SkyAnchor: Optical Design for Anchoring Mid-air Images onto Physical Objects

For glass-free mixed reality (MR), mid-air imaging is a promising way of superimposing a virtual image onto a real object. We focus on attaching virtual images to non-static real life objects. In previous work, moving the real object causes latency in the superimposing system, and the virtual image seems to follow the object with a delay. This is caused by delays due to sensors, displays and computational devices for position sensing, and occasionally actuators for moving the image generation source. In order to avoid this problem, this paper proposes to separate the object-anchored imaging effect from the position sensing. Our proposal is a retro-reflective system called "SkyAnchor," which consists of only optical devices: two mirrors and an aerial-imaging plate. The system reflects light from a light source anchored under the physical object itself, and forms an image anchored around the object. This optical solution does not cause any latency in principle and is effective for high-quality mixed reality applications. We consider two types of light sources to be attached to physical objects: reflecting content from a touch table on which the object rests, or attaching the source directly on the object. As for position sensing, we utilize a capacitive marker on the bottom of the object, tracked on a touch table. We have implemented a prototype, where mid-air images move with the object, and whose content may change based on its position.