טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentKarl David
SubjectExtreme Far Field Remote Sensing Using Laser Speckle:
Theory and Application
DepartmentDepartment of Physics
Supervisors Professor Emeritus Stephen Lipson
Dr. Aner Lev


Abstract

The aim of this work is to study, in depth, the theory and practical potential for remote sensing of the dynamical movement of a rough surface (tilt motion) using laser speckles. The intended application is to sense acoustically-induced movements of rough surfaces from a remote location.


The work focuses on extending known work on speckle correlation photography, especially on the practical problems and their solutions. The thesis includes theoretical estimates of the parameters required in such a system to achieve sub-pixel resolution, and the expected accuracies and signal-to-noise ratios possible under different conditions and using different algorithms. It includes theory, simulations and some experiments, the main goal being to push the boundaries of high frequency detection and remote sensing distance.


The algorithms tested include two basic surface-fit algorithms, parabolic and Gaussian surface-fits, and the naturally arising Nyquist type interpolation algorithm. Also tested were anti-decorrelation algorithmic approaches for both integer pixel and sub-pixel situations.


The algorithms were tested for performance both with classical fields and with photon limited detectors. Moreover, the algorithms were tested for performance under various realistic limitations such as camera readout noise, column noise, fixed pattern noise, etc.


Overall, it appears that under most conditions the preferred approach which combines both computational efficiency and desired accuracies is the parabolic surface fit together with both anti-decorrelation algorithms combined. Also, as was expected, in many cases and without computational time constraints, it appears that the Nyquist type interpolation algorithm fares the best.


The research potential of the field is great and the results obtained give ideas for future research in the field of cross-correlation interpolation. Such topics include elimination of turbulence effects on speckle correlation, use of wideband lasers, structured illumination speckles, stereo-vision speckle correlation and non-stiff speckle image registration.