JP4849669B2 - Image reading apparatus, shading correction method thereof, and program - Google Patents

Description

  The present invention relates to an image reading apparatus, a shading correction method, and a program thereof, and more particularly to an image reading apparatus that reads an image while conveying a document, a shading correction method, and a program thereof.

  In general, an image reading apparatus that reads an image while conveying a document irradiates the conveyed document with a light source, and condenses reflected light from the document by a rod lens array or the like. Thereafter, the collected reflected light is photoelectrically converted to generate document image data based on an output signal from a line image sensor or the like. However, since the light source and the rod lens array have uneven light quantity and uneven sensitivity of the line image sensor, uniform document reading cannot be performed as it is. Therefore, conventionally, in order to enable uniform document reading, an image obtained from the output value of the line image sensor at the time of document reading is used by using the output value when the white color reference member is read by the line image sensor. Data correction is performed. This correction is generally performed after optimizing the light emission amount of the light source that irradiates the document and optimizing the amplification factor (gain) when amplifying the image signal output of the line image sensor. Hereinafter, a series of corrections for the line image sensor to uniformly read the image information of the document including the above-described adjustment of the light emission amount and gain will be referred to as “shading correction”.

  In addition, this type of image reading apparatus detects the boundary between the document and the background, the skew of the document, and the color of the member disposed on the back of the document in order to prevent the back side image of the document from showing through. Or a color other than white (generally black).

  A shading correction method by a conventional image reading apparatus will be described with reference to FIG.

  In FIG. 10, the image reading device 1 a reads the image information of the document D by the line image sensor 11 while conveying the document D. However, the image reading apparatus 1a moves the line image sensor 11 in the direction of the arrow S and reads the color reference member 17 before reading the document D. Accordingly, correction data for shading correction of image data obtained based on the output of the line image sensor 11 is stored for each pixel.

  Note that the movement of the line image sensor 11 to the color reference member reading position is detected by the output of the position detection sensor 120.

  Thereafter, the image reading apparatus 1a returns the line image sensor 11 to the original reading position, and reads the reflected light from the original D with the line image sensor 11 while conveying the original D. Thereafter, the image data obtained from the output from the line image sensor 11 is subjected to shading correction with reference to correction data stored in advance, and the corrected image data is used as image information of the document D.

  As described above, in the image reading apparatus 1a configured to move the line image sensor 11 between the color reference member reading position and the document reading position, if the document reading position is deviated, a registration error in document reading is caused. In order to prevent this misregistration, the line image sensor is generally positioned when reading a document based on the output of the position detection sensor 120.

  The series of operations described in FIG. 10 is generally performed according to instructions from the control means (CPU).

  In addition, there is a technique in which a color reference member is moved instead of moving a line image sensor between reading a document and reading a color reference member (see, for example, Patent Document 1). Specifically, the color reference member is exposed to the document transport path when reading the color reference member, and is retracted to a position where it does not contact the document transported when reading the document.

  As described above, in the image reading apparatus that switches the relative position between the line image sensor and the color reference member between reading the color reference member and reading the original image, the image reading position of the line image sensor is obtained using the position detection sensor 120 described above. Is generally detected. As described above, when the image reading position is not detected, the image reading position is not only displaced, but the color reference member may be scratched or the document itself may be damaged. is there.

On the other hand, an image reading apparatus that detects an image reading position without using the position detection sensor 120 has also been proposed. Specifically, first, a reference position mark is provided on the color reference member, and the line image sensor is moved to a position facing the color reference member to read the image. Thereafter, the position of the reference position mark is determined based on the read image data, and the document image reading position and the color reference member reading position are positioned (see, for example, Patent Documents 2 and 3).
JP 2005-102017 A JP-A-4-196669 JP 2004-120599 A

  However, it is necessary to install a position detection sensor so that it is possible to clearly determine when the line image sensor is at the color reference member reading position and when it is at the document image reading position. For example, the above determination can be made by installing a position detection sensor in the vicinity of the movement path of the line image sensor or on the line image sensor. However, if the position detection sensor is installed at such a position, the movement of the line image sensor may be hindered, and the structural restriction increases.

  Even when the position detection sensor is installed away from the line image sensor, the above determination can be made by separately installing a member that is linked to the movement operation of the line image sensor. However, the installation of such interlocking members is not only a structural restriction but also an obstacle to the reduction in size and weight of the apparatus.

  Furthermore, providing the position detection sensor itself leads to an increase in the cost of the entire image reading apparatus.

  On the other hand, when the position detection mark is provided on the color reference member, the position detection mark cannot be arranged on the line where the shading correction data is acquired by the line image sensor. For this reason, it is necessary to provide a position mark at a position other than the line where shading correction is performed by the line image sensor, and the color reference member to which the position mark is added becomes large, which hinders downsizing of the product. Furthermore, since the position detection mark must be arranged on the color reference member using a color member having a color different from that of the color reference member, the cost of the color reference member is increased.

  Further, if the position detection sensor is not installed and the position detection mark is not accurately arranged on the color reference member, the positioning of each unit varies. For this reason, it is necessary to adjust the distance between the position detection sensor or the color reference member and the color reference member reading position and the document image reading position for each unit, leading to an increase in manufacturing cost.

  An object of the present invention is to reduce the size of a document image reading position and a color reference member reading position without setting a position detection sensor or arranging a position detection mark on the color reference member. An object of the present invention is to provide an image reading apparatus, a shading correction method, and a program that can achieve both low cost and high-precision image reading.

