Abstract: An image pickup apparatus includes a zoom lens and an image pickup element. The zoom lens includes a first positive lens unit, a first negative lens unit, a stop, and a second positive lens unit. For zooming, the first positive lens unit is stationary, the first negative lens unit moves, and the second positive lens unit moves. A position at a telephoto end of the first negative lens unit is on the image side of a position at the wide angle end. A position at a telephoto end of the second positive lens unit is on the object side of a position at the wide angle end. For focusing, the first positive lens unit is stationary. A first positive lens unit object-side system has a negative refractive power. A first positive lens unit image-side system has a positive refractive power. The image pickup apparatus satisfies predetermined conditional expressions.

Abstract: A zoom lens includes a negative lens unit arranged closest to an enlargement conjugate side among lens units having negative refractive power included in the zoom lens, at least one positive lens unit having positive refractive power arranged closer to the enlargement conjugate side than the negative lens unit, and a rear lens unit including at least one lens unit and arranged closer to a reduction conjugate side than the negative lens unit, wherein a distance between adjacent lens units is changed during zooming, a stop is arranged closer to the reduction conjugate side than the negative lens unit, the rear lens unit includes at least one positive lens, and the positive lens satisfies a predetermined condition.

Abstract: A projection lens, in order along an optical axis from an image formation side to an image source side, includes a first lens, an aperture, a second lens, a third lens, and a fourth lens. The first lens is a meniscus lens with positive refractive power and a convex surface thereof facing the image formation side, and has at least an aspheric surface. The second lens is a biconcave lens with negative refractive power, and has at least an aspheric surface. The third lens is a biconvex lens with positive refractive power, and the fourth lens is a biconvex lens with positive refractive power, and has at least an aspheric surface. Therefore, the projection lens has a small size and high zoom ratio.

Abstract: Adaptive optical zoom systems and methods are described herein. One example of a method for adaptive optical zoom includes receiving an image at a focal plane array through a number of variable focal length elements, determining a quality of the image, and altering an amperage of the number of variable focal length elements to increase the quality of the image.

Abstract: A large aperture zoom optical system and an image pickup apparatus have a five-lens-group arrangement of positive-negative-positive-negative-positive refractive powers. At the time of zooming, the fifth lens group is fixed, and at least the second lens group, the third lens group and the fourth lens group are moved. The third lens group for use in focusing is composed of a single lens element.

Abstract: A zoom lens has first through fourth lens groups from the object side to the image side, and changes the magnification by changing their intervals. The first and third lens groups and the second and fourth lens groups have negative and positive powers, respectively. When changing the magnification from the wide-angle end to the telescopic end, the interval between the first and the second lens groups is reduced. The first lens group includes a reflective optical element. The second lens group includes at least two lenses, and the lens nearest to the image is a single plastic positive lens. The third lens group is configured by a single plastic negative lens. When the focal length of the single lens nearest to the image in the second lens group is defined as f2L and the focal length of the third lens group is defined as f3, “0.60<|f2L/f3|<1.60” is satisfied.

Abstract: The endoscope objective lens is configured such that focusing from the farthest object to the nearest object is achieved by moving at least one lens group other than the most object-side lens group along the optical axis. One of the at least one lens group to be moved during focusing is a negative lens group. The one negative lens group that is moved during the focusing consists of a cemented lens that is formed by a positive lens and a negative lens cemented together in this order from the object side. The cemented surface of the cemented lens is oriented such that the concave surface faces the object side. Given conditional expressions are satisfied.

Abstract: A zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, and a positive fifth lens group. Upon zooming from the short to long focal length extremities, the distance between the first and second lens groups increases, and the distance between the second and third lens groups decreases. The following conditions are satisfied: 0.30<f1/ft<0.43, and 7.0<M2t/M2w<17.0. f1 designates the focal length of the first lens group, ft designates the focal length of the zoom lens system at the long focal length extremity, and M2w and M2t designate the lateral magnifications of the second lens group when focusing on an object at infinity at the short and long focal length extremities, respectively.

Abstract: A zoom lens system wherein a positive lens unit located closest to an object side is fixed with respect to an image surface in zooming, a negative lens unit, among lens units located on an image side relative to an aperture diaphragm, is a focusing lens unit which moves along an optical axis in focusing, and the conditions: ?1.8<fn/fW<?0.3 and 0.1<T1/fW<1.5 (fn: a composite focal length of the negative lens unit, T1: an axial thickness of the positive lens unit located closest to the object side, fW: a focal length of the entire system at a wide-angle limit) are satisfied.

