JP2009272891A - Image reader, image forming apparatus, image reading method, and image formation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress variations in reading values of a white roller, and to raise precision of shading correction without increasing the number of blocks when shading correction data is generated based on white reference data obtained by reading the white roller. <P>SOLUTION: A CPU 138 of an ADF control part 133 which functions as a shading data generation means receives a detection signal of a white roller rotation position detection sensor 170 and a line synchronization signal from a CIS unit 135 by a CPU interruption input. Upon receiving the detection signal of the sensor 170, the white reference data read by the CIS 135 is fetched in one rotation period of the white roller 137 by an XSLEAD signal indicating a fetching range. Timings of roller division areas A, B, C, D are counted for the number of times set as count values from the detection signal of the sensor 170, an XSSCAN signal indicating a reading range in timing of each area is generated, the white reference data is fetched, and shading data is generated by average value and peak value processing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that reads a document fed by a roller at a reading position (sub-scanning) by an image sensor that photoelectrically converts an image by line scanning (main scanning), and relates to shading correction on a feeding roller surface that keeps the document at the reading position. By using the white reference for the image, the image reading apparatus, the image reading method, and the data read by the image reading apparatus can read the white data from the roller surface before and after the document reading or between the documents. The present invention relates to an image forming apparatus (a copying machine, a facsimile, an MFP that combines copying / facsimile functions, etc.) and an image forming method.

Conventionally, for image input in an image forming apparatus such as a copying machine, a facsimile machine, an MFP (Multi-Function Peripherals) that combines copying / facsimile / scanner delivery functions, etc., a scanner or a single-function machine as a component unit of the apparatus Are widely used.
A scanner used for such image input generally employs a reading method in which a document image is scanned two-dimensionally (main / sub) to obtain a pixel signal. The main scanning in the two-dimensional scanning is performed by scanning when converted into a line image (video) signal by a CCD (Charge Coupled Device) line image sensor (hereinafter referred to as “CCD” or “image sensor”). Sub-scanning is performed by relatively displacing the original image and the CCD by a scanning mechanism. That is, the line image signal is sampled by this main / sub scanning to represent a two-dimensional image of the document surface.

The document read by the scanner may be a sheet or a book (in this case, a booklet in which a plurality of sheets are bound, a book, etc.), and both of the image reading devices installed in the copying machine are There are many things corresponding to.
The reading of a sheet document may be a single sheet or a bundle of a plurality of sheets, and an ADF (ADF) that supplies a document to a reading position one by one from a bundle set on a document tray so as to cope with a bundle of a plurality of sheets. A configuration is adopted in which an original document can be continuously read by using an Automatic Document Feeder. In the reading with this ADF operated, as a method capable of increasing the processing speed, a fixed position on the conveyance path of the ADF is set as a reading position, and an original conveyed at a constant speed is read by an image sensor that reads an image at that position. A method (hereinafter referred to as “ADF reading”) is employed.

By the way, in image reading using a line image sensor such as a CCD, shading correction is conventionally applied to a fluctuation element unique to a device appearing in a sensor output. In this correction, data for shading correction is obtained by reading a white reference such as a reference white plate with a line image sensor.
In the case of ADF reading, the line image sensor is in a fixed relationship with respect to the reading position on the conveyance path. Therefore, a place where a white reference to be read in order to obtain shading correction data is provided in order to increase the processing speed. It is advantageous to use a member that holds the original document surface at the reading position. Conventionally, a member such as a roller that conveys the document at the reading position is used as a white reference, and the member is read when there is no document. . In particular, when a CIS (contact image sensor) is provided in the ADF transport path, the roller surface facing the CIS, holding the document at the reading position and feeding it is a white roller, and reads the roller surface when there is no document. Thus, the methods disclosed in Patent Documents 1 and 2 below are known in which shading correction data is acquired.

In the method of Patent Document 1 below, when data for shading correction is obtained by reading a white roller serving as a white reference, a predetermined range of the surface of the white roller is read, and the obtained image data is divided into L lines. An average value of the image data of each line of the block is obtained by an average value circuit. The operation of sequentially comparing the preceding and succeeding average values of each block with a comparator is repeated, and the peak value among all the average values is obtained as white shading data.
In the method of Patent Document 2 below, when data for shading correction is obtained by reading a white roller serving as a white reference, an error that occurs in the read data obtained by reading the white plate roller surface due to a change in the mounting position of the white plate roller or the like. Further, the white shading data read from the white roller is corrected using the read data of the white reference original read.
JP 2002-152510 A JP 2006-72838 A

However, in the conventional techniques disclosed in Patent Documents 1 and 2, since the reading position of the white roller for obtaining shading correction data is not defined, it is considered that the reading position changes in the rotation direction of the white roller every time reading is performed. As a result, the reading value varies, and the accuracy of shading correction is reduced. Further, in Patent Document 1, a configuration intended to improve accuracy in the direction of increasing the number of blocks read by the white roller is shown. However, when the number of blocks is increased, on the other hand, continuous reading of a plurality of documents is performed. In this case, it takes a long time to read the white roller between documents, and the processing speed is reduced. These points are not taken into account. Also in the above-mentioned patent document 1, since reading of a white reference document is added, the processing speed cannot be reduced.
Therefore, an object of the present invention is to eliminate the above-described problems that may occur due to the prior art that generates shading correction data based on white reference data obtained by reading a white roller, and to suppress variations in reading values of the white roller, It is to improve the accuracy of shading correction without increasing the number of blocks, and to suppress a decrease in processing speed.

The present invention includes an image sensor that reads an image in a line scanning format in a main scanning direction at a reading position on a document conveying path, and a feed roller that guides a document conveyed in a sub-scanning direction to the reading position. A white roller for white reference, correction data generation means for generating shading correction data based on white reference data obtained by the image sensor reading the white roller, and a document read by the image sensor. An image reading apparatus having a shading correction unit that performs shading correction on the image data using the correction data generated by the correction data generation unit, and includes a white roller rotation position detection unit that detects a rotation position of the white roller, The correction data generation means converts the white reference data read by the image sensor into the The position detection signal detected by the color roller rotation position detection means is taken in a predetermined range as a reference, and is blocked by a predetermined number of lines, and an average value of the number of lines is obtained for the white reference data for each block, and each block obtained A maximum value among the average values is generated as shading correction data.
The present invention is also an image sensor that reads an image in a line scan format in the main scanning direction at a reading position on the document conveyance path, and a feed roller that guides the document conveyed in the sub-scanning direction to the reading position. A white roller used as a white reference for shading correction, correction data generation means for generating shading correction data based on white reference data obtained by the image sensor reading the white roller, and a document is read by the image sensor. An image reading apparatus having a shading correction unit that performs shading correction on the image data obtained by the correction data generated by the correction data generation unit, wherein the correction data generation unit includes white reference data read by the image sensor. In a predetermined range, block it with a predetermined number of lines, and A means for obtaining an average value of the number of lines for data and generating a maximum value among the obtained average values of each block as shading correction data, and immediately before starting a document reading operation when the image reading apparatus is turned on. The first correction data generation mode in which the range in which white reference data is captured at the timing after document reading is set to be equal to or more than one rotation period of the white roller, or the range in which white reference data is captured between document image readings is the white color. A second correction data generation mode that is performed with less than one rotation period of the roller is executed according to the setting.
The present invention is also an image forming apparatus including an image input unit, an image processing unit that converts an input image into image forming data, and an image forming unit that forms an image based on the image forming data. The image reading device is used as the image input means.
The present invention also includes a step of reading an image in a line scan format in the main scanning direction at a reading position on the document conveyance path by an image sensor, and a white roller having a roller surface as a white reference for shading correction, and conveying the image in the sub scanning direction. Guiding a document to be read to the reading position, a correction data generating step of generating shading correction data based on white reference data obtained by the image sensor reading the white roller, and reading the document by the image sensor. A white roller rotation position for detecting a rotation position of the white roller, wherein the image reading method includes a shading correction step of performing shading correction on the image data obtained in the correction data generation step. A detection step, and in the correction data generation step, the white roller rotation position detection step The white reference data read by the image sensor in a predetermined range with reference to the output position detection signal is taken, and the block is formed with a predetermined number of lines, and the average value of the number of lines is obtained for the white reference data for each block. The maximum value among the average values of each block is generated as shading correction data.
The present invention also includes a step of reading an image in a line scanning format in the main scanning direction at a reading position on the document conveying path by an image sensor, and a roller surface transporting in the sub scanning direction by a white roller having a white reference for shading correction. A step of guiding a document to the reading position; a correction data generation step of generating shading correction data based on white reference data obtained by the image sensor reading the white roller; and a step of reading the document by the image sensor. A shading correction step of performing shading correction on the obtained image data with the correction data generated in the correction data generation step. In the correction data generation step, the image sensor reads the image data. White reference data is captured within a predetermined range, and is blocked with a predetermined number of lines. For the white reference data, the average value of the number of lines is obtained, the maximum value among the obtained average values of each block is generated as shading correction data, and the document reading operation starts when the image reading device is turned on The first correction data generation mode in which the range in which the white reference data is captured immediately before and after the document reading is set to be equal to or more than one rotation period of the white roller, or the range in which the white reference data is captured between document image readings. The second correction data generation mode performed when the white roller is less than one rotation cycle is executed according to the setting.
The present invention is also an image forming method including an image input step, an image processing step for converting an input image into image formation data, and an image formation step for forming an image based on the image formation data. The image reading method is used as the image input step.

