Abstract: A zoom lens for projection substantially consists of a first lens-group having negative refractive power, and a second lens-group through a fifth lens-group having positive refractive power, arranged in this order from a magnification side. The zoom lens is configured to be telecentric on a reduction side. The first lens-group and the fifth lens-group are fixed while the second lens-group through the fourth lens-group move during magnification change. The fourth lens-group includes at least three positive lenses, and a most-magnification-side lens in the fourth lens-group has a convex surface facing the magnification side. Further, when a focal length of an entire system at a wide angle end is fw, and a focal length of the fourth lens-group is f4, and a full angle of view at a wide angle end is 2?, conditional formulas (1) and (7) are satisfied: 7.5<f4/fw<14.5??(1); and 70°?2???(7).

Abstract: Provided are an ocular zoom optical system which has a wide apparent field of view even on a low power side and in which aberrations are favorably corrected while a sufficient eye relief is secured over the entire zoom range, and an optical instrument including the ocular zoom optical system. The ocular zoom optical system 3 includes, in order from the object side: a first lens group G1 having a negative refractive power; a second lens group G2 having a positive refractive power; and a third lens group G3 having a positive refractive power and at least one aspheric surface. An intermediate image I? is formed between the first lens group G1 and the second lens group G2. During zooming, the third lens group G3 is fixed on the optical axis, and the first lens group G1 and the second lens group G2 are moved in directions opposite to each other with the intermediate image I? interposed therebetween.

Abstract: The endoscope objective lens is configured such that focusing from the farthest object to the nearest object is achieved by moving at least one lens group other than the most object-side lens group along the optical axis. One of the at least one lens group to be moved during focusing is a negative lens group. The one negative lens group that is moved during the focusing consists of a cemented lens that is formed by a positive lens and a negative lens cemented together in this order from the object side. The cemented surface of the cemented lens is oriented such that the concave surface faces the object side. Given conditional expressions are satisfied.

Abstract: A variable magnification optical system includes, in order from the object side, a negative first lens group and a positive second lens group, wherein the interval between these lens groups in the optical axis direction is changed during magnification change. The most image-side lens and the second most image-side lens of the first lens group are a negative single lens with a concave surface facing the object side and a positive single lens, respectively. The second lens group includes, in order from the object side, a positive lens disposed at the most object-side position with at least one surface thereof being an aspherical surface, a first cemented lens formed by a negative lens and a positive lens, and a second cemented lens formed by a negative lens and a positive lens.

Abstract: A projection zoom lens has a negative first lens group which is fixed when changing magnification, second through fifth lens groups that move when changing magnification, and a positive sixth lens group which is fixed when changing magnification, in this order from a magnification side. The reduction side is telecentric. When changing magnification from a wide angle end to a telephoto end, the second lens group moves toward the magnification side. The first and second lenses from the reduction side of the fifth lens group are a positive lens and a negative lens, respectively. The sixth lens group is constituted by a single positive lens. The projection zoom lens satisfies a predetermined Conditional Formula.

Abstract: Provided are a variable power optical system in which the value of the entire length with respect to the image height is reduced and the aberration is well corrected, and an image pickup device comprising the same. Specifically provided is a variable power optical system comprising, in order from the object side, at least a first lens group having negative refractive power, a variable power group having positive refractive power, and a final lens group having positive refractive power, wherein the variable power group is provided with, in order from the object side, a first lens element having positive refractive power, a second lens element, and a third lens element, the second lens element has a convex shape on the object side, and the final lens group comprises a positive lens, the variable power optical system satisfying the following conditional expression: 10?VdLg?45 ?1.0<(R2a?R2b)/(R2a+R2b)<1.

Abstract: A zoom lens includes: a first lens group having a negative power; and a second lens group having a positive power, in this order from an object side. The first lens group includes a first lens having a negative power and a second lens having a positive power. The zoom lens satisfies conditional formulae 1.6<|f1|/fw<2.5 (1); 1.6<f2/fw<2.4 (2); 0.32<d2/fw<0.60 (3); 2.5<ft/fw<4.5 (4); 1.56<nd2<1.66 (5); and ?d2<33 (6), when f1: the focal length of the first lens group, f2: the focal length of the second lens group, fw: the focal length of the entire system at the wide angle end, d2: the distance between the first and second lenses along an optical axis, ft: the focal length of the entire system at the telephoto end, nd2: the refractive index of the second lens at the d line, and ?d2: the Abbe's number of the second lens at the d line.

