Patent ID: 8189176
Filing Date: 2012-05-29
Classification: G01P,G01S

Abstract:
1. A method of detecting the velocity of a moving object comprising the steps of: passing a beam of convergent or divergent coherent light through an optical mask having a pattern of alternating opaque and non-opaque regions formed thereon, whereby an image of alternating light and dark fringes is projected along the entire coherence length of the light beam and whereby the mask is positioned within the beam of coherent light so as to eliminate, reduce or incorporate into the resulting image any diffraction effects; causing the moving object to pass through the projected image such that a portion of the light beam is reflected from the moving object as a series of pulses; detecting the pulses and the pulse frequency; and calculating the velocity of the object as a function of the pulse frequency and the known separation of the fringes of the image.