Abstract: A zoom lens includes a first lens group having a negative power, a second lens group having a positive power, and a third lens group having a positive power arranged in this order from an object side and an aperture stop which is moved integrally with the second lens group, and performs zooming by changing a distance between the first and second lens groups and a distance between the second and third lens groups, wherein the second lens group is composed of a second group first lens having a positive power with a convex surface facing the object side, a cemented lens having a positive power as a whole, and a second group fourth lens having a negative power and at least one aspheric surface with a concave surface facing the image side arranged in this order from the object side.

Abstract: A zoom lens includes, 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, an aperture stop, 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. During zooming, the first lens unit and the aperture stop do not move and the second, third, and fourth lens units move along different loci. Lateral magnifications of the second lens unit at a wide angle end and at a telephoto end and lateral magnifications of the third lens unit at the wide angle end and at the telephoto end are each appropriately set based on predetermined mathematical conditions.

Abstract: The present invention has, in order from an object: a first lens group (G1) having positive refractive power; a second lens group (G2) having negative refractive power; a third lens group (G3) having positive refractive power; and a fourth lens group (G4) having positive refractive power, wherein zooming is performed by changing an air gap between the lens groups, the fourth lens group (G4) includes, in order from the object, a first positive lens component (La), a second positive lens component (Lb) having a convex surface facing the object, and a negative lens component (Lc), and the following conditional expression is satisfied: 0.00<(Rb2?Rb1)/(Rb2+Rb1)<1.00, where Rb2 denotes a radius of curvature of an image side surface of the second positive lens component (Lb) which constitutes the fourth lens group (G4), and Rb1 denotes a radius of curvature of an object side surface of the second positive lens component (Lb) which constitutes the fourth lens group (G4).

Abstract: A zoom lens system comprising: a positive first lens unit; a negative second lens unit; a positive third lens unit; a fourth lens unit; and an aperture diaphragm provided between the third lens unit and the fourth lens unit, wherein in zooming, the first to third lens units are moved along an optical axis to perform magnification change, the third lens unit includes two or more lens elements and one or more inter-lens-element air spaces, and the conditions: ?7.0<f1/f2<?4.0 and fT/fW>9.0 (f1 and f2: composite focal lengths of the first and second lens units, fW and fT: focal lengths of the entire system at a wide-angle limit and a telephoto limit) are satisfied.

Abstract: A zoom lens according to the invention includes in order starting from an object side a first lens group having a positive refractive power; a second lens group having a negative refractive power and selectively moveable along an optical axis for zooming; an aperture stop; a third lens group having a positive refractive power and including a third-A lens group including a doublet lens including a positive lens and a negative lens and having at least one aspherical surface, selectively moveable along the optical axis for image blur compensation, and having a positive refractive power, and a third-B lens group including a positive lens and a negative lens; and a fourth lens group having a positive refractive power and selectively moveable along the optical axis to compensate for a variation in an image plane caused by the zooming and to perform focusing.

Abstract: A zoom lens system of lens units, the system including, in object-side-to-image-side order: a first lens unit having positive optical power; a second lens unit; an aperture diaphragm; one or more additional lens units, with a first of the additional lens units being a first focusing-lens unit having negative optical power and moving along the optical axis in the zoom lens system focusing; an image blur compensating lens unit, adjacent the first focusing-lens unit and movable in a direction perpendicular to the optical axis in order to optically compensate image blur; with the lens system satisfying: 0.1<(T1+T2)/H<2.0 (T1 being the axial thickness of the first lens unit, T2 being the axial thickness of the second lens unit, and H being the height of an image the zoom lens system forms on an image surface on the image-side end of the zoom lens system).

