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

Abstract: A variable focal length lens system including: a first lens group having positive power; a second lens group having negative power; a third lens group having positive power; and a fourth lens group having positive power sequentially arranged from a side where an object is present. An aperture stop is disposed between the second and third lens groups. The first to fourth lens groups are so moved that the distance between the first and second lens groups increases, the distance between the second and third lens groups decreases, and the distance between the third and fourth lens groups decreases when a lens position setting is changed from a wide angle end state to a telescopic end state. The third lens group includes a negative lens and a positive lens disposed on the image side thereof. The variable focal length lens system satisfies the following conditional expression. 0.35<f3/|f3a|<0.

Abstract: A lens barrel includes: a variable focal length lens system including at least three movable lens groups; and guiding means for moving the variable focal length lens system forward and backward in an optical axis direction. The variable focal length lens system includes at least first, second and third lens groups having positive, negative and positive refracting power, respectively, arranged in this order from an object side. When a lens position setting is changed from a wide angle end state to a telescopic end state, at least the first and third lens groups are moved toward the object side such that air separation between the first and second lens groups monotonically increases and air separation between the second and third lens groups monotonically decreases. The guiding means includes a fixed frame, a rotating frame, a rectilinear guiding frame, a first guide frame, and a second guide frame.

Abstract: Disclosed herein is a variable focal length lens system including a first lens group, a second lens group, a third lens group, a fourth lens group, and a fifth lens group. The first to the fifth lens groups are arranged in order from an object side. The variable focal length lens system satisfies following conditional expressions (1) to (3): 0.95<f13T/ft<1.4??(1) 0.08<f2/f4<0.3??(2) 0.06<?3/ft<0.22??(3) where f13T is combined focal length of the first to third lens groups in the telephoto end state, ft is focal length of the lens system as a whole in the telephoto end state, f2 is focal length of the second lens group, f4 is focal length of the fourth lens group, and ?3 is an amount of travel of the third lens group from the wide-angle end state to the telephoto end state.

Abstract: A lens barrel includes: a variable focal length lens system including at least three movable lens groups; and guiding means for moving the variable focal length lens system forward and backward in an optical axis direction. The variable focal length lens system includes at least first, second and third lens groups having positive, negative and positive refracting power, respectively, arranged in this order from an object side. When a lens position setting is changed from a wide angle end state to a telescopic end state, at least the first and third lens groups are moved toward the object side such that air separation between the first and second lens groups monotonously increases and air separation between the second and third lens groups monotonously decreases. The guiding means includes a fixed frame, a rotating frame, a rectilinear guiding frame, a first guide frame, and a second guide frame.

Abstract: Disclosed herein is a variable focal length lens system including a first lens group, a second lens group, a third lens group, a fourth lens group, and a fifth lens group. The first to the fifth lens groups are arranged in order from an object side. The variable focal length lens system satisfies following conditional expressions (1) to (3): 0.95<f13T/ft<1.4 ??(1) 0.08<f2/f4<0.3 ??(2) 0.06<?3/ft<0.22 ??(3) where f13T is combined focal length of the first to third lens groups in the telephoto end state, ft is focal length of the lens system as a whole in the telephoto end state, f2 is focal length of the second lens group, f4 is focal length of the fourth lens group, and ?3 is an amount of travel of the third lens group from the wide-angle end state to the telephoto end state.

Abstract: A variable focal length lens system includes first to fourth lens groups which have positive, negative, positive, and positive refractive powers, respectively, and are arranged in this order from an object side to an image side. An aperture diaphragm is arranged in the vicinity of the third lens group. The variable focal length lens system satisfies the following Conditional expressions 1 and 2: ?0.04<fw/R23<0.18, and??[Conditional expression 1] 0.48<fw/R24<0.72??[Conditional expression 2] (where fw indicates the focal length of the entire lens system at the wide-angle end, R23 indicates the curvature radius of a surface of the cemented lens closest to the object side in the second lens group, and R24 indicates the curvature radius of a cemented surface of the cemented lens in the second lens group).

Abstract: A variable focal distance lens system 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 positive refractive power, which are sequentially disposed from an object side to an image side. The system satisfies ?0.65<(R33?R34)/(R33+R34)<?0.25 and ?1.0<(R22?R23)/(R22+R23)<?0.6, wherein R33 represents the radius of curvature of the most image-side surface of a cemented lens of the third lens group, R34 represents the radius of curvature of the object-side surface of a positive lens of the third lens group disposed on the most image side, R22 represents the radius of curvature of the image-side surface of a negative lens of the second lens group disposed on the most object side, and R23 represents the radius of curvature of the most object-side surface of a cemented lens of the second lens group.

Abstract: A variable-focal-length lens system includes first to fifth lens groups having positive, negative, positive, negative, and positive refractive powers, respectively, from the object side. As the lens-position state changes from wide-angle to telephoto, the air space between the first and second lens groups increases, the air space between the second and third lens groups decreases, the air space between the third and fourth lens groups changes, the air space between the fourth and fifth lens groups increases, the first lens group moves monotonously toward the object, the second lens group is fixed in the optical-axis direction, and the third and fourth lens groups move toward the object. Conditions 0.2<D23w/ft<0.4, 0.1<f2/f4<0.4 are satisfied, D23w, ft, and f2 and f4 being the air space between the second and third lens groups at wide-angle, lens system's overall focal length at telephoto end, and focal lengths of the second and fourth lens groups, respectively.

