Control system for detecting intrusion of a light curtain

Details Control system for detecting intrusion of a light curtain Control system for detecting intrusion of a light curtain

1993-07-16

1995-04-04

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250214B, 340556, G01V 904, G06M 700

Patent

active

054040086

ABSTRACT:
A light curtain system having a series of light emitting diodes is arranged to produce a beam of light which is modulated at about 40 KHz. The light is broadcast across a physical space in which intrusion detection is desired and received by respectively arranged photo diodes. Each of the light emitting diodes is connected in parallel to a single modulated power supply. Each photo diode produces an electrical signal having a magnitude which is proportional to the amount of light incident thereon. The signal produced by each photo diode is sequentially sampled and then compared to a reference value. If an intrusion in the respective region of the light curtain has occurred, the magnitude of the sampled signal will be less than the reference value providing indicia of an intrusion. Upon such a detection, the light curtain system provides indicia of the intrusion such that consequential remedial action in response thereto may be performed.

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