Ghost reduction and brightness enhancement of aerial images using lens diffusers in MMAP

In recent years, attempts have been made to operate devices in a non-contact manner from a hygienic point of view, and technologies to make displays appear in mid-air have attracted attention. One device that projects an aerial image is called a micro-mirror array plate (MMAP). Although it is relatively easy to realize an aerial display, it has the disadvantage that ghosting is visible at the same time as the aerial image. Conventional methods responded to this problem by blocking the light rays that form ghosts, but this resulted in a decrease in brightness. In this study, we proposed a method to reduce ghosts without shading by using a directional light source and a lens diffuser. Experimental results showed that at all angles from 0° to 25°, the operating range of the MMAP used, the brightness of the aerial image improved and the luminance of the ghost was reduced compared to the conventional method using louvers. The results of this study can in principle be applied to the dihedral corner reflector array (DCRA).