| 摘要 |
A variable focus lens system for eyeglasses is disclosed. The system consists of superimposed first and second thin lenses, simulating Alvarez lenses, with one side of each lens divided into Fresnel zones and zone boundaries. The second lens element is slidable for focus adjustment. The Fresnel zone boundary surfaces are made parallel to the user's optical line of sight to reduce visual obstructions, and the zone boundaries may be restricted to areas near the lens periphery to further reduce visual obstructions. The Fresnel zone boundaries may follow paths which enable equal, constant step size for the boundaries along their lengths. An opaque light absorbing coating may be applied to the zone boundaries to reduce light scattering. A fixed prescription lens, having the user's distance and astigmatism corrections, is superimposed on the first and second lens elements. In a second embodiment, a lens element may have at least one additional Fresnel lens component mated and bonded to it, forming a composite lens element. A composite lens element may have internal antireflection layers between the mated lenses, to further reduce internal reflections. The outer smooth sides of a lens element or composite lens element may have antireflection coating applied. |
