We describe a robust system to retrieve the phase using a temporal phase unwrapping approach. Combining the polarization Michelson interferometer with a polarizing sensor and temporal phase unwrapping algorithms the phase unwrapping procedure is not only simplified, but also the computing time is reduced one order of magnitude compared with other algorithms and we can analyze dynamic events in real-time, i.e., 7.4fps. In the approach taken, each pixel is processed independently obtaining the phase difference for a specific time opening the possibility of real-time analysis and the masking process is avoided limiting the noise propagation in spatial manner. Validation experiments are presented.
In this paper, we show the results and feasibility of a designed software for obtaining and graphing aberrations in 2D, and the post-processing necessary for the detection of the centroids. This software is designed to be used in low-cost and highly affordable commercial devices such as Raspberry pi and Raspberry pi HQ Camera. Preliminary results will also be presented.
We present a demodulation approach for a rotating polarizer-analyzer polarimeter dedicated to retardance measurements.
Through the Mueller matrix approach and the theoretical Fourier transform, we developed a demodulation algorithm
considering the two linear polarizers' initial orientation as calibration. We present experimental results showing the
feasibility of our proposal.
We propose a polarizing Michelson interferometer coupled to a pixelated polarizing camera to visualize dynamic phase objects. Considering the capabilities of the polarizing camera, we employed a temporal phase unwrapping algorithm to process information. Experimental results are presented showing the capabilities of our proposal.
We propose to use the fast Fourier transformation (FFT) to analyze the spectral data of passively mode-locked fiber lasers, with the purpose of characterizing and classifying the different pulsed regimes arising in these lasers. The results show temporal information at the sub-ps scale. Specially, in the Fourier domain, the spectra of bound solitons depict several solitons with relative phases of π/2 and close to 0, distributed into a window that extends beyond the limited span of the autocorrelator. Besides, the FFT amplitude traces can help to classify the multi-pulse regimes generated by the laser; in particular, the exponential decay of intensity in such amplitude traces can be a fingerprint of noise-like pulses. Furthermore, the amplitude traces show some modulation that we attribute to Kelly’s sidebands. The proposed technique allows examining spectra from a mode-locked fiber laser independently of the active medium or laser cavity configuration without the need to use ultrafast photo- detectors.
We present a calibration approach for rotating polarizer-analyzer polarimeter dedicated to retardance measurements. The rotating polarizer-analyzer polarimeter is based on retrieving a partial Mueller matrix measurement of a transparent sample to be later associated with its phase retardation properties. Through the Mueller matrix approach, we developed a calibration procedure considering the initial orientation of the two linear polarizers used, and we present experimental results showing the feasibility of our calibration approach.
In this paper, we report an experimental study of the supercontinuum (SC) generated by molecules of solitons (MS) and noise-like pulses (NLP) in two different types of optical fibers: 500m of standard fiber (SMF-28, Corning) and 100m of High-Nonlinearity Fiber with a zero dispersion-slope (HNLF-ZS, Furukawa). We extracted information on the inner structure of SC by using a nonlinear optical loop mirror (NOLM) as an intensity filter. The NOLM suppresses pulses with low peak power, which is especially pronounced for wavelengths longer than ~1750 nm for both fibers, and particularly in the region between 1450 nm and 1640 nm for the High-Nonlinearity fiber. It is worth mentioning that depending on the application, the required properties of SC light can vary considerably. Therefore, it is the main importance to know the properties of the different SC sources.
In this work, we proposed the usage of a rotating polarizer-analyzer polarimeter to retrieve retardance parameters of a sample by treating it as an elliptical retarder that can be characterized by three parameters: total retardance, fast axis orientation and an ellipticity related parameter. By employing the Mueller matrix approach, we developed the demodulation algorithm to retrieve each parameter with the association of the Fourier series analysis. We present experimental results considering dextrose concentrations diluted in distilled water scaling in a range from 30mg/dl to 45mg/dl. For comparison purposes, we employed the method of rotating an analyzer and compare the optical activity variation for both methods.
We present a polarization sensitive measurement focused on retrieve elliptical phase retardation properties. The system is based on rotating two linear polarizers. And a demodulation algorithm is proposed to retrieve a partial matrix of Muller from the intensity output signal. The polarimetry setup also employs a monochrome camera as detection system and a HeNe laser as light source. Simulation and experimental results in transparent samples are presented showing the feasibility of the measurement and the potential usage in a multiwavelength arrangement.
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.
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.
We report an optical implementation of a parallel phase-shifting quasi-common path interferometer using two modified Michelson interferometers to generate two interferograms. By using a displaceable polarizer’s array, placed on the image plane, we can obtain four phase-shifted interferograms in two captures. The system operates as a quasi-common path interferometer generating four beams, which are to interfere with alignment procedures on the mirrors of the Michelson configurations. The optical phase data are retrieved using the well-known four-step algorithms. To present the capabilities of the system, experimental results obtained from transparent structures are presented.
