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Surface shape measurement by phase-shifting digital holography with a wavelength shift
Ichirou Yamaguchi1, Takashi Ida, Masayuki Yokota
1Department of Electronic Engineering, Faculty of Engineering, Gunma University, Gunma, Japan. ichiyama@el.gunma-u.ac.jp
Applied Optics
|October 28, 2006
Summary
Surface contouring using phase-shifting digital holography is demonstrated. This method accurately maps diffuse surfaces by analyzing phase differences from laser diode mode hopping, avoiding tilt removal and shadowing issues.
Area of Science:
- Optics and Photonics
- Metrology
- Surface Science
Background:
- Phase-shifting digital holography is a powerful technique for surface metrology.
- Existing methods like dual-incidence holography can suffer from tilt removal and shadowing effects.
- Laser diode current tuning induces mode hopping, altering the emitted wavelength.
Purpose of the Study:
- To propose and experimentally verify a novel surface contouring method using phase-shifting digital holography.
- To leverage laser diode mode hopping for accurate surface profiling.
- To overcome limitations of previous contouring techniques, specifically tilt removal and shadowing.
Main Methods:
- Recording digital holograms before and after laser diode mode hopping.
- Utilizing phase-shifting interferometry to reconstruct phase information.
- Computing the difference in reconstructed phases at different wavelengths.
- Applying the phase difference to derive surface contours of diffusely reflecting surfaces.
Main Results:
- Successful surface contouring of a diffusely reflecting surface was achieved.
- The proposed method eliminates the need for tilt component removal.
- The technique is inherently free from shadowing effects, unlike dual-incidence methods.
- Experimental and numerical simulations confirmed the method's validity.
Conclusions:
- Phase-shifting digital holography offers an effective approach for surface contouring.
- Utilizing laser diode mode hopping provides a practical means for generating wavelength shifts.
- The method presents significant advantages in simplicity and robustness over prior techniques.
