Abstract: A zoom lens having, in order from the 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 the second lens group G2 is constituted only by three or more cemented lenses.

Abstract: A retrofocus wide-angle lens system is provided, wherein the entire the wide-angle lens system is divided at a position that satisfies the following condition (1) between a theoretical front lens group having a negative refractive power, and a theoretical rear lens group having a positive refractive power including the diaphragm, at a minimum focal length, and wherein a flat parallel plate is disposed at the position that satisfies the following condition (1): 1.2<|fF/f|<4.0??(1), wherein fF designates the focal length of the theoretical front lens group having a negative refractive power, and f designates the focal length of the entire the wide-angle lens system.

Abstract: A zoom lens system, in order from an object side to an image side, comprising a first lens unit having negative optical power and at least one subsequent lens unit, wherein a second lens unit is located closest to the object side in the subsequent lens units, an interval between the first lens unit and a lens unit which is one of the at least one subsequent lens unit varies in zooming, the condition: LT/HT<13.6 (LT is an overall length of lens system at a telephoto limit, HT is an image height at a telephoto limit) is satisfied, and at least one lens element in the second lens unit satisfies the conditions: vd<40, and 0.0002122×vd2?0.01687×vd+1.8157?nd>0 (1.40?nd<1.67) or 0.001181×vd2?0.07563×vd+2.873?nd>0 (1.67?nd<2.50) (vd is an Abbe number to the d-line of the lens element constituting the second lens unit, nd is a refractive index to the d-line of the lens element constituting the second lens unit); an imaging device; and a camera are provided.

Abstract: A zoom lens system comprising, in order from an object side: a first lens group G1 having negative refractive power; and a second lens group G2 having positive refractive power, a distance between the first lens group and the second lens group varying upon zooming from a wide-angle end state to a telephoto end state, the first lens group G1 including, in order from the object side, a first lens component having negative refractive power, a second lens component having negative refractive power, a third lens component having positive refractive power, and a fourth lens component having positive refractive power, thereby providing a downsized zoom lens system having excellent optical performance, an optical apparatus equipped therewith and a method for manufacturing the zoom lens system.

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 zoom lens includes, sequentially from an object side, a first lens group having a negative refractive power; and a second lens group having a positive refractive power, where focal length is varied by changing a distance between the first lens group and the second lens group, and a first conditional expression 0.8<|f1/f2|<1.0 is satisfied, f1 being the focal length of the first lens group and f2 being the focal length of the second lens group.

Abstract: Provided is a zoom lens system including a compact focusing lens unit and having a suppressed change in image magnification at the time of movement of the focusing lens unit. A zoom lens system of the present invention, in order from an object side to an image side, includes, a first lens unit G1 having negative optical power, a second lens unit G2 having positive optical power, a third lens unit G3 having positive optical power, and a fourth lens G4. Condition (10): 1.4<DL/YM<2.5 and condition (11): 1.2<BFW/YM<1.6 are satisfied (where, 100<2?W<140, DL is an effective diameter of the lens surface closest to the image side, BFW is the back focus at a wide-angle limit, YM is the maximum image height at a wide-angle limit, and ?W is a half view angle (°) at a wide-angle limit).

Abstract: A zoom lens for projection includes a negative first group composed of two lenses, a second group composed of a positive lens, an aperture stop, a third group composed of a positive lens, a fourth group composed of a negative fourth-group-first lens, a fourth-group-second lens arranged in such a manner that a negative air lens is formed between the fourth-group-first lens and the fourth-group-second lens, and a positive fourth-group-third lens, and a fifth group composed of a positive lens having a convex surface facing the magnification side of the zoom lens, which are arranged in this order from the magnification side. Further, the following formula (1) is satisfied: ?0.6<(R72+R71)/(R72?R71)<0.6??(1), where R71 is a radius of curvature of a magnification-side surface of the fourth-group-third lens, and R72 is a radius of curvature of a reduction-side surface of the fourth-group-third lens.

Abstract: A zoom lens for projection includes a negative magnification-side lens group fixed while magnification is changed, a plurality of lens groups that move while magnification is changed, and a positive reduction-side lens group fixed while magnification is changed which are arranged in this order from the magnification side. The magnification-side lens group is composed of a negative front-group and a positive rear-group, arranged in this order from the magnification side. The rear-group is composed of a positive lens, a negative lens and a positive lens, arranged in this order from the magnification side, and focusing is performed by moving the rear-group. Further, the following formulas (1) and (2) are satisfied: 1.73<NdRpAVE??(1); and 60<?dRn??(2), where NdRpAVE is an average value of refractive indices of the positive lenses in the rear-group, and ?dRn is the Abbe number of the negative lens in the rear-group.

