Patent ID: 7324124

Claim:
A thermal printer adapted to print using a donor ribbon having sets of donor material patches each set including at least one colored donor material patch and a protective material donor patch, said donor ribbon absorbing a greater portion of an applied non-visible light in an area of the donor ribbon having unused protective donor material than in areas that do not have unused protective donor material; the thermal printer comprising: a donor transport system having a motorized system for advancing the donor ribbon relative to a printhead; a light source radiating non-visible light onto the donor ribbon; and, a light sensor positioned to sense a non-absorbed portion of the non-visible light radiated onto the donor ribbon and to generate a light sensor signal indicative of the non-visible light received; a controller being adapted to position the donor ribbon relative to the light source and the light sensor, to cause the light source to radiate non-visible light onto the donor ribbon and to receive the light sensor signal; said controller further being adapted to use the light sensor signal to identify whether the portion of the donor web confronting the light source and light sensor has unused protective donor material.