JPS60196743A - Slit illuminating device - Google Patents

Abstract

PURPOSE:To enhance the use efficiency of luminous flux to illuminate uniformly an area having an effective length of a slit with a low power and a low cost by providing a cylindrical reflective mirror forming a part of the circle which has the first focus as the center. CONSTITUTION:A slit illuminating device is provided with an elliptic cylindrical reflective mirror 201 forming an about half of an ellipse which has the first focus in a light source position 101 and has the second focus in a slit position 102, a cylindrical reflective mirror 203 forming an about half of a circle 202 which has the first focus as the center, and a cylindrical reflective mirror 205 forming a part of a circle 204 which has the second focus as the center. Three 6V20W halogen lamps 301 are used as incandescent lamps of spot light sources, and plane reflective mirrors 302 are provided on the outside a lit effective length L. In this invention, the use efficiency of luminous flux is improved considerably by two cylindrical reflective mirrors and plane reflective mirrors, and the area having the effective length of the slit is illuminated uniformly with a low power and a low cost.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an optical system of a slit illumination device, more specifically,
The present invention relates to an optical system of a slit illumination device for an image reading scanner.

[Prior art]

As shown in FIG. 1, the optical system of a conventional slit illumination device includes an elliptical cylindrical reflecting mirror 104 forming a part of an ellipse 103 with a first focus at a light source position 101 and a second focus at a slit position 102. There are many things used. In this case, in order to secure the optical path 105 of the imaging optical system, a part of the elliptical cylindrical surface reflecting mirror cannot be formed, and the light beam within the angle θ1 cannot be used. Furthermore, due to the slit 106, an elliptical cylindrical surface reflecting mirror cannot be formed and there is a light flux that is not utilized. As described above, the optical system of the conventional slit illumination device has the problem of low luminous flux utilization efficiency.

In addition, conventional slit lighting devices are often used in copying machines, and use halogen lamps with a length of 200 W or more and a power consumption of 200 W or more. On the other hand, for dual image reading scanners, 60 W class light is used. Energy is sufficient, and it is possible to reduce the cost of the power supply section and heat treatment section. However, if you try to use a 60W class halogen lamp with a length of 200111 or more, you will have to either make the diameter of the filament very thin and use it for a short life, or use it under lighting conditions with a low color temperature, or most of the filament will There is no other way to short it and use it as multiple point light sources.
There were problems in terms of lifespan, color temperature, and cost. [Purpose] The present invention is intended to solve these problems, and its purpose is to increase luminous flux utilization efficiency, reduce power consumption, and reduce costs. The object of the present invention is to provide an optical system capable of uniformly illuminating the effective length of a slit at a low cost.

〔overview〕

The slit illumination device of the present invention has an elliptical cylindrical surface reflecting mirror forming a part of an ellipse with a first focal point at the light source position and a second focal point at the slit position. The slit has a cylindrical reflecting mirror that forms a part of the slit, a plurality of incandescent lamps that form a point light source, and a flat reflecting mirror that forms a part of a plane including the ellipse and circle. It is characterized by having a cylindrical surface reflecting mirror that is installed outside the length and further forms a part of a circle centered on the second focal point.

〔Example〕

Hereinafter, the present invention will be described in detail based on examples.

As shown in FIG. 2, the slit illumination device of the present invention has an elliptical cylindrical surface reflecting mirror 201 that forms about half of an ellipse 103 with a first focus at the light source position 101 and a second focus at the slit position 102, A cylindrical surface reflecting mirror 20 having a cylindrical surface reflecting mirror 203 forming about half of a circle 202 centered on the first focal point and forming a part of a circle 204 centered on the second focal point.
Also, as shown in Figure 3, a 6V20TII halogen lamp 50 is used as an incandescent lamp forming a point light source.
Of the luminous flux emitted from the O halogen lamp 301, which uses three O2 halogen lamps and has a flat reflector 302 installed outside the slit effective length L200, the luminous flux reflected by the elliptical cylindrical reflector 201 is located at the slit position 102. focus on. The light beam reflected by the cylindrical reflecting mirror 205 passes near the filament again and is focused on the slit position 102 by the elliptical cylindrical reflection 1!2 D 1 . As described above, the light beams within the angles θ1 and θ2 in FIG. 1 could be used.

Of the light scattered on the document surface, the light flux that does not enter the optical path 105 of the condensing optical system is returned to the slit position 102 by the cylindrical reflecting mirror 205 and is scattered again and used.

A light beam emitted from the halogen lamp 301 outside the slit effective length L is returned within the effective length by the plane reflector 602. At this time, by considering the position of the plane reflection m302 and the positions of the left and right halogen lamps 301, the position where the virtual image 503 is formed, and the reflectance of the plane reflection mirror 302, we were able to set the position with the least unevenness in the amount of light.

〔effect〕

As described above, according to the present invention, the luminous flux utilization efficiency can be greatly increased by using two cylindrical reflecting mirrors and a flat reflecting mirror, and by using a plurality of incandescent lamps, the slit can be This has the effect that an optical system that uniformly illuminates the effective length of the lens can be realized at low cost.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional slit illumination device. Fig. 2 is an explanatory diagram of the slit illumination device of the present invention ◇ Fig. 6 is an arrangement diagram of a lamp and a plane reflecting mirror in the slit illumination device of the present invention. 101... Light source position 102... Slit position 103... Ellipse 104... Conventional elliptical cylindrical reflecting mirror 105... Optical path of imaging optical system 106... Slit 201...・Elliptical cylindrical surface reflecting mirror 201 in the present invention...
-Circle 203 centered on the light source position...Cylindrical reflecting mirror 204 centered on the light source position
...Cylindrical surface reflecting mirror 501 centered on the slit position.
...Halogen lamp 302...Flat reflecting mirror 303...Virtual image device of halogen lamp Applicant Suwa Seikosha Co., Ltd. Agent Patent attorney Mogami Nuri Figure 2

Claims (1)

[Claims] 1) A slit illumination device having an elliptical cylindrical surface reflecting mirror forming a part of an ellipse with a first focal point at the light source position and a second focal point at the slit position, with the first focal point as the center. 2) A slit lighting device characterized by having a cylindrical reflecting mirror forming a part of a circle; 2) A slit lighting device according to claim 1, characterized by having a plurality of incandescent lamps forming a point light source. . 3) The slit illumination device according to claim 1, wherein a plane reflecting mirror forming a part of a plane including the ellipse and the circle is installed outside the effective length of the slit. 4) The slit illumination device according to claim 1, further comprising a cylindrical reflecting mirror that forms part of a circle centered on the second focal point.