Patent ID: 8773779
Filing Date: 2014-07-08
Classification: G02B,Y10T

Abstract:
1. A lens system comprising, in order from an object, a front-side lens group having a positive refractive power and a rear-side lens group having a positive refractive power; wherein the front-side lens group comprises in order from the object: a first lens component having a positive refractive power; a second lens component having a positive refractive power; a third lens component having a positive refractive power; a fourth lens component having a negative refractive power; an aperture stop; a fifth lens component having a negative refractive power; a sixth lens component having a positive refractive power; and a seventh lens component having a positive refractive power; wherein the rear-side lens group includes a cemented lens constructed by cementing a positive lens and a negative lens together in order from the object; wherein, upon focusing from infinity to the object at a short distance, the front-side lens group and the rear-side lens group move along an optical axis by respective amounts of movement different from each other so as to increase a distance between the front-side lens group and the rear-side lens group; and wherein the lens system satisfies the following conditional expression: where fF denotes a focal length of the front-side lens group, and fR denotes a focal length of the rear-side lens group.