Abstract: A 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 fourth lens unit having a positive refractive power. In the zoom lens, each lens unit moves to perform zooming. In addition, an amount of movement Mm of the fourth lens unit when zooming from a wide angle end to an intermediate zooming position, an amount of movement Mt of the fourth lens unit when zooming from the wide angle end to a telephoto end, a focal length fw of an entire system at the wide angle end, and focal lengths f3 and f4 of the respective third lens unit and fourth lens unit are properly set.

Abstract: Provided is a zoom lens, 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. The first lens group (G1 includes only, in order from the object, a cemented lens of a negative lens (L11) and a positive lens (L12), and a positive meniscus lens (L13) having a convex surface facing the object, an aperture stop (S) for determining brightness is disposed to the object side of the third lens group (G3), and upon zooming, all of the four groups (G1 to G4) move and the aperture stop (S) moves together with the third lens group (G3), and the conditional expression ?dp1>85.0 is satisfied, where ?dp1 denotes an Abbe number of the positive lens (L12), which is disposed closest to the object in the first lens group (G1), at the d-line as a standard.

Abstract: A zoom lens substantially consists of 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 side, wherein the distance between the first lens group and the second lens group increases and the distance between the second lens group and the third lens group decreases, and the distance between the third lens group and the fourth lens group decreases while changing magnification. The fourth lens group substantially consists of a positive fourth-a lens group composed of a biconvex-shape lens, a negative meniscus-shape lens, and a biconvex-shape lens and a negative fourth-b lens group composed of a positive meniscus-shape lens and a biconcave-shape lens in this order from the object side, and only the fourth-b lens group is moved toward the image side while focusing.

Abstract: A zoom lens includes a first lens group, a second lens group, a third lens group and a fourth lens group, all of which are arranged in sequence from an object side to an image side along an optical axis. The first lens group is with positive refractive power. The second lens group is with negative refractive power. The third lens group is with positive refractive power. The fourth lens group is with positive refractive power. The first lens group includes a first lens and a second lens, both of which are arranged in sequence from the object side to the image side along the optical axis, wherein the first lens group and the first lens satisfy the following condition: ?1.2<fG1/f1<?0.58, wherein fG1 is an effective focal length of the first lens group and f1 is an effective focal length of the first lens.

Abstract: The zoom lens substantially consists of a positive first lens group which is fixed while changing magnification, a negative second lens group which moves while changing magnification, a positive third lens group which moves while changing magnification, and a positive fourth lens group which is fixed while changing magnification in this order from the object side. The image formation magnification rates of the second lens group and the third lens group simultaneously pass a ?1× point while changing magnification from the wide angle to the telephoto. The second lens group substantially consists of a negative second-a lens group and a positive second-b lens group which independently move while changing magnification in this order from the object side, and the third lens group substantially consists of a positive third-a lens group and a positive third-b lens group which independently move while changing magnification in this order from the object side.

Abstract: Disclosed is a zoom lens having 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 is changed, a distance between the second lens group G2 and the third lens group G3 is changed, and the fourth lens group G4 is moved toward the object first, then moved toward an image. The third lens group G3 has a first positive lens L31, a negative lens L32 and a second positive lens L33, and the fourth lens group G4 has two lenses: L41 and L42.

Abstract: A zooming optical system has, from the object side, a positive first group, a negative second group, a positive third group, a positive fourth group, and a negative fifth group. During zooming, at least the third to fifth groups move relative to the image plane, and focusing is achieved by moving the fourth group along the optical axis. The conditional formula ?1.0<M5/f5<?0.1 is fulfilled, where M5 is the distance along the optical axis from the position of the fifth group at the wide-angle end to the position of the fifth group at the telephoto end and f5 is the focal length of the fifth group.

Abstract: A zoom lens includes in order from an object 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 positive refractive power which moves during zooming; and a fourth lens unit having a positive refractive power which does not move for zooming, the third lens unit moving to an image side and then to the object side for zooming from a wide angle end to a telephoto end, in which a focal length (f1) of the first lens unit, a focal length (f2) of the second lens unit, a focal length (f3) of the third lens unit, and a lateral magnification (?3w) of the third lens unit at the wide angle end when a ray enters from infinity are appropriately set.

