JP2007129278A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately eliminate the effect of a change in the intensity of light rays emitted onto an original. <P>SOLUTION: The image reading apparatus includes: a light source for emitting light rays to a read object; a line sensor for receiving the light rays reflected from the read object and outputting data; a correction data determining section 213 for determining correction data on the basis of shading board data which the line sensor outputs by receiving the light rays reflected from a shading board whose reflection factor is predetermined; a shading correction section for using the correction data to correct original data which the line sensor outputs by receiving the light rays reflected from an original; and a gradation characteristic detection section 234, a gradation characteristic comparison section 233, and a selector 232 for revising the correction data used by the shading correction section on the basis of the original data which the line sensor outputs by receiving the light rays reflected from the original. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus that reads an original while conveying it.

  In recent years, in scanners, facsimiles, copiers, etc., a line sensor in which a plurality of photoelectric conversion elements are arranged in a main scanning direction is fixed and installed, and a line sensor is conveyed by conveying a document in a sub scanning direction orthogonal to the main scanning direction. In some cases, a reading method for reading a document (hereinafter referred to as “document transport method”) is employed. A cathode ray tube is used as a lamp serving as a light source, and the light amount distribution in the main scanning direction varies depending on the individual difference and the period of use. For this reason, by reading a shading plate with a known reflectivity before reading the document, the light amount distribution in the main scanning direction is stored, and the data obtained by reading the document is corrected according to the stored light amount distribution. So-called shading correction is performed.

  On the other hand, the intensity of light emitted from the lamp changes with time. In the document transport method, the shading plate cannot be read by the line sensor while a plurality of documents are being transported continuously. For this reason, the document transport method has a problem that it cannot cope with a change in the light emission intensity of the lamp while a plurality of documents are continuously transported.

  In order to solve this problem, Japanese Patent Laid-Open No. 2002-271591 discloses a light source that irradiates a reading position of a document, a reference plate for shading correction, and an elapsed time after the light source starts to turn on. Clocking means for performing, shading correction data creating means for creating the shading correction data corresponding to the elapsed time from the start of lighting by turning on the light source and reading the reference plate during a time period when the document is not read, Shading correction data storage means for storing shading correction data created by the shading correction data creation means, and shading correction data corresponding to the elapsed time from the start of lighting of the light source when the document is read. Image information of the original read out sequentially from the correction data storage means Image reading apparatus is described characterized by comprising a correction to shading correction means.

However, the image reading apparatus described in Japanese Patent Application Laid-Open No. 2002-271591 discloses the state of the light source while the light source is turned on and the reference plate is read to generate shading correction data corresponding to the elapsed time from the start of lighting. It is assumed that the state of the light source matches during reading. For this reason, if the change in the light emission intensity of the light source while reading the document is different from the change in the light emission intensity of the light source measured while creating the shading correction data, the shading correction cannot be performed accurately. There is.
Japanese Patent Laid-Open No. 2002-271591

  The present invention has been made to solve the above-described problems, and one of the objects of the present invention is based on a change in the intensity of light applied to a document from data obtained by receiving light reflected by the document. An object of the present invention is to provide an image reading apparatus capable of accurately removing the influence.

  In order to achieve the above-described object, according to an aspect of the present invention, an image reading apparatus includes an irradiation unit that irradiates light to a reading target, and a photoelectric conversion unit that receives light reflected by the reading target and outputs data. And correction data determining means for determining correction data based on data output by receiving light reflected by a reference plate having a predetermined reflectance, and the photoelectric conversion means is reflected by the manuscript. Correction data used by the correction means based on the data output by receiving and outputting the light reflected by the original by the photoelectric conversion means And changing means for changing.

  According to the present invention, the correction data determined based on the data that the photoelectric conversion means receives and outputs the light reflected by the reference plate is the data that the photoelectric conversion means receives and outputs the light reflected by the document. Will be changed based on. For this reason, even if the intensity of the light emitted by the irradiating means changes with time, the reading means reflects the light reflected by the document using correction data corresponding to the intensity of the light emitted by the irradiating means. The data received and output is corrected. As a result, it is possible to provide an image reading apparatus capable of accurately removing the influence of a change in the intensity of light applied to a document from data obtained by receiving light reflected from the document.

  Preferably, the electronic device further includes a time measuring unit that measures an elapsed time after the irradiation unit has irradiated the light, and the changing unit limits the range of correction data that can be changed based on the elapsed time measured by the time measuring unit. Limiting means.

  According to the present invention, the range of correction data that can be changed is limited based on the elapsed time since the irradiation means has irradiated light. For this reason, it is possible to prevent the correction data that is changed based on the data that the photoelectric conversion means receives and outputs the light reflected from the document from being changed to an incorrect value.

  Preferably, the image forming apparatus further includes a document conveying unit that conveys the document to a predetermined reading position and a reflecting plate that is fixedly provided at a position facing the irradiation unit, and the changing unit passes the document through the reading position. Limiting means for limiting the range of correction data that can be changed based on data that is received and output by the photoelectric conversion means previously received by the reflector.

  According to this invention, the range of correction data that can be changed is limited based on the data that the photoelectric conversion means receives and outputs the light reflected by the reflecting plate before the document passes the reading position. For this reason, it is possible to prevent the correction data that is changed based on the data that the photoelectric conversion means receives and outputs the light reflected from the document from being changed to an incorrect value.

  Preferably, the correction data determining means generates reference correction data from data output by receiving light reflected from the reference plate by the photoelectric conversion means and a predetermined target value. And second correction data generation means for generating at least one variation correction data from the reference correction data and a predetermined coefficient.

  According to the present invention, the reference correction data is generated from the data that the photoelectric conversion means receives and outputs the light reflected by the reference plate and the predetermined target value, and the reference correction data is determined in advance. At least one variation correction data is generated from the coefficients. For this reason, the correction data can be easily generated.

  Preferably, the changing means includes document data comparison means for comparing the first data output from the photoelectric conversion means and the second data output from the photoelectric conversion means, and based on the comparison result by the document data comparison means. The correction data used by the correction means is changed.

  Preferably, the photoelectric conversion means includes a plurality of line sensors having filters having different spectral sensitivities, and the correction data determination means receives data reflected by the reference plate and outputs the data reflected by the line sensors. Based on this, the correction data corresponding to each of the plurality of line sensors is determined, and the correction means receives the data reflected by the document from each of the plurality of line sensors and outputs the data corresponding to each of the plurality of line sensors. Correction is performed using the correction data, and the change unit changes the correction data used for correction by the correction unit based on data output by receiving the light reflected from the document by each of the plurality of line sensors.

  According to another aspect of the present invention, an image reading apparatus includes an irradiation unit that irradiates light to a reading target, a photoelectric conversion unit that receives light reflected by the reading target and outputs data, and a plurality of correction data. Storage means for storing in advance, data for receiving and outputting light reflected by a reference plate having a predetermined reflectance by the photoelectric conversion means, and reference correction data and at least one of a plurality of correction data Selection means for selecting one fluctuation correction data, and reference correction data selected by the selection means and at least one fluctuation correction data based on data output by receiving light reflected from the original by the photoelectric conversion means Setting means for selecting any one of the data and setting it as execution correction data, and data for receiving and outputting the light reflected from the original by the photoelectric conversion means, And correction means for correcting using data.

  According to the present invention, the reference correction data and at least one variation correction data are selected from the plurality of correction data based on the data that the photoelectric conversion means receives and outputs the light reflected by the reference plate. The photoelectric conversion means receives one of the light reflected from the original and outputs it, and one of the selected reference correction data and at least one variation correction data is selected as execution correction data. Is set. For this reason, even if the intensity of the light irradiated by the irradiation unit changes with time, execution correction data corresponding to the intensity of the light irradiated by the irradiation unit is selected from the plurality of correction data. The execution correction data is used to correct the data that the photoelectric conversion means receives and outputs the light reflected from the document. As a result, it is possible to provide an image reading apparatus capable of removing the influence due to the change in the intensity of the light applied to the original from the data obtained by receiving the light reflected by the original.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<First Embodiment>
FIG. 1 is a perspective view of an MFP (Multi Function Peripheral) including an image reading apparatus according to the first embodiment of the present invention. Referring to FIG. 1, MFP 100 includes an image reading device 110 for reading a document, and an image forming device 121 provided below the image reading device 110. A part of the image reading apparatus 110 is housed in the main body 120 and includes an automatic document feeder (ADF) 111. The image forming apparatus 121 is housed below the image reading apparatus 110 of the main body 120, and forms an image on a recording medium such as paper based on image data output by the image reading apparatus 110 reading a document. MFP 100 includes a communication interface for connecting to a network such as a facsimile, a local area network (LAN), and a public switched telephone network (PSTN).

