Minimization of aberrations for the Mark IV holographic architecture using optical software modeling

Abstract

The Mark IV holographic video display, created by Daniel Smalley in the Object-Based Media Group at the MIT Media Lab, generates a three-dimensional image by illuminating a guided wave acousto-optic modulator, upon which is written a multiplexed acoustic hologram, with red, green, and blue lasers. Despite remarkable gains attained during Mark IV's inception, the reconstructed images still possess undesirable aberrations. This work's chief aim is to mitigate these aberrations by replacing many of the current optical elements with higher-end components through the aid of optical software modeling. Modeling of the optical setup is performed with a raytracing software package called FRED. Given that Mark IV's original reflector is not a high-precision optical element, the light that reflects off of its surface produces images that are distorted both horizontally and vertically at the viewing screen. To decrease the aberrations, several differently shaped reflectors are created in the model, and the coherent point spread function of the rays that pass through the image plane is analyzed. Additionally, the polygon mirror's horizontal scanning and the galvanometer's vertical scanning are simulated to generate point spread functions over the area of the image plane. And by further measuring the aberrations and computing the corresponding point spread functions at a variety of depths, the resolution is characterized across a view volume. Based on these FRED simulations, a reflector with high resolution and point spread functions that exhibit a tight concentration of energy is purchased to replace the original one.