Abstract: A zoom lens system includes a positive first lens group, a negative second lens group, and positive third and fourth lens groups. Upon zooming from the short to long focal length extremities, the distance between the first and second lens groups increases and the distance between the second and third lens groups decreases. The first lens group includes a positive first sub-lens group which remains at a stationary position during focusing and a positive second sub-lens group which moves during focusing. Condition (1) is satisfied: 0.35<f1b/f1a<0.57??(1), wherein f1b and f1a designate the focal length of the second and first sub-lens groups, respectively.

Abstract: A zoom lens includes 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, being disposed in order from an object side, and an aperture stop disposed at an object side of the third lens group. When changing the magnification from a wide angle end to a telephoto end, an interval between the first and second lens groups increases, an interval between the second and third lens groups decreases, and an interval between the third and fourth lens groups changes.

Abstract: A high zoom-ratio zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, in that order from the object side. Upon zooming from the short to long focal length extremities, at least the first through third lens groups are moved along the optical axis direction, wherein an amount of movement of the first lens group is greater than that of the third lens group. The following conditions (1), (2) and (3) are satisfied: 0.9<FT/F1<2??(1), 3<F1/FW<7??(2), and ?8<F1/F2<?5??(3), wherein FT and FW designate the entire focal length of the zoom lens system at the long and short focal length extremities, respectively; and F1 and F2 designate the focal length of the first and second lens groups, respectively.

Abstract: A zoom lens includes, in order from an object side to an image side and arranged along an optical axis, first to fifth lens units having positive, negative, positive, positive or negative, and positive refractive power, respectively. When zooming, the second lens unit moves monotonically to the image side, the third lens unit moves to the object side in a convex locus, the fifth lens unit moves nonlinearly, and the first and fourth lens units do not move. The fourth lens unit includes a first sub lens unit and a second sub lens unit; the first sub lens unit is an image-stabilizing lens unit that includes a first lens having negative refractive power and a second lens having positive or negative refractive power. The focal length of the fourth lens unit, the focal length of the entire system at the wide-angle end, the Abbe numbers of the materials of the first and second lenses are set appropriately based on predetermined conditions.

Abstract: A zoom lens includes a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, which are arranged in this order from the object side of the zoom lens. The focal length of the entire system of the zoom lens is changeable by changing a distance between the second lens group and the third lens group. The first lens group includes two cemented lenses, each composed of a negative meniscus lens and a positive lens cemented together in this order from the object side, and a positive lens, and the two cemented lenses and the positive lens being arranged in this order from the object side. Further, a predetermined formula related to the focal length of the first lens group and the focal length of the entire system is satisfied.

Abstract: A zoom lens system includes a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power. The lens groups can move along the optical axis of the zoom lens system. The zoom lens system satisfies the formula: 0.15<|L3|/Lt<0.25. L3 is a movement vector of the third lens group during the zoom lens system moves from a wide-angle state to a telephoto state. The movement vector is a positive value when the zoom lens system moves from a subject side to an image side thereof. The movement vector is a negative value when the zoom lens system moves from the image side to the subject side. Lt is the total length of the zoom lens system along the optical axis in the telephoto state.

Abstract: A zoom lens system includes, in order from the subject side to the image side thereof, a first lens group of positive refractive power, a second lends group of negative refractive power, a third lens group of positive refractive power, and a fourth lens group of positive refractive power. The zoom lens system satisfies the following formulas: ?0.15<L3/Lt<?0.35, wherein, L3 is the movement vector of the third lens group during the zoom lens system moves from the wide-angle state to the telephoto state. The movement vector is a positive value when the third lens group moves from the object side to the image side. The movement vector is a negative value when the third lens group moves from the image side to the object side. Lt is the total length of the zoom lens system along the optical axis when in the telephoto state.

Abstract: A zoom lens includes positive, negative, positive, and positive lens units, and the second lens unit includes negative, negative, negative and positive lenses. The first and third lens units are fixed and the second and fourth lens units are moved in zooming. 0.01<|f2/?(fw*ft)|<0.35 and 0.070<D2/TL<0.105 are satisfied. fw and ft are focal lengths of an overall system at wide angle and telephoto ends, f2 is a focal length of the second lens unit, TL is a distance on an optical axis from a lens surface closest to an object plane to an image plane when a distance from a lens surface closest to the image plane to the image plane is aerially converted, and D2 is a distance on the optical axis from a lens surface closest to the object plane in the second lens unit to the lens surface closest to the image plane in the second lens unit.

