Abstract: A zoom lens system includes, in the following order from an object side toward an image side, a first lens group with negative power, a second lens group with positive power, a third lens group with negative power, and a fourth lens group with positive power. The first lens group includes, in the following order from the object side toward the image side, a first lens element having a negative meniscus shape with a concave surface facing the image side, a second lens element having a negative meniscus shape with a concave surface facing the image side, a third lens element with a concave surface facing the image side, a fourth lens element with a convex surface facing the object side, and a fifth lens element with a concave surface facing the object side. The third lens element and the fourth lens element compose a cemented lens.

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: Disclosed are an optical lens assembly and an electronic apparatus including the disclosed lens assembly. The optical lens assembly includes a first lens group having positive refractive power, an iris diaphragm, and a second lens group having positive refractive power, which are arranged from an object side to an image side of an optical axis, the object side facing an object for image capture and the image side facing an imaging surface of an image sensor. The first lens group includes a first air lens having negative refractive power and a convex surface facing the object side and a second air lens having negative refractive power and two convex surfaces. The second lens group includes a lens closest to the image side of the optical axis that has positive refractive power and a convex surface facing the image side. The closest image-side lens includes an aspherical surface. The optical lens assembly has a maximum viewing angle of 130 degrees or more.

Abstract: A projection zoom lens includes, sequentially from an enlargement conjugate side: a first lens group having negative refractive power; a second lens group having positive or negative refractive power; a third lens group having positive refractive power; a fourth lens group having negative refractive power; a fifth lens group having positive refractive power; and a sixth lens group having positive refractive power, and configured to perform a magnification variation by changing the interval between the respective lens groups, wherein the fourth lens group includes at least one positive lens and at least one negative lens, at least one of the positive lenses included in the fourth lens group satisfies the following Conditional Expressions: 0.71??g_Fp+0.004×?dp?0.73 and 15??dp?25, and the back focus of the entire projection zoom lenses satisfies the following Conditional Expression 1.0?BF/Fw?2.7.

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: A projection lens system includes a first lens group including a 1a-th lens group having a negative refractive power, a 1b-th lens group having a positive or negative refractive power, and a 1c-th lens group having a positive or negative refractive power. During a zoom, the first lens group remains stationary on an optical axis. During a focus from a remote distance side to a close distance side, the 1a-th lens group remains stationary on the optical axis while the 1b-th and 1c-th lens groups move toward the enlargement conjugate side along different loci respectively. Conditional formula ?4.7<fl/fw<?2.5 is fulfilled at both the remote and close distance sides, where fl represents a focal length of the first lens group, and fw represents a focal length of the entire system at a wide-angle end.

Abstract: A projection optical system projects onto a projection surface an image ray bundle formed on an image display element, and includes a transmissive optical system positioned on a side of an emission surface of the image display element and having positive power, and a reflective optical system including at least one mirror for reflecting, toward the projection surface, light rays emitted from the transmissive optical system. The transmissive optical system includes at least one positive lens disposed closer to the image display element than an aperture stop, along with first and second positive lenses having a meniscus shape, and a negative lens disposed therebetween, which are closer to the projection surface than the aperture stop is. During focusing, spacing between the first positive lens and the negative lens and spacing between the second positive lens and the negative lens remain unchanged.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, a negative third lens group and a positive fourth lens group, in that order from the object side. Upon zooming from the short to long focal length extremities, at least the first lens group, the second lens group and the fourth lens group are moved in the optical axis direction. The third lens group includes a negative first sub-lens group and a negative second sub-lens group, in that order from the object side. The second sub-lens group is provided with a negative single lens element and a positive single lens element, wherein an air lens is formed between the negative single lens element and the positive single lens element.

Abstract: A zoom lens, including, in order from an object side: a negative first unit being not moved for zooming; a second unit including at least one sub-unit that is moved during zooming, and having a positive refractive power as a whole; a negative third unit including an aperture stop, being not moved for zooming; a fourth unit including at least one sub-unit and being moved during zooming; and a fifth unit being not moved for zooming, at least three sub-units among the sub-units included in the second and fourth units being moved during zooming, in which focal lengths of the first and third units, and a movement amount of a sub-unit that is moved most in the second unit and a movement amount of a sub-unit that is moved most in the fourth unit during zooming from a wide angle end to a telephoto end satisfy predetermined conditions.

