JP2010220076A - Image-reading apparatus, image forming apparatus, shading correction method, and shading correction control program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically and accurately perform gray balance adjustment, without a reference chart, when replacing components in an image reading apparatus. <P>SOLUTION: An image reader includes a white plate data forming section 24 for reading a reference white plate to form reference white plate data; a data storage section 28 for storing second reference plate data, acquired by reading a second reference plate; a shading correction section 25 for normalizing image data using the reference white plate data; and a gray balance adjusting section 27 for performing gray balance adjustment from a result of comparing data of the read second reference plate with the second reference plate data stored in the data storage section 28. On the basis of the read level of the second reference plate and the read level of the second reference plate stored in the data storage means; the gray balance adjusting section 27 corrects a gray balance coefficient which is multiplied in normalization processing; and the shading correction section 25 outputs image data on which shading correction has been performed, based on the corrected gray balance coefficient. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that optically reads a document image, in particular, an image reading apparatus that performs shading correction using the first and second reference white plates, a copying machine including the image reading apparatus, a facsimile machine, and a digital composite The present invention relates to an image forming apparatus such as an image forming apparatus, a shading correction method executed by the image reading apparatus, and a computer program for executing the shading correction method by a computer.

  FIG. 7 is a diagram showing a schematic configuration of a reading device of a reduction optical system at the time of reading a pressure plate that has been conventionally performed. As shown in the figure, the scanning operation in the reduction optical system is performed when the platen is read from the document 2 placed on the contact glass while the first carriage 1 moves in the sub-scanning direction (the arrow A direction in the figure). The reflected light is guided to the imaging lens 3 through the first mirror 8a, the second mirror 8b, and the third mirror 8c, and this reflected light is passed through the imaging lens 3 to a photoelectric conversion element (hereinafter referred to as CCD). 4 is imaged, converted into an analog electric signal by photoelectric conversion in the CCD 4 and read as document information. The reflector 7 reflects the light from the scanner lamp 6 as a light source and adjusts the light amount profile in such a manner that it strikes the original. The second mirror 8b and the third mirror 8c are mounted on the second carriage 9, and the first and second carriages 1 and 9 travel in the sub-scanning direction at a 2-to-1 speed, respectively, and read a document image.

  In an image processing circuit (not shown), analog processing and digital processing are performed on the analog electrical signal obtained from the CCD 4, and image information is read as digital data. Further, in order to make the main scanning distribution of the original uniform, the shading correction is performed, but the read data of the reference white plate 5 for that is acquired every time before the original is scanned. At the time of sheet-through reading, as shown in FIG. 8, the first carriage 1 moves immediately below the reference white plate 13 before the document is sent to the reading surface by the sheet-through conveyance drum 11, and then the DF glass serving as the document reading surface. 14 to read the document surface. A scanner lamp 6, a reflector 7, and a first mirror 8 a are mounted on the first carriage 1 as in FIG. 7, and the second mirror 8 b, the third mirror 8 c, and the imaging lens 3 are mounted as in FIG. 7. The photoelectric conversion is performed by the CCD 4.

  FIG. 9 is a block diagram showing a processing circuit inside the image reading apparatus for explaining the flow and processing of image data. In FIG. 9, the image reading device 106 includes a CCD 4, an analog processing circuit 21, an A / D converter 22, an averaging circuit 23, a white board forming unit 24, a shading correction unit 25, and a memory 26. Outputs data Dsh after shading correction. That is, the reflected light from the reference white plate 5 or 13 is input to the CCD 4 in the reduction optical system, is photoelectrically converted by the CCD 4, and is converted into an analog electric signal. The converted analog electric signal is subjected to predetermined processing by the analog processing circuit 21 and converted into a digital electric signal by the A / D converter 22 at the next stage. The digitally converted digital data is averaged in the sub-scanning direction by the averaging circuit 23, and the digital reference white plate data Wx is formed by the white plate data forming unit 24 with the number of data for one line. The shading correction unit 25 performs shading correction of the document data Dx read at this time using the reference white plate data Wx.

