Image reading device and image formation device

Abstract

To provide an image reading device capable of suppressing deterioration of an accuracy of a shading compensation.SOLUTION: An image reading device comprises: a reading unit 301 that is for reading an image formed in a sheet; a white reference board 305 that is for performing a shading correction; and a glass movement part 1c that is for moving the reading unit 301. In a case where a conveyance direction of the sheet is a first direction; a width direction of the sheet orthogonal to the first direction is a second direction; and a direction orthogonal to the first and second directions is a third direction, the glass movement part 1c can moves the reading unit 301 to a first position and a second position where the position in the third direction is different from the first position. The glass movement part 1c moves the reading unit 301 to the second position in a case of performing the shading correction to adjust a first distance from the reading unit 301 to the sheet in the third direction and a second distance from the reading unit 301 to the white reference board 305.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image reading device that reads an image formed on a sheet, and an image forming apparatus that includes such an image reading device. [Background technology]

[0002] The printing machine market is expanding in the commercial and industrial printing fields. The printing methods used by such printers include electrophotography, which is also expanding into the offset printing market, and inkjet, which has succeeded in cultivating a wide range of markets with its large format, low initial cost, and ultra-high speed.

[0003] Inkjet printers include, for example, line head type recording devices in which a recording head fixed to a main body ejects droplets in conjunction with a transported sheet to print an image on the sheet. When a line head type recording device is used in commercial printing or industrial printing fields that require high image quality, an image reading device is provided downstream of the recording head in the sheet transport direction. The image reading device reads the image formed on the sheet. The results of reading by the image reading device are used to detect droplet ejection defects by the recording head, and to adjust color shifts, uneven image density, and geometric characteristics of the image to be printed. Here, the geometric characteristics of the image refer to the shape, position, etc. of the image.

[0004] An image reading device reads a sheet by irradiating light from a light source onto the sheet and receiving the reflected light with a line sensor. The image reading device performs shading correction when reading the sheet. Shading correction is performed to correct variations in the light quantity distribution of the light irradiated onto the sheet and variations in the sensitivity of the line sensor that receives the reflected light. When performing shading correction, a white reference plate, which is a white reference member, is read. It is preferable that the position of the white reference plate is the same as the position when the sheet is read. In particular, it is preferable for the distance of the white reference plate from the light source or line sensor to be the same as the distance between the sheet and the light source or line sensor when reading the sheet, in order to perform shading correction with high accuracy.

[0005] Patent Document 1 discloses an image reading device that generates an initial value of correction data for shading correction from read data of a white reference plate attached to the image reading device and read data read in a state where a white reference plate different from the white reference plate is placed at the reading position of the document. The initial value of correction data is stored in advance in the image reading device and is used during shading correction. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2011-130288 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, unless correction data is acquired in advance using a separate white reference plate for correction data and the data of the white reference plate is corrected, there is a risk that the accuracy of the shading correction will decrease. In view of the above-mentioned problems, the main object of the present invention is to provide an image reading device capable of suppressing a decrease in the accuracy of the shading correction. [Means for solving the problem]

[0008] The image reading device of the present invention comprises a reading means for reading an image formed on a sheet, a reference member for performing shading correction, and a moving means for moving the reading means, and when the conveying direction of the sheet is a first direction, the width direction of the sheet perpendicular to the first direction is a second direction, and the direction perpendicular to the first direction and the second direction is a third direction, the moving means is capable of moving the reading means to a first position and a second position which is a different position in the third direction from the first position, and the moving means moves the reading means to the first position when reading a sheet, and moves the reading means to the second position when performing the shading correction, thereby adjusting a first distance from the reading means to the sheet and a second distance from the reading means to the reference member in the third direction. The image forming apparatus of the present invention comprises an image forming means for forming an image on a sheet, a reading means for reading the image formed on the sheet by the image forming means, a reference member for performing shading correction, and a moving means for moving the reading means, wherein when the conveying direction of the sheet is a first direction, the width direction of the sheet perpendicular to the first direction is a second direction, and the direction perpendicular to the first direction and the second direction is a third direction, the moving means is capable of moving the reading means to a first position and a second position which is a different position in the third direction from the first position, and the moving means moves the reading means to the first position when reading the sheet, and moves the reading means to the second position when performing the shading correction, thereby adjusting the first distance from the reading means to the sheet and the second distance from the reading means to the reference member in the third direction. Effect of the Invention

