Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Patent
1980-06-12
1983-10-04
Rosenberger, R. A.
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
351221, A61B 310
Patent
active
044075723
ABSTRACT:
A keratometer is disclosed for remotely measuring corneal curvature in at least sphere, cylinder, and axis. Assuming the eye is precisely positioned from measurement, light sources are overlapped and imaged to a virtual image position behind the human cornea. The sources of light - preferably three in number (although more than three can be used) - each have their own discrete paths from the source to the eye and then to their own discrete detector. Between the light source and the eye, each light path is interrupted by a moving boundary locus having a transparent portion, an opaque portion, and a boundary therebetween. The moving boundary locus is in turn imaged by reflection from the cornea being measured to a real image position superimposed to and upon a light detector. The detector for each eye path is aligned to and toward the virtual image produced by the light source in the precisely positioned eye. Stray light emanating from the position other than the vicinity of a virtual image position of the light source on the cornea cannot be received by the detector. By measuring the displacement on the eye of the virtual images of each moving boundary of the locus with its associated discrete light path, a caratometric measurement can be made with as few as three light sources, three detectors, and three separate and discrete paths therebetween.
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patent: 3941486 (1976-03-01), Tyler
patent: 4180325 (1979-12-01), Humphrey
patent: 4182572 (1980-01-01), Humphrey
patent: 4199816 (1980-04-01), Humphrey
Humphrey Instruments Inc.
Rosenberger R. A.
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