JP2007005860A - Light irradiating unit, image reading mechanism, image reader and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light irradiating unit capable of efficiently guiding a light from a light-emitting object such as a light-emitting diode, and illuminating an illumination object; and to provide an image reading mechanism, an image reader, and image forming apparatus. <P>SOLUTION: The light irradiating unit 100 is provided with a light-emitting diode array 110 provided with a light-emitting surface, and a light guide 120 for emitting the light incident from a light receiving surface 121 from an emitting surface 122. The unit 100 enters a light from the diode array 110 from the light-receiving surface 121 of the light guide 120 and emits it from the emitting surface 122. In this unit, a minute air layer (d) is provided between the light-emitting object and the light-receiving surface of the light guide, and the refractive index of the light guide 120 for air is set at √2 or more. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light irradiation unit, an illumination mechanism, an image reading apparatus, and an image forming apparatus, and in particular, a light irradiation unit of a type in which light from a light emitter having a light emitting surface is incident from an end surface of a light guide and emitted from an opposite surface. The present invention relates to an image reading mechanism, an image reading apparatus, and an image forming apparatus.

  As shown in FIGS. 15 and 16, an image reading apparatus 300 that irradiates light on a document and reads reflected light of the document by a light conversion element composed of a CCD, a CMOS, or the like uses a cylindrical xenon lamp 301 as a light source. The document D on the contact glass 302 is irradiated with the irradiation light of the xenon lamp 301, and the reflected light of the document D is guided to the light conversion element 303 through the lens 309. I am trying to convert it into a signal. Such an image reading apparatus 300 includes a first carriage 305 including a first mirror 304 that deflects reflected light from the document D, a second mirror 306 that further deflects light from the first mirror 304, and a third mirror 307. The first carriage 305 and the second carriage 306 move to scan the document D. In this example, the first carriage 305 is provided with a reflector 310 that reflects light from the xenon lamp 301 to optimize the illuminance distribution, as shown in FIG.

  In such an image reading apparatus 300, the illuminance on the original surface is required to have a ripple-free illuminance distribution in the main scanning direction so as not to cause uneven illuminance as shown in FIG. In the sub-scanning direction, as shown in FIG. 3B, an illuminance distribution with a small illuminance outside the reading range is required as a countermeasure against flare.

  In addition, in such an image reading apparatus, there are demands for the rising speed of the light source, energy saving, and long life, and the use of a light emitting diode (LED) as the light source is being studied. However, if the illumination system is composed only of light emitting diodes having a light emitting surface that is small enough to be regarded as a point light source, the amount of light is reduced and a uniform illuminance distribution shape cannot be obtained in the main scanning direction. It is necessary to employ a light guide member that guides the light.

  That is, in an image forming apparatus such as a monochrome, full-color, digital copying machine such as an MFP, a reading apparatus that requires high image quality such as a general-purpose scanner, and an analog copying machine, a point light source such as a light emitting diode (LED) and a light guide. It is necessary to optimize the members, collect light efficiently, and obtain a uniform illuminance distribution.

  In response to such a demand, the following techniques have been proposed. Japanese Patent Application Laid-Open No. 2004-228561 is a light guide that is a column-shaped light-transmitting member having an end surface as a light incident surface and at least a part of a side surface as a light exit surface, and restricts a light beam incident from the light incident surface. Is provided.

  Patent Document 2 illuminates an image surface, and in an image reading apparatus that converts image information read based on light from the image surface into an electrical signal, means for illuminating the light of the light source on the image surface; It has means that can set the distribution of the amount of light that irradiates the image surface, and means that converts the traveling direction of the light beam from the light source and converges the light beam that has passed through the image surface in a specific direction. What to do is described.

  Japanese Patent Application Laid-Open No. 2004-228688 discloses an elongated light guide for a reading device for irradiating a document in a line along a first reading direction that is a longitudinal direction of a line sensor, in the first reading direction. A predetermined light source is disposed on a corresponding end face in the longitudinal direction of the light guide, and light from the light source is guided in the light guide along the first reading direction so that the document is the line sensor. A light emitting surface for irradiating the first reading direction in a line, and in the first reading direction for diffusing and / or reflecting light from the light source along the first reading direction. And at least a portion of the reflective portion that is relatively close to the light source, when viewed from the light source side, the center of the width of the reflective portion So that the normal passing through the center deviates from the center of the side including the reflection part. With arranging the serial reflective portion, which is provided an inclined surface that is inclined relative to the surface having the reflective portion is described.

