Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Folding
Patent
1976-02-26
1979-05-22
Sacher, Paul A.
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Folding
351 33, 351 39, 351 25, A61B 302, A61B 300
Patent
active
041556321
ABSTRACT:
The disclosure relates to a method and apparatus for testing eyesight in the presence of controlled varying degrees of contrast at a target which is being viewed. The contrast ratio of the illumination of the portion of a target having a series of test patterns with respect to the illumination of the background of the target surrounding the patterns affects intraocular light scattering in a subject's eyes. In one disclosed embodiment an eye chart is provided which has opaque symbols on an illuminated background. By means of a transparent surface which is partly reflective, such as a half-silvered mirror, a veiling light is superimposed uniformly upon the light transmitted from the illuminated background of the target toward the subject's eyes. By varying the level of the background light or the veiling light or the darker (polarized) portions of the target pattern with a polarizing filter, or all, different contrast ratios of the light directed from the location of the target toward the subject's eyes can be presented. The disclosure additionally relates to the measurement of the effect of varying contrast ratios of a target on a subject's eyes by the use of a plurality of different charts, each having a background and a pattern thereon which provide a different contrast ratio to the subject's eyes.
REFERENCES:
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patent: 4027954 (1977-06-01), Good
Matthew Luckiesh, Test Charts Representing a Variety of Visual Tasks, Mar. 1944, pp. 270-274, Amer. Jour. of Opht.
Acadia Associates
Bovernick Rodney B.
Sacher Paul A.
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