JPS64861B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in an apparatus for reading color information of a document. Generally, in order to read the color information of a document, a plurality of filters each having different light transmission characteristics are used, and the document image is read optically while separating the colors for each filter. Conventionally, as this type of color information reading device, the first
As shown in the figure, the image plane of the original 1 is illuminated with a slit (the illumination light source is not particularly shown),
In an optical system configured to sequentially read original images by focusing the reflected light onto an image sensor such as a CCD line sensor 3 via a lens 2, a plurality of color separation filters 4 are arranged on the circumference. A rotary disk 5 is provided, which is rotated by a motor 7 in synchronization with the drive of the CCD line sensor 3 (drive circuit 6) to switch the filter 4.
By repeatedly reading the information on the same main scanning line of the document 1 multiple times for each filter, each read output of the CCD line sensor 3 is sent to the signal processing circuit 8, where each output level is determined. While comparing, a logical judgment is made for each color and the color information is read. However, in the conventional color information reading device configured in this way, there is a limit to high-speed reading because the filters 4 are switched by the rotating disk 5, and the filters 4 are switched sequentially. Since the filters 4 are used in different colors, they are easily affected by variations in the color resolution or spectral transmission characteristics of each filter 4, and since they have rotary drive parts, they are structurally unreliable. The space factor is poor due to the dead space of the rotating disk 5, and the power consumption is large due to the motor drive. The present invention has been made in consideration of the above points, and
By performing color separation in a stationary and fixed state, color information can be read at high speed and with high reliability, making the entire system more compact and requiring less power consumption. A reading device is provided. The color information reading device according to the present invention focuses on the spectral characteristics of the spatial light modulation element, uses it as a color separation filter, and controls the applied voltage as appropriate, thereby instantly detecting transmitted light. The wavelength is switched to perform color separation of optical image information incident thereon. Generally, as shown in FIG. 2, a spatial light modulator has a characteristic that its optical rotation varies depending on the wavelength and applied voltage. Therefore, conversely, it is possible to change the wavelength that results in the same optical rotation depending on the applied voltage. This means that the peak spectrum can be selected as transmitted light. The function of such a spatial light modulator is the same as a kind of color separation filter, and in Fig. 2, if the applied voltage is set to V ₁ , the optical rotation of red light with a wavelength of 600 nm is ), and if an analyzer is applied to this, the transmitted light will have the spectral characteristic a shown by the dotted line in FIG. 3. Furthermore, if the voltage applied to the spatial light modulator is set to V ₂ , blue light with a wavelength of 450 nm is obtained with the same optical rotation θ, and as the transmitted light, the third
A product having the spectral characteristics b shown by the dotted line in the figure is obtained. In this way, the spatial light modulation element can serve as multiple types of color separation filters with one element, and the switching of the color separation characteristics can be performed by changing the applied voltage without any dynamic changes in the optical system. It has the characteristic that it can be done instantly just by doing the following. Therefore, in the color information reading device according to the present invention, as shown in FIGS. 4 and 5, a polarizer 10 having a spatial light modulator 9 having such characteristics is disposed on its incident side. It is installed in the optical system for reading the original image together with the analyzer 11 arranged on the emission side, and the color separation is performed and the selected optical information is transmitted to the lens 2.
The optical system is configured to form an image on the CCD line sensor 3 via the CCD line sensor 3. Further, the voltage applied to the spatial light modulation element 9 is controlled by the drive circuit 12 in synchronization with the drive of the CCD line sensor 3. moreover,
The output signal of the CCD line sensor 3 is sent to the signal processing circuit 8, where the image information for each line is accumulated in an analog shift register, and after binary sampling, each of the voltages V ₁ and V ₂ on the same line is The configuration is such that a logical determination for each color is performed based on a combination of the respective binarized information read at the time of application. The operation of the color information reading device according to the present invention configured as described above when reading two-color information of a document image will now be described. In this case, the spatial light modulation element 9 is provided with two types of color separation filter functions, and the document image is repeatedly read by each color separation for each main scanning line of the document 1. It is necessary to alternately switch the voltage applied to the light modulation element 9 at a cycle twice as long as the main scanning cycle of the original 1. Now, if black, white, and red information in the document 1 is to be read, the spatial light modulation element 9 has a filter characteristic that transmits red light as shown in a in FIG. 3, and a filter characteristic that transmits at least one other color of light. In this case, the spatial light modulator 9
By applying the applied voltages V ₁ and V ₂ to , respectively, the spectral transmission characteristics shown by a and b in FIG. 3 are obtained. In addition, at this time, as shown in FIG. 3, it is not possible to obtain spectral transmission characteristics with good color separation by simply switching the respective applied voltages V ₁ and V ₂ to the spatial light modulation element 9. A filter 13 having a spectral transmission characteristic of c indicated by a dashed dotted line is provided in front of the polarizer 10 (see FIGS. 4 and 5), and the spatial light modulator 9 is connected to the spatial light modulator 9 when the applied voltages V ₁ and V ₂ are switched. The spectral output is made to have the d characteristic shown by the solid line in the figure to improve color separation. In this state, the voltage applied to the spatial light modulator 9
When V ₁ and V ₂ are switched, when red information in the original image is read, if the applied voltage is V ₁ , the CCD line sensor 3 will output red as a level almost the same as the white level (high level). If the level is output and the applied voltage is V ₂ then
The CCD line sensor 3 outputs a red level that is almost the same level as the black level (low level), and the signal processing circuit 8 converts it into two values according to the output of the CCD line sensor 3. By making a logical judgment on the read information at each applied voltage V ₁ and V ₂ on the same main scanning line, the red, black, and white color information is determined as shown in the table above. Become. In addition, at this time,
When the blue information in the original image is read by switching the voltages V ₁ and V ₂ applied to the spatial light modulator 9,
If the applied voltage is V ₁ , the CCD line sensor 3 will output a blue level, which is almost the same level as the black level (low level), and if the applied voltage is V ₂ , it will output a white level (high level). The blue level will be output as almost the same level, and the combination of each binary information will produce blue, black,
Information on each color of white will be read.

