Design and fabrication of DOEs on multi-freeform surfaces via complex amplitude modulation

A non-iterative design and precise fabrication method of diffractive optical elements (DOEs) on multiple freeform surfaces is proposed and investigated in this paper. Complex amplitude modulation (CAM) technology is applied to design complicated DOEs. The wave-front for desired DOEs fabrication is interfered with a plane wave and then be encoded to a pure phase hologram. Simulations for different DOEs (binary and gray scales) on freeform surfaces are performed and the relative errors are 0.56% and 0.78%, respectively. Since the reconstructed optical fields generated by spatial light modulator (SLM) can be recorded into light-sensitive materials (photopolymer), the DOEs fabrication is realized by optical exposure. The results show that the proposed method can design and fabricate DOEs on multi-freeform surfaces at one time with high quality. Since the CAM method ensures precise reconstruction without iterations, the fabrication is accurate as well as the design is fast. It is expected that the proposed method could be applied in the precise 3D optical fabrication and processing in the future.