Patent Publication Number: US-8976430-B2

Title: Document reader

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a document reader. 
     2. Description of the Related Art 
     In related art document readers, shading correction is performed to a read image using shading correction data in order to reduce variation (“shading”) in the amount of light received along the longitudinal direction (i.e., the main scanning direction) of a linear sensor which reads a document. The shading correction data is generated in accordance with read luminance distribution in the main scanning direction in which a white component is read before the reading of the document is started. Usually, control is made to read the document after the generation of the shading correction data in response to a user instruction to start reading of the document. Recently, a method of starting generation of the shading correction data including switching-on of a light source in response to a user manipulation with which an instruction to start reading of the document other than an instruction to start reading of the document may be recognized in order to shorten the time to elapse before reading of the document is completed has been proposed (see the U.S. Patent Application Publication No. 2008/0278774). The user manipulation with which an instruction to start reading of the document may be recognized includes placing a document on a document table, an input operation other than the instruction to start reading of the document to a manipulation unit and closing a pressure board. 
     Recently, more compact automatic document feeders (hereinafter, “ADFs”) and increased document reading speed contribute shorter time to elapse before a document fed from a document tray of the ADF reaches a document reading point. Therefore, in an apparatus described in the U.S. Patent Application Publication No. 2008/0278774, generation of shading correction data is started in response to a user manipulation with which an instruction to start reading of the document may be recognized in order to shorten the time to elapse between an issue of a user instruction to start reading of the document and completion of reading of the document. 
     It is not always enough, however, to start generation of shading correction data in advance of an issue of the instruction to start reading of the document. Since reading ability of a linear sensor easily varies due to self temperature rise at the start of the driving of the linear sensor, it is not desirable to start generation of the shading correction data in advance of the instruction to start reading of the document in a case in which generation of the shading correction data is completed between an issue of the instruction to start reading of the document and reading of the document is started. This is because, in this case, image quality may be impaired due to variation in reading ability after the generation of the shading correction data without any shortening of the time between an issue of the instruction to start reading of the document and the completion of reading of the document. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention includes a feeding unit which feeds a document, a reading unit which reads the document which is being fed by the feeding unit across a reading point; a manipulation unit which receives an instruction regarding a document reading mode and an instruction to start reading of the document, and a generation unit which generates shading correction data from a read value of a reference member of the reading unit, wherein the generation unit selects, in accordance with the document reading mode received by the manipulation unit, a first mode in which generation of the shading correction data is started before the instruction to start reading of the document is issued or a second mode in which generation of the shading correction data is started after the instruction to start reading of the document is issued. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a document reader. 
         FIG. 2  is a control block diagram of the document reader. 
         FIG. 3  is an external view of a manipulation unit of a controller. 
         FIG. 4  is a control flowchart of the controller. 
         FIG. 5  illustrates a relationship between time to generate shading correction data and document feeding time. 
         FIG. 6  is a control flowchart of the document reader. 
         FIGS. 7A to 7C  are control flowcharts of the document reader. 
         FIGS. 8A and 8B  are timing charts illustrating a relationship among an instruction from the controller, feeding of a document and processing of a linear sensor. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  is a sectional view of a document reader  100  which includes an automatic document feeder (hereinafter, ADF) of an embodiment. In a document flow reading mode, the ADF feeds a bundle of documents placed on a document tray  1  one at a time and reads an image on the document while the document is being fed. First, a pickup roller  2  feeds the uppermost document of the bundle of documents placed on the document tray  1 . The documents fed by the pickup roller  2  are separated into one sheet by a separation roller  3  which is constituted by a feed roller  4  and a retard roller  5 . Each document is fed through a post-separation sensor  11  and a pre-resist sensor  14  by a drawing roller  6  and a feeding roller  13  until its leading end abuts a resist roller  15 . This configuration prevents oblique travelling of the documents. 
