Abstract: A variable magnification optical system comprises, in order from an object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power and a fourth lens group G4 having negative refractive power; upon varying a magnification, a distance between the first lens group G1 and the second lens group G2 being varied, a distance between the second lens group G2 and the third lens group G3 being varied, and a distance between the third lens group G3 and the fourth lens group G4 being varied; upon focusing, the fourth lens group G4 being moved; and a predetermined conditional expression being satisfied.

Abstract: A zoom optical system comprises, in order from an object: a front lens group (GFS) having a positive refractive power; an M1 lens group (GM1) having a negative refractive power; an M2 lens group (GM2) having a positive refractive power; an RN lens group (GRN) having a negative refractive power; and a subsequent lens group (GRS). Upon zooming, the distance between the front lens group (GFS) and the M1 lens group (GM1) changes, the distance between the M1 lens group (GM1) and the M2 lens group (GM2) changes, and the distance between the M2 lens group (GM2) and the RN lens group (GRN) changes. Upon focusing from an infinite distant object to a short distant object, the RN lens group (GRN) moves.

Abstract: A lens assembly includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged on an optical axis from an object side to an image side. The first lens is a meniscus lens having a negative refractive power. The second lens has a positive refractive power. The third lens has a positive refractive power, and has a convex image-side surface. The fourth lens has a positive refractive power. The fifth lens has a negative refractive power, and has a concave image-side surface. The lens assembly is formed compact, and has wide viewing angle and telecentric optical design.

Abstract: Provided is an optical system, including, 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 positive refractive power; a third lens unit having a negative refractive power; and a fourth lens unit having a positive refractive power, in which the second lens unit is configured to move in an optical axis direction during focusing, in which the third lens unit is configured to move, during image blur correction, in a direction having a vertical direction component with respect to an optical axis, and in which a configuration of the first lens unit and arrangement of an aperture stop and the third lens unit are each appropriately set.

Abstract: A zoom lens unit includes, in order from an object side to an image side, a first lens group having positive refractive power and a focus function, a second lens group having negative refractive power, which moves when changing a magnification, a third lens group which moves when changing a magnification, and a fourth lens group having positive refractive power, which is fixed when changing a magnification, wherein the following condition (1) is fulfilled: |M2W·M3W·M4W|<0.14??(1) where M2W represents an imaging magnification of the second lens group at a wide-angle end, M3W represents an imaging magnification of the third lens group at the wide-angle end, and M4W represents an imaging magnification of the fourth lens group at the wide-angle end.

Abstract: A zoom lens includes, in order from the object side, a positive first group, a negative second group, a stop, a positive third group, a negative fourth group, and a positive fifth group. During magnification change from the wide-angle end to the telephoto end, the first to fourth groups are moved to always increase the distance between the first and second groups, always decrease the distance between the second and third groups, and change the distance between the third and fourth groups and the distance between the fourth and fifth groups. The third group includes, in order from the object side, at least a positive lens, a positive lens, a negative lens, and a positive lens, and satisfies condition expression (1) below: 25<?dD??dA<70??(1), where ?dA and ?dD are Abbe numbers at the d-line of the most object-side lens A and the most image-side lens D.

Abstract: A zoom lens system comprising a positive first lens unit; a negative second lens unit; and subsequent five or six lens units, wherein an aperture diaphragm is provided, intervals between the adjacent lens units vary in zooming, the first lens unit moves in zooming and is fixed in focusing, and the conditions: BF/fW<0.66, DA/LW>0.42, and DAIR/Y<2.00 (BF: distance from an image-side surface apex of a most-image-side lens element to an image surface, fW: focal length of system at wide-angle limit, DA: sum of optical axial thicknesses of the lens units in system, LW: overall length of system at wide-angle limit, DAIR: maximum of air spaces between the lens elements constituting system at wide-angle limit, Y=fT×tan(?T), fT: focal length of system at telephoto limit, ?T: half view angle at telephoto limit) are satisfied.

