Zoom lens and image pickup apparatus using the same

A zoom lens comprising:

• a first lens group of negative refractive power;
• a second lens group of positive refractive power;
• a third lens group of positive refractive power;
• and
• a fourth lens group of negative refractive power arranged in the above-mentioned order from the object side to the image side;
• at least the first lens group, the second lens group and the third lens group being driven to move and change the gaps separating the lens groups at the time for the zoom lens to be driven to zoom from the wide angle end to the telescopic end;
• the first lens group comprising a negative lens component of negative refractive power and a positive lens component of positive refractive power arranged sequentially on the optical axis in the above-mentioned order from the object side to the image side with a gap separating them;
• the total number of lens components in the first lens group being two;
• the second lens group comprising a negative lens, a first positive lens and a second positive lens;
• the negative lens component of the first lens group comprising negative lenses satisfying the requirements of conditional formula (2) shown below:
• 1.78<ndG1n<2.40 (2),
• where
• ndG1n is the refractive index of any of the negative lenses in the negative lens component of the first lens group at d line.

A zoom lens comprising:

• a first lens group of negative refractive power;
• a second lens group of positive refractive power;
• a third lens group of positive refractive power;
• and
• a fourth lens group of negative refractive power arranged in the above-mentioned order from the object side to the image side;
• at least the first lens group, the second lens group and the third lens group being driven to move and change the gaps separating the lens groups at the time for the zoom lens to be driven to zoom from the wide angle end to the telescopic end;
• the first lens group comprising a negative lens component of negative refractive power and a positive lens component of positive refractive power arranged on the optical axis in the above-mentioned order from the object side to the image side with a gap separating them;
• the total number of lens components in the first lens group being two;
• the second lens group comprising a negative lens, a first positive lens and a second positive lens;
• the fourth lens group comprising a negative lens component;
• the total number of lens components of the fourth lens group being one;
• the zoom lens satisfying the requirements of conditional formula (8-1) shown below:
• 4.0<ft/fw<20.0 (8-1),
• where
• ft is the focal length of the entire optical system of the zoom lens at the telescopic end, and
• fw is the focal length of the entire optical system of the zoom lens at the wide angle end.

A zoom lens comprising:

• a first lens group of negative refractive power;
• a second lens group of positive refractive power;
• a third lens group of positive refractive power;
• and
• a fourth lens group of negative refractive power arranged in the above-mentioned order from the object side to the image side;
• at least the first lens group, the second lens group and the third lens group being driven to move, the fourth lens group being fixed, and change the gaps separating the lens groups at the time for the zoom lens to be driven to zoom from the wide angle end to the telescopic end;
• the first lens group comprising a negative lens component of negative refractive power arranged at the extremity of the object side in the first lens group;
• the second lens group comprising a negative lens, a first positive lens and a second positive lens;
• the fourth lens group comprising a negative lens component having a concave surface directed to the object side;
• the total number of lens components of the fourth lens group being one;
• the negative lens component in the first lens group and the negative lens component in the fourth lens group satisfying the requirements of conditional formula (1) shown below:
• −0.80<rGlnr/rG4nf<−0.40 (1),
• where
• rG1nr is the radius of paraxial curvature of the image side surface of the negative lens component in the first lens group;
• and
• rG4nf is the radius of paraxial curvature of the object side surface of the negative lens component in the fourth lens group.

A zoom lens comprising:

• a first lens group of negative refractive power;
• a second lens group of positive refractive power;
• a third lens group of positive refractive power;
• and
• a fourth lens group of negative refractive power arranged in the above-mentioned order from the object side to the image side;
• at least the first lens group, the second lens group and the third lens group being driven to move and change the gaps separating the lens groups at the time for the zoom lens to be driven to zoom from the wide angle end to the telescopic end;
• the first lens group comprising a negative lens component of negative refractive power arranged at the extremity of the object side in the first lens group;
• the second lens group comprising a negative lens, a first positive lens and a second positive lens;
• the fourth lens group comprising a negative lens component having a concave surface directed to the object side;
• the total number of lens components of the fourth lens group being one;
• the zoom lens satisfying the requirements of conditional formula (8-1) shown below:
• 4.0<ft/fw<20.0 (8-1),
• where
• ft is the focal length of the entire optical system of the zoom lens at the telescopic end, and
• fw is the focal length of the entire optical system of the zoom lens at the wide angle end.