Light guide body, illumination device, and image reading device

Abstract

To provide an illumination device that can improve transfer of a long light guide body with a fine shape to reduce discrete light source images as bright and dark stripes in a glossy document, and an image reading device including the same.SOLUTION: A plurality of light sources are arranged in a main scanning direction. The pitch between adjacent light sources is wider in a center part in a main scanning direction than the other areas. An illumination device according to the present invention comprises a long light guide body that guides rays of light from the light sources to a surface to be irradiated. The light guide body has gates, which are inflow ports for resin material in injection molding, on at least both ends in the main scanning direction, has an incident surface on which the rays of light from the light sources are incident, and an emission surface having a fine shape in which the surface to be irradiated is irradiated with the rays of light from the incident surface, has a gate in an intermediate part between the gates on both ends in the main scanning direction, and has projections between the gate in the intermediate part and the respective gates on the ends in the main scanning direction.SELECTED DRAWING: Figure 6a

Description

Technical Field

[0001] The present invention relates to a lighting device including a light guide, and is suitable for, for example, image reading devices such as image scanners, copiers, and facsimiles, and image forming devices.

Background Art

[0002] Conventionally, an image reading device that reads an image line by line forms an image of a reading area on a document surface illuminated linearly by a lighting device at a predetermined magnification by an imaging optical system on a reading means such as a line sensor, and reads the image.

[0003] In addition, in recent years, as a light source of a lighting device in an image reading device, those using a light emitting diode (hereinafter referred to as LED) are known. In a lighting device using an LED, in order to form an elongated illuminated area in the reading line direction (hereinafter referred to as the main scanning direction), an LED array in which a large number of LEDs are arranged in the main scanning direction is used as a light source. A lighting device is known to have a configuration in which a light guide made of a translucent member efficiently guides light from each LED to the illuminated area on the document surface. In a lighting device using an LED array, unevenness in illuminance occurs in the illuminated area on the document surface due to the pitch of the LEDs, and unevenness in image density occurs due to the unevenness in illuminance when an image is formed according to the read image data.

[0004] Therefore, in a lighting device using an LED array, in order to suppress the occurrence of uneven illuminance, for example, if a light guide described in Patent Document 1 is used, a fine shape can be provided on the emission surface of the light guide to diffuse light.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the configuration described in Patent Document 1, when reading a thick document such as a book, the center of the document is likely to curl (curve) and become raised in the sub-scanning direction perpendicular to the main scanning direction. In the case of a glossy document (glossy document), a phenomenon occurs in which discrete light source images (mirror images of each LED) caused by light reflected (specularly reflected) from the surface of the curved part are reflected as light and dark stripes. The light and dark stripes caused by the reflection of the light source image become more pronounced when the light diffusion property of the fine shape of the light exit surface of the light guide is weakened.

[0007] In injection molding, the pressure weakens as the distance from the gate increases, resulting in insufficient transfer. In the case of a long light guide with a fine shape, a single gate is likely to cause transfer of the fine shape over the entire length (main scanning), so gates are generally provided at both ends. However, in the case of a fine shape with a large aspect ratio to enhance light diffusion, a two-point gate at both ends of the main scanning is likely to cause insufficient transfer of the fine shape in the center of the main scanning away from the gate. In the case of an illumination device in an image reading device that arranges multiple light sources in the main scanning direction, the pitch of the light sources in the center of the main scanning is generally arranged larger than the pitch of the light sources at the ends of the main scanning in order to compensate for the loss of light at the ends due to the cosine fourth power law of the reduction optical system. Therefore, if the transfer in the center of the main scanning is insufficient, the diffusion due to the fine shape is weakened, and the light and dark stripes due to the reflection of the light source image in the center of the main scanning in the glossy original become stronger.

[0008] In addition, a weld occurs in the middle of the two gates. When a weld occurs, the transfer of the fine shape of the light guide's emission surface in the weld area is insufficient. When the transfer of the fine shape is insufficient, the diffusion effect of the fine shape is weakened, and the light source image in the weld area is reflected in the glossy document, resulting in strong light and dark stripes.

[0009] Therefore, an object of the present invention is to provide an illumination device that can reduce the light and dark stripes of discrete light source images on a glossy original by improving the transfer of light from a long light guide having a fine shape, and an image reading device equipped with the same.

Means for Solving the Problem

[0010] In order to achieve the above object, a lighting device according to the present invention includes a plurality of light sources arranged in a main scanning direction, and an adjacent light source pitch is wider at the center of the main scanning than in other regions. The lighting device includes a long light guide that guides light from the light sources to an irradiated surface. In injection molding, gates serving as inlets of a resin material are provided at least at both ends of the main scanning. The light guide has an incident surface on which light from the light sources is incident, and an emission surface having a fine shape through which light from the incident surface irradiates toward the irradiated surface. The light guide has a gate at an intermediate portion between the gates at both ends of the main scanning, and has a protruding portion between the gate at the main scanning end portion and the gate at the intermediate portion.

Effect of the Invention

[0011] According to the present invention, it is possible to provide a lighting device that can reduce the bright and dark stripes of a discrete light source image caused by a glossy original by improving the transfer of a long light guide having a fine shape, and an image reading device including the same.

Brief Description of the Drawings

[0012]

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Mode for Carrying Out the Invention

[0013] Hereinafter, the light guide, the lighting device, and the image reading device according to the present embodiment will be described in detail based on the accompanying drawings. Note that the drawings shown below may be drawn at scales different from the actual ones in order to facilitate understanding of the present embodiment. Also, in each drawing, the same members are denoted by the same reference numerals, and redundant explanations are omitted.

[0014] Hereinafter, the light guide, the lighting device, and the image reading device according to the first embodiment of the present invention will be described. FIG. 1 shows a schematic front view of an image forming apparatus 100 including an image reading apparatus 101 according to the present embodiment.

[0015] Note that the image forming apparatus 100 shown below is merely an example, and a facsimile apparatus, an inkjet printer, a copying machine, etc. equipped with an image reading apparatus 101 also fall under the image forming apparatus equipped with the image reading apparatus according to the present embodiment.

[0016] As shown in FIG. 1, the image forming apparatus 100 includes an image forming apparatus main body 102 (image forming unit) for forming an image on a recording sheet, and a paper feed cassette 103 mounted below the image forming apparatus main body 102 for stacking the recording sheet. Further, the image forming apparatus 100 includes an image reading apparatus 101 mounted above the image forming apparatus main body 102 for reading an image of a document.

[0017] Inside the image forming apparatus main body 102, image forming means (not shown) is disposed substantially at the center, and below it, paper feeding means (not shown) for feeding the recording sheet including the paper feed cassette 103 is disposed.

[0018] Also, above the image forming apparatus main body 102, an image reading apparatus 101 including a CCD image sensor or the like as reading means for reading an image of a document is disposed.

[0019] And a space is provided between the image reading apparatus 101 and the image forming apparatus main body 102, and a main body paper discharge portion 104 for stacking the recording sheet conveyed and discharged by the image forming apparatus main body 102 is formed.

[0020] In the image forming apparatus main body 102, as image forming means, a print engine using a conventionally well-known electrophotographic method is provided, and a laser writing portion (not shown), an electrophotographic process portion having a photosensitive surface, a fixing portion, etc. are incorporated.

[0021] Also, as paper feeding means, paper feeding rollers (not shown) or the like for separating and feeding the recording sheet placed on the paper feed cassette 103 are incorporated, and the recording sheet is supplied to the image forming means.

[0022] Figures 2(a) and (b) show a perspective view and a cross-sectional view of the image reading apparatus 101 according to the present embodiment, respectively.