In order to achieve the above object, an image reading apparatus according to claim 1 is a reading sensor that reads an image at a sensor facing position in an image reading apparatus that reads an image formed on the original by conveying the original. A contact glass for guiding the document to the first position, a color reference member installed at a position different from the first position, and a moving mechanism for reciprocating the relative position between the sensor facing position and the color reference member A driving unit that drives a moving mechanism provided in the reading unit by a driving motor that is different from a transport motor used when transporting a document, and a sensor of the reading sensor when acquiring shading correction data The sensor facing position of the reading sensor when reading the document image data is set to the second position where the facing position is set on the color reference member. And control means for driving and controlling the drive means so as to position 1, the control means reciprocates relative position of the color reference member and the sensor facing position by rotating the drive motor in the same direction A reading data acquisition unit that moves and acquires reading data when moving based on an output signal of the reading sensor; and a sensor facing position based on the reading data when moving other than the installation area of the color reference member and the area And detecting a plurality of motor drive amounts of the drive motor corresponding to each detection of the boundary portion when the sensor facing position crosses the boundary portion a plurality of times. a motor driving amount obtaining means, based on the plurality of motor drive amount obtained by the motor driving amount obtaining means, moving the sensor facing position to the first position Characterized in that it comprises a drive amount calculating means for calculating a first positioning drive amount used when causing.

To achieve the above object, the shading correction method according to claim 7 is the shading correction method of an image reading apparatus for reading an image formed on the original by conveying the original, wherein the image reading apparatus includes a sensor. A reading sensor for reading an image at a facing position, a contact glass for guiding the document to a first position, a color reference member installed at a position different from the first position, and the sensor facing position and the color reference member A reading unit having a moving mechanism that reciprocally moves relative position to the reading unit, and a driving unit that drives a moving mechanism provided inside the reading unit by a driving motor that is different from a conveying motor used when the document is conveyed. In the shading correction method, the sensor facing position of the reading sensor at the time of obtaining shading correction data is determined based on the color reference. A control step for drivingly controlling the driving means so that the sensor facing position of the reading sensor at the time of document image data reading is set to the first position at a second position set on the member; The reading data acquisition during movement acquires the reading data during movement based on the output signal of the reading sensor by reciprocating the relative position between the sensor facing position and the color reference member by rotating the drive motor in the same direction. A detection step for detecting that the sensor facing position is at a boundary between the color reference member installation region and a region other than the region based on the reading data at the time of movement; and A motor drive amount acquisition step for acquiring a plurality of drive amounts of the drive motor corresponding to each detection of the boundary when straddling a plurality of times; and A drive amount calculating step for calculating a first positioning drive amount used when moving the sensor facing position to the first position based on the plurality of motor drive amounts acquired in the data drive amount acquisition step. It is characterized by that.

In order to achieve the above object, the program according to claim 8 is a program that causes a computer to execute a shading correction method of an image reading apparatus that reads an image formed on the original by conveying the original. The apparatus includes a reading sensor that reads an image at a sensor facing position, a contact glass that guides the document to a first position, a color reference member that is installed at a position different from the first position, and the sensor facing position. Driving that drives a moving mechanism provided in the reading unit by a reading motor having a moving mechanism that reciprocally moves relative to the color reference member and a driving motor that is different from a conveying motor that is used to convey the original. And the program stores a sensor pair of the reading sensor when acquiring shading correction data. A control module that drives and controls the driving means so that the sensor facing position of the reading sensor at the time of document image data reading is set to the first position at a second position where the position is set on the color reference member; The control module reciprocates the relative position between the sensor facing position and the color reference member by rotating the drive motor in the same direction, and acquires reading data at the time of movement based on an output signal of the reading sensor. A reading data acquisition module at the time of movement, a detection module for detecting that the sensor facing position is at a boundary between the installation area of the color reference member and other area based on the reading data at the time of movement, and the sensor facing position Motor drive that acquires a plurality of drive amounts of the drive motor corresponding to each detection of the boundary when the boundary crosses the boundary multiple times Drive amount calculation for calculating a first positioning drive amount used when moving the sensor facing position to the first position based on the acquisition module and the plurality of motor drive amounts acquired by the motor drive amount acquisition module And a module.

According to the present invention, the relative position between the sensor facing position and the color reference member is obtained by reciprocating by rotating a drive motor different from the transport motor used for transporting the document in the same direction . Based on the reading data at the time of movement, it is detected that the sensor facing position is at the boundary between the color reference member installation area and other areas, and each detection of the boundary when the sensor facing position crosses the boundary multiple times a plurality of motor drive amount of the drive motor corresponding acquired by the motor drive amount acquisition means, based on a plurality of motors driving amount acquired by the motor drive quantity acquisition unit, a first position in which the document is guided to the sensor facing position Since the first positioning drive amount used when moving to the position is calculated, the reading sensor and the document are made to face each other based on the motor drive amount without separately providing a positioning sensor. Can be performed in the positioning accurately, can both read size and low price and high precision image.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing an image reading apparatus according to an embodiment of the present invention. In addition, this structure illustrates the structure of this invention, and is not restricted to this.

  In FIG. 1, the image reading apparatus 1 includes a pickup roller 2 that picks up a document D, and a feeding roller 3 that feeds the document D picked up by the pickup roller 2 into the image reading apparatus 1. Further, the image reading apparatus 1 includes a separation roller 4 that separates the picked-up originals D one by one, a registration roller 5 that is arranged in a pair for conveying the original D, and image information on the upper surface of the original D. The reading unit 61 is provided. In addition, the image reading apparatus 1 includes a reading unit 62 that reads image information on the lower surface of the document D, and a transport roller 7 that is disposed downstream of the reading units 61 and 62 and arranged in pairs.