[Table] As described above, in the color information reading device according to the present invention, an optical system path for reading a document image by focusing reflected light from the document surface onto an image sensor through a lens.
A spatial light modulator with a polarizer in front and an analyzer in the rear is provided, and by controlling the switching of the voltage applied to the spatial light modulator, the wavelength of the transmitted light can be switched instantaneously. With this system, multiple color separation filter characteristics can be switched quickly and stably in a stationary and fixed state, and it is also compact and consumes low power. It has various excellent advantages. In addition, in the present invention, a filter is provided on the incident side of the spatial light modulation element to pass only light in a specific wavelength range according to the spectral transmission characteristics by switching the applied voltage of the spatial light modulation element, and the spatial light modulation element is used in the signal processing circuit. When each output signal from the image sensor is binarized each time the voltage applied to the modulation element is switched, and a logical color judgment is made based on the combination of the results, color information with good color separation is read. It has the excellent advantage of being able to perform value conversion optimally, thereby allowing accurate color determination.

[Brief explanation of drawings]

Fig. 1 is a simplified configuration diagram showing a conventional color information reading device, Fig. 2 is a diagram showing the wavelength-optical rotation characteristic of the spatial light modulator with respect to the applied voltage, and Fig. 3 is a diagram showing the spatial light when changing the applied voltage. FIG. 4 is a diagram showing the spectral output characteristics of the modulation element, FIG. 4 is a simplified configuration diagram showing an embodiment of the color information reading device according to the present invention, and FIG. 5 is a side view of the optical system in the same embodiment. 1... Original, 2... Lens, 3... CCD line sensor, 4... Filter, 5... Rotating disk, 6... Drive circuit, 7... Motor, 8... Signal processing circuit, 9... Spatial light modulation element, 10... Polarizer , 11...analyzer, 12...
Drive circuit, 13...filter.

Claims (1)

[Claims] 1 A polarizer is placed on the input side and an analyzer is placed on the output side in the optical system path that images the light reflected from the document surface onto the image sensor, and by controlling the switching of the applied voltage, the transmitted light is A spatial light modulation element that performs wavelength switching, and a filter placed on the incident side of the spatial light modulation element that allows only light in a specific wavelength range to pass according to the spectral transmission characteristics by switching the applied voltage of the spatial light modulation element. The signal processing circuit binarizes each output signal from the image sensor each time the voltage applied to the spatial light modulation element is switched, and then performs a logical color judgment based on the combination of the results. A color information reading device configured to read color information of a document.