WO2013062010A1 - 照明ユニット及びそれを用いた画像読取装置 - Google Patents
照明ユニット及びそれを用いた画像読取装置 Download PDFInfo
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- WO2013062010A1 WO2013062010A1 PCT/JP2012/077485 JP2012077485W WO2013062010A1 WO 2013062010 A1 WO2013062010 A1 WO 2013062010A1 JP 2012077485 W JP2012077485 W JP 2012077485W WO 2013062010 A1 WO2013062010 A1 WO 2013062010A1
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- light
- scanning direction
- illumination
- light source
- light emitting
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/00976—Arrangements for regulating environment, e.g. removing static electricity
- H04N1/00978—Temperature control
- H04N1/00989—Temperature control by natural convection, e.g. using fins without a fan
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/024—Details of scanning heads ; Means for illuminating the original
- H04N1/028—Details of scanning heads ; Means for illuminating the original for picture information pick-up
- H04N1/02815—Means for illuminating the original, not specific to a particular type of pick-up head
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21K—NON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR
- F21K9/00—Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
- F21K9/60—Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction
- F21K9/61—Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction using light guides
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21K—NON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR
- F21K9/00—Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
- F21K9/60—Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction
- F21K9/62—Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction using mixing chambers, e.g. housings with reflective walls
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21K—NON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR
- F21K9/00—Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
- F21K9/60—Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction
- F21K9/64—Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction using wavelength conversion means distinct or spaced from the light-generating element, e.g. a remote phosphor layer
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21K—NON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR
- F21K9/00—Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
- F21K9/60—Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction
- F21K9/65—Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction specially adapted for changing the characteristics or the distribution of the light, e.g. by adjustment of parts
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
- F21V29/00—Protecting lighting devices from thermal damage; Cooling or heating arrangements specially adapted for lighting devices or systems
- F21V29/50—Cooling arrangements
- F21V29/70—Cooling arrangements characterised by passive heat-dissipating elements, e.g. heat-sinks
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/024—Details of scanning heads ; Means for illuminating the original
- H04N1/028—Details of scanning heads ; Means for illuminating the original for picture information pick-up
- H04N1/02815—Means for illuminating the original, not specific to a particular type of pick-up head
- H04N1/02845—Means for illuminating the original, not specific to a particular type of pick-up head using an elongated light source, e.g. tubular lamp, LED array
- H04N1/0285—Means for illuminating the original, not specific to a particular type of pick-up head using an elongated light source, e.g. tubular lamp, LED array in combination with at least one reflector which is in fixed relation to the light source
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/024—Details of scanning heads ; Means for illuminating the original
- H04N1/028—Details of scanning heads ; Means for illuminating the original for picture information pick-up
- H04N1/02815—Means for illuminating the original, not specific to a particular type of pick-up head
- H04N1/02845—Means for illuminating the original, not specific to a particular type of pick-up head using an elongated light source, e.g. tubular lamp, LED array
- H04N1/02865—Means for illuminating the original, not specific to a particular type of pick-up head using an elongated light source, e.g. tubular lamp, LED array using an array of light sources or a combination of such arrays, e.g. an LED bar
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21W—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO USES OR APPLICATIONS OF LIGHTING DEVICES OR SYSTEMS
- F21W2131/00—Use or application of lighting devices or systems not provided for in codes F21W2102/00-F21W2121/00
- F21W2131/40—Lighting for industrial, commercial, recreational or military use
- F21W2131/403—Lighting for industrial, commercial, recreational or military use for machines
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
- F21Y2103/00—Elongate light sources, e.g. fluorescent tubes
- F21Y2103/10—Elongate light sources, e.g. fluorescent tubes comprising a linear array of point-like light-generating elements
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
- F21Y2115/00—Light-generating elements of semiconductor light sources
- F21Y2115/10—Light-emitting diodes [LED]
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B27/00—Photographic printing apparatus
- G03B27/32—Projection printing apparatus, e.g. enlarger, copying camera
- G03B27/52—Details
- G03B27/54—Lamp housings; Illuminating means
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/04—Apparatus for electrographic processes using a charge pattern for exposing, i.e. imagewise exposure by optically projecting the original image on a photoconductive recording material
- G03G15/04036—Details of illuminating systems, e.g. lamps, reflectors
- G03G15/04045—Details of illuminating systems, e.g. lamps, reflectors for exposing image information provided otherwise than by directly projecting the original image onto the photoconductive recording material, e.g. digital copiers
Definitions
- the present invention relates to an illumination unit for performing linear illumination on an object to be read such as a printed matter or a book document, and an image reading apparatus using the illumination unit.
- the image reading apparatus is an apparatus that reads an entire image by scanning an image at a reading position using a one-dimensional imaging device, and includes an illumination unit that performs illumination when reading a document.
- the image reading apparatus it is necessary to read image information with high accuracy and at high speed, and a configuration of an illumination unit that efficiently and uniformly illuminates a document is disclosed.
- the direction in which the one-dimensional imaging elements are arranged is called a main scanning direction
- the scanning direction is called a sub-scanning direction.
- the direction orthogonal to both the main scanning direction and the sub-scanning direction is referred to as the depth of focus direction in the reading optical system, and is referred to as the illumination depth direction in the illumination unit.
- the document illumination unit disclosed in Patent Document 1 includes point light sources such as a plurality of LEDs (Light Emitting Diodes) arranged in the main scanning direction.
- the light emission direction from the point light source is substantially parallel to the normal direction of the document table on which the document is placed and is opposite to the document table.
- the light from the point light source is guided to the document surface as illumination light by a plurality of reflecting surfaces arranged to face the point light source.
- the condensing system illumination device disclosed in Patent Document 2 has a light source arranged at the focal position of the reflecting surface on the parabola, and two kinds of curvatures for condensing light from the light source and light from the reflecting surface. And a lens.
- the document illumination device disclosed in Patent Document 3 includes LED elements arranged side by side in the main scanning direction, and a reflector that surrounds the LED elements.
- the shape of the reflector is a parabolic quadratic curved surface.
- Patent Document 4 discloses a configuration of a light guide, an illumination unit, and an image reading illumination device that has a large illumination depth and a wide illumination width in the sub-scanning direction and can realize illumination with high illuminance.
- Patent Document 5 discloses an image reading apparatus in which a circuit board provided with a light emitting diode is fixed to a metal support member, and the support member is fixed to a carriage.
- JP 2010-199875 A (FIGS. 1 to 9) Japanese Examined Patent Publication No. 4-15457 (FIGS. 1 to 3) Japanese Patent Laying-Open No. 2005-234108 (FIGS. 1 and 2) JP 2009-272215 A (FIG. 3) Japanese Patent Laying-Open No. 2007-306309 (FIG. 4)
- an image reading apparatus for example, when a reading optical system having a large depth of focus that can clearly form an image of an object to be read having irregularities on the surface, such as a book document or a banknote with a saddle, illumination with a large illumination depth is used. Equipment is needed. This is because, when an uneven original is read, if there is an illuminance distribution in the illumination depth direction, brightness fluctuations occur in the read image.
