Shadowless projector using coded large-aperture Fresnel lens

This paper proposes a delay-free shadowless projection mapping (PM) system using a coded large-aperture (LA) Fresnel lens. The LA projection is an effective approach for realizing shadow suppression without delay, but it often suffers from significant blur. We introduce the coded LA projector, where an aperture mask attached to the lens adjusts the deblurring and shadow suppression performance. We have two technical contributions to specify an optimal hardware and software configuration for the coded LA projector. Firstly, we formulate the Fresnel lens surface profile and introduce a differentiable ray tracing simulator for the coded LA projector. This simulator enables efficient calculation of the optimal aperture pattern without the need for physical projection. Secondly, we propose an optimization framework for the aperture pattern based on the specific norms characteristic of shadowless projectors. Specifically, the aperture pattern is optimized under a linear combination of three loss functions: the broadband modulation transfer function (MTF), light transmission efficiency, and shadow suppression performance. We implemented a proof-of-concept prototype and validated these techniques through simulation and projection experiments.