Abstract: A variable power optical system is provided and includes: in order from the object side, a first lens group having a negative refractive power and including a negative lens group and a positive lens group; a stop; and a second lens group having a positive refractive power and including a sub-lens group on the most object side, the sub-lens group including a first lens having a positive refractive power having at least one aspherical surface, a second lens having a positive refractive power, and a third lens having a positive refractive power. The second lens group is moved to the object side along an optical axis thereof to perform a variable power operation from a wide angle end to a telephoto end of the variable power optical system, and the first lens group is moved to make a correction of an image plane position in accordance with the variable power operation.

Abstract: A variable magnification optical system includes a negative first lens group, a stop and a positive second lens group, arranged from the object side in the order mentioned above. The magnification of the variable magnification optical system is changed by changing a distance between the first lens group and the second lens group in the direction of an optical axis. The first lens group includes a negative plastic lens, and the second lens group includes a positive plastic lens. Further, the following formulas (1) and (2) are satisfied: 5.0<fpp/fw<7.5??(1); and ?7.0<fpn/fw<?6.0??(2), where fpn is the focal length of the plastic lens having negative refractive power, fpp is the focal length of the plastic lens having positive refractive power, and fw is the focal length of the entire system of the variable magnification optical system at a wide angle end.

Abstract: A zoom lens for projection includes a negative first lens group, a positive second lens group, a positive third lens group, and a positive fourth lens group, which are arranged from the magnification side of the zoom lens in the order mentioned above. The first lens group and the fourth lens group are fixed during zooming, but the second lens group and the third lens group move on optical axis Z of the zoom lens toward the magnification side, based on an operation for operating the zoom lens from wide end to tele end, in such a manner that a distance between the second lens group and the third lens group changes. Further, the following formula (1) is satisfied: 17<FG3/fw??(1), where FG3 focal length of the third lens group, and fw: focal length of entire system at wide end.

Abstract: A zoom lens includes a first lens unit with a negative refractive power, a second lens unit with a positive refractive power, and a third lens unit with a positive refractive power in order from the object side to the image side. The first lens unit includes a negative lens and a positive lens. When the curvature radius of the object side surface and that of the image side surface of the negative lens are respectively defined as R11 and R12 and the curvature radius of the object side surface and that of the image side surface of the positive lens are respectively defined as R21 and R22, the following conditional expression is satisfied: ?5.6<(R12+R21)/(R12?R21)<?4.7 and 1.5<(R11+R22)/(R11?R22)<2.3.

Abstract: A compact wide-angle zoom lens and an image pickup device having the same. The zoom lens includes a first lens group having a negative refractive power and a second lens group having a positive refractive power in an order from an object side to an image side, performs zooming by varying a distance between the first and second lens groups, and performs focusing by using a first lens closest to the object side in the second lens group.

Abstract: In a zoom lens ZL1 having a plurality of lens groups G1 to G2 which are disposed in order from an object, where a refractive index average value of the lens components which constitute the zoom lens ZL1 is defined as ndav and a refractive index average value of the lens components which constitute the first lens group G1 which is disposed to closest to the object among the plurality of lens groups G1 to G2 is defined as ndGlav, the zoom lens ZL1 is constituted to satisfy the conditional expression ndav?1.80 and to satisfy the conditional expression ndGlav?1.85.

Abstract: A variable magnification optical system for projection includes a first-lens-group having negative refractive power, and which is fixed when magnification of the variable magnification optical system is changed, a second-lens-group having negative refractive power, and which is movable when magnification of the variable magnification optical system is changed, a third-lens-group having positive refractive power, and which is movable when magnification of the variable magnification optical system is changed, and a fourth-lens-group having positive refractive power, and which is fixed when magnification of the variable magnification optical system is changed, which are arranged from the magnification side of the variable magnification optical system in the order mentioned above. The reduction side of the variable magnification optical system is telecentric, and formula (11) is satisfied: 1.