Abstract: An image pickup 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 negative refractive power, arranged in order from an object side to an image side, the fourth lens group being configured to travel along an optical axis through focusing operation. In the image pickup lens, following conditional expression (1) is satisfied, f/f4<?0.35??(1) where f is a total focal length of the image pickup lens, and f4 is a focal length of the fourth lens group.

Abstract: A zoom lens includes: a first lens group having a negative refractive power; and a second lens group having a positive refractive power, provided in this order from an object side. Magnification is changed by moving the first lens group and the second lens group. The first lens group includes 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, provided in this order from the object side. The zoom lens satisfies predetermined conditional formulae.

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 lens group and the second lens group, the first lens group is formed of a first lens having a negative refractive power, a second lens having a positive refractive power, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, disposed in order from the object side. Then, when the focal length of the entire system at the wide angle end is taken as fw and the focal length of the second lens group are taken as f2, the zoom lens is configured to satisfy a conditional expression give below: 0.00<fw/f2<0.35??(1-1).

Abstract: Provided is a zoom lens, including, in order from an object: a first lens group (G1) having positive refractive power; a second lens group (G2) having negative refractive power; a third lens group (G3) having positive refractive power; and a fourth lens group (G4) having positive refractive power. The first lens group (G1 includes only, in order from the object, a cemented lens of a negative lens (L11) and a positive lens (L12), and a positive meniscus lens (L13) having a convex surface facing the object, an aperture stop (S) for determining brightness is disposed to the object side of the third lens group (G3), and upon zooming, all of the four groups (G1 to G4) move and the aperture stop (S) moves together with the third lens group (G3), and the conditional expression ?dp1>85.0 is satisfied, where ?dp1 denotes an Abbe number of the positive lens (L12), which is disposed closest to the object in the first lens group (G1), at the d-line as a standard.

Abstract: Including, in order from an object side: a first lens group having positive power; a second lens group having negative power; and a third lens group having positive power, each distance between respective lens groups varying upon zooming; the third lens group including, in order from the object side, a first sub-group having positive power, a second sub-group having positive power, a third sub-group having negative power, and a fourth sub-group having positive power, the first sub-group being movable along an optical axis for focusing, the third sub-group being movable in a direction including a component perpendicular to the optical axis, thereby correcting an image blur, and a given condition being satisfied, thereby providing a compact zoom lens having high optical performance with disposing a focusing lens and a vibration reduction lens in the same lens group, an optical apparatus equipped therewith, and a method for manufacturing the zoom lens.

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 includes in order from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a positive refractive power, and a last lens group having a positive refractive power. At the time of zooming from a wide angle end to a telephoto end, the second lens group and the third lens group move, and one of the fourth lens group, the fifth lens group, and the last lens group moves.

Abstract: An optical system includes, 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; upon zooming from a wide-angle end state W to a telephoto end state T, a distance between the first lens group G1 and the second lens group G2 varying, and the second lens group G2 moving, and the second lens group G2 including a focusing lens group Gf that carries out focusing from an infinity object to a close object, and a decentering lens group Gs that is movable in a direction having a component perpendicular to an optical axis, thereby providing an optical system capable of establishing both of internal focusing and a decentering lens group with obtaining compactness and excellent optical performance, an optical apparatus equipped with the optical system, and a method for manufacturing the optical system.

Abstract: Provided is an image blur correction apparatus including a lens unit including at least one lens, and being turnable in a first direction and a second direction, a fixed member turnably supporting the lens unit in the first direction and the second direction, a first drive unit including a pair of first thrust generation units that applies thrust and is positioned on opposite sides sandwiching one of the first supporting and second supporting axe, a second drive unit including a pair of second thrust generation units that applies thrust and is positioned on opposite sides sandwiching another of the first and second supporting axe, a pair of first detection units being positioned on opposite sides sandwiching one of the first and second supporting axe, and a pair of second detection units being positioned on opposite sides sandwiching another of the first and second supporting axe.

