JPS60130964A - Color reader - Google Patents

Abstract

PURPOSE:To improve the reading speed by using an LED for a light source to be repeated for flickering among plural light sources irradiating an original. CONSTITUTION:A blue fluorescent light 13, a green fluorescent light 15 and a red LED array 22 are arranged below a platen glass 12 on which an original 11 is mounted. The array 22 is arranged with many red LED in a line and they are covered with a pillar lens. Since the response speed of flickering is fast in the re LED, the lighting operation of the blue fluorescent light 13 is attained at the same time as the distinguishment to decrease the reading cycle of one line.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color reading device that can read color images using a plurality of light sources.

[Prior art]

Color image processing devices such as color copying machines and color facsimile machines separate image information on a document into two or more colors and convert them into electrical signals. There are two types of color reading devices: ■ One that separates light beams using static optical components such as a guichroic mirror, and ■ One that separates light beams by rotating a disc with multiple filters attached in the optical path. The one you select is traditionally used.

However, the former method has a drawback in that the spectral characteristics change depending on the incident angle of the mirror and the like. On the other hand, the latter requires a disk rotation mechanism, which has problems with its accuracy and reliability.

Therefore, a color reading device using a plurality of light sources with different spectral characteristics has been proposed. FIG. 1 shows the reading section of a color reading device that reads three colors.

Near the platen glass 12 on which the original 11 is placed, □ is a front light lamp 13 that selectively emits blue wavelength components;
A total of three fluorescent lamps are arranged: a red fluorescent lamp 14 that selectively irradiates red wavelength components and a green fluorescent lamp 15 that selectively irradiates green wavelength components. The document 11 is configured to move in an arrow direction (sub-scanning direction) perpendicular to the longitudinal direction of these fluorescent lamps 13 to 15 (perpendicular to the drawing). Light reflected from the original 110 by the fluorescent lamps 13 to 15 is focused by a common optical lens 16 and formed into an image on an image sensor 17. In the image sensor 17, photoelectric conversion elements are arranged in a line in the longitudinal direction of the fluorescent lamps 13 to 15, and images are read line by line.

FIG. 2 shows the blinking timing of each fluorescent lamp and the image signal after photoelectric conversion. In this color reading device, 1
The time required to read the line is divided into approximately four equal parts, and the first small section t
1 only, the Aotatami light lamp 13 is turned on (same ff1a>).

For example, the blue Tatami light lamp 12, which uses calcium dungestate as a phosphor, has good blinking response characteristics and almost no afterglow. In the next small section t2, the green fluorescent lamp 14 is turned on (b in the same figure).
. At this time, the blue image signal 18 is read out from the image sensor 17 (d in the same figure). Further next subsection t3
The parting wall light 15 is turned on (C in the same figure).

At this time, a green image signal 19 is read out from the image sensor 17 (d in the same figure). The parting wall light 13 uses, for example, magnesium germanate as a phosphor, and has poor blinking response characteristics. N0 Afterglow time is long, about 2 msec. The last small section t4 is used for processing this afterglow. During this sub-section t4, the red image signal 2O in the sub-section t3 is read out (d in the figure). Thereafter, the reading operation for each line is repeated in the same way.As explained above, the proposed color reading device reads by flashing a fluorescent light, so the device is small, inexpensive, and It has the advantage of high reliability. However, since fluorescent lamps generally have poor blinking response characteristics, reading scanning during the afterglow time is limited, making it impossible to increase the reading speed sufficiently.

[Purpose of the invention]

In view of these circumstances, an object of the present invention is to provide a color reading device that can perform high-speed reading while blinking a plurality of light sources.

[Structure of the invention]

In the present invention, a light emitting diode is used in place of a fluorescent lamp for a light source that must repeatedly blink and has poor afterglow characteristics compared to a fluorescent lamp among a plurality of light sources that illuminate an original. This makes it possible to improve the reading speed.

, 〔Example〕 The present invention will be described in detail with reference to Examples below.

