Abstract: A zoom lens includes, in order from an object side to an image side: a first lens unit having positive optical power; a second lens unit having negative optical power; a third lens unit having positive optical power and an aperture stop; a fourth lens unit having negative optical power; and a fifth lens unit having positive optical power, in which, during zooming from a wide-angle end to a telephoto end, the first lens unit stays, the second lens unit moves toward the image side, and the third lens unit moves together with the aperture stop.

Abstract: A zoom optical system includes three lens groups, arranged as follows from the object side: a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. The first lens group includes, arranged as follows along the optical axis, a lens element having negative refractive power, a prism for bending the optical axis, and a lens element having positive refractive power. The second and third lens groups are movable along the optical axis for zooming with only the third lens group reversing its direction of movement along the optical axis during zooming from the wide-angle end to the telephoto end. The third lens group includes a stop, a cemented lens component, and at least one aspheric surface that may be made of plastic. The first lens group also includes at least one aspheric surface.

Abstract: A varifocal lens that corrects aberrations in the visible and near-infrared regions includes, in order from the object side, a first lens group of positive refractive power, a second lens group of negative refractive power, and third and fourth lens groups, each of positive refractive power. The second lens group moves along the optical axis to vary the focal length, and the fourth lens group is independently movable to compensate for movement of the image plane due to movement of the second lens group during varifocal adjustment. Aspheric lens surfaces are disclosed. Certain conditions are satisfied that relate to Abbe number and index of refraction of different lens elements, the distance between the first and third lens groups, the chromatic aberration and focal length of the first lens group, and the movement of the second lens group and the focal length change associated with this movement.

Abstract: A zoom lens has first to fifth lens groups G1 to G5 having positive, negative, positive, positive, and negative refractive power, in order from an object side. The first lens groups G1 includes a prism L2 for bending a light path. Zooming is performed by adjusting a focal length by linear movement of the second lens group G2 and fourth lens group G4 and compensating an image surface position by nonlinear movement of the fifth lens group G5. Focusing is performed by moving the fifth lens group G5.

Abstract: A simple two-group zoom optical system that favorably corrects aberrations includes, in order from the object side, a first lens group of negative refractive power, a stop, and a second lens group of positive refractive power. The first lens group includes, in order from the object side, a lens element having negative refractive power and a meniscus shape with its concave surface on the image side, a biconcave lens element, and a lens element having positive refractive power. The second lens group includes, in order from the object side, a lens element having positive refractive power and at least one aspheric surface, a lens element having negative refractive power, and a biconvex lens element. Certain conditions are satisfied that relate to the focal lengths of the zoom optical system, the focal lengths of the two lens groups, and to the Abbe numbers of lens elements.

Abstract: A projection optical unit has two lens groups. A first projection optical unit disposed closest to an image display element, temporarily forms a first enlarged image (magnification: M1) at the image display element side, rather than at a second projection optical unit. The first enlarged image is subsequently projected in an enlarged form (magnification: M2, wherein M2>M1) onto a screen via the second projection optical unit. A field lens group having positive refractive power is disposed between the first projection optical unit and the second projection optical unit. Consequently, the relationship between F2, which is the F-value of the second projection optical unit, and F1, which is the F-value of the first projection optical unit, becomes F2=F1/M1, whereby it is possible to realize very-wide-angle imaging at a field angle exceeding 90 degrees.

Abstract: A zoom lens system comprises, in order from an object side, positive, negative, positive, negative, and positive refractive power lens groups, and while changing the magnification, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, the distance between the third lens group and the fifth lens group increases, and the second lens group moves more towards the object side at the telephoto end than the wide-angle end.

Abstract: Disclosed is a compact zoom lens system having a image stabilizing function. This zoom lens system is provided with a plurality of lens units of which the interval between adjacent ones is changed during zooming. Shake correction is effected by a part of a lens unit of negative optical power of the plurality of lens units. Specifically, the lens unit of negative optical power is comprised of two lens components of negative optical power, and one of these two lens components is moved so as to have a component in a direction perpendicular to an optical axis to thereby change the imaging position of the zoom lens system.

Abstract: A zoom lens system, in order from the object side to the image side, comprises a first lens unit G1 having positive optical power, a second lens unit G2 having negative optical power, a third lens unit G3 having positive optical power and a fourth lens unit G4 having positive optical power. Magnification varying is performed by varying the distances between the lens units by moving the lens units along the optical axis. The third lens unit G3 comprises at least two lens elements including a third lens unit object side lens element which is a positive lens element disposed on the most object side and whose high-curvature surface faces the object side and a third lens unit image side lens element which is a negative lens element disposed on the most image side and concave to the image side.

