Research on the background stray light suppression method of a dim target projector based on the orthogonal polarization extinction principle.

Aiming at the problem of background stray light affecting the display of dim target scenes in existing projectors, a stray light suppression optical engine based on a polarizer is proposed. First, the effect of the background stray light of traditional LCOS target projectors on the display of dim targets is analyzed with simulation, and the sources of stray light in the target projector were analyzed as well. Secondly, we theoretically analyze the causes of different stray light paths and stray light polarization states, propose the method of stray light suppression based on the polarizer, and calculate the rotation angle of the polarizer. Then, we simulate and analyze the stray light suppression effect of the polarizer-based target projector model. Finally, a dim target projector test experiment system is built to verify the actual level of stray light suppression. The simulation results show that the highest stray light energy of the target projector with the polarizer-based stray light suppression optical engine has decreased by 2.37 times compared to the conventional LCOS target projector, the stray light coefficient has decreased from the previous 2.12% to 0.60%, and the simulated contrast ratio has been improved by 2.98 times. The experimental results show that the polarizer-based stray light suppression optical engine is able to reduce the peak gray level of the background stray light energy of the projected display image of the target projector by nearly 2 times, and improve the contrast of the gray level by 2.79 times. The suppression of dim target projector background stray light and the improvement of the contrast of the projected display image are realized.