| 摘要 |
A prosthesis for visually handicapped persons provides for collection and concentration of available light to thereby assist the visually handicapped with seeing under conditions of reduced or diffuse lighting. The prosthesis has a pair of spaced tubular housing members each of which contains an imaging lens in the portion remote from the user's eye and a concentrating lens in spaced relationship from the imaging lens and closer to the user's eye than the imaging lens. The concentrating lens may be generally pear-shaped and have an entrance pupil of greater diameter than the exit pupil. The convex entrance surface may have a radius of curvature of about 1.8 to 2.2 times the radius of curvature of the convex exit surface. The intermediate lens surface may be generally parabolic in configuration. The concentrating lens is preferably substantially symmetrical about its longitudinal axis. The portion of the concentrating lens surrounded by the generally parabolic surface preferably has an axial extent of about 45 to 55 percent of the total axial length of the concentrating lens. The lens system is also usable in microsurgery, and cameras and a plurality of concentrating lenses may be employed in a solar collector.
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