JP2011259509A - Image scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image scanning device in which a shading correction mechanism is constituted of a less number of components than ever before with the increased degree of freedom of the design and the reduced size and weight.SOLUTION: An image scanning device comprises scanning units 61, 62 and a driving unit 10. The scanning unit comprises a line image sensor 11 for scanning a document image at a document scanning position, a color reference member 17, and a movement mechanism for moving the line image sensor 11 so that the document carried to the scanning position and the color reference member 17 can be scanned respectively, and is fixed to the body of the image scanning device. The driving unit 10 moves the line image sensor 11 to a position where the document carried to the scanning position and the color reference member 17 can be scanned respectively by driving the movement mechanism which the scanning unit has from outside of the scanning unit.

Description

  The present invention relates to an image reading apparatus that reads an image formed on a document while conveying the document.

  In general, an image reading apparatus that reads an image of an original while conveying the original illuminates the original with a light source, collects reflected light from the original with a rod lens array or the like, and reads the image of the original with a line image sensor or the like. However, since there is unevenness in the light amount of the light source and the rod lens array and unevenness in the sensitivity of the line image sensor, there is a problem that uniform image reading cannot be performed as it is.

  Therefore, in order to enable uniform image reading, a line image is read when reading a document image using shading correction data generated based on an output signal when a white color reference member is read by a line image sensor. Image data obtained from the output signal of the sensor is corrected. When importing the correction data used in this correction, the light amount adjustment for optimizing the light emission amount of the light source for illuminating the document and the amplification factor for amplifying the image signal output of the line image sensor are optimized. Gain adjustment is performed. Further, it is common to perform shading correction that corrects unevenness in the light amount of the light source and the rod lens array and unevenness in sensitivity of the line image sensor in units of pixels of the line image sensor. The correction for the line image sensor to uniformly read the image information of the document including the above-described light amount adjustment and gain adjustment is referred to as “shading correction”.

  In this type of image reading apparatus, a line image sensor reads a document image for the purpose of detecting the boundary between the document and the background, detecting the skew state of the document, and preventing the back side image of the document from showing through. The color of the member arranged on the back side of the document at the reading position is a color other than white (generally black).

  A schematic configuration and operation of a conventional general image reading apparatus will be described with reference to FIG.

  The image reading apparatus 1000 in FIG. 11 reads image information of the document D by the line image sensor 110 through the contact glass 150 while conveying the document D. The image reading apparatus 1000 includes a pickup roller 2 that picks up the document D, a feed roller 3 that feeds the document D picked up by the pickup roller 2 into the apparatus, and a separation that separates the picked-up document D one by one. The roller 4 includes a registration roller 5 and a conveyance roller 7 that are arranged in pairs at opposite positions and convey the document D.

  The image reading apparatus 1000 first moves the line image sensor 110 in the direction of arrow S in the figure before reading the image of the document D, and causes the line image sensor 110 to read the color reference member 170. The color reference member 170 is disposed at a position facing the line image sensor 110 after the line image sensor 110 has moved in the direction of arrow S in the drawing.

  Then, image data obtained based on the output of the line image sensor 110 when the color reference member 170 is read by the line image sensor 110 is stored for each pixel of the line image sensor 110 as shading correction data for shading correction. . Thereafter, the image reading apparatus 1000 returns the line image sensor 110 to the original position (original image reading position), and causes the line image sensor 110 to read image information of the original D while conveying the original D. At the time of reading the image of the document D, the shading correction is performed on the image data obtained from the output of the line image sensor 110 with reference to the correction data stored in advance. Whether or not the line image sensor 110 has moved to the color reference member reading position for reading the color reference member 170 can be determined by the output of the position detection sensor 120. The position detection sensor 120 is detection means for detecting the position of the line image sensor 110.

