Abstract: A zoom lens includes, in order from the object side, a negative first lens group, a positive second lens group and a positive third lens group, wherein, during magnification change from the wide-angle end to the telephoto end, at least the first and second lens groups are moved such that the interval between the first and second lens groups decreases and the interval between the second and third lens groups increases. The first lens group includes a negative meniscus first-group first lens with a convex object-side surface, a negative meniscus first-group second lens with a convex object-side surface, and a positive first-group third lens with a convex object-side surface, and the second lens group includes a positive lens, a cemented lens formed by a positive lens and a negative lens, a positive lens and a negative lens, in order from the object side. The zoom lens satisfies given conditional expressions.

Abstract: A zoom lens includes a front group, an aperture stop, and a rear group. The front group includes a lens unit configured not to move during zooming and a front variable power lens unit including one or more lens units and configured not to move during zooming. The rear group includes, in order from a magnification conjugate side to a reduction conjugate side, a rear variable power lens unit having one or more lens units and configured to move during zooming, and a lens unit configured not to move during zooming. The aperture stop moves during zooming, and the front group has an auxiliary stop which moves during zooming. A length from a focal point position of the front group to the aperture stop, and imaging magnifications of the rear group, at a wide angle end and a telephoto end, are set to adequate values.

Abstract: In a zoom lens, at least a first group of negative optical power and a second group of positive optical power are included from an object side, when zooming is performed from a wide-angle end to a telephoto end, a distance between the first and the second groups is reduced and an aperture is moved together with the second group. The first group is formed with a front group composed of only negative lenses and a rear group which is composed of two lenses, a positive and a negative from the object side and which has a positive optical power as a whole and the zoom lens satisfies a conditional formula: 0.06<T1/Lmax<0.11 (T1 is a distance on an optical axis between the front and rear groups, and Lmax is the maximum total length of the zoom lens in zooming).

Abstract: A zoom lens includes: a first lens group having a negative power; and a second lens group having a refractive power, in this order from an object side. The zoom lens satisfies the following conditional formulae: 1.0<D2g/D1g<1.6, 0.08<D2t/ft<0.19, 1.15?ft/|f1|<1.8, and 1.1<ft/f2<1.9, wherein D1g is the distance from a most object side lens surface to a most image side lens surface within the first group, D2g and D2t are the distance from a most object side lens surface to a most image side lens surface within the second group and the distance between an object side partial second lens group and an image side partial second lens group when focused on infinity at a telephoto end, respectively, ft is the focal length of the entire system at the telephoto end, and f1 and f2 are the focal lengths of the first group and the second group, respectively.

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 in zooming, the first lens unit moves with locus of a convex to the image side and the second lens unit moves to the object side, and the conditions: 0<(DaW?DaT)/TLW<0.26 and 0<TG2G/TGa11<0.4 (DaW: optical axial interval between the first and second lens units at the wide-angle limit, DaT: optical axial interval between the first and second lens units at the telephoto limit, TLW: overall length of the lens system at the wide-angle limit, TG2G: optical axial thickness of the second lens unit, TGall: sum of optical axial thicknesses of the respective lens units) are satisfied.

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 projector for projecting light onto a projection surface includes a first group (1) with a negative meniscus, a second group (2) with positive refractive power, a third group (3) with a single lens, a fourth group (4) with a lens with positive refractive power, and a field lens (5) with positive refractive power, such that the light passes through the projection objective from the fourth to the first group. In order to be provide a high image quality with a small number of optical components and the smallest dimensions, the projector is configured so the common focal width of the fourth group (4) and the field lens (5) is smaller than twice the image circle diameter (9) of the projection objective and the maximum free diameter (8) is smaller than the overall focal width, and in particular smaller than 0.8 times the overall focal width of the projection objective.

Abstract: The zoom lens includes: a positive first lens unit; a positive second lens unit disposed in an image side of the first lens unit, at least a part of the second lens unit constituting an image stabilizing lens unit configured to move with a component perpendicular to an optical axis; the zoom lens being configured to change an interval between neighboring lens units during zooming; and an aperture stop arranged in the image side of the first lens unit, wherein a focal length of the first lens unit, a focal length of the image stabilizing lens unit, a focal length at a wide angle end of an optical system Lr arranged on the image side of the image stabilizing lens unit, and a focal length of an entire system at the wide angle end are appropriately set.

