Image reading device and image forming system

Abstract

To determine a position of a reading unit at a home position in a short time with a simple configuration.SOLUTION: A scanner comprises: a document platen 31 on which a document is placed; a frame 32 that is provided along edges of the document platen 31; a reading unit that reads the document in a main scanning direction; a moving mechanism that moves the reading unit in a sub scanning direction intersecting with the main scanning direction; a white reference member 60 that is provided on the frame 32 to be adjacent to the document platen 31 in the sub scanning direction and has a longer length in the main scanning direction than that of the document platen 31; and a control section that controls the moving mechanism. The reading unit includes a first reading section 41 that reads an area corresponding to the document platen 31, and a second reading section 42 that reads an area corresponding to the frame 32. The control section detects a boundary B between the frame 32 and the reference member 60 according to a read value obtained by the second reading section 42, while controlling the moving mechanism to move the reading unit, and determines a position of the reading unit 40 at a home position H separated from the boundary B by a predetermined distance D.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to an image reading device and an image forming system. [Background technology]

[0002] The image reading device includes a reading unit that irradiates light onto an original document and guides the reflected light from the original document to a photoelectric conversion element. The image reading device also includes a mechanism that moves the reading unit in a predetermined direction to read an original document placed on a platen. The reading unit has a home position, and when a reading job is input, the image reading device acquires white reference data by reading a white reference member while moving the reading unit from the home position as a starting point, and then reads the original document. Therefore, a mechanism for positioning the reading unit at the home position is required.

[0003] As a method for positioning the reading unit, a configuration in which a sensor such as a photointerrupter is used to detect the reading unit at a predetermined position is considered. However, this configuration has the problem of increasing the size of the device and increasing costs. Therefore, a technology has been considered in the past in which the reading unit reads a mark indicating the home position to position the reading unit (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-5119 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, it is possible that the reading unit may stop at a location other than the home position due to a voltage drop in the power supply during execution of a reading job. In that case, if the mark for detecting the home position has a simple shape, it will be difficult to distinguish it from the document placed on the document table. To avoid this, it is possible to make the mark more complex in shape, but this would also complicate the algorithm for detecting the mark, which would result in a problem of long detection times.

[0006] SUMMARY OF THE PRESENT INVETION The present invention has been made in consideration of the above circumstances, and has an object to provide an image reading device and an image forming system that can position a reading unit at a home position in a short time with a simple configuration. [Means for solving the problem]

[0007] In order to solve the above problem, the image reading device of the present invention comprises a transparent platen on which a document is placed, a frame arranged along the edge of the platen, a reading unit that reads the document in a main scanning direction, a moving mechanism that moves the reading unit in a sub-scanning direction that intersects the main scanning direction, a white reference member that is arranged on the frame adjacent to the platen in the sub-scanning direction and has a length in the main scanning direction longer than that of the platen, and a control unit that controls the moving mechanism, wherein the reading unit includes a first reading unit that reads an area corresponding to the platen and a second reading unit that reads an area corresponding to the frame, and the control unit detects the boundary between the frame and the reference member based on the reading value of the second reading unit while moving the reading unit with the moving mechanism, and positions the reading unit at a home position that is a predetermined distance away from the boundary.

[0008] In the image reading device of the present invention, the home position is set on the side of the reference member, and the control unit may detect the boundary while moving the reading unit toward the reference member when the reading value of the second reading unit indicates that the reading unit is stopped at a position where the second reading unit faces the frame, and may detect the boundary while moving the reading unit toward the frame when the reading value of the second reading unit indicates that the reading unit is stopped at a position where the second reading unit faces the reference member.

[0009] In the image reading device of the present invention, the second reading unit may have a plurality of photoelectric conversion elements arranged in the main scanning direction, and the control unit may detect the boundary using the minimum value of the read values ​​of the plurality of photoelectric conversion elements.

[0010] In the image reading device according to the present invention, the control unit may detect the boundary by using a minimum value of average values ​​of read values ​​for each set of the plurality of photoelectric conversion elements.

