Abstract: An image capturing optical assembly includes, in order from an object side to an image side, a first lens group, a second lens group and a third lens group, wherein the first lens group includes a first lens element and a second lens element, the second lens group includes a third lens element, a fourth lens element and a fifth lens element, and the third lens group includes a sixth lens element, a seventh lens element and an eighth lens element. At least one surface of at least one of the lens elements of each lens group is aspheric. At least one surface of at least one of the lens elements includes at least one inflection point.

Abstract: A zoom lens system includes, in order from the object side to the image side, a first lens group having negative power and a second lens group having positive power. The first lens group includes at least two negative lenses. When zooming, one of the first lens group and the second lens group is fixed relative to the imaging surface, and the other moves along an optical axis to change an angle of view.

Abstract: A wide-angle lens includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens, all of which are arranged in sequence from an object side to an image side along an optical axis. The first lens is a convex-concave lens with negative refractive power and includes a convex surface facing the object side and a concave surface facing the image side. The second lens is a biconcave lens with negative refractive power. The third lens is a biconvex lens with positive refractive power. The fourth lens includes a convex surface facing the object side. The fifth lens is with positive refractive power and includes a convex surface facing the image side. The sixth lens is a biconvex lens with positive refractive power. The seventh lens is a biconcave lens with negative refractive power. The eighth lens is a biconvex lens with positive refractive power.

Abstract: A zoom lens includes: a first lens unit having a negative refractive power; and a rear group having a positive refractive power, in which, when a focal length of the zoom lens is a shortest focal length, a maximum image height is lower than a half of a diagonal length of an image pickup region, and when a focal length of the zoom lens at which the maximum image height becomes a half of the diagonal length of the image pickup region is defined as an intermediate focal length, a focal length of the zoom lens at a longest focal length, a half angle of field of the zoom lens at the longest focal length, and other such factors are appropriately set so that the maximum image height is increased continuously from the shortest focal length to the intermediate focal length.

Abstract: A variable magnification optical system consists of a negative first lens group, a stop that is fixed relative to an image plane during magnification change, and a positive second lens group, which are in this order from an object side. A distance between the first lens group and the second lens group in an optical axis direction becomes shorter when magnification is changed from a wide-angle end to a telephoto end. The first lens group consists of a positive lens having a convex object-side surface and two negative lenses, in this order from the object side. The variable magnification optical system satisfies the following formula (1) about Abbe number ?d1 of the positive lens in the first lens group for d-line: 25.5<?d1<50??(1).

Abstract: A zoom lens including, along an optical axis and in order from an object space to an image space: first lens group with negative power; an aperture stop; a second lens group with positive power; a third lens group with positive power; and a fourth lens group. The second and third lens groups and the aperture stop are axially movable for zooming. At least one lens element in the first lens group is moveable to provide for focusing. The aperture stop moves independently of the lens groups during zooming and has a clear aperture that changes size during zooming.

Abstract: A zoom lens system includes, in order from an object, a front group G1 having negative refractive power, a rear group G2 having positive refractive power, zooming being conducted by varying a distance between the front group G1 and the rear group G2, the front group G1 including at least a negative lens and a positive lens, and the rear group G2 including, in order from an object side, a first partial group LA having positive refractive power, a second partial group LB having negative refractive power, a third partial group LC having positive refractive power and a negative lens LD, and predetermined conditions being satisfied, thereby providing a zoom lens system which is compact in size, and has small back focus and excellent optical property.

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

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

Abstract: A zoom lens system has, in order from the enlargement side, a first lens group that remains stationary during zooming and that has a negative optical power and a plurality of lens groups that move during zooming. The first lens group includes three lens groups each having a negative optical power, namely a 1a-th lens group, a 1b-th lens group, and a 1c-th lens group. The 1a-th lens group remains stationary during focusing and includes at least one positive lens element. The 1b-th lens group moves toward the reduction side during focusing from infinity to a close distance. The 1c-th lens group moves toward the enlargement side during focusing from infinity to a close distance.