  By the way, when the shading correction is performed, the document data Dx is normalized with the reference white plate data Wx. The gray balance coefficient Xref is set to a normalized value so that the output Dsh_x after the shading correction becomes a predetermined level Dtarget_x. Multiplication is performed for each of Red, Green, and Blue (hereinafter referred to as RGB). This is because the gray balance coefficient Xref of each machine is set in the memory 26 for each machine, for example, by reading a reference chart in the process in order to absorb variations in reading levels for each RGB and machine.

For each shading correction

Therefore, the gray balance coefficient Xref is calculated as shown in equation (2).

  Of course, if the reference white plate, lamp, lens block, etc. are replaced in the market after setting the gray balance coefficient Xref, the reading level will change, so the gray balance coefficient Xref is set again and the output level is not changed. Need to be adjusted to be the same.

However, if replacement of parts in the image reader as described above occurs in the market, to reset the gray balance coefficient again, bring the reference chart used in the process to the market and make the same adjustments. Must-have. Such adjustment work is complicated and needs to be performed by a service person, which takes time and causes a problem that the operation of the image reading apparatus is interrupted for a long time.

  As a technique for dealing with this problem, for example, an invention described in Patent Document 1 (Japanese Patent Laid-Open No. 8-27512) is known. In order to be able to adjust the gray balance of full-color reading input without providing a gray scale reference plate, the present invention stores gray scale image data in advance, reads the image data, and prints the image. The printed image is printed in black by the means, and this is read and input by the image reading means and compared with the stored gray scale, and the gray balance of the read input is adjusted according to the comparison result.

  According to the invention described in Patent Document 1, the gray scale reference plate is certainly unnecessary, but it cannot be said that the adjustment accuracy is good due to variations in the printer unit, paper quality to be printed, artificial variations, and the like.

  Therefore, the problem to be solved by the present invention is to automatically and accurately perform gray balance adjustment without a reference chart when replacing components in the image reading apparatus.

  In order to solve the above-mentioned problem, the first means includes a reading means for reading document information by two reading methods of a pressure plate reading method and a sheet through method, and a reference white plate for obtaining shading correction information read by the reading means. And a second reference plate for obtaining shading correction information, and the reference white plate by reading the reference white plate every time document information is read. White plate data forming means for forming data, data storage means for reading the second reference plate and storing the acquired second reference plate data, and shading correction for normalizing image data using the reference white plate data The second reference plate data stored in the data storage means and the data of the read second reference plate And a gray balance adjusting means for adjusting a gray balance based on a difference between the two, the gray balance adjusting means, the read level of the second reference plate after shading correction obtained at a predetermined timing, and the data storage. Correcting the gray balance coefficient multiplied during the normalization process by the shading correction means based on the reading level of the second reference plate stored in the means, and the shading correction means is based on the corrected gray balance coefficient The image data after shading correction is output.

  The second means is characterized in that, in the first means, the data storage means stores only the second reference plate data acquired after the gray balance adjustment performed before shipment.

  The third means is characterized in that, in the first or second means, the correction of the gray balance coefficient of the gray balance adjusting means is executed every time the image is read.

  A fourth means is any one of the first to third means, wherein the second reference plate is installed upstream and downstream of the reading means in the sub-scanning movement direction with respect to the reference white plate. It is characterized by that.

  A fifth means is any one of the first to third means, wherein the second reference plate is installed upstream of the reference white plate in the sub-scanning movement direction with respect to the reference white plate. To do.

  The sixth means is any one of the first to fifth means, wherein the gray balance coefficient is corrected by the gray balance adjusting means when the value of the reference white plate read data when the power is turned on is the value when the power is turned on the last time. It is characterized in that it is executed when there is a change exceeding a preset threshold value.

  The seventh means is characterized in that the image forming apparatus includes an image reading apparatus according to any one of the first to sixth means.

  The eighth means is an image reading device comprising: reading means for reading document information by two reading methods of a pressure plate reading method and a sheet through method; and a reference white plate read by the reading means to obtain shading correction information. A shading correction method for an apparatus, the first step being provided at a position different from the reference white plate, reading a second reference plate for obtaining shading correction information, and storing the acquired second reference plate data; A second step of reading the reference white plate every time when reading document information to form reference white plate data, and a third step of normalizing image data using the reference white plate data formed in the second step And the read second reference plate data and the second reference plate data stored in the data storage means, and based on the difference between the two. A fourth step of performing gray balance adjustment, and in the fourth step, the reading level of the second reference plate after completion of the third step acquired at a predetermined timing is stored in the first step. Based on the read level of the second reference plate, the gray balance coefficient multiplied in the normalization process performed in the third step is corrected. In the third step, the gray balance coefficient is corrected based on the corrected gray balance coefficient. The image data after shading correction is output.

