Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Patent
1991-01-03
1993-09-28
Bovernick, Rodney B.
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
351214, 351221, A61B 310
Patent
active
052490033
ABSTRACT:
An ocular refractivity measuring apparatus includes a light receiving optical system, an illuminating optical system, an imaging device and a calculator. The light receiving optical system includes a light dividing member and an obturating plate. The obturating plate has a linear edge so as to obturate part of an opening of the light receiving optical system. The light dividing member is closer to a fundus of an eye to be measured in an optical path than the obturating plate. The illuminating optical system has a light source for projecting light in a direction perpendicular to the linear edge of the obturating plate, to the light dividing member so as to illuminate the fundus of the eye via the light dividing member. The imaging device is provided on a light receiving surface of the light receiving optical system at a position substantially conjugate with a pupil of the eye for detecting the amount of light in two regions of the pupil of the eye separated in a direction perpendicular to the linear edge of the obturating plate. The calculator calculates the refractivity of the eye in accordance with the ratio of the amount of light in the two regions of the pupil of the eye separated in a direction perpendicular to the linear edge detected by the imaging device and in accordance with the distance between the two regions.
REFERENCES:
patent: 4650301 (1987-03-01), Humphrey
patent: 4755041 (1988-07-01), Ishikawa
"Measurement of Ocular Refractive Power By A Planar Light Souce/Knife Edge Method", Kogaku (Optics), vol. 18, No. 10 (Oct. 1989) pp. 545-546.
Bovernick Rodney B.
Canon Kabushiki Kaisha
Dang Hung Xuan
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