Abstract: In a zoom lens including a positive first lens unit, negative second lens unit, positive third lens unit, and positive fourth lens unit, the fourth lens unit includes a 41 lens group, a 42 lens group, and a 43 lens group. the lateral magnification of the third lens unit at a wide-angle end when an infinite object is focused, the focal length of the fourth lens unit, the lens configuration length of the fourth lens unit, the air interval between the 41 and 42 lens groups, the air interval between the 42 and 43 lens groups, the focal length of the 42 lens group, the average values of the Abbe constants and partial dispersion ratios of positive lens of the 42 lens group, the average values of the Abbe constants and partial dispersion ratios of negative lenses of the 42 lens group, and the like are appropriately set.

Abstract: A zoom lens includes a first lens unit, a second lens unit, a third lens unit and a fourth lens unit that includes a 41 lens group and a 42 lens group. The 41 lens group includes a 411 lens group and a 412 lens group. A lens surface on a most image side of the 411 lens unit has a shape convex to the image side and a lens surface on the most object side of the 412 lens unit has a shape concave to the object side. A curvature radius r411 of the lens surface on the most image side of the 411 lens unit, a curvature radius r412 of the lens surface on the most object side of the 412 lens unit, and lateral magnification ?3w of the third lens unit at a wide-angle end are respectively appropriately set.

Abstract: A zoom lens includes a positive first lens group fixed during zooming, a negative second lens moved to the image side upon zooming from the wide angle end to the telephoto end, a negative third lens group for image plane correction during zooming, and a positive fourth lens group fixed during zooming. The first lens group is composed of a negative first lens group front group, a positive first lens group middle group, and a positive first lens group rear group, disposed in order from the object side. The first lens group front group is composed of two negative lenses and one positive lens, disposed in order from the object side. Focusing is performed by moving only the first lens group middle group in an optical axis direction. The zoom lens satisfies a predetermined conditional expression.

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: The zoom lens includes a front unit including a first positive lens unit and a second positive or negative lens unit, a reflective mirror and a rear unit including two or more lens units. During zooming, the reflective mirror is not moved, and the first lens unit and at least two lens units of the rear unit are moved. When the zoom lens is retracted into a body of an image pickup apparatus, at least one of rotation of the reflective mirror such that a normal line thereto is brought closer to parallel to an optical axis of the rear unit and axial movement thereof in a direction of the optical axis of the rear unit is performed. The front unit is moved into a space formed by the at least one of the rotation and the axial movement. Conditions of 10.5<ft/|fn|<30.0 and 0.80<(Lf?L)/Lm<1.30 are satisfied.

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: There is provided a zoom lens including, in order from an object side to an image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power. In zooming from a wide-angle end to a telescopic end, the first lens group moves to the object side in a manner that a distance toward the second lens group shortens, and a distance between the third lens group and the fourth lens group lengthens. The third lens group includes a single lens or a single cemented lens.

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; a positive third lens unit; and a positive fourth lens unit, wherein the first lens unit includes a positive first lens subunit, which does not move for focusing, a positive second lens subunit, which moves during the focus adjustment, and a positive third lens subunit, which does not move for focusing; and focal lengths of the first lens unit, the second lens unit, the third lens unit, a magnification of the third lens unit U3 at a wide angle end, focal lengths of the first lens subunit, the second lens subunit appropriately satisfy certain relations.

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 telephoto lens system includes a first lens group having a positive refractive power, and comprising at least three positive lenses and one negative lens; a second lens group having a negative refractive power, and which moves along an optical axis to perform a focusing operation; a third lens group having a positive refractive power, and comprising a cemented lens in which a positive lens having a convex surface toward the object side and a positive lens having a convex surface toward the image side are bonded to each other, a bi-convex positive lens, and a negative lens having a concave surface toward the object side, and the first through third lens groups are disposed sequentially from the object side to the image side.