[0009] According to the present invention, it is possible to suppress a decrease in accuracy of shading correction. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing the configuration of an image forming system. [Diagram 2]FIG. 4 is a diagram illustrating the configuration of a print module. [Diagram 3] 2A to 2D are diagrams illustrating the configuration of an image reading device. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] 5A and 5B are explanatory diagrams of a mechanism for moving the reading height of a reading unit. [Figure 7] 5A and 5B are explanatory diagrams of a mechanism for moving the reading height of a reading unit. [Figure 8] 5A and 5B are explanatory diagrams of a mechanism for moving the reading height of a reading unit. [Figure 9] 5A and 5B are explanatory diagrams of a mechanism for moving the reading height of a reading unit. [Figure 10] 5A and 5B are explanatory diagrams of a mechanism for moving the reading height of a reading unit. [Figure 11] 4 is a flowchart showing a sheet reading process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0012] FIG. 1 is a configuration diagram of an image forming system according to the present embodiment. The image forming system 100 is a printing machine used, for example, in the commercial / industrial printing field. The image forming system 100 according to the present embodiment is a sheet-fed inkjet recording device that forms an ink image on a sheet using two liquids, a reaction liquid and an ink, to generate a product. The image forming system 100 includes a paper feed module 1000, a print module 2000, a drying module 3000, a fixing module 4000, a cooling module 5000, an inversion module 6000, and a paper discharge stacking module 7000. A cut sheet (hereinafter simply referred to as a "sheet") on which an image is printed is supplied from the paper feed module 1000, undergoes a predetermined process in each module, and is discharged from the paper discharge stacking module 7000 as a product.

[0013] The paper feed module 1000 includes multiple storage containers 1100a-1100c (three tiers in this embodiment). Each of the storage containers 1100a-1100c can store sheets. Each of the storage containers 1100a-1100c can be pulled out to the front side of the device, and is pulled out to the front side of the device to store sheets. The paper feed module 1000 feeds sheets one by one to the print module 2000. To achieve this, each of the storage containers 1100a-1100c is provided with a separation belt and a transport roller. Note that the number of storage containers 1100a-1100c is just an example, and there may be one tier, two tiers, or four or more tiers.

[0014] The print module 2000 is an inkjet type image forming device that forms an image on a sheet fed from the paper feed module 1000. The print module 2000 includes a pre-imaging registration correction unit 2100, a print belt unit 2200, and a recording unit 2300. The pre-imaging registration correction unit 2100 corrects the inclination and position of the sheet fed from the paper feed module 1000 and conveys the sheet to the print belt unit 2200.

[0015] The print belt unit 2200 and the recording unit 2300 are disposed facing each other across the sheet transport path, downstream of the pre-imaging registration correction unit 2100 in the sheet transport direction. The print belt unit 2200 adsorbs and transports the sheet transported from the pre-imaging registration correction unit 2100. The recording unit 2300 is an image forming unit that forms an image by performing a recording process (printing) on ​​the sheet transported by the print belt unit 2200 from above using a recording head. The recording head prints by ejecting ink onto the sheet. The sheet is adsorbed and transported by the print belt unit 2200, so that a constant clearance is maintained between the sheet and the recording head.

[0016] A plurality of recording heads are arranged along the sheet transport direction. The recording heads of this embodiment are eight line-type recording heads corresponding to the four colors of Y (yellow), M (magenta), C (cyan), and K (black), as well as the reaction liquid and three special colors. The number of colors and recording heads is not limited to eight. The inkjet method may employ a method using a heating element, a method using a piezoelectric element, a method using an electrostatic element, a method using a MEMS element, or the like. Ink of each color is supplied to the recording head from an ink tank (not shown) via an ink tube.

[0017] The sheet printed by the recording unit 2300 is transported by the print belt unit 2200. An image reading device 1, which is an in-line scanner, is disposed downstream of the recording unit 2300 in the transport direction. The image reading device 1 is used to detect the misalignment and color density of the image formed on the sheet and correct the printed image. Specifically, the result of reading the sheet by the image reading device 1 is used to calculate the coordinates of the marks formed on the edge of the sheet and the four corners of the sheet. Based on the marks and the coordinates of the four corners of the sheet, the right angle and skew of the image, the leading and left registrations, the main magnification and the sub-magnification, etc. are adjusted to correct the image misalignment. In addition, the pixel value (brightness value) is analyzed from the result of reading the dedicated chart by the image reading device 1 and used to adjust the ejection amount of the recording head. The color density is corrected by adjusting the ejection amount of the recording head.

[0018] The drying module 3000 dries the sheet on which an image has been formed by the print module 2000. The drying module 3000 dries the sheet to reduce the liquid component contained in the ink, thereby improving the fixation of the sheet and the ink. The drying module 3000 includes a decoupling unit 3200, a drying belt unit 3300, and a hot air blowing unit 3400.