Abstract: On condition that a first lens group adopts at least one plastic lens; a second lens group adopts at least any two adjacent plastic lenses; the first lens group monotonously moves from an object side to an image plane side in a zooming; the second lens group monotonously moves from the image plane side to the object side; wherein fw/fpi represents a ratio of refractive power of the entire system achieved at a wide angle end to refractive power of the respective lenses; P1 represents a total of fw/fpi of the plastic lenses of the first lens group; and P2 represents a total of fw/fpi of the plastic lenses of the second lens group, the following conditional expressions ?0.22<P1<?0.01 and ?0.15<P2<?0.03, are both fulfilled.

Abstract: An imaging lens SL mounted in a digital single lens reflex camera 1 is composed of, in order from an object side, 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 focusing on a near-distance object point from an infinite-distance object point, at least one of the first lens group G1 and the second lens group G2 is moved so as to change a distance between the first lens group G1 and the second lens group G2, and the imaging lens satisfies a given conditional expression, thereby providing a downsized imaging lens suited to an imaging apparatus such as a single lens reflex camera, having a less of change in overall length and optimal to driving an intra-lens-barrel motor.

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: 1.5<LT/(Ir×Z)<2.6 where, Z=fT/fW>4.

Abstract: A zoom lens including a first lens group and a second lens group arranged in sequence from a magnified side toward a reduced side is provided. The first lens group has a negative refractive power and includes a first lens, a second lens, a third lens, and a fourth lens arranged in sequence from the magnified side toward the reduced side, of which the refractive powers are respectively positive, negative, negative, and positive. The second lens group has a positive refractive power and includes a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a tenth lens, and an eleventh lens arranged in sequence from the magnified side toward the reduced side, of which the refractive powers are respectively positive, negative, positive, negative, positive, negative, and positive. The eighth lens, the ninth lens, and the tenth lens together form a triple cemented lens.

Abstract: Providing a zoom lens system having excellent optical performance with a high zoom ratio, an imaging apparatus, and a method for zooming the zoom lens system. The system including, in order from an object, a first group G1 having negative refractive power, a second group G2 having positive refractive power, a third group G3 having negative refractive power, and a fourth group G4 having positive refractive power. An aperture stop S is disposed between the second group G2 and the fourth group G4. Upon zooming from a wide-angle end state to a telephoto end state, each group is moved such that a distance between the second group G2 and the third group G3 increases, a distance between the third group G3 and the fourth group G4 decreases, and the aperture stop S is moved together with the third group G3. Given conditions are satisfied.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group, in this order from the object. Each of the negative first lens group, the positive second lens group and the positive third lens group moves along the optical axis upon zooming. The positive second lens group includes a positive first lens element, a negative second lens element, and a negative third lens element, in this order from the object. The zoom lens system satisfies the following conditions: 2<f2/rb<3??(1) 0.4<f2/f3<0.8??(2) wherein f2 designates the focal length of the positive second lens group; f3 designates the focal length of the positive third lens group; and rb designates the radius of curvature of the image-side surface of the negative third lens element of the positive second lens group.

Abstract: Provided is a zoom lens in which both higher-order components of distortion and lateral chromatic aberration are corrected in a retrofocus type optical system. The zoom lens includes, in order from a magnifying side, a first lens unit which is negative, a second lens unit which is positive, and a rear lens group which is positive. A solid material having high dispersion and high extraordinary dispersion is used for a negative lens included in the first lens unit to provide a suitable shape and refractive power.

Abstract: A zoom lens includes: first, second and third lens groups having negative refracting power, positive refracting power and positive refracting power, respectively, disposed in the order from an object side. During zooming from a wide angle end to a telephoto end, the first lens group is moved and the second lens group is moved together with a stop toward the object such that an air space between the first and second lens groups decreases and an air space between the second and third lens groups increases. The second lens group includes positive and negative lenses aspherically shaped on at least a side thereof facing the object and having a convex or concave surface facing the object, the negative lens being positioned on the image side of the positive lens. The zoom lens is configured to satisfy the following Conditional Expressions (1) and (2) 0.7<R2f/R2r<2.0??(1) 1.0<|Sga/Sgs|<1.5??(2).

