What's it about?

Freeform optical components are gaining popularity with designers due to their ability to improve optical and aerodynamic performance for many applications. The challenges involved with the manufacturing and metrology of these shapes, which have little or no symmetry, has been discussed at previous talks and conferences. This paper will focus on the challenges that Optimax faced as we scaled up our freeform polishing process from parts with approximately 150 mm diameters, to polishing components with diameters over 600 mm. The large format platform, designed, built, and programmed at Optimax, utilizes a pick-and-place style, 6-axis robotic arm for the polishing motion. In order to scale up the platform from our existing robotic polishers, a larger robotic arm was used. The associated challenges include: timing considerations for both the polishing and metrology, obtaining sufficient material removal for reliable measurements, and difficulties modelling robot joint positions for collision prevention.

These issues have been investigated and mitigated through proprietary techniques and novel solutions, some of which will be explored in this paper. One such technique currently under development at Optimax is deflectometry; which is a noninterferometric method involving fringe reflection and ray tracing to calculate the mid-spatial frequency (MSF) error on a part surface. Deflectometry is able to measure MSF error two orders of magnitude faster than the current method, and has been implemented in-situ, mitigating another challenges involved with larger freeform optics: the logistics of moving them around a shop floor safely.