- Patent Document 1 Since the document illumination unit disclosed in Patent Document 1 is composed of a plurality of reflection surfaces, the angle component of the illumination light beam directed from each reflection surface toward the document surface has a plurality of peaks. As a result, there is a problem that illumination with uniform illuminance is difficult for a document such as a book document whose distance changes from the document table.
- the illumination device disclosed in Patent Document 2 it is possible to bring the illumination light beam close to a parallel ray by a combination of a paraboloid and a lens. Illumination with uniform illumination is relatively easy.
- the illumination device disclosed in the same document is composed of a parabolic reflector and a lens having two types of curvature, the size of the optical system becomes large and it is difficult to reduce the size of the illumination device. There was a problem of cost.
- LED elements are arranged in the main scanning direction, a reflecting plate surrounding the LED elements is provided, and the shape of the reflecting plate is a parabolic quadratic curved surface. For this reason, it is possible to make the illumination light beam approach a parallel light beam, and it is relatively easy to illuminate a document such as a book document with a uniform illuminance on a document whose distance changes from the document table.
- the reflecting plate surrounding the LED element is provided, there is a problem that the optical system becomes large and it is difficult to reduce the size of the lighting device.
- Patent Document 4 shows a configuration in which a parallel light beam is extracted using a light guide.
- Patent Document 5 discloses an image reading apparatus in which a circuit board provided with a light emitting diode is fixed to a metal support member, and the support member is fixed to a carriage. In such a configuration, the heat generated in the light emitting diode is exhausted to the carriage via the support member, so that the temperature of the carriage rises and the temperature of other electronic components provided on the carriage rises. As a result, there has been a problem that performance is degraded.
- An object of the present invention is to provide an illumination unit and an image reading apparatus that suppresses a temperature rise of a light source or the like due to heat generated from the light source, has a large illumination depth, and high illuminance.
- the illumination unit includes a light source in which light emitting elements are arranged in an array in the main scanning direction, A light source substrate that extends in the main scanning direction and includes a light emitting element mounting portion on which the light source is provided and a non-light emitting element mounting portion that extends from the light emitting element mounting portion in a direction perpendicular to the main scanning direction; , A cylindrical paraboloid shape having a curvature with respect to the sub-scanning direction has a shape cut along an axial plane perpendicular to the apex of the cylindrical paraboloid shape along the main scanning direction.
- a parabolic mirror provided at the apex, comprising a fixed portion extending from the apex in the outer direction of the cylindrical paraboloid shape, and irradiating the irradiation area of the irradiated object with light emitted from the light source;
- a heat dissipation plate that extends in the main scanning direction and has a contact portion and a non-contact portion that are in close contact with a surface opposite to the surface on which the light emitting element of the light source substrate is mounted;
- the light source is disposed such that a central axis in a light emission direction is perpendicular to the axial plane, and includes a focal position of the cylindrical paraboloid shape in a light emission region,
- the non-light emitting element mounting portion of the light source substrate is sandwiched between the contact portion of the heat sink and the fixing portion of the parabolic mirror.
- the original since it is possible to illuminate the original with substantially parallel rays, the original can be efficiently illuminated.
- the change in the amount of light is small with respect to the illumination depth direction, a bright image can be obtained even if the distance from the document is large.
- linear illumination with a large illumination depth and a uniform intensity distribution in the sub-scanning direction can be obtained.
- FIG. 1 is a perspective view showing an image reading apparatus according to Embodiment 1 of the present invention. It is a figure which shows the paraboloid shape corresponded in the subscanning direction cross-sectional shape of a cylindrical paraboloid mirror. It is an optical path figure of the sub-scanning direction cross section of the illumination unit by Embodiment 1 of this invention. It is an example of the sub-scanning direction illuminance distribution by Embodiment 1 of this invention. It is sectional drawing of the subscanning direction of the illumination unit by Embodiment 2 of this invention.
- FIG. 4 is a structural diagram of a white LED that obtains white light by mixing with secondary light emission by a yellow fluorescent material using a blue light emitting diode as a light source.
- FIG. 4B is a sectional view taken along line A-A ′ in FIG. It is sectional drawing of the subscanning direction of the illumination unit by Embodiment 3 of this invention. It is a figure which shows the arrangement direction of the LED array by Embodiment 3 of this invention. It is an example of the subscanning direction illuminance distribution by Embodiment 3 of this invention. It is sectional drawing of the subscanning direction of the illumination unit by Embodiment 4 of this invention. It is an example of the sub-scanning direction illuminance distribution by Embodiment 4 of this invention. It is sectional drawing of the illumination unit by Embodiment 5 of this invention.
- Embodiment 5 of this invention It is detail drawing of the cylindrical paraboloid block and light ray by Embodiment 5 of this invention. It is a perspective view which shows the image reading apparatus by Embodiment 6 of this invention. It is an optical path figure of the subscanning direction cross section by Embodiment 6 of this invention. It is an optical path figure of the subscanning direction cross section by Embodiment 7 of this invention. It is an example of the sub-scanning direction illumination intensity distribution by Embodiment 7 of this invention. It is sectional drawing of the illumination unit by Embodiment 8 of this invention. It is sectional drawing of the subscanning direction of the illumination unit by Embodiment 9 of this invention. It is a perspective view of the illumination unit by Embodiment 10 of this invention.
- Embodiment 12 It is a figure which shows the illuminance distribution of the main scanning direction edge part by Embodiment 10 of this invention. It is a perspective view which shows the image reading device by Embodiment 11 of this invention. It is sectional drawing of the subscanning direction of the illumination unit by Embodiment 11 of this invention. It is sectional drawing of the subscanning direction of the illumination unit by Embodiment 12 of this invention. It is a sub-scanning direction sectional view of an image reading device by Embodiment 12 of the present invention.
- FIG. 1 is a perspective view showing an image reading apparatus according to Embodiment 1 of the present invention.
- the image reading apparatus includes a top glass 3, an illumination unit 2, an imaging optical system 1, and the like.
- the top glass 3 is a transparent glass plate for holding a reading object (illuminated body) such as a document 7.
- the illumination unit 2 is a unit that performs linear illumination on the surface of the document 7.
- the imaging optical system 1 is a unit for imaging light from the document 7 on the imaging device 40.
- the direction in which the document 7 is scanned by electrical scanning of the image sensor 40 is referred to as a main scanning direction 11, and the direction in which the document 7 moves relative to the image reading device is referred to as a sub-scanning direction 12.