Abstract: A zoom lens system, in order from an object side to an image side, comprising a front unit and a rear unit, wherein the rear unit, in order from the object side to the image side, comprises: a subsequent first lens unit and a subsequent second lens unit having negative optical power and being a focusing lens unit which moves along an optical axis at the time of focusing from an infinity in-focus condition to a close-object in-focus condition, the subsequent first lens unit comprises a first-N sub lens unit having negative optical power and a first-P sub lens unit having positive optical power, and the first-N sub lens unit or the first-P sub lens unit is an image blur compensating lens unit which moves in a direction perpendicular to the optical axis in order to optically compensate image blur; an interchangeable lens apparatus; and a camera system are provided.

Abstract: A fish eye lens system and a photographing apparatus including the same, the fish eye lens system including, in an order from an object side to an image side: a first lens group having a negative refractive power; an aperture stop; and a second lens group having a positive refractive power, wherein the first lens group includes, in the order from the object side to the image side, a (1-A)-th lens group having a negative refractive power, a (1-B)-th lens group having a negative refractive power, and a (1-C)-th lens group including at least one positive lens, and wherein the (1-B)-th lens group is moved to perform focusing.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group, in that order from the object side, wherein upon zooming from the short to long focal length extremities, the distance between the first lens group and the second lens group decreases, and the distance between the second lens group and the third lens group increases. The second lens group includes a positive first sub-lens group and a negative second sub-lens group, in that order from the object side. In at least part of the zooming range of the zoom lens system, the second sub-lens group and the third lens group each serves as a focusing lens group that is moved along the optical axis during a focusing operation.

Abstract: An inner focus type zoom lens includes a first lens group that has positive refracting power and is normally located at a fixed position, a second lens group that has negative refracting power and is movable in an optical axis direction for zooming, a third lens group that has positive refracting power, a fourth lens group that is movable for correction of a focal position due to the zooming and for focusing, and a fifth lens group that has positive refracting power, in order from an object side, wherein the first lens group includes a negative lens, a first positive lens, and a second positive lens arranged in order from the object side, wherein a first face of the negative lens has a shape of a concave surface turned on the object side, and wherein the zoom lens satisfies the following conditional equation (1) ?10.0<G1R1/fw<?3.0.

Abstract: A zoom lens with a bent optical path comprising, in order from the object side to the image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a rear lens unit group having a positive refractive power as a whole. The first lens unit includes a reflecting member. The rear lens unit group includes three lens unit including, in order from the object side to the image side, 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. The distances between the lens units change during zooming from the wide angle end to the telephoto end. The zoom lens satisfies the predetermined conditional expressions.

Abstract: A zoom lens including first to fifth lens units in order from an object side toward an image. The refractive powers of the first to the fifth lens units are positive, negative, positive, negative and positive, respectively. The distance between the first and the second lens units is increased at the time of zooming from the wide angle end to the telephoto end, and the distance between the second and the third lens unit is decreased at the time of zooming from the wide angle end to the telephoto end. The first lens unit and the fourth lens unit are fixed for the zooming. When M2 and M3 are the amounts of movement of the second lens unit and the third lens unit at the time of zooming from the wide angle end to the telephoto end, respectively, the conditional expression; 0.2<|M2/M3|<5.0 is satisfied.

Abstract: A zoom lens includes sequentially from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and a fifth lens group having a negative refractive power. The zoom lens satisfies given conditions to implement a compact, large aperture ratio zoom lens having excellent optical performance and compatible with solid state image sensors capable of recording full high vision images.

Abstract: A zoom lens and an image pickup apparatus are disclosed. The zoom lens includes, in order from an object side to an image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and a fifth lens group having a positive refractive power. The fifth lens group includes a fixed group having a negative refractive power, and a movable group having a positive refractive power and being movable in a direction substantially orthogonal to the optical axis. The image formed on an image surface is movable in a direction substantially orthogonal to the optical axis by moving the movable group of the fifth lens group in the direction substantially orthogonal to the optical axis. The fifth lens group is satisfied predetermined conditions.

