Lens system for use with an optical disk

摘要

A lens system for use with an optical disk consisting of a positive lens (+) and a negative lens (-) cemented to the positive lens satisfying the conditions of nu +- nu ->20, DELTA N+/ DELTA N-<0.1 and DELTA N->0 where nu is the Abbe number and DELTA N is the temperature coefficient of the refractive index, whereby the temperature and wavelength dependence of the focal length is minimized.