  According to the present invention, it is possible to improve the accuracy of shading correction without increasing the white reference data obtained by reading with the white roller and without increasing the document reading time.

In the following embodiment, the image reading apparatus and the image forming apparatus of the present invention are shown in a form integrated in a color copying machine as the image forming apparatus. That is, a scanner provided as a constituent unit for a color copying machine to input an image of a document is an embodiment of the image reading apparatus according to the present invention.
However, the image reading apparatus of the present invention may constitute a single apparatus. In addition, here, an embodiment in which the image forming apparatus of the present invention is implemented in a color copying machine is shown, but for an invention that does not require color reading, only a plurality of color components in color are replaced with a single color. Thus, even a monochrome copying machine can be implemented in the same manner as this embodiment.

First, an outline of a color copying machine according to an embodiment of the present invention will be described. FIG. 1 is a diagram showing an outline of the overall configuration of a color copying machine according to this embodiment.
The color copying machine shown in FIG. 1 is roughly composed of an image reading device and an image recording device (print engine). The image reading apparatus includes an image reading unit (scanner) 2, an image processing unit 3, and an ADF (Automatic Document Feeder) 15. The image recording apparatus includes an image writing unit 4, a drum unit 8, a developing unit 10, an intermediate transfer unit 9, a paper feeding unit 11, a fixing unit 12, and a copier mechanism unit 6. In addition, in order to perform a control operation common to both the reading and recording apparatuses, a system control unit 1 as a main controller, a rendition unit 5 as a UI (User Interface), and an image display unit (LCD: Liquid Crystal Display) 7.

The outline of the operation when color copying is performed by this color copying machine is as follows. The image reading unit 2 sub-scans the original irradiated with the illumination light from the light source, and the reflected light from the original is a 3-line CCD or the like. The image sensor reads the image and sends the image data to the image processing unit 3. For the sub-scanning of the document, a method of moving the reading system and a method of moving the document by the ADF 15 are used in combination. Further, in the sub-scanning by ADF, reading is further performed using a contact image sensor (CIS) method and a method using a reduction optical system. The reading unit 2 will be described in detail in each embodiment described later.
The image processing unit 3 sends image data subjected to image processing such as scanner γ correction, color conversion, main scanning scaling, image separation, processing, area processing, gradation correction processing to the image writing unit 4.

The image writing unit 4 controls light emission of an LD (laser diode) according to image data. In the drum unit 8, an electrostatic latent image is created by writing with a laser beam from the LD on a uniformly charged rotating photosensitive drum, and toner is attached by the developing unit 10 to be visualized. The image formed on the photosensitive drum is transferred onto the transfer belt of the intermediate transfer unit 9. In the case of full-color copying, toners of four colors (black: Bk, cyan: C, magenta: M, yellow: Y) are sequentially stacked on the intermediate transfer belt. In this example, a single photosensitive drum is used, but a so-called tandem type image forming unit having four color drums may be employed.
In the case of full-color copying, the transfer paper is fed from the paper feeding unit 11 in synchronization with the intermediate transfer belt at the time when the image forming and transferring processes of Bk, C, M, and Y are completed, and the paper is transferred. The toner is transferred from the intermediate transfer belt to the transfer paper at the same time on the transfer paper. The transfer paper onto which the toner has been transferred is sent to the fixing unit 12 through the conveying unit, and is thermally fixed by the fixing roller and the pressure roller and is discharged.

When performing the above-described copy operation, copy conditions such as a copy mode set by the user's selection are input by the operation unit unit 5. The operation mode to be executed in accordance with the copy conditions such as the set copy mode is notified to the system control unit 1, and the system control unit 1 performs control processing for executing the set copy mode. At this time, the system control unit 1 issues a control instruction to units such as the image reading unit 2, the image processing unit 3, the image writing unit 4, and the image display unit 7.
FIG. 2 is a diagram illustrating an example of an operation panel of the operation unit 5. As shown in FIG. 2, the operation panel of the operation unit 5 includes a numeric keypad 41, a mode clear / preheat key 42, an interrupt key 43, an image quality adjustment key 44, a program key 45, a print start key 46, a clear / stop key 47, An area processing key 48, a brightness adjustment knob 49, a touch panel key (on the LCD panel 26 in FIG. 3) 50, and an initial setting key 51 are provided.

  The numeric keypad 41 is used when inputting numerical values such as the number of copies. The mode clear / preheat key 42 is used to cancel the set mode and return to the initial setting, or to set the preheat state when the key is continuously pressed for a predetermined time or longer. The interrupt key 43 is used to interrupt during copying and to copy another document. The image quality adjustment key 44 is used when adjusting the image quality. The program key 45 is used to register or call a frequently used mode. The print start key 46 is a key for starting copying. The clear / stop key 47 is used to clear an input numerical value or to interrupt copying during copying. The area processing key 48 is used when executing an area processing / editing mode on the image display unit (display editor) 7. The brightness adjustment knob 49 adjusts the brightness of the screen of the LCD panel (see FIG. 3 below). The touch panel key 50 sets a key area in the same range as the range of various keys displayed on the LCD panel, and when the touch panel detects a press within the set range, processing of the set key is performed. I do. The initial setting key 51 is pressed when the user selects each initial setting.

Further, in order to display the image read from the image reading unit 2 on the image display unit 7 (FIG. 1), the image reading unit 2 starts reading the original image in accordance with a control instruction from the system control unit 1 and reads the image. The image signal from the unit 2 is subjected to image processing suitable for display on the image display device in the image processing unit 3, and then the image data of the document is output to the image display device such as an LCD panel.
FIG. 3 is a functional block diagram showing a circuit configuration of the image display unit 7. As shown in FIG. 3, the image display unit 7 is connected to the system control unit 1 via a command line and to the image processing unit 3 via a data line, and includes a FIFO (line buffer) 21, a DRAM (image Data memory) 22, CPU 23, VRAM (video memory) 24, LCDC (LCD controller) 25, LCD (liquid crystal panel) 26, ROM 27, SRAM 28, serial communication driver 29, image data signal buffer (driver / receiver) 30, keyboard 31 Is provided.

  The image data output from the image processing unit 3 is stored in the DRAM 22 for storing image data by the DMA controller built in the CPU 23 via the FIFO 21 of the image display unit 7. Since the image data control signal is sent to the image display unit 7 together with the image data, it is possible to capture only the effective image area. Valid image data stored in the DRAM 22 is DMA-transferred to the VRAM 24 by the CPU 23. At this time, the CPU 23 can transfer an arbitrary portion of the image data in the DRAM 22 and can perform processing such as enlargement / reduction and thinning. The image data transferred to the VRAM 24 is displayed on the LCD panel 26 under the control of an LCDC (LCD controller) 25.

  FIG. 4 is a diagram showing an example of the LCD panel of the image display unit 7 shown in FIG. The image display unit 7 displays an image on the LCD panel 26. In addition, a display editor for performing editing / processing area designation / mode setting in the display screen may also be used. Each setting key in FIG. 4 corresponds to the keyboard 31 in the functional block diagram of FIG. The reading key is a key for starting reading of a document and displaying the entire read image on the display, and the brightness adjustment key is a key for adjusting the brightness of the display.