[0019] The sheet printed by the recording unit 2300 of the print module 2000 is transported to the decoupling unit 3200 in the drying module 3000. The decoupling unit 3200 weakly holds the sheet by air pressure from above and friction of the belt and transports it. This prevents the portion of the sheet remaining on the print belt unit 2200 from shifting while straddling the decoupling unit 3200 and the print belt unit 2200.

[0020] The sheet conveyed from the decoupling section 3200 is adsorbed and conveyed by the drying belt unit 3300, and at the same time, hot air is blown onto the ink-applied surface (image printed surface) from the hot air blowing section 3400 arranged above the belt to dry it. Note that the drying method may be a combination of a method of applying hot air, a method of irradiating the sheet surface with electromagnetic waves (ultraviolet rays, infrared rays, etc.), and a conductive heat transfer method by contact with a heating element.

[0021] The fixing module 4000 heats the sheet dried in the drying module 3000 to dry the ink, thereby fixing the image to the sheet. The fixing module 4000 includes a fixing belt unit 4100 having an upper belt unit and a lower belt unit. The fixing module 4000 fixes the ink to the sheet by passing the sheet conveyed from the drying module 3000 between the heated upper belt unit and lower belt unit.

[0022] The cooling module 5000 cools the sheet on which the image has been fixed by the fixing module 4000, thereby solidifying the ink softened by heating and suppressing temperature changes of the sheet caused by downstream devices. The cooling module 5000 includes a plurality of cooling units 5100. The plurality of cooling units 5100 cool the high-temperature sheet transported from the fixing module 4000. Each cooling unit 5100 has a cooling box, a fan, and a nozzle formed on the transport guide. The fan increases the pressure in the cooling box by taking in outside air into the cooling box. The air taken into the cooling box is blown onto the sheet by the nozzle. The sheet is cooled by blowing air onto the sheet in this manner. The plurality of cooling units 5100 are arranged on both sides of the transport path, and can cool the sheet from both sides.

[0023] A transport path switching unit is provided in the cooling module 5000. The transport path switching unit switches the transport path of the sheet depending on whether the sheet is transported to the reversing module 6000 or to a double-sided transport path used for double-sided printing. During double-sided printing, the sheet is transported to a transport path below the cooling module 5000, and then transported through a double-sided transport path of the fixing module 4000, the drying module 3000, the print module 2000, and the paper feed module 1000. The double-sided transport section of the fixing module 4000 is provided with a first reversing section 4200 that reverses the front and back sides of the sheet. The sheet is once transported to the first reversing section 4200, then reversed and transported to the drying module 3000 side, thereby reversing the print side of the image and enabling printing on the back side. The sheet is then transported again to the pre-imaging registration correction section 2100, the print belt unit 2200, and the recording section 2300 of the print module 2000, where it is printed.

[0024] The inversion module 6000 includes a second inversion unit 6400. The inversion module 6000 can invert the front and back sides of the sheet being conveyed by the second inversion unit 6400. This allows the orientation of the front and back sides of the sheet to be discharged to be changed. The discharge stacking module 7000 includes a top tray 7200 and a stacking unit 7500. The discharge stacking module 7000 aligns and stacks the sheets conveyed from the inversion module 6000.

[0025] (Print Module) 2 is a diagram illustrating the configuration of the print module 2000. The print module 2000 includes a plurality of recording heads 10 constituting a recording section 2300, a print belt unit 2200 that transports a sheet S, and an image reading device 1. The recording heads 10 form an image on the sheet S by ejecting ink from above onto the sheet S that has been fed one by one from the paper feed module 1000 and passed through a pre-imaging registration correction section 2100.

[0026] When an image is formed, the sheet S is sucked and adsorbed to the print belt unit 2200 and conveyed in the conveying direction. By being sucked and adsorbed to the print belt unit 2200, the conveying behavior of the sheet S is stabilized, and the distance from the recording head 10 during image formation is kept constant. The print belt unit 2200 includes a plurality of (four in this embodiment) tension rollers 21-24 and a print belt 25 stretched between the tension rollers 21-24. The sheet S is sucked and adsorbed to the belt surface of the print belt 25 stretched between the tension roller 21 and the tension roller 24. Since an image is formed on the belt surface, in this embodiment, the belt surface between the tension roller 21 and the tension roller 24 is referred to as an image forming surface 26.