Abstract: A zoom lens, including, in order from an object side to an image side (a) a first lens unit of negative optical power, (b) a second lens unit of positive optical power, and (c) a third lens unit of positive optical power, wherein a separation between the first lens unit and the second lens unit and a separation between the second lens unit and the third lens unit are varied to effect variation of magnification, and wherein, during the variation of magnification from a wide-angle end to a telephoto end with an infinitely distant object focused on, the third lens unit moves monotonically toward the image side or moves with a locus convex toward the image 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 third group of lenses is constructed by subsequently arranging those four lenses from an object side to an image side which include a positive lens, a cemented lens of a positive lens and a negative lens, and a positive lens, both of a surface of the third group of the lenses nearest to the object side and a surface of the third group of the lenses nearest to the image side are so aspheric that positive refractive power becomes gradually weaker as a location of the third group of the lenses departs from an optical axis; and a following conditional formula is satisfied: ?0.5<(Y? max/R34I)<0.0 where R34I is a curvature radius of the surface of the third group of the lenses nearest to the image side, and Y? max is a maximum image height.

Abstract: A zoom lens system, in sequence from an object side to an image side, includes a first lens group having positive refractive power and fixed for gathering incoming light; a second lens group having negative refractive power for changing a focal length of the zoom lens system; a third lens group having positive refractive power and made stationary; a fourth lens group having positive refractive power and movable for compensating for a fluctuation of an image plane position; and a fifth lens group having positive refractive power and movable for focusing purpose. During zooming from a wide-angle end to a telephoto end, the second and fourth lens groups are moved independently toward the third lens group in such a manner that spacing between the first lens group and the second lens group increases and spacing between the third lens group and the fourth lens group decreases.

Abstract: A zoom lens includes a most object-side lens unit remaining fixed on the optical axis when the magnification of the zoom lens is changed and a focusing operation is performed; a most image-side lens unit remaining fixed when the focusing operation is performed; and a plurality of moving lens units lying between the most object-side lens unit and the most image-side lens unit, moved along the optical axis when the magnification is changed. The most object-side lens unit includes, in order from the object side, a negative lens component, a reflective optical component having a reflecting surface for bending the optical path, and a positive lens component. The most image-side lens unit has at least one aspherical surface. An electronic imaging device includes an electronic image sensor located on the image side of the zoom lens.

Abstract: A lens (1), a lens (2) and a lens (3) constitute a first group of lenses, a lens (4), a lens (5), a lens (6) and a lens (7) constitute a second group of lenses, and a lens (8) constitutes a third group of lenses in a zoom lens of the present invention. The second group of lenses is constituted by a first positive lens (4), a negative lens (5) which is in a meniscus shape which faces its convex shape toward a side of an object (70), a second positive lens (6) in a meniscus shape which faces its convex shape toward the object (70) side, and the third positive lens (7), which are in order from the object (70) side.

Abstract: A zoom lens optical system includes a first optical group with a first lens having negative refraction, a second lens having positive refraction, and a light path changing unit to change the path of an incident light passing through the first lens to have light incident on the second lens. A second optical group is provided for varying magnification. The second optical group has a third lens having negative refraction, a fourth lens, and a fifth lens, wherein the fourth and fifth lenses are integrally connected and have negative refraction. A third optical group includes an iris diaphragm, a sixth lens having positive refraction, and a seventh lens having negative refraction. A fourth optical group is provided for focusing. The fourth optical group has an eighth lens and a ninth lens being integrally connected and both having positive refraction.

Abstract: A zoom optical system with a vibration correction function includes, from the object side, a first lens group having positive refractive power and that is stationary during zooming, a second lens group having negative refractive power and that moves along the optical axis during zooming, a third lens group having positive refractive power that includes a stop, and a fourth lens group having positive refractive power. Two of the second, third, and fourth lens groups move along the optical axis during zooming. A fifth lens group may be included. At least part of one of the third, fourth, or fifth lens groups that does not move along the optical axis during zooming is movable in a direction that intersects the optical axis in order to correct for blurring of an image due to vibration of the zoom optical system. An imaging device uses the zoom optical system.

Abstract: A first group optical system having a positive refracting power, a second group optical system having a negative refracting power, and a third group optical system having a positive refracting power are sequentially arranged from an object side toward an image side. At least the first group optical system and the third group optical system move so that a distance between the first group optical system and the second group optical system becomes minimum at short focal-length side, and a distance between the second group optical system and the third group optical system becomes minimum at long focal-length side. The third group optical system includes a triplet lens formed with a negative lens, a positive lens, and a negative lens.

