JPS6488511A - Zoom lens - Google Patents

Abstract

PURPOSE:To obtain a zoom lens even with large in aperture ratio and high performance to satisfy miniaturization, light weight, and low cost by constituting the titled lens of specific lens groups of a first group having a positive refracting power, a second group having a negative refracting power, and a third group having the positive refracting power in the above sequence observing from an object side. CONSTITUTION:The titled lens is constituted of the first group having the positive refractive power, the second group having the negative refracting power, and the third group having the positive refracting power. The first group is constituted of two lenses, a convex meniscus lens at the object side and a biconvex lens whose strong plane is faced with the object side, and the second group is constituted of three lenses in total, a negative lens whose strong plane is faced with an image side and the negative lens group as a whole in which the negative lens and a positive lens are cemented. The lens is constituted so that the first group and the second group are moved at the time of zooming, and the first group maintains an image plane position at that time, and the second group performs a role of variable power and the third group image-forms a radiating light beam after being emitted from the second group. In such a way, it is possible to obtain the zoom lens in which entire length is reduced remarkably and is constituted of a few number of sheets of lenses, and realizable to attain the miniaturization, the light weight, and the low cost with large in aperture ratio, and attainable the high performance even when it is used in a wide angle of view area.