Abstract: A zoom lens includes first to fourth lens groups having negative, positive, negative, and positive refractive power, respectively, and arranged in order from an object side. The first lens group includes negative lenses. The fourth lens group is configured of one positive lens. A zooming operation from wide end to telephoto end allows the first to third lens groups to travel along an optical axis, and allows the fourth lens group to be fixed. A focusing operation allows the third lens group to travel along the optical axis. The conditional expressions 1<(R1a+R1b)/(R1a?R1b)<5 and 2<(R4a+R4b)/(R4a?R4b)<7 are satisfied where R1a and R1b are curvature radii on the object side and on the image side of a most-object-sided negative lens in the first lens group, respectively, and R4a and R4b are curvature radii on the object side and on the image side of the positive lens in the fourth lens group, respectively.

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 second lens unit having a positive refractive power, a focus lens unit having a negative refractive power, configured to move in focusing, and a final lens unit having a positive refractive power, disposed closest to the image side. The focus lens unit and the final lens unit are disposed so as to be adjacent to each other, each lens unit moves so that a distance between adjacent lens units changes in zooming, and a focal length of the final lens unit fimg, a focal length of the focus lens unit ff, and a focal length of an entire system at a wide-angle end fw are appropriately set.

Abstract: A variable-magnification projection optical system substantially consists of a negative first lens group that is disposed at the most enlargement-side position and is fixed during magnification change, a positive last lens group that is disposed at the most reduction-side position and is fixed during magnification change, and a plurality of lens groups that are disposed between the first lens group and last lens group and are moved during magnification change. The lens groups that are moved during magnification change substantially consist of three lens groups, wherein the most enlargement-side lens group is a negative lens group. Predetermined conditional expressions relating to a back focus of the entire system on the reduction side at the wide-angle end, a focal length of the entire system at the wide-angle end, a focal length of the last lens group, and a focal length of the first lens group are satisfied.

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. During zooming from a wide-angle end to a telephoto end, the first lens unit moves with a locus convex toward the image side, and the third lens unit moves toward the object side. The first lens unit includes, in order from the object side to the image side, a negative first lens, a positive second lens, and a positive third lens. A distance (d12) between the first lens and the second lens, a focal length (fw) of the entire zoom lens at the wide-angle end, and a refractive index (Np) of a positive lens having the lowest refractive index among the refractive indices of materials of all positive lenses included in the first lens unit are appropriately set based on predetermined mathematical conditions.

Abstract: A variable-magnification projection optical system substantially consists of a negative first lens group that is disposed at the most enlargement-side position and is fixed during magnification change, a positive last lens group that is disposed at the most reduction-side position and is fixed during magnification change, and a plurality of lens groups that are disposed between the first lens group and last lens group and are moved during magnification change. The most enlargement-side lens group (the second lens group) of the lens groups that are moved during magnification change has a negative refractive power. Predetermined conditional expressions relating to a back focus of the entire system on the reduction side at the wide-angle end, a focal length of the entire system at the wide-angle end, a focal length of the second lens group and a focal length of the last lens group are satisfied.

Abstract: The zoom lens includes, in order from an object side to an image side, a first lens unit having a negative refractive power, a rear unit including one or more lens units, a distance between every adjacent lens units varies during zooming, and an aperture diaphragm on the image side of the first lens unit, a combined focal length of the rear unit at a wide-angle end being positive. One lens unit LG on the object side of the aperture diaphragm is made of a solid material, and includes an optical element GnNL having a negative refractive power and another optical element having a positive refractive power, and the predetermined conditions are satisfied.

Abstract: In a zoom lens, at least a first group of negative optical power and a second group of positive optical power are included from an object side, when zooming is performed from a wide-angle end to a telephoto end, a distance between the first and the second groups is reduced and an aperture is moved together with the second group. The first group is formed with a front group composed of only negative lenses and a rear group which is composed of two lenses, a positive and a negative from the object side and which has a positive optical power as a whole and the zoom lens satisfies a conditional formula: 0.06<T1/Lmax<0.11 (T1 is a distance on an optical axis between the front and rear groups, and Lmax is the maximum total length of the zoom lens in zooming).

Abstract: A zoom lens includes, sequentially from an enlargement conjugate side to a reduction conjugate side: a 1st lens unit having negative refractive power not moved during zooming; plural lens units that are moved during zooming; and a final lens unit having positive refractive power that is not moved during zooming. A final moving lens unit having positive refractive power and disposed nearest to the reduction conjugate side among the plural lens units that are moved during zooming is moved toward the enlargement conjugate side during zooming from a wide angle end to a telephoto end, and the final moving lens unit includes one or more cemented lenses, and the final moving lens unit includes one or more negative lenses and one or more positive lenses. Predetermined conditional expressions are satisfied to maintain wide angle of view and high image quality along the entire zoom range.

