One of the principal roles of simulation technology is to provide a platform on which to study the performance of a system before that system is manufactured, in order to preempt as many potential pitfalls as possible. One of the most common phenomena that can detrimentally affect the performance of a system is stray light, which may have multiple sources, spurious internal reflections in the system among them. In this use case we analyze the presence of such reflections in a collimation lens system for a high-NA laser diode, we model the effect the resulting ghost images have on the detected field (a concentric ring pattern caused by the interference of the main collimated beam and a secondary divergent one produced by the stray light), and identify the need for an antireflection coating on key surfaces of the lens system in question.