JP2010004110A - Image reader and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform shading correction with excellent reliability on photo images formed on the back surface (second surface) of a document and to efficiently perform the shading correction on character images. <P>SOLUTION: The image of a first surface of the document read by a scanner 10 and the image of a second surface of the document read in a second read means 26, are subjected to shading correction by a black level correction coefficient, a white level correction coefficient and a light distribution correction coefficient based on the result of reading a black reference plane and a white reference plane. When the image of the second surface of the document read in the second read means 26 is a character image, a simple shading correction is applied to image data obtained by the second read means 26 by the light distribution correction coefficient calculated on the basis of the result that the second read means 26 reads a margin part at the distal end part of the second surface of the document. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that reads an original image and an image forming apparatus including the image reading apparatus, and in particular, an image is formed not only on the front surface (first surface) but also on the back surface (second surface). The present invention relates to a technique capable of reading both images at once in a document.

  In an image forming apparatus such as a copying machine in which an ADF (automatic document feeder) is provided on the image forming apparatus main body, a document fed from the ADF is usually fed by a first reading unit provided in the image forming apparatus main body. An image corresponding to the image on the first surface on the recording sheet is read by a printer provided in the image forming apparatus main body based on the read image data of the original. Print.

  In addition, a double-sided simultaneous reading type image reading apparatus that provides an ADF with a second reading unit that reads an image formed on the back surface (second surface) of the document and reads an image on the second surface of the fed document. Has been developed. The image on the second side of the original is printed on the second side of the original by the printer provided in the image forming apparatus main body, similarly to the first side, based on the image data on the second side of the original read by the second reading unit. An image corresponding to the surface image is printed.

The first reading unit provided in the image forming apparatus main body exposes the first surface of the document with light emitted from a first linear light source configured by a xenon lamp, a fluorescent lamp, and the like, and reflects the reflected light. Are reduced by a reduction optical system, and then received by a CCD (first line sensor) in which a plurality of photoelectric conversion elements are arranged in a line.
A second line sensor is provided in the second reading unit provided in the ADF. As the second line sensor, a contact line sensor (CIS: Contact Image Sensor) is usually used. The second reading unit is provided with a second linear light source configured by an LED (light emitting diode), a xenon lamp, or the like, and the reflected light applied to the second surface of the document by the second linear light source is short. An image is formed on the second line sensor which is a CIS by the focus lens array.

In such an image reading apparatus, the amount of light emitted from the first linear light source and the second linear light source is non-uniform in the axial direction in each of the first reading unit and the second reading unit. In order to correct errors such as exposure unevenness due to exposure and lens image formation unevenness, shading correction is performed in each of the first reading unit and the second reading unit.
In the shading correction, a correction coefficient necessary for shading correction is usually calculated before reading the document image by the first reading unit and the second reading unit, and then the image of the document image is calculated by the first reading unit and the second reading unit. When the data is obtained, the image data is corrected based on the calculated correction coefficients.

  In a double-sided simultaneous reading type image reading apparatus, normally, a black reference surface and a white reference surface for obtaining black reference data and white reference data necessary for shading correction are read by a first reading unit and a second reading unit, respectively. It is provided in a possible position. At the time of shading correction, reflected light from the black reference surface and the white reference surface is read by the first reading unit and the second reading unit, respectively, and black reference data and white reference data necessary for correction are obtained. A correction coefficient necessary for shading correction is calculated based on the obtained black reference data and white reference data.

  As the correction coefficient for shading correction, the black level correction coefficient for adjusting the black level in each of the first line sensor and the second line sensor, and the white level in each of the first line sensor and the second line sensor are adjusted. And a light distribution correction coefficient for adjusting variations in output voltages of the first line sensor and the second line sensor due to variations in the respective light amounts in the first linear light source and the second linear light source, There is.

  As described above, the shading correction by the first reading unit and the second reading unit requires the black reference surface and the white reference surface for obtaining the black reference data and the white reference data in the first reading unit and the second reading unit, respectively. become. However, as the second line sensor used in the second reading unit, a contact type line sensor (CIS) is usually used because it is disposed in a position close to the first reading unit in the ADF. Therefore, there is a problem that it is not easy to secure a space for providing the black reference surface and the white reference surface around the second line sensor.

In Patent Document 1, in the configuration using the CIS in the second reading unit, the white reference data set in advance and the second reading unit are read without providing a white reference surface for obtaining white reference data. A configuration is disclosed in which shading correction of the second reading unit is performed based on the background data of the original. With such a configuration, the operation of reading the white reference plane is not necessary when the shading correction of the second reading unit is performed.
JP 2004-207790 A

  In the configuration disclosed in Patent Document 1, since the light distribution correction coefficient for shading correction of the second reading unit is simply calculated based on the background data of the document, the image data of the document image is reproducible. There is a possibility that it cannot be obtained well. In particular, when a high-definition original image such as a photographic image is read, an image corresponding to the high-definition photographic image cannot be faithfully reproduced by using a simple light distribution correction coefficient based on the background data of the original. There is a fear.

  The present invention has been made to solve the above-described problems, and is suitable for high-definition images when the image formed on the back surface (second surface) of the document is high-definition like a photographic image. Provided is an image reading apparatus capable of performing simple shading correction and capable of quickly performing shading correction in the case of a non-definable character image, and an image forming apparatus including the image reading apparatus With the goal.

  In order to achieve the above object, an image reading apparatus according to the present invention includes a first reading unit that reads an image on a first side of a document, a second reading unit that reads an image on a second side of the document, and the first reading unit. A first shading correction unit that performs shading correction on the image data of the first surface obtained by one reading unit based on a reading result of the first white reference surface by the first reading unit; and the second reading unit. Second shading correction means for performing shading correction on the image data of the second surface obtained by the means based on the reading result of the second white reference surface by the second reading means, and the image of the second surface Simple shading correction means for performing shading correction on the data based on the reading result of the margin part of the second surface of the document by the second reading means. To.