[0011] In the image reading device according to the present invention, the set of the plurality of photoelectric conversion elements may be capable of reading a range wider than an expected range of foreign matter.

[0012] Moreover, an image forming system according to the present invention is characterized in that it includes any one of the image reading devices described above, and an image forming device that forms an image of the original document read by the first reading unit on a sheet. Effect of the Invention

[0013] According to the present invention, the reading unit can be positioned at the home position in a short time with a simple configuration. [Brief description of the drawings]

[0014] [Figure 1] 1 is a perspective view showing an external appearance of a multifunction peripheral according to an embodiment of the present invention; [Diagram 2]1 is a front view showing a schematic internal configuration of a multifunction peripheral according to an embodiment of the present invention; [Diagram 3] 1 is a perspective view of a scanner according to an embodiment of the present invention; [Figure 4] 1 is a front view showing a schematic internal configuration of a scanner according to an embodiment of the present invention; [Diagram 5] 2 is a plan view showing the underside of the top plate of the scanner according to the embodiment of the present invention; FIG. [Figure 6] 1 is a plan view showing a schematic internal configuration of a scanner according to an embodiment of the present invention; [Figure 7] 2 is a plan view showing the positional relationship between a reference member, a first reading unit, a second reading unit, and a manuscript table according to an embodiment of the present invention. FIG. [Figure 8] FIG. 2 is a block diagram showing the electrical configuration of the scanner according to the embodiment of the present invention. [Figure 9] 4 is a flow diagram of the operation of a scanner according to an embodiment of the present invention. [Figure 10] This is an example of white foreign matter adhering to the top plate. [Figure 11] This is an example in which a black foreign object is attached to the reference member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, a multifunction device 100 (an example of an image forming system) according to an embodiment of the present invention will be described with reference to the drawings. The multifunction device 100 includes a printer 1 (an example of an image forming device) and a scanner 110 (an example of an image reading device).

[0016] First, an overview of the configuration of the printer 1 will be described. Fig. 1 is a perspective view showing the external appearance of the multifunction device 100. Fig. 2 is a front view showing a schematic internal configuration of the multifunction device 100. In the following description, the front side of the paper in Fig. 2 is the front side (front side) of the multifunction device 100, and the left and right directions are described based on the direction when the multifunction device 100 is viewed from the front. In each figure, U, Lo, L, R, Fr, and Rr respectively indicate up, down, left, right, front, and rear.

[0017] The printer 1 includes a rectangular parallelepiped main housing 3. A paper feed cassette 4 that stores sheets S, and a paper feed roller 5 that feeds sheets S from the paper feed cassette 4 are provided in the lower part of the main housing 3. An imaging device 6 that forms a toner image by electrophotography, and a fixing device 7 that fixes the toner image to the sheet S are provided above the paper feed cassette 4. A pair of discharge rollers 8 that discharges the sheet S on which the toner image has been fixed, and a discharge tray 9 on which the discharged sheets S are stacked are provided in the upper part of the main housing 3.

[0018] Inside the main body housing 3, a transport path 10 is provided that runs from the paper feed roller 5 through the image forming device 6 and the fixing device 7 to a discharge roller pair 8. A plurality of transport roller pairs 17 that transport the sheet S are provided on the transport path 10. A registration roller pair 18 is provided upstream of the image forming device 6 in the transport direction.

[0019] Each part of the printer 1 is controlled by a control unit 2. A scanner 110 is provided above the printer 1. An operation panel 19 is provided in front of the scanner 110. The operation panel 19 includes a display panel, a touch panel superimposed on the display surface of the display panel, and a keypad adjacent to the display panel. The control unit 2 displays a screen showing the operation menus for the printer 1 and scanner 110 on the display panel, and controls each part of the printer 1 and scanner 110 in response to operations detected by the touch panel and the keypad.

[0020] Next, an overview of the image forming operation of the printer 1 will be described. When a print job is input to the printer 1 from an external computer or the like, the paper feed roller 5 feeds the sheet S from the paper feed cassette 4 to the transport path 10, the registration roller pair 18, whose rotation has been stopped, corrects any skew of the sheet S, and the registration roller pair 18 feeds the sheet S to the image forming device 6 at a predetermined timing. The image forming device 6 forms a toner image according to the print job and transfers it to the sheet S. Next, the fixing device 7 fixes the toner image to the sheet S, and the discharge roller pair 8 discharges the sheet S to the discharge tray 9. The cleaning device 16 removes any toner remaining on the photosensitive drum 11.

