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Separation algorithm for a 2D refractive index distribution and thickness profile of a phase object by laser
Kwangchun Lee1, Sung Yoon Ryu, Yoon Keun Kwak
1Department of Mechanical Engineering, School of Mechanical, Aerospace and Systems Engineering, Korea Advanced Institute of Science and Technology, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea.
The Review of Scientific Instruments
|June 3, 2009
Summary
A novel algorithm simultaneously measures the 2D refractive index and thickness of transparent samples using three wavelengths. This optical technique achieves high accuracy, enabling precise material characterization.
Area of Science:
- Optical Metrology
- Materials Science
- Interferometry
Background:
- Accurate characterization of transparent materials is crucial for various scientific and industrial applications.
- Simultaneous measurement of refractive index and thickness profiles presents a significant metrological challenge.
Purpose of the Study:
- To propose and validate a novel separation algorithm for simultaneously measuring the 2D refractive index distribution and thickness profile of transparent samples.
- To demonstrate the algorithm's capability using a multiwavelength Mach-Zehnder interferometer.
Main Methods:
- Development of a separation algorithm utilizing three distinct wavelengths (635, 660, and 675 nm).
- Implementation of a Mach-Zehnder interferometer equipped with laser diode-based multiwavelength sources.
- Employing a liquid crystal retarder and a four-bucket algorithm for optical phase calculation.
- Experimental validation using a glass rod, slide glass, glass wafer, and cover glass.
Main Results:
- Achieved high accuracy in refractive index distribution measurement (less than 0.0003).
- Successfully calculated the thickness profile based on the measured refractive index.
- Demonstrated the algorithm's effectiveness in separating refractive index and thickness profiles in two dimensions.
Conclusions:
- The proposed three-wavelength separation algorithm enables accurate and simultaneous 2D measurement of refractive index and thickness for transparent materials.
- This method offers a robust solution for non-destructive characterization of optical properties and surface topography.