Abstract: A zoom lens comprises a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a rear group including at least two lens units and having a positive refractive power as a whole, in order from an object side to an image side. An interval of each of the lens units changes in a zoom operation, the rear group includes a lens unit R having a positive refractive power at the most image side, the lens unit R includes a lens having a concave surface at the image side and having an aspherical surface shape where a negative refractive power becomes stronger with increasing distance from an optical axis, and focal lengths f1, fR, and fw of the first lens unit, the lens unit R, and a whole system at a wide-angle end, respectively, are appropriately set.

Abstract: A zoom lens includes, in order from an object side toward an image side: a first lens unit having a positive refractive power and provided with a positive lens; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power and provided with a diffraction plane of a diffraction optical element; a fourth lens unit having a positive refractive power to perform focusing; and an aperture stop between the second lens unit and the third lens unit. According to a change of magnification from a short focal end to a long focal end, the first lens unit is stationary, the second lens unit is moved to the image side, the third lens unit is moved to the object side, and the fourth lens unit is moved, and the positive lens satisfies the following condition formulas: 1.45<nd<1.65;??[1] 60.0<?d<95.0; and??[2] 0.005<Pg,F?(?0.001802×?d+0.6483)<0.

Abstract: A zoom lens consists of 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 an object side. When magnification is changed from wide angle end to telephoto end, the first lens group and the third lens group are fixed, and the second lens group moves toward an image side, and the fourth lens group moves. The first lens group consists of a cemented lens of a negative lens and a positive lens, and two positive lenses, which are in this order from the object side. The third lens group consists of a negative partial lens group including a cemented lens, and a positive partial lens group, which are in this order from the object side.

Abstract: A zoom lens, in order from an object side to an image side, includes 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 first lens unit is fixed and at least the second and fourth lens unit are moved during zooming, the third lens unit is configured by a cemented lens formed by cementing a negative lens having a meniscus shape convex towards the object side and a positive lens, the fourth lens unit is configured by a cemented lens formed by cementing a negative lens having a meniscus shape convex towards the object side and a positive lens, and focal lengths f3 and f4 of the third lens unit and the fourth lens unit are appropriately set.

Abstract: A zoom lens includes a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive refractive power, and a fourth lens unit having positive refractive power. During zooming from a wide-angle end to a telephoto end, each lens unit moves so that a distance between the first lens unit and the second lens unit increases, and a distance between the second lens unit and the third lens unit decreases. Each of the first lens unit, the second lens unit, and the third lens unit consists of a single positive lens and a single negative lens, and the fourth lens unit consists of a single positive lens. Focal lengths of the entire zoom lens at the wide-angle end and the telephoto end and focal lengths of the first lens unit and the second lens unit are appropriately set.

Abstract: A zoom lens system includes in order from an object side to an image side a first lens unit having a positive refracting power; a second lens unit having a negative refracting power; a third lens unit having a positive refracting power; and a fourth lens unit having a positive refracting power. At the time of zooming from a wide angle end to a telephoto end, each of distances between the first lens unit and the second lens unit, between the second lens unit and the third lens unit, and between the third lens unit and the fourth lens unit is changed, and the first lens unit is moved. The first lens unit includes a lens component having positive refracting power, a total number of lens components included in the first lens unit is one, and the third lens unit includes five lens elements.

Abstract: A zoom lens comprises a first lens unit G1 having a positive refractive power, a second lens unit G2 having a negative refractive power, and a plurality of lens units G3 and G4. Zooming from a wide angle end to a telephoto end is carried out by changing a distance between the lens units. One of the first lens unit G1 and the second lens unit G2 has, or both the first lens unit G1 and the second lens unit G2 have a specific arrangement.

Abstract: A projection lens, in order along an optical axis from an image formation side to an image source side, includes a first lens, an aperture, a second lens, a third lens, and a fourth lens. The first lens is a meniscus lens with positive refractive power and a convex surface thereof facing the image formation side, and has at least an aspheric surface. The second lens is a biconcave lens with negative refractive power, and has at least an aspheric surface. The third lens is a biconvex lens with positive refractive power, and the fourth lens is a biconvex lens with positive refractive power, and has at least an aspheric surface. Therefore, the projection lens has a small size and high zoom ratio.

