Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a negative 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. The third lens group includes a negative lens element having a concave surface on the image side, a positive lens element having a convex surface on the image side, and a negative lens element having convex surface on the image side, in that order from the object side. An electronic imaging apparatus using this zoom lens system is also disclosed.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a negative 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, wherein the following condition (1) is satisfied: ?2.45<f1/f2<?2.05??(1), wherein f1 designates the focal length of the first lens group, and f2 designates the focal length of the second lens group.

Abstract: When at least two resin lenses having oppositely signed power factors are disposed in positions that are not relatively far away from each other in a lens group disposed on a high magnification side with respect to an aperture stop, the difference in temperature between the two resin lenses can be reduced, whereby the amount of change in the focal point of an overall projection zoom lens can be reduced. The lens groups on the high magnification side with respect to the aperture stop, which are close to the atmosphere, experience a relatively small increase in temperature when in use. The focus shift due to variation in temperature can therefore be reliably reduced by disposing the resin lenses, which are readily affected by an increase in temperature, on the high magnification side with respect to the aperture stop.

Abstract: A projection zoom lens is formed of the following lens groups sequentially arranged from the high magnification side: a first lens group fixed at the time of zooming and having negative power; a second lens group moved along the optical axis at the time of zooming and having negative power; a third lens group moved at the time of zooming and having positive power; a fourth lens group moved at the time of zooming; and a fifth lens group fixed at the time of zooming and having positive power. When the total lens system operating at the wide angle end has a focal length Fw, and the first lens group has a focal length F1, the following conditional expression is satisfied. ?0.5<Fw/F1<?0.

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 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: An embodiment of this invention provides a zoom lens that primarily 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. The second lens group comprises several lenses, in which the focal length of the first lens from the object side is efl3, the focal length of the second lens from the object side is efl4, and efl3 and efl4 satisfy: 0<efl3/efl4<0.3.

Abstract: A projection zoom lens includes: a first lens group that has a negative refractive power, is fixed when power varies, and has a focusing function; a second positive lens group; a third positive lens group; a fourth negative lens group; a fifth positive lens group; and a sixth lens group that has a positive refractive power, is fixed when power varies, and includes an aperture diaphragm arranged closest to a magnification side. The first to sixth lens groups are arranged in this order from the magnification side, and the second to fifth lens groups are moved when power varies. All lenses are single lenses. The ratio of the back focal length Bf of the entire system to the focal length f of the entire system at a wide angle end is more than 2.5. The Fno. is constant in the entire power variation range.

Abstract: A zoom lens includes a first lens group of negative refractive power, a second lens group of positive refractive power and a third lens group of positive refractive power. The zoom lens satisfies the following condition formulas: 0.68<|f2/f1|<0.85, and 0.65<L2/fT<0.86, where f1 represents an effective focal length of the first lens group, f2 represents an effective focal length of the second lens group, L2 is a displacement of the second lens group when the zoom lens varies from a wide-angle state to a telephoto state, and fT represents an effective focal length of the zoom lens which is in the telephoto state.

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 zoom lens 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 GH3 having positive refractive power, wherein the second lens group G2 is constituted only by three or more cemented lenses.

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 variable magnification optical system of the present invention and an image pickup device and a digital apparatus including this are provided with a four-component optical system of negative-negative-positive-negative arrangement, wherein a first lens group thereof includes only one negative lens as a lens having an optical power, and a third lens group thereof satisfies a conditional expression of 1.4<?3t/?3w<4 when ?3t and ?3w respectively denote image magnifications of the third lens group at a telephoto end and at a wide-angle end. The variable magnification optical system, the image pickup device and the digital apparatus having such a construction can be further downsized.

Abstract: A zoom lens and a photographing device including the zoom lens, the zoom lens including 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, which are sequentially arranged in the direction from an object side to an image side. During zooming from a wide angle position to a telephoto position, an interval between the first lens group and the second lens group decreases, and an interval between the second lens group and the third lens group increases. The first lens group comprises a first lens, a second lens being a negative lens formed of plastic, and a third lens being a positive lens formed of plastic. Therefore, the zoom lens is compact and low-priced and has a high magnification.

