zoom lens

Abstract

Abstract PURPOSE:To prevent a shift in focal point during zooming operation by shifting lens groups in relative position associatively with the zooming operation so that the position of an image plane is held constant while a lens group of focusing is fixed when a subject is at finite distance from the image plane. CONSTITUTION:The zoom lens system consists of a fixed lens group B1, lens groups B2 and B3 which move for zooming operation, and the lens group B4 for focusing. When object distance is 4m, the lens group B4 is at a position C3 and zoom tracks of the lens groups B2 and B4 are so determined that the image plane F is held constant in said state. Positions B4' and B4'' are extension positions for focusing on a subject at 2m object distance and at infinite distance respectively, C2 is the track of the focusing position within the entire zooming range, and C1 is the track in focusing on the infinite-distance body.

Inventors

• 👤 Tsunefumi Tanaka
• 👤 常文 田中

Bibliographic Details