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, in that order from the object side. Upon zooming from the short to long focal length extremities, each of the first through fourth lens groups move along the optical axis thereof. The following conditions (1) and (2) are satisfied: 1.05<ft/f1<1.75??(1), and 3.7<M3t/M3w<6.3??(2), wherein f1 designates the focal length of the first lens group, ft designates the focal length of the entire zoom lens system at the long focal length extremity, and M3t and M3w designate the lateral magnifications of the third lens group when focusing on an object at infinity at the long and short focal length extremities, respectively.

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, in that order from the object side. Upon zooming from the short to long focal length extremities, each of the first through fourth lens groups move along the optical axis thereof. The following conditions (1) and (2) are satisfied: 1.05<ft/f1<1.75??(1), and 3.7<M3t/M3w<6.3??(2), wherein f1 designates the focal length of the first lens group, ft designates the focal length of the entire zoom lens system at the long focal length extremity, and M3t and M3w designate the lateral magnifications of the third lens group when focusing on an object at infinity at the long and short focal length extremities, respectively.

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, in that order from the object side. Upon zooming from the short to long focal length extremities, 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 changes. The second lens group includes a negative lens element having a concave surface on the image side, a negative lens element having a concave surface on the image side, and a plastic positive lens element having an aspherical surface on at least one side and having a convex surface on the object side, in that order from the object side.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group, in that order from the object side, wherein upon zooming from the short focal length extremity to the long focal length extremity, the distance between the first lens group and the second lens group is decreased, and the distance between the second lens group and the third lens group is decreased. A reflection prism having a negative refractive power is provided between the third lens group and the imaging plane, and wherein the following condition (1) is satisfied: P2?d<32??(1), wherein P2?d designates the Abbe number with respect to the d-line of the reflection prism, which is provided between the third lens group and the imaging plane.

Abstract: An imaging device is provided with an imaging sensor having a rectangular imaging surface, an image-forming optical system for forming an image onto the imaging surface, and a prism disposed between the image-forming optical system and the imaging sensor for bending an optical path. A mask, having a rectangular opening, limits light that is to be incident on the imaging sensor. The aspect ratio (long side/short side) of the mask rectangular opening of the mask is larger than that of the rectangular imaging surface, and the peripheral light quantity difference between the short and long sides on the rectangular imaging surface is smaller than in the case of these two aspect ratios being equal to each other.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group. The second lens group includes a positive lens element, and two negative lens elements. The following conditions (1) and (2) are satisfied: 2.0<|VD1t?VD1w|/(ft/fw)<3.4??(1), and 0.89<|m2w/m3w|??(2), wherein VD1t and VD1w designate the distances, at the long and short focal length extremities, from the image-side surface of the lens element provided closest to the image side within the first lens group to the object-side surface of the positive lens element provided closest to the object side within the second lens group; ft and fw designate the entire focal length of the zoom lens system at the long and short focal length extremities; and m2w and m3w designate the lateral magnification of the second and third lens groups at the short focal length extremity when focused on an object at infinity.

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, in that order from the object side. Upon zooming from the short to long focal length extremities, 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 changes. The second lens group includes a negative lens element having a concave surface on the image side, a negative lens element having a concave surface on the image side, and a plastic positive lens element having an aspherical surface on at least one side and having a convex surface on the object side, in that order from the object side.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group, in this order from the object. Each of the negative first lens group, the positive second lens group and the positive third lens group moves along the optical axis upon zooming. The positive second lens group includes a positive first lens element, a negative second lens element, and a negative third lens element, in this order from the object. The zoom lens system satisfies the following conditions: 2<f2/rb<3??(1) 0.4<f2/f3<0.8??(2) wherein f2 designates the focal length of the positive second lens group; f3 designates the focal length of the positive third lens group; and rb designates the radius of curvature of the image-side surface of the negative third lens element of the positive second lens group.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group, in that order from the object side, wherein upon zooming from the short focal length extremity to the long focal length extremity, the distance between the first lens group and the second lens group is decreased, and the distance between the second lens group and the third lens group is decreased. A reflection prism having a negative refractive power is provided between the third lens group and the imaging plane, and wherein the following condition (1) is satisfied: P2?d<32??(1), wherein P2?d designates the Abbe number with respect to the d-line of the reflection prism, which is provided between the third lens group and the imaging plane.

Abstract: An imaging device is provided with an imaging sensor having a rectangular imaging surface, an image-forming optical system for forming an image onto the imaging surface, and a prism disposed between the image-forming optical system and the imaging sensor for bending an optical path. A mask, having a rectangular opening, limits light that is to be incident on the imaging sensor. The aspect ratio (long side/short side) of the mask rectangular opening of the mask is larger than that of the rectangular imaging surface, and the peripheral light quantity difference between the short and long sides on the rectangular imaging surface is smaller than in the case of these two aspect ratios being equal to each other.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group. The second lens group includes a positive lens element, and two negative lens elements. The following conditions (1) and (2) are satisfied: 2.0<|VD1t?VD1w|/(ft/fw)<3.4 ??(1), and 0.89<|m2w/m3w|??(2), wherein VD1t and VD1w designate the distances, at the long and short focal length extremities, from the image-side surface of the lens element provided closest to the image side within the first lens group to the object-side surface of the positive lens element provided closest to the object side within the second lens group; ft and fw designate the entire focal length of the zoom lens system at the long and short focal length extremities; and m2w and m3w designate the lateral magnification of the second and third lens groups at the short focal length extremity when focused on an object at infinity.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group, in this order from the object. Each of the negative first lens group, the positive second lens group and the positive third lens group moves along the optical axis upon zooming. The positive second lens group includes a positive first lens element, a negative second lens element, and a negative third lens element, in this order from the object. The zoom lens system satisfies the following conditions: 2<f2/rb<3??(1) 0.4<f2/f3<0.8??(2) wherein f2 designates the focal length of the positive second lens group; f3 designates the focal length of the positive third lens group; and rb designates the radius of curvature of the image-side surface of the negative third lens element of the positive second lens group.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group, in this order from the object. Each of the negative first lens group, the positive second lens group and the positive third lens group moves along the optical axis upon zooming. The positive second lens group includes a positive first lens element, a negative second lens element, and a negative third lens element, in this order from the object. The zoom lens system satisfies the following conditions: 2<f2/rb<3 ??(1) 0.4<f2/f3<0.8 ??(2) wherein f2 designates the focal length of the positive second lens group; f3 designates the focal length of the positive third lens group; and rb designates the radius of curvature of the image-side surface of the negative third lens element of the positive second lens group.

Abstract: A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group, in this order from the object. Each of the negative first lens group, the positive second lens group and the positive third lens group moves along the optical axis upon zooming. The positive second lens group includes a positive first lens element, a negative second lens element, and a negative third lens element, in this order from the object. The zoom lens system satisfies the following conditions: 2<f2/rb<3 ??(1) 0.4<f2/f3<0.8 ??(2) wherein f2 designates the focal length of the positive second lens group; f3 designates the focal length of the positive third lens group; and rb designates the radius of curvature of the image-side surface of the negative third lens element of the positive second lens group.