     The document which has passed the resist roller  15  is fed toward a document flow reading glass  51  and is fed to a platen upstream roller  16  and a platen roller  17 . The platen roller  17  is in contact with the document flow reading glass  51 . A front side of the document passing the platen roller  17  is illuminated with a light source  53 . Light reflected from the document is led to a front side CCD linear sensor  58  (“first reading unit”) through mirrors  54 ,  55  and  56  and a lens  57 , and an image on the front side of the document is read by a linear sensor  58 . The document fed by the platen roller  17  passes a platen downstream roller  18  and is fed to a reverse side reading roller  19 . The reverse side reading roller  19  is in contact with the moving glass  22 . A reverse side of the document passing the reverse side reading roller  19  is illuminated with the light source  21 . An image on the reverse side of the document is read by a reverse side CCD linear sensor  20  (“second reading unit”). The document fed by the reverse side reading roller  19  passes an output sensor  23  and is output onto a document output tray  25  by a paper ejecting roller  24 . In the document flow reading mode, as described above, one side of the document being fed across a reading point of the front side CCD linear sensor  58  is read by the front side CCD linear sensor  58  and the other side of the document being fed across the reading point of the reverse side CCD linear sensor  20  is read by the reverse side CCD linear sensor  20 . 
     A white component  60  is read by the front side CCD linear sensor  58  before the start of the document in order to generate shading correction data of the image on the front side. A white component affixed to a part of the moving glass  22  is read in order to generate the shading correction data of a white level of the image on the reverse side. In the fixed document reading mode, the image of the document placed on the pressure board glass  52  is read by the front side CCD linear sensor  58  while a front side reading unit  59  is moving to the right. 
       FIG. 2  is a control block diagram of a document reader. The document reader  100  is connected to a controller  200  and is provided with a CPU  12 , ROM  80  and RAM  90 . The controller  200  is provided in, for example, an electrophotographic image forming device and controls an image forming device and the document reader  100 . A control program is stored in the ROM  80 . Input data and data for operation are stored in the RAM  90 . The CPU  12  controls: a separation motor  37  which drives the pickup roller  2 , the feed roller  4  and the retard roller  5 ; a feed motor  38  which drives the drawing roller  6  and the feeding roller  13 ; and a lead motor  31  which drives the platen upstream roller  16 , the platen roller  17 , the platen downstream roller  18 , the reverse side reading roller  19  and the paper ejecting roller  24 . The CPU  12  controls an optical motor  40  which moves the front side reading unit  59 . Signals from the document detection sensor  7 , the post-separation sensor  11 , the pre-resist sensor  14  and the output sensor  23  are input to the CPU  12 . The CPU  12  performs light control of the light sources  21  and  53 . The image data read by the front side CCD linear sensor  58  and the reverse side CCD linear sensor  20  is temporarily stored in image memory  71  via an image processing unit  70 . 
     A CPU  101  of the controller  200  transmits and receives data regarding image reading control to and from the CPU  12  via a serial communication line. The image processing unit  70  of the document reader  100  transmits the image data to an image processing unit  102  via an image line. The data received from the document reader  100  is stored in image memory  103  of the controller  200 . An input operation by a user to the document reader  100  is performed on a manipulation unit  210  of the controller  200 . Data in accordance with the setting on the manipulation unit  210  is input to the CPU  101 . 
       FIG. 3  is an external view of the manipulation unit  210  of the controller  200 . The manipulation unit  210  is a liquid crystal display unit which includes a touch panel at the upper portion. Soft keys for the setting of the document reading mode and for the instruction to start reading of the document may be displayed on the liquid crystal display unit. When a full color key of a color/monochrome select key  300  is pressed, a color reading mode is selected and the document is read in a full color mode. When a monochrome key is pressed, a monochrome reading mode is selected and the document is read in a monochrome mode. When a single-side key of a single-side/double-side select key  301  is pressed, a single-side mode is selected. When a double-side key is pressed, a double-side mode is selected. When a high-speed feeding key of a feeding mode key  302  is pressed, a high-speed feeding mode is selected. When a silent feeding key is pressed, a low-speed feeding mode is selected. In the high-speed feeding mode, the document is fed to the reading point at a predetermined speed and, in the low-speed feeding mode, the document is fed to the reading point at a speed lower than the predetermined speed. When a start key  303  is pressed, reading of the document in the selected document reading mode is started. 