[0027] The print belt 25 is provided with a number of suction holes for sucking the sheet S, and rotates in the direction of the arrow Y. A vacuum (not shown) is provided in the space surrounded by the print belt 25 for suction. The print belt 25 sucks the sheet S to the image forming surface 26 by the suction force of the vacuum, and conveys the sucked sheet S in the conveying direction by rotating. The sheet S sucked to the image forming surface 26 is conveyed with a certain clearance secured between the print belt 25 and the recording head 10. The print belt 25 functions as a conveying means for carrying and conveying the sheet S. In the recording unit 2300, a plurality of recording heads 10 are arranged in a line along the conveying direction of the sheet S. As described above, the recording unit 2300 of this embodiment has eight line-shaped recording heads 10 corresponding to the reaction liquid and three special colors in addition to the four colors of black, yellow, magenta, and cyan.

[0028] The image reading device 1 is disposed along the image forming surface 26 downstream of the recording head 10 in the conveying direction of the sheet S, and reads a test image printed on the sheet S conveyed by the print belt unit 2200. The test image is, for example, an image for detecting the geometric characteristics of the image on the sheet S or the image density of the image on the sheet S. The geometric characteristics or image density of the image are detected based on the reading result (read image) of the sheet S by the image reading device 1. When correcting the geometric characteristics, a correction value of the geometric characteristics is generated based on the difference between the geometric characteristics obtained from the read image and the nominal geometric characteristics. The printing position of the image during image formation is adjusted by this correction value. When correcting the image density, a correction value of the image density is generated based on the difference between the actual image density obtained from the read image and the ideal image density. The image density during image formation is adjusted by this correction value (the amount of droplets discharged from the recording head 10 is adjusted).

[0029] (Image reader) Fig. 3 is an explanatory diagram of the configuration of image reading device 1. Image reading device 1 is configured by combining inner box 1b, glass moving unit 1c, outer box 1d, etc. Fig. 3(a) is an external perspective view of the housing of image reading device 1. Fig. 3(b) is an external perspective view of inner box 1b. Fig. 3(c) is an external perspective view of glass moving unit 1c. Fig. 3(d) is an external perspective view of outer box 1d.

[0030] As shown in Fig. 3(b), a reading unit 301 for reading an image is attached to the inner box 1b. Although hidden on the back side of the inner box 1b in Fig. 3(b), two reading units 301 are arranged side by side in a direction perpendicular to the conveying direction of the sheet S. By arranging the two reading units 301 in this manner, it is possible to read a sheet S having a large width (length in the width direction perpendicular to the conveying direction of the sheet S). Two control boards 302 are provided corresponding to the two reading units 301. The control boards 302 are control units that control the operation of the corresponding reading units 301.

[0031] The inner box 1b is provided with two inner box short shafts 303 and an inner box long shaft 312. During shading correction, the two inner box short shafts 303 cause the inner box 1b to move up and down. The upward direction is the direction away from the image forming surface 26, and the downward direction is the direction toward the image forming surface 26. The inner box long shaft 312 restricts the left and right movement of the inner box 1b. The left direction is the conveying direction of the sheet S, and the right direction is the opposite direction to the conveying direction of the sheet S. The inner box long shaft 312 is configured to allow the inner box 1b to move up and down but restrict the left and right movement by fitting with an inner box movement restricting member 313 (see FIG. 3(a)) of the housing.

[0032] As shown in Fig. 3(c), glass moving section 1c includes two reading glasses 304 corresponding to two reading units 301, flag 307, and glass moving member 306 that receives inner box minor axis 303. White reference plate 305, which is a reference member for performing shading correction, is attached to each of the two reading glasses 304. Two reading glasses 304 are attached to glass moving member 306. During shading correction, the entire glass moving section 1c including white reference plate 305 moves leftward (in the minor axis direction of glass moving section 1c).

[0033] In Fig. 3(d), the housing of the outer box 1d shown in Fig. 3(a) is omitted. The outer box 1d includes a motor 308, a photosensor 309, two cams 310 at the front and back in the figure, and a shaft 311. The glass moving member 306 abuts against the peripheral surfaces of the two cams 310. Therefore, when the motor 308 is driven and the two cams 310 rotate, the glass moving member 306 is pushed into the cams 310 and moves. The driving force of the motor 308 is transmitted to the cam 310 at the front side by the shaft 311. The photosensor 309 detects the position of the glass moving unit 1c by switching between a light-transmitting state and a light-blocking state by a flag 307 provided on the glass moving unit 1c.

