Abstract: A composite optical element includes a glass lens and a resin lens that are joined together. The resin lens has an aspheric shape. When Nd is a refractive index of the resin lens, ?d is an Abbe number of the resin lens, and ?gF is a partial dispersion ratio of the resin lens, Nd, ?d, and ?gF are appropriately set.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive refractive power, a fourth lens unit having positive refractive power, and a fifth lens unit having negative refractive power. During zooming from a wide-angle end to a telephoto end, a distance between adjacent lens units changes, the first lens unit and the third lens unit are fixed, and the second lens unit and the fourth lens unit move. The third lens unit includes a negative lens and a positive lens. A predetermined condition is satisfied.

Abstract: An optical system includes, in order from an object side to an image side, a front unit of a positive refractive power, a diaphragm, and a rear unit of a positive refractive power. The front unit includes, in order from the object side to the image side, a positive lens L11, a positive lens L12, and a negative lens L13. The rear unit includes, in order from the object side to the image side, a negative lens L21, a positive lens L22, and a positive lens L23. A predetermined condition is satisfied.

Abstract: Provided is a zoom lens including, from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power; a fourth lens unit having a negative refractive power; a fifth lens unit having a positive refractive power; a sixth lens unit having a negative refractive power; a seventh lens unit having a positive refractive power; and an eighth lens unit having a negative refractive power, in which an interval between each pair of adjacent lens units is changed for zooming.

Abstract: An imaging optical system includes, in order from an enlargement conjugate side to a reduction conjugate side, a first lens unit having a positive refractive power, a second lens unit having a positive refractive power, and a third lens unit. A distance between adjacent lens units varies in focusing from a far side to a near side. An intermediate image is formed inside the second lens unit. In focusing from the far side to the near side, the second lens unit moves to the reduction conjugate side, and the third lens unit moves to the enlargement conjugate side.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, a fourth lens unit having a negative refractive power, and a rear lens unit having a positive refractive power and disposed closest to an image plane. During zooming from a wide-angle end to a telephoto end, the second lens unit moves to the object side, and each distance between adjacent lens units changes. A predetermined condition is satisfied.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a rear unit having a plurality of lens units, a distance between adjacent lens units changing during zooming. A predetermined condition is satisfied.

Abstract: A rear attachment lens according to the aspect of the embodiments is configured to vary a focal length of a system by being attached to an image side of a master lens. The rear attachment lens includes a positive lens arranged closest to the image side in which a lens surface on the image side of the positive lens has a shape convex toward the image side. A focal length of the rear attachment lens, a magnification of the rear attachment lens when attached to the master lens, and a distance from the lens surface on the image side of the positive lens to a rear principal point position of the rear attachment lens when attached to the master lens are appropriately set.

Abstract: An optical system includes, in order from an object side to an image side, a front unit of a positive refractive power, a diaphragm, and a rear unit of a positive refractive power. The front unit includes, in order from the object side to the image side, a positive lens L11, a positive lens L12, and a negative lens L13. The rear unit includes, in order from the object side to the image side, a negative lens L21, a positive lens L22, and a positive lens L23. A predetermined condition is satisfied.

Abstract: Provided is an optical system including: a first lens unit having a positive refractive power; a second lens unit having a positive refractive power and disposed at the image side of the first lens unit; and a third lens unit having a positive refractive power and disposed closest to the image side, in which intervals between adjacent lens units are changed during focusing. The first lens unit does not move during focusing. The second lens unit moves to the object side along an optical axis during focusing from infinity to a close distance. The second lens unit includes, in order from the object side to the image side, a positive lens, a negative lens, and an aperture stop. The third lens unit includes a positive lens and a negative lens. A length of the third lens unit on the optical axis and an air-equivalent back focus are appropriately set.

Abstract: Provided is an optical system including: a first lens unit having a positive refractive power; a second lens unit having a positive refractive power and disposed at the image side of the first lens unit; and a third lens unit having a positive refractive power and disposed closest to the image side, in which intervals between adjacent lens units are changed during focusing. The first lens unit does not move during focusing. The second lens unit moves to the object side along an optical axis during focusing from infinity to a close distance. The second lens unit includes, in order from the object side to the image side, a positive lens, a negative lens, and an aperture stop. The third lens unit includes a positive lens and a negative lens. A length of the third lens unit on the optical axis and an air-equivalent back focus are appropriately set.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a rear unit having a plurality of lens units, a distance between adjacent lens units changing during zooming. A predetermined condition is satisfied.

