The variable magnification optical system consists of a front group, a middle group, and a rear group, in order from an object side. The front group consists of two or fewer lens groups and has a negative refractive power. The middle group includes only one lens group that has a positive refractive power as a lens group. The rear group consists of three or less lens groups. An aperture stop is disposed between a lens surface closest to an image side in the front group and a lens surface closest to the object side in the rear group. The front group includes at least three negative lenses and at least one positive lens. A negative meniscus lens convex toward the object side is disposed closest to the object side in the front group. The variable magnification optical system satisfies predetermined conditional expressions.

A zoom lens system according to the present disclosure includes a plurality of lens groups each of which is made up of at least one lens element. The zoom lens system includes, in order from an object side to an image side: a first focusing lens group having a negative power; and a second focusing lens group having a positive power, wherein when zooming is performed from a wide end to a telephoto end, the first focusing lens group and the second focusing lens group move along an optical axis, when focusing is performed from an infinity focusing state to a proximity object focusing state, the first focusing lens group and the second focusing lens group move to perform the focusing, and a predetermined condition is satisfied.

A projection system includes first and second lens groups respectively having negative and positive power sequentially arranged from the enlargement side toward the reduction side. The first lens group includes a first-a lens group having negative power, a first-b lens group located at the reduction side of the first-a lens group and having negative power, and a first-c lens group located at the reduction side of the first-b lens group and having positive power. The first-b lens group and the first-c lens group each move in the direction of the optical axis during focusing. The projection system satisfies 0.2<|F/F1b|<0.6 (1), 0.0<F/F1c<0.14 (2), BF/F>5.0 (3), where F, F1b, and F1c represent the respective focal lengths of the overall projection system, first-b lens group, and first-c lens group, and BF represents the back focal length in air.

A stereoscopic picture taking systems includes a first camera having a first optical objective, and a second camera having a second optical objective, where the optical characteristics of the two objectives are substantially identical. The stereoscopic system also includes a plane semi-reflecting plate in front of the first objective and inclined by a predetermined angle on the optical axis of the first objective. The stereoscopic picture taking system also includes an optical element having a plane reflecting surface disposed at the level of the second objective and inclined by the same predetermined angle on the optical axis of the second objective such way that the main part of the optical axis of the second objective is substantially parallel to the optical axis of the first objective. This optical element can be a plane mirror or a return prism. The first objective has a plate of identical optical thickness.

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.

The present disclosure relates to optical lens, and provides a zoom lens including, from an object side to an image side in sequence: a first lens having a negative refractive power, a second lens having a positive refractive power, a third lens having a negative refractive power, a fourth lens having a positive refractive power, a fifth lens group having a negative refractive power; distances between adjacent two of the first lens, the second lens, the third lens, the fourth lens and the fifth lens group are variable in the direction of the optical axis; the fifth lens group including a fifth lens having a positive refractive power and a sixth lens having a negative refractive power; wherein the zoom lens satisfies conditions of: f_Tele/f_Wide>1.8; −1.85≤f3/f2≤−1.20; and 2.00≤f4/f2≤3.00.

A projection zoom lens is essentially constituted by, in order from the magnification side: a negative first lens group, which is fixed when changing magnification; a positive second lens group, which moves when changing magnification; a plurality of other lens groups; and a final lens group, which is fixed when changing magnification. The distances among all adjacent lens groups change when changing magnification. The first through third lenses from the magnification side within the first lens group are a first single lens having an aspherical surface with a concave surface toward the magnification side and a negative refractive power in the paraxial region, a second single lens having an aspherical surface, and a third lens. A first lens group front group constituted by the first through third lenses has a negative refractive power. Predetermined conditional formulae are satisfied.

An optical lens sequentially includes, from an object side to an image side, a first lens having a negative focal power, a second lens having a negative focal power; a third lens having a positive focal power, a fourth lens having a negative focal power, a fifth lens having a negative focal power, a sixth lens having a positive focal power, and a seventh lens having a negative focal power. The optical lens satisfies the following relation: −5<f2/f1<15, maximum optical distortion ≤10%. Where, f1 is a focal length of the first lens, and f2 is a focal length of the second lens.

A projection zoom lens includes, sequentially from an enlargement conjugate side: a first lens group having negative refractive power; a second lens group having positive or negative refractive power; a third lens group having positive refractive power; a fourth lens group having negative refractive power; a fifth lens group having positive refractive power; and a sixth lens group having positive refractive power, and configured to perform a magnification variation by changing the interval between the respective lens groups, wherein the fourth lens group includes at least one positive lens and at least one negative lens, at least one of the positive lenses included in the fourth lens group satisfies the following Conditional Expressions: 0.71≦θg_Fp+0.004×νdp≦0.73 and 15≦νdp≦25, and the back focus of the entire projection zoom lenses satisfies the following Conditional Expression 1.0≦BF/Fw≦2.7.

Provided is a zoom lens, which includes lens units, in which an interval between each pair of adjacent lens units is changed during zooming, the zoom lens including, in order from an object side to an image side: a first lens unit having a negative refractive power; a first lens subunit having a positive refractive power; and a second lens subunit having a negative refractive power. During focusing from infinity to minimum object distance, the first lens subunit is moved toward the object side, and the second lens subunit is moved toward the image side. Further, a movement amount of the first lens subunit during focusing from infinity to minimum object distance at a telephoto end, a movement amount of the second lens subunit during focusing from infinity to minimum object distance at the telephoto end, and a focal length at the telephoto end are appropriately set.