[0034] FIG. 4 is a cross-sectional view of the image reading device 1. This cross-sectional view shows a cross section of the image reading device 1 cut in the conveying direction of the sheet S. The reading unit 301 includes light sources 401a and 401b, reflecting mirrors 402a, 402b, 402c, 402d, and 402e, an imaging lens 403, a light receiving unit 404, and a sensor board 405. The light sources 401a and 401b irradiate light onto the sheet S on the image forming surface 26. The light sources 401a and 401b are configured by arranging a plurality of light emitting elements, such as LEDs (Light Emitting Diodes), in a line. The light receiving unit 404 receives the light reflected by the sheet S of the light irradiated from the light sources 401a and 401b. The reflecting mirrors 402a to 402e are an optical system that guides the light reflected by the sheet S to the imaging lens 403. The imaging lens 403 forms an image on the light receiving surface of the light receiving section 404 from the reflected light guided by the reflecting mirrors 402a to 402e.

[0035] The light receiving unit 404 outputs a reading result (read image) which is an electrical signal corresponding to the reflected light received on the light receiving surface. This reading result is an analog signal representing the image read from the sheet S. The light receiving unit 404 is configured with a plurality of photoelectric conversion elements, such as CCD (Charge Coupled Device) sensors, lined up in the same direction as the row of light emitting elements. The light receiving unit 404 is mounted on a sensor board 405. The sensor board 405 is connected to the control board 302, and transmits the reading result (read image) which is an analog signal output from the light receiving unit 404 to the control board 302. The configuration of the control board 302 will be described later.

[0036] The reading unit 301 reads an image with the main scanning direction being the direction in which the light emitting element rows of the light sources 401a and 401b and the photoelectric conversion element row of the light receiving unit 404 are aligned. The main scanning direction is, for example, a direction perpendicular to the transport direction of the sheet S. The reading unit 301 reads an image on the sheet S transported along the transport direction with the transport direction of the print belt 25 perpendicular to the main scanning direction being the sub-scanning direction.

[0037] A white reference plate 305 provided on a reading glass 304 is read by the reading unit 301 during shading correction. The light receiving unit 404 has manufacturing variations for each photoelectric conversion element (each pixel). In addition, it is not easy to make the light irradiated from the light sources 401a and 401b uniform in the main scanning direction. For this reason, even if an image is read from a sheet S on which an image of uniform image density is formed, there is a possibility that the digital values ​​of the image data, which are the reading results, will vary for each position in the main scanning direction.

[0038] In order to suppress such variations, shading correction is performed. Specifically, the reading unit 301 reads a white reference plate 305. From the reading result of the white reference plate 305, a correction value is derived such that the reading result (e.g., luminance value) of each pixel in the main scanning direction becomes uniform to a specific value. This correction value corrects the irradiation amount of the light sources 401a and 401b, the sensitivity variation of the photoelectric conversion element of the light receiving unit 404, or the reading result of the image of the sheet S, thereby correcting the manufacturing variation and the variation in the amount of light.

[0039] It is preferable that the distance from the reading unit 301 to the white reference board 305 when reading the white reference board 305 is the same as the distance from the reading unit 301 to the sheet S when reading the sheet S. Such a distance from the reading unit 301 to the object to be read (the white reference board 305 or the sheet S) is hereinafter referred to as the "reading height." Since the variation in the light distribution of the light sources 401a and 401b differs depending on the reading height, if the reading height during shading correction differs from the reading height during reading of the sheet S, appropriate shading correction will not be performed, which may result in deterioration of image quality.

[0040] 5 is an explanatory diagram of the control board 302. The control board 302 is electrically connected to the light sources 401a, 401b and the light receiving section 404 of the reading unit 301. The control board 302 is further electrically connected to the motor 308 and the photosensor 309. As described above, the motor 308 is a drive source for moving the glass moving section 1c on which the white reference plate 305 is provided. In FIG. 5, the image reading device 1 is connected to the print module 2000.

[0041] The control board 302 is an information processing device including a central processing unit (CPU) 501, a read only memory (ROM) 502, and a random access memory (RAM) 503. The CPU 501 executes a computer program stored in the ROM 502 using the RAM 503 as a working area to control the operation of the image reading device 1. In addition, the control board 302 includes a lighting control unit 504 for controlling the operation of the light sources 401a and 401b, a drive control unit 505 for controlling the operation of the motor 308, an A / D conversion unit 506 for processing the reading result (read image), and an image processing unit 507. The lighting control unit 504, the drive control unit 505, the A / D conversion unit 506, and the image processing unit 507 are connected to the CPU 501. The control board 302 may be realized by a discrete product or a one-chip semiconductor product. Examples of one-chip semiconductor products include MPUs (Micro-Processing Units), ASICs (Application Specific Integrated Circuits), and SOCs (System-On-a-Chips).

[0042] The lighting control unit 504 controls the turning on and off of the light sources 401a and 401b under the control of the CPU 501. The drive control unit 505 transmits a drive signal to the motor 308 under the control of the CPU 501 to control the movement of the glass moving unit 1c on which the white reference plate 305 is provided.