  In such an image reading apparatus 1000, when the line image sensor 110 moves between the color reference member reading position and the document image reading position, if the line image sensor 110 deviates from the document image reading position, the document reading registration is performed. It will cause a shift. In order to prevent this misregistration, the position detection sensor 120 is generally used to position the line image sensor 110 during document reading. The series of operations described above is generally performed according to instructions from a control unit such as a CPU (Central Processing Unit).

  In addition, some image reading apparatuses move the color reference member instead of moving the line image sensor when reading a document and reading a color reference member. For example, a technique has been proposed in which the color reference member is exposed to the document conveyance path when the color reference member is read, and is retracted to a position where the color reference member does not contact the conveyed document when reading the document (for example, see Patent Document 1).

JP 2005-102017 A

  However, in the image reading apparatus capable of reading the front and back sides of the document as described in Patent Document 1, the color reference member and the shading correction mechanism must be arranged at the position where the reading sensor faces. The degree of freedom is reduced, making it difficult to reduce the size and weight easily.

  In addition, in the conventional image reading apparatus shown in FIG. 11, the position detection sensor 120 must be provided in order to prevent misregistration. Further, in the image reading apparatus described in Patent Document 1, since the shading correction mechanism for exposing the color reference member to the document conveyance path is provided, the number of parts increases and the structure becomes complicated. is there.

  The present invention has been made in view of the above problems, and the shading correction mechanism can be configured with a smaller number of parts than conventional ones, and can be reduced in size and weight by increasing the degree of design freedom. An object is to provide an image reading apparatus.

  In order to achieve the above object, an image reading apparatus according to the present invention is an image reading apparatus that reads an image of a document while conveying the document, a reading sensor that reads an image of the document at a reading position of the document, and a color reference A reading unit having a member, a moving mechanism for moving the reading sensor so as to be able to read the original conveyed to the reading position and the color reference member, respectively, and fixed to the main body of the image reading apparatus; Drive means for moving the reading sensor and the color reference member to positions where the reading sensor is moved by moving the moving mechanism of the reading unit from the outside of the reading unit. It is characterized by providing.

  According to the present invention, in an image reading apparatus having a structure in which the reading unit is fixed to the main body of the image reading apparatus, the shading correction mechanism can be configured with a smaller number of parts than in the past, and the degree of design freedom is increased. Can be reduced in size and weight.

1 is a cross-sectional view showing a schematic internal structure of an image reading apparatus according to an embodiment of the present invention as viewed from the side. FIG. 2 is a block diagram illustrating a schematic electrical configuration of the image reading apparatus 1 of FIG. 1. (A) is a vertical partial sectional view of a reading unit at the time of reading a document image, and (b) is a horizontal partial sectional view of the reading unit at the time of reading a document image. (A) is a vertical partial sectional view of the reading unit at the time of reading the color reference member, and (b) is a horizontal partial sectional view of the reading unit at the time of reading the color reference member. 4A and 4B are structural diagrams around a drive unit, where FIG. 5A shows a state when reading a document image, and FIG. 5B shows a state when reading a color reference member. 4A and 4B are structural diagrams of the periphery of a driving unit viewed from the document conveyance direction, where FIG. 5A shows a state in which the apparatus is closed when reading the color reference member, and FIG. 5B shows a state in which the apparatus is opened when reading the color reference member. It is a figure which shows an output waveform when rotating a pulse motor at a fixed speed and performing image reading operation with a line image sensor. 2A and 2B are vertical partial cross-sectional views illustrating an example of a reading unit, in which FIG. 1A shows a state when reading a document, and FIG. 2B shows a state when reading a color reference member. 4A and 4B are vertical partial cross-sectional views illustrating another example of a reading unit, in which FIG. 5A shows a state when reading a document, and FIG. 5B shows a state when reading a color reference member. FIG. 4 is a partial cross-sectional view showing an example of the layout of a color reference member, where (a) is a color reference member disposed on the surface opposite to the document transport surface of the contact glass, and (b) is a document transport surface of the glass holding member. When arranged, (c) shows a case where the glass holding member is arranged on the surface opposite to the document conveying surface, and (d) shows a case where the relay unit is omitted from the layout of FIG. It is an internal structure figure which looked at the conventional image reading apparatus from the side.