  An image forming apparatus according to the present invention includes the image reading device and a printer that forms an image on a recording sheet based on image data read by the image reading device.

  The image reading apparatus and the image forming apparatus according to the present invention perform a first shading correction for performing shading correction on the image data obtained by the first reading unit based on the reading result of the first white reference plane by the first reading unit. And second shading correction means for performing shading correction on the image data obtained by the second reading means based on the reading result of the second white reference plane by the second reading means. When the original images on the first and second sides of the original are high definition like photographic images, image data with excellent reproducibility and reliability can be obtained. If the original image on the second side is not as high-definition as a character image, the margin portion on the second side of the original is applied to the image data obtained by the second reading unit by the simple shading correction unit. The shading correction can be quickly performed based on the reading result by the second reading means.

  Preferably, the image processing apparatus further includes instruction means for instructing that the image on the second side of the document is in a photographic mode, and when the photographic mode is not instructed by the instruction means, the shading correction by the simple shading correction means is performed. It is characterized by that. Thereby, when the image on the second surface of the document is not in the photo mode, the simple shading correction can be quickly executed by the simple shading correction means.

Preferably, one of the second shading correction unit and the simple shading correction unit is selectively used according to sheet characteristics of the document. Thereby, simple shading correction can be performed appropriately.
Preferably, the simple shading correction unit is based on a reading result by the first reading unit of a margin portion of the first surface of the document and a reading result of the first white reference surface by the first shading correction unit. The reading result by the second reading unit of the margin part of the second surface of the document is corrected. Thereby, the reliability of the simple shading correction by the simple shading correction means can be improved.

  Preferably, the first reading unit includes a first linear light source disposed so as to face the first surface of the conveyed document so as to irradiate light along a direction orthogonal to the document conveyance direction. A reduction optical system for reducing and projecting light from the first linear light source reflected by the first surface of the document, and a first line sensor for receiving light reduced and projected by the reduction optical system. It is characterized by providing. Thereby, it is possible to reliably obtain image data of the first surface of the document for performing shading correction by the first shading correction means.

  Preferably, the first shading correction unit adjusts the black level of the first line sensor based on the reading result of the first black reference plane by the first reading unit, and the first white color by the first reading unit. The white level adjustment and light distribution correction of the first line sensor are performed based on the reading result of the reference surface. Thereby, the reliability of the shading correction by the first shading correction means can be improved.

  Preferably, the second reading unit includes a second linear light source disposed so as to face the second surface of the conveyed document so as to irradiate light along a direction orthogonal to the document conveying direction. A contact-type second line sensor that receives light from the second linear light source reflected by the second surface of the document. Thereby, the image data of the second surface of the document for performing the shading correction by the second shading correction means can be obtained with certainty.

Preferably, the second shading correction unit adjusts the black level of the second line sensor based on the reading result of the second black reference plane by the second reading unit, and the second white color by the second reading unit. The white level adjustment and light distribution correction of the second line sensor are performed based on the reading result of the reference surface. Thereby, the reliability of the shading correction by the second shading correction means can be improved.

  Preferably, the rotating device further includes a rotating body rotatably arranged at the image reading position of the second line sensor, and the rotating body has at least two side surfaces positioned at the image reading position, and the two side surfaces. The second black reference surface and the second white reference surface are provided on each of the first and second reference surfaces. Thereby, the second black reference surface and the second white reference surface for shading correction by the second shading correction means can be reliably read.

<Schematic configuration of image forming apparatus>
FIG. 1 is a block diagram showing a schematic configuration of an image forming apparatus provided with an image reading apparatus according to an embodiment of the present invention.
The image forming apparatus includes an image forming apparatus main body 1 provided with a main component for forming a toner image on a recording sheet such as a recording sheet, and an ADF (automatic function) provided on the image forming apparatus main body 1. A document feeder 2) and a post-processing device 3 for performing post-processing such as sorting on the recording sheets on which the image is formed by the image forming device main unit 1. The image forming device main unit 1 and The ADF 2 is provided with an image reading device 4 according to the present invention.

<Schematic configuration of image reading apparatus>
FIG. 2 is a diagram showing a schematic configuration of the image reading device 4. As shown in FIG. 2, the ADF 2 includes a document mounting table 21 on which a plurality of documents D are placed. The document D on the document mounting table 21 is sent out from the document mounting table 21 to the conveying path 20 by the sending roller 22, separated into one sheet by the separation roller 23, and supplied to the registration roller 24. The registration roller 24 conveys one supplied document D to the platen roller 25 in a predetermined posture and at a predetermined timing. The document D transported by the registration roller 24 is transported while being pressed against the outer peripheral surface of the platen roller 25 by a pressing roller 27 over a substantially half circumference, and passes over the slit glass 13 provided on the upper surface of the image forming apparatus main body 1. .

The slit glass 13 is arranged in a state of extending linearly along a direction orthogonal to the document conveying direction. On the upper part of the image forming apparatus main body 1, a scanner 10 serving as a first reading unit that reads an image of a first surface (front surface) facing the lower side of the document D passing over the slit glass 13 is provided on the slit glass 13. It is provided below.
The ADF 2 is provided with second reading means 26 for reading an image on a second surface (back surface) opposite to the first surface (front surface) of the document D that has passed over the slit glass 13. The second reading unit 26 constitutes the image reading device 4 (see FIG. 1) together with the scanner 10 as the first reading unit provided in the image forming apparatus main body 1.

The document D that has passed over the slit glass 13 passes through the conveyance path immediately below the second reading unit 26, and the image on the second surface of the document D is read by the second reading unit 26 during the passage. The document D that has passed through the lower area of the second reading unit 26 is discharged onto a paper discharge tray 29 by a paper discharge roller 28.
Below the second reading unit 26, a hexagonal columnar rotating body 81 is provided so as to face the document D with respect to the conveyance path. The rotating body 81 is arranged in a state where the axis is along the direction orthogonal to the conveyance direction of the document D. The rotating body 81 is rotatable around the axis, and each of the six side surfaces is positioned at a reading position facing the second reading means 26. As will be described later, each side surface of the rotator 81 includes a pair of document guide surfaces for conveying the document D and second black reference data for shading correction of image data obtained by the second reading unit 26. And a pair of second black reference planes and a pair of second white reference planes for obtaining second white reference data.

