how to measure the surface waviness of an job square in shape????

DEAR STUDENT,

Surface waviness is the periodic component of surface texture. It arises most frequently from induced vibrations of a single-point surface generator, and when surface profiles are Fourier analyzed it usually occupies a spatial frequency band between those of surface form and roughness. Optical surfaces, such as metal mirrors or infrared (IR) optics, generated by single-point diamond turning, are often influenced to some degree by waviness. The periodic nature of such a surface results in diffraction of a reflected or transmitted beam, giving rise to multiple images rather than a single image when the beam is brought into a focus. A surface generated by the more common process involving area contact between the lap and the work surface is unlikely to suffer in this way. Polishing by the use of a flexible lap at speed can give rise to an orange-peel effect that can exhibit dominant spatial frequencies when Fourier analyzed. Similar patterns are sometimes seen on painted surfaces.