A 3X3 plastic optical fiber (POF) twisted coupler has been fabricated as a compact sensor of multiple variables. The POFs are twisted into a combined body and the clad was removed by chemical method. Three LEDs of red, green, and blue colors can be used to shape a broad spectrum. Each led was connected at a different input port of the coupler. Since the twisted coupler makes the coupling of light from the input ports, we have a wide spectrum at each one output port. We develop a different sensor at each one output coupler: mass concentration (At the output-1), and curvature (At the output-2). The multi-sensing proposed in this work can increase the number of sensors as increase the number of output ports, and the bandwidth increase as increase the colors of light sources. On the other hand, we can use a wide spectrum lamp in a single input port and in the same way make multiple sensors in the output ports. The variation is evident in all wavelengths of the spectrum for measurements of sugar concentrations and fiber curvature. However, we can directly associate the sugar concentration variations with the spectrum in a range from 570 to 600 nm; and across the full spectrum for curvature measurements.
Solar concentrators generate energy according to the amount of radiant flux that is converted into electrical energy using a solar cell. The optimal alignment of the solar cell and the aperture stop of the concentrator photovoltaic (CPV) solar system is a critical parameter for fabricating and manufacturing steps. We designed, developed, fabricated, and verified an optoelectronic system to test alignment of CPV solar system modules that is portable and robust to implement as a step in the assembly line. In addition to the components employed in systems previously, we implement an alignment module. It consists of a thin prism in four orientations in a plane normal to the optical axis of the unit under test and its control system. Its advantage is robustness against its positioning and orientation errors. Simulations and experimental results are presented.
We simulate the interference patterns of solar systems, incorporating an Estrella and two Tierras, as detected by a rotational shearing interferometer, to compare with laboratory setup. Three rays are propagated to represent each wavefront in the interferometer, using the exact ray tracing technique. Then, the phase, with which light beams are incident into the detection plane is used to calculate the orientation of the incident wavefront. Finally, all the incident wavefronts are summed together to obtain the resulting interference pattern.
Mueller matrix polarimetric imaging (MMPI) provides precise microstructural information of biological samples and has been applied to the detections of various abnormal tissues. Once the Mueller matrix is determined for a particular anisotropic material, polar decomposition is applied to determine the singular values of optical anisotropies, such as depolarization, diattenuation, retardance and optical rotation. In this work, ex-vivo cancerous and noncancerous tissues were imaged by the MMPI technique using 3 different radiation wavelengths (460, 532 and 633 nm). The samples under study were cancerous and noncancerous tissues from colon. The results show that the optical anisotropies from biological samples are different. As we know, cancer changes the structure and concentration of biomedical substances from healthy tissue. One of the structures that is affected by cancer is collagen. This structure contributes to the diatenuation and retardance values. Therefore the values of diatenuation and retardance are different from the malignant and healthy tissues. We demonstrate that MMPI and polar decomposition are useful tools to discriminate healthy tissue and cancerous tissue from different parts of the body.
We describe preliminary experimental results on the identification of a planet in a simulated solar system using a rotationally shearing interferometer. We use two lasers, placed at approximately 90 degrees with respect to each other, each with a beam expander and a common collimator lens, to simulate the wave fronts from the star and offaxis planet. We confirm the theoretical prediction that the off-axis planet produces fringes whose density increases with the angle of rotation of the Dove prism in the rotational shearing interferometer. The star generates a uniform wave front that is invariant to the angle of rotation of the Dove prism, enhancing the variable fringes arising from tilted off-axis planet wave front. The inclination and density of planet fringes are under control of the experimentalist.
The use of transillumination to diagnose and consequently treat illnesses has been widely accepted for a long time. However, some kinds of radiation are harmful to the human body, as is the case for x-rays. In this work, we propose using infrared radiation as an illumination source, ballistic photons to transilluminate thin samples and separate scattered radiation from the pass-through radiation for potential future applications in biological research. Infrared radiation is less energetic and harmful than x-rays. Ballistic photons can supply information about the propagation medium, which in turn may allow us to detect inclusions below 9 mm in size (the limit of x-ray radiation) in the medium. In the initial research, we model biological tissue with controlled thickness of samples of pig tissue that has been processed for human consumption, i.e., slices of ham, to study the effects of ballistic photons and to assess the scope of this technique. The combination of an alternative illumination source and a simulated tissue allows us to assess calibration and the diagnostic technique. To detect irradiance, we implemented a Mach-Zehnder interferometer with a 633 nm wavelength He-Ne laser (NIR). As a detector, we used a Sony XCD-SX910 camera. We measure maximum and minimum irradiances generated by ballistic radiation as a function of the thickness of the tissue model and the measured point. The results of these measurements and their comparison are presented.
