JPS6126999Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a two-color reading device that has a function of separately reading red and black for an original written in two colors, such as red and black.

One type of two-color reading device is shown in FIG. In the figure, 1 is the manuscript, 2
and 3 are fluorescent lamps for document illumination having green and red spectral distributions, respectively. Also, 4 is a lens,
5 is a solid-state image sensor typified by a CCD image sensor.

Next, the operation will be explained. In the reading device shown in FIG. 1, main scanning is performed by a shift register built into the solid-state image sensor 5, as shown in FIG. . The scanning of the solid-state image sensor 5 is performed continuously as shown in FIG. 2a, while the timing of lighting up the green and red fluorescent lamps and the timing of sub-scanning feeding of the original are shown in FIG. 2b, respectively. , c and d, this is performed in synchronization with the scanning of the solid-state image sensor 5. That is, first, the document is stopped, and the green fluorescent lamp 2 is turned on during the first main scanning period to accumulate green light information of the reading line on the document surface in the solid-state image sensor 5. Then, during the next main scanning period, the accumulated optical information is extracted as a green signal, and the red fluorescent lamp 3 is turned on to accumulate the red optical information of the same reading line on the document surface in the solid-state image sensor 5. Furthermore, the optical information accumulated during the next main scanning period is extracted as a red signal, and the document is moved by the sub-scanning line pitch in preparation for reading the next line. By repeating such a reading operation, a photoelectric conversion signal as shown in FIG. 2e is obtained from the solid-state image sensor 5. As is clear from this figure, for each main scanning line, the green signal when lit by green fluorescent lamp 2 and the red signal when lit by red fluorescent lamp 3 are displayed in chronological order. can get.

Next, FIG. 3 shows an example of the spectral reflectance characteristics of each of the red part, the black part, and the white part of the background of the document on the manuscript surface. In addition, green fluorescent light 2
The wavelength distribution range of the emitted light flux of the red fluorescent lamp 3 is shown below the horizontal axis in FIG. As is clear from the figure,
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For black and white backgrounds, the reflectance is almost the same whether illuminated with green fluorescent lamp 2 or red fluorescent lamp 3, but for red parts, red fluorescent lamp 3 The reflectance when illuminated is much higher than the reflectance when illuminated with the green fluorescent lamp 2. Therefore, the difference between the red signal and the green signal shown in FIG. 2e is taken, and if the difference is greater than a certain value, it can be identified as a red portion. Furthermore, a signal corresponding to the black portion of the document surface is obtained by subtracting the signal indicating the red portion from the signal obtained by binarizing the green signal using a predetermined threshold value.

By the way, in the operating principle shown in FIG. 2, the fluorescent lamp needs to be turned on intermittently, so the response time for turning on and off needs to be sufficiently short with respect to the scanning time of the solid-state image sensor 5. For example, in facsimile machines, the reading time for one line is often selected to be 10ms to 50ms, and in order to perform two-color reading by sequentially turning on the green and red fluorescent lamps within this time, at least Desirably, the response time of the lamp is less than a few hundred microseconds. The response time of a fluorescent lamp is divided into the time required for the fluorescent lamp itself to start and stop discharging, and the afterglow time of the fluorescent lamp. The former is normally small enough to several hundred microseconds and is not a problem, but the afterglow of fluorescent lamps varies greatly depending on the fluorescent lamp. Regarding the afterglow time of fluorescent lamps that are generally put into practical use, some phosphors on the short wavelength side of blue to green have a sufficiently short afterglow time, but fluorescent lights on the long wavelength side of red color have sufficiently short afterglow times. As for the body, no one with a short afterglow time has been put into practical use, and the size is usually from several ms to several + ms. Therefore, when the reading speed of one line is increased, the emission time of the red fluorescent lamp 3 and the emission time of the green fluorescent lamp 2 partially overlap, as shown in FIG. There was a drawback that the red and green signals could not be separated because the signals partially overlapped with each other.

