Method and device for detecting distance between eye-examining i

Details Method and device for detecting distance between eye-examining i Method and device for detecting distance between eye-examining i

1977-09-13

1980-04-08

Evans, F. L.

Optics: eye examining, vision testing and correcting

Spectacles and eyeglasses

Folding

351 13, 354 62, 356 3, A61B 314

Patent

active

041969790

ABSTRACT:
A method and a device for making the distance between a human eye and an eye-examining instrument coincide with a preset distance. A miniature light source disposed on the image end of an objective lens of the instrument illuminates the eye. The light specularly reflected by the surface of a cornea is converged. The miniature light source is positioned to have the converging point lie on the surface of an image of the fundus formed by the objective lens. Accordingly if the distance between the human eye and the instrument coincides with a preset distance, the image of the light source on the image surface of the objective lens becomes sharp. An operator looking into a view finder correctly adjusts the position of the instrument by moving the latter until the image of the light source becomes sharp.

REFERENCES:
patent: 3871772 (1975-03-01), Munnerlyn
patent: 3904280 (1975-09-01), Tate, Jr.

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