The analysis and control of stray light, composed of ghost images and flare, is an important but complex task for the design of imaging systems. Ghost images arise from multiple reflections off of surfaces in the primary optical path. Ghost images that impinge on the image plane at or near a focus is of specific concern—flare can arise from light reflecting off of lens mounts, non-optical surfaces of the lenses (such as flats and edges), and as a reflection off of the detector itself re-imaged back onto the detector. Modeling light reflected off of the detector can be complicated by diffraction from the microstructure of the detector. In this application note, we will discuss various computational approaches to simulating stray light in an imaging lens. All computation was done with Synopsys software, specifically CODE V, RSoft Photonic Device Tools, and LightTools.