1. In an optical system comprising a light source, a light outlet, and an optical element disposed between the light source and the light outlet, a method of monitoring for optical system faults, the method comprising: detecting, via a light sensor configured to receive light from an interface surface of the optical element closest to the light source, an intensity of light traveling from the interface surface of the optical element to the light sensor; if a first optical system fault condition, due to a change in location of the optical element, is identified based upon the intensity of light, then modifying operation of the optical system in a first manner; and if a second optical system fault condition, due to a physical object blocking an optical path, is identified based upon the intensity of light, then modifying operation of the optical system in a second manner that is different than the first manner.