Abstract: A zoom lens system includes, in order from the object side to the image side, a first, a second, and a third lens groups. The first lens group includes, in order from the object side to the image side, a first and a second lenses. The second lens group is capable of floating to realize an image stabilizating function and includes, in order from the object side to the image side, a third to sixth lenses. The zoom lens system satisfies various formulas, including 0.3<d2a/D2<0.4, wherein d2a is the distance between image-side surfaces of the fifth lens and of the sixth lens, and D2 is a width of the second lens group along an optical axis of the zoom lens system.

Abstract: A negative first lens group, a positive second lens group, a negative third lens group, a positive fourth lens group, a negative fifth lens group, and a positive sixth lens group are disposed in this order from the magnification side. The reduction side is made telecentric. While changing magnification, the second lens group through the fifth lens group are moved, and the first lens group and the sixth lens group are fixed. Predetermined conditional expressions are satisfied.

Abstract: A zoom lens comprises, in order from its object side, a first lens unit having a negative refractive power and a second lens unit having a positive refractive power. The first lens unit comprises a first lens having a negative refractive power and a second lens having a positive refractive power. The zoom lens satisfies the following conditional expressions (1), (2), and (3): n1n?1.70??(1), n1p?1.70??(2), and |?1n??1p?31??(3), where n1n is the refractive index of the first lens having a negative refractive power in the first lens unit for the d-line, ?1n is the Abbe constant of the first lens having a negative refractive power in the first lens unit, n1p is the refractive index of the second lens having a positive refractive power in the first lens unit for the d-line, and ?1p is the Abbe constant of the second lens having a positive refractive power in the first lens unit.

Abstract: There is provided a zoom lens including, in order from an object side to an image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power. In zooming from a wide-angle end to a telescopic end, the first lens group moves to the object side in a manner that a distance toward the second lens group shortens, and a distance between the third lens group and the fourth lens group lengthens. The third lens group includes a single lens or a single cemented lens.

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, in order from its object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power. At a time of zooming from the wide angle end to the telephoto end, the lens units move in such a way that the distance between the first lens unit and the second lens unit decreases and the distance between the second lens unit and the third lens unit increases. The zoom lens satisfies the conditions “0.35<|f1|/ft<0.55” and “1.80<Npa”, where ft is the focal length of the entire system at the telephoto end, f1 is the focal length of the first lens unit, and Npa is the average of the refractive indices of the materials of all the positive lenses in the entire system.

Abstract: A zoom lens including, from an object: a front group having negative power; and a rear group having positive power, the rear group including, from the object, a positive lens, a negative lens having a concave surface facing the object, a cemented positive lens constructed by a negative lens and a positive lens, and a cemented lens constructed by a positive lens and a negative lens, the rear group further including a focusing group disposed to the object side of the positive lens La for focusing from infinity to a close object by moving from the object side to an image side, a distance between the front group and the rear group being varied thereby zooming from a wide-angle end state to a telephoto end state, and given condition being satisfied, thereby providing a downsized zoom lens having wide angle of view and excellent optical performance with fewer lenses.

Abstract: A zoom lens includes: a first lens group having a negative refractive power; and a second lens group having a positive refractive power, provided in this order from an object side. Magnification is changed by moving the first lens group and the second lens group. The first lens group includes a first lens having a negative refractive power, a second lens having a positive refractive power, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, provided in this order from the object side. The zoom lens satisfies the following conditional formulae, when fw is the focal length of the entire system at the wide angle end, f1 is the focal length of the first lens group, and f2 is the focal length of the second lens group: 0.00<fw/f2<0.43??(1-5) 0.56<|f1/f2|<2.00??(2-4).

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. The second lens group constitutes a focusing lens group. The following conditions (1) and (2) are satisfied: 0.4<|d12w/f1|<1.06??(1); and d12w<d23w??(2), wherein f1 designates the focal length of the first lens group, and d12w and d23w designate the air distances between the first and second lens groups, and the second and third lens groups respectively, at the short focal length extremity.

Abstract: In a zoom lens in which a first lens group having a negative refractive power and a second lens group having a positive refractive power are disposed in order from the object side and zooming is performed by moving the first lens group and the second lens group, the first lens group is formed of a first lens having a negative refractive power, a second lens having a positive refractive power, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, disposed in order from the object side. Then, when the focal length of the first lens group is taken as f1 and the focal length of the second lens group is taken as f2, the zoom lens is configured to satisfy a conditional expression give below: 0.00<|f1/f2|<1.04??(1-4).