FIG. 5 shows an example of a screen displayed on the LCD panel 26. As shown in FIG. 5, on the LCD screen, color mode, automatic density, manual density, image quality mode (automatic image separation), automatic paper selection, paper tray, paper automatic scaling, scaling (same size), sorting, There is a mode selection display such as a stack, and further sub-screen selection displays such as create, color processing, double-sided, and variable magnification are also provided. Further, the LCD panel 26 is used as a touch panel, and a key having the same size as each display unit is set. Some keys can be expanded by pressing the key down.
FIG. 6 shows an example of screen development by pressing the scaling key in FIG. When the scaling key is pressed, the scaling setting screen is scrolled up from the bottom of the screen. On the scaling setting screen, a key for fixed-size scaling (a scaling mode in which a scaling ratio is set in advance) is set. For example, when a 71% touch panel key is pressed, a scaling factor of 71% is selected. In this screen, a zoom key, a size scaling key, and an independent scaling / enlarged continuous shooting key are set on the left side of the screen to select a scaling mode other than the standard scaling.

  The touch panel detection circuit and its operation will be described. FIG. 7 is a diagram illustrating an example of the configuration of the touch panel detection circuit. FIG. 8 shows a setting state of potentials of the X and Y electrodes of the touch panel in the detection circuit of FIG. As shown in FIG. 7, the touch panel detection circuit includes a touch panel 71, a controller 72, an A / D converter 73, and an operation switching circuit. The controller 72 sets the detection terminal to the high state, and sets the potentials X1, X2, Y1, and Y2 of each electrode of the touch panel 71 as shown in FIG. Since the Y1 and Y2 circuits are pulled up by resistors, Y1 becomes + 5v when the touch panel 71 is OFF, and 0V when the touch panel 71 is ON. Therefore, the ON / OFF state is confirmed from the output of the A / D converter 73. When the controller 72 detects the ON state of the touch panel 71, the controller 72 switches to the measurement mode. In the X direction, X1 is + 5v and X2 is 0v, and the potential at the input position is connected to the A / D converter 73 through Y1 to calculate coordinates. Also, the coordinates in the Y direction are calculated in the same manner by switching circuits. By such a detection circuit, the pressed position of the touch panel 71 is detected.

Regarding the operation unit 5 in which the above-described image display unit and various input keys are integrated on the operation panel (see FIG. 2), the circuit configuration and the outline of the operation will be described below. FIG. 9 is a functional block diagram illustrating an example of the circuit configuration of the operation unit. As shown in FIG. 9, the operation unit 5 includes a CPU 53, an address latch 54, an LCDC (LCD controller) 55, an address decoder 56, a system reset 57, a ROM 58, an LED driver 59, a keyboard 60, a touch panel 61, an LCD module 62, and a ROM 63. RAM 64 and optical transceiver 65 are provided.
The address signal from the CPU 53 is taken into the address latch 54, and the address signal is given to each memory for access control to the memory. Part of the address signal output from the address latch 54 enters the address decoder 56, where a chip select signal for each IC is generated and used to create a memory map. The address enters the ROM 58 (or RAM) memory or LCDC 55 and is used for address designation.

  On the other hand, a data bus from the CPU 53 is connected to the ROM 58 and the LCDC 55 to perform bidirectional data communication. In addition to the address bus and data bus from the CPU 53, the LCDC 55 is connected to an LED driver 59, a keyboard 60, an analog touch panel 61, an LCD module 62, a display data ROM 63, a RAM 64, and the like. The LCDC 55 creates display data from the data in the ROM 63 and the RAM 64 by a signal from the keyboard or a signal from the touch panel 61, and controls the screen display of the LCD module 62. Further, an optical transceiver 65 as an optical fiber connector is connected to the CPU 53 and performs communication with the outside.

Next, a scanner (image reading apparatus) that is installed in the above-described color copying machine and to which the present invention is applied will be described.
A scanner used for image input generally employs a reading method in which an original image is scanned two-dimensionally (main / sub) to obtain a pixel signal. The main scanning in the two-dimensional scanning is based on scanning when converting to a line image (video) signal by the CCD line image sensor, and the sub-scanning is based on relative displacement between the original image and the CCD by a scanning mechanism. That is, the two-dimensional image of the document surface is converted into a line image signal by this main / sub scanning.
The document read by the scanner may be a sheet or a book. The sheet may be a single sheet or a bundle of a plurality of sheets. Further, there are cases where both front and back sides of a sheet original are to be read. The image sensor is also related to the manuscript to be handled, and either a manuscript image is input via a reduction optical system or a contact type that is in direct contact with the manuscript surface and the image is inputted at a magnification of 1: 1. An image sensor (CIS) is used.

The scanner exemplified in the present embodiment has a configuration that can handle the above-described various documents, and includes a mode in which a book or sheet document is placed on a platen glass for reading, and a sheet document bundle placed on a document tray. A mode in which the document is fed one by one by the ADF 15 and the document is read in the middle of conveyance, and a CIS (contact image sensor) is provided in the conveyance path of the ADF, and the other side of the sheet document is read by this CIS. The reading operation in each mode is possible.
FIG. 10 is a diagram showing a schematic configuration of the scanner of the present embodiment.
The image reading apparatus shown in FIG. 10 includes a moving mechanism that moves a reading carriage (first carriage 174, second carriage 176) relative to a document (not shown) placed on a contact glass 180 as a scanning mechanism. And a mechanism (ADF15) for moving the document relative to the stationary reading system. Further, as a reading system, an optical system including a transmission system (mirror group) and a reduction optical system (lens 178), a system using a CCD 111 that receives a document image formed by the optical system, and a conveyance path of the ADF 15 are provided. And a system using CIS135.

With the above configuration, in the flat bed reading mode (reading a document placed on the contact glass 180) mode, the light source (xenon lamp) is moved while changing the position in the sub-scanning direction by moving the first carriage 174 and the second carriage 176. ) 110 illuminates the document surface, and the reflected light from the original passes through the first, second, and third mirror groups, passes through the lens 178, and is placed on the CCD 111 mounted on the SBU (Sensor Board Unit) substrate. Imaged and photoelectrically converted.
In the sheet-through ADF reading mode, the originals stacked on the original tray 151 of the ADF 15 are sent one by one toward the paper discharge tray 152 via the pickup roller 153 and the conveyance drum 154, and the reading window 181 opened in the conveyance path. Is read by a reading system shared with the flat bed reading while feeding (sub-scanning) through this window. At this time, the reading system uses the first carriage 174 and the second carriage 176 locked in the reading position (FIG. 17 is in the locking position). However, the reading operation similar to the above flatbed reading is performed except for locking.

In the CIS reading mode, a document image is read by the CIS 135 provided in the conveyance path of the ADF 15. At this time, as shown in FIG. 10, the CIS 135 reads the back image while the above-described sheet-through ADF reading (using the reduction optical system of the lens 178) is the front side of the document.
Further, by enabling a reading operation in which the front side image reading by the sheet-through ADF reading and the back side image reading by the CIS reading are performed in one pass, it is possible to read both sides almost simultaneously although there is a difference in reading position.
For both the image sensor of the CCD 111 and the CIS 135, the sensor output is subjected to shading correction (detailed later). Data used for this correction is obtained by reading a white reference with an image sensor. In the scanner of FIG. 10, a reference white plate 182 is provided as a white reference for the CCD 11. Also, for the CIS 135, a roller that is arranged opposite to the sensor and guides the document is a white roller 137, and the roller surface is used as a white reference.

Here, a processing system of a read image signal and a scanner (image reading unit 2) control system in the image reading apparatus of the present embodiment will be described.
FIG. 11 is an overall block diagram mainly showing a processing system for a read image signal and a scanner control system.
The CPU 101 of the processing / control system (hereinafter referred to as a scanner IPU control unit) shown in FIG. 11 executes a program stored in the ROM 102 and reads / writes data and the like in the RAM 103 to control the entire scanner IPU control unit. Is going.
The CPU 101 is connected to the system control unit 104 (corresponding to the system control unit 1 in FIG. 1) by serial communication, and performs an operation instructed by transmission / reception of commands and data.
The system control unit 104 is connected to the operation display unit 105 by serial communication, and can set an instruction such as an operation mode by a key input instruction from a user (see the above description regarding the system control unit 1 in FIG. 1). ).

