Optical system

A variable focus optical system comprising:

• a forward lens unit and a rear lens unit, said forward lens unit having at least two lens groups, each of said lens groups being movable along the optical axis for varying the focal length of the optical system, and at least one of said lens groups being movable along the optical axis for focussing the optical system on an object located at a distance closer than the usual focal range of the optical system, first and second control means being selectively operable for varying the focal length of the optical system, said first control means comprising first cam follower means cooperating with first cam means for controlling the movememnt of said lens groups according to a first law of motion wherein the image of an object located at said usual focal range remains in a constant image plane, said second control means comprising second cam follower means cooperating independently with at least second and third cam means for controlling the movement of at least one of said lens groups according to a second law of motion wherein the image of an object located at a distance closer than said usual focal range remains in said image plane, each of said at least second and third cam means defining a distinct distance closer than said usual focal range said first and at least second and third cam means being arranged on a common carrier structure, and actuating means for selectively engaging said second cam follower means with each of said at least second and third cam means.

A variable focus optical system comprising a forward lens unit and a rear lens unit, said forward lens unit having at least two lens groups, each of said lens groups being movable along the optical axis for varying the focal length of the optical system, and at least one of said lens groups being movable along the optical axis for focussing the optical system on an object located at a distance closer than the usual focal range of the optical system, first and second control means being selectively operable for varying the focal length of the optical system and comprising cam follower means, said control means comprising first cam means being arrange as a contact face of an aperture in a first carrier means, for being rigidly scanned by said cam follower, said first cam means controlling the movement of said lens groups according to a first law of motion at which the image of an object located at said usual focal range remains in a constant image plane, said second control means comprising second cam means for being rigidly scanned by said cam follower means and being arranged on second carrier means, said second carrier means controlling the movement of at least one of said lens groups according to a second law of motion at which the image of an object located at a distance closer than said usual focal range remains in said image plane, and biasing means acting on said first and second control means whereby said cam follower is arranged to be switched from rigidly scanning the first cam to rigidly scanning the second cam by changing the direction of the force of said biasing means.

A variable focus optical system comprising a forward lens unit and a rear lens unit, said forward lens unit having at least two lens groups, each of said lens groups being movable along the optical axis for varying the focal length of the optical system, and at least one of said lens groups being movable along the optical axis for focussing the optical system on an object located at a distance closer than the usual focal range of the optical system, first and second control means being selectively operable for varying the focal length of the optical system and comprising cam follower means, said first control means comprising first cam means cooperating with said cam follower means and controlling the movement of said lens groups according to a first law of motion at which the image of an object located at said usual focal range remains in a constant image plan, said second control means comprising second cam means cooperating with said cam follower means, coupling means mounted on said system and adapted for having an attachment means inserted therein for defining a plane located at a distance closer than said usual focal range, said coupling means being arranged in front of said forward lens unit, said second cam means controlling the movement of at least one of said lens groups according to a second law of motion at which the image of an object located at said distance closer than said usual focal range remains in said image plane, sensing means for controlling an operative condition of said second control menas in response to the existence of said attachment means inserted into said coupling means.

A variable focus optical system comprising a forward lens unit and a rear lens unit, said forward lens unit having at least two lens groups, each of said lens groups being movable along the optical axis for varying the focal length of the optical system, and at least one of said lens groups being movable along the optical axis for focussing the optical system on an object located at a distance closer than the usual focal range of the optical system, first and second control means being selectively operable for varying the focal length of the optical system and comprising cam follower means, said first control means comprising first cam means for at least a first part of the travel of said cam follower means and controlling the movement of said lens groups according to a first law of motion at which the image of an object located at said usual focal range remains in a constant image plane, said second control means comprising second cam means for at least a second part of the travel of said cam follower means, coupling means mounted on said system for coupling thereto an attachment means defining a plane located at a distance closer than said usual focal range, said coupling means being arranged in front of said forward lens unit, said second cam means controlling the movement of at least one of said lens groups according to a second law of motion at which the image of an object located at said distance closer than said usual focal range remains in said image plane, and locking means for preventing an insertion of said attachment means into said coupling means, said locking means having an inoperative position in an operative condition of said second control means.

A variable focus optical system in combination with a negative front lens attachment, said negative front lens attachment defining a focal plane at a distance closer than the usual focal range of the optical system, the optical system consisting of a forward lens unit and a rear lens unit, said forward lens unit having at least two lens groups, each of said lens groups being movable along the optical axis for varying the focal length of the optical system and at least one of said lens groups being movable along the optical axis for focussing the optical system on an object located at said distance at which the focal plane of said front lens attachment is located, first and second control means being selectively operable for varying the focal length of the optical system and comprising cam follower means, said first control means comprising first cam means cooperating with said cam follower means for at least a first part of travel of said cam follower means and controlling the movement of said lens groups according to a first law of motion at which the image of an object located at said usual focal range remains in a constant image plane, said second control means comprising second cam means cooperating with said cam follower means for at least a second part of travel of said cam follower means and controlling the movement of at least one of said lens groups according to a second law of motion at which the image of an object located at said focal plane of said front lens attachment remains in said image plane.