An invisible infra-red beam is superimposed over the image and sensors detect the reflections that are created whenever and wherever the image is touched.

Nor is it possible simply to crank up the power of the source beam, because infra-red light at high intensity can cause eye damage.

LaserMotive USES special cells made with arsenic and gallium, elements better able to capture the near-infra-red wavelengths of its laser beam.