Abstract: A projection optical system includes a first lens unit that moves in a direction of an optical axis in adjusting an amount of field curvature and a second lens unit located closer to a reduction side than the first lens unit. The first lens unit includes an aspherical lens satisfying predetermined conditional equations.

Abstract: The imaging optical system makes magnification conjugate side and reduction conjugate side predetermined positions conjugate to each other and forms an intermediate image conjugate to both the predetermined positions. The optical system includes a magnification side positive lens as a first lens disposed on the magnification conjugate side further than an intermediate imaging position, a reduction side positive lens as a third lens disposed on the reduction conjugate side further than the intermediate imaging position, and a negative lens as a second lens disposed between these positive lenses. Conditions of 5<?2??1<80, 5<?2??3<80, 0.03<N1?N2<1.0 and 0.03<N3?N2<1.0 are satisfied where ?1, ?2 and ?3 represent Abbe numbers of materials of the first, second and third lenses, N1, N2 and N3 represent refractive indices of the materials of the first, second and third lenses.

Abstract: An imaging optical system includes a first lens unit (B1) having a negative refractive power configured not to move for zooming from a wide-angle end to a telephoto end, and a plurality of lens units (B2 to B7) configured to move so that a space between lens units adjacent to each other changes during the zooming, the first lens unit includes a first lens subunit (B1a) having a negative refractive power, a second lens subunit (B1b) having a negative refractive power, and a third lens subunit (B1c) having a positive refractive power, the first lens subunit (B1a) is configured not to move for focusing from an infinity to a close range, and the second lens subunit (B1b) and the third lens subunit (B1c) constitute a focus moving unit configured to move, during the focusing, while a space between the second and third lens subunits is narrowed.

Abstract: Provided is an imaging optical system including, in order from an enlargement conjugate side to a reduction conjugate 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 positive refractive power; a fourth lens unit having a negative refractive power; and a fifth lens unit having a positive refractive power. In the imaging optical system, both of an enlargement conjugate point on the enlargement conjugate side and a reduction conjugate point on the reduction conjugate side are conjugate with an internal intermediate imaging position. The first lens unit and the fifth lens unit are stationary for focusing. The second lens unit, the third lens unit, and the fourth lens unit move on loci different from one another during the focusing.

Abstract: A projection optical system includes a first lens unit that moves in a direction of an optical axis in adjusting an amount of field curvature and a second lens unit located closer to a reduction side than the first lens unit. The first lens unit includes an aspherical lens satisfying predetermined conditional equations.

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.

Abstract: An imaging optical system includes a first lens unit (B1) having a negative refractive power configured not to move for zooming from a wide-angle end to a telephoto end, and a plurality of lens units (B2 to B7) configured to move so that a space between lens units adjacent to each other changes during the zooming, the first lens unit includes a first lens subunit (B1a) having a negative refractive power, a second lens subunit (B1b) having a negative refractive power, and a third lens subunit (B1c) having a positive refractive power, the first lens subunit (B1a) is configured not to move for focusing from an infinity to a close range, and the second lens subunit (B1b) and the third lens subunit (B1c) constitute a focus moving unit configured to move, during the focusing, while a space between the second and third lens subunits is narrowed.

Abstract: Provided is an imaging optical system including, in order from an enlargement conjugate side to a reduction conjugate 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 positive refractive power; a fourth lens unit having a negative refractive power; and a fifth lens unit having a positive refractive power. In the imaging optical system, both of an enlargement conjugate point on the enlargement conjugate side and a reduction conjugate point on the reduction conjugate side are conjugate with an internal intermediate imaging position. The first lens unit and the fifth lens unit are stationary for focusing. The second lens unit, the third lens unit, and the fourth lens unit move on loci different from one another during the focusing.

Abstract: The imaging optical system makes magnification conjugate side and reduction conjugate side predetermined positions conjugate to each other and forms an intermediate image conjugate to both the predetermined positions. The optical system includes a magnification side positive lens as a first lens disposed on the magnification conjugate side further than an intermediate imaging position, a reduction side positive lens as a third lens disposed on the reduction conjugate side further than the intermediate imaging position, and a negative lens as a second lens disposed between these positive lenses. Conditions of 5<?2??1<80, 5<?2??3<80, 0.03<N1?N2<1.0 and 0.03<N3?N2<1.0 are satisfied where ?1, ?2 and ?3 represent Abbe numbers of materials of the first, second and third lenses, N1, N2 and N3 represent refractive indices of the materials of the first, second and third lenses.