  FIG. 2 is a diagram showing an outline of the internal configuration of the image reading apparatus 110. The ADF 111 includes a pair of timing rollers 151 for transporting the document 150 to the document reading position L, an upper restriction plate 153 for guiding document transportation in the vicinity of the document reading position L, and the document 150 that has passed the document reading position L. And a roller pair 152 for conveying the document 150 to discharge the document.

  The ADF 111 sequentially transports a plurality of documents 150 to the document reading position L one by one. The ADF 111 separates one document from the top of the stacked plurality of documents 150 and supplies it to the timing roller pair 151. The upper restriction plate 153 has a background plate 154 in the vicinity of the document reading position L on the document path side. Since the background plate 154 reflects the light transmitted through the document, it is desirable that the background plate 154 has a high reflectance and a uniform reflectance. This is because if the reflected light is uneven, it becomes noise.

  A portion housed in the main body 120 of the image reading apparatus 110 includes a document table 155 made of a transparent member, a sheet passing guide 157 that forms a part of the document transport path, and the document table 155 and the sheet passing guide. 157, a light source 159 for irradiating light, a reflecting member 160 for reflecting light from the light source 159, reflecting mirrors 161 and 162, a slider 158, a lens 163, and the like. And a reading unit 219 in which three line sensors are arranged in the main scanning direction.

  The document 150 is conveyed by the timing roller pair 151 between the document table 155 and the upper regulating plate 153 in the direction of the arrow D1. The image is sequentially read by the reading unit 219 at the reading position L while being conveyed. The direction in which the ADF 111 transports the document is the sub-scanning direction at the reading position L.

  The slider 158 holds the light source 159, the reflecting member 160, and the reflecting mirror 161. The slider 158 can reciprocate in the direction D2 in the figure, and stops at a position below the document reading position L while reading the document, and at a position below the shading plate 156 before reading the document. Stop. As the slider 158 moves, the reflection mirror 162 moves, so that the optical path length of the reflected light is kept substantially constant.

  When the slider 158 is positioned below the shading plate 156, the light emitted from the light source 159 is applied to the shading plate 156. Part of the light emitted from the light source 159 is reflected by the shading plate 156, further reflected by the reflecting mirrors 161 and 162, and guided to the lens 163. The lens 163 collects light incident thereon and forms an image on each line sensor of the reading unit 219.

  When the slider 158 is positioned below the document reading position L, the light emitted from the light source 159 is irradiated to the document reading position L. If the document 150 exists at the document reading position L, a part of the light emitted from the light source 159 is reflected by the document and further reflected by the reflection mirrors 161 and 162 and guided to the lens 163. The lens 163 collects light incident thereon and forms an image on each line sensor of the reading unit 219. If the original 150 does not exist at the original reading position L 1, part of the light emitted from the light source 159 is reflected by the background plate 154 and further reflected by the reflecting mirrors 161 and 162 and guided to the lens 163. The lens 163 collects light incident thereon and forms an image on each line sensor of the reading unit 219.

  When the ADF 111 transports a plurality of documents in order, the image reading apparatus 110 moves the slider 158 below the shading plate 156 and stops it before the ADF 111 starts transporting the document, and the shading correction described later. Data is generated. After generating the shading correction data, the image reading apparatus 110 moves the slider 158 below the document reading position L to stop it, and causes the ADF 111 to transport a plurality of documents in order.

  The reading unit 219 includes three line sensors. Each of the three line sensors has a plurality of photoelectric conversion elements arranged in a main scanning direction substantially perpendicular to the sub-scanning direction. Each of the three line sensors has filters having different spectral sensitivities, and the plurality of photoelectric conversion elements receive light transmitted through the filters. Specifically, a filter that transmits light of each wavelength of red (R), green (G), and blue (B) is included. Therefore, a line sensor having a red (R) filter outputs R data indicating the intensity of red light, and a line sensor having a green (G) filter outputs G data indicating the intensity of green light. The line sensor that outputs and has a blue (B) filter outputs B data indicating the intensity of blue light.

  FIG. 3 is a block diagram illustrating an example of a circuit configuration of the MFP. Referring to FIG. 3, MFP 100 is connected to bus 229, and includes a CPU (Central Processing Unit) 210 for controlling the entire MFP 100, a non-volatile memory (ROM) 211, and a random access memory (RAM). ) 212, correction data determination unit 213, image processing unit 215, light source control unit 217, reading unit 219, image forming unit 221, slider control unit 223 that controls the movement of the slider 158, and ADF 111. A document conveyance control unit 225 for controlling and an operation unit 227 for receiving an input of an operation by the user are included.

  The light source control unit 217 is connected to the light source 159 and switches between turning on and off the light source 159. The slider control unit 223 is connected to a motor 224 for moving the slider 158 and controls driving of the motor 224. The slider control unit 223 positions the slider 158 by controlling the motor 224. That is, the slider control unit 223 moves the slider 158 to a position below the shading plate 156 or a position below the document reading position L.

  Data (R data, G data, and B data) output by the reading unit 219 is output to the image processing unit 215. The image processing unit 215 processes image data output from the reading unit 219. The image processing unit 215 will be described later, but the image processing unit 215 includes a shading correction unit that performs shading correction on image data.

  The ROM 211 stores a plurality of correction data corresponding to R data, G data, and B data. The plurality of correction data includes a plurality of reference correction data and a plurality of variation correction data corresponding to each of the plurality of reference correction data.

  Here, the correction data will be described. The reference correction data is a value determined based on data (hereinafter referred to as “shading plate data”) that is received by the reading unit 219 and received by the light reflected by the shading plate 156. Further, the data that the reading unit 219 receives and outputs the light reflected from the document 150 is hereinafter referred to as “document data”. Since the reflectance of the shading plate 156 is known in advance and is not changed, the intensity of light emitted from the light source 159 is proportional to the shading plate data. For this reason, a coefficient for correcting the shading plate data to the reference value is determined from the shading plate data. The reference correction data includes a plurality of values corresponding to the obtained coefficient. Assuming that the brightness can be in the range of 0 to 255, for example, if the shading board data is 230, if the reference value is 255, the coefficient is 255/230. According to this coefficient, one reference correction data having values corresponding to the respective values of 0 to 255 is determined. Therefore, one reference correction data has 256 values. The reference correction data is determined in advance corresponding to each of the values in the range of 0 to 255 that the shading plate data can take, and is stored in the ROM 211. That is, the ROM 211 stores 256 reference correction data for each of R data, B data, and B data.

  The fluctuation correction data is one or more data corresponding to one reference correction data. Here, a total of 12 levels of fluctuation correction data of 10 levels on the plus side and 2 levels on the minus side are associated with one reference correction data. The plus level fluctuation correction data is used when the intensity of light emitted from the light source 159 becomes weaker than when the shading plate data is acquired. The minus level fluctuation correction data is used when the intensity of light emitted from the light source 159 becomes stronger than when the shading plate data is acquired. Here, when the shading plate data is acquired, the level of the correction data determined by the shading plate data is set to “0”, and the intensity of light emitted from the light source 159 is the intensity at the time when the shading plate data is acquired. Compared to the above, the level of the correction data when 2 gradations are lowered is plus 1 level, the level when 4 gradations are lowered is plus 2 levels,..., The level when 20 gradations are lowered Is 10 levels, the level when 2 gradations are increased is minus 1 level, and the level when 4 gradations are increased is minus 2 level. Therefore, the correction data for level 0 is reference correction data, and the correction data for levels other than level 0 is fluctuation correction data. Hereinafter, the correction data of level N (N is an integer of −2 ≦ N ≦ 10) will be referred to as correction data (N).

