an optical element for receiving light from an object, the zoom relay system being adapted to generate an image of the object on an image plane; and

a single varifocal lens group positioned along an optical axis, the single varifocal lens group comprising a first lens subgroup, a second lens subgroup and a single varifocal freeform lens between the first lens subgroup and the second lens subgroup along the optical axis, the single varifocal freeform lens comprising two lens plates, the lens plates being configured to be disposed along a dimension transverse to the optical axis, such that, when the single varifocal lens group is moved along the optical axis to adjust the magnification, the lens plates of the single varifocal freeform lens are displaced in the transverse dimension relative to each other to provide compensation, such that, when the magnification is changed, a distance between the object and the image plane remains constant; wherein the first lens subgroup, the second lens subgroup, and the single varifocal freeform lens are stationary with respect to each other as the single varifocal lens group is moved along the optical axis to adjust the magnification.