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: An ultra lightweight golf club shaft which includes a butt section, a tip section, and a tapered section interconnecting the same. The tapered section can be a constant taper, or include a plurality of step portions interconnected by frustoconical transition areas. The shafts are extremely durable and allow a faster club head speed and a better feel than with the previous prior art shafts.

Abstract: An ultra lightweight golf club shaft which includes a butt section, a tip section, and a tapered section interconnecting the same. The tapered section can be a constant taper, or include a plurality of step portions interconnected by frustoconical transition areas. The shafts are extremely durable and allow a faster club head speed and a better feel than with the previous prior art shafts.

Abstract: A shaft for a golf club includes a first series of step portions, with the step portions increasing in diameter along the shaft from a tip or hosel end of the shaft toward a grip end. The step portions are separated from adjacent step portions by transitional portions which consist of a relatively gentle taper which smoothly link the surfaces of one step portion with another. A second series of step portions is disposed between the first series of step portions and the grip end of the shaft, with the diameter of the step portions increasing by a predetermined amount from the first series of step portions toward the grip end. The second series of step portions are separated from adjacent step portions and from the grip end further transitional portions which are similar to the transitional portions discussed above.

Abstract: A shaft for a golf club includes a first series of step portions, with the step portions increasing in diameter along the shaft from a tip or hosel end of the shaft toward a grip end. The step portions are separated from adjacent step portions by transitional portions which consist of a relatively gentle taper which smoothly link the surfaces of one step portion with another. A second series of step portions is disposed between the first series of step portions and the grip end of the shaft, with the diameter of the step portions increasing by a predetermined amount from the first series of step portions toward the grip end. The second series of step portions are separated from adjacent step portions and from the grip end further transitional portions which are similar to the transitional portions discussed above.