  The correction data (N) other than level 0 (variation correction data) corresponds to the correction data (0) (reference correction data), and is based on the shading plate data used to determine the correction data (0). Determined. Like the reference correction data, the fluctuation correction data has 256 values corresponding to all the values 0 to 255. For example, when the shading board data used to determine the correction data (0) is 230, the correction data (0) value corresponding to the original data value 230 and the time when the shading board data is acquired. The value of the correction data (−2) corresponding to the original data value 234 when the gradation is lower by 4 tones than the intensity of the same is 255. The ROM 211 stores 12 levels of fluctuation correction data corresponding to 256 pieces of reference correction data for each of R data, G data, and B data.

  Here, the number of levels of the fluctuation correction data is set to 12 levels, 10 levels on the plus side and 2 levels on the minus side, and the level interval is 2 gradations. However, the number of levels and the level interval are limited to these. What is necessary is just to determine according to the characteristic of the light source 159 instead of a thing.

  The correction data determination unit 213 determines correction data used by the image processing unit 215 for shading correction, and outputs the determined correction data to the image processing unit 215. Specifically, the correction data determination unit 213 selects one reference correction data from among a plurality of reference correction data stored in the ROM 211 based on the shading plate data. The reference correction data is output to the image processing unit 215 as correction data used by the image processing unit 215 for shading correction. Further, the correction data determination unit 213 receives the reference correction data and the reference correction data selected previously based on the data (document data) output by receiving the light reflected from the document 150 by the reading unit 219. One of a plurality of corresponding variation correction data is selected, and execution correction data used for shading correction is set. The set execution correction data is output to the image processing unit 215 as correction data used by the image processing unit 215 for shading correction.

  The image forming unit 221 controls the image forming apparatus 121 to cause the image forming apparatus 121 to form an image on a recording medium such as paper based on the image data processed by the image processing unit 215 to visualize the image data. Let

  The document conveyance control unit 225 is connected to the ADF 111 and controls the conveyance of the document 150. The document conveyance control unit 225 detects the position where the document 150 exists in the path for conveying the document of the ADF 111 and outputs the position of the document to the CPU 210. Therefore, the CPU 210 can determine whether or not the document 150 exists at the document reading position L.

  Operation unit 227 is provided on the upper surface of main body unit 120 of MFP 100 and includes an input unit such as a keyboard and a display unit such as a liquid crystal display device. The input unit receives an input of a user operation, and the display unit displays predetermined information and provides the user with information. The display unit supports input of an operation by the user.

  FIG. 4 is a functional block diagram illustrating an outline of functions of the image processing unit. Referring to FIG. 4, image processing unit 215 is connected to reading unit 219 and correction data determination unit 213. The image processing unit 215 receives analog data (R data, G data, and B data) for one line from the reading unit 219, and receives correction data from the correction data determination unit 213. The image processing unit 215 includes an analog / digital conversion unit (A / D conversion unit) 251, a shading correction unit 252, a line connected in series in order to sequentially process data for one line output from the reading unit 219. It includes an interval correction unit 253, a chromatic aberration correction unit 254, a noise detection processing unit 255, and a printer interface 256.

  The A / D conversion unit 251 receives one line of analog data (R data, G data, and B data) from the reading unit 219, and converts the input analog data into digital data. The A / D conversion unit 251 outputs digital data (R data, G data, and B data) to the shading correction unit 252 and the correction data determination unit 213. The correction data determination unit 213 determines correction data used by the image processing unit 215 for shading correction according to the input digital data (R data, G data, and B data), and the determined correction data is used. The result is output to the shading correction unit 252.

  The shading correction unit 252 performs shading correction processing on the digital data input from the A / D conversion unit 251 according to the correction data input from the correction data determination unit 213. The shading correction process is a process for removing uneven illumination of the light source 159 from the data input from the A / D conversion unit 251. The shading correction unit 252 outputs the shading corrected data to the interline correction unit 253. The interline correction unit 253 executes a process of synchronizing the R data, the G data, and the B data so that each of the R data, the G data, and the B data becomes the same line of the document. The chromatic aberration correction unit 254 executes processing for correcting distortion in the main scanning direction caused by the lens 163. The noise detection processing unit 255 detects noise from each of the R data, G data, and B data, and executes processing for removing the detected noise. The printer interface 256 outputs data (R data, G data, B data) input from the noise detection processing unit 255 to the image forming apparatus 121.

  FIG. 5 is a functional block diagram showing an outline of the function of the correction data determination unit. Referring to FIG. 5, correction data determination unit 213 includes a correction data selection unit 231, a selector 232, a gradation characteristic comparison unit 233, and a gradation characteristic detection unit 234. Shading plate data and document data are input to the correction data determination unit 213. There are three types of shading board data and document data, R data, G data, and B data, respectively, but since they are the same in any case, only one data will be described here for the sake of simplicity. When simply referred to as shading board data or document data, any one of R data, G data, and B data is indicated.

  Of the data output from the A / D converter 251, the shading plate data is input to the correction data selector 231. Based on the shading plate data, the correction data selection unit 231 selects one reference correction data from among a plurality of correction data stored in the ROM 211 and variation correction data corresponding to the reference correction data. select. The correction data selection unit 231 sets the selected reference correction data to level 0 correction data (0), and changes the correction data to the correction data (levels minus 2, minus 1, plus 1 to 10). N) (N is an integer of −2 ≦ N <0 and 0 <N ≦ 10), and stores them in the RAM 212 as correction data.

  The correction data selection unit 231 may generate the reference correction data and the fluctuation correction data based on the shading plate data. In this case, it is not necessary to store a plurality of correction data in the ROM 211. The correction data selection unit 231 obtains a coefficient for correcting the shading plate data to the reference value from the shading plate data. The reference correction data includes a plurality of values corresponding to the obtained coefficient. Specifically, assuming that the lightness can take a range of 0 to 255, when the shading board data is 230, the coefficient is 255/230 if the reference value is 255. According to this coefficient, one reference correction data having values corresponding to the respective values of 0 to 255 is determined. For example, the correction data selection unit 231 obtains reference correction data including an integer part obtained by rounding, rounding down, or rounding up a value obtained by multiplying each value of 0 to 255 by a coefficient (255/230). Generate. However, the correction data selection unit 231 sets the reference correction data to 255 when the value obtained by multiplying any of the values 0 to 255 by the coefficient exceeds 255. Therefore, the correction data selection unit 231 generates one reference correction data having 256 values. Since the intensity of light emitted from the light source 159 varies in the main scanning direction, the correction data selection unit 231 generates reference correction data for each of the plurality of photoelectric conversion elements provided in the reading unit 219. To do. The generation of the reference correction data is not limited to the method described above, and various other methods can be used.

  The fluctuation correction data is one or more data corresponding to one reference correction data. The correction data selection unit 231 obtains 12-level fluctuation correction data by multiplying the reference correction data by a coefficient. Further, the correction data selection unit 231 may obtain the fluctuation correction data by using the shading plate data used to determine the reference correction data. Since the shading plate data used to determine the reference correction data is 230 and the reference value is 255, the correction data selection unit 231 obtains the coefficient 255 / (230-2N). However, N is an integer other than 0 which is not less than −2 and not more than 10. Accordingly, twelve correction data (N) are determined. Here, as an example, generation of fluctuation correction data having a level Level of minus 2 will be described. In this case, the coefficient is (255 / (230-2 × (−2)) The correction data selection unit 231 has correction data (−) having values corresponding to the respective values of 0 to 255 according to the coefficient. For example, an integer part obtained by rounding, rounding down, or rounding up a decimal point after a value obtained by multiplying each value of 0 to 255 by a coefficient (255 / (230-2 × (−2))) is obtained. The correction data (−2) is obtained, but when the value obtained by multiplying any of the values 0 to 255 by the coefficient exceeds 255, the correction data selection unit 231 sets the correction data (−2) as the correction data (−2). Therefore, the correction data selection unit 231 generates one correction data (−2) having 256 values, and the intensity of light emitted from the light source 159 varies in the main scanning direction. Because there is for correction The data selection unit 231 generates correction data (−2) for each of the plurality of photoelectric conversion elements included in the reading unit 219. Note that, here, 12-level fluctuation correction data is obtained. The number of levels is not limited to this, and the generation of fluctuation correction data is not limited to the method described above, and various other methods can be used.

