Dr. Percival Almoro of the Photonics Group participated as an invited speaker at the SPECKLE 2015 International Conference on Optical Metrology held last August 24-26 2015 in Guanajuato, Mexico. Dr. Almoro presented a technique that combines holograms and statistics in locating distant rough objects. Utilizing the statistics of the phase of light extracted from a hologram, the technique permits the conception of a high-resolution technique with a precision level of the light source wavelength (less than one micrometer). The abstract of the paper is shown below:
Title: Enhanced Axial Localization of Rough Objects Using Statistical Fringe Processing Algorithm
Authors: Percival F. Almoro and Timothy Joseph T. Abregana
Abstract: Fringe patterns carry valuable spatio-temporal information about the object being investigated. Fringe processing, however, is hampered by the presence of speckle noise which is a by-product of coherent metrology of optically rough surfaces. A speckle noise-robust fringe processing algorithm we developed based on the statistical properties of fringe patterns is revisited. The algorithm evaluates the change in the standard deviation of fringe patterns yielding a 2-D contrast map of spatial frequencies along the transverse directions. Application of the algorithm along the axial direction has not been reported. Here a technique for enhanced axial localization of rough test objects based on the statistical fringe processing algorithm is demonstrated experimentally. The main advantages of the localization technique are robustness against speckle noise and high axial resolution in the range of the light source wavelength.
Below is the citation of the full manuscript as included in the conference proceedings:
Percival F. Almoro, Timothy Joseph T. Abregana, “Enhanced axial localization of rough objects using statistical fringe processing algorithm”, Proceedings of SPIE Vol. 9660, 96600F (2015) SPIE Digital Library
More insights on the technique including related applications may be found in the following papers:
[1] Maallo, A. M. S., and P. F. Almoro. 2011. Numerical correction of optical vortex using a wrapped phase map analysis algorithm. Optics Letters 36: 1251-1253. [2] Catalan, F. C. I., Maallo, A. M. S., and P. F. Almoro. 2012. Fringe analysis and enhanced characterization of sub-surface defects using fringe-shifted shearograms. Optics Communications 285: 4223-4226. [3] Escoto E., Muldera, J., Dasallas, L., Estacio, E., and P. F. Almoro. 2014. Mapping of Temporal Coherence Function for Ultrafast Lasers via Statistical Fringe Analysis of Reconstructed Phase Maps. Optics Communications 329: 190-195.