JPS58127952A - Illuminating device for original - Google Patents

Abstract

PURPOSE:To improve illuminating efficiency considerably and to permit effective economization of energy and suppression of an increase in the temp. in the machine by disposing a retroreflective material near the original plane of a lighting device for originals where a light source and the original move relatively. CONSTITUTION:An illuminating light source 1 of an illuminating device is located at one focus of an ellipsoidal reflecting mirror 2 and the original plane of an original 4 placed on original glass 3 is located at the other focus so that the light reflected on the original plane is imaged on a photosensitive drum which is not shown, through a projecting lens 5. A retroreflective material 6 is installed on the opposite side of the light source 1 roughly perpendicularly to the glass 3. According to such constitution, the loss in the quantity of light is decreased, illuminating efficiency is improved markedly, and the effective economization of energy and suppression of an increase in the temp. in the machine are made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an illumination device for a document in an electrophotographic copying machine, a facsimile machine, or the like.

BACKGROUND ART In general, in this type of lighting device, there is a tendency to reduce the amount of light as much as possible, mainly in order to save energy and suppress a rise in temperature inside the machine. Furthermore, there is the disadvantage that photoreceptors, photoelectric conversion sensors, and the like are forced to become increasingly sensitive.

On the other hand, the light utilization rate of the optical system including the projection lens is extremely poor, and if the original is a completely diffusing surface, the same magnification optical system will
/32F (F, lens F number). In fact, in text manuscripts, etc., 90% or more of the background is white, and the light reflected from the white background is diffused. That is, most of the light irradiated onto the document surface is diffusely reflected light and does not function effectively as irradiation light.

Purpose The present invention was made in view of the above-mentioned circumstances, and its purpose is to effectively utilize the light amount of the document illumination light source by illuminating the document surface again with the diffusely reflected light that has not been effective in the past. An object of the present invention is to provide an illuminating device for a document that can be used to illuminate documents.

SUMMARY In order to achieve the above objectives, a document illumination device according to the present invention includes a retroreflective material in the vicinity of the document surface.

Here, the retroreflector is an optical system that reflects and emits light at an angle approximately equal to the incident angle, as shown in Figures 1 and 2. ) has been commercialized as This retroreflective material is available in two types: a spherical internal reflection type (shown in Figure 1) that has a semicircular reflecting surface, and an external internal reflection type (shown in Figure 2) that has a saw-toothed reflective surface on the back surface. ), and any of them can be used in the present invention.

Embodiment FIG. 3 shows a first embodiment of the document illumination device according to the present invention.

This first embodiment is used in a slit exposure type electrophotographic copying machine, and the illumination light source (1) is an elliptical reflector (2).
The original glass (3
) is placed on the original (4), and light reflected from the original surface forms an image on a photoreceptor drum (not shown) via a projection lens (5). On the other side of the light source (1), the retroreflective material (6) described above is installed almost perpendicularly to the document glass (3).

In this device, either an optical system including a light source (1) or a document glass (3) exposes a document image onto a photoreceptor drum by slit exposure while moving in the left-right direction in FIG. light source(
The document surface illuminated by 1) has a constant width in the scanning direction.
However, this is because it is not advisable to narrow down the aperture of the elliptical reflector (2) because it reduces the amount of output light.

The retroreflector (6) plays the role of returning the light that has been diffusely reflected and dispersed from the white portion of the document back to the surface of the document. The reflective surface of this retroreflective material (6) can be made large, and by changing it, the solid angle with respect to the document surface can be increased, so the amount of retroreflection can at least increase the effective amount of light that irradiates the document through repeated reflections. can be achieved.