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

  FIG. 1 is a sectional view showing a schematic internal structure of an image reading apparatus according to an embodiment of the present invention as viewed from the side. This structure is an example of the structure of this invention, and is not restricted to this.

  In FIG. 1, an image reading apparatus 1 includes a pickup roller 2 that picks up a document D, a feeding roller 3 that feeds the document D picked up by the pickup roller 2 into the apparatus, and one sheet of the document D that has been picked up. Separation roller 4 that separates each one, registration roller 5 that is arranged in pairs at opposite positions, and conveys document D, and reading that reads image information on the upper surface (front surface) of document D conveyed by registration roller 5 A unit 61, a reading unit 62 for reading image information on the lower surface (back surface) of the conveyed document D, a downstream side of the reading units 61 and 62, and a pair of opposing positions. A transport roller 7 for transporting the document D;

  The image reading apparatus 1 includes an upper frame 81 that can rotate around a rotation shaft 81a, and a lower frame 82 that pivotally supports the rotation shaft 81a. A document D is placed between the upper frame 81 and the lower frame 82. The document D is transported by being sandwiched. The upper frame 81 can be manually rotated (opened / closed) to remove the document D staying in the apparatus when a paper jam or the like of the conveyed document D occurs.

  The upper frame 81 accommodates the feeding roller 3, the registration roller 5, the reading unit 61, and the conveyance roller 7, and the lower frame 82 accommodates the separation roller 4, the registration roller 5, the reading unit 62, and the conveyance roller 7. . A portion (not shown) that supports the rotating shaft 81a is configured integrally with the lower frame 82, and extends to both side surfaces (front and back in the figure) so as to sandwich the upper frame 81.

  The reading unit 62 is fixed to the lower frame 82. On the other hand, the reading unit 61 is swingably supported by the upper frame 81 by a plurality of swing arms 9. The swing arm 9 has one end of the swing arm 9 pivotally supported by the upper frame 81 and the other end pivotally supported by the reading unit 61. As a result, the reading unit 61 itself can move in parallel in the vertical direction, and an image can be smoothly read and conveyed from a thick original. Since one end of the swing arm 9 has a snap fit structure, assembly is easy.

  The drive unit 10 is housed in a portion that supports the rotary shaft 81a in the lower frame 82, and projects straightly from the side surfaces of the reading units 61 and 62 in the same direction (frontward in the drawing). , 18y, and a drive motor and a drive motor. The drive unit 10 presses and drives the straight cam ends 18x and 18y, whereby the reading units 61 and 62 are switched from the original reading state to the color reference member reading state.

  Next, a series of operations at the time of image reading of the document D in the image reading apparatus 1 will be described.

  First, the linear cam ends 18x and 18y are pressed by the drive unit 10, and the reading units 61 and 62 are caused to read color reference members (to be described later) by a line image sensor. The image reading device 1 generates shading correction data based on a read signal obtained by reading and stores the data for each pixel. Thereafter, pressing of the straight cam ends 18x and 18y by the drive unit 10 is stopped, and the document D is taken into the apparatus by the pickup roller 2 and the feeding roller 3, and separated by the separation roller 4 one by one.

  The document D is nipped and transported (sub-scanned) by the pair of registration rollers 5 and the pair of transport rollers 7, and the front and back images are read by the reading units 61 and 62 in the main scanning direction (a direction orthogonal to the document transport direction). ) Is repeatedly read. At the time of document reading, shading correction is performed on image data generated from output signals of the line image sensors of the reading units 61 and 62 with reference to the stored shading correction data. After the image is read, the document D is discharged outside the apparatus while being nipped and conveyed by the pair of conveying rollers 7. The generation and storage of the shading correction data may be performed only once for all the stacked originals, or may be performed again every few sheets.

  FIG. 2 is a block diagram showing a schematic electrical configuration of the image reading apparatus 1 of FIG.