Abstract: A variable focal length lens system including: a first lens group having positive power; a second lens group having negative power; a third lens group having positive power; and a fourth lens group having positive power sequentially arranged from a side where an object is present. An aperture stop is disposed between the second and third lens groups. The first to fourth lens groups are so moved that the distance between the first and second lens groups increases, the distance between the second and third lens groups decreases, and the distance between the third and fourth lens groups decreases when a lens position setting is changed from a wide angle end state to a telescopic end state. The third lens group includes a negative lens and a positive lens disposed on the image side thereof. The variable focal length lens system satisfies the conditional expression, 0.35<f3/|f3a|<0.8.

Abstract: In a lithographic projection system, a corrective optic in the form of one or more deformable plates is mounted within telecentric image or object space for making one-dimensional or two-dimensional adjustments to magnification. The deformable plate, which can be initially bent under the influence of a preload, contributes weak magnification power that influences the magnification of the projection system by changing the effective focal length in object or image space. An actuator adjusts the amount of curvature through which the deformable plate is bent for regulating the amount of magnification imparted by the deformable plate.

Abstract: In a zoom lens system, an optical apparatus, and a manufacturing method, there are provided, in order from an object side: a first lens group having positive power, a second lens group having negative power, a third lens group having positive power, a fourth lens group having negative power, a fifth group having positive power, and an aperture stop disposed to an image side of the second lens group. Upon zooming from a wide-angle end state to a telephoto end state, a distance between the first lens and second lens groups increases, a distance between the second and third lens groups decreases, a distance between the third and fourth lens groups varies, and a distance between the fourth and fifth lens groups varies. With given conditions being satisfied, high optical performance with suppressing variation in aberrations are achieved.

Abstract: A zoom lens assembly may enlarge/reduce an image without shifting a position of a lens set. A housing, a zoom lens unit and a drive unit may be provided. The zoom lens unit may include a plurality of lenses stationarily arranged within the housing by being spaced apart in prescribed distance from each other along an optic axis. The plurality of the lenses respectively have variable refractive indexes without a position shift. The drive unit may pressurize a prescribed one of the lenses to vary the refractive index of the prescribed lens. The controller may control the drive unit to change a focal distance of the zoom lens unit to enlarge or reduce an image.

Abstract: An imaging lens, an optical apparatus equipped therewith, and a method for manufacturing the imaging lens are provided. The imaging lens includes a front lens group having negative refractive power disposed to the most object side and a rear lens group having negative refractive power, disposed to an image side of the front lens group and moving at least a portion thereof in a direction including a component substantially perpendicular to an optical axis. The rear lens group includes G3a having negative refractive power, G3b having negative refractive power, and G3c having positive refractive power. G3b is disposed between G3a and G3c. G3b side lens surface of G3a is a concave surface facing G3b. G3b is a negative meniscus lens shape having a concave surface facing G3a. At least one lens surface among optical surfaces of G3a, G3b and G3c is an aspherical surface.

Abstract: Providing an optical system having excellent optical performance with sufficiently correcting spherical aberration and curvature of field, an imaging apparatus, and a method for forming an image by the optical system. The optical system includes a plurality of lens groups, at least one of the plurality of lens groups having an A lens that satisfies at least one of given conditional expressions.

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

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, an aperture stop, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power. In the zoom lens, during zooming from a wide-angle end to a telephoto end, the first lens unit is configured to remain stationary, the second lens unit, the third lens unit, and the fourth lens unit are configured to move separately from one another, and the aperture stop is configured to move along a locus convex towards the object side.

Abstract: A zoom lens including, in order from object side to image side: a first positive lens unit which does not move for zooming; a second negative lens unit which moves during zooming; a third positive lens unit which moves during zooming; a fourth lens unit which moves during zooming; and a fifth positive lens unit which does not move for zooming. The second unit passes through a point at which magnification of the second unit becomes ?1 during zooming from wide-angle end to telephoto end, and ?1<?34<?0.3, and 4.0<|m2/m3|<15 are satisfied where ?34 represents a magnification of a combined unit including the third and fourth units at a zoom position fz at which the magnification of the second unit becomes ?1, and m2 and m3 respectively represent displacements of the second and third units on optical axis at the zoom position fz with reference to the wide-angle end.