[0021] Next, the configuration of the scanner 110 will be described. FIG. 3 is a perspective view of the scanner 110. FIG. 4 is a front view showing a schematic internal configuration of the scanner 110. FIG. 5 is a plan view showing the lower surface of the top plate portion 32T of the scanner 110. FIG. 6 is a plan view showing a schematic internal configuration of the scanner 110. FIG. 7 is a plan view showing the positional relationship between the reference member 60, the first reading unit 41, the second reading unit 42, and the manuscript table 31. FIG. 8 is a block diagram showing the electrical configuration of the scanner 110.

[0022] The scanner 110 comprises a transparent platen 31 on which an original is placed, a frame 32 arranged along the edge of the platen 31, a reading unit 40 that reads the original in the main scanning direction, a moving mechanism 50 that moves the reading unit 40 in a sub-scanning direction that intersects the main scanning direction, a white reference member 60 that is arranged on the frame 32 adjacent to the platen 31 in the sub-scanning direction and has a length in the main scanning direction longer than that of the platen 31, and a control unit 30 that controls the moving mechanism 50. The reading unit 40 includes a first reading unit 41 that reads an area corresponding to the platen 31, and a second reading unit 42 that reads an area corresponding to the frame 32. The control unit 30 detects a boundary B between the frame 32 and the reference member 60 from a read value of the second reading unit 42 while moving the reading unit 40 with the moving mechanism 50, and positions the reading unit 40 at a home position H that is a predetermined distance D away from the boundary B. In this embodiment, the main scanning direction and the sub-scanning direction are the front-rear direction and the left-right direction, respectively.

[0023] [Document holder] The document table 31 (see FIGS. 3 to 6) is formed of a rectangular glass plate slightly larger than the A4 size sheet S. The long sides of the document table 31 are parallel to the sub-scanning direction, and the short sides are parallel to the main scanning direction.

[0024] Frame The frame 32 is formed in a roughly rectangular box shape, and includes a rectangular bottom plate portion 32B and a top plate portion 32T, and side plate portions 32S provided between the four sides of the bottom plate portion 32B and the four sides of the top plate portion 32T. The top plate portion 32T is provided with an opening 32A of a size corresponding to the document table 31. A pressing plate 33 of a size slightly larger than the opening 32A is provided above the top plate portion 32T. The pressing plate 33 can be opened and closed with a hinge 33H provided at the rear of the opening 32A as a fulcrum. The inner surface of the frame 32 is preferably black or a dark color close to black and made of a material with low reflection.

[0025] [Reading unit] The reading unit 40 (see Figs. 4 and 7) is a CIS (Contact Image Sensor) and includes a light source 44, a lens 45, a first reading section 41, a second reading section 42, and a housing 46. The light source 44 is, for example, a side light type including an LED (Light Emitting Diode) provided at an end in the main scanning direction and a light guide that guides the light of the LED to the document. The lens 45 is, for example, a rod lens array including a plurality of rod lenses arranged in the main scanning direction. The first reading section 41 and the second reading section 42 are image sensor arrays including a plurality of photoelectric conversion elements 43 arranged in the main scanning direction. The photoelectric conversion elements 43 are, for example, CMOS (Complementary Metal-Oxide-Semiconductor field-effect transistor) image sensors.

[0026] The housing 46 accommodates the light source 44, the lens 45, the first reading unit 41, and the second reading unit 42. The housing 46 is formed in a roughly rectangular box shape with the main scanning direction as the longitudinal direction, and a rectangular opening 46A with the main scanning direction as the longitudinal direction is provided at the top. The first reading unit 41 and the second reading unit 42 are provided at the bottom of the housing 46. The first reading unit 41 is provided in a range corresponding to the document table 31, and the second reading unit 42 is provided in a range corresponding to the top plate portion 32T behind the document table 31. The lens 45 is provided above the first reading unit 41 and the second reading unit 42, and the light source 44 is provided on the left and right or one of the left and right of the lens 45.