  The image reading apparatus 1 includes an upper frame 81 and a lower frame 82, and the upper frame 81 is rotatable about a rotation shaft 81a. In addition, when the conveyed document D is jammed, the document D staying in the image reading device 1 is removed, so that the image reading device 1 can be manually opened and closed.

  A reading unit 62 is fixed to the lower frame 82. In addition, the reading unit 61 is swingably supported by the swing arm 9 on the upper frame 81 and can be translated in the vertical direction. Therefore, the thick original can be smoothly conveyed. One end of the swing arm 9 is pivotally supported by the upper frame 81 and the other end is pivotally supported by the reading unit 61. Since one end of the swing arm 9 is snap fit, it is easy to assemble.

  With the above configuration, the image reading apparatus 1 operates as follows when reading an image of the document D.

  First, as shown in FIG. 3 to be described later, the reading units 61 and 62 read the color reference member 17 included therein and output a reading signal for shading correction, and the image reading apparatus 1 generates and stores shading correction data. .

  Thereafter, the document D is taken into the image reading device 1 by the pickup roller 2 and the feeding roller 3 and separated one by one by the separation roller 4. While the document D is nipped and transported (sub-scanned) by the registration roller 5 and the transport roller 7, the images in the main scanning direction (direction orthogonal to the document transport direction) on both sides thereof are read by the reading units 61 and 62. At the time of reading, the image data generated from the output signals of the reading units 61 and 62 is corrected with reference to the shading correction data described above. After the image reading is completed, the document D is nipped and conveyed by the pair of conveying rollers 7 and is discharged to the outside of the image reading apparatus 1.

  FIG. 2 is a block diagram schematically showing the data flow of the image reading apparatus 1 of FIG.

  2, the image reading apparatus 1 includes line image sensors 11 ′ and 11 and light sources 111 ′ and 111 built in the line image sensors 11 ′ and 11 in reading units 61 and 62 (not shown), respectively. . The control board (not shown) of the image reading apparatus 1 includes an A / D conversion unit 100 that converts the image signals from the line image sensors 11 ′ and 11 into analog signals after performing analog processing such as amplification and black level clamping. Prepare. Further, the control board controls the line image sensors 11 ′, 11, the light sources 111 ′, 111, the A / D converter 100, and the like, and performs various image processing (shading correction, etc.) on the image data obtained by digitizing the image signal. And image processing means 101 for performing the above.

  The control board includes an image storage unit (image memory) 102 for storing image data and an interface unit 103 with an external host device. The interface unit 103 is connected to an external host device through a signal line 109.

  Further, the control board includes a control unit (CPU) 104 that controls the image reading apparatus, and a storage unit (work memory) 105 that is used to operate the CPU 104.

  The image processing means 101, CPU 104 and work memory 105 are connected to each other via a bus 108.

  The CPU 104 is configured to be able to access the image memory 102 via the image processing unit 101.

  Therefore, the CPU 104 can process the image data held in the image memory 102 according to the program written in the work memory 105.

  The image reading apparatus 1 includes a transport motor 112 that transports a document, and a pulse motor 21 that moves the line image sensors 11 ′ and 11 to a document image reading position and a color reference member reading position when the document is read.

  The conveyance motor 112 is a motor that conveys a document, and the motor driver IC 107 controls the operation of the conveyance motor 112 based on an instruction from the CPU 104.

  The pulse motor 21 is a component that constitutes the driving means 10, and the motor driver IC 106 controls the operation of the pulse motor 21 based on an instruction from the CPU 104.

  Next, reading of the color reference member will be described with reference to FIGS. In the following description, the reading unit 61 has basically the same structure as the reading unit 62. Accordingly, the reading unit 61 will be described only with respect to differences from the reading unit 62, and a duplicate description will be omitted.

  3A and 3B are cross-sectional views showing the configuration of the reading unit 62 in FIG. 1, wherein FIG. 3A shows a state when reading a document, and FIG. 3C shows a state when reading a color reference member. 3A and 3C are side views of the reading unit 62, and FIGS. 3B and 3D are top views of the reading unit 62. FIG.

  As shown in FIG. 3, the reading unit 62 includes a line image sensor 11 that reads an image, a sensor box 12 that holds the line image sensor 11, and a substrate 13 that operates the line image sensor 11. The reading unit 62 includes a flat cable 14 that connects the line image sensor 11 and the substrate 13, a contact glass 15 that guides the document to the document reading position 15 a, and a glass holding member 16 that holds the contact glass 15. Further, the reading unit 62 includes a color reference member 17 serving as a white reference, a rectilinear cam 18 that moves the line image sensor 11, and a tension spring 22 that urges the line image sensor 11 in a direction to return the line image sensor 11 to its original position. .

  The sensor box 12 has a through hole 12a through which the flat cable 14 passes, and the through hole 12a has a bowl shape to avoid dust.

  The color reference member 17 is provided at a position shifted from the document reading position 15a on the surface of the contact glass 15 by a method such as adhesion, sticking with a tape, painting or printing. The white reference surface serving as the white reference is a close contact surface between the color reference member 17 and the contact glass 15.

  The line image sensor 11 has a protrusion 11a, and the protrusion 11a is fitted into the elongated hole 12b of the sensor box 12, and movement in the main scanning direction is restricted. Thus, the sensor facing position by the line image sensor 11 is always on the contact glass 15 held by the glass holding member 16.

