Reading device and image forming device

Abstract

To provide a reading device and an image forming apparatus that, when an object to be read and a reading surface are separated from each other, can prevent a reduction in illuminance in an image formed by a lens array on a sensor surface from light reflected on the object to be read.SOLUTION: A reading device reading an object to be read in an image forming apparatus is provided with a lens array and a light guide body. The lens array is provided in an attitude in which an optical axis is along a height direction intersecting with a reading surface. The light guide body is adjacent to the lens array with respect to a sub scanning direction intersecting with both the height direction and a main scanning direction, and locates the maximum illuminance of illumination light illuminating the object to be read on the opposite side of the lens array with respect to the deepest position of the depth of field of the lens array with respect to the height direction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] An embodiment of the present invention relates to a reading device and an image forming device. [Background technology]

[0002] In the image forming apparatus, the illuminance at the reading portion of the object to be read is set to a predetermined illuminance by irradiating the object to be read with light from a light source such as an LED (Light Emitting Device) through a light guide. This allows the reading device provided in the image forming apparatus to properly read the object to be read. For example, when a lens array is used in the reading optical system provided in the reading device, the object to be read and the reading surface may be separated. In this case, if the illuminance when the object to be read and the reading surface are not separated (contacting each other) is the same as the illuminance illuminating the object to be read, the optical efficiency of the lens array is lower than when the object to be read and the reading surface are not separated. As a result, the illuminance of the image formed on the sensor surface by the lens array may decrease. Therefore, when the object to be read and the reading surface are separated, it is required to suppress the decrease in illuminance of the image formed on the sensor surface by the lens array using the light reflected from the object to be read. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-70411 A [Patent Document 2] JP 2014-123941 A Summary of the Invention [Problem to be solved by the invention]

[0004] The problem that the present invention aims to solve is to provide a reading device and an image forming device that can suppress a decrease in illuminance in an image formed on a sensor surface by a lens array using light reflected from an object to be read when the object to be read is separated from the reading surface. [Means for solving the problem]

[0005] According to an embodiment, a reading device for reading an object in an image forming apparatus includes a lens array and a light guide. The lens array is disposed with an optical axis aligned along a height direction intersecting with a reading surface. The light guide is adjacent to the lens array in a sub-scanning direction intersecting with both the height direction and the main scanning direction, and positions the maximum illuminance of illumination light for illuminating the object on the opposite side of the lens array with respect to the deepest position of the depth of field of the lens array in the height direction. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram of an image forming apparatus provided with a reading device according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing the configuration of an image forming unit that forms a black image and its periphery in an image forming apparatus provided with a reading device according to an embodiment. [Diagram 3] FIG. 3 is a schematic diagram showing a configuration in which the reading device according to the embodiment is provided on a reading stand of an image forming apparatus. [Figure 4] FIG. 4 is a schematic perspective view of a lens array provided in the reading device according to the embodiment. [Diagram 5] FIG. 5 is a schematic diagram showing a configuration in which the reading device according to the embodiment is provided in a scanner unit of an image forming apparatus. [Figure 6] FIG. 6 is a schematic diagram showing a configuration in which a reading device according to a modified example is provided on a reading stand of an image forming apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, the embodiment will be described with reference to the drawings. In this embodiment, the image forming device 1 will be described with the direction along the direction of gravity as the vertical direction (the direction indicated by the arrows ZA and ZB), the direction along the longitudinal direction of the reading device as the depth direction (the direction indicated by the arrows YA and YB), and the direction intersecting (perpendicular or substantially perpendicular) both the vertical direction and the depth direction as the width direction (the direction indicated by the arrows XA and XB). The longitudinal direction of the reading device 10 is the main scanning direction, and the direction intersecting (perpendicular or substantially perpendicular) the main scanning direction is the sub-scanning direction.

[0008] 1 is a schematic diagram of an image forming apparatus 1 according to an embodiment. The image forming apparatus 1 is a multi-function peripheral (MFP) that integrates functions such as copying, scanning, and printing. One example of the image forming apparatus 1 is a solid-state scanning type LED copier having an exposure optical system that uses a semiconductor light-emitting element such as an LED as a light source. The image forming apparatus 1 includes a housing 2, a reading table 3, and a scanner unit 4.

[0009] The reading table 3 is supported by the housing 2 and is disposed vertically above the housing 2. The reading table 3 has a reading surface 31 that forms the upper surface of the reading table 3. The object to be read is placed on the reading surface 31. The object to be read is, for example, a manuscript. The reading surface 31 is, for example, the upper surface of a manuscript glass table provided on the reading table 3. The scanner unit 4 is disposed vertically above the reading table 3. The scanner unit 4 functions as an object to be read holder by pressing the object to be read placed on the reading surface 31 from above in the vertical direction.