Abstract: A first lens unit having negative power, a second lens unit having positive power, a third lens unit having negative power, and a fourth lens unit having positive power are disposed in this order from an object side. At least the first lens unit to the third lens unit move to change intervals between lens units so that magnification is varied. The second lens unit has at least one air interval inside and is split into two lens units with a boundary of an air interval closest to an image side in the second lens unit, which includes a second-a lens unit on the object side and a second-b lens unit on the image side, and the second-b lens unit is moved in a plane substantially perpendicular to an optical axis for damping vibrations.

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: The zoom lens comprises, from an object side, a first lens group, a second lens group that includes an aperture stop moving integrally therewith, a third lens group, and a fourth lens group having, respectively, negative, positive, negative, and positive refracting power, and during zooming from a wide-angle end to a telephoto end, a spacing between the first and second lens groups becomes narrow, between the second and third lens groups changes, and between the third and fourth lens groups grows wide, and the first lens group includes a first lens having negative refracting power, a second lens having a reflective surface for bending a light ray coming out of an object and a third lens having positive refracting power, and in said second lens group, a most image-plane-side surface of a lens having negative refracting power is configured in a concave shape on an image plane side.

Abstract: A zoom lens disposed between an object side and an image side and including a first, second, third, and fourth lens group is provided. The first lens group has a negative refractive power and includes a first lens and a prism arranged in sequence from the object side to the image side. The first lens is an aspheric lens. A distance between the first lens and the prism is L, an effective focal length of the zoom lens at a wide-end is fw, and 1.58<L/fw<1.88. The second lens group disposed between the first lens group and the image side has a positive power and includes a first double cemented lens. The third lens group disposed between the second lens group and the image side has a negative power and includes a second double cemented lens. The fourth lens group has a positive power.

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, each lens unit being moved during zooming, wherein the second lens unit includes two positive lenses, a negative lens, a positive lens in order from the object side to the image side, and an average refractive index Nd2p for d-line of materials of the positive lenses in the second lens unit and a refractive index Nd2n for d-line of a material of the negative lens in the second lens unit are appropriately set.

Abstract: A zoom lens includes in order from an object side to an image side and arranged along an optical axis thereof, a first lens unit having a negative refractive power, and a second lens unit having a positive refractive power. A distance between each lens unit changes when zooming from a wide-angle end to a telephoto end. The first lens unit includes a first lens sub-unit including a positive lens element and a negative lens element, and having a negative refractive power, and a second lens sub-unit including a single negative lens element. Focusing is performed by moving the second lens sub-unit in an optical axis direction, a focal length of the second lens sub-unit f1b and a focal length of the entire zoom lens fw at a wide-angle end are suitably set based on predetermined mathematical expressions.

Abstract: A zoom lens includes a first lens group, a second lens group, a third lens group, and a fourth lens group. The first lens group includes a first lens that has positive refractive power, a second lens that has negative refractive power, and a prism. The second lens group includes a third lens that has positive refractive power and a fourth lens that has negative refractive power. The third lens group includes a stop, a fifth lens that has positive refractive power, and a sixth lens that has negative refractive power. The fourth lens group includes a seventh lens that has positive refractive power. Upon changing magnification from a wide-angle end to a telephoto end, the first and fourth lens groups are fixed, the second lens group first moves toward an image plane side and then moves toward an object side, and the third lens group linearly moves toward the object side.

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: An optical system for observation of a front-direction object and a substantially-lateral-direction object includes, in order from the front-direction-object side, a front group with a negative refracting power having a reflecting/refracting optical element, an aperture stop, and a rear group with a positive refracting power having a moving lens component movable along the optical axis. The reflecting/refracting optical element has a first face formed on the front-direction-object side, a second face formed on the image side, and a third face formed as a transmitting surface between the first face and the second face. The first face has a first transmitting surface formed with the optical axis being at a center thereof and a first reflecting surface annularly formed around the first transmitting surface and directed toward an image side.

Abstract: A zoom lens includes, in order from an object side to an image side: first, second and third lens groups having a negative refractive power, a positive refractive power and a positive refractive power, respectively. The first lens group includes a single compound aspheric lens formed of a spherical glass lens having a negative refractive power and a resin lens having a positive refractive power and an image side surface thereof is aspheric, and the conditional expressions (1) to (4) are satisfied f11/fw<?1.8,??(1) 1.55<n11,??(2) 55<?11, and??(3) G1r1<?16.5,??(4) where f11 and fw are focal lengths of the spherical glass lens and the whole lens system at a wide-angle end, respectively, n11 and ?11 are a refractive index and an Abbe number, respectively, of the spherical glass lens at the d-line, and G1r1 is a radius of curvature of an object side surface of the spherical glass lens.