Abstract: A zoom lens includes, in order from the object side to the image side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit including a lens. The distance between the first lens unit and the second lens unit is smaller at the telephoto end than at the wide angle end, and the distance between the second lens unit and the third lens unit changes during zooming from the wide angle end to the telephoto end. The first lens unit consists, in order from the object side, of a front sub lens unit having a negative refractive power, an optical path bending member, and a rear sub lens unit having a positive refractive power. The front sub lens unit includes a biconcave single lens, and the rear sub lens unit includes one or two single lenses.

Abstract: A zoom lens ZL having, in order from an object: a first lens group G1 having negative refractive power; a second lens group G2 having positive refractive power; and a third lens group G3 having positive refractive power, wherein, upon zooming from the wide-angle end state to the telephoto end state, at least the first lens group G1 and the second lens group G2 move along the optical axis so that the distance between the first lens group G1 and the second lens group G2 decreases, and the distance between the second lens group G2 and the third lens group G3 increases, the lens closest to the object in the second lens group G2 is a positive lens, and the object side lens surface of this positive lens is an aspherical surface of which radius of curvature increases in a direction from the optical axis to the periphery of the lens.

Abstract: A zoom lens system comprising a negative first lens unit, a positive second lens unit, a negative third lens unit, and a positive fourth lens unit, wherein the second lens unit is composed of an object-side second lens unit and an image-side second lens unit, the object-side second lens unit has positive optical power, an aperture diaphragm is located between the object-side second lens unit and the image-side second lens unit, and the conditions: ?0.5<f2O/f2I<1.0 and 0.12<d2O/fW<0.35 (f2O: a composite focal length of the object-side second lens unit, f2I: a composite focal length of the image-side second lens unit, d2O: an optical axial distance from a most object side lens surface of the object-side second lens unit to the aperture diaphragm, fW: a focal length of the entire system at a wide-angle limit) are satisfied.

Abstract: A zoom lens includes a first lens group G1 that is negative, a second lens group G2 that is negative, and a third lens group G3 that is positive. The first lens group G1 includes a first lens L1 that is negative and a prism P, and the second lens group G2 includes a second lens L2 that is positive and a third lens L3 that is negative. The third lens group G3 includes a stop ST, a fourth lens L4 that is positive, and a fifth lens L5 that is negative. According to this configuration, upon changing magnification from a wide-angle end to a telephoto end, the first lens group G1 is secured, the second lens group G2 first moves to the image plane side and then moves to the object side, and the third lens group G3 linearly moves to the object side.

Abstract: A zoom lens includes an aperture stop and a plurality of lens units which are moved during zooming. The plurality of lens units includes, on an object side of the aperture stop, a lens unit Lp having a positive refractive power and a lens unit Ln having a negative refractive power which is disposed to be adjacent to an image side of the positive lens unit Lp. At least one of the positive lens unit Lp and the negative lens unit Ln includes two or less lenses which are moved during focusing, and a focal length Fp of the positive lens unit Lp and a focal length Fn of the negative lens unit Ln are appropriately set based on predetermined mathematical conditions.

Abstract: With comprising, in order from an object side: a first lens group G1 having negative refractive power; a second lens group G2; and a third lens group G3, the first lens group G1 includes, in order from the object side, a front group having negative refractive power, and a reflection optical element P that folds an optical path, a position of the first lens group G1 being fixed along the optical axis upon zooming from a wide-angle end state W to a telephoto end state T, and satisfying a given conditional expression, thereby providing a downsized zoom lens having a reflection optical element and a wide angle of view with thinning its profile by means of shortening a distance along an optical axis between the most object side lens surface and an object side optical surface of the reflection optical element.

Abstract: A zoom lens system includes a negative first lens group, positive second and third lens groups, wherein upon zooming from the short to the long focal length extremities, the distance between the first and second lens groups decreases and the distance between the second and third lens groups changes. The second lens group includes a biconvex positive lens element with an aspherical surface on each side, and a negative meniscus lens element with an aspherical surface, and a concave surface on the image side. The following condition (1) is satisfied: 5<m2t/m2w<8??(1), wherein m2t and m2w designate the lateral magnifications of the second lens group at the long and short focal length extremities, respectively, when focused on an object at infinity.

