Misfit of rigid tools and interferometer subapertures on off-axis aspheric mirror segments

Abstract

Abstract. Rigid tools can confer advantages at certain stages of manufacturing off-axis mirror segments, but the misfit due to surface asphericity and asymmetry poses constraints on their application. Types of misfit are classified and, using least squares, the best-fit tool forms with different distances from the pole of the parent asphere are calculated. The outer mirror segment for the European extremely large telescope is taken as a case-study, assuming a rigid tool size of 150 mm. A simple independent approximation validates the calculation. A close parallel is wavefront misfit in subaperture interferometry, which is also considered. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Research on edge-control methods in CNC polishing

“…The diameter of 50 mm was selected for compatibility with processing a full-size segment, to meet the criterion that the aspheric misfit would be well below the slurry particle size [11]. This step also helped to remove certain midspatial frequency features resulting from small-tool corrections.…”