Abstract: A multiple-resolution optical device used to scan objects of variable sizes in various resolutions and forming corresponding images onto an image sensor is disclosed. The multiple-resolution optical device according to the present invention comprises a light source, a mirror set, and a lens set. The mirror set reflects the light from the light source projected onto the object and provides a plurality of optical paths. The lens set selects one of the optical paths to provide an object distance and an image distance whereby the corresponding image is clearly formed on the image sensor in response to said size. Hence, an optimal resolution is acquired and the optical resolution for optical scan processing is substantially enhanced.