Abstract: A zoom lens includes a first lens unit having a positive refractive power which does not move for zooming; a second lens unit having a negative refractive power which moves during zooming; a third lens unit having a negative refractive power which moves during zooming; a fourth lens unit having a positive refractive power which moves during zooming; and a fifth lens unit having a positive refractive power which does not move for zooming. Air intervals (L2w and L2t) between the second lens unit and the third lens unit at a wide-angle end and at a telephoto end, respectively, an air interval (L3w) between the third lens unit and the fourth lens unit at the wide-angle end, a focal length (f1) of the first lens unit, and a combined focal length (f23w) of the second lens unit and the third lens unit at the wide-angle end are appropriately set.

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

Abstract: A zoom lens system 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 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: To provide an image forming optical system that can achieve good correction of chromatic aberration, which is seriously needed particularly when the zoom ratio is high, while achieving slimness and a high zoom ratio and to provide an electronic image pickup apparatus equipped with such an image forming optical system, an image forming optical system has a lens group A including a lens component made up of a positive lens LA and a negative lens LB cemented together and having a negative refracting power as a whole. The lens group A is arranged between a lens group I closest to the object side and an aperture stop. The distance between the lens group I and the lens group A changes for zooming. The lens component has an aspheric cemented surface, and a certain condition concerning the shape of the aspheric surface is satisfied.

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 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: 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: 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: 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: 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 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: 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 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 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 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 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 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, 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, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein in zooming, the intervals between the respective lens units vary, and the condition (I-1): 2?W/FW?34 (fT/fW>2.0, ?W: a half view angle (°) at a wide-angle limit, FW: an F-number at a wide-angle limit, fT: a focal length of the entire system at a telephoto limit, fW: a focal length of the entire system at a wide-angle limit) is satisfied, having a high resolution and a short overall optical length (overall length of lens system), and still having a view angle of 70° or greater at a wide-angle limit, which is satisfactorily adaptable for wide-angle image taking, and yet having a large aperture with an F-number of about 2.0 at a wide-angle limit; an imaging device; and a camera.

Abstract: An image pickup lens includes: a first lens group including a single negative lens and a single positive lens disposed in order from the object side to the image side and having a positive refracting power; and a second lens group having a positive refracting power. The first and second lens groups are disposed in order from the object side to the image side. The first lens group is fixed, when the image pickup object distance varies from the infinity to the proximity, with respect to an image surface while the second lens group is moved from the image side to the object side to carry out focusing.

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: An observation optical system has a negative lens unit including a cemented lens, arranged at the most object-side position; an annular reflecting mirror placed on the image side of the negative lens unit, with a reflecting surface facing the image side; and an imaging lens unit arranged on the image side of the negative lens unit and the annular reflecting mirror.

Abstract: The projection zoom lens system includes a negative first lens group, a positive second lens group, a third lens group, a positive fourth lens group, a fifth lens group, and a positive sixth lens group. The lens system is nearly telecentric on a reduction side. During zooming, the second to fifth lens groups are moved while the first and six lens groups remain stationary. The third lens group includes a positive lens LP having a convex surface directed to a magnification side, and a negative lens LN having a concave surface which is directed to the reduction side and has a curvature stronger than a magnification-side surface of the negative lens LN. The conditional expression of 5.0?|fG3/RLN-2| is satisfied. Here, fG3 denotes a focal length of the third lens group, and RLN-2 denotes a radius of curvature of the reduction-side surface of the negative lens LN.

Abstract: A projection zoom lens is provided and includes: in order from the magnification side, a negative first lens group performing focusing with being fixed during power-varying; a positive second lens group, a positive third lens group, a positive fourth lens group, a positive fifth lens group, which are moved with correlation; and a positive sixth lens group fixed during the power-varying. An aperture diaphragm is moved between the fourth lens group and the fifth lens group during the power-varying to keep Fno constant in the whole power-varying region. In addition, the expression of 1.7<Bf/f<3.0 is satisfied, where f is a focal length of the whole system, and Bf is a back focal length (air conversion distance) of the whole system.