- a direction perpendicular to the main scanning direction 11 and the sub-scanning direction 12 is a depth direction 13.
- the direction in which the document 7 is separated from the top glass 3 is defined as a positive direction.
- the image reading device moves and scans the document while the document 7 is fixed.
- the document 7 is transported by drum transport or the like while the image reading device is fixed.
- the document may be moved and scanned.
- the imaging optical system 1 is disposed along the optical path from the document 7 to the imaging device 40, and is configured by a lens array, a reduction optical system, and the like.
- the image sensor 40 is a line sensor such as a CMOS (Complementary Metal Oxide Semiconductor), a CCD (Charge Coupled Device Image Sensor), etc., which is mounted on the substrate 4 and includes a photoelectric conversion circuit that performs photoelectric conversion and a driving unit thereof.
- CMOS Complementary Metal Oxide Semiconductor
- CCD Charge Coupled Device Image Sensor
- the illumination unit 2 is installed between the top glass 3 and the imaging optical system 1, irradiates light on the original 7 positioned above the top glass 3, and reads the reading line along the x direction on the surface of the original 7. Line illumination along 8 is performed.
- the illumination unit 2 includes an LED array 220, an LED substrate 230, and the cylindrical parabolic mirror 20.
- the LED array 220 includes LED chips 210 that are LED light sources arranged in a straight line in the main scanning direction.
- the LED substrate 230 is a substrate on which the LED array 220 is mounted.
- the cylindrical parabolic mirror 20 is a cylindrical concave mirror that irradiates illumination light toward the reading line 8 by converting light emitted from the LED array 220 into a substantially parallel light beam.
- the cylindrical parabolic mirror 20 has a curvature in the sub-scanning direction 12 and does not have a curvature in the main scanning direction 11.
- FIG. 2 shows a paraboloid shape corresponding to the cross-sectional shape of the cylindrical parabolic mirror 20 in the sub-scanning direction.
- -22 it is formed only by a semi-cylindrical paraboloid y + 21.
- the z-axis is referred to as a paraboloid axis, and a plane that includes the paraboloid axis and is orthogonal to the y-axis is referred to as a cylindrical paraboloid axis surface 25.
- FIG. 3 shows an optical path diagram of a cross section in the sub-scanning direction according to the first embodiment of the present invention.
- FIG. 3 shows a case where the illumination unit 2 is arranged on one side with respect to the imaging optical axis 101.
- the illumination unit 2 needs to be tilted from the imaging optical axis 101 in order to avoid interference with the imaging optical axis 101.
- the illumination area 104 is an area that extends in the sub-scanning direction 12, and further, the focal depth in order to cope with wrinkles and floating of the book document and the document. Is increased, the illumination area 104 also extends in the depth direction 13.
- the illumination unit 2 needs a substantially parallel light beam having a certain width in the sub-scanning direction 12 and uniform. Furthermore, if a certain amount of width is secured in the sub-scanning direction 12, the illuminance decreases and the reading speed decreases, so it is necessary to improve the utilization efficiency of LED light.
- the LED light emitting region 218 is disposed at a position including the cylindrical paraboloid focal position 23.
- the illumination light beam 103 emitted from the cylindrical paraboloid focal position 23 is reflected by the cylindrical parabolic mirror 20, passes through the top glass 3 as a parallel light beam, and reaches the illumination region 104.
- a central axis 105 in the light emitting direction of the LED is arranged in a direction perpendicular to the cylindrical paraboloid axis surface 25. At the central axis 105 in the LED emission direction, the emission intensity of the LED becomes the maximum value, so that the LED light can be efficiently incident on the cylindrical parabolic mirror 20.
- illumination light close to parallel light can be obtained efficiently, so that the document 7 can be illuminated efficiently and the change in the amount of light can be reduced with respect to the illumination depth direction. Therefore, a bright image can be obtained even if the distance between the document 7 and the top glass 3 is increased.
- FIG. 4 shows the illumination illuminance distribution in the sub-scanning direction according to Embodiment 1 of the present invention.
- FIG. 4A shows the illuminance distribution in the sub-scanning direction when the illumination unit 2 is arranged on one side with respect to the imaging optical axis 101 as shown in FIG.
- the illuminance distribution in the sub-scanning direction is asymmetric with respect to the sub-scanning direction 12, and when the imaging optical axis 101 and the illumination optical axis 102 are shifted due to an assembly error or the like, the imaging light The illuminance on the axis 101 changes.
- FIG. 4A shows the illuminance distribution in the sub-scanning direction when the illumination unit 2 is arranged on one side with respect to the imaging optical axis 101 as shown in FIG.
- the illuminance distribution in the sub-scanning direction is asymmetric with respect to the sub-scanning direction 12, and when the imaging optical axis 101 and the illumination optical axis 102 are shifted
- FIG. 4B shows the illuminance distribution in the sub-scanning direction when the illumination unit 2 is arranged on both sides of the imaging optical axis 101 as shown in FIG. Since the illuminance distribution in the sub-scanning direction is the sum of the illumination light from the illumination units 2 on both sides, the illuminance distribution is symmetric with respect to the sub-scanning direction 12.
- the change in illuminance in the depth direction can be controlled by setting the crossing position of the optical axes of the illumination units on both sides. Note that it is better to set the illuminance distribution of the illumination units on both sides symmetrically with respect to the imaging optical axis 101.
- the focal length f of 20 is suitably about 10 mm to 20 mm.
- FIG. FIG. 5 is a sectional view in the sub-scanning direction of the illumination unit according to Embodiment 2 of the present invention.
- the cylindrical parabolic mirror 20 and the LED substrate 230 are aligned using the positioning pins 231. Thereby, the positional relationship of the cylindrical paraboloid mirror 20 and the LED light emission area
- FIG. 6 is a structural diagram of a white LED that obtains white light by mixing a secondary light emission with a yellow fluorescent material using a blue light emitting diode as a light source.
- the white LED has a depression in the LED package 211, a blue light emitting diode 212 is mounted, and a yellow fluorescent material 213 is filled around the depression to fill the depression.
- a part of the light emitted from the blue light emitting diode 212 is emitted as it is to the outside of the LED package 211 and becomes blue light constituting white light. Further, another part of the light emitted from the blue light emitting diode 212 is absorbed by the yellow fluorescent material, and the yellow fluorescent material emits light in the green to red region.
- the blue light emitting region is the region of the blue light emitting diode 212, and the green to red light emitting region is the entire yellow fluorescent material. That is, the light emitting areas are different between blue light and green to red light.
- the light emitting region of green to red light may be considered as the peripheral portion of the blue light emitting diode 212, and the light emitting region of the blue light emitting diode 212 is used as a reference in order to efficiently convert light of all wavelengths into parallel rays. I came to the conclusion.
