Patent ID: 7286304
Filing Date: 2007-10-23
Classification: G02B

Abstract:
1. A variable focal length lens system, comprising, in order and from an object side: a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; and a fourth lens group having a positive refractive power, wherein as the lens position state changes from a wide-angle end state, where a focal length is shortest, to a telephoto end state, where the focal length is longest, at least each of the lens groups from the first lens group through the fourth lens group is mobile, the second lens group moves towards an image side and the third lens group moves towards the object side in such a manner that a gap between the first lens group and the second lens group increases, and a gap between the second lens group and the third lens group decreases, while the fourth lens group moves in a direction of an optical axis so as to compensate for changes in a position of an image plane which accompany movements of each of the lens group, the first lens group is closer to the object in the telephoto end state as compared to the wide-angle end state, the second lens group includes, in order and from the object side, a negative lens of a meniscus shape having a concave surface and an aspheric surface on the image side, and a cemented negative lens of a bi-concave lens and a positive lens of a meniscus shape and whose convex surface is turned towards the object, and following conditional equations (1) and (2) are satisfied: