through of the original can be accurately suppressed. Specifically, the reflectance of each contact surface is calculated from the document brightness value Vm acquired with the document presses having different reflectivities on the back surface and the contact surface brightness value Vt of each contact surface, thereby obtaining the equation (3). ) Can be used to calculate the document luminance value acquired in an ideal state where there is no show-through of the document, so that image data of the document M without show-through can be generated.

As previously proposed, in the method of reading a document with the contact surface being black and the contact surface having a reflectance of 0, a ₄ = 0 in equation (3), the equation (3) 5) holds.

That is, even when the reflectance of the contact surface is 0, the document luminance value is different from the document luminance value acquired in an ideal state where there is no show-through of the document. This is because the component of the light reflected by the back print layer Mb without reaching the contact surface is included in the original luminance value of the original M read. From this, it can be said that the present invention is more accurate in suppressing the show-through than in the case where the show-through of the document is suppressed by the conventional technique.

The scanner 10 according to the first embodiment is arranged side by side in the document conveyance direction, each of which is arranged at two or more reading units for reading a document, and a position facing each reading unit,
Since there are two or more document holders having different reflectances on the contact surface that comes into contact with the document, it is possible to easily obtain the document luminance value Vm of the document with the document holders having different reflectances on the back side. . Specifically, since the document holders having different reflectivities are arranged opposite to the respective reading units, it is not necessary to replace the document holders having different reflectances each time the document is read. Each document luminance value Vm of the document with the document presser having different reflectivity on the back side can be acquired only by passing.

According to the scanner 10 according to the first embodiment, since the reading unit and the five document presses are provided, the show-through of the document can be accurately suppressed. Specifically, the formula (3)
Has five unknowns (x ₀ , C, D, E, and F). Therefore, in order to calculate x ₀ equal to the original luminance value acquired in an ideal state where there is no show-through of the original, For a certain region, five pairs of x and a ₄ are required. By providing five reading units and five document pressing units, five document luminance values Vma, Vmb, Vmc, Vmd, Vme and contact surface luminance values Vta, Vtb, Vtc, Vtd, Vte can be acquired. ₀ can be obtained.

B. Second embodiment:
B1. Scanner configuration:
In the first embodiment, the sheet feed type scanner has been described. In the second embodiment, a flat bed type scanner will be described. In the second embodiment, components having the same reference numerals as those in the first embodiment have the same functions and the like as those in the first embodiment, and thus description thereof is omitted.

FIG. 6 is an explanatory diagram illustrating the appearance of the scanner in the second embodiment. As shown in FIG. 6, the scanner 30 includes a case 31 that houses internal mechanisms such as the light receiving unit 110 and the light emitting unit 120, a document placing plate 34 disposed on the upper surface of the case 31, and a hinge 33 on the case 31. And a document presser 32 which is rotatably attached to the document presser 32. A liquid crystal panel 340 whose reflectance can be changed is disposed on the surface of the document holder 32 facing the document placement plate 34. The scanner 30 reads a document with the liquid crystal panel 340 in contact with the back surface of the document by placing the document on the document placement plate 34 and pressing the document from above with the document holder 32. That is, the scanner 30 can read the document by changing the reflectance of the liquid crystal panel 340 to change the reflectance of the back surface of the document. In this embodiment, the liquid crystal panel corresponds to the “contact surface” in the claims.

FIG. 7 is an explanatory diagram illustrating the schematic configuration of the scanner in the second embodiment. The case 31 includes a carriage 300 for reading the document M placed on the document placement plate 34, a drive motor 350, a pulley 351, a belt 352 provided between the drive motor 350 and the pulley 351, and a guide shaft. 330 and the control unit 200.

The carriage 300 includes a light emitting unit 320, a mirror 321, a lens 322, and a light receiving unit 31.
0. The light emitting unit 320 includes a light emitting element such as an LED, and irradiates the original M with light. The reflected light emitted from the light emitting unit 320 and reflected by the document M is reflected by the mirror 321 and the lens 3.
The light receiving unit 110 is irradiated via 22. The light receiving unit 310 includes a linear CCD as in the first embodiment. The scanner 30 according to the present embodiment will be described as a reduction optical system scanner that reduces and projects an original on a CCD, but may be a contact type scanner. Further, the image sensor constituting the light receiving unit 310 is not limited to the CCD, and may be constituted by, for example, a CMOS image sensor.