  Ninth means is an image reading device comprising: reading means for reading document information by two reading methods of a pressure plate reading method and a sheet-through method; and a reference white plate that is read by the reading means and obtains shading correction information. A shading correction control program for executing shading correction of a device by a computer, provided at a position different from the reference white board, reading a second reference board for obtaining shading correction information, and obtaining the second reference Using a first procedure for storing board data, a second procedure for reading the reference white board each time document information is read to form reference white board data, and the reference white board data formed by the second procedure A third procedure for normalizing the image data, the read data of the second reference plate, and the data recording A second procedure for comparing the second reference plate data stored in the means and adjusting the gray balance based on the difference between the second reference plate data. In the fourth procedure, the fourth procedure is obtained at a predetermined timing. Gray multiplied at the time of the normalization process performed in the third step based on the reading level of the second reference plate after the execution of the procedure 3 and the reading level of the second reference plate stored in the first step The balance coefficient is corrected, and the third procedure outputs image data after shading correction based on the corrected gray balance coefficient.

  In the embodiment described later, the reading means is a reading optical system including the carriage 1, the scanner lamp 6, the first to third mirrors 8a, 8b, and 8c, the imaging lens 3, and the CCD 4, and the reference white plate is denoted by reference numeral 5. The second reference plate is the second reference plate 15, 16, 17, the white plate data forming means is the white plate data forming unit 24, the data storage means is the data storage unit 28, the shading correction means is the shading correction unit 25, The gray balance adjusting means corresponds to the gray balance adjusting unit 27, respectively.

  According to the present invention, the second reference plate is installed separately from the reference white plate, and the gray balance coefficient is based on the data of the second reference plate and the second reference plate read data stored in the data storage means in advance. Therefore, the gray balance adjustment at the time of replacement of the components in the image reading apparatus can be performed automatically and accurately without a reference chart.

It is a figure which shows schematic arrangement | positioning of the reading part of the image reading apparatus which concerns on Example 1 in embodiment of this invention. 1 is a block diagram showing a system configuration of an image reading apparatus 106 in Embodiment 1. FIG. It is a flowchart which shows the process sequence which reads a 2nd reference | standard board and correct | amends the gray balance coefficient Xref. FIG. 6 is a diagram illustrating a schematic arrangement of a reading unit of an image reading apparatus according to a second embodiment. 12 is a flowchart illustrating a processing procedure for correcting a gray balance coefficient Xref by reading a second reference plate in Embodiment 2. 1 is a diagram illustrating an outline of a system configuration of an entire image forming apparatus including image reading apparatuses of Embodiments 1 and 2. FIG. It is a figure which shows the state at the time of the pressure plate reading of the image reading apparatus currently implemented conventionally. It is a figure which shows the state at the time of sheet | seat through reading of the image reading apparatus implemented conventionally. It is a block diagram showing a processing circuit inside the image reading device for explaining the flow and processing of image data.

  The present invention provides a reference plate (hereinafter referred to as a second reference plate) that is different from the reference white plate when the gray balance coefficient is set again when parts in the image reading apparatus are replaced in the market. Then, by using the second reference plate data and the second reference plate read data stored in the data storage means in advance, the gray balance coefficient is corrected from the difference between them, so that The gray balance adjustment at the time of component replacement can be performed automatically and accurately without a reference chart.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, parts equivalent to those in the conventional example shown in FIGS. 7 to 9 described above are denoted by the same reference numerals, and redundant description will be omitted as appropriate. Further, the reading method itself is performed in the state of FIG. 7 in the pressure plate reading, and in the state of FIG. 9 in the sheet through reading.

