Manufacturing of optical elements via computed axial lithography (CAL)

Computed Axial Lithography (CAL) is a promising manufacturing technique for microscale optical elements. CAL would also be attractive for custom macroscopic (centimeter-scale) optical components because of its speed and ability to work with a wide range of photopolymer precursors. However, the imaging performance of lenses printed with CAL is impacted by surface profile errors that are on the order of the projected pixel size. To develop CAL for manufacturing optics, this form error needs to be reduced through further optimization of the delivered light dose distribution and improved control of exposure and postprocessing parameters. Using a plano-convex model geometry, we formulated a simulation model that accurately predicts the height profile of a printed lens surface. We elucidate the important role of the diffusion of oxygen or radical scavengers during polymerization in determining the final shape of a printed lens. We have developed an optimization framework that corrects form errors by harnessing mass transport effects. The framework simulates the form error via an interpolation scheme that tracks a relevant objective function (degree of oxygen depletion or polymerization) at the exact surface points of a lens rather than on the grid points of a voxelized reconstruction. We will demonstrate simulation results of reduced form error at both pixel and sub-pixel sized scale as well as experimental results of improved lenses printed by optimized projection sets. We expect our algorithms will also advance CAL in other precision manufacturing applications and printing for materials with high diffusivity such as hydrogel.