Design of a medical and laboratory equipment management program for the new standards certification achievement in Mexico.

Certification for healthcare institutions in Mexico is ruled by 2009 standards homologated with the Joint Commission International criteria. Nowadays, healthcare requires of medical equipment and devices, so it has become necessary to implement guidelines for its adequate management in order to reach the highest level of quality and safety at the lowest cost. The objective of this work was to develop a Medical and Laboratory Equipment Management Program, oriented to the improvement of quality, effectiveness and efficiency of the technological resources in order to meet the certification requirements. The result of this work allows to have an auto evaluation tool that focuses the efforts of the National Institute for Respiratory Diseases to the achievement of the new requirements established for the certification.

Robust wave-front estimation from multiple directional derivatives.

A quadratic cost functional for computing an estimate of a wave front from multiple directional derivatives is presented. This functional is robust to noise and is specially suited for moiré deflectometry, Ronchi testing, and lateral shearing interferometry.

Piecewise smooth phase reconstruction.

A well-founded and computationally fast method is presented for filtering and interpolating noisy and discontinuous wrapped phase fields that preserves both the 2pi discontinuities that come from the wrapping effect and the true discontinuities that may be present. It also permits the incorporation of an associated quality map, if it is available, in a natural way. Examples of its application to the computation of the isoclinic phase from photoelastic data and to the recovery of discontinuous phase fields from speckle interferometry are presented.

Regularization methods for processing fringe-pattern images.

A powerful technique for processing fringe-pattern images is based on Bayesian estimation theory with prior Markov random-field models. In this approach the solution of a processing problem is characterized as the minimizer of a cost function with terms that specify that the solution should be compatible with the available observations and terms that impose certain (prior) constraints on the solution. We show that, by the appropriate choice of these terms, one can use this approach in almost every processing step for accurate and robust interferogram demodulation and phase unwrapping.

Phase unwrapping through demodulation by use of the regularized phase-tracking technique.

Most interferogram demodulation techniques give the detected phase wrapped owing to the arctangent function involved in the final step of the demodulation process. To obtain a continuous detected phase, an unwrapping process must be performed. Here we propose a phase-unwrapping technique based on a regularized phase-tracking (RPT) system. Phase unwrapping is achieved in two steps. First, we obtain two phase-shifted fringe patterns from the demodulated wrapped phase (the sine and the cosine), then demodulate them by using the RPT technique. In the RPT technique the unwrapping process is achieved simultaneously with the demodulation process so that the final goal of unwrapping is therefore achieved. The RPT method for unwrapping the phase is compared with the technique of least-squares integration of wrapped phase differences to outline the substantial noise robustness of the RPT technique.

Adaptive quadrature filters for multiple phase-stepping images.

We present a new technique for the recovery of local phase from multiple phase-stepping fringe images that uses adaptive quadrature filters constructed by use of Bayesian estimation theory and complex-valued Markov random fields as prior models. It is shown that with this technique it is possible to perform accurate phase reconstructions even for extremely noisy fringe images and that the performance of this technique is nearly independent of the particular noise model, as long as the noise spectrum is wideband.

Fast algorithm for integrating inconsistent gradient fields.

A discrete Fourier transform (DFT) based algorithm for solving a quadratic cost functional is proposed; this regularized functional allows one to obtain a consistent gradient field from an inconsistent one. The calculated consistent gradient may then be integrated by use of simple methods. The technique is presented in the context of the phase-unwrapping problem; however, it may be applied to other problems, such as shapes from shading (a robot-vision technique) when inconsistent gradient fields with irregular domains are obtained. The regularized functional introduced here has advantages over existing techniques; in particular, it is able to manage complex irregular domains and to interpolate over regions with invalid data without any smoothness assumptions over the rest of the lattice, so that the estimation error is reduced. Furthermore, there are no free parameters to adjust. The DFT is used to compute a preconditioner because there is highly efficient hardware to perform the calculations and also because it may be computed by optical means.

Robust procedure for fringe analysis.

A robust procedure for analyzing fringe patterns obtained from speckle interferometric techniques is proposed. The fringes generally are observed only in a region S of a rectangular lattice L. We give a method for computing (from S) the region R, where the unwrapped phase is to be computed; this computation is done by use of a morphological filter (in particular, a closing filter). We then use a fast-unwrapping algorithm to compute the phase: a preconditioned conjugate-gradient algorithm that uses the discrete Fourier transform.

Phase-locked-loop interferometry applied to aspheric testing with a computer-stored compensator.

A recently developed technique for continuous-phase determination of interferograms with a digital phase-locked loop (PLL) is applied to the null testing of aspheres. Although this PLL demodulating scheme is also a synchronous or direct interferometric technique, the separate unwrapping process is not explicitly required. The unwrapping and the phase-detection processes are achieved simultaneously within the PLL. The proposed method uses a computer-generated holographic compensator. The holographic compensator does not need to be printed out by any means; it is calculated and used from the computer. This computer-stored compensator is used as the reference signal to phase demodulate a sample interferogram obtained from the asphere being tested. Consequently the demodulated phase contains information about the wave-front departures from the ideal computer-stored aspheric interferogram. Wave-front differences of ~ 1 λ are handled easily by the proposed PLL scheme. The maximum recorded frequency in the template's interferogram as well as in the sampled interferogram are assumed to be below the Nyquist frequency.

Automatic fringe detection algorithm used for moire deflectometry.

An automatic fringe detection algorithm applied to moire deflectometry is presented. This algorithm is based on a set of points linked together and with a behavior similar to a rubber band, in which these points are attracted to fit the moire fringes. The collective behavior of these points gives rise to a final state which is their regularly spaced alignment along the fringe pattern. The algorithm is dynamic in the sense that it tracks the fringe even when it suffers continuous deformations. Once the rubber band is adapted, the rubber band's points coordinates are obtained and their distance to the starting straight line is found, as required by moire deflectometry.

Pulfrich refractometer for 1-D gradients.

A refractometer based on the critical angle condition was constructed and found useful for determining 1-D distributions of refractive index. The method is particularly convenient when transient liquids are tested, although it is applicable to solid samples. The device is simple and straightforward in its use, allowing realtime measurements with no additional optical system. The sensitivity can be changed with the size of the apparatus.