Abstract: A zoom lens includes a first lens group that has a lens having negative refractive power and a light path changing member; a second lens group that includes a lens having positive refractive power and a lens having negative refractive power, and has negative refractive power as a whole; a third lens group that includes a stop, a front group lens having positive refractive power, and a rear group lens having negative refractive power, and has positive refractive power as a whole; and a fourth lens group having positive or negative refractive power. Upon changing magnification from a wide-angle end to a telephoto end, the first lens group and the fourth lens group are fixed. The second lens group moves to the object side after the second lens group moves to an image side, and the third lens group linearly moves to the object side.

Abstract: This invention discloses an optical zoom lens assembly, sequentially arranged from an object side to an image side along an optical axis comprising: a first lens-group, a second lens-group and a third lens-group. The first lens-group with negative refractive power comprises at least one positive lens, and at least one negative lens. The second lens-group with positive refractive power comprises at least one positive lens, and at least one negative lens. The third lens-group with a positive refractive power comprises at least one aspheric lens. Therein, refractive indexes of the first lens-group, the second lens-group and the third lens-group are small than 1.69. Therefore, the present invention can reduce manufacturing costs and provide good image quality to be applied to cameras, cell phone cameras and other devices.

Abstract: Including: a front lens group Gf disposed to an object side of an aperture stop; and a rear lens group Gr disposed to an image side of the aperture stop; the front lens group including a sub-lens group Ga having negative refractive power, the sub-lens group Ga including, in order from the most object side, at least three negative lenses, at least one of the three negative lens being an aspherical negative meniscus lens, the aspherical negative meniscus lens having a shape that negative refractive power is getting smaller from the center to the periphery, a cemented lens constructed by a positive lens, a negative lens, and a positive lens being disposed to the image side of the sub-lens group Ga, and given conditional expressions being satisfied, thereby providing a wide-angle lens having high optical performance with a wide angle of view.

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 positive first lens group that is fixed during magnification change, a negative second lens group that is movable during magnification change, a positive third lens group that is movable during magnification change, a positive fourth lens group that is movable during magnification change, and a positive fifth lens group that is fixed during magnification change are arranged in this order from the enlargement side. The system is telecentric at the reduction side. Conditional expression (1) is satisfied: L/Im?<15.0??(1), where L is a distance along the optical axis from the most enlargement-side lens surface to the most reduction-side lens surface when the projection distance is infinity, and Im? is a maximum effective image circle diameter at the reduction side.

Abstract: A zoom lens system includes a negative first lens group, positive second and third lens groups, wherein 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 changes. The second lens group includes a biconvex positive lens element with an aspherical surface on each side, and a negative meniscus lens element with an aspherical surface, and a concave surface on the image side. Conditions (1) and (2) are satisfied: ?d>80??(1), and Pg—F>0.53??(2), wherein ?d designates the Abbe number at the d-line of the biconvex positive lens element within the second lens group, and Pg_F designates the partial dispersion ratio of the biconvex positive lens element within the second lens group.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit of a negative refractive power, a second lens unit of a positive refractive power, and a third lens unit of a positive refractive power, an interval between the first lens unit and the second lens unit and an interval between the second lens unit and the third lens unit being configured to change in zooming from a wide angle end to a telephoto end. The first lens unit includes, in order from the object side to the image side, a negative lens and a positive lens. The predetermined conditions are satisfied.

Abstract: An embodiment of this invention provides a zoom lens, which comprises, 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 a third lens group having positive refractive power. Further, the zoom lens satisfies the following conditions: (1) DG1/fw>0.72; (2) DG2/fw<0.72; and (3) TTL/fw<7.0, wherein fw is the focal length of the optical zoom lens at a wide-angle end, DG1 is the thickness of the first lens group, DG2 is the thickness of the second lens group, and TTL is the total thickness of the zoom lens, i.e., the distance between the object side of the first lens group and an image-forming plane of the zoom lens.

Abstract: A zoom lens includes: a first lens group having negative refractive power; a diaphragm; a second lens group having positive refractive power; a third lens group having negative refractive power; and a fourth lens group having positive refractive power, arranged in order from an object side. The first lens group is configured by at least one negative lens and one positive lens. The third lens group is configured by one negative lens. Then power is changed from a wide angle end state to a telephoto end state, the first, second, and third lens groups are moved in the direction of an optical axis, and the fourth lens group is fixed. When focusing, the third lens group is moved in the direction of the optical axis so as to satisfy the following Conditional Equations, ?2.8<f3/fw<?0.5??(1) 2.0<f4/fw<15.0??(2).