Abstract: A zoom lens comprises a plurality of lens units including a first lens unit disposed most adjacent to an enlargement side and having negative refractive power, wherein one or more lens units of the plurality of lens units are moved in the direction of the optical axis thereof during magnification change, and wherein the first lens unit includes a 1-1st lens unit comprising at least one lens of negative refractive power and moved during focusing and a 1-2nd lens unit having positive refractive power, and fixed during focusing.

Abstract: Photographic wide angle zoom objective of the retrofocus type having a group of negative refractive power (VG?) comprising four lens components (L1, L2, L3, L4) and being a front group when seen from the object side, and having a rear group of positive refractive power (HG+) including six lens components (L5, L6, L7, L8, L9, L10) and facing an image plane, the distance between the rear group (HG+) and the image plane (BE) being increased, and the distance between the front group (VG?) and image plane (BE) being reduced, during an increase in the focal length, characterized in that the first two lens components (L1, L2) have a negative refractive power when seen from the object side in the light direction, the third and fourth lens components (L3, L4) are grouped into a cemented component with a positive total refractive power and the fifth lens component (L5) has a positive refractive power, the sixth and seventh lens components (L6, L7) are grouped into a cemented component with a positive total refractive p

Abstract: A compact zoom lens includes a first lens group (1, 3) of negative refractive power disposed on an object side and a second lens group (2, 4) of positive refractive power disposed on an image side. Both the first and second lens groups are movable. The first and second lens groups defines a variable distance therebetween. During zooming from the wide-angle end to the telephoto end, the second lens group moves toward the object side and the variable distance between the first and second lens groups decreases. The compact zoom lens has a long back focal length with various aberrations satisfactorily corrected.

Abstract: A zoom lens system is disclosed that includes a front first lens group including a first lens of divergent meniscus and a second lens of plano-convex; an intermediate second lens group including a third lens of plano-concave, a fourth lens of plano-concave, and a fifth lens of plano-convex; and a rear third lens group including a sixth lens of double-convex, a seventh lens of double-convex, an eighth lens of plano-concave, and a ninth lens of plano-concave. The sixth and ninth lenses are non-spherical lenses formed of a plastic material, and the zoom lens system satisfies the following conditions (a) 0.16<fw/f1<0.21 (b) ?0.78<fw/f2<?0.64 (c) 0.70<fw/f3<0.75 (d) 0.47<log Z3/log Z<0.76.

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 first lens unit moves in a locus convex toward the image side and the second lens unit moves toward the object side during zooming from a wide-angle end to a telephoto end. The object side principal point position of the first lens unit is within the first lens unit. The movement locus of the image side principal point position of the first lens unit during zooming from the wide-angle end to the telephoto end intersects with the movement locus of the object side principal point position of the second lens unit during zooming from the wide-angle end to the telephoto end.

Abstract: A zoom lens includes a first lens group with a negative refractive power and a second lens group with a positive refractive power. The first lens group includes a first lens, a second lens, a third lens and a fourth lens arranged in sequence and refractive powers thereof are negative, negative, negative and positive respectively. The first and second lenses are meniscus lenses and two surfaces of the second lens are aspheric surfaces. The third lens is a biconcave lens and the fourth lens is a biconvex lens. The second lens group includes a fifth lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens arranged in sequence and refractive powers thereof are positive, positive, positive, negative and positive respectively. A cemented doublet lens is composed of the seventh and eighth lenses. The ninth lens is a biconvex lens.

Abstract: A compact zoom lens suitable for an imaging optical system using a solid-state image sensing device is provided. The zoom lens includes 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. The first through third lens groups are sequentially arranged from an object side toward an image side. The first, second, and third lens groups move when magnification changes from the wide-angle position to the telephoto position, and a refractive index G1n of at least one lens element included in the first lens group satisfies 1.90<G1n<2.00.