The carriage 300 is slidably attached to the guide shaft 330. Carriage 3
00 is the guide shaft 3 as the belt 352 is driven by the drive motor 350.
30 reciprocates in the axial direction. The control unit 200 includes functional units similar to those in the first embodiment. The movement control unit 230 controls the reciprocation of the carriage 300. Further, the control unit 200 controls the reflectance of the liquid crystal panel 340.

B2. Scanner behavior:
With reference to FIG. 8, the image data generation processing by the scanner 30 will be described. FIG. 8 is a flowchart showing a flow of image data generation processing of the scanner in the second embodiment.

The control unit 200 sets the reflectance of the liquid crystal panel 340 (step S300). Specifically, the control unit 200 holds information about a plurality of preset reflectances, and controls the liquid crystal panel 340 so as to have one reflectance among the plurality of reflectances set. In the present embodiment, the control unit 200 holds information about five different reflectances.

The control unit 200 reads the document M (step S310). Specifically, the control unit 200 controls the reciprocation of the carriage 300 and scans the document M to obtain the reflection luminance value of the document M. As in the first embodiment, the control unit 200 in the document M
A reflection luminance value is acquired for each region corresponding to each pixel constituting the image data.

The reading of the original is continued until the entire reading of the original M is completed (step S3).
20: NO). When reading of the entire document M is completed (step S320: YES), the control unit 200 determines whether or not the document M has been read by setting the liquid crystal panel 340 to all the set reflectances (step S320). S330). When the control unit 200 has not read the original M at all the reflectances (step S330: NO),
The liquid crystal panel 340 is controlled so that the reflectance that has not yet been used for reading the document M is set among the set reflectances (step S300), and reading of the document M with the set liquid crystal panel 340 on the back is read. Perform (step S310).

When reading the document M at all the reflectances (step S330: YES), the control unit 200 performs a luminance value correction process. Since the luminance value correction process is the same as that of the first embodiment, the description thereof is omitted. Note that the reflectance of the contact surface used for the luminance value correction processing uses information about the reflectance held in advance. Image data in a state where there is no show-through of the document M is generated by the brightness value correction processing (step S350). In addition,
The image processing unit 240 may perform image processing such as edge enhancement and saturation adjustment on the generated image data of the document M.

According to the scanner 30 according to the second embodiment described above, the present invention is not limited to the sheet feed type scanner, and can be realized even with a flatbed type scanner, for example. In addition, the present invention can be realized even if two or more light receiving parts or light emitting parts are not provided.

The scanner 30 according to the second embodiment includes a reading unit that reads a document, and a document presser that is disposed on the back side of the document and that can change the reflectance of a contact surface that contacts the document. Therefore, it is possible to easily obtain the document luminance value Vm of the document with the document presses having different reflectivities on the back side. Specifically, since the reflectance of the back surface of the document can be changed by controlling the liquid crystal panel, there is no need to replace the document presser with a different reflectance each time the document is read. By repeating the process, it is possible to acquire each document brightness value Vm of the document with the document presses having different reflectances on the back side. In addition to the liquid crystal panel, the reflectance may be changed by a half mirror device or the like.

According to the scanner 30 according to the second embodiment, the correction unit has the original luminance value Vm of the original read with the contact surface set to five different reflectances as the back surface, and 5 with the contact surface set. Since the original brightness value Vm is corrected using the two reflectances, the show-through of the original can be accurately suppressed. Specifically, since Equation (3) has five unknowns (x ₀ , C, D, E, and F), x equal to the original luminance value acquired in an ideal state where there is no show-through of the original.
_In order to calculate ₀ , five pairs of x and a ₄ are required for a certain area of the document. By reading each document with the contact surface set to five different reflectances on the back side, five document luminance values can be obtained, and the five document luminance values and the five contact surface luminance values are used. Thus, x ₀ can be obtained.
Here, since there are five unknowns (x ₀ , C, D, E, F) according to the equation (3), it is necessary to read the contact surface with five reflectances in order to obtain them. Where
When there are more unknowns, such as when there is an external influence such as noise, it may be possible to read a contact surface with a reflectance of 5 or more, or if the equation can be approximated or there is a known number, An unknown can be obtained by reading a contact surface having two or more reflectances instead of five.

