JP2012137715A - Image reading apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To read an image of a document by efficiently irradiating an irradiation object with light from a light source.SOLUTION: In the image reading apparatus, an illumination section includes an LED unit 503 having a plurality of LEDs 501 mounted thereon, a cylindrical lens 507 having a curved surface having a curvature in a direction orthogonal to a main scanning direction, an elliptic diffusion plate 509, a light guide body 505 having a first light-emitting surface 411 and a second light-emitting surface 412, and a reflection mirror 541 which irradiates a document with light from the second light-emitting surface 412, the light from the LED unit 503 passes through the cylindrical lens 507 and the elliptic diffusion plate 509, is emitted from the first light-emitting surface 411 of the light guide body 505, and irradiates the document, or is emitted from the second light-emitting surface 412 of the light guide body 505, is reflected on the reflection mirror 541, and irradiates the document.

Description

  The present invention relates to an image reading apparatus and an image forming apparatus that efficiently irradiate a document with light from a light source.

  As an image reading device that reads an image of an original, an illumination unit that irradiates light on the original, a mirror that reflects light from the original to form an optical path, an imaging lens that forms an image of the light, and an image are formed 2. Description of the Related Art An image reading device including a CCD (Charge coupled Device) that reads an image of a document from light is known.

  Further, in Patent Document 1, the light exit surface of the light guide disposed on the optical path between the light source and the document is cut obliquely, and the light totally reflected on the light exit surface is totally reflected inside the light guide, Subsequently, an image reading apparatus configured to emit light toward an irradiation target such as a document without reflecting on any surface is described.

JP 2007-158556 A

  However, in the method of Patent Document 1, only total reflection is used and the light exit surface is a flat surface, so that the amount of light irradiated outside the effective irradiation range increases. Moreover, the light condensing state to irradiation object is also bad. Furthermore, since it is necessary to dispose the light guide at a position away from the reading position in order to guide the total reflected light to the irradiation surface, there is a problem that it is difficult to reduce the size of the apparatus.

  SUMMARY An advantage of some aspects of the invention is to provide an image reading apparatus and an image forming apparatus that read an image of a document by efficiently irradiating the document with light from a light source. It is.

  An image reading apparatus according to a first aspect of the present invention includes a light source having a plurality of light emitting units arranged in the main scanning direction, a convex curved surface having a curvature in the sub-scanning direction orthogonal to the main scanning direction, and the convexity. A cylindrical lens having a flat surface facing the curved surface, and transmitting light from the light source from the flat surface side toward the convex curved surface side; a light incident surface on which light transmitted through the cylindrical lens enters; and the original document A first light-emitting surface from which light is emitted on the side, a second light-emitting surface on which light is emitted on a surface different from the surface including the first light-emitting surface, the first light-emitting surface, and the second light-emitting surface A light guide having a reflecting surface that reflects light toward the first light exit surface, reflecting means for reflecting light emitted from the second light exit surface toward the document, and the document One or a plurality of mirrors that reflect the light reflected to form an optical path An imaging lens that forms an image of light reflected by the one or more mirrors, and an image forming position of the imaging lens, and reads an image of the document based on the image formed by the imaging lens An image reading unit, wherein the light guide is disposed at a position where light transmitted through the cylindrical lens enters the second light exit surface and the reflection surface of the light guide. And

  According to the present invention, the cylindrical lens is provided to make the light from the light source substantially parallel light, so that the number of reflections in the light guide is reduced, and the light from the light source is irradiated onto the document while maintaining the light intensity distribution. Will be. As a result, the light distribution in the sub-scanning direction on the document becomes smoother than before, and light from the light source can be efficiently irradiated onto the document, so that an image with high image quality can be obtained.

  A second aspect of the present invention is the image reading apparatus according to the first aspect, wherein the light diffusivity in the main scanning direction is light between the cylindrical lens and the light guide in the sub scanning direction. A diffusion plate having a higher diffusivity than the above is disposed.

  An LED (Light Emitting Diode) mainly used as a light source at present is a light source with strong directivity, and light emitted from the central portion of the LED light emitting surface in the normal direction is the most light emitted from the LED. As the irradiation intensity increases and the irradiation direction tilts from the normal direction, the light irradiation intensity decreases rapidly. For this reason, light with high irradiation intensity is intensively applied to a portion of the document surface facing the light emitting surface of the LED, and light with low irradiation intensity is irradiated to a portion not facing the light emitting surface of the LED. That is, the irradiation distribution irradiated on the document surface is not uniform in the main scanning line direction. Furthermore, there is a problem that a halation phenomenon occurs when the light with high irradiation intensity is regularly reflected on a surface having an angle such as a binding margin of a book and the reflected light enters the image sensor.

