of optical surfaces without the need for expensive, difficult -to- manufacture

The design of a long -trace surface profiler for the non -contact measurement of surface profile, slope error and curvature on cylindrical synchrotron radiation (SR) mirror is presented here. The optical system is based upon the concept of a pencil -beam interferometer with an inherent large depth -offield. The key feature of the optical system is the zero pathdifference beam splitter, which separates the laser beam into two colinear, variable separation probe beams. A linear array detector is used to record the interference fringe in the image, and analysis of the fringe location as a function of scan position allows one to reconstruct the surface profile. The optical head is mounted on an air bearing slide with the capability to measure 38" long aspheric optics, typical of those encountered in SR applications. A novel feature of the optical system is the use of a transverse "outrigger" beam which provides information on the relative alignment of the scan axis to the cylinder optic symmetry axis.