Copying machine for microfilm

Details Copying machine for microfilm Copying machine for microfilm

1982-01-08

1983-08-09

Prescott, A. C.

Photocopying

Projection printing and copying cameras

Combined with or convertible to a contact printer

355 14C, 355 55, G03G 1500, G03G 1504

Patent

active

043975402

ABSTRACT:
A copying machine has an optical mechanism which varies a back focal length of a lens. A control circuit generates a control signal so that the optical mechanism changes the back focusing length of the lens so the lens is first focused on an upper surface of a microfilm and then on a lower surface of the microfilm. An optical sensor generates separate light quantity signals for each focusing position of the lens and these signals are held and compared in a circuit which then determines which surface of the microfilm bears a picture. The optical mechanism then appropriately adjusts the back focal length of lens.

REFERENCES:
patent: 3662662 (1972-05-01), Dewan
patent: 3691922 (1972-09-01), Konig et al.
patent: 4018520 (1977-04-01), Aste
patent: 4238157 (1980-12-01), Strauch et al.
patent: 4268165 (1981-05-01), Bradmon
patent: 4351606 (1982-09-01), Franko
patent: 4360264 (1982-11-01), Baker et al.

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