JPS6285564A - Picture input device - Google Patents

Abstract

PURPOSE:To secure the uniform intensity of the illumination light on an original by separating the optical path of an illumination system from that of a sensor system by means of a half mirror. CONSTITUTION:A sloping mirror 1 is set on an original 2 and a sensor 3 and an illumination light source 4 are set at both sides of the mirror 1 respectively. The light delivered from the source 4 transmits through the mirror 1 and illuminates evenly the original 2. The half of the illuminated light is reflected by the mirror 1. Here the reflected light quantity is equal at any area and therefore the quantity of the transmitted light is almost equal. Thus the surface of the original 2 is evenly illuminated. The reflected light sent from the original 2 is made incident on the sensor 3 by the mirror 1. Thus it is possible to separate the optical path of the illumination system from that of the sensor system by the mirror 1. Then the position and the type of the illumination light source can be selected freely regardless of the position of the sensor 3. As a result, the approximately equal intensity is secured for the illumination light on the original 2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image input device, such as a facsimile machine or a character reading/recognition device, which serves as a means for inputting image information.

Images refer to black and white line drawings such as letters and drawings, grayscale black and white images containing neutral colors taken of objects, and color images taken of entire objects.

The image has a two-dimensional expansion and is flat.

Three-dimensional objects are not treated as images here.

Inputting an image means dividing the image into vertical and horizontal pixels, and detecting all the shading values for each pixel using a sensor.

All target images are simply referred to as manuscripts, and include the various two-dimensional images mentioned above.

B. Prior art image input devices generally have their own illumination light source and shine light onto a target document, detect the reflected light with a sensor, and convert it into an electrical signal corresponding to the intensity of the light.

FIG. 7 shows a conventional image input device. In this image input device, an image sensor 33 and a lens are arranged vertically above the center of the original 32, and illumination light sources 34 and 34 are arranged around the image sensor 33 and a lens.

Since the image sensor 33 is located in the center, the illumination light source 34.3
4 cannot be placed above the center.

Therefore, there is a drawback that the amount of light illuminating the original 32 is not uniform.

FIG. 8 shows the light amount distribution along a certain straight line on the original. Even if there are two illumination light sources on this straight line, the amount of irradiated light will have a non-uniform distribution with two peaks.

This is because the light source is directional and the light intensity peaks at the point where the extension of the central axis of the light source intersects with the document.

In this case, it appears that it is sufficient to use an illumination light source with a wide illumination range.

FIG. 9 shows another conventional example. Here, a wide illumination light source 44 that generates parallel light is installed behind the sensor 43. This should improve the uniformity of the light amount distribution at the peripheral edge of the document.

FIG. 10 is a graph showing the light quantity distribution in the arrangement of FIG. 9. It is true that the light intensity distribution becomes more uniform in the peripheral area.

However, the sensor 43 gets in the way of the central part, so the light does not reach the central part, and the central part of the document 42 becomes dark.

Even for the same line drawing, the photocurrent output after imaging differs depending on the strength of the illumination. Therefore, in order to correctly input the brightness and darkness of an image, the amount of light must be uniform throughout the document.

In conventional image input devices, the sensor gets in the way,
The problem with this method is that it does not provide uniform lighting.

(1) Problems to be Solved by the Invention It is an object of the present invention to provide an image input device that can uniformly irradiate the entire document and obtain a uniform image input.

B) Means for solving the problem In the present invention, a half mirror is installed above the original, and a sensor and an irradiation light source gold film are placed at the position where the light emitted from the original passes through and the position where it is reflected, respectively. I did it like that.

In this way, the difficult problem of non-uniformity of the amount of irradiated light on the document surface can be solved.

FIG. 1 shows a first embodiment of the invention.

A tilted half mirror 1 is provided above a document 2, and a sensor 3 and an illumination light source 4 are provided on both sides of the half mirror 10. The illumination light source 4 has a large area and emits two parallel beams.

Based on the light emitted from the document, in this example, the sensor 3 is located at the reflective position, and the illumination light source 4 is located at the transmitting position.

The light emitted from the illumination light source 4 travels approximately in parallel, completely passes through the herb mirror, and uniformly illuminates the entire document 2.

Of course, half of the irradiated light is reflected by the half mirror 1. However, since the amount of reflected light is the same everywhere, the amount of transmitted light is also almost the same, and the surface of the document can be uniformly irradiated.

The reflected light from the original 2 is reflected by the half mirror 1 and enters the sensor 3. Here, the sensor 3 refers to a condensing optical system such as a lens, and a two-dimensional or bar-dimensional image sensor.

All that is required is a sensor and a light source on both sides of the half mirror. Figure 2 shows a sensor 3 installed directly above the document.
The illumination light source 4 is located on the side of the half mirror. Tsumashi illumination light source 4. is at the reflective position when viewed from the original 2. sensor 3
is in the transparent position. This lighting is also a lighting with 9 Hiroga.

In this case, a light source having an area equal to or larger than the original document will be referred to as a wide-area light source.

With a wide-area light source, the illumination light is emitted almost in parallel, so the brightness of the document surface is uniform.

In the example shown in FIG. 2, the light emitted from the illumination light source 4 is reflected by the half mirror and hits the original 2. In the example shown in FIG.

Reflected light from the original passes through the half mirror 1 and enters the sensor 3.

Creating a wide-area light source requires various ingenuity.

One is the actual light emitting body (lamp, LED, LD, etc.)
This means juxtaposing a large number of two-dimensionally. Although this is ideal as a light source, it is expensive because it uses a large number of light emitters.

