JPS61167279A - Color reading circuit - Google Patents

Abstract

PURPOSE:To provide for high speed reading with inexpensive construction by simultaneously scintillating at least two different kinds of optical sources at a preset period, reading the first image at a common lighting period and reading the second image while there is the remnant light. CONSTITUTION:At least two kinds of light sources 211, 212... are simultaneously scintillated at preset period by scintillating means 22. The first image is read by an image sensor 19 during the period these light sources 211, 212... are lighted together, the second image is read by the sensor 19 during the period the remnant light from one light source exists, and picture signals 241, 242 outputted over two domains from the sensor 19 are outputted to a color separating circuit 25. The circuit 25 effects color separation on the basis of the signals 241, 242. Since no bright line spectrum exists in the remnant light component, pure wavelength components can be obtained with accurate and facilitated color separation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color reading device for separating and reading a color image into two or more colors.

"Prior art" For example, two of the color reading devices using image sensors
A color reading device separates image information on a document into two colors, such as red and blue, and reads a color image.

FIG. 8 shows such a conventional reading device using one type of light source. In this apparatus, a document 11 is irradiated with a white light source 12. After the reflected light passes through the lens 13,
The optical path is branched by a half mirror 14. Optical filters 15□ and 15□ and image sensors 161 and 162 are respectively arranged on the optical path after the branching, and light rays in a wavelength range corresponding to blue or red are detected.

This device has the problem that an expensive image sensor →J° must be used for each color, which increases the cost.

In contrast, FIG. 9 shows a conventional color reading device that uses a common image sensor.

This device is equipped with two types of light sources: a red fluorescent lamp 181 and a blue fluorescent lamp 182. These fluorescent lamps18. ．． At 18°, lighting is repeated exclusively at each lighting timing shown in FIG. The image sensor 19 cyclically reads each red and blue image information in synchronization with these lighting timings.

Although the latter color image reading device reduces the number of expensive optical components, it still requires a light source for each color to blink at high speed. However, many red light sources in particular have a long afterglow, which poses an obstacle to improving reading speed.

Therefore, for light sources with a relatively long afterglow, a color reading device has been proposed in which images are read by continuously lighting the light source (Japanese Patent Application No. 58-1495).
6'9). This device has the same device configuration as that shown in FIG. 9, but as shown in FIG. 11, a red fluorescent lamp 18. is turned on continuously (FIG. 2A), and the blue fluorescent lamp 182 is caused to blink repeatedly (FIG. 1B). This color reading device can use a normal red light source with a long afterglow, and is extremely advantageous in terms of cost. However, with this latter device, the difference in the integral value of the lighting time of the two types of light sources increases over time, and the difference in heat generation temperature of these light sources becomes significant, eventually causing the balance of light intensity to collapse. There was a problem.

``Problems to be Solved by the Invention'' That is, conventional color reading devices have had problems in that they are expensive and that there are limits to the reading speed and accuracy of color separation.

In view of these circumstances, it is an object of the present invention to provide a color reading device that can be constructed at a relatively low cost and that can perform high-speed reading.

"Means for Solving Problems" In the present invention, as shown in principle in FIG.
Types of light sources 21. ．． 2], . . . at the same time at a predetermined period;
．． The image sensor 23 reads the first image in the section where 212... are commonly lit, and reads the second image in the section where at least the afterglow of one of the light sources remains. and these two from the image sensor 19.
Image signal 24 output over a period. ．． The color reading device is equipped with a color separation circuit 25 that performs color separation based on H.242.

That is, in the present invention, at least two types of light sources 21, .
21. ...... is controlled to turn on, the document is read for the wavelength component when these light sources are commonly turned on, and in the section where these are controlled to turn off, the document is read for the wavelength component due to the afterglow of at least one type of light source. Read the manuscript for the ingredients. As a result, while maintaining the light balance,
High-speed reading becomes possible.

"Example" The present invention will be described in detail below with reference to Examples.