The system control unit 104 transmits and receives commands and data to the ADF control unit 133 connected by serial communication, and causes the operation according to the command to be performed.
The ADF control unit 133 controls the entire ADF 15 including the CIS 135. The CPU 138 in the ADF control unit 133 uses the RAM 140 as a work memory for processing data necessary for the control operation, and is a control program stored in the ROM 139. Etc.
By connecting to the ADF_I / O 134, the CPU 138 transmits the detection results of the sensors such as the conveyance motor, paper feed motor, various clutches in the ADF, sensors such as the registration sensor, the conveyance sensor, and the paper discharge sensor to the system control unit 104. The ADF 15 is controlled in accordance with an instruction from the system control unit 104.
In the CPU 138, the output of the white roller rotation position detection sensor 170 and the line synchronization signal (XSLSYNC) of the CIS unit (detailed later) 135 are respectively input to the interrupt input terminal of the CPU. The CIS reading is controlled by sending an XSLEAD signal indicating the shading capture range and an XSSCAN signal indicating the reading range to the CIS unit 135 side. Each signal is synchronized with the line synchronization signal (XSLSYNC), and the XSLEAD signal becomes the XSHGATE signal and the XSSCAN signal becomes the XSFGATE signal. In addition, since the point regarding the shading correction of the CIS read image is a characteristic part of the scanner of this embodiment, it will be described in detail later.

On the other hand, the CPU 101 is connected to a document detection sensor, HP (home position) sensor, pressure plate (contact glass 180 cover) opening / closing sensor, cooling fan, etc. as 1 / O106. The operation is controlled.
The scanner motor driver 107 is driven by the PWM output from the timing circuit 112, generates an excitation pulse sequence, and drives the pulse motor 108 for document scanning drive.
In the reading system using the reduction optical system (lens 178), the original image is illuminated by the halogen lamp 110 driven under the lamp regulator 109, and the reflected light from the original surface passes through the transmission mirror group and the lens 178 and passes through the CCD 111. The image on the original surface is read by forming an image on the light receiving surface.

The CCD 111 is a three-line type for color, and a driving clock is given to each line by the timing circuit 112 on the scanner IPU control unit, and is denoted as red, green, blue (hereinafter referred to as “R”, “G”, and “B”, respectively). ) Analog image signals of each odd field (hereinafter referred to as “ODD”) and even field (hereinafter referred to as “EVEN”) are output to the emitter followers 113 to 115.
Analog outputs from the emitter followers 113 to 115 are input to the analog processing circuits 116 to 118, respectively, a subtraction method CDS is executed in the analog processing circuit, line clamping is performed by detecting the optical black portion of the CCD, and ODD and EVEN Each amplifier gain adjustment is performed to correct the output difference.
After gain adjustment, the signals are combined by a multiplexer, and finally, after the DC level offset adjustment (detailed in the operation of the phase adjustment mode described later), the R, G, and B signals are converted into RGB A / D converters ( (Hereinafter referred to as [ADC]) 119-121.

The R, G, and B analog signals input to the ADCs 119 to 121 are digitized and input to the shading correction circuit 122. The shading correction circuit 122 has a function of correcting unevenness in the amount of light in the illumination system and variations in pixel output of the CCD 111.
The shading-corrected image data is input to the inter-line correction memories 123 and 124, and the image data of the number of lines B and G and B and R of the 3-line CCD 111 is delayed by the memory to read the B, G, and R read image signals. Are aligned to one or more lines and output to the dot correction circuit 125.
In the dot correction circuit 125, the image data output from the inter-line correction memories 123 and 124 is corrected for dot deviation within one line of R, G, and B data.
Next, with the scanner γ correction 126, correction data is obtained by applying reflectance linear data for each color in a lookup table method.

The image data after γ correction is input to the RGB filter, color conversion process, scaling process, and create process circuit 130 via the automatic document color determination circuit 128, the automatic image separation circuit 129, and the delay memory 127.
The automatic document color determination circuit 128 performs ACS (chromatic / achromatic determination) processing, that is, determination of black and gray. The automatic image separation circuit 129 also performs edge determination (determined by the continuity of white and black pixels), halftone determination (determined by the repetitive pattern of peak / valley peak pixels in the image), and photo determination (character / halftone dot). If there is image data outside), the area of the character and print (halftone dot) part and the photograph part is determined and transmitted to the CPU 101, and the subsequent RGB filter, color conversion, printer gamma correction, YMCK filter, gradation processing Used to switch parameters and coefficients.

The R, G, B image data that has passed through the delay memory 127 is input to the RGB filter of the RGB filter, color conversion process, scaling process, and create process circuit 130.
The RGB filter performs processing such as R, G, and B MTF correction, smoothing, edge enhancement, and through by switching and setting filter coefficients in accordance with the determination result of the previous region.
In the subsequent color conversion processing circuit, YMCK conversion, UCR, and UCA processing are executed from the R, G, and B data.
Further, enlargement / reduction processing is executed on the main-scan image data input to the scaling processing circuit. After this processing, the image data is branched, and a part of the branched image data is input to the image display unit 132 via the I / F. By doing so, the read image can be displayed on the LCD panel (see FIG. 3) of the image display unit 132 in the color copying machine, and the read result can be monitored.

The create processing circuit performs create editing and color processing. In create editing, italics, mirroring, shadowing, hollowing processing, etc. are executed. In color processing, color conversion, specified color deletion, undercolor processing, and the like are performed.
The write processing circuit 131 such as printer γ correction and YMCK filter sets coefficients used for printer γ conversion and YMCK filter based on the determination of the previous area. Dither processing is performed in the gradation processing included in the writing processing, and test timing generation such as writing timing setting, image area, white area setting, gray scale and color patch can be performed in the video control. The image data is written so that it can be output to an LD (laser diode) and output to the LD.
The processing in each functional block is executed by performing setting and operation of each processing by a program stored in the ROM 102 connected to the CPU 101 in accordance with an instruction from the system control unit 104.

The CIS unit 135 shown in FIG. 11 will be described.
The CIS unit 135 is related to a system for reading the back side of a document using a contact image sensor, and is a light source (not shown) such as LED, SLA (Selfoc (registered trademark) lens array), sensor element, ADC, digital processing (output level adjustment and Processing such as shading correction). The CIS unit 135 also receives a command and a driving clock from the ADF control unit 133 and reads image data.
Image data output from the CIS unit 135 is input to the subsequent image processing unit 136 by LVDS (Low Voltage Differential Signaling). In the image processing unit 136, processing equivalent to the image processing functions 127 to 131 of the reduction optical system detected by the CCD 111 described above is performed, and the image is written to the LD where image writing is performed by the image writing unit 4.

FIG. 12 is a block diagram showing the CIS unit of FIG. 11 in more detail, and mainly shows the processing system of the read image signal.
The original illuminated by the light source (1) 155 and the light source (2) 156 is imaged on the R, G, and B line sensors 141, 142, and 143 at the same magnification by an SLA (not shown). The R, G, and B line sensors are arranged in RGB order in the sub-scanning direction, and here, an example of an interval of two lines is shown. Each RGB line sensor is divided into a plurality of chips (3 chips) of channels (8 ch) and each 8 ch ADC (for R, G, B) 144, 145, 146 is processed in parallel for each of the plurality of chips as digital image data. The data is input to the data rearrangement processing circuit 147.
The data rearrangement processing circuit 147 converts each color parallel data into serial data of one line of each RGB color.
Image data serially processed in one line is input to a shading correction circuit 148 to correct non-uniform light quantity and sensor pixel output variation in the illumination system.
The image data after the shading correction is passed through the interline correction circuit 150 having the RB data bus switching circuit (1) 149 and the RB data bus switching circuit (2) 151 in the previous stage and the subsequent stage (the operation of switching the RB data bus will be described later). To do).
The output after line-to-line correction is input to the image correction processing circuit 152, and the image correction processing circuit 152 having an internal configuration shown in FIG. To the processing unit on the main body side shown.

