We are developing a form measurement system for the surfaces of freeform optics and large conventional optics. The specifications of the optics are diameters up to 1.5 m and radii of curvature down to 10 m. This includes optics like telescope mirror segments and synchrotron optics. Using a Fizeau interferometer, we propose a subaperture stitching method that involves vertically aligning the interferometer’s optical axis to the local surface gradient and measuring the absolute distance from the interferometer’s reference flat to the specimen. Experimental results for the absolute distance measurement are shown.
Absolute distance interferometry for subaperture stitching of large freeform optics