Abstract: When focal lengths are discretely set, zoom positions are set, relative to a focal length fr at a position at which a movement direction of a correction group, is reversed, such that a difference value between a focal length which is the closest to the focal length fr and falling between a focal length fw at a wide angle end and the focal length fr, and a next focal length is larger than a difference value between any remaining adjacent focal lengths. By moving from the zoom position of the closest focal length directly to the zoom position of the next focal length, a movement range of the correction group can be made smaller than a movement range in the case where the lens position of the focal length fr is set as the zoom position.

Abstract: A zoom lens and imaging apparatus implementing four lens groups including 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 having a positive refractive power. When a positional state is varied from a wide-angle-end state to a telephoto-end state, the second lens group is moved to an image side, and the fourth lens group is moved to compensate for image plane variation caused by the movement of the second lens group.

Abstract: A zoom lens system includes, in order from an 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. During zooming from a wide-angle end to a telephoto end, a space between the first lens unit and the second lens unit narrows, at least the second lens unit moves only toward the object side, and the third lens unit is constituted of one positive lens.

Abstract: A zoom lens system includes, in order from an object side to an image side, first, second, third, and fourth lens units having positive, negative, positive, and positive optical powers, respectively. The first lens unit includes one negative lens element and two positive lens elements, and moves during zooming. The zoom lens system satisfies the following condition: 0.05<f1/(st1×ft/fw)<0.2 1.5<?3T/?3W<3.6 where f1 denotes a focal length of the first lens unit, st1 denotes a distance between positions of the first lens unit at a wide-angle end and at a telephoto end, fw and ft denote focal lengths of the entire system at the wide-angle end and at the telephoto end, respectively, and ?3W and ?3T denote lateral magnifications of the third lens unit at the wide-angle end and at the telephoto end, respectively.

Abstract: A zoom lens device includes, 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, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power. The zoom lens device is formed so that a distance Ximg between a position of the first lens unit at the wide-angle end and a position of the first lens unit that is maximally moved towards the image side, a distance Xobj between the position of the first lens unit at the wide-angle end and a position of the first lens unit that is maximally moved towards the object side, and a focal length fw of the zoom lens device at the wide-angle end are suitable values.

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 system comprising, in order from an object along an optical axis: a first lens group having a negative refractive power; a second lens group having a positive refractive power; and a third lens group having a positive refractive power; the following conditional expression being satisfied: 0.6<Ymax×ft/f12<1.0 where Ymax denotes the maximum image height of the zoom lens system, ft denotes a focal length of the zoom lens system in a telephoto end state, and f1 denotes a focal length of the first lens group.

Abstract: A zoom lens system comprising a plurality of lens units each composed of at least one lens element, wherein an interval between at least any two lens units is changed so that an optical image is formed with a continuously variable magnification, the zoom lens system comprises a first lens unit having positive power, a second lens unit that includes a lens element having a reflecting surface and has negative power and subsequent lens units including at least one lens unit having positive power, and the condition: 0.50<(C?S)/H<1.00(C=?{square root over ( )}(2R·dR?dR2), S is a sag of the image side surface of the most object side lens element in the second lens unit at height H, H is one-half of an optical axial thickness of the lens element having a reflecting surface, R is a radius of curvature of the image side surface, and dR is an interval between the most object side lens element and the lens element having a reflecting surface) is satisfied.

Abstract: The invention provides a zoom lens, including a plurality of lens groups. When the zoom lens is in operation, the plurality of lens groups are aligned on a common optic axis, and the zoom lens forms a first plane and a second plane conjugated with the first plane. To retract the zoom lens, at least one of the lens groups is rotated around an axis perpendicular to the common optical axis and toward the first plane, and at least one of the rest of the lens groups is moved toward the second plane along the common optical axis. As a result, overall length of the zoom lens is shortened when it is retracted to obtain the miniaturization.

