Incremental PCA algorithm for fringe pattern demodulation.

This work proposes a new algorithm for demodulating fringe patterns using principal component analysis (PCA). The algorithm is based on the incremental implantation of the singular value decomposition (SVD) technique for computing the principal values associated with a set of fringe patterns. Instead of processing an entire set of interferograms, the proposed algorithm proceeds in an incremental way, processing sequentially one (as minimum) interferogram at a given time.

Robust weighted principal components analysis demodulation algorithm for phase-shifting interferometry.

We present an asynchronous phase-shifting demodulation approach based on the principal component analysis demodulation method that is robust to typical problems as turbulence, vibrations, and temporal instabilities of the optical setup. The method brings together a two-step and a phase-shifting asynchronous demodulation method to share their benefits while reducing their intrinsic limitations. Thus, the proposed approach is based on a two-fold process.

Modeling of a neutron irradiator using Monte Carlo.

The Nuclear Engineering Department of the Military Institute of Engineering (SE/7-IME) is designing and simulation a neutron irradiator with 1 Ci of Am-Be source. The objective of this irradiator is to generate a flux of neutrons to be used in research and teaching maintaining, for purposes of radiological protection, the rate of ambient dose equivalent, H*(10), below 10 μSv/h at 30 cm from the surface. This paper presents the proposed irradiator, values of H*(10) at different distances from the irradiator and the neutron flux in different points of the beam irradiation, all calculated using the MCNPX code.

Reconstruction of local frequencies for recovering the unwrapped phase in optical interferometry.

In optics, when interferograms or digital holograms are recorded and their phase is recovered, it is common to obtain a wrapped phase with some errors, noise and artifacts such as singularities due to the non linearities of the demodulation process. This paper shows how to reconstruct the frequency field of the wrapped phase by using adaptive Gabor filters. Gabor filters are Gaussian quadrature filters tuned in at a certain frequency.

Volume estimation of tonsil phantoms using an oral camera with 3D imaging.

Three-dimensional (3D) visualization of oral cavity and oropharyngeal anatomy may play an important role in the evaluation for obstructive sleep apnea (OSA). Although computed tomography (CT) and magnetic resonance (MRI) imaging are capable of providing 3D anatomical descriptions, this type of technology is not readily available in a clinic setting. Current imaging of the oropharynx is performed using a light source and tongue depressors.

Comparative analysis of hospital and forensic laboratory ethanol concentrations: A 15 month investigation of antemortem specimens.

Quantitative serum alcohol concentrations from regional hospitals (from specimens collected at time of hospital admission) were compared to results from whole blood (from specimens collected at the time of hospital admission) concentrations measured at the San Diego County Medical Examiner's Office (SDCMEO). Over a 15 month period (January 2012 to March 2013), the postmortem forensic toxicology laboratory analyzed a total of 2,321 cases. Of these, 280 were hospital cases (antemortem) representing 12% of the overall Medical Examiner toxicology casework.

High-resolution low-noise 360-degree digital solid reconstruction using phase-stepping profilometry.

In this paper we describe a high-resolution, low-noise phase-shifting algorithm applied to 360 degree digitizing of solids with diffuse light scattering surface. A 360 degree profilometer needs to rotate the object a full revolution to digitize a three-dimensional (3D) solid. Although 360 degree profilometry is not new, we are proposing however a new experimental set-up which permits full phase-bandwidth phase-measuring algorithms.

Robust adaptive phase-shifting demodulation for testing moving wavefronts.

Optical interferometers are very sensitive when environment perturbations affect its optical path. The wavefront under test is not static at all. In this paper, it is proposed a novel and robust phase-shifting demodulation method.

Windowed phase unwrapping using a first-order dynamic system following iso-phase contours.

In this work, we show a windowed phase-unwrapping technique that uses a first-order dynamic system and scans the phase following its iso-phase contours. In previous works, we have shown that low-pass first-order dynamic systems are very robust and useful in phase-unwrapping problems. However, it is well known that all phase-unwrapping methods have a minimum signal-to-noise ratio that they tolerate.

Fast two-dimensional simultaneous phase unwrapping and low-pass filtering.

Here, we present a fast algorithm for two-dimensional (2D) phase unwrapping which behaves as a recursive linear filter. This linear behavior allows us to easily find its frequency response and stability conditions. Previously, we published a robust to noise recursive 2D phase unwrapping system with smoothing capabilities.

Role of the filter phase in phase sampling interferometry.

Any linear phase sampling algorithm can be described as a linear filter characterized by its frequency response. In traditional phase sampling interferometry the phase of the frequency response has been ignored because the impulse responses can be made real selecting the correct sample offset. However least squares methods and recursive filters can have a complex frequency response.

Noise robust linear dynamic system for phase unwrapping and smoothing.

Phase unwrapping techniques remove the modulus ambiguities of wrapped phase maps. The present work shows a first-order feedback system for phase unwrapping and smoothing. This system is a fast sequential unwrapping system which also allows filtering some noise because in deed it is an Infinite Impulse Response (IIR) low-pass filter.

Regularized least squares phase sampling interferometry.

In phase sampling interferometry, existing temporal analysis methods are sensitive to border effects and cannot deal with missing data. In this work we propose a quadrature filter that allows a reliable dynamic phase measurement for every sample, even in the cases involving few samples or missing data. The method is based on the use of a regularized least squares cost function that enforces the quadrature character of the filter.

N-dimensional regularized fringe direction-estimator.

It has been demonstrated that the vectorial fringe-direction field is very important to demodulate fringe patterns without a dominant (or carrier) frequency. Unfortunately, the computation of this direction-filed is by far the most difficult task in the full interferogram phase-demodulation process. In this paper we present an algorithm to estimate this fringe-direction vector-field of a single n-dimensional fringe pattern.

A self-tuning phase-shifting algorithm for interferometry.

In Phase Stepping Interferometry (PSI) an interferogram sequence having a known, and constant phase shift between the interferograms is required. Here we take the case where this constant phase shift is unknown and the only assumption is that the interferograms do have a temporal carrier. To recover the modulating phase from the interferograms, we propose a self-tuning phase-shifting algorithm.

Steerable spatial phase shifting applied to single-image closed-fringe interferograms.

It is well known that spatial phase shifting interferometry (SPSI) may be used to demodulate two-dimensional (2D) spatial-carrier interferograms. In these cases the application of SPSI is straightforward because the modulating phase is a monotonic increasing function of space. However, this is not true when we apply SPSI to demodulate a single-image interferogram containing closed fringes.