JPH0334764A - Picture reader - Google Patents

Abstract

PURPOSE:To eliminate the need for a circuit correcting the difference in spectral characteristics by providing a spectral characteristic correction means having a spectral characteristic opposite to a spectral characteristic of a diffusion means in a visual light region between a 2nd light source and a photoelectric conversion means. CONSTITUTION:A color correction filter 32 having an opposite spectral characteristic to a spectral characteristic of a white acrylic plate in the visual light region is provided between a light source 31 for reading a picture by a transmission light, the spectral characteristic of the light transmitting through the said white acrylic plate 4 and lighting a transmission original is made nearly the same spectral characteristic as that of the light source 11 for picture reading by a reflected light; an ND filter 33 correcting the luminous quantity of the said light source 31 is provided between the light source 31 and the white acrylic plate 4 to make the luminous quantity of the light transmitted through the said white acrylic plate 4 and radiating the original is mae nearly equal to the luminous quantity of the light source 11. Thus, a correction circuit correcting the difference from the spectral characteristic is not required.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an image reading device such as a color image scanner used as a manual device such as a copying machine or a facsimile machine.

(Prior Art) Conventionally, in a color image reading device using an RGB sensor that reads color image information, a document placed on a document table is illuminated with a first light source for reading reflected light, and the reflected light is used as a photoelectric sensor. In addition to the function of reading image information by converting it, OH
For transparent originals such as P-sheets, a device has been developed that also has the function of illuminating the original with a second light source for reading transmitted light and reading image information by photoelectrically converting the transmitted light. . In any case of reading, the photoelectric conversion is performed using one photoelectric conversion element.

In such an image reading device, illumination for reading a transparent original is achieved by interposing, for example, a white acrylic plate between the original and the second light source to uniformly diffuse the illumination light. There is. In other words, the light emitted from the second light source and transmitted through the white acrylic plate is used as a secondary light source to illuminate the transparent original. therefore,
The light reflected from the document by the first light source and the light transmitted through the document by the secondary light source have different document surface illuminance (the amount of light on the document surface) and spectral characteristics, and the image data read from the reflective white reference document and the transmitted white The value will be different from the image data obtained by reading the reference original. Therefore, if one photoelectric conversion element is used in common to photoelectrically convert the reflected light and transmitted light as they are, image information with different characteristics can be obtained, and even if this image information is written on recording paper, a good image can be obtained. There was a problem in that it was not possible to obtain

Therefore, in order to match the characteristics of the image data read with reflected light and the image data read with transmitted light, color correction is performed on one of the image data using a digital conversion circuit. It has the disadvantage that a large amount of /\-ware is required to construct the circuit, and the circuit construction is complicated.

In addition, the spectral characteristics of the light transmitted through the white acrylic plate are as follows:
Light in a predetermined wavelength range is absorbed by the white plate, and the intensity of the light in that wavelength range is reduced. For this reason, when the photoelectrically converted electric signal is A/D converted, the S/N ratio becomes poor in the above wavelength range, and the obtained image information also contains noise. Even if such image information is recorded, a good image cannot be obtained.

(Problem to be Solved by the Invention) As described above, the present invention uses a correction circuit because the characteristics of the image h' read using reflected light and the image information read using transmitted light are different. The disadvantage is that a large amount of hardware is required and the circuit configuration is 1 m long, and the spectral characteristics of the secondary light source when reading a document using transmitted light are light is absorbed, and the intensity of light in that wavelength range decreases, causing S
This was done to solve the problem that since the N ratio deteriorates, the obtained image information also contains noise, and even if this image information is recorded, a good image cannot be obtained. It does not require a large amount of hardware to correct spectral characteristics, and has a good S/N ratio over the entire visible light range.
Therefore, it is an object of the present invention to provide an image reading device that can obtain image information that does not include noise.

[Structure of the Invention] (Means for Solving the Problems) The image reading device of the present invention illuminates a document placed on a document table from one side with a first light source, and converts the reflected light into a photoelectric conversion device. a first reading means that reads image information by photoelectric conversion; and a second light source that diffuses light from a second light source to illuminate the document placed on the document table from the other side; and a second reading means for reading image information by photoelectrically converting light with the photoelectric conversion means, the transmission by the diffusion means is provided between the second light source and the photoelectric conversion means. It is characterized in that it does not include a spectral characteristic correction means for correcting the spectral characteristics.

