Directional backlight module based on pixelated nano-gratings

A directional backlight is of great interest in the field of glasses-free 3D display, privacy display, and energy efficient display. In this paper, a directional backlight module including a LED light bar, a collimating lens, a diffuser, and a waveguide is proposed. The waveguide is covered by nanogratings with a density gradience to optimize the illumination uniformity and to preserve the angular divergence of the emitted light. The proposed directional backlight achieved a divergence angle of ±6.17° and a uniformity of 88%. The directional backlight based on pixelated nanogratings features good uniformity, thin form factor, low cost, and large tolerance of the fabrication process, thus can be used in the illumination of glass-free 3D display, privacy display, and energy efficient display.