[0023] As shown in FIGS. 2(a) and (b), the image reading apparatus 101 includes an ADF 201 (Automatic Document Feeder), which is a conveyance unit, and a reader 202 provided below the ADF 201 for reading an image of one document surface (front surface, first surface) of a document conveyed by the ADF 201.

[0024] The ADF 201 separates a plurality of documents and feeds them to the reader 202. The ADF 201 includes a document tray 204 for placing a plurality of documents to be fed, and document conveyance means 203 for separating and feeding the documents placed on the document tray 204 one by one and conveying them to the reader 202. Further, the ADF 201 includes a discharge tray 205 for placing the discharged documents after the image reading by the reader 202.

[0025] As shown in FIG. 2(b), the ADF 201 is provided with a pickup roller 300 and a separation roller pair 301 for separating and feeding a plurality of documents G placed on the document tray 204 as members constituting the document conveyance means 203. Further, the ADF 201 is provided with a plurality of roller pairs (pull-out roller pair 302, conveyance roller pair 303, registration roller pair 304, lead 1 roller pair 305, lead 2 roller pair 307, lead 3 roller pair 309, discharge roller pair 310) for conveying the document G separated and fed by the separation roller pair 301, and a first platen roller 306 and a second platen roller 308 as members constituting the document conveyance means 203.

[0026] Specifically, the document conveyance means 203 includes a pull-out roller pair 302 provided downstream of the pickup roller 300 and the separation roller pair 301 for pulling out the document G conveyed from the separation roller pair 301.

[0027] Further, as the document conveying means 203, there are included a pair of conveying rollers 303 provided downstream of the pair of pulling rollers 302 for conveying the document G conveyed by the pair of pulling rollers 302 to the downstream pair of rollers, and a pair of registration rollers 304 provided downstream of the pair of conveying rollers 303 for correcting the inclination of the document G.

[0028] Furthermore, as the document conveying means 203, there are included a pair of lead 1 rollers 305, a first platen roller 306 (first conveying member), a pair of lead 2 rollers 307, a second platen roller 308, and a pair of lead 3 rollers 309 provided downstream of the pair of registration rollers 304 for stabilizing the reading of the image of the document G.

[0029] As shown below, when the first platen roller 306 reads the image of one document surface of the document G conveyed by the first image reading unit 314, while urging the document G onto the first platen glass 311, the document G is conveyed at a predetermined interval with respect to the first platen glass 311.

[0030] Also, as the document conveying means 203, there is included a pair of discharging rollers 310 provided downstream of the pair of lead 3 rollers 309 for discharging the document G after reading the image to the discharge tray 205.

[0031] And, a reader 202 is provided below the ADF 201. Inside the reader 202, a first image reading unit 314 for reading the surface image of the document G conveyed onto the first platen glass 311 (first light transmitting member) by the ADF 201 and the image of the document placed on the document table glass 313 is provided so as to be movable along a rail (not shown) in the sub-scanning direction T (direction orthogonal to the main scanning direction).

[0032] When the first image reading unit 314 reads the surface image of the document G conveyed by the ADF 201 (document streaming reading), it stops at the first position A below the first platen glass 311 provided on the opposite side (downward) of the first platen roller 306 to perform image reading.

[0033] On the other hand, when reading the image of the document G placed on the document table glass 313 (document fixed reading), the first image reading unit 314 moves and scans along the sub-scanning direction T from the first position A to the second position B by driving a motor (not shown) controlled by the control unit 316, thereby reading the document image on the document table glass 313.

[0034] Then, the image data of the document read by the first image reading unit 314 is processed by the control unit 316.

[0035] Furthermore, inside the ADF 201, in order to read the image of the other document surface (the back surface, the second surface which is the opposite side of the first surface) of the document G being conveyed, a second platen glass 312 is provided on the opposite side of the second platen roller 308. Also, a second image reading unit 315 is provided at a position C facing the second platen roller 308 with the second platen glass 312 interposed therebetween.

[0036] Thereby, when the document G is conveyed by the ADF 201, the first image reading unit 314 and the second image reading unit 315 can read the images of both the front and back sides of the document G.

[0037] The first platen glass 311, the second platen glass 312, and the document table glass 313 are made of materials having translucency such as acrylic resin, polyester resin, polycarbonate resin, and glass.

[0038] As shown in FIG. 3, in the image reading apparatus 101 according to the present embodiment, the document G placed on the document table glass 313 is illuminated by the lighting device 403 inside the first image reading unit 314.

[0039] Then, the diffuse reflection light from the document G is reflected by the reflection optical system 404 (the first folding mirror 404a, the second folding mirror 404b, the third folding mirror 404c, and the fourth folding mirror 404d), and is condensed onto the light receiving unit 405 (image reading sensor) by the imaging optical system 406 (reduction optical system), and the image data of the document G is obtained.

[0040] The light receiving unit 405 (image reading sensor) consists of an image sensor. As the image sensor, a CCD image sensor, a CMOS image sensor, etc. can be adopted. They can be not only line sensors in which a large number of pixels are arranged in a row in the main scanning direction (Y direction), but also sensors in which a large number of RGB pixels are arranged in a row in the main scanning direction, or sensors in which a line sensor of R pixels, a line sensor of G pixels, and a line sensor of B pixels are arranged in parallel in three rows.

[0041] Then, by moving and scanning the first image reading unit 314 along the sub-scanning direction T from the first position A to the second position B, the light receiving unit 405 can read the image information of the entire document surface of the document G in a line sequential manner. The image information read by the light receiving unit 405 is transmitted as an electrical signal through an interface to an external device such as an image processing unit (not shown) or a personal computer.

[0042] Next, the configuration of the lighting device 403 in the first image reading unit 314 of the image reading apparatus 101 according to the present embodiment and the effects thereof will be described.

[0043] FIG. 4 shows a schematic view of a main part of an injection mold for a light guide body 604 of the lighting device 403 according to the present embodiment. As shown in FIG. 4(a), the light guide body 604 is made by injection molding. Resin is injected from the resin inlet 501, and the resin is injected into the cavity 502 through a plurality of runners (runner 503a, runner 503b, runner 503c) and subsequent gates (gate 504a, gate 504b, gate 504c).

[0044] Here, the problem will be described with reference to FIG. 28. FIG. 28(a) shows a schematic view of the main part of the injection mold for the light guide 1404 of the lighting device 1303 according to Comparative Example 1. The injection mold according to Comparative Example 1 has the same configuration as the injection mold according to the present embodiment, except that it has gates at both ends in the longitudinal direction (main scanning) (two-point gates) and no protruding portions. Resin is injected from the resin inlet 501, and the resin is injected into the cavity 502 through the runner 503a, the runner 503b, and the subsequent gates 504a and 504b. In the cavity 502, the central portion is farther from the gates 504a and 504b than the end portions, so the pressure weakens and the transfer to the mold is insufficient. As will be described later, in the case of a long light guide having a fine shape, if the transfer is insufficient, the light diffusion weakens. FIG. 28(b) shows the resin flow in the cavity 502. The resin injected from the gates 504a and 504b at both ends in the longitudinal direction (main scanning) propagates while tracing the trajectory of the flow pattern 506. Then, the resin flow fronts collide with each other at the center of the main scanning, and a weld line 507 is generated. When welding occurs, the transfer of the fine shape in the weld line 507 portion is insufficient, and the light diffusibility weakens.

[0045] Here, the injection mold according to the present embodiment that can solve the problems in Comparative Example 1 will be described below with reference to FIG. 4. As shown in FIG. 4(a), in addition to the gates 504a and 504b at both ends in the longitudinal direction (main scanning), a gate 504c is added in the middle of the longitudinal direction (main scanning), so that the resin flow length propagating in the cavity 502 from each gate can be shortened. Thereby, even in the case of a long light guide having a fine shape, the insufficient transfer of the fine shape can be improved.

