Cascaded design for microstructured optical diffusers using a Gaussian scattering-kernel model

A cascaded design method for surface-relief diffusers composed of concave ellipsoidal microstructures is presented. In this method, area-weighted Gaussian scattering kernels for broad parameter screening are combined with ray tracing for local refinement. In Stage I, a continuous surface is generated for each candidate parameter set. Local surface normals within the effective region of each microstructure are used to calculate output ray angles according to Snell’s law. Their mean and covariance define a two-dimensional Gaussian scattering kernel, while the effective-region area determines its weight. The superposition of all kernels is used for broad parameter search. In Stage II, the selected parameter region is refined by ray tracing. For a nearly circular 30 ^∘ target, a final horizontal FWHM of 29.92 ^∘ is obtained. For an anisotropic 30 ^∘ /20 ^∘ target, the final principal FWHMs are 30.01 ^∘ and 20.05 ^∘ . The same optimized surfaces are further evaluated for spatial coherence and polarization, with DoLP values of 0.9980 and 0.9991, respectively.