Patent ID: 7956341

Claim:
A system for detecting a level of fluid in a surgical cassette, comprising: a linear light array comprising: a first light source to project a first beam of light into a first cassette wall along a first transmission path, wherein the first transmission path has an angle of incidence with the first cassette wall so that at least a majority of the first light beam is refracted at an inner surface of the first cassette wall so that at least a majority of the first beam of light is incident on an inner surface of a second cassette wall at an angle that allows at least a majority of the first beam of light to refract out of an outer surface of the second cassette wall if a cassette material/first fluid interface at the inner surface of the first cassette wall intersects the first transmission path; and a second light source arranged along a vertical axis with respect to the first light source to project a second beam of light into the first cassette wall along a second transmission path, wherein the second transmission path has an angle of incidence with the first cassette wall so that at least a majority of the second light beam is internally reflected at the outer surface of the second wall if the cassette material/second fluid interface intersects the second transmission path at the inner surface of the first cassette wall; and a linear sensor array comprising a first portion positioned to receive the first beam of light and a second portion positioned to receive the second beam of light and produce an output signal to indicate whether each of the first and second portions are illuminated.