<Configuration of Scanner of Image Forming Apparatus Main Body>
A flat platen glass 16 on which a document is placed is provided on the upper portion of the image forming apparatus main body 1. The platen glass 16 is disposed downstream of the slit glass 13 in the document conveying direction.
The scanner 10 provided in the image forming apparatus main body 1 reads the image of the first surface of the document D passing through the slit glass 13 and the image of the document placed on the platen glass 16. The scanner 10 has a first linear light source 15a that emits light toward the first surface of the document D that passes over the slit glass 13, and a first surface of the document D that is irradiated from the first linear light source 15a. A reduction optical system 15 for reducing and projecting the reflected light and a first line sensor 11 for receiving the light reduced and projected by the reduction optical system 15 are provided.

The first linear light source 15a is arranged along a direction orthogonal to the document conveying direction. The first line sensor 11 is constituted by a CCD (Charge Coupled Device) having a plurality of photoelectric conversion elements arranged along a direction orthogonal to the document conveying direction.
The reduction optical system 15 includes a first mirror 15b that reflects light reflected from the first surface of the original that is emitted from the first linear light source 15a and passes through the slit glass 13, and the first mirror. A pair of second mirror 15c and third mirror 15d that reflect the light reflected by 15b approximately at right angles to reverse the direction of the light, and the light reflected by the third reflecting mirror 15d is the first line sensor. 11 is provided with a projection lens 15e for reducing and projecting to 11. The linear light source 15a and the first mirror 15b are configured to be slidable integrally in the direction indicated by the arrow A as the first unit 151, and the second mirror 15c and the third mirror 15d are the second unit 152. Are configured to be slidable integrally in the direction indicated by the arrow A.

  When reading an image of the first surface (surface directed downward) of the document placed on the platen glass 16, the first unit 151 slides in the direction indicated by the arrow A along the lower surface of the platen glass 16. At the same time, the second unit 152 follows the first unit 151 and is slid along the same direction at a speed of 1/2. As a result, the first line sensor 11 reads an image of the first surface of the document placed on the platen glass 16.

  A reference plate 17 for shading correction of the first line sensor 11 is provided at a position on the slit glass 13 side on the lower surface of the platen glass 16. The reference plate 17 is configured as a long plate extending linearly along a direction orthogonal to the document conveying direction. A lower surface of the reference plate 17 is provided with a first black reference surface 17a and a first white reference surface 17b which are arranged adjacent to each other in the document transport direction. The first black reference surface 17a and the first white reference surface 17b are reference surfaces for obtaining first black reference data and first white reference data for shading correction of the output of the first line sensor 11.

<Configuration of ADF Reading Unit and its Periphery>
FIG. 3 is a diagram showing a schematic configuration of the second reading means 26 provided in the ADF 2 together with the configuration of the peripheral portion thereof. The second reading unit 26 includes a pair of second linear light sources 26 a that irradiate light onto the second surface (back surface) of the document D that passes through the conveyance path, and each of the first reflected light beams from the second surface of the document D. A second line sensor 26b that receives light from the two-line light source 26a is provided.

Each second linear light source 26a is configured to be long by an LED, a xenon lamp, or the like, and extends in a direction perpendicular to the document conveyance direction on the upstream side and the downstream side in the document conveyance direction. Is arranged.
The second line sensor 26b is a contact type line sensor having a plurality of photoelectric conversion elements arranged in a straight line so as to receive reflected light over the entire width direction of the document D (direction orthogonal to the document transport direction). Each of the linear light sources 26a is arranged in parallel with each other at a position between the linear light sources 26a.

  A hexagonal columnar rotating body 81 disposed below the second reading unit 26 is attached to a cover 95 that covers the lower surface of the ADF 2. The cover 95 is rotatable in a direction away from the second reading unit 26 (a direction indicated by an arrow B in FIG. 3), and the ADF 2 is opened upward with respect to the image forming apparatus main body 1. Thus, when the cover 95 is rotated in the direction of arrow B, the conveyance path of the document D between the second reading unit 26 and the rotating body 81 is opened. The cover opening / closing sensor 89 detects that the conveyance path is opened by the cover 95.

A cleaning member 86 such as a brush is provided below the rotating body 81, and dust such as paper dust attached to each side surface of the rotating body 81 is removed by the cleaning member 86 by rotating the rotating body 81. Is done.
<Configuration of rotating body>
FIG. 4A is a perspective view of the rotating body 81, and FIG. 4B is a side view of the rotating body 81. A smooth document guide in which a pair of side surfaces facing each other among the six side surfaces provided on the hexagonal columnar rotating body 81 guides the document in a state along the conveyance path of the document D when the document D passes through. A pair of side surfaces adjacent to each other is a second black reference surface 81b and a second white reference surface 81c used for shading correction of the second reading unit 26.

  A rotating body drive motor 84 that is a stepping motor is connected to one end portion of the rotating body 81 via a pair of gears 82 and 83. Each document guide surface 81a, each second black reference surface 81b, and each second white reference surface 81c of the rotator 81 are in a state along the transport path of the document D and face the second reading unit 26. It is rotated so as to be positioned at the reading position. As a result, each document guide surface 81a, each second black reference surface 81b, and each second white reference surface 81c emit light emitted from each second linear light source 26a of the second reading unit 26 to the second line sensor 26b. Is reflected so that it can receive light. At the other end of the rotator 81, each document guide surface 81a, each second black reference surface 81b, and each second white reference surface 81c are positioned at a reading position facing the second reading means 26. A side surface position sensor 85 that detects the presence of the sensor is provided.