[0027] Below the document table 31, light emitted by the light source 44 is reflected by the document placed on the document table 31 or by the pressing plate 33. The reflected light is collected by the lens 45 and enters the first reading unit 41. Below the top plate 32T behind the document table 31, light emitted by the light source 44 is reflected by the top plate 32T. The reflected light is collected by the lens 45 and enters the second reading unit 42. The first reading unit 41 and the second reading unit 42 convert the reflected light into an electric charge to generate an electric signal, which is then transmitted to the control unit 30.

[0028] [Movement mechanism] The moving mechanism 50 (see FIGS. 4 and 6) includes a rail 51, a slider 52, and a belt drive unit 53. The rail 51 is provided on the upper surface of the bottom plate portion 32B along the main scanning direction. The slider 52 is provided on the bottom of the housing 46 of the reading unit 40. The slider 52 has, for example, a shape that straddles the rail 51, and is slidable along the rail 51. At the left end of the rail 51, the leftward movement of the slider 52 is restricted so that the reading unit 40 does not deviate from the reference member 60 to the left. The belt driving unit 53 includes a motor 53M provided at one end of the bottom plate portion 32B in the sub-scanning direction, a driving pulley 53D provided on the shaft of the motor 53M, a driven pulley 53N provided at the other end of the bottom plate portion 32B in the sub-scanning direction, and a belt 53B wound around the driving pulley 53D and the driven pulley 53N, and the belt 53B is connected to the housing 46. Note that instead of the belt driving unit 53, a rack and pinion, a ball screw, a linear motor, or the like may be used.

[0029] [Reference part] The reference member 60 (see FIGS. 4 to 7) is a rectangular plate with its longitudinal direction in the main scanning direction, and is made of resin, metal, or synthetic paper, with a white underside. The reference member 60 is provided on the underside of a portion of the top plate 32T to the left of the document table 31. The length of the reference member 60 in the main scanning direction is longer than the short side of the document table 31, and the rear end of the reference member 60 is located behind the rear end of the second reading unit 42.

[0030] [Control Unit] Each part of the scanner 110 is controlled by the control unit 30 (see FIG. 8). The control unit 30 includes a calculation unit 30P, a storage unit 30M, and a communication unit 30C. The calculation unit 30P is, for example, a central processing unit (CPU). The storage unit 30M includes a storage medium such as a read only memory (ROM), a random access memory (RAM), and an electrically erasable programmable read only memory (EEPROM). The calculation unit 30P executes various processes by reading and executing a control program stored in the storage unit 30M. The communication unit 30C is a communication interface connected to the control unit 2 of the printer 1 via a signal line, and communicates with the printer 1. The control unit 30 may be realized by an integrated circuit that does not use software.

[0031] For example, assume that the printer 1 forms an image using monochrome image data of 256 gradations (0 to 255, where 0 is black and 255 is white). The control unit 30 corrects the read values ​​of each photoelectric conversion element 43 of the first reading unit 41 by converting the read value represented by the electrical signal received from the first reading unit 41 when the first reading unit 41 reads the reference member 60 into the maximum value of 256 gradations. The control unit 30 also converts the read value represented by the electrical signal received from the first reading unit 41 when the first reading unit 41 reads a document into 256 gradations to generate image data and send it to the printer 1.

[0032] Furthermore, when the power is turned on, the control unit 30 determines whether the reading unit 40 faces the frame 32 or the reference member 60, using the read value of the second reading unit 42. Specifically, a determination threshold is set between the read value of the frame 32 and the read value of the reference member 60. If the read value is less than the threshold, the control unit 30 determines that the reading unit 40 faces the frame 32. On the other hand, if the read value is equal to or greater than the threshold, the control unit 30 determines that the reading unit 40 faces the reference member 60.

