Multiple-exposure adaptive selection algorithm for high dynamic range 3D fringe projection measurement

In order to cover the high dynamic exposure range requirement of high reflective surface, a multiple-exposure adaptive selection algorithm of phase shifting 3D measurement is developed. At first, the camera response curve function is calibrated with the sequence images of different exposure times. The nonlinear curve function shows the relationship between the image intensity value and exposure amount. The relative irradiance value of all the image pixels is computed based on the linear relation between the exposure time and exposure amount. Both relative irradiance value cover the highest and lowest gray value of the fringe image is set the threshold. Then, the adaptive selection algorithm for exposure time is proposed based on the double threshold principle. At last, different exposure time node is selected adaptively. The sequences images with multi-exposure time are fused. In order to evaluate the performance of this method, some typical metal parts and blade with high range of reflectivity surfaces are used for 3D measurement and construction. The experiment results verify the feasibility of the proposed method.