Abstract: An imaging optical system includes a first lens group having positive power, a second lens group, and a third lens group. The first lens group includes a sub-lens group G1A, an aperture stop, and a sub-lens group G1B. The sub-lens group G1A includes a lens L1A1 and a lens L1A2. An object-side surface of the lens L1A1 is convex toward an object. The third lens group includes a lens L3E having negative power and a lens L3P located adjacent to, and closer to the object than, the lens L3E.

Abstract: An imaging optical system includes: a front group having positive power; an aperture stop; a single lens Fn arranged adjacent to the aperture stop and having negative power; and a rear group having power. The front group includes: a first lens having positive power; a second lens having negative power; and a lens LG1R having positive power. The rear group includes a lens LGnR having negative power and located closest to the image. While focusing to make a transition from an infinity in-focus state to a close-object in-focus state, neither the front group nor the rear group moves but the single lens Fn moves along an optical axis toward the image. The imaging optical system satisfies the inequality: 0.38<fLG1R/fG1<1.75, where fG1 is a focal length of the front group and fLG1R is a focal length of the lens LG1R.

Abstract: An imaging optical system includes, in order from an object side to an image side, a first lens group having negative optical power, a second lens group having positive optical power, a third lens group having negative optical power, and a fourth lens group with negative optical power. A lens disposed closest to the object side in the second lens group has a concave surface directed toward the object side, and a lens disposed closest to the object side in the fourth lens group has positive optical power. Each distance between the lens groups changes when zooming from a wide-angle end to a telephoto end on photographing.

Abstract: An imaging optical system includes, in order from an object side to an image side, a first lens group having negative optical power, a second lens group having positive optical power, a third lens group having negative optical power, and a fourth lens group with negative optical power. A lens disposed closest to the object side in the second lens group has a concave surface directed toward the object side, and a lens disposed closest to the object side in the fourth lens group has positive optical power. Each distance between the lens groups changes when zooming from a wide-angle end to a telephoto end on photographing.

Abstract: The zoom lens system includes a first lens group with positive power, a second lens group with negative power, a third lens group with positive power, a fourth lens group with negative power, and a fifth lens group with positive power. An aperture stop is provided between the second and the third lens groups. The third lens group includes lens element L3a and L3b with positive power, lens element L3c with negative power, and lens element L3d with positive power. The lens elements L3c and L3d are cemented. The lens element L3b corrects image blurring. The fourth lens group moves when focusing. When zooming, the first to the fourth lens group move. Here, condition (1) below is satisfied. 0.24<fL3b/fG3<3.0??(1) Where fL3b is a focal length of the lens element L3b, and fG3 is a focal length of the third lens group.

Abstract: A lens system in the present disclosure includes: a first lens group that is moved toward an image side along an optical axis in focusing from a far-object in-focus state to a near-object in-focus state, and has positive optical power; and a second lens group that is disposed on the image side relative to the first lens group and has optical power. The lens system satisfies the following conditions (1) and (2). 0.5<|fg1/WD|<2.0??(1) 20<|fg2/f|<700??(2) where fg1 is a focal length of the first lens group, WD is a distance, on the optical axis, from an object surface to a lens surface located closest to an object side of the first lens group, fg2 is a focal length of the second lens group, and f is a focal length of the lens system under the far-object in-focus state.

Abstract: A single focal length lens system includes, in order from an object side to an image side, a first lens unit having positive optical power and a second lens unit including a lens element that moves in a direction of an optical axis with respect to an image surface in focusing from an infinity in-focus condition to a close-object in-focus condition. The first lens unit includes an aperture diaphragm and a lens element A located on the object side of the aperture diaphragm. A lens element B having positive optical power and a lens element C having negative optical power are located on the image side of the aperture diaphragm. Abbe numbers of the lens elements A, B, and C to the d-line and partial dispersion ratios of the lens elements A, B, and C for the g-line and the F-line satisfy a predetermined relation.