Abstract: A zoom lens includes 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. When the zoom lens is zoomed from a wide-angle end state to a telephoto end state, the first lens group is moved toward the object side so that a distance between the first and second lens groups increases and the third lens group is moved toward the object side so that a distance between the second and third lens groups decreases. The second lens group includes three lenses: negative, positive, and negative lenses in order from the object side to the image side. The third lens group includes three lenses: positive, negative, and positive lenses in order from the object side to the image side.

Abstract: An apparatus includes a zoom lens and an image pickup element. The zoom lens includes an optical path reflecting lens group including a reflecting member and having a positive refracting power, a movable negative lens group that is disposed in the optical path on the image side of the optical path reflecting lens group, has a negative refracting power, and moves during zooming, a movable positive lens group that is disposed in the optical path on the image side of the movable negative lens group, has a positive refracting power, and moves during zooming, and an aperture stop disposed in the optical path between the movable negative lens group and the movable positive lens group. The optical path reflecting lens group is a lens group located closest to the object side in the zoom lens.

Abstract: A high zoom-ratio zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, in that order from the object side, wherein upon zooming from the short to the long focal length extremities, the first through fourth lens groups are moved along the optical axis direction, wherein an amount of movement of the first lens group is greater than that of the third lens group. The following conditions (1) and (2) are satisfied: 1.4<FT/F1<2.4??(1), and 5<M2T/M2W<10??(2), wherein FT designates the entire focal length at the long focal length extremity, F1 designates the focal length of the first lens group, and M2T and M2W designate the magnification of the second lens group with respect to an object at infinity at the long and short focal length extremities, respectively.

Abstract: A zoom lens includes a first lens unit having a positive refractive power, a second lens unit having a negative refractive power and configured to move during a zooming operation, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power and configured to move during a zooming operation. The first lens unit has a negative lens closest to an object side, and includes at least five lenses.

Abstract: A zoom optical system including, in order from an object side: a first group having positive power; a second group having negative power; a third group having positive power; and a fourth group having positive power, at least a portion of lenses within said third group composing a movable group which moves in a direction having a component perpendicular to an optical axis, a distance between said first group and said second group, a distance between said second group and said third group and a distance between said third group and said fourth group being variable upon zooming from a wide-angle end state to a telescopic end state, thereby providing a zoom optical system capable of correcting a camera shake by the movable group with realizing high optical performance, a high zoom ratio, and a small f-number, an optical apparatus equipped therewith, and a method for manufacturing thereof.

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, and a fourth lens group. During zooming from a wide angle position to a telephoto position, the interval between the first lens group and the second lens group increases, the interval between the second lens group and the third lens group decreases, and an interval between the third lens group and the fourth lens group varies. The fourth lens group includes, sequentially from the object side, a first sub-lens group having a positive refractive power, a second sub-lens group having a negative refractive power, and a third sub-lens group. The second sub-lens group of the fourth lens group is moved along an optical axis to perform focusing.

Abstract: A variable power optical system ZL is constructed of, in order from the object side, a first lens unit G1 having a positive refractive power, a second lens unit G2 having a negative refractive power, a third lens unit G3 having a positive refractive power, and a fourth lens unit G4 having a positive refractive power. During variation in power from a wide-angle end state to a telephoto end state, a space between the first lens unit G1 and the second lens unit G2 increases, a space between the second lens unit G2 and the third lens unit G3 decreases, and a space between the third lens unit G3 and the fourth lens unit G4 varies, and a part of the third lens unit G3 is configured to move in directions perpendicular to the optical axis.

Abstract: In an image pickup apparatus including an image sensor and a zoom lens configured to form an image on the image sensor, the zoom lens includes, in order 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, a third lens unit having a positive refractive power, and a subsequent lens group including one or more lens units. In the zoom lens, during zooming, the first lens unit is stationary, the third lens unit moves along a locus convex towards the object side, and three or more lens units including the third lens unit and the image sensor move. An optical total length of the zoom lens is longer at a telephoto end than at a wide-angle end.