Abstract: An optical system includes an aperture stop, a unit A configured to move during a distortion adjustment, and a unit B disposed at an image side relative to the unit A and configured to move with a locus different from a locus of the unit A during the distortion adjustment, the optical system changes from a first optical state having a first distortion to a second optical state having a second distortion larger than the first distortion, and focal lengths of the units A and B, moving amounts of the units A and B during a change from the first to second optical states, distances from the aperture stop to the units A and B, distances from a lens surface of the unit A closest to the object side to an image plane, and a total optical length of the optical system satisfy a predetermined condition.

Abstract: An optical imaging lens includes a first lens element, a second lens element, a third lens element, and a fourth lens element from an object side to an image side in order along an optical axis. The first lens element to the fourth lens element each include an object-side surface and an image-side surface. The first lens element has positive refracting power. The second lens element has negative refracting power. At least one of the object-side surface and the image-side surface of the third lens element is an aspheric surface. At least one of the object-side surface and the image-side surface of the fourth lens element is an aspheric surface. A maximum distance between the image-side surface of the first lens element and the object-side surface of the second lens element in a direction parallel to the optical axis is less than 0.2 mm.

Abstract: An optical system includes a reflective optical system on a magnification side along an optical path of the projection optical system and a refractive optical system on a reduction side along the optical path. The reflective optical system includes one reflective optical element having a power. The refractive optical system includes a front group on the magnification side and a rear group on the reduction side. The front group having, in order from the magnification side toward the reduction side, a first lens group with a positive or negative refractive power, a second lens group, and a third lens group with a positive refractive power. The rear group has a positive refractive power. The first lens group moves to the magnification side, and the second lens group and the third lens group move to the reduction side in a change in focus from a long distance to a short distance.

Abstract: A projection zoom lens assembly for a digital cinema projection system includes three optical groups. A first optical group includes one or more wide angle lenses for projecting digital cinema images. A second optical group includes a set of zoom optical groups each comprising two or more lenses, including a first independently movable zoom group, a second independently movable zoom group, and a third zoom group. A third optical group includes multiple lenses for receiving images for projection.

Abstract: A zoom lens system includes: a first lens group having a negative refractive power; a second lens group having a positive refractive power; and an aperture between the first and second lens groups, wherein the first lens group and the second lens group are sequentially arranged from an object side to an image side, wherein the zoom lens system performs zooming and focusing by moving the second and first lens groups, respectively, along an optical axis, and satisfies 2.5<(fw/ft)×(Tw/Y)<4.5, where fw denotes an entire focal length at a wide-angle end, ft denotes an entire focal length at a telephoto end, and Tw denotes a distance between an image plane and an object side lens surface of a lens closest to the object side of the first lens group at the wide-angle end, and Y denotes a radical axis image height.

Abstract: A four-piece infrared single wavelength lens system includes, in order from the object side to the image side: a first lens element with a refractive power, a stop, a second lens element with a positive refractive power, a third lens element with a positive refractive power, and a fourth lens element with a positive refractive power. The focal length of the first lens element is f1, the focal length of the second lens element and the third lens element combined is f23, and they satisfy the relation: ?210<f1/f23<365. When the above relation is satisfied, a wide field of view can be obtained and the resolution can be improved evidently.

Abstract: A wide angle zoom lens includes sequentially from the object side, a first lens group having a negative refractive power overall and three lenses, including first to third lenses, having a negative refractive power and disposed farthest on the object side; a second lens group having a positive refractive power overall and one or more sets of cemented lenses; and a third lens group having a negative refractive power. This ultra wide angle zoom lens varies intervals between the first lens group, the second lens group, and the third lens group on the optical axis to zoom from the wide angle end to the telephoto end and satisfies given conditions to thereby enable a high zoom ratio, large diameter, and high resolution.

Abstract: A variable magnification optical system consists of a first lens-group having negative refractive-power, a stop and a second lens-group having positive refractive-power in this order from an object-side. The first lens-group includes an L11 negative meniscus lens, an L12 negative lens and a C11 cemented lens, in which a biconcave lens and a positive lens are cemented together in this order from the object-side, in this order from the object-side. The second lens-group includes an L21 positive lens that is arranged closest to the object-side and includes at least one aspheric surface, and an object-side surface of which is convex, and only two cemented lenses toward an image-side of the L21 positive lens, and each of which consists of a negative lens and a positive lens cemented together in this order from the object-side. The following conditional expressions (1) and (2) are satisfied: ?1.0<Rf11/Rf12<0.7??(1); and 55.0<?dave1??(2).

