Presence detecting apparatus and method for automatic doors

摘要

A presence detecting apparatus and method are disclosed, the apparatus including an emitter array and receiver array configured, oriented and shielded to provide an effective detection area characterized by a truncated elliptical footprint, a background compensation network for automatically compensating for variations in environmental conditions in the detection area to provide a substantially constant detection sensitivity, and discriminating circuitry for discriminating signals indicative of a body in the detection area from transient and steady state signals. The emitter circuits and receiving and detecting circuits are capable of asynchronous operation, and the receiver array and detector array are housed so that the receiver array is substantially isolated from selected electromagnetic signals from the detector array.