Off the glass imaging rain sensor

Abstract

An assembly (10) for sensing moisture (20) on the exterior surface (22) of a windshield (14) from a position spaced from the interior surface (18) of the windshield (14). The assembly (10) includes a focal plane detector (12) comprising a plurality of pixels (24) adapted for disposition in spaced relationship to the interior surface (18) of the sheet of glass (14), as on the backside of the rearview mirror. An imaging lens (16) is adapted for disposition between the focal plane detector (12) and the interior surface (18) of the sheet of glass (14) for directing light rays from moisture (20) on the exterior surface (22) of the sheet of glass (14) through the imaging lens (16) to produce a real image of the moisture (20) on said focal plane detector (12). A processing circuit (28) establishes a steady-state level of analog signals (26) representing a non-moisture (20) condition of the exterior surface (22) of the glass (14) and scans the analog signals (26) and analyzes the data to produce a wiper signal (30) in response to a deviation from the steady-state level. The processing circuit (28) also changes the steady-state level in response to permanent changes, e.g., scratches, in the non-moisture (20) condition of the exterior surface (22) of the glass (14). For use in the absence of daytime light, a light source (32) is adapted for disposition in spaced relationship to the interior surface (18) of the sheet of glass (14) for directing light to the exterior surface (22) of the glass (14) whereby light rays generated by the light source (32) are directed from moisture (20) on the exterior surface (22) of the sheet of glass (14) through said imaging lens (16) to produce the real image of the moisture (20) on said focal plane detector (12).

Dependencies are inferred from the claim text.