Abstract: A zoom lens includes a first lens band having a positive focal length, a second lens band having a negative focal length, and at least third to fifth lens bands having positive focal lengths. An aperture diaphragm is located in the vicinity of the third lens band. When magnification i.e., zooming is performed from short to long focal point ends, the second lens band smoothly moves toward the third lens band and the fourth lens band simultaneously moves from the fifth lens band side toward a long focal point end so as to share a magnification function together with the second lens band.

Abstract: A zoom lens, including, in order from an object side to an image side (a) a first lens unit of negative optical power, (b) a second lens unit of positive optical power, and (c) a third lens unit of positive optical power, wherein a separation between the first lens unit and the second lens unit and a separation between the second lens unit and the third lens unit are varied to effect variation of magnification, and wherein, during the variation of magnification from a wide-angle end to a telephoto end with an infinitely distant object focused on, the third lens unit moves monotonically toward the image side or moves with a locus convex toward the image side.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group. Upon zooming from the short focal length extremity to the long focal length extremity, a distance between the negative first lens group and the positive second lens group decreases, and a distance between the positive second lens group and the positive third lens group increases. When zooming is being performed, the negative first lens group remains stationary, and the positive second lens group and the positive third lens group are moveable along the optical axis of the zoom lens system; and the zoom lens system satisfies the following conditions: 1.5<f3/f2<2.5 ??(1) 0.8<f2/(fw*ft)1/2<1.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group. Upon zooming from the short focal length extremity to the long focal length extremity, a distance between the first lens group and the second lens group decreases, and a distance between the second lens group and the third lens group increases. When zooming is being performed, the third lens group remains stationary, and the first lens group and the second lens group are moveable along the optical axis of the zoom lens system; and the zoom lens system satisfies the following conditions: 3.0<f3/f2<3.5??(1) 1.4<|f1/fW|<2.0??(2) 0.8<f2/fW<1.5??(3) wherein f1 designates the focal length of the first lens group; f2 designates the focal length of the second lens group; f3 designates the focal length of the third lens group; and fw designates the focal length of the entire zoom lens system at the short focal length extremity.

Abstract: A zoom lens according to the present invention includes, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a negative refractive power, and a fourth lens unit having a positive refractive power. During a magnification change from the wide-angle end through the telephoto end, the first lens unit and the fourth lens unit shift from the image-surface side toward the object side, a space between the first lens unit and the second lens unit increases, and spaces between individual lens units change. During a focusing from an object at the infinite distance onto an object at a near distance, the second lens unit and the third lens unit individually shift independently.

Abstract: A zoom lens, including, in order from an object side to an image side (a) a first lens unit of negative optical power, the first lens unit consisting of, in order from the object side to the image side, a negative lens and a positive lens, (b) a second lens unit of positive optical power, and (c) a third lens unit of positive optical power, wherein a separation between the first lens unit and the second lens unit and a separation between the second lens unit and the third lens unit are varied to effect variation of magnification, wherein, during the variation of magnification from a wide-angle end to a telephoto end with an infinitely distant object focused on, the third lens unit moves monotonically toward the image side or moves with a locus convex toward the image side.

Abstract: A zoom lens, having a camera shake correction function, that is capable of preventing degradation of chromatic aberration while correcting camera shake, and can be small, light-weight and power-saving, is provided. The zoom lens is composed of four groups of lenses having positive, negative, positive and positive refractive powers, arranged in that order from an object side to an image plane side, where a second lens group conducts zooming and a fourth lens group conducts focus adjustment. The second lens group is made of a concave meniscus lens, a concave lens, a double convex lens, and a concave lens, arranged in that order from the object side to the image plane side, and it includes also at least one aspheric surface. A third lens group includes a cemented lens having a cemented surface whose convex surface faces the object side, and can be shifted in a perpendicular direction with respect to an optical axis in order to correct image fluctuations during a camera shake.

Abstract: A zoom lens apparatus includes a first optical lens group having a negative focal length, a second optical lens group having a positive focal length, and a third optical lens group having a positive focal length, arranged in this order from a subject. The lens groups move such that a distance between the first and second optical lens groups is decreased and a distance between the second and third optical lens groups is increased at a scaling change to a long focal length edge. The second optical lens group includes two positive lenses, a negative meniscus lens, and a positive meniscus lens. The zoom lens system satisfies an inequality condition 0.15<(N22?N23)<0.40, in which N22 is a refractive index of the negative meniscus lens and N23 is a refractive index of the positive meniscus lens conjoined with the negative meniscus lens.

