Optical precipitation sensor for monitoring the accumulation of precipitation upon automotive glass

An improved precipitation sensor to sense the presence of water upon an automotive glass of the type having an optical emitter, an optical receiver, a first mirror surface for collimating light emitted from said optical emitter and having a first leading edge, a second mirror surface for focusing said emitted light upon said optical receiver and having a second leading edge, and an electronic circuit in electrical communication with said optical emitter and said optical receiver, the improvement comprising:

• said precipitation sensor including an intermediate reflector having a first reflective region proximate said emitter and a second reflective region proximate said receiver;
• said second mirror surface being aspheric and positioned to focus said emitted light upon said receiver;
• said second reflective region having a second mean reflective point being displaced from said automotive glass at a distance at least as great as a distance said second leading edge of said second mirror surface is displaced from said automotive glass;
• said second leading edge laterally disposed such that said second mirror surface is positioned between said receiver and substantially all ambient light exiting from said automotive glass toward said receiver.