  Therefore, by inserting an elliptical diffuser plate as in the invention described in claim 2, the light in the sub-scanning direction can be diffused only in the main scanning direction without having the angle of the above-mentioned book or the like. It is possible to prevent partial light concentration on the surface. Accordingly, since there is no light having a high irradiation intensity that is regularly reflected from the document surface, the halation phenomenon can be suppressed.

  According to a third aspect of the present invention, there is provided an image forming apparatus according to the first or second aspect, and an image forming unit that forms an image on a sheet based on image data obtained by the image reading apparatus. It is provided.

  According to the present invention, the same effect as that of the first or second aspect of the invention can be achieved.

  By providing a cylindrical lens and making the light from the light source substantially parallel, the number of reflections in the light guide is reduced, and the light from the light source is irradiated onto the document while maintaining the light intensity distribution. As a result, the light distribution in the sub-scanning direction on the document becomes smoother than before, and light from the light source can be efficiently irradiated onto the document, so that an image with high image quality can be obtained.

1 is a diagram illustrating an outline of an internal structure of an image forming apparatus. FIG. 3 is a schematic plan view showing an internal structure of a reading unit. The figure seen from the arrow S direction of the image reading apparatus shown in FIG. Sectional drawing explaining the structure of an illumination part. The elements on larger scale of the light guide shown in FIG. FIG. 4 is a perspective view of the LED unit shown in FIG. 3. The figure which showed the optical path of the light from a light source. 6 is a graph showing a light distribution in the sub-scanning direction on a document surface.

  Embodiments of the present invention will be described below with reference to the drawings. First, the image forming apparatus 1 according to the present embodiment will be described with reference to FIGS. FIG. 1 is a diagram showing an outline of the internal structure of the image forming apparatus 1. FIG. 2 is a schematic plan view showing the internal structure of the reading unit 301. FIG. 3 is a view of FIG. 2 viewed from the direction of the arrow S. In this embodiment, an image forming apparatus to which the present invention is applied will be described as an example. However, this embodiment can be realized only by an image reading apparatus 300 described later. In the present embodiment, the side (the right side in FIG. 1) on which a later-described manual feed tray 65 is disposed is the front side of the image forming apparatus 1.

  The image forming apparatus 1 includes an image reading device 300 disposed on the upper side, and an apparatus main body M that forms a toner image on the paper T based on image information from the image reading device 300 disposed on the lower side. The image reading apparatus 300 includes a document feeding unit 70 that feeds a predetermined document G, and a reading unit 301 that reads an image of the document G. The document feeding unit 70 is connected to the reading unit 301 by a connecting unit (not shown) so as to be opened and closed, and also has a function of protecting a reading surface 302A described later.

  When the document feeding unit 70 is in the closed state, the document G is placed on the document placing unit 71 formed on the upper surface of the document feeding unit 70. The document G placed on the document placement unit 71 is moved to a first reading surface 303A constituting a reading surface 302A in the reading unit 301 by a feed roller (not shown). In this case, an illumination unit 347 and a mirror unit 349, which will be described later, are fixed at the first position 303. Then, the original G is moved so as to slide on the first reading surface 303 </ b> A, whereby an image formed on the surface of the original G is read by the CCD 358.

  When the document feeder 70 is in an open state, the document G is placed on the second reading surface 304A that constitutes the reading surface 302A. In this case, the illumination unit 347 and the mirror unit 349 are disposed at the second position 304 and move in the sub-scanning direction X at the second position 304, respectively. The illumination unit 347 and the mirror unit 349 are moved while keeping a length of an optical path H (optical path length) to be described later constant. Thereby, the image of the document G placed on the second reading surface 304A is read.

  The apparatus main body M includes photosensitive drums 2a, 2b, 2c, and 2d as image carriers, charging units 10a, 10b, 10c, and 10d, laser scanner units 4a, 4b, 4c, and 4d, and developing units 16a and 16b. 16c, 16d, toner cartridges 5a, 5b, 5c, 5d, toner supply devices 6a, 6b, 6c, 6d, intermediate transfer belt 7, primary transfer rollers 37a, 37b, 37c, 37d, secondary An intermediate transfer unit 200 including a transfer roller 8 and a fixing device 9 are provided. In addition, the apparatus main body M includes a paper feed cassette 52 that is disposed so as to be able to be pulled out below the apparatus main body M and is stored in a state where the sheets T are stacked. Further, the apparatus main body M includes a transport path 54 through which the paper T sent out from the paper feed cassette 52 is transported.

