Aerial imaging steganography method for aerial imaging by retro-reflection with dual acrylic ball.

This paper proposes a novel steganography method to show an aerial image that is formed with aerial imaging by retro-reflection by use of dual transparent balls made of acrylic resin. Our optical system forms a floating image screen in front of an acrylic ball that is placed on a beam splitter. We have confirmed our proposed optical system by performing optical ray-tracing simulations and experiments with a prototype aerial display. The ray-tracing results show that an acrylic ball plays the role of a ball lens, reducing the area of the retro-reflector and improving the luminance of the aerial image. Then, we measured the luminance distribution of the aerial image formed by the proposed method by imaging the aerial image of the stripe pattern with a luminance meter. From the measurement results, the luminance of the aerial image at a radius of about 5 mm from the center of the acrylic ball (radius 35 mm) was almost the same as that of the conventional method. In addition, an aerial image was observed within a radius of 25 mm, although the luminance was low. Thus, the simulation and experimental results confirm the effective range of aerial imaging in the proposed method. [ABSTRACT FROM AUTHOR]