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

A method for detecting water upon an automotive windshield generally opaque to infrared light, said method comprising:

• emitting visible light through an optical notch upon a first aspheric mirror surface;
• collimating said visible light;
• reflecting said visible light with a first reflective region;
• reflecting said visible light from said automotive windshield generally opaque to infrared light;
• reflecting said visible light with a second reflective region;
• shielding a receiver from ambient light passing through said automotive windshield with a second aspheric minor surface;
• and,
• reflecting said visible light with said second mirror surface upon said receiver.

A method for detecting water upon an automotive windshield generally opaque to infrared light, said method comprising:

• emitting visible light upon a first aspheric mirror surface;
• collimating said visible light;
• reflecting said visible light with a first reflective region;
• reflecting said visible light from said automotive windshield generally opaque to infrared light;
• reflecting said visible light with a second reflective region;
• shielding a receiver from ambient light passing through said automotive windshield with a second aspheric mirror surface;
• and,
• reflecting said visible light with said second mirror surface through an optical notch, upon said receiver.

A system comprising:

• windshield wipers disposed for removing water from the exterior surface of a windshield of an automobile, said windshield wipers defining at least one arc of sweep across said exterior surface of said windshield;
• control circuitry for controlling operation of said windshield wipers;
• and
• a precipitation sensor adapted to detect water upon said exterior surface of said windshield, said sensor comprising:
• an optical emitter emitting light in at least a visible range through an optical notch;
• a first mirror surface in optical communication with said optical emitter and adapted to reflect and collimate light emission from said optical emitter;
• an optical receiver;
• a second mirror surface in optical communication with said optical receiver adapted to focus collimated light through an optical notch and upon said optical receiver, said second mirror surface positioned between said receiver and substantially all ambient light exiting from said windshield toward said receiver, blocking said ambient light exiting from said windshield from impinging on said receiver;
• an intermediate reflector in optical communication with said first mirror surface and with said second mirror surface;
• and
• an electronic circuit in electrical communication with said optical receiver to sense the presence of water upon said exterior surface of said windshield and operate said control circuitry.