  The photosensitive drums 2a, 2b, 2c, and 2d are cylindrical members, and are arranged so as to be rotatable in the direction of an arrow about a rotation axis perpendicular to FIG. An electrostatic latent image is formed on the surface of each of the photosensitive drums 2a, 2b, 2c, and 2d. The charging units 10a, 10b, 10c, and 10d are disposed above the photosensitive drums 2a, 2b, 2c, and 2d, respectively, and the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d are uniformly positive (positive polarity). Charge.

  The laser scanner units 4a, 4b, 4c, and 4d are disposed above the photosensitive drums 2a, 2b, 2c, and 2d, respectively, spaced apart from the photosensitive drums 2a, 2b, 2c, and 2d. It has a polygon mirror, a polygon mirror driving motor, and the like. Each of the laser scanner units 4a, 4b, 4c, and 4d scans and exposes the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d based on image information related to the image read by the reading unit 301. As a result, the charges charged on the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d are removed, and an electrostatic latent image is formed.

  Each of the developing devices 16a, 16b, 16c, and 16d is disposed on the side (left side in FIG. 1) of the photosensitive drums 2a, 2b, 2c, and 2d, and is formed on the photosensitive drums 2a, 2b, 2c, and 2d. The toner image of each color is developed on the electrostatic latent image. Each of the developing devices 16a, 16b, 16c, and 16d corresponds to four toner colors of yellow, cyan, magenta, and black, and developing rollers 116a, 116b, and 116c that can be disposed to face the photosensitive drums 2a, 2b, 2c, and 2d. 116d and a stirring roller for stirring the toner.

  Each of the toner cartridges 5a, 5b, 5c, and 5d contains toner of each color supplied to each of the developing devices 16a, 16b, 16c, and 16d. In this embodiment, yellow toner, cyan toner, and magenta Toner and black toner. Each of the toner supply devices 6a, 6b, 6c, and 6d supplies the toners of the respective colors stored in the toner cartridges 5a, 5b, 5c, and 5d to the developing devices 16a, 16b, 16c, and 16d, respectively.

  The toner images of the respective colors developed on the photosensitive drums 2a, 2b, 2c, and 2d are sequentially transferred to the intermediate transfer belt 7. The intermediate transfer belt 7 is arranged so as to be stretched between the driving roller 35 and the tension roller 36. Since the tension roller 36 is biased to the side away from the drive roller 35 by the spring 38, a predetermined tension is applied to the intermediate transfer belt 7.

  Primary transfer rollers 37a, 37b, 37c, and 37d are arranged to face each other on the opposite side of the intermediate transfer belt 7 from the photosensitive drums 2a, 2b, 2c, and 2d. Predetermined portions of the intermediate transfer belt 7 are sandwiched between the primary transfer rollers 37a, 37b, 37c, and 37d and the photosensitive drums 2a, 2b, 2c, and 2d, respectively. The predetermined portion thus sandwiched is pressed against the surface of each of the photosensitive drums 2a, 2b, 2c, and 2d. In this way, primary transfer nips N1a, N1b, N1c, and N1d are formed, and the color toner images developed on the photosensitive drums 2a, 2b, 2c, and 2d are sequentially transferred to the intermediate transfer belt 7. As a result, a full-color toner image is formed on the intermediate transfer belt 7.

  The primary transfer rollers 37a, 37b, 37c, and 37d are respectively transferred to the intermediate transfer belt 7 with the respective color toner images developed on the photosensitive drums 2a, 2b, 2c, and 2d by a voltage application unit (not shown). The primary transfer bias is applied.

  The secondary transfer roller 8 secondarily transfers the toner image primarily transferred to the intermediate transfer belt 7 onto the paper T. A secondary transfer bias for transferring the toner image on the intermediate transfer belt 7 to the paper T is applied to the secondary transfer roller 8 by a voltage application unit (not shown).