[0043] Under the control of the CPU 501, the A / D conversion unit 506 converts the reading result (read image), which is an analog signal output from the light receiving unit 404, into a digital signal and transmits it to the image processing unit 507. Under the control of the CPU 501, the image processing unit 507 performs various image processing on the reading result (read image), which is a digital signal acquired from the A / D conversion unit 506, and generates image data representing the image read from the sheet S. The image data is transmitted from the control board 302 to the print module 2000, a personal computer, etc.

[0044] The print module 2000 includes an image analysis unit 2400, a pre-imaging registration correction unit 2100, a print belt unit 2200, and a recording unit 2300. The image analysis unit 2400 analyzes image data acquired from a control board 302 and calculates various correction values. The correction values ​​calculated by the image analysis unit 2400 are fed back to the pre-imaging registration correction unit 2100, the print belt unit 2200, and the recording unit 2300, and are used to adjust geometric characteristics and image density unevenness.

[0045] A mechanism for moving the reading height of the reading unit 301 in conjunction with the movement of the position of the white reference plate 305 during shading correction will be described with reference to FIGS.

[0046] Fig. 6 is a cross-sectional view of the image reading device 1 when the cam 310 is at a first angle (e.g., 0 degrees). Fig. 6(a) is a cross-sectional view in the sub-scanning direction at the location of the cam 310. Fig. 6(b) is a cross-sectional view in the sub-scanning direction at the location of the reading unit 301. In this case, the reading unit 301 reads the sheet S transported to the image forming surface 26.

[0047] When the cam 310 is at the first angle, the cam 310 pushes the glass moving part 1c to the right side in FIG. 6(a) (upstream side in the conveying direction of the sheet S) relative to the rotation axis 601 of the cam 310. In this case, the inner box short axis 303 is located in a recess in the upper side of the glass moving member 306. Therefore, the reading unit 301 moves (lowers) toward the image forming surface 26. By moving toward the image forming surface 26, the reading unit 301 is at a reading height (h1) that matches the sheet S being conveyed to the image forming surface 26.

[0048] FIG. 7 is a cross-sectional view of image reading device 1 when cam 310 is at a second angle (e.g., 45 degrees). FIG. 7(a) is a cross-sectional view in the sub-scanning direction at cam 310. FIG. 7(b) is a cross-sectional view in the sub-scanning direction at flag 307 and photosensor 309. In this state, flag 307 changes photosensor 309 from a light-transmitting state to a light-blocking state. This allows control board 302 to grasp the position of glass moving section 1c. From this position, control board 302 can input a signal of a predetermined number of pulses to motor 308 to move glass moving section 1c to a desired position.

[0049] That is, when the photosensor 309 changes from the light-transmitting state to the light-shielding state, the control board 302 determines that the white reference plate 305 has started to move to the reading position of the reading unit 301. When the photosensor 309 changes from the light-transmitting state to the light-shielding state, the control board 302 moves the glass moving unit 1c by a predetermined amount from that position, thereby moving the white reference plate 305 to the reading position of the reading unit 301.

[0050] Fig. 8 is a cross-sectional view of the image reading device 1 when the cam 310 is at a third angle (for example, 123 degrees). Fig. 8(a) is a cross-sectional view in the sub-scanning direction at the location of the cam 310. Fig. 8(b) is a cross-sectional view in the sub-scanning direction at the location of the reading unit 301. In this case, the reading unit 301 reads the white reference plate 305 to perform shading correction (first sampling).

[0051] When the cam 310 is at the third angle, the cam 310 pushes the glass moving part 1c to the left side in FIG. 8(a) (downstream side in the conveying direction of the sheet S) relative to the rotation shaft 601. In this case, the inner box short shaft 303 rides up on the upper side of the glass moving member 306. Therefore, the reading unit 301 moves (rises) in the opposite direction to the image forming surface 26. By moving in the opposite direction to the image forming surface 26, the reading unit 301 is at a reading height (h2) that matches the white reference plate 305.

[0052] That is, the reading height of the reading unit 301 changes as the inner box short shaft 303 falls into a recess on the upper side of the glass moving member 306 or rides up on the upper side in conjunction with the movement of the glass moving part 1c by the cam 310. This makes it possible to make the reading height (h1) when reading the sheet S and the reading height (h2) during shading correction the same. Since the reading heights are the same, shading correction is performed appropriately and degradation of image quality can be suppressed.