  As shown in FIG. 12B, the image correction process 152 includes a dot correction circuit 157, a joint correction circuit 158, a scanner γ correction circuit 159, and a color correction circuit 160. These processes are performed by the CIS unit. By performing within 135, it becomes possible to perform image correction processing peculiar to CIS, and further image quality can be improved. The dot correction circuit 157 corrects the deviation of dots within one line that cannot be corrected by interline correction. Since the joint correction circuit 158 has a plurality of sensor chips arranged on the CIS structure to constitute the entire sensor, a gap of one pixel is left between the chips. This process corrects one pixel in the gap from the image data at both ends of the chip. The scanner γ correction circuit 159 corrects the reflectance linear data for each chip or each pixel using a lookup table method. The color correction circuit 160 performs correction for each chip or each pixel using a three-dimensional lookup table. The CIS control unit 154 performs control related to the entire CIS unit 135 such as light source control of the light sources (1) 155 and (2) 156, control of each correction processing circuit, serial communication with the ADF control unit 133, and the like.

The RB data bus switching for line-to-line correction performed in the CIS unit 135 will be described.
When the arrangement of the R, G, and B line sensors 141, 142, and 143 in FIG. 12 is indicated as the document conveyance direction (1) and the image data is read in the order of R → G → B indicated by the downward arrow, RB The data bus switching circuit (1) 149 sends image data in the direction indicated by the solid line. That is, in this operation, the image data is in a through state and is not switched. Accordingly, in the inter-line correction circuit 150, since the line interval is 2 lines, R data is delayed by 4 lines in the inter-line correction memory 1 and 2 lines are delayed in the inter-line correction memory 2 for G data. It can be a line reading. The RB data bus switching circuit (2) 151 sends image data in the direction indicated by the solid line. Also in this case, the image data is through and is not switched.
On the other hand, when the arrangement of the R, G, and B line sensors 141, 142, and 143 in FIG. 12 is indicated as the document conveyance direction (2) and the image data is read in the order of B → G → R indicated by the upward arrow. The RB data bus switching circuit (1) 149 sends image data in the direction indicated by the dotted line. That is, in this operation, the image data bus is switched by a selector circuit (not shown), and R data is switched to the B input of the interline correction circuit 150 and B data is switched to the R input of the same circuit. Accordingly, since the line interval is 2 lines in the inter-line correction circuit 150, the same line of RGB is read by delaying 4 lines in the inter-line correction memory and 2 lines in the G data for the B data. In this case, the RB data bus switching circuit (2) 151 is switched by a selector circuit (not shown) in the direction indicated by the dotted line. By this switching, RGB input appropriate for the subsequent image correction processing can be performed.

Although the above shows the correction value between lines at the same magnification, the line is set according to the conveyance speed at the time of zooming. For example, when the magnification is 200%, the conveyance speed is ½ times the same magnification, and the same RGB is obtained by delaying 8 lines in the interline correction memory 1 and 4 lines in the interline correction memory 2 for G data. Line image data can be used.
Thus, when the enlargement magnification is increased, the memory between lines is increased according to the ratio. In the case of 50% reduction, the conveyance speed is double that of the same magnification. By delaying two lines in the interline correction memory 1 and delaying one line in the interline correction memory 2 with respect to G data, the same line of RGB is obtained. Image data.
In zoom zooming, a line shift within one line occurs. In this case, the dot correction circuit 157 needs to correct less than one line. For correction of less than one line, a value is calculated by performing interpolation processing from lines before and after the target line. By complementing and calculating by a cubic function convolution method, image data on the same RGB line can be output.
Further, the inter-line correction circuit 150 provided in the CIS unit 135 makes it significant that the color correction circuit 160 for correcting the color variation between chips for each chip or for each pixel is mounted in the CIS unit. By correcting the spectral distribution variation of the sensor filter that cannot be removed by the shading correction by this correction, it is possible to prevent the cause of image deterioration due to stripes and unevenness. Even if there is a variation from chip to chip due to a change in the lot of sensor filters, it can be corrected and high image quality can be achieved. In color correction, RGB data of the same line is required, so interline correction is required in order to perform color correction in the CIS unit.

Next, shading correction applied to CIS reading in the above-described scanner will be described.
A line image sensor that reads a document image has a variation element unique to the device such as non-uniformity of light quantity in an illumination system and variation in sensor pixel characteristics, and a change caused by such an element appears in a read signal of the line image sensor. In order to normalize the read signal of the line image sensor in which such a change has occurred, the read signal is subjected to shading correction. In this correction, the read signal from the sensor is adjusted by the correction data so that the read pixel data becomes a uniform white level output when the white reference plane is read by the line image sensor. As the correction data, image (pixel) data read by a line image sensor that should correct a white reference such as a reference white plate is obtained as shading correction data (hereinafter also referred to as “shading data”) and used for correction. .

In this scanner, as a white reference for the CCD 11, a reference white plate 182 is provided at a position away from the reading window 181 that is a reading position for ADF reading.
On the other hand, the white reference for the CIS 135 uses the roller surface of the roller itself that is disposed opposite to the CIS 135 fixed to face the document conveyance path and guides the document, and thus the roller is a white roller 137.
In the correction method using the white roller 137 as a white reference, if there is no document at the fixed reading position of the CIS 135, the CIS 135 can immediately read the roller surface of the white roller 137 and obtain shading data. The shading data can be acquired. In this respect, there is an advantage that the shading data can be acquired at a higher speed than the case where the reference white plate 182 is moved to a position where the reference white plate 182 is provided and read in the correction method using the reference white plate 182 as a white reference.

Next, the shading data generation process in the correction method using the white roller 137 as a white reference will be described.
As described above, the correction method using the white roller 137 as a white reference has an advantage that the shading data can be acquired at high speed. As an operation that takes advantage of this advantage, correction between documents is shortened in continuous reading of a plurality of documents. The merit can be further increased by performing in time and performing high-precision reading at high speed.
When the correction is executed, the CIS 135 reads the roller surface of the white roller 137 at a timing such as between the originals in continuous reading of a plurality of originals, for example, when there is no original at the reading position. Capture in a predetermined range and block with a predetermined number of lines. Furthermore, a generation process is performed in which shading correction data for each pixel is obtained through an averaging process for each block of a predetermined number of lines.

In this embodiment, as a process for generating the above-described shading correction data, the following process is executed as a basic process.
First, the CIS 135 reads the roller surface of the white roller 137 during the assertion period of the XSHGATE signal (signal indicating the shading capture range synchronized with the line synchronization signal XSLSYNC) determined according to the predetermined capture range. The white roller reading data is taken in as white reference data. That is, the assertion period of the XSHGATE signal is divided into m blocks for each L line valid data, and the white roller reading data is taken in. In the following description, the first block of the m block is expressed from the first block, and the first line in the m block is expressed from the first line.
Next, a simple average of the white reference data is obtained for the L lines in each block for each pixel, and the peak value among the simple average values obtained for each pixel in each of the m blocks is used as shading data. The peak value of each pixel described above does not have to be in the same block.

The processing process described above can be expressed by the following mathematical formula.
“Arithmetic expression in each pixel m block”
Dm (n) = INT [ΣD (n) / L]
Dm (n): Calculation data of the mth block of the nth pixel
First line in m block = (m−1) × L + 1
Last line in m block = m x L
D (n): nth pixel read data ΣD (n): D (n) 1 to L line addition value
L: Number of lines in one block
INT []: Rounding off the decimal point “Shading data detection method”
When Dp (n) <Dm (n)
Dp (n) = Dm (n)
When Dp (n) ≥ Dm (n)
Dp (n) = Dp (n)
Dp (n): n-th pixel shading data (peak value)
The first block
Dp (n) = Dm (n)
“Shading correction calculation”
Data after shading = (read data / (shading data-SBAEREF)) x 1023 (at 10bit)
In this shading correction calculation, a correction (SBAEREF) is subtracted from the shading data for correction. Shading data is generated during the XSHGATE signal assertion period, but if the XSHGATE signal is negated in the middle of the last block (if the number of lines set in the block is less than this), the shading data is calculated from the results up to the previous block. Is generated.

Next, an embodiment of the shading data generation means that generates shading data using the white reference data capture range and capture timing as control conditions in the above-described processing process will be described.
The white roller 137 used for acquiring the white reference data becomes dirty due to a change over time, and the white reference data read by the CIS 135 shows the stain as an error. Conventionally, in order to minimize the influence of dirt on the white roller, the XSHGATE signal is generated with a length of one rotation period or more of the white roller to generate shading data, and the XSHGATE signal is fixedly operated. . Therefore, if the shading correction operation is performed for each original in continuous reading of a plurality of originals, the speed-up is hindered (see the description of FIG. 17 below).

