Importance

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Abstract

A compact moisture sensor for mounting on the inner surface of a windshield to detect moisture, such as rain, on the outer surface of the windshield and control the windshield wipers accordingly includes a coupler having a collimator and focuser and a housing for detachably covering the coupler. A planar circuit board disposed within the housing includes emitters and detectors mounted such that the axes of emission and detection are perpendicular to the windshield when the housing is secured to the coupler. The collimator and focuser are disposed adjacent the emitter and detector respectively such that the optical axes of the collimator and focuser form oblique angles with respect to the emission and detection axes. Two emitters and two detectors are used to form four optical paths of equal length and optical efficiency. In operation, a light beam from the emitter enters the windshield at a forty-five degree angle and is reflected back from the outer surface of the windshield to the detector, which generates a control signal based on the amount of light reflected from the outer surface. Moisture on the outer surface of the windshield reduces the amount of light reflected to the detector which signals control circuitry for operating the windshield wipers.

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First Claim