To create a wide-area light source more easily and easily, diffusers, lenses,
Combine a lamp with a mirror, etc.

In the example shown in FIG. 3, a wide area illumination light source 4 is configured by a lamp 5 and a diffuser plate 6 installed in front of the lamp 5.

The diffuser plate 6 is a slightly opaque plate that widely diffuses the light that passes through it. Instead of diffusing light by refraction, it does so by scattering. Therefore, the diffusion plate 6 may be a flat plate or a curved plate, but may have a uniform thickness.

At the diffuser plate 6, the light becomes as follows. First, some light is reflected off the surface of the board and is lost. Some light enters the plate and passes through without being scattered even once.

Some light is scattered once and then transmitted. Some of them exit the diffuser plate after being subjected to multiple scattering. Since it is not transparent, it absorbs a lot of light, and some light components are absorbed.

In this way, although the light has different phases and propagation directions, when it exits the bottom surface of the diffuser plate, the light output is almost uniform within the plane. Therefore, uniform wide-area illumination is achieved within the area of the document.

Further, the sensor 3 consists of a lens 8 that collects reflected light and an image sensor (two-dimensional or -dimensional) 7.

When a light source and a sensor are moved (referred to as scanning) with respect to the original 2, a one-dimensional image sensor may be used.

If it is not moved, a two-dimensional image sensor is used.

Diffusion plates are inexpensive, but a lot of light energy is lost through reflection, scattering, and absorption, so they do not necessarily provide strong illumination light.

If the lamp output is small, it is better to use a diffuser plate or a lens.

FIG. 4 shows such an example.

As the illumination light source 4, a combination of a lamp 5 and a lens 9 is used. Such a light source is provided directly above the document 2. The sensor 3 is provided on the side of the half mirror 1.

If the lamp 5 is at the focal point of the lens 9, the light passing through the lens 9 becomes parallel light. In order to uniformly illuminate the original 2 with parallel light, a lens larger than the original is required.

If such a large lens is difficult to obtain, a smaller lens may be used. In this case, place the lamp closer to the focal point to produce diffused light rather than parallel light.

Even if the light is not parallel, when there is no lens at all, uniform irradiation light can be obtained and the irradiation light intensity can be increased. Lenses can emit more uniform and stronger light than diffusers, but they are more expensive.

In the examples shown in FIGS. 5 and 6, the positions of the light source and the sensor are replaced with respect to the half mirror.

Of the two positions above and on which side of the half mirror, it is arbitrary to place the light source and where to place the sensor. This is something that should be designed freely in terms of accommodation space and other considerations.

Lenses are an excellent optical system, but they are heavy and expensive, so they can be replaced with mirrors. In this case, a parallel light source can be created by combining a concave mirror and a lamp.

As the concave surface of the mirror, a paraboloid, an ellipsoid of revolution, a hyperboloid of revolution, or a part of a spherical surface is used. An appropriate concave surface can be selected depending on the expansion of the light center of the lamp and the size of the original.

(6) Function Since there is a half-mirror, the illumination can be set from above the document and the reading from the horizontal direction, or the reading from above the document and the illumination from the horizontal direction. The reading direction and the reading direction can be separated.

Since the optical paths of the illumination system and the sensor system can be separated by a half mirror, the position and type of the illumination light source can be freely selected without being restricted by the sensor position.

As a result, the intensity of the illumination light on the document can be made almost uniform. There are no shadows caused by the sensor or deviations in light intensity due to the sensor position.

Therefore, it is possible to input a correct image that corresponds to the original shading of the original.

[Brief explanation of drawings]

FIG. 1 is a principle diagram showing a first arrangement example of an image input device of the present invention. FIG. 2 is a principle diagram showing a second arrangement example of the present invention. FIG. 3 is a diagram showing an example of the arrangement of an embodiment using a diffuser plate. FIG. 4 is a diagram showing an example of the arrangement of an embodiment using lenses. FIG. 5 is a layout example diagram of another embodiment using a diffuser plate. FIG. 6 is a layout example diagram of another embodiment using lenses. FIG. 7 is a diagram showing an example of the arrangement of a conventional image input device. FIG. 8 is a graph of the light intensity distribution on the document in the arrangement shown in FIG. 7. FIG. 9 is a diagram showing an example of the arrangement of a conventional image input device. FIG. 10 is a light amount distribution graph on the original in the arrangement shown in FIG. 9. 1...Half mirror 2...Original 3...Sensor 4...Illumination light source 5...Lanph. 6... Diffusion plate γ... Image sensor 8... Sen'9...
・Inventor
Previous 1) Naoki Patent Applicant Sumitomo Electric Industries, Ltd. Figure 1 Figure 3 Figure 4 Figure 5 Figure 8 Between 1 & L11-1 6'A Figure 10

Claims (6)

[Claims] (1) In an image input device consisting of an illumination light source that provides illumination light to a document and a sensor that receives reflected light from the document, a half mirror is used to transmit either the illumination light or the reflected light, and the other An image input device characterized by reflecting. (2) Claim No. 1 characterized in that the central axis of the illumination light source or the sensor, or the projection thereof onto the half mirror, is arranged so as to coincide with the central axis of the area to be read of the document. The image input device described in (1). (3) The image input device according to claim (2), characterized in that an image sensor is used as the sensor. (4) The image input device according to claim (3), characterized in that a lamp and a diffusion plate are used as the illumination light source. (5) The image input device according to claim (3), characterized in that a lamp and a lens are used as the illumination light source. (6) The image input device according to claim (3), characterized in that a lamp and a concave mirror are used as the illumination light source.