Abstract: A head-mountable device can provide passive cooling that utilizes surfaces of an optical assembly to allow heat to be managed in a manner that does not detrimentally impact the visual information displayed to the user. Lenses can be coated with a transparent and thermally conductive material, such as silver nanowire. Such a thermal layer can provide superior thermal conductivity, transmittance, flexibility, flat transmission, low cost, and angular color stability. The thermal layer can passively manage heat by increasing the surface area across which heat can be efficiently dissipated.

Abstract: An electronic device such as a head mounted device may have a head-mounted support structure. A portion of the head-mounted support structure may form a transparent housing member through which real-world objects can be viewed from eye boxes. A display system for the head-mounted device may have a display device that provides image light to a waveguide and may have an output coupler that couples the image light out of the waveguide toward the eye box. Peripheral portions of the transparent housing member or other peripheral device structures may be provided with a peripheral display that emits diffuse light into a user's peripheral vision. The peripheral display may use light guide structures, light sources, reflective structures, and other structures that provide transparency to real-world light.