A pattern is projected onto a screen by a projector using an illumination having a non-visible wavelength. A camera, displaced several inches from the projector, observes the projected pattern whose signals are then stored to create a reference frame. The pattern is then projected onto the screen a second...http://www.google.co.uk/patents/US6789903?utm_source=gb-gplus-sharePatent US6789903 - Generating an inhibit signal by pattern displacement
