In an interactive display system, a projected image on a display surface and a vision system used to detect objects touching the display surface are aligned, and optical distortion of the vision system is compensated. Also, calibration procedures correct for a non-uniformity of infrared (IR) illumination of the display surface by IR light sources and establish a touch threshold for one or more uses so that the interactive display system correctly responds to each user touching the display surface. A movable IR camera filter enables automation of the alignment of the projected image and the image of the display surface and help in detecting problems in either the projector or vision system.