Abstract: Zoom lens for SLR digital cameras. The lens is at least 75 degrees wider in field angle at the wide-angle end, about 3 to 4 in f-stops at the wide-angle end and approximately 6 to 7 at the telephoto end, and about a 15:1 zoom range. Four groups of lens pieces exert positive, negative, positive, and positive refractivities from the wide-angle end to the telephoto end as a result of the 1st and 2nd lens groups being split more, the 2nd and 3rd lens groups coming closer to each other, and the 3rd and 4th lens groups also coming closer to each other. The 3rd lens group has the leading set of lens pieces closer to objects and the trailing set of lens pieces can 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.

Abstract: A zoom optical system includes, in order from its object side along its optical axis, a first lens group G1 having a positive refracting power, a second lens group G2 having a negative refracting power, a third lens group G3 having a positive refracting power, and a fourth lens group G4 having a positive refracting power, wherein at least one of the first, second, third and fourth lens groups G1, G2, G3, G4 comprises a front group having a positive refracting power including at least two lenses and a rear group having a negative refracting power, and during zooming from the wide angle end state W to the telephoto end state T, the distance between the front group and the rear group does not change, and during focusing onto an object, the front group moves along the optical axis.

Abstract: A zoom lens includes a first, third and fourth lens group of positive refracting power, a second lens group of negative refracting power, wherein, during zooming from a wide-angle end to a telephoto end, at least the first lens group moves, wherein the third lens group includes, a first lens sub-group of positive refracting power and a second lens sub-group of negative refracting power, wherein the second lens sub-group includes a single negative lens, wherein the first lens sub-group of the third lens group is moved in a direction having a perpendicular component relative to an optical axis to correct image blur to be produced when the zoom lens vibrates, and wherein, when a focal length of the first lens group is denoted by f1 and the focal length of the whole system at the wide-angle end is denoted by fw, a conditional expression 11.962?f1/fw<20.0 is satisfied.

Abstract: A zoom lens including four lens units having positive, negative, positive, and positive refractive power in order from an object side to an image side thereof, wherein the distance between the adjacent lens units changes when zooming: wherein the third lens unit includes, in order from the object side to the image side, a first lens subunit having negative refractive power and a second lens subunit having positive refractive power. The zoom lens is configured to displace an image formed by the zoom lens in a direction perpendicular to its optical axis by moving the second lens subunit so as to have a component perpendicular to the optical axis, wherein the curvature radius of a surface, closest to the object, of the first lens subunit and the curvature radius of a surface second closest to the object, of the first lens subunit are set at appropriate values.

Abstract: Anti-vibration zoom lens optics of four lens groups where a unit associated with an aperture stop and an anti-vibration unit can be spaced apart from each other without interference between their driving mechanisms. The four groups include a leading, first lens group of positive refractivity, a succeeding second lens group of negative refractivity, a third lens group of positive refractivity, and a trailing, fourth lens group of positive refractivity all arranged in this order from the front end closest to the object to the rearmost. The fourth lens group include three subsets of lens pieces, a leading, first subset, a succeeding, second subset, and a trailing, third subset all arranged in this order from the front end closest to the object to the rearmost, and the second subset of lens pieces are moved perpendicular to the optical axis to compensate for blur in the imaging plane.

Abstract: A zoom lens includes, from the object side to the image side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power. At least the second and fourth lens groups are moved along the optical axis during zooming. The second lens group includes, from the object side to the image side, three negative lenses and one positive lens and satisfies 0.54<|f2|/?(fw·ft)<0.66 where f2 is the focal length of the second lens group, and fw and ft are the focal lengths of the entire optical system at the wide-angle end and at the telephoto end, respectively.

Abstract: A zoom lens system and a photographing apparatus including the same, wherein the zoom lens system includes a first lens group including one or more lenses, and an optical member for changing a path of light, and 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, wherein zooming is performed by varying air gaps between the first through fourth lens groups.

Abstract: Provided is a zoom lens system includes, in order 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; a third lens unit having a positive refractive power; and a fourth lens unit having a positive refractive power, the second and fourth lens units move on an optical axis during zooming. The third lens unit includes, in order from the object side to the image side: a third A lens unit having a negative refractive power; and a third B lens unit having a positive refractive power, the third B lens unit including a positive lens and a negative lens being joined together. When curvature radii of surfaces of the cemented lens on the object side and the image side are R3A and R3B, respectively, the following condition is satisfied: 5<|(R3A+R3B)/(R3A?R3B)|<30.