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, a third lens unit having a positive refractive power, and a rear lens unit including one or more lens units and having an overall positive refractive power. In the zoom lens, the third lens unit includes a first subunit having a positive refractive power and including one lens component having a positive refractive power, an aperture stop, and a second subunit including a negative lens. In the third lens unit of the zoom lens, a focal length of each of the first subunit and the second subunit is appropriately set.

Abstract: A zoom lens includes a focus unit, a zoom unit, an aperture stop, and an imaging unit having a splitting element that are arranged in that order from an object side to an image side. The splitting element includes an incident surface for a light beam, a half mirror surface for splitting the light beam into reflected light and transmitted light, a splitting exit surface from which the reflected light is emitted, and an exit surface from which the transmitted light is emitted. The incident surface and the exit surface are perpendicular to an optical axis of the zoom lens. The ratio of the distance from the aperture stop to the exit surface and the equivalent air length from the aperture stop to an image plane of the zoom lens and the ratio of the effective diameters of the exit surface and the splitting exit surface are set properly.

Abstract: A compact zoom lens which projects an image from a DMD on to a screen in an enlarged scale is provided. There is provided a zoom lens including, in order from a magnifying side, a first lens group having a positive or negative refractive power as a whole, a second lens group having a negative refractive power as a whole, a third lens group having a positive or negative refractive power as a whole, a fourth lens group having a positive refractive power as a whole and a fifth lens group having a positive refractive power as a whole, wherein a variable power as a whole lens system of the zoom lens is established by configuring such that the first lens group and the fifth lens group are left fixed, the second lens group, the third lens group and the fourth group are made to move on an optical axis.

Abstract: A zoom lens system includes, in order from an object side, a first lens unit G1 having a positive refracting power, a second lens unit G2 having a negative refracting power, a third lens unit G3 having a positive refracting power, and a fourth lens unit G4 having a positive refracting power, and at the time of zooming from a wide angle end to a telephoto end, a space between the lens units changes, and the first lens unit includes two lenses namely, a negative lens and a positive lens, and satisfies the following conditional expression ?0.75<SF1p<?0.1??(1) where, SF1p is defined as SF1p=(R1pf+R1pr)/(R1pf?R1pr), when R1pf is a paraxial radius of curvature of a surface on the object side, of the positive lens in the first lens unit, and R1pr is a paraxial radius of curvature of a surface on an image side, of the positive lens in the first lens unit.

Abstract: Providing a zoom lens system with a vibration reduction function, a high zoom ratio, and a wide angle of view, an imaging apparatus, a method for vibration reduction, and a method for varying a focal length. The system includes, in order from an object, 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. Upon zooming from a wide-angle end to a telephoto end, a distance between the first and the second lens groups increases, a distance between the second and the third lens groups decreases, and a distance between the third and the fourth lens groups varies. The third lens group consists of a front group and a rear group. Vibration reduction is carried out by moving only the rear group perpendicularly to the optical axis. Given conditions are satisfied.

Abstract: A zoom lens having five lens groups arranged in succession. The zoom lens is configured such that when zooming from a short focal length end toward a long focal length end, the second lens group lens moves toward the third lens group and the fourth lens group moves toward a side of the third lens group, and the fifth lens group corrects the zooming and a shift in a position of an imaging plane of the zoom lens caused by movement of the third lens group and the fourth lens group.

Abstract: A zoom lens system comprises a first lens unit having a positive refractive power, a second lens unit having a negative refractive power and a third lens unit having a positive refractive power, and during zooming from a wide-angle end to a telephoto end, a space between a first lens unit and a second lens unit and a space between the second lens unit and a third lens unit are changed, the space between the first lens unit and the second lens unit is enlarged in the telephoto end as compared with the wide-angle end, and the space between the second lens unit and the third lens unit is narrowed in the telephoto end as compared with the wide-angle end.