  The gradation characteristic detection unit 234 receives document data among the data output from the A / D conversion unit 251. The gradation characteristic detection unit 234 detects gradation characteristics from document data, and stores the detected gradation characteristics in the RAM 212. Here, the gradation characteristic is the maximum brightness of the original data for one original. The gradation characteristic detection unit 234 detects the maximum value of brightness from the original data for one original, and detects the detected maximum value as the gradation characteristic. Since the document data is input for each line, the gradation characteristic detecting unit 234 updates the maximum value every time the document data for one line is input, and the document data for one document is input. Later, the maximum value is detected as a gradation characteristic. The gradation characteristic detection unit 234 stores the detected gradation characteristic in the RAM 212. Thus, every time document data for one document is input, the gradation characteristics of the document are stored in the RAM 212. Here, the gradation characteristics are detected from the document data for one original. However, the original may be divided into a plurality of areas, and the gradation characteristics may be detected for each of the divided areas. . In this case, the gradation characteristic detecting unit 234 detects and stores the gradation characteristic every time document data of an area obtained by dividing the document is input.

  The gradation characteristic comparison unit 233 reads the gradation characteristic stored in the RAM 212 and compares the gradation characteristic corresponding to the first document with the gradation characteristic corresponding to the last document. The first document refers to a document that is first read by the reading unit 219 after the reading unit 219 reads the shading plate 156. The last document refers to the document read last by the reading unit 219. For example, when the reading unit 219 reads two originals, the first original read is the first original, and the second original read is the last original. Further, when the reading unit 219 continues to read the original and five originals are read, the first original is the first original and the last original is the fifth original. is there. The gradation characteristic comparison unit 233 sets the gradation characteristic corresponding to the first document to the variable Data1, sets the gradation characteristic corresponding to the last document to the variable Data2, and the ratio Sel between them (= Data1 / Data2). Is calculated and the level is determined. The gradation characteristic comparison unit 233 outputs the determined level to the selector 232. The gradation characteristic comparison unit 233 first determines the level since the original data of the second original is input and before the original data of the third original is input. The unit 233 outputs level 0 to the selector 232 before first determining the level. The level is a plus level if Sel is less than 1, and a minus level if Sel is greater than 1. Specifically, compared to Data1, if Data2 is 2 gradations high, minus 1 level, if Data2 is 4 gradations high, minus 2 level, if Data2 is 2 gradations low, plus 1 level, and Data2 is 4 gradations lower. If Data2 is 20 gradations low, it is a plus 10 level.

  The selector 232 receives the level from the gradation characteristic comparison unit 233. The selector 232 reads the input level correction data from the RAM 212 and outputs it to the shading correction unit 252.

  FIG. 6 is a flowchart illustrating an example of the flow of reading processing executed by the MFP according to the first embodiment. Referring to FIG. 6, CPU 210 is in a standby state until an instruction to start reading a document by the user is received (NO in step S01), and when the reading start instruction is received, the process proceeds to step S02. CPU 210 detects acceptance of a reading start instruction by detecting an instruction of a start button provided in operation unit 227.

  The CPU 210 causes the slider control unit 223 to move the slider 158 below the shading plate 156 (step S02). Thereafter, the CPU 210 causes the light source control unit 217 to turn on the light source 159 (step S03). As a result, the reading unit 219 receives the light reflected by the shading plate 156 and outputs shading plate data. The shading board data is output to the correction data determination unit 213.

  Next, the correction data determination unit 213 selects the correction data (N) from the ROM 211 using the input shading plate data (step S05). The correction data (N) includes reference correction data with a level of 0 (N = 0) and fluctuation correction data with levels of -2, -1, 1-10. The correction data determination unit 213 stores the selected correction data (N) in the RAM 212.

  Next, the correction data determination unit 213 selects the correction data (0) that is the reference correction data with the level 0 (step S05), and sends the correction data (0) to the shading correction unit 252 of the image processing unit 215. ) Is output (step S06). Accordingly, the shading correction unit 252 sets the input correction data (0) as correction data to be used for shading correction, and sets the correction data ( 0) is used to execute the shading correction process. The shading correction unit 252 performs shading correction using the set correction data until the next correction data is input.

  The CPU 210 causes the slider control unit 223 to move the slider 158 below the document reading position L (step S07). Next, the CPU 210 causes the document conveyance control unit 225 to start document conveyance (step S08). As a result, the reading unit 219 receives the light reflected by the document passing through the document reading position L and outputs document data (step S09). The document data is output to the correction data determination unit 213 and the image processing unit 215.

  When the correction data determination unit 213 receives document data for one document, the correction data determination unit 213 detects gradation characteristics for the document (step S10). Then, the correction data determination unit 213 executes correction data determination processing to determine correction data (step S11). Although the correction data determination process will be described later, the correction data determination unit 213 outputs the determined correction data to the shading correction unit 252 of the image processing unit 215. The shading correction unit 252 sets the correction data input from the correction data determination unit 213 as correction data used for shading correction. The shading correction unit 252 executes shading correction using the set correction data until the next correction data is set.

  The CPU 210 receives whether or not there is a document to be transported next from the document transport control unit 225, and determines whether or not there is a document to be transported next (step S12). If there is a document to be conveyed next, CPU 210 returns the process to step S08, and if not, the process proceeds to step S13. In step S13, the CPU 210 causes the light source control unit 217 to turn off the light source 159.

  FIG. 7 is a diagram showing an example of the flow of the gradation characteristic detection process executed in step S10 of FIG. Referring to FIG. 7, every time document data is input from reading unit 219, correction data determination unit 213 detects the maximum value of lightness in the document data (step S51). Then, the correction data determination unit 213 determines whether or not input of document data for one document has been completed (step S52). The correction data determination unit 213 returns the process to step S51 if the input of the original data for one original is not completed, and returns the process to the reading process if completed. In step S51, if the maximum value of brightness detected from the document data input later is larger than the maximum value of brightness detected so far, the maximum value of the document data input later is determined. Update to the maximum value detected from. As a result, the maximum value of lightness is detected as the gradation characteristic of the original data for one original. As described above, the correction data determination unit 213 detects gradation characteristics corresponding to a document after the document data for one document is input.

  FIG. 8 is a diagram illustrating an example of the flow of correction data determination processing executed in step S11 of FIG. Referring to FIG. 8, correction data determination unit 213 determines whether or not the gradation characteristic detected in step S10 in FIG. 6 corresponds to the first original (step S21). The correction data determination unit 213 advances the process to step S22 if the gradation characteristic corresponds to the first original, and advances the process to step S23 if not. In step S22, the correction data determination unit 213 sets the gradation characteristic detected in step S10 of FIG. 6 to the variable Data1. In step S23, the correction data determination unit 213 sets the gradation characteristic detected in step S10 of FIG. 6 to the variable Data2. That is, the gradation characteristic detected from the original read first by the reading unit 219 is set in the variable Data1, and the gradation characteristic detected from the original read last by the reading unit 219 is set in the variable Data2. Is set.

The correction data determination unit 213 advances the process to step S24 after step S23. The correction data determination unit 213 calculates the ratio Sel using the following equation (1) (step S24).
Sel = Data1 / Data2 (1)
Further, the correction data determination unit 213 obtains the level Level using the function F (Sel) (step S25). The correction data determination unit 213 selects the level level correction data (Level) obtained in step S25 from the correction data (N) stored in the RAM 212 (step S26), and the image processing unit 215. The correction data (Level) is output to the shading correction unit 252 (step S27). Thus, the shading correction unit 252 sets the input correction data (Level) as correction data for use in shading correction, and sets the correction data ( Level) is used to execute shading correction processing.

  When the gradation characteristic corresponding to the second and subsequent original data is detected, the correction data determination unit 213 determines the level of the correction data and outputs the determined level to the shading correction unit 252. Therefore, the shading correction unit 252 performs shading correction on the original data obtained by reading the first and second originals using the correction data (0), and obtains the third and subsequent originals. The original document data is subjected to shading correction using the correction data (Level) at the level Level determined by the correction data determination unit 213.