[0010] The image forming apparatus 1 includes a reading device 10 inside the reading table 3, which reads information written on the surface of the object to be read. The reading device 10 can move in the sub-scanning direction along the reading surface 31 by a drive mechanism (not shown). In addition, in the reading table 3, a reading glass 5 is arranged next to the reading surface 31 in the sub-scanning direction of the reading device 10. The reading device 10 can be arranged vertically below the reading glass 5. In addition, the reading device 10 is provided inside the scanner unit 4. The reading device 10 provided in the scanner unit 4 does not move from a predetermined position in the scanner unit 4. In the scanner unit 4, the object to be read, such as a document, is transported in the transport direction indicated by the arrow along the transport path R. The detailed configuration of the reading device 10 will be described later.

[0011] The image forming apparatus 1 includes an image forming unit 30 inside a housing 2. The image forming apparatus 1 includes a cylindrical intermediate transfer belt 40 above the image forming unit 30 in the vertical direction. The image forming unit 30 includes image forming sections 301-304 along the width direction of the image forming apparatus 1. In this embodiment, four colors, yellow, cyan, magenta, and black, are used in the image forming section. The image forming sections 301-304 form images of yellow, cyan, magenta, and black, respectively. The image forming sections 301-304 include photoconductor drums 311-314, developers (developing devices) 331-334, and exposure devices 501-504. Since the image forming sections 301-304 have the same configuration, the image forming section 304 will be described, and descriptions of the image forming sections 301-303 of other colors will be omitted.

[0012] FIG. 2 is a schematic diagram showing the image forming unit 304 that forms a black image and the configuration of the periphery thereof. The image forming unit 304 has a photoconductor drum 314, an electrostatic charger 324, an exposure device 504, a developing device (developing device) 334, a primary transfer roller 344, a cleaner 354, and a blade 364. The photoconductor drum 314 is rotatable about a rotation axis extending in the depth direction. The photoconductor drum 314 has an outer circumferential surface that contacts the intermediate transfer belt 40. A drive mechanism (not shown) of the image forming unit 30 rotates the photoconductor drum 314 in the direction of the arrow (clockwise direction) shown in the figure. The photoconductor drum 314 rotates in contact with the intermediate transfer belt 40, thereby moving the intermediate transfer belt 40 in a circular motion.

[0013] The primary transfer roller 344 faces the photoconductor drum 314 at a location vertically below the primary transfer roller 344, with the intermediate transfer belt 40 sandwiched therebetween. The primary transfer roller 344 is rotatable about a rotation axis extending in the depth direction. The primary transfer roller 344 has an outer circumferential surface that contacts the inner circumferential surface of the intermediate transfer belt 40. In other words, the intermediate transfer belt 40 moves in a circular motion, passing between the photoconductor drum 314 and the primary transfer roller 344 in the vertical direction.

[0014] The charging charger 324 uniformly charges the surface of the photosensitive drum 314. The exposure device 504 irradiates the surface of the photosensitive drum 314 with exposure light based on a color-separated black image signal. As a result, the exposure device 504 forms an electrostatic latent image based on the black image signal on the surface of the photosensitive drum 314. The developing device 334 supplies black toner (developer) to the electrostatic latent image formed on the surface of the photosensitive drum 314, forming a black toner image on the surface of the photosensitive drum 314. The primary transfer roller 344 transfers the black toner image formed on the surface of the photosensitive drum 314 onto the toner images of other colors, superimposed on the toner images of other colors, onto the intermediate transfer belt 40. The cleaner 354 and the blade 364 remove the toner remaining on the surface of the photosensitive drum 314. The toner images of each color transferred onto the surface of the intermediate transfer belt 40 move toward between the pair of secondary transfer rollers 37 (371, 372) as the intermediate transfer belt 40 rotates. At this time, the photoconductor drum 314 rotates, and the exposure device 504 writes an electrostatic latent image on the surface of the photoconductor drum 314. Then, as the photoconductor drum 314 rotates a certain amount, the exposure device 504 forms an electrostatic latent image for black, which is color-separated and corresponds to the entire image of the original, on the surface of the photoconductor drum 314.

[0015] As shown in Fig. 1, the image forming apparatus 1 has a pair of secondary transfer rollers 37 that transfer the toner images of each color, which have been transferred and overlapped on the surface of the intermediate transfer belt 40, onto a sheet of paper P. One secondary transfer roller 371 is one of the rollers around which the intermediate transfer belt 40 is wrapped. The other secondary transfer roller 372 faces the one secondary transfer roller 371, with the intermediate transfer belt 40 sandwiched therebetween. The toner images of each color, which have been transferred and overlapped on the surface of the intermediate transfer belt 40, pass through a nip formed between the pair of secondary transfer rollers 37 as the intermediate transfer belt 40 rotates.

