We present a method for identifying inexpensive, off-the-shelf laser pointers in a multiuser interaction environment on large-scale displays. We identify a laser pointer\u27s personality, a measure of its output in a particular context. Our method requires a set of inexpensive and unmodified green lasers, a large screen, a projector, and a camera with an infrared (IR) filter. The camera detects the IR spillover from the green laser beam, while ignoring color information projected onto the screen. During a calibration phase, a radial histogram of each laser\u27s IR spillover are used to represent the laser\u27s personality. Our system is able to identify the spots of a specific laser, allowing multiple users to simultaneously interact in the environment. In addition, we present a series of applications that take advantage of tracked and identified laser pointers to demonstrate large-scale, multiuser interactions
