An optical coupler for coupling an optical instrument with an imaging system, comprising: an object lens assembly adapted for receiving and transmitting collimated or nearly collimated light from an object in a visible and near-infrared wavelength range, an imaging lens assembly, characterised by: a prism assembly comprising adjoining prisms, with at least one of the adjoining prisms made of a different material having different indices of refraction than the other adjoining prisms, the prism assembly being adapted for - receiving light from the object lens assembly and - splitting the received light into separate VIS and NIR paths having different optical path lengths, the VIS and NIR paths following separate optical paths through the materials with different indices of refraction for compensating for an optical path length difference between the VIS and NIR focal plane locations, and - recombining the separate VIS and NIR paths, and whereby - said imaging lens assembly being adapted to receive the VIS and NIR paths from the prism assembly, and - 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. an object lens assembly adapted for receiving and transmitting collimated or nearly collimated light from an object in a visible and near-infrared wavelength range, an imaging lens assembly, characterised by: a prism assembly comprising adjoining prisms, with at least one of the adjoining prisms made of a different material having different indices of refraction than the other adjoining prisms, the prism assembly being adapted for - receiving light from the object lens assembly and - splitting the received light into separate VIS and NIR paths having different optical path lengths, the VIS and NIR paths following separate optical paths through the materials with different indices of refraction for compensating for an optical path length difference between the VIS and NIR focal plane locations, and - recombining the separate VIS and NIR paths, and whereby - said imaging lens assembly being adapted to receive the VIS and NIR paths from the prism assembly, and - 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. - receiving light from the object lens assembly and - splitting the received light into separate VIS and NIR paths having different optical path lengths, the VIS and NIR paths following separate optical paths through the materials with different indices of refraction for compensating for an optical path length difference between the VIS and NIR focal plane locations, and - recombining the separate VIS and NIR paths, and whereby - said imaging lens assembly being adapted to receive the VIS and NIR paths from the prism assembly, and - 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.