Micro-mirror-array based off-axis flat lens for near-eye displays

Abstract

We developed an off-axis diffractive lens using a micro-mirror array on a flat substrate. MMA creates an on-axis converging beam from a 45 degrees off-axis diverging illumination beam and functions similar to a large and bulky elliptical mirror. The array consists of individual micro-mirrors with normal directions that vary across the component. The size, normal direction and the center height of each micro-mirror are optimized to achieve a phase matching condition so that the smallest focal spot size is achieved at the design wavelength. Design can also be optimized for full color applications using a synthetic design wavelength. A sample MMA of size 3 mm by 5 mm is fabricated using grayscale lithography. The designed MMA is used to illuminate a computer-generated hologram in a near-eye display system. Experimental results verify the premises of the designed component.