Abstract: A zoom lens includes, in order from an object side to an image side thereof, 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. A distance between adjacent ones of the lens units changes during zooming. The first lens unit consists of, in order from the object side to the image side thereof, one negative lens element and one positive lens element. Lengths of travel M1 and M2 of the first lens unit and the second lens unit, respectively, during zooming from a wide-angle end to a telephoto end, focal lengths f1 and f2 of the first lens unit and the second lens unit, respectively, and a zoom ratio Z of the zoom lens are set appropriately.

Abstract: Provided is a zoom lens having, 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 the first lens group (G1), the second lens group (G2) and the third lens group (G3) move along the optical axis for zooming, and the conditional expressions (1) and (2) are satisfied. 8.000<?2T/?2W<12.000??(1) 2.000<?3T/?3W<5.000??(2) where ?2T denotes the lateral magnification of the second lens group (G2) in the telephoto end state, ?2W denotes the lateral magnification of the second lens group (G2) in the wide-angle end state, ?3T denotes the lateral magnification of the third lens group (G3) in the telephoto end state, and ?3W denotes the lateral magnification of the third lens group (G3) in the wide-angle end state.

Abstract: A zoom lens including a first lens group, a second lens group, a third lens group, and a fourth lens group with positive, negative, positive, and positive refractive powers respectively arranged in sequence from an object side to an image side is provided. The first lens group includes a first lens and a second lens. The second lens group includes a third lens, a fourth lens, and a fifth lens. The third lens group includes a sixth lens. The fourth lens group includes a seventh lens, an eighth lens, and a ninth lens. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens respectively having negative, positive, negative, negative, positive, positive, positive, negative, and positive refractive powers are arranged in sequence from the object side to the image side.

Abstract: There is provided a zoom lens including a first focus lens group having negative refractive power and moving in orientation to an image side along an optical axis in focusing from a long distance to a short distance, and a second focus lens group having positive refractive power, the second focus lens group being arranged on a closer side to an image relative to the first focus lens group and moving along the optical axis in focusing. The first and second focus lens groups move in association with each other.

Abstract: A zoom lens comprises in order from an object side a first lens unit having a positive refractive power. The first lens unit consist one positive lens. The zoom lens satisfies the following conditional expressions (1) and (2). Fno(W)<2.7??(1) 3.1<ft/fw where, Fno(W) denotes an F-number of the zoom lens at a wide angle end, ft denotes a focal length at a telephoto end of the overall zoom lens system, and fw denotes a focal length at the wide angle end of the overall zoom lens system.

Abstract: In a zoom lens including a positive first lens unit, negative second lens unit, positive third lens unit, and positive fourth lens unit, the fourth lens unit includes a 41 lens group, a 42 lens group, and a 43 lens group. the lateral magnification of the third lens unit at a wide-angle end when an infinite object is focused, the focal length of the fourth lens unit, the lens configuration length of the fourth lens unit, the air interval between the 41 and 42 lens groups, the air interval between the 42 and 43 lens groups, the focal length of the 42 lens group, the average values of the Abbe constants and partial dispersion ratios of positive lens of the 42 lens group, the average values of the Abbe constants and partial dispersion ratios of negative lenses of the 42 lens group, and the like are appropriately set.

Abstract: A zoom lens includes a first lens unit, a second lens unit, a third lens unit and a fourth lens unit that includes a 41 lens group and a 42 lens group. The 41 lens group includes a 411 lens group and a 412 lens group. A lens surface on a most image side of the 411 lens unit has a shape convex to the image side and a lens surface on the most object side of the 412 lens unit has a shape concave to the object side. A curvature radius r411 of the lens surface on the most image side of the 411 lens unit, a curvature radius r412 of the lens surface on the most object side of the 412 lens unit, and lateral magnification ?3w of the third lens unit at a wide-angle end are respectively appropriately set.

