JP6720022B2 - Lighting device and image reading device - Google Patents

Description

The present invention relates to an illumination device used for an image reading device such as a facsimile, a copying machine, an image scanner, and various other optical devices, and an image reading device including the illumination device.

2. Description of the Related Art Conventionally, in image reading devices such as facsimiles, copiers, and image scanners, an illumination device that irradiates linear light in the main scanning direction (line image sensor array direction) is used to read an image of a document with a line image sensor. Widely used. Many lighting devices include a rod-shaped light guide and a light source arranged near the end face of the light guide, and light incident from the end face of the light guide is directed toward the opposite end while repeating total reflection inside the light guide. While being propagated, the light is diffused and reflected by the reflecting surface in the longitudinal direction, and linear light is emitted from the light emitting surface facing the reflecting surface toward the document surface.

In general, such an illuminating device is required to have a uniform illuminance distribution along the main scanning direction on the reading surface of the document. Therefore, by forming a light-scattering pattern by printing white paint on the surface of the light guide in the longitudinal direction, the intermediate part in the longitudinal direction is formed continuously and the vicinity of the end is intermittently formed, thereby making There is known a line illumination device in which the intensity of the emitted light is suppressed and the intensity of the emitted light is made uniform in the longitudinal direction of the light guide body (for example, see Patent Document 1).

In addition, an illumination device is provided in which a light-diffusing concavo-convex portion is provided on the light-exiting surface of the light guide member in the vicinity of an end portion of the light-guiding member near the light source in the longitudinal direction to diffuse the emitted light in the line width direction orthogonal to the longitudinal direction. It is known (for example, see Patent Document 2). Thereby, the irradiation peak due to the emitted light near the light source is eliminated, and an appropriate and uniform illuminance distribution is obtained in the longitudinal direction.

Similarly, in the illumination device of the image reading device, in order to make the brightness and the illuminance of the emitted light uniform in the longitudinal direction of the light guide body, the light extraction surface emitting the light from the light guide body and the first light diffusion surface facing the light extraction surface. A light source module has been proposed in which a light diffusion structure is provided on each of the surface and the surface (for example, see Patent Document 3). The first light diffusing structure of the first light diffusing surface has a plurality of diffusing portions arranged at a high density as the distance from the end of the light guide is increased to make the intensity distribution of the emitted light uniform, and the width of the light diffusing portion in the longitudinal direction is The second light diffusing structure on the light extraction surface, which has a fixed rectangular shape, is combined to facilitate control of the brightness and illuminance of emitted light.

Furthermore, in Patent Document 3, a second embodiment in which the diffusion portions of the first light diffusing structure are arranged at equal intervals in the longitudinal direction and the width of the second light diffusing structure is widened from the end portion of the light guide toward the center. A form of light source module is described. The brightness and the illuminance distribution of the emitted light are similarly uniformly controlled by the pattern shape of the second light diffusion structure.

JP, 2002-125098, A JP, 2008-140726, A JP, 2010-205565, A

In the conventional illumination device described in Patent Document 1 described above, there is a possibility that uneven illuminance may occur on the document reading surface along the longitudinal direction due to the discontinuous light scattering pattern of the light guide body. This illuminance unevenness causes unevenness in the read image of the original document, thus deteriorating the image quality.

In the illuminating device described in Patent Document 2, the amount of light emitted from the light exit surface to the original surface abruptly changes at the boundary of the light diffusing concavo-convex portion along the longitudinal direction of the light guide, and a read image of the original appears There is a risk of changing the shade. Further, in the vicinity of the end portion where the light source of the light guide is provided, a considerable amount of emitted light is scattered out of the reading area in the sub-scanning direction (direction orthogonal to the main scanning direction) of the document surface by the uneven portion for light diffusion. There is a problem of doing.

In the light source module described in Patent Document 3, a considerable amount of emitted light is scattered outside the reading area in the sub-scanning direction of the document surface by the second light diffusing structure over the entire length of the light extraction surface in the longitudinal direction. .. Therefore, there arises a problem that the illuminance is reduced over the entire document reading area.

Particularly, in the optical module of the second embodiment in Patent Document 3, the width of the second light diffusing structure is formed to be narrower from the central portion of the light guide toward both ends. In the portion where the width of the second light diffusion structure is narrow, the influence of the manufacturing tolerance appears to be larger than in the portion where the width is wide. As a result, variations in the illuminance distribution are likely to occur in the individual light guides and/or between the light guides.