Patent Document 4 discloses an image sensor that includes a light source that illuminates an image original and an optical system that guides light reflected and scattered on the image original to an optical sensor using an imaging lens. In an optical system having a contact glass, a monochromatic light source is used, and a diffraction grating is disposed directly under the illumination light source to illuminate the illumination light and divide the diffraction light into transmitted light and diffracted light. It is described that light is further transmitted through an optical path along the contact glass, is reflected by a mirror, and irradiates the image original from one side, and the other light is irradiated from the other side.

JP 2000-48616 A JP 2001-109084 A Japanese Patent No. 0392117 Japanese Utility Model Publication No. 05-046169

  As described above, in an image forming apparatus using a light emitting diode for illumination, in order to guide light so as to obtain an illuminance distribution that satisfies the above requirements efficiently with a light guide member (light guide plate), It is desired to devise the structure and arrangement to obtain desired illumination characteristics.

  Accordingly, an object of the present invention is to provide a light irradiation unit, an image reading mechanism, an image reading apparatus, and an image forming apparatus that can efficiently guide light from a light emitter such as a light emitting diode and illuminate an illumination target. To do.

  The invention of claim 1 includes a light emitter having a light emitting surface and a light guide that emits light incident from a light receiving surface that is one end surface from an exit surface that is the other end surface, and guides light from the light emitter. In a light illumination unit that enters from the light receiving surface of the body and exits from the exit surface, a fine air layer is provided between the light emitting body and the light receiving surface of the light guide, and the refractive index of the light guide to the air Is a light irradiation unit characterized in that √2 or more.

  According to a second aspect of the present invention, in the light irradiation unit according to the first aspect, the air layer causes the light emitting surface of the light source and the incident surface of the light guide member to be incident on the light receiving surface of the light guide member. It is characterized by having a dimension that satisfies the conditions and a separation.

  According to a third aspect of the present invention, in the light irradiation unit of the first or second aspect, the light receiving surface of the light guide member is formed in the same shape as or larger than the light emitting surface of the light source.

  The invention of claim 4 is characterized in that in the light irradiation unit according to any one of claims 1 to 3, a light source having directivity is used.

  According to a fifth aspect of the present invention, in the light irradiation unit according to any one of the first to fourth aspects, a reflective member extending in the vicinity of the air layer is provided.

  According to a sixth aspect of the present invention, in the light irradiation unit according to any one of the first to fourth aspects, the reflecting member is attached to the light guide member.

  The invention according to claim 7 is the light irradiation unit according to claim 5, wherein a material that forms a reflection surface is used for a component that holds or fixes the light source and the light guide member.

  The invention of claim 8 is characterized in that, in the light irradiation unit of claim 5, of the parts for holding or fixing the light source and the light guide member, a portion between the light source and the light guide member is used as a reflection surface. To do.

  According to a ninth aspect of the present invention, in the light irradiation unit according to any of the fifth to eighth aspects, a reflection member is provided that is attached to the light guide plate at an arbitrary angle.

  According to a tenth aspect of the present invention, in the light irradiation unit according to the ninth aspect, the reflecting member reflects the light emitted from the light guide plate and irradiates the illuminated member.

  According to an eleventh aspect of the present invention, in the light irradiation unit according to any one of the first to tenth aspects, the light emitter is a light emitting diode.

  The invention of claim 12 is the light irradiation unit according to claim 11, wherein the light emitter is a light emitting diode array.

  According to a thirteenth aspect of the present invention, in the light irradiation unit according to the eleventh aspect, the light guide includes a light receiving surface extending in the extending direction of the light emitting diode light emitting surface of the light emitting diode array.

  The invention of claim 14 is the light irradiation unit according to claim 13 or 14, wherein the light guide has an emission surface with a predetermined width dimension and emits light that is continuous in the width direction.

  According to a fifteenth aspect of the present invention, there is provided an illumination mechanism that reads image information of a document by irradiating the document surface with light and converting reflected light from the document into an electrical signal by a light conversion element. It is the illumination mechanism characterized by including the light irradiation unit.

  A sixteenth aspect of the present invention is an image reading apparatus including the illumination mechanism according to the fifteenth aspect.

  A seventeenth aspect of the invention is an image forming apparatus including the image reading device of the sixteenth aspect.

  The present invention has the following effects.

  Embodiments as the best mode for carrying out the present invention will be described below with reference to the drawings.

  1 is a sectional view showing an embodiment of an image forming apparatus according to the present invention, FIG. 2 is an enlarged sectional view of the image reading apparatus shown in FIG. 1, and FIG. 3 is an image reading mechanism of the image reading apparatus shown in FIG. It is sectional drawing which shows

  The image forming apparatus 10 according to the present exemplary embodiment mainly includes a reading unit 11 that reads a document, an image forming unit 12 that forms an image, an automatic document feeder (ADF) 13, and documents sent from the ADF 13. A document discharge tray 14, a sheet feed unit 19 including sheet cassettes 15 to 18, and a sheet discharge unit (discharge tray 20) for stacking recording sheets are configured.