  The secondary transfer roller 8 is brought into contact with and separated from the intermediate transfer belt 7. Specifically, the secondary transfer roller 8 is configured to be movable between a contact position where the secondary transfer roller 8 is in contact with the intermediate transfer belt 7 and a spaced position where the secondary transfer roller 8 is separated from the intermediate transfer belt 7. Specifically, the secondary transfer roller 8 is moved to the contact position when the toner image primarily transferred onto the surface of the intermediate transfer belt 7 is secondarily transferred to the paper T, and is separated from the other position. Moved to. Here, the contact / separation operation of the secondary transfer roller 8 is performed by rotating the entire intermediate transfer unit 200.

  The intermediate transfer unit 200 accommodates the secondary transfer roller 8 and rotatably supports the secondary transfer roller 8, a rotation drive gear 210 disposed on the side surface of the housing 201, and the secondary transfer roller 8, a roller side gear 220 disposed on the side surface of the housing 201 and an idle gear 230 disposed in contact with the rotation drive gear 210 and the roller side gear 220. The intermediate transfer unit 200 includes a position at which the secondary transfer roller 8 can contact the intermediate transfer belt 7 around a rotation shaft (not illustrated) and a position at which the intermediate transfer belt 7 does not contact the intermediate transfer belt 7 by a contact / separation unit (not illustrated). Is rotated.

  A counter roller 108 is disposed on the side of the intermediate transfer belt 7 that faces the secondary transfer roller 8. A predetermined portion of the intermediate transfer belt 7 is sandwiched between the secondary transfer roller 8 and the opposing roller 108. Then, the paper T is pressed against the surface of the intermediate transfer belt 7 (the side on which the image is primarily transferred). In this way, the secondary transfer nip N2 is formed, and the toner image primarily transferred to the intermediate transfer belt 7 is secondarily transferred to the paper T.

  The fixing device 9 melts and fixes each color toner constituting the toner image secondarily transferred onto the paper T. The fixing device 9 includes a heating roller 9a heated by a heater, and a pressure roller 9b pressed against the heating roller 9a. The heating roller 9a and the pressure roller 9b convey the paper T onto which the toner image is secondarily transferred so as to sandwich the paper T. By being conveyed so as to be sandwiched between the heating roller 9a and the pressure roller 9b, the toner transferred onto the paper T is melted and fixed.

  A belt cleaning device 40 for cleaning the intermediate transfer belt 7 is disposed between the secondary transfer roller 8 and the tension roller 36. The belt cleaning device 40 includes a cleaning brush 41 that is in sliding contact with the surface of the intermediate transfer belt 7, a cleaning roller 42 that is disposed so as to be in contact with the cleaning brush 41, and a tip that is in contact with the surface of the cleaning roller 42. The blade 43 is disposed, and the recovery spiral 44 is disposed below the blade 43.

  On the lower side of the apparatus main body M, a paper feed cassette 52 that stores paper T is disposed so as to be able to be pulled out in the horizontal direction, and the paper T is stored in a stacked state. In the paper feed cassette 52, a placement plate 60 on which the paper T is placed is disposed. The paper T placed on the placement plate 60 is sent out to the transport path 54 by the cassette paper feed unit 51 disposed at the paper feed side end (the right end in FIG. 1) of the paper feed cassette 52. The cassette paper feed unit 51 includes a double feed prevention mechanism including a forward feed roller 61 for taking out the paper T on the placement plate 60 and a paper feed roller pair 63 for feeding the paper T one by one to the transport path 54. Prepare.

  A conveyance path 54 for conveying the paper T is formed between the cassette paper feeding unit 51 and the paper discharge unit 50. The conveyance path 54 includes a first conveyance path 55 from the cassette paper feeding unit 51 to the secondary transfer roller 8, a second conveyance path 56 from the secondary transfer roller 8 to the fixing device 9, and a discharge unit from the fixing device 9. And up to 50 third conveyance paths 57. Further, a branching claw 58 is provided at the outlet of the fixing device 9, and the paper T is placed in the first conveyance path 55 between the branching claw 58 and a curved path 55 a described later in the first conveyance path 55. A return conveyance path 59 for returning is formed.

  The first conveyance path 55 conveys the paper T fed from the paper feed cassette 52 upward, while turning the conveyance direction to the left in FIG. 1 and the curved path 55a to the secondary transfer roller 8. Straight path 55b. In the first conveyance path 55, a guide plate and a roller pair that convey the paper T while guiding it are arranged. Further, a sensor for detecting the paper T and a registration roller pair 80 for adjusting the skew (oblique paper feeding) of the paper T and the timing of the toner image are arranged in the first transport path 55. The sensor is disposed immediately before (on the upstream side) the registration roller pair 80 in the transport direction of the paper T. The registration roller pair 80 conveys the paper T by performing the above-described correction and timing adjustment based on the detection signal information from the sensor.