[0033] Here, if a determination is made using one photoelectric conversion element 43, when a white foreign matter FW is attached to the frame 32, even if the reading unit 40 actually faces the frame 32, the control unit 30 may erroneously determine that the reading unit 40 faces the reference member 60. On the other hand, when a black foreign matter FB is attached to the reference member 60, even if the reading unit 40 actually faces the reference member 60, the control unit 30 may erroneously determine that the reading unit 40 faces the frame 32.

[0034] Therefore, in this embodiment, the judgment is performed using a plurality of photoelectric conversion elements 43 arranged in the main scanning direction. Specifically, the second reading section 42 has a plurality of (16 in this example) photoelectric conversion elements 43 (see FIG. 7). The control section 30 divides the plurality of photoelectric conversion elements 43 of the second reading section 42 into a plurality of groups of adjacent photoelectric conversion elements (in this example, four groups of four elements (first group 421, second group 422, third group 423, fourth group 424)), obtains an average value of the read values ​​for each group, and performs judgment using the minimum average value for each group. The reason for obtaining the average value for each group is to reduce the influence of the variation in the read values ​​due to electrical noise. The number of photoelectric conversion elements 43 in one group is the number that can read an area wider than the expected size of the black foreign matter FB. In this embodiment, the size of the black foreign matter FB is assumed to be a size equivalent to a maximum of three photoelectric conversion elements 43. It is also assumed that the size of the white foreign matter FW is larger than the size of the black foreign matter FB.

[0035] Next, the operation of the scanner 110 will be described. In this embodiment, when the power is turned on, the reading unit 40 is positioned at the home position H. The home position H is set on the side of the reference member 60, and when the reading unit 40 is located at the home position H, the first reading section 41 and the second reading section 42 face the reference member 60. Usually, when the power is turned on, the reading unit 40 stops at the home position H (see FIGS. 4 and 7), but the reading unit 40 may stop at a position other than the home position H. The reading unit 40 may stop at a position other than the home position H when the power voltage drops during the execution of a reading job, before the power is turned on after assembly in a factory, or when the reading unit 40 is displaced from the home position H due to vibration during movement, etc.

[0036] Fig. 9 is a flow chart of the operation of scanner 110. When scanner 110 is powered on, control unit 30 executes processing according to the flow chart of Fig. 9. Hereinafter, the minimum value of the average values ​​of the read values ​​for each group of 16 photoelectric conversion elements 43 divided into four groups of four adjacent elements will be referred to as the minimum average value.

[0037] First, the control unit 30 judges whether the reading unit 40 faces the reference member 60 (step S01). Specifically, if the minimum average value is equal to or greater than a threshold value (e.g., 30), the control unit 30 judges that the reading unit 40 faces the reference member 60 (step S01: YES), moves the reading unit 40 a small distance to the right (step S02), and judges whether the boundary B between the frame 32 and the reference member 60 has been detected (step S03). If the minimum average value continues to be equal to or greater than the threshold value, the control unit 30 judges that the boundary B has not been detected (step S03: NO), and repeats the processing from step S02 onward. On the other hand, if the minimum average value changes from equal to or greater than the threshold value to less than the threshold value, the control unit 30 judges that the boundary B has been detected (step S03: YES), and proceeds to the processing of step S06.

[0038] On the other hand, in step S01, if the read value is less than the threshold value, the control unit 30 determines that the reading unit 40 is not facing the reference member 60 (facing the frame 32) (step S01: NO), moves the reading unit 40 a small distance to the left (step S04), and determines whether or not the boundary B between the frame 32 and the reference member 60 has been detected (step S05). If the minimum average value continues to be less than the threshold value, the control unit 30 determines that the boundary B has not been detected (step S05: NO), and repeats the processing from step S04 onwards. On the other hand, if the minimum average value changes from less than the threshold value to equal to or greater than the threshold value, the control unit 30 determines that the boundary B has been detected (step S05: YES), and proceeds to the processing of step S06.

[0039] In step S06, the control unit 30 moves the reading unit 40 to the left by a predetermined distance D. The predetermined distance D is the distance between the boundary B between the frame 32 and the reference member 60 and the home position H, and is a known value. Through this process, the reading unit 40 is positioned at the home position H. At the home position H, the first reading unit 41 and the second reading unit 42 face the reference member 60.