Abstract: The zoom lens system includes a first lens group with positive power, a second lens group with negative power, a third lens group with positive power, a fourth lens group with negative power, and a fifth lens group with positive power. An aperture stop is provided between the second and the third lens groups. The third lens group includes lens element L3a and L3b with positive power, lens element L3c with negative power, and lens element L3d with positive power. The lens elements L3c and L3d are cemented. The lens element L3b corrects image blurring. The fourth lens group moves when focusing. When zooming, the first to the fourth lens group move. Here, condition (1) below is satisfied. 0.24<fL3b/fG3<3.0??(1) Where fL3b is a focal length of the lens element L3b, and fG3 is a focal length of the third lens group.

Abstract: A lens system in the present disclosure includes: a first lens group that is moved toward an image side along an optical axis in focusing from a far-object in-focus state to a near-object in-focus state, and has positive optical power; and a second lens group that is disposed on the image side relative to the first lens group and has optical power. The lens system satisfies the following conditions (1) and (2). 0.5<|fg1/WD|<2.0??(1) 20<|fg2/f|<700??(2) where fg1 is a focal length of the first lens group, WD is a distance, on the optical axis, from an object surface to a lens surface located closest to an object side of the first lens group, fg2 is a focal length of the second lens group, and f is a focal length of the lens system under the far-object in-focus state.

Abstract: A single focal length lens system includes, in order from an object side to an image side, a first lens unit having positive optical power and a second lens unit including a lens element that moves in a direction of an optical axis with respect to an image surface in focusing from an infinity in-focus condition to a close-object in-focus condition. The first lens unit includes an aperture diaphragm and a lens element A located on the object side of the aperture diaphragm. A lens element B having positive optical power and a lens element C having negative optical power are located on the image side of the aperture diaphragm. Abbe numbers of the lens elements A, B, and C to the d-line and partial dispersion ratios of the lens elements A, B, and C for the g-line and the F-line satisfy a predetermined relation.

Abstract: An imaging optical system, in order from an object side to an image side, includes: a first lens unit having positive optical power; and a second lens unit. In focusing from an infinity in-focus condition to a close-object in-focus condition, the first lens unit moves along an optical axis, and the second lens unit is fixed with respect to an image surface. The imaging optical system is compact, sufficiently suppresses occurrence of various aberrations, has high resolution from the infinity in-focus condition to the close-object in-focus condition, is bright and highly efficient, and is suitable for wide-angle photographing.

Abstract: A zoom lens system, in order from an object side to an image side, includes a first lens unit having positive optical power; a second lens unit having negative optical power; a third lens unit having positive optical power; a fourth lens unit having negative optical power, and a subsequent lens unit. The first lens unit includes a negative lens element and a positive lens element. In the zoom lens system, the conditions: 1.47<nd2<1.57 and 60<vd2<75 (nd2: a refractive index to a d-line of the positive lens element, vd2: an Abbe number to a d-line of the positive lens element) are satisfied.

Abstract: Compact and lightweight zoom lens systems having less aberration fluctuation in association with focusing, lens barrels, interchangeable lens apparatuses, and camera systems are provided. The zoom lens system comprises: a first lens unit having positive optical power; a first focusing lens unit which is located on an image side relative to the first lens unit, has negative optical power, and moves along an optical axis in zooming and focusing; and a second focusing lens unit which is located on the image side relative to the first focusing lens unit, has positive optical power, and moves along the optical axis in the zooming and the focusing, and satisfies the condition: |d2T/d1T|<1.0 (d1T: an amount of movement of the first focusing lens unit in focusing at a telephoto limit, d2T: an amount of movement of the second focusing lens unit in focusing at a telephoto limit).