  As shown in FIG. 3, since a cleaning member 86 such as a brush for cleaning the rotating body 81 is provided below the rotating body 81, the rotating body 81 rotates to rotate the rotating body 81. Dust such as paper dust adhering to each side surface is removed. Therefore, the pair of second black reference surfaces 81b and the pair of second white reference surfaces 81c can be used in a clean state where dust such as paper dust is not attached, and the second reference black data and the second Reference white data can be obtained accurately.

<Processing in Image Forming Apparatus Main Body>
Returning to FIG. 1, the image forming apparatus main body 1 stores the read image data on the first surface of the document D read by the scanner 10 and the document D read by the second reading unit 26 in the ADF 2. A printer 6 for forming the image by a known electrophotographic method based on the read image data of the second surface, and an image data control unit 5 for controlling the printer 6 are provided.

<Processing of image data>
Image data obtained by each of the first line sensor 11 of the scanner 10 and the second line sensor 26 b of the second reading unit 26 is read by the reading processing unit 51 in the image data processing unit 5, yellow (Y), magenta (M ), Cyan (C), and black (K) image data corresponding to each reproduction color, and after being compressed by the compression unit 52, is input to the image memory 55 via the image memory control unit 53, for example. .

  The image memory 55 is constituted by a DRAM, for example, and is provided with a compression memory 55a and a page memory 55b for storing compressed image data corresponding to each of Y, M, C, and K reproduction colors output from the compression unit 52. It has been. Image data is stored in and read from the image memory 55 by the image memory control unit 53. The image memory control unit 53 outputs image data corresponding to the compressed reproduction colors Y, M, C, and K to the decompression unit 54.

  A main control unit 57 that controls the entire image forming apparatus controls the scanner control unit 12, the ADF control unit 91, and the printer control unit 62 based on compressed image data corresponding to each color of Y, M, C, and K, respectively. A predetermined instruction is given, and a predetermined instruction is also given to the image memory control unit 53. Thereby, the scanner control unit 12, the ADF control unit 91, and the printer control unit 62 control the scanner 10, ADF2, and printer 6, respectively. The printer control unit 62 also controls the post-processing device 3 that performs various processes on the printed paper. The main control unit 57 executes each control based on various programs stored in the nonvolatile memory 58.

The decompressing unit 54 decompresses the compressed image data corresponding to the input reproduction colors Y, M, C, and K and outputs the compressed image data to the writing processing unit 56. The writing processing unit 56 generates a driving signal for driving a laser diode (LD) 61 provided in the printer 6 for each reproduction color of Y, M, C, and K.
The printer 6 is provided with image forming portions 63Y, 63M, 63C, and 63K corresponding to Y, M, C, and K reproduction colors. Each of the image forming units 63Y, 63M, 63C, and 63K is provided with a photosensitive drum and a charger, a developing unit, a transfer unit, a cleaner, and the like disposed around the photosensitive drum.

  From the laser diode (LD) 61, laser light corresponding to each reproduction color of Y, M, C, and K is emitted based on the drive signal generated by the writing processing unit 56. Laser light emitted from a laser diode (LD) 61 exposes and scans the respective photosensitive drums corresponding to Y, M, C, and K reproduction colors in the main scanning direction. Each photosensitive drum is charged by a charger before being exposed to laser light from a laser diode (LD) 61, and an electrostatic latent image is formed by being exposed in the charged state. The electrostatic latent image formed on each photoconductive drum is developed and visualized by each corresponding color toner by a developing unit for each color of Y, M, C, and K. The toner images of the respective colors on the respective photosensitive drums are transferred onto the predetermined area of the recording sheet so as to overlap at the transfer position by the action of the electric field of the transfer portion. Thereby, a full-color toner image is formed on the recording sheet.

Note that the printer controller 62 controls the rotation of the photosensitive drum of each image forming unit and the conveyance of the recording sheet in the printer 6.
<Operation unit>
The image forming apparatus main body 1 includes an operation unit including a touch input type LCD (liquid crystal) panel 71 and an operation control unit 72 that controls display on the LCD panel 71 based on an instruction from the main control unit 57. 7 is provided. On the LCD panel 71, the operation control unit 72 instructs the start of the image forming operation, the instruction of the duplex mode for printing the double-sided image in the document on which the image is formed on both sides, and the photographic mode for reading the photographic document with high quality. And a screen for setting the number of prints is displayed, and the operator touches a predetermined position on the displayed screen, whereby a predetermined signal is input to the main controller 57.

<ADF control block>
FIG. 5 is a block diagram of a control system in ADF2. In the ADF control unit 91 provided in the ADF 2, each side surface of the sheet feed sensor 88 that detects that the document D on the document mounting table 21 is fed to the platen roller 25 and the rotating body 81 is positioned at the reading position. The side position sensor 85 for detecting that the output signal is received, and the respective output signals from the LCD panel 71 in the operation unit 7 are input. The ADF control unit 91 outputs a predetermined signal to the ADF drive unit 92 based on the output signals from the paper feed sensor 88, the side surface position sensor 85, and the LCD panel 71 that are input. The ADF drive unit 92 is configured to rotate the feed roller 22, the branch roller 23, the platen roller 25, and the like in order to feed the document D based on a signal from the ADF control unit 91, and a rotating body. The rotating body drive motor 84 that rotationally drives 81 and the on / off of each second linear light source 26a in the second reading means 26 are controlled.

<Control of ADF shading correction>
FIG. 6 is a flowchart showing the control content of the shading correction of the image reading device 4. The shading correction of the image reading device 4 is executed by a reading processing unit 51 provided in the image data control unit 5. In response to an instruction to start an image forming operation from the LCD panel 71, the reading processing unit 51 first calculates three correction coefficients necessary for shading correction of the output of the first line sensor 11 provided in the scanner 10. A full calculation is executed (see step S1 in FIG. 6, and so on). In this full calculation, a black level correction coefficient for black level adjustment, a white level correction coefficient for white level adjustment, and a light distribution correction coefficient for correcting variation in the amount of light in the first linear light source 15a. Everything is calculated individually. Each calculated correction coefficient is initially set in the reading processing unit 51. Details of the full calculation of the correction coefficient for the first line sensor 11 will be described later.

