An aerial image display device includes a display, a convex mirror, and a concave mirror. The convex mirror reflects image light emitted from the display. The concave mirror reflects, in a direction different from a direction toward the convex mirror, the image light reflected from the convex mirror to form an aerial image as a real image. The concave mirror has a greater curvature than the convex mirror.

A two-mirror assembly, which includes a first mirror which is an aspherical mirror, a second mirror located away from the first mirror, and an open cavity formed between the first mirror and the second mirror. Embodiments of the invention provide open cavities that are stable cavities including a direct injection stability and a real ray stability.

A mirror assembly is disclosed. The mirror assembly includes an ellipsoid optical surface. The mirror assembly includes a hyperboloid optical surface, wherein the ellipsoid optical surface and the hyperboloid optical surface are arranged in a Wolter mirror configuration. The mirror assembly includes a substrate. The substrate includes a first portion, wherein the ellipsoid optical surface is located on the first portion of the substrate. The substrate includes a second portion, wherein the hyperboloid optical surface is located on the second portion of the substrate, wherein the first portion and the second portion form a monolithic body.