Due to the vast number of imaging lenses that are available on the market, actually choosing a lens for a given application can be a daunting task. Part one of this article covered the most common types of lenses used for machine vision. Part two will cover how to actually go about selecting a lens once it is known what type of lens is needed. Generally, the working distance and field of view are required to be known before the proper selection of a lens can take place. Following that, the smallest feature size that needs to be resolved on the object needs to be known; this can be referred to as the object space resolution.
For the purposes of this discussion, fixed focal length lenses, zoom lenses, and macro lenses can be assumed to operate on the same principles, and can be chosen in the same fashion. This assumes that zoom lenses are being specified at individual focal lengths, and that their zoom functionality has been locked down.