<First Modification of Tone Characteristic Detection Processing>
The correction data determination unit 213 uses the maximum brightness value of the original data for one original as the gradation characteristic of the original. In the gradation characteristic detection process in the first modification, the maximum value of the brightness of a detection area predetermined in the document is used as the gradation characteristic. The predetermined detection area in the document is, for example, a margin portion of the document. The margin of the document may be an area within a few millimeters from the edge of the document. There are regions of a predetermined width along the four sides of the document.

  FIG. 9 is a diagram illustrating an example of the flow of the gradation characteristic detection process in the first modification. The gradation characteristic detection process in the first modification is a process executed by the correction data determination unit 213 in step S10 of FIG. Referring to FIG. 9, every time document data is input from reading unit 219 via A / D conversion unit 251, correction data determination unit 213 determines whether or not the document data is included in the detection area. Judgment is made (step S61). The correction data determination unit 213 determines that the document data is included in the detection area if at least part of the document data is included in the detection area. In this case, the correction data determination unit 213 extracts a portion included in the detection area from the document data. The correction data determination unit 213 advances the process to step S62 if the document data is included in the detection area, and advances the process to step S63 if not.

  The correction data determination unit 213 detects the maximum value of brightness among the document data included in the detection area (step S62). Then, the correction data determination unit 213 determines whether or not input of document data for one document has been completed (step S63). The correction data determination unit 213 returns the process to step S61 if the input of the original data for one original has not been completed, and returns the process to the reading process if completed. In step S62, if the maximum value detected from the document data inputted later is larger than the maximum value detected so far, the maximum value detected from the document data inputted later is detected. Update to value. As a result, the maximum value of lightness is detected as the gradation characteristic among the document data included in the detection area of the document. As described above, the correction data determination unit 213 detects gradation characteristics corresponding to a document after the document data for one document is input.

  According to the gradation characteristic detection processing in the first modified example, the maximum value of the brightness of the margin portion of the document is set as the gradation characteristic. For this reason, the gradation characteristics can be detected from the background area of the document, and the detection accuracy of the gradation characteristics can be improved.

  Although the maximum brightness value of the detection area is the gradation characteristic, the gradation is determined from the document data output by the reading unit 219 reading the mark so that a predetermined mark is attached to a predetermined portion of the document. The characteristic may be detected.

<Second Modification of Tone Characteristic Detection Processing>
In the gradation characteristic detection process in the second modification, the maximum value of brightness in the area where the saturation in the document is equal to or less than a predetermined value is used as the gradation characteristic. An area where the saturation is equal to or less than a predetermined value is an achromatic area. Normally, papers with white backgrounds are often used in business. Therefore, by setting the maximum value of lightness in areas where saturation is equal to or less than a predetermined value as a gradation characteristic, The gradation characteristics can be detected.

  In the gradation characteristic detection process in the second modification, the saturation data is obtained from the three original data of R data, G data, and B data. Therefore, the correction data determination unit 213 receives the original data corrected between lines. Must be entered. Therefore, the interline correction unit 253 shown in FIG. 4 is arranged between the A / D conversion unit 251 and the shading correction unit 252, and the document data synchronized by the interline correction unit 253 is converted into the shading correction unit 252 and the shading correction unit 252. The data is input to the correction data determination unit 213. In addition, the correction data determination unit 213 includes a line buffer in order to detect a region to be processed. Here, the size of the area is assumed to be an area of 5 pixels vertically and horizontally. For this reason, the line buffer has a storage capacity for five lines.

  FIG. 10 is a diagram illustrating an example of the flow of gradation characteristic detection processing in the second modification. The gradation characteristic detection process in the second modification is a process executed by the correction data determination unit 213 in step S10 of FIG. Referring to FIG. 10, when document data is input from reading unit 219 via A / D conversion unit 251 and interline correction unit 253, correction data determination unit 213 stores the data sequentially in a line buffer. Then, regions are sequentially selected in the main scanning direction, and the saturation of all the pixels included in the selected region is detected (step S71). Saturation is the difference between the maximum and minimum values of R data, G data, and B data that a pixel has. Since 25 pixels are included in the region, 25 saturations are also detected. Here, the maximum value is the saturation of the region.

  Then, the correction data determination unit 213 determines whether or not the saturation of the region is smaller than the threshold value Ref1 (step S72). The correction data determination unit 213 advances the process to step S73 for the area where the saturation is smaller than the threshold value Ref1, and advances the process to step S74 for the other area. In step S73, the correction data determination unit 213 detects the maximum value of the brightness of the pixels included in the area where the saturation is smaller than the threshold value Ref1, as the brightness of the area. The maximum value of brightness is detected for each of R data, G data, and B data. The correction data determination unit 213 detects the maximum value of the lightness of the plurality of regions if there are a plurality of regions with saturation smaller than the threshold value Ref1.

  Then, the correction data determination unit 213 determines whether or not input of document data for one document has been completed (step S74). The correction data determination unit 213 returns the process to step S71 if the input of the original data for one original has not been completed, and returns the process to the reading process if completed. In step S73, if the maximum brightness value detected from the document data input later is greater than the maximum brightness value detected so far, the correction data determination unit 213 inputs the maximum brightness value later. Update to the maximum value of brightness detected from document data. As a result, the maximum brightness value is detected as the gradation characteristic in each of the R data, the G data, and the B data in an area where the saturation in the document is equal to or less than a predetermined value. As described above, the correction data determination unit 213 detects the gradation characteristics corresponding to the original for each of the R data, the G data, and the B data after the original data for one original is input.

<Third Modification of Tone Characteristic Detection Processing>
In the gradation characteristic detection process in the third modified example, the average value of the lightness in the area where the saturation in the document is not more than a predetermined value and the lightness is not less than the predetermined value is used as the gradation characteristic. A region where the saturation is not more than a predetermined value is an achromatic region, and a region where the lightness is not less than the predetermined value in the achromatic region is a region close to white. Therefore, an area in which the saturation in the document is equal to or less than a predetermined value and the lightness is equal to or greater than a predetermined value corresponds to a white background area of the document.

  In the gradation characteristic detection process in the third modification, the saturation is determined from the three original data of R data, G data, and B data. Therefore, the correction data determination unit 213 receives the original data corrected between lines. Must be entered. For this reason, the interline correction unit 253 shown in FIG. 4 is arranged between the A / D conversion unit 251 and the shading correction unit 252, and the document data corrected by the interline correction unit 253 is the shading correction unit 252. And input to the correction data determination unit 213. In addition, the correction data determination unit 213 includes a line buffer in order to detect a region to be processed. Here, the size of the area is assumed to be an area of 5 pixels vertically and horizontally. For this reason, the line buffer has a storage capacity for five lines.

  FIG. 11 is a diagram illustrating an example of the flow of gradation characteristic detection processing in the third modification. The gradation characteristic detection process in the third modification is a process executed by the correction data determination unit 213 in step S10 in FIG. Referring to FIG. 11, when document data is input from reading unit 219 via A / D conversion unit 251 and interline correction unit 253, correction data determination unit 213 stores the data sequentially in a line buffer. Then, regions are sequentially selected in the main scanning direction, and the saturation of all the pixels included in the selected region is detected (step S81). Since 25 pixels are included in the region, 25 saturations are also detected. Here, the maximum value is the saturation of the region.

  Then, the correction data determination unit 213 determines whether the saturation of the region is smaller than the threshold value Ref1 and whether the brightness is larger than the threshold value Ref2 (step S82). The brightness is an average value of R data, G data, and B data of a pixel. Since 25 pixels are included in the area, 25 brightnesses are detected. Here, the average value is used as the brightness of the area. The correction data determination unit 213 advances the process to step S83 for areas where the saturation is smaller than the threshold value Ref1 and the lightness is greater than the threshold value Ref2, and advances the process to step S84 for the other areas. In step S83, the correction data determination unit 213 determines the brightness of the pixels included in the region where the saturation is less than the threshold value Ref1 and the brightness is greater than the threshold value Ref2, for each of the R data, the G data, and the B data. Addition is performed for each R data, G data, and B data. At this time, the correction data determination unit 213 counts the number of pixels to which the brightness is added. If there are a plurality of areas where the saturation is smaller than the threshold value Ref1 and the lightness is larger than the threshold value Ref2, the correction data determination unit 213 adds the brightness of all the pixels in the plurality of areas.

