Abstract: A zoom lens is constructed by two lens groups in which a first lens group having a positive focal length is arranged on an object side and a second lens group having a negative focal length is arranged on an image side. A zooming operation is performed by changing a distance between the first and second lens groups. The first lens group has first to fourth lenses sequentially arranged from the object side toward the image side. The first lens is constructed by a positive meniscus lens having a convex face directed onto the object side. The second lens is constructed by a biconcave lens. The third lens is constructed by a positive lens. The fourth lens is constructed by a biconvex lens. The second lens group has fifth to seventh lenses sequentially arranged from the object side toward the image side. The fifth lens is constructed by a positive meniscus lens having a convex face directed onto the image side.

Abstract: A camera shake compensating optical system has a first lens and a second lens from the object side. The image side surface of the first lens is convex to the object side. The object side surface of the second lens is convex to the object side. A direction in which a luminous flux is transmitted is slightly changed by a relative displacement of the second lens with respect to the first lens. By an obtained transmission deflection angle, blur of an image taken when the taking optical system is inclined is compensated for. The relative displacement is made so that an incident surface of the first lens and an exit surface of the second lens are not decentered from the optical axis of the taking optical system.

Abstract: A zoom lens system for use in a copying apparatus has first, second and third lens units of negative, positive and negative, respectively. Zooming is performed while the conjugate distance is kept constant by varying the distance between the first and second lens units and the distance between the second and third lens units and varying at a magnification either larger or smaller than unity the distance between the second and third lens elements of the second lens unit. The first lens unit has a lens element strongly concave to the object side. The second lens unit has a positive meniscus lens element, a bi-concave lens element and a bi-convex lens element. The third lens unit has a negative meniscus lens element concave to the image side.

Abstract: A zoom lens system having a field angle of about 44.degree. to 47.degree. at the wide angle end, a zoom ratio of about 2.6 to 3 and an F-number on the order of 2.8, which is reduced in value while making sure of a back focus and which is improved in terms of its capability to form images. The zoom lens system includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power and a fourth lens group consisting of three lens elements and having a positive refractive power as a whole, the second and third lens groups being movable for zooming.

Abstract: A real-image variable magnification finder is capable of blocking deleterious rays of light without increasing the lens diameter or the size of the erecting prism even of the view angle is large. The improved finder includes, in order from the object side, objective lens system II, condenser lens III with which the image of the object formed by the objective lens system II is directed to eyepiece lens system V, erecting prism system IV for inverting the image of the object, and eyepiece lens system V, and the objective lens system II comprises at least two zooming groups IIA and IIB that will move along the optical axis and light shielding means A that is provided between the zooming groups for blocking deleterious rays of light.

Abstract: A zoom lens system includes from one side to the other side: a first lens unit of a negative power having a negative lens element concave to the one side; a second lens unit of a positive power having a positive meniscus lens element convex to the one side, a biconcave lens element whose one side surface has a larger radius of curvature and a biconvex lens element; and a third lens unit of a negative power having a negative meniscus lens element concave to the other side. In order to perform zooming, the distance between the first lens unit and the second lens unit and the distance between the second lens unit and the third lens unit are varied, and the entire zoom lens system is moved along the optical axis.

Abstract: A zoom lens comprises a first lens unit having a positive refractive power, a second lens group having a negative refractive power, an iris and a third lens unit having a positive refractive power, arranged in this sequence as viewed from an object. The third lens unit comprises a lens unit 3a and a lens unit 3b arranged in this sequence as viewed from the object, with a large air gap therebetween. Zooming from a short focal length end to a long focal length end is effected by moving the second lens group from a unit side to a image side and moving the first lens unit and the third lens unit to depict convex loci toward the object. The zoom lens meets the condition of-0.3<HF.sub.3 /f.sub.3 <0.20.5<l.sub.3 /f.sub.3 <1.5whereHF.sub.3 is a distance between an apex of a lens of the third lens group facing the object and a front principal point of the third lens unit,f.sub.3 is a focal length of the third lens unit, andl.sub.3 is an air gap between the lens unit 3a and the lens unit 3b.

Abstract: A compact zoom lens, which can attain a compact lens system while maintaining a simple lens arrangement including six lenses, and can minimize deterioration of performance caused by a variation upon assembling, is disclosed. The compact zoom lens includes a positive first lens group G.sub.1 and a negative second lens group G.sub.2. The first lens group G.sub.1 has, in turn from the object side, a positive meniscus lens component L.sub.1 with the convex surface facing the object side, a meniscus-shape junction negative lens component L.sub.2 constituted by a double-concave negative lens component L.sub.2n and a double-convex positive lens component L.sub.2p, and a double-convex positive lens component L.sub.3. The second lens group G.sub.2 has, in turn from the object side, a positive meniscus lens component L.sub.4 with the convex surface facing the image side, and a negative meniscus lens component L.sub.

Abstract: A zoom lens comprises first to fourth lens groups in order from the subject end. Second to third lens groups move along optical axis of the zoom lens for zooming between a wide-angle end where the zoom lens has the shortest focal length and a telephoto end where the zoom lens has the longest focal length. During the zooming, first lens group remains stationary. As the second lens group moves towards the image end for zooming from the wide-angle end to the telephoto end, the third and fourth lens groups are moved so as to initially decrease a relative axial distance therebetween and subsequently increase the axial distance, thereby correcting changes in focus caused by the axial movement of the second lens group during zooming.

Abstract: A telephoto zoom lens, when viewed from the object, comprises: a first lens group having positive refracting power; a second lens group having negative refracting power; a third lens group having positive refacting power; a fourth lens group having positive refracting power; and a fifth lens group having negative refacting power, wherein, when magnification is varied from the wide angle end to the telephoto end, an air interval between the first lens group and the second lens group is enlarged, an air interval between the second lens group and the third lens group is reduced, an air interval between the third lens group and the fourth lens group is enlarged and an air interval between the fourth lens group and the fifth lens group is reduced.

Abstract: A zoom lens comprising, from front to rear, a first lens unit of negative power, a seconde lens unit of positive power, a third lens unit of positive power and a fourth lens unit of negative power, wherein zooming from the wide-angle end to the telephoto end is performed by moving at least the second and fourth lens units toward the object side in such a way that the air separations between the first and second lens units and between the third and fourth lens units are shorter in the telephoto end than in the wide-angle end.