A projection system has a zooming function and is configured that light rays from a telecentric system enter. The projection system is formed of seven lens groups. The first and seventh lens groups are fixed when the projection magnification is changed, and the second, third, fourth, fifth, and the sixth lens groups move along the optical axis when the projection magnification is changed. The second lens group is formed of one positive lens. The third lens group is formed of one positive lens. The fourth lens group is formed of one or two positive lenses and one negative lens having the center of curvature located at the magnifying side. The fifth lens group is formed of one negative lens having a magnifying-side aspheric surface and a demagnifying-side aspheric surface with each of the surfaces having the center of curvature located at the demagnifying side.

A zoom lens in which a distance between adjacent lens units changes during zooming includes in order from an object side to an image side a first lens unit fixed during zooming and having positive refractive power, three or more moving lens units movable during zooming, and a final lens unit fixed during zooming and having positive refractive power. At least part of the first lens unit moves during focusing. At least one of a moving lens unit closest to an image plane among the three or more moving lens units and the final lens unit includes a first lens having positive refractive power. A predetermined condition is satisfied.

Pop-out lens systems for compact digital cameras, comprising an image sensor and a lens with a field of view FOV>60 deg and having i lens elements L1-Li starting with L1 from an object side toward an image side, each lens element Li having a respective focal length f.sub.i, the lens elements divided into two lens groups G1 and G2 separated by a big gap (BG), the lens having a pop-out total track length TTL<20 mm in a pop-out state and a collapsed total track length c-TTL in a collapsed state, wherein BG>0.25TTL, wherein either G1 can move relative to G2 and to the image sensor for focusing or G1 and G2 can move together relative to the image sensor for focusing, and wherein a ratio c-TTL/TTL<0.7.

A zoom optical system comprises, in order from an object: a front lens group (GFS) having a positive refractive power; an M1 lens group (GM1) having a negative refractive power; an M2 lens group (GM2) having a positive refractive power; an RN lens group (GRN) having a negative refractive power; and a subsequent lens group (GRS). Upon zooming, the distance between the front lens group (GFS) and the M1 lens group (GM1) changes, the distance between the M1 lens group (GM1) and the M2 lens group (GM2) changes, and the distance between the M2 lens group (GM2) and the RN lens group (GRN) changes. Upon focusing from an infinite distant object to a short distant object, the RN lens group (GRN) moves.

Provided is a collapsible lens barrel including a base barrel, a drive device including a linear motion member reciprocating in an optical axis direction and a drive source for driving the linear motion member, a cam frame provided with a cam groove, a drive device frame that is engaged with the cam groove and causes the drive device to reciprocate in the optical axis direction, a focus lens group frame that holds a focus lens group, and a contact part and an arm that extend from the focus lens group frame toward an object side and are engaged with the linear motion member to cause the focus lens group frame to reciprocate in the optical axis direction.

Provided is a zoom lens including: positive first unit; negative second unit; aperture stop; positive third unit; positive fourth unit; and rear lens group including at least one lens unit, wherein the fourth unit includes a positive lens, and wherein an amount of movement of the fourth unit during zooming from wide angle end to telephoto end, distances between the aperture stop and the fourth unit at the wide angle end and between the aperture stop and the fourth unit at the telephoto end, focal lengths of the fourth unit and of the zoom lens at the wide angle end, a length of the zoom lens at the wide angle end, an Abbe number of material of the positive lens with respect to d-line, and a partial dispersion ratio of the material of the positive lens with respect to g-line and F-line are each appropriately set.

Provided is a zoom lens including: a positive first unit; a negative second unit; a positive third unit; a positive fourth unit; a positive fifth unit; and a sixth unit, wherein the first unit is moved toward the object side for zooming from wide angle end to telephoto end, and an interval between each pair of adjacent units is changed for zooming, wherein the fifth unit is moved for focusing, and wherein a focal length at wide angle end, a focal length of the fifth unit, an F-number of the zoom lens at wide angle end, a total length at wide angle end, a distance from a lens surface on the object side of the fifth unit to an image plane at wide angle end at infinity, and a movement amount of the fifth unit for zooming from wide angle end to telephoto end at infinity are appropriately set.

The zoom lens includes a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, a negative fifth lens group, and a positive sixth lens group in order from an object side. All distances between adjacent lens groups change during zooming. The first lens group consists of a negative lens, a positive lens, and a positive lens in order from the object side. Only the fourth lens group moves to an image side during focusing from a long range to a short range. Conditional Expression is related to lateral magnification of the fourth lens group and a lateral magnification of the sixth lens group is satisfied.

The zoom lens includes a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, a negative fifth lens group, and a positive sixth lens group in order from an object side. All distances between adjacent lens groups change during zooming. The first lens group consists of a negative lens, a positive lens, and a positive lens in order from the object side. Only the fourth lens group moves to an image side during focusing from a long range to a short range. Conditional Expression related to a distance from a lens surface of the first lens group closest to the object side to an image plane and a distance from a lens surface of the second lens group closest to the object side to the image plane is satisfied.

Pop-out lens systems for compact digital cameras, comprising an image sensor and a lens with a field of view FOV>60 deg and having i lens elements L1-Li starting with L1 from an object side toward an image side, each lens element Li having a respective focal length f.sub.i, the lens elements divided into two lens groups G1 and G2 separated by a big gap (BG), the lens having a pop-out total track length TTL<20 mm in a pop-out state and a collapsed total track length c-TTL in a collapsed state, wherein BG>0.25?TTL, wherein either G1 can move relative to G2 and to the image sensor for focusing or G1 and G2 can move together relative to the image sensor for focusing, and wherein a ratio c-TTL/TTL<0.7.