  Then, the correction data determination unit 213 determines whether or not the input of the document data for one document has been completed (step S84). Correction data determination unit 213 returns the process to step S81 if the input of the original data for one original has not been completed, and advances the process to step S85 if the input has been completed.

  In step S85, the correction data determination unit 213 calculates an average value of brightness for each of the R data, the G data, and the B data from the total obtained by adding the brightness in step S83 and the counted number of pixels. Thereby, the average value of the brightness for each of the R data, G data, and B data of the pixels included in the region where the saturation in the document is smaller than the threshold value Ref1 and the brightness is larger than the threshold value Ref2 is a gradation characteristic. Detected as As described above, the correction data determination unit 213 detects gradation characteristics corresponding to the original for each of the R data, the G data, and the B data after the original data for one original is input.

  In the gradation characteristic detection processing in the third modification, the average value of the brightness of pixels in the document data in which the saturation is smaller than the threshold value Ref1 and the lightness is larger than the threshold value Ref2 is used as the gradation characteristic. Therefore, it is possible to detect gradation characteristics in which the influence of fluctuations in the reading system including the light source 159, the lens 163, and the reading unit 219 is reduced.

<Fourth Modification of Tone Characteristic Detection Processing>
In the gradation characteristic detection process in the fourth modified example, the average value of lightness in an area where the saturation is not more than a predetermined value and the change in lightness is not more than a predetermined value in the document is used as the gradation characteristic. A region where the saturation is equal to or less than a predetermined value is an achromatic region, and a region where the change in lightness is equal to or less than a predetermined value in the achromatic region is a region that is likely to be a white background. Therefore, an area in which the saturation in the document is equal to or less than a predetermined value and the change in brightness is equal to or less than the predetermined value corresponds to a white background area of the document.

  In the gradation characteristic detection process in the fourth modification, since the saturation is obtained from the three original data of R data, G data, and B data, the correction data determination unit 213 receives the original data corrected between lines. Must be entered. For this reason, the interline correction unit 253 shown in FIG. 4 is arranged between the A / D conversion unit 251 and the shading correction unit 252, and the document data corrected by the interline correction unit 253 is the shading correction unit 252. And input to the correction data determination unit 213. In addition, the correction data determination unit 213 includes a line buffer in order to detect a region to be processed. Here, the size of the area is assumed to be an area of 5 pixels vertically and horizontally. For this reason, the line buffer has a storage capacity for five lines.

  FIG. 12 is a diagram illustrating an example of the flow of gradation characteristic detection processing in the fourth modification. The gradation characteristic detection process in the fourth modification is a process executed by the correction data determination unit 213 in step S10 of FIG. Referring to FIG. 12, when document data is input from reading unit 219, correction data determination unit 213 stores the data in order in a line buffer. Then, regions are sequentially selected in the main scanning direction, and the saturation of all the pixels included in the selected region is detected (step S91). Since 25 pixels are included in the region, 25 saturations are also detected. Here, the maximum value is the saturation of the region.

  Next, the correction data determination unit 213 calculates a dynamic range DR that is a difference between the maximum value and the minimum value of the brightness of the pixels included in the region (step S92). The brightness is an average value of R data, G data, and G data. Then, the correction data determination unit 213 determines whether or not the saturation detected in step S91 is smaller than the threshold value Ref1 and the dynamic range DR is smaller than the threshold value Ref3 (step S93). If the saturation is smaller than threshold value Ref1 and dynamic range DR is smaller than threshold value Ref3, correction data determination unit 213 proceeds to step S94, and otherwise proceeds to step S95. In step S94, the correction data determination unit 213 determines the brightness of the pixels included in the region in which the saturation detected in step S91 is smaller than the threshold value Ref1 and the dynamic range DR is smaller than the threshold value Ref3 as R data, Addition is performed for each G data and B data, and a total is obtained for each of R data, G data, and B data. At this time, the correction data determination unit 213 counts the number of pixels to which the brightness is added. The processing from step S91 to step S95 is executed for all the areas selected from the document data stored in the line buffer.

  Then, the correction data determination unit 213 determines whether or not the input of document data for one document has been completed (step S95). The correction data determination unit 213 returns the process to step S91 if the input of the original data for one original has not been completed, and advances the process to step S96 if completed. When returning the processing to step S91, the correction data determination unit 213 executes the above-described processing after the next five lines are stored in the line buffer.

  In step S96, the correction data determination unit 213 adds the brightness for each of the R data, G data, and B data obtained in step S94, and accumulates the R data, G data, and B data, and the counted number of pixels. The average value of brightness is calculated for each of R data, G data, and B data. As a result, an average value of brightness for each of the R data, G data, and B data in a region where the saturation is not more than a predetermined value and the change in brightness is not more than a predetermined value in the document is detected as the gradation characteristic. As described above, the correction data determination unit 213 detects gradation characteristics for each of R data, G data, and B data corresponding to a document after the document data for one document is input.

  In the gradation characteristic detection process according to the fourth modification, the light source 159 has the lightness 159 because the average value of the lightness in the area of the document data in which the saturation is not more than a predetermined value and the change in lightness is not more than the predetermined value is used. In addition, it is possible to detect gradation characteristics in which the influence of fluctuations in the reading system including the lens 163 and the reading unit 219 is reduced.

  As described above, the MFP 100 according to the first embodiment receives and outputs the light reflected by the ROM 211 that stores a plurality of correction data in advance and the shading plate 156 having a predetermined reflectance by the reading unit 219. A correction data selection unit 231 for selecting reference correction data and 12-level fluctuation correction data from a plurality of correction data based on the shading plate data to be received, and light reflected by the document by the reading unit 219 A gradation characteristic comparison unit 233 and a selector 232 for selecting any one of the reference correction data and the 12-level fluctuation correction data and setting the execution correction data based on the original data to be output, and the reading unit The document data that the 219 receives and reflects the light reflected from the document is corrected using the set execution correction data. And a loading correction unit 252. For this reason, the reference correction data and the 12-level fluctuation correction data are selected based on the shading plate data that the reading unit 219 receives and outputs the light reflected by the shading plate 156, and the reading unit 219 reflects the original. One of the selected reference correction data and 12-level fluctuation correction data is selected and set as execution correction data based on the original data output by receiving the received light. Therefore, even if the intensity of light emitted from the light source 159 changes with time, execution correction data corresponding to the intensity of light emitted from the light source 159 is selected from the plurality of correction data. Using the execution correction data, the document data output by the reading unit 219 receiving and reflecting the light reflected by the document is corrected. As a result, it is possible to remove the influence due to the change in the intensity of the light applied to the original from the data obtained by receiving the light reflected by the original.

  In MFP 100, the reference correction data (correction data (0)) determined based on the shading board data is changed based on the document data. For this reason, even if the intensity of the light emitted from the light source 159 changes with time, the document data is corrected using the fluctuation correction data corresponding to the intensity of the light emitted from the light source 159. As a result, it is possible to accurately remove the influence due to the change in the intensity of the light applied to the original from the original data obtained by receiving the light reflected by the original.

  Further, MFP 100 generates reference correction data from shading plate data and a predetermined target value, and correction data that generates 12-level fluctuation correction data from the reference correction data and a predetermined coefficient. And a selection unit 231. For this reason, the correction data can be easily generated.

<Second Embodiment>
Next, an MFP according to the second embodiment will be described. The MFP in the second embodiment is obtained by changing the correction data determination unit 213 of the MFP 100 in the first embodiment. Since other configurations are similar to those of MFP 100 in the first embodiment, description thereof will not be repeated here.

  FIG. 13 is a functional block diagram showing an outline of functions of the correction data determination unit of the MFP according to the second embodiment. Referring to FIG. 13, correction data determination unit 213A is different from correction data determination unit 213 in the first embodiment shown in FIG. 5 in that timer 235 and restriction unit 236 are added. The selector 232A is changed.

