Enlarged mid-air image display based on slim DOE waveguide

Abstract

Currently, Mid-Air Display (MAD) technology is of a great interest to practitioners. Potential application in consumer products with large aperture “floating” image displays, like TV, monitor, ATM, vending machine, home appliance, etc., and contactless user interface for remote control increase their attractiveness. In order to obtain enlarged mid-air image size at maintaining large horizontal Field of View (FoV) and high light display efficiency, the following challenges are to be solved: developing high fill-factor Diffractive Optical Elements (DOE) architecture with optimal size of out-coupling aperture and designing custom-made projection optics with specified exit pupil matched to in-coupling DOE. As a possible solution to abovementioned problems, the authors propose a MAD based on commercially available projector source, custom-made projection optics and designed corner DOE waveguide architecture with focusing Fresnel lens. The mid-air image is formed at the back focal plane of the Fresnel lens, between the viewer and the display. For mid-air image with five-inch diagonal and 32° horizontal FoV, we take waveguide out-coupling aperture of 245 x 145 mm2 and Fresnel lens with back focal length of 220 mm and obtain image brightness ~1000 cd/m2 due to custom projection optics. Basic contactless user interaction was also implemented.