JPS64862B2 - - 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 while being synchronized with the drive of the CCD line sensor 3 (drive circuit 6) to switch the filter 4, so that the same main scan of the document 1 can be performed. By repeatedly reading the information on the line multiple times for each filter, the output of each read CCD line sensor 3 is sent to the signal processing circuit 8, where each output level is compared and the information is divided into different colors. The color information is read by making a logical judgment. 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. Recently, as shown in FIG. 2, a real image of a document image at the same magnification can be read by combining a focusing light transmitter array SLM 9 and a 1-line solid-state image sensor 10 using an amorphous semiconductor such as Sachicon. However, in such an optical system configuration, if a conventional color separation filter using a rotating disk is installed in the optical system path, each filter section becomes long and the rotation circle becomes longer. The diameter of the plate has become extremely large, making it difficult to actually adopt such a method. 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, and the entire device can be made more compact and consume less power.
In particular, the present invention provides a color information reading device that is optimal when using an optical system for reading a real image of equal magnification as shown in FIG. The color information reading device according to the present invention focuses on the spectral characteristics of the spatial light modulation element, and installs this as a color separation filter on the light source side for document illumination, and controls the applied voltage as appropriate. The wavelength of the light is instantaneously switched to perform color separation of image information using light reflected from the surface of the document. In general, a spatial light modulator has a characteristic that its optical rotation varies depending on the wavelength and applied voltage, as shown in FIG. 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. 3, if the applied voltage is set to V ₁ , the optical rotation θ (deg/mm) of red light with a wavelength of 600 nm If an analyzer is applied to this, the transmitted light will have the spectral characteristic a shown by the dotted line in FIG. 4. Furthermore, if the voltage applied to the spatial light modulator is set to V ₂ , blue light with a wavelength of 450 nm can be obtained with the same optical rotation θ, and its transmitted light has the spectral characteristic b shown by the dotted line in Figure 4. You will get something with . 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. 5 and 6, the spatial light modulator 11 having such characteristics is provided with a polarizer 12 disposed on the incident side thereof. and an analyzer 13 disposed on the emission side, which is provided on the illumination light source 14 side via a condensing lens 15 and a filter 16, and the light transmitted through the spatial light modulation element 11 passes through an optical fiber bundle 17 as a transmission path. The light beam is sent to the original 1 and is configured to irradiate the image surface in a line in the main scanning direction. Further, in this embodiment, the reflected light from the document surface is
An optical system is used that sends the original image to the one-line solid-state image sensor 10 through the SLM 9 and reads the original image at the same magnification. CCD
It goes without saying that the line sensor 3 may also be used. Note that the filter 1
6 is because it is not possible to obtain spectral transmission characteristics with good color separation as shown in FIG. 4 by simply switching the applied voltages V ₁ and V ₂ of the spatial light modulation element 11. The color separation is achieved by providing a spectral transmission characteristic of c shown by a dashed line, and by making the spectral output of the spatial light modulation element ₁₁ have a characteristic of d shown by a solid line in the figure when the applied voltages _V 1 and V 2 are switched. It is designed to improve sexual performance. Further, the voltage applied to the spatial light modulation element 11 is controlled by the drive circuit 18 in synchronization with the driving of the one-line solid-state image sensor 10. Further, the output signal of the 1-line solid-state image sensor 10 is sent to the signal processing circuit 8, where the image information for 1 line is accumulated in an analog shift register, and after binary sampling, the voltages V ₁ and V ₂ on the same line are The configuration is such that a logical determination for each color is performed based on a combination of the respective binarized information read at each application of . 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 11 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 11 at a period twice the main scanning period of the original 1. Now, if we are to read black, white, and red information in the document 1, the spatial light modulation element 11 has a filter characteristic that transmits red light as shown in a in FIG. 4, and a filter characteristic that transmits at least one other color of light. Here, by applying voltages V ₁ and V ₂ to the spatial light modulator 11, the spectral transmission characteristics shown by d in FIG. 4 are obtained. When the voltage applied to the spatial light modulator 11 is set to V ₁ in this state, only light with a wavelength range sensitive to red passes through the spatial light modulator 11 and illuminates the document surface in a line. Only the red information on the line is extracted and it is 1 line solid-state image sensor 1.
0, and when the applied voltage is V ₂ , only light with a specific wavelength range that shows no sensitivity to red passes through the spatial light modulator 11 and irradiates the document surface in a line. Black and white information other than the upper red color is extracted and read by the 1-line solid-state image sensor 10. That is, by switching the applied voltages V ₁ and V ₂ of the spatial light modulator 11, when the red part in the original image is irradiated, if the applied voltage is V ₁ , the 1-line solid-state image sensor 10 will emit white light. level (high level)
If almost the same red level is output and the applied voltage is V ₂ at that time, the 1-line solid-state image sensor 1
From 0 onwards, a red level that is almost the same as the black level (low level) is output, and the signal processing circuit 8
By making a logical judgment on the read information at each applied voltage V ₁ and V ₂ on the same main scanning line that has been binarized by Determination of each color information will be made. At this time, by switching the applied voltages V ₁ and V ₂ of the spatial light modulation element 11, when reading the blue information in the original image, if the applied voltage is V ₁ , the information from the 1-line solid-state image sensor 10 is read. The blue level will be output at almost the same level as the black level (low level), and if the applied voltage is V ₂ at that time, the blue level will be output at almost the same level as the white level (high level). , each color information of blue, black, and white is read by a combination of the respective binarized information.