  The timer 235 measures the elapsed time since the light source 159 is turned on. The restriction unit 236 receives the time counted by the timer 235, and restricts correction data that can be selected by the selector 232A according to the inputted time. Here, it is possible to select correction data with a level of −2 to +2 until the first T minutes, and it is possible to select correction data with a level of −2 to +4 from T minutes to 2T, After 2T, all levels of correction data can be selected. It is known that the change in intensity of light emitted from the light source 159 decreases with time and stabilizes at a predetermined value when a predetermined time elapses. Therefore, the width of change in the intensity of light emitted from the light source 159 can be roughly predicted according to the elapsed time. By restricting the correction data that can be selected with the passage of time, it is possible to prevent erroneous detection of gradation characteristics due to erroneous detection of gradation characteristics.

  The selector 232 </ b> A receives the level from the gradation characteristic comparison unit 233, but determines the correction data to be selected with priority given to the level selection restriction input from the restriction unit 236. For example, if the level is limited to a range of −2 to +4 by the limiting unit 236, even if the level Level5 is input from the gradation characteristic comparison unit 233, the maximum level +4 of the limited level is selected. The correction data (4) is selected.

  FIG. 14 is a flowchart illustrating an example of the flow of reading processing executed by the MFP according to the second embodiment. The difference from the reading process executed by the MFP in the first embodiment shown in FIG. 6 is that step S03A is added between step S03 and step S04, and step S11A is changed. is there. Since the processes executed in other steps are the same, the description will not be repeated here. In step S03A, correction data determination unit 213A starts timer 235 and causes timer 235 to start measuring time. Here, the time counted by the timer 235 is referred to as a timer value t.

  FIG. 15 is a flowchart showing an exemplary flow of the correction data determination process executed in step S11A of FIG. Referring to FIG. 15, the difference from the correction data determination process shown in FIG. 8 is that steps S31 to S35 are added between steps S25 and S26. Since the processes executed in other steps are the same, the description will not be repeated here.

  Correction data determination unit 213A compares timer value t with threshold value T and threshold value 2T in step S31. The correction data determination unit 213A advances the process to step S32 if the timer value t is smaller than the threshold value T, and advances the process to step S34 if the timer value t is greater than or equal to the threshold value T and smaller than 2T. If the threshold value is 2T or more, the process proceeds to step S26.

  In step S32, the correction data determination unit 213A determines whether or not the level Level obtained in step S25 exceeds +2. If so, the process proceeds to step S33, and if not, the process proceeds to step S26. In step S33, the correction data determination unit 213A sets the level Level to +2, and advances the process to step S26.

  In step S34, the correction data determination unit 213A determines whether or not the level Level obtained in step S25 exceeds +4. If so, the process proceeds to step S35, and if not, the process proceeds to step S26. In step S35, the correction data determination unit 213A sets the level Level to +4 and advances the process to step S26.

  Therefore, the correction data determining unit 213A limits the selectable correction data level to −2 to +2 if the timer value t is smaller than the threshold value T, and the timer value t is equal to or greater than the threshold value T and 2T. If it is smaller, the level of selectable correction data is limited to -2 to +4. If the timer value t is equal to or greater than the threshold value 2T, correction data of all levels can be selected.

  As described above, MFP 100 according to the second embodiment includes timer 235 that measures the elapsed time since light source 159 has emitted light, and based on the elapsed time since light source 159 has emitted light. The selectable variation correction data is limited. For this reason, it is possible to prevent the fluctuation correction data that is changed based on the document data output by receiving the light reflected by the document from the reading unit 219 from being changed to an incorrect value.

<Third Embodiment>
Next, an MFP according to the third embodiment will be described. The MFP according to the third embodiment is obtained by changing the correction data determination unit 213 of the MFP 100 according to the first embodiment. Since other configurations are similar to those of MFP 100 in the first embodiment, description thereof will not be repeated here.

  FIG. 16 is a functional block diagram illustrating an outline of functions of the correction data determination unit of the MFP according to the third embodiment. Referring to FIG. 16, correction data determination unit 213B is different from correction data determination unit 213 in the first embodiment shown in FIG. 5 in that background plate gradation characteristic detection unit 237 and comparison unit 238. Are added and the selector 232B is changed.

  Of the data output from the A / D conversion unit 251, the background plate gradation characteristic detection unit 237 receives data output by receiving light reflected by the background plate 154 (hereinafter referred to as “background plate data”). Entered. The background plate gradation characteristic detection unit 237 detects the gradation characteristic from the background plate data and outputs the detected gradation characteristic to the comparison unit 238. The background plate gradation characteristic detection unit 237 may detect the gradation characteristic from the background plate data by the same process as the gradation characteristic detection unit 234 detects the gradation characteristic from the document data. The gradation characteristic may be an average value of the background plate data. When the ADF 111 continuously conveys the document, the ADF 111 conveys the document with a predetermined interval between the previous document and the subsequent document. Since the predetermined interval exists, the reading unit 219 reflects the light reflected by the background plate 154 between the time when the previous document passes through the document reading position L and the time when the subsequent document reaches the document reading position L. Receive light. Therefore, background plate data is input to the background plate gradation characteristic detection unit 237 immediately before the document passes the document reading position L. Since the background plate data is input immediately before the document passes the document reading position L, the background plate gradation property detection unit 237 detects the gradation property corresponding to each document.

  The comparison unit 238 calculates the ratio V of the gradation characteristic detected by the background plate gradation characteristic detection unit 237 and the reference value Ref. The comparison unit 238 limits correction data that can be selected by the selector 232B according to the calculated ratio V. Here, if the ratio V is greater than the threshold value Th1, it is possible to select correction data having a level of −2 to +2. Correction data up to +4 can be selected, and correction data for all levels can be selected if the ratio V is equal to or less than the threshold value Th2. It is known that the change in intensity of light emitted from the light source 159 decreases with time and stabilizes at a predetermined value when a predetermined time elapses. For this reason, the gradation characteristic Data0 detected from the background plate data gradually becomes a small value.

  The selector 232B receives the level from the gradation characteristic comparison unit 233, and determines the correction data to be selected with priority given to the level selection restriction input from the comparison unit 238. For example, if the level is limited to the range of −2 to +4 by the comparison unit 238, even if the level Level5 is input from the gradation characteristic comparison unit 233, the maximum level +4 of the limited level is selected. The correction data (4) is selected.

  FIG. 17 is a flowchart illustrating an example of the flow of correction data determination processing executed by the correction data determination unit of the MFP in the third embodiment. This correction data determination process is executed in step S11 of FIG. Referring to FIG. 17, the difference from the correction data determination process shown in FIG. 8 is that step S41 to step S43 are added before step S21, and step S45 is between step S25 and step S26. Step S49 is added. Since the processes executed in other steps are the same, the description will not be repeated here.

  In step S41, the correction data determination unit 213B detects gradation characteristics from the background plate data. Then, the correction data determination unit 213B sets the detected gradation characteristic to the variable Data0 (step S42). Further, the correction data determination unit 213B calculates a ratio V between the gradation characteristic Data0 and the reference value Ref (step S43).

  In step S45, the correction data determination unit 213B compares the ratio V with the threshold value Th1 and the threshold value Th2. The correction data determination unit 213B proceeds to step S46 if the ratio V is greater than the threshold value Th1, and proceeds to step S48 if the ratio V is greater than the threshold value Th2 and less than or equal to the threshold value Th1. If the ratio V is equal to or less than the threshold value Th2, the process proceeds to step S26.

  In step S46, the correction data determination unit 213B determines whether or not the level Level obtained in step S25 exceeds +2. If so, the process proceeds to step S47, and if not, the process proceeds to step S26. In step S47, the correction data determination unit 213B sets the level Level to +2, and advances the process to step S26.

  In step S48, the correction data determination unit 213B determines whether or not the level Level obtained in step S25 exceeds +4. If so, the process proceeds to step S49. If not, the process proceeds to step S26. In step S49, the correction data determination unit 213B sets the level Level to +4 and advances the process to step S26.