Abstract: A zoom lens comprises in order from an object 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 negative refractive power. The second lens unit comprises in order from the object side, a positive lens, a negative lens, and a positive lens. At the time of zooming from a wide angle end to a telephoto end, the first lens unit moves toward the object side, and the fourth lens unit moves, and a distance between the first lens unit and the second lens unit decreases monotonically, a distance between the second lens unit and the third lens unit increases monotonically, and a distance between the third lens unit and the fourth lens unit increases monotonically.

Abstract: A zoom lens system, in order from an object side to an image side, comprising a first lens unit having negative optical power, a second lens unit having positive optical power, and at least one subsequent lens unit having optical power, wherein in zooming from a wide-angle limit to a telephoto limit, the lens units are moved along an optical axis such that an air space between at least any two lens units among the lens units should vary, so that variable magnification is achieved, wherein the first lens unit includes a lens element having a reflecting surface for bending a light beam incident from the object, and wherein the condition is satisfied: 0.20<|fG1|/fT<0.52 (fT/fW?4.0, fG1 is a composite focal length of the first lens unit, and each of fT and fW is a focal length of the entire system at a telephoto limit or a wide-angle limit), an imaging device and a camera are provided.

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: A zoom lens for projection includes a first negative lens group, a second positive lens group, a third positive lens group, a fourth lens group, and a fifth positive lens group, which are sequentially arranged from the magnification side of the zoom lens. The first lens group and the fifth lens group are fixed, and the second lens group, the third lens group and the fourth lens group move along the optical axis of the zoom lens when magnification of the zoom lens is changed. Each of the first lens group and the second lens group is composed of two lenses. Each of the third lens group and the fifth lens group is composed of a positive lens, and the fourth lens group is composed of five lenses. Further, the reduction side of the zoom lens is telecentric.

Abstract: Disclosed is a projection variable focusing lens and a projection display device that has a reduction side which is telecentric, a high magnifying power, a small size, a light weight, and a low manufacturing cost and is capable of correcting all aberrations occurring when power varies with good balance. A projection variable focusing lens that moves only one lens group when power varies includes a first negative lens group G1, a second positive lens group G2, and a third positive lens group G3, arranged in this order from a magnification side. When a focal length varies, only the second lens group G2 is moved along an optical axis X. During focusing, the first lens group G1 is moved along the optical axis X. A reduction side is substantially telecentric.

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, in order from an object side to an image side, comprising: a negative first lens unit; and at least one subsequent lens unit, wherein an interval between the first lens unit and the at least one subsequent lens unit varies in zooming, the zoom lens system is provided with: an escaping lens unit that, at the time of retracting, escapes along an axis different from that at the time of image taking; and an image blur compensating lens unit that moves in a direction perpendicular to an optical axis in order to optically compensate image blur, and the escaping lens unit is a lens unit that is different from the image blur compensating lens unit; an imaging device; and a camera are provided.

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 wide-angle zoom lens system includes a negative fist lens group, a positive second lens group, and a positive third lens group, in this order from the object. Upon zooming from the short focal length extremity to the long focal length extremity, each of the negative fist lens group, the positive second lens group and the positive third lens group move along the optical axis thereof while a distance between the negative fist lens group and the positive second lens group decreases, and a distance between the positive second lens group and the positive third lens group also decreases. The wide-angle zoom lens system satisfies the following condition: 2.45<f3/fw<3.5??(1) wherein f3 designates the focal length of the positive third lens group; and fw designates the focal length of the entire wide-angle zoom lens system at the short focal length extremity.

Abstract: An optical system includes, in order from an object side to an image side, a first lens unit, a stop, and a second lens unit. The first lens unit includes a first negative lens having a meniscus shape and a negative refractive power at a position closest to the object side and a negative lens Gn having a negative refractive power at a position closer to the image side than the first negative lens. The second lens unit includes a positive lens Gp having a positive refractive power. A material of each of the negative lens Gn and the positive lens Gp satisfies the following condition: ?gF?(?0.001682·?d+0.6438)?0.01 where “?d” denotes an Abbe number of a lens material and “?gF” denotes a relative partial dispersion with respect to g-line light and F-line light.