  In FIG. 2, reference numeral 11 denotes a line image sensor (reading sensor) in the reading units 61 and 62. Reference numeral 111 denotes a light source built in the line image sensor 11.

  Reference numeral 100 denotes an A / D converter that converts an image signal obtained from the line image sensor 11 into a digital signal after analog processing such as amplification and black level clamping. An image processing unit 101 performs control of the line image sensor 11, the light source 111, the A / D conversion unit 100, and the like, and performs various image processing (such as shading correction) on image data obtained by digitizing an image signal.

  An image storage unit (image memory) 102 stores image data. Reference numeral 103 denotes an interface unit for connecting to an external host device or a network through a signal line 109. A control unit (CPU) 104 controls the image reading apparatus 1. A storage unit (work memory) 105 is used for the CPU 104 to operate.

  The image processing unit 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 perform processing using the image data held in the image memory 102 according to the program written in the work memory 105.

  Reference numeral 112 denotes a transport motor that transports a document. The transport motor 112 operates under the control of the motor driver 107 based on an instruction from the CPU 104. The pulse motor 21 is a component constituting the drive unit 10, and the line image sensor 11 is arranged between a document image reading position for reading an image of the document D and a color reference member reading position for reading a color reference member. Move with. Further, the pulse motor 21 operates under the control of the motor driver 106 based on an instruction from the CPU 104.

  Next, the configuration of the reading units 61 and 62 in FIG. 1 will be described with reference to FIGS.

  3A is a vertical partial cross-sectional view of the reading units 61 and 62 at the time of reading the original image, and FIG. 3B is a horizontal partial cross-sectional view of the reading units 61 and 62 at the time of reading the original image. 4A is a vertical partial cross-sectional view of the reading units 61 and 62 when reading the color reference member, and FIG. 4B is a horizontal partial cross-sectional view of the reading units 61 and 62 when reading the color reference member. Since the reading unit 61 and the reading unit 62 have the same structure, the reading unit 62 will be described.

  As shown in FIGS. 3 and 4, the reading unit 62 includes a line image sensor 11 that reads an image, a sensor box (case) 12 that houses the line image sensor 11, and a substrate 13 that operates the line image sensor 11. 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 15a, a glass holding member 16 that holds the contact glass 15, and a color reference having a white reference surface. The member 17 includes a rectilinear cam 18 for moving the line image sensor 11 to a predetermined position, and a tension spring 22 for urging the rectilinear cam 18 to return the moved line image sensor 11 to its original position. Is done.

  As shown in FIGS. 3A and 4A, the sensor box 12 has a through hole 12a through which the flat cable 14 passes. The through-hole 12a has a bowl shape to prevent entry of dust and dirt.

  The color reference member 17 is provided on the side of the document conveying surface on the contact glass 15 and at a position different from the document reading position 15a. The white reference surface of the color reference member 17 is in close contact with the contact glass 15 by any method such as adhesion, sticking with tape, painting or printing. For this reason, even when the conveyed document D rubs against the color reference member 17, the white reference surface is not damaged, and the whiteness does not decrease due to adhesion of paper dust or dirt.

  The line image sensor 11 has protrusions 11a and 11b extending beyond the side of FIG. The protrusion 11 a is fitted in a cam groove 18 a provided in the rectilinear cam 18. Further, the protrusion 11a is fitted into a long hole 12b provided in the sensor box 12, and thereby movement in the main scanning direction is restricted. On the other hand, the protrusion 11 b is fitted in a cam groove 18 b provided in the rectilinear cam 18.

  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 provided on the sensor box 12 are fitted, and a tension spring 22. And a hook portion 18e to be hooked.

