Patent ID: 7499224

Claim:
A bent type zoom optical system, comprising, in order from its object side, a positive first lens group adapted to remain fixed upon zooming, a negative second lens group adapted to move toward an image plane side upon zooming from a wide-angle side to a telephoto side, a third lens group adapted to remain fixed upon zooming, and a unit designed such that a combined focal length distance between said third lens group and an image plane is positive, wherein said positive first lens group includes a first reflecting member and a negative single lens on an object side of said first reflecting member, and said third lens group comprises, in order from its object side, a stop, a second reflecting member and a positive lens unit, wherein said second reflecting member is located in such a way as to bend an optical path in a direction orthogonal to a plane defined by an optical axis of said first lens group on an entrance side thereof and an optical axis bent by said first reflecting member, and wherein said unit includes a positive fourth lens group and a positive fifth lens group, and said fourth and fifth lens groups move such that, upon zooming, the fourth lens group is positioned more on the object side and the fifth lens group is positioned more on the image plane side on the telephoto side than at the wide-angle end.