REFRACTION TYPE SMALL ZOOM LENS OPTICAL SYSTEM

摘要

A refraction-type small zoom lens optical system is provided to keep high resolving power in performing an AF(Auto-Focusing) operation from a short distance to a long distance with a few lenses and to secure the short full length. A refraction-type small zoom lens optical system is composed of a first lens group having the negative refractive force and comprising optical parts having a light reflecting surface; a second lens group having the negative refractive force; a third lens group having the positive refractive force; and a fourth lens group having the positive refractive force. The first, second, third and fourth lens groups are aligned from an object in order. The zoom lens optical system changes magnification by moving the second, third, and fourth lens groups and performs an AF operation by moving the second lens group when the object moves at a long or short distance. In changing magnification, an iris moves together with the third lens group. The distance from the first lens of the first lens group to an image surface is fixed although the lenses are moved in changing magnification or adjusting the focus.