Method of and apparatus for detecting presence or absence of pho

Details Method of and apparatus for detecting presence or absence of pho Method of and apparatus for detecting presence or absence of pho

1987-12-21

1989-10-24

Rosenberger, Richard A.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

G03D 1300

Patent

active

048764566

ABSTRACT:
Photosensors having light emitting elements and light receiving elements are provided in a path for carrying a film. The light emitting elements emit periodic pulsed light. When the film is present in the positions of the photosensors, the periodic pulsed light is reflected by the film to enter the light receiving elements, whereby presence of the film is detected. Activation time and activation interval of the light emitting elements for generating the periodic pulsed light are determined so that accumulated exposure value in each portion on the film is less than a critical exposure value of photosensitive material provided in the film.

REFERENCES:
patent: 4021832 (1977-05-01), Krehbiel et al.
patent: 4566016 (1986-01-01), Masuda

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