Simulation of relief-type diffractive lenses in ZEMAX using parametric modelling and scalar diffraction.

Abstract

For the simulation of relief-type diffractive surfaces, an efficient method has been developed and described. Based on zone decomposition, our approach maps the transmitted wavefront by ray tracing, while point spread function/modulation transfer function (PSF/MTF) plots are calculated by scalar diffraction, taking light diffracted into multiple orders into account inherently. Using a parametric user-defined surface, our solution makes the analysis and optimization of diffractive lenses possible directly inside optical design software. Implementation was carried out in ZEMAX in the form of a swift Windows Dynamic Link Library extension using an approximative, non-iterative algorithm. The average computation time increments relative to standard built-in surfaces are 38% and 21% for PSF and MTF calculations, respectively. Application of our method is illustrated by the analysis of diffractive intraocular lenses. For validation, numerical results were compared with analytical formulae and industry-standard measurements. The ray-tracing error caused by our approximation proved to be less than ${7} \cdot {{10}^{ - 6}}$7⋅10 wavelength, and the difference from the theoretical MTF calculations is 1%-2%. The RMS difference of the simulated-measured through-focus MTF values at 50 lp/mm is 0.031, equaling ${2}\sigma $2σ measuring accuracy.