Measurement of mid-spatial frequency errors on freeform optics using deflectometry

Freeform optics have emerged as a new tool for optical designers and integrators. Manufacturing innovations are gradually increasing availability of precision freeform optics. As optics manufacturers strive to improve quality and decrease cost, some focus is placed on improvements in the challenging metrology requirements for freeforms. One relevant technique to be discussed here is the use of deflectometry to measure mid-spatial frequency error in-process or in-situ during the manufacturing of freeform parts. Deflectometry can measure the mid-spatial frequency error on freeform parts orders of magnitude faster than traditional tactile metrology tools at similar or better accuracy.