Abstract: A zoom lens system comprises, in order from an object side, a negative first lens group G1, a positive second lens group G2 and a positive third lens group that has positive refractive power. In the zoom lens system, zooming is carried out by moving the first lens group and the second lens group, the first lens group consists of two or three lenses that include a negative glass lens located closest to the object side, the second lens group consists, in order from the object side, of a cemented lens composed of a positive glass lens and a negative glass lens and a plastic meniscus lens that is convex on the object side and both surfaces of which are aspherical, the third lens group consists of one positive plastic lens, and a combined focal length f2 of the second lens group and a focal length Lf23 of the plastic meniscus lens in the second lens group satisfy the following condition 0<|f2/Lf23|<0.3.

Abstract: A fisheye lens system includes a negative first lens group and a positive second lens group, which are defined with respect to a maximum air-distance between lens elements constituting the fisheye lens system. The negative first lens group includes a first negative meniscus lens element having the convex surface facing toward the object, a second negative meniscus lens element having the convex surface facing toward the object, and a negative third lens element.

Abstract: A zoom lens having at least a first lens group including a reflection member for bending an optical axis fixedly during zooming and having a negative refractive power, a second lens group having a negative refractive power, and a third lens group arranged in the order from an object side is provided. In the zoom lens, an image can be shifted into a direction perpendicular to the optical axis by moving either of the second and the third lens groups (“shift lens group”) in a direction perpendicular to the optical axis, and a following conditional expression (1) is satisfied, 0.5<(1???)×?b<3.0,??(1) where: ??: a magnification of the shift lens group in a maximum telephoto state, and ?b: a magnification of a lens group arranged on an image surface side of the shift lens group in the maximum telephoto state.

Abstract: Provided is a projection lens, including: a plurality of moving lens units that move on an optical axis for zooming; and a plurality of plastic lenses containing plastic, in which when a focal distance of an i-th positive lens from a predetermined plane side of N positive lenses of the plurality of plastic lenses is given by fpi, a focal distance of a j-th negative lens from the predetermined plane side of M negative lenses of the plurality of plastic lenses is given by fnj, and fp and fn are defined by 1 fp = ? i = 1 N ? 1 fpi 1 fn = ? j = 1 M ? 1 fnj (N and M each are a natural number, that is, an integer equal to or larger than 1), ?0.56<fn/fp<?0.05 is satisfied.

Abstract: A varifocal zoom lens includes: a first lens group having a negative refractive power; a second lens group having a positive refractive power, including a cemented lens component L21 formed by combining a positive lens having a convex surface on the object side and a negative lens having a concave surface on an image side and a positive lens component L22 disposed on the image side with respect to the cemented lens component L21, spaced from the cemented lens component L21 by an air space and having a convex surface on the object side and disposed behind the first lens group with respect to an object side; and a third lens group having a positive refractive power and disposed behind the second lens group with respect to the object side.

Abstract: A wide-angle 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. Upon zooming from the short focal length extremity to the long focal length extremity, the distance between the negative first lens group and the positive second lens group decreases, the distance between the positive second lens group and the negative third lens group increases, and the distance between the negative third lens group and the positive fourth lens group decreases; and the positive second lens group, the negative third lens group and the positive fourth lens group move toward the object. The wide-angle zoom lens system satisfies the following conditions: 1.2<|f(i=1)/fW|<2.0??(1) 1.5<f(i=2)/fW<2.2??(2) 2.5<|f(i=3)/fW|<3.6??(3) 3.2<f(i=4)/fW<4.

Abstract: A zoom lens includes a plurality of lens groups including a first lens group arranged on the foremost side and having negative optical power. Zooming is performed by moving at least one of the plurality of lens groups along a direction parallel to an optical axis of the zoom lens. The first lens group is fixed during the zooming. A first lens arranged on the foremost side, of the first lens group has negative refractive power. When an Abbe constant and a partial dispersion of a material configuring the first lens are respectively represented by ?dn and ?g,Fn, a focal distance of the first lens group is represented by f1, and an air-equivalent back focus upon focusing on an infinity object is represented by bf, the following conditions are satisfied: ?dn<32, 0.008<?g,Fn?(0.644?0.00168×?dn)<0.040, and |f1/bf|<0.9.