Zoom lens system in finite conjugate distance

Abstract

With a stop disposed at the center, a lens system are composed of four sheets of positive, negative, negative, and positive lenses. At the time of variable magnification, the whole lens system is moved while distances between the lenses are changed, whereby a low cost and a compact size are attained in a zoom lens system for copying. This lens system is constituted by four sheets of positive, negative, negative, and positive lenses (L.sub.1 to L.sub.4) which are disposed in pairs laterally symmetrical to each other with respect to the stop. At the time of reducing or enlarging, the distance between the first lens (L.sub.1) and second lens (L.sub.2), the distance between the third lens (L.sub.3) and fourth lens (L.sub.4), and the distance between the second lens (L.sub.2) and third lens (L.sub.3) are made larger than those under real-size magnification, while the whole system is moved with the distance from the object surface to the imaging surface being held substantially constant so as to attain variable power.

Dependencies are inferred from the claim text.