Abstract: In an audio/visual computer-generated presentation system in which material s presented to an audience through projection of the material to a screen, the position of a remotely-generated spot from a laser illuminator is detected by a so-called sensor which is positioned to detect light from the spot which is diffusely reflected off the screen along the portion of the optical path between the computer-driven light modulator and the screen, with the sensing of the position of the spot at the time of the generation of a selection signal being used to change the on-screen material. The on-axis sensor for detecting the light spot eliminates speed and accuracy problems associated with off-axis CCD camera detection, while at the same time providing a presenter with a robust method of selecting computer-generated material to be presented.