Abstract: A compact and lightweight zoom lens system having excellent imaging performance, which is favorably applicable to an interchangeable-lens type digital camera system, is provided. The zoom lens system of the present invention includes, in order from an object side to an image side, a first lens unit having positive optical power and composed of not more than two lens elements, a second lens unit having negative optical power, a third lens unit having negative optical power, and a fourth lens unit having positive optical power. In zooming from a wide-angle limit to a telephoto limit, the fourth lens unit moves along an optical axis. Further, the following conditions are satisfied: 1.50<nd1<1.72, 50<vd1<75 (nd1: a refractive index to the d line of a positive lens element constituting the first lens unit, vd1: an Abbe number of a positive lens element constituting the first lens unit).

Abstract: A single focal length lens system comprising: at least a front lens unit having positive or negative power, and being fixed in focusing; a focusing lens unit having positive power, and moving along an optical axis in focusing; and a rear lens unit having negative power, and being fixed in focusing, wherein the focusing lens unit includes: a cemented lens of a negative lens and a positive lens; and a positive single lens located on the image side relative to the cemented lens and having an aspheric surface, the rear lens unit is composed of one single lens, and the condition: ?0.5<fW/fGR<?0.1 (fW, fGR: focal lengths of the entire single focal length lens system, the rear lens unit) is satisfied.

Abstract: Compact and lightweight zoom lens systems having less aberration fluctuation in association with focusing, lens barrels, interchangeable lens apparatuses, and camera systems are provided. The zoom lens system comprises: a first lens unit having positive optical power; a first focusing lens unit which is located on an image side relative to the first lens unit, has negative optical power, and moves along an optical axis in zooming and focusing; and a second focusing lens unit which is located on the image side relative to the first focusing lens unit, has positive optical power, and moves along the optical axis in the zooming and the focusing, and satisfies the condition: |d2T/d1T|<1.0 (d1T: an amount of movement of the first focusing lens unit in focusing at a telephoto limit, d2T: an amount of movement of the second focusing lens unit in focusing at a telephoto limit).

Abstract: A single focal length lens system comprising a front lens unit, an aperture diaphragm, and a rear lens unit, wherein the front lens unit is composed of three or less lenses including a negative lens located closest to the object side and a positive lens located on the image side relative to the negative lens, and does not move along an axis in focusing, the rear lens unit includes a focusing lens unit moving along the axis and a fixed lens unit not moving along the axis in focusing, and the conditions: 0.4<fW/fGF<1.5, 0.9<fW/T1<4.5, and ?0.3<fW/fG1<0.3 (fW, fGF, fG1: focal lengths of the entire single focal length lens system, the focusing lens unit, the front lens unit, T1: an axial distance from an object side lens surface of the negative lens to the aperture diaphragm) are satisfied.

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

Abstract: Compact and lightweight zoom lens systems having less aberration fluctuation in association with focusing, lens barrels, interchangeable lens apparatuses, and camera systems are provided. The zoom lens system comprises: a first lens unit having positive optical power; a first focusing lens unit which is located on an image side relative to the first lens unit, has negative optical power, and moves along an optical axis in zooming and focusing; and a second focusing lens unit which is located on the image side relative to the first focusing lens unit, has positive optical power, and moves along the optical axis in the zooming and the focusing, and satisfies the condition: |d2T/d1T|<1.0 (d1T: an amount of movement of the first focusing lens unit in focusing at a telephoto limit, d2T: an amount of movement of the second focusing lens unit in focusing at a telephoto limit).

Abstract: A zoom lens system, in order from an object side to an image side, comprising: a first lens unit having positive optical power; a second lens unit having negative optical power; a third lens unit having positive optical power; a fourth lens unit having negative optical power, and a subsequent lens unit, wherein the first lens unit comprises a negative lens element having negative optical power, and a positive lens element having positive optical power, and wherein the conditions: 1.47<nd2<1.57 and 60<?d2<75 (nd2: a refractive index to a d-line of the positive lens element, ?d2: an Abbe number to a d-line of the positive lens element) are satisfied.