Abstract: An optical system according to the present invention is an optical system comprises a first lens unit having positive refractive power, a second lens unit having positive refractive power, and a third lens unit having negative refractive power, arranged in order from an object side to an image side. During focusing from infinity to a closest distance, the second lens unit moves to the object side, whereby a distance between adjoining lens units is changed. The second lens unit comprises an aperture stop. The following conditional expression is satisfied: 1.0<D3/BF<3.0, where D3 is a length of the third lens unit on an optical axis, and BF is a back focus distance.

Abstract: A rear attachment lens according to the aspect of the embodiments is configured to vary a focal length of a system by being attached to an image side of a master lens. The rear attachment lens includes a positive lens arranged closest to the image side in which a lens surface on the image side of the positive lens has a shape convex toward the image side. A focal length of the rear attachment lens, a magnification of the rear attachment lens when attached to the master lens, and a distance from the lens surface on the image side of the positive lens to a rear principal point position of the rear attachment lens when attached to the master lens are appropriately set.

Abstract: Provided is a zoom lens including, from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power; a fourth lens unit having a negative refractive power; a fifth lens unit having a positive refractive power; a sixth lens unit having a negative refractive power; a seventh lens unit having a positive refractive power; and an eighth lens unit having a negative refractive power, in which an interval between each pair of adjacent lens units is changed for zooming.

Abstract: An imaging optical system includes, in order from an enlargement conjugate side to a reduction conjugate side, a first lens unit having a positive refractive power, a second lens unit having a positive refractive power, and a third lens unit. A distance between adjacent lens units varies in focusing from a far side to a near side. An intermediate image is formed inside the second lens unit. In focusing from the far side to the near side, the second lens unit moves to the reduction conjugate side, and the third lens unit moves to the enlargement conjugate side.

Abstract: An optical system according to the present invention is an optical system comprises a first lens unit having positive refractive power, a second lens unit having positive refractive power, and a third lens unit having negative refractive power, arranged in order from an object side to an image side. During focusing from infinity to a closest distance, the second lens unit moves to the object side, whereby a distance between adjoining lens units is changed. The second lens unit comprises an aperture stop. The following conditional expression is satisfied: 1.0<D3/BF<3.0, where D3 is a length of the third lens unit on an optical axis, and BF is a back focus distance.

Abstract: Provided is an optical system including: a first lens unit having a positive refractive power; a second lens unit having a positive refractive power and disposed at the image side of the first lens unit; and a third lens unit having a positive refractive power and disposed closest to the image side, in which intervals between adjacent lens units are changed during focusing. The first lens unit does not move during focusing. The second lens unit moves to the object side along an optical axis during focusing from infinity to a close distance. The second lens unit includes, in order from the object side to the image side, a positive lens, a negative lens, and an aperture stop. The third lens unit includes a positive lens and a negative lens. A length of the third lens unit on the optical axis and an air-equivalent back focus are appropriately set.

Abstract: An optical system has a first optical axis on an incident side and a second optical axis on an exit side, and the first optical axis and the second optical axis are located at different positions. The optical system includes a reflection unit including a roof surface having a first reflection surface and a second reflection surface, and a third reflection surface parallel or orthogonal to a ridge line of the roof surface. The third reflection surface is different from the first reflection surface and the second reflection surface. The reflection unit is rotatable about the first optical axis.

Abstract: A zoom lens includes, in order from an enlargement conjugate side to a reduction conjugate side, a first lens unit (B1) having a negative refractive power, a second lens unit (B2) having a positive refractive power, a third lens unit (B3) having a positive refractive power, a stop (sto), a fourth lens unit (B4) having a positive refractive power, a fifth lens unit (B5) having a negative refractive power, a sixth lens unit (B6) having a negative refractive power, and a seventh lens unit (B7) having a positive refractive power, and when zooming from a wide-angle end to a telephoto end, the second lens unit (B2), the third lens unit (B3), the fourth lens unit (B4), the fifth lens unit (B5), and the sixth lens unit (B6) move from the reduction conjugate side to the enlargement conjugate side while a space between adjacent lens units changes.