Optical proximity detector

摘要

A proximity detector comprises a LED 4 which is driven by an oscillator 1 such that light pulses are directed towards a surface 7 whose distance from the detector is required to be measured, a photodiode 9 receiving light pulses reflected from surface 7 and producing a corresponding electrical signal, a phase detectors 13 giving I and Q phase differences between a signal received directly or via 90 DEG C phase shifter 14 from said oscillator 1 and that reflected from said surface 7, said phase differences being representative of the path length between transmitter and receiver. The detector may be used as an optical altimeter.