What's it about?

This paper will explain terms unique to prism manufacturing, explaining when they are useful.


Prisms are optical components with at least two polished plano surfaces separated by a wedge angle. These elements are used to reflect or refract light. With no spherical surfaces and a lack of an axis of symmetry, these items differ from one’s conventional image of a lens. Their distinctive characteristics give rise to its own language, the language of prisms. The terms here include:

1.1 Flatness

While spherical lenses are expected to have surface curvature, the plano surfaces of a prism are not. Form error specifications for spheres typically draw a distinction between radius error and irregularity (deviation from perfect), but form error specifications for prisms can be given as flatness, combined power and irregularity. Radius errors are not expected as they are for spheres, and flatness emphasizes this. Figure 1 shows how power and irregularity combine to show flatness...