Abstract: A wide angle lens may include a first lens having a negative power with a convex surface on an object side and a concave surface on an image side, a second lens having a negative power with a concave surface on the image side, a third lens having a positive power with a convex surface on the image side, a fourth lens having a positive power with a convex surface on the image side, a fifth lens being a plastic lens with a negative power with a concave surface on the object side and a concave surface on the image side, a sixth lens being a plastic lens with a positive power with a convex surface on the object side and a convex surface on the image side, and a diaphragm disposed between the third and fourth lenses. The fifth and sixth lenses constitute a cemented lens.

Abstract: A projection zoom lens includes: a first lens group having a negative refractive power provided most toward the magnification side, which is fixed when changing magnification; and at least two movable lens groups that move to change the relative distance therebetween in the direction of an optical axis when changing magnification. The first lens group is constituted by, in order from the magnification side to the reduction side, a front group having a negative refractive power and a rear group having a negative refractive power. The front group is fixed and only the rear group moves in the direction of the optical axis during focusing operations. Conditional Formula (1) related to the focal length f1a of the front group and the focal length f1b of the rear group is satisfied: f1b/f1a<0.8??(1).

Abstract: A zoom lens is a projection lens which is composed of a negative first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, a fifth lens group, and a positive sixth lens group in order from the enlargement conjugate side, and changes magnification by changing the intervals between the lens groups. At least the second, third, and fifth lens groups move when the magnification is changed, and the third lens group moves from the enlargement conjugate side to the reduction conjugate side when the magnification is changed from a telephoto end to a wide angle end. An aperture stop is disposed between the surface closest to the reduction conjugate side of the third lens group and the surface closest to the enlargement conjugate side of the fifth lens group, and is approximately telecentric on the reduction conjugate side.

Abstract: The projection zoom lens essentially consists of a positive first lens group fixed while changing magnification and the second lens group through the fourth lens group which move while changing magnification, and a fifth lens group fixed while changing magnification; and an aperture stop positioned between adjacent moving lens groups or within one moving lens group, wherein the numerical number of the zoom lens is set to be constant over the entire zoom range, the reduction side is configured to be telecentric, and the projection zoom lens satisfies conditional formulas (4) and (5): 2.0<Bf/Im???(4) L/Im?<12??(5), where, Bf: the back focus (air converted length) at the reduction side of the entire system at the wide angle end, Im?: the maximum effective image circle diameter, and L: the distance between the most-magnification-side lens surface and the most-reduction-side lens surface along the optical axis when the projection distance is infinite.

Abstract: A wide-angle lens system includes a first lens group, an aperture stop, and a second lens group having positive optical power. The first lens group includes, at least, a first lens element that has a meniscus shape convex on the object side, and has negative optical power, a second lens element that has a meniscus shape convex on the object side, and has negative optical power, a third lens element that is concave on the image side and has negative optical power, and a posterior lens element. The second lens element is an aspherical lens, and the second lens element satisfies a conditional expression: 0.3<(R21?R22)/(R21+R22)<0.8 where R21 is a radius of paraxial curvature on the object side of the second lens element, and R22 is a radius of paraxial curvature on the image side of the second lens element.

Abstract: A projection lens includes a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having negative refractive power, a fifth lens group having positive refractive power, and a sixth lens group having positive refractive power, in sequence from an enlargement conjugate side, the projection lens performing magnification by changing the spacing between the lens groups, wherein at the time of magnification from the telephoto end to the wide-angle end, the second, third, fourth, and fifth lens groups are moved, and an aperture stop is arranged between the surface of the third lens group closest to a reduction conjugate side and the surface of the fifth lens group closest to the enlargement conjugate side.

Abstract: A fixed focal-length lens system includes a negative first lens group, a positive second and third lens groups. The first and second lens groups move toward the object side during focusing from an object at infinity to an object at a close-up distance. The first lens group includes a negative lens element having a concave surface on the image side, at least two positive lens elements, and a negative lens element having a concave surface on the image side. The second lens group includes a negative lens element having a concave surface on the object side, and at least two positive lens elements. The third lens group includes at least one negative lens element, and at least one positive lens element. The following condition (1) is satisfied: ?0.3<fG2/fG1<?0.05??(1), wherein fG1 and fG2 designate the focal lengths of the first and second lens groups.