On the other hand, the respective conversion elements forming the image sensor that receives the reflected light from the document reading surface and photoelectrically converts the light reception sensitivity and the conversion efficiency vary in manufacturing. In order to simultaneously correct such variations in sensitivity of the image sensor and unevenness of illuminance in the illumination device, shading correction using a white reference plate has been generally performed conventionally. Specifically, a uniform and highly reflective white reference plate is brought into close contact with the platen glass surface to perform image reading, and the correction amount is calculated based on the output of each conversion element of the image sensor. The output of each conversion element is corrected when the document is read.

However, the reading surface of the document may be lifted from the platen glass if the document has creases, wrinkles, curl, or the like. Further, a document automatically conveyed by a so-called automatic document feeder (ADF) may pass through a position lifted from the platen glass. Since the unevenness of the light intensity distribution of the light emitted from the light guide changes depending on the height from the platen glass, the read image of the original floating from the platen glass will not be shaded even if the correction amount on the platen glass surface is used. There is a possibility that unevenness and deterioration of image quality cannot be eliminated.

Therefore, the present invention has been made in view of the above-mentioned problems of the conventional technology, and an object thereof is to provide a lighting device that emits linear light using a rod-shaped light guide body provided with a light source at an end thereof. To reduce the amount of light emitted along the longitudinal direction of the light guide, especially from the vicinity of the end of the light guide provided with the light source, suppress unevenness of the light intensity distribution, and improve the uniformity of the illuminance distribution. is there.

Further, an object of the present invention is to improve uniformity of light intensity distribution in a main scanning direction of a document reading surface in an image reading apparatus that photoelectrically converts reflected light of light applied to the reading surface of a document to form a read image, Even if the original reading surface floats from the platen glass, it is possible to obtain a high-quality read image without uneven density.

Lighting device of the present invention comprises a light guide rod-like formed of a translucent material, and a light source which light is incident from at least one end face in a longitudinal direction of the light guide, the light guide It includes a plurality of reflecting surfaces for reflecting the light incident on the light guide from the light source, and a light emitting surface for emitting light to the outside from the light guide, one of said plurality of reflecting surfaces the first of the reflective surfaces is, the longitudinal direction along comprising intermittently formed discontinuous pattern with a predetermined interval, having a first diffusion reflection pattern of diffuse reflection light, the plurality of reflection among surface, said second reflecting surface is one other different from the first reflecting surface, along the longitudinal direction to compensate for the predetermined interval of the discontinuous pattern of the first diffusion reflection pattern And a second diffuse reflection pattern for diffusely reflecting one continuous light.

In certain embodiments, the second diffusion reflection pattern, over the longitudinal length of said first diffusion reflection pattern has one continuous pattern.

In another embodiment, the width of the first diffuse reflection pattern in the direction orthogonal to the longitudinal direction is larger than the width of the second diffuse reflection pattern in the direction orthogonal to the longitudinal direction.

Moreover, in another embodiment, at least one reflecting surface and another at least one reflecting surface are provided on the same plane. In this case, the first reflecting surface and the second reflecting surface can be provided on the same plane with the groove interposed.

According to another aspect of the present invention, there is provided an image reading device including the above-described illumination device of the present invention and a photoelectric conversion unit that photoelectrically converts light emitted from the illumination device and reflected on a reading surface of a document. To be done.

In one embodiment, the light guide of the lighting device has at least one reflecting surface located farther than the other at least one reflecting surface with respect to the reading optical axis of the light reflected by the reading surface of the document. Is arranged as.

In another embodiment, the light guide of the lighting device is configured such that light emitted from the light emitting surface by being reflected vertically from the at least one reflecting surface and the other at least one reflecting surface is reflected by the reading surface of the original. It is arranged so as to intersect the optical axis for reading light.

ADVANTAGE OF THE INVENTION According to the illuminating device of this invention, at least 1 which has the 1st diffuse reflection pattern which diffuse-reflects light including the discontinuous pattern formed intermittently at a predetermined space|interval along the longitudinal direction of a light guide. It has a reflection surface and a second diffuse reflection pattern provided so as to reduce unevenness in the lengthwise direction of the light guide, that is, variation in the amount of light reflected from the first diffuse reflection pattern and emitted from the light emitting surface. By combining with at least one other reflecting surface, it is possible to improve the uniformity of the illuminance distribution on the document surface to be read.