Abstract: An image pickup apparatus includes a zoom lens including at least two movable lens groups; an image pickup element that converts an optical image formed with the zoom lens into an electric signal; and an image processor that electrically corrects a lateral chromatic aberration to be generated at the zoom lens. The zoom lens satisfies Conditional Expressions (1) and (2) as follows, ?5.0<W_ate(X)/T_ate(X)<?0.2??(1) 0.003<|Max_ate(10)/Himg |<0.03??(2) where W_ate(X) is an aberration amount of the lateral chromatic aberration from the C-line to the g-line, at a wide-angle end, corresponding to a (X×10) % image height, T_ate(X) is an aberration amount of the lateral chromatic aberration from the C-line to the g-line, at a telephoto end, corresponding to a (X×10) % image height, Max_ate(X) is one of W_ate(10) and T_ate(10), the one having a larger absolute value, and Himg is a diagonal length of the image pickup element.

Abstract: An image pickup apparatus includes an image pickup element and an optical system configured to form an image on the image pickup element. The optical system 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 and including a reflecting member configured to deflect an optical axis, and a rear lens unit having a positive refractive power and including at least one lens unit having a positive refractive power. The second lens unit is stationary for zooming. During zooming, the image pickup element moves, and an interval between the first lens unit and the second lens unit and an interval between the second lens unit and the rear lens unit vary.

Abstract: A zoom lens made up of a first lens group having positive refracting power, a second lens group having negative refracting power, a third lens group having positive refracting power, and a fourth lens group having positive refracting power, which are disposed in order from an object side, in which the first lens group and the third lens groups are stationary, and the zoom lens performs mainly variable power by shifting the second lens group in an optical axis direction, and performs correction for image position fluctuations and focusing by shifting the fourth lens group in the optical axis direction, is characterized in that the first lens group is composed of five lenses: a concave lens; a convex lens with a strong convexity facing to an image side; a cemented lens made up of a concave lens with a strong concavity facing to the image side, and a convex lens; and a convex lens with a strong convexity facing to the object side, which are disposed in order from the object side, and by satisfying each of the fo

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 comprises, in order from an 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 positive refractive power; a fourth lens unit having a negative refractive power; and a fifth lens unit having a positive refractive power, and during magnification change from a wide-angle end to a telephoto end, each of the space between the respective lens units changes.

Abstract: A magnification varying optical system that directs light from an object to an image sensor includes in order from the object side: a first lens unit having negative optical power and including an optical axis changing element that changes the optical axis; a second lens unit having positive optical power and including three lens elements; a third lens unit having negative optical power; and a fourth lens unit having positive optical power. In this magnification varying optical system, in magnification varying from the wide-angle end to the telephoto end, the first lens unit is stationary, the distance from the first lens unit to the second lens unit decreases, and the distance from the third lens unit to the fourth lens unit increases. The magnification varying optical system satisfies the specified conditions.

Abstract: An exemplary zoom lens for use in projection technology includes, in this order from the magnification side to the minification side thereof, a first lens group having negative refraction of power, a second lens group having positive refraction of power, a third lens group having positive refraction of power, a fourth lens group having negative refraction of power, and a fifth lens group having positive refraction of power, wherein the zoom lens satisfies the formulas: ?1.5<F1/Fw<?1.3, 1.5<F2/Fw<1.8, 1.8<F3/Fw<2.2, ?10<F4/Fw<?5, and 2.3<F5/Fw<2.8, where F1, F2, F3, F4, F5, and Fw respectively represent the effective focal length of the first lens groups, the second lens group, the third lens group, the fourth lens group, the fifth lens group, and the shortest effective focal length of the zoom lens.

Abstract: A four-unit zoom lens system includes in order from an object side, a first lens unit having a positive refracting power, a second lens unit having a negative refracting power, a third lens unit having a positive refracting power, and a fourth lens unit having a positive refracting power, in which at a time of zooming from a wide angle end to a telephoto end, at least the first lens unit, the second lens unit, and the third lens unit move, and a space between the lens units changes, and a total number of lenses in the second lens unit is not more than three, and the zoom lens system satisfies the following conditional expressions. 1.2<(?2t/?2w)/(?3t/?3w)<6.0 and ??(1A) 3.0<ft/fw<20.

