Lens system and image pickup apparatus
AssigneeNittoh Inc.
InventorKeiichi Mochizuki
Life of this patent
Estimating the term…
Abstract
A lens system (10) for image pickup includes, in order from an object side (11), a first lens group (G1) that has negative refractive power and is fixed during focusing, a second lens group (G2) that has positive refractive power and moves during focusing, a third lens group (G3) that has positive refractive power and is fixed during focusing, and a fourth lens group (G4) that has a stop disposed on the object side, is disposed closest to an image plane side, has positive refractive power, and is fixed during focusing. The first lens group includes a first lens (L11) with positive refractive power that is disposed closest to the object side.
Claims20
A lens system for image pickup comprising, in order from an object side:
- a first lens group that has negative refractive power and is fixed during focusing;
- a second lens group that has positive refractive power and moves during focusing;
- a third lens group that has positive refractive power and is fixed during focusing;
- and
- a fourth lens group that has a stop disposed on the object side, is fixed during focusing, has positive refractive power, and is disposed closest to an image plane side,
- wherein the first lens group includes:
- a first lens with positive refractive power that is disposed closest to the object side;
- a first sub-lens group that has negative refractive power and includes the first lens and a lens with negative refractive power disposed closest to an image plane side;
- and
- a second sub-lens group that has negative refractive power and is disposed on the image plane side with a distance apart from the first sub-lens group;
- and
- a distance W0 along an optical axis from a surface that is closest to the object side in the first sub-lens group to an image forming plane, a distance W1 along the optical axis from the surface that is closest to the object side to a surface that is closest to the image plane side in the first sub-lens group, and a distance W2 along the optical axis from the surface that is closest to the object side in the first sub-lens group to a surface that is closest to the object side in the second sub-lens group satisfy following conditions:
- 0.05<W1/W0<0.15
- 0.17<W2/W0<0.29.
A lens system for image pickup comprising, in order from an object side:
- a first lens group that has negative refractive power and is fixed during focusing;
- a second lens group that has positive refractive power and moves during focusing;
- a third lens group that has positive refractive power and is fixed during focusing;
- and
- a fourth lens group that has a stop disposed on the object side, is fixed during focusing, has positive refractive power, and is disposed closest to an image plane side,
- wherein the first lens group includes:
- a first lens with positive refractive power that is disposed closest to the object side;
- a first sub-lens group that has negative refractive power and includes the first lens and a lens with negative refractive power disposed closest to an image plane side;
- and
- a second sub-lens group that has negative refractive power and is disposed on the image plane side with a distance apart from the first sub-lens group;
- and
- the second sub-lens group includes a negative meniscus lens that is concave on the object side.
A lens system for image pickup comprising, in order from an object side:
- a first lens group that has negative refractive power and is fixed during focusing;
- a second lens group that has positive refractive power and moves during focusing;
- a third lens group that has positive refractive power and is fixed during focusing;
- and
- a fourth lens group that has a stop disposed on the object side, is fixed during focusing, has positive refractive power, and is disposed closest to an image plane side,
- wherein the first lens group includes a first lens with positive refractive power that is disposed closest to the object side, and
- the second lens group is composed of a cemented lens composed, from the object side, of a lens with negative refractive power and a lens with positive refractive power, and
- the lens with positive refractive power in the cemented lens being a low anomalous dispersion lens.
Dependencies are inferred from the claim text.