1 is a schematic perspective view showing the overall configuration of an image reading device according to the present invention. FIG. 3 is a plan view of a reading carriage provided with an illumination device according to the present invention. FIG. 3 is an enlarged sectional view of the reading carriage of FIG. 2. FIG. 3 is an exploded perspective view showing a part of the reading carriage of FIG. 2. FIG. 3 is a perspective view of the light guide body of FIG. 2. Sectional drawing of the light guide of FIG. The bottom view which shows the 1st, 2nd diffuse reflection pattern of the light guide of FIG. The bottom view similar to FIG. 7 which shows the modification of a 1st, 2nd diffuse reflection pattern. The schematic diagram explaining the orientation of the illumination light in the illuminating device of FIG. The schematic diagram explaining the orientation of a light guide. Explanatory drawing of the illuminance distribution of a longitudinal direction by the direct light of a light guide and the reflected light from a reflector. FIG. 6 is a diagram showing a light intensity distribution in the sub-scanning direction due to direct light from a light guide and reflected light from a reflector. Illustration of illuminance distribution in the longitudinal direction (main scanning direction) due to direct light from the light guide FIG. 14 is an explanatory diagram of an illuminance distribution similar to FIG. 13 in a comparative example. FIG. 6 is a diagram showing a light intensity distribution in the sub-scanning direction due to direct light from a light guide.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the attached drawings, similar components are denoted by similar reference numerals throughout the present specification.

FIG. 1 schematically shows the entire configuration of an image reading apparatus including a lighting device of the present preferred embodiment according to the present invention. The image reading apparatus 1 according to the present embodiment is a flat bed type image scanner that constitutes an image reading unit as a part of the image forming apparatus. A platen cover or an automatic document feeder (ADF) (not shown) can be mounted on the upper portion of the image reading apparatus 1 so as to be openable and closable via a hinge mechanism.

The image reading apparatus 1 has a low-height, generally rectangular box-shaped apparatus housing 2, and a platen glass 3 made of a large rectangular transparent glass plate is fixed to the upper surface of the apparatus housing 2. The original to be read is placed on the upper surface of the platen glass 3 with its reading surface facing downward, and closes to the upper surface of the platen glass by closing the platen cover. Alternatively, the document is conveyed while being in contact with the upper surface of the platen glass 3 by the ADF, or while being slightly floating above the upper surface of the platen glass 3 on the platen glass 3.

An image reading mechanism of a reduction optical system including a reading carriage 4 and a reading unit 5 is mounted inside the device housing 2. As will be described later, the reading carriage 4 is provided with an illuminating device of the present invention that irradiates the original reading surface with linear light. In the present embodiment, the illuminating device is arranged so as to emit linear light along the main scanning direction (reading width direction) of the document, that is, the front-back direction in FIG. In the image reading mechanism of this embodiment, the reading carriage 4 and the reading unit 5 are separately configured, but in another embodiment, they may be integrally configured.

Inside the device housing 2, a pair of guide rails 6 extending linearly along the front and rear sides thereof are provided over substantially the entire width of the left and right sides. The reading carriage 4 is disposed immediately below the platen glass 3, and both front and rear ends thereof are supported by the guide rail 6 so as to be able to travel in the left-right direction, that is, in the direction orthogonal to the main scanning direction (sub-scanning direction).

When reading a document placed on the platen glass 3, the reading carriage 4 is driven by a drive motor (not shown) via a wire 7 or the like, and along the guide rail 6, the reading direction of the document, that is, the sub-scanning direction. And move in parallel with the platen glass 3. When reading the document conveyed on the platen glass 3 by the ADF, the reading carriage 4 is held in a stopped state at the reference position shown in FIG. 1, that is, one end position in the sub-scanning direction.

The reading unit 5 includes an image forming optical system 8 including a condensing lens and the like, and a line sensor (not shown) including a large number of light receiving elements such as CCDs or C-MOSs. The reading unit 5 is arranged at the end position in the sub-scanning direction on the side opposite to the reference position of the reading carriage with the condenser lens of the imaging optical system 8 facing the reading carriage 4. The reflected light from the document reading surface illuminated by the illumination device is imaged by the imaging optical system 8 and converted into image data by the line sensor.

2 and 3 schematically show the configuration of the reading carriage 4 of this embodiment. The reading carriage 4 has a carriage unit 11 extending between the guide rails 6 in the main scanning direction, and an illuminating device 12 integrated into the carriage unit. The carriage portion 11 has mounting portions 13 that are movably mounted on the adjacent guide rails 6 at both ends in the longitudinal direction (main scanning direction). The carriage portion 11 is integrally formed of, for example, a metal material and/or a hard synthetic resin material.

The illumination device 12 includes a light source unit, an illumination optical system that irradiates the light from the light source unit onto the document reading surface, and a reflection optical system that guides the reflected light from the document reading surface to the reading unit 5. The illumination optical system converts the light from the light source unit into linear light and emits the light, and a reflector 15 that reflects a part of the light emitted from the light guide toward the document reading surface. Composed of and.