  When the full correction calculation of the first line sensor 11 is executed, it is determined based on the output of the paper feed sensor 88 whether the document D is being conveyed in the ADF 2 (step S2). When the document D is being conveyed (“YES” in step S2), it is determined based on the output from the LCD panel 71 of the operation unit 7 whether the duplex mode is instructed (step S3). If the double-side mode is not instructed on the LCD panel 71 (“NO” in step S3), it is instructed to be a single-side mode in which only the image formed on the first surface (front surface) of the document is read and printed. As a result, a predetermined signal corresponding to the instruction is output to the scanner control unit 12.

  The scanner control unit 12 moves the scanner 10 immediately below the slit glass 13 before the document D reaches the slit glass 13, and moves the scanner 10 when the document D passes the slit glass 13. As a result, the image formed on the first surface (front surface) of the document D is read. From the first line sensor 11 of the scanner 10, data corresponding to the read image is output to the image memory control unit 53 via the reading processing unit 51 and the compression unit 52.

  In the reading processing unit 51, the first line sensor based on all of the black level correction coefficient, the white level correction coefficient, and the light distribution correction coefficient that are initially set by executing the full calculation on the image data output from the first line sensor 11. 11 output shading correction (hereinafter, this shading correction is referred to as full shading correction) (step S4), and the process proceeds to step S5. The printer 6 performs a printing operation based on the read image data.

In step S5, it is determined whether or not the document D is newly fed in the ADF2. If a new document D is being fed, the shading correction in step S4 is performed, and the printer 6 performs a printing operation on the new document D. When a new document D is not fed, the shading correction control ends.
When the duplex mode is instructed in step S3 (“YES” in step S3), the following processing is executed.

<Processing in photo mode>
The LCD panel in the operation unit 7 indicates whether or not a photo mode indicating that each image formed on the first surface (front surface) and the second surface (back surface) of the document is a high-definition image such as a photograph is instructed. A determination is made based on the output from 71 (step S6). The operator inputs to the LCD panel 71 that the document is a photo mode document. If it is determined that the photographic mode is instructed (“YES” in step S6), full calculation of the three correction coefficients for the second line sensor 26b of the second reading means 26 provided in the ADF 2 is performed. Execute (Step S7).

The full calculation of the correction coefficient for the second line sensor 26b is to calculate a black level correction coefficient, a white level correction coefficient, and a light distribution correction coefficient for the output of the second line sensor 26b. Details of the full calculation of the three correction coefficients for the second line sensor 26b will be described later.
Thereafter, when the document D is conveyed, the image formed on the first surface (front surface) of the document D is read by the scanner 10. At this time, data corresponding to the read image is output from the first line sensor 11 of the scanner 10 to the image memory control unit 53 via the reading processing unit 51 and the compression unit 52.

  The reading processing unit 51 converts the image data output from the first line sensor 11 into each of the three correction coefficients initially set by the full calculation of the correction coefficient for the first line sensor 11 executed in step S1. Based on this, full shading correction is performed (step S8). Based on the image data after the shading, the printing operation in the printer 6 is performed.

The document D that has passed over the slit glass 13 passes through the conveyance path immediately below the second reading means 26. In this case, the rotating body 81 is rotated and positioned so that the document guide surface 81 a faces the second reading unit 26.
When the document D passes directly below the second reading unit 26, the image on the second surface of the document D is read by the second reading unit 26. Image data corresponding to the read image is output from the second line sensor 26 b of the second reading unit 26 to the reading processing unit 51.

In the reading processing unit 51, the image data output from the second line sensor 26b is based on each of the three correction coefficients obtained by the full calculation of the correction coefficient for the second line sensor 26b executed in step S7. Thus, full shading correction is performed (step S9).
The printer 6 prints the image on the second surface based on the image data after the shading correction.

  The reading processing unit 51 determines whether or not the document D is newly fed in the ADF 2 (step S10). When a new document D is being fed, shading correction for the second line sensor 26b in steps S8 and S9 is executed, and the printer 6 prints based on the image data subjected to the shading correction. The action is executed.

<Processing when not in photo mode>
Next, the case where the mode is the duplex mode but not the photo mode (“NO” in step S6) will be described below.
If “NO” in the step S6, the reading processing unit 51 determines that a character mode in which the gradation image reproducibility such as a character other than a photograph is not required is instructed for the document image, and the ADF 2 is instructed. A second light distribution correction coefficient for correcting the light distribution of the output of the second line sensor 26b in the provided second reading means 26 is simply calculated (step S11).

The simple calculation of the second light distribution correction coefficient of the second line sensor 26b is based on the first light received by the respective light beams reflected by the margins at the leading edge of the first surface and the second surface of the document D being conveyed. The second light distribution correction coefficient of the second line sensor 26b is calculated based on the outputs of the line sensor 11 and the second line sensor 26b, and details thereof will be described later.
When the calculation of the second light distribution correction coefficient for the second line sensor 26b is executed, the second light distribution correction coefficient is formed on the first surface of the document D output from the first line sensor 11, as in the case of the photographic mode described above. The image data corresponding to the obtained image is subjected to full shading correction based on each of the three correction coefficients initially set by the full calculation of the correction coefficient for the first line sensor 11 executed in step S1 (step S12). ). Then, the printer 6 performs a printing operation corresponding to the image formed on the first surface of the document D.

  Further, shading correction based on only the second light distribution correction coefficient obtained by the simple calculation in step S11 is performed on the image data corresponding to the image formed on the second surface of the document D output from the second line sensor 26b. Hereinafter, this shading correction is referred to as simple shading correction) (step S13). In the printer 6, a toner image corresponding to the image formed on the second surface of the document D is formed on the second surface of the recording sheet.