Therefore, in the first embodiment, the most suitable range of the white reference data does not exceed one rotation cycle of the white roller 137 and can be adapted to less than one rotation cycle, and a constant position of the roller circumference of the white roller 137 can be applied. The capture timing is determined so that the white reference data can be captured as the capture range. In this embodiment as well, it is assumed that the above-described basic processing process for shading data is adopted.
For this purpose, white roller rotation position detection means for detecting the rotation position of the white roller 137 is provided, and white reference data read by the CIS 135 within a predetermined range based on the position detection signal detected by the white roller rotation position detection means. Take in.

FIG. 13 is a diagram illustrating an example of a white roller rotation position detection sensor as a white roller rotation position detection unit. A white roller 137 shown in FIG. 13 has a light shielding plate 171 provided with a cutout at one position in the rotation direction on the rotation shaft, and detects the presence or absence of light shielding by the transmission type optical detection sensor 170. In the configuration shown, it is possible to obtain an output of a detection signal at a fixed position of one rotation of the roller.
Thus, since the rotation period signal of the white roller 137 is obtained, when this rotation period is divided into a plurality of parts, as shown in FIG. 14, (A) no division, (B) two divisions, (C) four divisions, (D) The area can be blocked by a variation such as eight divisions, and white reference data for each block area can be captured. Since the blocked area is determined by the number of lines based on the line synchronization signal XSLSYNC based on the rotation period signal of the white roller 137, the position on the roller circumference is fixed. Further, the size of the area can be set to an arbitrary size by changing the setting of the number of lines of the line synchronization signal XSLSYNC.

  Next, by counting the timings of the A, B, C, and D areas of the four-roller area from the detection signal of the white roller rotation position detection sensor 170, the line synchronization signal XSLSYNC is counted as set as the count value of the four-division condition The XSSCAN signal indicating the reading range is generated at the timing of each area, and the white reference data is captured. The white reference data can be captured by transmitting a capture position designation command to the CIS unit 135 by serial communication. The capture position designation command is obtained from the XSSCAN signal. The start area and capture area can be set with the count number of the XSLSYNC signal in the sub-scanning area and the pixel clock number in the main scanning area. This is a function for storing an average value in a register in the CIS unit 135, and a function associated with the shading correction function in the CIS unit 135. With this function, it is possible to capture shading data of designated areas of the A, B, C, and D areas.

The operation of the timing chart of FIG. 15 described above is at least one timing after the document reading operation is started immediately before the document reading operation is started when the image reading apparatus is turned on, and the time for generating the shading data is relatively sufficient. It is an action when it can be taken. That is, this is an operation at a timing when it is possible to obtain the shading data in each of the four divided areas of the capture range by setting the capture range of the white reference data as a range of one rotation cycle.
The following shading data generation operation is performed at a timing when sufficient time cannot be taken unlike when the power is turned on, as in the case of performing between documents at the time of continuous reading of the document. Will be described.

FIG. 16 is a timing chart for explaining the block formation and the capture timing of each block at the time of continuous reading. FIG. 16 shows an example in which the area of one rotation period of the white roller 137 is divided into four as in FIG.
The operation shown in FIG. 16 is an operation that realizes a high-speed operation while minimizing image degradation without taking in data for one rotation cycle or more of the white roller for the second and subsequent sheets during continuous reading of a document. This is an example when
The CPU 138 of the ADF control unit 133 that functions as a shading data generation unit receives the detection signal of the white roller rotation position detection sensor 170 and the line synchronization signal XSLSYNC from the CIS unit 135 by CPU interrupt input. In response to the detection signal of the white roller rotation position detection sensor 170, the white reference data read by the CIS 135 within one rotation period of the white roller 137 is taken in by the XSLEAD signal indicating the shading take-in range based on this detection signal. At this time, the XSLEAD signal is set by the count value of the synchronization signal XSLSYNC from the detection signal of the white roller rotation position detection sensor 170 as virtual white data capture timing.

The CPU 138 of the ADF control unit 133 counts the line synchronization signal XSLSYNC from the detection signal of the white roller rotation position detection sensor 170, so that the set virtual white data capture timing area is any of A, B, C, and D. The XSSCAN signal in the designated area (C area in the example of FIG. 16) is generated, white reference data is taken in, and the average value is stored as shading data in a register in the CIS unit 135.
In this shading data generation operation, the difference between the value written in the register in the C area stored in the previous generation operation (the operation in FIG. 15) and the value written in the register in the current operation is calculated as the above-mentioned “shading correction”. By storing in SBAEREF, which is a correction value of the shading correction calculation formula shown in “Calculation”, and executing the calculation, shading correction over the entire region can be performed.

As a shading data generation operation performed between originals during continuous reading of an original, according to a conventionally used method, white reference data fetching and original image reading are performed at the timing shown in FIG. Is called.
That is, an XSLEAD signal that is equal to or more than one rotation period of the white roller is output from the ADF control unit, a process of generating shading data based on the acquired white reference data is performed, and the obtained data is held in a register. Thereafter, the XSSCAN signal is output from the ADF control unit in accordance with the ADF document conveyance, and the document image is read. The same control as the first sheet is performed for the second and subsequent sheets. At this time, as shown in FIG. 17, even after the second continuous reading, shading data generation processing is performed based on white reference data equal to or more than one rotation cycle of the white roller, which is the same as that of the first sheet. This was an obstacle to speeding up the interval. Also, the white roller rotation position is not detected.
Compared to such a conventional technique, according to the shading data generation operation performed between the continuously-read originals shown in the above embodiment, the generation operation is shortened by taking in the white reference data of a part of the block and generating the shading data. This can be done in time and does not reduce the speed of the reading operation. In addition, since the white reference data taken from a part of the block is taken in a certain range of the roller circumference of the white roller, variation in the reading value of the white roller can be suppressed, and the accuracy of the shading data can be maintained. .

In this embodiment, as described above, when power is supplied to the image reading apparatus, when the operation for generating shading data is performed immediately before the start of the document reading operation or after the document reading, the white roller 137 corresponds to one rotation cycle. Although the operation of taking in the white reference data is performed, if the shading correction that can omit this take-in operation can be performed, the continuous reading of the document can be further accelerated.
Therefore, the white roller 137 is read at the time of initial setting (factory shipment), and the obtained white reference data and the average value of the white reference data of each block after block formation are taken into the nonvolatile memory 165 of the CIS unit 135 and input. deep.
In this way, in the shading data generation operation performed every time, it is only necessary to perform the remaining correction calculation necessary for the shading correction by using the shading data fetched into the nonvolatile memory 165, and in the continuous reading of the document. Even if the distance between documents is short, it is possible to cope with it, and the speed can be further increased.

As an example of the white roller rotation position detection means, an example (FIG. 13) is shown in which the light shielding plate 171 is first provided on the rotation shaft and the light detection is detected. Next, the white roller rotation position detection means. As another embodiment, an example will be shown in which the above-described optical detection sensor 170 is not required to be newly provided.
In this embodiment, the rotation position of the roller is detected from an image signal obtained by reading the marking on the roller surface of the white roller 137 with the CIS 135.
FIG. 18 shows different shapes of markings applied to the roller surface of the white roller 137 in this embodiment, and explains the relationship between the markings and the areas A, B, C, and D of the white reference data capture range to be blocked. It is a figure to do.

Example 1 in FIG. 18 is a method of drawing the diagonal line marked as marking 1 on the white roller 137 for one round, and depending on where in the main scanning pixel position the image of the diagonal line comes, , C, D castle can be determined.
Example 2 is a method of forming a triangular mark indicated as marking 2 on the white roller 137, and by detecting the width of the marking in the main scanning direction, each A, B, C, D region of the capture range Can be determined. Since this method is based on the detection of the width, there is an advantage that even if there is a backlash on the main scanning side of the roller, it is not affected.
Example 3 is a method of forming a mark with a different marking width for each region marked as marking 3 on the white roller 137, and by detecting the marking width in the main scanning direction, each of the capture ranges A and B , C and D regions can be determined. This method fixes the number of regions, but the region determination accuracy is improved.