[0046] In addition, a protruding portion 505a is provided in the middle portion between the gate 504a (longitudinal end portion) and the gate 504c (longitudinal central portion), and a protruding portion 505b is provided in the middle portion between the gate 504b (longitudinal end portion) and the gate 504c (longitudinal central portion). FIG. 4(b) shows the flow of the resin in the cavity 502. The resin injected from the three-point gates of the gates 504a and 504b at both ends of the longitudinal direction (main scanning) and the gate 504c at the longitudinal (main scanning) center propagates while tracing the locus of the flow pattern 506. Then, the resin flow fronts collide with each other between the gate 504a and the gate 504c, and between the gate 504b and the gate 504c, generating a weld line 507. Here, by providing the protruding portions 505a and 505b, the occurrence location of the weld line 507 can be shifted to the protruding portions 505a and 505b. Thereby, even in a long light guide having a fine shape, it is possible to improve the insufficient transfer of the fine shape due to welding.

[0047] FIG. 5 shows a schematic main part diagram for explaining the warpage of the light guide 604 according to the present embodiment. As will be described later with reference to FIGS. 6a to 6d, the short-side (sub-scanning) cross-section of the light guide 604 is uneven in thickness, and the volume is large on the emission surface side. Therefore, warpage occurs due to the influence of shrinkage, resulting in upward convexity (warp A). Here, by providing the protruding portions 505a and 505b, in the longitudinal (main scanning) middle portion, since the volume can be increased, a downward convex (warp B) force is applied, so that the amount of warpage of the upward convex (warp A) can be reduced.

[0048] FIGS. 6a to 6d show schematic main part diagrams of the lighting device 403 according to the present embodiment. FIG. 6a is a perspective view, FIG. 6b is a YZ cross-sectional view, FIG. 6c is an enlarged view near the incident surface 605 at the main scanning center, and FIG. 6d is an explanatory diagram of the light rays incident on the incident surface 605. An enlarged view of the region A of the lighting device 403 is shown in FIG. 10, a cross-section A (ZX cross-section) is shown in FIG. 7, and a cross-section B (ZX cross-section) is shown in FIG. 8.

[0049] As shown in FIGS. 6A and 6B, in the lighting device 403 according to the present embodiment, a plurality of light sources 601 (white light-emitting diodes, LEDs) arranged at predetermined intervals in the main scanning direction (Y direction), a holding member 603 (light source substrate, LED substrate) for holding the light sources 601, and a light guide 604 for transmitting the light from the light-emitting surface 602 of the light sources 601 through the platen glass 313 and guiding it to the irradiated surface (document G) are provided. The light source 601 uses a side view type light source configured such that the light-emitting surface 602 of each light-emitting element is perpendicular to the holding member 603, but is not limited thereto, and a top view type light source may also be used. FIG. 31 is an explanatory diagram showing the light distribution characteristics of the light source 601. Since the LEDs used for the light source 601 are excellent in terms of cost, in many cases, the phosphor is exposed with a flat surface shape without using a resin lens or the like for condensing light in particular. In the case of such an LED, the light distribution characteristics of the output light become characteristics called Lambert emission as shown in FIG. 31. In FIG. 31, the 0° direction is the sub-scanning direction (Z direction). That is, the direction perpendicular to the light-emitting surface 602 of the light source 601 (normal direction) is the 0° direction in FIG. 31. As is clear from FIG. 31, the direction in which the strongest light is emitted from the holding member 603, that is, the direction with high luminance is the 0° direction. Each light-emitting element emits the strongest light in the normal direction (maximum intensity direction) of the light-emitting surface 602, and widely emits light in the range of ±90° from the normal direction.

[0050] Next, the emission spectrum of the light source 601 will be described. FIG. 32 is an example of an emission spectrum of a general white light-emitting diode (LED) used for the light source 601. In FIG. 32, the horizontal axis represents the wavelength of light, and the vertical axis represents the spectral intensity. The white light-emitting diode is a blue LED chip that emits light rays with a wavelength of about 450 nm, and by exciting and fluorescing yellow or orange phosphors filled around it, these lights are mixed to emit a white color. Although a white light-emitting diode (LED) is used as the light-emitting element, it is not limited to this, and an EL element or the like may be used. As the light emitted from the light-emitting element, white light is desirable, but it is not limited to this, and light such as blue, green, and blue may be used. As the material of the holding member 603, aluminum, glass epoxy (a material obtained by impregnating glass fibers with an epoxy resin and subjecting it to a heat curing treatment to form a plate shape), or the like can be used.

[0051] As shown in FIGS. 6a and 6b, there are gate marks 611a and 611b at both ends of the main scan, and a gate mark 611c in the middle of the both-end gates. The surface of the gate marks (gate marks 611a, 611b, 611c) formed by cutting each gate (gate 504a, gate 504b, gate 504c) may be rough or polished to a mirror surface. By providing the gate 504c in the middle in addition to the both-end gates (gate 504a and gate 504b) of the main scan, it is possible to improve the insufficient transfer of the fine shape of the emission surface 606 of the light guide 604 described later. The interval (pitch) between adjacent light sources 601 becomes narrower from the central portion C to the middle portion C1 and then to the end portion C2. Due to the influence of the cosine fourth power law by the imaging optical system 406, the amount of light received by the light receiving portion 405 decreases toward the end of the main scan in proportion to the fourth power of the cosine of the inclination with respect to the central portion of the main scan (imaging angle 0). In order to compensate for this decrease in the amount of light, the interval between adjacent light sources 601 is in the relationship of central portion C > middle portion C1 > end portion C2. In the present embodiment, the interval between adjacent light sources 601 is central portion C = 10.0 mm, middle portion C1 = 8.7 mm, and end portion C2 = 5.0 mm.

[0052] As shown in FIG. 6c, a gate trace 611c is provided with a gate 504c (jump gate) at the center of the main scan, near the incident surface 605, and between adjacent light sources 601. The gate trace 611c may be separated from the incident surface 605 in the Z direction as long as it is within the region B. The method for obtaining the region B will be described with reference to FIG. 6d. Assuming that the refractive index of the air layer is 1, the refractive index of the light guide 604 is n, the incident angle of the light ray a with respect to the normal of the light guide 604 is θ1, and the exit angle of the light ray b incident on the light guide 604 with respect to the principal ray is θ2, according to Snell's law, θ2 = sin -1 (sinθ1 / n). When the angle of the most divergent light ray emitted from the light emitting surface 602 of the light source 601 is θ1 = 90°, and the material of the light guide 604 is acrylic resin (PMMA, n = 1.49), then θ2 = sin -1 (sin90° / 1.49) = 42.2°. Again, referring to FIG. 6c for explanation. Even if the light emitting surface 602 of the light source 601 and the incident surface 605 are in contact, there is a slight air layer between the light emitting surface 602 and the incident surface 605. Therefore, the light ray emitted at θ1 = 90° enters the light guide 604 at θ2 = 42.2°. With respect to the pitch C of the adjacent light sources 601, the width of the outer shape of the light source 601 is the interval F. Assuming that the width of the light source 601 in the main scanning direction in this embodiment is 4.0 mm, then the interval F = interval C - width of the light source 601 = 10.0 mm - 4.0 mm = 6.0 mm. From trigonometric functions, the distance G in the Z direction is obtained as (6.0 mm / 2) / tan42.2° = 3.3 mm. Therefore, the region B is a triangular range of 6.0 mm in the Y direction and 3.3 mm in the Z direction.

