Design Method of Time-Multiplexed Ultrashort Throw Ratio Projection System with Low Distortion and Uniform Resolution

Abstract

Time-multiplexed laser projection is recognized as a promising projection technology owing to its broad color gamut and high energy efficiency. The escalating demands for enhanced laser safety and reduced space occupation necessitate the development of ultrashort throw ratio (UTR) projectors. However, the inherent mechanical deflection limitations and distortions of micro electro mechanical systems (MEMS) scanners pose significant challenges to achieving UTR projection. To address these constraints, trapezoidal distortion is first eliminated by ensuring vertical laser incidence on MEMS mirrors during the initial projection phase. Subsequently, a systematic design methodology for UTR laser MEMS projection systems is proposed, incorporating a miniaturized catadioptric projection objective that maintains uniformly optical étendue distribution. This configuration achieves a throw ratio of 0.27, reduces pillow distortion to 0.4%, and ensures consistent resolution across the entire screen. Segmentation and modular assembly of the catadioptric objective at telecentric intermediate image planes enhances the efficiency of initial structural design phase. The developed projection prototype experimentally validates the efficacy of the projection system designed through the proposed methodology in decreasing the projection ratio, correcting distortion, and maintaining uniform projection resolution across the full field of view.