JP2876696B2 - Color document reader - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color document reading apparatus using an accumulation type image sensor.

[Prior Art] A conventional color document reading apparatus using a plurality of light sources is described in the fifth,
As shown in FIG. 6, when turning on a plurality of light sources, they were all turned on and off at the same timing.

[Problems to be Solved by the Invention] As shown in FIGS. 5 and 6e, the lamp power supply current concentrates in a relatively short period of time, and a large-capacity capacitor or a large current element is supplied to compensate for this. For example, there is a problem that a power supply having a larger capacity than necessary is required.

Therefore, an object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a color document reading apparatus capable of performing sufficient monochrome reading or color reading with a power supply having an appropriate capacity.

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. In the apparatus, when performing monochrome reading by turning on a plurality of light sources having different emission wavelengths in one accumulation period, the lighting period of at least one light source is shifted from the lighting periods of the other light sources, and the lighting is performed. . In addition, two light sources among a plurality of light sources having different emission wavelengths are turned on in one accumulation period, and when performing color reading with a complementary color, the lighting period of one light source is shifted from the lighting period of another light source to be turned on. It is characterized by the following. Further, the plurality of light sources having different emission wavelengths are a red LED, a blue LED, and a green LED.

[Operation] When the light source is turned on as described above, the current required in a short time is reduced, and a power supply element having a capacity corresponding to the current can be used.
It can be stored in an appropriate power supply capacity. In addition, the life of the device is prolonged due to the decrease in the power supply current, and the reliability of the entire device is increased.

EXAMPLES Hereinafter, the present invention will be described based on examples. FIG. 1 shows an embodiment relating to monochrome reading of the present invention.
b, c, d, and e are the lighting times of the green, red, and blue LED light sources, the output of the image sensor (for example, a CCD line sensor), and the LEDs.
FIG. 3 is a diagram illustrating a relationship between power supply currents. FIG. 2 shows an example of a reading unit of a color document reading apparatus used in the present invention, and light sources 2, 3, and 4 are shown.
The original placed on the original glass 1 illuminated by the imaging device forms an image on the contact image sensor 6 by the equal-magnification lens 5, and the image information is sequentially read while moving the reading unit.
It reads all images on the document surface.

FIG. 1 shows an example in which three light sources are turned on within one accumulation period. Since the lighting timings of all the light sources are shifted, the maximum value of the light source power source current is one for each light source. Is equal to the maximum of This is a much lower current value than when all the light sources are turned on at the same time. FIG. 3 is an embodiment relating to color reading of the present invention.
This is a case of reading with complementary colors of green, red, and blue, yellow, cyan, and magenta. Also in this example, the maximum value of the light source power supply current is the maximum value for each light source (see FIG. 6 showing a conventional example).

FIG. 4 shows another embodiment relating to the monochrome reading of the present invention. In this example, only the light source that requires the most current is shifted in lighting timing from the other two light sources, so that the load on the power source is not so large. The reading can be realized in the fastest time determined only by the reading time of the sensor without applying any time.

[Effects of the Invention] As described above, according to the present invention, by turning on the light source as described above, the current required in a short period of time is reduced, and a power supply element having a capacity corresponding thereto can be used. Can fit in capacity. In addition, there is an effect that the life of the element is prolonged due to the decrease in the power supply current, and the reliability of the entire device is increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the light source lighting timing, the image sensor output, and the light source power supply current in monochrome reading according to the present invention. FIG. 2 is a sectional view of a reading section of the color document reading apparatus used in the present invention. FIG. 3 is a diagram showing the relationship between the lighting timing of the light source, the output of the image sensor, and the power source current of the light source, showing one embodiment of the color reading of the present invention. FIG. 4 is a diagram showing the relationship between the lighting timing of the light source, the image sensor output, and the light source power supply current, showing another embodiment of the monochrome reading of the present invention. 5 and 6 are diagrams showing the relationship between the lighting timing of the conventional light source, the output of the image sensor, and the light source power supply current. 1 ... Original glass 2 ... Red LED 3 ... Blue LED 4 ... Edge LED 5 ... 1: 1 lens 6 ... Contact image sensor

Claims (3)

(57) [Claims] 1. A color document reading apparatus for reading a document image by illuminating a plurality of light sources having different light emission wavelengths in synchronization with a reading timing of a storage type image line sensor. A color document reading apparatus characterized in that when performing monochrome reading by turning on all of the plurality of light sources, the lighting period of at least one light source is shifted from the lighting periods of the other light sources, and the color document reading apparatus is turned on. 2. A color document reading apparatus for reading a document image by illuminating a plurality of light sources having different light emission wavelengths in synchronization with a reading timing of a storage type image line sensor. A color document reading apparatus characterized in that when two of the plurality of light sources are turned on to perform color reading with a complementary color, the lighting period of one light source is shifted from the lighting period of the other light source to turn on. 3. The color document reading apparatus according to claim 1, wherein the plurality of light sources having different emission wavelengths are a red LED, a blue LED, and a green LED.