  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 arrow f in the figure. When the document is read, as shown in FIG. 3B, the rectilinear cam end 18y (the rectilinear cam end 18x in the case of the reading unit 61), which is one end of the rectilinear cam 18, is connected to the sensor box 12 (reading units 61 and 62). It will be in the state which protruded from. On the other hand, when the color reference member is read, as shown in FIG. 4B, the rectilinear cam end 18y (or the rectilinear cam end 18x in the case of the reading unit 61) is pushed into the sensor box 12 (reading units 61 and 62). It becomes a state.

  Thus, the linear cam 18 is slidably engaged with the line image sensor 11 and driven in the main scanning direction which is the longitudinal direction of the line image sensor 11, thereby moving the line image sensor 11 in the sub-scanning direction. It can be moved to either the original image reading position or the color reference member reading position.

  Next, the structure of the drive part 10 of FIG. 1 is demonstrated with reference to FIG.5 and FIG.6.

  5A and 5B are structural diagrams of the periphery of the drive unit 10, where FIG. 5A shows a state when reading a document image, and FIG. 5B shows a state when reading a color reference member.

  5A and 5B, the rectilinear cam end 18x is an end portion of the rectilinear cam 18 protruding from the side surface of the reading unit 62, and the rectilinear cam end 18y is a rectilinear cam from the side surface of the reading unit 61. This is an end portion of the rectilinear cam 18 projecting in the same direction as the end 18x.

  The drive unit 10 rotates the eccentric cam 20 around the rotary shaft 20b by pushing the push plate 19 for pushing the straight cam ends 18x and 18y, the eccentric cam 20 for transmitting the drive force to the push plate 19, and the push plate 19. And a pulse motor 21 that operates.

  The push plate 19 is provided with a contact surface 19a that contacts the eccentric cylindrical surface 20a of the eccentric cam 20, and a contact surface 19b that contacts the rectilinear cams 18x and 18y. The push plate 19 is configured to rotate about the rotation shaft 19d by pressing the contact surface 19a in contact with the eccentric cylindrical surface 20a by the rotation of the eccentric cam 20 about the rotation shaft 20b. When the push plate 19 rotates about the rotation shaft 19d, the straight cam ends 18x and 18y protruding from the reading units 61 and 62 are pushed into the inside.

  The reading unit 61 and the reading unit 62 have a rectilinear cam of the reading unit 62 with respect to the rotating shaft 19d so that the distances between the rotating shaft 19d of the push plate 19 and the rectilinear cam end 18x and the rectilinear cam end 18y are different. The linear cam end 18x of the reading unit 61 is disposed farther from the end 18y. When the reading units 61 and 62 are arranged in this way, as shown in FIG. 5A, the push plate 19 comes into contact with the rectilinear cam end 18y when reading a document image. On the other hand, the contact surface 19b is not in contact with the rectilinear cam end 18x. Accordingly, the reading unit 61 supported by the swing arm 9 so as to be swingable can smoothly move up and down following the thickness of various documents.

  6A and 6B are structural views of the periphery of the driving unit 10 as viewed from the document conveyance direction. FIG. 6A shows a state in which the apparatus is closed when reading the color reference member, and FIG. Show.

  The state where the apparatus is closed is a state where the upper frame 81 and the lower frame 82 are joined together as shown in FIG. On the other hand, the state in which the device is open is a state in which the upper frame 81 is rotated about the rotation shaft 81a and lifted upward.

  As shown in FIGS. 6A and 6B, the push plate 19 has a sloped portion 19c at a contact portion with the straight cam end 18x facing the reading units 61 and 62. If the apparatus is opened when the color reference member is read, the rectilinear cam 18 is pulled by the tension spring 22, so that the rectilinear cam end 18 x that has been pushed inside by the push plate 19 is pressed from the push plate 19. Will come off and protrude from the reading unit 61. If the apparatus is closed from this state, there is a possibility that the straight cam end 18x and the push plate 19 may collide and be damaged if the push plate 19 is not provided with the inclined surface portion 19c.