Abstract: A zoom lens is provided which has a wide angle of view and is bright and in which the entire lens system is compact and which can achieve high optical characteristic over the entire zoom range.

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: Provided is a zoom lens in which a variation in aberration with respect to a temperature change is small and excellent optical characteristics can be easily obtained. The zoom lens includes multiple lens units in which a distance between adjacent ones of the multiple lens units changes for zooming. When an average value of a change in refractive index with respect to a temperature change within a temperature range of from 0° C. to 40° C. is ?Nav, at least one lens unit L of the multiple lens units includes multiple optical elements A made of materials satisfying a conditional expression: |?Nav|>5.0×10?5. When an anomalous partial dispersion ratio for a g-line and an F-line is ??gF??, at least one optical element A? of the multiple optical elements A satisfies a conditional expression: |??gF??|>0.0272.

Abstract: Provided are a zoom lens and an electronic device including the same. The zoom lens includes, in order from an object side to an image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. When zooming from a wide angle position to a telephoto position, an interval between the first lens group and the second lens group decreases, an 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 increases. The second lens group includes, in a sequence from the object side, a positive lens, a positive lens, a positive lens, and a negative lens.

Abstract: A projection zoom lens in which a magnification change operation is performed by moving three to four lens groups as moving groups, wherein a first lens group, which is a lens group on the most-magnification side, substantially consists of a moving group having a negative refractive power; a lens group on the most-reduction side is composed of a moving group having a positive refractive power; and the first lens group which is the lens group the most-magnification side substantially consists of two lenses. In this case, conditional formula (1) below is satisfied, where fw is the focal length of the entire system at the wide angle end and fm is the focal length of the lens group on the most-magnification side: ?3.5<fm/fw<?1.0??(1). This achieves miniaturization and cost reduction, and corrects various aberrations satisfactorily.

Abstract: A zoom lens includes, in order from the 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. The first lens unit includes a negative lens and a positive lens. The zoom lens satisfies the following conditional expression (1): ?d13/ft<0.4??(1) where ?d13 is the total sum of the thickness of the lenses included in the first to third lens units of the zoom lens on the optical axis, and ft is the focal length of the entire zoom lens system at the telephoto end.

Abstract: A zoom lens for projection substantially consists of a negative first lens group, a positive second lens group, a positive third lens group, a negative fourth lens group, a positive fifth lens group, and a positive sixth lens in this order from a magnification side. The first lens group and the sixth lens group are fixed and the second lens group through the fifth lens group move during magnification change. A reduction side is telecentric. First through fourth lenses from the magnification side in the fifth lens group are a negative meniscus-shaped single lens with its convex surface facing the magnification side, a positive single lens, a biconcave lens and a biconvex lens, respectively, and the biconcave lens and the biconvex lens are cemented together.

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 second lens unit having a positive refractive power, and a third lens unit having a negative refractive power. At the time of zooming, distances between the lens units change, and a distance between the first lens unit and the second lens unit at a telephoto end is shorter than a distance between the first lens unit and the second lens unit at a wide angle end, and an aperture stop is disposed on an image side of an image-side surface of the first lens unit, and on an object side of an image-side surface of the second lens unit, and the zoom lens satisfies the conditional expressions.

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 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 unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power. At the time of zooming, distances between the lens units change, and a distance between the first lens unit and the second lens unit at a telephoto end is shorter than at a wide angle end. An aperture stop is disposed on the image side of an image-side surface of the first lens unit, and on the object side of an image-side surface of the second lens unit. The second lens unit includes two sub lens units. The object-side sub lens unit in the second lens unit includes one lens component. The following conditional expressions are satisfied. 3.0<?D12/ERS<4.5 1.05<|f3/fUN21|<2.

Abstract: A zoom lens system includes a negative first lens group and a positive second 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 first lens group and the second lens group move in the optical axis direction while the distance therebetween mutually decreases. The first lens group includes a negative first sub-lens group and a positive second sub-lens group, in that order from the object side, wherein the second sub-lens group constitutes a focusing lens group that is moved in the optical axis direction during a focusing operation.

Abstract: The imaging lens substantially consists of a negative first lens group in which a biconvex lens, a cemented lens, a plurality of lenses including a positive lens and a negative lens are arranged; a positive second lens group including a cemented lens; a negative third lens group in which a single lens forming a meniscus lens with a convex surface toward the object side or a plurality of lenses constituted in such a manner that the absolute value of the radius of curvature of a lens surface disposed on the most image side is smaller than the absolute value of the radius of curvature of a lens surface disposed on the most object side; and a positive fourth lens group including a positive lens in this order from the object side. This imaging lens is configured in such a manner that conditional expression (1) is satisfied: 0.7<|f3|/f<4.0.

