Research On 3D Shape Measurement Technology Based On Binary Phase-shifting Methods

In optical 3D shape measurement field, the commonly used method is generated digital sinusoidal fringes by computer to measurement. This method brings good measurement effects but there are still some defects, such as projector's non-linear gamma error which will cause non-sinusoidal and when actual measurements the projector needs frequent calibration; computer generated sinusoidal fringes need 256 gray levels, using 8-bit data, limiting the measuring rate. In order to solve these shortcomings above, this paper proposes binary fringe projection profilometry, and combined with phase-shifting algorithm, in order to achieve high precision on 3D shape measurement.This paper using the traditional method of projecting sinusoidal fringe directly to realize 3D measurement as a reference, is devoted to the study of binary phase-shifting methods. The measurement system includes phase-shifting method, phase unwrapping algorithm, binary fringe projection analysis and system calibration. Phase-shifting method applies to the static scene, with high measuring accuracy and spatial resolution and different phase-shifting algorithms of the binary fringes to perform 3D measurement, the accuracy is different. About projecting the binary fringes to realize 3D measurement is divided into two parts:the projector is on defocusing condition and focusing condition. Defocusing projector is to produce ideal sinusoidal fringe patterns by the binary fringe patterns, whose principle is that 0 and 1 these two grays avoiding the nonlinear effect of Gamma error, and the actual projection onto the surface of the object is sinusoidal fringes. The focus condition of projector is to projecting binary fringe patterns (black and white stripes) directly and the different steps of phase-shifting algorithms are performed.A projector, a camera and a computer set up the experiment, and all the algorithms are written by MATLAB processing software. Phase shift method for 3-D measurement experiment of traditional directly projecting sinusoidal fringe and binary stripes are performed. Experimental results show that the proposed method of 3-D shape measurement is simple, low equipment cost, and higher measurement precision based on binary fringe projection and phase-shifting algorithm.