FIG. 3 shows the reading section of the color reading device of this embodiment. Below the platen glass 12 on which the original 11 is placed are a blue tatami light 13, a green fluorescent light 15, and a red LE light.
A D array 22 is arranged. A red LED array consists of a large number of red LEDs (light emitting diodes) arranged in rows and covered with columnar lenses. Red L E, D
The length of the light emitting portion of the array 22 is +1 + -1' the same as the length of the platen glass 12, and is placed parallel to it at a distance of approximately 1 cm.

FIG. 4 shows the electric circuit of this color reading device. Image signal 24 output from the image sensor 17
The shading correction circuit 25 adjusts the signal level in the scanning direction. The analog image signal 261 thus obtained is converted into an 8-bit digital image (No. 3 28) by the A/D converter 27.
91 controls the blinking of the blue light lamp 13 and the red LED array 22, and distributes the digital image signal 28 to the first or second line memory 31, 32 or the color separation calculation circuit 33 at a predetermined timing.

The first line memory '31 delays the supplied digital image signal 281 by two rasters.

This digital image signal 28. are the light beams of the red LED array 22 blinking at the timing shown in FIG.
As shown in Figure 3, an image (No. 3) is read by simultaneously irradiating the light beam of the linear light lamp 15 that is always on.
is delayed by one raster. This digital image signal 282 is an image signal read by simultaneously irradiating the light beam of the front wall light 13 which blinks at the timing shown in FIG. It is. The image signal 28 directly supplied to the color separation calculation circuit 33. is an image signal read in a state where only the line change light lamp 15 is on. The delayed digital image signals 34.35 output from the first and second line memories 31.32 are supplied to the color separation calculation circuit 33 at the same timing as the digital image signal 283.

The color separation calculation circuit 33 creates an image signal 36 of magenta color component as a complementary color of green. Furthermore, the (green+red) color information and the green only information are subtracted to create an image signal 37 of the cyan color component as the complementary color. Furthermore, the (green+blue) color information and the green only information are subtracted to create an image signal 38 of the yellow component as the complementary color. These operations can be performed using digital subtracters, inverters, and the like. In this way, three color image signals 36 to 38 are created for each line.

As explained above, since the red light emitting diode (red light emitting diode) has a fast blinking response speed, the front wall light 13 can be turned on at the same time as the red light emitting diode is turned off as shown in FIG. In this embodiment, the replacement light lamp 15, which tends to leave afterglow more easily than the front wall light 13, is turned on continuously, but it can be turned on and off to make it blink.
You can also strain it. In this case, it is also possible to use an array of light emitting diodes as the green light source.

〔Effect of the invention〕

As explained above, according to the present invention, since a light emitting diode and a fluorescent lamp are used as a light source, power consumption can be reduced compared to a system using only a fluorescent lamp. A sufficient amount of light can be secured with one light source (1 light source).

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the reading section of a conventional color reading device.
Fig. 2 is a timing chart showing the lighting timing of the light source of this device and the output timing of the image signal after photoelectric conversion, and Figs. 3 to 5 are for explaining one embodiment of the present invention. Of these, FIG. 3 is a schematic configuration diagram of the reading section, FIG. 4 is a block diagram showing the main parts of the electric circuit, and FIG. 5 is various timing diagrams showing the lighting timing of the light source. 11... Manuscript, 13... Front wall light, 15... Line replacement light, 17... Image sensor, 22... Red LED array, 29... Timing control circuit, 33...
・Color separation calculation circuit. Applicant Fuji Xerox Co., Ltd. Agent Patent Attorney Umeo Yamauchi Figure 1 Figure 2 Figure 2 18 19 20 18 19 20 Figure 3 Figure 4

Claims (1)

[Claims] A plurality of different light sources that illuminate the same document, a reading element that reads light based on the light irradiated onto the document by these light sources, a lighting control means that changes the lighting state of these light sources in a series, and Lighting □A color separation circuit that inputs the output signals of the reading element for each of the irradiation lights changed by the control means and processes them to perform desired color separation, and at least one of the plurality of light sources emits fluorescent light. A color reading device characterized in that the light is a light emitting diode and at least one other light emitting diode.