Figure 2 shows red and blue 2 as an example of this color reading device.
This is a schematic representation of a color reading device that reads colors. This apparatus is equipped with two types of fluorescent lamps, a red fluorescent lamp 181 and a blue fluorescent lamp 182, for illuminating the document 31. Each fluorescent lamp18. ．． 18
2 is turned on by lighting circuits 320 and 322. The lighting timing of these lighting circuits 320 and 322 is controlled by two lighting control units 33. ．． It is done by 33 degrees.

FIG. 3 shows the lighting timing of these fluorescent lamps 180 and 182 and the signal waveform of the image signal read out. In this device, both fluorescent lamps 181 and 182 simultaneously repeat the blinking operation at intervals of 1 m5ec (aSc in the same figure).
). Calcium tungstate, for example, is used as the phosphor of the blue fluorescent lamp 182, and as shown in the figure, the amount of light increases rapidly when the lamp starts to turn on, and similarly rapidly decreases to zero when the lamp is turned off. On the other hand, in the case of the red fluorescent lamp 18+, magnesium germanate is used as the phosphor in this example, and although the light intensity attenuates to some extent when the lamp is turned off, the afterglow component remains considerably until the next time it is turned on. It remains to a certain extent.

The red, blue, and bicolor fluorescent lamps 181 and 182 have spectral characteristics that roughly divide the visible region into two, as shown in FIG. Therefore, these fluorescent lamps 18, . In section A where the lights 182 are lit at the same time, the original 31 is irradiated with approximate white light that is a mixture of these lights. In addition, in section B other than this, only the red fluorescent lamp 18□
Irradiation is performed using red light.

Such switching of the irradiation light is performed by the line synchronization signal 35. That is, the line synchronization signal 35 generated prior to the start of reading one scan of each line is transmitted to the double-point controllable section 33. ．． 332, and in synchronization with this, on/off control of lighting is performed simultaneously.

The line synchronization signal 35 is also supplied to an image sensor drive circuit 36. The image sensor drive circuit 36 serially outputs a transfer lock 37 for transferring an image for one scan each time the line synchronization signal 35 is supplied. The image sensor 19 that has been supplied with the transfer lock 37 is
In section A shown in FIG. 3, an image (d
No. 38Δ is output, and in section B, a similar image signal 38B is output by irradiation with white light. These image signals 38A
, 38B are supplied to the A/D conversion circuit 41 in synchronization with the video clock 39 output from the image sensor drive circuit 36, and are sequentially A/D converted.

The digital image signals 42A and 42B after A/D conversion are supplied to a switch circuit 43, and are alternately output one line at a time from output terminals T1 and T2 in accordance with a line synchronization signal 35. In other words, in this color reading device, the original 31 is scanned twice with different irradiation lights to finish reading one line, but in section A, a digital image signal is obtained by quantizing the image signal 38A output from the image sensor 19. 42
A is first output from one output terminal T1, and in the next section B, a quantized digital image signal 42B is output from the other output terminal TI2. The digital image signal 42A output from the output terminal Tl is delayed by one scan by the line memory 45, and becomes a delayed image signal 46Δ. The delayed image signal 46A is serially output in a state in which the bits correspond strictly to the digital image signal 42B outputted from the other output terminal T2 of the switch circuit 43, and is supplied to the color separation memory 47.

The color separation memory 47 is composed of a ROM (read-only memory), and takes in two types of image signals 42B and 46A for each pixel in synchronization with the video clock 39, and performs color separation using these as address information. It turns out. The principle of color separation by this color separation memory 47 will be explained next.

FIG. 5 shows two types of fluorescent lamps 18. ．． 182 represents the wavelength components of the light beam irradiated onto the original and the signal level of the image signal output from the image sensor. Figure a shows the case where a white background (ground color) part of the document is read, and the fluorescent lamp 181.18
White light as a mixed light of 2 is also a fluorescent lamp 18. Nearly 100% of the red light is reflected. As a result, the signal levels of the image signals due to these reflected lights are both the highest.

On the other hand, when a pure black portion of a document is read, almost no reflection occurs for any of the wavelength components, and the signal levels are both close to zero, as shown in the figure.