- FIG. 7 is a sectional view in the sub-scanning direction of the illumination unit according to Embodiment 3 of the present invention.
- the illumination region 104 needs to be irradiated with light having a wide illuminance distribution in the sub-scanning direction 12 in order to increase the illumination depth.
- the LED array 210 is arranged in the LED array 220 in the direction in which the blue light emitting diode major axis 215 is a cylindrical parabolic mirror axis. It is better to match the surface direction.
- FIG. 9 is a calculation example of the illuminance distribution in the sub-scanning direction on the top glass 3 when the center of the blue light emitting diode 212 is aligned with the cylindrical parabolic mirror focal position 23.
- 9A shows the distribution in the sub-scanning direction
- FIG. 9B shows the illuminance change in the depth direction when the sub-scanning direction is the center of the illumination area.
- FIG. 10 is a sectional view in the sub-scanning direction of the illumination unit according to the fourth embodiment of the present invention.
- the fourth embodiment is configured to further suppress a decrease in illumination illuminance in the illumination depth direction as compared with the third embodiment described above.
- the cylindrical parabolic mirror focal position 23 is configured to coincide with the side of the blue light-emitting diode 212 on the cylindrical parabolic mirror vertex 24 side.
- the light beam emitted from the side of the blue light emitting diode 212 on the side of the cylindrical parabolic mirror vertex 24 is converted into a parallel light beam by the cylindrical parabolic mirror 20 and guided to the irradiation region 104.
- the light beam emitted from the side opposite to the cylindrical parabolic mirror vertex 24 of the blue light-emitting diode 212 becomes a light beam 106 inclined in the sub-scanning direction from the illumination optical axis 102 by the cylindrical parabolic mirror 20, and the irradiation region. 104.
- the illuminance distribution in the sub-scanning direction has a gentle gradient on the + side in the sub-scanning direction as shown in FIG.
- the peak illuminance position of the sub-scanning direction distribution moves in the sub-scanning direction + direction according to the illumination optical axis angle ⁇ . Therefore, by appropriately setting the position of the illumination unit 2 and the illumination optical axis angle ⁇ , each position in the depth direction on the imaging optical axis 101, as shown in FIG. 11A, 0 mm in FIG.
- the illuminance at 4 mm and 8 mm can be matched.
- the illumination illuminance at 8 mm on the top glass can be made substantially equal to the illumination illuminance on the top glass surface (0 mm).
- the illumination illuminance distribution in the sub-scanning direction can be asymmetrically blunted, so the illumination in the sub-scanning direction in the depth direction of blue light and green to red light due to different light emitting regions The amount of change in the illuminance distribution can be further reduced.
- FIG. FIG. 12 is a cross-sectional view of a lighting unit according to Embodiment 5 of the present invention.
- the illumination unit according to Embodiment 5 of the present invention uses a cylindrical paraboloid block 30 that is a solid block molded of a transparent resin or the like as a cylindrical paraboloid mirror.
- the cylindrical paraboloid focal position 23 is in the LED light emitting region 218.
- the light emitted from the LED chip 210 is directed to the cylindrical parabolic mirror 20, is incident on the cylindrical parabolic block 30 from the cylindrical parabolic block incident surface 31, and is internally reflected by the cylindrical parabolic mirror 20.
- the illumination region 104 is irradiated from the cylindrical paraboloid block exit surface 32 as parallel rays.
- FIG. 13 shows a detailed view of the cylindrical paraboloid block 30 and light rays.
- the cylindrical paraboloid block incident surface 31 is arranged parallel to the cylindrical paraboloid axial surface 25 and perpendicular to the central axis 105 of the LED chip 210 in the light emitting direction. Since the cylindrical paraboloid block 30 is molded from a resin or the like, it has a higher refractive index than air. Therefore, the light emitted from the LED light emitting region 218 is refracted in the direction of the central axis 105 of the light emitting direction of the LED chip 210 at the cylindrical paraboloid block entrance surface 31 when entering the cylindrical paraboloid block 30. As a result, the divergence angle of the cylindrical paraboloid block 30 becomes narrow and reaches the cylindrical parabolic mirror 20.
- the cylindrical paraboloid block emission surface 32 is molded into a prism shape composed of a surface substantially parallel to the light beam reflected by the cylindrical parabolic mirror 20 and a surface substantially vertical.
- the light beam can be emitted without changing the angle of the light beam reflected by the cylindrical parabolic mirror 20.
- FIG. FIG. 14 is a perspective view showing an image reading apparatus according to Embodiment 6 of the present invention.
- the image reading apparatus includes a top glass 3, an illumination unit 2, an imaging optical system 1, and the like.
- the top glass 3 is a transparent glass plate for holding a reading object such as a document 7.
- the illumination unit 2 is a unit that performs linear illumination on the surface of the document 7.
- the imaging optical system 1 is a unit for imaging light from the document 7 on the imaging device 40.
- the illumination unit 2 includes the LED array 220, the LED substrate 230, the light guide plate 400, and the cylindrical parabolic mirror 20.
- the LED array 220 includes LED chips 210 that are LED light sources arranged in a straight line in the main scanning direction.
- the LED substrate 230 is a substrate on which the LED array 220 is mounted.
- the light guide plate 400 guides the light emitted from the LED array 220 to the cylindrical parabolic mirror 20.
- the cylindrical parabolic mirror 20 emits illumination light toward the reading line 8 by making light emitted from the light guide plate 400, that is, light emitted from the LED chip 210 through the light guide plate 400 into a substantially parallel light beam. It is a cylindrical concave mirror.
- FIG. 15 shows an optical path diagram of a cross section in the sub-scanning direction according to the sixth embodiment of the present invention.
- the LED light emitting region 218 is disposed close to the light guide plate incident surface 401 that is one end surface of the light guide plate 400.
- the light guide plate 400 is a parallel flat substrate made of a plate-like transparent material extended in the main scanning direction, and the surface facing the surface close to the LED chip 210, that is, the light guide output surface 402 is a cylindrical paraboloid. It is arranged at a position including the surface focal position 23.
- the illumination light beam 103 emitted from the light guide plate emission surface 402 in the vicinity of the cylindrical paraboloid focal point position 23 is reflected by the cylindrical parabolic mirror 20, and the top plate passes through the glass 3 as a substantially parallel light beam.
- the illumination unit 2 generally needs to be tilted from the imaging optical axis 101 in order to avoid interference with the imaging optical axis 101.
- the illumination area 104 is an area that extends in the sub-scanning direction 12, and further, the focal depth in order to cope with wrinkles and floating of the book document and the document. Is increased, the illumination area 104 also extends in the depth direction 13. For this reason, the illumination unit 2 needs a substantially parallel light beam having a certain width in the sub-scanning direction 12 and uniform.