Abstract: The zoom lens with a wide angle of view, a high zoom ratio and high optical performance includes, in order 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, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power. The second and fourth lens units are moved on an optical axis for zooming. The second lens unit is constituted by, in order from the object side to the image side, three negative lens elements and one positive lens element. The zoom lens satisfies 0.54<|f2|/?(fw·ft)<0.66, where f2 represents a focal length of the second lens unit, fw and ft represent focal lengths of the entire zoom lens at a wide-angle end and at a telephoto end, respectively.

Abstract: A wide-angle zoom lens includes 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, the second lens group, the third lens group, and the fourth lens group move along an optical axis of the zoom lens in focusing. The wide-angle zoom lens satisfies the formulas: 1.6<f3/fw<2.1, where f3 is the effective focal length of the third lens group, and fw is the effective focal length of the wide-angle zoom lens in a wide angle state.

Abstract: A zoom lens system, in order from an object side to an image side, comprising a positive first lens unit, a negative second lens unit, a positive third lens unit, and a positive fourth lens unit, wherein the first lens unit is composed of a cemented lens element of one object side negative lens element and one image side positive lens element, the fourth lens unit is composed of one lens element, in zooming, the first to fourth lens units are individually moved along an optical axis so that air spaces between the respective lens units vary for magnification change, and the conditions: vdL12<43.50 and fT/fW?6.0 (vdL12: an Abbe number of the positive lens element in the first lens unit, fT and fW: focal lengths of the entire system at a telephoto limit and a wide-angle limit) are satisfied; an imaging device; and a camera.

Abstract: A zoom lens of the present invention includes a first lens group, a second lens group, an aperture, a third lens group, a fourth lens group, and an image surface in sequence along an optical axis from an object side to an image side. The first lens group has positive refractive power, and includes at least two lenses. The second lens group has negative refractive power, and includes three lenses. The third lens group has positive refractive power, and includes at least two lenses. The fourth lens group has positive refractive power. The zoom lens is switched to a telephoto mode from a wide-angle mode by moving the first lens group toward the object side, moving the second lens group toward the image side, and moving the third lens group toward the object side.

Abstract: Superzoom lenses are disclosed. The superzoom lenses include, in order from an object side to an image side on an optical axis, a first lens group, a second lens group, an aperture, a third lens group, and a fourth lens group. The first lens group has positive optical power. The second lens group has negative optical power and is consisted of a convex lens and a concave lens. The third lens group has positive optical power. The fourth lens group has positive optical power. The superzoom lenses satisfy the following relationship when the superzoom lenses are collapsed: 3?LW/ID<5 wherein LW stands for the optical path length, and ID stands for the diameter of the image circle.

Abstract: The present invention is a variable power zoom lens that is suitable to APS-format single-lens reflex cameras. The zoom lens has the foremost or first lens group G1 of positive refractivity, the second lens group G2 of negative refractivity, the third lens group G3 of positive refractivity, and the fourth lens group G4 of positive refractivity disposed in sequence from a position closer to the object toward the image plane, and it meets requirements as defined in conditional formulae as follows: 6<Lw/(Ft/Fw)<10 where Lw is the entire length of the lens optics (i.e., from the front surface of the foremost lens piece to the image plane) at the wide-angle end, Ft is a focal length of the lens optics in whole at the telephoto end, and Fw is the focal length of the lens optics in whole at the wide-angle end.

Abstract: An image-pickup apparatus includes an image-pickup element that photoelectrically converts an optical image formed by an image-pickup optical system having a zoom function, and a correcting part that performs correction processing for a distortion component in image data generated based on an output from the image-pickup element, the distortion component corresponding to a distortion of the image-pickup optical system. The image-pickup optical system provides a first zoom range in which a distortion amount at a certain image height is larger than a predetermined value and a second zoom range in which a distortion amount at the certain image height is smaller than the predetermined value. The correcting part performs the correction processing so that the distortion component remains in a first corrected image data in the first zoom range is larger than the distortion component remaining in a second corrected image data in the second zoom range.