  The rectilinear cam 18 includes cam grooves 18a and 18b into which the projections 11a and 11b of the line image sensor 11 are fitted, elongated holes 18c and 18d into which the projections 12c and 12d of the sensor box 12 are fitted, and a hook to which the tension spring 22 is hooked. Part 18e. The rectilinear cam 18 is locked to the locking portion 12e of the sensor box 12 by a tension spring 22 and pulled in the direction of the arrow f, and one end protrudes from the sensor box 12 when reading a document.

  The reading unit 62 is switched between a state at the time of reading the original and a state at the time of reading the color reference member 17 by the driving means 10 (FIG. 1) provided on the side of the reading unit 62.

  FIGS. 4A and 4B are top views showing the configuration of the driving unit 10 in FIG. 1, in which FIG. 4A shows a state during document reading, and FIG. 4B shows a state during color reference member reading.

  In FIG. 4, the driving means 10 includes a push plate 19 that pushes the rectilinear cam 18 of the reading unit 62, an eccentric cam 20 that transmits a driving force to the push plate 19, and a pulse motor 21 that rotates the eccentric cam 20. The pulse motor 21 rotates step by step by a predetermined angle by switching excitation.

  The rectilinear cam 18 ′ protruding from the reading unit 61 is disposed so that the distance from the rotation shaft 19 d of the push plate 19 is farther than the rectilinear cam 18 protruding from the reading unit 62. As shown in FIG. 4A, when the document is read, the rectilinear cam 18 ′ protruding from the reading unit 61 does not come into contact with the pressing plate 19, and the reading unit 61 can move smoothly following documents of various thicknesses. it can.

  The push plate 19 is provided with a contact surface 19 a that contacts the eccentric cylindrical surface 20 a of the eccentric cam 20 and a contact surface 19 b that contacts the rectilinear cam 18, and the rotational shaft 19 d is centered by the rotation of the eccentric cam 20. Rotate as

  The pulse motor 21 is driven and controlled by the CPU 104 via the motor driver IC 106, so that when the shading correction data is acquired, the eccentric cam 20 rotates at a constant speed around the rotation shaft 20b. Along with this driving, the position where the line image sensor 11 faces (hereinafter referred to as “sensor facing position”) moves so as to reciprocate on the contact glass 15.

  For example, when the sensor facing position 101a before the start of driving the pulse motor 21 is in a position not facing the color reference member 17 as shown in FIG. 3A, the sensor facing position is determined by one rotation of the pulse motor 21. One reciprocation is made on the contact glass 15 as follows.

  First, simultaneously with the start of the driving, the sensor facing position 101a starts to move in the direction toward the color reference member 17 from the original reading position shown in FIG. Thereafter, as shown in FIG. 3C, when the sensor facing position 101a moves to a position where the color reference member 17 affixed to the contact glass 15 can be read, the moving direction is reversed, and the sensor facing position 101a is again shown in FIG. Return to the position shown in (a).

  5A and 5B are diagrams showing the relationship between the push plate 19 and the straight cam 18 when reading the color reference member. FIG. 5A shows a state in which the apparatus 1 remains closed when reading the color reference member, and FIG. The state in which the apparatus 1 is opened when the color reference member is read is shown.

  In FIG. 5, the pressing plate 19, which is one component of the driving means 10, has a sloped portion 19 c on the reading unit 61 side. Here, the state in which the apparatus 1 is closed when the apparatus 1 is viewed from the document conveying direction is a state in which the upper frame 81 and the lower frame 82 are joined together and the apparatus 1 is opened as shown in FIG. Is a state where the upper frame 81 is rotated about the rotation shaft 81a and lifted up.

  As shown in FIG. 5, when the apparatus 1 is opened at the time of reading the color reference member, the linear cam 18 is pulled by the tension spring 22 as shown in FIG. 3, so that one end of the linear cam 18 is read. It protrudes from the unit 61. When the apparatus 1 is closed again in this state, the rectilinear cam 18 protruding from the reading unit 61 is pushed by the inclined surface portion 19c of the push plate 19 in the process of closing the apparatus 1. Thereby, it is possible to prevent the rectilinear cam 18 from colliding with the rectilinear cam 18 and the push plate 19.

  With the configuration described above, the image reading apparatus 1 can drive the rectilinear cams 18 of the two reading units 61 and 62 with one driving means 10. Further, with this configuration, it is not necessary to attach a second motor or a drive transmission mechanism associated with the motor to the two reading units 61 and 62. Therefore, the space for attaching them can be reduced, the apparatus can be miniaturized, and the apparatus can be made inexpensive.

  FIG. 6 is a diagram used to explain a method for determining an image acquisition position.

  The CPU 104 stops the pulse motor 21 when reading a document image, and determines the image acquisition position (shading correction data acquisition position and document reading position) via the motor driver IC 106 so as to rotate the pulse motor 21. Drive control is performed. Further, the CPU 104 reciprocates a position facing the line image sensor 11 (hereinafter referred to as “sensor facing position”) on the contact glass 15 by the above drive control, and a value based on the output signal (hereinafter referred to as “sensor output value”). ) To get.

For example, when the sensor facing position 101a is at the position shown in FIG. 3A before the pulse motor 21 is rotated and the reciprocating movement of the reading sensor is started, the sensor facing position is determined by rotating the pulse motor 21 twice. Two reciprocations are made on the contact glass 15 as follows.

  First, simultaneously with the start of the driving, the sensor facing position 101a starts to move in the direction of the color reference member 17 from the position shown in FIG. Thereafter, when the sensor facing position 101a moves to a position facing the color reference member 17 as shown in FIG. 3C, the moving direction is reversed and the position returns to the position shown in FIG. 3A again.