- the cylindrical paraboloid of the light guide plate exit surface 402.
- the illumination width in the sub-scanning direction 12 can be set by a combination of widths in the direction of the plane mirror axis surface.
- the size of the light emitting area of the LED is directly related to the illumination width in the sub-scanning direction 12, but in the sixth embodiment, the size of the sub light emitting area is not related to the size of the light emitting area of the LED.
- the illumination width in the scanning direction can be set.
- the light guide plate 400 even if the light emitting areas are different between blue light and green to red light.
- the directivity can be made uniform, and the illumination width in the sub-scanning direction can be matched. Therefore, the same amount of change can be obtained for blue light and green to red light even when the illumination intensity changes in the depth direction.
- the LED light source is a white LED that obtains white light by mixing with a secondary light emission by a yellow fluorescent material using a blue light emitting diode as a light source, since the light emitting region is different, the blue light and the green to red light
- the light guide plate 400 can make the directivity uniform. Thereby, the amount of change in the illuminance distribution in the sub-scanning direction in the depth direction can be made the same regardless of the color of the light.
- LED substrate 230 and the light guide plate 400 are fixed to the cylindrical parabolic mirror 20 by positioning pins 231 and the light guide plate support portion 405, respectively, and maintain the mutual positional relationship.
- FIG. FIG. 16 shows an optical path diagram in the sub-scanning direction section according to the seventh embodiment of the present invention.
- a scatterer 410 that covers the light guide plate exit surface 402 is disposed in the vicinity of the light guide plate exit surface 402.
- the scatterer 410 has a thin plate shape, and a sheet surface such as a resin is embossed or coated with beads.
- a material obtained by directly embossing or applying beads on the light guide plate exit surface 402 may be employed.
- the light guide plate 400 the light emitted from the LED chip 210 is reflected by the light guide surface 403, and the light intensity is made uniform at the light guide output surface and the directivity of the emitted light is leveled by multiple reflections. Do.
- the light guide distance is short, the number of reflections on the light guide surface 403 is small, and the light emitted from the light guide has a directivity distribution according to the number of reflections. As a result, as shown in FIG.
- the sub-scanning direction illuminance literature has a wavy distribution corresponding to the number of reflections in the sub-scanning direction, and the illumination light spreads slightly in the sub-scanning direction 12. , Proceed in the depth direction 13.
- the illuminance change in the depth direction 13 at the 0 mm position in the sub-scanning direction is also a wavy change. Therefore, even if the original is a blank original whose distance from the top glass 3 to the original surface continuously changes, the illumination illuminance changes non-monotonically. As a result, a density distribution occurs in the read image.
- the scatterer 410 is provided so as to cover the light guide plate exit surface 402 in the vicinity of the light guide plate exit surface 402, so that the directional distribution of the light emitted from the light guide is determined by the scatterer 410. Relaxed or converted to a roughly uniform diffusion distribution. Therefore, the light after passing through the scatterer 410 has a smooth directivity distribution.
- the sub-scanning direction illuminance distribution is not a wavy distribution, and as a result, the illuminance changes monotonously in the depth direction as shown in FIG.
- a blank original whose distance from the top glass 3 to the original surface continuously changes can be read as a monotonous density change. With such a monotonous density change in the depth direction, the density distribution of the original document can be reproduced with a simple correction.
- FIG. FIG. 18 is a cross-sectional view of a lighting unit according to Embodiment 8 of the present invention.
- the cylindrical paraboloid block 30 and the light guide plate 400 which are solid blocks in which the cylindrical paraboloid mirror 20 is molded of a transparent resin or the like, are integrally molded.
- the cylindrical paraboloid focal position 23 is on the light exit surface 402 of the light guide plate 400.
- the light guide emitting surface 402 corresponds to a coupling position between the light guide plate 400 and the cylindrical paraboloid block 30.
- the light guide emitting surface 402 does not exist as a physical surface.
- the light emitted from the LED chip 210 is incident on the light guide plate 400 and is incident on the cylindrical paraboloid block 30 through the light guide plate exit surface 402 toward the cylindrical parabolic mirror 20.
- the light beam internally reflected by the cylindrical paraboloid mirror 20 is applied to the illumination area 104 from the cylindrical paraboloid block emission surface 32 as a substantially parallel light beam.
- the cylindrical paraboloid block emission surface 32 is formed into a prism shape composed of a plane substantially parallel to the light beam reflected by the cylindrical paraboloid mirror 20 and a plane substantially perpendicular to the cylindrical paraboloid mirror 20.
- the light beam can be emitted without changing the angle of the reflected light beam.
- FIG. FIG. 19 is a sectional view in the sub-scanning direction of the illumination unit according to the ninth embodiment of the present invention.
- the LED substrate 230 includes a part or all of the reflection sheet 232 in the region where the LED chip 210 is not mounted on the surface where the LED chip 210 is mounted. With this configuration, a part of the light emitted from the LED chip 210 that strikes the LED substrate 230 such as the illumination light beam 106 from the LED light emitting region that is not at the focal position of the cylindrical parabolic mirror 20 is guided to the illumination region 104. Because it is possible to illuminate the document efficiently.
- the reflection sheet 232 may be any sheet that reflects the wavelength of light emitted from the LED chip 210, and a metal plate such as an aluminum plate, a resin scattering sheet, or the like can be used.
- metal plates such as an aluminum plate, it can also be made to act as a thermal radiation body which thermally radiates the heat_generation
- FIG. FIG. 20 is a perspective view of a lighting unit according to the tenth embodiment of the present invention.
- reflecting mirrors 300 are provided at both ends of the cylindrical parabolic mirror 20 in the main scanning direction.
- the cylindrical parabolic mirror 20 has no curvature in the main scanning direction. Therefore, in the absence of the reflecting mirror 300, the component in the main scanning direction of the light rays emitted from the LED array 220 proceeds without being refracted, and from the end surface of the cylindrical parabolic mirror 20 to the outside of the illumination unit 2. Proceed to.
- the reading line 8 (see FIG. 1) of the document 7 reaches the outside in the main scanning direction, and does not act effectively as illumination light. Therefore, by providing the reflecting mirror 300, by reflecting the light traveling outward in the main scanning direction of the cylindrical parabolic mirror 20, a part of the light is returned to the reading line 8 of the document 7, thereby providing illumination light. It can be used effectively.
- FIG. 21 is a diagram showing the illuminance distribution at the end in the main scanning direction according to the tenth embodiment of the present invention.
- the horizontal axis indicates the position of the LED chip 210a of the corresponding LED array 220 and the end LED 210b disposed at the end in the main scanning direction in the main scanning direction.
- the reflection mirror 300 When there is no reflection mirror 300, the amount of light leaking to the outside of the end LED 210b is large, so that the illuminance in the main scanning direction decreases toward the end inside the end LED 210b.