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: Provided is a zoom lens having high optical performance over the entire zoom range. The zoom lens includes 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, which are provided in order from an object side to an image side. During zooming, intervals between the respective lens units change. A focal length (fW) of the entire zoom lens at a wide angle end, a focal length (f3) of the third lens unit, and a movement amount (m2) of the second lens unit during zooming from the wide angle end to a telephoto end are suitably set.

Abstract: A zoom lens comprises a first lens group having a negative refractive power and a second lens group having a positive refractive power in order from object to image sides, an interval between the first and second lens groups changes in a zoom operation, the first lens group is constituted by negative and positive lenses in order from the object to image sides, the negative and positive lenses of the first lens group are arranged at intervals, the second lens group is constituted by three lenses including positive and negative lenses in order from the object to image sides, and a radius of curvature of a lens surface at the object side of the negative lens constituting the first lens group, a shape of a negative lens having the maximum refractive power constituting the second lens group, and a refractive power of the second lens group are appropriately set.

Abstract: An optical system having a larger total lens length than a focal length includes lenses L and NL on at least one of a magnification conjugate side and a reduction conjugate side with respect to an aperture stop. The lens L satisfies conditional expressions as follows, ?1.68×10?3·?L+0.590<?L<3.15×10?4·?L2?1.86×10?2·?L+0.878, and 5<?L<27, where ?L and ?L are an Abbe number and a gF-line partial dispersion ratio of the lens L. The refractive power of the lens L is positive when located at the magnification conjugate side, or negative when located at the reduction conjugate side.

Abstract: A zoom lens includes, in order from the object side, an object side lens group having a negative refracting power at the wide angle end and including at least one negative lens unit, and an image side lens group having a positive refracting power at the wide angle end and including at least one positive lens unit including a cemented doublet lens component. The distance between the two lens groups is smaller at the telephoto end than at the wide angle end. The cemented doublet lens component includes, in order from the object side, a negative object side lens having a concave surface facing the image side, and positive image side lens having a meniscus shape with a concave surface facing the image side. The cemented doublet lens component is located closest to the image side in the positive lens unit. The zoom lens satisfies specific conditions.

Abstract: An imaging lens SL installed in an SLR camera includes a front group disposed to the most object side and having negative power, and a rear group disposed to an image side of the front group and having negative power. At least a portion of the rear group is movable perpendicularly to an optical axis. The rear group includes a first negative component having negative power, a second negative component having negative power, and a positive component having positive power. The second negative component is disposed between the first negative component and the positive component. The second negative component side surface of the first negative component faces the second negative component, and the second negative component having a negative meniscus shape with a concave surface facing the first negative component. Thereby providing an imaging lens having excellent optical performance, an optical apparatus equipped therewith, and a method for manufacturing thereof.

Abstract: A variable magnification optical system includes first lens group having negative refractive-power, an aperture-stop and second lens group having positive refractive-power, arranged from the object-side. A negative lens having a concave surface facing the image-side is arranged on the most object side of the first lens group, and an aspheric lens having a concave surface facing the object-side and an aspheric surface facing the image-side is arranged on the most image side of the first lens group. A positive lens having a convex surface facing the image-side is arranged, on the object-side of the aspheric lens, immediately before the aspheric lens. The image-side surface of the aspheric lens at the most image side of the first lens group includes a portion having higher positive power on the outside of positions through which outermost rays of an axial beam pass, compared with the vicinity of the optical axis.

Abstract: A zoom lens includes sequentially from an object side a first lens group having a negative refractive power; a diaphragm; and a second lens group having a positive refractive power. Zoom from a wide angle edge to a telephoto edge is performed by displacement of the second lens group along an optical axis, toward the object side. Correction of imaging plane variation accompanying zoom, is performed by displacement of the first lens group along the optical axis. The second lens group includes a positive first lens disposed farthest on the object side and having at least one aspheric surface, and a cemented lens that includes a negative lens, a positive lens, and a negative lens. Furthermore, a first condition ?d2p>75 is satisfied, ?d2p being the Abbe number for a d-line in the positive lens included in the cemented lens of the second lens group.