Abstract: A zoom lens includes a positive first lens group, which is fixed during changing magnification and during focusing, a negative second lens group, which is moved during changing magnification, a positive third lens group, which is fixed during changing magnification and during focusing, a positive fourth lens group, which is moved during changing magnification and during focusing, and a negative fifth lens group, which is moved during changing magnification, which are in this order from an object side. A lens group constituting the first lens group consists of a negative front group and a positive rear group in this order from the object side. The second lens group consists of four lenses of a negative lens, a positive lens, a negative lens, and a positive lens or a negative lens arranged in this order from the object side.

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 including a first lens unit having a positive refractive power, a second lens unit having a negative reflective power, a third lens unit having a positive refractive power, and a rear lens group including one or more lens units in this order from an object side to an image side, wherein distances between the respective lens units vary during the zooming operation, wherein the first lens unit consists of three lenses including one negative lens, and a partial dispersion ratio of a material for the negative lens of the first lens unit, an Abbe number of the same, a focal length of the entire system at a wide angle end and a focal length of the first lens unit are set individually and adequately.

Abstract: A zoom lens system comprising a negative first lens unit, a positive second lens unit, a negative third lens unit, and a positive fourth lens unit, wherein the second lens unit is composed of an object-side second lens unit and an image-side second lens unit, the object-side second lens unit has positive optical power, an aperture diaphragm is located between the object-side second lens unit and the image-side second lens unit, and the conditions: ?0.5<f2O/f2I<1.0 and 0.12<d2O/fW<0.35 (f2O: a composite focal length of the object-side second lens unit, f2I: a composite focal length of the image-side second lens unit, d2O: an optical axial distance from a most object side lens surface of the object-side second lens unit to the aperture diaphragm, fW: a focal length of the entire system at a wide-angle limit) are satisfied.

Abstract: A zoom lens includes sequentially from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and a fifth lens group having a negative refractive power. The zoom lens satisfies given conditions to implement a compact, wide angle, large aperture ratio zoom lens having excellent optical performance and compatible with solid state image sensors capable of recording full high vision images.

Abstract: A zoom lens includes a first lens unit, a second lens unit, a third lens unit, a fourth lens unit and a fifth lens unit. In the zoom lens, air intervals L2w, L3w between the second lens unit and the third lens unit and between the third lens unit and the fourth lens unit at a wide-angle end, a focal length f1 of the first lens unit, a combined focal length f23w of the second lens unit and the third lens unit at the wide-angle end, a focal length fw of the whole system at the wide-angle end, a zoom ratio Z, and a smallest value L2z1a of the air interval between the second lens unit and the third lens unit in a wide angle zoom range in which a magnification-varying ratio relative to that at the wide-angle end ranges from Z0.02 to Z0.35 are appropriately set.

Abstract: An inner focus lens, in order from an object side to an image side, comprising: a first lens unit having positive optical power; a second lens unit having negative optical power; and a third lens unit having positive optical power, wherein the second lens unit is moved along an optical axis so that focusing from an infinite-distance object side to a short-distance object side is achieved, the first lens unit includes a bi-convex air lens, and the following conditions: 0.65<|f2/f|<5.00 and 0.5<f23/f1<9.0 (f2: a focal length of the second lens unit, f and f23: a focal length of the entire system and a composite focal length of the second and third lens units in an infinity in-focus condition, f1: a focal length of the first lens unit) are satisfied; an interchangeable lens apparatus; and a camera system are provided.

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 includes, in order from an object side to an image side, a first lens unit of a negative refractive power, a second lens unit of a positive refractive power, and a third lens unit of a positive refractive power, an interval between the first lens unit and the second lens unit and an interval between the second lens unit and the third lens unit being configured to change in zooming from a wide angle end to a telephoto end. The first lens unit includes, in order from the object side to the image side, a negative lens and a positive lens. The predetermined conditions are satisfied.

Abstract: A zoom lens system, in order from an object side to an image side, comprising a positive first lens unit, a negative second lens unit, a positive third lens unit, and a positive fourth lens unit, wherein the first lens unit is composed of a cemented lens element of one object side negative lens element and one image side positive lens element, the fourth lens unit is composed of one lens element, in zooming, the first to fourth lens units are individually moved along an optical axis so that air spaces between the respective lens units vary for magnification change, and the conditions: vdL12<43.50 and fT/fW?6.0 (vdL12: an Abbe number of the positive lens element in the first lens unit, fT and fW: focal lengths of the entire system at a telephoto limit and a wide-angle limit) are satisfied; an imaging device; and a camera.

