Ultrashort throw lenses with catadioptric relay suitable for flat and curved screens

Abstract

In the past two decades, to realize high resolutions and low distortions while miniaturizing optical systems, various ultrashort throw lenses (USTs) have been proposed. In this work, ultrashort throw lenses with a catadioptric relay (USTCRs) with rotational symmetry are proposed to provide the solution. First, the initial design method of the USTCR and the optimized design solution are presented. Although this optical system with a throw ratio of 0.26:1 has resolutions and distortions equivalent to those of conventional UST with one aspherical mirror, the depth of focus (DOF) on the panel side becomes 1.31 times deeper with appropriate corrections of the field curvature. The total length of the lens is reduced to 0.89 times, the area of the main mirror is reduced to 0.22 times, and the number of lenses is reduced from 13 to 9 elements. Based on these results, several optical designs for USTCR have been tried and an optical design with robustness has been proposed. By optimizing the power of each lens group, the decenter sensitivity improved to 0.46 times for parallel decenter and 0.55 times for tilt decenter. By optimizing glass materials, the shift of focal plane can be suppressed to 0.56 times when the temperature increases by 30 °C. An USTCR suited for a curved screen has also been proposed. By introducing appropriate constraints that correct distortions, high resolutions and low distortions have been realized while maintaining a wide angle of view. USTCRs suited for various curved screens are currently underway.