(Function) The present invention provides image information by providing a diffusion means between the second light source and the photoelectric conversion means, illuminating the original with light transmitted through the diffusion means, and photoelectrically converting the transmitted light of the transparent original. In an image reading device that reads a spectral characteristic, a spectral characteristic correction means is provided between the second light source and the photoelectric conversion means to adjust the spectral characteristic H, which is the opposite of the spectral characteristic of the diffusing means in the visible light range. The spectral characteristics of the light that passes through and illuminates the transparent original are made to have approximately flat characteristics in the visible light range, which is approximately the same as that of the first light source, so that the light as image information input to the photoelectric conversion means is The characteristics are the same for the first reading means and the second reading means, so a circuit for correcting the difference in spectral characteristics is not required.
Furthermore, it is possible to obtain image information with a good signal-to-noise ratio over the entire visible light range.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing the appearance of the transparent unit 3 of the image reading device in an open state. In the figure, a document placement table 2 for placing a document is provided on the top surface of the main body 1 of the apparatus. This document mounting table 2 is made of, for example, a transparent glass plate. A transmission unit 3 that can be stacked and opened is provided on the document table 2. A white acrylic temporary 4 having light transmittance is provided at a portion of the transmission unit 3 that is in contact with the original table 2. As shown in FIG.

This white acrylic plate 4 acts as a diffusion means for diffusing light from a light source 31, which will be described later.

FIG. 1 is a cross-sectional view showing the general configuration of the image reading device, which mainly generates image information by photoelectrically converting the U and I light from the document placed on the document table 2. and a transmissive unit 3 that photoelectrically converts transmitted light illuminating a transparent original placed on an original placing table 2 and reads it as image information.

Below the document mounting table 2 of the main body of the image reading device, there is a
A first carriage 10 is provided.

The first carriage 10 is supported by a carriage support means (not shown) and is driven by a carriage drive means (not shown) to move along the document table 2 in the direction of arrow AB in the drawing.

The first carriage 10 includes a light source (first light source) 11 that illuminates the original, a rod lens array 12 that collects reflected light from the original, and a photoelectric converter for the light collected by the rod lens array 12. A photoelectric converter 13 made of, for example, a CCD or the like is mounted. These move together in the direction of arrow AB in the figure.

Further, a white reference document 20 is provided at the end of the document a placement table 2 at a position facing the first carriage 10 .

This white reference original 20 is used when reading the original using reflected light, and provides a reference value for correction performed when reading the original.

On the other hand, inside the transmission unit 3, there is a first
A second carriage 30 is provided opposite the carriage 10. This second carriage 30 is supported by a carriage support means (not shown) and is driven by a carriage drive means (not shown), so that the second carriage 30 is
It is adapted to move in the direction of arrow CD in the figure along the document table 2 in synchronization with the carriage 10.

The second carriage 30 is equipped with a light source (second light source) 31 for illuminating the transparent original, and a color correction filter 31 and an ND filter 33 provided in the optical path of the light emitted from the light source 31. These move together in the direction of arrow CD in the figure.

Further, the above-mentioned white acrylic plate 4 receives and diffuses the light emitted from the light source 31 and output through the color correction filter 32 and the ND filter 33, and uses the diffused light as a secondary light source on the document mounting table. This illuminates the transparent original placed on the screen 2.

The color correction filter (spectral characteristic correction means) 32 includes a third
As shown in the figure, in the visible light range, the spectral characteristic A of light transmitted through the white acrylic plate 4 when no filter is used.
It is composed of a filter having a spectral characteristic B opposite to that of the filter. By interposing the color correction filter 32 in the light emitted from the light source 31, the light transmitted from the light source 31 through the color correction filter 31 and the white acrylic plate 4 can be seen in the visible light range, as shown in C in FIG. The light has approximately flat characteristics, and has approximately the same spectral characteristics as the spectral characteristics of the reflected light from the original obtained when the original is illuminated by the light source 11.

This light having the spectral characteristic C passes through the original, is collected by the rod lens array 12, and is guided to the photoelectric converter 13.

Further, the ND filter 33 attenuates the light emitted from the light source 31. Since the light illuminated by the light source 11 on the document is dispersed on the surface of the document, the amount of reflected light from the document guided to the photoelectric converter 13 is quite small. On the other hand, the light irradiated onto the transparent original by the light source 31 is direct light, although it is mediated by the color correction filter 32 and the white acrylic plate 4, so the amount of light is larger than the reflected light. Therefore, an imbalance occurs in the amount of light guided to the photoelectric converter 13, and if left as is, the levels of both image signals obtained by photoelectric conversion will be the same. Therefore, by interposing the ND filter 33 to attenuate the light from the light source 31, the amount of light guided to the photoelectric converter 13 is made the same.

Next, the operation in the above configuration will be explained.

First, the case of image reading using reflected light will be explained. When a reading start switch (not shown) is pressed, the first carriage 10 is moved by a carriage moving means (not shown) to a position facing the white reference document 20, and the light source 11 is turned on. Reflected light from the white reference original 20 illuminated by the light source 11 is collected by the rod lens array 12 and guided to the photoelectric converter 13 . Then, in the photoelectric converter 13, the reflected light is converted into an electric signal according to the intensity of the reflected light, and is stored in a storage means (not shown). The signal stored in this storage means is used as a reference signal for subsequent document reading.

Next, the original is read. That is, the first carriage 10 is moved to the position of the original placed on the original placing table 2 made of transparent glass, and the light from the original illuminated by the light source 11 is focused by the rod lens array 12. photoelectric converter] 3. The photoelectric converter 13 converts the signal into an electric signal corresponding to the intensity of the reflected light, and after performing image correction such as shading correction, the signal is binarized and stored in an image memory (not shown).

