Aerial Imaging by Retro-Reflection for Mid-Air Image Display and Camera Viewpoint Transfer

Previously, a telepresence system, called Levitar, was proposed to allow communication through computer-graphics (CG) avatars in real space. Levitar employs micro-mirror array plates (MMAPs) to display mid-air images and optically transfer the camera viewpoint to the mid-air image-display position optically. This system captures the first-person view of a mid-air image avatar; however, it has a limitation that the stray light caused by MMAPs reduces its range. Therefore, in this study, we propose an optical system to capture a wider range of mid-air viewpoints. The proposed optical system uses aerial imaging by retro-reflection (AIRR) instead of MMAPs for mid-air image display and camera viewpoint transfer. AIRR is a mid-air imaging system that includes a beam splitter and retro-reflector. However, in contrast to MMAPs, it does not generate stray light. The optical transfer of the camera viewpoint by AIRR enables the capture of a large area. To evaluate the range of the capturing area when using cameras with MMAPs and AIRR, we conducted experiments under different camera gaze directions and effective angle of view. The results indicate that AIRR maintains a constant resolution up to 40 degrees of the camera gaze direction, whereas MMAPs have a lower resolution above 30 degrees, and the area of the marker detection rate of over 80% is approximately 54% larger for AIRR than for MMAPs. This implies that AIRR achieved a wider imaging range than MMAPs for mid-air telepresence systems.