[0040] Next, the control unit 30 determines whether or not a reading job has been received (step S07). Specifically, when a reading operation is performed on the operation panel 19, the control unit 2 of the printer 1 transmits a reading job indicating the content of the operation to the control unit 30. If the control unit 30 determines that a reading job has not been received (step S07: NO), it repeats the process of step S07, and if it determines that a reading job has been received (step S07: YES), it proceeds to the process of step S08.

[0041] In step S08, the control unit 30 reads the reference member 60 while moving the reading unit 40 to the left to obtain white reference data, and stops the reading unit 40 at the acceleration start position A (see FIG. 4) (step S08). Next, the control unit 30 accelerates the reading unit 40 to the right to a predetermined speed, and when the reading unit 40 is moved to the left end of the document table 31, the control unit 30 causes the first reading unit 41 to start reading the document (step S09). The control unit 30 causes the first reading unit 41 to read the document while moving the reading unit 40 to the right while maintaining the predetermined speed, and generates image data. When generating the image data, the control unit 30 corrects the image data based on the white reference data. The control unit 30 estimates the size of the document in parallel with the generation of the image data, and determines whether reading up to the right end of the document has been completed (step S10). If the control unit 30 determines that the reading is not complete (step S10: NO), it repeats the process of step S10, and if the control unit 30 determines that the reading is complete (step S10: YES), it proceeds to the process of step S04. In this way, the reading unit 40 is positioned at the home position H again.

[0042] Here, an example of determination will be shown assuming that there is no variation in the read values ​​of the 16 photoelectric conversion elements 43 and that the inner surface of the frame 32 is black.

[0043] 10 shows an example in which a white foreign object FW is attached to the top plate portion 32T. In this example, a white foreign object FW having a size equivalent to 12 photoelectric conversion elements 43 (approximately 1.0 mm in the case of 300 dpi (dots per inch)) is attached to the positions corresponding to the first group 421 to the third group 423 of the top plate portion 32T. In this example, the reading unit 40 stops to the right of the foreign object FW due to the above-mentioned voltage drop or other cause. In this case, the average values ​​of the read values ​​of the first group 421 to the fourth group 424 are all 0, so the minimum average value is also 0. If the threshold value is 30, the minimum average value is less than the threshold value, so the control unit 30 determines that the reading unit 40 is not facing the reference member 60 (step S01: NO) and executes the processes of steps S04 and S05.

[0044] Before the reading unit 40 reaches the position of the foreign object FW, the average values ​​of the read values ​​of the first set 421 to the fourth set 424 are all 0, and therefore the minimum average value is also 0. Since the minimum average value continues to be less than the threshold value, the control unit 30 determines that the reading unit 40 has not detected the boundary B (step S05: NO), and repeats the processes of steps S04 and S05.

[0045] When the reading unit 40 reaches the position of the foreign object FW, the average values ​​of the first set 421 to the third set 423 are all 255. However, the average value of the fourth set 424 is 0, so the minimum average value is also 0. Since the minimum average value remains below the threshold value, the control unit 30 determines that the reading unit 40 has not detected the boundary B (step S05: NO), and repeats the processes of steps S04 and S05.

[0046] When the reading unit 40 passes the position of the foreign object FW, the average values ​​of the read values ​​of the first group 421 to the fourth group 424 are all 0, and therefore the minimum average value also becomes 0. Since the minimum average value continues to be less than the threshold value, the control unit 30 determines that the reading unit 40 has not detected the boundary B (step S05: NO), and repeats the processes of steps S04 and S05.

[0047] When the reading unit 40 reaches boundary B, the average values ​​of the read values ​​of the first set 421 to the fourth set 424 all change from 0 to 255, and therefore the minimum average value also changes from 0 to 255. Because the minimum average value has changed from less than the threshold value to greater than or equal to the threshold value, the control unit 30 determines that the reading unit 40 has detected boundary B (step S05: YES), and proceeds to the processing of step S06.