[0053] Fig. 9 is a cross-sectional view of the image reading device 1 when the cam 310 is at a fourth angle (e.g., 180 degrees). Fig. 9(a) is a cross-sectional view in the sub-scanning direction at the location of the cam 310. Fig. 9(b) is a cross-sectional view in the sub-scanning direction at the location of the reading unit 301. In this case, the reading unit 301 reads the white reference plate 305 to perform shading compensation (second sampling).

[0054] When cam 310 is at the fourth angle, cam 310 pushes glass moving portion 1c to the left side in Fig. 9(a) (downstream side in the conveying direction of sheet S) relative to rotation shaft 601. In this case, inner box short shaft 303 remains in the state of Fig. 8(a) and rides up on the upper side of glass moving member 306, and reading unit 301 moves (rises) in the opposite direction to image forming surface 26. By moving in the opposite direction to image forming surface 26, reading unit 301 is at a reading height (h2) aligned with white reference plate 305.

[0055] 8(b) and 9(b), the reading height (h2) is the same, but the position of the white reference plate 305 is different in the transport direction of the sheet S. The white reference plate 305 is located further downstream in the transport direction of the sheet S in FIG. 9(b) than in FIG. 8(b). Therefore, different positions of the white reference plate 305 in the transport direction of the sheet S are read by the reading unit 301 in the first sampling and the second sampling. This makes it possible to reduce the influence of dust during shading correction. This technology is well known, so a description thereof will be omitted.

[0056] FIG. 10 is a cross-sectional view of image reading device 1 when cam 310 is at a fifth angle (e.g., 315 degrees). FIG. 10(a) is a cross-sectional view in the sub-scanning direction at cam 310. FIG. 10(b) is a cross-sectional view in the sub-scanning direction at flag 307 and photosensor 309. In this state, flag 307 changes photosensor 309 from a light-shielding state to a light-transmitting state. This allows control board 302 to grasp the position of glass moving unit 1c. From this position, control board 302 can input a signal of a predetermined number of pulses to motor 308 to move glass moving unit 1c to a desired position.

[0057] That is, when photosensor 309 changes from a light-shielding state to a light-transmitting state, control board 302 determines that white reference plate 305 has started to move from the reading position of reading unit 301 to its original position (home position). When photosensor 309 changes from a light-shielding state to a light-transmitting state, control board 302 moves glass moving unit 1c by a predetermined amount from that position, thereby moving white reference plate 305 to the home position. Reading unit 301 also moves to a position for reading sheet S in conjunction with the movement of glass moving unit 1c.

[0058] 11 is a flowchart showing the process of reading a sheet S by the reading unit 301. This process starts when the sheet S, on which an image has been formed by the recording unit 2300, is conveyed by the print belt unit 2200 to the reading position of the reading unit 301. The reading unit 301 starts up, for example, at the start of a print job.

[0059] The control board 302 determines whether or not image reading of the sheet S by the reading unit 301 has started (S1101). The start of image reading of the sheet S by the reading unit 301 is determined, for example, by a change in an analog signal acquired from the light receiving unit 404. In this case, for example, the print belt 25 is configured in black, and the color of the sheet S is a color other than black (for example, white). If image reading has not started (S1101: N), the control board 302 waits until image reading by the reading unit 301 starts. If image reading has started (S1101: Y), the control board 302 drives the motor 308 to perform shading correction (S1102).

[0060] As described in FIG. 7, the control board 302 judges whether the state of the photosensor 309 has changed from the light-transmitting state to the light-shielding state (S1103). If the light-transmitting state remains (S1103: Y), the control board 302 waits until the state of the photosensor 309 changes to the light-shielding state. If the state changes to the light-shielding state (S1103: Y), the control board 302 drives the motor 308 for a predetermined number of pulses (S1104). As a result, as described in FIG. 8, the inner box short shaft 303 rides on the upper side of the glass moving member 306, and the reading unit 301 rises. Therefore, the reading height of the reading unit 301 becomes a height (h2) that matches the white reference plate 305 (S1105). In this state, the control board 302 executes the first sampling of the white reference plate 305 to perform shading correction (S1106).

[0061] 9, the control board 302 drives the motor 308 for a predetermined number of pulses (S1107) and executes a second sampling of the white reference plate 305 to perform shading correction (S1108). The control board 302 generates shading correction data in which the influence of dust is reduced, based on the sampling results (reading results) from the first sampling and the second sampling (S1109).

