Ophthalmoscopic instrument having working position detecting means

Abstract

Ophthalmoscopic instrument having working position detector. An object lens has an optical axis and is adapted to be positioned to confront a patient's eye at a working distance. The patient's cornea has a center of curvature. An observing optical system focuses a light beam reflected from the eye and passing through an objective lens on an image plane. A detecting system detects that the eye is properly positioned with respect to the objective lens. The detecting system includes at least two apertures allowing light beams from a single target mark to pass therethrough. A target mark projection system projects the beams passed through the respective apertures in directions crossing each other on the optical axis of the objective lens so that a target mark image is formed at the center of curvature of the cornea when the eye is properly positioned with respect to the objective lens. A target mark image plane forms a target mark image by mirror reflection from the cornea of the light beams projected through the target mark projection system when the patient's eye is properly positioned, and a target mark image observation system provides observation of the target mark image on the target mark image plane in superposition with a reference mark.