Abstract: Provided is an imaging optical system and an image acquisition apparatus that can be suitably used in a small-diameter endoscope while having an ultra-wide angle of view. Provided is an image optical system (1) containing, in order from the object side, a negative front group (FG), an aperture stop (S), and a positive back group (BG), wherein the front group (FG) contains, in order from the object side, a negative first lens (L1) and a negative second lens (L2), and the back group (BG) contains a cemented lens (CL) constituted of at least three lenses (L5, L6, L7) joined together.

Abstract: A zoom lens includes: a first lens group having two lens components including a negative lens component of negative refractive power and a positive lens component of positive refractive power; a second lens group including a negative lens, a first positive lens and a second positive lens; a fourth lens group having one lens component including a negative lens component having a concave surface directed to the object side; the negative lens components in the first and fourth lens groups satisfying conditional formula (1): ?0.80<rG1nr/rG4nf<?0.40??(1), where rG1nr is the radius of paraxial curvature of the image side surface of the negative lens component in the first lens group; and rG4nf is the radius of paraxial curvature of the object side surface of the negative lens component in the fourth lens group.

Abstract: A zoom lens has a plurality of lens units including, in order from its object side to image side, a first lens unit having a negative refracting power composed of two lens elements including a biconcave negative lens and a positive lens, and a second lens unit having a positive refracting power composed of four lens elements including a positive lens and a negative lens. During zooming from the wide angle end to the telephoto end, a distance between the lens units changes, and the second lens unit moves toward the object side. The zoom lens has an aperture stop that moves integrally with the second lens during the zooming and satisfies a specific condition.

Abstract: A zoom lens includes, in order from its object side, a first lens unit having a negative refracting power, a second lens unit having a positive refracting power, and a third lens unit having a refracting power. During zooming from the wide angle end to the telephoto end, the distance between the first lens unit and the second lens unit decreases, the distance between the second lens unit and the third lens unit changes. The first lens unit includes, in order from the object side, a first lens element, which is a negative lens element, and a second lens element, which is a positive lens element. The negative lens element and the positive lens element satisfy specific conditions.

Abstract: A zoom lens has a plurality of lens units including, in order from its object side to image side, a first lens unit having a negative refracting power composed of two lens elements including a biconcave negative lens and a positive lens, and a second lens unit having a positive refracting power composed of four lens elements including a positive lens and a negative lens. During zooming from the wide angle end to the telephoto end, a distance between the lens units changes, and the second lens unit moves toward the object side. The zoom lens has an aperture stop that moves integrally with the second lens during the zooming and satisfies a specific condition.

Abstract: A zoom lens includes, in order from its object side, a first lens unit having a negative refracting power, a second lens unit having a positive refracting power, a third lens unit having a negative refracting power, and a fourth lens unit having a positive refracting power. The zoom lens further includes an aperture stop disposed between the first lens unit and the third lens unit. During zooming from the wide angle end to the telephoto end, distances between the lens units change, the first lens unit moves first toward the image side and thereafter toward the object side, the second lens unit moves in such a way as to be located closer to the object side at the telephoto end than at the wide angle end, the distance between the second lens unit and the third lens unit is larger at the telephoto end than at the wide angle end, and the aperture stop moves in such a way as to be located closer to the object side at the telephoto end than at the wide angle end.

Abstract: A zoom lens includes, in order from the object side thereof, a first lens unit having a positive refracting power, which is movable during zooming, a second lens unit having a negative refracting power, which is movable during zooming, a third lens unit having a positive refracting power, which is movable during zooming, a fourth lens unit having a positive refracting power, which is movable during zooming, a fifth lens unit having a positive refracting power, which is movable or stationary during zooming. The zoom lens further includes an aperture stop that moves integrally with the third lens unit during zooming. The first lens unit is located closer to the object side at the telephoto end than at the wide angle end, and the third lens unit is located closer to the object side at the telephoto end than at the telephoto end.