  Thereafter, when the pulse motor 21 is continuously rotated, the moving direction becomes the direction toward the color reference member 17 again. After that, when the sensor facing position 101a moves again to a position facing the color reference member 17, the moving direction is reversed again and returns to the original position.

  FIG. 6 shows the driving amount of the driving means 10 represented by the number of steps that the pulse motor 21 has rotated in units of a predetermined angle during this reciprocating operation and the sensor output value corresponding thereto. Here, when the document is not on the contact glass 15, the sensor output value when the sensor facing position is on the installation area of the color reference member 17 is I1, and the sensor output value when the sensor facing position is in the other area is almost 0. It becomes. Here, it is assumed that the sensor output value, which is an analog signal, is converted into digital data by the A / D converter 100 and further offset correction is performed. Therefore, when the sensor output value is between 0 and I1, it can be determined that the sensor facing position is on the boundary of the installation area of the color reference member 17.

  In the present embodiment, determination value I2 (0 <I2 <I1) is held in advance in work memory 105, and the sensor facing position is located on the boundary from the start of driving (the sensor output value changes across I2). The driving amounts L1, L5, and L9 of the driving unit 10 are obtained.

  Here, the boundary detected when the sensor facing position is moving in the direction toward the color reference member 17, and the boundary detected when the sensor is moving in the direction opposite to the direction detected immediately after that. It can be said that the intermediate point with the portion is in a state where the sensor facing position is surely located in the installation area of the color reference member 17. Therefore, the shading correction image is set to be acquired at this intermediate point. In the example of FIG. 6, an intermediate point 1 between the boundary when the driving unit 10 is driven to the driving amount L1 and the boundary when the driving unit 10 is driven to the driving amount L5 (corresponding to the driving amount L3 of FIG. 6). ) Is set to be a position for acquiring a shading correction image.

  On the other hand, a boundary portion detected when the sensor facing position is moving in the reverse direction and a boundary portion detected when moving in the direction toward the color reference member 17 detected immediately thereafter It can be said that the intermediate point is a state where the sensor facing position is surely located in an area other than the installation area of the color reference member 17. Therefore, this intermediate point is set to the document reading position 15a. In the example of FIG. 6, an intermediate point 2 between the boundary when the driving unit 10 is driven to the driving amount L5 and the boundary when the driving unit 10 is driven to the driving amount L9 (corresponding to the driving amount L7 of FIG. 6). ) Is set to be the original reading position 15a.

  While moving the sensor facing position as described above, the pulse motor 21 rotates the eccentric cam 20 at a constant speed. Therefore, the sensor facing position can be uniquely determined by the driving amount (hereinafter referred to as “step number”) of the pulse motor 21 from a predetermined rotation angle. However, immediately after the power is turned on, the current rotation angle of the pulse motor 21 and thus the current position of the sensor facing position cannot be recognized.

  Therefore, in the present embodiment, the drive amounts (number of steps) L1, L5, and L9 obtained with the stop position of the pulse motor 21 immediately after the power is turned on as the origin are held in the work memory 105, and immediately after the power is turned on. The stop position of the pulse motor 21 is set to the drive start position. Thereafter, using the held driving amount, the CPU 104 moves from the driving start position to an optimum position for reading the document (intermediate point 1) and an optimum position for reading the color reference member 17 (intermediate point 2). The number of steps required for each is calculated. Accordingly, the sensor facing position when the pulse motor 21 is driven by the calculated number of steps from the driving start position can be determined as each image acquisition position.

  In addition, an error in the size of the color reference member 17 and a movement error when the reading position of the line image sensor 11 moves from the pulse motor 21 through the push plate 19 and the linear cam 18 are individual differences of the image reading device 1. In this case, the CPU 104 reads the sensor output value every time the driving amount (step number) of the driving means 10 advances by one step or several steps, as will be described with reference to FIG. Thereby, the shading correction data acquisition position can be determined with high accuracy.

  FIG. 11 is a flowchart illustrating a procedure of shading correction data acquisition processing executed by the CPU 104.

  In this processing, the sensor facing position when the line image sensor 11 is stationary is assumed to be in the above-described boundary portion or an area other than the installation area of the color reference member 17 unless otherwise specified.

  In FIG. 11, first, it is determined whether or not to start the determination of the image acquisition position and the shading correction data acquisition position (step S100). As a result of the determination, when starting, the process proceeds to step S101. When not starting, the process waits. In this step, for example, it may be determined that the process is started when there is a predetermined user input, or it may be determined that the process is started when a predetermined time elapses after the apparatus is activated.

  Next, it is determined whether or not a document is present on the contact glass 15 (step S101). If the result of this determination is that there is a document, the user is notified that the document needs to be removed (step S102), and the processing from step S101 is performed. Here, in step S101, the pulse motor 21 is rotated once to read an image by the line image sensor 17, and the sensor facing position moves between the installation area of the color reference member 17 and the other area. When the difference in brightness is small and the boundary portion cannot be found, it is determined that the document exists on the contact glass 15. The determination may be made using a document detection sensor that detects the passage of the document.

  On the other hand, if the result of determination in step S101 is that there is no original, image reading by the line image sensor 11 is started again, and control is started to rotate the pulse motor 21 at a constant speed (step S103).

  Thereafter, the drive amount (number of steps) of the pulse motor 21 is incremented by 1 (step S104), the sensor output value from the line image sensor 11 is acquired (step S105), and the acquired sensor output value crosses the threshold value I2. It is determined whether or not it has changed (step S106).

