Patent ID: 8786943
Filing Date: 2014-07-22
Classification: G02B

Abstract:
1. An imaging system having reduced susceptibility to thermally-induced stress birefringence, for projecting an image of an object plane onto a display surface, comprising: imaging optics including relay optics that image the object plane onto an intermediate image plane and projection optics that image the intermediate image plane onto the display surface; wherein one of either the relay optics or the projection optics is a reflective optical system that includes reflective optical elements, and the other of the relay optics or the projection optics is a refractive optical system having a negligible or low susceptibility to thermal stress birefringence, the refractive optical system including: wherein the refractive lens elements in the first and second groups of refractive lens elements that are immediately adjacent to the aperture stop are fabricated using optical materials having a negligible susceptibility to thermal stress birefringence as characterized by a thermal stress birefringence metric, and the other refractive lens elements in the first and second groups of refractive lens elements, that are not the refractive lens elements immediately adjacent to the aperture stop, are fabricated using optical materials having at most a moderate susceptibility to thermal stress birefringence as characterized by the thermal stress birefringence metric.