  Therefore, the correction data determination unit 213B limits the level of selectable correction data to −2 to +2 if the ratio V is greater than the threshold value Th1, and the ratio V is greater than the threshold value Th2 and the threshold value. If the value is equal to or less than Th1, the level of selectable correction data is limited to -2 to +4. If the ratio V is equal to or less than the threshold value Th2, correction data for all levels can be selected.

  As described above, MFP 100 according to the third embodiment includes ADF 111 that transports a document to document reading position L and background plate 154 that is fixedly provided at a position facing light source 159, and the document is a document. A comparison unit 238 is provided that limits the range of correction data that can be changed based on background plate data that is received by the reading unit 219 and received by the reading unit 219 before passing the reading position L. Since the reflectance of the background plate is determined in advance, the intensity of light emitted from the light source 159 is proportional to the background plate data. Since the variation correction data that can be selected based on the background plate data before the document passes the document reading position L is limited, the variation correction data that is changed based on the document data is changed to an incorrect value. Can be prevented.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

<Appendix>
(1) It further comprises time measuring means for measuring an elapsed time since the irradiation means irradiates light,
The selection means includes restriction means for restricting reference correction data and at least one variation correction data that can be selected from the plurality of correction data based on the elapsed time measured by the time measurement means. The image reading apparatus according to claim 7.
(2) Document conveying means for conveying the document to a predetermined reading position;
A reflection plate fixedly provided at a position facing the irradiation means;
The selection means can select from among the plurality of correction data based on data output by the photoelectric conversion means receiving and reflecting the light reflected by the reflecting plate before the document passes through the reading position. The image reading apparatus according to claim 7, further comprising a restriction unit that restricts the reference correction data and the at least one variation correction data.
(3) The setting unit includes a document data comparison unit that compares the first data output from the photoelectric conversion unit and the second data output from the photoelectric conversion unit, and the comparison by the document data comparison unit is performed. The image reading apparatus according to claim 7, wherein one of the reference correction data and the at least one variation correction data selected by the selection unit is selected based on the result.
(4) The photoelectric conversion means includes a plurality of line sensors having filters having different spectral sensitivities,
The selection means is configured to receive reference correction data and at least one variation correction data out of the plurality of correction data, based on data output by receiving light reflected by the reference plate by each of the plurality of line sensors. Select data for each of the plurality of line sensors,
The setting means is configured to calculate the reference correction data and the at least one variation correction data for each of the plurality of line sensors based on data output by receiving light reflected from the document by each of the plurality of line sensors. Select one of them and set it as execution correction data.
The correction means corrects data output by receiving and reflecting light reflected from the original by each of the plurality of line sensors using execution correction data set for each of the plurality of line sensors. The image reading apparatus described.

1 is a perspective view of an MFP including an image reading apparatus according to a first embodiment of the present invention. 2 is a diagram illustrating an outline of an internal configuration of an image reading apparatus. FIG. 2 is a block diagram illustrating an example of a circuit configuration of an MFP. FIG. It is a functional block diagram which shows the outline | summary of the function of an image process part. It is a functional block diagram which shows the outline | summary of the function of the correction data determination part. 6 is a flowchart illustrating an example of a flow of a reading process executed by the MFP according to the first embodiment. It is a figure which shows an example of the flow of the gradation characteristic detection process performed by step S10 of FIG. It is a figure which shows an example of the flow of the data determination process for correction | amendment performed by step S11 of FIG. It is a figure which shows an example of the flow of the gradation characteristic detection process in a 1st modification. It is a figure which shows an example of the flow of the gradation characteristic detection process in a 2nd modification. It is a figure which shows an example of the flow of the gradation characteristic detection process in a 3rd modification. It is a figure which shows an example of the flow of the gradation characteristic detection process in a 4th modification. FIG. 10 is a functional block diagram illustrating an outline of functions of a correction data determination unit of an MFP according to a second embodiment. 10 is a flowchart illustrating an example of a flow of a reading process executed by the MFP according to the second embodiment. It is a flowchart which shows an example of the flow of the data determination process for correction | amendment performed by FIG.14 S11A. FIG. 10 is a functional block diagram illustrating an outline of functions of a correction data determination unit of an MFP according to a third embodiment. 14 is a flowchart illustrating an example of a flow of correction data determination processing executed by a correction data determination unit of an MFP according to a third embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 MFP, 110 Image reading apparatus, 120 Main body part, 121 Image forming apparatus, 150 Document, 154 Background plate, 155 Document base, 156 Shading plate, 157 Paper feed guide, 158 Slider, 159 Light source, 160 Reflective member, 161, 162 Reflection mirror, 162 lens, 163 lens, 201 timing roller pair, 202 roller pair, 203 upper restriction plate, 205 document table, 213, 213A, 213B correction data determination unit, 215 image processing unit, 217 light source control unit, 219 reading , 221 image forming unit, 223 slider control unit, 224 motor, 225 document conveyance control unit, 227 operation unit, 229 bus, 231 correction data selection unit, 232, 232A, 232B selector, 233 gradation characteristic comparison unit, 234 Gradation characteristic detection 235 timer, 236 limiting unit, 237 background plate tone characteristic detection unit, 238 comparison unit, 251 A / D conversion unit, 252 shading correction unit, 253 interline correction unit, 254 chromatic aberration correction unit, 255 noise detection processing unit, 256 Printer interface.

Claims (7)

Irradiating means for irradiating the reading object with light;
Photoelectric conversion means for receiving light reflected by the reading object and outputting data;
Correction data determining means for determining correction data based on data received by the photoelectric conversion means reflected by a reference plate having a predetermined reflectance and output;
Correction means for receiving and outputting the light reflected by the original by the photoelectric conversion means using the correction data; and
An image reading apparatus comprising: a changing unit configured to change correction data used for correction by the correction unit based on data output by the photoelectric conversion unit receiving light reflected from the document. Further comprising a time measuring means for measuring an elapsed time since the irradiation means irradiates light,
The image reading apparatus according to claim 1, wherein the changing unit includes a limiting unit that limits a range of the correction data that can be changed based on an elapsed time counted by the timing unit. A document conveying means for conveying the document to a predetermined reading position;
A reflection plate fixedly provided at a position facing the irradiation means;
The changing unit limits the range of the correction data that can be changed based on data output by the photoelectric conversion unit receiving and reflecting the light reflected by the reflecting plate before the document passes through the reading position. The image reading apparatus according to claim 1, further comprising a limiting unit. The correction data determination means is a reference correction data generation means for generating reference correction data from data output by receiving light reflected from the reference plate by the photoelectric conversion means and a predetermined target value. When,
The image reading apparatus according to claim 1, further comprising a fluctuation correction data generation unit that generates at least one fluctuation correction data from the reference correction data and a predetermined coefficient.   The changing unit includes a document data comparison unit that compares the first data output from the photoelectric conversion unit and the second data output from the photoelectric conversion unit, and is based on a comparison result by the document data comparison unit. The image reading apparatus according to claim 1, wherein correction data used by the correction unit is changed. The photoelectric conversion means includes a plurality of line sensors having filters having different spectral sensitivities,
The correction data determining means determines correction data corresponding to each of the plurality of line sensors based on data output by receiving and outputting light reflected by the reference plate.
The correction unit corrects data output by receiving light reflected from the original by each of the plurality of line sensors using the correction data corresponding to each of the plurality of line sensors,
2. The image reading according to claim 1, wherein the changing unit changes correction data used for correction by the correction unit based on data output by receiving and reflecting light reflected by the document by each of the plurality of line sensors. apparatus. Irradiating means for irradiating the reading object with light;
Photoelectric conversion means for receiving light reflected by the reading object and outputting data;
Storage means for storing a plurality of correction data in advance;
Based on data output by the photoelectric conversion means receiving and reflecting light reflected by a reference plate having a predetermined reflectance, reference correction data and at least one variation correction data are selected from the plurality of correction data. A selection means for selecting
One of the reference correction data and the at least one variation correction data selected by the selection means based on data output by the photoelectric conversion means receiving light reflected from the document. Setting means for selecting and setting execution correction data;
An image reading apparatus comprising: correction means for correcting data output by receiving light reflected from the original by the photoelectric conversion means using the set execution correction data.

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