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Harmonics rejection in pixelated interferograms using spatio-temporal demodulation.

J M Padilla1, M Servin, J C Estrada

  • 1Centro de Investigaciones en Óptica A. C. Loma del Bosque 115, Lomas del Campestre C.P.37150. León, Guanajuato, México.

Optics Express
|October 15, 2011
PubMed
Summary
This summary is machine-generated.

This study addresses non-ideal conditions in pixelated phase-mask interferometry. Temporal phase-shifting techniques are proposed to accurately estimate wavefront phase by removing complex harmonics from non-sinusoidal fringes.

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Area of Science:

  • Optical metrology
  • Wavefront sensing
  • Interferometry

Background:

  • Pixelated phase-mask interferograms are standard in spatial phase-shifting interferometry for single-shot wavefront encoding.
  • Ideal demodulation methods fail under non-ideal conditions like CCD non-linearity, introducing harmonics that degrade phase estimation.

Purpose of the Study:

  • To investigate the impact of non-ideal conditions on pixelated interferogram demodulation.
  • To propose and evaluate methods for accurate phase estimation in the presence of complex harmonics.

Main Methods:

  • Two-dimensional Fourier demodulation was applied to identify remaining complex harmonics.
  • Temporal phase-shifting algorithms (2-step and 3-step) were developed to eliminate specific harmonics.

Main Results:

  • 2D Fourier demodulation effectively rejects most harmonics but leaves complex ones (e.g., -3rd, +5th).
  • A 2-step phase-shifting algorithm removes -3rd and +5th harmonics.
  • A 3-step algorithm removes -3rd, +5th, -7th, and +9th harmonics.

Conclusions:

  • Temporal phase-shifting is crucial for accurate wavefront phase estimation from non-ideal pixelated interferograms.
  • The proposed algorithms effectively mitigate harmonic distortions, improving phase measurement fidelity.