Abstract: A zoom lens system comprising a plurality of movable lens units which individually move along an optical axis at the time of zooming from a wide-angle limit to a telephoto limit during image taking, wherein at least two of the movable lens units are focusing lens units which move along the optical axis at the time of focusing from an infinity in-focus condition to a close-object in-focus condition in at least one zooming position, and among the focusing lens units, a lens unit having the absolute value, which is not the greatest absolute value, of a wobbling value at a wide-angle limit is a wobbling lens unit which senses a moving direction of the focusing lens units at the time of focusing by wobbling itself in a direction along the optical axis; an interchangeable lens apparatus; and a camera system are provided.

Abstract: Provided is an image blur correction apparatus including a lens unit including at least one lens, and being turnable in a first direction and a second direction, a fixed member turnably supporting the lens unit in the first direction and the second direction, a first drive unit including a pair of first thrust generation units that applies thrust and is positioned on opposite sides sandwiching one of the first supporting and second supporting axe, a second drive unit including a pair of second thrust generation units that applies thrust and is positioned on opposite sides sandwiching another of the first and second supporting axe, a pair of first detection units being positioned on opposite sides sandwiching one of the first and second supporting axe, and a pair of second detection units being positioned on opposite sides sandwiching another of the first and second supporting axe.

Abstract: A zoom lens includes a first lens unit of a positive refractive power, a second lens unit of a negative refractive power, a third lens unit of a positive refractive power, and a fourth lens unit of a positive refractive power, wherein the first lens unit does not move for zooming, at least the second and fourth lens units are moved during zooming, the first lens unit includes at least one positive lens, and an Abbe number and a relative partial dispersion of a material of the positive lens, an average refractive index of materials of negative lenses included in the second lens unit, a movement amount of the second lens unit for zooming from a wide-angle end to a telephoto end, a focal length of the second lens unit, and a focal length of the entire zoom lens at the telephoto end are appropriately set.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group, in that order from the object side, wherein upon zooming from the short focal length extremity to the long focal length extremity, the distance between the first lens group and the second lens group decreases, and the distance between the second lens group and the third lens group increases. The second lens group includes a positive first sub-lens group and a negative second sub-lens group, in that order from the object side. The second sub-lens group is a negative single lens element serving as an image-stabilizer lens group which moves in directions orthogonal to the optical axis to change the imaging position to correct image shake.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group, in that order from the object side, wherein upon zooming from the short to long focal length extremities, the distance between the first lens group and the second lens group decreases, and the distance between the second lens group and the third lens group increases. The second lens group includes a positive first sub-lens group and a negative second sub-lens group, in that order from the object side. In at least part of the zooming range of the zoom lens system, the second sub-lens group and the third lens group each serves as a focusing lens group that is moved along the optical axis during a focusing operation.

Abstract: An inner focus type zoom lens includes a first lens group that has positive refracting power and is normally located at a fixed position, a second lens group that has negative refracting power and is movable in an optical axis direction for zooming, a third lens group that has positive refracting power, a fourth lens group that is movable for correction of a focal position due to the zooming and for focusing, and a fifth lens group that has positive refracting power, in order from an object side, wherein the first lens group includes a negative lens, a first positive lens, and a second positive lens arranged in order from the object side, wherein a first face of the negative lens has a shape of a concave surface turned on the object side, and wherein the zoom lens satisfies the following conditional equation (1) ?10.0<G1R1/fw<?3.0.

Abstract: A zoom lens including first to fifth lens units in order from an object side toward an image. The refractive powers of the first to the fifth lens units are positive, negative, positive, negative and positive, respectively. The distance between the first and the second lens units is increased at the time of zooming from the wide angle end to the telephoto end, and the distance between the second and the third lens unit is decreased at the time of zooming from the wide angle end to the telephoto end. The first lens unit and the fourth lens unit are fixed for the zooming. When M2 and M3 are the amounts of movement of the second lens unit and the third lens unit at the time of zooming from the wide angle end to the telephoto end, respectively, the conditional expression; 0.2<|M2/M3|<5.0 is satisfied.