Abstract: A zoom lens system is composed of negative, positive, negative, and positive lens groups, of which at least the first to third move during zooming. During zooming from the wide-angle end to the telephoto end, the distance between the first and second lens groups decreases, the distance between the second and third lens groups varies, and the distance between the third and fourth lens groups increases. The conditional formulae 1.0?|f2/f1|?1.5 and 2.0?|f4/f1|?5.0 are fulfilled (f1, f2, and f4 representing the focal lengths of the first, second, and fourth lens groups).

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a negative refractive power and a second lens unit having a positive refractive power. A distance between the first lens unit and the second lens unit varies during zooming. The first lens unit includes, in order from the object side to the image side, a negative lens and a positive lens of which an object-side lens surface has a convex shape. An Abbe number of a material of the positive lens of the first lens unit, a focal length of the first lens unit, a distance between an image-side lens surface of the first lens unit and an object-side lens surface of the second lens unit at a telephoto end, and focal lengths of the entire zoom lens at a wide-angle end and the telephoto end are appropriately set.

Abstract: A zoom lens includes an imaging lens unit having a positive refractive power and provided nearest to an image-side end, and a focusing lens unit having a positive refractive power and provided on an object side of the imaging lens unit. A distance between the imaging lens unit and the focusing lens unit changes during zooming. The focusing lens unit moves during focusing. The imaging lens unit includes, at a position thereof nearest to an object-side end, a negative meniscus lens component that is concave on the object side thereof.

Abstract: The present invention is directed to providing a large aperture telephotographing zoom lens that employs an inner-focusing system to enable quick focusing and avoid a great aberration when the zoom lens renders the close object in focus. The zoom lens comprises at least five groups of lens pieces arranged in series, namely, the foremost or first lens group of positive refractivity positioned the closest to the object, the succeeding second lens group of negative refractivity, the third lens group of negative refractivity, the fourth lens group of positive refractivity, and the rearmost or fifth lens group of positive refractivity. During varying the magnification for zooming in a transition from the wide-angle end to the telephoto end, all the lens pieces of the second, third, and fourth lens groups are moved toward the image plane, and the third lens group alone is displaced for focusing.

Abstract: A zoom lens and an image pickup apparatus having such a zoom lens are provided. The zoom lens includes a first lens group in which each lens has negative refractive power, a second lens group in which each lens has positive refractive power, a third lens group in which each lens has positive refractive power. These lens groups are arranged in this order from an object side to an image side. The first lens group includes a negative lens and a positive lens which are arranged in this order from an image side to an object side. The third lens group includes a positive lens. Both surfaces of the negative lens of the first lens group are aspherical surfaces, respectively. Both surfaces of the positive surfaces of the third lens group are aspherical surfaces, respectively.

Abstract: The invention provides a zoom optical system comprising at least three lens groups and designed to implement zooming by varying a separation between the respective lens groups. The zoom optical system includes, on an image plane side with respect to a stop, a lens group comprising a plurality of lenses and having positive refracting power throughout. The lens group having positive refracting power includes therein a first lens and a second lens in order from the object side, an image plane side surface of the first lens being convex toward the object side, and an object side surface of the second lens being concave toward the object side.

Abstract: An inner focus lens, in order from an object side to an image side, comprising: a first lens unit having positive optical power; a second lens unit having negative optical power; and a third lens unit having positive optical power, wherein the second lens unit is moved along an optical axis so that focusing from an infinite-distance object side to a short-distance object side is achieved, the first lens unit includes a bi-convex air lens, and the following conditions: 0.65<|f2/f|<5.00 and 0.5<f23/f1<9.0 (f2: a focal length of the second lens unit, f and f23: a focal length of the entire system and a composite focal length of the second and third lens units in an infinity in-focus condition, f1: a focal length of the first lens unit) are satisfied; an interchangeable lens apparatus; and a camera system are provided.

