JP2001007990A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader which irradiates a large-sized document with a sufficient quantity of light to read an image of high quality. SOLUTION: This image reader is provided with a target glass 1 provided in a paper feeding line where a document is sent, cold cathode-ray tubes 2 which are arranged zigzag under the target glass 1 with a scanning axis S of the read position of reflected light between them and have end parts superposed one over the other, light source reflection mirrors 3 which are so arranged that they face cold cathode-ray rubes 2 with the scanning axis S between them, a lens 4 which couples light thrown to the image face of the document on the target glass 1, and a CCD image sensor 5 as a line image sensor which reads an image coupled by the lens 4. An effective irradiation range of the cold cathode-ray tubes 2 is used to irradiate the document zigzag with light from both sides of the scanning axis S, and thus, the image face of even a large-sized document is irradiated with a sufficient quantity of light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus used for reading a large-size sheet, and more particularly, to an image reading apparatus having a light source for reading a high-quality image.

[0002]

2. Description of the Related Art An image reading device provided in a copier or the like is a
Basically, a line image sensor in which photoelectric conversion elements such as D are arranged in a line in the main scanning direction is provided, and an image is read by the scanning. FIG. 5 is a schematic view of a reading optical system of a conventional image reading apparatus viewed in a main scanning direction.

[0005] In FIG. 5, an image forming apparatus includes a paper feed path for feeding a document (not shown) with a read image surface facing downward in a direction indicated by an arrow in FIG. And an image reading unit for scanning and reading an image of the original to be read. The image reading unit includes a light source 1
There is provided an optical system for irradiating the image surface of the document on the target glass 11 from 2 with the light, coupling the reflected light by a lens 13 and making it incident on a line image sensor 14.

Here, as the light source 12, there is a cold cathode tube or the like. A cold cathode tube having a length of about A4 size to A3 size in the longitudinal direction has been developed. Further, since the cold-cathode tube is resistant to low temperatures and has a light amount of 40,000 to 100,000 lux, which is larger than that of an LED or a fluorescent lamp, it is suitable as a light source of an image reading apparatus of a normal size such as A3 size.

[0005]

However, in the case of realizing an image reading apparatus for a large original such as A0 size, the cold-cathode tube has only a length corresponding to A3 size. Can not be used as it is.

At this time, even when the cold cathode tubes are arranged in a line in the main scanning direction and used in a continuous state, the cold cathode tubes are provided with socket portions at both ends, and the light source has an effective irradiation range. For this reason, the amount of light in the connected portion of the adjacent cold cathode tubes becomes insufficient.

In view of the above, the present invention provides an image reading apparatus which irradiates a sufficient amount of light to a large-sized document and enables high-quality image reading.

[0008]

In order to solve this problem, the present invention provides a staggered arrangement of light sources of an image forming apparatus such that the ends of the light sources overlap each other with a scanning axis interposed therebetween. The light source irradiates the image surface of the document with light.

Thus, light is radiated to the zigzag from both sides of the scanning axis, and a sufficient amount of light can be obtained even for a large-sized original, so that a high-quality image can be read.

[0010]

According to a first aspect of the present invention, there is provided an image reading apparatus for irradiating an image surface of a document with light from a light source and reading the reflected light, wherein the light source sandwiches the ends of the reading position across the reading position. This is an image reading device characterized by being staggered and superimposed, irradiating the staggered light from both sides of the reading position with respect to the image surface of the original, and using a relatively small light source. A sufficient amount of light can be applied to the image surface of the original. As a result, it is possible to apply a cold-cathode tube or the like, which is relatively small and resistant to low temperatures and has a large amount of light, to an image reading apparatus used for reading large-sized paper.

According to a second aspect of the present invention, there is provided the image reading apparatus according to the first aspect, wherein an end of the light source is overlapped to a part of an effective irradiation range of the light source. By irradiating the other light source with a small amount of light outside the effective irradiation range at the end of one light source, a sufficient amount of light can be given to the image surface of the document.