It should be noted that the retroreflective material (6) does not necessarily need to be provided near the original, provided that it has an ideal shape in which the angle of incidence and the angle of reflection are exactly equal. However, if it is a spherical reflective type as shown in Figure 1, there is astigmatism that prevents it from converging to a single point depending on the incident angle, and it is preferable to install it near the illuminated part of the document due to deviation from the ideal. . Therefore, it is appropriate for the optical system used in the present invention to be a slit exposure type optical system or a single point scanning optical system that satisfies this requirement. Furthermore, the reflective surface of the retroreflective material (6) cannot fully rely on total reflection due to a critical angle, and requires reflective treatment such as vacuum deposition, plating, or silver mirror reaction. The reflective material is silver.

Aluminum etc. are suitable.

Note that the retroreflector (6) may be installed below the elliptic mirror (2) as shown by the dotted line in FIG.

FIG. 4 shows a second embodiment, in which as a means for projecting an original image,
It uses a focusing light transmitter (Q) and a retroreflector (6).
) is installed above the reflector (2) and on the opposite side of the light source (1).

Using a fiber optic system as in this example is advantageous because it can be installed relatively close to the document, so when the photoreceptor drum is made small in diameter, it is difficult to use the fiber optic system during slit exposure due to the This is advantageous if you do not have enough. However, as the size of the light source (1) increases, the slit width becomes smaller, so that the light gathering power of the reflecting mirror (2) becomes insufficient. The retroreflector (6) increases the amount of light incident on the convergent light transmitter (7) and can eliminate such problems.

In general, retroreflective materials used for road signs, vehicle and horse signs, etc. are intended to return light emitted from a point light source to the vicinity of the point light source, and have very good retroreflection performance. On the other hand, in an illumination device such as a copying machine, the light source is a linear light source in order to correspond to the width direction of the document surface, and the exposure surface has a constant width in the scanning direction. For this reason, the returning light only needs to return to the illuminated part, and does not necessarily have to have the completely same angle of incidence and reflection. Rather, it is better to prevent light loss as much as possible.

FIG. 5 shows a modified example based on such considerations, in which the retroreflective material (6) takes the form of a Fresnel mirror concave mirror having a vapor-deposited reflective surface (6).
6) Since the number of reflections inside is small, it is possible to reduce the loss of light quantity. Even if the stepped shape extends uniformly in the longitudinal direction of the slit-shaped illuminated part,
Or they may be separated.

The material of the retroreflective material used in the present invention is glass.

A transparent material such as plastic may be used, and its manufacturing method.

The dimensions etc. may be set as appropriate. Further, it may be a flexible material or a molded product with a flat or curved surface. Furthermore, a film for preventing reflected and scattered light may be provided on the surface, and a filter film for improving color balance may also be provided. Furthermore, a specular reflective material and a retroreflective material may be used in combination.

Effects As is clear from the above explanation, because the present invention places a retroreflective material near the document surface, the diffuse reflected light on the document surface, which conventionally did not function effectively as illumination light, can be absorbed by the retroreflector. Using the characteristics of the reflective material, it is returned to the illuminated area,
It can significantly improve lighting efficiency, save energy,
Extremely effective in suppressing temperature rise inside the machine. Furthermore, the retroreflective material does not require strict positioning, is easy to assemble, and is inexpensive.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of the retroreflective material, FIG. 3 is a cross-sectional view showing the first embodiment of the document illumination device according to the present invention, and FIG. 4 is a cross-sectional view showing the second embodiment. , FIG. 5 is a sectional view showing a modification. (1)... Light source for illumination, (3)... Original glass, (
4)...Manuscript, (6)...Retroreflective material. Patent applicant Minolta Camera Co., Ltd. Agent
Patent attorney Hao Aoyama and 2 others

Claims (1)

[Scope of Claims] 1. A document illumination device in which a light source and a document move relative to each other, characterized in that a retroreflective material is disposed near the surface of the document. 2. The document illumination device according to claim 1, wherein the retroreflective material is disposed integrally with a light source section. 3. The document illumination device according to claim 1 or 2, wherein the retroreflective material is of a spherical internal reflection type. ,4. 3. The document illumination device according to claim 1, wherein the retroreflective material is of a polyhedral internal reflection type.