Patent ID: 7372011
Filing Date: 2008-05-13
Classification: G01C

Abstract:
1. A method for detecting a moving, relatively thin beam of laser light, and distinguishing between illumination of photodetectors by such a moving, relatively thin beam of laser light, and illumination of photodetectors by an omnidirectional pulse of light, comprising the steps of: positioning a plurality of photodetector arrays in a generally vertical row, each array including a plurality of photodetector elements arranged in a generally vertical array row, such that the photodetector elements in said arrays are collectively arranged in a generally vertically oriented, extended row, each of said photodetector elements providing an electrical output when illuminated, for each array, providing a portion of the electrical output of each photodetector element in the array as a first reference signal related to the spacing of the photodetector element from a first end of the array row, and providing a portion of the electrical output of each photodetector element in the array as a second reference signal related to the spacing of the photodetector element from the second end of said array row, determining the sum of the first and second reference signals from said photodetector arrays, determining the difference between the largest of the first and second reference signals from said photodetector arrays and the smallest of the first and second reference signals from said photodetector arrays, dividing said sum of the first and second reference signals from said photodetector arrays by said difference between the largest of the first and second reference signals from said photodetector arrays and the smallest of the first and second reference signals from said photodetector arrays, thereby providing a quotient, and interpreting the quotient as indicating illumination of said photodetectors by a moving, relatively thin beam of laser light when said quotient is less than a predetermined level, and interpreting the quotient as indicating illumination of said photodetectors by an omnidirectional pulse of light when said quotient is greater than said predetermined level.