According to a third aspect of the present invention, there is provided the image reading apparatus according to the first or second aspect, wherein an end of the light source is covered with a non-light transmitting mask.
A uniform light amount can be obtained using only the stable portion by covering the transient portion where the amount of light emitted from the end of the light source is unstable.

According to a fourth aspect of the present invention, the outer surface of the mask is light-reflective, and a light reflector is provided at a position facing the light source except for the mask portion with the reading position interposed therebetween. The image reading apparatus according to claim 3, wherein the light source and the light-reflective mask outer surface at a position facing one light source face each other with the scanning axis of the light source interposed therebetween. Light can be irradiated to the image surface of the original from both sides of the original, and it is possible to prevent shadows from appearing even on an original having irregularities.

According to a fifth aspect of the present invention, there is provided the image reading apparatus according to the third or fourth aspect, wherein the outer surface of the mask is white, and the light from the light source is reflected by the white mask. Light can be applied to the image surface of the document from both sides of the position opposing the scanning axis.

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG.

(Embodiment) FIG. 1 is a schematic view of a reading optical system of an image reading apparatus according to an embodiment of the present invention as viewed from a target glass surface, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG. 1 is a diagram showing details of a B portion, (a) is a diagram showing a state where a cap is attached, (b) is a diagram showing a state where a cap is removed, and FIG. 4 is a light intensity distribution of a cold cathode tube. FIG.

As shown in FIGS. 1 and 2, an image reading apparatus according to an embodiment of the present invention includes a target glass 1 provided in a paper feed path for feeding a document, and an image reading position below the target glass 1. A cold-cathode tube 2 as a light source staggered with the scanning axis S interposed therebetween, a light-source reflecting mirror 3 as a light reflector disposed at a position facing the cold-cathode tube 2 with the scanning axis S interposed, and a target glass A lens 4 for combining light irradiated on the image surface of the original on
And a CCD image sensor 5 as a line image sensor for reading an image combined by the above.

At both ends of the cold cathode tube 2, sockets 2 for fixing the cold cathode tube 2 to the device and supplying power to the cold cathode tube 2 are provided.
1 (see FIG. 3B). The area from the root of the socket 21 of the cold-cathode tube 2 to a region about 5 mm inside is the effective irradiation range in which a uniform light amount can be obtained. The area from the root of the socket 21 to about 5 mm inside is a transition area, and is a range in which the amount of irradiated light is unstable (see FIG. 4).

When the cold cathode tubes 2 are arranged in a staggered manner with the scanning axis S interposed therebetween, only a part of the socket 21 at the end of the cold cathode tube 2 can be overlapped. 2 are arranged such that the effective irradiation ranges of the respective cold cathode tubes 2 partially overlap. This is to mutually complement the insufficient light amount due to the sockets 21 at both ends of the cold-cathode tube 2 that do not irradiate light and the transient portion where the irradiating light amount is unstable. In addition, in addition to the illustrated example, a plurality of cold cathode tubes 2 may be arranged so as to overlap with each other so that light can be irradiated substantially uniformly on the scanning axis S.

Further, the end of the cold cathode tube 2 of the present embodiment is covered with the socket 21, the transient portion and a part of the effective irradiation range by the cap 6 as a non-light transmitting mask. Then, the end face 61 of the cap 6 on the effective irradiation range side of each of the cold cathode tubes 2 staggered with the scanning axis S interposed therebetween.
(See FIG. 3A). Since the width of the transition area varies depending on the product, the cold-cathode tube 2 covers the transient section where the irradiated light amount is unstable, and attempts to obtain a uniform light amount using only the stable section. (See FIG. 4).

That is, by covering the portion from the socket 21 to a part of the area defined as the effective irradiation range in the specification of the product with the cap 6 that does not transmit light, and by arranging the end faces 61 in a staggered manner, the scanning axis is changed. Cold cathode tube 2 in S direction
Are arranged in a line, and it is possible to irradiate an image on the scanning axis S with a uniform amount of light.

