An apparatus for reading data encoded as an array of dots printed on a substrate together with an image. The dots of the array are substantially invisible to an average unaided human eye. The apparatus includes a light source for illuminating the substrate; a detector for receiving the illumination from the light source reflected off the substrate, the detector outputting a first signal representative of the array of dots, the detector extending a distance that is less than a width of the substrate; a decoder interconnected to said detector for receiving and decoding said first signal to obtain the data encoded by the array of dots; and a top substrate covering the detector and the light source. The top substrate has an emission portion and a reception portion. The emission portion is shaped with a semicircular cross section adapted to focus illumination from the light source onto the substrate. The reception portion is shaped to define a series of microlenses adapted to focus illumination reflected off the substrate into the detector.