Self regulating microfilm frame detection circuit

Details Self regulating microfilm frame detection circuit Self regulating microfilm frame detection circuit

1978-12-18

1980-08-26

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250214B, 353 26A, G06K 714

Patent

active

042197376

ABSTRACT:
A system for optically detecting the presence of indicating markers on microfilm frames and for ignoring stray marks and smudges. As light shines through the microfilm and is detected by a photo-transistor, the system self regulates to provide an absolute baseline value, called a prescaler, for each frame of microfilm. Then, as each mark appears on the microfilm and interrupts the light path to the photo-transistor, the degree or extent of light blockage is measured as a deviation from the baseline for that frame. If the deviation exceeds a predetermined threshold, the mark is counted as a marker; otherwise the mark is ignored as a stray spot or smudge. The threshold is also self regulated based on a percentage of the amount that the light blockage of the marker in the immediately preceding frame deviated from the baseline for that frame.

REFERENCES:
patent: 3328590 (1967-06-01), C. B. Kapsambelis
patent: 3660670 (1972-05-01), Howard
patent: 3789215 (1974-01-01), Penny
patent: 4027154 (1977-05-01), Flint

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