JPS649788B2 - - Google Patents

Description

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

[Prior art]

A color image reading device using an image sensor usually separates image information on a document into three colors, blue, green, and red, and reads a color image.

FIG. 1 shows a conventional color image 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, it passes through the two half mirrors 1
4 and 15, the optical path is branched into three directions. Optical filters 16 ₁ to 16 ₃ are provided in the optical path after branching.
and image sensors 17 ₁ to 17 ₃ are arranged, and the light rays after spectroscopy are detected.

This device has a problem of high cost due to the use of a plurality of expensive image sensors and half mirrors.

In contrast, FIG. 2 shows a conventional color image reading device that uses a common image sensor. This device has a red light source 18 ₁ and a green light source 1.
Three light sources, 8 ₂ and a blue light source 18 ₃ are provided. These light sources 18 ₁ to 18 ₃ repeat lighting exclusively at each lighting timing shown in FIG. 3. The image sensor 19 cyclically reads red, green, and blue image information in synchronization with these lighting timings.

Although the latter color image reading device reduces the number of expensive optical parts, it requires three types of independent light sources, which increases the size of the device. Another disadvantage is that the circuit for driving these three types of light sources in a time-division manner is complicated.

[Purpose of the invention]

In view of the above circumstances, an object of the present invention is to provide a color image reading device that can read three colors with a simple configuration.

[Structure of the invention]

In the present invention, two types of light sources whose peak wavelengths of emission distributions are different from each other and whose peak wavelength of the sum of the emission distributions is between the respective peak wavelengths, and a predetermined period of at least one of these two types of light sources are provided. a common reading element that outputs two color signals corresponding to the two types of light sources using reflected light or transmitted light of the document irradiated by the two types of light sources; A specific color discrimination means that receives two color signals as input and discriminates three types of specific colors: two specific colors corresponding to two types of light sources and a third specific color corresponding to the sum of the two types of light sources. and a color image reading device.

Then, three types of signals are created from two types of image signals obtained by different irradiation lights on the same original portion, and based on these, it is possible to read three colors.

〔Example〕

The present invention will be explained in detail with reference to Examples below.

FIG. 4 shows the reading section of the color image reading device of this embodiment. This device has 11 originals.
Two types of light sources 21 and 22 are provided for irradiating light. Light reflected from the original 11 by these light sources 21 and 22 is converged onto an image sensor 19 by a lens 13. The image sensor 19 is a line sensor in which light-receiving elements are arranged in a row in the direction perpendicular to the figure, and reads image information line by line while moving the original 11 stepwise in the direction of the arrow (sub-scanning direction). There is. The first light source 21 has a Gaussian-type emission distribution biased toward the short wavelength side, as shown by a curve 23 in FIG. 5, and the peak wavelength is about 450 nm (blue).
The second light source 22 has a Gaussian-type emission distribution biased toward the longer wavelength side, as shown by a curve 24 in the figure, and the peak wavelength is about 570 nm (red).

FIG. 6 shows the circuit configuration of this color image reading device. The timing control circuit 24 of this device is supplied with a clock signal (not shown) and controls the image sensor 19, two types of light sources 21, 2.
2 and a document conveyance motor drive circuit 25. Figure 7 shows this timing control, and the shaded area 2 in Figure a.
Reference numeral 6 indicates a lighting section of the first light source 21, and a shaded area 27 in FIG. The image sensor 19 scans an image 28 once in each of these lighting sections. (Figure c). After scanning for two lines, as shown in d in the same figure, in the interval t until the start of the next scan,
A document conveyance motor drive circuit 25 drives a document conveyance motor (not shown). As a result, the original 11 is sub-scanned by the number of lines. In this way, reading of the original 11 is repeatedly executed.

Now, the image signal 29 sequentially outputted from the image sensor 19 is converted by the A/D converter 31 into a digital signal 32 of 16 gradations (4 bits). Of these, the digital image signal 32 ₁ obtained when the first light source 21 is turned on is temporarily stored in the random access memory 33. Then, with the second light source 22 turned on, the digital image signal 32 ₂
When obtained, it is read out at this timing and supplied to both the read-only memory 34 and the adder 35. At this time, the digital image signal 32 ₂
is similarly input to both the read-only memory 34 and the adder 35. The adder 35 adds the two digital image signals 32 ₁ and 32 ₂ , converts the addition result into 16 steps, and generates the digital image signal 36
Create. This digital image signal 36 is also supplied to the read-only memory 34.

