Direct Comparison Of Mechanical And Optical Measurements Of The Finish Of Precision Machined Optical Surfaces

This paper compares two methods of measuring the finish of precision-machined optical surfaces: the older and well-established use of a mechanical stylus gauge (Talystep) and the recently developed optical technique based on interference microscopy (Wyko NCP). Results are found to be in good quantitative agreement for both random and periodic surface features providing appropriate filtering procedures are included in the data analysis to account for the differing transfer functions and bandwidths of the two measurement techniques. These results affirm the use of these techniques for the quantitative measurement and specification of machined optical-surfaces.