The diamond machining machine possesses the attributes of a measuring machine when machining is not taking place. Considering that the disturbances produced by machining will affect the tool workpiece relationship, one may expect this disturbance will disappear when the process is complete. Systematic errors may be eliminated by complementary measurements on the same machine structure in the absence of machining disturbances. In-process measurements may be real time if segregation in the frequency domain is possible. Effective measurements may also be made with little time lag between machining and measuring. Diamond machining opens the process to the use of interferometry on the workpiece as a measuring means. Ordinarily flats and spheres may be checked against easily produced wave front references. Advent of the chordal aspherical generator makes it possible to check aspherical surfaces of revolution in many cases. Examples of in-process configurations and techniques are presented with analysis of the capabilities and limitations which ensue. Key elements are air bearing machine elements, diamond tools, and interferometry with data reduction by micro-computers.
Gordon J Watt,
"In-Process Measurement Of Optical Surfaces", Proc. SPIE 0676, Ultraprecision Machining and Automated Fabrication of Optics, (13 February 1987); doi: 10.1117/12.939519; https://doi.org/10.1117/12.939519