JP2985221B2 - Color document reader - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a document reading apparatus using an accumulation type image sensor.

[Related Art] In a conventional document reading apparatus using a plurality of light sources, as shown in FIGS. 4 and 5, when a plurality of light sources are turned on, they are all turned on and off at the same timing.

[Problems to be solved by the invention] However, as shown in FIG.
When three types of light sources such as fluorescent lamps and LEDs having green and blue wavelength ranges are used, even if all three types of light sources have the same irradiation time, the sensor does not have the same brightness. Therefore, even when trying to read in monochrome by turning on the three light sources, the output value of a color including a specific color, that is, the same color as a light source capable of outputting a large output in the same time as compared with other light sources, becomes large. It was a natural image.

In addition, as shown in FIG. 5, when the above light sources are turned on two by two to read a color image in green, red and blue complementary colors of yellow, magenta and cyan, the color balance of green, red and blue is also reduced. The image collapsed, resulting in an unnatural image.

Therefore, the present invention is to solve such a conventional problem, and an object of the present invention is to provide a document reading apparatus capable of obtaining a natural image with good color balance by a simple method.

Means for Solving the Problems A color document reading apparatus according to the present invention reads a document image by lighting a plurality of light sources having different emission wavelengths in synchronization with the reading timing of an accumulation type image line sensor. The apparatus includes means for measuring a reference lighting time at which the output of the image line sensor enters a predetermined level when the reference plane is irradiated for each light source, and turns on a plurality of light sources having different emission wavelengths in one accumulation period. In this case, a time obtained by multiplying the reference lighting time by a desired coefficient is set as the lighting time for each light source. The reference surface is white, and the desired coefficient is a reciprocal of the number of light sources to be turned on. In addition, multiple light sources with different emission wavelengths are available with red, blue and green LEDs.
It is characterized by being.

[Operation] When the light source is turned on as described above, the color balance by the light source can be arbitrarily selected, and a natural image with good color balance can be easily obtained.

EXAMPLES Hereinafter, the present invention will be described based on examples. FIG. 1 is a specific example according to the present invention, wherein a, b, c, d, and e are green;
FIG. 7 is a diagram illustrating a relationship between red and blue light source lighting times, an output of an image sensor (for example, a CCD line sensor), and a color component ratio of an image sensor output when a white document is read. Second
FIG. 1 shows an example of a reading section of a document reading apparatus used in the present invention. A document placed on a document glass 1 forms an image on a contact image sensor 6 by a 1: 1 lens 5 and the image information moves through the reading section. While reading sequentially, all the images on the document surface are read. In the procedure for reading with this apparatus, first, the reading unit is moved to a position directly below the white reference surface 7 on the original glass 1. Next, the reference lighting time required for the output of the image sensor 6 to reach the reference level is measured for each of the fluorescent lamps 2, 3, and 4 used as the light source. FIG. 1 shows an example of simultaneous lighting of three lamps, and a broken line indicates a lighting time required to enter the reference level obtained by the above-described procedure. When reading a document, after moving the reading section below the document, multiply each reference lighting time by 1/3 so that the output components of the image sensor 6 become green, red, blue, and 1: 1: 1. The value obtained is the actual lighting time. Thereby, each color component is standardized, and only a specific color is not emphasized, so that a natural image can be obtained.

FIG. 3 shows another embodiment of the present invention in which green, red and blue complementary colors of yellow, cyan and magenta are read. In this example as well, since the lighting time of each light source is set to 1/2 of the reference lighting time so that the color components are 1: 1, correct yellow, magenta, and cyan data with color balance are line-sequentially Can be read.

Although the above values are based on a color component ratio of 1: 1, it is possible to provide a simple color correction function by intentionally shifting the color component ratio.

[Effects of the Invention] As described above, the present invention has an effect that a natural image with good color balance can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the light source lighting timing and the image sensor output according to the present invention. FIG. 2 is a sectional view of a reading section of the document reading apparatus used in the present invention. FIG. 3 is a diagram showing a relationship between a light source lighting timing and an image sensor output according to another embodiment of the present invention. 4 and 5 are diagrams showing the relationship between the lighting timing of a conventional light source and the output of an image sensor. 1 original glass 2 red fluorescent lamp 3 blue fluorescent lamp 4 green fluorescent lamp 5 equal-magnification lens 6 contact image sensor 7 white reference surface

Claims (3)

(57) [Claims] In a color document reading apparatus for reading a document image by illuminating a plurality of light sources having different emission wavelengths in synchronization with a reading timing of a storage type image line sensor, a reference surface is illuminated for each of the light sources. Means for measuring a reference lighting time at which the output of the image line sensor is at a predetermined level. When lighting a plurality of light sources having different emission wavelengths in one accumulation period, the reference lighting time is preferably set to a desired value. A color document reading apparatus wherein a time obtained by multiplying the light source by the coefficient is used as the lighting time of each light source. 2. The color document reading apparatus according to claim 1, wherein the reference surface is white, and the desired coefficient is a reciprocal of the number of light sources to be turned on. 3. A light source having different emission wavelengths,
3. The color document reading device according to claim 1, wherein the color document reading device is a red LED, a blue LED, and a green LED.