In the carriage portion 11, a groove portion 16 is formed along the longitudinal direction of the light guide body to accommodate the light guide body 14. The light guide body 14 arranged in the groove portion 16 is sandwiched by the fixing member 17 from above and is held by the carriage portion 11 at a predetermined position and orientation. The fixing member 17 is detachably mounted by engaging the elastically deformable claw portion 18 with the hook portion of the carriage portion 11. The reflector 15 is fixed to the carriage unit 11 with its reflection surface facing the light guide body 14 in parallel with the light guide body in the main scanning direction.

The reflection optical system is composed of a plurality of reflection mirrors that guide the reflected light from the document reading surface toward the condenser lens of the reading unit 5. The number and the arrangement of the plurality of reflection mirrors are set so that a predetermined optical path length from the document reading surface to the condenser lens can be obtained. In order to simplify the drawing, FIG. 2 shows a first reflecting mirror 19 that directly reflects the reflected light from the document reading surface, and a second reflecting mirror 20 that reflects the reflected light from the first reflecting mirror. Are exemplarily described.

The light source unit has the two light source units 21 arranged near both ends in the longitudinal direction of the light guide 14 mounted on the carriage unit 11 as described above. As shown in FIG. 4, the light source unit 21 includes a light emitting body 22 which is a light source, a circuit board 23 on which the light emitting body is mounted, and a reflector member 24 which is laminated on the front surface of the circuit board on which the light emitting body 22 is mounted. Have. The light emitting body 22 is a light emitting element including, for example, a white LED chip. A circular hole 24a is formed in the reflector member 24 so that the light emitting body 22 is arranged inside thereof. A heat sink 26 is provided on the back surface of the circuit board 23 via a heat transfer sheet 25.

As shown in FIG. 4, the light source unit 21 is detachably attached to the carriage unit 11 by a clip 27 formed of a U-shaped plate spring when viewed from the side. Each light source unit 21 is arranged so that the reflector member 24 is brought into contact with the adjacent end surface of the light guide body 14. By interposing the reflector member 24 between the circuit board 23 and the end surface of the light guide 14, a gap of a predetermined size can be defined between the end surface of the light guide 14 and the light emitter 22. Accordingly, the light of the light emitting body 22 can be incident from the end surface of the light guide body 14 without leaking to the outside. Furthermore, it is advantageous to vapor-deposit a metal thin film of aluminum, silver, or the like, for example, on the inner surface of the circular hole 24a of the reflector member 24 so as to have a high reflectance because light of the light emitting body 22 is not substantially lost.

In another embodiment, a plurality of light emitters can be arranged in each light source unit 21. In addition to LEDs, various known light emitting elements such as organic or inorganic EL (electric luminescence) and LD (laser diode) can be adopted as the light emitting body 22. When a white LED is used for the light emitting body 22 as in the present embodiment, the line sensor of the reading unit 5 outputs only a monochrome image. When it is desired to output a color image, red, green and blue LEDs may be used corresponding to the three primary colors of RGB. Instead of these three-color LEDs, a white LED and red, green, and blue optical color filters may be combined to read a color image. Alternatively, a 3-line line sensor having RGB color filters may be used.

As shown in FIG. 5, the light guide 14 has a length in the longitudinal direction corresponding to the original reading width of the reading carriage 4, and is a transparent material having a high light-transmitting property such as glass, acrylic resin, or epoxy resin. Thus, it is formed in a uniform cross-sectional shape over the entire length. The light guide 14 has a substantially inverted trapezoidal cross-sectional shape shown in FIG. 6, and has a light emitting surface 31 on the upper surface thereof, and first and second reflecting surfaces 32, 33 on the bottom surface facing the light emitting surface 31 with a narrow groove 34 interposed therebetween. It is provided. The light emitting surface 31 is surface-processed into a lens surface having a constant curvature or a convex curved surface whose curvature changes stepwise or continuously in the circumferential direction. Note that in FIG. 5, in order to show the entire light guide body 14 in the drawing, a part of the central portion of the light guide body 14 is omitted for drawing.

The first and second reflecting surfaces 32 and 33 are symmetrical with respect to the central axis 14a orthogonal to the bottom surface at the center position in the width direction, that is, at the same distance on the same plane with the narrow groove 34 sandwiched from the central axis 14a. It is formed with a width. First and second diffuse reflection patterns 35 and 36, which will be described later, are provided on the first and second reflection surfaces 32 and 33, respectively. Further, the light emitting bodies 22 of each light source unit 21 are arranged so as to be located on the central axis 14a.