Abstract: A zoom lens and optical apparatus includes, in order from a magnification conjugate side, a first lens unit that has a positive refractive power and is fixed during magnification variations, and a magnification-variable unit configured to move for magnification variations. The first lens unit includes, in order from the magnification conjugate side, a first lens sub-unit that has a positive refractive power and is configured to move during focusing, and a second lens sub-unit that has a positive refractive power and moves during focusing. The first lens sub-unit and the second lens sub-unit move and reduce an interval between the first lens sub-unit and the second lens sub-unit for focusing from infinity to a close end. A surface of the second lens sub-unit closest to the magnification conjugate side has a concave shape on the magnification conjugate side.

Abstract: Provided is a zoom lens, including in order from a magnification conjugate side to a reduction conjugate 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 positive refractive power; a fourth lens unit having a negative refractive power; a fifth lens unit having a negative refractive power; and a sixth lens unit having a positive refractive power. The first and sixth lens units do not move for zooming, while the second to fifth lens units move to the magnification conjugate side during zooming from a wide-angle end to a telephoto end. Each of the second and third lens units is composed of a single positive lens. Movement amounts of the second, third and fourth lens units during zooming from the wide-angle end to the telephoto end satisfy appropriate relationships.

Abstract: Provided is a zoom lens, including in order from a magnification conjugate side to a reduction conjugate 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 positive refractive power; a fourth lens unit having a negative refractive power; a fifth lens unit having a negative refractive power; and a sixth lens unit having a positive refractive power. The first and sixth lens units do not move for zooming, while the second to fifth lens units move to the magnification conjugate side during zooming from a wide-angle end to a telephoto end. Each of the second and third lens units is composed of a single positive lens. Movement amounts of the second, third and fourth lens units during zooming from the wide-angle end to the telephoto end satisfy appropriate relationships.

Abstract: A zoom lens and optical apparatus includes, in order from a magnification conjugate side, a first lens unit that has a positive refractive power and is fixed during magnification variations, and a magnification-variable unit configured to move for magnification variations. The first lens unit includes, in order from the magnification conjugate side, a first lens sub-unit that has a positive refractive power and is configured to move during focusing, and a second lens sub-unit that has a positive refractive power and moves during focusing. The first lens sub-unit and the second lens sub-unit move and reduce an interval between the first lens sub-unit and the second lens sub-unit for focusing from infinity to a close end. A surface of the second lens sub-unit closest to the magnification conjugate side has a concave shape on the magnification conjugate side.

Abstract: Provided is a zoom lens, including in order from a magnification conjugate side to a reduction conjugate 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 positive refractive power; a fourth lens unit having a negative refractive power; a fifth lens unit having a negative refractive power; and a sixth lens unit having a positive refractive power. The first and sixth lens units do not move for zooming, while the second to fifth lens units move to the magnification conjugate side during zooming from a wide-angle end to a telephoto end. Each of the second and third lens units is composed of a single positive lens. Movement amounts of the second, third and fourth lens units during zooming from the wide-angle end to the telephoto end satisfy appropriate relationships.

Abstract: A zoom lens includes a negative lens unit having a negative refractive power, at least one positive lens unit having a positive refractive power, an intermediate lens unit including a stop, and at least one reduction side lens unit, in order from a magnification conjugate side to a reduction conjugate side, at least two magnification side movable lens units in the negative lens unit and the at least one positive lens unit, and at least one reduction side movable lens unit in the at least one reduction side lens unit are moved during zooming, and conditions of 0.9<(XT·?Tb·?W)/(XW·?Wb·?T)<1.1, 0.9<?W/?T<1.1, 0.8<(?TS·?Tb)/(?WS·?Wb)<1.2, and 1.4<fT/fW are satisfied.

Abstract: A zoom lens includes a negative lens unit having a negative refractive power, at least one positive lens unit having a positive refractive power, an intermediate lens unit including a stop, and at least one reduction side lens unit, in order from a magnification conjugate side to a reduction conjugate side, at least two magnification side movable lens units in the negative lens unit and the at least one positive lens unit, and at least one reduction side movable lens unit in the at least one reduction side lens unit are moved during zooming, and conditions of 0.9<(XT·?Tb·?W)/(XW·?Wb·?T)<1.1, 0.9<?W/?T<1.1, 0.8<(?TS·?Tb)/(?WS·?Wb)<1.2, and 1.4<fT/fW are satisfied.