JP2007166213A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus capable of preventing a show-through in dual-side color reading. <P>SOLUTION: The image reading apparatus wherein a contact image sensor 1 comprising light sources 11, a full-scale imaging lens 12, and photoelectric conversion elements 13 is respectively arranged on both sides of an original opposite to each other, and each of the contact image sensors 1 has the light sources 11 and the photoelectric conversion elements 13 for each of R, G, B colors and simultaneously reads images on both sides of the original in line-sequence. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image reading apparatus capable of simultaneous reading on both sides by using a line-sequential contact type image sensor using an equal magnification optical sensor.

2. Description of the Related Art Conventionally, in an image processing apparatus equipped with an image reading device such as a facsimile machine or a copy machine, when reading the front side of a document on which image data is recorded, the image data recorded on the back side is transparently read together with the surface data. There is a problem that so-called show-through occurs.
Such a problem becomes more prominent with the spread of copiers that simultaneously read both front and back sides and the frequency of handling originals with image data recorded on both front and back sides due to reuse of the back side of used paper. ing. In particular, the double-sided simultaneous reading method has a great influence because the illumination on the opposite side is transmitted.
For this reason, in the case of the double-sided simultaneous reading method, there are many configurations in which the reading positions on the front and back sides are largely separated so as not to be affected by illumination on the opposite side. However, when such a configuration is adopted, the time required to read one original is increased by the difference between the front and back image reading positions, which leads to sacrifice in productivity. Even if the reading positions on the front and back sides are separated to some extent, there is a considerable concern about the effects of illumination on the other side, especially for high-speed equipment that requires a high-brightness illumination system. In the case of use, it is conceivable that the effect of miniaturization, which is the advantage, is impaired.

As a countermeasure against show-through during simultaneous scanning on both sides, a technique has also been proposed that compares and corrects the data on both sides of the scanned data. Since there is concern about the occurrence of images, it is desirable to propose a fundamental preventive measure instead of such a corrective measure.
From the viewpoint of preventing show-through, Patent Document 1 proposes a technique for preventing show-through by making the emission wavelength distribution of the light source and the spectral sensitivity characteristic of the photoelectric conversion element different between the current front and back surfaces. With this technology, even if there is transmitted light from the light source on the back side, the spectral sensitivity characteristics of the photoelectric conversion element on the front side are sensitive to the spectral characteristics of the light source on the front side. The influence can be eliminated.
JP 2000-188668 A

However, according to the above technique, it is possible to cope with a monochrome document, but there is a problem that document information cannot be read when the document is in color. If the technique disclosed in Patent Document 1 is used for reading a color manuscript using a color contact image sensor that is generally used at present, the same effect as in monochrome mode cannot be obtained.
For example, in a sensor having one type of light source and one photoelectric conversion element for each RGB, the light source is affected by the back surface because it has spectral characteristics covering each color of RGB, and the light source is set for each color of RGB. Even in the case of a line-sequential sensor that uses photoelectric conversion elements that are sensitive to all RGB and the light sources are turned on in RGB order, the photoelectric conversion elements are also sensitive to all RGB, so the influence of the light source from the back surface is affected. You will definitely receive it.
The present invention has been made in view of such a background, and an object thereof is to provide an image reading apparatus capable of preventing show-through during color double-sided reading.

In order to achieve the above object, an invention according to claim 1 is an image reading apparatus in which a contact image sensor composed of a light source, an equal-magnification imaging lens, and a photoelectric conversion element is disposed opposite to the front and back surfaces of a document. The light source and the photoelectric conversion element are provided for each color of RGB, and images on both sides of the document are simultaneously read by line sequential.
According to a second aspect of the present invention, the image reading apparatus according to the first aspect is characterized in that when the images on both sides of the original are simultaneously read, the color to be read is different between the front side and the back side.
According to a third aspect of the present invention, in the image reading apparatus according to the first aspect, one of the front and back sides of the document is two colors and the other is one color, and the reading operation is performed by a combination that does not have a common color for both. Features.
According to a fourth aspect of the present invention, in the image reading apparatus according to the first aspect, when a monochrome document is read, a reading operation is performed by a combination of the front surface R, the rear surface B, and the front surface B, the rear surface R.

  The present invention is an image reading apparatus in which a contact image sensor including a light source, an equal-magnification imaging lens, and a photoelectric conversion element is disposed opposite to the front and back surfaces of a document, and includes a light source and a photoelectric conversion element for each of RGB colors. Since the images on both sides of the document are read simultaneously in line sequential manner, show-through during color duplex reading can be prevented.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an image reading apparatus according to an embodiment of the present invention. This image reading apparatus is configured by disposing a contact image sensor 1 on the front and back surfaces of a document so as to face each other. The contact image sensor 1 includes a light source 11, an equal magnification imaging lens 12, and a photoelectric conversion element (image sensor) 13.
The image reading apparatus of the present invention has a structure having a light source 11 and photoelectric conversion elements 13 for each color of RGB in order to read an image while preventing show-through from both sides of a document. The light source 11 is configured such that RGB can be individually turned on and off using LEDs or the like. Ideally, the spectral characteristics do not overlap with each other as shown in FIG.
The reflected light of the original from the light source 11 forms an image on the photoelectric conversion element 13 by the equal magnification imaging lens 12. Similarly to the light source 11, the photoelectric conversion element 13 has RGB characteristics ideally as shown in FIG. 3 and can control charge accumulation and transfer for each RGB.
In the configuration of the image reading apparatus according to the present invention, the document illumination light source 11 and the photoelectric conversion element 13 are provided for each color of RGB on the front side and the back side of the document, respectively. It can be read by this method, and in some cases, it is possible to simultaneously operate all RGB light sources and sensors.
When the document is single-sided, the light source on the opposite side does not light up, so all RGB light sources and sensors can be operated simultaneously without worrying about show-through due to transmitted light from the opposite side. It is also possible to use such that color reading operation is performed only on one side in a reading time of 1/3 of the line sequential method in reading.

