Simulating the Appearance of Aerial Images formed by Aerial Imaging by Retroreflection

Abstract Ray tracing, combined with ideal retroreflection and mathematical simulation methods, has been used to design aerial imaging systems based on retroreflection. Although aerial images are blurred and have lower brightness than the light source, existing simulation methods do not focus on the appearance of these characteristics. In this study, we propose a computer graphics (CG) -based simulation using the ray tracing method to generate CG renditions of aerial images with reproduced luminance and blurring. CG models of three optical elements (light source, half-mirror, and retroreflector) were created on the basis of existing optical element models to simulate aerial images obtained through retroreflection in aerial imaging systems. By measuring the image formation positioning, we determined that the rendered aerial images consistently formed at a plane-symmetrical position relative to the axis of the half-mirror model, with a mean absolute error of 0. 55\, mm 0. 55 mm. We also compared rendered and actual aerial images in terms of luminance and sharpness characteristics, and found that the mean absolute percentage error of luminance remained within 0. 0376 0. 0376. Furthermore, the directional dependence of blur was effectively reproduced using the retroreflector bidirectional reflectance distribution function developed in this study.