Patent ID: 7830621
Filing Date: 2010-11-09
Classification: G02B

Abstract:
1. A zoom lens optical system comprising: a first lens group that has a negative refractive power in total and includes an optical part having a surface which reflects light; a second lens group that has a negative refractive power in total; an iris; a third lens group that has a positive refractive power in total; and a fourth lens group that has a positive refractive power in total, wherein the first lens group, the second lens group, the iris, and the third lens group are sequentially arranged from an object side, the second lens group, the third lens group, and the fourth lens group are moved to vary magnification, thereby obtaining a variable magnification effect, the second lens group is moved to perform focus adjustment when a distance to an object is changed between a long distance and a short distance, the distance from a first lens of the first lens group to an imaging surface is fixed even when the lens moves during a change in magnification and the focus adjustment, and the zoom lens optical system satisfies the following expression where TTL indicates the distance between the imaging surface and the surface of the first lens group closest to the object on an optical axis, and fw indicates a focal length when the zoom lens optical system is at the widest angle.