Thereafter, the reading processing unit 51 determines whether or not the document D is newly fed in the ADF 2 (step S14). When a new document D is being fed, the shading correction in steps S12 and S13 and the printing operation for the image of the new document D in the printer 6 are executed.
<Full correction coefficient calculation for the first line sensor>
FIG. 7 is a flowchart showing a full calculation subroutine in step S1 of FIG. In the full calculation of the correction coefficient for the first line sensor 11, first, light from the first linear light source 15 a in the scanner 10 is reflected by the first black reference surface 17 a of the reference plate 17, and the first line sensor 11. 1, the first unit 151 and the second unit 152 of the reduction optical system 15 are slid in the direction of arrow A as indicated by a broken line in FIG. In this case, the second unit 152 is slid by a distance 1/2 that of the first unit 151.

  When the first linear light source 15a is turned on in this state, the first black reference surface 17a of the reference plate 17 is irradiated with light, and the reflected light is received by the first line sensor 11 ( Step S21 in FIG. The first line sensor 11 outputs a voltage corresponding to the amount of light reflected by the first black reference surface 17 a of the reference plate 17 to the reading processing unit 51 in the image data control unit 5.

The reading processing unit 51 adjusts the level of the output voltage for black of the first line sensor 11 based on the output voltage of the first line sensor 11 based on the amount of light reflected by the first black reference surface 17a. The first black level correction coefficient is calculated (step S22).
Thereafter, the first optical source 15a of the reduction optical system 15 is reflected so that the light from the first linear light source 15a in the scanner 10 is reflected by the first white reference surface 17b of the reference plate 17 and received by the first line sensor 11. The unit 151 and the second unit 152 are each slid by a predetermined distance.

  When the first linear light source 15a is turned on in this state, the first white reference surface 17b of the reference plate 17 is irradiated with light, and the reflected light is received by the first line sensor 11 ( Step S23). The first line sensor 11 outputs a voltage corresponding to the amount of light reflected by the first white reference surface 17 b of the reference plate 17 to the reading processing unit 51 in the image data control unit 5.

The reading processing unit 51 stores the output voltage of the first line sensor 11 based on the amount of light reflected by the first white reference surface 17b as white reference data, and the first line based on the white reference data. A first white level correction coefficient for adjusting the level of the output voltage with respect to the white color of the sensor 11 is calculated (step S24).
Further, the reading processing unit 51 uses the first linear light source based on the output voltage from the first line sensor 11 based on the amount of light from the first linear light source 15a reflected by the first white reference surface 17b. A first light distribution correction coefficient for correcting variations in output voltage due to variations in the amount of light in the axial direction 15a is calculated (step S25). This first light distribution correction coefficient is the voltage at any position in the axial direction of the first linear light source 15a (corresponding to the main scanning direction) when the first white reference surface 17b is read. It is a coefficient necessary to obtain a voltage corresponding to the average value of the light amount in the first linear light source 15a so that the values are substantially the same.

  Thus, the full calculation of the three correction coefficients for the first line sensor 11 is completed, and the calculated first black level correction coefficient, first white level correction number, and first light distribution correction coefficient are read out. Stored in the unit 51. Then, based on the calculated first black level correction coefficient, first white level correction number, and first light distribution correction coefficient, shading correction of the output of the first line sensor 11 in step S4, step S8, and step S12 of FIG. Is done.

<Full correction coefficient calculation for the second line sensor>
FIG. 8 is a flowchart showing a subroutine for full calculation of three correction coefficients for the second line sensor 26b in step S7 of FIG. In the full correction calculation of the correction coefficient for the second line sensor 26b, first, the rotating body drive motor 84, which is a stepping motor, is set so that the second black reference surface 81b of the rotating body 81 faces the second reading means 26. Driven. Positioning of the second black reference surface 81b at the reading position facing the second reading means 26 is detected by a side detection sensor 85 provided on the rotating body 81. Thereafter, each second linear light source 26a of the second reading means 26 is turned on to irradiate the second black reference surface 81b with light, and the reflected light from the second black reference surface 81b is received by the second line sensor 26b. (Step S31 in FIG. 8). The second line sensor 26 b outputs a voltage corresponding to the amount of light reflected by the second black reference surface 81 b of the rotator 81 to the reading processing unit 51 in the image data control unit 5.

The reading processing unit 51 adjusts the level of the output voltage of the second line sensor 26b for black based on the output voltage of the second line sensor 26b based on the amount of light reflected by the second black reference surface 81b. The second black level correction coefficient is calculated (step S32).
When the second black level correction coefficient is calculated, the rotating body drive motor 84 is driven so that the second white reference surface 81c of the rotating body 81 faces the second reading means 26. The fact that the second white reference surface 81 c is positioned at the reading position facing the second reading means 26 is detected by a side surface detection sensor 85 provided on the rotating body 81.

  In this state, each linear light source 26a of the second reading unit 26 is turned on to irradiate the second white reference surface 81c with light, and the reflected light from the second white reference surface 81c is received by the second line sensor 26b. (Step S33 in FIG. 8). The second line sensor 26 b outputs a voltage corresponding to the amount of light reflected by the second white reference surface 81 c of the rotator 81 to the reading processing unit 51 in the image data control unit 5.

The reading processing unit 51 adjusts the level of the output voltage for the white of the second line sensor 26b based on the output voltage of the second line sensor 26b corresponding to the amount of light reflected by the second white reference surface 81c. Therefore, the second white level correction coefficient necessary for this is calculated (step S34).
Further, in the reading processing unit 51, based on the output voltage of the second line sensor 26b based on the amount of light from the second linear light source 26a reflected by the second white reference surface 81c, the second linear light source 26a. A second light distribution correction coefficient for correcting variations in output voltage due to variations in the amount of light in the axial direction is calculated (step S35). The second light distribution correction coefficient is obtained by using the second linear light source so that the output voltage of the second line sensor 26b obtained by reading the second white reference surface 81c is substantially the same at any position in the main scanning direction. This is a coefficient necessary to obtain a voltage corresponding to the average value of the amount of light at 26a.