The image information stored in this image memory is supplied to, for example, a printer, a copying machine, etc., and image recording is performed.

Next, the case of image reading using transmitted light will be explained. Image reading using transmitted light is used to read images formed on transparent films such as OHP sheets, for example.

First, when a reading start switch (not shown) is pressed, the first carriage 10 and the second carriage 30 are moved in conjunction with each other by carriage moving means (not shown) to the white reference document reading position, and the light source 31 is turned on. . here,
The white reference original reading position is a predetermined area provided at the end of the transparent glass of the original placing table 2, where the image ii! Similar to the reading of the white reference original 20 in the case of reading, this is provided to obtain a reference signal.

Next, the light emitted from the light source 31 is transmitted to a color correction filter 3
2, the spectral characteristics are corrected, and the ND filter 33
The amount of light is attenuated and the white acrylic plate 4 is irradiated with the light. The light, which is diffused and made uniform by passing through the white acrylic plate 4, is focused by the rod lens array 12 and guided to the photoelectric converter 13. Then, it is converted into an electric signal according to the intensity of the incident light by the photoelectric converter 13, and is stored in a storage means (not shown). The signal stored in this storage means is used as a reference signal for subsequent transparent document reading.

Next, the transparent original is read. That is, the first carriage 10 and the second carriage 30 are moved together to the position of the original placed on the original placing table 2 made of transparent glass, and the light emitted from the light source 31 is emitted from the color correction filter 32.
, the light transmitted through the transparent original illuminated by the light transmitted through the ND filter 33 and the white acrylic plate 4 is focused by the rod lens array 12 and guided to the photoelectric converter 13. The photoelectric converter 13 converts the signal into an electrical signal corresponding to the intensity of the transmitted light, and after performing image correction such as shading correction, the signal is binarized and stored in an image memory (not shown). The image information stored in this image memory is supplied to, for example, a printer or a copying machine, and image recording is performed.

In this way, between the light source 31 for image reading using transmitted light and the white acrylic plate 4, a color correction filter 3 having a spectral characteristic opposite to that of the white acrylic plate 4 in the visible light range is installed.
By providing the light source 31, the spectral characteristics of the light that passes through the white acrylic plate 4 and illuminates the transparent original can be made substantially flat, similar to that of the light All for image reading using reflected light. By providing an ND filter 33 for correcting the amount of light from the light source 31 between the white acrylic plate 4 and the white acrylic plate 4, the amount of light that passes through the white acrylic plate 4 and illuminates the document can be made approximately equal to the amount of light from the light source 11. -, the spectral characteristics of the light input to the photoelectric converter 13 are the same when reading an image using transmitted light and when reading an image using reflected light, and therefore the spectral characteristics differ. No need for a correction circuit to correct
Furthermore, it is possible to obtain image information with a good signal-to-noise ratio over the entire visible light range.

In the above embodiment, the color correction filter 32 and the N
A D filter 33 is provided, the light generated from the light source 31 passes through the color correction filter 32 and the ND filter 33, the light diffused by the white acrylic plate 4 illuminates a transparent original, and the transmitted light is converted into a photoelectric converter] 1, the color correction filter 32 and the ND filter 33 are configured to lead to the white acrylic plate 4 and the photoelectric converter 1 when reading a document using transmitted light.
It may be configured to be inserted between 1 and 1.

In this case as well, the same effects as in the above embodiment can be achieved.

[Effects of the Invention] As explained above, according to the present invention, a large amount of hardware for correcting spectral characteristics is not required, and an image with a good S/N ratio over the entire visible light range and therefore free of noise can be obtained. An image reading device that can obtain information can be provided.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which Fig. 1 is a sectional view showing a schematic configuration of an image reading device of the invention, Fig. 2 is an external perspective view of the transmission unit in an open state, and Fig. 3 The figure is a diagram for explaining spectral characteristics. ]...Image reading device main body, 2...Document placement table, 3...
... Transmission unit, 4... White acrylic plate (diffusion means), 1... First carriage, ]1... Light source (first light source), 12... Rod lens array, 13... Photoelectric converter (photoelectric conversion means), 20...white reference original, 3
0...Second carriage, 31...Light source (second light source)
32... Color correction filter (spectral characteristic correction means) 33
...ND filter. Figure Figure Figure Figure

Claims (1)

[Scope of Claims] A first reading means for illuminating a document placed on a document table from one side with a first light source and reading image information by photoelectrically converting the reflected light by a photoelectric conversion means; , the light from the second light source is diffused by the diffusion means to illuminate the document placed on the document mounting table from the other side, and the transmitted light is photoelectrically converted by the photoelectric conversion means to read image information. and a second reading means, characterized in that a spectral characteristic correction means for correcting the transmission spectral characteristics by the diffusion means is provided between the second light source and the photoelectric conversion means. image reading device.