Method and apparatus for presenting test images at different dis

Details Method and apparatus for presenting test images at different dis Method and apparatus for presenting test images at different dis

1979-10-02

1981-11-03

Corbin, John K.

Optics: eye examining, vision testing and correcting

Spectacles and eyeglasses

Folding

351 36, 351 39, A61B 302

Patent

active

042982537

ABSTRACT:
Method and apparatus for presenting test images to a subject at different distances and a constant visual angle. The test indicia are located at a single predetermined distance from the viewer. An optical system is provided between the test indicia and the viewer for including a lens system and at least one reflecting element or plane mirror. Displacements of the lens system along its optic axis and the plane mirror(s) along an axis parallel to a continuation of the lens system optic axis are coordinated so that the visual angle for the viewer remains the same regardless of the distance of the test image from the viewer. A single set of test indicia may be used for all potential image distances without having to vary the visual angle.

REFERENCES:
patent: 3969020 (1976-07-01), Lynn et al.
patent: 4179196 (1979-12-01), Persson et al.

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