Patent ID: 6333825
Filing Date: 2001-12-25
Classification: G02B

Abstract:
A vari-focal lens comprising:a plurality of power varying lens groups including a focusing lens group, which are guided so as to be movable in a direction of an optical axis of said plurality of power varying lens groups to vary a focal length thereof, said focusing lens group being moved in said optical axis direction by different amounts of movement at different focal lengths, respectively, to bring an object at the same object distance into focus;a zooming ring manually rotated about said optical axis;a focusing ring manually rotated independently of said zooming ring about said optical axis;a focusing lens frame which supports said focusing lens group;an intermediate moving frame which supports said focusing lens frame and is guided so as to be movable in said optical axis direction;a zoom cam ring which moves said intermediate moving frame and each of said plurality of power varying lens groups in said optical axis direction according to a predetermined zoom path when said zooming ring is rotated;a focus cam ring which rotates together with said zoom cam ring about said optical axis and is movable in said optical axis direction relative to said zoom cam ring, said focus cam ring comprising focus cams for compensating for a deviation of a focal plane from an in-focus position thereof at a focal length determined by a rotational position of said zooming ring; andfirst cam followers formed on said focusing lens frame and corresponding second cam followers formed on said intermediate moving member, said first cam followers and second cam followers being engaged with said focus cams of the focus cam ring;wherein said focus cam ring moves in said optical axis direction relative to said focusing lens frame and said intermediate moving frame, and at the same time, rotates about said optical axis while being guided by said focus cams to thereby change a position of engagement of said first cam followers and said second cam followers relative to said focus cams.