Abstract: A projection zoom lens is constituted by: a negative first lens group; a positive moving second lens group; a positive moving third lens group; a positive final lens group; at least one lens group positioned between the final lens group and the third lens group; and an aperture stop provided between adjacent moving lens groups. The aperture stop is a variable stop, of which the aperture diameter changes such that the numerical aperture of the zoom lens becomes constant. The zoom lens satisfies Conditional Formulae below: 2.8<Bf/Im???(1?) L/Im?<12??(2) wherein Bf is the back focus of the entire system at the reduction side at the wide angle end, Im? is the maximum effective image circle diameter at the reduction side, and L is the distance from the lens surface most toward the magnification side to the lens surface most toward the reduction side when the projection distance is infinity.

Abstract: A wide-angle lens having a field angle larger than 180 degrees includes, in order from an object side to an image side, a front group, a reflection surface, and a back group, wherein the front group includes three lenses having a negative refractive power, the reflection surface is configured to curve an optical axis of the front group at 90 degrees toward the back group, the back group includes four lenses having a positive refractive power, a front principle point is set between a second lens and a third lens from the object side in the front group, and a focal length of an entire system f and a distance between an intersection of the reflection surface and the optical axis of the front group and the front principle point d satisfy the following condition (1). 7.0<d/f<9.

Abstract: A wide-angle lens includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens, all of which are arranged in sequence from an object side to an image side along an optical axis. The first, second lens are convex-concave lenses with negative refractive power and include a convex surface facing the object side and a concave surface facing the image side respectively. The third lens is with positive refractive power and includes a convex surface facing the image side. The fourth, seventh lens are biconvex lenses. The fifth, sixth lens are with refractive power. The fifth lens and the sixth lens satisfy: ?10<f56/f<?2 wherein f56 is an effective focal length of a combination of the fifth lens and the sixth lens, and f is an effective focal length of the wide-angle lens.

Abstract: A zoom lens consists of a negative first lens group, a stop, a positive second lens group, a negative third lens group, a positive fourth lens group, and a positive fifth lens group in this order from the object side. The first lens group through the fourth lens group move along the optical axis while changing magnification such that 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 increased. The fifth lens group is fixed with respect to an image surface while changing magnification. The first lens group consists of a first lens, a second lens, a third lens, and a fourth lens in this order from the object side.

Abstract: A retrofocus-type wide-angle lens consists of a negative first lens-group, a positive second lens-group, and a positive third lens-group in this order from an object-side. The first lens-group consists of a positive meniscus-lens with its convex surface facing the object-side and three negative meniscus-lenses with their convex surfaces facing the object-side in this order from the object-side. The second lens-group includes two cemented lenses, and a lens closest to an image-side in the second lens-group is one of the at least two cemented lenses. The third lens-group consists of a 3a-th lens-group, which consists of a positive meniscus-lens with its convex surface facing the object-side and a negative meniscus-lens with its convex surface facing the object-side, and a 3b-th lens-group, which includes at least two cemented lenses and has positive refractive power as a whole, in this order from the object-side.

Abstract: A zoom lens substantially consists of a negative first lens group, a positive second lens group, a negative third lens group, a positive fourth lens group, and a positive fifth lens group in this order from the object side; wherein the first lens group through the fourth lens group move along the optical axis while changing magnification from the wide angle end to the telephoto end so as to change the distances among one another such that 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 increased; the fifth lens group is fixed with respect to an image surface while changing magnification; and conditional formulas (1) and (2) below are satisfied: 0.15<|f1|/f2<1.00??(1) 0.1<f4/f5<1.1??(2).

Abstract: Provided is an image pickup apparatus including a zoos lens and a solid-state image pickup element. The zoom lens includes a first lens unit having a negative refractive power, an aperture stop, and a second lens unit having a positive refractive power. The first lens unit consists of a first lens sub-unit having a negative refractive power, which consists of two negative lenses, and a second lens sub-unit having a positive refractive power. The first lens unit and the second lens unit are configured to move in different loci for zooming. Each of a full-open f-number (Fnow) of the zoom lens, a focal length of the zoom lens, a focal length of the first lens sub-unit, and a pixel pitch (P) of the solid-state image pickup element is appropriately set.