Abstract: A zoom lens is such that spacings between a plurality of lens units are properly changed and thereby the magnification of the zoom lens is changed. The most object-side lens unit of this zoom lens has a positive refracting power and comprises, in order from an object side, a negative lens, a reflecting member for changing an optical path, and a positive lens, without cementing the reflecting member and the positive lens as well as the reflecting member and the negative lens, and at least one of surfaces of the negative lens and the positive lens is configured as an aspherical surface to satisfy the following condition: 0.0001<|Y49|/ihw<0.1 where Y49 is an aspherical amount of the aspherical surface at a position where a chief ray of light incident on the most object-side lens unit at an angle of 49° with the optical axis is incident on a most object-side aspherical surface in the lens unit and ihw is an image height at a wide-angle position.

Abstract: An apparatus has a zoom lens and an image pickup element disposed on the image side of the zoom lens that converts an optical image formed by the zoom lens into an electrical signal. The zoom lens includes, in order from the object side to the image side, a negative first lens unit, a negative second lens unit, a positive third lens unit, and a negative fourth lens unit. During zooming from the wide angle end to the telephoto end, the distance between the first lens unit and the second lens unit changes, the distance between the second lens unit and the third lens unit changes, and the distance between the third lens unit and the fourth lens unit changes, the distance between the second lens unit and the third lens unit being smaller at the telephoto end than at the wide angle end. The first lens unit includes a reflecting surface that deflects the optical path, and the zoom lens satisfies the following condition (1): ?100<fg4/ihw<?2.5 (1).

Abstract: A three-unit zoom lens system includes in order from an object side thereof, a first lens unit G1 having a negative refracting power, a second lens unit G2 having a positive refracting power, a third lens unit G3 having a positive refracting power or a negative refracting power, and an aperture stop which is on an image plane side of the first lens unit G1, and on an object side of a lens surface nearest to the image side, of the second lens unit G2, and which moves integrally with the second lens unit. At the time of zooming from the wide angle end to the telephoto end, a distance between the first lens unit G1 and the second lens unit G2 is narrowed, and a distance between the second lens unit G2 and the third lens unit G3 changes. The second lens unit G2 moves toward the object side at the time of zooming from the wide angle end to the telephoto end. The second lens unit includes a positive lens made of plastic, which is disposed nearest to the object.

Abstract: A zoom lens, which changes a magnification by properly changing distances between a plurality of lens components, has, in order from the object side, a first lens component with positive power, a second lens component with negative power, a third lens component with positive power, a fourth lens component with positive power, and a fifth lens component with positive power, and the first lens component has a reflecting member changing an optical path. The zoom lens satisfies the following conditions: 1.6<?2(t)/?2(w)<10.0 3.3<?4(t)/?4(w)<10.0 where ?2(t) is a lateral magnification of the second lens component in a telephoto position in infinite focusing, ?2(w) is a lateral magnification of the second lens component in a wide-angle position in infinite focusing, ?4(t) is a lateral magnification of the fourth lens component in the telephoto position in infinite focusing, and ?4(w) is a lateral magnification of the fourth lens component in the wide-angle position in infinite focusing.

Abstract: A zoom lens comprises, in order from an object side, a first lens group with a negative refracting power; a second lens group with a positive refracting power; a third lens group with a positive refracting power; and a fourth lens group with a refracting curved surface. Upon zooming from a wide-angle end to telephoto end, at least the first lens group, second lens group, and third lens group move, and a spacing between the respective lens groups are changed. The first lens group comprises; in order from the object side to an image side, a negative lens component with a negative refracting power and a positive lens component with a positive refracting power which are arranged on an optical axis with a predetermined spacing therebetween. The total number of the lens components in the first lens group is two.

Abstract: A zoom lens includes: a first lens group including a negative lens component of negative refractive power and a positive lens component of positive refractive power arranged on the optical axis in the above-mentioned order from the object side to the image side with a gap separating them; the total number of lens components in the first lens group being two; a second lens group including a negative lens, a first positive lens and a second positive lens; a fourth lens group including a negative lens component having a concave surface directed to the object side; the total number of lens components of the fourth lens group being one; the negative lens component in the first lens group and the negative lens component in the fourth lens group satisfying the requirements of conditional formula (1) shown below: ?0.80<rG1nr/rG4nf<?0.

Abstract: A zoom lens has a plurality of lens units including, in order from its object side to image side, a first lens unit having a negative refracting power composed of two lens elements including a biconcave negative lens and a positive lens, and a second lens unit having a positive refracting power composed of four lens elements including a positive lens and a negative lens. During zooming from the wide angle end to the telephoto end, a distance between the lens units changes, and the second lens unit moves toward the object side. The zoom lens has an aperture stop that moves integrally with the second lens during the zooming and satisfies a specific condition.

