Patent ID: 8374497

Claim:
An autofocusing zoom lens, which is capable of being detachably mounted on an image pickup apparatus and includes, in order from an object side to an image side, a focusing lens unit configured to move during focusing, a variable-magnification lens unit configured to move during variation of magnification, and a variable diaphragm capable of varying an aperture diameter, the autofocusing zoom lens comprising: a position detection unit configured to detect a position of the focusing lens unit; a magnification-varying state detection unit configured to detect a position of the variable-magnification lens unit; and an aperture value detection unit configured to detect an aperture value of the variable diaphragm; a distance measurement unit configured to measure a distance to an object; a communication unit configured to communicate with the image pickup apparatus; a video signal receiving unit configured to receive a video signal from the image pickup apparatus; a first autofocusing unit configured to drive the focusing lens unit based on a result of detection by the distance measurement unit; and a second autofocusing unit configured to drive the focusing lens unit based on the video signal from the image pickup apparatus, wherein a near point distance Sn and a far point distance Sf are obtained based on a focal length F and a diameter of a permissible circle of confusion δ, wherein if a current focus position Obj and a resolution Det of the distance measurement unit satisfy the following first condition: Sf −Obj>0 or Obj− Sn> 0, the focusing lens unit is not driven, wherein if the first condition is not satisfied and the following second condition is satisfied: ( Sf−Sn )−Det<0 and Sf −Obj<0 or Obj− Sn< 0, the focusing lens unit is driven based on the second autofocusing unit, and if the second condition is not satisfied, the focusing lens unit is driven based on the first autofocusing unit.