Abstract: An f-theta lens system for a camera that provides a wide field-of-view, relatively low distortion, and a compact footprint. The lens system comprises four molded plastic elements with seven aspheric surfaces. Within a total thickness of 2.5 millimeters, the system is able to provide an image that is 1.2 millimeters across with a horizontal field of view of 127 degrees. The images produced by the system are well-suited for use with conventional face tracking algorithms designed to process rectilinear images produced by cameras with a narrower field of view.

Abstract: In a zoom lens in which a first lens group having a negative refractive power and a second lens group having a positive refractive power are disposed in order from the object side and zooming is performed by moving the first and the second lens groups, the first lens group is formed of a first lens having a negative refractive power, a second lens, a third lens having a negative refractive power, and a fourth lens having a positive refractive power. Then, when the focal length of the second lens, the focal length of the entire system at the wide angle end, the focal length of the first lens group, and the focal length of the second lens group are taken as fG12, fw, f1, and f2 respectively, the zoom lens is configured to satisfy conditional expressions give below: 0.00<fw/f2<0.50??(1-1); and ?0.19<f1/fG12<0.16??(2-1).

Abstract: A zoom lens includes 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 is disposed between the first lens group and the third lens group. The second lens group includes at least an aspheric glass lens. Through using the aspheric glass lens, the imaging quality of the disclosed zoom lens is not sensitive to temperatures changes.

Abstract: A zoom lens substantially consists of a first lens group having a negative refractive power and a second lens group having a positive refractive power arranged in order from the object side; that changes magnification by moving the first lens group and the second lens group; and wherein the first lens group is configured by a first lens having a negative refractive power, a second lens, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, arranged in order from the object side. The zoom lens satisfies a predetermined conditional expression.

Abstract: A zoom lens system having a negative first lens group and a positive second lens group, from an object side, and achieving zooming by varying a group-to-group distance. The second lens group includes a three-element cemented lens which is a set of three lens elements cemented together including, from the object side, a negative first lens, a positive second lens, and a negative third lens, and the three-element cemented lens fulfills conditional formulas 0.08<(rs2+rs1)/(rs2?rs1)<0.5, 27<v2-v1<40, 20<v2-v3<38 (rs1, rs2 represent the curvature radius of the sides of cemented surfaces of the three-element cemented lens on the object side and the image side respectively, and v1-3 represent the Abbe numbers of the first to third lenses of the three-element cemented lens).

Abstract: An inner focus lens system, in order from an object side, comprising: a first lens unit including a most-object-side negative first lens element; a positive second lens unit; and a negative third lens unit, wherein an aperture diaphragm is included, the first lens unit, the third lens unit, and the aperture diaphragm are fixed relative to an image surface in focusing, the second lens unit moves relative to the image surface in the focusing, and the conditions: BF/Y<1.7 and TH/f>1.6 (BF: distance from an apex of an image-side surface of a most-image-side lens element to the image surface; Y: maximum image height; TH: distance from an apex of an object-side surface of a most-object-side lens element to the apex of the image-side surface of the most-image-side lens element; f: focal length of the lens system) are satisfied.

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 first lens group including two aspherical lenses, a second lens group consisting of three negative meniscus lenses, each negative meniscus lens having a convex surface facing the enlargement side, a third lens group having a negative refractive power and including at least one cemented lens, and a fourth lens group having a positive refractive power and including at least two cemented lenses and one aspherical lens are arranged in this order from the enlargement side. Predetermined conditional expressions are satisfied.

Abstract: A wide angle lens includes: a positive first lens group, a second lens group, constituted by two or fewer lenses, that moves during focusing operations, and a third lens group that includes at least one positive lens, provided in this order from the object side. The first lens group includes at least a positive meniscus lens with a convex surface toward the object side, a negative meniscus lens with a convex surface toward the object side, a lens having a concave surface with a radius of curvature having a smaller absolute value toward the image side, a negative lens, a cemented lens formed by a positive lens and a negative lens, and an aperture stop provided adjacent to the cemented lens toward the image side thereof, provided in this order from the object side. The wide angle lens satisfies a predetermined conditional formula.

Abstract: A zoom lens consisting of, 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 first lens group G1 including, in order from the object side, a first negative meniscus lens having a convex surface facing the object side, a negative lens, a second negative meniscus lens having a convex surface facing the object side, and a positive lens, a distance between the first lens group G1 and the second lens group G2 being varied thereby carrying out zooming, and given conditional expressions being satisfied, thereby providing a zoom lens having excellent optical performance and high resolution with being compact and lightweight, an optical apparatus, and a method for manufacturing the zoom lens.