[0048] 11 shows an example in which a black foreign matter FB is attached to the reference member 60. In this example, a black foreign matter FB having a size equivalent to three photoelectric conversion elements 43 (approximately 0.25 mm in the case of 300 dpi) is attached to the position of the reference member 60 corresponding to the second set 422. In this example, the reading unit 40 is stopped to the left of the foreign matter FB due to the above-mentioned voltage drop or other cause. In this case, the average values ​​of the read values ​​of the first set 421 to the fourth set 424 are all 255, so the minimum average value is also 255. Since the minimum average value is equal to or greater than the threshold value, the control unit 30 determines that the reading unit 40 faces the reference member 60 (step S01: YES) and executes the processes of steps S02 and S03.

[0049] Before the reading unit 40 reaches the position of the foreign object FB, the average values ​​of the read values ​​of the first set 421 to the fourth set 424 are all 255, and therefore the minimum average value is also 255. Since the minimum average value continues to be equal to or greater than the threshold value, the control unit 30 determines that the reading unit 40 has not detected the boundary B (step S03: NO), and repeats the processes of steps S02 and S03.

[0050] When the reading unit 40 reaches the position of the foreign matter FB, the average values ​​of the first set 421, the third set 423, and the fourth set 424 are all 255, but the average value of the second set 422 is 255×1÷4=63.75, so the minimum average value is 63.75. By setting the threshold between 0 and 63.75, it is possible to prevent erroneous determination of a black foreign matter FB having a size equivalent to a maximum of three photoelectric conversion elements. Therefore, in this embodiment, as an example, the threshold is set to 30. Since the minimum average value continues to be equal to or greater than the threshold, the control unit 30 determines that the reading unit 40 has not detected the boundary B (step S03: NO), and repeats the processes of steps S02 and S03.

[0051] When the reading unit 40 passes the position of the foreign object FB, the average values ​​of the read values ​​of the first group 421 to the fourth group 424 are all 255, and therefore the minimum average value is also 255. Since the minimum average value continues to be equal to or greater than the threshold value, the control unit 30 determines that the reading unit 40 has not detected the boundary B (step S03: NO), and repeats the processes of steps S02 and S03.

[0052] When the reading unit 40 reaches boundary B, the average values ​​of the read values ​​of the first set 421 to the fourth set 424 all change from 255 to 0, and therefore the minimum average value also changes from 255 to 0. Because the minimum average value has changed from greater than or equal to the threshold value to less than the threshold value, the control unit 30 determines that the reading unit 40 has detected boundary B (step S03: YES), and proceeds to the processing of step S06.

[0053] According to the scanner 110 of this embodiment described above, the reading unit 40 includes a first reading section 41 that reads the area corresponding to the platen 31, and a second reading section 42 that reads the area corresponding to the frame 32. The control section 30 moves the reading unit 40 using the moving mechanism 50, detects the boundary B between the frame 32 and the reference member 60 from the reading value of the second reading section 42, and positions the reading unit 40 at the home position H that is a predetermined distance D away from the boundary B. Therefore, the reading unit 40 can be positioned at the home position H in a short time with a simple configuration.

[0054] Furthermore, according to the scanner 110 of this embodiment, the home position H is set on the side of the reference member 60, and when the reading value of the second reading unit 42 indicates that the reading unit 40 is stopped at a position where the second reading unit 42 faces the frame 32, the control unit 30 detects boundary B while moving the reading unit 40 toward the reference member 60, and when the reading value of the second reading unit 42 indicates that the reading unit 40 is stopped at a position where the second reading unit 42 faces the reference member 60, the control unit 30 detects boundary B while moving the reading unit 40 toward the frame 32, so that the boundary B can be detected in a short time.

[0055] Furthermore, according to the scanner 110 of this embodiment, the second reading unit 42 is equipped with a plurality of photoelectric conversion elements 43 arranged in the main scanning direction, and the control unit 30 detects the boundary B using the minimum value of the reading values ​​of the plurality of photoelectric conversion elements 43, thereby preventing erroneous detection due to the adhesion of foreign matter.