The side surface connecting the light emitting surface 31 and the first reflecting surface 32 is a first upper side surface 38 which is continuous with the light emitting surface 31 with the first projecting portion 37 interposed therebetween, and a first lower side surface which is continuous with the first reflecting surface 32. And 39. Similarly, the side surface connecting the light emitting surface 31 and the second reflecting surface 33 has a second upper side surface 42 that is continuous with the light emitting surface 31 with the second protruding portion 41 interposed therebetween and a second side surface that is continuous with the second reflecting surface 33. It is composed of a lower side surface 43. The first and second protrusions 37, 41 are formed over the entire length of the light guide 14.

As shown in FIG. 2, when the light guide 14 is housed in the groove 16 of the carriage unit 11, the fixing member 17 is engaged with the first projecting portion 37 exposed to the upper side so that the light guide 14 can be more reliably secured. Can be held in place and orientation. In addition, a protrusion 44 for positioning the light guide 14 with respect to the carriage 11 is formed on the second protrusion 41 at a predetermined position in the longitudinal direction.

In the present embodiment, the first and second lower side surfaces 39 and 43 are formed so as to spread outward from the first and second reflecting surfaces 32 and 33 with respect to the central axis 14a. On the other hand, the first and second upper side surfaces 38, 42 are formed substantially parallel to the central axis 14a. Thereby, the range in which the light totally reflected by the first and second upper side surfaces 38 and 42 in the light transmitting body 14 is emitted from the light emitting surface 31 to the outside is narrowed inward, that is, so as not to be excessively diffused to the outside. be able to.

FIG. 7 shows the first and second diffuse reflection patterns 35 and 36 formed on the first and second reflection surfaces 32 and 33. The first and second diffuse reflection patterns 35 and 36 are formed by applying a reflective paint having a high reflectance such as white ink to the first and second reflection surfaces 32 and 33 by silk printing or the like. The light incident on the first and second diffuse reflection patterns 35 and 36 in the light guide body 14 is diffusely reflected, that is, reflected at an angle different from the incident angle. As described above, since the first and second reflection surfaces 32 and 33 are on the same plane, silk printing of the first and second diffuse reflection patterns 35 and 36 can be performed in one step using one common plate. It can be carried out. In another embodiment, it is possible to form an uneven surface that also diffusely reflects by subjecting the reflecting surface to etching or molding.

In FIG. 7, the first diffuse reflection pattern 35 has a discontinuous pattern portion 51 in which a plurality of short rectangular patterns 51a are intermittently formed in the range of a predetermined length from both ends of the light guide 14 along the longitudinal direction. , And a continuous pattern portion 52 composed of one long rectangular pattern 52a arranged between them. The short rectangular patterns 51a have the same size and shape, and are arranged linearly at regular intervals. The long rectangular pattern 52a has the same constant width as the short rectangular pattern 51a over the entire length, and is arranged on the same straight line as the discontinuous pattern portion 51. On the other hand, the second diffuse reflection pattern 36 is formed as one long rectangular pattern which is continuous with a constant width over the entire length in the longitudinal direction. In other words, the second diffuse reflection pattern 36 is provided so as to at least partially supplement the gap, that is, the intermittent portion of each rectangular pattern 51a of the discontinuous pattern portion 51.

The light emitted from the light emitting body 22 of each light source unit 21 enters the light guide body 14 from both end surfaces thereof, and propagates in the longitudinal direction while repeating total reflection on the inner surface of the light guide body 14. The light incident on the first and second reflection surfaces 32 and 33 in the light guide 14 is diffused and reflected at the portions where the first and second diffuse reflection patterns 35 and 36 are formed, and the first and second diffuse reflections are performed. Total reflection is performed at the portions where the patterns 35 and 36 are not formed. The light reflected from the first and second diffuse reflection patterns 35 and 36 toward the light emitting surface 31 is totally reflected on the light emitting surface 31 when the incident angle to the light emitting surface is a predetermined critical angle or more. The light is then returned to the inside of the light guide body 14, but if it is smaller than the predetermined critical angle, it is emitted to the outside through the light emitting surface 31. As a result, linear light is emitted from the light emitting surface 31 over substantially the entire length of the light guide body 14.

Generally, when a pattern is formed by silk printing (or other method), the manufacturing tolerance is the same regardless of the size of the pattern. Therefore, the smaller the dimension, the larger the influence of the tolerance. .. In the present embodiment, the width w1 of the first diffuse reflection pattern 35 is set larger than the width w2 of the second diffuse reflection pattern 36. Therefore, in the longitudinal direction of the light guide body 14, that is, the main scanning direction, the influence of the tolerance is reduced in the intensity distribution of the light reflected by the first diffuse reflection pattern 35 and emitted from the light guide body 14, and thus the original reading surface. The variation in the illuminance distribution part is reduced.