Abstract: The invention relates to an eyepiece optical system that, albeit being of small size, works in favor of gaining an angle of field and optical performance, and an electronic view finder incorporating such an eyepiece optical system. Specifically, the invention is characterized by comprising, in order from an object side to an exit side thereof, a first lens group that is a single lens that has positive refracting power and is in a meniscus configuration concave on its object side, a second lens group that is a single lens that has negative refracting power and is in a meniscus configuration concave on its object side, and a third lens group that is a single lens that has positive refracting power, wherein an object-side concave lens surface in the first lens group is an aspheric surface, an object-side concave lens surface in the second lens group is an aspheric surface, and an exit-side lens surface in the third lens group is an aspheric surface.

Abstract: A zoom lens having less distortion and exhibiting good imaging performance is provided. A zoom lens includes a first lens unit provided at the extremity of an enlargement conjugate side and having a negative refractive power, and a final lens unit provided at the extremity of a reduction conjugate side and having a positive refractive power. The final lens unit includes a cemented lens at the extremity of the reduction conjugate side. The cemented lens has a positive refractive power. The zoom lens satisfies specific conditional expressions.

Abstract: A zoom lens system ZL mounted in an electronic still camera 1 etc is constructed to include, in order from an object side, a first lens group G1 having negative refractive power and a second lens group G2 having positive refractive power, in which the second lens group G2 has two cemented lenses. A distance between the first lens group G1 and the second lens group G2 changes when a lens position state changes from a wide-angle end state to a telephoto end state, thereby providing the zoom lens system exhibiting preferable optical performance, an optical apparatus including the zoom lens system and a magnification varying method using the zoom lens system.

Abstract: A zoom lens includes, in order from an object side along an optical axis: 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. Upon zooming from a wide-angle end state to a telephoto end state, a distance between the first lens group G1 and the second lens group G2 varies, and a distance between the second lens group G2 and the third lens group G3 varies, and a given conditional expression is satisfied.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit of negative refractive power, a second lens unit of positive refractive power, and a third lens unit of positive refractive power. The zoom lens changes the distances between the lens units during zooming. The following condition is satisfied: 0.3<|f1/fT<0.5 2.3<|f1/fw<3.5, where f1 is a focal length of the first lens unit, fT is a focal length of the zoom lens at a telephoto end, and fw is a focal length of the zoom lens at a wide-angle end.

Abstract: A zoom lens system ZL installed in an electronic still camera 1 and the like comprising, in order from an object side: a first lens group G1 having negative refractive power; and a second lens group G2 having positive refractive power; the second lens group including at least two cemented lenses each of which includes a positive lens disposed to the object side and a negative lens disposed to an image side, a distance between the first lens group and the second lens group varying upon zooming from a wide-angle end state to a telephoto end state, thereby providing a zoom lens system having excellent optical performance, an optical apparatus equipped with the zoom lens system, and a method for manufacturing the zoom lens system.

Abstract: A zoom lens includes: first, second and third lens groups having negative refracting power, positive refracting power and positive refracting power, respectively, disposed in the order listed from an object side to an image side, wherein during zooming from a wide angle end to a telephoto end, the first lens group is moved and the second lens group is moved toward the object such that an air space between the first and second lens groups decreases and an air space between the second and third lens groups increases; and the first lens group is formed by first and second lenses, the first and second lenses being disposed in the order listed from the object side to the image side, and the zoom lens satisfying the following Conditional Expressions (1) and (2) nd12>2.0??(1) ?d12<21.6??(2).

Abstract: Disclosed herein is a zoom lens formed by arranging 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 in order from an object side to an image side, wherein at a time of varying power from a wide-angle end to a telephoto end, the first lens group is moved, and the second lens group is moved to the object side such that an air interval between the first lens group and the second lens group is decreased and such that an air interval between the second lens group and the third lens group is increased.

Abstract: A projection lens includes a first lens group with a negative refractive power, a second lens group with a negative refractive power, and a third lens group with a positive refractive power, wherein the second lens group is disposed between the first lens group and the third lens group. The first lens group includes an aspheric lens. The second lens group includes a first lens and a second lens. The third lens group includes a third lens, a forth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, and a twelfth lens.

Abstract: A zoom lens system comprising a first lens unit having negative power, a second lens unit having positive power and a third lens unit having positive power, wherein: the first lens unit comprises a first lens element having a concave surface at least on the image side and negative power and a second lens element having a convex surface at least on the object side and positive power; the second lens unit comprises a cemented lens element fabricated by two lens elements having optical power of mutually different signs and one single lens element; in zooming, all of the lens units move along an optical axis; and conditions (1): 5.0<?iW<20.0 and (I-2): n11?1.9 (where, 3.