  Then, when the document D is set on the document table 21 of the ADF 13 and an operation on an operation unit (not shown), for example, a press operation of a print key is performed, the uppermost document D is sent out in the direction of the arrow B1 by the rotation of the pickup roller 22. Then, by the rotation of the document conveying belt 23, the paper is fed onto the contact glass 24 fixed to the image reading unit 11 and stops there. The image of the document D placed on the contact glass 24 is read by the reading device 25 positioned between the image forming unit 12 and the contact glass 24. The reading device 25 includes a light irradiation unit 100 that illuminates the document D on the contact glass 24, an optical system 26 that forms an image of the document, a lens 27, and a photoelectric conversion element 28 that includes a CCD that forms an image of the document. After the image reading is completed, the document D is transported in the direction of the arrow B2 by the rotation of the document transport belt 23 and discharged onto the document discharge tray 14. In this way, the document D is fed one by one onto the contact glass 24 and the document image is read by the image reading unit 11.

  On the other hand, inside the image forming unit 12, a photoconductor 30 as an image carrier is disposed. The photosensitive member 30 is driven to rotate clockwise in the drawing, and the surface is charged to a predetermined potential by the charging device 31. Further, the writing unit 32 emits a laser beam L that is light-modulated in accordance with image information read by the document reading device 25, and the charged surface of the photosensitive member 30 is exposed with the laser beam L. An electrostatic latent image is formed on the surface of the body 30. When the electrostatic latent image passes through the developing device 33, the electrostatic latent image is transferred to the recording medium P fed between the photosensitive member 30 and the transfer device 34 by the opposing transfer device 34. The surface of the photoconductor 30 after the toner image is transferred is cleaned by a cleaning device 35.

  A plurality of paper feed cassettes 15 to 18 arranged below the image forming unit 12 contain recording media P such as paper, and the recording media P is fed from any of the paper feed cassettes 15 to 18 in the direction of arrow B3. The toner image formed on the surface of the photoreceptor 30 as described above is transferred onto the surface of the recording medium P. Next, the recording medium P is passed through the fixing device 36 in the image forming unit 12 as indicated by an arrow B4, and the toner image transferred to the surface of the recording medium P by the action of heat and pressure is fixed. The recording medium P that has passed through the fixing device 36 is conveyed by the discharge roller pair 37, discharged to the discharge tray 20 as indicated by an arrow B5, and stacked.

  Hereinafter, the image reading device 25 according to this example will be described. As shown in FIG. 2, the image reading device 25 includes a light irradiation unit 100 as a light source. The image reading device 25 irradiates the light D from the light irradiation unit 100 onto the document D on the contact glass 24 and guides the reflected light of the document D to the light conversion element 28 via the lens 27. Convert to electrical signal. The image reading device 25 includes a first carriage 29 including a light irradiation unit 100 and a first mirror 101 that deflects reflected light from the document D, a second mirror 201 that further deflects light from the first mirror 101, and a second mirror 201. A second carriage 200 including three mirrors 202 is provided, and the first carriage 29 and the second carriage 200 perform a predetermined movement to scan the document D.

  As shown in FIGS. 3 and 4, the light irradiation unit 100 includes a light emitting diode array 110 that is a light emitter, a light guide 120, a base 130, and a reflector 140. The light emitter is configured by arranging a light emitting diode array 110 formed by arranging a number of top view type white light emitting diodes 111 in a line on a substrate 130. The light guide 120 is a substantially rectangular optical plastic member having a substantially rectangular shape and having an air layer d having a minute dimension spaced from the light emitting surface 112 of the light emitting diode array 110. The light guide 120 is opposed to the light emitting surface 112 and receives a light receiving surface 121 on which white light enters, an exit surface 122 on which the incident light exits, and side surfaces 123 and 124 that totally reflect the light traveling inside the light guide. With. The reflector 140 includes a reflecting surface 141 that faces the exit surface 122 of the light guide 120.

  In this example, as the optical plastic constituting the light guide 120, one having a refractive index of √2 or more is used, and for example, an acrylic resin, a polycarbonate resin, or the like is employed. The reason why the refractive index is set to √2 or more is as follows.

