Phase-Shifting Interference Microscopy with Multi-wavelength Optical Phase Unwrapping

2007 ◽  
Author(s):  
N. Warnasooriya ◽  
M.K. Kim
Keyword(s):  
Phase Unwrapping ◽  
Phase Shifting ◽  
Interference Microscopy ◽  
Optical Phase ◽  
Multi Wavelength

scholarly journals Multi-Wavelength Digital-Phase-Shifting Moiré Based on Moiré Wavelength

2019 ◽  
Vol 9 (9) ◽  
pp. 1917 ◽  
Author(s):  
Fatemeh Mohammadi ◽  
Jonathan Kofman
Keyword(s):  
Continuous Phase ◽  
Phase Unwrapping ◽  
Phase Shifting ◽  
Surface Shape ◽  
Digital Phase ◽  
Temporal Phase ◽  
Single Pattern ◽  
Multi Wavelength ◽  
Phase Map ◽  
Surface Discontinuities

Multi-wavelength digital-phase-shifting moiré was demonstrated using multiple moiré wavelengths determined by system calibration over the full working depth. The method uses the extended noisy phase map as a reference to unwrap the phase map with a shorter wavelength, and thus achieve a less noisy and more accurate continuous phase map. The moiré wavelength calibration determines a moiré-wavelength to height relationship that permits pixelwise refinement of the moiré wavelength and height during 3D reconstruction. Only a single pattern has to be projected and, thus, a single image captured to compute each phase map with a different wavelength to perform digital-phase-shifting moiré temporal phase unwrapping. Only two captured images are required for two-wavelength phase unwrapping and three captured images for three-wavelength phase unwrapping. The method has been demonstrated in the 3D surface-shape measurement of an object with surface discontinuities and spatially isolated objects.

scholarly journals An Error-Reduction Method for Temporal Phase Unwrapping Based on Double Three-Step Phase-Shifting and Least-Squares Fitting

2012 ◽  
Vol 6-7 ◽  
pp. 76-81
Author(s):  
Yong Liu ◽  
Ding Fa Huang ◽  
Yong Jiang
Keyword(s):  
Least Squares ◽  
Reduction Method ◽  
Intermediate Phase ◽  
Error Reduction ◽  
Phase Unwrapping ◽  
Phase Shifting ◽  
Surface Measurement ◽  
Acquisition Time ◽  
Least Squares Fitting ◽  
Temporal Phase

Phase-shifting interferometry on structured light projection is widely used in 3-D surface measurement. An investigation shows that least-squares fitting can significantly decrease random error by incorporating data from the intermediate phase values, but it cannot completely eliminate nonlinear error. This paper proposes an error-reduction method based on double three-step phase-shifting algorithm and least-squares fitting, and applies it on the temporal phase unwrapping algorithm using three-frequency heterodyne principle. Theoretical analyses and experiment results show that this method can greatly save data acquisition time and improve the precision.

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