System and method for tracking a signal source

A system for monitoring the movements of a performer over the area over which the performer is to move and for tracking the movements with a light beam produced by a spotlight, said system comprising:

• at least one movable miniaturized transmitting means, adapted to be carried by a performer, for transmitting an omnidirectional signal capable of being tracked;
• at least first and second detector means for sensing said omnidirectional signal and for respectively producing first and second output signals in response thereto, said detector means being remotely spaced from one another at different locations relative to the area over which the performer is to move and being positioned in a predetermined, fixed pattern with respect to the area over which the performer is to move;
• phase detector means coupled to detector means for receiving said output signals and for producing an output in accordance with the phase difference between the output signals produced by said first and second detector means, said phase detector means comprising a first channel for receiving said first output signal and including a first multiplying means for multiplying the first and second output signals, and a low pass filter, and a second channel for receiving said second output signal and including a phase shifter, a second multiplying means for multiplying the first signal and the output signal from the phase shifter, and a second low pass filter;
• command position signal generating means coupled to said phase detector means for receiving said output from said phase detector and for generating a position command signal in accordance therewith;
• servo motor means;
• servo network means coupled to said command position signal generating means for receiving said command signal and for controlling said servo motor means in accordance therewith;
• movable tracking means coupled to and driven by said servo motor means in response to said command signal for tracking the transmitting means carried by the performer, said tracking means comprising a fixed spotlight for producing a light beam and a rotatable mirror for reflecting said beam so as to track said transmitting means, said rotatable mirror being controlled by said servo motor and positioned to receive said light beam produced by said spotlight;
• and
• mirror position detector means coupled to said rotatable mirror and to said servo network means for providing tracking error signals to said servo network means so as to control the tracking movement of said mirror.