  The second transport path 56 is a linear transport path that is inclined downward toward the fixing device 9 side. A transport belt 156 that transports the paper T in a state where the paper T is placed is disposed in the second transport path 56. A sensor for detecting the paper T is disposed at a predetermined position in the second transport path 56.

  The third transport path 57 is formed so as to extend obliquely upward to the left in FIG. 1 from the exit of the fixing device 9. The third conveyance path 57 is configured to have a vertical conveyance path 57 a that is located on the downstream side of the branch claw 58 in the conveyance direction and formed upward. The paper T conveyed by the third conveyance path 57 passes through the upper surface side of the branch claw 58 and is then conveyed substantially vertically upward and is discharged from the paper discharge unit 50 to the outside of the apparatus main body M. The third transport path 57 includes a guide plate and a roller pair that transport the paper T while guiding the paper T, like the other transport paths.

  The return conveyance path 59 branches from the branch claw 58 to the lower side opposite to the third conveyance path 57 and passes below the fixing device 9, the second conveyance path 56, the secondary transfer roller 8, and the registration roller pair 80. Furthermore, it forms so that it may go upwards. The return conveyance path 59 is formed so as to merge with the curved path 55 a in the first conveyance path 55. The return conveyance path 59 is a conveyance path for returning the paper T that has passed through the fixing device 9 to the upstream side of the registration roller pair 80 arranged on the upstream side of the secondary transfer roller 8. This is a conveyance path used when printing an image, so-called double-sided printing.

  A manual paper feed section 64 is provided on the right side surface of the apparatus main body M in FIG. The manual paper feed unit 64 includes a manual feed tray 65 that forms a side wall in the closed state, and a paper feed roller 66. The manual feed tray 65 has a lower end rotatably attached (openable and closable) in the vicinity of the curved path 55 a of the first transport path 55, and allows the paper T placed on the open manual feed tray 65 to pass through the first transport path 55. Paper is fed to the curved path 55a.

  Next, the reading unit 301 constituting the image reading apparatus 300 will be described. As shown in FIG. 2, the reading unit 301 has a contact glass 335 on which the document G is placed, a pair of guide rails 345, a drive shaft 350 to which a drive pulley 351 is attached, and a driven pulley 352 attached. A support shaft 353, an illumination unit 347, a mirror unit 349, an imaging lens 357, a CCD 358, and an optical sensor 362 are provided.

  The reading unit 301 includes a contact glass 335 that is disposed on the upper surface (front side in FIG. 2) and on which the document G is placed. The contact glass 335 is disposed substantially parallel to the horizontal plane when the image forming apparatus 1 is disposed in a normal state. The pair of guide rails 345 are disposed between the side surfaces 306a and 306b (left and right in FIG. 2) of the reading unit 301. The pair of guide rails 345 are installed in parallel with the contact glass 335 described above. An illumination unit 347 and a mirror unit 349 are movably mounted on the pair of guide rails 345.

  The drive shaft 350 is disposed on the side surface 306a side so as to be orthogonal to the guide rail 345. The drive shaft 350 is forwardly and reversely driven by a drive motor (not shown). A drive pulley 351 having a large diameter portion and a small diameter portion is attached to both ends of the drive shaft 350 and outside the guide rail 345 in the main scanning direction Y.

  The support shaft 353 is disposed on the side surface 306b side so as to be orthogonal to the guide rail 345. A driven pulley 352 having the same diameter as that of the drive pulley 351 is attached to both ends of the support shaft 353 and outside the guide rail 345 in the main scanning direction Y. A driving wire 354 a is stretched over the large diameter portions of the driving pulley 351 and the driven pulley 352. The lighting unit 347 is fixed to the driving wire 354a. A drive wire 354 b is stretched over the small diameter portions of the drive pulley 351 and the driven pulley 352. The mirror unit 349 is fixed to the drive wire 354b.

  As the drive shaft 350 is rotated by the drive motor, the drive wires 354a and 354b are rotated. As the drive wires 354a and 354b are rotated, the illumination unit 347 and the mirror unit 349 are moved along the guide rail 345 in the sub-scanning direction X (the left-right direction in the drawing). Since the diameter ratio of the large diameter portion and the small diameter portion of the driving pulley 351 and the driven pulley 352 is 2: 1, the ratio of the moving distance between the illumination unit 347 and the mirror unit 349 is 2: 1.