  As shown in FIG. 5, generally, the light emitted from the light emitting diode (LED) emits light in the range of −90 ° to 90 °, although the relative luminous intensity decreases as the radiation angle increases. FIG. 6 shows a state in which the light guide member is used to guide the irradiation light toward the irradiated surface. Consider the transmittance when the light guide member is a transparent member such as glass or resin and all light is totally reflected on the side surface of the light guide member. Then, as shown in FIG. 7, since the maximum incident angle that can occur is 90 °, if the incident angle is θ1 = 90 °, the refraction angle is θ2, and the refractive index is n, then 1 × sin90 = n × sinθ2. Holds. If the light having the maximum incident angle is not refracted on the side surface, all the light is totally reflected. Therefore, considering the case of θ4 = 90 °, the relationship is n × sin θ3 = 1 × sin90. From these two formulas, if θ2 = θ3 = 45 ° and the transmittance n is 1 / sin 45 ° = √2 or more, the incident light is not refracted on the side as shown in FIG. Therefore, all incident light reaches the irradiation surface without processing the side surface into a reflection surface by vapor deposition or the like, or using a separate reflection member.

  In this example, as shown in FIGS. 3, 5, 8, and 9, a small air layer d is formed between the light receiving surface 121 of the light guide 120 and the light emitting surface 112 of the white light emitting diode 111. Is forming. The air layer d can be determined by the light emission characteristics of 110. That is, as shown in FIG. 14, since the light emission characteristics differ depending on the type of the light emitting diode, the dimension of the air layer d is set in accordance with the thickness t of the light guide 120 for the light emission characteristics. FIG. 15A shows a case where the emission peak is dull, and FIG. 15B shows a case where the emission characteristic is sharp. In this example, the light emission amount is small (the angle formed between the light emitting surface and the radiation direction is small), for example, a predetermined radiation angle set to guide only light of 50% or more of the maximum radiation amount into the light guide 120. Dimension. The reference value of the radiation amount can be set arbitrarily. In this way, only light with a radiation angle less than that can reach the document surface, and flare components can be reduced. The light emitting surface 112 of the white light emitting diode 111 is small, but microscopically, it is considered that the light emitting surface 112 emits light as shown in FIG. It is desirable to enlarge it.

  Further, in the present invention, when it is desired to guide the light from the incident light emitting diode array 110 to the light guide 120 as much as possible, the light is guided between the light emitting diode array 110 and the light guide 120 as shown in FIG. A reflecting member 151 such as a mirror can be provided in the space between the optical members. By providing the reflection member 151 in this manner, the light that is lost can reach the incident surface of the light guide member. At this time, it is desirable that the reflecting member 151 extends beyond the light emitting surface of the light emitting diode array 110 from the viewpoint of preventing light leakage.

Moreover, when providing a reflection member, it is preferable from a viewpoint of a reduction in a number of parts and cost to make it serve as the connection member of the light emitting diode array 110 and the light guide 120. FIG. That is, as shown in FIG. 11, the reflecting member 152 can also serve as a member for attaching the light guide 120 to the light emitting diode array 110.

  Further, as shown in FIG. 13, the reflection member 153 can be set at an angle that opens toward the light emitting diode array 110. By setting in this way, it is possible to prevent light (shown by a wavy line in FIG. 13) having a large radiation angle (a radiation angle is shallow with respect to the light emitting surface of the white light emitting diode) from entering the light guide member. According to this example, a flare component having a large radiation angle can be eliminated.

  Further, in this example, by selecting the size, mounting position, and mounting angle of the reflecting surface 141 of the reflector 140, harmful light out of the light exiting surface 122 of the light guide 120 can be eliminated. it can. That is, as shown in FIG. 12, light emitted from the exit surface 122 at a shallow angle (flare: indicated by a wavy line in FIG. 12) is absorbed by the reflector 140 and is not irradiated on the document D.

  In the above example, a top view type light emitting diode is used, but a side view type light emitting diode can be used as shown in FIG. In this case, the mounting state of the base 230 is set so that the direction of the light emitting surface 212 of the white light emitting diode 211 faces the light guide 120.

  In addition to the image forming apparatus of the above-described type, the light irradiation unit 100 shown in each of the above examples can be applied to other types of image forming apparatuses, digital copiers such as monochrome, full color, MFP, analog scanners such as general-purpose scanners, etc. Can be used.

