GB784371A - Ophthalmic apparatus - Google Patents

Abstract

784,371. Ophthalmoscopes. DUDRAGNE, R. A. Nov. 9, 1955 [Nov. 15, 1954], No. 32025/55.. Class 97(1) In an ophthalmoscope, an observing optical system is located on the opposite side of the optical axis of a photographic system to an illuminating system and, the latter comprises a low intensity source for continuous illumination of the fundus and a gas discharge tube capable 'of giving a photographic flash exposure. The translocation of the illuminating system enables the straight line between the operator's eye Oo and the patient's eye Op to be kept free from any obstruction. As shown, incandescent filament lamp S1 and gas discharge lamp S2, having diaphragms DS1 and DS2 respectively, are in conjugate positions with respect to lens L3 and diaphragms DS2 and Dp are in conjugate positions with respect to lens L4. Lens L1 forms an image of the fundus which is projected by lens L2 on to the film F or reflected by mirrors Me, Mv for observation. Although only part of the fundus is illuminated when the apparatus is held stationary, practically the whole of it can be illuminated on rotating the apparatus through an angle of 210 degrees about the axis OpF. In another form, prism P is located in front of lens L1, which is of sphero-parabolic form, and the prism is so near to the patient's eye that an unobstructed view of the eye is necessary to avoid injury. The light from the incandescent lamp is reflected by a half-silvered plate into an optical system consisting of four achromatic doublets and the light from the discharge tube is transmitted by the plate into the system.