Patent ID: 8284405
Filing Date: 2012-10-09
Classification: G01H

Abstract:
1. An apparatus using modulated light for sensing vibration of a surface, comprising: an optical detector for sensing intensity of light diffusely reflected from a surface and modulated by vibration of the surface, and for generating a direct electrical current that is a temporal function of sensed light intensity; the direct electrical current being coupled to a transimpedence amplifier for converting the direct electrical current into a voltage; a second amplifier for amplifying the voltage to an amplified voltage; an analog-to-digital converter for converting the amplified voltage into a first digital signal and a second digital signal; the first digital signal being generated by sensing intensity of light modulated by ambient vibration and by a singular vibration source; the second digital signal being generated by sensing intensity of light modulated only by ambient vibration; a signal processor for converting the first digital signal into a first time domain function and for converting the second digital signal into a second time domain function; the first time domain function being displayed as a first graph and the second time domain function being displayed as a second graph; and means for comparing the first and second graphs, to discern a vibration signature for the singular vibration source.