Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Folding
Patent
1975-03-17
1976-03-30
Sacher, Paul A.
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Folding
350190, 351 34, 351 39, A61B 302, G02B 306
Patent
active
039471861
ABSTRACT:
The invention is a test lens made to fit a standard optometrist's trial-lens frame. The lens is a crossed-cylinder astigmator of about .+-. 5 diopter strength, preferably formed by cementing together a first planoconvex cylinder lens of about 5 diopter strength and a second equal-strength plano-concave cylinder lens with a parallelogram grid sandwiched between them, the grid lines being about one millimeter apart in each of the parallel sets, and inclined one set to the other at an angle of about 73 degrees, the axes of principal curvature of the lens elements being perpendicular one to the other, and respectively parallel one to each of the diagonals of the grid elements. The subject under test views monocularly a spectrally pure point source through the test lens. Ideally, he sees an undistorted pattern of vertical and horizontal lines; but depending on the nature of his refractive defect, various distortions of the grid pattern are seen which the subject may then sketch, or identify, with the aid of an atlas of variously distorted patterns.
REFERENCES:
patent: 3574464 (1971-04-01), Howland
Larsen Jack
Sacher Paul A.
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