Abstract: The image pickup lens is composed of, in order from the object side, an aperture stop; a first lens with positive refractive power, including a convex surface facing the object side; a second lens with negative refractive power, including a concave surface facing an image side; a third lens with positive refractive power, including a convex surface facing the image side; a fourth lens with positive refractive power, having a meniscus shape including a convex surface facing the image side; and a fifth lens with negative refractive power, including a concave surface facing the image side. The image pickup lens satisfies conditional expressions relating to curvature radiuses of the object-side surface and the image-side surface of the fourth lens, a distance on an optical axis from the aperture stop to a focal point at the image side, and a focal length of the total system of the image pickup lens.

Abstract: An inner focus lens, in order from an object side to an image side, comprising: a first lens unit having positive optical power; a second lens unit having negative optical power; and a third lens unit having positive optical power, wherein the second lens unit is moved along an optical axis so that focusing from an infinite-distance object side to a short-distance object side is achieved, the first lens unit includes a bi-convex air lens, and the following conditions: 0.65<|f2/f|<5.00 and 0.5<f23/f1<9.0 (f2: a focal length of the second lens unit, f and f23: a focal length of the entire system and a composite focal length of the second and third lens units in an infinity in-focus condition, f1: a focal length of the first lens unit) are satisfied; an interchangeable lens apparatus; and a camera system are provided.

Abstract: A zoom lens optical system includes a first lens unit having a positive refractive index, a second lens unit which is arranged behind the first lens unit and has a negative refractive index, a third lens unit which is arranged behind the second lens unit and has a positive refractive index, and a fourth lens unit which is arranged behind the third lens unit and has a positive refractive index. An aperture is arranged within the third lens unit to prevent reduction of shutter speed due to large diameter of the zoom lens optical system.

Abstract: In an image forming optical system which includes in order from an object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, and a fourth lens group G4, and which includes maximum of five lens groups, and at the time of zooming from a wide angle end to a telephoto end, when a focal length of the overall image forming optical system is in a range of 1.2 fw to 1.8 fw, the first lens group G1 moves to be positioned more toward the object side than a position at the wide angle end, in a rectangular coordinate system in which, a horizontal axis is let to be ?d(LA) and a vertical axis is let to be nd(LA), when a straight line expressed by nd(LA)=a×?d(LA)+b(LA)(provided that a=?0.0267) is set, the image forming optical system satisfies a predetermined conditional expression.

Abstract: A zoom lens includes, in order from an object side, a positive first lens unit without moving for zooming, a negative second lens unit for magnification, a positive third lens unit for magnification, a negative fourth lens unit compensating for image plane variation due to magnification, and a positive fifth lens unit without moving for zooming. When assuming a focal length of the entire system at a wide angle end as fW, and a zoom ratio as Z, a focal length fM at an intermediate zoom position is expressed by the equation: fM=fW×?Z. When assuming an interval between the second and third lens units at the wide angle end as L2W, and a maximum value of the interval between the second and third lens units in a zoom range from the wide angle end to the focal length fM as L2max, the following conditional expression is satisfied: 1.1<L2max/L2W<55.0.

Abstract: Provided is a zoom lens for imaging an object on an imaging surface. The zoom lens includes, in the order from an object side to an image side thereof, a first lens group with positive refraction power, a second lens group with negative refraction power, a third lens group with positive refraction power, and a fourth lens group with positive refraction power. The first lens group includes a first surface. The zoom lens satisfies the formula: 0.15<|L3|/Lt<0.25, where L3 is a distance of the movement of the third lens group along an optical axis of the zoom lens when the zoom lens is switched between a wide-angle state and a telephoto state, and Lt is a distance from the first surface to the imaging surface.

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.