GB509990A - Improvements in telescope eye-pieces - Google Patents

Abstract

509,990. Lenses. ZEISS, C., [Firm of]. Dec. 17, 1938, No. 36770. Convention date, Dec. 24, 1937. [Class 97 (i)] Relates to a telescope eye-piece system comprising three convergent air-spaced components, in which the sum of the air spaces is not more than one-third the focal length, the rear component (facing the eye) is a single lens whose rear surface has a curvature the magnitude of which lies between the refractive power of this lens and the negative value of this power, the medial component has at most one cemented surface, the front lens of this component and that lens of the front component which lies next thereto are convergent and at least one surface of one of these two lenses is cemented. According to the invention at least eleven-twentieths of the algebraic sum of the refractive powers of the cemented surfaces of the said convergent lenses of the medial and front components are produced by one of these surfaces and the numerical value of this sum exceeds one-twelfth of the sum of the numerical values of the curvatures of those surfaces of the said two lenses which face each other. The medical component may be a single lens and the rear surface of this component is preferably convex towards the eye. The front component may be a cemented triplet, the medial lens of which is divergent. Data are given for three examples.