Abstract: A zoom lens includes first to fifth lens units arranged in sequence from an object side to an image side, and having positive, negative, positive, negative, and positive refractive powers in that order. The zoom lens performs zooming by moving the first to fifth lens units. The fourth lens unit includes a negative lens, which is moved in such a manner as to have a component in a direction orthogonal to an optical axis so as to shift an image formed with an entire system in the direction orthogonal to the optical axis. The zoom lens satisfies the condition, 0.50<|ft/f4|<1.50, where ft is a focal length of the entire system, and f4 is a focal length of the fourth lens unit, both at the telephoto end.

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: Disclosed is a zoom lens, which includes, in sequence from an object side to an image side, a positive first lens group, a negative second lens group, a positive third lens group, a positive fourth lens group, a fifth lens group, a negative sixth lens group and a positive lens group. The first, third, fifth and seventh lens groups are fixed. When the zoom lens is made to zoom from a wide-angle end to a telephoto end, the second and fourth lens groups move toward the third lens group, while the sixth lens group moves toward the seventh lens group. The absolute value of the ratio of the focal distance of the second lens group to that of the sixth lens group is within a range between 0.1 and 0.5.

Abstract: A variable focal length lens system includes first to fourth lens groups having positive, negative, positive, and positive powers, respectively, and a fifth lens group arranged in this order from an object side. When a lens zoom position is changed from a wide-angle to a telephoto, the first to fourth groups are movable and the second group is moved towards the image side and the third group is moved towards the object side so that a distance between the first and second groups increases and a distance between the second and third groups decreases, and the fourth group is moved along an optical axis direction so as to compensate for the positional change in the image plane. The fifth group includes a negative subgroup having negative power and a positive subgroup disposed on the image side of the negative subgroup and having positive power, and a predetermined condition is satisfied.

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 lend band and the fourth lens band simultaneously moves from the fifth lens band side toward a long focal point end so as to shear a magnification function together with the second lens band.

Abstract: An optical unit for forming an object image according to the present invention includes: a reflection member for bending an optical axis of the optical unit; a front lens group arranged closer to an object side of the optical unit than the reflection member; a rear lens group arranged closer to an image forming side of the optical unit than the reflection member; and a driver for driving the optical unit. The driver drives the reflection member and the front lens group in a predefined first direction and in a predefined second direction.

Abstract: Object is to provide an inner-focusing type zoom lens system carrying out focusing by moving a portion of a first lens group suitable for an auto-focus SLR camera. 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, and a third lens group having positive refractive power. Upon zooming from a wide-angle end state to a telephoto end state, a distance between the first and the second lens groups increases, and a distance between the second and the third lens groups decreases. The first lens group is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. Focusing from infinity to a close-range object is carried out by moving only the 1B lens group G1B to the object.

Abstract: In this invention, to provide a compact zoom lens having a small number of optical element groups to be driven and a simple moving mechanism, at least one of a plurality of optical element groups arranged in the lens system includes a refractive power variable element of a transmission type which has a compensation function to correct focus movement caused by zooming and a focus function to correct focus movement caused by a variation in inter-object distance. The refractive power variable element is a liquid optical element including a first liquid having a conductivity or a polarity and a second liquid which is not mixed with the first liquid, the first liquid and the second liquid being enclosed in a container fluid-tight so as to define an interface therebetween having a predetermined shape, the liquid optical element being arranged such that a refractive power thereof is adjusted by changing a curvature of the interface.

Abstract: An optical device vibrator has a driving mechanism and a controller. The driving mechanism repeatedly changes position or angle of an optical device in predetermined cycles in order to vibrate the optical device. The controller controls driving of the driving mechanism and changes a setting for the position or angle serving as a reference for the repeated change based on predetermined correction information.