[0016] The image forming apparatus 1 includes a paper feed cassette 61 capable of accommodating a plurality of sheets of paper P of a predetermined size in a stacked manner, located at the bottom inside the housing 2 in the vertical direction. The paper feed cassette 61 is, for example, pulled out from the front side of the housing 2 in the depth direction and stored inside the housing 2 facing the rear side in the depth direction. The image forming apparatus 1 includes a pickup roller 62 that picks up the paper P accommodated in the paper feed cassette 61. The pickup roller 62 rotates with its circumferential surface in contact with the paper P, thereby picking up the paper P from the paper feed cassette 61 one sheet at a time.

[0017] The image forming apparatus 1 includes a paper discharge tray 63 at an upper portion of the housing 2 in the vertical direction. The paper discharge tray 63 is provided below the reading table 3 in the vertical direction. In the image forming apparatus 1, a conveying path 64 is provided between the pickup roller 62 and the paper discharge tray 63. The conveying path 64 conveys the paper P taken out from the paper feed cassette 61 toward the paper discharge tray 63. The conveying path 64 passes through a nip between a pair of secondary transfer rollers 37. A plurality of pairs of conveying rollers 641 are arranged on the conveying path 64, and a conveying guide for guiding the conveying of the paper P may be arranged. The image forming apparatus 1 includes a pair of paper discharge rollers 631 at the end of the conveying path 64 for discharging the paper P to the paper discharge tray 63. The pair of paper discharge rollers 631 can rotate in both a forward direction in which the paper P is discharged to the paper discharge tray 63 and a reverse direction in which the paper P is returned to the conveying path 64.

[0018] The image forming apparatus 1 includes a pair of fixing rollers 65. The pair of fixing rollers 65 is located above the pair of secondary transfer rollers 37 in the vertical direction. The conveying path 64 goes toward the pair of paper discharge rollers 631 via the pair of fixing rollers 65. The pair of fixing rollers 65 heats and presses the paper P conveyed by the conveying path 64, and fixes the toner image transferred to the surface of the paper P to the surface of the paper P. The image forming apparatus 1 also includes a reversing conveying path 66 that reverses the paper P with an image formed on one side and conveys the paper P to the nip between the pair of secondary transfer rollers 37. The reversing conveying path 66 includes a pair of conveying rollers 661 that rotate with the paper P sandwiched therebetween and convey the paper P. The reversing conveying path 66 may also be provided with a conveying guide (not shown). The image forming apparatus 1 includes a gate 67 on the opposite side of the pair of paper discharge rollers 631 from the paper discharge tray 63 side in the width direction. The gate 67 is disposed on the conveying path 64 and switches the conveying destination of the paper P to the paper discharge tray 63 or the reverse conveying path 66 .

[0019] The image forming apparatus 1 rotates the pickup roller 62 to take out the paper P from the paper feed cassette 61. The image forming apparatus 1 rotates a plurality of conveying rollers 641 to convey the paper P taken out from the paper feed cassette 61 toward the paper discharge tray 63 via the conveying path 64. At this time, the image forming apparatus 1 transfers a toner image of each color onto the surface of the intermediate transfer belt 40 in accordance with the timing of conveying the paper P. The toner image is conveyed to the nip between the pair of secondary transfer rollers 37 by the rotational movement of the intermediate transfer belt 40. The image forming apparatus 1 applies a transfer voltage to the paper P from the pair of secondary transfer rollers 37, and transfers the toner image of each color onto the surface of the paper P. The image forming apparatus 1 conveys the paper P to which the toner image has been transferred to the nip between the fixing rollers 65. The image forming apparatus 1 heats and presses the paper P. As a result, the image forming apparatus 1 melts the toner image and presses it against the surface of the paper P, and fixes the toner image to the paper P. The paper P on which the image has been fixed passes through a paper discharge roller 631 and is discharged onto a paper discharge tray 63 .

[0020] When a double-sided mode in which an image is also formed on the back side of the paper P is selected, the image forming apparatus 1 switches the conveying direction of the gate 67 to the reverse conveying path 66 immediately before the paper P discharged toward the paper discharge tray 63 passes through the nip of the paper discharge rollers 631. The image forming apparatus 1 reverses the paper discharge rollers 631 and conveys the paper P to the reverse conveying path 66. After turning over the paper P, the image forming apparatus 1 conveys the paper P again to the nip of the pair of secondary transfer rollers 37. The image forming apparatus 1 forms a toner image based on image data to be formed on the back side of the paper P on the front side of the intermediate transfer belt 40. The image forming apparatus 1 runs the intermediate transfer belt 40 on which the toner images of each color are formed, and sends the toner images of each color to the nip of the pair of secondary transfer rollers 37. As described above, the image forming apparatus 1 transfers and fixes the toner image on the back side of the paper P, and discharges the paper P to the paper discharge tray 63 via the paper discharge rollers 631.