Abstract: A zoom lens includes a first lens group and a second lens group disposed between the first lens group and an image side. The first lens group has three lenses. Refractive powers of the three lenses arranged from an object side to the image side are respectively negative, negative, and positive. The second lens group has five lenses. Refractive powers of the five lenses arranged from the object side to the image side are respectively positive, negative, positive, negative, and positive. Effective focal lengths (EFL) of the first and the second groups are respectively f1 and f2. The EFL of the zoom lens is fw when the zoom lens is switched to a wide end. The zoom lens satisfies ?2.8<f1/fw<?2.5 and 0.75<|f1/f2|<0.9.

Abstract: In a zoom lens for projection, a lens group arranged farthest to the reduction side is fixed when the magnification of the zoom lens is changed, and is composed of a negative aspheric lens made of a plastic material having at least one aspheric surface and a positive lens. At least one positive lens arranged on the reduction side of a lens having the smallest effective diameter among lenses composing the zoom lens satisfies the following formula (1): ?a>80(here,(dn/dt)<0)??(1), where ?a: Abbe number of a material forming the at least one positive lens for d-line, and dn/dt: a change in the refractive index of the material forming the at least one positive lens for d-line when temperature changes from 20° C.

Abstract: A three-lens group zoom lens in an N-P-P configuration; the first, second, and third lens groups are arranged sequentially from an object side to an image side; during zooming from a wide-angle to a telephoto position the distance between the first lens group and the second lens group is reduced and the distance between the second lens group and the third lens group is changed, and the zoom lens satisfies the following inequalities ?1.3<f1/f2<?1.0 1.6<f2/fw<2.3 4.5<f3/fw<5.2, where, f1, f2, and f3, respectively, denote the focal lengths of the first, second and third lens groups, and fw denotes the focal length of the overall zoom lens at the wide-angle position.

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 third lens unit having a negative refractive power, and a fourth lens unit having a positive refractive power. In the zoom lens, an interval between every adjacent ones of the first through fourth lens units varies during zooming, the second lens unit includes at least one negative lens, and the third lens unit includes at least one positive lens. An Abbe number and a relative partial dispersion of a material of the at least one negative lens (?d2N, ?gF2N) and an Abbe number and a relative partial dispersion of a material of the at least one positive lens (?d3P, ?gF3P) are appropriately set.

Abstract: A variable power optical system is provided and includes: in order from the object side, a first lens group having a negative refractive power and including a negative lens group and a positive lens group; a stop; and a second lens group having a positive refractive power and includes a sub-lens group having a positive refractive power as a whole and arranged on the most object side, the sub-lens group including a first lens having a positive refractive power having at least one aspherical surface, a second lens having a negative refractive power, and a third lens having a positive refractive power. The second lens group is moved to the object side along an optical axis to perform a variable power operation from the wide angle end to the telephoto end with moving the first lens group to make a correction of an image plane position.

Abstract: An image forming optical system according to the present invention is characterized in that, in an image forming optical system having a positive lens group, a negative lens group, and an aperture stop, the positive lens group is disposed at an object side of the aperture stop, the positive lens group has a cemented lens which is formed by cementing a plurality of lenses, in a rectangular coordinate system in which a horizontal axis is let to be Nd and a vertical axis is let to be ?d, when a straight line indicated by Nd=?×?d+? (where, ?=?0.017) is set, Nd and ?d of at least one lens forming the cemented lens is included in both of areas namely, an area which is determined by a line when a lower limit value is in a range of a following conditional expression (1a), and a line when an upper limit value is in a range of the following conditional expression (1a), and of an area determined by following conditional expressions (2a) and (3a). 1.45<?<2.15??(1a) 1.30<Nd<2.

Abstract: A zoom lens includes a negative first lens group, a positive second lens group, and a positive third lens group; wherein, when changing power from a wide-angle end state to a tele end state, the first lens group moves such that air space between the first lens group and the second lens group decreases, and air space between the second lens group and the third lens group increases, and the second lens group moves toward the object side; and wherein the first lens group includes a negative lens with both faces formed aspherically and the concave face facing the image side, and a positive meniscus lens with at least one face formed aspherically and the convex face facing the object side, satisfying 2.8<|f1/fw|<3.3 where f1 represents the focal length of the first lens group, and fw represents the entire focal length in the wide-angle end state.

