Wide spectral bandwidth virtual image display optical system

TLDR: In this article, the authors proposed a virtual image display optical system, which consists of an image source, a combiner, and a relay group consisting of a catatrioptic relay group and a refractive lens group.

Abstract: A virtual image display optical system. The system includes an image source, a combiner, and a relay group. The relay group is a catatrioptic relay group that includes a reflective optical element, and a refractive lens group that includes at least one doublet and a diffractive lens. For some applications, the catatrioptric relay group may be replaced by a hybrid refractive-diffractive relay group, thus eliminating the reflective element. The diffractive optical element of the hybrid optical element is encoded on one side of a lens. The hybrid optical element forms a refractive/diffractive achromat to provide for primary chromatic aberration correction. The refractive lens group is also an achromat to provide for chromatic aberration correction. Power distribution between the hybrid optical element and the refractive lens group is such that secondary chromatic aberration of the refractive lens group is balanced out by the secondary chromatic aberration of the hybrid optical element. The diffractive optical element is designed using higher order wavefront correction terms encoded on one side to reduce spherochromatism and secondary spherochromatism of the relay group. One lens may have a conic or an aspherical surface to further reduce the spherochromatism and secondary spherochromatism. Asymmetrical aberration and distortion resulting from the combiner are compensated for by the reflective optical element. To minimize the residual aberration of the optical system, the reflective optical element is tilted and/or decentered. The system has a relatively wide spectral bandwidth, has good image quality, has simple optics, is ultracompact, and provides wide field coverage and large field overlaying.