Automatic windshield wiping apparatus by using microwaves for vehicles

Claim 1

An automatic windshield wiping apparatus for vehicles comprising: a raindrops detecting device adapted to be located near the windshield of a vehicle, said raindrops detecting device comprising: a microwave oscillator for generating output microwaves, a waveguide having two ends operatively connected at one end to receive the output microwaves from said microwave oscillator and having the other end adapted to be disposed opposingly to one surface of said windshield so as to irradiate said output microwaves generated from said microwave oscillator on said one surface of said windshield, and first means associated with said oscillator and said waveguide for receiving a part of said microwaves irradiated on said one surface of said windshield and for producing an output signal responsive to the received microwaves, a switching circuit connected in circuit with said raindrops detecting device and including a reference signal source means for providing a reference signal and a differential amplifier for comparing the output signal produced by said first means with said reference signal and producing a further output signal when said output signal from the first means is substantially different from said reference signal, and second means connected in circuit with said switching circuit for driving a wiper on said windshield responsive to the further output signal produced by said differential amplifier.