  Therefore, by providing the inclined plate 19c on the push plate 19, the straight cam end 18x protruding from the reading unit 61 in the process of closing the apparatus is pushed into the inside while contacting the inclined plate 19c. It is possible to prevent the 18x and the push plate 19 from colliding and being damaged. In addition, by adding a roundness (corner R) as shown in the figure to the end of the rectilinear cam end 18x that comes into contact with the slope-shaped portion 19c, there is an effect of further preventing the rectilinear cam end 18x and the push plate 19 from being damaged at the time of collision. Increase.

  By having such a configuration, the image reading apparatus 1 can drive the rectilinear cams 18 of the two reading units 61 and 62 with one drive unit 10. For this reason, it is not necessary to provide the two reading units 61 and 62 with a motor for driving the units and a drive transmission mechanism associated with the motors. As a result, it is possible to reduce the size of the apparatus by reducing the space in which they are provided, and to reduce the number of parts compared to the conventional apparatus and to make the apparatus inexpensive.

  Further, each linear cam 18 can be driven from the outside of the reading units 61 and 62 to move the position of the line image sensor 11. When the image reading apparatus is a single-sided reading apparatus, it is configured by an upper frame 81 and a lower frame 82 provided with a reading unit, and the driving unit 10 can be provided in the lower frame 82 provided with no reading unit. The degree of freedom can be increased.

  Next, the operation reference position detection operation of the pulse motor 21 will be described with reference to FIG.

  FIG. 7 is a diagram showing a change in output value with respect to the number of steps of the pulse motor 21 (driving amount of the driving means) when the image reading operation of the line image sensor 11 is performed simultaneously with the rotation of the pulse motor 21 at a constant speed. .

  When the pulse motor 21 is rotated once, the line image sensor 11 moves from a position not facing the color reference member 17 as shown in FIG. 3A to a position facing the color reference member 17 as shown in FIG. It moves again and returns to a position not facing the color reference member 17 as shown in FIG. In the meantime, reading is performed by the line image sensor 11, and a line image sensor output value as shown in FIG. 7 is stored in the image memory 102. Here, the line image sensor output value is a value obtained by converting the line image sensor output, which is an analog signal, into digital data by the A / D conversion unit 100 and further performing offset correction.

  The CPU 104 reads out image data read from the color reference member 17 at a position facing the color reference member 17 and image data read at a position not facing the color reference member 17 from the image data stored in the image memory 102. The process which detects the boundary part of is performed. The CPU 104 stores the position of the pulse of the pulse motor 21 and calculates a desired stop position, so that the original image reading position and color reference member reading can be performed from the current operation reference position of the pulse motor 21. Know the number of steps required to move to a position. This number of steps is the drive amount of the drive unit 10.

  The boundary (A) when the line image sensor 11 moves from a position not facing the color reference member 17 as shown in FIG. 3A to a position facing the color reference member 17 as shown in FIG. 4A. Again, as shown in FIG. 3A, the intermediate point (1), which is an intermediate point between the boundary part (B) when moved to a position not facing the color reference member 17, faces the color reference member 17. It can be said that it is the optimal position to do.

  Further, a boundary portion (B) when the line image sensor 11 moves from a position facing the color reference member 17 as shown in FIG. 4A to a position not facing the color reference member 17 as shown in FIG. 3A. ) And again the intermediate point (2), which is the intermediate point between the boundary part (C) when moved to the position facing the color reference member 17 as shown in FIG. It can be said that it is an optimal position that does not oppose.

  However, an error in the size of the color reference member 17, and the reading position of the line image sensor 11 is moved from the pulse motor 21 through the push plate 19 and further through the linear cam 18, so that a movement error occurs.

  Therefore, in order to detect the optimum position, the pulse motor 21 is rotated at a constant speed and at the same time the reading operation is performed, and the pulse motor necessary for moving between the respective boundary portions from the change of the output value shown in FIG. The driving amounts L1 and L2 of 21 are obtained as the number of steps. As a result, the drive amounts L + L1 ′ and L + L1 + L2 ′ required to move from the current operation reference position of the pulse motor 21 to the intermediate point (1) and intermediate point (2) between the boundary portions can be obtained as the number of steps. it can.

