Total Internal Reflection (TIR)

TIR refers to the condition where a ray makes too large an angle with respect to the normal of a surface to meet the refraction condition as specified by Snell's Law. This usually occurs when a ray with a large angle of incidence is refracting from a high index media to a lower index media, such as from glass to air. When doing sequential ray tracing, rays which TIR are considered errors, and are terminated. Physically, the ray would reflect rather than refract from the boundary, but OpticStudio does not consider this effect when doing sequential ray tracing. For non-sequential ray tracing, rays which TIR are properly reflected.