[0053] As shown in FIG. 7, the light guide 604 has an incident surface 605 on which light from the light emitting surface 602 of the light source 601 is incident, an exit surface 606 from which light from the incident surface 605 exits toward the irradiated surface, and a first light guide surface 607 (the surface closer to the irradiated surface) and a second light guide surface 608 (the surface farther from the irradiated surface) that face each other and guide light from the light emitting surface 602 of the light source 601 to the reflecting surface 609. And it has a reflecting surface 609 that is inclined so as to bend with respect to the second light guide surface 608 and guides to the exit surface 606, and a connecting surface 610 that faces the reflecting surface 609 and connects the first light guide surface 607 and the exit surface 606. The connecting surface 610 may be continuously connected to the first light guide surface 607 or the exit surface 606.

[0054] The light emitted from the light emitting surface 602 of the light source 601 and incident on the incident surface 605 is guided to the reflecting surface 609 while undergoing total reflection at the first light guide surface 607 and the second light guide surface 608. Then, after total reflection at the reflecting surface 609, the light emitted from the exit surface 606 illuminates a linearly long region in the main scanning direction (Y direction) in the reading region 401 of the document G. As the material of the light guide 604, a light-transmissive inorganic material such as glass or a light-transmissive organic material such as acrylic resin, polyester resin, or polycarbonate resin can be used. Among them, it is preferable to use a synthetic resin material that is easy to mold such as plastic, and in this embodiment, acrylic resin (PMMA) is adopted. In order to illuminate the reading region 401 of the document G while enhancing the light collection efficiency, the distance between the first light guide surface 607 and the second light guide surface 608 of the light guide 604 becomes wider from the incident surface 605 to the reflecting surface 609. Then, in the sub-scanning cross section (ZX cross section), the optical path is bent by the reflecting surface 609 (reflective light collection part) and guided to the exit surface 606 that has a light collection function in the sub-scanning direction and emits to the outside. The shape of the sub-scanning cross section (ZX cross section) of the light guide 604 is not limited to that shown in this embodiment as long as it can guide the light from the light emitting surface 602 of the light source 601 to the irradiated surface of the document G.

[0055] As shown in FIG. 3, the image reading apparatus 101 according to the present embodiment includes two identical illumination devices 403, and each illumination device 403 is symmetrically arranged with the reading optical axis 402 interposed therebetween. With this configuration, it becomes possible to illuminate the reading area 401 of the document G from both sides.

[0056] With respect to the cross-section A (ZX cross-section) shown in FIG. 7, FIG. 8 shows a cross-section B (ZX cross-section) including the protruding portion 505b. Note that the sub-scanning cross-section (ZX cross-section) including the protruding portion 505a is the same as that in FIG. 8. By protruding the protruding portion 505b with respect to the connection surface 610 (dashed line in FIG. 8), the generation position of the weld line 507 can be shifted from the emission surface 606 to the protruding portion 505b. Thereby, it is possible to improve the insufficient transfer of the fine shape of the emission surface 606 described later.

[0057] As shown in FIG. 6b, when the lengths in the main scanning direction (Y direction) of the gate marks (gate mark 611a, gate mark 611b) at the main scanning end portion and the gate mark 611c at the intermediate portion formed by cutting the gate are D, and the lengths in the main scanning direction (Y direction) of the protruding portion 505a and the protruding portion 505b are the widths E, 0.05 < E / D < 0.35 ···(1) it is the light guide 604 that satisfies the above.

[0058] The conditional expression (1) defines the lengths of the protrusions 505a and 505b with respect to the total length of the light guide 604. By keeping within the range of the conditional expression (1), while suppressing the material cost of the light guide 604, the weld line 507 can be shifted to the protrusions 505a and 505b. As will be described later, the light and dark stripes of the discrete light source images due to the glossy original can be reduced, and a good image can be obtained. When the upper limit value of the conditional expression (1) is 0.35 or more, the material (PMMA) used for the light guide 604 increases, the material cost rises, and the cost increases. When the lower limit value of the conditional expression (1) is 0.05 or less, the weld line 507 cannot be completely shifted to the protrusions 505a and 505b, and the weld line 507 remains on the emission surface 606. When the weld line 507 appears on the emission surface 606, due to insufficient transfer of the fine shape, the light and dark stripes of the discrete light source images due to the glossy original appear in the image. Therefore, it is desirable to fall within the range of the conditional expression (1).

[0059] In this embodiment, the specific numerical values are D = 163.5 mm and E = 30.0 mm. Since E / D = 0.18, the conditional expression (1) is satisfied.

[0060] Figs. 9a to 9f are schematic diagrams of the main parts for explaining the optical path in the cross-section B of the lighting device 403 in Fig. 8. Fig. 9a shows representative light rays A to E among the light rays emitted from the light-emitting surface 602 of the light source 601. Region C shows the protruding portion 505b protruding from the connection surface 610. Here, the optical paths of the respective representative light rays will be explained with reference to Figs. 9b to 9f. The light ray A shown in Fig. 9b is a light ray that, among the light rays emitted from the light-emitting surface 602, reaches the reflecting surface 609 directly without total reflection at the first light guide surface 607 and the second light guide surface 608. Then, it is totally reflected at the reflecting surface 609 and illuminates the reading region 401 from the emission surface 606. The light ray B shown in Fig. 9c is a light ray that, among the light rays emitted from the light-emitting surface 602, reaches the reflecting surface 609 after total reflection once at the first light guide surface 607. Then, it is totally reflected at the reflecting surface 609 and illuminates the reading region 401 from the emission surface 606. The light ray C shown in Fig. 9d is a light ray that, among the light rays emitted from the light-emitting surface 602, reaches the reflecting surface 609 after total reflection once at the second light guide surface 608. Then, it is totally reflected at the reflecting surface 609 and illuminates the reading region 401 from the emission surface 606. The light ray D shown in Fig. 9e is a light ray that, among the light rays emitted from the light-emitting surface 602, reaches the reflecting surface 609 after total reflection once at the second light guide surface 608 and then total reflection once at the first light guide surface 607. Then, it is totally reflected at the reflecting surface 609 and illuminates the reading region 401 from the emission surface 606. The light ray E shown in Fig. 9f is a light ray that, among the light rays emitted from the light-emitting surface 602, reaches the reflecting surface 609 after total reflection once at the first light guide surface 607 and then total reflection once at the second light guide surface 608. Then, it is totally reflected at the reflecting surface 609 and illuminates the reading region 401 from the emission surface 606. Since the optical paths of the light rays A to E do not pass through the region C of the protruding portion 505b, the influence on the optical characteristics can be reduced even if the protruding portion 505b is provided.

[0061] The emission surface 606 of the light guide 604 has a fine shape (diffusion structure) for diffusing light as shown in Fig. 10.

[0062] Here, the problem will be described with reference to FIGS. 29a to 29h and FIGS. 30a to 30e. FIGS. 29a to 29h show the sub-scanning cross-sectional (ZX cross-section) views of the lighting device 1303 according to Comparative Example 1. Here, for convenience, the lighting device 1303 is configured for one-sided illumination with respect to the reading optical axis 1302. The lighting device 1303 according to Comparative Example 1 has the same configuration as the lighting device 403 according to the present embodiment, except that it is one-sided illumination, has both-end gates, and the light guide 1404 has no protrusions.

