Working distance detecting device for ophthalmic apparatus

Details Working distance detecting device for ophthalmic apparatus Working distance detecting device for ophthalmic apparatus

1981-06-03

1984-03-06

Corbin, John K.

Optics: eye examining, vision testing and correcting

Eye examining or testing instrument

Objective type

354 62, A61B 314, G03B 2900

Patent

active

044350511

ABSTRACT:
An eye fundus camera is disclosed having a working distance detecting device. The eye fundus camera includes an illuminating system having a ring-shaped aperture through which the illuminating light beam is projected to the eye to be examined through an objective lens. The working distance detecting device includes an opaque portion formed in said ring-shaped aperture and having a width in circumferential direction. A light receiving portion is provided around the objective lens at a position corresponding to the opaque portion in the image of the ring-shaped aperture formed by beams of the illuminating light reflected from the cornea of the eye so that the working distance can be detected based on the width of the opaque portion of the image of the ring-shaped aperture.

REFERENCES:
patent: 4219258 (1980-08-01), Araki
patent: 4257687 (1981-03-01), Kohayakawa

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