Abstract: There is disclosed a zoom lens having small variations of aberration and field angle during focusing and having a small system as a whole. The zoom lens includes a first lens unit having a positive optical power, a second lens unit having a negative optical power, a third lens unit having a negative optical power, a fourth lens unit having a positive optical power, and a fifth lens unit having a positive optical power, in order from an object side to an image side. During zooming, the second lens unit and third lens unit are moved, and during focusing, the fifth lens unit is moved. The fifth lens unit consists of one negative lens element and two positive lens elements in order from the object side to the image side, and the following conditions are satisfied: 0<?5<0.35 1.85<?5p/?5n.

Abstract: A rear focus zoom lens is disclosed that includes, in order from the object side: 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 including a stop; a fourth lens group having negative refractive power; and a fifth lens group having positive refractive power. The second lens group and the third lens group are moved along the optical axis for zooming, the fourth lens group is moved along the optical axis for focusing, and the fourth lens group comprises a doublet consisting of a negative lens element and a positive lens element. The fifth lens group may have a specified configuration which includes an aspherical surface and that satisfies a specified condition which insures that aberrations are satisfactorily corrected over the entire range of zoom.

Abstract: A zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group. Upon zooming, the second lens group moves from the object side to the image side, and the fourth lens group moves in order to compensate the move of the image plane. The fourth lens group includes sub-lens groups, wherein a first sub-lens group satisfies specific conditions. The first sub-lens group has an aspherical surface on at least the object-side surface thereof. The aspherical surface is formed so that the higher a height from the optical axis in a radial direction becomes the weaker the refractive power is, compared with a paraxial spherical surface.

Abstract: The zoom lens has, in order from the object to image sides, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power, wherein the second lens unit and the fourth lens unit move during zooming. The following condition is satisfied: ?23<20.0, N23>1.9, ?1.0<f2/f2t<?0.05, where f2 represents a focal length of the second lens unit, ft represents a focal length of the entire system at a telephoto end zoom position, and ?23 and N23 represent an Abbe number and a refractive index of the material forming the third lens of the second lens unit, respectively.

Abstract: A three-group zoom lens includes first, second, and third lens groups, of negative, positive, and positive or negative refractive power, respectively. The second lens group includes a stop and the third lens group moves for focusing. When zooming from the wide-angle end to the telephoto end, the first and second lens groups become closer together. The zoom lens preferably satisfies specified conditions that ensure compactness, ease of manufacture, and favorable correction of aberrations. The zoom lens includes aspheric lens elements with lens surfaces defined by an aspheric lens equation that: (a) includes at least one non-zero coefficient of an even power of Y, and at least one non-zero coefficient of an odd power of Y, where Y is the distance of a point on the aspheric lens surface from the optical axis, and/or (b) includes at least one non-zero coefficient of Yi, where i is even and 16 or greater.

Abstract: The invention provides a zoom lens system much more reduced in size and cost than ever before and best-suited for use on portable information terminals of small size. The zoom lens system comprises, in order from an object side thereof, a first lens group G1 having positive refracting power and designed to be fixed during zooming, a second lens group G2 having negative refracting power and designed to move from the object side to an image plane side of the system for zooming from a wide-angle end to a telephoto end of the system, a third lens group having refracting power and designed to move from the image plane side to the object side for zooming from the wide-angle end to the telephoto end, and a fourth lens group G4 having positive refracting power and designed to be movable during zooming.

Abstract: The invention provides a zoom lens device that can include lens groups. A third lens group (compensator lens group) can be disposed between two lens groups (a second and a fourth lens groups) forming a variator lens group. The two lens groups (the second and fourth lens groups) forming the variator lens group can be retained by a common variator-lens frame and moved together. Accordingly, a zoom lens device, an optical apparatus, and a projector can be provided in which, even when a plurality of lens groups are assembled, degradation of optical characteristics due to decentering between the lens groups can be prevented.

Abstract: A zoom lens system includes a movable-positive first lens group, a movable-negative second lens group, a movable-positive third lens group, and a movable-positive fourth lens group. Upon zooming from the short to the long focal length extremities, all the lens groups are arranged to move in a manner that the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, the distance between the third lens group and the fourth lens group increases, and the distance between the first lens group and the third lens group does not change. Upon zooming from the short to the long focal length extremities, the fourth lens group first moves toward the image and thereafter moves toward the object in a U-turn path.