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 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 includes, in order from an object side to an image side: first and second lens units having negative and positive refractive powers, respectively; a middle lens group; and a final lens unit having a positive refractive power, wherein the middle lens group comprises a focus lens unit that has a negative refractive power and moves toward the image side during focusing from infinity to a short distance, the intervals between adjacent lens units vary during at least one of zooming and focusing, and wherein the focal length fimg of the final lens unit, the focal length ff of the focus lens unit, and the focal length fw of the entire system at the wide angle end are appropriately configured.

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 a front unit including one lens unit having a negative refractive power, and a rear unit including an aperture stop and one or more lens units and having a positive refractive power as a whole, and an interval between adjacent lens units changes during zooming such that an interval between the front unit and rear unit decreases at a telephoto end when compared to a wide angle end. The front unit includes a negative lens G11 in a position closest to the object side, and a lens surface of the negative lens G11 on the image side has an aspherical shape by which the positive refractive power increases from a center to an edge. Various parameters for the zoom lens according to the present invention are properly set.

Abstract: A zoom lens includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power and a third lens group having a positive refractive power, wherein, during magnification change from the wide-angle end to the telephoto end, at least the first lens group and the second lens group are moved along the optical axis such that the interval between the first lens group and the second lens group is decreased and the interval between the second lens group and the third lens group is increased. The second lens group includes, in order from the object side, a positive lens, a cemented lens formed by a positive lens and a negative lens, a positive lens and a negative lens. The zoom lens satisfies given conditional expressions.

Abstract: A zoom lens includes, in order from the object side, a negative first lens group, a positive second lens group and a positive third lens group, wherein, during magnification change from the wide-angle end to the telephoto end, at least the first and second lens groups are moved such that the interval between the first and second lens groups decreases and the interval between the second and third lens groups increases. The first lens group includes a negative meniscus first-group first lens with a convex object-side surface, a negative meniscus first-group second lens with a convex object-side surface, and a positive first-group third lens with a convex object-side surface, and the second lens group includes a positive lens, a cemented lens formed by a positive lens and a negative lens, a positive lens and a negative lens, in order from the object side. The zoom lens satisfies given conditional expressions.

Abstract: Provided is a zoom optical system which includes, in order from an object, a first lens group having negative refractive power and other lens groups, and in which an interval between each lens group changes upon zooming, wherein the first lens group includes a first negative lens which is disposed closest to the object and has a diffractive optical element on an image side lens surface, and a positive lens disposed closer to the image than the first negative lens, and the glass material used for the positive lens satisfies the following conditions expressions: ?1p?35 and ?(?g, F)?0.

Abstract: A zoom lens for projection substantially consists of a first lens-group having negative refractive-power, and which is arranged on a most magnification-side, and which is fixed during magnification change, a second lens-group having negative refractive-power, and which is arranged on a reduction-side of the first lens-group, and which is fixed during magnification change, a last lens-group having positive refractive-power, and which is arranged on a most reduction-side, and which is fixed during magnification change, and three lens-groups arranged between the last lens-group and the second lens-group, and which move during magnification change. The zoom lens is configured to be telecentric on a reduction-side, and focusing is performed by moving only the second lens-group.

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

Abstract: A zoom lens system that includes a first lens group including at least one lens and having a negative refractive power, and a second lens group including at least one lens and having a positive refractive power in an order from an object side to an image side, wherein the zoom lens system is configured to perform zooming by changing a distance between the first lens group and the second lens group and satisfies: 2<|f1/fw|<2.5 and 0.60<|f1/f2|<0.85, wherein f1 indicates a synthetic focal length of the first lens group, fw indicates an overall focal length at a wide angle end, and f2 indicates a synthetic focal length of the second lens group.

Abstract: A zoom lens including a plurality of lens units, and two variable stops having an aperture diameter changing for zooming, the lens units being configured to change intervals between the respective neighboring lens units for zooming, the zoom lens having an F-number which is constant over an entire zoom range, the two variable stops including a first variable stop disposed on an object side, and a second variable stop disposed on an image side. A distance (Sw1) from the first variable stop to an image plane at a wide-angle end, a distance (Sw2) from the second variable stop to the image plane at the wide-angle end, and a distance (Tkw) from an exit pupil position to the image plane at the wide-angle end are each set appropriately.

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.