1. An optical coupler comprising: an object lens assembly receiving light from an object in a visible (VIS) and near-infrared (NIR) wavelength range, a prism assembly receiving light from the object lens assembly and splitting the received light into separate VIS and NIR paths having different optical path lengths, and an imaging lens assembly which receives the separate VIS and NIR paths from the prism assembly and recombines the separate VIS and NIR paths, with the optical properties of the object lens assembly, the prism assembly and the imaging lens assembly being selected so as to form an image of the object in an image plane while correcting for aberrations in the NIR.