Grazing incidence interferometry for high precision measurements of cylindrical form deviations

Grazing incidence interferometers equipped with diffracting elements (compu ter generated holograms) are now being used to measure the cylindricity, ro undness and straightness of cylindrical parts. The method is non-contact, w ith automatic work piece alignment and is capable of recording thousand of points on the surface in a few seconds. It incorporates parallel data acqui sition of the cylindrical surfaces, so that an excellent radial resolution can be obtained. There are some questions regarding the basic theory and th e accuracy when measuring workpieces with short wavelength errors. Experime ntal results using a CylinderMaster CM 25, and a modification for measuring blind holes are presented.