Abstract: A zoom lens system comprising: a negative first lens unit; a positive second lens unit; and a positive third lens unit, wherein the first to third lens units are individually moved along an optical axis to vary magnification in zooming, the first lens unit is composed of two lens elements and includes a positive lens element having at least one aspheric surface, the third lens unit is composed of one lens element, and the condition: 1.74<Ir/?{square root over ((|DL1×fG1|))} (DL1: an optical axial thickness of an object side first lens element in the first lens unit, fG1: a focal length of the first lens unit, Ir=fT×tan(?T), fT and ?T: a focal length of the entire system and a half value of maximum view angle at a telephoto limit) is satisfied; an imaging device; and a camera are provided.

Abstract: According to various aspects, an optical zoom lens system and a method magnifying an image using an optical zoom lens system are disclosed. In one example, the optical zoom lens system comprises a first lens group including a first focus-tunable lens and a first negative lens, a second lens group, positioned after the first lens group in an optical path, a third lens group, positioned after the second lens group in the optical path, and a fourth lens group, positioned after the third lens group in the optical path, including a second focus-tunable lens and a second negative lens.

Abstract: The invention relates to an electronic image pickup system whose depth dimension is extremely reduced, taking advantage of an optical system type that can overcome conditions imposed on the movement of a zooming movable lens group while high specifications and performance are kept. The electronic image pickup system comprises an optical path-bending zoom optical system comprising, in order from its object side, a 1-1st lens group G1-1 comprising a negative lens group and a reflecting optical element P for bending an optical path, a 1-2nd lens group G1-2 comprising one positive lens and a second lens group G2 having positive refracting power. For zooming from the wide-angle end to the telephoto end, the second lens group G2 moves only toward the object side. The electronic image pickup system also comprises an electronic image pickup device I located on the image side of the zoom optical system.

Abstract: A zoom lens includes, in order from an object side to an image side, a positive first lens unit, a negative second lens unit, an aperture stop, a positive third lens unit, and a positive fourth lens unit. The third lens unit includes, in that order, a positive first lens sub-unit, and a negative second lens sub-unit. The second lens sub-unit is movable in a direction having a component perpendicular to an optical axis to change an image forming position in a direction perpendicular to the optical axis. A distance on the optical axis between the aperture stop and the third lens unit at a wide-angle end, a composite focal length of the first lens unit and the second lens unit at the wide-angle end, a focal length of the first lens sub-unit, and a focal length of the second lens sub-unit are appropriately set.

Abstract: A zoom lens includes first to third lens units having positive, negative, and positive refractive power, respectively, and a rear lens group having positive refractive power. An aperture stop is arranged between a lens surface of the second lens unit closest to the image side and a lens surface of the third lens unit closest to the image side. The third lens unit includes first and second positive lenses each including an aspheric surface, and a negative lens. In the third lens unit, a refractive index of the first positive lens, and an Abbe number and relative partial dispersion of the second positive lens are appropriately set.

Abstract: A zoom lens includes, in order from its object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power. At a time of zooming from the wide angle end to the telephoto end, the lens units move in such a way that the distance between the first lens unit and the second lens unit decreases and the distance between the second lens unit and the third lens unit increases. The zoom lens satisfies the conditions “0.35<|f1|/ft<0.55” and “1.80<Npa”, where ft is the focal length of the entire system at the telephoto end, f1 is the focal length of the first lens unit, and Npa is the average of the refractive indices of the materials of all the positive lenses in the entire system.

Abstract: A zoom lens system, in order from an object side to an image side, comprising a first lens unit having negative optical power, a second lens unit having positive optical power, a third lens unit having negative optical power, and a fourth lens unit having positive optical power, wherein the second lens unit is, in order from the object side to the image side, composed of an object-side second lens unit and an image-side second lens unit, the image-side second lens unit moves in a direction perpendicular to an optical axis to optically compensate image blur, and the condition: 1<|f2I/fW|<10 (f2I: a composite focal length of the image-side second lens unit, fW: a focal length of the entire system at a wide-angle limit) is satisfied.

Abstract: A microscope system and observation control method. An electric zoom consecutively changes a magnification for a sample. A revolver includes a plurality of objective lenses of different magnifications and switches the objective lens placed in an observation optical path to intermittently change the magnification for the sample. A control section calculates a total magnification at which the sample is observed based on a magnification provided by the electric zoom and the magnification of the objective lens currently placed in the observation optical path. The control section operates when the revolver switches the objective lens placed in the observation optical path, to determine a target magnification that is the magnification of the electric zoom required to keep the total magnification obtained after the switching of the objective lens equal to the total magnification obtained before the switching of the objective lens.

