Patent ID: 7224473

Claim:
A method for detecting a moving, relatively thin beam of laser light, and distinguishing between such a moving, relatively thin beam of laser light and an omni-directional pulse of light, comprising the steps of: positioning a plurality of photo-detectors in a generally vertical row, each of said photo-detector elements providing an electrical output when illuminated, positioning an additional photo-detector at a point remote from said plurality of photo-detectors, providing a portion of the electrical output of each photo-detector in the row as a first reference signal related to the spacing of the photo-detector from a first end of the row, and providing a portion of the electrical output of each photo-detector in the row as a second reference signal related to the spacing of the photo-detector from the second end of said row, providing the electrical output of said additional photo-detector as a third reference signal, and interpreting a third reference signal of sufficiently low amplitude as indicating simultaneous illumination of one or more of said photo-detectors in said row as illumination by a thin beam of laser light, and interpreting a third reference signal of sufficiently high amplitude as indicating simultaneous illumination of one or more of said photo-detectors in said row as illumination by an omni-directional pulse of light.