Abstract: A variable focal length lens system including: a first lens group having positive power; a second lens group having negative power; a third lens group having positive power; and a fourth lens group having positive power sequentially arranged from a side where an object is present. An aperture stop is disposed between the second and third lens groups. The first to fourth lens groups are so moved that the distance between the first and second lens groups increases, the distance between the second and third lens groups decreases, and the distance between the third and fourth lens groups decreases when a lens position setting is changed from a wide angle end state to a telescopic end state. The third lens group includes a negative lens and a positive lens disposed on the image side thereof. The variable focal length lens system satisfies the conditional expression, 0.35<f3/|f3a|<0.8.

Abstract: A zoom lens includes a positive first lens group, a negative second lens group, a positive third lens group, and a fourth lens group. The first through third lens groups move such that the distance between the first and second lens groups is greater while the distance between the second lens group and the third lens group is less at the telephoto end compared to the wide angle end, and the fourth lens moves with the third lens group. The third lens group includes a fixed positive subgroup, including at least one positive lens and one negative lens, and a movable subgroup provided toward an image side of the fixed lens group including one negative lens that moves perpendicular to an optical axis to correct an image plane when camera shake occurs. The fourth lens group includes a fixed subgroup and a movable subgroup that moves during focusing operations.

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 real-image variable-magnification viewfinder substantially consists of, in order from the object side: an objective lens system substantially consisting of a positive first lens, a negative second lens, a positive third lens, and a positive fourth lens; an erect optical system formed by a plurality of optical members; and a positive eyepiece lens system. The first lens and the third lens are fixed relative to the optical axis direction during magnification change, and the second lens and the fourth lens are moved in the optical axis direction during magnification change. All optical surfaces of all the optical members forming the erect optical system are planar surfaces. At least one of the optical members forming the erect optical system is made of a glass material. A predetermined 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: A zoom lens includes, in order from an object side to an image side thereof, 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 lens group including one or more lens units. A distance between adjacent ones of the lens units changes during zooming. The second lens unit and the third lens unit each include a resin lens element. A focal length f2p of the resin lens element included in the second lens unit, a focal length f3p of the resin lens element included in the third lens unit, and a focal length ft of the zoom lens at a telephoto end are set to satisfy predetermined mathematical conditions.

Abstract: A zoom lens includes, in order from an enlargement side to a reduction side, a first lens unit having positive refractive power and not moving for zooming, a second lens unit having negative refractive power and moving for zooming, a stop, a zooming lens unit having positive refractive power and moving for zooming, and a final lens unit having positive refractive power and not moving for zooming. During zooming from a wide-angle end to a telephoto end, the second lens unit moves to the reduction side and the zooming lens unit moves to the enlargement side. The zooming lens unit includes a cemented lens. The cemented lens includes a negative lens and a positive lens cemented in order from the enlargement side. A cemented surface of the cemented lens has a convex shape on the enlargement side. The zoom lens satisfies predetermined conditions.

Abstract: A zoom lens including, in order from an object: 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, wherein when f2 denotes a focal length of the second lens group, and fw denotes a focal length of the zoom lens in the wide-angle end state, the following conditional expression being satisfied: 1.90<(?f2)/fw<3.00.

Abstract: A zoom lens includes, in order from an object side to an image side: 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 includes a positive first lens subunit, which does not move for focusing, a positive second lens subunit, which moves during the focus adjustment, and a positive third lens subunit, which does not move for focusing; and focal lengths of the first lens unit, the second lens unit, the third lens unit, a magnification of the third lens unit U3 at a wide angle end, focal lengths of the first lens subunit, the second lens subunit appropriately satisfy certain relations.

Abstract: A zoom lens system including: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group and a fourth lens group having positive refractive power, wherein an interval between the first and second lens groups, an interval between the second and third lens groups, and an interval between the third and fourth lens groups change during zooming from a wide-mode to a tele-mode, wherein the first lens group comprises one negative lens and three positive lenses sequentially from the object to the image, wherein the zoom lens system satisfies an condition below: 0.8<f13/f14<1, and wherein f13 denotes a focal length of a positive lens of the first lens group disposed second from the image to the object, and f14 denotes a focal distance of a positive lens of the first lens group disposed closest to the image.