  Here, two contacts 355 are provided at portions of the illumination unit 347 and the mirror unit 349 that are in contact with the upper surface of the guide rail 345. The contact surface of each contact 355 with the guide rail 345 is spherical. Accordingly, the illumination unit 347 and the mirror unit 349 are smoothly moved in the sub scanning direction X.

  An ISU base 356 that is a support member is attached to the side surface 306 a side of the bottom surface of the reading unit 301. An imaging lens 357 and a CCD 358 are attached to the upper surface of the ISU base 356 in a predetermined positional relationship.

  The imaging lens 357 is installed on a lens support 359 that is fixed to the ISU base 356. The lens support base 359 is disposed such that its position can be adjusted by a guide member 360 disposed on the CCD 358 side. The imaging lens 357 is arranged at the substantially center in the sub-scanning direction X of the reading unit 301 and on the end side opposite to the original G side in the optical path H (see FIG. 3). The imaging lens 357 forms an image of the incident light beam H4 (see FIG. 3) at a predetermined position. That is, the imaging lens 357 forms an image of the original G at a predetermined position.

  The CCD 358 is mounted on a CCD substrate 361 disposed on the back surface of the guide member 360 and is disposed at an image forming position on the image forming lens 357. The light beam from the imaging lens 357 is incident on the CCD 358 through the opening window 360 a formed near the center of the guide member 360. The optical axis of the light beam incident on the CCD 358 is corrected by finely adjusting the position of the guide member 360. The optical sensor 362 is arranged on the ISU base 356, and detects the size of the document (left and right direction in FIG. 2) depending on whether or not the reflected light from the document G placed on the contact glass 335 is received.

  Next, the lighting unit 347 will be described. The illumination unit 347 includes an illumination unit 347a, a first mirror 347b, and a first frame 347c that houses the illumination unit 347a and the first mirror 347b. The illuminating unit 347a includes a plurality of LEDs 501, a light guide 505 having a first light exit surface 411 and a second light exit surface 412 arranged in proximity to or in contact with the plurality of LEDs 501, and light from the second light exit surface 412 as a document. And a reflection mirror 541 for irradiating the light source. The illumination unit 347a will be described in detail later.

  The first mirror 347b is disposed on the lower side in the thickness direction Z of the illumination unit 347, and is disposed so that the reflection surface faces the document G and the second mirror 349a. The first mirror 347b reflects the light beam H1 from the document to the second mirror 349a.

  The first frame 347c accommodates the illumination unit 347a and the first mirror 347b, and is fixed to a drive wire 354a that is spanned over the large diameter portions of the drive pulley 351 and the driven pulley 352. The first frame 347c is moved in the sub-scanning direction X along the guide rail 345 by rotating the driving wires 354a and 354b.

  The mirror unit 349 includes a second mirror 349a, a third mirror 349b, and a second frame 349c that houses the second mirror 349a and the third mirror 349b. The second mirror 349a is disposed on the upper side in the thickness direction Z of the second frame 349c. The second mirror 349a is arranged so that the reflection surface faces the first mirror 347b and the third mirror 349b. The second mirror 349a reflects the light beam H2 from the first mirror 347b to the third mirror 349b side.

  The third mirror 349b is disposed on the lower side in the thickness direction Z of the second frame 349c, and is disposed so that the reflection surface faces the second mirror 349a and the imaging lens 357 side. The third mirror 349b reflects the light beam H3 from the second mirror 349a to the imaging lens 357 side.

  The first mirror 347b, the second mirror 349a, and the third mirror 349b form an optical path H for allowing the light from the original G to enter the imaging lens 357. As described above, since the illumination unit 347 moves at the speed A in the sub-scanning direction X and the mirror unit 349 moves at the speed A / 2 in the sub-scanning direction X, the length of the optical path H is also during the image reading operation. Held constant.

  FIG. 4 is a cross-sectional view for explaining the configuration of the illumination unit 347a, and FIG. 5 is a partially enlarged view for explaining the light guide 505 in FIG. FIG. 6 is a perspective view for explaining the LED unit 503, and FIG. 7 is a diagram showing an optical path of light emitted from the LED unit 503. Hereinafter, the illumination unit 347a will be described in detail.

