Two-frequency grating used in phase-measuring profilometry.

We present a method that uses two groups of fringe patterns on one grating for phase-measuring profilometry. A two-frequency grating is projected onto the object. The high frequency is N (N = 3, 4, 5, :...) times greater than the low frequency. Using a proper phase shift, we calculated the wrapped phases of the two frequencies. When the linearity of the two phases are considered, an accurate phase of the high frequency can be unwrapped. Because the low frequency is N times more insensitive to height discontinuity, the system is more tolerable to height discontinuity.

[1]  Mitsuo Takeda,et al.  Spatiotemporal frequency multiplex heterodyne interferometry , 1992 .

[2]  D R Burton,et al.  Multichannel Fourier fringe analysis as an aid to automatic phase unwrapping. , 1994, Applied optics.

[3]  Dongqing Wang,et al.  Two-dimensional color Schlieren system , 1990 .

[4]  David P. Towers,et al.  Automatic interferogram analysis techniques applied to quasi-heterodyne holography and ESPI , 1991 .

[5]  X. Su,et al.  Phase-stepping grating profilometry: utilization of intensity modulation analysis in complex objects evaluation , 1993 .

[6]  M. Takeda,et al.  Fourier transform profilometry for the automatic measurement of 3-D object shapes. , 1983, Applied optics.

[7]  Louis A. Romero,et al.  A Cellular Automata Method for Phase Unwrapping , 1986, Topical Meeting On Signal Recovery and Synthesis II.

[8]  V. Srinivasan,et al.  Automated phase-measuring profilometry: a phase mapping approach. , 1985, Applied optics.

[9]  H Zhao,et al.  Phase-unwrapping algorithm for the measurement of three-dimensional object shapes. , 1994, Applied optics.

[10]  X. Su,et al.  Improved Fourier transform profilometry for the automatic measurement of 3D object shapes , 1990 .

[11]  T. R. Judge,et al.  A review of phase unwrapping techniques in fringe analysis , 1994 .

[12]  V. Srinivasan,et al.  Automated phase-measuring profilometry of 3-D diffuse objects. , 1984, Applied optics.

[13]  D J Bone,et al.  Fourier fringe analysis: the two-dimensional phase unwrapping problem. , 1991, Applied optics.

[14]  J. M. Huntley,et al.  Temporal phase-unwrapping algorithm for automated interferogram analysis. , 1993, Applied optics.