Abstract: A method and a device for making the distance between a human eye and an eye-examining instrument coincide with a preset distance. A miniature light source disposed on the image end of an objective lens of the instrument illuminates the eye. The light specularly reflected by the surface of a cornea is converged. The miniature light source is positioned to have the converging point lie on the surface of an image of the fundus formed by the objective lens. Accordingly if the distance between the human eye and the instrument coincides with a preset distance, the image of the light source on the image surface of the objective lens becomes sharp. An operator looking into a view finder correctly adjusts the position of the instrument by moving the latter until the image of the light source becomes sharp.

Abstract: An ophthalmoscopic photographing and observing system eliminates rays of light reflected and scattered at the cornea and the crystalline lens of a human eye. An illuminating optical system is provided with light shielding stops at positions conjugate to the corneal surface, the iris, and the rear face of the crystalline lens of an eye being examined. The sizes of these light shielding stops are such that an image of the stop conjugate to the corneal surface covers an area on the cornea where the light reflected by the fundus of the eye passes through the cornea covered with an image of the stop which is conjugate to the corneal surface; an image of the stop which is conjugate to the rear surface of the crystalline lens covers an area on the rear face of the crystalline lens where the light reflected by the fundus of the eye passes through. A ring-shaped aperture stop is conjugate to the iris.

Abstract: The present invention relates to an eye fundus camera free from undesired reflected and diffused light beams. The camera uses a photographic optical system including an objective lens, a reflecting means, an aperture means, a photographic lens system for imaging the eye fundus to be inspected in sequence on a photographic plane and an illumination optical system including at least a light source, a relay lens and a ring-shaped aperture. The optical system leads the light beam from the light source to the eye to be inspected through the reflecting means and the objective lens, whereby the ring-shaped aperture is positioned in the illumination optical system in such a manner that the image of the ring-shaped aperture is formed near the iris in the eye to be inspected while the aperture is positioned in such a manner that the conjugate position of the aperture with reference to the objective lens is near the cornea to the eye to be inspected.

Abstract: A catoptric system adapted for X-ray fluoroscopic photography comprises a spherical concave reflector disposed to reflect fluorescence light coming from the object plane to a field flattener of positive power positioned in front of a photographic film. In one embodiment of the invention, the reflector is constituted by a negative meniscus lens having a primary surface facing the object plane and with the secondary surface being mirrored. In order to facilitate minimization of the reflector diameter, there is provided a positive meniscus lens, having a concave surface facing the object plane, positioned between the reflector and field flattener to thereby assist in converging the rays of light from the object plane before impingement on the reflector.