Provided is a zoom lens including, from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power; a fourth lens unit having a negative refractive power; a fifth lens unit having a positive refractive power; a sixth lens unit having a negative refractive power; a seventh lens unit having a positive refractive power; and an eighth lens unit having a negative refractive power, in which an interval between each pair of adjacent lens units is changed for zooming.

An optical system includes, in order from an object side to an image side, first to fourth lens units. A distance changes between adjacent lens units during focusing from infinity to a close distance. The optical system includes an aperture stop disposed on the image side of the second lens unit, a final lens unit, the first lens unit and the final lens unit being fixed relative to the image plane during the focusing, and focus lens units disposed on the object side and the image side of the aperture stop. A focus lens unit closest to the image plane among the focus lens units moves toward the image side during the focusing. The optical system is configured to increase an absolute value of an imaging magnification at a shortest imaging distance to 0.5 times or higher. The final lens unit includes positive and negative lenses. A predetermined condition is satisfied.

An optical system includes, in order from an object side to an image side, first to fourth lens units. A distance changes between adjacent lens units during focusing from infinity to a close distance. The optical system includes an aperture stop disposed on the image side of the second lens unit, a final lens unit, the first lens unit and the final lens unit being fixed relative to the image plane during the focusing, and focus lens units disposed on the object side and the image side of the aperture stop. A focus lens unit closest to the image plane among the focus lens units moves toward the image side during the focusing. The optical system is configured to increase an absolute value of an imaging magnification at a shortest imaging distance to 0.5 times or higher. The final lens unit includes positive and negative lenses. A predetermined condition is satisfied.

A zoom lens includes, in order from an object side to an image side, a first lens unit having a positive refractive power, a plurality of zooming lens units configured to move along an optical axis in zooming and including a lens unit having a negative refractive power, and a final lens unit having a positive refractive power. A distance between each pair of adjacent lens units changes in zooming. The first lens unit includes, in order from the object side to the image side, a first subunit having a negative refractive power, a second subunit having a negative refractive power, and at least one subsequent subunit, a distance between each pair of adjacent subunits changing for focusing. The second subunit is configured to move along the optical axis for focusing. A predetermined condition is satisfied.

The zoom lens consists of, in order from an object side: a first lens group that has a positive refractive power; a second lens group that has a positive refractive power; a third lens group that has a negative refractive power; a fourth lens group; and a fifth lens group that has a positive refractive power. The first lens group and the fifth lens group remain stationary with respect to an image plane during zooming. The second lens group, the third lens group, and the fourth lens group are moved by changing distances between the lens groups and adjacent groups in a direction of an optical axis during zooming, and are positioned to be closer to the image side at a telephoto end than at a wide-angle end. Conditional Expression (1) is satisfied.
0.8<pr1/f1<2.6(1).

The zoom lens consists of, in order from an object side: a first lens group that has a positive refractive power; a second lens group that has a positive refractive power; a third lens group that has a negative refractive power; a fourth lens group; and a fifth lens group that has a positive refractive power. The first lens group and the fifth lens group remain stationary with respect to an image plane during zooming. The second lens group, the third lens group, and the fourth lens group are moved by changing distances between the lens groups and adjacent groups in a direction of an optical axis during zooming, and are positioned to be closer to the image side at a telephoto end than at a wide-angle end. Conditional Expression (1) is satisfied.
0.8<pr1/f1<2.6(1).

An imaging optical system consists of, in order from a magnification side: a first optical system that forms an intermediate image on a position conjugate to a magnification side imaging surface; and a second optical system that re-forms the intermediate image on a reduction side imaging surface. The first optical system includes at least two focusing lens groups that move with different loci during focusing. The imaging optical system satisfies predetermined conditional expressions relating to the focusing lens groups.

In a zoom lens in which the interval between adjacent lens units changes during zooming, a magnification-varying lens group includes a lens group V having a negative refractive power and a lens unit C having a negative or positive refractive power. The lens group V includes a first magnification-varying lens group V1 including a lens unit V1a having a negative refractive power and a lens unit V1b having a negative refractive power. The lens units V1a and V1b move toward the image side such that the interval between the two lens units is largest at the telephoto end. The lens unit interval m1 on the optical axis between the lens units V1a and V1b at the wide angle end and the maximum lens unit interval m2 on the optical axis between the lens units V1a and V1b during zooming are set as appropriate.

In a zoom lens in which the interval between adjacent lens units changes during zooming, a magnification-varying lens group includes a lens group V having a negative refractive power and a lens unit C having a negative or positive refractive power. The lens group V includes a first magnification-varying lens group V1 including a lens unit V1a having a negative refractive power and a lens unit V1b having a negative refractive power. The lens units V1a and V1b move toward the image side such that the interval between the two lens units is largest at the telephoto end. The lens unit interval m1 on the optical axis between the lens units V1a and V1b at the wide angle end and the maximum lens unit interval m2 on the optical axis between the lens units V1a and V1b during zooming are set as appropriate.

An ophthalmic surgical microscope includes a beam coupler positioned along an optical path of the surgical microscope between a first eyepiece and magnifying/focusing optics, the beam coupler operable to direct the OCT imaging beam along a first portion of the optical path of the surgical microscope between the beam coupler and a patient's eye (an OCT image being generated based on a reflected portion of the OCT imaging beam). The surgical microscope additionally includes a real-time data projection unit operable to project the OCT image generated by the OCT system and a beam splitter positioned along the optical path of the surgical microscope between a second eyepiece and the magnifying/focusing optics. The beam splitter is operable to direct the projected OCT image along a second portion of the optical path of the surgical microscope between the beam splitter and the second eyepiece such that the projected OCT image is viewable through the second eyepiece.