TELEPHOTO LENS WITH INTERNAL FOCUSING Russian patent published in 2003 - IPC

FIELD: optics. SUBSTANCE: telephoto lens comprises first and second optical components with positive refraction installed in sequence in direction of propagation of optical beam and made of positive and negative lenses. First component includes positive and negative lenses cemented together, second component can move along optical axis of device and include negative meniscus facing space of objects with its convex surface and positive lens glued together. Equivalent focal distance of entire system, focal distance of second component, gap between first and second components and Abbe numbers of materials of first and second components satisfy relations given in formula of invention. EFFECT: reduced energy losses of light with preservation of aperture ratio and high-quality image with increase of angular field of vision. 1 dwg