- the reflection mirror 300 the amount of illumination light at the end in the main scanning direction can be increased by reflecting the light traveling outward in the main scanning direction. As a result, by providing the reflection mirror 300, it is possible to extend the region where the illuminance in the main scanning direction is constant to the vicinity of the LED 210b at the end compared to the case where the reflection mirror 300 is not provided.
- the amount of illumination light at the end in the main scanning direction can be increased, so that the length of the illumination unit in the main scanning direction can be effectively shortened.
- FIG. FIG. 22 is a perspective view showing an image reading apparatus according to Embodiment 11 of the present invention.
- FIG. 23 is a sectional view in the sub-scanning direction of the illumination unit according to the eleventh embodiment of the present invention.
- a heat radiating plate is provided in the illumination unit 2 according to the first embodiment of the present invention.
- a plate-like heat sink 50 formed of a metal such as aluminum on the surface of the LED substrate 230 opposite to the mounting surface of the LED chip 210 is an LED substrate. 230 is arranged in close contact with. Further, the cylindrical parabolic mirror 20, the LED substrate 230, and the heat sink 50 are integrally coupled by a coupling screw 51.
- the image reading apparatus includes an imaging optical system positioning projection 1a, an illumination system positioning projection 50a, an imaging optical system positioning hole 52a, and an illumination system positioning hole 52b.
- the imaging optical system positioning protrusion 1 a is provided in the imaging optical system 1.
- the illumination system positioning protrusions 50 a are provided on the heat sink 50.
- the imaging optical system positioning hole 52 a and the illumination system positioning hole 52 b are provided in the structure support plate 52.
- the imaging optical system positioning projection 1a is fitted into the imaging optical system positioning hole 52a, and the illumination system positioning projection 50a is fitted into the illumination system positioning hole 52b. Thereby, the imaging optical system 1 and the illumination unit 2 are fixed.
- the heat sink 50 is attached in close contact with the LED substrate 230 on the surface of the LED substrate 230 opposite to the mounting surface of the LED chip 210. Thereby, the heat generated in the LED chip 210 is efficiently exhausted to the heat radiating plate 50, and the temperature rise of the LED chip 210 is suppressed. As a result, stable operation of the illumination unit and the image reading apparatus is possible.
- the heat radiating plate 50 is only partly in contact with the housing, and most of the heat radiating plate 50 is away from the housing, so that the heat of the LED chip 210 is not transferred to the housing. Therefore, since the temperature of the light receiving portion provided at the bottom of the housing does not increase, the light receiving portion can receive the image information of the document 7 with high sensitivity.
- heat radiating plate 50 according to the eleventh embodiment of the present invention may be provided in the illumination units 2 according to the second to tenth embodiments of the present invention. Also by this, the same effect can be obtained.
- FIG. 24 and 25 are cross-sectional views in the sub-scanning direction of the illumination unit and the image reading apparatus including the illumination unit according to the twelfth embodiment of the present invention, respectively.
- the image reading apparatus according to the twelfth embodiment includes a top glass 3, an illumination unit 2, a first lens mirror 507, a plane mirror 508, an aperture 509, an opening 510, a second lens mirror 511, and a sensor IC 512. , A first sensor substrate 513a, a second sensor substrate 513b, a signal processing IC (ASIC) 514, an electronic component 515, a housing 516, and a bottom plate 517.
- ASIC signal processing IC
- the top glass 3 is a transparent glass plate that supports a document 7 such as a document or media.
- the illumination unit 2 is the same as the illumination unit 2 according to the eleventh embodiment, and is a unit that performs linear illumination on the surface of the document.
- the illumination unit 2 includes the LED chip 210, the LED substrate 230, the heat sink 50, and the cylindrical parabolic mirror 20. Prepare.
- the LED chip 210 is a light source that emits light.
- the LED substrate 230 is a substrate on which the LED chip 210 is fixed and wiring for supplying current to the LED chip 210 is provided.
- the heat sink 50 receives the heat generated by the LED chip 210 through the LED substrate 230 and radiates it into the air.
- the cylindrical paraboloid mirror 20 has a mirror surface that reflects the light emitted from the LED chip 210 in the direction of the document supported by the top glass 3 into substantially parallel light and reflects it.
- a first lens mirror (also referred to as a first lens) 507 is a concave first lens mirror that receives scattered light from the document 7.
- the plane mirror 508 receives and reflects substantially parallel light from the first lens 507.
- the aperture 509 receives substantially parallel light from the plane mirror 508 and blocks light passing therethrough and restricts light passing therethrough.
- the opening 510 is a portion provided on or near the surface of the aperture 509 and provided with an opening through which light received by the aperture 509 is transmitted.
- a second lens mirror (also referred to as a second lens) 511 is a concave second lens mirror that receives and collects the light passing from the aperture 509.
- a sensor IC 512 receives reflected light from the second lens 511 that has passed through the opening 510 and photoelectrically converts the reflected light, and a sensor IC (Integrated Circuit) having a MOS semiconductor configuration including a driving unit thereof. It is.
- the first sensor substrate 513a and the second sensor substrate 513b are sensor substrates on which the sensor IC 512 is placed, and are arranged side by side in the sub-scanning direction as shown in FIG.
- a signal processing IC (ASIC) 514 is an IC that performs signal processing on the signal photoelectrically converted by the sensor IC 512.
- the electronic component 515 is a capacitor, a resistor, or the like placed on the sensor substrate 513.
- the housing 516 is a hollow member to which an imaging optical system that is an imaging means constituted by a sensor IC and a mirror is fixed.
- the bottom plate 517 is a plate-like member to which a lens and a housing 516 are fixed and closes a bottom opening of the housing 516.
- Light from the LED chip 210 is reflected by the cylindrical parabolic mirror 20 and is irradiated onto the document 7 as substantially parallel light.
- the scattered light reflected by the document 7 is reflected by the concave first lens 507 as collimated light inclined to one side in the sub-scanning direction (leftward in FIG. 25).
- Light from the first lens 507 is reflected by the plane mirror 508 so as to be inclined to one side in the sub-scanning direction.
- the light from the plane mirror 508 is irradiated with a substantially parallel light beam on the window (opening 510) of the aperture 509.
- the light emitted from the window 510 is reflected by being tilted to one side in the sub-scanning direction by the second lens 511 and is incident on the sensor IC 512 for each light beam, so that the image information becomes an inverted image on the light receiving surface of the sensor IC 512. Form an image.
- Scattered light emitted from the left illumination unit 2 and reflected by the original 7 as an irradiated object is inclined to the other side in the sub-scanning direction (leftward in FIG. 25) as shown in FIG. Then, the light enters the sensor IC 512 of the first sensor substrate 513a.