Abstract: A zoom lens system comprising a plurality of lens units each composed of at least one lens element, wherein an interval between at least any two lens units is changed so that an optical image is formed with a continuously variable magnification, the zoom lens system comprises a first lens unit having positive power, a second lens unit that includes a lens element having a reflecting surface and has negative power and subsequent lens units including at least one lens unit having positive power, and the condition: 0.50<(C?S)/H<1.00(C=?{square root over ( )}(2R·dR?dR2), S is a sag of the image side surface of the most object side lens element in the second lens unit at height H, H is one-half of an optical axial thickness of the lens element having a reflecting surface, R is a radius of curvature of the image side surface, and dR is an interval between the most object side lens element and the lens element having a reflecting surface) is satisfied.

Abstract: A zoom lens unit includes: a positive first lens group; a negative second lens group; and a positive subsequent lens group as a whole, the subsequent lens group includes a third lens group, and an aperture stop is disposed between the second lens group and the third lens group, and a lens construction including the first and the second lens groups satisfies the condition (1): 1.0<ri/ri+1<5.0, in which ri and ri+1 are curvature radii of lens surfaces Si and Si+1 in the lens construction, respectively, the lens surfaces Si and Si+1 being “i”th and “i+1”th lens surfaces, respectively, counted from the object side, and a reflectivity-reducing treatment adapted to reduce intensity of a ghost image is performed on each lens surface forming at least one of pairs of lens surfaces satisfying the condition (1).

Abstract: A telescopic zoom lens system includes first through fourth lens groups, wherein upon zooming from the short to long focal length extremities, the first and fourth lens groups remain stationary, the second lens group moves toward the image side, and the third lens group moves toward the image side and thereafter moves toward the object side. The first lens group includes positive first and second sub-lens groups, the second sub-lens group being a focusing lens group and including a negative meniscus lens element having a convex surface on the object side and a positive lens element having a convex surface on the object side. The following condition (1) is satisfied: 2.7<flR/ft<3.5; ??(1) wherein flR and ft designate the focal lengths of the second sub-lens group and the entire zoom lens system at the long focal length extremity, respectively.

Abstract: A zoom lens system includes a first group G1 of positive power, a second group G2 of negative power, a third group G3 of positive power and a fourth group G4 of positive power. Upon zooming, at least the first group G1, the second group G2 and the third group G3 move on an optical axis in such a way that, at a telephoto end with respect to a wide-angle end, the space between the first group G1 and the second group G2 and the third group G3 becomes narrow and the space between the third group G3 and the fourth group G4 becomes wide. The zoom lens system satisfies a condition that defines the ratio of the total length (length from the first surface of the lens system to an image plane) to the focal length of the zoom lens system at the wide-angle end.

Abstract: Providing a zoom lens system that can excellently correct aberrations over entire range from a wide-angle end state W to a telephoto end state T in spite of having a high zoom ratio including, in order from an object, a first group G1 having positive power, a second group G2 having negative power, a third group G3 having positive power, a fourth group G4 having negative power, and a fifth group G5 having positive power. When zooming from the wide-angle end state W to the telephoto end state T, a distance between the first group G1 and the second group G2 increases, a distance between the second group G2 and the third group G3 decreases, a distance between the third group G3 and the fourth group G4 increases, and a distance between the fourth group G4 and the fifth group G5 decreases. Given conditions are satisfied.

Abstract: An object is to provide a zoom lens system having compactness of about a normal lens, small number of lens elements, a zoom ratio about 2.9, good productivity, and high optical performance. The system includes, in order from the object, a first lens group with negative power and a second lens group with positive power. Zooming is performed by varying a distance between the first lens group and the second lens group. The first lens group includes at least a negative lens and a positive lens. The second lens group includes a front lens group with positive power and a rear lens group with positive power. The front lens group includes a positive lens and a cemented lens constructed by a positive lens cemented with a negative lens. The rear lens group includes a cemented lens constructed by a negative lens cemented with a positive lens. Given conditions are satisfied.

Abstract: A zoom lens system comprising a multiple of lens units with various positive and negative powers that can, in at least one exemplary embodiment, be used to reduce ghost light.