The light source reflection mirror 3 reflects light of the cold cathode tube 2 from a position opposite to the cold cathode tube 2 with the scanning axis S interposed therebetween, and the light source reflection mirror 3 and the cold cathode tube 2 form an image of a document. Light is emitted from both sides of the scanning axis S. Light may be irradiated from one side of the scanning axis S on a document directly written or printed on the original, but the scanning axis S may be applied to a document having irregularities such as a photograph or paper attached to the original.
When light is irradiated from one side, a shadow is generated. Light is emitted from both sides of the scanning axis S in order to prevent the occurrence of this shadow.

The light source reflecting mirror 3 is arranged between the sockets 21 of the cold cathode tubes 2 in the same row among the staggered cold cathode tubes 2. In such a case, if the socket 21 which does not irradiate or reflect light causes a shadow on the socket 21 side of the document, the outer surface of the cap 6 covering the socket 21 is white. Cap 6 facing cold cathode tube 2
If the outer surface is white, the outer surface of the cap 6 reflects light, so that the light from the cold-cathode tube 2 can be reflected by the outer surface of the cap 6 together with the light source reflecting mirror 3.

In the above configuration, the target glass 1
The light directly illuminated by the cold cathode tubes 2 arranged in a staggered manner on the image of the original passing therethrough and the light source reflecting mirror 3
And the light reflected by the light-reflecting cap 6 is uniformly radiated from both sides of the scanning axis S that is the reading position.
The image can be scanned and read by the image sensor 5. That is, by arranging the cold cathode tubes 2 in a staggered manner, it is possible to irradiate light over a wide range, and a high-quality image can be obtained even for a large-sized document.

[0025]

According to the present invention, the following effects can be obtained.

(1) According to the first aspect of the present invention, a staggered light is applied to the image surface of the document from both sides of the reading position, and a sufficient amount of light is applied to the image surface even if a relatively small light source is used. can do. As a result, it is possible to apply a cold-cathode tube or the like, which is relatively small and resistant to low temperatures and has a large amount of light, to an image reading apparatus used for reading large-sized paper. In other words, a large-sized document is irradiated with sufficient light, so that a high-quality image can be read.

(2) According to the second aspect of the present invention, a portion having a small amount of light outside the effective irradiation range at one end of one light source is complemented by irradiating the other light source with a sufficient amount of light, so that a sufficient amount of light can be imaged on the document. Can be given to a surface.

(3) According to the third aspect of the present invention, it is possible to cover a transient portion where the amount of light emitted from the end of the light source is unstable and to obtain a uniform amount of light using only a stable portion.

(4) According to the fourth and fifth aspects of the present invention,
By a light reflector and a light-reflective mask outer surface at a position facing one light source, it is possible to irradiate the image surface of the document from both sides of the light source and the position facing the light source with the scanning axis interposed therebetween, It is possible to prevent shadows from appearing even on a document having irregularities.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a reading optical system of an image reading apparatus according to an embodiment of the present invention as viewed from a target glass surface.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

3A and 3B are views showing details of a portion B in FIG. 1, wherein FIG. 3A shows a state in which a cap is mounted, and FIG. 3B is a view showing a state in which the cap is removed.

FIG. 4 is an explanatory diagram showing a light intensity distribution of a cold cathode tube.

FIG. 5 is a schematic view of a reading optical system of a conventional image reading apparatus viewed in a main scanning direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Target glass 2 Cold cathode tube 3 Light source reflection mirror 4 Lens 5 CCD image sensor 6 Cap 21 Socket 61 End face S Scanning axis

Claims (5)

[Claims] 1. An image reading apparatus which irradiates light from a light source onto an image surface of a document and reads the reflected light, wherein the light sources are arranged in a staggered manner with their ends overlapping each other across a reading position. Image reading device. 2. The light source according to claim 1, wherein an end of the light source is overlapped with a part of an effective irradiation range of the light source.
The image reading device according to claim 1. 3. An image reading apparatus according to claim 1, wherein an end of said light source is covered with a non-light transmitting mask. 4. The mask according to claim 3, wherein the outer surface of the mask is light-reflective, and a light reflector is provided at a position facing the light source except for the mask portion with the reading position interposed therebetween. The image reading device according to claim 1. 5. An outer surface of the mask is white.
The image reading device according to claim 1.