Abstract: A zoom lens includes, in order from its object side, a first lens unit having a negative refracting power, a second lens unit having a positive refracting power, a third lens unit having a negative refracting power, and a fourth lens unit having a positive refracting power. The zoom lens further includes an aperture stop disposed between the first lens unit and the third lens unit. During zooming from the wide angle end to the telephoto end, distances between the lens units change, the first lens unit moves first toward the image side and thereafter toward the object side, the second lens unit moves in such a way as to be located closer to the object side at the telephoto end than at the wide angle end, the distance between the second lens unit and the third lens unit is larger at the telephoto end than at the wide angle end, and the aperture stop moves in such a way as to be located closer to the object side at the telephoto end than at the wide angle end.

Abstract: A zoom lens includes, in order from its object side, a first lens unit having a negative refracting power, a second lens unit having a positive refracting power, and a third lens unit having a refracting power. During zooming from the wide angle end to the telephoto end, the distance between the first lens unit and the second lens unit decreases, the distance between the second lens unit and the third lens unit changes. The first lens unit includes, in order from the object side, a first lens element, which is a negative lens element, and a second lens element, which is a positive lens element. The negative lens element and the positive lens element satisfy specific conditions.

Abstract: A three-unit zoom lens system includes in order from an object side thereof a first lens unit G1 having a negative refracting power, a second lens unit G2 having a positive refracting power, a third lens unit G3 having a negative refracting power, and an aperture stop which is at an image side of the first lens unit G1, and at the object side of a lens surface nearest to the image side of the second lens unit G2, and which moves integrally with the second lens unit. At a time of zooming from a wide angle end to a telephoto end, a distance between the first lens unit G1 and the second lens unit G2 is narrowed, and a distance between the second lens unit G2 and the third lens unit G3 changes. The second lens unit G2 moves toward the object side at the time of zooming from the wide angle end to the telephoto end. The third lens unit G3 moves to be positioned at the object side at the telephoto end, with respect to the wide angle end.

Abstract: A zoom lens includes, in order from the object side thereof, a first lens unit having a positive refracting power, which is movable during zooming, a second lens unit having a negative refracting power, which is movable during zooming, a third lens unit having a positive refracting power, which is movable during zooming, a fourth lens unit having a positive refracting power, which is movable during zooming, a fifth lens unit having a positive refracting power, which is movable or stationary during zooming. The zoom lens further includes an aperture stop that moves integrally with the third lens unit during zooming. The first lens unit is located closer to the object side at the telephoto end than at the wide angle end, and the third lens unit is located closer to the object side at the telephoto end than at the telephoto end.

Abstract: A three-unit zoom lens includes, in order from the object side, a negative first lens unit G1, a positive second lens unit G2 and a third lens unit G3, wherein during zooming from the wide angle end to the telephoto end the distance between the first lens unit G1 and the second lens unit G2 decreases and the distance between the second lens unit G2 and the third lens unit G3 changes. The first lens unit G1 is composed of one negative lens component including, in order from the object side, a negative lens having a concave surface directed toward the image side and a positive lens having a convex surface directed toward the object side. The second lens unit G2 includes at least one negative lens and a plurality of positive lenses, wherein at least three lenses among these lenses are cemented to adjacent lenses, the total number of lens components included in the second lens unit G2 is two or less. The third lens unit is composed of one lens component composed of two or less lenses.

Abstract: A zoom lens includes, in order from the object side thereof, a first lens unit G1 having a negative refracting power and a second lens unit G2 having a positive refracting power. During zooming from the wide angle end to the telephoto end, the distance between the first lens unit G1 and the second lens unit G2 decreases. Letting the term “lens component” refer to a lens member whose surfaces that are in contact with air on the optical axis include only two surfaces, one being an object side surface and the other being an image side surface, the first lens unit G1 is comprised of a negative lens component in the form of a cemented lens having a negative refracting power that has, in order from the object side, a negative lens having a concave surface directed toward the image side and a positive lens having a convex surface directed toward the object side, and the second lens unit G2 includes a lens component in the form of a cemented lens having at least one negative lens and a positive lens.