Abstract: A lens includes a front group including a plurality of lens groups; and a rear group that is provided on an image side of the front group and that includes a negative lens and a positive lens. The positive lens has a flat lens surface on its image side, and is tiltable about a spherical center of its object side lens surface that is convex on the object side. When a lens system is inclined, the positive lens is tilted in relation to the optical axis of the lens system based on: a focal length of the overall lens system; an angle of the optical axis of the lens system after being inclined in relation to the optical axis before being inclined; a distance between the image side lens surface of the positive lens and the image plane; and a refractive index of the positive lens.

Abstract: A variable focal length lens system includes: a first lens group having a positive refracting power; a second lens group having a negative refracting power; a third lens group having a positive refracting power; a fourth lens group having a negative refracting power; a fifth lens group having a negative refracting power; and a sixth lens group having a positive refracting power; the first to sixth lens groups being disposed in order from an object side.

Abstract: A lens includes a front group including a plurality of lens groups; and a rear group that is provided on an image side of the front group and that includes a negative lens and a positive lens. The positive lens has a flat lens surface on its image side, and is tiltable about a spherical center of its object side lens surface that is convex on the object side. When a lens system is inclined, the positive lens is tilted in relation to the optical axis of the lens system based on: a focal length of the overall lens system; an angle of the optical axis of the lens system after being inclined in relation to the optical axis before being inclined; a distance between the image side lens surface of the positive lens and the image plane; and a refractive index of the positive lens.

Abstract: A variable focal distance lens system 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 positive refractive power, which are sequentially disposed from an object side to an image side. The system satisfies ?0.65<(R33?R34)/(R33±R34)<?0.25 and ?1.0<(R22?R23)/(R22±R23)<?0.6, wherein R33 represents the radius of curvature of the most image-side surface of a cemented lens of the third lens group, R34 represents the radius of curvature of the object-side surface of a positive lens of the third lens group disposed on the most image side, R22 represents the radius of curvature of the image-side surface of a negative lens of the second lens group disposed on the most object side, and R23 represents the radius of curvature of the most object-side surface of a cemented lens of the second lens group.

Abstract: A variable-focal-length lens system includes first to fifth lens groups having positive, negative, positive, negative, and positive refractive powers, respectively, from the object side. As the lens-position state changes from wide-angle to telephoto, the air space between the first and second lens groups increases, the air space between the second and third lens groups decreases, the air space between the third and fourth lens groups changes, the air space between the fourth and fifth lens groups increases, the first lens group moves monotonously toward the object, the second lens group is fixed in the optical-axis direction, and the third and fourth lens groups move toward the object. Conditions 0.2<D23w/ft<0.4, 0.1<f2/f4<0.4 are satisfied, D23w, ft, and f2 and f4 being the air space between the second and third lens groups at wide-angle, lens system's overall focal length at telephoto end, and focal lengths of the second and fourth lens groups, respectively.

Abstract: A variable focal length lens system includes first to fourth lens groups which have positive, negative, positive, and positive refractive powers, respectively, and are arranged in this order from an object side to an image side. An aperture diaphragm is arranged in the vicinity of the third lens group. The variable focal length lens system satisfies the following Conditional expressions 1 and 2: ?0.04<fw/R23<0.18, and??[Conditional expression 1] 0.48<fw/R24<0.72??[Conditional expression 2] (where fw indicates the focal length of the entire lens system at the wide-angle end, R23 indicates the curvature radius of a surface of the cemented lens closest to the object side in the second lens group, and R24 indicates the curvature radius of a cemented surface of the cemented lens in the second lens group).

Abstract: A zoom lens includes: a front group including a plurality of movable lens groups; and a rear group that is provided on an image side of the front group and that includes a negative lens and a positive lens. The positive lens has a flat lens surface on its image side, and is tiltable about a spherical center of its object side lens surface that is convex on the object side. When a lens system is inclined, the positive lens is tilted in relation to the optical axis of the lens system based on: a focal length of the overall lens system; an angle of the optical axis of the lens system after being inclined in relation to the optical axis before being inclined; a distance between the image side lens surface of the positive lens and the image plane; and a refractive index of the positive lens.

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: To provide a zoom lens capable of achieving stable optical quality by inhibiting an effect of assemble errors during manufacturing. A zoom lens includes a positive first lens group G1, a negative second lens group G2, a positive third lens group G3, and a positive fourth lens group G4, which are arranged from an object side in that order, and during variation in lens position from a wide angle end state to a telescopic end state, G1 and G3 are fixed, G2 is moved toward an image side, G4 moves so as to compensate fluctuations in image-surface position due to the shift of G2, and an aperture diaphragm S is fixed adjacent to the object side of G3, etc.

Abstract: A zoom lens and an imaging apparatus are disclosed. The zoom lens includes, in order from an object side to an image-plane 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 negative refractive power, and a fifth lens group having a positive refractive power. During a change of a lens zoom position from a maximum wide angle state to a maximum telephoto state, at least the second lens group moves toward an image side, the third lens group moves toward an object side, and the fourth lens group is fixed in an optical-axis direction. An aperture stop is disposed near the object side of the third lens group. The first to fifth lens groups satisfy predetermined conditions.

Abstract: A variable focal length lens system includes: a first lens group having a positive refracting power; a second lens group having a negative refracting power; a third lens group having a positive refracting power; a fourth lens group having a negative refracting power; a fifth lens group having a negative refracting power; and a sixth lens group having a positive refracting power; the first to sixth lens groups being disposed in order from an object side.