Patent ID: 8670186
Filing Date: 2014-03-11
Classification: G02B

Abstract:
1. A zoom lens, substantially consisting of a first lens group which has a positive power and is fixed at the time of zooming, a second lens group which has a negative power and is moved along an optical axis at the time of zooming, an aperture stop, a third lens group which has a positive power and is fixed at the time of zooming, and a fourth lens group which is moved along the optical axis at the time of zooming to correct a change in image plane position arising from the zooming for focusing, disposed in this order from an object side, wherein: the third lens group is composed of a third group first lens which is a single lens with at least one surface being aspheric and has a positive power and a third group second lens which is a single lens with an image side surface being concave to the image side and has a negative power, disposed in this order from the object side; and the zoom lens simultaneously satisfies conditional expressions (1) and (2) given below: where: Nd f fw is a focal length of the overall lens system at a wide angle end; and ft is a focal length of the overall lens system at a telephoto end.