JPH06217083A - Original reader - Google Patents

Abstract

PURPOSE:To reduce the arrangement space of a lighting source between the glass plate of a reading stand and a reading unit, and to uniformly and stably illuminate the reading part of an original. CONSTITUTION:In an original reader in which an original 1 on a glass plate 2 is lineally illuminated from a lower part and the linear image of the original 1 is image-formed o the light receiving face of an image sensor 8 by image pickup optical systems 6 and 7 arranged at the lower part of the glass plate 2, a long EL(electro-luminesense) element 31 is used as the lighting source, a prism array 41 in which plural long micro-prisms are arrayed in parallel to the EL element 31, and integrated like a plate is used as a light guide which guides lights from the EL element 31 obliquely to the width direction, and converges the lights to a reading part A, and the EL element 31 and the prism array 41 overlapped on the EL element 31 are disposed just under the glass plate 2 in parallel to the glass plate 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading device in a facsimile machine, a copying machine, an image scanner or the like, and more particularly to an improvement of a light source system for linearly illuminating a read part of a document.

[0002]

2. Description of the Related Art FIG. 6 schematically shows a conventional typical configuration of a document reading apparatus. In FIG. 6, the transparent glass plate 2
Is a reading table, and the original 1 is placed on the upper surface of the glass plate 2 and fed in the arrow direction (sub-scanning). Below the glass plate 2, an LED array 32, which is a linear light source for illuminating the original 1, and a reading unit 5 are arranged.

The LED array 32 is an original 1 on the glass plate 2.
In order to linearly illuminate the reading point A portion in the main scanning direction orthogonal to the sub-scanning direction and not to interfere with the optical system of the reading unit 5, the illumination optical axis of the LED array 32 is directed obliquely upward. The substrate is installed obliquely with respect to the glass plate 2. In the reading unit 5, an imaging optical system including a mirror 6 and a lens 7 for capturing a reflected light from the illuminated original 1 and forming a linear image of the original 1, and an image forming surface of the lens 7 are arranged. A one-dimensional image sensor 8 such as an installed CCD is incorporated.

The linear image of the original 1 is scanned by the self-scanning of the image sensor 8, and the original 1 is fed in the arrow direction by a sub-scanning mechanism (not shown). A two-dimensional image of the document 1 is read by the main scanning and the sub scanning, and the image information is output from the image sensor 8 as an electric signal.

A document reading apparatus using a fluorescent lamp 33 as an illumination light source as shown in FIG. 7 is also known. Also in this case, the reading point A is linearly illuminated by guiding the light from the fluorescent lamp 33 obliquely upward so as not to interfere with the optical system of the reading unit 5.

[0006]

LED as an illumination light source
In the conventional document reading apparatus using the array 32 (FIG. 6),
As described above, since the substrate of the LED array 32 has to be installed obliquely with respect to the glass plate 2, the size of the installation space of the light source in the vertical direction (direction of arrow B in the figure) becomes relatively large, and the device This has been an obstacle to the thinning and downsizing of the.

In a conventional document reading apparatus using a fluorescent lamp 33 as an illumination light source (FIG. 7), since the diameter of the fluorescent lamp 33 itself is large, the vertical direction of the light source installation space (direction of arrow B in the figure) is also present. The size is relatively large, which is an obstacle to making the device thinner and smaller.

In a device using the LED array 32 as a light source, the original 1 cannot be uniformly illuminated due to variations in the amount of light of a large number of LED chips in the array, and the read image quality deteriorates. was there.

Further, a mercury-based fluorescent lamp as a light source has various problems such as temperature characteristics, a life and a rising characteristic, and a xenon-based fluorescent lamp as a light source has problems such as infrared emission. . In any case, it is necessary to design the device in consideration of these, and there is a problem that the device becomes complicated.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to reduce the installation space of the illumination light source between the glass plate of the reading stand and the reading unit (the thinning of the apparatus and An object of the present invention is to provide a document reading device capable of easily downsizing and illuminating a reading portion of a document uniformly and stably (improving reading image quality).

[0011]

According to a first aspect of the present invention, an original on a transparent glass plate is illuminated linearly from below the glass plate, and an image pickup optical system arranged below the glass plate is used for the above-mentioned purpose. In a document reading apparatus for forming a linear image of a document on a light receiving surface of an image sensor, a long EL (electro luminescence) element is used as the illumination light source, and light from the EL element is oblique in its width direction. As a light guide for guiding the light to the reading portion and condensing it on the reading portion, a prism array formed by arranging a number of long minute prisms in parallel with the EL element and integrating them in a flat plate shape is used, and the prism is provided on the EL element. A stack of the arrays was placed directly below the glass plate in parallel with it.