1 is a cross-sectional view illustrating a schematic structure of an image forming apparatus according to an embodiment. FIG. 2 is a cross-sectional view illustrating a schematic structure of an image reading apparatus used in the image forming apparatus illustrated in FIG. 1. It is sectional drawing which shows the structure of the light irradiation unit used for the image reading apparatus shown in FIG. It is a perspective view which shows the structure of the light irradiation unit shown in FIG. It is a figure explaining the light emission characteristic of a light emitting diode, and the positional relationship of a light guide. It is explanatory drawing for determining the refractive index of a light guide. It is explanatory drawing for determining the refractive index of a light guide. It is a figure explaining the dimension and arrangement position of a light guide. It is a figure explaining the dimension and arrangement position of a light guide. It is sectional drawing which shows the state which provided the reflection member in the light irradiation unit. It is sectional drawing which shows the state which provided the reflection member in the light irradiation unit. It is sectional drawing which shows the reflective state of the light of the state which provided the other type of reflector in the light irradiation unit. It is sectional drawing which shows the reflective state of the light of the state which provided the other type of reflector in the light irradiation unit. It is a figure which shows the state of the emitted light when a reflector is provided in the light reflection unit. It is a figure which shows the light emission characteristic of the light emitting diode of a different characteristic. It is sectional drawing which shows schematic structure of the conventional image reading apparatus. It is sectional drawing which shows the structure of the conventional light irradiation unit. It is a figure which shows the light distribution characteristic of the light irradiation unit of an image reading apparatus.

Explanation of symbols

10: Image forming apparatus 11: Reading unit 12: Image forming unit 13, ADF 13: Automatic document feeder (ADF)
14: Document discharge trays 15, 16, 17, 18: Paper feed cassette 19: Paper feed unit 20: Paper discharge tray 21: Document table 22: Pickup roller 23: Document transport belt 24: Contact glass 25: Image reading device 26 : Optical system 27: Lens 28: Photoelectric conversion element 28: Light conversion element 29: First carriage 30: Photoconductor 31: Charging device 32: Unit 33: Developing device 34: Transfer device 35: Cleaning device 36: Fixing device 37: Discharge roller pair 100: light irradiation unit 101: first mirror 110: light emitting diode array 111: light emitting diode array 112: light emitting surface 120: light guide 121: light receiving surface 122: exit surface 123, 124: side surface 130: base 140: Reflector 141: Reflecting surface 151: Reflecting member 152: Reflecting member 153: Reflecting member 201: Second mirror 202: First 3 mirror 211: white light emitting diode 212: light emitting surface 230: substrate 300: image reading device 301: xenon lamp 302: contact glass 303: light conversion element 304: first mirror

Claims (17)

A light emitter having a light emitting surface, and a light guide that emits light incident from the light receiving surface that is one end surface from the light emitting surface that is the other end surface, and the light from the light emitter is incident from the light receiving surface of the light guide. In the light illumination unit that emits from the exit surface,
A light irradiation unit characterized in that a minute air layer is provided between the light emitter and the light receiving surface of the light guide, and the refractive index of the light guide with respect to the air is √2. The air layer is provided with a size and a distance that satisfy a condition that light having a predetermined radiation angle or more does not enter the light receiving surface of the light guide member between the light emitting surface of the light source and the light incident surface of the light guide member. 1 light irradiation unit. 3. The light irradiation unit according to claim 1, wherein the light receiving surface of the light guide member is formed in the same shape as or larger than the light emitting surface of the light source. 4. The light irradiation unit according to claim 1, wherein a light source having directivity is used. The light irradiation unit according to claim 1, further comprising a reflection member extending in the vicinity of the air layer. The light irradiation unit according to claim 1, wherein the reflection member is attached to the light guide member. 6. The light irradiation unit according to claim 5, wherein a material that forms a reflection surface is used for a component that holds or fixes the light source and the light guide member. 6. The light irradiation unit according to claim 5, wherein, of the components for holding or fixing the light source and the light guide member, a portion between the light source and the light guide member is used as a reflection surface. The light irradiation unit according to claim 5, further comprising a reflection member that is attached to the light guide plate at an arbitrary angle. The light irradiation unit according to claim 9, wherein the reflection member reflects the light emitted from the light guide plate and irradiates the illuminated member. The light emitting unit according to claim 1, wherein the light emitter is a light emitting diode. The light emitting unit according to claim 11, wherein the light emitter is a light emitting diode array. 12. The light irradiation unit according to claim 11, wherein the light guide includes a light receiving surface extending in an extending direction of the light emitting diode light emitting surface of the light emitting diode array. 15. The light irradiation unit according to claim 13, wherein the light guide has an emission surface having a predetermined width dimension and emits light that is continuous in the width direction.   15. An illumination mechanism for reading image information of a document by irradiating the document surface with light and converting reflected light from the document into an electrical signal by a light conversion element, comprising the light irradiation unit according to claim 1. An illumination mechanism characterized by that. An image reading apparatus comprising the illumination mechanism according to claim 15. An image forming apparatus comprising the image reading apparatus according to claim 16.