Abstract: To provide a zoom lens system with a vibration reduction having a long back focal length suitable for a digital SLR camera, a high zoom ratio, and a wide angle of view of 70° or more. The system includes, in order from the object, a first positive lens group, a second negative lens group, a third positive lens group, and a fourth positive lens group. Upon zooming from wide-angle end state to telephoto end state, a distance between the first and second lens groups increases, a distance between the second and third lens groups decreases, and a distance between the third and fourth lens groups varies. The third lens group is composed of a positive front lens group and a negative rear lens group. Image plane correction upon camera shake can be performed by shifting only the rear lens group substantially perpendicularly to the optical axis. Given conditions are satisfied.

Abstract: A plurality of lens units in an optical unit has at least: from the object side toward the image side, a first lens unit having a positive optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power. When at least the first lens unit moves from the image side to the object side in zooming from the wide-angle end position to the telephoto end position, at least one gap between the lens units varies. Predetermined conditional formulae are satisfied.

Abstract: A zoom lens, comprising, 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 during zooming, and wherein, during zooming from a wide-angle end to a telephoto end, the first lens unit moves so that its motion comprises (a) moving toward the image side and (b) moving thereafter toward the object side, and the third lens unit moves so that its motion comprises (a) moving toward the image side and (b) moving thereafter toward the object side.

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

Abstract: A compact zoom lens system includes, from the object side to the image side, a negative first lens group (1), a positive second lens group (2), a positive third lens group (3) and a positive fourth lens group (4). The first lens group is stationary, and both the second and third lens groups are movable for effecting focal length change. The fourth lens group is also movable to compensate for image plane shift due to focal length change and thereby maintain the position of the image plane. The compact zoom lens system has a significantly reduced lens count and thus has an overall length of only 20 mm while achieving an approximately 3× zoom ratio. Sufficient back focal length is ensured even for such a short overall length. By employing aspheric lenses (10, 20, 301, 31, 41) for aberration correction, a high level of optical performance can be ensured.

Abstract: A zoom optical system includes a function of preventing blurring of an image due to movements, such as shaking of the zoom optical system, by moving a lens element of the third lens group, in order from the object side, of four lens groups in a direction that is perpendicular to the optical axis in order to correct for movements of the zoom optical system that would otherwise create a blurred image. The second lens group from the object side has negative refractive power and the other three lens groups have positive refractive power. The second and fourth lens groups move along the optical axis during zooming. The zoom optical system satisfies certain conditions related to the configuration of the lens elements and lens groups of the zoom optical system in order to prevent blurring and to provide a compact zoom optical system having excellent correction of aberrations.

Abstract: There is provided a zoom lens capable of achieving stable optical quality even at the time of manufacture. The zoom lens includes a first lens group having positive refraction, a second lens group having negative refraction, a third lens group having positive refraction, and a fourth lens group having positive refraction, each being arrayed in this order from an object side, wherein: when a magnification changes from a wide-angle end condition having the shortest focal length to a telescopic end condition having the longest focal length, the first lens group and the third lens group are fixed in predetermined positions relative to the optical axis direction; the second lens group moves to the image side; and the fourth lens group moves to compensate fluctuation of the position of the image plane which is generated following moving of the second lens group.

Abstract: A zoom optical system according to the present invention is provided with, in order from an object side thereof: a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group having a negative refractive power; and a fourth lens group having a positive refractive power. The zoom optical system moves at least the second lens group and the third lens group for zooming operation from a wide-angle end to a telephoto end. The zoom optical system moves the third lens group for a focusing operation. The first lens group is provided with, in order from the object side of the zoom optical system, a meniscus lens having a negative refractive power whose concave surface faces an image side of the zoom optical system, a reflective optical element, and at least one lens.

Abstract: The invention provides a zoom lens system that is reduced in terms of both size and cost. The zoom lens system comprises a first positive lens group G1, a second negative lens group G2, a stop S, a third positive lens group G3 and a fourth positive lens group G4. During zooming from a wide-angle end to a telephoto end of the system, while the first lens group G1 remains fixed, the second lens group G2 moves from an object side to an image plane side of the system, the third lens group G3 moves from the image plane side to the object side, and the fourth lens group G4 moves to keep an image plane at a constant position.