Overhead projector

Details Overhead projector Overhead projector

1980-01-15

1982-07-06

Shepperd, John W.

Optics: image projectors

Lamp control

353 87, 353DIG3, 353102, G03B 2120, G03B 21132

Patent

active

043380069

ABSTRACT:
A disclosed projector includes a condenser lens, a plurality of light source means having different focal lengths and disposed around the condenser lens, a projecting lens with an adjustable distance from the condenser lens, and a stage glass located between the condenser and projecting lens for carrying a transparent positive thereon. Depending on the size of the transparent positive, one of the light source means is selected and the distance between the condenser and projecting lens is adjusted, so as to project an image of substantially fixed magnitude with a constant brightness regardless of said size of the transparent positive.

REFERENCES:
patent: 2669156 (1954-02-01), Fitzgerald
patent: 2878718 (1959-03-01), Post
patent: 2937569 (1960-05-01), Wilton
patent: 3244069 (1966-04-01), Field
patent: 3529146 (1970-09-01), Betlejewski et al.
patent: 3719419 (1973-03-01), Davee

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