Abstract: A compact and lightweight zoom lens system having excellent imaging performance, which is favorably applicable to an interchangeable-lens type digital camera system, is provided. The zoom lens system of the present invention includes, in order from an object side to an image side, a first lens unit having positive optical power and composed of not more than two lens elements, a second lens unit having negative optical power, a third lens unit having negative optical power, and a fourth lens unit having positive optical power. In zooming from a wide-angle limit to a telephoto limit, the fourth lens unit moves along an optical axis. Further, the following conditions are satisfied: 1.50<nd1<1.72, 50<vd1<75 (nd1: a refractive index to the d line of a positive lens element constituting the first lens unit, vd1: an Abbe number of a positive lens element constituting the first lens unit).

Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having negative refractive power, a second lens unit having positive refractive power, and a third lens unit having positive refractive power. A distance between every adjacent ones of the first to third lens units varies during zooming. The second lens unit includes, in order from the object side to the image side, a positive lens and a cemented lens in which a positive lens and a negative lens are cemented. A focal length (f2) of the second lens unit, a focal length (fT) of the entire zoom lens at a telephoto end, and an average refractive index (Npave) of materials of the positive lenses included in the entire zoom lens are appropriately set.

Abstract: Provided is a zoom lens including a focus lens portion, a zoom portion, an aperture stop, and a relay portion that does not move for zooming but comprises a negative fourth-first unit, a fourth-second unit interchangeable for an optical path, a positive fourth-third unit, and a fourth-fourth unit inserteable for the optical path for shifting a focal length range of an entire system to a long focal length side after removing the fourth-second unit from the optical path, and a distance on an optical axis between the aperture stop and a last lens surface of the fourth-fourth unit in a state of inserting the fourth-fourth unit in the optical path, a distance on the optical axis between a first lens surface and the last lens surface of the fourth-fourth unit, and an aperture diameter in an opened state of the aperture stop satisfy a predetermined conditions.

Abstract: The present invention relates to an imaging lens, the imaging lens including, in an ordered way from an object side, a first movable lens having a positive (+) refractive power, a second lens having a negative (?) refractive power, a third lens having a positive (+) refractive power, a fourth lens having a positive (+) refractive power, and a fifth lens having a negative (?) refractive power.

Abstract: Provided are a telephoto zoom lens system and an electronic apparatus including the telephoto zoom lens system. The telephoto zoom lens system includes a first lens group having a positive refractive power and is fixed when zooming and focusing, a second lens group having a negative refractive power, a third lens group having a negative refractive power and performs focusing, a fourth lens group having a positive refractive power, and a rear lens group comprising one or more lens groups located between the fourth lens group and an image side. At least one lens group of the rear lens group is fixed while zooming, and a focal length thereof is unchanged while zooming.

Abstract: A zoom lens system comprising a plurality of movable lens units which individually move along an optical axis at the time of zooming, wherein a lens unit located closest to an object side is fixed relative to an image surface at the time of zooming, at least two of the movable lens units are focusing lens units which move along the optical axis at the time of focusing in at least one zooming position, and the condition: 0.1<T1/fW<1.5 (T1: an axial thickness of the lens unit located closest to the object side, fW: a focal length of the entire system at a wide-angle limit) is satisfied; an interchangeable lens apparatus; and a camera system are provided.

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

Abstract: A zoom lens includes: first, second, third and fourth lens groups having negative power, positive power, negative power and positive power, respectively, and sequentially arranged from an object side toward an image side. When the magnification at a wide angle side is changed to the magnification at a telescopic side, the first lens group is so moved along an optical axis that the distance between the first lens group and the second lens group decreases, and the second third and fourth lens groups are moved from the image side toward the object side, the third lens group is moved along the optical axis for focusing, and the zoom lens satisfies the following conditional expression (1) ?2.0<f3/?(fw×ft)<?0.3??(1) where f3, fw and ft represent the focal lengths of the third lens group, the entire lens system at the wide angle end, and the entire lens system at the telescopic end, respectively.

Abstract: Disclosed herein is a zoom lens including a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power. The respective lens groups move in magnification variation from a wide angle end to a telephoto end. The fourth lens group is moved in optical axis direction to correct variation of an imaging position in association with magnification variation and perform correction of the imaging position in association with object distance change. Condition expression (1) is satisfied. 0.60<f1/(fw·ft)1/2<1.

