Adaptive optical three-dimensional measurement with structured light

Abstract

The described 3-D measurement system with fringe projection appliesthe principle of uniform scale representation by the exclusive useof phase measurement values for the coordinates of each point. Thetest object is successively illuminated with a grating structurefrom at least three different directions with a telecentric system,where gray code is combined with five 90-deg phase shifts. A CCDcamera records the intensity distribution of the fringes that appearas intersection lines on the surface of the object. This providesthe linearly independent absolute phase values that are necessaryfor the calculation of the coordinates. Note that all coordinates(x,y,z) are determined with the same accuracy. To compensate theinfluence of specular reflections or shadowed areas up to 15 lightprojection directions can be used. Moreover, the object can be rotatedaround a second axis, yielding other views of the object. Thus weacquire different patches of the object that are transformed intoa global coordinate system without any interactive user help. Duringthis procedure, correlation methods or special points are not necessary.The calibration of the 3-D orientation of the second axis is realizedwith a special calibration body.