       FIG. 4  is a control flowchart of the CPU  101  of the controller  200 . The CPU  101  of the controller  200  initializes the mode select keys  300 ,  301  and  302  after the power supply is switched on (S 20 - 0 ). In the present embodiment, the color mode, the single-side mode and the high-speed feeding mode are set to the initial values. Next, whether or not a paper sheet exists is determined by the document detection sensor  7  of the document reader  100  (S 20 - 1 ). If it is determined that a paper sheet exists, it is determined whether or not the color/monochrome select key  300  is pressed (S 20 - 2 ). If the color/monochrome select key  300  has been pressed, then it is determined whether or not the color mode is selected (S 20 - 3 ). If the color mode has been selected, the CPU  12  of the document reader  100  is notified of the color mode as a document reading mode advance notice (S 20 - 4 ). If the monochrome mode has been selected by means of the color/monochrome select key  300 , the CPU  12  is notified of the monochrome mode as the document reading mode advance notice (S 20 - 5 ). 
     The CPU  101  then determines whether or not the single-side/double-side select key  301  is pressed (S 20 - 6 ). If the single-side/double-side select key  301  has been pressed, then it is determined whether or not the double-side mode is selected (S 20 - 6 ). If the double-side mode has been selected, the CPU  12  is notified of the double-side mode as the document reading mode advance notice (S 20 - 8 ). If the single-side mode has been selected by means of the single-side/double-side select key  301 , the CPU  12  is notified of the single-side mode as the document reading mode advance notice (S 20 - 9 ). 
     The CPU  101  then determines whether or not the feeding mode key  302  is pressed (S 20 - 14 ). If the feeding mode key  302  has been pressed, it is determined whether or not the silent feeding mode is selected (S 20 - 11 ). If the silent feeding mode has been selected, the CPU  12  is notified of the low-speed feeding mode as the document reading mode advance notice. If the high-speed feeding mode has been selected by means of the feeding mode key  302 , the CPU  12  is notified of the high-speed feeding mode as the document reading mode advance notice. 
     The CPU  101  then determines whether or not the start key  303  is pressed (S 20 - 14 ). If the start key  303  has been pressed, the document detection sensor  7  determines whether or not a paper sheet exists (S 20 - 15 ). If a paper sheet exists, an instruction to start reading of the document with the ADF is issued to the CPU  12 . If no paper sheet exists, an instruction to start reading of the document with the pressure board is issued to the CPU  12 . After the document reading operation is completed (S 20 - 18 ), the process returns to Step S 20 - 0  and the mode selection state is initialized. 
       FIG. 5  illustrates a relationship between time to generate the shading correction data Ts and document feeding time Tf in each mode in the document flow reading mode. The document feeding time Tf is the time until the document fed from the document tray  1  reaches the reading point. A table illustrating the relationship between the time to generate the shading correction data Ts and the document feeding time Tf is stored in the ROM  80 . The shading correction data is generated in the front side CCD linear sensor  58  in the following manner: the white component  60  is read with the light source  53  not being turned on in order to generate black shading correction data; and then, the light source  53  is turned on and the white component  60  is read in order to generate white shading correction data. The shading correction data is generated in the reverse side CCD linear sensor  20  in the following manner: a white component affixed to the moving glass  22  is searched for; the white component is read with the light source  21  not being turned on in order to generate black shading correction data; and then, the light source  21  is turned on and the white component is read in order to generate white shading correction data. 