  The illumination unit 347a includes an LED unit 503 to which a plurality of LEDs 501 are attached, a cylindrical lens 507 having a curved surface having a curvature in a direction orthogonal to the main scanning direction, an elliptical diffuser plate 509, a first light exit surface 411, and A light guide 505 having a second light exit surface 412 and a reflection mirror 541 that reflects light from the second light exit surface 412 toward the document G are provided.

  As shown in FIG. 6, the LED unit 503 is configured by arranging a plurality of LEDs 501 in the main scanning direction Y at regular intervals. The cylindrical lens 507 is an optical element configured by a curved surface having a curvature on only one side of the plane and the other side facing each other in a direction orthogonal to the main scanning direction. The cylindrical lens 507 transmits the light emitted from the LED unit 503 from the flat surface side to the curved surface side. Since the curved surface that becomes the light exit surface has a curvature in a direction orthogonal to the main scanning direction, the light spreading in the direction orthogonal to the main scanning direction is refracted to become almost parallel light, and the light in the main scanning direction is transmitted as it is. To do.

  FIG. 8 is a graph showing the light distribution in the sub-scanning direction on the original G. In FIG. 8, a graph G1 is based on the conventional illumination unit, and a graph G2 is based on the illumination unit 347a shown in the present embodiment. By providing the cylindrical lens 507 and making the light emitted from the LED unit 503 substantially parallel light, the light incident from the light incident surface 400 of the light guide 505 is not reflected on any other surface. The proportion of light that travels directly to the second light exit surface 412 and the reflection surface 421 increases. That is, the number of reflections in the light guide 505 from when light enters to when it exits decreases, and the light emitted from the LED unit 503 is irradiated onto the original G while maintaining the light intensity distribution. become. Therefore, the light distribution in the sub-scanning direction on the document G is smoother than the conventional one, and the light from the LED unit 503 can be efficiently irradiated onto the document G.

  The elliptical diffuser plate 509 is a diffuser plate whose light diffusion rate in the main scanning direction is higher than the light diffusion rate in the sub-scanning direction. The LED 501 is a light source with strong directivity, and among the light emitted from the LED 501, the light emitted from the central portion of the LED light emitting surface in the normal direction has the highest irradiation intensity, and the irradiation direction is from the normal direction. The light irradiation intensity rapidly decreases as the inclination is increased. For this reason, light having a high irradiation intensity is intensively applied to a portion of the document surface facing the light emitting surface of the LED 501, and light having a low irradiation intensity is irradiated to a portion not facing the light emitting surface of the LED. That is, the irradiation distribution irradiated on the document surface is not uniform in the main scanning line direction. Furthermore, there is a problem that a halation phenomenon occurs when the light with high irradiation intensity is regularly reflected on a surface having an angle such as a binding margin of a book and the reflected light enters the image sensor.

  Therefore, by arranging an elliptical diffusion plate 509 having a light diffusion rate in the main scanning direction higher than that in the sub-scanning direction on the light incident surface 400 side, the light in the sub-scanning direction is not diffused and the main light is not diffused. Only the scanning direction can be diffused, and partial concentration of light on an angled surface of the above-described book or the like can be prevented. Accordingly, since there is no light having a high irradiation intensity that is regularly reflected from the document surface, the halation phenomenon can be suppressed.

  Conventionally, an elliptical diffusion plate (two in total) is attached to each of the first light exit surface 411 and the second light exit surface 412. However, by providing the elliptical diffuser plate 509 on the light incident surface 400 side as in the present invention, the same effect as the conventional one can be obtained and only one elliptical diffuser plate is required, so that the cost can be reduced.

  The light guide 505 includes a light incident surface 400 formed on one end 505a side, a first light output surface 411 and a second light output surface 412 formed on the other end 505b side, a first light output surface 411, and a second light output surface. 412 has a reflective surface 421 connecting the 412. The light guide 505 is arranged so that one end 505a faces the elliptical diffusion plate 509 side and the other end 505b faces the contact glass 335 side, and light transmitted through the cylindrical lens 507 and the elliptical diffusion plate 509 is further guided. The second light exiting surface 412 and the reflecting surface 421 are arranged at a position where the light enters. That is, the light guide 505 is disposed so that most of the light transmitted through the cylindrical lens 507 and the elliptical diffuser plate 509 hits the second light exit surface 412 and the reflection surface 421.

  The first light exit surface 411 is disposed to face the original G, and emits light that has entered the light entrance surface 400 and is reflected by the reflection surface 421. The reflection surface 421 is formed in a portion where the second light exit surface 412 is not formed on the side facing the elliptical diffuser plate 509, and the light received by the reflection surface 421 is reflected toward the first light exit surface 411. Formed at an angle. That is, the lights H01a and H01b emitted from the first light exit surface 411 are light reflected by the reflection surface 421.

