JPH0132032Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a slit exposure type illumination device, and more particularly to a slit exposure type illumination device suitable for illuminating a document surface glass at a low angle of incidence.

FIG. 1 shows a typical lighting system for a conventional copying machine, in which a light source 1 is placed at one focal point of an elliptical reflector 2, and the light beam from the light source 1 is reflected by the ellipse reflector 2. The light is focused on the other focal point of the elliptical reflecting mirror 2.

However, in this type of apparatus, the light beam reflected by the portion A of the elliptical reflecting mirror 2 enters the document surface glass 3 at a large angle of incidence. Original glass 3
As shown in Fig. 2b, when the incident angle θ shown in Fig. 2a exceeds 60 degrees, the transmittance of the luminous flux is reflected by the document surface glass 3, and the transmittance of the light beam decreases sharply, resulting in a significant decrease in illumination efficiency. There is a difficulty in doing so. Further, in the part B shown in FIG. 1, the reflected light beam is deflected by the light source 1 itself, and the illumination efficiency is reduced accordingly. The reflected light beam in part B near the apex of the reflecting mirror has a disadvantage of poor condensing ability. Furthermore, the light beam C shown in FIG. 1 illuminates the outside of the illumination slit 4, and not only does it not contribute effectively to slit exposure, but also the light may leak to the outside and cause harmful effects.

As a countermeasure against this problem, elliptical reflectors 5 and 6 of different shapes are arranged on the back side of the light source 1, respectively, as shown in FIG. A method has been proposed in which the light reflected by the elliptical reflector 6, which has a large incident angle, is passed through a plane mirror 7 to reduce the incident angle and illuminate the illumination slit 4.

This method can be expected to solve the problem of high incident angle luminous flux and reduce light leakage. Furthermore, the eclipse caused by the light source 1 also has a reflecting mirror shape as a cylindrical reflecting mirror 8 centered at the position of the light source 1 to return the reflected light flux to the light source 1. light source 1
In the method of returning the luminous flux to , the radiant energy of the radiant heat radiation of a halogen lamp or the like returns to the light source filament section and heats the filament, so it can be returned to radiant energy again and is efficient.

However, in this improved device, the light beam reflected by the elliptical reflector 6 illuminates the illumination slit 4 via the plane mirror 7, so the distance between the focal points of the elliptical reflector becomes longer and the light condensing ability becomes poorer. In addition, there is a problem in that the amount of light decreases due to the reflectance of the plane mirror.

This invention was devised in view of the current situation.
The purpose is to provide a slit exposure type illumination device that can reduce the amount of light that directly enters the eye by eliminating light beams at high incident angles, and can increase the amount of light with a compact device.

Therefore, in the present invention, an elliptical reflector located on the lower surface side of the cylindrical reflector is connected to one end of the open edge of the cylindrical reflector disposed downward under the original surface glass, and the cylindrical reflector is A filament-type light source is placed at the center of the elliptical reflector and at the primary focus position of the elliptical reflector, and the secondary focus position of the elliptical reflector is near the top surface of the document surface glass, and the light is reflected by the elliptical reflector to a light angle of 60° or less. It is characterized in that the document surface is irradiated with a slit-shaped light beam having a high incidence angle, and the amount of light is increased by eliminating the light beam having a high incidence angle.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 4, reference numeral 11 denotes a filament type light source such as a halogen lamp, and this light source 11 is disposed below the document surface glass 12. As shown in FIG. The light source 11 is located between the light source 11 and the document surface glass 12.
A cylindrical reflecting mirror 13 having a focal point at the position is disposed substantially downward, and an elliptical reflecting mirror 14 having a primary focus at the position of the light source 11 is arranged on the lower surface side of the light source 11 between the cylindrical reflecting mirror 13 and its abutting surface. are connected together.

The emitted light flux from the light source 11 is reflected by the elliptical reflector 14 to become a slit light flux, and is focused near the upper surface of the original glass 12, which is the secondary focus position of the elliptical reflector 14, and illuminates the illumination slit 15. At the same time, the light beam reflected by the cylindrical reflecting mirror 13 returns to the light source 11 again. The light beam reflected by this cylindrical reflecting mirror 13 has a high incident angle with respect to the document surface glass 12.

At this time, the fourth of the light beams reflected by the cylindrical reflecting mirror 13
The light flux in the shaded area in the figure simply returns to the light source 11, but about 30% of the light flux in the meshed area passes through the light source 11. Since the passed light flux is once condensed at the light source 11 position, it appears as an increase in the light flux reflected by the elliptical reflecting mirror 14.

In addition, in FIG. 4, the broken line L is the imaging light flux and specular reflection limit line determined from the lens and slit width, as in the case of FIGS. 1 and 3, and the illumination optical system is installed within this line. This causes flare, etc., which is unfavorable in terms of image quality. Therefore, in this embodiment, as shown in the figure, the illumination optical system is set to the specular reflection limit line L.
It is installed outside.

FIG. 5 shows another embodiment of the present invention, in which an elliptical reflector 16 is installed in addition to the configuration shown in FIG. The illumination slit 15 is illuminated as a slit light flux together with the reflected light flux from the elliptical reflector 14 following the cylindrical reflector 13.

With this configuration, the amount of light can be further increased,
It is possible to further improve lighting efficiency.

As explained above, according to the present invention, a cylindrical reflecting mirror is arranged facing downward, and an elliptical reflecting mirror is connected to one end of the open edge of this reflecting mirror. Since the configuration has a filament type light source placed at the primary focus position of the reflector, the light beam with a high incidence angle to the original glass is reflected by the cylindrical reflector, and it is possible to achieve a high incidence angle without using a flat reflector. By eliminating the luminous flux, it is possible to reduce the amount of light that directly enters the eyes. In addition, since all the reflected light can be irradiated onto the document surface as a slit beam without using a flat reflector, the optical path length to the document surface can be shortened, which not only improves light convergence but also prevents light loss. Because the light source is a filament type, the light beam reflected by the cylindrical reflector passes through it without being hindered, and all of these light beams are reflected by the elliptical reflector. The light beam is reflected by the cylindrical reflector and is returned to the light source, so the radiant energy of the radiant heat is returned to the filament of the light source, heating it and returning it to radiant energy. This can be done efficiently and the lighting efficiency can be increased.
Furthermore, since the structure is simple and can be made compact, it does not take up much space to be incorporated into a copying machine, and it is possible to provide a compact illumination device with a large amount of light and good illumination efficiency.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing a conventional example, Figure 2a is an explanatory diagram of the angle of incidence on the document surface glass, Figure b is a graph showing the relationship between transmittance and angle of incidence, and Figure 3 is an improved conventional example. FIG. 4 is a schematic diagram showing one embodiment of the present invention, and FIG. 5 is a schematic diagram showing another embodiment of the present invention. 11...Light source, 12...Document surface glass, 13...
...Cylindrical reflector, 14...Elliptical reflector, 15...Illumination slit, 16...Elliptical reflector, L...Specular reflection limit line.

Claims (1)

[Scope of utility model registration request] An elliptical reflector located on the lower surface side of the cylindrical reflector is connected to one end of the open edge of a cylindrical reflector disposed facing downward below the document surface glass, and the elliptical reflector is located at the center of the cylindrical reflector and the elliptical A filament type light source is placed at the primary focal point of the reflecting mirror, the secondary focal point of the elliptical reflecting mirror is near the top surface of the original glass, and the elliptical reflecting mirror reflects the light into a slit-shaped light beam with an incident angle of 60° or less. A slit exposure type illumination device characterized in that the surface of a document is irradiated with light.