  As described above, the driving amount to the intermediate point (1) and the driving amount to the intermediate point (2) are calculated as driving amounts for determining the position of the line image sensor 11 when reading the color reference member and reading the original image, respectively. can do. This eliminates the need to add a position detection sensor for detecting the current operation reference position of the line image sensor 11.

  Even if the line image sensor 11 is moved to a position not facing the color reference member 17, the difference in brightness between the original surface and the surface of the color reference member 17 is small if a document or the like exists on the contact glass 15. Since the boundary cannot be found, an error may be displayed to notify or prompt the user to remove the document.

  By the way, immediately after the product is turned on, it is impossible to recognize where the current stop position of the pulse motor is. 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, in the operation of searching for the boundary between the color reference member 17 and the portion that is not the color reference member, 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 are performed with predetermined initial values. (Especially immediately after factory assembly). The above-described method of “finding an image of the color reference member 17 and an image that is not the color reference member 17” can be easily determined based on the magnitude relationship between the output value from the line image sensor 11 and a predetermined threshold value.

  However, it is possible that the image of the color reference member 17 and the image that is not the color reference member 17 cannot be distinguished from the threshold value due to the influence of variations in the light source. In such a case, the maximum value and the minimum value of the output value from the line image sensor 11 are held during one rotation of the pulse motor, and the average value thereof is used as a threshold value or the image of the color reference member 17 is displayed. It is also possible to use a method such as changing the light amount setting value of the light source or the gain setting value of the A / D conversion unit 100 so that the image that is not the color reference member 17 can be distinguished from the threshold value. The gain setting value may be changed for an amplifier that amplifies an analog signal before A / D conversion, or may be calculated for digital data after A / D conversion.

  With the above-described configuration, the image reading apparatus 1 rotates the pulse motor 21 during the reading operation of the color reference member performed before the image reading operation so that the push plate 19 and the straight cam 18 are in the state shown in FIG. The sensor 11 is moved to a position facing the color reference member 17 (see FIG. 4A). When the line image sensor 11 and the color reference member 17 face each other and the color reference member 17 covers the effective reading range of the line image sensor 11, the line image sensor 11 reads the color reference member 17. As a result, correction data generated based on the output of the line image sensor 11 is stored for each pixel as shading correction data for shading correction. After that, the image reading apparatus 1 rotates the pulse motor 21 to bring the push plate 19 and the straight cam 18 into the state shown in FIG. 4A and move the line image sensor 11 to a position where it does not face the color reference member 17 (FIG. 3 (a)).

  According to the above embodiment, the reading units 61 and 62 include the glass holding member 16 that holds the contact glass 15, the line image sensor 11 that reads an image of the conveyed document, and the reading position on the contact glass 15. The color reference member 17 is disposed at different positions, and the line image sensor 11 and a movement mechanism that relatively moves the color reference member 17 so that the original and the color reference member can be read alternately. Then, the driving unit 10 drives the moving mechanism from outside the reading unit 61 to move at least one of the line image sensor 11 and the color reference member 17. Thus, the moving mechanism (the cam member 18, the tension spring 22 and the like) for moving the line image sensor 11 between the document image reading position and the color reference member reading position and the driving unit 10 for driving the moving mechanism are provided. It can be configured with a smaller number of parts than before. Even if the color reference member 17 is arranged on the document conveyance path, the line image sensor 11 reads the white color reference surface of the color reference member 17 that is in close contact with the contact glass 15 when shading correction data is acquired. Therefore, shading correction can be performed with high accuracy without cleaning.

  In the above embodiment, only the line image sensor 11 is moved. However, the present invention is not limited to this. That is, the line image sensor 11 and the glass holding member 16 may be moved relative to each other so that the line image sensor 11 and the color reference member 17 move to a position where they do not face each other. For example, as shown in FIG. 8, only the glass holding member 16 may be moved between (a) reading a document and (b) reading a color reference member. Further, as shown in FIG. 9, both the line image sensor 11 and the glass holding member 16 may be moved between (a) reading a document and (b) reading a color reference member.