  FIG. 1 is a diagram illustrating a schematic arrangement of a reading unit of an image reading apparatus according to Example 1 of the present embodiment. In this embodiment, since the gray balance adjustment at the time of shading correction is performed using the second reference plate, it is necessary to read in the order of reference white plate reading, second reference plate reading, and document reading. Therefore, the second reference plate 16 is provided between the reference white plate 15 and the DF glass (original reading surface) 14. The original reading surface is the contact glass 10 at the time of reading the pressure plate, and the DF glass 14 at the time of sheet-through reading. In FIG. 1, the second reference plate is provided on the sheet metal in the reading device before and after the reference white plate 5 in the sub-scanning direction. 15 and 16 are installed. In the present embodiment, the second reference plate on the downstream side in the sub-scanning direction with respect to the reference white plate 5 is the second reference plate for sheet-through reading, and the second reference plate on the upstream side in the sub-scanning direction is the second plate for reading pressure plate. This is referred to as a reference plate 16.

  The second reference plates 15 and 16 do not have to be strictly colorimetrically controlled as in the process chart described in the above-described conventional example. Alternatively, instead of a patch or a plate, a method of directly reading the value of the sheet metal after coating the sheet metal with a uniform color or performing a rust prevention process or a dustproof process may be used. This embodiment is an example using a reference plate.

  FIG. 2 is a block diagram illustrating a system configuration of the image reading apparatus 106 according to the first embodiment. In this system, read data is output as digital image data subjected to shading correction. 9 is different from the conventional example shown in FIG. 9 in that a gray balance adjustment unit 27 and a data storage unit 28 are provided in the shading correction unit 25. In the present embodiment, the white board forming unit 24, the shading correction unit 25, the memory 26, the gray balance adjustment unit 27, and the data storage unit 28 constitute the shading control unit 20.

  Each unit in the shading control unit 20 is executed by the CPU of the shading control unit 20. The CPU controls each unit by executing a control program stored in a ROM (not shown) while using the RAM as a work area and a data buffer.

  First, in the pre-shipment process, the person in charge reads a predetermined reference chart with the CCD 4 in the same manner as in the past, and based on the equation (2) in the device in the pre-shipment process so that the level becomes a preset value. The gray balance coefficient Xref for the machine is calculated and written in the memory 26 in the image reading device 106. With the gray balance coefficient Xref set, the second reference plates 15 and 16 of the second reference plate 15 for sheet through reading and the second reference plate 16 for pressure plate reading are read. In this reading, the carriage 1 moves directly below the second reference plates 15 and 16, and the read values of the second reference plates 15 and 16 are written in the data storage unit 28. Therefore, this reading mode is provided in the image reading apparatus. A value written in the data storage unit 28 in this mode is set as Gtarget_x, which becomes a reference value when the image reading device 106 reads the pressure plate and when reading through the sheet.

  When used on the user side after shipment, the gray balance coefficient Xref is corrected so that the second reference plates 15 and 16 always have the reference value. FIG. 3 is a flowchart showing a processing procedure for correcting the gray balance coefficient Xref by reading the second reference plates 15 and 16, and is executed by the CPU.

  In FIG. 3, when the reading is started, first, it is determined whether the reading command is the reading mode of the pressure plate reading or the sheet through reading (step S101). If the pressure plate is read, the scanner lamp 6 is turned on, and the carriage 1 starts to move in the sub-scan rear end direction. When the carriage 1 comes directly under the reference white plate 5, the value of the reference white plate 5 is read (step S102), and the white plate forming unit 24 forms the reference white plate data Wx. Thereafter, in the conventional art, the original area is entered and the original data is read. However, in order to adjust the gray balance coefficient Xref before the original is read, the pressure plate reading second plate installed between the reference white plate 5 and the contact glass 10 is used. The data Dx of the second reference plate 15 is fetched (step S102).

The acquired data of the pressure plate reading second reference plate 15 is subjected to shading correction by the shading correction unit 25 by the previously acquired reference white plate data Wx. The gray balance adjustment unit 27 compares the shading corrected second reference plate data Gx for reading plate Gx with the second reference plate data Gtarget_x stored in the data storage unit 28 in the above-described process (step S104). Next, the gray balance coefficient Xref is corrected so as to correct the difference based on the comparison result (step S105). This correction is

It is calculated based on the equation (3) shown by

  Thereafter, the original data is read using the corrected gray balance coefficient Xref_rev, and shading correction is performed based on Expression (4) (step S106).