[0021] The image forming apparatus 1 includes a control unit 70 that controls the operation of each of the above-mentioned mechanisms. The control unit 70 includes a processor such as a CPU, and a memory. The control unit 70 executes various processes by the processor executing a program stored in the memory. The control unit 70 controls the reading device 10 to obtain an image from the read surface of the object to be read. The control unit 70 controls the image forming unit 30 to form an image on the surface of the paper P. In one example, the control unit 70 inputs image data read by the reading device 10 to the image forming unit 30. The control unit 70 controls the operation of the conveying rollers 641 and 661 to convey the paper P through the conveying path 64 and / or the reverse conveying path 66. The control unit 70 transfers and fixes a toner image based on the image data onto the paper P conveyed through the secondary transfer roller 37 and the fixing roller, and causes the paper P to be discharged to the paper discharge tray 63 via the paper discharge rollers 631.

[0022] In such an image forming apparatus 1, when the reading device 10 reads the surface of the object to be read, the reading device 10 irradiates illumination light toward the surface to be read, so that the illuminance of the surface to be read is sufficient for the reading device 10 to acquire an image. However, when the surface to be read is separated from the reading surface 31, the illuminance may decrease in an image formed on the sensor surface by the lens array from the light reflected by the surface to be read. In this case, the image acquired by the reading device 10 becomes dark, for example, in a portion where the illuminance is insufficient. Therefore, for example, when the distance between the manuscript surface (surface to be read) and the reading surface varies depending on the location, such as in a book, or when the distance between the manuscript surface and the surface to be read at the reading position varies due to the document being transported at high speed using a document feeder, a difference in brightness occurs in an area where the brightness is originally uniform. In the reading device 10 of this embodiment, as described below, by setting a position where the illumination light illuminating the surface to be read has maximum illuminance at a predetermined position, the brightness of the image formed on the sensor surface by the lens array using the light reflected from the surface to be read can be made constant regardless of the degree to which the surface to be read is away from the reading surface 31.

[0023] The reading device 10 according to this embodiment will be described below. The reading device 10 according to this embodiment can be provided in the reading table 3 and / or the scanner unit 4. When the reading device 10 is provided in both the reading table 3 and the scanner unit 4, the image forming apparatus 1 can obtain an image of the surface to be read from the object to be read by controlling both reading devices 10. The reading device 10 according to this embodiment is a reading device using a contact optical system (CIS: Contact Image Sensor). Therefore, the reading device 10 according to this embodiment does not use a so-called reduction optical system.

[0024] FIG. 3 is a schematic diagram showing the configuration of the reading device 10 and its surroundings provided on the reading table 3 of the image forming apparatus 1 according to the embodiment. In FIG. 3, as in FIG. 1, the vertical direction, the depth direction, and the width direction are defined. In addition, in the reading device 10, the direction that intersects (is perpendicular or substantially perpendicular to) both the main scanning direction and the sub-scanning direction (directions indicated by arrows XC and XD) is defined as the height direction (direction indicated by arrows ZC and ZD). The height direction of the reading device 10 coincides with or substantially coincides with the vertical direction. Note that FIG. 3 shows the reading device 10 from one direction of the main scanning direction. In addition, the reading device 10 shown in FIG. 3 is provided inside the reading table 3 of the image forming apparatus 1, and is disposed below the reading surface 31 in the height direction.

[0025] The reading device 10 includes a housing 11, a substrate 12, a sensor 13, light guides 14 and 15, a light blocking member 16, a light source 18, and a lens array 20. The housing 11 includes a pair of side walls extending in the main scanning direction and facing each other in the sub-scanning direction, and a partition wall extending between the pair of side walls in the sub-scanning direction. The partition wall is disposed above the lower ends of the pair of side walls in the height direction. Therefore, the lower ends of the pair of side walls protrude downward from the lower surface of the partition wall in the height direction. Thus, the housing 11 is formed in an H-shape or a substantially H-shape when projected from the main scanning direction. The substrate 12 is provided on the lower surface of the partition wall in the height direction, and is provided between the pair of side walls in the sub-scanning direction. The sensor 13 is mounted on the substrate 12. The sensor 13 is a line sensor in which imaging elements that convert light into electrical signals are arranged along the main scanning direction. The sensor 13 is one or more line sensors. The sensor 13 is, for example, a Charge Coupled Device (CCD), a Complimentary Metal Oxide Semiconductor (CMOS), etc. The position where an image is formed by a lens array 20 (described later) is a sensor surface of the sensor 13.

[0026] The light guides 14 and 15 are a pair of optical elements for irradiating the illumination light (diffused light) emitted by the light source 18 toward the reading surface 31. The light guides 14 and 15 extend along the main scanning direction. The light guides 14 and 15 are provided away from the upper surface of the partition wall of the housing 11 toward the reading surface 31 in the height direction. The light guides 14 and 15 are arranged apart from each other in the width direction. In this embodiment, the light guides 14 and 15 have the same or substantially the same shape. The light guide 14 includes a diffusion portion 141 and an exit surface 142, and the light guide 15 includes a diffusion portion 151 and an exit surface 152. Since the light guides 14 and 15 have the same configuration, the light guide 14 will be described and the description of the light guide 15 will be omitted.