Abstract: A small zoom lens apparatus capable of carrying out focusing through manual operations in an autofocus mode. The zoom lens apparatus includes a variator lens unit, an object-side focus lens unit placed closer to an object than the variator lens unit and an image plane-side focus lens unit placed closer to an image plane than the variator lens unit. Driving of the object-side focus lens unit through manual operations is allowed when the autofocus mode is set.

Abstract: The invention relates to a zoom lens system which is compatible with a TTL optical finder having a diagonal field angle of at least 70° at the wide-angle end and about 7 to 10 magnifications and is fast as represented by an F-number of about 2.8 at the wide-angle end. The zoom lens system comprises a first lens group G1 which is movable along its optical axis during zooming and has positive refracting power, a second lens group G2 which moves toward the image side along the optical axis during zooming from the wide-angle end to the telephoto end and has negative refracting power and rear lens groups G3 to G6 having at least two spacings variable during zooming. In particular, the focal length f1 of the first lens group G1 should meet 6<f1/L<20 where L is the diagonal length of an effective image pickup surface I located in the vicinity of an image-formation plane.

Abstract: A lens (1), a lens (2) and a lens (3) constitute a first group of lenses, a lens (4), a lens (5), a lens (6) and a lens (7) constitute a second group of lenses, and a lens (8) constitutes a third group of lenses in a zoom lens of the present invention. The second group of lenses is constituted by a first positive lens (4), a negative lens (5) which is in a meniscus shape which faces its convex shape toward a side of an object (70), a second positive lens (6) in a meniscus shape which faces its convex shape toward the object (70) side, and the third positive lens (7), which are in order from the object (70) side.

Abstract: A three-unit zoom lens includes, in order from the object side, the first lens unit with positive refracting power, the second lens unit with positive refracting power, and the third lens unit with negative refracting power. When the magnification of the zoom lens is changed, extending from the wide-angle position to the telephoto position, individual lens units of the three-unit zoom lens are moved toward the object side so that a space between the first lens unit and the second lens unit, after being increased as the lens units are moved from the wide-angle position toward the proximity of the middle position, is decreased as they are moved toward the telephoto position, and a space between the second lens unit and the third lens unit is also decreased accordingly. In this case, the three-unit zoom lens has a variable magnification ratio of 2 or higher and the first lens unit is constructed with a single lens element.

Abstract: A focusing apparatus applied to a telescopic lens system includes more than two lens groups. The focusing apparatus includes two focusing mechanisms which are operable independently from each other, and are adapted to vary both absolute and relative positions of two lens groups in the optical axis direction.

Abstract: A zoom lens barrel structure includes a first lens frame including an outer ring portion, an inner ring portion, a flange wall, and a first cam follower; a cam ring positioned between the outer and inner ring portions; a second lens frame having a second cam follower, positioned inside the inner ring portion; a first cam groove formed on an outer peripheral surface of the cam ring, the first cam follower being engaged in the first cam groove; a second cam groove formed on an inner peripheral surface of the cam ring so that the second cam follower engages in the second cam groove; a linear guide ring, positioned around the first lens frame; and a linear guide mechanism, provided between the inner ring portion of the first lens frame and the second lens frame, for guiding the second lens frame linearly along the optical axis.

Abstract: A lens barrel having a zoom lens system including a plurality of variable power lens groups which includes a switching lens group having two sub-lens groups which are optically operable in mutually close and distant positions, the lens barrel includes a first sub-lens group frame for supporting one sub-lens group; a second sub-lens group frame for supporting the other sub-lens group; a switching lens group frame for supporting the first and second sub-lens group frames; a shift mechanism for selectively moving the first and second sub-lens group frames in the switching lens group frame to the mutually close and distant positions; and a switching lens group frame moving mechanism for moving the switching lens group frame with the other variable power lens group(s) along a predetermined path to vary the focal length; wherein combined movement of the shift mechanism and the switching lens group frame moving mechanism provides a zoom path for the sub-lens groups.

Abstract: A zoom lens includes a first to fourth lens unit. Zooming is performed by moving the lens units so that a spacing between the first and the second lens unit at a telephoto end is larger than the spacing between the first and the second lens unit at a wide-angle end, and so that the spacing between the third and the fourth lens unit at the telephoto end is smaller than the spacing between the third and the fourth lens unit at the wide-angle end. If focal lengths of the first and the fourth lens units are f1 and f4, and if the focal length of entire system at the wide-angle end and the focal length of the entire system at the telephoto end are fw and ft, conditions expressed by 0.2<f1/ft<0.5, −0.2<f4/ft<−0.05 and 3.7<ft/fw<6.0 are satisfied.

