Objective of variable focal length
AssigneeCanon Kabushiki Kaisha
InventorsNozomu Kitagishi, Hiroki Nakayama, Shigeyuki Suda, Jun Hattori, Akihisa Horiuchi
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Abstract
An objective of variable focal length includes a plurality of lens units of which the first, counting from front, is of negative power and the second is of positive power. At least the first and second lens units are moved with variation of the air separation therebetween to vary the focal length of the entire system. The objective is characterized in that at least one of the lens units is included with at least one refractive index distribution type lens arranged on the common optical axis of the other lenses.
Claims18
An objective of variable focal length comprising a plurality of lens units, of which the first lens unit, counting from an object side, has a negative refractive power and a second unit has a positive refractive power, at least said first and said second lens units being moved axially with their air separation being varied to vary the focal length of the entire system, whereby at least one of said lens units includes at least one refractive index distribution type lens varying in refractive index that is arranged on a common optical axis with said plurality of lens units, wherein said refractive index distribution type lens comprises a distribution of refractive indexes so that a change in aberrations due to a variation of the objective focal length is restricted.
Dependencies are inferred from the claim text.