JPH0918654A - Image reader - Google Patents

Abstract

PURPOSE: To prolong the service life of each light source with a simple configuration. CONSTITUTION: One light source is selected among plural light sources 31, 41, 51 and only one light source selected with respect to one read line in the subscanning direction of an original is lighted and then one light source is selected among the plural light sources to obtain an image signal of read one line. Then the light source is switched for each original with a light source changeover mode switch 11.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for reading a color image in different colors. 2. Description of the Related Art Conventionally, there is a light source switching method as one of the color original reading methods which takes advantage of the solid scanning method using a line image sensor. This method is a method of illuminating an original by switching the illumination light using an illumination light source body of a plurality of colors or a color filter of white light, and performing photoelectric conversion with a single line image sensor, that is, color separation into a plurality of colors. Is a method of switching the illumination light. FIG. 4 is a schematic configuration diagram of this conventional method. In FIG. 4, 1 is a document, 2 is a document feed roller, and 3 is a document feed roller.
Is a red fluorescent lamp, 4 is a green fluorescent lamp, 5 is a blue fluorescent lamp, 6 is a lens, 7 is a line image sensor consisting of a photoelectric conversion element, 8 is a paper conveyance motor, 9 is a light source lighting control unit, and 10 is a mirror. is there. FIG. 5 is a diagram showing the timing of the conventional monochrome reading mode. In FIG. 5, al is a scan of the line image sensor 7 of the first original 1 and is a.
Reference numeral 2 denotes the scanning scan of the line image sensor 7 of the second original 1, and a3 denotes the line image sensor 7 of the third original 1.
, G, h, and i are the lighting periods of the red fluorescent lamp 3, the green fluorescent lamp 4, and the blue fluorescent lamp 5, respectively, e'is the output signal of the line image sensor 7, and f is the original reading 1
The sub-scanning timing pulse for rotating the document feed port 2 by the line, (A) the reading operation of the first document 1, (B) the reading operation of the second document 1,
(C) shows the reading operation of the third original 1. Next, the color reading operation of the original 1 will be described with reference to FIG. First, the red fluorescent lamp 3, the green fluorescent lamp 4, and the blue fluorescent lamp 5 are sequentially turned on for each l times, a white reference plate (not shown) is irradiated, and the reflected light from the original 1 is redirected by the mirror 10. , Line image sensor 7 that collects light with lens 6
Read with to perform shading correction. Then, the document feed roller 2 in which the document 1 is rotated by the paper transport motor 8
The paper is fed by, and the sub-scanning is performed line by line. Manuscript l
Then, the sub-scanning is temporarily stopped on the reading line, and the red fluorescent lamp 3 illuminates the original 1 first, and the reflected light is condensed by the lens 6 and photoelectrically converted by the line image sensor 7 to convert one line of red color. Information is read and the red fluorescent lamp 3 is turned off. Then, the green fluorescent lamp 4 is turned on, the green information is read as described above, and the green fluorescent lamp 4 is turned off. Next, the blue fluorescent lamp 5 is turned on, the blue information is read as described above, and the blue fluorescent lamp 5 is turned off. Finally, the document feed roller 2 is rotated by the paper feed motor 8 to feed the paper to the next reading line. The red, blue, and green image signals thus obtained are sequentially output. By repeating the above operation, the color reading of the original 1 for 1 sheet is performed. Next, for reading that does not require reproduction in a monochrome original or in color, as shown in FIGS. Only the lamp 4 is turned on and fixed so as to obtain a monochrome image signal. However, at the present time when the monochrome document spread rate is high, a color reading device often reads the monochrome document. In such a case, if the green light source is always turned on in monochrome reading as described above, the life of the green light source body is significantly shorter than that of the red and blue light source bodies. Further, since red, green, and blue fluorescent lamps are used as the light source body, it is inevitable that the image reading device becomes large. Furthermore, the red, green, and blue fluorescent lamps have an afterglow time of several msec or more even when the power is turned off, and in order to avoid overlapping of color information, the next fluorescent light is emitted during this afterglow time. I can't turn on the light. Therefore, there is a problem that the operation speed of the image reading device is limited. The present invention has been made in view of the above-mentioned conventional problems, and a first object thereof is to provide an image reading apparatus capable of extending the life of each light source with a simple structure. That is. A second object of the present invention is to provide an image reading apparatus capable of downsizing the entire apparatus and shortening the reading time. In order to achieve the first object, the image reading apparatus according to claim 1 of the present invention comprises a plurality of light source bodies having different wavelength ranges for illuminating an original.
Lighting control means for sequentially turning on these light source bodies for a predetermined period with respect to one line for reading a document, and reflected light from the document illuminated by the plurality of light source bodies in the sub-scanning direction of the document for each light source body. In a line image sensor including a photoelectric conversion unit that sequentially scans the plurality of light source units, and extracts a plurality of signals read by the plurality of light source units in time series. From this, only one light source is turned on to read the original, and the selection switching means for sequentially switching the light source to be turned on for each original is provided. In order to achieve the above second object, the image reading device according to claim 2 of the present invention is the image reading device according to claim 1, wherein the plurality of light source bodies are light emitting diodes. To do. According to another aspect of the image reading apparatus of the present invention, during the monochrome reading, one light source is selected from a plurality of light sources by the selection switching means, and only one selected light source is turned on. To scan the original. According to the image reading apparatus of the second aspect, in addition to the operation of the image reading apparatus of the first aspect, the plurality of light source bodies are light emitting diodes. An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic configuration diagram of an image reading apparatus according to an embodiment of the present invention. In FIG. 1, the same parts as those of the conventional FIG. 4 described above are denoted by the same reference numerals. 1 is different from FIG. 4 in that the structure of the light source body and the light source changeover mode switch 11 are added to the structure of FIG. That is, according to the present invention, as shown in FIG.
