Patent ID: 8000032
Filing Date: 2011-08-16
Classification: G02B

Abstract:
1. An internally focusing lens system, comprising: a first lens group with positive refractive power; a second lens group with negative refractive power; and a third lens group with positive refractive power, the first, second and third lens groups arranged in that order from an object side of the lens system to an image side of the lens system; wherein the third lens group comprises at least one lens element, the second lens group is movable toward the image side and the first and third lens groups remain stationary during focusing of the lens system from an infinitely distant object to a nearby object, and the following conditions are satisfied: wherein F is a focal length of the internally focusing lens system at the time of focusing of the infinitely distant object, F wherein the TTL is in a range from 5 millimeters to 10 millimeters.