Abstract: A zoom lens includes, in an order from an object side, four groups of a positive group, a negative group, a positive group, and a negative group. For varying magnification from a wide-angle end to a telephoto end, the first group is configured to be moved toward the object side, the second group is configured to be moved toward an image side, the third group is configured to be moved toward the object side, and the fourth group is configured to be moved toward the object side, and conditional equations of ?0.63<f2/f1<?0.25, ?10<f2/y?max <?3, and 6<f1/y?max<20 (f1: the focal distance of the first group; f2: the focal distance of the second group; y?max: the maximum image height) are satisfied.

Abstract: A zoom lens system having a negative first lens group and a positive second lens group, from an object side, and achieving zooming by varying a group-to-group distance. The second lens group includes a three-element cemented lens which is a set of three lens elements cemented together including, from the object side, a negative first lens, a positive second lens, and a negative third lens, and the three-element cemented lens fulfills conditional formulas 0.08<(rs2+rs1)/(rs2?rs1)<0.5, 27<v2-v1<40, 20<v2-v3<38 (rs1, rs2 represent the curvature radius of the sides of cemented surfaces of the three-element cemented lens on the object side and the image side respectively, and v1-3 represent the Abbe numbers of the first to third lenses of the three-element cemented lens).

Abstract: A zoom lens system having a negative first lens group and a positive second lens group, from an object side, and achieving zooming by varying a group-to-group distance. The second lens group includes a three-element cemented lens which is a set of three lens elements cemented together including, from the object side, a negative first lens, a positive second lens, and a negative third lens, and the three-element cemented lens fulfills conditional formulas 0.08<(rs2+rs1)/(rs2?rs1)<0.5, 27<v2-v1<40, 20<v2-v3<38 (rs1, rs2 represent the curvature radius of the sides of cemented surfaces of the three-element cemented lens on the object side and the image side respectively, and v1-3 represent the Abbe numbers of the first to third lenses of the three-element cemented lens).

Abstract: A zoom lens includes, in an order from an object side, four groups of a positive group, a negative group, a positive group, and a negative group. For varying magnification from a wide-angle end to a telephoto end, the first group is configured to be moved toward the object side, the second group is configured to be moved toward an image side, the third group is configured to be moved toward the object side, and the fourth group is configured to be moved toward the object side, and conditional equations of ?0.63<f2/f1<?0.25, ?10<f2/y?max<?3, and 6<f1/y?max<20 (f1: the focal distance of the first group; f2: the focal distance of the second group; y?max: the maximum image height) are satisfied.

Abstract: A digital still camera switches an image sensor between moving picture shooting and still picture shooting. The digital still camera includes a variable-magnification optical system having a plurality of lens groups of which four are movable. At least one of the movable lens groups travels different movement trails for magnification variation between during zooming in moving picture shooting and during zooming in still picture shooting.

Abstract: A taking lens system is provided with, from the side of the object to be photographed, 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. Zooming is performed by moving the first to fourth lens units (G1) to (G4), and focusing is performed by moving the fourth lens unit (G4). When the distance from the most object-to-be-photographed side surface (r1) of the first lens unit (G1) to the imaging surface at the wide angle end is TLw, the overall focal length of the taking lens system at the telephoto end is ft, the overall focal length of the taking lens system at the wide angle end is fw, and the focal length of the first lens unit (G1) is fl, relationships 0.5?TLw/ft?1.0 and 6.0?fl/fw?20.0 are satisfied.

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 image pickup optical system according to the present invention includes: a first lens group having a positive power; a second lens group having a negative power; a third lens group having a positive power; and a fourth lens group having a positive power which consists of a front group with a negative power and a rear group with a positive power. The first lens group moves to the object side and a distance between each neighboring lens groups changes, for varying power of the image pickup optical system. One group of the front group and the rear group in the fourth lens group consists of one lens which moves substantially perpendicular to an optical axis for a shake compensation. The image pickup optical system fulfills the predetermined conditional formula according to a focal length of the first lens group.

Abstract: A variable magnification optical system for forming an optical image of an object on a light-receiving surface of an image sensor with variable magnification includes: from the object side, at least 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. In magnification variation from the wide angle end to the telephoto end, at least the first lens unit moves. Conditional formulae (1) and (2) below are fulfilled: (1) 6.0<fl/fw<20.0 and (2) 1.83<Ndave, where fl represents the focal length of the first lens unit, fw represents the focal length of the entire system at the wide angle end, and Ndave represents the average refractive index for a d-line among all lens elements included in the second lens unit.

Abstract: An image pickup optical system according to the present invention is provided for forming a light flux from an object into an optical image on an image pickup element. The image pickup optical system includes: a first lens group having a positive power; a second lens group having a negative power; a third lens group having a positive power; a fourth lens group having a negative power; and a fifth lens group. A distance between each neighboring lens groups changes with the fourth lens group statically positioned, for varying power of the image pickup optical system. The fourth lens group moves in a direction substantially perpendicular to an optical axis for shake compensation. The image pickup optical system fulfills the predetermined conditional formulas according to focal lengths of the first and fourth lens groups.

