A/D photodiode signal conversion apparatus

Details A/D photodiode signal conversion apparatus A/D photodiode signal conversion apparatus

1986-12-11

1988-03-29

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

35821327, 35821313, 35821311, H01J 4014

Patent

active

047345896

ABSTRACT:
A method and apparatus for directly converting an analog photodiode signal to digital form using a switched capacitor successive approximation A/D converter. The charge extracted from a video line during a predetermined time interval by a photodiode is compared with charges successively injected onto the video line by a plurality of capacitors of decreasing capacitance value having a reference voltage sequentially impressed thereon. The voltage on the video line is compared with a threshold voltage for each of the capacitors, and the capacitor is returned to its previous state if it is found to have injected sufficient charge to increase the voltage on the video line to above the threshold voltage. The states of the capacitors at the conclusion of the process is a digital representation of the light intensity at the photodiode.

REFERENCES:
patent: 4584608 (1986-04-01), Soneda et al.
patent: 4589026 (1986-05-01), Ozawa et al.
patent: 4617471 (1986-10-01), Suzuki et al.
patent: 4673821 (1987-01-01), Morita

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