  On the other hand, at the time of sheet-through reading, like the pressure plate reading, the carriage 1 first moves directly below the reference white plate 5, reads the value of the reference white plate 5, and forms the reference white plate data Wx (step S107). Then, a return operation is performed to read the sheet-through reading second reference plate 16 between the DF glass (original reading surface) 14 and the reference white plate 5, and take in the data Dx (step S108). The correction of the gray balance coefficient is the same as steps S104 and S105 (steps S109 and S110). Thereafter, the original is read on the DF glass 14 (original reading) surface, and shading correction is performed with the corrected gray balance coefficient Xref_rev (step S111). This operation is performed every time a plurality of sheets are read (step S112).

  As described above, this is performed every time scanning is performed in both the pressure plate reading and the sheet through reading, so that the reference value is corrected every time even when the lens block (imaging lens 3), the scanner lamp 6 and the reference white plate 5 are replaced. Therefore, a stable reading level can be ensured without change before and after replacement.

  In the first embodiment, the second reference plates 15 and 16 are installed before and after the reference white plate 5 in the sub-scanning direction, and the gray balance coefficient is corrected in each scan using the second reference plates 15 and 16. Thus, the gray balance is adjusted automatically without manual adjustment even when the parts in the reader are replaced. However, by placing the second reference plates 15 and 16 at the above-described positions, the space of the second reference plates 15 and 16 is adjusted. Therefore, the reading operation takes time, and productivity may be reduced. Considering that the reading level changes only at the time of component replacement, it is possible to read the second reference plate only at the time of component replacement and perform gray balance adjustment. Hereinafter, a description will be given of a second embodiment in which the second reference plate is read only at the time of parts replacement and gray balance adjustment is performed.

FIG. 4 is a diagram illustrating a schematic arrangement of the reading unit of the image reading apparatus according to the second embodiment. The system configuration itself is the same as that of the first embodiment.
In the second embodiment, the second reference plate is not placed between the reference white plate 5 and the original reading surface, and is installed in a place where normal reading operation is not hindered. That is, in FIG. 4, the second reference plate 17 is installed on the most upstream side in the sub-scanning direction of the pressure plate document reading surface. In the process before shipment, the target value Gtarget_x of the second reference plate is written in the data storage unit 28 of FIG. Then, the gray balance is adjusted based on this target value.

  FIG. 5 is a flowchart showing a processing procedure for correcting the gray balance coefficient Xref by reading the second reference plate 17 in the second embodiment, which is executed by the CPU.

  When used on the user side after shipment, the reading operation is performed in the same manner as before without reading the second reference plate during normal operation after power-on. However, when the power is turned on, the carriage 1 moves immediately below the reference white plate 5 (step S201), and attention is paid to the reference white plate data (when gain is 1) when the gain adjustment is started by the reference white plate 5 (step S202). Since the gain value is initialized to 1 time every time the gain adjustment is started, the reference white plate data (when the gain is 1 time) is referred to as reference white plate initial data.

  Next, the reference white plate initial data is compared with the reference white plate initial data when the power is turned on last time (step S203). When the difference between the current reference whiteboard initial data and the previous reference whiteboard initial data is less than a certain threshold value Wth (step S203—YES), the components in the image reading device 106 are not replaced or have been replaced. Assuming that the reading level has not changed from before the replacement, it is determined that there is no need for gray balance adjustment, and the reading value of the reference white plate 5 read this time is stored in the memory without reading the second reference plate (step S204). Then, the gain is adjusted (step S205), the carriage 1 is returned to the home position (step S209), and the process is finished.

  On the other hand, if the difference between the current value and the previous value is equal to or greater than the threshold value (step S203—NO), it is considered that the part in the image reading device 106 has been replaced, and the read value of the reference white plate 5 read this time is stored in the memory. After performing the gain adjustment (step S205), the value of the second reference plate 17 installed on the most upstream side in the sub-scanning direction of the pressure plate original reading surface 1 is read (step S206). As in the first embodiment, the gray balance coefficient is corrected by the gray balance adjusting unit 27 (steps S207 and S208), the carriage 1 is returned to the home position (step S209), and the process is completed.

  In step S204, the reading data of the reference white plate is stored as initial data in the memory in the white plate forming unit 24 every time it is read and used as the previous value when the power is turned on next time.

