Optical instrument for internal medical examination - has light conductor with refraction index dependent on radial distance from centre

摘要

The optical instrument comprises a transparent light conductor fitting in a hollow tube, while an ocular lens is mounted on the outside of this conductor, and a second light conductor is provided for illumination purposes. The first conductor has an index of refraction in cross-section at right angles to the central axis conforming to the equation:- n= N (1 - ar2), where N represents the index of refraction at the centre of a cross-sectional surface perpendicular to the centre line, n is the index of refraction at a point at a radial distance r from this centre and a is a positive constant.