Abstract: The zoom lens includes, in order from an object side to an image side, a first lens unit having a negative refractive power, and a rear lens group including one or more lens units and having as a whole a positive refractive power. The first and rear lens group are moved during zooming so that a distance therebetween decreases at a telephoto end as compared with at a wide-angle end. The first lens unit includes an image side aspheric lens having a negative aspheric amount and one or more object side aspheric lenses disposed on the object side further than the image side aspheric lens. A condition of 0.060<?Aspi×Ndi/BLD1<0.200 is satisfied where Aspi represents an aspheric amount of an i-th object side aspheric lens, Ndi represents a refractive index of the i-th object side aspheric lens, BLD1 represents a length of the first lens unit.

Abstract: An inner focus lens system, in order from an object side, comprising: a first lens unit including a most-object-side negative first lens element; a positive second lens unit; and a negative third lens unit, wherein an aperture diaphragm is included, the first lens unit, the third lens unit, and the aperture diaphragm are fixed relative to an image surface in focusing, the second lens unit moves relative to the image surface in the focusing, and the conditions: BF/Y<1.7 and TH/f>1.6 (BF: a distance from an apex of an image-side surface of a most-image-side lens element to the image surface, Y: a maximum image height, TH: a distance from an apex of an object-side surface of a most-object-side lens element to the apex of the image-side surface of the most-image-side lens element, f: a focal length of the lens system) are satisfied.

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: In an optical system including, in order from an object side to an image side: a front unit (LF) having a negative refractive power; an aperture stop; and a rear unit (LR) having a positive refractive power, the front unit (LF) includes a meniscus-shaped negative lens (g1) closest to the object side, and a focal length (fw) of the entire optical system, a focal length (fg1) of the meniscus-shaped negative lens (g1), and a curvature radius (R2) of a lens surface on the image side of the meniscus-shaped negative lens (g1) are appropriately set.

Abstract: An imaging optical system includes a first optical unit having positive refractive power making an image at an image plane at an enlargement-side of the imaging optical system and an intermediate image at an intermediate image position in the imaging optical system conjugate to each other, and a second optical unit having positive refractive power making the intermediate image and an image at an image plane at a reduction-side of the imaging optical system conjugate to each other, wherein, when a focal length of the first optical unit is denoted by fF and a focal length of the second optical unit is denoted by fR, the following condition is satisfied: 0<fF/fR<0.8, and wherein the second optical unit includes a negative lens disposed on the optical axis closest to the enlargement side.

Abstract: A zoom lens includes a first lens-group having positive refractive power, a second lens-group having negative refractive power, a third lens-group having positive refractive power, and a fourth lens-group having positive refractive power, in this order from an object side, and a stop located between a most image-side surface of the second lens-group and a most image-side surface of the third lens-group. Distances between the lens-groups change when magnification is changed from a wide-angle end to a telephoto end. The second lens-group consists of a negative lens, a biconcave lens and a positive lens in this order from the object side. The third lens-group consists of a positive lens, a cemented lens of a positive lens and a negative lens, a negative meniscus lens with its concave surface facing the object side, and a biconvex lens in this order from the object side. A predetermined conditional formula is satisfied.

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 substantially consists of a negative first lens group, a stop, a positive second lens group, a negative third lens group, a positive fourth lens group, and a positive fifth lens group in this order from the object side; wherein the first lens group through the fourth lens group move along the optical axis while changing magnification such that 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 increased; the fifth lens group is fixed with respect to an image surface while changing magnification; and the first lens group substantially consists of an eleventh lens, a twelfth lens, a thirteenth lens, and a fourteenth lens in this order from the object side.

Abstract: A zoom lens substantially consists of a negative first lens group, a positive second lens group, a negative third lens group, a positive fourth lens group, and a positive fifth lens group in this order from the object side; wherein the first lens group through the fourth lens group move along the optical axis while changing magnification from the wide angle end to the telephoto end so as to change the distances among one another such that 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 increased; the fifth lens group is fixed with respect to an image surface while changing magnification; and conditional formulas (1) and (2) below are satisfied: 0.15<|f1|/f2<1.00??(1) 0.1<f4/f5<1.1??(2).