The read-only memory 34 uses the supplied three types of digital image signals 32 ₁ , 32 ₂ , and 36 as address information to discriminate colors from this 12-bit data. This principle will be explained based on FIG.
Image information is written on the original 11 using writing instruments prepared in advance in three colors: blue, green, and red. When the first light source 21 (FIG. 6) is turned on, the specific sensitivity of the image sensor 19 is within the first region 37 near the peak of the curve 23 in the part where the blue writing tool is used. value. Second light source 22 (sixth
) is lit, the specific sensitivity of the image sensor 19 becomes a value within the second region 38 near the peak of the curve 24 in the area where a red writing instrument is used.

The luminescence distributions represented by both curves 23 and 24 are simply added, and the specific sensitivity, with the maximum value as 100%, is a curve 39 represented by a broken line. This curve 39 is approximately
The specific sensitivity has a peak at 500 nm (green). Therefore, in the area where a green writing instrument is used, the peak of its specific sensitivity is a value within the third region 41 near the peak of the curve 39, which has a peak between the peaks of the curves 23 and 24.

The read-only memory 34 stores the discrimination results 42 to 42 of blue, red, and green colors corresponding to the addresses corresponding to the areas 37, 38, and 41, respectively.
44 is written. Therefore, for example, when a portion where a blue writing instrument is used is read, a blue discrimination result 42 will be output. Since each region 37, 41, 38 is set in relation to the wavelength components of the light sources 21, 22, the writing instrument does not necessarily have to have three primary colors. That is, by selecting a light source, it is possible to read any three specific colors.

[Modified example]

FIG. 8 shows a modification of the embodiment described above. With this color image reading device,
A subtracter 46 is used to subtract the digital image signal 32 ₁ read from the random access memory 33 and the digital image signal 32 ₂ directly output from the A/D converter 31. Therefore, the timing control circuit 47 controls the first light source 21 as shown in FIG.
The section indicated by the shaded area 48 is lit. Also the second
The light source 22 is turned on continuously as indicated by the diagonal line 49 (b in the figure). In the case of this modification, the curve 3 is
A light emission distribution corresponding to curve 9 is obtained, and in a state where the light is off, a light emission distribution corresponding to curve 24 is obtained. Digital image signal 5 that is the output of the subtracter 46
1 is a value obtained by converting these differences into specific sensitivity, and the specific sensitivity curve corresponds to curve 23. The read-only memory 34 uses three types of digital image signals 32 ₁ , 32 ₂ , 51 as address information,
Based on the principle already explained, the discrimination results 42 to 44 for each color are output.

In the embodiments and modifications described above, each color is discriminated using a read-only memory, but three color signals, which are two color signals and their sum signal or difference signal, are compared by a comparison circuit. It is also possible to make these determinations based on the magnitude relationship of the specific sensitivities. Further, the light source used in the present invention may be a white light source, and in this case, an optical filter is used to set the wavelength range to a predetermined range.

〔Effect of the invention〕

As described above, according to the present invention, the device is simplified and its reliability is improved. Furthermore, by replacing the light source, it is possible to read color image information that combines desired specific colors.

[Brief explanation of the drawing]

1 and 2 are schematic configuration diagrams showing the reading section of a conventional color image reading device, respectively.
The figure is a timing diagram showing the lighting timing of each light source in the conventional example shown in Figure 2, Figures 4 to 7 are for explaining one embodiment of the present invention, and Figure 4 is a reading unit 5 is a characteristic diagram showing the specific sensitivity of the image sensor for each light source in relation to the color read, FIG. 6 is a block diagram showing the configuration of the electric circuit, and FIG. 7 is a diagram of this device. FIG. 8 is a block diagram showing the configuration of an electric circuit in a modified example of the present invention, and FIG. 9 is a timing chart showing the lighting timing of the light source in this modified example. 11... Original, 19... Image sensor, 2
1, 22...Light source, 24, 47...Timing control circuit, 34...Read-only memory, 35
...Adder, 46...Subtractor.

Claims (1)

[Scope of Claims] 1. Two types of light sources whose emission distributions have different peak wavelengths and whose peak wavelength of the sum of the emission distributions is between the respective peak wavelengths, and at least one of these two types of light sources. a light source blinking control means that blinks at a predetermined cycle; and a common light source that outputs two color signals corresponding to the two types of light sources using reflected light or transmitted light of the document irradiated by the two types of light sources. a reading element; a signal generating section that inputs the two color signals and outputs three color signals that are a sum signal or a difference signal; a signal generating section that receives the three color signals and is compatible with the two types of light sources; It is characterized by comprising a specific color discrimination means comprising a discrimination section that outputs the discrimination results of three specific colors: two specific colors and a third specific color corresponding to the sum of the two types of light sources. color image reading device. 2. The color image reading device according to claim 1, wherein the determining section is a memory. 3. The color image reading device according to claim 1, wherein the discrimination section includes a comparison circuit that compares the magnitudes of the three color signals.