C. Variation:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

C1. Modification 1:
FIG. 9 is an explanatory diagram illustrating a schematic configuration of a scanner according to the first modification. The scanner 10 according to the first embodiment includes five light receiving units 110a, 110b, 110c, 110d, and 11.
0e and five document holders 130a, 130b, 130c, 130d, and 130e are provided. However, even in a sheet-feed type scanner, as shown in FIG. If it is provided, the show-through of the document can be accurately suppressed. Specifically, in equation (3), equation (6) is satisfied the reflectivity of the contact surface 130t when a ₄ is sufficiently small.

In this case, since the equation has four unknowns (x ₀ , C, E, F), if four pairs of x and a ₄ are obtained for a certain area of the document, x ₀ is obtained from the simultaneous equations. be able to. That is, it can be configured by the four light receiving units 110 and the light emitting unit 120.

If there are two or more of the light receiving units 110 and the light emitting units 120, x on the right side of the expression (3)
By appropriately approximating the correlation between the portion other than ₀ and a ₄ , x ₀ can be obtained from two or more document luminance values and contact surface luminance values.

Also, the original M is a monochrome image, and the transmittance and reflectance of the pigment and mount used are R
If the image sensor is constant regardless of the GB light source, and the RGB color sensor is used, the reflectance of the contact surface 130t is set to change in RGB.
With 0 and the light emitting unit 120, three pairs of x and a ₄ can be obtained. In this case, if there are two light receiving units 110 and two light emitting units 120, six pairs of x and a ₄ can be obtained.

C2. Modification 2:
FIG. 10 is an explanatory diagram illustrating a schematic configuration of a scanner according to the second modification. Although the document holder 130 of the first embodiment includes a flat contact surface 130t, the document holder does not necessarily have to have a flat contact surface. For example, as shown in FIG. 10, the document presser may be formed by a roller 150. In this case, the contact area between the roller 150 and the document M is the contact surface 150t.

C3. Modification 3:
FIG. 11 is a flowchart showing the flow of image data generation processing of the scanner in the third modification. As shown in FIG. 2, the scanner 10 according to the first embodiment performs step S110.
, The reflection luminance value of the area for one line in the direction orthogonal to the conveyance direction of the document M is acquired,
In each step S120, the luminance value correction process is performed in step S120.
As shown in FIG. 4, the entire original is read (step S410), image data is generated (step S420), and then brightness value correction processing (step S430) is performed to correct the pixel values of each pixel constituting the image data. It is good also as an aspect to do. In this case, the image data of the entire document corresponds to “document reading information” in the claims. The pixel value may be a luminance value or an RGB gradation value.

C4. Modification 4:
Although the scanner 10 according to the first embodiment reads the contact surface 130t before reading the document M, the contact surface 130t may be read after the document M is read, or the document M may be read. It may be performed before and after reading. In this case, if the reflectance of the contact surface calculated from each of the contact surface luminance value acquired before reading the document M and the contact surface luminance value acquired after reading the document M is the same, Since it can be considered that the reflectance of the contact surface is constant even at the time of reading, the show-through can be more accurately suppressed.

In this embodiment, as shown in FIG. 2, the scanner 10 reads the contact surface 130t (step S100), and calculates the reflectance of the contact surface 130t from the acquired contact surface luminance value. May be a mode in which the reflectance of the contact surface 130t recorded in advance is used. In this case, the brightness value correction process can be performed without reading the contact surface 130t.

