Patent ID: 6124691
Filing Date: 2000-09-26
Classification: B60S,Y10S

Abstract:
A moisture sensor for detecting moisture on the surface of a transparent material and controlling the actuation of a moisture removal system accordingly, said moisture sensor comprising:an emitter for generating a low duty cycle pulsatile moisture sensing signal which is influenced by the presence of moisture on the surface of the transparent material;a detector for receiving said pulsatile moisture sensing signal and contributing to the production of a pulsatile detector output signal having a fundamental frequency and signal components including harmonics of said fundamental frequency;a pre-demodulation circuit connected to said detector and including an input for receiving said pulsatile detector output signal and an output for providing a pulsatile pre-demodulation signal, said pre-demodulation circuit further including an amplifier for providing gain to said pulsatile pre-demodulation signal and a band-pass filter connected to said input for attenuating unwanted low frequency ambient light noise signal components and passing most of the useable signal information from said pulsatile detector output signal including most of said harmonics; anda demodulation circuit for converting said pulsatile pre-demodulation signal to a dc signal for indicating the presence of moisture on the surface of the transparent material.