arXiv subjects

Manuel Servin

Publications and source records attributed to Manuel Servin.

20 records · Page 2Linked to original sources

arXiv2012

Digital interferometric demodulation of Placido mires applied to corneal topography

This paper presents a novel digital interferometric method to demodulate Placido fringe patterns. This is a synchronous method which uses a computer-stored conic-wavefront as demodulating reference. Here we focus on the experimental aspects to phase-demodulate Placido mires applied to corneal topography. This synchronous method is applied to two topographic Placido images and their de-modulated corneal-slope deformation is estimated. This conic-interferometric method is highly robust against typical "noise" signals in Placido topography such as: reflected eyelashes and iris structures. That is because the eyelashes and the iris structures are high frequency "noisy" signals corrupting the reflected Placido mire, so they are filtered-out by this method. Digital synchronous interferometry is here applied for the first time to demodulate corneal topographic concentric-rings images (Patent pending at the USPTO).

physics.optics↗

arXiv2012

Linear analysis of the 4-step Carré phase shifting algorithm: spectrum, signal-to-noise ratio, and harmonics response

We analyze the nonlinear Carré 4-steps algorithm including its frequency response, signal-to-noise ratio, and harmonics rejection using linear systems theory. At first sight the previous statement as well as the title of this paper seems paradoxical. How can we analyze the 4-step non-linear Carré Phase Shifting Algorithm (PSA) using linear system theory? The short answer is that the non-linear Carré algorithm may be decomposed into two building blocks. The first block is a tunable linear 4-step PSA, and the second one is a non-linear phase-step estimator. Although this fact is well known from the derivation of the Carré algorithm, nobody has properly exploited it. In other words, to this day, we do not have explicit mathematical formulae for a) the spectrum, b) the harmonics rejection, and c) the signal-to-noise ratio of the non-linear Carré algorithm. These are the properties of the Carré's PSA that we show here with novel and explicit mathematical formulae.

physics.optics↗