In the second invention, a long EL element is used as the illumination light source, and a long light guide is provided for guiding light from the EL element obliquely in the width direction and condensing the light on the reading portion. The prism in which the above-mentioned prism was superposed on the above-mentioned EL element was arranged directly below the glass plate such that the EL element and the glass plate were parallel to each other.

In the third invention, a long EL element is used as the illumination light source, and a long light guide is provided for guiding light from the EL element obliquely in the width direction and condensing the light on the reading portion. The cylindrical concave lens of No. 1 was used, and the cylindrical concave lens stacked on the EL element was arranged directly below the glass plate such that the EL element and the glass plate were parallel to each other.

[0014]

The emission characteristics of the EL element are extremely stable and uniform, and the variation in the amount of light emitted from each part of a long EL element is extremely small. Light from the EL element is guided in an oblique direction by the light guide including the prism array or prism or cylindrical concave lens, and is condensed on the reading portion of the original on the glass plate.

[0015]

1 and 2 show the schematic construction of an embodiment of the first invention. As shown in both figures, the document 1 is fed in the direction of the arrow along the upper surface of the transparent glass plate 2 which is the reading table (sub scanning). Immediately below this glass plate 2 is E which will be described in detail below.
The L element 31 and the prism array 41 are arranged, and the reading unit 5 is further arranged below them. The configuration of the reading unit 5 is basically the same as the conventional one, and an image of the illuminated linear portion of the document 1 is formed on the light receiving surface of the image sensor 8 by the mirror 6 and the lens 7.

The EL element 31 is a long element having a length substantially equal to the length of the linear illumination portion of the original 1, and is joined to the lower surface of the glass plate 2 with a prism array 41 interposed therebetween. By the way, as shown in FIG. 8, when the EL element 31 is directly bonded to the lower surface of the glass plate 2, the light from the element is emitted almost right above, and therefore the reading at a position deviated to the side of the EL element 31 is performed. Almost no illumination light hits the portion A (the EL element 31 is arranged immediately below the reading portion A,
This cannot be done because it interferes with the optical system of the reading unit 5).

Therefore, in the present invention, the prism array 41 is interposed between the EL element 31 and the glass plate 2.
As shown in detail in FIG. 2, the prism array 41 includes a large number of elongated micro prisms E on a single transparent optical glass plate.
The elements are arranged in parallel with the L element 31 and integrated, and the angle of the inclined surface of each micro prism is sequentially increased from left to right, and the light from the EL element 31 is directed leftward toward the reading portion A. Bend to, and focus the light near the reading portion A with an appropriate irradiation width. It can be said that the prism array 41 is a Fresnel lens instead of a cylindrical lens. Since the flat prism array 41 and the EL element 31 are superposed and bonded to the lower surface of the glass plate 2 in this manner, the installation dimension of the light source system in the vertical direction (arrow B in the figure) becomes extremely small. As shown in FIG. 1, the glass plate 2 and the reading unit 5 can be arranged close to each other, and the device can be thinned and downsized.

FIG. 3 shows the main structure of the second embodiment of the invention. The structure of the light guide is different from that of the embodiment of FIG. 1, and here, a single long prism 42 is superposed on and bonded to the light emitting surface of the EL element 31. The combined component of the EL element 31 and the prism 42 is arranged immediately below the glass plate 2 so that the EL element 31 is parallel to the glass plate 2.
Almost in the same manner as in the above-described embodiment, the light is bent to the left by the optical prism 42 from the EL element 31 and is condensed near the reading portion A with an appropriate irradiation width. The installation size of this light source system is slightly larger than that of the embodiment shown in FIG. 1, but is much smaller than the conventional one.

FIG. 4 shows the essential structure of the third embodiment of the invention. This is similar to the embodiment of FIG. 3, and the inclined surface of the prism 42 is a concave curved surface in order to improve the light-collecting characteristics of the prism 42 in FIG. That is, the light guide of the embodiment of FIG. 4 is the cylindrical concave lens 43.

Although the reduction lens system is used as the image pickup optical system in all of the above three embodiments, the present invention is not limited to this, and is applicable to a document reading apparatus using a contact type image pickup optical system. The present invention can also be applied to this case, and in that case, the same operational effect as that of the above-described embodiment can be obtained.