Abstract: A zoom lens system has, in order from the enlargement side, a first lens group that remains stationary during zooming and that has a negative optical power and a plurality of lens groups that move during zooming. The first lens group includes three lens groups each having a negative optical power, namely a 1a-th lens group, a 1b-th lens group, and a 1c-th lens group. The 1a-th lens group remains stationary during focusing and includes at least one positive lens element. The 1b-th lens group moves toward the reduction side during focusing from infinity to a close distance. The 1c-th lens group moves toward the enlargement side during focusing from infinity to a close distance.

Abstract: A zoom lens includes first to third lens units having positive, negative, and positive refractive power, respectively, and a rear lens group having positive refractive power. An aperture stop is arranged between a lens surface of the second lens unit closest to the image side and a lens surface of the third lens unit closest to the image side. The third lens unit includes first and second positive lenses each including an aspheric surface, and a negative lens. In the third lens unit, a refractive index of the first positive lens, and an Abbe number and relative partial dispersion of the second positive lens are appropriately set.

Abstract: A zoom lens includes a first lens group having a positive refractive power, 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, which are disposed in order from an object side. The first lens group has a negative lens and a positive lens having a convex surface at an object side, which are disposed in order from the object side. An interval between the first lens group and the second lens group is increased and an interval between the second lens group and the third lens group is decreased when changing a magnification of the zoom lens from a wide angle end to a telephoto end. The first lens group and the third lens group are moved from positions at the wide angle end toward positions, which are at object sides thereof, at the telephoto end, respectively.

Abstract: A zoom lens includes, in an order from an object side to an image surface side: a first lens group having positive refractive power and including a negative lens and a positive lens; a second lens group having negative refractive power and including a negative lens having a meniscus shape concave to the image surface side; a third lens group having positive refractive power and including an aspherical lens having at least one aspherical surface; and a fourth lens group having positive refractive power. During zooming from a wide angle position to a telephoto position, the first through fourth lens groups all move, and the third lens group moves from the image surface side to the object side and then back to the image surface side.

Abstract: A zoom lens includes, in order from an object side to an image side, first to fourth lens units having positive, negative, positive and positive refractive powers, respectively. The intervals between adjacent lens units vary during zooming. The first lens is disposed nearer to an object at the telephoto end than at the wide angle end. Each of the first lens unit to the fourth lens unit includes at least one negative lens. The lens total length Lt, the focal length ft, the mean value N2an of the refractive indices of materials of negative lenses of the second lens unit, the mean value NAan of the refractive indices of materials of the negative lenses included in the entire system, and the mean value NAap of the refractive indices of materials of the positive lenses included in the entire system are appropriately configured.

Abstract: A zoom lens including a first lens unit having a positive refractive power, a second lens unit having a negative reflective power, a third lens unit having a positive refractive power, and a rear lens group including one or more lens units in this order from an object side to an image side, wherein distances between the respective lens units vary during the zooming operation, wherein the first lens unit consists of three lenses including one negative lens, and a partial dispersion ratio of a material for the negative lens of the first lens unit, an Abbe number of the same, a focal length of the entire system at a wide angle end and a focal length of the first lens unit are set individually and adequately.

Abstract: An image-forming lens includes, in order from an object side to an image side, a first group having a negative power as a whole, the first group consisting of a positive meniscus lens having a convex surface on the object side and a negative meniscus lens having a convex surface on the object side, the positive meniscus lens and the negative meniscus lens being cemented, an aperture stop, a second group consisting of a positive meniscus lens having a convex surface on the image side, a third group consisting of a positive meniscus lens having a convex surface on the image side, a fourth group consisting of a lens having a negative power, and a fifth group consisting of a biconcave lens.

Abstract: A zoom lens includes a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive refractive power, and a fourth lens unit having positive refractive power, in order from an object side to an image side. During zooming, the first lens unit is not moved, and the second lens unit, the third lens unit, and the fourth lens unit are moved to change an interval between adjacent lens units. A moving amount m2 of the second lens unit during zooming from a wide angle end to a telephoto end, a focal length f2 of the second lens unit, and a focal length fw of a whole system at the wide angle end are each set appropriately.

Abstract: A 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 fourth lens unit having a positive refractive power, and is configured to move the second lens unit, the third lens unit, and the fourth lens unit during a zooming operation to change an interval between adjacent lens units. A moving amount of the second lens unit during a zooming operation from a wide angle end to a telephoto end, a focal length of the second lens unit, and transverse magnification of the third lens unit at the wide angle end and the telephoto end are individually set appropriately.