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a negative refractive power, a rear lens group having a positive refractive power as a whole and including at least one lens unit. An interval between the first lens unit and the rear lens group at the telephoto end is smaller than that at the wide angle end. The first lens unit includes a first aspheric lens having a positive aspheric amount, and a second aspheric lens having a negative aspheric amount on the image side of the first aspheric lens. The predetermined conditional expressions are satisfied.

Abstract: A zoom lens includes, in order from the object side to the image side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit including a lens. The distance between the first lens unit and the second lens unit is smaller at the telephoto end than at the wide angle end, and the distance between the second lens unit and the third lens unit changes during zooming from the wide angle end to the telephoto end. The first lens unit consists, in order from the object side, of a front sub lens unit having a negative refractive power, an optical path bending member, and a rear sub lens unit having a positive refractive power. The front sub lens unit includes a biconcave single lens, and the rear sub lens unit includes one or two single lenses.

Abstract: A zoom lens has a plurality of lens units including, in order from its object side to image side, a first lens unit having a negative refracting power composed of two lens elements including a biconcave negative lens and a positive lens, and a second lens unit having a positive refracting power composed of four lens elements including a positive lens and a negative lens. During zooming from the wide angle end to the telephoto end, a distance between the lens units changes, and the second lens unit moves toward the object side. The zoom lens has an aperture stop that moves integrally with the second lens during the zooming and satisfies a specific condition.

Abstract: A zoom lens system comprising: a first lens unit having negative optical power; a second lens unit; and at least one subsequent lens unit, wherein in zooming, the first lens unit moves along an optical axis, and at least an interval between the second lens unit and a lens unit which is one of the at least one subsequent lens unit varies, in focusing, an interval between the first lens unit and the second lens unit varies, at least one aspheric surface is included in the at least one subsequent lens unit, and the condition: 0.1<d1W/d2W<0.4 (d1W, d2W: an air space between the first lens unit and the second lens unit, an air space between the second lens unit and the lens unit which is one of the at least one subsequent lens unit and is located closest to the object side, at a wide-angle limit, in an infinity in-focus condition) is satisfied; an interchangeable lens apparatus; and a camera system are provided.

Abstract: A projection lens system includes, in order from a screen-side to an SLM-side thereof, a first lens group of negative refractive power which includes a first lens, and a second lens group of positive refractive power. The second lens group includes a second to fifth lenses in order from the screen-side to the SLM-side of the projection lens system. The projection lens system satisfies the following condition formulas: 1.95<|F1/Fw|<2.15, 0.5<|f4/Fw|<0.7, and 1.05<|f5/Fw|<1.25, where F1 is the effective focal length of the first lens group, f4 is the focal length of the fourth lens, and f5 is the focal length of the fifth lens, Fw is the effective focal length of the projection lens system which is in the wide-angle state.

Abstract: A zoom lens comprising, in order from an object side to an image side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power. The second and third lens units are configured to move in an optical axis direction for a magnification variation, and the first lens unit is configured to move in the optical axis direction to reduce an image-plane fluctuation associated with the magnification variation. Expressions ?0.83?f1/f2??0.40 and ?4.6?f1/fw??2.5 T are satisfied where f1 is a focal length of the first lens unit, f2 is a focal length of the second lens unit, and fw is a focal length of the entire zoom lens at a wide angle end.

Abstract: A variable power optical system includes, in order from the object side, a first lens group having negative refractive power, a variable power group having positive refractive power, and a final lens group having positive refractive power. The variable power group is provided with, in order from the object side, a first lens element having positive refractive power, a second lens element, and a third lens element. The second lens element has a convex shape on the object side. The final lens group includes a positive lens. The variable power optical system satisfies the following conditions: 10?VdLg?45 ?1.0<(R2a?R2b)/(R2a+R2b)<1.0 where VdLg is the Abbe number of the positive lens of the final lens group with respect to the d line, R2a is the curvature radius of the object-side surface of the second lens element, and R2b is the curvature radius of the image-side surface of the third lens element.

