Local frequency and envelope estimation by Teager-Kaiser energy operators in white-light scanning interferometry

Area of Science:

• Optics and Photonics
• Signal Processing
• Metrology

Background:

• White light scanning interferometry (WLSI) is a key technique for high-resolution surface profiling.
• Accurate surface extraction is crucial for metrology applications but can be challenging due to noise and signal variations.
• Existing methods like peak fringe scanning and phase shifting algorithms have limitations in complex scenarios.

Purpose of the Study:

• To introduce a new, robust method for surface extraction in WLSI.
• To leverage the Teager-Kaiser energy operator for enhanced signal analysis in interferometry.
• To demonstrate the superiority of the proposed method over conventional techniques.

Main Methods:

• Development of a surface extraction scheme based on the Teager-Kaiser energy operator and its extended versions.
• Utilizing the operator's ability to extract local instantaneous envelope and frequency from AM-FM signals.
• Implementing an iterative phase re-estimation with a novel TK cross-energy operator-based correlation technique.

Main Results:

• The proposed method demonstrates substantially effective surface extraction compared to peak fringe scanning, five-step phase shifting, and continuous wavelet transform methods.
• Experimental results confirm the method's robustness against noise.
• The technique also shows resilience to fluctuations in the carrier frequency.

Conclusions:

• The Teager-Kaiser energy operator-based method provides a significant advancement in WLSI surface extraction.
• This approach offers improved accuracy and reliability, particularly in the presence of noise and signal instability.
• The method presents a promising alternative for high-precision surface metrology.