Edible Retroreflector Made of Candy

Recently, methods of projecting images onto food using a projector have been the subject of various studies because they have the potential to intervene in the visual appreciation of food, and also because such technology has the potential to create new production methods and services related to food. Since projection can be achieved easily using an optical marker, an edible retroreflector made of agar has been proposed; however, an agar retroreflector had the drawback of a short lifetime. In this paper, we propose an edible retroreflector made of candy, which is resistant to drying and can be used for a long time. Two types of retroreflectors, one with single layer and the other with two layers, were proposed and fabricated. The evaluation experiments showed that the proposed retroreflectors had sufficient reflection coefficient $R$ of up to 84.76 for the single-layered prototype and up to 173.05 for the two-layered prototype. These coefficients are comparable to the coefficient 70 of commercially available glass-bead-type retroreflectors, which are strong enough to be used as markers for a camera. The prototype was also able to maintain its functionality for 10 days from the fixed-point observation. Furthermore, dynamic projection mapping on a pancake and motion capture were successfully demonstrated to show the potential applications.