[0056] Furthermore, according to the scanner 110 of this embodiment, the control unit 30 detects the boundary B using the minimum value of the average values ​​of the read values ​​for each set of multiple photoelectric conversion elements 43, thereby reducing the effects of variations in the read values ​​due to electrical noise.

[0057] Furthermore, according to the scanner 110 of this embodiment, the set of multiple photoelectric conversion elements 43 can read a wider range than an expected foreign object, so that erroneous detection due to the attachment of a foreign object can be prevented.

[0058] The above embodiment may be modified as follows.

[0059] In the above embodiment, an example is shown in which boundary B is detected using the minimum value (minimum average value) of the average values ​​of the read values ​​for each set of multiple photoelectric conversion elements 43, but the configuration may also be such that boundary B is detected using the minimum value of the read values ​​of multiple photoelectric conversion elements 43 of the second reading unit 42.

[0060] In the above embodiment, an example was shown in which the boundary B is detected using the minimum value of the average value of the read values ​​for each group of the photoelectric conversion elements 43, but the boundary B may be detected using the maximum value of the average value of the read values ​​for each group of the photoelectric conversion elements 43. In this configuration, when a white foreign object FW having a size equivalent to three photoelectric conversion elements 43 is attached to a position corresponding to the second group 422 of the top plate portion 32T, the average values ​​of the first group 421, the third group 423, and the fourth group 424 are all 0, but the average value of the second group 422 is 255×3÷4=191.25, so that the maximum value of the average value of the read values ​​for each group is 191.25. Therefore, by setting the threshold value between 191.25 and 255 (for example, 230), it is possible to prevent erroneous determination of this foreign object FW.

[0061] In the above embodiment, an example was shown in which the home position H was set on the reference member 60 side, but the home position H may also be set on the frame 32 side.

[0062] In the above embodiment, an example was given in which the reading unit 40 was a CIS, but the present invention may also be applied to a scanner 110 that uses a reduction optical system. [Explanation of symbols]

[0063] 1. Printer (image forming device) 30 Control section 31 Manuscript stand 32 Frames 40 Reading Unit 41 First reading section 42 Second reading section 43 Photoelectric conversion element 50 Moving mechanism 60 Reference Material 100 Multifunction printers (image forming systems) 110 Scanner (image reading device)

Claims

1. A transparent platen on which the manuscript is placed; a frame provided along an edge of the document table and having a black or dark color close to black; a reading unit for reading the document in a main scanning direction; a moving mechanism that moves the reading unit in a sub-scanning direction that intersects with the main scanning direction; a white reference member provided on the frame so as to be adjacent to the document table in the sub-scanning direction, the white reference member having a length in the main scanning direction longer than that of the document table; A control unit that controls the movement mechanism, the reading unit includes a first reading section that reads an area corresponding to the document platen, and a second reading section that reads an area corresponding to the frame; The control unit detects the boundary between the frame and the reference member using the reading value of the second reading unit while moving the reading unit using the moving mechanism, and positions the reading unit at a home position a predetermined distance away from the boundary.

2. The home position is set on the reference member side, The control unit is When the read value of the second reading unit indicates that the reading unit is stopped at a position where the second reading unit faces the frame, the boundary is detected while moving the reading unit toward the reference member; The image reading device according to claim 1, characterized in that when the reading value of the second reading unit indicates that the reading unit is stopped at a position where the second reading unit faces the reference member, the boundary is detected while moving the reading unit in the direction of the frame.

3. the second reading unit includes a plurality of photoelectric conversion elements arranged in the main scanning direction, 3. The image reading device according to claim 2, wherein the control unit detects the boundary by using a minimum value of read values ​​of the plurality of photoelectric conversion elements.

4. 4. The image reading device according to claim 3, wherein the control unit detects the boundary by using a minimum value of average values ​​of read values ​​for each set of the plurality of photoelectric conversion elements.

5. 5. The image reading device according to claim 4, wherein the set of the plurality of photoelectric conversion elements is capable of reading a range wider than an expected range of foreign matter.

6. An image reading device according to any one of claims 1 to 5, an image forming apparatus that forms an image of the document read by the first reading unit on a sheet;

Images