[0063] In a lighting device in a general image reading apparatus, when LEDs are arranged as light sources in the main scanning direction, each LED can be regarded as being close to a point light source. When reading a thick, double-page original G such as a book as shown in FIG. 29a, in the sub-scanning cross-section (ZX cross-section), the central portion of the original G is likely to curl (bend) and float. For example, in the case of a glossy original (glossy manuscript), depending on the posture (tangent Q of the reading position of the original) at the reading position H of the curved portion of the original G with respect to the first platen glass 311 as shown in FIG. 29b, the specularly reflected light L may coincide with the reading optical axis 1302. Therefore, it is guided by the reflection optical system 1304 to the imaging optical system 1306 and condensed on the light receiving portion 1305. Thus, there has been a problem that the light source 1401, which is a particularly bright part, becomes a bright light source image (mirror image), and the discrete light source images (mirrors of each LED) are reflected in the read image as light and dark stripes. FIG. 29g shows an image in which the discrete light source images are read as light and dark stripes. And the light source image distribution is shown in FIG. 29h with the main scanning direction of the light and dark stripes as section M. In FIG. 29h, the horizontal axis represents the main scanning direction (Y direction), and the vertical axis represents the luminance. As described with reference to FIG. 28, due to the both-end gates, the light-emitting surface 1406 of the light guide 1404 has insufficient transfer of the fine shape at the center of the main scanning. Therefore, the diffusion in the main scanning direction is weak, and as shown in FIG. 29h, the luminance difference PP (the difference between the maximum value I max and the minimum value I min is large, and the light and dark stripes become prominent. In the welded portion, the luminance difference PP becomes locally large, and the light and dark stripes are more prominent than other regions in the central portion.

[0064] Note that, as shown in FIG. 29c, since the posture (tangent line Q of the document reading position) at the reading position H of the curved portion of the document G with respect to the platen glass 313 is in the opposite direction to that in FIG. 29b, the regular reflection light L does not coincide with the reading optical axis 1302 and is not focused on the light receiving portion 1305. Therefore, the light source 1401 does not appear in the image read as a bright light source image (mirror image).

[0065] FIG. 29d shows a schematic diagram of the main part of the lighting device 1303, and the sub-scanning cross-section (ZX cross-section) of cross-section A is shown in FIG. 29b or FIG. 29c. FIG. 29e shows a YZ cross-sectional view of the lighting device 1303. The interval (pitch) between adjacent light sources 1401 becomes narrower from the central portion C to the intermediate portion C1 and then to the end portion C2 in order to compensate for the decrease in the amount of light due to the influence of the cosine fourth power law. When the interval between the light sources 1401 becomes narrower, the luminance difference PP (the difference between the maximum value I max and the minimum value I min becomes smaller, and the light and dark stripes become less noticeable. Therefore, the light and dark stripes are most noticeable at the main scanning central portion and become sensitive to insufficient transfer of fine shapes. FIG. 29f shows the main scanning light amount distribution in the reading area 1301 of the document G of the lighting device 1303. The horizontal axis represents the main scanning direction (Y direction), and the vertical axis represents the light amount. In order to compensate for the decrease in the amount of light due to the influence of the cosine fourth power law, the interval between adjacent light sources 1401 is narrowed from the main scanning central portion to the end portion to increase the light amount. Note that the light amount is slightly decreased at the outermost ends (outside ±145 mm in Comparative Example 1). Due to the restriction on the size of the holding member 1403 in the main scanning direction (Y direction), the light source 1401 cannot be arranged further outside the end of the light guide 1404. Therefore, for example, the main scanning central portion can be illuminated by light rays from the light sources 1401 arranged in both the + direction and the - direction of the main scanning direction (Y direction), while the main scanning end portion can only be illuminated by light rays from the light source 1401 arranged on one side. Thus, the outermost ends have a slightly decreased light amount within a range where there is no hindrance to image formation.

[0066] Figs. 30a to 30e show cross-sectional views (ZX cross-sections) of the upstream illumination device 1503a and the downstream illumination device 1503b according to Comparative Example 2. The difference from Comparative Example 1 is that the second image reading unit 315 is at position C shown in Fig. 2(b), and the back surface image of the document G is read by the ADF 201 in a document feed reading mode. The second platen glass 312 is provided at the reading position H of the image on the back surface of the document G to be conveyed. Here, the reading position H includes not only the surface of the second platen glass 312 but also the paper surface position of the document G conveyed at the interval t between the second platen glass 312 and the second platen roller 308 corresponding to various types of documents (plain paper, thick paper, thin paper, etc.). Due to the influence corresponding to various types of documents, when the document G to be conveyed is plain paper (including glossy documents of equivalent thickness), the document G to be conveyed is inclined (inclination angle θ) even at the reading position H with respect to the second platen glass 312 compared to the conventional case. As the document G is conveyed, the light receiving unit 1505 can read the image information of the entire document surface of the document G in a line sequential manner.

[0067] When reading the document G conveyed as shown in FIG. 30a, in the sub-scanning cross-section (ZX cross-section), the document G is likely to be inclined at the reading position H with respect to the second platen glass 312. For example, in the case of a glossy document (glossy document), depending on the posture (tangent Q of the reading position of the document) of the conveyed document G at the reading position H with respect to the second platen glass 312 as shown in FIG. 30b, the direct reflection light L of the upstream illumination device 1503a coincides with the reading optical axis 1502. Therefore, it is guided to the imaging optical system 1506 by the reflection optical system 1504 and condensed on the light receiving unit 1505. Thus, there has been a problem that the light source 1601, which is a particularly bright part, becomes a bright light source image (mirror image), and the discrete light source images (mirror images of each LED) are reflected in the read image as light and dark stripes. FIG. 30d shows an image in which the discrete light source images are read as light and dark stripes. Here, since the document G is conveyed and read, the light and dark stripes of the light source image appear as streaks in the image. And the light source image distribution is shown in FIG. 30e with the main scanning direction of the light and dark stripes as the cross-section N. Similar to Comparative Example 1, in Comparative Example 2, due to the both-end gates, the upstream emission surface 1606a of the upstream light guide 1604a has insufficient transfer of the fine shape at the center of the main scanning. Therefore, the diffusion in the main scanning direction is weak, and as shown in FIG. 30e, the luminance difference PP (the difference between the maximum value I max and the minimum value I min ) becomes large, and the light and dark stripes become prominent. In the welded part, the luminance difference PP becomes locally large, and the light and dark stripes are more prominent than other regions in the central part.

[0068] Note that while the direct reflection light L of the upstream illumination device 1503a is condensed on the light receiving unit 1505, as shown in FIG. 30c, the direct reflection light L of the downstream illumination device 1503b does not coincide with the reading optical axis 1502, so it is not condensed on the light receiving unit 1505. Therefore, the light source 1601 does not appear in the read image as a bright light source image (mirror image). Since the downstream illumination device 1503b does not have the light source image (mirror image) appearing in the image, the downstream emission surface 1606b of the downstream light guide 1604b may be provided with a fine shape similar to the upstream light guide 1604a, or may be a mirror surface.

[0069] The fine shape of the light-emitting surface 606 of the light guide 604 according to this embodiment will be described with reference to FIG. 10. FIG. 10 is an enlarged view of region A of the lighting device 403. The fine shape of the light-emitting surface 606 improves the diffusibility of light. A cross-section C (XY cross-section) in the main scanning direction (Y direction) is shown in FIG. 11. In FIG. 11, the horizontal axis represents the main scanning direction (Y direction), and the vertical axis represents the height of the fine shape. The fine shape of the light-emitting surface 606 consists of 14 types of concavo-convex structures and is continuously connected in the main scanning direction (Y direction). The widths (intervals) A of the 14 types of concavo-convex structures are equal at 0.042 mm. The heights B of the 14 types are in the range of 0.011 mm to 0.030 mm. The aspect ratio (the ratio of the height B to one width A) is 0.25 < B / A < 1.00 ···(2) the fine shape of the light-emitting surface 606 that satisfies this condition.