[0027] The diffusion section 141 diffuses the illumination light incident from the light source 18 into the light guide 14 inside the light guide 14. In this embodiment, the illumination light is incident on the light guide 14 from an end in the main scanning direction. The diffusion section 141 is formed on the lower surface in the height direction of the light guide 14. The diffusion section 141 may be, for example, a groove formed in the light guide 14, or may be formed by white ink applied to the light guide 14. The exit surface 142 is a surface from which the illumination light diffused by the diffusion section 141 is emitted from the light guide 14. The exit surface 142 is formed along the main scanning direction (longitudinal direction) of the light guide 14 and faces the diffusion section 141. That is, the exit surface 142 is formed on the upper surface in the height direction of the light guide 14. In one example, the exit surface 142 is a cylindrical lens surface. A reflector may be attached to the surface of the diffusion section 141. Furthermore, a light source such as an LED may be provided on the surface of the diffusion section 141 .

[0028] A lens array 20 and a light blocking member 16 are provided between the pair of light guides 14, 15 in the sub-scanning direction. The light blocking member 16 covers the lens array 20 from the outer side in the sub-scanning direction and from the upper side in the height direction. The lens array 20 and the light blocking member 16 extend along the main scanning direction. The pair of light guides 14, 15 are adjacent to the light blocking member 16 from the outer side in the sub-scanning direction. The lens array 20 forms an image on the sensor 13 of the illumination light reflected from the surface to be read of the object to be read. Therefore, the lens array 20 is disposed at a position where the light emitted from the lens array 20 forms an image on the sensor 13.

[0029] The light shielding member 16 suppresses the incidence of light other than the reflected light from the read surface of the object to the lens array 20. The light shielding member 16 includes a light shielding wall disposed between the lens array 20 and the reading surface 31 in the height direction, and a pair of light shielding side walls disposed between the lens array 20 and the light guides 14 and 15 in the sub-scanning direction. The light shielding wall extends between the pair of light shielding side walls in the sub-scanning direction. The light shielding wall of the light shielding member 16 is formed with a slit 17 penetrating the light shielding wall in the height direction. The slit 17 is formed in the light shielding member 16 along the main scanning direction. The reflected light from the read surface passes through the slit 17 and enters the lens array 20 from the upper side in the height direction. Thus, the slit 17 functions as an aperture in the sub-scanning direction.

[0030] FIG. 4 is a perspective view of the lens array 20 provided in the reading device 10 of the embodiment. In FIG. 4, the main scanning direction, the sub-scanning direction, and the height direction are defined as in FIG. 3. The lens array 20 includes an incident surface 21 and an exit surface 22. The incident surface 21 is a surface where the illumination light reflected by the surface to be read enters the lens array 20. The incident surface 21 is formed, for example, as a curved surface having different (anisotropic) curvatures at each portion of the incident surface 21, and functions as an incident-side lens surface. The optical axis of the incident surface 21 extends along the height direction at the center of the incident surface 21 in the sub-scanning direction. The exit surface 22 is a surface that enters the lens array 20 and emits the light guided inside the lens array 20 toward the sensor 13 of the reading device 10. The exit surface 22 is formed, for example, as a curved surface having different (anisotropic) curvatures at each portion of the exit surface 22, and functions as an exit-side lens surface. The optical axis of the exit surface 22 extends along the height direction at the center in the sub-scanning direction of the exit surface 22. In the lens array 20, the optical axis of the entrance surface 21 and the optical axis of the exit surface 22 are parallel or approximately parallel to each other.

[0031] 4 is an example, and the shape of the lens array 20 provided in the reading device 10 may be different from that in Fig. 4. For example, the lens array provided in the reading device 10 may be a rod lens array.

[0032] 3, the lens array 20 of this embodiment is provided in the reading device 10 in such a position that the incident surface 21 is located on the reading surface 31 side in the height direction, and the exit surface 22 is located on the sensor 13 side in the height direction. The lens array 20 is provided in the reading device 10 in such a position that the optical axis of the incident surface 21 is along the height direction. Therefore, the optical axis of the incident surface 21 of the lens array 20 is perpendicular or approximately perpendicular to the reading surface 31.

[0033] In the reading device 10 of this embodiment, the pair of light guides 14, 15 position the maximum illuminance of the illumination light illuminating the object to be read on the opposite side of the lens array 20 with respect to the deepest position of the depth of field of the lens array 20 in the height direction. The depth of field is the range of the position of the object where the lens forms a sufficiently clear image of the object in front of and behind the focal point of the lens on the side where the object is located. That is, it is the range of the position of the read surface where the lens forms a sufficiently clear image of the read surface in front of and behind the focal point of the lens on the side where the read surface of the object is located. In the reading device 10, the depth of field of the lens array 20 is a range D defined on the object side of the incident surface 21 of the lens array 20 in the height direction. In this embodiment, the position closest to the incident surface 21 of the depth of field is the closest position QA, and the position farthest from the incident surface 21 of the depth of field is the deepest position QB. In Figure 3, lens array 20 is arranged so that the optical axis of incident surface 21 of lens array 20 is aligned along the height direction, so that the position of the depth of field closest to incident surface 21 in the height direction is closest position QA, and the position of the depth of field farthest from incident surface 21 in the height direction is deepest position QB.