Abstract: An adjustable lens includes a first lens member having a first corrugated surface, a second lens member having a second corrugated surface, and blackout regions disposed between the first and second corrugated surfaces. The first corrugated surface includes a periodic structure of alternating ridge and groove sections. The second corrugated surface includes a periodic structure of alternating ridge and groove sections. The blackout regions are positioned to block image light passing through either the ridge sections of the first lens member, or alternatively, the groove sections of the first lens member.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group, in that order from the object side. The second lens group constitutes a focusing lens group. The following conditions (1) and (2) are satisfied: 0.4<|d12w/f1|<1.06??(1); and d12w<d23w??(2), wherein f1 designates the focal length of the first lens group, and d12w and d23w designate the air distances between the first and second lens groups, and the second and third lens groups respectively, at the short focal length extremity.

Abstract: A telephoto zoom lens system includes a first lens group having a positive focal length, a second lens group having a negative focal length, a third lens group having a positive or negative focal length, a fourth lens group having a positive focal length, and a fifth lens group for performing hand shake compensation by allowing a portion of the fifth lens group to move perpendicularly to the optical axis. During zooming, the first and fifth lens groups are fixed and the second, third, and fourth lens groups move, and the third or fourth lens group is a focusing lens group.

Abstract: An image pickup apparatus includes a taking optical system and an image pickup element. The taking optical system includes at least two zoom optical systems having the same focal length range. The distance between the optical axes of any two zoom optical systems among the plurality of zoom optical systems is substantially constant over a range from an incidence surface to an image pickup surface of the image pickup element. The plurality of zoom optical systems are arranged in such a way as to form images of an object respectively in different regions on the image pickup surface of the same image pickup element.

Abstract: Provided is a zoom lens that has a plurality of lens groups and performs zooming by changing spaces between the plurality of lens groups. A final lens group closest to an image side includes, in order from an object side to an image side: a first partial lens group that has a negative refractive power; a second partial lens group that has a positive refractive power; and a third partial lens group that has a positive refractive power. Image blur is corrected by shifting the second partial lens group in a direction substantially perpendicular to an optical axis. Assuming that a focal length of the first partial lens group is fGF, a focal length of the second partial lens group is fGS, and a focal length of a whole lens system of the lens groups in a telephoto end state is ft, the following expressions are satisfied: ?0.24<fGF/ft<?0.09; and 0.12<fGS/ft<0.32.

Abstract: A projection optical system which, when projecting an image of an optical modulator onto a projection surface on an enlarged scale, differs the aspect ratio of the image of the optical modulator and the aspect ratio of the image projected onto the projection surface, and includes, in order from the projection surface, a first group which is an enlargement optical system; a second group includes an adjustment optical component with a surface rotationally asymmetrical to an optical axis, when defining at least one direction of the vertical direction and the horizontal direction of the optical modulator as an adjustment direction in which conversion adjustment using compression or extension is performed, the adjustment optical component having at least one optical system which differs in power between the adjustment direction and another direction; and a third group which has a correction optical component with a surface rotationally symmetrical to the optical axis.

Abstract: A microscope system for imaging of an object that can be placed in an object plane of a microscope system includes an imaging system for providing at least one pair of optical imaging paths that include a stereoscopic angle in the object plane. The imaging system includes a first subsystem comprising a first plurality of optical lenses that are commonly traversed by both optical imaging paths of the at least one pair of optical imaging paths. The imaging system also includes a second subsystem comprising a second plurality of optical lenses that are traversed by only one optical imaging path. At least two optical lenses of the first plurality of optical lenses and at least two optical lenses of the second plurality of optical lenses are displaceable relative to one another along a common optical imaging path to respectively vary a magnification of the representation of the object.

Abstract: A zoom lens system comprising: a negative first lens unit including at least one positive lens element; a positive second lens unit including at least one negative lens element; and subsequent lens units including an aperture diaphragm, wherein the subsequent lens units include a most-image-side lens unit fixed to an image surface in focusing, a first focusing lens unit is provided between the aperture diaphragm and the most-image-side lens unit, and the conditions: 1.0<LSW/{fT×tan(?T)}<2.6 and 0.8<LG1G2/fW<2.8 (LSW: axial distance from aperture diaphragm to image surface at wide-angle limit, fT: focal length of entire system at telephoto limit, ?T: half view angle at telephoto limit, LG1G2; axial distance between most-image-side lens element in first lens unit and most-object-side lens element in second lens unit at wide-angle limit, fW: focal length of entire system at wide-angle limit) are satisfied.