On the other hand, when reading a document portion written with red ink or a red ballpoint pen, the white light emitted by the blue fluorescent lamp 182 is absorbed, and the signal level of the image signal obtained is as shown in the figure. It is shown as the waveform on the left side of C.
It is an intermediate value.

In the case of single irradiation with the red fluorescent lamp 181, the reflectance is high (,:3r), so the No. 14 level is also high (
(C right side in the same figure). In the manuscript portion written with blue ink or square ballpoint pen, the same results as in the red manuscript portion are obtained with respect to white light (left side of d in the same figure). Red light is hardly reflected and the signal level is close to zero (left side of d in the figure).

In this way, the signal levels of the two types of image signals 42B and 46A change depending on the color state of the portion of the document to be read. Therefore, by expressing these signal levels, for example, on the vertical and horizontal axes, a color distribution map can be obtained.

FIG. 6 shows this color distribution map.

In this figure, the signal level of the digital image signal 42B for white light as a mixed light of red and blue is expressed in percentage on the horizontal axis, and the signal level of the digital image signal 46A for red is similarly expressed on the vertical axis. It represents.

The color separation memory is constituted by a ROM having the contents shown in FIG.
Image signals 51R and 51BL are separated at pixel ri for red, blue and black using address information 6A.
, outputs 518K. 3 types of image signals 51R151B
L, 51BK is a recording unit of a printer or copying machine (not shown),
Or it will be sent to a display device and recorded or displayed.

In the embodiment described above, as shown in FIGS. 3a and 3c, red, blue, and both fluorescent lamps 18. ．． The lighting control time and the lighting control time of 182 were made equal, but the red fluorescent lamp 18
In order to bring the amount of light of the afterglow component of the lamp close to that when the lamp is turned on, the lighting control of both fluorescent lamps 180 and 18□ may be performed independently. FIG. 7, which corresponds to FIG. 3, shows an example of such independent control, in which the blue fluorescent lamp 18
20. Red fluorescent lamp with lighting time 18. It is shorter than that of .

"Effects of the Invention" As explained above, according to the present invention, since images are read using afterglow, the accuracy of color separation is improved. That is, since there is no bright line spectrum in the afterglow component, purer wavelength components can be obtained, making color separation easier and more accurate.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the principle of the present invention, Figures 2 to 6
The figures are for explaining one embodiment of the present invention, of which Figure 2 is a schematic configuration diagram of a color reading device, Figure 3 is an explanatory diagram showing lighting control of two types of light sources, and Figure 4 is an explanatory diagram showing lighting control of two types of light sources. are characteristic diagrams of these light sources, Figure 5 is various waveform diagrams showing image signal levels for various document parts, Figure 6 is an explanatory diagram of the contents of the color separation memory, and Figure 7 is other lighting of the two types of light sources. An explanatory diagram showing control, FIG. 8 is a schematic diagram of the optical system of a color reading device using a plurality of image sensors, and FIG. 9 is a schematic diagram of the optical system of a color reading device using a plurality of light sources. FIG. 10 is a timing diagram for explaining the lighting control of the light source in the conventional color reading device shown in FIG.
The figure is a timing diagram for explaining another conventional lighting control. 18... Fluorescent lamp 19... Image sensor, 21... Light source, 22... Flashing means, 25... Color separation circuit, 32...Lighting circuit, 33...Lighting control section, 47...Color separation memory. Applicant: Fuji Xerox Co., Ltd. Representative
To the CO of patent attorney Umeo Yamauchi ω 6 ha cd ID Q' ”,,
, J Ri I Q Figure 6 Figure 8 Figure 9 Figure 10

Claims (1)

[Claims] 1. Flashing means for simultaneously flashing at least two types of light sources at a predetermined period; a first image is read in a section where these light sources are commonly turned on; an image sensor that reads a second image in a section where at least afterglow remains, and a color separation circuit that performs color separation based on image signals output from the image sensor over these two sections. A color reading device characterized by: 2. Claim 1, characterized in that one of the two types of light sources is a light source with a longer afterglow than the other.
Color reading device as described in section.