Abstract: A zoom lens system includes a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power. The lens groups can move along the optical axis of the zoom lens system. The zoom lens system satisfies the formula: 0.15<|L3|/Lt<0.25. L3 is a movement vector of the third lens group during the zoom lens system moves from a wide-angle state to a telephoto state. The movement vector is a positive value when the zoom lens system moves from a subject side to an image side thereof. The movement vector is a negative value when the zoom lens system moves from the image side to the subject side. Lt is the total length of the zoom lens system along the optical axis in the telephoto state.

Abstract: A zoom lens includes a first lens group having a positive refractive power, and a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power arranged in order from an object side, the third lens group having a first positive lens, a second positive lens, and a negative lens, and a third positive lens in order from the object side. When zooming from short to long focal end, the zoom lens is moved so that the interval between the first and second lens groups increases, that between the second and third lens groups decreases, that between the third and fourth lens groups increases, and the first and third lens groups are positioned closer to the object at the long focal end than the short focal end.

Abstract: A zoom lens system includes a first unit having a positive refractive power, a second unit having a negative refractive power that moves for magnification-varying, a third unit having one of a positive refractive power and a negative refractive power that moves for magnification-varying, and a fourth unit having a positive refractive power.

Abstract: An image forming optical system of the present invention includes at least one cemented lens which includes a first lens element (e1), a second lens element (e2), and a third lens element (e3). The first lens element e1 is cemented to a surface on one side of the second lens element e2, and the third lens element e3 is cemented to the other surface of the second lens element e2. The first lens element e1 is a positive lens, and a combined refracting power of the second lens element e2 and the third lens element e3 is negative. The cemented lens satisfies a predetermined conditional expression.

Abstract: A 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, which are disposed in order from an object side, and an aperture stop disposed at an object side of the third lens group. When changing the magnification from a wide angle end to a telephoto end, an interval between the first and second lens groups increases, an interval between the second and third lens groups decreases, and an interval between the third and fourth lens groups increases. The first lens group includes a negative lens, a positive lens, and a positive lens, in order from the object side. Predetermined conditions of a refractive index of the negative lens E1 for a d line, an Abbe number for d line, and a relative partial dispersion are satisfied.

Abstract: A zoom lens includes first and second lens units having positive and negative refractive powers, an aperture stop, and third and fourth lens units having positive and negative refractive powers in order from an object side to an image side. During zooming from a wide angle end to a telephoto end, the first lens unit remains fixed, and the second and fourth lens units move. The first lens unit includes negative, positive, negative, positive, and positive lenses in order from the object side to the image side, the third and fourth lens units include two or more lenses. Focal lengths of the first and third lens units and of the entire system at the wide angle end, the thickness of the first lens unit on an optical axis, and the distance between principal points between the first and the second lens units at a wide angle end are appropriately set.

Abstract: A zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, in this order from the object. Upon zooming from the short focal length extremity to the long focal length extremity, all of the first through fourth lens groups move along the optical axis. The zoom lens system satisfies the following condition: 3<T1/F2<4 . . . (1) wherein T1 designates the traveling distance of the first lens group upon zooming from the short focal length extremity to the long focal length extremity; and F2 designates the focal length of the second lens group.

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: 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 and a photographing apparatus having the zoom lens including 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, wherein the first lens group, the second lens group, the third lens group, and the fourth lens group are arranged sequentially from an object side, wherein the second lens group includes a first aspherical lens having a negative refractive power, and a second aspherical lens having a positive refractive power.

Abstract: A zoom lens system includes, in order from the subject side to the image side thereof, a first lens group of positive refractive power, a second lends group of negative refractive power, a third lens group of positive refractive power, and a fourth lens group of positive refractive power. The zoom lens system satisfies the following formulas: ?0.15<L3/Lt<?0.35, wherein, L3 is the movement vector of the third lens group during the zoom lens system moves from the wide-angle state to the telephoto state. The movement vector is a positive value when the third lens group moves from the object side to the image side. The movement vector is a negative value when the third lens group moves from the image side to the object side. Lt is the total length of the zoom lens system along the optical axis when in the telephoto state.

Abstract: A zoom lens system and an image capturing apparatus having 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, wherein the first through fourth lens groups are sequentially arranged from an object side to an image side, and the third lens group includes a first positive lens, a doublet lens including a second positive lens and a third negative lens, and a fourth positive lens sequentially arranged from the object side.