<Example 1>
Next, the operation of the embodiment will be described with reference to FIG. In color reading, a red LED (LEDr), a green LED (LEDg), and a blue LED (LEDb) are alternately turned on every accumulation time. The present invention is characterized in that the colors of the LEDs that are turned on simultaneously on the front surface and the back surface of the document are different. In addition, when the LEDs are turned on, only the output of the photoelectric conversion element 13 (having sensitivity) corresponding to each color LED is made effective.
As a result, an R image signal, a G image signal, and a B image signal are output from the three photoelectric conversion elements 13 in a line-sequential format, respectively. In the subsequent image processing unit, the data from the three photoelectric conversion elements 13 for each color are combined into color data for one line. Therefore, color image data for one line is formed in three accumulation times.
The spectral characteristics of the light source 11 and the photoelectric conversion element 13 are as shown in FIG. 2 and FIG. 3, so that the colors to be turned on at the same time on the front surface and the back surface of the document are different from each other as described above. Since the influence of the transmitted light can be eliminated, the show-through due to the transmitted light from the opposite surface can be prevented.

<Example 2>
The operation of the second embodiment will be described with reference to FIG. Unlike the method in which red LED, green LED, and blue LED are alternately turned on every one accumulation time, only the red LED on the front side and the green LED on the back side are turned on at the same time. In this case, only the green LED is turned on on the front surface, and the red LED and the blue LED are turned on simultaneously on the back surface. The combination of LEDs to be turned on may be a combination of red green / blue and green blue / red.
In addition, as for the photoelectric conversion element 13, only the sensor corresponding to the color lit on the surface side (having sensitivity) is effective on the surface side. Therefore, in the case of the above lighting pattern, the color corresponding to red and blue ( The output of the photoelectric conversion element 13 (with sensitivity) becomes effective at the same time, and only the output of the photoelectric conversion element 13 corresponding to green (with sensitivity) becomes effective on the opposite side.
By repeating this operation alternately on the front and back sides, color image data for one line can be acquired in two storage times, so by combining the three color data obtained in two storage times in the subsequent image processing unit. Color image data for one line can be formed. Since the spectral characteristics of the light source 11 and the photoelectric conversion element 13 are as shown in FIGS. 2 and 3, the light sources for two colors are turned on simultaneously, and the remaining one color is turned on the opposite side. It is not affected by the transmitted light on the side.
Compared with the line sequential method in which the light source 11 is provided for each color of RGB and the photoelectric conversion element 13 having sensitivity to all RGB is used and the light source 11 is lit in the RGB order, the show-through is suppressed, and one line worth Since the time for obtaining image data can be shortened to 2/3, the effect of shortening the reading time can also be obtained.

<Example 3>
Next, the operation of the third embodiment will be described with reference to FIG. When performing a monochrome reading operation, only the data for one color is used on the front and back surfaces, so that only one line of monochrome image is obtained from one color LED and the corresponding photoelectric conversion element 13 in one storage time. Get the data.
At this time, the spectral characteristics of the light source 11 and the photoelectric conversion element 13 are as shown in FIGS. 2 and 3 in the same manner as in the color reading operation described above. Thus, the influence of the transmitted light from the opposite surface side can be eliminated.

1 is a configuration diagram of an image reading apparatus according to an embodiment of the present invention. It is a figure which shows the spectral characteristic of a light source. It is a figure which shows the spectral characteristic of a photoelectric conversion element. It is a figure which shows the 1st example of the circuit of LED, the lighting timing of LED, and the output timing of a photoelectric conversion element. It is a figure which shows the 2nd example of the lighting timing of LED, and the output timing of a photoelectric conversion element. It is a figure which shows the 3rd example of the lighting timing of LED, and the output timing of a photoelectric conversion element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Close contact type image sensor, 11 Light source, 12 1 time magnification imaging lens, 13 Photoelectric conversion element

Claims (4)

  An image reading apparatus in which a contact image sensor composed of a light source, an equal-magnification imaging lens, and a photoelectric conversion element is disposed opposite to the front and back surfaces of a document, and the light source and the photoelectric conversion element are provided for each RGB color, and each line An image reading apparatus that sequentially reads images on both sides of a document simultaneously.   2. The image reading apparatus according to claim 1, wherein when the images on both sides of the document are read simultaneously, the colors read on the front side and the back side are different.   2. The image reading apparatus according to claim 1, wherein one of the front and back sides of the document is two colors and the other is one color, and the reading operation is performed by a combination having no common color.   2. The image reading apparatus according to claim 1, wherein when reading a monochrome document, a reading operation is performed by a combination of the front surface R, the rear surface B, and the front surface B, the rear surface R.

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