The intensity distribution of the emitted light by the first diffuse reflection pattern 35 is not uniform as a whole along the longitudinal direction of the light guide 14. In the range corresponding to the continuous pattern portion 52, the intensity distribution of emitted light is substantially constant. On the other hand, in the range corresponding to the discontinuous pattern portion 51, the light amount of the emitted light decreases at the intermittent portion of the rectangular pattern 51a that is short along the longitudinal direction, and thus the intensity distribution of the emitted light has a wavy shape corresponding to the decrease. Fluctuates.

This wavy fluctuation causes unevenness in the amount of light when the emitted light is viewed at the same height position that is a predetermined distance away from the light guide body along the longitudinal direction of the light guide body 14. Here, the unevenness of the light intensity is a variation in the light intensity, that is, the light intensity due to the difference in the light illuminance distribution. If the original is irradiated with light with a difference in light intensity distribution along the main scanning direction, and the reflected light is continuously read in the sub-scanning direction by a line sensor such as CCD that has uniform sensitivity characteristics, then the data is formed. The formed image has a striped pattern along the main scanning direction. The second diffuse reflection pattern 36 is provided so that the intensity distribution of the emitted light eliminates, reduces, or reduces the variation of the intensity distribution of the emitted light caused by the first diffuse reflection pattern 35.

FIG. 8 shows another embodiment of the first and second diffuse reflection patterns 35 and 36 formed on the first and second reflection surfaces 32 and 33. This embodiment differs from the embodiment of FIG. 7 in that the second diffuse reflection pattern 36 continuous in the longitudinal direction is composed of the width varying pattern portions 53 at both ends and the constant width pattern portion 54 at the center. The width variation pattern portion 53 is provided in the same range as the discontinuous pattern portion 51 of the first diffuse reflection pattern 35 in the longitudinal direction, and is formed so that the width w21 gradually decreases toward the end portion of the light guide 14. There is. The constant width pattern portion 54 has a width w22 which is equal to or smaller than that of the first diffuse reflection pattern 35 over the entire length thereof.

In yet another modification, the width variation pattern portion 53 of FIG. 8 is formed by a plurality of short rectangular patterns which are intermittently arranged along the longitudinal direction, like the discontinuous pattern portion 51 of the first diffuse reflection pattern 35. can do. In that case, the short rectangular patterns are arranged so as to at least partially fill or supplement the gaps, that is, the intermittent portions of the rectangular patterns 51a of the discontinuous pattern portion 51.

The first diffuse reflection pattern 35 is not limited to the configuration shown in FIG. 7 described above. For example, the length of the short rectangular pattern 51a can be set to be longer and/or the interval between the rectangular patterns 51a can be set to be shorter from the end to the center of the light guide 14. Also, the setting range of the discontinuous pattern portion 51 in the longitudinal direction of the light guide body 14 is appropriately set according to the design conditions of the image reading device 1 and the reading carriage 4, the original reading width, the optical characteristics of the reading portion 5, and the like. Or it can be changed.

FIG. 9 shows the arrangement of the illumination optical system and the reflection optical system of the illumination device 12 in the reading carriage 4, and the orientation of the illumination light with which the document on the platen glass 3 is illuminated. In the figure, reference symbol Lx is a reading optical axis of reflected light which is vertically reflected from the reading surface Ds of the document D on the platen glass 3 toward the first reflecting mirror 19. The intersection of the reading optical axis Lx and the upper surface of the platen glass 3 is the reading position Px of the document in the sub scanning direction X. In the figure, R0 is a target illumination area in the sub-scanning direction at a height position Z0 on the upper surface of the platen glass 3, and R1 is a sub-scanning direction at a certain height position Z1 from the upper surface of the platen glass 3. This is the target illumination area.

The light guide 14 and the reflector 15 of the illumination optical system are arranged so that the light emitting surface 31 and the reflecting surface 15a face the document reading position Px, and the reading optical axis Lx passes through an intermediate position between them. At this time, the gap defined between the light guide 14 and the reflector 15 along the main scanning direction Y is the reading opening width Sw of the reflected light reflected from the document reading surface Ds.

