Optical design of a freeform, gradient-index, head-mounted display

Abstract

.I present the results of an optical design study into the performance benefits of non-rotationally symmetric “freeform” gradient-index (GRIN) media on a pupil-relay head-mounted display. A range of design variants are presented based on freeform-GRIN lenses consisting of ternary base-material combinations that are enabled by recent developments in additive manufacture. The optical performance of these designs is compared to homogeneous solutions comprising combinations of spherical, aspheric, toric, and freeform surfaces. I show that freeform-GRIN media represent powerful degrees of freedom for aberration correction in tilted and off-axis optical systems, performing comparably to homogeneous freeform optics while illustrating significant potential reductions in lens count and mass.

Exploring the unique chromatic properties of multi-material gradient-index optics

“…And although results were promising, no designs were fabricated and further research has not been published since 2017. The potential for multi-material three-dimensional (3D) ink-jet printing has also motivated the recent work of Boyd, where multi-material F-GRIN have been investigated for the first time [31,32]. The present work seeks to continue prior multi-material GRIN research by developing theory, design intuition, showing the added utility of a fourth base material, and highlighting a previously unexplored effect for multimaterial GRIN.…”

“…Numerous design studies have shown the utility of refractive index distributions that vary along two independent spatial dimensions [44][45][46][47]. And more recently, their usefulness in multi-material F-GRIN systems has also been demonstrated [31,32]. The following sections reexamine the first-order properties when axial dependence is introduced and investigate more complicated design forms where the refractive index varies in two independent spatial dimensions.…”

“…Much of this analysis is not new [31,32] or unique to multi-material F-GRIN (in that binary F-GRIN can achieve this effect as well) [44][45][46][47]. What is new and unique to multi-material F-GRIN is the idea that, when axial-dependence is introduced, the 𝑉 "#$% and 𝑃 "#$% can also vary in 𝑧.…”