  As a result of the determination in step S106, when the sensor output value does not change across I2, directly when the sensor output value changes across I2, the current number of steps of the pulse motor 21 is obtained (step S106). S107), the process proceeds to step S108.

  Thereafter, the number of acquisitions of the number of steps in step S107 is counted (step S108). As a result of step S108, when the number of acquisition times is less than 3, the processing from step S104 is performed. Hereinafter, for simplification of description, the values of the number of steps will be described as S1, S2, S3 in the order of acquisition. Here, S1 corresponds to the drive amount L1 in FIG. 6, S2 corresponds to the drive amount L5, and S3 corresponds to the drive amount L9.

  On the other hand, when the number of times of acquisition is three as a result of step S108, the pulse motor 21 is rotated until the number of steps (S1 + S2) / 2 (L3 in FIG. 6: intermediate point 1) is reached (step S109). The image of the color reference member 17 at the sensor facing position is read for each pixel by the line image sensor 11, and image data based on this is acquired as shading correction data (step S110). Thereafter, the pulse motor 21 is rotated until the number of steps reaches (S2 + S3) / 2 (L7: intermediate point 2 in FIG. 6), the image reading position is determined (step S111), and this process is terminated.

  As a result, the preparation for reading the document image in the next step at the optimum sensor facing position and the acquisition of the optimum shading correction data are completed.

  After that, each time a document reading command is received, the original position is moved without moving the sensor facing position, the image at the current sensor facing position is read for each pixel by the line image sensor 11, and this is sequentially acquired as a document image. To do. Shading correction is performed on the acquired document image based on the shading correction data set in step S110.

  According to the process of FIG. 11, the CPU 104 controls the driving unit 10 to acquire the sensor output value while reciprocating the sensor facing position of the line image sensor 11 on the contact glass 15 (steps S103 to S105). Drive amounts S1, S2, and S3 from the start of driving until the sensor output value changes across the threshold value I2 are detected (step S108). Thereafter, when the pulse motor 21 is driven from the driving start time to the number of steps (S1 + S2) / 2, the image data for each pixel read by the line image sensor 11 is set as shading correction data at the sensor facing position. . In preparation for reading the document image, the pulse motor 21 is driven from the driving start time to the number of steps (S2 + S3) / 2. As a result, the document image can be reliably read at the sensor facing position. Further, in order to determine whether or not the line image sensor 11 is positioned at the intermediate points 1 and 2 in FIG. 6, a position detection sensor is not installed and a position detection mark is not arranged on the color reference member. The document image reading position and the color reference member reading position can be positioned, and both downsizing and cost reduction and high-accuracy image reading can be achieved.

  As described above, the current rotation angle of the pulse motor 21 cannot be recognized immediately after the image reading apparatus 1 is started. That is, the position of the line image sensor 11 is not fixed. For this reason, at this time, neither the light amount adjustment of the light source nor the gain adjustment of the A / D conversion unit 100 can be performed. Therefore, the detection operation of the boundary portion is performed with predetermined initial values for the light amount setting value of the light source, the gain setting value of the A / D conversion unit 100, and the shading correction data, particularly immediately after factory assembly. .

  In this embodiment, the boundary portion is detected when the sensor output value changes across I2. However, due to the influence of variations in the light source, an image of the color reference member 17 and an image that is not the color reference member 17 are detected. In some cases, the threshold cannot be distinguished.

  In such a case, while the pulse motor 21 makes one rotation, the maximum value and the minimum value of the output value from the line image sensor 11 are held, and the average value thereof is used instead of the predetermined determination value. desirable. Further, the light amount setting value of the light source and the gain setting value of the A / D conversion unit 100 are changed so that the image of the color reference member 17 and the image that is not the color reference member 17 can be distinguished from a predetermined determination value. A method can also be used. The change of the gain setting value may be performed on an amplifier that amplifies an analog signal before A / D conversion, or may be performed by calculation on digital data after A / D conversion.

  Further, the image reading apparatus 1 has a configuration in which only the line image sensor 11 moves, but is not limited thereto. That is, the line image sensor 11 and the glass holding member 16 may be relatively moved so that the sensor facing position moves. For example, as shown in FIG. 7, only the glass holding member 16 may move, or as shown in FIG. 8, both the line image sensor 11 and the glass holding member 16 may move.

  In the image forming apparatus 1, the color reference member 17 is installed on the surface of the contact glass 15. However, the present invention is not limited to this. In other words, the color reference member 17 only needs to be provided at a sensor facing position by the line image sensor 11 and at a position away from the document reading position 15a. Specifically, as shown in FIG. 9, (a) on the contact glass 15, the surface opposite to the surface through which the document passes while contacting, or (b) on the glass holding member 16, It may be provided on the surface on which the document is placed. Further, (c) it may be provided on the glass holding member 16 on the surface opposite to the surface on which the document is placed.

  In the case of (b), when the line image sensor 11 moves, the amount of movement increases as it jumps over the relay part 16a connecting the contact glass 15 and the color reference member 17, so that the relay part as shown in (d). 16a may be eliminated.

  In addition, the color reference member 17 of the present embodiment and the color reference members 17 of (b) and (d) have such strength and thickness that the scratches do not occur even when they come into contact with the document during document transport. Is desirable. On the other hand, since the color reference member 17 of (a) and (c) is installed on the surface opposite to the surface 15b on the side where the document is placed, it is in direct contact with the document when the document is conveyed. Moreover, since it is sealed in the reading unit, it is advantageous in that it is free from scratches, paper dust, and dust.