This invention was made in order to eliminate the drawbacks of such conventional two-color reading devices, and the red fluorescent lamp 3 mentioned above has a red signal that is always on and outputs a red signal and a red + green signal. By discriminating the green signal by calculating from the above, the red signal and the green signal can be separated even in high-speed reading.

FIG. 5 shows signal waveforms for two-color document reading based on this invention. As shown in the figure, the green fluorescent lamp 2 is lit intermittently as in the prior art, but the red fluorescent lamp 3 is lit continuously. Further, the document is moved in the same manner as d in FIG. Therefore, a (green+red) signal and a red signal are obtained in time series for one scanning line. It is easy to understand that a green signal can be obtained by delaying the (green+red) signal by one scanning period of the solid-state image sensor 5 using a delay circuit and taking the difference from the red signal. In this way, the green signal and the red signal can be separated, and by performing the same processing on both signals as in a conventional two-color reader, a signal indicating the red portion and a signal indicating the black portion are obtained. be able to.

In the two-color reading device based on this idea,
Since the red fluorescent lamp 3 having a long afterglow time is always on, there is no restriction on the reading speed caused by the afterglow time of the red fluorescent lamp 3. Furthermore, as mentioned above, the afterglow time of the green fluorescent lamp 2 is often sufficiently small, and as a result, the reading speed can be increased several times or more compared to conventional devices.
The effect is great.

In the above embodiment, a two-color reading device that uses red and green fluorescent lights to illuminate the original and reads the red and black parts of the original separately was shown. The same thing can be done even if a light source other than a lamp (for example, a halogen lamp covered with a color filter) is used. Furthermore, the same applies to two types of light sources (for example, blue and yellow light sources) in the case of a two-color reading device that separately reads two colors other than red and black (for example, blue and black), and the afterglow time of one of them is A similar effect can be expected even if the longer light source (for example, the yellow light source) is turned on continuously and the other one is turned on intermittently.

Furthermore, although the above embodiment has been described assuming that the afterglow time of the green fluorescent lamp is short, even when the afterglow time of two types of light sources is long, one light source with a longer afterglow time is turned on continuously. Similar effects can also be obtained in this case. This will be briefly explained. If the afterglow times of light sources R and G are respectively r and g, and the predetermined lighting time is T, then according to the conventional method, in order to separate the signals of each color, the reading time of one line must be 2T + r + g. However, with this method, by continuously lighting the light source R with a long afterglow time, the reading time for one line can be reduced.
2T+g, and as a result, the reading time for one line can be shortened by r (time) compared to conventional devices, resulting in the effect of high-speed reading.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration of two-color document reading;
The figure is a timing diagram showing the relationship between lighting of a fluorescent lamp and signal processing in a conventional two-color document reading device. The figure is a diagram for explaining the influence of the afterglow time of the red fluorescent lamp, and Figure 5 is a timing diagram showing the relationship between the lighting of the fluorescent lamp and signal processing in a two-color document reading device based on this invention. It is. In the figure, 1 is a document, 2 is a green fluorescent lamp, 3 is a red fluorescent lamp, 4 is a lens, and 5 is a solid-state image sensor. 〓〓〓〓〓

Claims (1)

[Scope of claims for utility model registration] (1) R and G2 with different spectral radiant energy distributions
In a document reading device configured to illuminate a document surface with different types of light sources and to separate and read information written on the document surface in two types of colors, the light source with the longer afterglow time among the light sources is used. R lights up continuously, and light source G, which has a shorter afterglow time, lights up intermittently in synchronization with the main scanning timing, and the signals read out during the scanning period when the light sources R and G are irradiated at the same time. A two-color original reading device characterized by comprising means for subtracting a signal R read out during a scanning period in which only the light source R is irradiated from R+G to obtain a signal G. (2) The two-color document reading device according to claim 1, wherein the light source R is a red fluorescent lamp and the light source G is a green fluorescent lamp.