     In the present embodiment, in the single-side mode and, at the same time, in the color mode, it is only necessary to consider the front side CCD linear sensor  58 ; therefore, the time to generate the shading correction data Ts is 600 milliseconds. In the single-side mode and, at the same time, in the monochrome mode, it is only necessary to consider the front side CCD linear sensor  58 ; therefore, the time to generate the shading correction data Ts is 300 milliseconds. In the double-side mode and, at the same time, in the color mode, it is necessary to also consider the reverse side CCD linear sensor  20 ; therefore, the time to generate the shading correction data Ts is 900 milliseconds. In the double-side mode and, at the same time, in the monochrome mode, it is necessary to also consider the reverse side CCD linear sensor  20 , the time to generate the shading correction data Ts is 600 milliseconds. In the reverse side CCD linear sensor  20  used in the double-side mode, it is necessary to search for the white member affixed to the moving glass  22  and therefore the time to generate the shading correction data Ts is longer than that in the single-side mode by 300 milliseconds. In the single-side mode and, at the same time, in the high-speed feeding mode, the document feeding time until the document fed from the document tray  1  reaches the front side reading point (i.e., the platen roller  17 ) is 500 milliseconds in both the color mode and monochrome mode. In the single-side mode and, at the same time, in the low-speed feeding mode, the document feeding time until the document reaches the front side reading point is 700 milliseconds in both the color mode and the monochrome mode. In the double-side mode and, at the same time, in the high-speed feeding mode, the document feeding time until the document fed from the document tray  1  reaches a reverse side reading point (i.e., the reverse side reading roller  19 ) is 740 milliseconds in the color mode and is 580 milliseconds in the monochrome mode. In the double-side mode and, at the same time, in the low-speed feeding mode, the document feeding time until the document reaches the reverse side reading point is 940 milliseconds in the color mode and is 780 milliseconds in the monochrome mode. 
       FIGS. 6 and 7A  to  7 C are control flowcharts of the CPU  12  of the document reader  100 . First, after the power supply is switched on, the CPU  12  (S 1001 ) initializes a monochrome/color variable Vc to the color mode, a one-side/both-side variable Vd to a single-side mode and a feeding mode variable Vf to a high-speed feeding mode on the RAM  90  (S 1002 ). The CPU  12  then notifies the CPU  101  of the controller  200  of the document detection state detected by the document detection sensor  7  (S 1003 ). The CPU  12  determines whether or not a document reading mode advance notice is received from the CPU  101  (S 1004 ). If the mode advance notice has been received, values of the variable Vc, Vd and Vf corresponding to the received mode advance notice are updated (Steps S 1005  to S 1016 ). Next, the time to generate shading correction data Ts and the document feeding time Tf of the front side CCD linear sensor  58  are obtained with reference to the table of  FIG. 5  (S 1017 ). The CPU  12  then determines whether or not Ts&gt;Tf is true (S 1018 ). If Ts&gt;Tf is true, generation of the shading correction data of the front side CCD linear sensor  58  is started (S 1019 ). If it is determined at Step S 1018  that Ts&gt;Tf is not true, generation of the front side shading correction data is stopped, and driving of the light source  53  and the front side CCD linear sensor  58  is stopped (S 1020 ). The CPU  12  then determines whether or not the variable Vd is the double-side mode (S 1021 ). If the variable Vd is the double-side mode, the time to generate the shading correction data Ts and the document feeding time Tf are obtained with reference to the table of  FIG. 5  (S 1022 ). The CPU  12  then determines whether or not Ts&gt;Tf is true (S 1023 ). If Ts&gt;Tf is true, generation of the shading correction data of the reverse side CCD linear sensor  20  is started (S 1024 ). If it is determined at Step S 1021  that the variable Vd is not the double-side mode, or if it is determined at Step S 1023  that Ts&gt;Tf is not true, generation of reverse side shading correction data is stopped, and driving of the light source  21  and the reverse side CCD linear sensor  20  is stopped (S 1025 ). 
