"Swiss Army" Lens
A Swiss Army Knife® (see Figure 2) is a compact, foldable knife that includes an assortment of handy tools such as screw drivers, scissors, toothpicks, and files in addition to the blade itself. Likewise, Bigshot's polyoptic wheel features several optical modules that are used to take different types of photos, and can be thought of as a "Swiss Army" Lens. Each module works with the primary imaging lens (which is attached to the circuit board) to capture a different type of photo. The tools in a Swiss Army Knife must be small enough to fit inside. The modules in the polyoptic wheel also face restrictions, but these restrictions are optical ones. Since the primary lens's focus is already fixed, the modules should not introduce any additional focusing. That is, they should not produce any net convergence or divergence of a beam of light; they can only transform a collimated (parallel) beam of light into another collimated beam. Such a system is called an afocal system [1]. Although an afocal system must keep the rays in a beam parallel to each other, it can change the direction of the beam as a whole or compress the light rays within the beam, as Figure 3 shows. This allows optical engineers to design modules that can increase or decrease the primary lens's field of view [2].
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