  As described above, the full calculation of the correction coefficient for the second line sensor 26b is completed, and the calculated first black level correction coefficient, first white level correction number, and first light distribution correction coefficient are read processing unit 51. Is remembered. Then, full shading correction of the output of the second line sensor 26b in step S9 of FIG. 6 is performed by the calculated first black level correction coefficient, first white level correction number, and first light distribution correction coefficient.

<Simple calculation of the second light distribution correction coefficient for the second line sensor>
FIG. 9 is a flowchart showing a subroutine for simplified calculation of the second light distribution correction coefficient in step S11 of FIG. The simple calculation of the second light distribution correction coefficient is to simply obtain the second light distribution correction coefficient without reading the white reference surface 81c by the second reading means 26, and the document D on the document table 21 in the ADF 2 is obtained. It starts by passing over the slit glass 13.

  When the document D passes over the slit glass 13, the first linear light source 15a of the scanner 10 provided in the image forming apparatus main body 1 is turned on. As a result, light is applied to the blank portion at the leading edge of the document D that passes over the slit glass 13, and the light reflected at the blank portion at the leading edge of the document D is received by the first line sensor 11. . In the first line sensor 11, a voltage corresponding to the amount of received light is output to the reading processing unit 51 in the image data processing unit 5 (step S41).

  In the reading processing unit 51, for example, when obtaining the first white level correction coefficient and the first light distribution correction coefficient for the first line sensor 11 in step S24, the white reference surface 17b is irradiated with the first linear light source 15a. Since the output from the first line sensor 11 based on the reflected light is previously obtained and stored as white reference data, the white reference data and the actual output voltage from the first line sensor 11 currently read are Is calculated (step S42).

Thereafter, the document D that has passed over the slit glass 13 passes through the conveyance path immediately below the second reading means 26. In this case, the rotating body 81 is positioned so that the document guide surface 81 a faces the second reading unit 26.
When the document D passes through the conveyance path immediately below the second reading unit 26, the scanner 10 reads the margin portion of the leading end portion on the second surface of the document D (the margin portion at the leading end portion of the first surface). Corresponding to the back side of the corresponding portion) is read by the second reading means 26. The second line sensor 26 b of the second reading unit 26 receives the light reflected by the margin part of the leading end portion on the second surface of the document D.

The second line sensor 26b outputs a voltage corresponding to the amount of received light to the reading processing unit 51 in the image data processing unit 5 (step S43).
In the reading processing unit 51, the data related to the difference calculated in step S42 is converted for the second line sensor 26b, the output voltage of the second line sensor 26b is corrected (step S44), and the corrected second line is corrected. Based on the output of the sensor 26b, a second light distribution correction coefficient necessary for correcting the light distribution of the output of the second line sensor 26b is calculated (step S45).

  In this case, the difference calculated in step S42 corresponds to a potential difference when each of the white space on the white reference surface and the first surface of the original is read. The margin portions on the first and second sides of the document are the same as the background portion of the document and thus have the same reflection characteristics. The second line sensor 26b also reads the margin portion on the second surface of the document. Sometimes the same level of difference should be obtained, but because both output voltages are different due to different output characteristics, the same difference cannot be applied. Therefore, the white color obtained when the correlation between the output characteristic of the first line sensor 11 and the output characteristic of the second line sensor 26b is obtained in advance and the first line sensor 11 is read using the correlation. The difference from the reference data is converted into a difference of a size that is expected to be generated when the second reading unit 26 reads the difference, and the difference in the second reading unit 26 obtained by the conversion is converted by the second reading unit 26. Applying to the data of the second line sensor 26b corresponding to the read blank portion, the second reading means 26 corrects the value to the value obtained when the white reference surface is read, and uses the corrected data. A second light distribution correction coefficient is generated. As described above, the second light distribution correction coefficient for the second line sensor 26b is simply calculated.

When the second light distribution correction coefficient necessary for correcting the light distribution of the output of the second line sensor 26b is simply calculated, the second line sensor in step S13 in FIG. 6 is obtained by the obtained second light distribution correction coefficient. 26b is subjected to simple shading correction.
In the document D on which the character image is formed, a margin part where the character image is not formed is usually provided at the periphery, and the margin part is a background part of the document D. And usually have similar reflection characteristics. Therefore, based on the output voltage of the first line sensor 11 with respect to the blank portion, the output voltage of the second line sensor 26b with respect to the blank portion is corrected, and the first calculated based on the corrected output voltage of the second line sensor 26b. By performing the light distribution correction using the two light distribution correction coefficients, the corrected image data has good reproducibility with respect to the character image on the document D.

In addition, since the simple shading correction does not require the use of reflected light from the second black reference surface 81b and the second white reference surface 81c of the rotator 81, the rotator 81 is rotated and stopped so that the second black reference surface is corrected. Time for positioning the surface 81b and the second white reference surface 81c becomes unnecessary, and the processing time can be shortened.
In the above-described embodiment, the second light distribution coefficient for simple shading correction is calculated based on the white reference data obtained in step S1, but the present invention is not limited to such a configuration. White reference data obtained by various timings may be used.

  Also, based on the instruction whether the image of the document is in the photo mode, it has been determined whether to perform full shading correction or simple shading correction on the image data on the second side of the document. It is not limited to the configuration. For example, it may be determined whether to perform full shading correction or simple shading correction based on the sheet characteristics (reflection characteristics) of the document itself such as paper quality and color constituting the document. Specifically, simple shading correction can be prohibited when the original has sheet characteristics as thin paper. This is because thin paper is usually harder to shield than plain paper and thick paper, so that the accuracy may be lowered if the light distribution characteristics are corrected by receiving the reflected light in the margin of the original. Since the OHP sheet also transmits light, simple shading correction can be prohibited as in the case of thin paper. It should be noted that simple shading correction can be prohibited even when the original is not white and is colored, or when it has light transmission. It should be noted that the determination of the sheet characteristics of the document can be configured to accept input of sheet characteristics from the LCD panel in the operation unit. In addition, the sheet characteristic is optically determined by irradiating light to the conveyed document, receiving the reflected light by an optical sensor, and detecting the light transmittance of the document from the received light amount. Good.