Abstract: An image forming device is provided with: a zoom lens system TL that performs magnification varying by changing the distance between the lens units; and an image sensor SR that converts an optical image formed by the zoom lens system TL into an electric signal. The zoom lens system TL comprises three lens units of negative, positive, positive configuration. The second lens unit Gr2 comprises three single lens elements of, from the object side, a positive lens element L21, a negative meniscus lens element L22 convex to the object side and a positive lens element L23. A condition 1.0<|P22/P21|<2.0 (P21 is the optical power of the object side positive lens element L21 in the second lens unit GR2, and P22 is the optical power of the negative meniscus lens element L22 in the second lens unit GR2) is satisfied.

Abstract: An image pickup optical system according to the present invention is provided for forming a light flux from an object into an optical image on an image pickup element. The image pickup optical system includes: a first lens group having a positive power; a second lens group having a negative power; a third lens group having a positive power; a fourth lens group having a negative power; and a fifth lens group. A distance between each neighboring lens groups changes with the fourth lens group statically positioned, for varying power of the image pickup optical system. The fourth lens group moves in a direction substantially perpendicular to an optical axis for shake compensation. The image pickup optical system fulfills the predetermined conditional formulas according to focal lengths of the first and fourth lens groups.

Abstract: An image pickup optical system according to the present invention includes: a first lens group having a positive power; a second lens group having a negative power; a third lens group having a positive power; and a fourth lens group having a positive power which consists of a front group with a negative power and a rear group with a positive power. The first lens group moves to the object side and a distance between each neighboring lens groups changes, for varying power of the image pickup optical system. One group of the front group and the rear group in the fourth lens group consists of one lens which moves substantially perpendicular to an optical axis for a shake compensation. The image pickup optical system fulfills the predetermined conditional formula according to a focal length of the first lens group.

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 image forming device is provided with: a zoom lens system TL that performs magnification varying by changing the distance between the lens units; and an image sensor SR that converts an optical image formed by the zoom lens system TL into an electric signal. The zoom lens system TL includes at least a negative first lens unit GR1 and a positive second lens unit GR2, and at least the first lens unit GR1 and the second lens unit GR2 move in zooming from the wide angle end (W) to the telephoto end (T). The second lens unit GR2 includes three lens elements of, from the object side, a positive meniscus lens element L21 convex to the object side, a negative lens element L22 and a positive lens element L23, and the following condition is satisfied: ?1.0<(CR1?CR2)/(CR1+CR2)<0.0 (CR1 is the front radius of curvature of the most object side lens element L21 in the second lens unit GR2, and CR2 is the rear radius of curvature of the most object side lens element L21 in the second lens unit GR2).

Abstract: The present invention provides a compact, high-performance, and easy-to-manufacture taking optical system that offers an extremely high zoom ratio. The taking optical system includes, from the subject side, a first lens group having a positive optical power, a second lens group having a negative optical power, a third lens group having a positive optical power, and a fourth lens group having a positive optical power. The taking optical system achieves zooming by the movements of the first to fourth lens groups and focusing by the movement of the fourth lens group. The taking optical system fulfills the following conditions: 0.05?f3/f4?0.95 and 7.0?f1/fw?20.0, where f1, f3, and f4 represent the focal lengths of the first, third, and fourth lens groups, respectively, and fw represents the focal length of the entire taking optical system at the wide-angle end thereof.

Abstract: A variable-magnification optical system has a plurality of lens groups that image a light beam from the object side on an image sensor, an optical aperture stop that intercepts part of the light beam heading for the image sensor, and a reflective mirror that changes the optical axis of the light beam of which part has been intercepted by the optical aperture stop. The plurality of lens groups include at least lens groups arranged in a positive-negative-positive-positive optical power arrangement, and at least two of the lens groups are moved for zooming from the wide-angle end to the telephoto end. The variable-magnification optical system fulfills a prescribed conditional formula.

Abstract: A digital still camera switches an image sensor between moving picture shooting and still picture shooting. The digital still camera includes a variable-magnification optical system having a plurality of lens groups of which four are movable. At least one of the movable lens groups travels different movement trails for magnification variation between during zooming in moving picture shooting and during zooming in still picture shooting.

Abstract: A variable-magnification optical system has a plurality of lens groups that image a light beam from the object side on an image sensor, an optical aperture stop that intercepts part of the light beam heading for the image sensor, and a reflective mirror that changes the optical axis of the light beam of which part has been intercepted by the optical aperture stop. The plurality of lens groups include at least lens groups arranged in a positive-negative-positive-positive optical power arrangement, and at least two of the lens groups are moved for zooming from the wide-angle end to the telephoto end. The variable-magnification optical system fulfills a prescribed conditional formula.

Abstract: A zoom lens system for forming an optical image of a subject on the image-sensing surface of an image sensor has three lens units, namely, from the object side thereof, a first lens unit having a negative optical power, a second lens unit having a positive optical power, and a third lens unit having a positive optical power. The lens units each include at least one plastic lens element. The zoom lens system as a whole includes at least one glass lens element that fulfills a prescribed conditional formula.