     The CPU  12  then determines whether an instruction for document reading operation with the ADF has been received from the CPU  101  (S 1026 ). If the instruction for document reading operation with the ADF has been received, it is determined whether or not generation of the shading correction data of the front side CCD linear sensor  58  has already been started (S 1031 ). If generation of the shading correction data has not been started yet, generation of the shading correction data of the front side CCD linear sensor  58  is started (S 1032 ). After generation is started, or if it is determined at Step S 1031  that generation of the shading correction data of the front side CCD linear sensor  58  has already started, then it is determined whether or not generation of the shading correction data of the reverse side CCD linear sensor  20  has already been started (S 1033 ). If generation of the shading correction data has not been started yet, generation of the shading correction data of the reverse side CCD linear sensor  20  is started (S 1034 ). After generation is started, or if it is determined at Step S 1033  that generation of the shading correction data of the reverse side CCD linear sensor  20  has already started, the document reading operation with ADF is started (S 1027 ). When the document reading operation is completed (S 1030 ), the process returns to Step S 1002 . If the instruction for document reading operation with the ADF has not been received at Step S 1026 , it is determined whether or not the instruction for document reading operation with the pressure board has been received (S 1028 ). If the instruction for document reading operation with the pressure board has been received, generation of the shading correction data of the front side CCD linear sensor  58  is performed and then the document reading operation with the pressure board is started (S 1029 ). When the document reading operation is completed (S 1030 ), the process returns to Step S 1002 . If the instruction for document reading operation with the pressure board has not been received at Step S 1028 , it is determined whether or not one minute has elapsed since the most recent document reading mode advance notice is received (S 1035 ). If one minute has elapsed, generation of the shading correction data of the front side CCD linear sensor  58  and generation of the reverse side CCD linear sensor  20  are stopped (S 1036 ) and the process returns to Step S 1003  with the values of the variables Vc, Vd and Vf unchanged. If one minute has not elapsed since the most recent document reading mode advance notice is received at Step S 1035 , then it is determined whether or not 10 seconds have elapsed since generation of the shading correction data of the most recent front side CCD linear sensor  58  is completed (S 1037 ). If 10 seconds have elapsed, generation of the shading correction data of the front side CCD linear sensor  58  is started (S 1038 ). After generation is started or if 10 seconds have not elapsed at Step S 1037 , it is determined whether or not 10 seconds have elapsed since generation of the shading correction data of the most recent reverse side CCD linear sensor  20  is completed (S 1039 ). If 10 seconds have elapsed, generation of the shading correction data of the reverse side CCD linear sensor  20  is started (S 1040 ). After generation is started or if 10 seconds have not elapsed at Step S 1039 , the process returns to S 1003  with the values of the variables Vc, Vd and Vf unchanged. 
       FIGS. 8A and 8B  are timing charts illustrating a relationship among an instruction from the controller, feeding of the document and processing of the linear sensor. The horizontal axis represents time and the vertical axis represents the kind of instruction from the controller  200 , the document position of the first sheet, the operation of the front side CCD linear sensor  58  and the operation of the reverse side CCD linear sensor  20 .  FIG. 8A  illustrates an operation in a case in which the user selected the monochrome mode and the double-side mode and then pressed the start key  303 . If a monochrome mode advance notice is notified, no shading correction data is generated for both the front and reverse sides; when a double-side mode advance notice is notified thereafter, correction data is generated for only the reverse side CCD linear sensor  20 . Then, when the instruction to start reading of the document is issued, generation of the shading correction data of the front side CCD linear sensor  58  is started. In this case, as compared with a case in which generation of the shading correction data for both the front and reverse sides is started at the time when the instruction to start reading of the document is issued, a possibility that the document is not capable of passing the reverse side reading point until the completion of generation of the shading correction data is reduced; and therefore it is possible to reduce time since the user presses the start key  303  until the completion of reading of the document. 
       FIG. 8B  illustrates an operation in a case in which the user selected the double-side mode and the low-speed feeding mode and then pressed the start key  303 . If the double-side mode advance notice is notified, the shading correction data is generated for both the front and reverse sides; and then, correction of the shading data is stopped when notification of the low-speed feeding mode is instructed. Then, when an instruction to start reading of the document is issued, generation of the shading correction data for both the front and reverse sides is started again. In this case, as compared with a case in which generation of the correction data is started at the time when the double-side mode advance notice is issued, the time since the completion of generation of the correction data until the reading is started is reduced; therefore, image quality of the read image is increased. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2010-282234 filed Dec. 17, 2010, which is hereby incorporated by reference herein in its entirety.