[0070] Conditional expression (2) defines the diffusibility of the fine shape. By keeping within the range of conditional expression (2), the diffusion by the fine shape can be improved, the light and dark stripes of the discrete light source image due to the glossy original can be reduced, and a good image can be obtained. When the upper limit value of conditional expression (2) is 1.00 or more, there is concern about insufficient transfer due to molding. When the lower limit value of conditional expression (2) is 0.25 or less, the diffusion by the fine shape weakens, and the light and dark stripes of the discrete light source image due to the glossy original appear in the image. Therefore, it is desirable to fall within the range of conditional expression (2).

[0071] In this embodiment, the specific numerical values are A = 0.042 mm, B = 0.011 mm to 0.030 mm. Since B / A = 0.26 to 0.71, conditional expression (2) is satisfied.

[0072] The ratio of one width A of the fine shape to the interval (pitch) C between adjacent light sources 601 at the center of the main scanning is 50 < C / A < 500 ···(3) the lighting device 403 that satisfies this condition.

[0073] The conditional expression (3) defines the unevenness of the light quantity (illuminance unevenness). By keeping within the range of the conditional expression (3), the unevenness of the light quantity can be suppressed, and a good image can be obtained. When the lower limit value of the condition (3) is 50 or less, the width A of the fine shape becomes large with respect to the interval (pitch) C between adjacent light sources 601, and there is concern about the unevenness of the light quantity (illuminance unevenness) due to the width of the fine shape. When the upper limit value of the conditional expression (3) is 500 or more, the width A of the fine shape becomes fine with respect to the interval (pitch) C between adjacent light sources 601, and there is concern that the influence of diffraction (wave optics) appears and a difference occurs from the result of geometric optics that treats light as light rays. Therefore, it is desirable to fall within the range of the conditional expression (3).

[0074] In the present embodiment, the specific numerical values are A = 0.042 mm and C = 10.0 mm. Since C / A = 238, the conditional expression (3) is satisfied.

[0075] The 14 types of concavo-convex structures of the fine shape on the emission surface 606 have a rotationally symmetric shape that is easy to mold and can be expressed by a mathematical formula (function). One type of the shape of the concavo-convex structure has a sixth-order coefficient = -3,000,000,000 × B, a fourth-order coefficient = 7,700,000 × B, and a second-order coefficient = -5,080 × B.

[0076] FIG. 12 shows a cross-section D (ZX cross-section) in the sub-scanning direction of an enlarged view of the region A shown in FIG. 10. In FIG. 12, the horizontal axis indicates the sub-scanning direction (Z direction), and the vertical axis indicates the height of the fine shape. The solid line shown in FIG. 12 is a cross-section (cross-section E) with a height B = 0.030 mm as shown in FIG. 11. The broken line indicates a cross-section (cross-section F) with a height B = 0.011 mm. As described above, one type of the shape of the fine shape has a sixth-order coefficient = -3,000,000,000 × B, a fourth-order coefficient = 7,700,000 × B, and a second-order coefficient = -5,080 × B. In the sub-scanning direction (Z direction), they are continuously connected at a pitch of 0.008 mm.

[0077] FIG. 13 shows the main scanning light quantity distribution in the reading area 401 of the manuscript G of the lighting device 403. The horizontal axis indicates the main scanning direction (Y direction), and the vertical axis indicates the light quantity. In order to compensate for the light quantity decrease due to the influence of the cosine fourth power law, the interval between adjacent light sources 601 is narrowed from the center to the end of the main scanning to increase the light quantity. As is clear from FIG. 13, in the middle part of the main scanning where the protruding portions 505a and 505b are provided, no local light quantity decrease due to the protruding portions occurs. Even when the protruding portions 505a and 505b are provided, the light quantity in the reading area 401 is suppressed to a decrease of about 0.2%.

[0078] FIG. 14 shows the light source image distribution when a glossy manuscript G (glossy manuscript) is illuminated by the lighting device 403, guided to the imaging optical system 406 by the reflection optical system 404, and condensed on the light receiving portion 405. In FIG. 14, the horizontal axis indicates the main scanning direction (Y direction), and the vertical axis indicates the luminance. As shown in FIG. 14, the luminance difference PP (the difference between the maximum value I max and the minimum value I min of the luminance) becomes smaller compared to the comparative example, and the light and dark stripes are reduced.

[0079] As described above, according to the lighting device 403 according to the present embodiment, by improving the transfer of the long light guide 604 having a fine shape, it is possible to reduce the light and dark stripes of the discrete light source images due to the glossy manuscript.

[0080] [Embodiment 2] Hereinafter, a second embodiment of the present invention will be described. Since the image reading device according to the present embodiment is the same as the configuration of the image reading device 101 according to the first embodiment except for the first image reading unit, the description thereof will be omitted.

[0081] The difference from the first image reading unit 314 according to the first embodiment is that the first image reading unit 314 is stopped at the first position A shown in FIG. 2(b), and the surface image of the manuscript G is read by the ADF 201 in a manuscript feed reading method, illuminating the reading area 701 from one side using one lighting device 703, the fine shape of the light emitting surface 906 of the light guide 904, the positions and shapes of the protruding portions 805a and 805b, and the position of the gate 504c.

[0082] FIG. 15 is a schematic diagram of a main part of the first image reading unit 314 according to the present embodiment. The light emitting surface 906 of the light guide 904 has a fine shape for diffusing light. FIG. 16 shows a schematic diagram of a main part of an injection mold for the light guide 904 of the lighting device 703 according to the present embodiment. As shown in FIG. 16, in contrast to the first embodiment, the positions of the protruding portion 805a and the protruding portion 805b are further on the end side than the middle portion. Since the runner 503c is shorter than the runners 503a and 503b, the flow distance until the resin flow fronts collide with each other from the resin inlet 501 is more likely to be closer to the end than the middle portion. Therefore, by setting the positions of the protruding portion 805a and the protruding portion 805b further on the end side than the middle portion, the generation location of the weld line 507 can be more effectively shifted to the protruding portion 805a and the protruding portion 805b. Thus, even for a long light guide having a fine shape, it is possible to improve the insufficient transfer of the fine shape due to welding.

[0083] FIG. 17 shows a schematic diagram (perspective view) of a main part of the lighting device 703 according to the present embodiment. And a cross section G (ZX cross section) including the protruding portion 805b of the lighting device 703 is shown in FIG. 18. Since the cross section A (ZX cross section) is the same as FIG. 7 of the first embodiment, the description is omitted. A cross section in the main scanning direction (Y direction) of an enlarged view of a region D (not shown) is defined as cross section C, and a cross section in the sub-scanning direction (Z direction) is defined as cross section D. FIG. 19 shows a cross section C (XY cross section) of the light emitting surface 906. In FIG. 19, the horizontal axis represents the main scanning direction (Y direction), and the vertical axis represents the height of the fine shape. FIG. 20 shows a cross section D (ZX cross section) of the light emitting surface 906. In FIG. 20, the horizontal axis represents the sub-scanning direction (Z direction), and the vertical axis represents the height of the fine shape.

