Zoom lens and image pickup apparatus using the same
AssigneeCanon Kabushiki Kaisha
InventorKenji Shinohara
Life of this patent
Estimating the term…
Abstract
A zoom lens includes a first lens unit with a negative refractive power, a second lens unit with a positive refractive power, and a third lens unit with a positive refractive power in order from the object side to the image side. The first lens unit includes a negative lens and a positive lens. When the curvature radius of the object side surface and that of the image side surface of the negative lens are respectively defined as R11 and R12 and the curvature radius of the object side surface and that of the image side surface of the positive lens are respectively defined as R21 and R22, the following conditional expression is satisfied: −5.6<(R12+R21)/(R12−R21)<−4.7 and 1.5<(R11+R22)/(R11−R22)<2.3.
Claims8
A zoom lens comprising:
- a first lens unit with a negative refractive power;
- a second lens unit with a positive refractive power;
- and a third lens unit with a positive refractive power, which are arranged in order from the object side to the image side, wherein
- the first lens unit includes a negative lens and a positive lens, and
- when the curvature radius of the object side surface of the negative lens and the curvature radius of the image side surface of the negative lens are respectively defined as R11 and R12 and the curvature radius of the object side surface of the positive lens and the curvature radius of the image side surface of the positive lens are respectively defined as R21 and R22, R11, R12, R21, and R22, f1 denotes a focal length of the first lens unit and f3 denotes a focal length of the third lens unit, the following conditional expressions are satisfied:
- −5.6<(R12+R21)/(R12−R21)<−4.7
- 1.5<(R11+R22)/(R11−R22)<2.3 and
- −0.6<f1/f3<−0.3.
Dependencies are inferred from the claim text.