Spatial Frequency Multiplex Heterodyne Technique for Absolute Measurement of Instantaneous Phase Distribution, and Its Applications

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The purpose of this research project is to develop a new scheme of heterodyne profilometry that can perform the instantaneous measurement of the absolute phase distribution of an object with large height discontinuities and/or surface isolations. The main accomplishments are summarized in the following :1. Invention of Spatial Frequency Multiplex and Scan Method for Absolute Phase MeasurementAs an alternative to the conventional temporal frequency scan method using a frequency tunable light source, a spatial frequency scan method was proposed for the absolute phase measurement. By means of spatial frequency multiplexing, the proposed technique can determine the absolute phase from a single fringe pattern, which makes possible the measurement of instantaneous phase distribution.2. Clarification of the Relation between the Temporal and Spatial Frequency Scan MethodsA unified theory was given to the basic principles of the various absolute phase measurement technique using temporal and spatial frequency scanning methods.3. Development of New Phase Unwrapping AlgorithmA new phase unwrapping algorithm that eliminates phase singular points was developed and experimentally verified.4. Experimental Demonstration of the Instantaneous Shape Measurement of Objects in Dynamic MotionAn experimental system was constructed and the validity of the proposed spatial frequency multiplex and scan method was demonstrated for objects in fast motion.