Next, the reading unit 5 in the apparatus shown in FIG.
FIG. 5 showing a modified example will be described. In the reading unit 5 of FIG. 5, a dew condensation preventing coat 11 is applied to the surface of the mirror 6. Further, the lens 7 and the image sensor 8 are attached to the lens barrel 9
The cover glass 10 is provided in contact with the front surface of the lens 7, and the front surface of the cover glass 10 (the surface opposite to the lens 7) is provided with the dew condensation preventing coat 11. As the dew condensation preventing coat 11, for example, a moisture absorbing type anti-fog polymer is used. A dew condensation preventing coat may be formed on the glass plate 2 if necessary. According to this configuration, even if the ambient temperature of the apparatus rapidly rises from a low temperature, the dew condensation preventing coat 11 is formed on the surfaces of the mirror 6 and the cover glass 10, so that dew condensation does not occur in the main optical path of the imaging optical system. Does not happen. In a conventional apparatus that does not take measures against such dew condensation, dew condensation occurs in the main optical path of the optical system due to a sharp rise in the ambient temperature, and the image of the original image formed on the image sensor 8 becomes dark and the image is disturbed. Occurs and the read image quality deteriorates. By the way, it is possible to attach a heater or a hot air supply mechanism as a measure against dew condensation,
As compared with the measure for forming the dew condensation preventing coat 11 as shown in FIG. 5, it is a large-scale and complicated measure, and the dew condensation preventing coat is superior in terms of downsizing of the device and cost reduction.

[0022]

As described above in detail, in the present invention, since the long EL element is used as the light source for illuminating the read original, the original reading portion is illuminated with stable and even light. Therefore, the read image quality is improved. Also,
Since the light from the EL element is guided to the reading part by using a light guide consisting of a prism array or prism or a cylindrical concave lens, the vertical dimension of the installation space of the light source system including this light guide and the EL element is significantly larger than the conventional size. As a result, the device can be downsized and thinned easily.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a document reading device according to an embodiment of the first invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a schematic configuration diagram of only a main part of a document reading apparatus according to an embodiment of the second invention.

FIG. 4 is a schematic configuration diagram of only a main part of a document reading apparatus according to an embodiment of the third invention.

5 is a schematic configuration diagram showing a modified example of the reading unit in FIG.

FIG. 6 is a schematic configuration diagram of a conventional document reading device.

FIG. 7 is a schematic configuration diagram of only a main part of another conventional document reading apparatus.

FIG. 8 is an explanatory view of light distribution when an EL element is directly bonded to a glass plate.

[Explanation of symbols]

 1 original 2 glass plate 5 reading unit 6 mirror 7 lens 8 image sensor 9 lens barrel 10 cover glass 11 condensation prevention coat 31 EL element 32 LED array 33 fluorescent lamp 41 prism array 42 prism 43 cylindrical concave lens

Claims (3)

[Claims] 1. A document on a transparent glass plate is linearly illuminated from below the glass plate, and a linear image of the document is received by an image sensor by an image pickup optical system arranged below the glass plate. In a document reading apparatus that forms an image on a surface, a long EL element is used as the illumination light source, and a large number of light guides are provided to guide light from the EL element obliquely in the width direction thereof and focus it on a reading portion. The prism array formed by arranging the long microprisms in parallel with the EL element and integrating them in a flat plate shape is used.
An original reading device characterized in that an element on which the prism array is superposed is arranged directly below the glass plate in parallel therewith. 2. An original on a transparent glass plate is linearly illuminated from below the glass plate, and a linear image of the original is received by an image sensor by an image pickup optical system arranged below the glass plate. In a document reading device that forms an image on a surface, a long EL element is used as the illumination light source, and a long light guide is provided for guiding light from the EL element obliquely in the width direction and condensing the light on a reading portion. A document reading apparatus, wherein a prism having a length is used, and a stack of the prisms on the EL element is arranged directly below the glass plate such that the EL element and the glass plate are parallel to each other. 3. An original document on a transparent glass plate is linearly illuminated from under the glass plate, and a linear image of the original document is received by an image sensor by an imaging optical system arranged below the glass plate. In a document reading device that forms an image on a surface, a long EL element is used as the illumination light source, and a long light guide is provided for guiding light from the EL element obliquely in the width direction and condensing the light on a reading portion. Document reading, characterized in that a scaled cylindrical concave lens is used, and a stack of the cylindrical concave lens on the EL element is arranged directly below the glass plate so that the EL element and the glass plate are parallel to each other. apparatus.