JPH06197197A - Picture reader - Google Patents

Abstract

PURPOSE:To read pictures with high quality regardless of the size of an original by simple constitution by providing plural straight tubular light sources parallelly arranged so that respective end parts mutually face with each other on a surface parallel to an original platen. CONSTITUTION:Respective fluorescent tubes 11 are parallelly arranged so that respective end parts 11a mutually face with each other on the surface parallel to the original platen with a read element (contact type image sensor) 15 at a center. The respective fluorescent tubes 11 are short compared with the sensor 15 and the difference of light quantities at their center parts 11b and the respective end parts 11a is small. Thus, the light quantity of the end part 11a of the fluorescent tube 11 where the light quantity is less can be compensated by the light quantity of the end part 11a of the other fluorescent tube 11 facing with the end part 11a. That is, the light quantity of the respective end parts 11a is approximately doubled and becomes equivalent to the light quantity of the center part 11b. Thus, the nonuniformity of the light quantity due to that the light quantity of the end parts 11a of the respective fluorescent tubes 11 is less can be dissolved by the simple constitution, the original can be irradiated with generally uniform light quantity regardless of the size and the pictures can be read with the high quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device such as an image scanner or a facsimile.

[0002]

2. Description of the Related Art FIG. 3 shows a schematic structure of a conventional image reading apparatus. In the figure, reference numeral 2 denotes a transparent document table on which a document is placed. Reference numeral 10 denotes an optical system for optically reading the image of the document P, which includes a light source (11) and a reading element (contact type image sensor) 15. Normally, a linear fluorescent tube 11 is used as the light source. Here, when light is emitted from the light source (11) to the original P through the original table 2 while moving the optical system 10 relative to the original table 2, the reflected light from the original P illuminated by the light is read by the reading element 1.
Guided to 5. Then, the reflected light is converted into an electric signal (image signal) by the reading element 15, and the image is read based on the signal.

[0003]

By the way, in the above-mentioned image reading apparatus, when the short fluorescent tube 11 is used as the light source, the difference in the light amount between the central portion and each end of the fluorescent tube 11 is small, but the fluorescent tube is small. The larger the dimension of 11, the larger the difference in light amount.

Therefore, in an image reading apparatus capable of reading a large size image such as A1 and A0 sheets, the difference in light amount between the central portion and each end portion of the fluorescent tube 11 becomes large. As described above, when the amount of light from the light source (fluorescent tube 11) is not uniform, the amount of light reflected from the document P is not uniform, and even if the same color is read, the image signal output from the reading element 15 is distorted and the amount of light is small. The few places will be dark.

In order to prevent the occurrence of such inconvenience, FIG.
Further, as shown in FIG. 4, a shading circuit for interposing a shading plate 19 between the light source (fluorescent lamp 11) and the reading element 15 to make the amount of light hitting the original P uniform or to electrically correct the unevenness of the amount of light. (Not shown) is attached.

However, the document P that is to be read in either case
The larger the size of, the more difficult it is to make the light amount uniform and correct, and the image quality deteriorates. Particularly, when the fluorescent tube 11 approaches the end of its life, the above-mentioned deterioration of image quality becomes more remarkable.

On the other hand, by using an LED (light emitting diode) as the light source, it is possible to make the light amount uniform regardless of the length, but since it is monochromatic light, unreadable colors occur (for example, , The red LED is the original P
Can't read the red color. ). In addition, it has the drawback of high cost and high power consumption.

In view of the above circumstances, an object of the present invention is to provide an image reading apparatus having a simple structure and capable of reading an image of high quality regardless of the size of a document.

[0009]

SUMMARY OF THE INVENTION An image reading apparatus according to the present invention includes a transparent document table for placing a document, and
An image reading apparatus that includes a light source that illuminates a document through the document table and a reading element that receives reflected light from the document illuminated by the document and converts the reflected light into an electrical signal. The light source is formed of a plurality of linear tubular light sources that are arranged in parallel on a plane parallel to the document table so that their one ends are opposed to each other.

[0010]

According to the present invention having the above-mentioned structure, since the light source is formed by a plurality of linear tubular light sources arranged in parallel so that one ends thereof are opposed to each other on a plane parallel to the document table, the light quantity is small. The light amount at the end of the linear tubular light source can be supplemented by the light amount at the end of another linear tubular light source facing the end.

Therefore, it is possible to illuminate the original with a uniform amount of light regardless of the size with a simple structure and read an image with high quality.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The image reading apparatus is capable of reading large size images such as A1 and A0 sheets, and has the same basic configuration as the conventional example (FIG. 3) as shown in FIGS. 1 and 2.
The light source is formed by a plurality of linear tubular light sources (four fluorescent tubes 11 in this embodiment) arranged in parallel on a plane parallel to the document table 2 so that their one ends (11a) face each other. The original P can be illuminated with a uniform amount of light regardless of its size. The same components as those in the conventional example (FIG. 3) are designated by the same reference numerals, and detailed description thereof will be omitted.

Here, as shown in FIG. 1, the fluorescent tubes 11 are parallel to each other with their one ends 11a facing each other on a plane parallel to the document table 2 around the reading element (contact type image sensor) 15. It is arranged. In addition, each fluorescent tube 11
Is shorter than the sensor 15, and the difference in the amount of light between the central portion 11b and each end portion 11a is small.

Next, the operation will be described. Since the light source is formed by four fluorescent tubes 11 arranged in parallel on the plane parallel to the document table 2 so that the respective one ends 11a thereof face each other, the end 11a of the fluorescent tube 11 where the light quantity is reduced becomes small. End portion 11 of another fluorescent tube 11 facing the end portion 11a.
It can be compensated by the light amount of a. That is, the amount of light at each end 11a is approximately doubled, and is equal to the amount of light at the center 11b.

Therefore, it is possible to eliminate the unevenness of the light quantity due to the small light quantity at the end 11a of each fluorescent tube 11 with a simple structure.

According to this embodiment, however, the light source is formed by the four fluorescent tubes 11 arranged in parallel on the plane parallel to the original table 2 so that their one ends 11a face each other. The original P can be illuminated with a uniform amount of light regardless of the size, and an image can be read with high quality.

Further, since the respective fluorescent tubes 11 are arranged in parallel with the reading element 15 as the center, the optical path lengths from the respective fluorescent tubes 11 to the reading element 15 through the original P are equalized, and an image with higher quality can be obtained. Can be read.

[0018]

According to the present invention, since the light source is formed of a plurality of linear tubular light sources arranged in parallel so that one ends of the light sources face each other, an image can be formed with a simple structure regardless of the size of the original. Can be read with high quality.

[Brief description of drawings]

FIG. 1 is a plan view for explaining an essential part of the present invention.

FIG. 2 is a side view for explaining the positional relationship among the fluorescent tube, the reading element, and the original.

FIG. 3 is a diagram for explaining a schematic configuration of a conventional image reading apparatus.

FIG. 4 is a diagram illustrating a shading plate interposed between a fluorescent tube and a contact image sensor in a conventional image reading device.

[Explanation of symbols]

 2 Platen 11 Fluorescent tube (linear tubular light source) 11a Fluorescent tube end 11b Fluorescent tube center 15 Contact image sensor (reading element)

Claims (1)

[Claims] 1. A document table having transparency for placing a document, a light source for irradiating the document with light through the document table, and a reflected light from the document illuminated with light to convert it into an electric signal. In an image reading apparatus that includes a reading element and optically reads an image of a document, a plurality of straight lines in which light sources are arranged in parallel on a plane parallel to the document table so that one ends thereof face each other An image reading device formed by a tubular light source.