  Other parts that are not particularly described are configured in the same manner as the first embodiment and the conventional example, and function in the same manner.

  As described above, according to the second embodiment, the gray balance coefficient Xref is appropriately corrected only when the reading level changes greatly due to part replacement or sudden characteristic change of the part. It is possible to automatically adjust without replacing the dedicated chart or the like when replacing the parts without impairing the productivity.

  Further, in the present embodiment including Examples 1 and 2, since the amount of variation is different for each RGB when performing color reading, the arithmetic processing of the above formulas (1) to (4) is executed for each RGB color, and gray balance is obtained. Make adjustments. Of course, the second reference plate data stored in the data storage unit 28 needs to be prepared for each of RGB colors and for three channels.

  FIG. 6 is a diagram illustrating an outline of a system configuration of the entire image forming apparatus including the image reading apparatuses according to the first and second embodiments. The image forming apparatus according to the present embodiment is an example of a multifunction machine having a copying function and other functions such as a printer function and a facsimile function. This multi-function machine can be selected by appropriately switching a copying function, a printer function, and a facsimile function with an application switching key of an operation unit (not shown). The copy mode is selected when the copy function is selected, the print mode is selected when the printer function is selected, and the facsimile mode is selected when the facsimile mode is selected.

  The image forming apparatus is for forming a monochrome image. The main body 100, a writing unit 118 installed on the upper part of the main body 100, an image reading device 106 installed on the writing unit 118, and further thereon. An automatic document feeder (hereinafter referred to as “ADF”) 101 is basically configured.

  In the copy mode, the operation is as follows. In the ADF 101, when a document bundle is placed on the document table 102 so that the image surface is on top, and a start key on an operation unit (not shown) is pressed, the lowermost document is fed to the feed roller 103 and the feed. The belt 104 is fed to a predetermined position on the contact glass 10. The ADF 101 has a count function that counts up the number of documents every time a document is fed. The document on the contact glass 10 is discharged onto a sheet discharge table 108 by a feeding belt 104 and a discharge roller 107 after image information is read by an image reading device 106 as an image input unit.

  When the document set detector 109 detects that there is a next document on the document table 102, the lowermost document on the document table 102 is similarly contact glass by the feed roller 103 and the feed belt 104. 10 is fed to a predetermined position. The feed roller 103, the feed belt 104, and the discharge roller 107 are driven by a transport motor (not shown).

  The image reading device 106 moves in the sub-scanning direction while illuminating with the scanner lamp 6 that irradiates the document on the contact glass 10, and scans the document in the process, and the reflected light is reflected on the first mirrors 8a, 8b, and 8c. Is read by a CCD (CCD image sensor) 4 that is a photoelectric conversion device via the imaging lens 3 that reflects the image in the direction of the imaging lens 3 and reduces and forms an image.

  The image data read from the original by the image reading device 106 is optically written corresponding to the original image by a writing unit 118 as writing means via an image processing means (not shown), and an electrostatic latent image is formed on the photosensitive drum 117. Form. The writing unit 118 includes a laser light emitting device 134, an fθ lens 135, a reflection mirror 136, and the like. The exposure light source is a laser beam, but is not limited to this. For example, an LED array may be used.

  The main body 100 includes a photosensitive drum 117, a developing device 119, a fixing device 121, a paper discharge unit 122, first to third paper feeding devices 110 to 112, a vertical conveyance unit 116, and the like. The photosensitive drum 117 is uniformly charged by a charger (not shown) and then exposed to light information from the writing unit 118 to form an electrostatic latent image. The electrostatic latent image on the photosensitive drum 117 is developed by the developing device 119 to become a toner image.

