The zoom lens consists of a first lens group, a front group, a middle group, and a rear group, in order from an object side. The first lens group has a positive refractive power and includes a negative lens and a positive lens, successively in order from a position closest to the object side to an image side. The front group consists of one or more lens groups that move during zooming and has a negative refractive power as a whole throughout an entire zoom range. The middle group includes only one lens group as a lens group. The rear group consists of a plurality of lens groups. An aperture stop is disposed between a lens surface closest to the image side in the front group and a lens surface closest to the object side in the rear group. The zoom lens satisfies predetermined conditional expressions.

A zoom lens includes, in order from an object side, a first lens group of which at least a part moves for focusing, a plurality of lens groups which move in zooming, an aperture stop, and a final lens group which does not move for zooming. The final lens group includes a separation element PR for separating an incident light thereon into a transmitted light and a reflected light, a relay unit LR having a positive refractive power on which the transmitted light is incident, and a relay unit LA having a positive refractive power on which the reflected light is incident. An inequality about Fwp/Fw is satisfied, where Fw is a focal length at a wide angle end of the zoom lens via the relay unit LR and FwP is a focal length at the wide angle end of the zoom lens via the relay unit LA.

A zoom lens includes, from an object side to an image side, a positive first lens unit configured not to move for zooming, at least three movable lens units configured to move for zooming, and a positive final lens unit closest to the image side in lens units and configured not to move for zooming. In the at least three movable lens units, a lens unit closest to the image side has a positive power, and a lens unit second closest to the image side has a negative power. The first lens unit includes a first sub unit closest to the object side and configured not to move for focusing and a second sub unit configured to move for focusing. The final lens unit includes a positive lens closest to the image side in elements having a refractive power in the final lens unit. Predetermined inequalities are satisfied.

A zoom lens includes, in order from object side, a positive first lens unit not moving for zooming, three or more intermediate lens units moving for zooming and a positive rear lens unit, in which each interval between adjacent lens units changes during zooming, an aperture stop is arranged in the rear lens unit, in a lens unit adjacent to the rear lens unit, or between the lens unit adjacent to the rear lens unit and the rear lens unit, the first lens unit includes, in order from the object side, negative subunit not moving for focusing, positive subunit moving for focusing, and positive subunit, a focal length of the first lens unit, a length on optical axis from most image-side surface to a rear principal point of the first lens unit, focal lengths of the zoom lens at wide angle end and at telephoto end are appropriately set.

A zoom lens includes in order from an object side to an image side: a first lens unit having a positive refractive power not moving for zooming; at least three lens units moving during zooming; and a final lens unit having a positive refractive power, wherein an interval between adjacent lens units changes during zooming, a refractive index and an Abbe number of positive lenses arranged closest to the object side among positive lenses included in the first lens unit, a focal length of the first lens unit, a focal length of the zoom lens at a wide angle end, a focal length of the zoom lens at a telephoto end, and a back focus of the zoom lens at the wide angle end are appropriately set.

Disclosed herein are a surgical microscope continuous zoom system and a surgical microscope. The continuous zoom system can be applied to a surgical microscope comprising a zoom cam (1). The continuous zoom system (2) includes: a front fixed lens set (21), a zoom lens set (22), a compensation lens set (23), a first rear fixed lens set (24) and a second rear fixed lens set (25) arranged sequentially along a main optical axis; the zoom lens set (22) and the compensation lens set (23) are configured, as driven by the zoom cam (1), to move simultaneously along the main optical axis between the front fixed lens set (21) and the first rear fixed lens set (24), to cause a system focal length value to change continuously and linearly; the zoom cam (1) comprises a first cam curve and a second cam curve; the first cam curve and the second cam curve are both exponential curves; the zoom lens set (22) moves following the first cam curve, and the compensation lens set (23) moves following the second cam curve.

A zoom lens includes a first lens unit with positive refractive power that does not move for zooming, an intermediate group including three or more lens units that move for zooming, and a rear lens unit with positive refractive power that does not move for zooming. The intermediate group includes a first intermediate negative lens unit that includes a single lens unit or two or more partial lens units and having negative refractive power that moves toward the image side during zooming from a wide-angle end to a telephoto end, a second intermediate negative lens unit having negative refractive power that moves during zooming, and an intermediate positive lens unit having positive refractive power that moves during zooming. At least one of lens units having negative refractive power disposed in the intermediate group moves in a convex locus toward the object side during zooming. Predetermined inequalities are satisfied.

Zoom lenses and image pickup apparatuses are provided herein. One or more zoom lenses may include a plurality of lens units, which include, in order from an object side to an image side, a first lens unit with positive refractive power that does not move for zooming, an intermediate group including at least three movable lens units that move for zooming, and a rear lens unit with positive refractive power that does not move for zooming. Each distance between adjacent lens units changes during zooming. The first lens unit includes a focus sub-lens unit that moves for focusing. One of the at least three movable lens units in the intermediate group includes an aperture stop. A predetermined inequality is satisfied.