Abstract: A zoom lens and an image pickup device including the same. The zoom lens includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. The first through fourth lens groups are sequentially arranged from an object side. The second lens group includes a lens formed of a material having a low refractive index.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group and a positive third lens group, in that order from the object side. Upon zooming from the short to long focal length extremities, the distance between the first and second lens groups decreases, and the distance between the second and third lens groups increases. The first lens group includes a negative lens element and a positive lens element; and the second lens group includes a cemented lens including a positive lens element and a negative lens element, and a negative lens element, in that order from the object side. The following conditions are satisfied by the zoom lens system: 1.8<ft/f2<2.4 ?1.5<f1/f2<?1.2 wherein ft designates the focal length of the entire the zoom lens system at the long focal length extremity, and f1 and f2 designate the focal lengths of the first and second lens groups, respectively.

Abstract: Providing a zoom lens system having a high zoom ratio being compact with high optical performance. The system includes, in order from an object along an optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, at least one lens group having positive refractive power, and an n-th lens group GN being disposed to the most image side. The n-th lens group GN with positive refractive power includes, in order from the object, a front group GNa and a rear group GNb having positive refractive power. Focusing on an object is carried out by moving the rear group GNb along the optical axis, and a given conditional expression is satisfied.

Abstract: A zoom lens includes a first lens group having a positive refracting power and normally fixed in position, a second lens group having a negative refracting power and movable along an optical axis, and a third lens group having a positive refracting power and normally fixed in position, disposed in order from the object side to the image side. Two thirds or more of lenses of the first to third lens groups are formed from a resin material. The zoom lens satisfies the following conditional expressions (1) and (2): 4.0<ft/fw??(1) ?100.0<f1 to 3/fw<?6.4??(2) where fw is a focal length of the entire lens system at the wide angle end, ft a focal length of the entire lens system at the telephoto end, and f1 to 3 a combined focal length of the first to third lens groups at all zoom positions.

Abstract: Providing a close-up lens with superb optical performance capable of focusing from infinity to a close distance allowing a life-size magnification by an internal focusing system with small moving amounts of focusing lens groups, an imaging apparatus, and a method for focusing a close-up lens. The close-up lens includes four lens groups, and is able to focus an object with an imaging magnification from ?=0 through at least ?=?0.5, wherein upon focusing, a first lens group and a fourth lens group are fixed with respect to an image plane, and a second lens group and a third lens group are moved along an optical axis.

Abstract: A zoom lens optical system includes a first lens unit having a positive refractive index, a second lens unit which is arranged behind the first lens unit and has a negative refractive index, a third lens unit which is arranged behind the second lens unit and has a positive refractive index, and a fourth lens unit which is arranged behind the third lens unit and has a positive refractive index. An aperture is arranged within the third lens unit to prevent reduction of shutter speed due to large diameter of the zoom lens optical system.

Abstract: A zoom lens includes, in order from object side: a positive first lens unit which does not move for zooming; a zoom lens unit including at least two lens units which move for zooming; a stop; and a positive imaging lens unit which does not move for zooming, in which: the first lens unit includes, in order from object side, a positive first sub-lens unit, a negative second sub-lens unit, and a positive third sub-lens unit; the third sub-lens unit includes a movable positive sub-third sub-lens unit; the second sub-lens unit and sub-third sub-lens unit are driven to object side for focusing to a close object; and focal length f12 of the second sub-lens unit, focal length f13f of the sub-third sub-lens unit, drive amount ?×12 of the second sub-lens unit in focusing, and drive amount ?×13f of the sub-third sub-lens unit in focusing satisfy ?2.5<f12/f13f<?0.4 and 0.05<?×13f/?×12<5.0.

Abstract: An inner focus lens system includes, from the object side, a first lens unit having a positive refractive power, an aperture stop, a second lens unit having a positive refractive power, and a third lens unit. The first lens unit includes a plurality of negative lenses and at least one positive lens, the lens located closest to the object side is a negative lens. The second lens unit includes at least one negative lens and at least one positive lens, and moves toward the object side for focusing from an infinite object distance to a close object distance such that the distance between the second lens unit and the aperture stop decreases and that the distance between the second lens unit and the third lens unit increases. The lens system satisfies the following conditions: 1<f1/f 14 (1), and 0.8<f23/f2<3 (2).