Abstract: A zoom lens system having a high zoom ratio and excellently correcting various aberrations over an entire zoom range between a wide angle end and a telephoto end to obtain high optical performance in the entire zoom range, includes, in order 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, a third lens unit, and a fourth lens unit. The fourth lens unit includes a front subunit and a rear subunit, the rear subunit being constituted by two negative lenses and at least three positive lenses. The rear subunit includes a first rear-subunit and a second rear-subunit. Each of the first rear-subunit and the second rear-subunit includes a negative lens and at least one positive lens. Lens materials are suitably set for the first rear-subunit and the rear second-subunit.

Abstract: A zoom lens comprises a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a rear group including at least one lens unit, in order from an object side to an image side. Each of the lens units is configured to move so that a total lens length at a wide-angle end is longer than that at a telephoto end to perform a zoom operation. A movement amount M1 of the first lens unit at the wide-angle end and the telephoto end with respect to an imaging surface, a focal length f1 of the first lens unit, and focal lengths fw and ft of a whole system at the wide-angle end and the telephoto end are appropriately set.

Abstract: A high-performance zoom lens system which is compact and has a wide view angle at a wide-angle limit and a high zooming ratio in a balanced manner, 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, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein the first lens unit is composed of at most two lens elements, the second lens unit is composed of two lens elements, the third lens unit is composed of three lens elements, in order from the object side to the image side, including an object side lens element having positive optical power, a lens element having negative optical power, and an image side lens element having positive optical power, and the conditions: ?2.0<f2/fW<?1.1, fT/fW>6.

Abstract: A zoom lens system includes, in the order from the object side to the image side thereof, a first lens group of positive refraction power, a second lens group of negative refraction power, a third lens group of positive refraction power, a fourth lens of positive refraction power, and an imaging plane. The first lens group and the third lens group are immovably mounted. The second lens group and the fourth lens group are movably mounted. The zoom lens system satisfies the formulae: 5<f3/f4<8.2; and 2.1<|f2/fw|<3.2, wherein f2-f4 respectively represent the effective focal lengths of the second, third and fourth lens groups, fw represents the shortest effective focal length of the zoom lens system.

Abstract: An image forming optical system characterized by comprising a positive first lens group, a negative second lens group, and third and subsequent lens groups having a positive composite refracting power, wherein the first lens group is composed of a cemented lens made up of one positive lens and one negative lens arranged in order from the object side, and the image forming optical system satisfies the following conditional expressions (1-1) and (2-1): 0.05<T1g/Flt<0.10??(1-1) 0.50<?gF<0.75??(2-1) where T1g is the thickness of the first lens group on the optical axis, Flt is the focal length of the entire image forming optical system at the telephoto end, and ?gF is the partial dispersion ratio (ng1?nF1)/(nF1?nC1) of the negative lens, where nd1, nC1, nF1, and ng1 are refractive indices of the negative lens respectively for the d-line, C-line, F-line, and g-line.

Abstract: A zoom lens system includes, in order from the object side to the image side, first, second, third, fourth lens units respectively having positive, negative, positive, and positive refractive powers. The lens units move from a wide-angle end to a telephoto end such that intervals between adjacent lens units vary during zooming. The first lens unit consists of first-a and first-b lens elements respectively having negative and positive refractive powers, and the second lens unit consists of second-a, second-b, and second-c lens elements respectively having negative, negative, and positive refractive powers. n12 and ?12 respectively represent the refractive index and the Abbe number of the first-b lens element, and fw and ft respectively present the focal length at the wide-angle end and the telephoto end of the zoom lens system. Values for at least n12, ?12, fw and ft are appropriately set based on predetermined conditions.

Abstract: A zoom lens includes, sequentially from an object side, a positive first lens group; a negative second lens group; a positive third lens group; and a positive fourth lens group, where 2.0?D23W/FW?3.0 is satisfied. D23W is an interval, at a wide angle edge, between a lens that among lenses of the second lens group, is farthest on an imaging plane side and a lens that among lenses of the third lens group, is farthest on the object side. FW is a focal length of an optical system of the zoom lens at infinity focus, at the wide angle edge.