US 5,317,350 AGranted

Overhead projector

AssigneeFuji Photo Film Co., Ltd.

InventorsMasaaki Nomura, Ko Aosaki, Takashi Kubo, Kenta Namioka, Koji Takanose

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Abstract

An overhead projector has a stage on which original material is placed. The stage has a Fresnel mirror. An electrostatic attracting structure is integral with the Fresnel mirror. The attracting structure includes a conductive membrane of ceramic and a resinous dielectric/protective layer. The conductive membrane consists of a pair of comb-shaped electrodes, which interfinger in coplanar fashion, and are covered by the dielectric/protective layer for insulation and protection. A power supply device applies a high voltage of direct current to the electrodes. The original material is attracted electrostatically by the electrodes, and can be kept flat on the stage. In a preferred embodiment, the power supply device incorporates a self-starting blocking oscillator, which is adapted to boost the voltage sufficiently for electrostatic attraction.

Claims40

Dependent claims

An overhead projector having a light source for illuminating an original material comprising a transparency and a projector head positioned above said original material and adapted to project an image of said original material onto a screen, said overhead projector comprising:

a stage on which said original material is supported, said stage having a Fresnel plate of which one surface is formed to be a Fresnel surface, and an electrostatic attracting structure on the upper side of said Fresnel plate and integral with said Fresnel plate, for attracting said original material electrostatically;
said electrostatic attracting structure including a conductive membrane constituting a pair of electrodes which are arranged in coplanar fashion and adjacent each other, a dielectric/protective layer covering said conductive membrane so as to protect said conductive membrane;
and
power supply means for applying a high voltage of direct current of opposite polarities to respective ones of said pair of electrodes.

1 more element

Dependencies are inferred from the claim text.