  In the above embodiment, the color reference member 17 is provided on the document conveying surface side on the contact glass 15. However, the present invention is not limited to this. That is, the color reference member 17 may be provided on the contact glass 15 or on the glass holding member 16 at a position deviated from the document reading position 15a. For example, as shown in FIG. 10, (a) the contact glass 15 may be provided on a surface opposite to the document conveying surface. Further, as shown in FIG. 10B, even on the document conveying surface of the glass holding member 16, it is provided on the surface opposite to the document conveying surface on the glass holding member 16 as shown in FIG. May be. In the case of FIG. 10 (b), when the line image sensor 11 moves, the amount of movement increases by jumping over the relay portion 16a connecting the contact glass 15 and the color reference member 17, so that FIG. ), The relay unit 16a may be eliminated.

  Further, the color reference member 17 shown in FIGS. 10B and 10D needs to have a strength and thickness so that the scratch due to the document conveyance does not reach the white reference surface. In the case of FIG. 10A and FIG. 10C, the position of the white reference surface of the color reference member 17 is different from the position of the upper surface of the contact glass that is the reading surface of the document, so that both surfaces are in focus. It is desirable to select the thickness of the contact glass 15 and the shape of the glass holding member 16. This is due to unevenness in the amount of light of the rod lens array (not shown) as one of the non-uniformities that require shading correction, and the shape (light amount distribution) of the unevenness in the amount of light differs at a position that is out of focus. Because. When the unevenness of the light amount of the rod lens array is small, the color reference member can be read at a position out of focus.

  Even in the case of FIGS. 10A to 10D, as a result, the line image sensor 11 and the color reference member 17 may be moved to positions that do not face each other. The color reference member 17, the glass holding member 16, etc. may move vertically or move in the middle of movement or rotate. 10A to 10D, since the white reference surface of the color reference member 17 is exposed inside the reading units 61 and 62, scratches, paper dust, dust, and the like are not attached. .

  In the above embodiment, the inclined plate 19c is provided on the push plate 19 to prevent the straight cam end 18x from being damaged when the apparatus is opened when reading the color reference member. On the other hand, as another embodiment, when the apparatus is opened / closed at the time of reading the color reference member, the opening / closing of the apparatus is detected and the pulse motor 21 is rotated so that the push plate 19 is in the state shown in FIG. The end 18x may be prevented from being damaged.

  The detection means for detecting opening and closing of the apparatus may be any detector including a micro switch, a light detection switch, a magnetic detection switch, and the like. Further, the read / output of the line image sensor 11 may be determined to be a value that is far from the normal value, so that the opening / closing of the apparatus may be determined. The combination with the electrical circuit can be used as a detection means for detecting opening and closing of the apparatus.

  In the above-described embodiment, an image reading apparatus capable of reading both sides of a document has been described. Needless to say, the present invention can be applied to an image reading apparatus for single-sided reading.

DESCRIPTION OF SYMBOLS 1 Image reading apparatus 10 Drive part 11,110 Line image sensor (reading sensor)
15, 150 Contact glass 16 Glass holding member 17, 170 Color reference member 18 Linear cam 18x, 18y Linear cam end 19 Push plate 20 Eccentric cam 21 Pulse motor 61, 62 Reading unit 102 Image memory 104 CPU

Claims (1)

An image reading apparatus that reads an image of a document while conveying the document,
A reading sensor that reads an image of a document at a reading position of the document, a color reference member, and a moving mechanism that moves the reading sensor so that the document conveyed to the reading position and the color reference member can be read. And a reading unit fixed to the main body of the image reading apparatus,
Drive means for moving the reading sensor and the color reference member to positions where the reading sensor is moved by moving the moving mechanism of the reading unit from the outside of the reading unit. An image reading apparatus comprising:

Images