The second embodiment described below relates to a mode in which the shading data generation operation (see the timing charts in FIGS. 15 and 16) shown in the first embodiment is adapted to ADF double-sided simultaneous reading.
The scanner of this embodiment shown in FIG. 10 can simultaneously read both sides of a document in ADF reading. When reading both sides, the front side is read by a reading system using a CCD 111 and the back side is read by a reading system by a CIS 135.
In the reading system based on the CIS 135 that reads the back surface, the generation operation shown in the first embodiment can be performed to generate the shading data. On the other hand, in the reading system using the CCD 111 that reads the surface, it is an existing method, but white reference data is obtained by reading the reference white plate 182 as a white reference.

However, since the reading system by the CCD 111 used for ADF reading is shared with flat bed reading (reading an original placed on the contact glass 180), when obtaining white reference data, it is used fixedly when reading an ADF original. It is necessary to move the reading system to the position of the reference white plate 182 to perform reading, and this requires time.
Therefore, when the shading data generation operation is performed on the reading system side by the CCD 111 that reads the front surface, the reading system side by the CIS 135 that reads the back surface requires a short operation time but may reduce the accuracy as shown in FIG. There is no need to take action. Therefore, in such a case, the shading data is generated using the operation method shown in FIG.

FIG. 19 is a timing chart for explaining the timing of taking in the white reference data and the document image reading operation when the above-described operation method is used in the ADF double-sided simultaneous reading. This figure shows a state during a continuous reading operation of a document.
When the shading data generation operation is performed every time on the reading system side by the CCD 111 that reads the surface, the reference white plate 182 is read each time the original image is not read in the chart (2) representing the surface reading operation in FIG. Therefore, a reciprocating operation of the carriage is performed, and while the carriage moves, the reference white plate 182 is read by the CCD 111 and white reference data is taken in.
Further, in the chart representing (1) back surface reading operation in FIG. 19, (2) the white roller 137 is read and white reference data is taken in using the time during which the carriage reciprocates in the front surface reading operation. Since this reading time is sufficient, white reference data for one rotation period of the white roller 137 can be captured.
In addition, since the high accuracy of the shading correction is ensured by acquiring the white reference data for one rotation period of the white roller 137, this mode can be set as the initial capture mode. If the surface is shaded every time, the initial capture mode will be repeated.

As described above, when the surface reading system performs the shading data generation operation every time, in order to increase the productivity of continuous reading (number of read originals per unit time), the surface is intermittently shaded. If the white reference data for one rotation period of the white roller 137 is fetched on the back side as described above and all blocks are processed, the processing time for this time will cause a decrease in productivity. Conceivable.
Therefore, even if the front surface side performs intermittent shading, the operation method as shown in FIG. 16 which requires only a short processing time on the back surface side can cope with high speed while maintaining accuracy.

FIG. 20 is a timing chart for explaining the timing of taking in white reference data and the continuous reading operation of a document when the above-described operation method of performing intermittent shading on the front side in ADF double-sided simultaneous reading is used.
When the shading data generation operation is intermittently performed on the reading system side by the CCD 111 that reads the surface, (2) in the chart representing the surface reading operation in FIG. For this reason, the carriage is reciprocated to read the reference white plate 182, and while the carriage moves, the CCD 111 reads the reference white plate 182 and takes in the white reference data.
Further, in the chart representing (1) back surface reading operation in FIG. 20, (2) the white roller 137 is read and the white reference data is taken in using the time during which the carriage reciprocates in the front surface reading operation. Since this reading time is sufficient, white reference data for one rotation period of the white roller 137 can be captured.

When there is no instruction for generating shading data on the front side in intermittent shading, the operation of reading the reference white plate 182 is not performed, and the document image reading is at a fast timing.
For this reason, on the back side, sufficient time cannot be taken to perform the operation of generating shading data by taking in the white reference data for one rotation period of the white roller 137. Therefore, at this time, as shown in the example of the operation of capturing only the C area in the chart representing the (1) back surface reading operation in FIG. 20, a part of the divided capturing range that can be processed in a short time. 16 is used as a processing area to generate shading data (this operation mode is referred to as an original reading capture mode).
Thus, by having the initial capture mode and the document reading capture mode, it is possible to realize high speed and high image quality.

When there is no instruction for generating shading data on the front side in intermittent shading, the operation of reading the reference white plate 182 is not performed, and the document image reading is at a fast timing.
For this reason, on the back side, there is not enough time to perform the shading data generation operation by taking in the white reference data for one rotation period of the white roller 137. Therefore, at this time, as shown in the example of the operation of capturing only the C area in the chart representing the (1) back surface reading operation in FIG. 20, a part of the divided capturing range that can be processed in a short time. 16 is used as a processing area to generate shading data (this operation mode is referred to as an original reading capture mode).
Thus, by having the initial capture mode and the document reading capture mode, it is possible to realize high speed and high image quality.

Next, another example of the shading data generation operation performed by the CIS reading system on the rear surface side in the case where the front surface side performs intermittent shading in the ADF double-sided simultaneous reading as described above (FIG. 20) will be described.
When the surface is intermittently shaded in order to increase the productivity of continuous reading, if the white reference data for one rotation period of the white roller 137 is taken in on the back side as described above and all blocks are processed. Since the processing time for this is a cause of lowering the productivity this time, an operation method that requires a short processing time on the back side is adopted.
In the operation example of FIG. 20 described above, as shown in the operation example of capturing only the C region, an operation method (see FIG. 16) in which a part of the divided capture range is used as a processing region is employed. Even when the front side performs intermittent shading and the reading operation of the reference white plate 182 is not performed and the original image is read quickly, white reference data is captured as much as possible in the generation operation of the shading data on the back side. In this way, it is possible to cope with high speed while maintaining accuracy.

FIG. 21 is a timing chart for explaining the timings of taking in white reference data and continuous reading operation of a document when the above-described operation method for performing intermittent shading on the front side in ADF double-sided simultaneous reading is used.
When the shading data generation operation is inconsequentially performed on the reading system side by the CCD 111 that reads the surface, it is instructed while the original image is not read in the chart representing the surface reading operation in (2) in FIG. The carriage reciprocates in order to read the reference white plate 182 only when the reference white plate 182 is read by the CCD 111 and the white reference data is taken in while the carriage moves.
Further, in the chart representing (1) back surface reading operation in FIG. 20, (2) the white roller 137 is read and the white reference data is taken in using the time during which the carriage reciprocates in the front surface reading operation. Since this reading time is sufficient, white reference data for one rotation period of the white roller 137 can be captured.

When there is no instruction for generating shading data on the front side in intermittent shading, the operation of reading the reference white plate 182 is not performed, and the document image reading is at a fast timing.
For this reason, on the back side, sufficient time cannot be taken to perform the operation of generating shading data by taking in the white reference data for one rotation period of the white roller 137. Also at this time, in this embodiment, as shown in (1) the back surface reading operation chart in FIG. 20, the white reference data is taken in less than one rotation cycle, so that the next document The white reference data is captured to the limit that shading data can be generated before reading is started, and shading data is generated.
In the example shown in FIG. 21 of this embodiment, the white reference data is taken in based on the detection signal of the white roller rotational position detection sensor, but it is taken in for one rotation cycle or less than one rotation cycle. In either case, the document image reading operation (control) signal may be determined as a reference.
High speed and high image quality can be realized by performing shading correction using the white reference data obtained by the above operation.