C5. Modification 5:
FIG. 12 is an explanatory diagram illustrating the appearance of the scanner according to the sixth modification. FIG. 13 is an explanatory diagram illustrating a schematic configuration of a scanner according to the sixth modification. The scanner 30 according to the second embodiment uses the liquid crystal panel 340 on the contact surface of the document press, but the document press does not use the liquid crystal panel 340 if the reflectance of the contact surface can be changed. May be. For example, as shown in FIG. 12, the scanner 30 includes a belt mechanism unit 360 in which the contact surface is formed of a film 361 and the reflectance of the contact surface can be changed by moving the film 361 in the direction of the black arrow. You may have. Specifically, as shown in FIG. 13, the belt mechanism 360 is configured to reflect the contact surface by driving a belt-shaped film 361 installed on the shaft 362 in the direction of a white arrow by a drive motor (not shown). The rate can be changed. Note that the film 361 may be wound around the shaft portion 362.

C6. Modification 6:
In the scanner 10 according to the present embodiment, a part of the configuration realized by the hardware in the above embodiment may be replaced by software. Conversely, a part of the configuration realized by the software is replaced by hardware. It may be replaced with wear.

C7. Modification 7:
The present invention can be realized by a printer, a digital still camera, a personal computer, a digital video camera, or the like in addition to a scanner. Also, a document reading method, an image processing method and apparatus, a computer program for realizing the functions of these methods or apparatuses, a recording medium recording the computer program, and data embodied in a carrier wave including the computer program It can be realized in the form of a signal or the like.

DESCRIPTION OF SYMBOLS 10, 30 ... Scanner 31 ... Case 32, 130 ... Document holder 33 ... Hinge 34 ... Document placing plate 110, 310 ... Light receiving part 120, 320 ... Light emitting part 130t ... Contact surface 140, 150 ... Roller 200 ... Control part 210 ... Light reception control unit 220 ... Light source control unit 230 ... Movement control unit 240 ... Image processing unit 241 ... Correction unit 300 ... Carriage 321 ... Mirror 322 ... Lens 330 ... Guide shaft 340 ... Liquid crystal panel 350 ... Drive motor 351 ... Pulley 352 ... Belt 360 ... belt mechanism 361 ... film 362 ... shaft M ... manuscript L1 ... surface print layer reflected light L2 ... back print layer reflected light L3 ... contact surface reflected light Mb ... back print layer Mf ... surface print layer Mm ... mount layer

Claims (8)

An original reading device,
An acquisition unit for acquiring document reading information of a document facing a document press having a plurality of reflectances;
An original reading apparatus comprising: a correction unit that corrects the original reading information by using the original reading information acquired by the acquisition unit and the reflectance of the original presser. The document reading device according to claim 1,
The acquisition unit
At least two reading units that are arranged side by side in the document transport direction and each read a document;
And at least two document pressers that are respectively arranged at positions facing each of the reading units and have different reflectivities on the contact surfaces on the side in contact with the document,
The document reading information is information obtained by reading the document with the contact surface on the back by the at least two reading units. The document reading device according to claim 2,
The document reading apparatus, wherein the acquisition unit includes at least five of the reading unit and the document presser. The document reading device according to claim 1,
The acquisition unit
A reading unit for reading a document;
A document presser disposed on the back surface of the document and capable of changing a reflectance of a contact surface in contact with the document;
The original reading information is information obtained by the original reading information obtained by reading the original facing the contact surface set to at least two different reflectances by the reading unit. The document reading device according to claim 4,
The correction unit uses document reading information of the document read with the contact surface set to at least five different reflectances as the back surface, and the at least five reflectances set to the contact surface. A document reading device for correcting the document reading information. An image processing method comprising:
Acquiring image data of a document with a document retainer having a plurality of reflectances on the back;
And a step of correcting the image data by using the image data of the document and the reflectance of the document presser. An original reading method,
Reading a document with a document holder having a plurality of reflectances on the back;
A document reading method comprising: correcting the document reading information by using the document reading information acquired by the reading and the reflectance of the document presser. An original reading method,
Reading the document with the document retainer set to at least two reflectances on the back;
A document reading method comprising: correcting the document reading information using the document reading information acquired by the reading and the set reflectance of the document presser.

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