Abstract: An image capture apparatus includes: a zoom lens; and an image pickup device converting an optical image formed by the zoom lens into an electric signal. The zoom lens includes, in order from the object side, a first lens group with a negative focal length, a second lens group with a positive focal length, a third lens group with a negative focal length, and a fourth lens group with a positive focal length. During zooming from a wide-angle end to a telephoto end, the first lens group moves along a locus having a convex shape toward an image side while decreasing an air space between the first and second lens groups, and the second and third lens groups move toward the object side while increasing an air space therebetween.

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, at least the first lens unit and the second lens unit move along an optical axis, on the image side relative to the second lens unit, an aperture diaphragm is arranged that moves along the optical axis integrally with the second lens unit during zooming, the second lens unit moves in a direction perpendicular to the optical axis, and the condition is satisfied: 1.00<(1?m2W)×m3W<1.50 where, Z=fT/fW>4.

Abstract: An zoom projection lens includes, in this order from the screen-side to the SLM-side thereof, a negative lens group and a positive lens group, and satisfies: ?2<?1/?2<?0.5, ?2<EFL1/EFL(W)<?1.5, 1.5<EFL2/EFL(W)<1.75, ?1.2<EFL1/EFL(T)<?1, 0.8<EFL2/EFL(T)<1.2, 0.5<EFL(W)/BFL(W)<0.6, 0.68<EFL(T)/BFL(T)<0.75, 6.2<TTL(W)/EFL(W)<6.5, and 3.5<TTL(T)/EFL(T)<3.6; where ?1 and ?2 represent refractive powers of the negative lens group and the positive lens group respectively, EFL(W), EFL(T), EFL1 and EFL2 represent effective focal lengths of the projection lens in a wide-angle state and in a telephoto state, the negative lens group, and the positive lens group respectively, TTL(W) and TTL(T) represent overall lengths of the projection lens in the wide-angle state and in the telephoto state respectively, and BFL(W) and BFL(T) represent rear focal lengths of the projection lens in the wide-angle state and in the telephoto state respectively.

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. Upon zooming from the short to long focal length extremities, the first through third lens groups move along an optical axis direction so that the distance between the first and second lens groups decreases, and the distance between the second and third lens groups increases. The first lens group includes a negative glass lens element and at least two plastic lens elements, in that order from the object side, and wherein the following condition (1) is satisfied: |f1/f1pc|<0.04 . . . (1), wherein f1 designates the focal length of the first lens group, and f1pc designates the combined focal length of the plastic lens elements that are provided within the first lens group.

Abstract: A wide angle lens system includes a first lens group having a negative refractive power and a second lens group having a positive refractive power arranged from an object side. The first lens group includes a first lens of a meniscus shape having a convex surface toward the object side, a second lens having a concave surface toward the object side, and a third lens having a convex surface toward the object side, and the second lens group includes a fourth lens having a convex surface toward the object side, a fifth lens having a concave surface toward the object side, and a sixth lens of a meniscus shape having a concave surface toward the object side. A photographing apparatus includes the wide angle lens system.

Abstract: A zoom lens including, in a sequence from an object side to an image plane 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 negative refractive power; and a fourth lens group having a positive refractive power. During 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 increases, and an interval between the third lens group and the fourth lens group decreases. When the location of an object changes from ? to a close location, the first lens group is moved toward the object to perform focusing.

Abstract: An electronic image pickup apparatus comprising a zoom lens system and an image pickup device disposed on an image side of the zoom lens system and which converts an image formed by the zoom lens system into an electric signal, the zoom lens system having, in order from an object side, a negative first lens unit, a positive second lens unit, a negative third lens unit, and a positive fourth lens unit, the first lens unit having, in order from the object side, a negative lens and a reflective optical element which reflects an optical path, and during zooming from a wide-angle end to a telephoto end, each space between the lens units which are adjacent with each other being changed, the first lens unit being arranged in a fixed position to the image pickup device, and at least the second lens unit and the third lens unit being moved.

Abstract: A zoom lens 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 GH3 having positive refractive power, wherein the second lens group G2 is constituted only by three or more cemented lenses.