JPS605663A - Color picture reader - Google Patents

Abstract

PURPOSE:To attain the reading of an original at a high speed by providing an optical filter comprising plural filter elements having different transmitted light band characteristic on an optical path from a light source reaching an image sensor. CONSTITUTION:A cylindrical optical filter where plural filter elements 6a-6c having different transmitted light band characteristic from each other are arranged around the shaft with an equal angular interval is provided freely turnably around the light source 1. The optical filter is turned at a prescribed period corresponding to the period of original reading scanning of the image sensor 4 by a motor 8. Thus, the filter elements 6a-6c are inserted sequentially selectively into the optical path 9 from the light source 1 to the original 2. Then three kinds of photoelectric transducing signals corresponding to the number of the filter elements 6a-6c are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to a color image reading device that is used in facsimiles and the like and photoelectrically reads color images on a document.

[Prior art]

In order to photoelectrically read the color image of a document, multiple light sources with different spectral characteristics are sequentially blinked individually in synchronization with the document reading scan period of the image sensor, and the original reflection sources are sequentially detected by the image sensor. By imaging the same scanning line of the original, multiple types of photoelectric conversion signals corresponding to the number of light sources are obtained, and then based on the levels of these photoelectric conversion signals, the scanning line of the original that has been read and scanned is determined based on the level of these photoelectric conversion signals. A color image reading device is used that discriminates the image color in .

As an example of such a conventional color image reading device, the above-mentioned light source ζ uses two fluorescent lamps, a red fluorescent lamp and a blue fluorescent lamp, to read three types of ``color'', ``red'', and ``black''. FIG. 1 shows an apparatus for reading a single color work.

That is, 1a is a blue fluorescent lamp, and b is a red fluorescent lamp. When these fluorescent lamps are turned on by a lighting circuit (not shown), a blue light signal BC is emitted from the blue fluorescent lamp 1a, and a blue light signal BC is emitted from the red fluorescent lamp 1b. The red light signal Re is J9. The light is emitted so as to illuminate the same part (line) of document 2.

The reflected light from the original 2 is imaged by a lens 3 onto an image sensor 4 made of, for example, a CCD (charge-coupled device) line sensor, and the image sensor 4 transmits an electrical signal (photoelectric signal) having a voltage level corresponding to the amount of light. converted signal -CE). 5 is the photoelectric conversion signal C
This is a color discrimination circuit that determines the E level ♀1.
6'jlr The image color of the scanned original 2 is sequentially determined.

Note that, for example, tungsten oxide is used as the phosphor for the blue fluorescent lamp 1a, and for the red fluorescent lamp 1,
As the phosphor b, for example, magnesium germanate has been used up.

[Problems with conventional technology]

As described above, in a color image reading device that sequentially blinks a plurality of light sources with different spectral characteristics and sequentially images the reflected light from the original on the image sensor, it is necessary to provide a plurality of light sources. Also, for example, in the case of the above example, the red-emitting phosphor (e.g., magnesium germanate) used in the red fluorescent lamp 1b is more expensive than the blue-emitting phosphor (e.g., calcium tungstate) used in the blue fluorescent lamp 1a. In general, the flickering response is poor and the afterglow time is long. Therefore, red fluorescent lamp 1
When b is blinked, reading scanning cannot be performed during the afterglow time, and this has the disadvantage of limiting the document reading speed. Furthermore, when a plurality of light sources are used, there is also the problem that the color balance of a color image taken at 811 changes over a long period of time due to uneven deterioration of the light sources.

[Purpose of the invention]

The present invention eliminates the drawbacks of conventional color image reading devices using multiple light sources and provides a color image reading device that enables high-speed YF and document reading with simple borrowing. The purpose is to

[41i of the Invention] In this invention, a single heating element is used, and an optical filter consisting of filter elements with different capsule structures having different transmitted light band characteristics is provided on the optical path from the light source to the image sensor. The filter elements are sequentially and selectively inserted into the optical path at a predetermined period corresponding to the period of the image sensor reading and failing the document.

〔Example〕

FIG. 2 shows an embodiment of a color image reading device according to the present invention.

In other words, in Fig. 2, reference numeral 1 is a light source that emits white light, and around this light source 1, a number of filter elements 6a, 6b, and 6c having different transmitted light band characteristics are arranged at equal angular intervals around the axis. A cylindrical optical filter 7 is rotatably provided. In this case, for example, the filter element 6a is a red filter, the filter element 6b is a green filter, and the filter element 6c is a blue filter. The optical filter 7 is rotated by a motor 8 at a predetermined period corresponding to the period of the original (11) reading scan by the image sensor 4, so that the filter elements 6a to 6c are rotated in the optical path from the light source 1 to the original. A plurality of lights having spectral characteristics corresponding to the emission wavelength band characteristics of the filter elements 6a to 6C are sequentially and selectively inserted into the filter elements 6a to 6C and sequentially illuminate the original in synchronization with the original reading scanning period of the image sensor 4. Therefore, three types of photoelectric conversion signals CF corresponding to the number of filter elements 6a to 6C of the optical filter 7 can be obtained from the image sensor 4 for the same scanning line of the original 2. Next, the photoelectric conversion signal C
It is only necessary to determine the level of E and to determine the color of the 20 images of the read and scanned documents consecutively.

In the above embodiment, the optical filter 7 is provided on the optical path 9 of direct light from the light source 1 to the original 2, but it is also provided on the optical path 9' of reflected light from the original 2 to the image sensor 4. may be provided.

In this case, a disc type optical filter in which a plurality of filter elements are arranged radially is suitable as the optical filter.

〔Effect of the invention〕

According to the color image reading device according to the present invention, the purpose can be achieved with a single light source, and therefore, it is possible to achieve the purpose with a single light source, and therefore, it is possible to achieve the purpose by using a single light source. Color images can be read at high speed and with high fidelity because there is no inconvenience that the document reading speed is limited, and there is no change in color balance due to variations in deterioration of a plurality of light sources.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic structure of an example of a conventional color image reading device, and FIG. 2 is a block diagram showing a schematic structure of an embodiment of a color image reading device according to the present invention. ■...Light source, 2...Document, 3...Lens, 4...Image sensor, 5...Color discrimination circuit, 5a, 5b,
5c... Filter element, 7. Optical filter, 8...
Motor, 9.9'... light path.

Claims (1)

[Claims] A light source for illuminating the original, an image sensor arranged so that the reflected light of the light irradiated onto the original from the light source is formed into an image, and configured to read and scan the image of the original, and each of them has a transmission light band characteristic. an optical filter including a plurality of different filter elements, and driving the optical filter to move the plurality of filter elements from the light source to the image sensor at a predetermined period corresponding to the period of document reading scanning by the image sensor. A color image reading device equipped with means for sequentially and selectively interposing the optical path along the optical path.