离焦条纹投影三维测量中正弦光栅的二值化方法研究

Abstract

The non-linear intensity response of digital projector can be eliminated in 3D shape measurement using defocused binary fringe projection technique.The speed of projecting can be increased and it is possible to realize high speed measurement as well.Typical binary fringes used in digital projection were adopted as a study subject.The relation between the fundamental frequency,higher harmonics and fringe period of binary fringe was studied through the theoretical analysis and experiments. According to suitable phase shifting algorithm,the performance of various binary fringes was measured using the measurement error of phase as its target.The results showed that sinusoidal fringe with high performance could be generated by defocusing the Ronchi grating and pattern generated using 2Derror diffusion algorithm under the condition that fringe with short period was adopted.The measurement accuracy of defocused Ronchi grating was higher than that of other pattern,when the algorithm of odd step phase-shifting with equal interval in one period was used for 3D measurement;the highest measurement accuracy was obtained by using defocused optimal pulse width modulation fringe,when the period of fringe was long.The research results provide the evidence for selection of binary grating in the 3Dmeasurement based on defocused projection.