- Scattered light irradiated from the right illumination unit 2 and reflected by the original 7 as the irradiated object follows an optical path in which the optical path shown in FIG. It enters the sensor IC 512 of 513b.
- the optical path incident on the sensor IC 512 mounted on the first sensor substrate 513a and the optical path incident on the sensor IC 512 mounted on the second sensor substrate 513b do not intersect with each other, thereby preventing light beam interference in the optical path. it can.
- the lighting unit 2 described in the eleventh embodiment of the present invention is used. However, the same operation is achieved even if the lighting unit described in the first to tenth embodiments of the present invention is used. An effect is obtained.
- 1 imaging optical system 1a imaging optical system positioning projection, 2 illumination unit, 3 top glass, 4 substrate, 7 original, 8 reading line, 11 main scanning direction, 12 sub-scanning direction, 13 depth direction, 20 cylindrical paraboloid Mirror, 21 semi-cylindrical paraboloid y +, 22 semi-cylindrical paraboloid y-, 23 cylindrical paraboloid focal point, 24 cylindrical paraboloid vertex, 25 cylindrical paraboloid axial surface, 30 cylindrical paraboloid block, 31 Cylindrical paraboloid block entrance surface, 32 Cylindrical paraboloid block exit surface, 40 image sensor, 50 heat sink, 50a illumination system positioning protrusion, 51 coupling screw, 52 structure support plate, 52a imaging optical system positioning hole, 52b Illumination system positioning hole, 101, imaging optical axis, 102 illumination optical axis, 103 illumination light beam, 104 illumination area, 105 central axis of light emission direction, 210 LED 211 LED package 212 Blue light emitting diode 213 Yellow fluorescent substance 214 Blue light emitting diode short
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Abstract
Description
主走査方向に延在する基板であって、前記光源が設けられる発光素子実装部と、前記主走査方向と垂直な方向に前記発光素子実装部から延びる非発光素子実装部とを有する光源基板と、
副走査方向に対して曲率を有する円筒放物面形状が、主走査方向に沿って前記円筒放物面形状の頂点に垂直な軸面で切り取られた形状をなし、前記円筒放物面形状の頂点に設けられ、前記頂点から前記円筒放物面形状の外側方向に延在する固定部を具備し、前記光源から放射された光を被照射体の照射領域に照射する放物面鏡と、
主走査方向に延在し、前記光源基板の前記発光素子が実装された面と反対の面に密着する密着部と非密着部とを有する放熱板とを備え、
前記光源は、光の発光方向の中心軸が前記軸面に垂直で、光の発光領域に前記円筒放物面形状の焦点位置を含むように配置され、
前記光源基板の前記非発光素子実装部が、前記放熱板の前記密着部と前記放物面鏡の前記固定部とで挟持されるものである。
図1は、本発明の実施の形態1による画像読取装置を示す斜視図である。画像読取装置は、天板ガラス3、照明ユニット2、撮像光学系1などで構成される。天板ガラス3は、原稿7などの読取対象物(被照射体)を保持するための透明なガラス板である。照明ユニット2は、原稿7の表面に線状照明を行うユニットである。撮像光学系1は、原稿7からの光を、撮像素子40に結像するためのユニットである。
なお、両側の照明ユニットの照度分布を、撮像光軸101に関して対称に設定するとさらに良い。
図5は、本発明の実施の形態2による照明ユニットの副走査方向断面図である。本発明の実施の形態2では、円筒放物面鏡20とLED基板230を位置決めピン231を用いて、位置あわせをする。これにより、円筒放物面鏡20とLED発光領域218の位置関係を正確に合わせることができる。その結果、照明光の平行性が保たれると共に、照明方向のばらつきも抑制でき、読み取りの明るさばらつきを低減できる。
図6は、青色発光ダイオードを発光源として黄色蛍光物質による2次発光と混合させることにより白色光を得る白色LEDの構造図である。白色LEDは、LEDパッケージ211の中に窪みがあり、青色発光ダイオード212が実装されており、その周囲に窪みを満たすように黄色蛍光物質213が充填されている。青色発光ダイオード212から放出された光は、一部がそのままLEDパッケージ211の外に放出され、白色光を構成する青色光となる。また、青色発光ダイオード212から放出された光の他の一部は、黄色蛍光物質に吸収され、黄色蛍光物質は、緑色から赤色の領域の光を放出する。これらが、白色光を構成する、緑色から赤色の光となる。従って、青色の発光領域は、青色発光ダイオード212の領域となり、緑色から赤色の発光領域は、黄色蛍光物質全域となる。すなわち、青色の光と緑色から赤色の光とで発光領域が異なる。
図10は、本発明の実施の形態4による照明ユニットの副走査方向断面図である。本実施の形態4は、前述の実施の形態3に比べ、さらに照明深度方向の照明照度の低下を抑制する構成である。図10では、円筒放物面鏡焦点位置23を青色発光ダイオード212の円筒放物面鏡頂点24側の辺を一致させる構成にした。
図12は、本発明の実施の形態5による照明ユニットの断面図である。本発明の実施の形態5に係る照明ユニットは、円筒放物面鏡として、透明樹脂等で成型された中実ブロックである円筒放物面ブロック30を用いる。実施の形態1同様、円筒放物面焦点位置23は、LED発光領域218にある。LEDチップ210から放出された光は、円筒放物面鏡20に向け、円筒放物面ブロック入射面31から円筒放物面ブロック30に入射され、円筒放物面鏡20で内面反射し、概略平行光線として、円筒放物面ブロック出射面32から照明領域104に照射される。