  A conveyor belt 120 is disposed below the photosensitive drum 117. The conveying belt 120 also serves as a conveying means and a transferring means for transfer paper as a recording medium. A transfer bias is applied from a power source (not shown), and the conveying belt 120 is conveyed from the vertical conveying unit 116 and sent out by a registration roller 149. The toner image on the photosensitive drum 117 is transferred to the transfer paper 207 while the transfer paper 207 is conveyed at the same speed as the peripheral speed of the photosensitive drum 117. The toner image 206 (FIG. 2) on the transfer paper 207 is fixed by the fixing device 121 and is discharged from the paper discharge unit 122 to the paper discharge tray 123. The photosensitive drum 117 is cleaned by a cleaning device (not shown) after the toner image is transferred. Here, the photosensitive drum 117, the charger, the writing unit 118, the developing device 119, and the transfer unit constitute an image forming unit that forms an image on transfer paper based on image data. The photosensitive drum 117 is rotationally driven at a constant speed by a main motor. In addition, a conveyance roller pair including a registration roller 149 is provided in a path for feeding the transfer paper 207 to the photosensitive drum 117. One of these conveying roller pairs is a driving roller, and the other is a driven roller. In FIG. 1, the driven roller in the registration roller 149 is denoted by reference numeral 150, and the driven roller of the conveyance roller pair is denoted by reference numeral 151.

  The paper discharge unit 122 is provided with a double-sided conveyance path. That is, the reverse conveyance path 125 fed by the conveyance roller pair 124 from the middle of the paper discharge unit 122, the image forming side conveyance path 126 that conveys the transfer paper reversed by the reverse conveyance path 125 to the vertical conveyance unit 116 side, and the reverse. A paper discharge conveyance path 127 is provided for returning the transferred transfer paper to the paper discharge unit 122 side again. Images can be formed on both sides of the transfer paper by this double-sided conveyance path, or discharged onto the paper discharge tray 123 with the image-formed side down.

  The first paper feeding device 110, the second paper feeding device 111, and the third paper feeding device 112 as the paper feeding means are stacked on the first tray 113, the second tray 114, and the third tray 115, respectively, when selected. The transfer sheet is fed, and the transfer sheet is conveyed by the vertical conveyance unit 116 to a position where it comes into contact with the photoconductor 117.

As described above, according to the present embodiment, the following effects can be obtained.
1) The second reference plates 15, 16, and 17 are installed separately from the reference white plate 5, the reading level of the second reference plates 15, 16, and 17 is changed, and the second stored in the data storage unit 28 in advance. Since the gray balance coefficient is corrected from the difference using the reference plate reading data, gray balance adjustment can be performed automatically and accurately without a reference chart when replacing parts in the image reading device. it can.
2) After adjusting the gray balance before shipment, the second reference plates 15, 16, and 17 are read and stored in the data storage unit 28, so that the target level (Gtarget) on the second reference plate is used instead of the reference chart. Can adjust the gray balance in the market.
3) Since the gray balance adjustment unit 27 performs the gray balance adjustment every time the document is read, it is possible to automatically correct the change in the reading level when replacing the components in the image reading apparatus after shipment.
4) Since the second reference plates 15 and 16 are provided on the sheet metal on the upstream side and the downstream side in the sub-scanning direction of the reference white plate, the second reference plate is placed immediately after reading the white plate at the time of pressure plate reading and sheet through reading, respectively. It becomes possible to read, and the reading process can be performed efficiently.
5) Since the gray balance adjustment is performed only when a change in the reading level due to a sudden change in the characteristic of the component is detected when replacing the component in the image reading apparatus, the correction operation can be performed only when necessary. A decrease in reading efficiency can be minimized.
6) By reading the second reference plate every time the original is read, the stability of the reading level can be obtained, but the productivity of the reading operation is slightly reduced by the operation of reading the second reference plates 15 and 16. Therefore, the second reference plate 17 is installed at a place outside the reading range of the normal reading operation. Accordingly, reading the second reference plate 17 only at the time of component replacement does not cause a decrease in productivity of the normal reading operation.
7) By applying the image reading apparatus according to the present embodiment to the image reading apparatus of the image forming apparatus, it is possible to ensure the same reading quality as before the replacement even when parts replacement occurs in the image reading apparatus after shipment. The image quality of the output image is not degraded.
There are effects such as.

  In addition, this invention is not limited to this embodiment, All the technical matters contained in the technical idea of the invention described in the claim are object.

  The present invention relates to an image reading apparatus for reading a document image, an image forming apparatus including the image reading apparatus, a network scanner to which the image reading apparatus is connected, a scanner connected to a personal computer and functioning as an image input apparatus for the personal computer. The present invention can be used for all devices having a function of reading and processing images.