[0084] As shown in Fig. 17, it has gate marks 911a and 911b at both ends of the main scan, and a gate mark 911c in the middle part between the both-end gates. By providing the gate mark 911c in the middle part in addition to the both-end gates (gate marks 911a and 911b) of the main scan, it is possible to improve the insufficient transfer of the fine shape of the emission surface 906 of the light guide 904. The gate mark 911c is at the center of the main scan, and a gate 504c (pin gate) is provided so as to be arranged on the connection surface 910. Even if the gate mark 911c is provided on the connection surface 910, as described in Figs. 9a to 9f of the first embodiment, the influence on the optical characteristics can be reduced. The interval (pitch) between adjacent light sources 901 is made narrower from the center part (interval C) to the middle part and then to the end part, compensating for the decrease in the amount of light toward the end of the main scan due to the influence of the cosine fourth power law by the imaging optical system 706.

[0085] As shown in Fig. 18, by protruding the protruding part 805b with respect to the connection surface 910 (dashed line in Fig. 18), the generation location of the weld line 507 can be shifted from the emission surface 906 to the protruding part 805b. Thereby, it is possible to improve the insufficient transfer of the fine shape of the emission surface 906.

[0086] As shown in Fig. 17, let the length in the main scan direction (Y direction) of the gate marks (gate marks 911a, 911b) at the end of the main scan and the gate mark 911c in the middle part be D, and the length in the main scan direction (Y direction) of each of the protruding parts 805a and 805b be E.

[0087] In this embodiment, the specific numerical values are D = 175.0 mm and E = 10.0 mm. Since E / D = 0.06, the conditional expression (1) is satisfied.

[0088] The fine shape of the light emitting surface 906 of the light guide 904 will be described. As shown in FIG. 19, the fine shape of the light emitting surface 906 consists of 14 types of concavo-convex structures and is continuously connected in the main scanning direction (Y direction). In the present embodiment, the specific numerical values are as follows: the widths (intervals) A of the 14 types of concavo-convex structures are equal and are 0.021 mm. The heights B of the 14 types are in the range of 0.010 mm to 0.020 mm. Since B / A = 0.48 to 0.95, the conditional expression (2) is satisfied.

[0089] The interval (pitch) C between adjacent light sources 901 at the center of the main scan is 10.0 mm. Since C / A = 476, the conditional expression (3) is satisfied.

[0090] The 14 types of concavo-convex structures of the fine shape of the light emitting surface 906 have a rotationally symmetric shape that is easy to mold and can be expressed by a mathematical formula (function). The shape of one type of concavo-convex structure has a sixth-order coefficient = -260,000,000,000 × B, a fourth-order coefficient = 112,000,000 × B, and a second-order coefficient = -18,000 × B. In the sub-scanning direction (Z direction), it is continuously connected at a pitch of 0.008 mm.

[0091] The solid line shown in FIG. 20 is a cross-section (cross-section H) with a height B = 0.020 mm as shown in FIG. 19. The dashed line indicates a cross-section (cross-section I) with a height B = 0.010 mm.

[0092] Since the main scanning light quantity distribution in the reading area 701 of the document G of the illumination device 703 is the same as that in FIG. 13 of the first embodiment, the description thereof will be omitted.

[0093] FIG. 21 shows the light source image distribution when a document G (glossy document) having glossiness is illuminated by the illumination device 703, guided to the imaging optical system 706 by the reflection optical system 704, and condensed on the light receiving unit 705. In FIG. 21, the horizontal axis indicates the main scanning direction (Y direction), and the vertical axis indicates the luminance. As shown in FIG. 21, the luminance difference PP (the difference between the maximum value I max and the minimum value I min of the luminance) with respect to the comparative example becomes smaller, and the light and dark stripes can be reduced.

[0094] As described above, according to the lighting device 703 according to the present embodiment, by improving the transfer of the long light guide 904 having a fine shape, it is possible to reduce the light and dark stripes of the discrete light source images due to the glossy original.

[0095] [Example 3] Hereinafter, a second embodiment of the present invention will be described. Since the image reading device according to the present embodiment is the same as the configuration of the image reading device 101 according to the first embodiment except for the first image reading unit, the description thereof will be omitted.

[0096] The difference from the first image reading unit 314 according to the first embodiment is that the second image reading unit 315 is stopped at the position C shown in FIG. 2(b), and the back surface image of the original G is read by the ADF 201 in a document feeding reading method, the fine shape of the upstream emission surface 1206a of the upstream light guide 1204a, the positions and shapes of the protrusions 1105a and 1105b, and the position of the gate mark 1211c.

[0097] FIG. 22 is a schematic diagram of the main part of the second image reading unit 315 according to the present embodiment. The upstream emission surface 1206a of the upstream light guide 1204a has a fine shape for diffusing light. As described in the above comparative example, since the light source image (mirror image) does not appear in the image in the downstream lighting device 1003b, the downstream emission surface 1206b of the downstream light guide 1204b may have a fine shape, may be subjected to embossing, or may be a mirror surface, similar to the upstream emission surface 1206a.

[0098] The injection mold of the upstream light guide 1204a of the upstream lighting device 1003a according to the present embodiment is the same as that of FIG. 16 of the second embodiment, so the description thereof will be omitted.

[0099] FIG. 23 shows a schematic diagram of the main part of the upstream illumination device 1003a according to the present embodiment. FIG. 23(a) is a perspective view, and FIG. 23(b) is an enlarged view of the vicinity of the upstream incident surface 1205a at the center of the main scan. And a cross section J (ZX cross section) including the protruding portion 1105b of the upstream illumination device 1003a is shown in FIG. 24. Since the cross section A (ZX cross section) is the same as FIG. 7 of the first embodiment, the description thereof is omitted. The cross section in the main scanning direction (Y direction) of the enlarged view of the region E not shown is defined as cross section C, and the cross section in the sub-scanning direction (Z direction) is defined as cross section D. FIG. 25 shows a cross section C (XY cross section) of the upstream emission surface 1206a. In FIG. 25, the horizontal axis represents the main scanning direction (Y direction), and the vertical axis represents the height of the fine shape. FIG. 26 shows a cross section D (ZX cross section) of the upstream emission surface 1206a. In FIG. 26, the horizontal axis represents the sub-scanning direction (Z direction), and the vertical axis represents the height of the fine shape.

[0100] As shown in FIG. 23(a), there are a gate mark 1211a and a gate mark 1211b at both ends of the main scan, and a gate mark 1211c in the middle of both end gates. By providing the gate mark 1211c in the middle in addition to the both end gates (gate mark 1211a and gate mark 1211b) of the main scan, it is possible to improve the insufficient transfer of the fine shape of the upstream emission surface 1206a of the upstream light guide 1204a.

[0101] As shown in FIG. 23(b), the gate mark 1211c is provided with a gate 504c (side gate) at the upstream incident surface 1205a at the center of the main scan and between adjacent light sources 1201. If the gate mark 1211c is within the region B, as described in FIG. 6c, the influence on the optical characteristics can be reduced, so it may be separated from the upstream incident surface 1205a in the Z direction. Since the method of obtaining the region B has been described in FIG. 6c of the first embodiment, it is omitted. The interval (pitch) between adjacent light sources 1201 is made narrower from the center (interval C) to the middle part and then to the end part, compensating for the decrease in the amount of light toward the end of the main scan due to the influence of the cosine fourth power law by the imaging optical system 1306.

[0102] As shown in FIG. 24, by protruding the protruding portion 1105b with respect to the upstream connection surface 1210a (dashed line in FIG. 24), the generation location of the weld line 507 can be shifted from the upstream emission surface 1206a to the protruding portion 1105b. Thereby, it is possible to improve the insufficient transfer of the fine shape of the upstream emission surface 1206a.

[0103] As shown in FIG. 23(a), let the length in the main scanning direction (Y direction) of the gate marks (gate marks 1211a and 1211b) at the main scanning end and the gate mark 1211c in the middle part be D, and the length in the main scanning direction (Y direction) of each of the protruding portions 1105a and 1105b be E.

