Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Folding
Patent
1975-04-07
1976-07-13
Sacher, Paul A.
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Folding
351 14, 356156, A61B 302
Patent
active
039690199
ABSTRACT:
A curvature measuring optical system in an ophthalmometer comprises a first and a second lens group and rotary prisms disposed between the two lens groups. The first lens group has the focal point thereof lying at the location of the virtual image of an index projected on the cornea of an eye to be examined. The second lens group focuses on the focal plane thereof a light beam made parallel by the first lens group. The rotary prisms separate the image into two images and are rotatable in the opposite directions from each other. The optical system is improved in that it further includes a light-intercepting member formed with at least three openings and disposed just behind the first lens group to divide the light beam between the two lens groups, and that the rotary prisms are a first rotary prism member disposed adjacent the second lens group and just behind one of the openings to cause a light beam passed through the one opening to be deflected on the focal plane in a predetermined direction and a second rotary prism member disposed adjacent the second lens group and just behind another one of the openings to cause a light beam passed through said another opening to be deflected on the focal plane in a direction perpendicular to direction of deflection by the first rotary prism member. The two rotary prism members may be rotated by rotating means therefor.
REFERENCES:
patent: 864769 (1907-09-01), Brewer
patent: 890580 (1908-06-01), Sutcliffe
patent: 1523528 (1925-01-01), Henker
patent: 1918540 (1933-07-01), Hautinger
Nippon Kogaku K.K.
Sacher Paul A.
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