Abstract: A zoom lens system of the present invention has a plurality of lens units each composed of at least one lens element and, in order from the object side to the image side, comprises: a first lens unit having negative optical power and composed of two lens elements; a second lens unit having positive optical power; and a third lens unit having positive optical power, wherein in zooming, the lens units are moved such that an interval between the first lens unit and the second lens unit should decrease and that an interval between the second lens unit and the third lens unit should increase, so that magnification change is achieved, and wherein the condition is satisfied: 2.50<tan(?W)×Z<6.00 where, Z=fT/fW>4.0, ?W>35, fT, fW: focal lengths of the entire system at a telephoto limit, a wide-angle limit, ?W: a half value of maximum view angle at a wide-angle limit.

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 focal length extremity to the long focal length extremity, 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. The second sub-lens group is a negative single lens element serving as an image-stabilizer lens group which moves in directions orthogonal to the optical axis to change the imaging position to correct image shake.

Abstract: A zoom lens system includes, from the object-side to the image-side thereof, a first lens group, a second lens group, and a third lens group. The first lens group includes a first lens and a second lens. The second lens includes a third lens, a fourth lens, and a fifth lens. The fourth lens and the fifth lens are attached to each other. The third lens group includes a sixth lens. The zoom lens system satisfies the following conditions: 0.35<f2/f3<0.7; 1.8<|f45/Fw|<3; 0.5<|f1|/Ft<0.9; 0.7<f3/Ft<1.2, wherein: f1 is a focal length of the first lens; f2 is a focal length of the second lens; f45 is a focal length of the attached fourth lens and fifth lens; Fw is a focal length of the zoom lens system at a wide-angle end; Ft is a focal length of the zoom lens system in a telephoto state.

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: This invention provides an imaging lens system including, in order from an object side to an image side: a first lens group with negative refractive power comprising a single first lens element with negative refractive power; a second lens group with positive refractive power comprising, in order from the object side to the image side: a second lens element with positive refractive power; a third lens element with negative refractive power; an aperture stop; and a fourth lens element with negative refractive power; and a third lens group with positive refractive power comprising a single fifth lens element with positive refractive power; wherein by moving the first lens group and the second lens group along the optical axis while keeping the third lens group stationary, the zooming operation is performed such that the system switches between a wide-angle mode and a telephoto mode.

Abstract: A zoom projection lens includes a first lens set and a second lens set arranged in sequence from an object side to an image side of the zoom projection lens. The first lens set has a negative optical power. The second lens set has a positive optical power. The first lens set has a first lens. The second lens set has a second lens, a third lens, a fourth lens, and an aperture stop disposed between the second lens and the third lens. The first lens is an aspherical plastic lens. One of the third and fourth lenses is an aspherical glass lens. The zoom projection lens satisfies: 1.463<|tt/lt|<1.505, in which, tt represents an overall length of the zoom projection lens, and lt represents a length of the zoom projection lens from the object side of the first lens to an image side of the fourth lens.

Abstract: A wide-angle zoom lens system includes a first lens group with negative refraction power, a second lens group with positive refraction power, and a third lens group with positive refraction power. The first lens group, the second lens group, and the third lens group move along an optical axis of the zoom lens system in focusing. The wide-angle zoom lens system satisfies the formulas: 0.77<|f2/f1|<1.1; and 0.7<L2/fT<1.08; wherein f1 is the effective focal length of the first lens group, f2 is the effective focal length of the second lens group, L2 is a distance of the second lens group moving from a wide-angle state to a telephoto state, and fT is the effective focal length of the wide-angle zoom lens system in the telephoto state.

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 focal length extremity to the long focal length extremity, the distance between the first lens group and the second lens group is decreased, and the distance between the second lens group and the third lens group is decreased. A reflection prism having a negative refractive power is provided between the third lens group and the imaging plane, and wherein the following condition (1) is satisfied: P2?d<32??(1), wherein P2?d designates the Abbe number with respect to the d-line of the reflection prism, which is provided between the third lens group and the imaging plane.

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 ZL comprising a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having positive refractive power, wherein the first lens group G1 includes a first lens having negative refractive power and a second lens which is a plastic lens having positive refractive power, the second lens group G2 includes a third lens having positive refractive power, a fourth lens having positive refractive power and a fifth lens having negative refractive power, the third lens group G3 includes a sixth lens having positive refractive power, and the conditional expressions: 1.50<(?f1)/fw<2.52, 0.4<(?f1)/fL2 <0.8, n2×n2×?2<77.0 are satisfied respectively.