  The second light exit surface 412 is disposed to face the reflection mirror 541 and emits the light incident on the light incident surface 400 toward the reflection mirror 541. The light emitted from the second light exit surface 412 is reflected by the reflection mirror 541 toward the original G side, and the light H02 reflected by the reflection mirror 541 includes the light H01a and H01b emitted from the first light exit surface 411. Irradiates the original G from different sides.

  The ratio of the light emitted from the first light emitting surface 411 (direct light) and the light emitted from the second light emitting surface 412 (indirect light) is distributed to a desired ratio by adjusting the area and angle of the reflecting surface 421. be able to. As a result, when there is a cut-and-paste portion on the document, the ratio of direct light and indirect light can be adjusted so as to reduce the shadow caused by this cut-and-paste, and a document image with good image quality can be acquired.

  The reflection mirror 541 is attached to the mirror holding portion 511 of the attachment member 510 and is disposed so that the reflection surface faces the second light exit surface 412 and the document G side. That is, the reflection mirror 541 is disposed on the opposite side of the light guide 505 with the light beam H02 as the center in the sub-scanning direction X, and reflects the light emitted from the second light exit surface 412 so as to be directed toward the original G side.

  As described above, the light beams H01a and H01b emitted from the first light exit surface 411 are applied to the document G from one side in the sub-scanning direction X. Further, the light emitted from the second light exit surface 412 is reflected by the reflection mirror 541 and applied to the original G from the other side in the sub-scanning direction X. The original G is irradiated with light H01a, H01b, and light H02 from one side and the other side in the sub-scanning direction X, respectively. By doing so, it is possible to suppress the occurrence of edge shadows in the read image.

  As described above, by providing the cylindrical lens 507 and making the light emitted from the LED unit 503 substantially parallel light, the number of reflections in the light guide 505 is reduced, and the light emitted from the LED unit 503 is The original G is irradiated while maintaining the light intensity distribution. In other words, the light distribution in the sub-scanning direction on the document G is a smooth distribution without unevenness, and the light from the LED unit 503 can be efficiently irradiated onto the document G. Also, since the light is diffused with a high diffusion rate in the main scanning direction by providing the elliptical diffusion plate 509, the light reflected by the binding margin portion when reading an image of a document with a binding margin such as a book is directly reflected. It is possible to suppress the halation phenomenon that occurs due to incidence on the CCD 358.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 300 Image reader 301 Reading part 347 Illumination unit 503 LED unit (light source)
505 Light guide 400 Light incident surface 411 First light exit surface 412 Second light exit surface 421 Reflective surface 507 Elliptical diffuser plate 509 Cylindrical lens 541 Reflective mirror (reflecting means)
349a Second mirror (mirror)
349b Third mirror (mirror)
357 Imaging lens 358 CCD (image reading means)

Claims (3)

A light source having a plurality of light emitting portions arranged in the main scanning direction;
A cylindrical surface having a convex curved surface having a curvature in the sub-scanning direction orthogonal to the main scanning direction and a plane opposed to the convex curved surface, and transmitting light from the light source from the planar side toward the convex curved surface side A lens,
Light is emitted on a light incident surface on which light transmitted through the cylindrical lens enters, a first light output surface on which light is emitted on the original side, and a surface different from the surface including the first light output surface. A light guide having a second light-emitting surface, a reflective surface that is a surface connecting the first light-emitting surface and the second light-emitting surface and reflects light toward the first light-emitting surface;
Reflecting means for reflecting the light emitted from the second light emitting surface toward the document;
One or more mirrors that reflect light reflected from the document to form an optical path;
An imaging lens for imaging light reflected by the one or more mirrors;
An image reading unit disposed at an image forming position of the image forming lens and reading an image of the original based on image formation by the image forming lens;
And the light guide is disposed at a position where light transmitted through the cylindrical lens is incident on the second light exit surface and the reflection surface of the light guide. .   The image reading apparatus according to claim 1, wherein a diffusion plate having a light diffusion rate in the main scanning direction higher than a light diffusion rate in the sub-scanning direction is disposed between the cylindrical lens and the light guide. The image reading apparatus according to claim 1 or 2,
Image forming means for forming an image on a sheet based on an image read by the image reading device;
An image forming apparatus.