[0034] The deepest position QB of the depth of field of the lens array 20 is appropriately set by the lens array 20 used in the reading device 10. In one example, the deepest position QB of the depth of field is set based on a range in which the modulation transfer function (MTF) of a 6Lp / mm resolution chart (black and white ladder chart) is 10% or more. In another example, it is set based on a range in which the MTF of a 6Lp / mm MTF measurement chart (a chart in which the shading changes sinusoidally) is 55% or more.

[0035] In the reading device 10, the light guides 14 and 15 cause the position where the illumination light has the maximum illuminance to be located above the reading surface 31 in the height direction. The illuminance of the illumination light irradiated from the light guides 14 and 15 to the read surface 31 increases in the height direction from the light guides 14 and 15 toward the position where the illumination light has the maximum illuminance, and decreases when the position where the illumination light has the maximum illuminance is exceeded. That is, the illuminance of the illumination light increases from the light guides 14 and 15 to the position where the illumination light has the maximum illuminance, and decreases when the position where the illumination light has the maximum illuminance is exceeded. In addition, in the reading device 10, the light guides 14 and 15 cause the straight lines LA and LB connecting the centers of curvature CA and CB of the exit surfaces 142 and 152 of the light guides 14 and 15 and the centers of the diffusion sections 141 and 151 to intersect with the optical axis O of the lens array 20, which passes through the center of the entrance surface of the lens array 20, at a position Q that is distal to the deepest position QB of the lens array 20 in the height direction. In the reading device 10, when projected in the main scanning direction, a straight line LA on the light guide 14 intersects with a straight line LB on the light guide 15 at a position Q on the opposite side of the lens array 20 from the deepest position QB in the height direction.

[0036] It is preferable that the exit surfaces 142, 152 of the light guides 14, 15 have a curvature that allows the light emitted from the exit surfaces 142, 152 to be diffused within a predetermined range. The light emitted from the exit surfaces 142, 152 spreads in a direction intersecting the straight lines LA, LB as it moves from the exit surfaces 142, 152 toward the reading surface 31. The curvature of the exit surfaces 142, 152 is smaller than the curvature at which the light emitted from the exit surfaces 142, 152 is condensed, and is smaller than the curvature at which the maximum illuminance of the light emitted from the exit surfaces 142, 152 is at the deepest position QB of the depth of field of the lens array 20. In one example, the distance between the exit surface 142 (152) and the diffusion section 141 (151) facing the exit surface 142 (152) is greater than the radius of curvature of the exit surface 142 (152) and is less than twice the radius of curvature of the exit surface 142 (152). In Fig. 3, the distance is the maximum length of the light guide 14 (15) in the direction along the straight line LA (LB). By setting the curvature of the exit surfaces 142, 152 in this manner, the light guides 14, 15 can appropriately adjust the illuminance of the illumination light.

[0037] Note that only the light guide 14 or only the light guide 15 may be provided in the reading device 10. In other words, the reading device 10 does not need to be provided with a pair of light guides, and may be provided with only one. Even in this case, the light guide 14 or the light guide 15 provided in the reading device 10 positions the maximum illuminance of the illumination light illuminating the object to be read on the opposite side of the lens array 20 with respect to the deepest position QB of the depth of field of the lens array 20 in the height direction.

[0038] FIG. 5 is a schematic diagram of the case where the reading device 10 is provided in the scanner unit 4. In FIG. 5, the main scanning direction, the sub-scanning direction, and the height direction are defined as in FIG. 3. The sub-scanning direction of the reading device 10 coincides or substantially coincides with the transport direction of the object to be read. When the reading device 10 is provided in the scanner unit 4, the reading device 10 has a reading surface 31. The reading surface 31 is provided on the opposite side of the lens array 20 from the substrate 12 in the height direction and faces the substrate 12. In this case, the reading surface 31 is attached to the housing 11. Also, except that the reading surface 31 is provided in the reading device 10 as described above, the configuration of the reading device 10 is the same as when the reading device 10 is provided in the reading table 3. Since the object to be read is placed below the scanner unit 4 in the height direction, the reading device 10 is provided in the scanner unit 4 in a position where the reading surface 31 is located on the lower side in the height direction. That is, the reading device 10 is provided in the scanner unit 4 in a position rotated by a predetermined angle about an axis along the main scanning direction from the position in which the reading device 10 is provided on the reading table 3.

