Model-free deflectometry for freeform optics measurement using iterative reconstruction technique

We present a novel model-free iterative data processing approach which improves surface reconstruction accuracy for deflectometry tests of unknown surfaces. This new processing method iteratively reconstructs the surface leading to reduced error in the final reconstructed surface. The method was implemented in a deflectometry system and a freeform surface was tested and compared to interferometric test results. The reconstructed departure from interferometric results was reduced from 44.39 µm RMS with traditional deflectometry down to 5.20 µm RMS with the iterative technique reported here.