Comparative analysis of nanometric inspection methods in fringeless speckle pattern interferometry

Area of Science:

• Optical Metrology
• Interferometry
• Nanotechnology

Background:

• Digital speckle pattern interferometry (DSPI) faces challenges with fringeless interferograms due to insufficient deformation.
• Traditional fringe processing algorithms are inadequate for analyzing these fringeless patterns.

Purpose of the Study:

• To propose and compare novel algorithms for analyzing fringeless speckle pattern interferograms.
• To enable fast inspection of nanometric displacement fields without multiple image acquisitions.

Main Methods:

• Development of algorithms using arccosine function and intensity image correlation.
• Implementation and analysis of implicit smoothing splines for phase recovery.
• Proposal of three distinct normalization methods for fringeless interferograms.
• Performance assessment using Structural Similarity Index (SSIM) via numerical simulations.

Main Results:

• Arccosine and correlation-based methods are suitable for fast inspection of nanometric displacements.
• Implicit smoothing splines demonstrate superior performance across various simulation conditions.
• The study evaluated methods under diverse illuminations, signal-to-noise ratios, phase excursions, and speckle sizes.

Conclusions:

• Novel algorithms effectively analyze fringeless speckle pattern interferograms.
• Implicit smoothing splines provide a robust solution for nanometric displacement field inspection.
• The proposed methods advance the capabilities of digital speckle pattern interferometry for precision measurements.