Detection system with improved noise tolerance
First Claim
1. An electro-optical detection system for detecting objects within the boundaries of a monitored zone, comprisinga plurality of emitter and photodetector pairs, each comprising an emitter for emitting a beam of pulses of light energy into the monitored zone, and a photodetector for detecting light energy including light energy from each of the beam pulses that is reflected from an object within the monitored zone and for generating light detection signals, and a controller for operating the emitter and photodetector pair and for evaluating the light detection signals to discriminate between a valid signal, comprising light energy of a beam pulse which is reflected from an object within the monitored zone, and invalid signals comprising other light energy, and which produces an object detection signal, including programmable range adjustment means for each of the emitter and photodetector pairs which selectively adjusts the evaluation of the light detection signals to adjust the effective boundaries of the monitored zone.
1 Assignment
0 Petitions
Accused Products
Abstract
An electro-optical detection system for detecting objects within the boundaries of a monitored zone, comprises a plurality of LED emitter and photodetector pairs. Each emitter (12) emits a beam of pulses of light energy into the monitored zone, and its paired photodetector (14) detects light energy including light energy from the beam that is reflected from an object within the monitored zone and generates light detection signals. A controller (10) operates the emitter and photodetector pairs and evaluates the light detection signals to discriminate between light energy of beams reflected from an object within the monitored zone and other light energy. The controller can selectively adjust the evaluation of the light detection signals to adjust the effective boundaries of the monitored zone.
-
Citations
10 Claims
-
1. An electro-optical detection system for detecting objects within the boundaries of a monitored zone, comprising
a plurality of emitter and photodetector pairs, each comprising an emitter for emitting a beam of pulses of light energy into the monitored zone, and a photodetector for detecting light energy including light energy from each of the beam pulses that is reflected from an object within the monitored zone and for generating light detection signals, and a controller for operating the emitter and photodetector pair and for evaluating the light detection signals to discriminate between a valid signal, comprising light energy of a beam pulse which is reflected from an object within the monitored zone, and invalid signals comprising other light energy, and which produces an object detection signal, including programmable range adjustment means for each of the emitter and photodetector pairs which selectively adjusts the evaluation of the light detection signals to adjust the effective boundaries of the monitored zone.
-
6. An electro-optical detection system for detecting objects within a monitored zone, including
an emitter for emitting a beam of pulses of light energy into the monitored zone, a photodetector for detecting light energy including light energy from the beam pulses that is reflected from an object within the monitored zone and for generating light detection signals, and a controller for operating the emitter and photodetector and for evaluating the light detection signals to discriminate between valid signals comprising light energy of the beam pulses which is reflected from an object within the monitored zone and invalid signals comprising other light energy, and which produces an object detection signal, including a bandwidth-limited receiver subject to noise, and a zero threshold detector for evaluating the combined noise and pulse response of the bandwidth-limited receiver at one or more spaced points in time which correspond with predetermined points in time when positive or negative peak voltage responses from reflected beam pulses are expected, an up/down counter employed to count up only if the detector reports the correct polarity of the expected responses, and to count down for all other responses, the up/down counter being biased to count down in the presence of noise only, whereby the false object detection signal rate in the absence of a valid object detection signal decreases exponentially with the length of the counter.
Specification