図14は、本発明の実施の形態6による画像読取装置を示す斜視図である。画像読取装置は、天板ガラス3、照明ユニット2、撮像光学系1などで構成される。天板ガラス3は、原稿7などの読取対象物を保持するための透明なガラス板である。照明ユニット2は、原稿7の表面に線状照明を行うユニットである。撮像光学系1は、原稿7からの光を、撮像素子40に結像するためのユニットである。
図16に、本発明の実施の形態7による副走査方向断面の光路図を示す。本実施の形態7では、導光板出射面402に近接して、導光板出射面402を覆う散乱体410が配設される。ここで、散乱体410は、薄板状のもので、樹脂等のシート面にエンボス加工、あるいはビーズ塗布加工が施されている。また、散乱体410として、導光板出射面402に直接エンボス加工、あるいはビーズ塗布加工を施したものが採用されても良い。
図18は、本発明の実施の形態8による照明ユニットの断面図である。本発明の実施の形態8による照明ユニットでは、円筒放物面鏡20が透明樹脂等で成型された中実ブロックである円筒放物面ブロック30と導光板400とが一体成型される。実施の形態8と同様、円筒放物面焦点位置23は、導光板400の出射面402にある。ここで、導光体出射面402は、導光板400と円筒放物面ブロック30との結合位置に相当する。円筒放物面ブロック30と導光板400とは上述のように一体成型されているため、導光体出射面402は、物理的な面としては存在しない。LEDチップ210から放出された光は、導光板400に入射され、導光板出射面402を経て円筒放物面鏡20に向け、円筒放物面ブロック30に入射される。円筒放物面鏡20で内面反射した光線は、概略平行光線として、円筒放物面ブロック出射面32から照明領域104に照射される。
図19は、本発明の実施の形態9による照明ユニットの副走査方向断面図である。本発明の実施の形態9では、LED基板230は、LEDチップ210が実装されている面のLEDチップ210が実装されていない領域の一部またはすべての反射シート232を備える。この構成により、LEDチップ210から放射された光の内、円筒放物面鏡20の焦点位置にないLED発光領域からの照明光線106など、LED基板230に当たる光の一部を照明領域104に導くことができるので、原稿を効率よく照明できる。
図20は、本発明の実施の形態10による照明ユニットの斜視図である。実施の形態10による照明ユニットでは、円筒放物面鏡20の主走査方向両端に反射ミラー300が設けられる。円筒放物面鏡20は、主走査方向には曲率を持たない。そのため、反射ミラー300がない場合、LEDアレイ220から放出された光線のうち主走査方向の成分は屈折せずに進行し、円筒放物面鏡20の主走査方向端面から、照明ユニット2の外側に進行する。その結果、原稿7の読み取りライン8(図1参照)の主走査方向外側に到達し、照明光として有効に作用しないことになる。そこで、反射ミラー300を設けることにより、円筒放物面鏡20の主走査方向外側に進行する光を反射することで、原稿7の読み取りライン8に一部の光を戻すことで、照明光として有効に使用することができる。
図22は、本発明の実施の形態11による画像読取装置を示す斜視図である。また、図23は、本発明の実施の形態11による照明ユニットの副走査方向断面図である。本発明の実施の形態11による画像読取装置は、本発明の実施の形態1の照明ユニット2に放熱板を設けたものである。本実施の形態では、図22、図23に示すように、LED基板230のLEDチップ210の実装面とは反対の面にアルミニウムなどの金属で形成された板状の放熱板50が、LED基板230に密着して配置されている。また、円筒放物面鏡20、LED基板230及び放熱板50は結合用ネジ51にて一体に結合している。
図24及び図25は、それぞれ、本発明の実施の形態12による照明ユニット及びこれを備える画像読取装置の副走査方向断面図である。実施の形態12による画像読取装置は、天板ガラス3と、照明ユニット2と、第1レンズミラー507と、平面鏡508と、アパーチャー509と、開口部510と、第2レンズミラー511と、センサIC512と、第1センサ基板513aと、第2センサ基板513bと、信号処理IC(ASIC)514と、電子部品515と、筐体516と、底板517とを備える。
Claims (13)
- 発光素子が主走査方向にアレイ状に配置された光源と、
主走査方向に延在する基板であって、前記光源が設けられる発光素子実装部と、前記主走査方向と垂直な方向に前記発光素子実装部から延びる非発光素子実装部とを有する光源基板と、
副走査方向に対して曲率を有する円筒放物面形状が、主走査方向に沿って前記円筒放物面形状の頂点に垂直な軸面で切り取られた形状をなし、前記円筒放物面形状の頂点に設けられ、前記頂点から前記円筒放物面形状の外側方向に延在する固定部を具備し、前記光源から放射された光を被照射体の照射領域に照射する放物面鏡と、
主走査方向に延在し、前記光源基板の前記発光素子が実装された面と反対の面に密着する密着部と非密着部とを有する放熱板とを備え、
前記光源は、光の発光方向の中心軸が前記軸面に垂直で、光の発光領域に前記円筒放物面形状の焦点位置を含むように配置され、
前記光源基板の前記非発光素子実装部が、前記放熱板の前記密着部と前記放物面鏡の前記固定部とで挟持される照明ユニット。 - 前記光源は、前記軸面に平行に配置された前記光源基板の前記放物面鏡に対向する面に設けられ、
前記光源基板は位置決めピンにより前記放物面鏡の前記固定部に固定されている請求項1に記載の照明ユニット。 - 前記光源は、青色発光ダイオードを前記発光素子として黄色蛍光物質による2次発光と混合させ白色を得る白色LEDであり、
前記青色発光ダイオードのチップの短軸方向が主走査方向と平行になるように配置した請求項1又は請求項2に記載の照明ユニット。 - 前記光源は、青色発光ダイオードを前記発光素子として黄色蛍光物質による2次発光と混合させ白色を得る白色LEDであり、
前記青色発光ダイオードのチップの前記放物面鏡の頂点側の辺を、前記放物面鏡の焦点位置と一致させるように配置した請求項1乃至請求項3のいずれか1項に記載の照明ユニット。 - 前記放物面鏡を中実の透明材料で構成した請求項1乃至請求項4のいずれか1項に記載の照明ユニット。
- 前記光源から放射された光を導くための導光板を備え、
前記放物面鏡は、前記光源から放射されて前記導光板を介した光を被照射体の照明領域に照射する請求項1に記載の照明ユニット。 - 前記導光板と前記放物面鏡との間に光を散乱する散乱体を設けた請求項6に記載の照明ユニット。
- 前記放物面鏡を中実の透明材料で構成し、前記導光板と一体化した請求項6に記載の照明ユニット。
- 前記光源基板の前記光源実装面であって、前記光源の実装部以外の部分に反射シートを設けた請求項1乃至請求項8のいずれか1項に記載の照明ユニット。
- 前記放物面鏡の主走査方向の端部に、反射鏡を設けた請求項1乃至請求項9のいずれか1項に記載の照明ユニット。
- 前記放熱板の前記非密着部は、前記光源基板の前記発光素子実装部とは反対側の端部側から、前記密着部に連続して、主走査方向と直行する方向に延在している請求項1乃至請求項10のいずれか1項に記載の照明ユニット。
- 請求項1乃至請求項11のいずれか1項に記載の前記照明ユニットと、
前記被照射体の前記照明領域において原稿で反射した光の散乱光を入射し、主走査方向に延在する受光部に前記被照射体の像を結像する撮像光学系と、
前記照明ユニット、前記撮像光学系および前記受光部を収納又は保持する筐体とを備え、
主走査方向に直交する副走査方向に相対的に原稿を走査し、前記被照射体の画像情報を得る画像読取装置において、
前記照明ユニットを、主走査方向に沿って前記撮像光学系の光軸の両側に配置した画像読取装置。 - 前記照明ユニットから射出される光の照射方向が、前記撮像光学系の光軸に対して対称になるように前記照明ユニットを配置した請求項12に記載の画像読取装置。
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