Abstract: An objective optical system of an embodiment according to the present invention is formed in such a way that: the objective optical system includes an immovable lens group which is arranged nearest to the object side, which is immovable in focusing, and which has negative power, and first and second movable lens groups at least one of which moves along the optical axis in focusing; and an amount of variation in magnification per movement of the first movable lens group is different from an amount of variation in magnification per movement of the second movable lens group.

Abstract: A zoom lens system is provided that includes a compactly constructed focusing lens unit and that has a suppressed change in the image magnification at the time of movement of a focusing lens unit. The zoom lens system according to the present invention comprises a plurality of lens units and an aperture diaphragm arranged in the lens unit. The plurality of lens units include a focusing lens unit that is arranged on an object side relative to the aperture diaphragm and that moves in a direction along the optical axis at the time of focusing. Further, the zoom lens system satisfies at least one of the following conditions: (1) 1.2<|fF/fW|<6.0; and (2) 0.10<|fF/fT|<1.8 (here, fT/fW>3.0, fF: a focal length of the focusing lens unit, fT: a focal length of the entire system at a telephoto limit, fW: focal length of the entire system at a wide-angle limit).

Abstract: In an image forming optical system which includes in order from an object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, and a fourth lens group G4, and which includes maximum of five lens groups, and at the time of zooming from a wide angle end to a telephoto end, when a focal length of the overall image forming optical system is in a range of 1.2 fw to 1.8 fw, the first lens group G1 moves to be positioned more toward the object side than a position at the wide angle end, in a rectangular coordinate system in which, a horizontal axis is let to be ?d(LA) and a vertical axis is let to be nd(LA), when a straight line expressed by nd(LA)=a×?d(LA)+b(LA)(provided that a=?0.0267) is set, the image forming optical system satisfies a predetermined conditional expression.

Abstract: Disclosed herein is a zoom lens, including: a first lens group having a positive refracting power; a second lens group having a negative refracting power; a third lens group having a positive refracting power; and a fourth lens group having a positive refracting power; the first, second, third and fourth lens groups being disposed in order from the object side; the lens groups moving upon zooming from a wide angle end to a telephoto end of the zoom lens such that the distance between the first lens group and the second lens group increases while the distance between the second lens group and the third lens group decreases.

Abstract: A zoom lens system wherein a positive lens unit located closest to an object side is fixed with respect to an image surface in zooming, a negative lens unit, among lens units located on an image side relative to an aperture diaphragm, is a focusing lens unit which moves along an optical axis in focusing, and the conditions: ?1.8<fn/fW<?0.3 and 0.1<T1/fW<1.5 (fn: a composite focal length of the negative lens unit, T1: an axial thickness of the positive lens unit located closest to the object side, fW: a focal length of the entire system at a wide-angle limit) are satisfied.

Abstract: An optical system includes at least one lens unit having a negative refractive power disposed closer to an object side than an aperture portion. The lens unit having a negative refractive power includes at least one positive lens and one negative lens. The ratio between the numbers of positive lenses and negative lenses included in the lens unit having a negative refractive power is appropriately set. The lens unit having a negative refractive power includes a plurality of negative lenses each having an appropriate Abbe number and relative partial dispersion and a positive lens having an appropriate Abbe number. A negative lens having the highest dispersion among the negative lenses is located in an appropriate position.

Abstract: Provided is a compact zoom lens with a high resolving power, a large aperture, and a high variable power. The zoom lens includes a positive first lens group, a moving negative second lens group, a stationary positive third lens group, and a moving positive fourth lens group. The first lens group includes a negative eleventh lens, a positive twelfth lens, and a positive thirteenth lens. The second lens group is composed of a negative twenty-first lens, a negative twenty-second lens, a positive twenty-third lens, and a negative twenty-fourth lens. The third lens group includes a positive thirty-first lens, a positive thirty-second lens, and a negative thirty-third lens. The fourth lens group is composed of a positive forty-first lens having one or more aspheric surfaces. The zoom lens satisfies the prescribed conditional expressions.