Abstract: A zoom lens includes, in order from an object side to an image side, first to fifth lens units respectively having positive, negative, positive, negative, and positive refractive powers. During zooming from a wide-angle end to a telephoto end, each of the lens units moves in such a way that a distance between the first and second lens units increases, a distance between the second and third lens units decreases, a distance between the third and fourth lens units increases, and a distance between the fourth and fifth lens units increases. The distances D34w and D34t between the third and fourth lens units, the distances D45w and D45t between the fourth and fifth lens units, focal lengths fw and ft of the entire zoom lens, and focal lengths f1 and f4 of the first and fourth lens units are appropriately set.

Abstract: A zoom lens includes, in order from an object side to an image side: a positive first lens unit; a positive second lens unit; and an aperture stop disposed between the first and second lens units and moving along a locus different from loci of the first and the second lens units during zooming, the first and second lens units being configured to change an interval therebetween during zooming, the second lens unit including at least one positive lens and at least one negative lens. A distance from a lens surface closest to the object side in the entire system to the aperture stop at a wide angle end, and a distance from the lens surface closest to the object side in the entire system to a lens surface closest to the object side in the second lens unit at the wide angle end are each appropriately set.

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 negative optical power, and a fourth lens unit having positive optical power, wherein the third lens unit moves along an optical axis in focusing from an infinity in-focus condition to a close-object in-focus condition, and the conditions: 0.5<|f3/fW|<2.0 and 0.005<d3/fW<0.070 (f3: a focal length of the third lens unit, d3: an optical axial thickness of the third lens unit, fW: a focal length of the entire system at a wide-angle limit) are satisfied; an interchangeable lens apparatus; and a camera system are provided.

Abstract: A zoom lens includes, in order from an object side, a positive first lens unit which does not move for zooming, a negative second lens unit which moves in an optical axis direction for zooming, a negative third lens unit which moves in the optical axis direction for zooming so as to correct image plane variation due to zooming, and a positive fourth lens unit which does not move for zooming. The fourth lens unit includes, in an order from the object side, a positive first sub lens unit and a positive second sub lens unit, which are separated by a largest air interval in the fourth lens unit. Abbe constants, partial dispersion ratios, and coefficients of the refractive index variation due to the temperature variation are appropriately set for lens materials forming the third lens unit, the first sub lens unit, and the second sub lens unit.

Abstract: A lens system comprises, on a side closest to an object, a first lens component having a positive refractive power and a second lens component having a positive refractive power in order from the object; and on a side closest to an image, a cemented lens constructed by cementing together a positive lens and a negative lens in order from the object; wherein the lens system satisfies the following conditional expressions: (n1+n2)/2>1.49 (?1+?2)/2>60 where n1 and ?1 denote a refractive index and an Abbe number of the first lens component at d-line, respectively, and n2 and ?2 denote a refractive index and an Abbe number of the second lens component at d-line, respectively.

Abstract: The disclosed internal focusing large-aperture medium telephoto lens has as lens groups a positive first lens group, a positive second lens group, and a third lens group, in that order from the object side. When focusing on nearby objects, the first lens group and the third lens group have a fixed position relative to the image surface, and the second lens group displaces toward the object side. The second lens group has only one negative lens, and, in order from the object side, has at least a positive lens, a negative lens, and a positive lens. The following expression is fulfilled: ?0.5<(R1+R2)(R1?R2)<?0.1 (wherein, R1: radius of curvature of the object side surface of the negative lens in the second lens group; R2: radius of curvature of the image side surface of the negative lens in the second lens group).

Abstract: A zoom lens includes: a first lens group having positive refracting power; a second lens group having negative refracting power; a third lens group having positive refracting power; a fourth lens group having positive refracting power; and a fifth lens group having positive refracting power arranged in this order from an object side toward an image side, wherein when the zoom lens undergoes zooming operation from a wide-angle end toward a telescopic end, the first lens group moves away from the second lens group toward an object to be imaged, the third lens group approaches the second lens group toward the object, and the fourth lens group approaches the third lens group toward the object, and the zoom lens satisfies the following conditional expression (1) 4.5<100×D(T,2?3)/fW<15??(1).