A system , comprising: a display comprising at least one layer to generate a digital display image; and an apparatus comprising a light source and a detector , the light source arranged to transmit non-visible light; wherein the detector is arranged to receive a pattern of reflected light from the display in response to the non-visible light being directed as incident light towards the display, the pattern of reflected light having at least two different polarization states, and the detector is further arranged to determine a spatial location of the detector relative to the display based on discriminating between the at least two polarization states; wherein the display further comprises a reflective layer to reflect the non-visible light generated from the light source and a position encoded contrast layer , the position encoded contrast layer comprising position encoded optical elements (ELE 1, ELE 2, ELE M) polarized to one polarization state of the at least two polarization states and a background area not occupied by the position encoded optical elements and polarized to another polarization state of the at least two polarization states to polarize the non-visible light reflected by the reflective layer to provide the pattern of reflected light from the display having the at least two polarization states; characterized in that : the light source is arranged to transmit the non-visible light in the form of non-visible light pulses strobed at a frequency and a duty cycle; and in that the display includes at least one linear polarizer layer to linearly polarize the non-visible light pulses reflected by the reflective layer to enable the position encoded optical elements (ELE 1, ELE 2, ELE M) and the background area to polarize the linearly polarized non-visible light pulses to the at least two different polarization states. a display comprising at least one layer to generate a digital display image; and an apparatus comprising a light source and a detector , the light source arranged to transmit non-visible light; wherein the detector is arranged to receive a pattern of reflected light from the display in response to the non-visible light being directed as incident light towards the display, the pattern of reflected light having at least two different polarization states, and the detector is further arranged to determine a spatial location of the detector relative to the display based on discriminating between the at least two polarization states; wherein the display further comprises a reflective layer to reflect the non-visible light generated from the light source and a position encoded contrast layer , the position encoded contrast layer comprising position encoded optical elements (ELE 1, ELE 2, ELE M) polarized to one polarization state of the at least two polarization states and a background area not occupied by the position encoded optical elements and polarized to another polarization state of the at least two polarization states to polarize the non-visible light reflected by the reflective layer to provide the pattern of reflected light from the display having the at least two polarization states; the light source is arranged to transmit the non-visible light in the form of non-visible light pulses strobed at a frequency and a duty cycle; and in that the display includes at least one linear polarizer layer to linearly polarize the non-visible light pulses reflected by the reflective layer to enable the position encoded optical elements (ELE 1, ELE 2, ELE M) and the background area to polarize the linearly polarized non-visible light pulses to the at least two different polarization states. <EOS>