The light guide 14 is arranged with its central axis 14a inclined so that the first reflecting surface 32 is located farther from the second reflecting surface 33 with respect to the reading optical axis Lx and closer to the platen glass 3. To do. As a result, the outgoing light L1 from the first diffuse reflection pattern 35 has a smaller incident angle to the document reading surface Ds than the outgoing light L2 from the second diffuse reflection pattern 36. That is, the emission light L1 from the first diffuse reflection pattern 35 has a wider irradiation range on the document reading surface Ds in the sub scanning direction than the emission light L2 from the second diffusion reflection pattern 36. As a result, the variation of the intensity distribution of the emitted light in the main scanning direction due to the discontinuous pattern portion 51 of the first diffuse reflection pattern 35 is compensated by the emitted light from the first diffuse reflection pattern 35, and is more effectively reduced or alleviated. be able to. Further, in another embodiment, a portion 31a of the emission surface 31 from which the light from the first diffuse reflection pattern 35 is emitted is roughened to diffuse the emission light L1 and reduce the intensity distribution in the main scanning direction. Fluctuations can also be suppressed.

Further, the light guide body 14 is arranged with a relatively large inclination so that its central axis 14a intersects the reading optical axis Lx at a position below the platen glass 3. As a result, the outgoing light L2 from the second diffuse reflection pattern 36 has a smaller incident angle to the reading optical axis Lx above the platen glass 3 than the outgoing light L1 from the first diffuse reflection pattern 35. That is, the light L2 emitted from the second diffuse reflection pattern 36 has a wider illumination range on the document reading surface Ds above the platen glass 3 than the light L1 emitted from the first diffuse reflection pattern 35. As a result, the reduction of the light intensity is suppressed in a wider range from the original reading position Px on the platen glass 3 than in the conventional case, and the range in which a clear image is obtained in the height direction Z with respect to the lifting of the original is expanded. be able to.

Further, in the light guide 14, as shown in FIG. 10, the emitted light Lv1 vertically reflected from the first diffuse reflection pattern 35 and the emitted light Lv2 vertically reflected from the second diffuse reflection pattern 36, It is arranged below the platen glass 3 so as to intersect the reading optical axis Lx. Thereby, the illumination range of the document reading surface Ds can be further expanded in the sub-scanning direction X. As a result, the intensity of the reflected light in the reading aperture width Sw can be increased and the intensity distribution can be made more uniform. Therefore, even in the sub-scanning direction, the uniformity of the illuminance distribution can be improved in the effective reading range of the reflected light.

FIG. 11 shows a longitudinal direction of the light guide body 14 in the longitudinal direction of the light guide body 14 by the illumination of the document surface by the direct light of the light guide body 14 and the illumination of the document surface by the reflected light from the reflector 15 in the illumination device 12 of the present embodiment. The illuminance distribution along the scanning direction is shown. In the figure, Id is the intensity distribution of the illumination light by the light directly emitted from the light guide body 14, and Ir is the intensity distribution of the illumination light by the light emitted from the light guide body 14 and reflected by the reflector 15. .. I0 is the intensity distribution of the illumination light at the height Z0 on the upper surface of the platen glass 3 due to both the direct light of the light guide 14 and the reflected light from the reflector 15, and I1 is the illumination at a certain height Z1 from the upper surface of the platen glass 3. This is the light intensity distribution. As shown in the figure, the influence of the discontinuous pattern portion 51 of the first diffuse reflection pattern 35 is reduced in both the light intensity distributions Id and Ir, which is more remarkable particularly in the light intensity distributions I0 and I1. ..

FIG. 12 shows the illuminance distribution along the sub-scanning direction of the light guide 14 due to the illumination of the document surface by the direct light of the light guide body 14 and the illumination of the document surface by the reflected light from the reflector 15. In the figure, J1 is the intensity distribution of the illumination light from the first diffuse reflection pattern 35 of the light guide 14, and J2 is the intensity distribution of the illumination light from the second diffuse reflection pattern 36. J0 is the intensity distribution of the illumination light at the height Z0 of the upper surface of the platen glass 3 formed by both the first diffuse reflection pattern 35 and the second diffuse reflection pattern 36. The distance from the document reading position Px in the sub-scanning direction X is positive on the light guide 14 side. As shown in the figure, it can be seen that the intensity of the illumination light is large in the sub-scanning direction and the intensity distribution exhibits high uniformity in a relatively wide range.

According to another embodiment of the present invention, it is possible to omit the reflector 15 in the illumination device 12 and illuminate the document reading surface only with the light guide 14. FIG. 13 shows the illuminance distribution along the longitudinal direction, that is, the main scanning direction, due to only the direct light of the light guide 14. In the figure, Kd is the intensity distribution of the illumination light on the light emitting surface 31 of the light guide 14, K0 is the intensity distribution of the illumination light at the height Z0 of the upper surface of the platen glass 3, and K1 is a certain height from the upper surface of the platen glass 3. It is the intensity distribution of the illumination light at Z1.