1 is a diagram showing an outline of the overall configuration of a color copying machine according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of an operation panel of the color copying machine shown in FIG. 1. FIG. 2 is a functional block diagram showing a circuit configuration of an image display unit of the color copying machine shown in FIG. 1. It is a figure which shows an example of the LCD panel of the image display unit shown in FIG. It is a figure which shows an example of the input screen displayed on the LCD panel shown by FIG. It is a figure which shows an example of the screen expansion | deployment by pressing down the scaling key on the input screen shown by FIG. It is a figure which shows one example of a structure of a touchscreen detection circuit. It is a figure showing the setting state of the electric potential of each electrode of X and Y of a touch panel in the detection circuit of FIG. It is a figure which shows an example of the circuit structure of the operation part unit in a color copying machine (FIG. 1) with a functional block. It is a figure which shows the image reading apparatus concerning this embodiment in which the operation | movement of CIS reading and sheet through ADF reading is possible. It is a figure which shows the whole block which mainly shows the processing system of a read image signal, and a scanner control system. It is a block diagram which shows the internal structure of a CIS unit (FIG. 11). It is a figure which shows the structure of the rotation position detection means of a reference | standard white roller. It is a figure which shows the example of a division | segmentation of the rotation period of a white roller. It is a timing chart explaining block formation of white reference data, and taking-in timing of each block. It is a timing chart for explaining white reference data blocking and fetching timing of each block (at the time of continuous reading). 10 is a timing chart for explaining the timing of taking in white reference data and the timing of a document image reading operation (conventional example). It is a figure which shows the other structure of the rotation position detection means of a reference | standard white roller. 6 is a timing chart for explaining white reference data fetching and document image reading operation timing (at the time of front and back reading operation). 10 is a timing chart for explaining another example of white reference data fetching and timing of document image reading operation (at the time of front and back reading operation). 10 is a timing chart for explaining another example of white reference data fetching and timing of document image reading operation (at the time of front and back reading operation).

Explanation of symbols

  1 .... System control unit 2 .... Image reading unit 3 .... Image processing unit 4 .... Image writing unit 5 .... Operation unit 7 ... Image display unit 15 .... ADF (automatic document) Feed device), 46 .. print start key, 50 .. touch panel key, 51 .. initial setting key, 101, 138 .. CPU, 104 .. system control unit, 105 .. operation display unit, 110. Xenon lamp), 111 ... 3 line CCD (image sensor), 133 ... ADF control unit, 135 ... CIS (CIS unit), 137 ... standard white roller, 151 ... document tray, 152 ... discharge tray 154 ··· Conveying drum, 157 ··· Discharge roller, 170 ··· White roller rotation position detection sensor, 180 ··· Contact glass, 181 ··· Reading .

Claims (14)

An image sensor for reading an image in a line scanning format in the main scanning direction at a reading position on the document conveyance path;
A feed roller for guiding a document conveyed in the sub-scanning direction to the reading position, a white roller having a roller surface as a white reference for shading correction;
Correction data generating means for generating shading correction data based on white reference data obtained by the image sensor reading the white roller;
An image reading apparatus having a shading correction unit that performs shading correction on correction data generated by the correction data generation unit for image data obtained by reading a document with the image sensor,
A white roller rotation position detecting means for detecting the rotation position of the white roller;
The correction data generation means takes in white reference data read by the image sensor within a predetermined range based on the position detection signal detected by the white roller rotation position detection means, blocks the predetermined number of lines, and An image reading apparatus characterized in that an average value of the number of lines is obtained for each white reference data, and a maximum value among the obtained average values of each block is generated as shading correction data. The image reading apparatus according to claim 1,
The image reading apparatus, wherein the correction data generation means captures white reference data for each block and stores the captured white reference data for each block. The image reading apparatus according to claim 2,
The correction data generation means captures and captures white reference data over one rotation period of the white roller at least at one timing after the document reading operation, at the start of the document reading operation, when the image reading apparatus is turned on. An image reading apparatus that accumulates white reference data and generates shading correction data based on the white reference data of each block accumulated before reading a document image. The image reading apparatus according to claim 2,
The correction data generating means takes in white reference data for one rotation period or more of the white roller at the time of initial setting of the image reading apparatus, and accumulates the taken white reference data in a nonvolatile storage means, whereby a document image An image reading apparatus that generates shading correction data based on white reference data of each block accumulated in the non-volatile storage unit before reading. The image reading apparatus according to any one of claims 1 to 4,
The image reading apparatus according to claim 1, wherein the white roller rotation position detection means is means for outputting a position signal by detecting light shielding by a member attached to the white roller shaft. The image reading apparatus according to any one of claims 1 to 4,
2. The image reading apparatus according to claim 1, wherein the white roller rotation position detecting means is a means for outputting a position signal by reading the marking on the roller surface of the white roller with the image sensor. The image reading apparatus according to any one of claims 1 to 6,
The correction data generation means performs a first correction data generation mode in which a range for capturing white reference data is set to be equal to or greater than one rotation cycle of the white roller, or a range for acquiring white reference data is a rotation cycle of the white roller. An image reading apparatus that executes a second correction data generation mode performed for less than a minute according to a setting. An image sensor for reading an image in a line scanning format in the main scanning direction at a reading position on the document conveyance path;
A feed roller for guiding a document conveyed in the sub-scanning direction to the reading position, a white roller having a roller surface as a white reference for shading correction;
Correction data generating means for generating shading correction data based on white reference data obtained by the image sensor reading the white roller;
An image reading apparatus having a shading correction unit that performs shading correction on image data obtained by reading an original with the image sensor using correction data generated by the correction data generation unit,
The correction data generating means takes in the white reference data read by the image sensor within a predetermined range, blocks it with a predetermined number of lines, calculates an average value of the number of lines for the white reference data for each block, and calculates each block obtained Is a means for generating the maximum value among the average values of the image data as shading correction data, and when the power to the image reading apparatus is turned on, the range in which the white reference data is captured at the timing immediately after the document reading operation is started, immediately after the document reading operation is started. The first correction data generation mode that is performed for one rotation cycle or more of the white roller, or the second correction data generation that is performed by setting the range in which the white reference data is taken during document image reading to be less than one rotation cycle of the white roller An image reading apparatus that executes a mode according to a setting. In the image reading apparatus according to claim 7 or 8,
The image sensor is a back image reading means in a configuration capable of simultaneously reading both sides of a document,
The correction data generation means defines an acquisition range of white reference data in the second correction data generation mode as a range that can be acquired within a document reading interval of the surface image reading means. . In the image reading apparatus according to claim 7 or 8,
The image sensor is a back image reading means in a configuration capable of simultaneously reading both sides of a document,
2. The image reading apparatus according to claim 1, wherein the correction data generation means captures the white reference data in the first correction data generation mode within the white reference data capture time of the intermittent shading correction in the surface image reading means. An image forming apparatus comprising: an image input unit; an image processing unit that converts an input image into image formation data; and an image formation unit that forms an image based on the image formation data.
An image forming apparatus using the image reading apparatus according to claim 1 as the image input unit. A step of reading an image in a line scanning format in a main scanning direction at a reading position on an original conveyance path by an image sensor;
A step of guiding a document conveyed in the sub-scanning direction to the reading position with a white roller having a roller surface as a white reference for shading correction;
A correction data generation step of generating shading correction data based on white reference data obtained by the image sensor reading the white roller;
An image reading method comprising a shading correction step of performing shading correction on the image data obtained by reading a document by the image sensor with the correction data generated in the correction data generation step,
A white roller rotation position detection step for detecting the rotation position of the white roller;
In the correction data generation step, the white reference data read by the image sensor in a predetermined range based on the position detection signal detected in the white roller rotation position detection step is taken, and is blocked at a predetermined number of lines. An image reading method characterized in that an average value of the number of lines is obtained for the white reference data and a maximum value among the obtained average values of each block is generated as shading correction data. A step of reading an image in a line scanning format in a main scanning direction at a reading position on an original conveyance path by an image sensor;
Guiding a document conveyed in the sub-scanning direction with a white roller having a roller surface as a white reference for shading correction, to the reading position;
A correction data generation step of generating shading correction data based on white reference data obtained by the image sensor reading the white roller;
A shading correction step of performing shading correction on the image data obtained by reading the document by the image sensor with the correction data generated in the correction data generation step,
In the correction data generation step, the white reference data read by the image sensor is captured in a predetermined range, is blocked in a predetermined number of lines, and an average value of the number of lines is obtained for the white reference data for each block, and each obtained block A range in which the white reference data is captured at the timing after the document reading operation is generated immediately before the start of the document reading operation when the image reading apparatus is turned on, when the maximum value of the average value is generated as the shading correction data. A first correction data generation mode that is performed for at least one rotation cycle of the roller, or a second correction data generation mode that is performed by setting the range in which the white reference data is captured during document image reading to be less than one rotation cycle of the white roller. An image reading method, which is executed according to a setting. An image forming method comprising: an image input step; an image processing step for converting an input image into image formation data; and an image formation step for forming an image based on the image formation data.
15. An image forming method using the image reading method according to claim 12 or 14 as the image input step.

Images