Abstract: A zoom lens is provided, and includes, in sequence from an object side: a first lens group with positive refractive power; a second lens group with negative refractive power; a third lens group with positive refractive power; a fourth lens group with positive refractive power; and a fifth lens group with negative refractive power. At the time of a magnification change from a wide-angle end to a telescopic end, the first lens group, the third lens group, and the fifth lens group are fixed in a direction of an optical axis, the second lens group moves along the optical axis from the object side to an image side for the magnification change, the fourth lens group moves along the optical axis to compensate for a change of a position of the image surface according to the movement of the second lens group, and performs focusing.

Abstract: Provided is a zoom lens for imaging an object on an imaging surface. The zoom lens includes, in the order from an object side to an image side thereof, a first lens group with positive refraction power, a second lens group with negative refraction power, a third lens group with positive refraction power, and a fourth lens group with positive refraction power. The first lens group includes a first surface. The zoom lens satisfies the formula: 0.15<|L3|/Lt<0.25, where L3 is a distance of the movement of the third lens group along an optical axis of the zoom lens when the zoom lens is switched between a wide-angle state and a telephoto state, and Lt is a distance from the first surface to the imaging surface.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a negative third lens group, in that order from the object side, wherein upon zooming from the short focal length extremity to the long focal length extremity, the distance between the first lens group and the second lens group decreases. The third lens group includes a negative lens element having a concave surface on the image side, a positive lens element having a convex surface on the image side, and a negative lens element having convex surface on the image side, in that order from the object side. An electronic imaging apparatus using this zoom lens system is also disclosed.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a positive refractive power, which does not move for zooming, a second lens unit having a negative refractive power, which moves during zooming, a third lens unit having a negative refractive power, which moves during zooming, an aperture stop, and a fourth lens unit having a positive refractive power, which does not move for zooming. The fourth lens unit includes a first lens sub-unit, a focal length conversion optical system configured to be inserted into or removed from an optical path, and a second lens sub-unit. A focal length of the second lens sub-unit, a distance from the aperture stop to a lens surface at the most object side of the second lens sub-unit, and an F-number of the entire zoom lens at a wide-angle end are appropriately set.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a negative third lens group, in that order from the object side, wherein upon zooming from the short focal length extremity to the long focal length extremity, the distance between the first lens group and the second lens group decreases, wherein the following condition (1) is satisfied: ?2.45<f1/f2<?2.05??(1), wherein f1 designates the focal length of the first lens group, and f2 designates the focal length of the second lens group.

Abstract: A zoom lens includes a negative lens unit having a negative refractive power and a positive lens unit having a positive refractive power arranged in order from an object side to an image side. For focusing from infinity to a closest distance, the negative lens unit moves towards the image side and the positive lens unit moves towards the object side. Predetermined mathematical conditions are satisfied to obtain high optical performance over the entire focusing range.

Abstract: Provided is a zoom lens comprising, in order from an object side to an image side, a first lens unit having positive refracting power; a second lens unit having negative refracting power; a third lens unit having positive refracting power; a fourth lens unit having negative refracting power; and a fifth lens unit having positive refracting power, wherein the lens units move when zooming from the wide-angle end to the telephoto end; the third lens unit and the fifth lens unit move together when zooming; the fifth lens unit includes an aperture stop in the optical path thereof; the third lens unit or the fourth lens unit moves during focusing; and the following conditional expression is satisfied: 0.5<|f2|/skw<3.0 where f2 is the focal length of the second lens unit, and skw is a back focus at the wide-angle end.