[0062] The control board 302 that has generated the shading correction data resumes motor drive (S1110) and determines whether the state of the photosensor 309 has changed from the light-shielding state to the light-transmitting state (S1111), as described in FIG. 10. If the light-shielding state remains (S1111: N), the control board 302 waits until the state of the photosensor 309 changes to the light-transmitting state. If the state changes to the light-transmitting state (S1111: Y), the control board 302 drives the motor 308 for a predetermined number of pulses (S1112). As a result, as described in FIG. 6, the inner box short shaft 303 is positioned in the recess on the upper side of the glass moving member 306, and the reading unit 301 is lowered. Therefore, the reading height of the reading unit 301 becomes the height (h1) that matches the sheet S (S1113).

[0063] In this state, the control board 302 causes the reading unit 301 to read the sheet S (S1114). When reading the sheet S, the operating conditions of the reading unit 301, such as the irradiation amount of the light sources 401a and 401b and the sensitivity variation of the photoelectric conversion element of the light receiving unit 404, or the reading result of the image of the sheet S, are corrected by the shading correction data. This corrects the manufacturing variation and the variation in the amount of light.

[0064] By the above-mentioned processing, the reading height of the reading unit 301 varies in conjunction with the movement of the white reference plate 305 for performing shading correction. Therefore, the reading height during shading correction and when reading the sheet S is kept the same. As a result, since highly accurate shading correction is performed, the image on the sheet S is read with high accuracy, and degradation of image quality can be suppressed.

[0065] In this embodiment, an example has been described in which the image reading device 1 is provided in an inkjet print module 2000. The image reading device 1 of this embodiment is also effective when provided in other devices, such as an in-line scanner of an electrophotographic image forming device.

Claims

1. A reading means for reading an image formed on a sheet, A reference member for performing shading correction, It comprises a drive source, a cam rotated by the drive source, and a moving means having a moving member that contacts the cam, When the sheet transport direction is defined as the first direction, the sheet width direction perpendicular to the first direction is defined as the second direction, and the direction perpendicular to both the first and second directions is defined as the third direction, The moving means is capable of moving the reading means to a first position and a second position which is different from the first position in the third direction. The moving means moves the reading means by the movement of the moving member due to the rotation of the cam, When reading the aforementioned sheet, the reading means is moved to the first position. When performing the shading correction, the reading means is moved to the second position to adjust the first distance from the reading means to the sheet and the second distance from the reading means to the reference member in the third direction. Image reading device.

2. The moving means is characterized by moving the reference member to the reading position of the reading means when performing the shading correction. The image reading device according to claim 1.

3. The moving means is characterized in that, when performing the shading correction, it moves the reference member and moves the reading means in conjunction with each other. The image reading device according to claim 2.

4. The reference member is attached to the movable member, The moving member moves as a result of the rotation of the cam, thereby causing the moving member to move the reference member. The image reading device according to claim 3.

5. The moving means is characterized in that, when performing the shading correction, it makes the adjustment such that the first distance and the second distance are the same. The image reading device according to claim 1.

6. The reading means reads the sheet that is adsorbed to a predetermined surface and transported, The moving means is characterized in that, when performing the shading correction, it moves the reference member in the first direction and the reading means in the third direction. The image reading device according to claim 1.

7. The moving means is characterized in that, once the reading of the reference member by the reading means is completed, it moves the reference member in the opposite direction to the first direction and moves the reading means in the opposite direction to the third direction. The image reading device according to claim 6.

8. The moving means is characterized by causing the reading means to read two different positions of the reference member in the first direction. The image reading device according to claim 6.

9. Image forming means for forming an image on a sheet, A reading means for reading the image formed on the sheet by the image forming means, A reference member for performing shading correction, It comprises a drive source, a cam rotated by the drive source, and a moving means having a moving member that contacts the cam, When the sheet transport direction is defined as the first direction, the sheet width direction perpendicular to the first direction is defined as the second direction, and the direction perpendicular to both the first and second directions is defined as the third direction, The moving means is capable of moving the reading means to a first position and a second position which is different from the first position in the third direction. The moving means moves the reading means by the movement of the moving member due to the rotation of the cam, When reading the aforementioned sheet, the reading means is moved to the first position. When performing the shading correction, the reading means is moved to the second position to adjust the first distance from the reading means to the sheet and the second distance from the reading means to the reference member in the third direction. Image forming apparatus.

10. The image forming means is characterized by correcting the image to be formed on the sheet based on the reading result of the image by the reading means. The image forming apparatus according to claim 9.

11. The system further comprises control means for generating shading correction data based on the reading result of the reference member by the reading means, The control means is characterized by correcting the operating conditions of the reading means when reading the sheet based on the shading correction data. The image forming apparatus according to claim 9.

12. The system further comprises control means for generating shading correction data based on the reading result of the reference member by the reading means, The control means is characterized by correcting the reading result of the sheet by the reading means based on the shading correction data. The image forming apparatus according to claim 9.

Images