Specifications: figure and finish are not enough
- Parks, R. E.
Several examples are given of optics apparently specified only by figure and finish. Although these optics met the specifications they did not produce good images. The presumed reason for the poor performance was the lack of a specification for mid-spatial frequency roughness. We show that a reasonable specification can be applied using the concept of a structure function, a mathematically simple function easily calculated from interferometric phase data at each pixel. An example wavefront is used to show how the specification can be developed from typical figure and finish specifications and include information about roughness in the mid-spatial frequency region.
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