Patent ID: 7221518

Claim:
A zoom lens optical system comprising: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; and a fourth lens group having positive refractive power, wherein the first through fourth lens groups are arranged sequentially from an object, zooming is performed from a wide angle position to a telephoto position so that the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the distance between the third lens group and the fourth lens group increases, and the first through fourth lens groups satisfy: 6 ≤ L W F W + L t F t ≤ 8 where L w denotes a distance between a first surface of an object-side lens of the first lens group and an image surface when in the wide angle position, L t denotes a distance between the first surface of the object-side lens of the first lens group and the image surface when in the telephoto position, F w denotes an overall focal length when in the wide angle position, and the F t denotes an overall focal length when in the telephoto position.