Patent ID: 6532061
Filing Date: 2003-03-11
Classification: G01N,G02B,G06T

Abstract:
A velocity measurement system for determining an indication of a velocity of an object passing through a field of view, comprising:(a) an optical element disposed to direct light traveling from an object passing through the field of view along a collection path; (b) at least one optical grating of substantially uniform pitch disposed in the collection path, said at least one optical grating modulating the light traveling along the collection path to produce modulated light having a modulation frequency proportional to a velocity of an object passing through the field of view; (c) at least one light sensitive detector on which the modulated light is incident, said at least one light sensitive detector producing an electrical signal responsive to the modulated light; and (d) means for converting the electrical signal into a sequence of digital samples, and processing the digital samples in the frequency domain to determine the modulation frequency, the indication of the velocity being determined as a function of the modulation frequency.