Abstract: A zoom lens primarily includes, in order from an object side to an image-forming side, a first lens group having negative refractive power; a second lens group having positive refractive power and at least consisting of a first lens and a second lens; and a third lens group having positive refractive power. The refractive index of the first lens (Nd21), the refractive index of the second lens (Nd22), the total length of the first lens group, the second lens group, and the third lens group (TTL), and the shortest focal length of the zoom lens (fw) satisfy the following conditions: Nd21?Nd22>0.1 and TTL/fw?1.3.

Abstract: A zoom lens includes, from an object side to an image side, first to fifth lens units having positive, negative, positive, negative, and positive refractive powers. A distance between the first and second lens units is longer, a distance between the second and third lens units is shorter, and a distance between the fourth and fifth lens units is longer at a telephoto end than at a wide angle end, and a distance between the third and fourth lens units differs between the telephoto end and the wide angle end. Focal lengths of the first and fourth lens units and the entire zoom lens at the wide angle end, a moving amount of the first lens unit during zooming, and a distance from a lens surface closest to the object side in the first lens unit to an image plane at the wide angle end are set properly.

Abstract: A zoom lens includes, in order from the object side to the 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 negative refractive power, and a rear lens group including a plurality of lens units and having a positive refractive power as a whole. The distances between adjacent lens units are changed during zooming. The third lens unit is moved during focusing. The focal length, fw, of the entire zoom lens system at the wide-angle end; the focal length, ft, of the entire zoom lens system at the telephoto end; the combined focal length, f12w, of the first and second lens units at the wide-angle end; and the combined focal length, f12t, of the first and second lens units at the telephoto end are appropriately set to satisfy predetermined conditions.

Abstract: A zoom lens includes a lens unit Ln having negative refractive power including two or less lenses moving during focusing and zooming, a lens unit Lp1 having positive refractive power disposed adjacent to an object side thereof, and a lens unit Lp2 having positive refractive power disposed adjacent to an image side thereof. The lens units Lp1 and Lp2 move during zooming. A distance Tlw between a lens surface nearest to the object side in the entire zoom lens and an image plane at a wide-angle end, a distance Dnw between the lens surface nearest to the image side of the lens unit Ln and the image plane at the wide-angle end, a back focus bfw at the wide-angle end, and a maximum amount of movement Mnz during focusing of the lens unit Ln at a telephoto end are appropriately set.

Abstract: A zoom lens includes N lens units, in which a lens unit having a positive refractive power is disposed closest to an object side. Each lens unit is moved to effect zooming. An (N?1)th lens unit and an N-th lens unit, counted from the object side, have positive refractive powers. The (N?1)th lens unit includes a first lens subunit having a positive refractive power and a second lens subunit having a negative refractive power in order from the object side to an image side. The second lens subunit is moved to have a component in a direction perpendicular to an optical axis to move an image position. A focal length fN of the N-th lens unit, a back focus bkt at the telephoto end, and an amount of movement mN of the N-th lens unit during zooming from a wide-angle end to a telephoto end are appropriately set.

Abstract: Providing a zoom lens system having a vibration reduction function capable of performing quick focusing with excellent optical performance even upon vibration reduction. The system including, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having positive refractive power. Upon zooming from a wide-angle end state to a telephoto end state, a distance between the first lens group G1 and the second lens group G2 varies, and a distance between the second lens group G2 and the third lens group G3 varies. The third lens group G3 carries out focusing from an infinity object to a close object. At least a portion of the fourth lens group G4 moves in a direction perpendicular to the optical axis.

Abstract: A variable power zoom lens of four groups of lens pieces respectively exerting positive, negative, positive, and positive refractivities varies the power from the wide-angle end to the telephoto end as a result of the 1st and 2nd lens groups being separated more, the 2nd and 3rd lens groups, and the 3rd and 4th lens groups, coming closer to each other. The 3rd lens group has a leading set of lens pieces closer to the object side having a positive refractivity as a whole and the trailing set of lens pieces have negative refractivity as a whole, and the trailing set alone are moved to be orthogonal to the optical axis to compensate for defocus in the imaging plane. The 2nd lens group is displaced closer to objects for focusing.