Abstract: A head-mounted display may include a display system and an optical system in a housing. The display system may have displays that produce images. Positioners may be used to move the displays relative to the eye positions of a user's eyes. An adjustable optical system may include tunable lenses such as tunable cylindrical liquid crystal lenses. The displays may be viewed through the lenses when the user's eyes are at the eye positions. A sensor may be incorporated into the head-mounted display to measure refractive errors in the user's eyes. The sensor may include waveguides and volume holograms, and a camera for gathering light that has reflected from the retinas of the user's eyes. Viewing comfort may be enhanced by adjusting display positions relative to the eye positions and/or by adjusting lens settings based on the content being presented on the display and/or measured refractive errors.

Abstract: A novel building construction including recycled or discarded tires uses compacted bales of such tires as a structural core material. Earth is graded or formed for a foundation in the usual manner, and the compacted bales are arranged either horizontally or vertically and secured together to form cores for floor or wall structures. The tire bale core is then covered with construction screen or reinforcement bar and finally with concrete. When such compacted bales include an axial hollow center, the bales may be concentrically arranged along the axial centers to form air passages for heating and cooling air flow through the floor and/or wall interior. The bales may be stacked to form floors more than one bale layer deep, if desired, and the walls may be constructed more than one bale in thickness in a similar manner.