  Normally, when the color reference member 17 of (a) and (c) is installed, the thickness of the contact glass 15 and the shape of the glass holding member 16 are selected so that both the surface 15b and the opposite surface are in focus. It is desirable to do. This is because the shape (light amount distribution) of the light amount unevenness differs at a position where the light amount unevenness of a rod lens array (not shown), which is one of the shading correction elements, deviates from the focused position. However, when the amount of light unevenness of the rod lens array is small, the color reference member can be read even at a position shifted from the in-focus position, and such a position is also included in the sensor facing position.

  Further, when the color reference members 17 of (a) to (d) are installed, it is only necessary that the sensor facing position is configured to reciprocate in a predetermined region, and the vertical or You may move in other directions.

  In the above-described embodiments, the push plate 19 is provided with the slope-shaped portion. However, the invention is not limited to this as long as the straight cam 18 can be prevented from being damaged when the apparatus is opened at the time of reading the color reference member. For example, when the apparatus is opened and closed during reading of the color reference member, the opening / closing of the apparatus is detected and the pulse motor 21 is rotated to bring the push plate 19 into the state shown in FIG. Good.

  The CPU 104 may be a dedicated control unit for performing processing from the above-described boundary detection to determination of the color reference member reading position and the document image reading position, or may control other parts of the image reading apparatus 1. Also, it may be a control means that is also used.

  In addition, a configuration in which a part or all of the processing of the control unit is performed by hardware combining a counter, a comparator, and the like can be used.

  Another object of the present invention is to supply a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or apparatus, and the computer of the system or apparatus (or CPU, MPU, or the like). Is also achieved by reading and executing the program code stored in the storage medium.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention. .

  Examples of the storage medium for supplying the program code include a floppy (registered trademark) disk, a hard disk, a magneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a DVD-ROM, a DVD-RAM, and a DVD. An optical disc such as RW or DVD + RW, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used. Alternatively, the program code may be downloaded via a network.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (Operating System) running on the computer based on the instruction of the program code Includes a case where the functions of the above-described embodiments are realized by performing part or all of the actual processing.

  Furthermore, after the program code read from the storage medium is written to a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the expanded function is based on the instruction of the program code. This includes a case where a CPU or the like provided on the expansion board or the expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

1 is a cross-sectional view schematically showing an image reading apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram schematically showing a data flow of the image reading apparatus in FIG. 1. 2A and 2B are cross-sectional views illustrating a configuration of a reading unit in FIG. 1, in which FIG. 1A illustrates a state when a document is read, and FIG. 2A and 2B are top views showing the configuration of the driving unit in FIG. 1, in which FIG. 1A shows a state when reading a document, and FIG. 2B shows a state when reading a color reference member. It is a figure which shows the relationship between the push plate at the time of color reference member reading, and a rectilinear cam, (a) shows the state with which an apparatus remains closed at the time of color reference member reading, (b) is an apparatus at the time of color reference member reading. Indicates open state. It is a figure used for demonstrating the determination method of an image acquisition position. 4A and 4B are cross-sectional views showing a first modification of the configuration of the reading unit, in which FIG. 5A shows a state when reading a document, and FIG. FIG. 10 is a cross-sectional view illustrating a second modification of the configuration of the reading unit, in which (a) shows a state when reading a document, and (b) shows a state when reading a color reference member. FIG. 10 is a cross-sectional view illustrating a third modification of the configuration of the reading unit, in which (a) a color reference member is provided on the surface opposite to the document conveying surface of the contact glass, The color reference member is provided on the original document conveying surface, and (c) the color reference member is provided on the opposite surface of the glass holding member from the original document conveying surface. It is a figure used for demonstrating the acquisition method of the shading correction data by the conventional image reading apparatus. It is a flowchart which shows the procedure of the acquisition process of the shading correction data performed by CPU.

Explanation of symbols

D Document 1 Image reading device 10 Driving means 11 Line image sensor 15 Contact glass 16 Glass holding member 17 Color reference member 104 CPU

Claims (8)

