Deformation and profile measurement using the digital projection grating method

Profile measurement of a moving object using an improved projection grating phase-shifting profilometry

“…(4) [18]. When the phase-shifting of each step is 2p 3 , one captured image can be divided into three parts.…”

“…After a phase unwrapping process [18], the phase difference caused by the profile will be obtained by subtracting the phase of the reference plane from that of the detected object surface. And then the phase difference maps of part A, part B and part C are combined together.…”

“…On the other hand, the advantage of the FTP is that only one frame of image is necessary instead of 3-5 phase-shifting images used in the PMP. Therefore, the FTP is suitable for the profile measurement of a moving object [16][17][18]. However, the desired frequency information can not be extracted accurately from the frequency domain by an adequate window because of the influence of nonlinear response of a detector, zero-order frequency component, high-frequency noise and the frequency leakage problem [6,7,19].…”

Deformation Measurement Using Dual-Frequency Projection Grating Phase-Shift Profilometry

“…Several measurement methods have been proposed to avoid the disadvantage of the conventional phase unwrapping process [6][7][8][9][10][11][12][13][14] . For example, a technique uses multichannel Fourier fringe analysis.…”

“…A general algorithm for dual-frequency phase-shift profilometry with projection grating method is proposed, and experimental results obtained with the method are presented and discussed. [12] As shown in Fig.1, the mathematical optical grating intensity representation on the corresponding any one image detector array of the undeformed surface and the deformed surface may be expressed as…”