The ballistic photons have been proposed for biological-tissue characterization. These photons keep its propagation direction when they are propagated through a material. They are rapidly attenuated in accordance with the density and thickness of the medium. The penetration depth for these photons is about 9 millimeters in human tissue. This attenuation may provide information to detect an inhomogeneity in the material (a possible tumor in human tissue). In order to enhance the detection of ballistic photons, interferometric setups have been proposed. Unfortunately, these setups only allow transmission measurement at a single point. We propose a novel technique using Risley prisms for area-scan with ballistic photons.
In the last thirty years, thousands of extra-solar planets have been detected. The overwhelming majority of these detections were performed by indirect techniques. Only a few tens have been detected by direct methods, because the current technology limitations. The rotational shearing interferometer (RSI) has been proposed as a promising technique for the direct detection of extra-solar planets. The RSI is insensitive to rotationally symmetrical wavefronts. This feature allows it to distinguish between a symmetrical wavefront generated by an star alone and an asymmetrical wavefront generated by a star-planet system. However the aperture and resolution of this method is limited by the size of the Dove prisms. We propose the use of an image-inverting interferometer (III) as alternative to the RSI. The III is equivalent to a RSI with a rotation of pi. It conserves the detection features of the RSI. Additionally the III uses mirrors instead Dove prisms avoiding its size limitations.
Skin monitoring under different diffuse spectral illumination conditions is important for assessment of a number of skin, respiratory and circulation conditions. We developed a prototype portable device designed for reflectivity of full back of hand with irradiation with blue LEDs. We are currently applying it to monitoring of vitiligo and age spots, and their temporal evolution.
We simulate the interference patterns of solar systems, incorporating an Estrella and two Tierras, as detected by a rotational shearing interferometer, to compare with laboratory setup. Three rays are propagated to represent each wavefront in the interferometer, using the exact ray tracing technique. Then, the phase, with which light beams are incident into the detection plane is used to calculate the orientation of the incident wavefront. Finally, all the incident wavefronts are summed together to obtain the resulting interference pattern.
We review the direct and indirect methods used for the detection of a planet outside our solar system. We compare the popular methods, emphasizing their attractiveness and exceptional features. The principal indirect planetdetection techniques are gravitational micro-lensing, transit intensity fluctuations, and spectroscopic radial velocity. Most of the research on the exo-solar planet detection within the last 20 years has been performed in conjunction with the star surveys. The direct methods include imaging, image reconstruction, astrometry, interferometry, nulling interferometry, rotational shearing interferometry, phase closure, and coronagraphy. Many of the imaging techniques involve the ground telescopes that are breaking the conventional rules of resolution, and ground-based interferometers. We observe that planet detection leads to novel concepts in the imaging science.
We present a novel interferometer that we call the differential shearing interferometer (DSI). It incorporates a set of Risley prisms in a Sagnac interferometric configuration. The Risley prisms deviates the beam in both propagation directions. This interferometer interferes two beams displaced in the same direction, but with different magnitudes. The resultant interferogram is the directional derivative of the wavefront. The interferometer sensitivity depends on the difference between the beam deviations. This deviation is controlled by the position of the Risley prisms inside the beam path and their angular orientations. The advantages of quasi-common-path configuration include its low sensitivity to vibrations.
The direct detection of exoplanets is obstructed by bright of a nearby star. Rotational shearing interferometer may cancels the light from the star in the infrared region when its OPD is λ2, however, this ideal condition are almost impossible to achieve. We propose a technique that incorporates a wedge prisms system to control the interferometer OPD, the interferometer is based in the Mach-Zhender configuration and incorporates two dove prisms as rotational shearing system. Simulated interference patterns are presented to evaluate the system feasibility.
Vectorial Shearing Interferometer is able to select variable shear and tilt along any wavefront direction. This system is self-referenced and with variable sensibility. We proposed this instrument to measure a phase object without rotational symmetry. Phase recovery is implemented by a Fourier-based algorithm and spatial unwrapping methods. We show results emphasizing the advantage in the easier selection of fringe density and directional derivative orientation for a speci c optical element.
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