Moisture sensor for detecting moisture on a windshield

A moisture sensor comprising:

• a housing and an internal body fitting within said housing;
• a window means on a front portion of said housing composed of a material transparent to radiant energy and having an outer front surface adapted to be optically coupled to an inside surface of a windscreen;
• said window means having an inner surface formed in a stepwise shape with a first planar surface oblique to said outer front surface, a second surface extending from said first surface substantially parallel to said outer front surface, an oblique third planar surface extending from said second surface, and a planar side surface adjacent said oblique third planar surface, and;
• said internal body having a front outer surface of a stepwise shape fitting to said inner surface of said window means, and having a radiant energy emitter with an emitter surface positioned at an oblique surface complementary to one of said window means oblique surfaces and a radiant energy sensor means positioned at another oblique surface complementary to the other of said window means oblique surfaces;
• such that when said internal body is fitted into said housing said window means provides an optical path between said radiant energy emitter means and said radiant energy sensor means passing internally through said window means and a windscreen optically coupled thereto, said optical path including internal reflections at an outer surface of said windscreen and at said planar side surface of said window means.