It has a red light source body 31 composed of an ED (light emitting diode), a green light source body 41 composed of a green LED (light emitting diode), and a blue light source body 51 composed of a blue LED (light emitting diode). The red light source body 31 includes a plurality of red LED chips 31 on a substrate 31b as shown in FIG.
It is equipped with a. As shown in FIG. 2B, the green light source body 41 includes a plurality of green LED chips 41a on a substrate 41b.
Wear it. The blue light source body 51 is formed by mounting a plurality of green LED chips 51a on a substrate 51b as shown in FIG. These red light source body 31 and green light source body 4
The lighting switching of the light source 1 and the blue light source body 51 is automatically performed by the switching operation of the light source switching mode switch 11. Further, the switching may be performed according to the color of the original. FIG. 3 is a diagram showing the timing in the monochrome reading mode in the image reading apparatus of the present invention.
In the figure, al to a3, f and (A) to (C) are the same as those in the conventional FIG. 5 described above, and b, c and d are red light source body 31, green light source body 41 and blue light source body, respectively. The lighting period of 51, e shows the output signal of the line image sensor 7, respectively. The color reading is the same as in the conventional example described above. Next, the operation of the image reading apparatus according to this embodiment will be described with reference to FIGS. First, the red light source 3l is lit once, the white reference plate (not shown) is illuminated, the reflected light from the original l is redirected by the mirror l0, and the light is condensed by the lens 6 and the line image sensor 7 is used. Shading correction is performed by reading the reflected light. Then, the document feed roller 2 in which the document 1 is rotated by the paper transport motor 8
The paper is fed by, and sub-scanning is performed for each reading line. The sub-scanning is temporarily stopped on the reading line of the original l, and the red light source 3l is used to set the original l
And the reflected light is condensed by the lens 6 and photoelectrically converted by the line image sensor 7 to read one line for reading, and after the red light source 31 is turned off, the next reading is performed by the document feeding roller 2. Feed the paper to the line. Next, the red light source 3l is turned on again, one line for reading is read, the red light source 31 is turned off, and the original 1 is conveyed by one line for reading. By repeating the above-mentioned operation, one original 1 can be read. Then, the information that the red light source body 3l is turned on is temporarily stored in the light source selection control unit 9, and when another original 1 is read next, the green light source body 41 is turned on by an instruction from the light source selection control unit 9. When the original 1 is read after being turned on, the blue light source 51 is turned on, and then the red light source 3l is turned on again.
By repeating the cycle of returning to lighting, the light source bodies 31, 41, 51 can be used evenly, and the life of each light source body 31, 41, 51 can be extended. In the above embodiment, the example in which the sub-scan is performed intermittently is shown. However, the document feeding roller 2 is continuously operated,
The same applies to reading by continuously lighting the light source bodies 31, 41, and 51. In this embodiment, the conventional fluorescent lamp, which is a light source, is replaced with an LED (light emitting diode), so that the light source itself can be made smaller and the overall size of the device can be reduced. Also, the afterglow time when the power is turned off is extremely short,
The next light source can be turned on quickly, and the reading operation speed can be shortened. As described above, according to the image reading apparatus of the first aspect of the present invention, at the time of monochrome reading, only one of the light source bodies is turned on to read the original. Since the light source bodies to be turned on by the selection switching means are sequentially switched for each original so that the respective light source bodies are used evenly, the life of the light source body can be extended as compared with the case where one light source body is continuously used. In addition, the user can select the light source to be turned on, and for example, a red document can use a green or blue light source to prevent dropout. Further, according to the image reading device of the second aspect of the present invention, by using the light emitting diode as the light source, the light source itself can be made smaller than the conventional fluorescent lamp, xenon tube, etc. Can be miniaturized. Furthermore, since the afterglow time when the power is turned off is extremely short, the next light source unit can be turned on quickly, and the reading operation speed can be shortened.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram of an image reading apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view of a light source body in the image reading apparatus according to the embodiment. FIG. 3 is a timing chart showing monochrome reading timing in the image reading apparatus according to the embodiment. FIG. 4 is a schematic configuration diagram of a conventional image reading apparatus. FIG. 5 is a timing chart showing the timing of monochrome reading in the conventional image reading apparatus. [Description of Codes] l Original 2 Original feeding roller 31 Red light source (light source) 3la Red LED chip 31b Substrate 41 Green light source (light source) 41a Green LED chip 41b Substrate 51 Blue light source (light source) 51a Blue LED Chip 51b Substrate 6 Lens (optical system) 7 Line image sensor 8 Paper transport motor 9 Light source lighting control unit (lighting control means) 10 Mirror 11 Light source switching mode switch (selection switching means)

Claims (1)

Claim: What is claimed is: 1. A plurality of light source bodies each having a different wavelength range for illuminating a document, and a lighting control means for sequentially lighting these light source units for one line for reading a document for a predetermined period. And a line image sensor comprising photoelectric conversion means for sequentially scanning the original in the sub-scanning direction for each light source with reflected light from the original illuminated by the plurality of light sources. In an image reading apparatus that extracts a plurality of signals read by the body in time series, only one light source is turned on from the plurality of light sources during monochrome reading to read a document, and the light source to be turned on is set for each document. An image reading apparatus characterized in that selection switching means for sequentially switching to is provided. 2. The image reading apparatus according to claim 1, wherein the plurality of light source bodies are light emitting diodes.