1 Carriage 3 Imaging lens 4 CCD
5 Reference white plate 6 Scanner lamp 8a, 8b, 8c Mirror 10 Contact glass 14 DF glass 15, 15, 17 Second reference plate 24 White plate data forming unit 25 Shading correction unit 27 Gray balance adjustment unit 27
28 Data storage

JP-A-8-275012

Claims (9)

Reading means for reading document information by two reading methods of a pressure plate reading method and a sheet through method;
A reference white plate which is read by the reading means and obtains shading correction information;
An image reading apparatus comprising:
A second reference plate provided at a position different from the reference white plate, for obtaining shading correction information;
White plate data forming means for reading the reference white plate every time document information is read to form reference white plate data;
Data storage means for reading the second reference plate and storing the acquired second reference plate data;
Shading correction means for normalizing image data using the reference white plate data;
A gray balance adjustment means for comparing the read second reference plate data with the second reference plate data stored in the data storage means, and performing gray balance adjustment based on the difference between the two,
With
The gray balance adjusting means is based on the reading level of the second reference plate after shading correction acquired at a predetermined timing and the reading level of the second reference plate stored in the data storage means. Correct the gray balance coefficient that is multiplied during normalization,
The image reading apparatus characterized in that the shading correction means outputs image data after shading correction based on the corrected gray balance coefficient. The image reading apparatus according to claim 1,
The image reading apparatus characterized in that the data storage means stores only the second reference plate data acquired after gray balance adjustment performed before shipment. The image reading apparatus according to claim 1 or 2,
An image reading apparatus according to claim 1, wherein the correction of the gray balance coefficient of the gray balance adjusting means is executed every time an image is read. The image reading apparatus according to any one of claims 1 to 3,
2. The image reading apparatus according to claim 1, wherein the second reference plate is installed on the upstream side and the downstream side in the sub-scanning movement direction of the reading unit with respect to the reference white plate. The image reading apparatus according to any one of claims 1 to 3,
The image reading apparatus, wherein the second reference plate is installed at a location outside the reading range of a normal reading operation. An image reading apparatus according to any one of claims 1 to 5,
The correction of the gray balance coefficient by the gray balance adjusting means is executed when the value of the reference white plate reading data when the power is turned on changes more than a preset threshold value compared to the value when the power is turned on the last time. An image reading apparatus.   An image forming apparatus comprising the image reading apparatus according to claim 1. Reading means for reading document information by two reading methods of a pressure plate reading method and a sheet through method;
A reference white plate which is read by the reading means and obtains shading correction information;
A shading correction method for an image reading apparatus comprising:
A first step of reading a second reference plate provided at a position different from the reference white plate, for obtaining shading correction information, and storing the acquired second reference plate data;
A second step of reading the reference white plate every time document information is read to form reference white plate data;
A third step of normalizing the image data using the reference white plate data formed in the second step;
A fourth step of comparing the read data of the second reference plate and the second reference plate data stored in the data storage means, and adjusting the gray balance based on the difference between the two,
With
In the fourth step, the third reference plate is read based on the read level of the second reference plate after completion of the third step acquired at a predetermined timing and the read level of the second reference plate stored in the first step. Correct the gray balance coefficient that is multiplied during the normalization process performed in the process of
In the third step, the shading correction method is characterized by outputting the image data after the shading correction based on the corrected gray balance coefficient. Reading means for reading document information by two reading methods of a pressure plate reading method and a sheet through method;
A reference white plate which is read by the reading means and obtains shading correction information;
A shading correction control program for executing shading correction of an image reading apparatus provided with a computer,
A first procedure which is provided at a position different from the reference white plate, reads a second reference plate for obtaining shading correction information, and stores the acquired second reference plate data;
A second procedure of reading the reference white plate every time when reading document information to form reference white plate data;
A third procedure for normalizing image data using the reference white plate data formed in the second procedure;
A fourth procedure for comparing the read data of the second reference plate and the second reference plate data stored in the data storage means, and adjusting the gray balance based on the difference between the two,
With
In the fourth procedure, the third reference plate is read based on the read level of the second reference plate after execution of the third procedure obtained at a predetermined timing and the read level of the second reference plate stored in the first step. Correct the gray balance coefficient that is multiplied during the normalization process performed in the process of
In the third procedure, the shading correction control program outputs the image data after the shading correction based on the corrected gray balance coefficient.

Images