Abstract: The invention relates to a zoom lens system which is compatible with a TTL optical finder having a diagonal field angle of at least 70° at the wide-angle end and about 7 to 10 magnifications and is fast as represented by an F-number of about 2.8 at the wide-angle end. The zoom lens system comprises a first lens group G1 which is movable along its optical axis during zooming and has positive refracting power, a second lens group G2 which moves toward the image side along the optical axis during zooming from the wide-angle end to the telephoto end and has negative refracting power and rear lens groups G3 to G6 having at least two spacings variable during zooming. In particular, the focal length f1 of the first lens group G1 should meet 6<f1/L<20 where L is the diagonal length of an effective image pickup surface I located in the vicinity of an image-formation plane.

Abstract: A zoom lens has the following lens components in the order named from the object side: a front lens component of a negative optical power, which has a first lens unit of a positive optical power and a second lens unit of a negative optical power in the order named from the object side; and a rear lens component of a positive optical power, which has a third lens unit of a positive optical power and a fourth lens unit of a positive optical power in the order named from the object side. The zoom lens varies a spacing between principal points of the front lens component and rear lens component by varying a spacing between the first lens unit and the second lens unit and a spacing between the third lens unit and the fourth lens unit, in order to effect zooming. The first lens unit and the fourth lens unit change their moving direction midway through zooming from the wide-angle end to the telephoto end.

Abstract: A compact zoom lens system maintains sufficient image-formation capabilities at a wide-angle end of greater than 700 and at a zoom ratio of greater than about 10. The zoom lens system comprises 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. For zooming from a wide-angle end to a telephoto end, the first to fifth lens groups are all movable. The first and third lens groups move toward the object side. Also, the spaces between the first and second lens groups and between the third and fourth lens groups widen. At least the fourth lens group or the fifth lens group makes a non-linear movement, compensating for a fluctuation of an image plane position with zooming. Focusing is carried out by moving the first and second lens groups as an integral unit.

Abstract: A zooming optical system uses has at least one lens unit having a variable magnification function and at least one deformable reflecting surface having a compensator or focussing function.

Abstract: The invention relates to a zoom lens system which is compatible with a TTL optical finder having a diagonal field angle of at least 70° at the wide-angle end and about 7 to 10 magnifications and is fast as represented by an F-number of about 2.8 at the wide-angle end. The zoom lens system comprises a first lens group G1 which is movable along its optical axis during zooming and has positive refracting power, a second lens group G2 which moves toward the image side along the optical axis during zooming from the wide-angle end to the telephoto end and has negative refracting power and rear lens groups G3 to G6 having at least two spacings variable during zooming. In particular, the focal length f1 of the first lens group G1 should meet 6<f1/L<20 where L is the diagonal length of an effective image pickup surface I located in the vicinity of an image-formation plane.

Abstract: A zoom lens comprises a first lens unit having positive refractive power, a second lens unit having negative refractive power, an aperture stop, a third lens unit having positive refractive power and kept fixed during zooming, a fourth lens unit having positive refractive power, and a fifth lens unit having negative refractive power, which are arranged in this order from an object side. In zooming from a wide-angle end to a telephoto end, the second lens unit is moved toward an image plane side such that a spacing between the first lens unit and the second lens unit is increased, and the aperture stop is also moved.

Abstract: A zoom lens system includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power. When the lens system is changed from a wide-angle end to a telephoto end, each lens group is moved to the object side such that the separation between the first lens group and the second lens group increases, the separation between the second lens group and the third lens group decreases, and the separation between the third lens group and the fourth lens group decreases. The fourth lens group is composed of four lens elements arranged, in order from the object, a first positive lens element, a first negative lens element, a second positive lens element, and a second negative lens element.

Abstract: A zoom lens system having multiple lens units including, sequentially in a direction from an enlargement side thereof toward a reduction side thereof, a first lens unit having a negative optical power, a second lens unit having a positive optical power, a third lens unit having a positive optical power, a fourth lens unit having a negative optical power, and a fifth lens unit having positive optical power. Additionally, during a zoom operation from a longest focal length condition to a shortest focal length condition, the zoom lens system can function such that the first lens unit and the fifth lens unit can remain stationary, while the second, third and fourth lens units are able to move.