[0104] In the present embodiment, the specific numerical values are D = 160.0 mm and E = 50.0 mm. Since E / D = 0.31, the conditional expression (1) is satisfied.

[0105] The fine shape of the upstream emission surface 1206a of the upstream light guide 1204a will be described. As shown in FIG. 25, the fine shape of the upstream emission surface 1206a is composed of 14 types of concavo-convex structures and is continuously connected in the main scanning direction (Y direction). In the present embodiment, the specific numerical values are that the widths (intervals) A of the 14 types of concavo-convex structures are equal at 0.168 mm. The heights B of the 14 types are in the range of 0.044 mm to 0.060 mm. Since B / A = 0.26 to 0.36, the conditional expression (2) is satisfied.

[0106] The interval (pitch) C between adjacent light sources 1201 at the center of the main scanning is 9.0 mm. Since C / A = 54, the conditional expression (3) is satisfied.

[0107] The 14 types of concavo-convex structures of the fine shape of the upstream emission surface 1206a have a rotationally symmetric shape that is easy to mold and can be expressed by a mathematical formula (function). The shape of one type of concavo-convex structure is that the coefficient of the sixth order = -875,000×B, the coefficient of the fourth order = 27,500×B, and the coefficient of the second order = -287.5×B. In the sub-scanning direction (Z direction), they are continuously connected at a pitch of 0.008 mm.

[0108] The solid line shown in FIG. 26 is a cross section (cross section H) with a height B = 0.060 mm as shown in FIG. 25. The dashed line indicates a cross section (cross section I) with a height B = 0.044 mm.

[0109] Since the main scanning light quantity distribution in the reading area 1001 of the original G of the upstream illumination device 1003a and the downstream illumination device 1003b is the same as that in FIG. 13 of the first embodiment, the description thereof is omitted.

[0110] FIG. 27 shows the light source image distribution when a glossy original G (glossy original) is illuminated by the upstream illumination device 1003a and the downstream illumination device 1003b, guided by the reflection optical system 1004 to the imaging optical system 1006, and condensed on the light receiving unit 1005. In FIG. 27, the horizontal axis represents the main scanning direction (Y direction), and the vertical axis represents the luminance. As shown in FIG. 27, the luminance difference PP (the difference between the maximum value I max and the minimum value I min of the luminance) with respect to the comparative example becomes smaller, and the stripes of light and dark can be reduced.

[0111] As described above, according to the upstream illumination device 1003a and the downstream illumination device 1003b according to the present embodiment, by improving the transfer of the long upstream light guide 1204a having a fine shape, it is possible to reduce the stripes of light and dark of the discrete light source images due to the glossy original.

[0112] [Modification Example] As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist thereof.

Explanation of Reference Numerals

[0113] 100 Image forming apparatus 101 Image reading apparatus 102 Image forming apparatus main body 103 Paper feed cassette 104 Main body paper discharge unit 201 ADF 202 Leader 203 Original conveying means 204 Original tray 205 Paper discharge tray 300 Pickup Roller 301 Separation Roller Pair 302 Pull-Out Roller Pair 303 Conveyor Roller Pair 304 Registration Roller Pair 305 Lead 1 Roller Pair 306 First Platen Roller 307 Lead 2 Roller Pair 308 Second Platen Roller 309 Lead 3 Roller Pair 310 Paper Discharge Roller Pair 311 First Platen Glass 312 Second Platen Glass 313 Document Table Glass 314 First Image Reading Unit (Carriage) 315 Second Image Reading Unit (Carriage) 316 Control Unit 401, 701, 1001, 1301 Reading Area 402, 1302, 1502 Reading Optical Axis 403, 703, 1303 Lighting Device 1003a, 1503a Upstream Lighting Device 1003b, 1503b Downstream Lighting Device 404, 704, 1004, 1304, 1504 Reflection Optical System 404a First Folding Mirror 404b Second Folding Mirror 404c Third Folding Mirror 404d Fourth Folding Mirror 405, 705, 1005, 1305, 1505 Light Receiving Unit (Line Sensor, Image Sensor) 406, 706, 1006, 1306, 1506 Imaging Optical System (Reduction Optical System) 407 Driving Unit 501 Resin Inlet 502 Cavity 503a, 503b, 503c Runner 504a, 504b, 504c Gate Protrusions 505a, 505b, 805a, 805b, 1105a, 1105b 506 Flow pattern 507 Weld line Light sources (LEDs) 601, 901, 1201, 1401, 1601 602 Light emitting surface Retention members (light source substrates) 603, 1403 Light guides 604, 904, 1404 605 Incident surface Exit surfaces 606, 906, 1406 607 First light guide surface 608 Second light guide surface 609 Reflective surface Connection surfaces 610, 910 Gate marks 611a, 611b, 611c, 911a, 911b, 911c, 1211a, 1211b, 1211c Upstream light guides 1204a, 1604a Downstream light guides 1204b, 1604b Upstream incident surface 1205a Downstream incident surface 1206b Upstream connection surface 1210a Upstream exit surface 1606a Downstream exit surface 1606b

Claims

1. A plurality of light sources are arranged in the main scanning direction, and the pitch between adjacent light sources is wider at the center of the main scanning than in other regions, and includes a long light guide that guides light from the light sources to the irradiated surface, the light guide has gates that serve as inlets for the resin material in injection molding at at least both ends of the main scanning, has an incident surface on which light from the light sources is incident and an emission surface having a fine shape through which light from the incident surface irradiates toward the irradiated surface, has a gate at an intermediate portion between the gates at both ends of the main scanning, and an illuminating device characterized by having a protruding portion between the gate at the end of the main scanning and the gate at the intermediate portion.

2. The light guide has a first light guide surface and a second light guide surface that face each other and guide light from the light sources to a reflecting surface, a reflecting surface that is inclined so as to bend with respect to the second light guide surface and guides light to the emission surface, and a connecting surface that faces the reflecting surface and connects the first light guide surface and the emission surface, The illuminating device according to claim 1, wherein the protruding portion is provided on the connecting surface.

3. When the width of the fine shape in the main scanning direction is A and the height is B, the aspect ratio of the fine shape is at least in a part of the main scanning direction 0.25 < B / A < 1.00 The illuminating device according to claim 1 or 2, characterized by satisfying the above.

4. When the width of the fine shape in the main scanning direction is A and the distance between the light sources at the center of the main scanning is C, 50 < C / A < 500 The illuminating device according to any one of claims 1 to 3, characterized by satisfying the above.

5. When the length of the gate at the end of the main scanning and the gate at the intermediate portion is D and the length of the protruding portion in the main scanning direction is E, 0.05 < E / D < 0.35 The illuminating device according to any one of claims 1 to 4, characterized by satisfying the above.

6. The illuminating device according to any one of claims 1 to 5, wherein the gate at the intermediate portion of the main scanning is provided between adjacent light sources in the vicinity of the incident surface of the light guide.

7. The illuminating device according to any one of claims 1 to 5, wherein the gate at the intermediate portion of the main scanning is provided on the connecting surface of the light guide.

8. The illuminating device according to any one of claims 1 to 7, wherein the protruding portion is located closer to the end of the main scanning than the center of the gate at the end of the main scanning and the gate at the intermediate portion.

9. An image reading device comprising the illuminating device according to any one of claims 1 to 8, a light receiving portion that receives light from the irradiated surface, and an imaging portion that guides light from the irradiated surface to the light receiving portion.

10. An image forming apparatus comprising: the image reading device according to claim 9; and an image forming unit configured to form an image on a photosensitive surface based on an image of an original document.

Images