The backlight unit should be used to illuminate the liquid crystal display (LCD) panel, and the typical light throughput
is around 5% for the color LCDs. This insufficient light efficiency is predominantly related to the use of the color
filter. In this paper, a three-step Talbot grating based on the fractional Talbot effect to realize the color separation in
the color LCD is proposed in order to increase the light efficiency. Simulation shows that, when the incident light is a
uniform plane wave, the light efficiency of 85% is obtained, which is far higher than that of using color filter's 33%
theoretically. This design is insensitive to the displacement along the direction of the movement of color separation
plane and the change of RGB wavelengths, and it is also insensitive to the grating's steps height. In addition, the
Talbot grating is feasible for fabrication.