[0039] Furthermore, when the reading device 10 obtains image information of the read surface of an object in the scanner unit 4, the reading device 10 obtains the image information of the read surface without moving from a predetermined position in the scanner unit 4. In this embodiment, the object is transported along a transport path provided inside the scanner unit 4, so that the read surface moves relative to the scanner unit 4. This allows the reading device 10 to obtain image information of the read surface at a predetermined position in the scanner unit 4.

[0040] In the reading device 10 of this embodiment, the illumination light emitted from the light source 18 is incident on the light guides 14, 15. The illumination light incident on the light guides 14, 15 is diffused inside the light guides 14, 15 and in the diffusion sections 141, 151, and is emitted from the emission surfaces 142, 152 of the light guides 14, 15. Since the light guides 14, 15 are disposed in the reading device 10 as described above, the illumination light emitted from the emission surfaces 142, 152 illuminates the reading surface 31. As a result, the surface to be read that is on the opposite side of the reading device 10 with respect to the reading surface 31 in the height direction is illuminated by the illumination light. After being reflected by the surface to be read, the illumination light proceeds toward the reading surface 31 as reflected light. The reflected light passes through the reading surface 31 and the slit 17 and enters the lens array 20. At this time, the slit 17 functions as an aperture for the light entering the lens array 20, so that a predetermined amount of light enters the lens array 20. Light incident on the lens array 20 from the entrance surface 21 of the lens array 20 is reflected inside the lens array 20 and emitted from the exit surface 22 of the lens array 20. The light emitted from the exit surface 22 reaches the sensor 13. The sensor 13 receives the reflected light from the surface to be read and obtains image information of the surface to be read.

[0041] In the reading device 10 of the present embodiment, the illuminance of the illumination light from the light source 18 is maximum on the opposite side of the lens array 20 in the height direction from the deepest position QB of the depth of field of the lens array 20. In addition, the illuminance of the illumination light increases as the illuminance of the illumination light increases from the lens array 20 toward the position where the illuminance of the illumination light is maximum in the height direction. Therefore, even if the surface to be read is separated from the reading surface in the height direction in the range D of the depth of field of the lens array 20, the illuminance of the image formed by the light reflected by the object on the sensor surface by the lens array can be made the same as the illuminance when the surface to be read is not separated from the reading surface. That is, in the reading device 10 of the embodiment, when the object to be read and the reading surface are separated, the decrease in the illuminance of the image formed by the light reflected by the object on the sensor surface by the lens array can be suppressed. Therefore, in the image forming device 1, the image information of the surface to be read can be appropriately acquired by the reading device 10.

[0042] In the reading device 10 of the present embodiment, the light guides 14, 15 are preferably a pair of light guides 14, 15 adjacent to the lens array 20 from both of the outer sides of the lens array 20 in the sub-scanning direction. Each of the pair of light guides 14, 15 includes a diffusion section 141, 151 for diffusing the incident illumination light, and an exit surface 142, 152 provided on the opposite side of the diffusion section 141, 151 in the height direction and having a predetermined curvature. In addition, in the projection from the main scanning direction, straight lines LA, LB passing through the center of the diffusion section 141, 151 and the center of curvature of the exit surface 142, 152 in one of the pair of light guides 14, 15 intersect with straight lines LA, LB passing through the center of the diffusion section 141, 151 and the center of curvature of the exit surface in the other of the pair of light guides 14, 15 on the opposite side of the lens array 20 with respect to the deepest position QB in the height direction. By arranging the light guides 14 and 15 in this manner, it is possible to further increase the illuminance in the range D of the depth of field of the lens array 20. Therefore, for example, the maximum illuminance of the illumination light can be set at a position farther away from the deepest position QB of the depth of field of the lens array 20. Therefore, in the reading device 10, even if the object to be read and the reading surface 31 are farther apart, it is possible to suppress a decrease in the illuminance of the image formed on the sensor surface by the lens array using the light reflected from the object to be read.

[0043] In the reading device 10 of this embodiment, the light guide 14 (15) includes a diffusion section 141 (151) that diffuses the incident illumination light, and an exit surface 142 (152) that is provided on the opposite side of the diffusion section 141 (151) in the height direction and has a predetermined curvature. In addition, in a projection from the main scanning direction, a straight line LA (LB) passing through the center of the diffusion section 141 (151) and the center of curvature of the exit surface 142 (152) intersects with the axis of the optical axis O of the lens array 20 on the opposite side of the lens array 20 with respect to the deepest position QB in the height direction. By disposing the light guide 14 (15) in the reading device 10 in this manner, even if the object to be read and the reading surface 31 are separated from each other, a decrease in illuminance in an image formed on the sensor surface by the lens array using light reflected from the object to be read can be suppressed.

