Patent ID: 7492459

Claim:
An optical droplet sensor configured for installation on a surface of a light transmissive structure, and operative to detect droplets attached on another surface of the light transmissive structure, the optical droplet sensor comprising: a light emitter; a light receiver; and a light guide located adjacent the light emitter and light receiver, the light guide including, a light entry surface having an externally protruding convex shape configured to receive light emitted from the light emitter into the light guide, a light exit surface having an externally protruding convex shape configured to release light guided through the light guide to external, and at least one of a primary side reflector having a metal-containing film and configured to direct light introduced into the light guide toward the light transmissive structure, wherein, light reflected from the transmissive structure is directed toward the light exit surface, and a secondary side reflector composed of a first side reflector having a metal-containing film and configured to direct light introduced into the light guide toward the light transmissive structure and a second side reflector having a metal-containing film and configured to direct light reflected from the light transmissive structure toward the light exit surface, wherein the light guide comprises a single unitary structure.