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. Upon zooming, the distance between the first and second lens groups increases, the distance between the second and third lens groups decreases, and the distance between the third and fourth lens groups increases. The first lens group includes a negative lens element, and two positive lens elements. The absolute value of the radius-of-curvature of the image-side surface of the negative lens element within the first lens group is smaller than the absolute value of the radius-of-curvature of the object-side surface of the positive lens element on the object side within the first lens group. The following condition (1) is satisfied: 1.95<n11??(1), wherein n11 designates the refractive index at the d-line of the negative lens element within the first lens group.

Abstract: An embodiment of this invention provides a zoom lens, which comprises a plurality of lens groups in order from an object side to an image-forming side with positive, negative, positive, and positive refractive power respectively. The lens groups comprise a plurality of aspheric lenses and/or free form lenses and a plurality of plastic lenses. The zoom lens satisfies the following equation: DG/fw<3.5 and TTL/fw<15.5, wherein DG denotes the total summation of the thickness of each lens group, fw denotes the focal length of the zoom lens at the wide-angle end, and TTL denotes a total thickness of the zoom lens at the wide-angle end.

Abstract: A zoom lens includes a positive first lens group, which is fixed during changing magnification and during focusing, a negative second lens group, which is moved during changing magnification, a positive third lens group, which is fixed during changing magnification and during focusing, a positive fourth lens group, which is moved during changing magnification and during focusing, and a negative fifth lens group, which is moved during changing magnification, which are in this order from an object side. A lens group constituting the first lens group consists of a negative front group and a positive rear group in this order from the object side. The second lens group consists of four lenses of a negative lens, a positive lens, a negative lens, and a positive lens or a negative lens arranged in this order from the object side.

Abstract: Wide-angle large-aperture zoom lens provides a field angle greater than 75° at the wide-angle end and a variable magnification power of 2.5 or greater, and can downsize a compensation mechanism for image blur due to hand tremors. The zoom lens includes a first lens group LG1 of positive refractive power, a second lens group LG2 of negative refractive power, a third lens group LG3 of positive refractive power, and a fourth lens group LG4 of positive refractive power, all arranged in sequence from the closest to an object to the closest to an imaging plane, and permits magnification power to vary by varying clearances between adjacent ones of the first lens group LG1 to the fourth lens group LG4. Part of the lens pieces in the third lens group is moved orthogonally to the optical axis to compensate for image blur due to hand tremors.

Abstract: A zoom lens includes in order from an object 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, and at the time of zooming, the first lens unit moves, and the zoom lens satisfies the following conditional expressions (1-1a), (1-2a), and (1-3a). 0.43<(?2T/?2W)/(?3T/?3W)<0.68??(1-1a) 0.4<(?1G/f1)/(?4G/f4)<2.3??(1-2a) 2.1<f3/fW<4.

Abstract: A zoom lens includes a first lens group, a second lens group, a third lens group and a fourth lens group, all of which are arranged in sequence from an object side to an image side along an optical axis. The first lens group is with positive refractive power. The second lens group is with negative refractive power. The third lens group is with positive refractive power. The fourth lens group is with positive refractive power. The first lens group includes a first lens and a second lens, both of which are arranged in sequence from the object side to the image side along the optical axis, wherein the first lens group and the first lens satisfy the following condition: ?1.2<fG1/f1<?0.58, wherein fG1 is an effective focal length of the first lens group and f1 is an effective focal length of the first lens.

Abstract: A zoom lens includes, in order from an object side, a positive first lens unit which does not move for zooming, a negative second lens unit which moves in an optical axis direction for zooming, a negative third lens unit which moves in the optical axis direction for zooming so as to correct image plane variation due to zooming, and a positive fourth lens unit which does not move for zooming. The fourth lens unit includes, in an order from the object side, a positive first sub lens unit and a positive second sub lens unit, which are separated by a largest air interval in the fourth lens unit. Abbe constants, partial dispersion ratios, and coefficients of the refractive index variation due to the temperature variation are appropriately set for lens materials forming the third lens unit, the first sub lens unit, and the second sub lens unit.

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.