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High-resolution, High-speed, Three-dimensional Video Imaging with Digital Fringe Projection Techniques
Published on: December 3, 2013
Phase errors due to speckles in laser fringe projection
Sara Rosendahl1, Emil Hällstig, Per Gren
1Division of Experimental Mechanics, Luleå University of Technology, SE-971 87 Luleå, Sweden. sara.rosendahl@ltu.se
Applied Optics
|April 15, 2010
Summary
Moving apertures reduce speckle contrast in projected interference fringes, minimizing phase error for accurate 3D shape measurement. This technique enhances measurement precision without compromising light coherence.
Area of Science:
- Optical metrology
- 3D shape measurement
- Interference fringe analysis
Background:
- Speckle contrast in projected interference fringes can degrade the accuracy of 3D shape measurements.
- Maintaining light coherence is crucial for precise fringe analysis.
- Phase error in fringe analysis is directly influenced by speckle contrast and fringe modulation.
Purpose of the Study:
- To investigate a method for reducing speckle contrast in projected interference fringes.
- To analyze the impact of speckle reduction on phase error in 3D shape measurement.
- To develop and validate a theoretical model for phase error.
Main Methods:
- Utilized a moving aperture technique to suppress speckles during image acquisition.
- Employed the spatial carrier method for phase extraction from fringe patterns.
- Derived an analytical expression for phase error, considering Fourier spectrum filtering.
- Verified findings through simulations and experimental validation.
Main Results:
- Demonstrated that phase error is linearly dependent on the ratio of speckle contrast to fringe modulation.
- Showed that moving the aperture by three diameters reduces speckle contrast and phase error by 60%.
- Achieved a phase error of 0.2 radians in experimental measurements.
Conclusions:
- A moving aperture effectively reduces speckle contrast and phase error in projected interference fringe measurements.
- The derived analytical expression accurately predicts phase error.
- The method offers a viable approach for enhancing the accuracy of 3D shape metrology.
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