On the other hand, FIG. 14 shows the illuminance distribution along the longitudinal direction in the light guide body of the comparative example in which only the first diffuse reflection pattern 35 is formed on the reflecting surface. In the figure, Md is the intensity distribution of the illumination light on the light emitting surface 31 of the light guide 14, M0 is the intensity distribution of the illumination light at the height Z0 of the upper surface of the platen glass 3, and M1 is a certain height from the upper surface of the platen glass 3. It is the intensity distribution of the illumination light at Z1. As can be seen by comparing FIGS. 13 and 14, by combining the first diffuse reflection pattern 35 and the second diffuse reflection pattern 36, the effect of the discontinuous pattern portion 51 of the first diffuse reflection pattern 35 is effectively reduced. To be done.

FIG. 15 shows a simulation result of the illuminance distribution along the sub-scanning direction of the light guide 14 by illuminating the original surface with the direct light of the light guide 14. In the figure, N1 is the intensity distribution of the illumination light from the first diffuse reflection pattern 35 of the light guide 14, and N2 is the intensity distribution of the illumination light from the second diffuse reflection pattern 36. N0 is the intensity distribution of the illumination light on the upper surface of the platen glass 3 by both the first diffuse reflection pattern 35 and the second diffuse reflection pattern 36. From the figure, even in the illuminating device in which the reflector 15 is omitted, the intensity of the illumination light is large in the sub-scanning direction, and high intensity distribution uniformity can be obtained in a relatively wide range.

Although the present invention has been described above with reference to the preferred embodiments, the present invention is not limited to the above embodiments, and various modifications or changes can be made within the technical scope thereof. Needless to say. For example, the light source unit 21 is arranged only at one end of the light guide 14, and the other end has a reflection surface for reflecting the light propagating in the light guide 14 toward the one end. Can be formed.

1 Image Reading Device 3 Platen Glass 4 Reading Carriage 5 Reading Unit 11 Carriage Unit 12 Illumination Device 14 Light Guide 15 Reflector 19 First Reflecting Mirror 21 Light Source Unit 22 Light Emitting Body 31 Light Emitting Surface 32 First Reflecting Surface 33 Second Reflecting Surface 35 first diffuse reflection pattern 36 second diffuse reflection pattern 51 discontinuous pattern portion 51a short rectangular pattern 52 continuous pattern portion 52a long rectangular pattern

Claims (8)

A rod-shaped light guide formed of a translucent material,
And a light source which light is incident from at least one end face in a longitudinal direction of the light guide,
The light guide body has a plurality of reflection surfaces that reflect light that has entered the light guide body from the light source, and a light emission surface that emits light from the light guide body to the outside.
A first diffuse reflection that diffuse-reflects light, wherein the first reflection surface, which is one of the plurality of reflection surfaces, includes a discontinuous pattern intermittently formed at a predetermined interval along the longitudinal direction. Have a pattern,
Among the plurality of reflecting surfaces, the second reflecting surface is one other different from the first reflecting surface, make up the predetermined interval of the discontinuous pattern of the first diffusion reflection pattern wherein An illumination device having a second diffuse reflection pattern that diffuses and reflects one continuous light along the longitudinal direction. The illumination device according to claim 1, wherein the second diffuse reflection pattern has one continuous pattern over the entire length of the first diffuse reflection pattern in the longitudinal direction. It said first width perpendicular to the longitudinal direction of the diffusion reflection pattern is set forth in claim 1 or 2, characterized in that greater than a width in the direction perpendicular to the longitudinal direction of the second diffusion reflection pattern Lighting equipment. Wherein the first reflecting surface and the second reflecting surface, the illumination device according to any one of claims 1 to 3, characterized in that provided on the same plane. The lighting device according to claim 1, wherein the first reflecting surface and the second reflecting surface are provided on the same plane with a groove interposed therebetween. A lighting device according to any one of claims 1 to 5,
An image reading apparatus comprising: a photoelectric conversion unit that photoelectrically converts light emitted from the illumination device and reflected on a reading surface of a document. The light guide of the illumination device, the first reflecting surface with respect to the reading light axis of the light reflected by the reading surface of the document, arranged so as to be positioned farther than said second reflective surface The image reading device according to claim 6, wherein In the light guide of the illumination device, the light vertically reflected from the first reflecting surface and the second reflecting surface and emitted from the light emitting surface is the light reflected on the reading surface of the document. 8. The image reading device according to claim 6, wherein the image reading device is arranged so as to intersect the reading optical axis.

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