Optical engine for head-mounted display apparatus

A method comprising:

• a) forming a prism assembly that defines an optical path from an incident surface to an output surface that is orthogonal to within +/−30 degrees relative to the incident surface,
• wherein the prism assembly has a curved reflective surface opposite the incident surface,
• and wherein the prism assembly encases a beam splitter disposed at an oblique angle to the defined optical path within the prism assembly and to both the incident surface and the output surface of the prism assembly;
• b) defining a sealed air gap between a display and the incident surface by bonding a shim to the incident surface and to a display surface;
• c) mounting the display, the shim, and the incident surface of the prism assembly within a frame that leaves the output surface of the prism assembly exposed;
• and
• d) coupling the display apparatus to a head-worn article.

A display apparatus comprising:

• a) a display that is energizable to emit image-bearing light from a planar display surface;
• b) a prism assembly that defines an optical path for conveyance of the emitted image-bearing light,
• wherein the optical path extends between an incident surface of the prism assembly and an output surface that is orthogonal to within +/−30 degrees relative to the incident surface,
• wherein the prism assembly has a concave reflective surface opposite the incident surface,
• and wherein the prism assembly encases a wire-grid polarization beam splitter disposed at an oblique angle to the defined optical path within the prism assembly and to both the incident surface and the output surface of the prism assembly and further has a quarter wave plate in the optical path between the beam splitter and the concave reflective surface;
• c) a shim bonded to the display surface and to the incident surface of the prism assembly, wherein the shim defines a sealed air gap of the optical path between the display surface and the incident surface;
• and
• d) a frame that houses the display, the shim, and the incident surface of the prism assembly,
• wherein the frame further provides one or more connection features for coupling the display apparatus to a head-worn article.