In addition, although the configuration is such that the reflected light of the margin part at the leading edge of the first surface and the second surface of the document is received in the simple calculation of the second light distribution correction coefficient, the present invention is not limited to this, for example, the first surface of the document In addition, it is possible to receive the reflected light from the margin part at the rear end of the second surface, or to receive one of the reflected light from the margin part at the tip and to receive the reflected light from the margin part at the rear end. .
Further, in the above embodiment, the rotating body 81 is provided below the second reading unit 26, and the second black reference surface 81b and the second white reference surface 81c are provided on each side surface of the rotating body 81. The second black reference surface 81b and the second white reference surface 81c are provided on the same flat plate so that the second black reference surface 81b and the second white reference surface 81c on the flat plate are read by the second reading means 26. In addition, a configuration in which a flat plate is slid or a configuration in which the second reading means 26 is slid may be used.

  The present invention can be widely applied to the technical field of an image forming apparatus such as a copying machine in which a second reading unit is provided in an ADF. According to the present invention, high-definition image data such as a photographic image by the second reading unit can be obtained with high reproducibility, and the shading correction processing of the character image can be efficiently performed. The utility value is extremely high.

1 is a block diagram showing an outline of an image forming apparatus provided with an image reading apparatus in an embodiment of the present invention. It is the schematic which shows the structure of the image reading apparatus shown in FIG. It is sectional drawing which shows schematic structure of the 2nd reading means provided in ADF with the structure of the peripheral part. (A) is a perspective view of the rotary body provided in ADF shown in FIG. 3, (b) is a side view which shows the structure of the rotary body. It is a block diagram of the control system in ADF. 5 is a flowchart showing control details of shading correction of the image reading apparatus of the present invention. FIG. 7 is a flowchart showing a subroutine for a full calculation of a correction coefficient for the first line sensor in the flowchart shown in FIG. 6. FIG. 7 is a flowchart showing a subroutine for a full calculation of correction coefficients for the second line sensor in the flowchart shown in FIG. 6. FIG. 7 is a flowchart showing a subroutine for simplified calculation of a second light distribution correction coefficient for the second line sensor in the flowchart shown in FIG. 6.

Explanation of symbols

1 Image forming apparatus body 2 ADF
3 Post-Processing Device 4 Image Reading Device 5 Image Data Control Unit 6 Printer 7 Operation Unit 10 Scanner 11 First Line Sensor 12 Scanner Control Unit 15 Reduction Optical System 15a First Linear Light Source 17 Reference Plate 17a First Black Reference Surface 17b First 1 white reference surface 25 platen roller 26 second reading means 26a second linear light source 26b second line sensor 51 reading processing unit 53 image memory control unit 56 writing processing unit 71 LCD panel 81 rotating body 81a document guide surface 81b second black Reference surface 81a Second white reference surface 84 Rotating body drive motor

Claims (10)

First reading means for reading an image on the first side of the document;
Second reading means for reading an image on the second side of the document;
First shading correction means for performing shading correction on the image data of the first surface obtained by the first reading means based on the reading result of the first white reference surface by the first reading means;
Second shading correction means for performing shading correction on the image data of the second surface obtained by the second reading means based on the reading result of the second white reference surface by the second reading means;
Simple shading correction means for performing shading correction on the image data of the second surface based on the reading result of the margin part of the second surface of the document by the second reading means;
An image reading apparatus comprising: Further comprising instruction means for instructing that the image on the second side of the document is in a photographic mode;
2. The image reading apparatus according to claim 1, wherein when the photo mode is not instructed by the instruction unit, shading correction is performed by the simple shading correction unit.   The image reading apparatus according to claim 1, wherein one of the second shading correction unit and the simple shading correction unit is selectively used according to sheet characteristics of the document.   The simple shading correction means is configured to determine the original based on a reading result by the first reading means of a margin portion of the first surface of the original and a reading result of the first white reference surface by the first shading correction means. 4. The image reading apparatus according to claim 1, wherein a reading result by the second reading unit of a blank portion of the second surface of the second image is corrected. 5. The first reading means includes
A first linear light source disposed so as to face the first surface of the conveyed document so as to irradiate light along a direction orthogonal to the conveying direction of the document;
A reduction optical system for reducing and projecting light from the first linear light source reflected by the first surface of the document;
A first line sensor that receives light reduced and projected by the reduction optical system;
The image reading apparatus according to claim 1, further comprising:   The first shading correction unit adjusts the black level of the first line sensor based on the reading result of the first black reference plane by the first reading unit, and the first white reference plane of the first reading unit is adjusted by the first reading unit. The image reading apparatus according to claim 5, wherein white level adjustment and light distribution correction of the first line sensor are performed based on a reading result. The second reading means includes
A second linear light source disposed so as to face the second surface of the conveyed document so as to irradiate light along a direction orthogonal to the conveying direction of the document;
A contact-type second line sensor that receives light from the second linear light source reflected by the second surface of the document;
The image reading apparatus according to claim 1, comprising:   The second shading correction means adjusts the black level of the second line sensor based on the reading result of the second black reference surface by the second reading means, and the second white reference surface of the second white reference surface by the second reading means. The image reading apparatus according to claim 7, wherein white level adjustment and light distribution correction of the second line sensor are performed based on a reading result. A rotating body rotatably arranged at the image reading position of the second line sensor;
The rotating body has at least two side surfaces positioned at the image reading position, and each of the two side surfaces is provided with the second black reference surface and the second white reference surface. The image reading apparatus according to claim 8. An image reading apparatus according to any one of claims 1 to 9,
A printer for forming an image on a recording sheet based on image data read by the image reading device;
An image forming apparatus comprising:

Images