Patent ID: 7948617

Claim:
A foreign-particle detection system for use with an optical instrument having a transmissive window with a first side and a second side, the system comprising: a radiation source to emit a radiation signal; a diffusing reflector to diffusively spread the radiation signal emitted by the radiation source over the first side of the transmissive window, the diffusing reflector positioned relative to the transmissive window to not obscure light incident on the transmissive window at a right angle to the transmissive window; a radiation detector to detect, at the second side of the transmissive window, the diffusively spread radiation signal transmitted by the transmissive window, and to generate a detected radiation signal based on the detected diffusively spread radiation signal; and a computation module communicatively coupled to the radiation detector to detect a presence of foreign particles on at least one of the first side or the second side of the transmissive window based on at least the detected radiation signal.