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit of negative refractive power, a second lens unit of positive refractive power, and a third lens unit of positive refractive power. The zoom lens changes the distances between the lens units during zooming. The following condition is satisfied: 0.3<|f1 |/fT<0.5, where f1 is a focal length of the first lens unit, and fT is a focal length of the zoom lens at a telephoto end.

Abstract: The invention relates to an optical system that is capable of providing a zoom lens having improved image-formation capability with a reduced number of lenses, and fabricating a slim yet high-performance digital or video camera. The optical system comprises a cemented lens having a cementing surface on its optical axis. Air contact surfaces on the light ray entrance and exit sides of the cemented lens G2 are aspheric, and at least one cementing surface in the cemented lens G2 satisfies condition (1). 6.4<|(r/R)|??(1) Here r is the axial radius of curvature of the cementing surface, and R is the maximum diameter of the cementing surface.

Abstract: Provided is a microminiaturized zoom optical system capable of sufficiently correcting aberration. The zoom optical system (100) includes a first lens group (101) having a negative optical power, a second lens group (102) having a positive optical power, and a third lens group (103) having a positive or negative optical power in this order from the object side. The zoom optical system is configured in such a manner that the interval between the first lens group (101) and the second lens group (102) is decreased in zooming from the wide angle end to the telephoto end. A positive lens element in the third lens group (103) or in a lens group closer to the image side than the third lens group (103) satisfies the following conditional expression: vp<40 where vp is the minimum value of the Abbe number of the positive lens element.

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. In the zoom lens, an interval between the first and second lens units becomes smaller at a telephoto end than at a wide-angle end during zooming. The first lens unit includes, in order from the object side to the image side, a first lens having a negative refractive power, a second lens having a negative refractive power, which is made of a plastic and has an aspheric lens surface, and a third lens unit having a positive refractive power. In the zoom lens, a refractive index and an Abbe number of the plastic (Nd, ?d), a focal length of the second lens (fn), and a focal length of the first lens unit (f1) are appropriately set.

Abstract: A zoom lens includes, in order from an enlargement conjugate side to a reduction conjugate side, a first lens unit of negative refractive power; a second lens unit of positive refractive power; a third lens unit of positive refractive power, the third lens unit having at least three lens elements; a middle lens unit including at least one lens unit; and a last lens unit of positive refractive power. All the lens units, except the first lens unit and the last lens unit, move during zooming. The zoom lens satisfies appropriate conditions.

Abstract: A projection zoom lens includes in order from an enlargement side: a first lens group with negative power; a second lens group with positive power; a third lens group with positive power; a fourth lens group with positive power; and a fifth lens group with positive power, wherein the first and fifth lens groups are fixed and the second, third, and fourth lens groups move when zooming from a wide angle side to a telescopic side, the second lens group includes only a positive lens which is convex toward the enlargement side, and assuming that the focal length at a wide angle end of a whole system including the first to fifth lens groups is F and the focal length of the second lens group is F2, the following conditional expression (1) is satisfied: 0.05<F/F2<0.23??(1).

Abstract: Apparatus, methods, and systems provide negatively-refractive focusing and sensing of electromagnetic energy. In some approaches the negatively-refractive focusing includes providing an interior focusing region with an axial magnification substantially less than one. In some approaches the negatively-refractive focusing includes negatively-refractive focusing with a transformation medium, where the transformation medium may include an artificially-structured material such as a metamaterial.

Abstract: A wide-angle projection lens and a projection apparatus using the same are provided. The wide-angle projection lens, from an image side of the projection apparatus, includes a first lens group, a second lens group and a third lens group. An aperture stop of the wide-angle projection lens is disposed in the third lens group. The first lens group has a negative effective refractive power and at least one aspheric lens surface. The second lens group has a first positive effective refractive power. The third lens group has a second positive effective refractive power. The effective focal length of the wide-angle projection lens is between 6.5 mm and 9.5 mm.

Abstract: A negative first group optical system, a positive second group optical system, and a positive third group optical system are sequentially arranged from the object side. A stop moving integrally with the second group optical system is provided on the object side of the second group optical system. The focal length is changed by changing distances between the group optical systems, and the third group optical system is moved on an optical axis. The first group optical system includes a negative meniscus lens, a negative meniscus lens, and a positive lens. The second group optical system includes a cemented lens of a positive lens and a negative lens, a positive lens, and a positive lens. The third group optical system includes one positive lens not including an aspherical surface.