[0044] In the image forming apparatus 1 of the present embodiment, the reading device 10 of the present embodiment is preferably provided on the reading table 3, and the reading device 10 of the present embodiment is preferably provided on the scanner unit 4. In such an image forming apparatus 1, for example, the front and back sides of the object to be read are read using the same optical system. Therefore, the color of the image of the front side of the object to be read and the image of the back side of the object to be read are the same or approximately the same. Therefore, when reading the object to be read, whether the reading table 3 or the scanner unit 4 is used, the difference in color between the acquired images is small. Therefore, in such an image forming apparatus 1, whether the object to be read is read using the reading table 3 or the scanner unit 4, an image with the same color can be acquired.

[0045] (Modification) 6 is a schematic diagram showing a modified example of the light guides 41, 42 provided in the reading device 10. The configuration of the reading device 10 according to this modified example is the same as that of the above-mentioned embodiment, except that the shapes of the light guides 41, 42 are different from those of the above-mentioned embodiment. The light guides 41, 42 according to this modified example are formed in a columnar shape extending in the main scanning direction. The light guides 41, 42 include diffusion sections 411, 421 and exit surfaces 412, 422, similar to the above-mentioned embodiment.

[0046] The light guide 41 (42) of this modification is different from the light guide 14 (15) of the embodiment in that the diffusion portion 411 (421) and the exit surface 412 (422) form an edge extending in the main scanning direction. That is, the diffusion portion 411 (421) and the exit surface 412 (422) are adjacent to each other. The centers of the curvature radii of the light guides 41 and 42 are points CC and CD. Even in this case, the maximum length of the light guide 41 (42) in the direction along the straight line LC (LD) is greater than the curvature radius of the exit surface 412 (422) and is smaller than twice the curvature radius of the exit surface 412 (422). Therefore, in the reading device 10 of this modification, the illuminance of the illumination light from the light source 18 is maximum on the opposite side of the lens array 20 from the deepest position QB of the depth of field of the lens array 20 in the height direction. Therefore, this modified example also provides the same functions and effects as the above-described embodiment.

[0047] According to at least one of these embodiments, the light guide of the reading device is adjacent to the lens array in a sub-scanning direction that intersects both the height direction and the main scanning direction, and the maximum illuminance of the illumination light that illuminates the object to be read is located on the opposite side of the lens array with respect to the deepest position of the depth of field of the lens array in the height direction. This makes it possible to provide a reading device and an image forming device that can suppress a decrease in illuminance in an image formed on the sensor surface by the lens array using light reflected from the object to be read when the object to be read and the reading surface are separated from each other.

[0048] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0049] 1...image forming apparatus, 2...casing, 3...reading table, 4...scanner unit, 10...reading device, 11...housing, 12...board, 13...sensor, 14, 15...light guide, 16...light blocking member, 17...slit, 18...light source, 20...lens array, 21...incident surface, 22...exiting surface, 141, 151, 411, 421...diffusion section, 142, 152, 412, 422...exiting surface, 311 to 314...photosensitive drum, 331 to 334...developer (developing device), CA to CD...center of curvature, LA to LD...straight line, O...optical axis, QB...deepest position.

Claims

1. A reading device for reading an object in an image forming apparatus, comprising: a lens array disposed with an optical axis aligned along a height direction intersecting with a reading surface; a light guide that is adjacent to the lens array in a sub-scanning direction that intersects both the height direction and the main scanning direction, and that positions a maximum illuminance of illumination light that illuminates the object to be read on an opposite side to the lens array with respect to a deepest position of a depth of field of the lens array in the height direction; A reading device comprising:

2. the light guides are a pair of light guides adjacent to the lens array from both sides outside the lens array in the sub-scanning direction, Each of the pair of light guides includes a diffusion section that diffuses the illumination light incident thereon, and an exit surface that is provided on an opposite side to the diffusion section in the height direction and has a predetermined curvature, When projected from the main scanning direction, a straight line passing through the center of the diffusion portion and the center of curvature of the exit surface in one of the pair of light guides intersects with a straight line passing through the center of the diffusion portion and the center of curvature of the exit surface in the other of the pair of light guides on the opposite side of the lens array with respect to the deepest position in the height direction.

2. A reading device according to claim 1.

3. the light guide includes a diffusion section that diffuses the illumination light incident thereon, and an exit surface that is provided on an opposite side to the diffusion section in the height direction and has a predetermined curvature, When projected from the main scanning direction, a straight line passing through a center of the diffusion portion and a center of curvature of the exit surface intersects with an axis of the optical axis of the lens array on the opposite side to the lens array with respect to the deepest position in the height direction.

2. A reading device according to claim 1.

4. a light source that emits the illumination light that is incident on the light guide; a sensor that is provided on the opposite side of the lens array from the reading surface in the height direction and receives light reflected by the object to be read, the sensor being configured to receive the illumination light; The reading device according to any one of claims 1 to 3, further comprising:

5. A reading device according to any one of claims 1 to 4, a photosensitive drum for forming an electrostatic latent image based on the image acquired by the reading device; a developing device that develops the electrostatic latent image on the photosensitive drum with a developer; An image forming apparatus comprising:

Images