JPH04365257A - Image reader - Google Patents

Abstract

PURPOSE:To suppress the dispersion of output levels by arranging respective line sensors so that a part away from a light source with low illuminance can be read by a sensor with high photosensitivity and a part near the light source with high illuminance can be read by a sensor with low photosensitivity. CONSTITUTION:The photosensitivity is highest at a line sensor 204 and lowest at a line sensor 206, and the ratio of the photosensitivity among line sensors 204-206 is 1:0.8:0.6, for example. The output image signal of the sensor is in proportion to the photosensitivity of the sensor and the quantity of light made incidental on the sensor, namely, to an original face. The respective sensors are arranged so that the sensor 204 with high photosensitivity can read a part A with low illuminance and the sensor 206 with low photosensitivity can read a part C with high illuminance. Therefore, the ratio of the output levels among the sensors 204-206 is the product of the illuminance ratio of original faces A-C and the photosensitivity ratio of the sensors 204-206 and becomes 0.6:0.64:0.6, and the output level dispersion caused by the photosensitivity of the sensors can be suppressed.

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, and more particularly to an apparatus that performs color reading using a plurality of reading elements arranged in parallel.

0002

2. Description of the Related Art Conventionally, this type of image reading apparatus has been constructed by illuminating an original 201 with a light source 202, as shown in FIG. Sensors 204, 205, 20
6, respectively. The line sensor 204 has a red filter that transmits red light disposed on the sensor light receiving surface, converts the red component of the imaged light into an electrical signal, and outputs the electrical signal as an image reading signal.

The line sensor 205 has a green filter that transmits green light disposed on the sensor light receiving surface, converts the green component of the imaged light into an electrical signal, and outputs the electrical signal as an image reading signal. The line sensor 206 arranges a blue filter that transmits blue light on the sensor light receiving surface, converts the blue component of the imaged light into an electrical signal, and outputs the electrical signal as an image reading signal. Color reading is performed in this way.

0004

[Problem to be Solved by the Invention] However, the conversion efficiency from light to electrical signals, that is, the light sensitivity, differs depending on the transmission characteristics of the sensor and each color filter. The image signal is large, and the output image signal of a sensor with low photosensitivity is small. Therefore, conventionally, such variations in sensor output level have been a drawback.

The present invention has been made in view of the above-mentioned conventional circumstances, and therefore, an object of the present invention is to provide a novel image reading device capable of eliminating the above-mentioned drawbacks inherent in the conventional technology. There is a particular thing.

[0006]

[Means for Solving the Problems] In order to achieve the above object, an image reading apparatus according to the present invention is an apparatus that reads an image using a plurality of reading elements arranged in parallel at predetermined intervals. The reading elements are arranged so that the high-sensitivity reading element reads an image on the document surface at a position far from the light source, and the reading element with low sensitivity reads the image on the document surface at a position close to the light source.

[0007]

Embodiment Next, an embodiment of the image reading apparatus according to the present invention will be specifically described with reference to FIG.

FIG. 1 is a block diagram showing one embodiment of the present invention.

Referring to FIG. 1, the components of the present invention are the same as those described in FIG. 2 as the prior art;
Therefore, the same reference numbers are given. A document 201 is illuminated by a light source 202, and an image of the document is captured through a lens 203 by line sensors 204, 205, and 206 arranged in parallel.
The red, green, and blue components of the original are converted into electrical signals.

In FIG. 1, portions A, B, and C of a document 201 are imaged by a lens 203 at positions A', B', and C'. FIG. 3 shows the illuminance distribution on the document surface. The brightness on the document surface is dark at A, which is far from the light source, and bright at C, which is close to the light source. For example, the ratio of the illuminance of A, B, and C on the document surface is 0.
．． The ratio is 6:0.8:1.

On the other hand, the light sensitivity of the line sensor 204 is the highest and the line sensor 206 is the lowest. For example, line sensor 204
, 205, and 206 are 1:0.8:0.6.

The output image signal of the sensor is proportional to the photosensitivity of the sensor and the amount of light incident on the sensor, that is, the brightness of the surface of the original. In this embodiment, each sensor is arranged so that the sensor 204 with high photosensitivity reads the part A where the illuminance is low, and the sensor 206 with low photosensitivity reads the part C where the illuminance is high.

With this arrangement, the sensors 204, 2
The ratio of the output signal levels of 05 and 206 is for original surfaces A, B, and C.
It is the product of the illuminance ratio of and the photosensitivity ratio of the sensors 204, 205, and 206, which is 0.6:0.64:0.6.

In this way, each sensor is arranged so that the sensor with high photosensitivity reads the area far from the light source and has low illuminance, and the sensor with low photosensitivity reads the area close to the light source and has high illuminance. Variations in output level due to photosensitivity can be reduced.

[0015]

[Effects of the Invention] As explained above, according to the present invention,
By arranging each line sensor so that the sensor with high light sensitivity reads the area far from the light source with low illuminance, and the sensor with low light sensitivity reads the area with high illuminance close to the light source, the output level due to the light sensitivity of the sensor can be adjusted. Variations can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram showing one embodiment of the present invention.

FIG. 2 is a configuration diagram of an optical system of a conventional reading device.

FIG. 3 is a diagram illustrating the illuminance distribution on the document surface.

[Explanation of symbols]

201...Manuscript 202...Light source for illumination 203...Lens

Claims (1)

[Claims] Claim 1: In a device that reads images using a plurality of reading elements arranged in parallel at predetermined intervals, the reading element with high sensitivity reads an image on the document surface at a position far from the light source, and the reading element with low sensitivity reads the image on the document surface at a position far from the light source. An image reading device characterized in that a reading element is arranged so as to read an image on a document surface at a position close to a light source.