Optical viewing system with two magnifications - comprises objective, eye piece, and mobile unit with divergent and convergent lenses

摘要

The double magnifying glass is intended for high precision viewing, and comprises an objective (1) and an eyepiece (3), the latter including the image formed by the image in its focal image plane. The lens combination provides a high magnification with a low magnification, this being obtained by placing a mobile optical unit on the optical axis. This does not alter the position of the focal image plane. The optical unit comprises a first diverging lens and a second diverging lens. If the focal length of the objective is F, the power of the divergent lens is p, the power of the converging lens is kp (k negative), the ratio of the two magnifications is r and the distance apart of the two lenses is d, then (1) kp = p X 1 - d kp (1+p) =1/r and (2) p = (kd2 -2kd + k+1)/kd(1-d), where the focal length F is assumed to be unity.