JPS59180501A - Fresnel lens assembly of overhead projector - Google Patents

Abstract

PURPOSE:To improve the heat resistance and light transmittance of a Fresnel lens by superposing a glass plate and a heat ray absorptive reflection film on the Fresnel lens made of silicone rubber and forming the same into a monolithic construction. CONSTITUTION:A Fresnel lens assembly 10 consists of a sheet of glass plate 11 having about 4 millimeter thickness, a Fresnel lens 12 which is joined to one surface of the glass plate, is made of silicone rubber and is, for example, about 2 millimeters in thickness and a heat ray reflective film 13 joined on the opposite side of the plate 11. The film 13 is made of SnO2, In2O3, etc. There are no deformation and warpage of the Fresnel lens by the effect of the heat with such construction and a sharp projected image is obtainable for a long period of time. Since the number of various transmitting materials to be used is decreased, the transmittance over the entire part of the system is improved and the much brighter image is obtd. with a lamp having the same power.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in Fresnel lens assemblies for over-the-hole projectors.

(Background of the invention) The conventional Fresnel lens of the Ohahe 7 gutter mouth projector is
It is made of acrylic resin, etc., and is placed separately below a glass plate that serves as a document mounting table, and further below that is a piece of glass that absorbs and reflects heat rays. Light from the light source passes through these Fresnel lenses and the glass plate, and further passes through the document placed on the document table before reaching the projection lens. Light from a light source undergoes optical loss at the glass plate or Fresnel lens. This structure has problems in that the Fresnel lens has poor heat resistance and low light transmittance. Fresnel lenses can also be made of highly heat-resistant materials, such as glass, but it is difficult to form prisms of a few tenths of a millimeter with current mounting technology.

(Objective of the Invention) An object of the present invention is to provide a Fresnel lens assembly for an overhead glow projector that is not affected by heat and has a high light transmittance of the entire system.

(Structure and Effects of the Invention) According to the present invention, in the Fresnel lens assembly of the overhesodopronoecta, which is disposed under the document table and is configured to transmit light from the light source, silicone rubber is used. It is possible to obtain a Fresnel lens assembly characterized in that it has an integral structure consisting of the produced Fresnel lens, a glass plate stacked on the Fresnel lens, and a heat ray absorbing/reflecting film stacked on the glass plate. In this structure,
There is no deformation or damage caused by the heat of the Fresnel lens, and clear projected images can be obtained over a long period of time.

Fortunately, because fewer sheets of each type of transmitting material are used, the transmittance of the entire system is increased, and a brighter image can be obtained with a lamp of the same capacity.

(Explanation of Embodiment) Fig. 1 shows the optical system of a conventionally structured over-rad projector. A heat ray absorbing and reflecting glass 3 is installed below the Fresnel lens 2. A light source lamp 4 is installed below this heat ray absorbing and reflecting glass plate, and the light from this lamp is reflected by a reflecting mirror 5, and then moving to a heat ray absorbing and reflecting glass plate 3, a Fresnel lens 2, a document table glass 1, The light passes through the original 6 placed on the original placing table and reaches a projection lens 7 placed above the original placing table.

FIG. 2 shows a Fresnel lens assembly 10 according to the present invention, which comprises a glass plate 11 having a thickness of about 4 mm and a silicone glass plate bonded to one side of the glass plate. It consists of a Fresnel lens 12 made of, for example, about 2 mm, made of comb, and a heat ray reflecting film 13 bonded to the opposite surface of a glass plate 11. The heat ray reflective film 13 has a thickness of 5n
It is made of O7, In2O3, etc.

FIG. 3 shows another embodiment of the present invention, in which the positions of the Fresnel lens 12 and the heat ray reflecting film 13 are exchanged with the glass plate 11 in between.

[Brief explanation of the drawing]

FIG. 1 shows an optical system of a conventional overhead glow projector, FIG. 2 is a schematic side view of a Fresnel lens assembly according to the present invention, and FIG. 3 is a diagram showing another embodiment of the present invention. 1...! Loading table, 10... Fresnel lens assembly, 11... Glass plate, 12... Fresnel lens,
13... Heat ray absorption film. Patent Applicant Toshiba Electric Materials Corporation Agent Patent Attorney Tatsuo Ito Attorney Patent Attorney Satoshi Ito Figure 1 Figure 2

Claims (1)

[Claims] (1) In the Fresnel lens assembly of an overhead gromjector, a Fresnel lens assembly made of silicone rubber is used. A Fresnel lens assembly characterized by having an integrated structure consisting of a glass plate overlaid on the Fresnel lens and a heat ray absorbing/reflecting film overlaid on the glass plate. (2. The Fresnel lens assembly according to claim 1, wherein the Fresnel lens is located on the side of the document table. (3) Claim 1 3. The Fresnel lens assembly according to item 1, wherein the Fresnel lens is located on the side farther from the original table.