Patent ID: 6154324
Filing Date: 2000-11-28
Classification: G02B

Abstract:
A macro lens system in which a focusing state is adjustable between an infinite focusing state, where said macro lens system focuses on an object at infinity, and a close focusing state where said macro lens system focuses on an object at the minimum object distance, the macro lens system comprising:a focusing lens group that moves along an optical axis between an infinite focusing position proximate an image plane at said infinite focusing state, and a close focusing position further from said image plane at said close focusing state than at said infinite focusing state, said focusing lens group comprising a first lens group having a positive power and a second lens group having a negative power, said first and second lens groups being driven to move, in a focusing operation, along said optical axis in the same direction, said first and second lens groups being located at positions closer to an object when the object is close than when said object is far, a distance between said first and second lens groups becoming larger as an object becomes closer;an aperture that is movable along said optical axis, said aperture being provided between said first and second lens groups; anda driving mechanism for independently moving said focusing lens group and said aperture along said optical axis, wherein said driving mechanism moves said aperture toward the object side to increase an effective F-number as said focusing lens group is moved to the object side, and wherein said driving mechanism moves, in a focusing operation, said aperture toward the object side as said first and second lens groups are moved towards the object, the moving amount of said aperture being smaller than the moving amount of said first lens group.