The imaging lens consists of, in order from the object side, a first positive lens group, a stop, a second positive lens group, and a third negative lens group. During focusing, the first lens group and the second lens group move integrally. The first lens group consists of three or less lenses. The first lens group includes a cemented lens in which a negative lens and a positive lens are cemented in order from the object side. The third lens group consists of, in order from the object side, a negative aspheric lens, a negative lens, and a positive lens. The lens closest to the image side in the second lens group is a biconvex lens, and the imaging lens satisfies a predetermined conditional expression regarding the radius of curvature of the surface of the biconvex lens.

The 1-2nd lens group is divided into three lens groups which move when focusing is performed during the magnification change. Even in a case in which the second optical group is formed of one mirror, it is possible for a primary image to contain appropriate aberration and to hereby reduce aberration of an image which is finally projected onto a screen through the second optical group.

The lens apparatus includes: a first optical unit (FOU) changes a field curvature amount of a projection optical system (POS) by shifting in an optical axis direction (OAD) of POS, a second optical unit (SOU) including a focus adjustment unit moves during focusing and a zoom adjustment unit moves during zooming, the SOU changing projection magnification and focus position of POS by shifting in OAD of POS, a first detection unit (FDU) detecting a position of FOU, a memory stores change information regarding changes in projection magnification and focus position of POS through shift of FOU and a control unit controls SOU to shift so as to reduce changes in projection magnification and focus position of POS at the same time caused due to shift of FOU, when field curvature amount of POS is changed, based on position of FOU detected by FDU and change information stored in memory.

The lens apparatus includes: a first optical unit (FOU) changes a field curvature amount of a projection optical system (POS) by shifting in an optical axis direction (OAD) of POS, a second optical unit (SOU) including a focus adjustment unit moves during focusing and a zoom adjustment unit moves during zooming, the SOU changing projection magnification and focus position of POS by shifting in OAD of POS, a first detection unit (FDU) detecting a position of FOU, a memory stores change information regarding changes in projection magnification and focus position of POS through shift of FOU and a control unit controls SOU to shift so as to reduce changes in projection magnification and focus position of POS at the same time caused due to shift of FOU, when field curvature amount of POS is changed, based on position of FOU detected by FDU and change information stored in memory.

Comprising a first lens group G1 having positive refractive power, disposed at the most object side, and an image side lens group disposed at a side closer to an image than the first lens group G1, upon zooming, at least a distance between the first lens group G1 and the image side lens group being varied, the image side lens group comprising a vibration reduction lens group GVR which is moved so as to have a component in a direction perpendicular to the optical axis and a focusing lens group GF which is moved along the optical axis upon focusing, thereby providing a variable magnification optical system which has a higher optical performance, an optical apparatus and a method for manufacturing a variable magnification optical system.

Comprising a first lens group G1 having positive refractive power, disposed at the most object side, and an image side lens group disposed at a side closer to an image than the first lens group G1, upon zooming, at least a distance between the first lens group G1 and the image side lens group being varied, the image side lens group comprising a vibration reduction lens group GVR which is moved so as to have a component in a direction perpendicular to the optical axis and a focusing lens group GF which is moved along the optical axis upon focusing, thereby providing a variable magnification optical system which has a higher optical performance, an optical apparatus and a method for manufacturing a variable magnification optical system.

A zoom lens system with a large zoom ratio is disclosed, which operates in a broad spectral range, including visible and infrared spectra. The zoom lens system comprises, in order from the object side to the image side, a positive first lens group, a negative second lens group, a positive third lens group, a positive fourth lens group, and a detection system, wherein zooming from a wide-angle end to a telephoto end is performed by axially moving the second and third lens groups. The system has a relatively long back focal length, and satisfies the following conditions: 0.2<|f2|/(f.sub.W*f.sub.T)½<2, 1<f4/|f2|<8, 0.3<|f2|/f3<1.5, where f.sub.W is the system focal length at the wide-angle end, f.sub.T is the system focal length at the telephoto end, (f.sub.W*f.sub.T).sup.1/2 is the geometric mean of the two focal lengths, and fi is the focal length of the i-th lens group.

A zoom lens system with a large zoom ratio is disclosed, which operates in a broad spectral range, including visible and infrared spectra. The zoom lens system comprises, in order from the object side to the image side, a positive first lens group, a negative second lens group, a positive third lens group, a positive fourth lens group, and a detection system, wherein zooming from a wide-angle end to a telephoto end is performed by axially moving the second and third lens groups. The system has a relatively long back focal length, and satisfies the following conditions: 0.2<|f2|/(f.sub.W*f.sub.T)½<2, 1<f4/|f2|<8, 0.3<|f2|/f3<1.5, where f.sub.W is the system focal length at the wide-angle end, f.sub.T is the system focal length at the telephoto end, (f.sub.W*f.sub.T).sup.1/2 is the geometric mean of the two focal lengths, and fi is the focal length of the i-th lens group.

A zoom lens comprising in order from an object side, a first lens unit having a negative refractive power, a second lens unit having a negative refractive power, a lens unit having a positive refractive power, and a rearmost lens unit having a negative refractive power, and the rearmost lens unit is positioned nearest to an image in the plurality of lens units, and at the time of zooming, distances between the lens units in the plurality of lens units change. Moreover, an image pickup apparatus includes the zoom lens, and an image pickup element having an image pickup surface.

A zoom lens comprising in order from an object side, a first lens unit having a negative refractive power, a second lens unit having a negative refractive power, a lens unit having a positive refractive power, and a rearmost lens unit having a negative refractive power, and the rearmost lens unit is positioned nearest to an image in the plurality of lens units, and at the time of zooming, distances between the lens units in the plurality of lens units change. Moreover, an image pickup apparatus includes the zoom lens, and an image pickup element having an image pickup surface.