The purpose of this paper is the measurement of spatial-temporal movements by using stereo vision and 3D optical flow algorithms applied at biological samples. Stereo calibration procedures and algorithms for enhance the contrast intensity were applied. The system was implemented for working at the first near infrared windows (NIR-I) at 850 nm due of the penetration depth obtained at this region in biological tissue. Experimental results of 3D tracking of human veins are presented showing the characteristics of the implementation.
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.
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.
We present a parallel polarizing phase shifting interferometer based in a Double Cyclic Shear Interferometer (DCSI) to analyze transparent samples. The system itself has the advantage of retrieve the derivative phase data map directly and ,due of its configuration itself, it presents betters stability against external configurations than other types of interferometers. The DCSI generates two π-shifted interferograms, which are recorded by the camera in a single-shot. The optical phase is processed by the four-step algorithm. Related simulations and experimental results obtained for transparent samples are also presented.
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.
This communication describes some details of polarization modulation that are useful in phase-shifting interferometry when applied to phase profile measurements of phase objects. Since non-destructive optical techniques allow surface measurement with high accuracy, a Mach-Zehnder configuration coupled to a 4-f arrangement using phase gratings placed on the Fourier plane was implemented to analyze phase objects. Each beam of the interferometer goes through a birefringent wave plate in order to achieve nearly circular polarization of opposite rotations, with respect to each other. The interference of the fields associated with replicated beams, centered on each diffraction order, is achieved varying the spacing of windows with respect to the grating period. Experimental results are presented for cases of four and nine simultaneously captured interferograms.
In this work we present a parallel polarizing phase shifting interferometer based in a Double Cyclic Interferometer
(DCSI) to analyze transparent samples. This system has the advantage of generating four beams that can interfere
properly; this can reduce the number of captures needed in phase shifting interferometry. The interferometric system
generates two π-shifted interferograms, which are recorded by the CCD camera in a single-shot. For the processing of
the optical phase data map, a parallel phase shift can be generated by placing a linear polarizer covering two patterns.
We analyze the cases of four patterns with arbitrary shifts captured in two shots. The unwrapped phase is processed by
Kreis methods. Experimental results obtained by the proposed interferometer are presented.
A Mach Zehnder (MZ) interferometer was implemented to analyze a phase object using polarization phase-shifting
interferometry. The Mach Zehnder interferometer produces two beams with circular polarization of opposite rotations
one respect to the other. The system is coupled to a 4-f system with phase grating in the Fourier plane, interference of the
fields associated with replicated beams centered on the diffraction orders is achieved by a proper choice of the beams
spacing with respect to the gratings period. The optical configuration allows obtaining n-interferograms in one shot. The
configuration presented does not require micro-polarizer arrays or additional software to eliminate noise caused by
vibration, as the system is stable itself and uses conventional polarizing filters. Considering the object under study a thin
phase object, experimental results are presented.
An interferometric method to measure the slope of phase objects is presented. The analysis was performed by
implementing of a polarizing phase shifting cyclic shear interferometer coupled to a grating interferometer. This system
can obtain four interference patterns with adjustable phase shifts and variable lateral shear. In order to extract the slope
of a phase object, is analyzed the optical phase applying the classical method of phase extraction.
We present experimental results obtained by using phase-shifting interferometry by polarization to measure the radial
slope of transparent samples, by implementing a Radial-Shear interferometer and using a grating to replicate the
interference patterns modulated by polarization; the interferometer is capable to process the optical phase data by
obtaining four interferograms in one-shot. The experimental results for transparent samples are presented in this
research.
Due to non-destructive optical techniques allows surface measurement with high accuracy, a Common Path
interferometer based on a Michelson configuration was implemented to analyze phase objects by using polarization
simultaneous phase-shifting interferometry. Each beam of the interferometer has a birefringent wave plate attached in
order to achieve nearly circular polarization of opposite rotations one respect to the other. The system is coupled to a 4-f
arrangement with Bi-Ronchi gratings collocated in the Fourier plane. The interference of the fields associated with
replicated beams, centered on each diffraction orders, is achieved varying the beams spacing with respect to the grating
period. The optical configuration allows obtaining n-interferograms simultaneously. The phase reconstruction is
performing by a three steps phase shifting algorithm. Experimental results are present for a phase object.
We measured the topography of lens by using a technique of diffuse reflection (fringe projection technique) and by a
method based on specular reflection technique (similar to Placido disk system). The obtained results with both
techniques are compared with those obtained with a spherometer. The retrieval of the three-dimensional shape of the
lens is an issue of great interest for wide medical application, particularly in ophthalmology.
We present a non-contact system for obtaining three-dimensional objects topography. The described system combines the fringe projection technique and the Talbot effect which is knowed like Talbot interferometry. In fringe projection technique, the digitalization is realized when black and white lines are projected over the object and this image is captured by the CCD. In Talbot interferometry, the object is collocated on one of the grating auto-image planes. The deformed grating image is captured by the CCD and superposed with other reference one that can be physical or computer generated (virtual/synthetic) for obtaining a moire pattern which gives information about the object topography. The topography of a coin and phalangeal articulation are obtained by using of this technique. The Spatial Synchronous Detection and Fourier Method were incorporate to retrieve the phase.
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