In an image reading apparatus that reads an image formed on the original by conveying the original,
A reading sensor for reading an image at a sensor facing position, a contact glass for guiding the document to a first position, a color reference member installed at a position different from the first position, and the sensor facing position and the color reference A reading unit having a moving mechanism for reciprocating the relative position with the member;
Driving means for driving a moving mechanism provided in the reading unit by a driving motor different from a conveying motor used for conveying an original;
The sensor facing position of the reading sensor at the time of shading correction data acquisition is set to the second position set on the color reference member, and the sensor facing position of the reading sensor at the time of document image data reading is set to the first position. Control means for driving and controlling the drive means,
The control means includes
Moving-time reading data acquisition means for rotating the driving motor in the same direction to reciprocate the relative position between the sensor facing position and the color reference member and acquiring reading data at the time of movement based on the output signal of the reading sensor. When,
Detecting means for detecting that the sensor facing position is at a boundary between the installation area of the color reference member and the area other than the area based on the reading data at the time of movement;
Motor drive amount acquisition means for acquiring a plurality of motor drive amounts of the drive motor corresponding to each detection of the boundary portion when the sensor facing position crosses the boundary portion a plurality of times;
Drive amount calculation means for calculating a first positioning drive amount used when the sensor facing position is moved to the first position based on the plurality of motor drive amounts acquired by the motor drive amount acquisition means. An image reading apparatus.   The drive amount calculation unit also calculates a second positioning drive amount used when moving the sensor facing position to the second position based on the plurality of motor drive amounts acquired by the motor drive amount acquisition unit. The image reading apparatus according to claim 1, wherein: In an image reading apparatus that reads an image formed on the original by conveying the original,
A reading sensor for reading an image at a sensor facing position, a contact glass for guiding the document to a first position, a color reference member installed at a position different from the first position, and the sensor facing position and the color reference A reading unit having a moving mechanism for reciprocating the relative position with the member;
Driving means for driving a moving mechanism provided in the reading unit by a driving motor different from a conveying motor used for conveying an original;
The sensor facing position of the reading sensor at the time of shading correction data acquisition is set to the second position set on the color reference member, and the sensor facing position of the reading sensor at the time of document image data reading is set to the first position. Control means for driving and controlling the drive means,
The control means includes
A reading data acquisition unit at the time of movement that acquires the reading data at the time of movement based on the output signal of the reading sensor by reciprocating the relative position between the sensor facing position and the color reference member by the drive motor;
Detecting means for detecting that the sensor facing position is at a boundary between the installation area of the color reference member and the area other than the area based on the reading data at the time of movement;
Motor drive amount acquisition means for acquiring a motor drive amount of the drive motor corresponding to the detection of the boundary portion;
Drive amount calculation means for calculating a first positioning drive amount used when moving the sensor facing position to the first position based on the motor drive amount acquired by the motor drive amount acquisition means;
The reading unit includes a first reading unit supported by a first frame and a second reading unit supported by a second frame for images formed on both sides of the document, and the first reading unit. The reading sensor, the contact glass, the color reference member, and the moving mechanism are respectively provided inside the second reading unit and the second reading unit.
The drive means is provided across one of the first frame and the second frame, and one end of the moving mechanism provided to protrude outward from the first reading unit and the second reading unit, respectively. Including means for driving a pressing member for pressing the part side to the inside,
The drive amount calculation unit moves the sensor facing position in the first reading unit and the second reading unit to the first position based on the motor drive amount acquired by the motor drive amount acquisition unit. An image reading apparatus that calculates a first positioning driving amount used at the time.   The drive amount calculation means also calculates a second positioning drive amount used when moving the sensor facing position to the second position based on the motor drive amount acquired by the motor drive amount acquisition means. The image reading apparatus according to claim 3.   The detection means detects that the sensor facing position is at a boundary portion of an installation area of the color reference member when the reading data at the time of movement changes across a threshold value. 5. The image reading apparatus according to any one of 4 above. A light source that irradiates light to the sensor facing position; and an amplifying unit that amplifies an output signal of the reading sensor;
When it is not possible to detect that the sensor facing position is at the boundary portion of the color reference member installation area based on the read data at the time of movement, the detection means includes the light amount of the light source, the amplification factor of the amplification means, and the 6. The image reading apparatus according to claim 5, wherein at least one of the threshold values is increased or decreased. In the shading correction method of the image reading apparatus for reading an image formed on the original by conveying the original,
  The image reading apparatus includes a reading sensor that reads an image at a sensor facing position, a contact glass that guides the document to a first position, a color reference member that is installed at a position different from the first position, and the sensor A reading unit having a moving mechanism for reciprocating a relative position between the facing position and the color reference member, and a moving mechanism provided inside the reading unit by a driving motor different from a conveying motor used for conveying an original. Driving means for driving,
  In the shading correction method, the sensor facing position of the reading sensor when reading shading correction data is set to the second position where the sensor facing position of the reading sensor is set on the color reference member. A control step of driving and controlling the driving means so as to be in the position 1;
  The control step includes
  The reading data acquisition during movement acquires the reading data during movement based on the output signal of the reading sensor by reciprocating the relative position between the sensor facing position and the color reference member by rotating the drive motor in the same direction. Steps,
  A detection step of detecting that the sensor facing position is at a boundary between the installation area of the color reference member and the area other than the area based on the reading data at the time of movement;
  A motor drive amount acquisition step of acquiring a plurality of drive amounts of the drive motor corresponding to each detection of the boundary portion when the sensor facing position crosses the boundary portion a plurality of times;
  A drive amount calculating step of calculating a first positioning drive amount used when moving the sensor facing position to the first position based on the plurality of motor drive amounts acquired in the motor drive amount acquisition step. A shading correction method characterized by that. In a program for causing a computer to execute a shading correction method of an image reading apparatus that reads an image formed on the original by conveying the original,
  The image reading apparatus includes a reading sensor that reads an image at a sensor facing position, a contact glass that guides the document to a first position, a color reference member that is installed at a position different from the first position, and the sensor A reading unit having a moving mechanism for reciprocating a relative position between the facing position and the color reference member, and a moving mechanism provided inside the reading unit by a driving motor different from a conveying motor used for conveying an original. Driving means for driving,
  The program is
  The sensor facing position of the reading sensor at the time of shading correction data acquisition is set to the second position set on the color reference member, and the sensor facing position of the reading sensor at the time of document image data reading is set to the first position. A control module for driving and controlling the driving means;
  The control module is
  Rotating the drive motor in the same direction causes the relative position between the sensor facing position and the color reference member to reciprocate to obtain read data during movement based on the output signal of the read sensor. Module,
  A detection module for detecting that the sensor facing position is at a boundary between the installation area of the color reference member and the area other than the area based on the reading data at the time of movement;
  A motor drive amount acquisition module for acquiring a plurality of drive amounts of the drive motor corresponding to each detection of the boundary portion when the sensor facing position crosses the boundary portion a plurality of times;
  A drive amount calculation module that calculates a first positioning drive amount used when the sensor facing position is moved to the first position based on the plurality of motor drive amounts acquired by the motor drive amount acquisition module; A program characterized by that.

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