TUCSON, Ariz. -- Machine vision successfully made the move from laboratory to industry. Now it looks as if it might make it in the theater as well. Arizona State University's Robb Lovell and John Mitchell have picked up where mainstream machine vision designers left off -- creating an "intelligent stage" that allows actors to truly steal the show. A system of video cameras tracks actors in a three-dimensional space, measuring presence and absence as well as motion and rates of change. One example, incorporated in the system's debut in 1992 during a production of Anamorphic Ambassador, is spotlight control. While an actress crouched on the stage, a computer-controlled spotlight narrowed to a strong spot. As she stood the light broadened and wildly bounced around the stage. "The intelligent stage is about controlling electronic media, anything from lights to music to video and graphics -- anything that a computer can control," Lovell said. Lovell began his educational career in computer science. When he combined his vocation with his avocation (dance), a computer-controlled theatrical environmental system was born. With the help of the Institute for Studies in the Arts in Tucson, a system that began by controlling musical pitch and volume has grown to include nearly every kind of audio and visual medium. The intelligent stage is actually a combination of three consumer-quality video cameras; a frame grabber from Galileo Corp. of Sturbridge, Mass.; a single red, green and blue video signal digitizer; a computer and lots of innovation. Each camera is encoded to represent one of the three primary colors, a design born of a limited budget. A new digitizer will allow full-color camera inputs. The digital signal is captured by a frame grabber and processed to measure absence or presence and movement. Based on a programmed set of cues, and using body movements, an actor can control the sound and lighting or start and stop visual sets such as graphics and projectors. Lovell hopes to incorporate scanning laser rangefinders into the intelligent stage and new red, green and blue media boards from either Imaging Technology Inc. of Bedford, Mass., or Matrox Electronics Ltd. of Quebec. However, while the lasers are getting cheaper, scanning systems are still too expensive for this project, he said. When asked if the intelligent stage had elicited calls from other groups, Lovell proudly stated that the British Broadcasting Corp. had recently interviewed the original group of designers, but admitted that very few theatrical groups have shown interest. "It's still a little heavy on the technology and preparation," he said. But, who can tell? Perhaps Lovell's double love will develop into a new wave of double majors.