An add-on device for an image scanner for scanning barcodes is provided. The add-on device includes a housing mounted to the standard range lens front on an image scanner, and a lens holder. The lens holder has a first position for holding a first lens, a second position being an aperture, and a third position for holding a second lens. A high-density lens is mounted in the first position. An extended range lens is mounted in the third position. The lens holder is mounted in the housing and is transverse to the optical axis of the standard range lens of the image scanner. Further, the lens holder is movable within the housing in order to alternately position the high-density lens, the aperture, and the extended range lens to be in alignment with the optical axis of the standard range lens of the image scanner.