[Table] As described above, in the color information reading device according to the present invention, a spatial light modulation element having a polarizer on the input side and an analyzer on the output side is arranged in the light source system for illuminating the document. By controlling the switching of the applied voltage, the wavelength of the illumination light can be switched instantaneously to perform color separation of image information using light reflected from the document surface, and it is possible to switch the characteristics of multiple color separation filters. can be performed at high speed and stably in a stationary and fixed state, and is also compact.
It has various excellent advantages such as low power consumption, especially as shown in Figure 2.
This is advantageous when using an optical system that combines an SLM and a 1-line solid-state image sensor to read original images at the same magnification. It has to be formed to have the same scanning width as one line of the surface, which makes it difficult to form.Furthermore, in the present invention, the voltage applied to the spatial light modulator is changed especially on the incident side of the spatial light modulator. A filter is provided that passes only light in a specific wavelength range according to the spectral transmission characteristics of When making a logical color judgment based on a combination of results, this is an excellent method that can read color information with good color separation and perform optimal binarization, thereby making it possible to make accurate color judgments. It has advantages.

[Brief explanation of drawings]

Fig. 1 is a simplified configuration diagram showing a conventional color information reading device, Fig. 2 is a diagram illustrating an example of the configuration of an optical system for reading a document image at the same magnification, and Fig. 3 is a diagram showing wavelength versus voltage applied to a spatial light modulation element. FIG. 4 is a diagram showing the optical rotation characteristics; FIG. 4 is a diagram showing the spectral output characteristics of the spatial light modulation element when the applied voltage is changed; FIG. 5 is a simplified configuration diagram showing an embodiment of the color information reading device according to the present invention. , FIG. 6 is a diagram showing the configuration of the illumination light source system in the same embodiment. 1... Original, 2... Lens, 3... CCD line sensor, 4... Filter, 5... Rotating disk, 6... Drive circuit, 8... Signal processing circuit, 9... SLM, 10... 1-line solid-state image sensor, 11... Space light modulation element, 12
...Polarizer, 13...Analyzer, 14...Light source for illumination, 1
5... Condenser lens, 16... Filter, 17... Optical fiber bundle, 18... Drive circuit.

Claims (1)

[Scope of Claims] 1. In an optical system that images reflected light from the document surface when the document surface is illuminated on an image sensor, a polarizer is provided on the input side in the system path on the illumination side of the document surface, and a polarizer is provided on the input side. A spatial light modulation element is provided with an analyzer on each side and switches the wavelength of the transmitted light by controlling the switching of the applied voltage. A filter is provided that allows only light in a specific wavelength range to pass according to the spectral transmission characteristics by switching the voltage, and the signal processing circuit processes each output signal from the image sensor each time the voltage applied to the spatial light modulation element is switched. A color information reading device configured to read color information of a document by binarizing it and then performing a logical color determination based on a combination of the results. 2 Illumination light whose wavelength has been switched by a spatial light modulator is irradiated onto the document surface in a line through an optical fiber bundle, and the reflected light is directed onto a one-line image sensor through a convergent light transmitter array. 2. The color information reading device according to item 1 above, wherein the color information reading device is configured to form an image. 3 Illumination light whose wavelength has been switched by a spatial light modulator is irradiated onto the document surface in a line through an optical fiber bundle, and the reflected light is directed onto a one-line image pickup device through a convergent light transmitter array. 2. A color information reading device according to item 1 or 2, characterized in that the color information reading device is configured to form an image.