David I. Serrano-Garcia

Dynamic temperature field measurements using a polarization phase-shifting technique

Abstract. In this study, an optical system capable of simultaneously grabbing three phase-shifted interferometric images was developed for dynamic temperature field measurements of a thin flame. The polarization phase-shifting technique and a Michelson interferometer that is coupled to a 4-f system with a Ronchi grating placed at the frequency plane are used. This configuration permits the phase-shifted interferograms to be grabbed simultaneously by one CCD. The temperature field measurement is based on measuring the refraction index difference by solving the inverse Abel transform, which requires information obtained by the fringe order localization. The phase map is retrieved by a three-step algorithm. Experimental results of a dynamic thin flame are presented.

Enhanced intensity variation for multiple-plane phase retrieval using a spatial light modulator as a convenient tunable diffuser

In the multiple-plane phase retrieval method, a tedious-to-fabricate phase diffuser plate is used to increase the axial intensity variation for a nonstagnating iterative reconstruction of a smooth object wavefront. Here we show that a spatial light modulator (SLM) can be used as an easily controllable diffuser for phase retrieval. The polarization modulation at the SLM facilitates independent formation of orthogonally polarized scattered and specularly reflected beams. Through an analyzer, the polarization states are filtered enabling beam interference, thereby efficiently encoding the phase information in the axially diverse speckle intensity measurements. The technique is described using wave propagation and Jones calculus, and demonstrated experimentally on technical and biological samples.

Dynamic interferometric measurements employing a pixelated polarization sensor and FFT spatial-temporal filtering techniques

We implemented a Michelson interferometer capable to follow temporal phase variations. The system uses polarization phase shifting techniques and is coupled to the pixelated polarization sensor. By considering the space-time stability obtained, the systems allow a 3D FFT phase demodulation algorithm that combines the spatial carrier due of the pixelated polarization mask and a low pass filtering in time. In the system implementation, we reduced the usage of polarization components by observing the back propagated interferogram and, in the speckle reduction part, a laser combined with a spatial filter and speckle reducer commercially available commonly employed for projection. Experimental results presenting the enhancement in space and time are presented.

Interferometric measurements of phase objects by using a simultaneous polarizing phase shifting Mach-Zehnder interferometer

In this research an interferometric system was developed that generates four simultaneous interferograms with independent phase shifts using modulated polarization. The proposed system consists of three coupled interferometers: the first system is a polarized Mach-Zehnder interferometer, which generates the pattern, the second and the third interferometer system, function as replicators of the first pattern, so the four patterns are generated. To show the novelty of the developed system, the calculation of optical path difference (OPD) for phase samples are shown.

Dynamic phase measurements based on a polarization Michelson interferometer employing a pixelated polarization camera

Abstract We implemented an interferometric configuration capable of following a phase variation in time. By using a pixelated polarization camera, the system is able to retrieve the phase information instantaneously avoiding the usage of moving components and the necessity of an extra replication method attached at the output of the interferometer. Taking into account the temporal stability obtained from the system, a spatial-temporal phase demodulation algorithm can be implemented on frequency domain for the dynamic phase measurement. Spatial resolution is analyzed experimentally using a USAF pattern, and dynamic phase measurements were done on air and water medium variations due to a jet flame and a living fish as a biological sample, respectively.

Mueller-matrix modeling and characterization of a dual-crystal electro-optic modulator.

A general mathematical model based on Mueller-matrix calculation is presented to describe the optical behavior of a dual-crystal electro-optic modulator. The two crystals inside the modulator are oriented at ± 45° with respect to the horizontal, thereby cancelling natural birefringence and temperature-induced birefringence. We describe the behavior of the modulator as a function of the ellipticity of the crystals, the rotation angles of the crystals and the applied voltage. By fitting the measured data with a Mueller-matrix model that uses values for the ellipticity and orientation angles of the crystals, the simulated data and the experimental measurements could be matched. This Mueller-matrix includes physical properties of the thermally compensated electro optic modulator, and the matrix can be used in simulations where these device-specific properties are important, for instance in the modeling of a polarization-sensitive optical coherence tomography system.

Mueller Matrix Polarimeter with Diattenuation Error Calibration Approach

A calibration algorithm for the Mueller matrix dual-rotating retarder polarimeter is presented. The Mueller matrix dual-rotating retarder polarimeter is composed by two rotating retarders and two fixed polarizers with the final purpose of retrieving the polarization properties of a sample. Even algorithms to calibrate the retardation error and azimuthal error already exists, the accuracy obtained with the system is limited. Our proposal is to take into account the diattenuation error of the two retarders, which can provide more accuracy in the result. The analytical equations is described and supported with experimental results showing the accuracy incremental in our proposal.

Phase sensitive computer tomographic measurement using a pixelated phase mask interferometry technique

A computed tomographic measurement based on sensing the introduced phase changes of a transparent sample is implemented. The interferometry system is composed by a polarizing Michelson interferometer coupled to a pixelated polarization camera in order to acquire the real-time phase information by polarization phase shifting techniques instantaneously. By obtaining measurements at different angles of rotation, added with computed tomographic algorithms, inner information of a sample was obtained. Characteristics of the implemented system are explained and experimental results showing inner distribution phase changes of a high temperature torch, at steady laminar flow conditions, are presented.

Dynamic temperature field measurements using a polarization phase shifting technique

An optical system capable of simultaneously grabbing three phase-shifted interferometric images was developed for dynamic temperature field measurements outside of a thin flame. The polarization phase shifting technique and a Michelson interferometer that is coupled to a 4-f system with a Ronchi grating placed at the frequency plane are used. This configuration permits the phase-shifted interferograms to be grabbed simultaneously by one CCD. The temperature field measurement is based on measuring the refraction index difference by solving the inverse Abel transform, which requires information obtained by the fringe order localization. Experimental results of a dynamic event are presented varying in time.

4D phase profile measurements using a single-shot phase shifting technique

In this paper, we propose a Quasi Common-Path Interferometer based on a two beams configuration using simultaneous phase shifting interferometry modulated by polarization. Due to the fact that the configuration is capable of obtaining two beams whose separation can be varied, according to the characteristics of the grid used, to obtain the interference patterns. It can be used to implement a quasi-common path interferometer that allows the measurement of dynamic events with high accuracy. For demodulate the fringe patterns generated by the optical system we using the conventional four step phase shifting method. Experimental results are also given.