Guillermo Garcia-Torales

Vectorial shearing interferometer

We describe a new type of shearing interferometer, with the capacity to control the amount and the direction of displacement shear. The vectorial shearing interferometer is based on the Mach-Zehnder configuration, by incorporating the displacement shearing system. It is composed of a pair of wedge prisms that modify with a high degree of precision the optical path length and the tilt of the sheared wave front with respect to that of the reference wave front. When the shearing direction is chosen along the CCD pixel rows and columns, a 2D derivative of the phase function is obtained, allowing its complete recovery in two-dimensions. The variable shear and tilt may be implemented along any other direction with the particularly beneficial characteristics that the number of fringes and their orientation may be controlled with the shear direction and its magnitude.

Black-body radiation, emissivity, and absorptivity

We review theoretical considerations that give rise to the blackbody radiation inside a cavity with completely absorbing walls at a specific temperature. We examine the applicability of this model to the experimentally observed properties of radiation sources. We assess relevance of emissivity and its far-reaching implications. We examine its changing nature and measurement challenges

Novel optical polarimeter using an analyzer mounted on rotator 360 stage

We describe a novel polarimetric configuration which can be used to develop a Saccharimeter. This polarimeter layout consists of an analyzer mounted on rotator 360 stage. The rotating carriage of the stage provides continuous rotation, and generates a reference wave which may be used to generate clock pulses for a digitizing instrument that measures the intensity of the beam emerging from the polarimeter. The detected optical signal is a phase modulated signal, which phase is demodulated by the use of coherent detection method. Finally, experimental results demonstrating the reliability of the instrument are presented.

A review on optical current transducers for power system metering

Current and Voltage sensors have existed as a special field for more than 100 years in Power Systems. In the last two decades there has been a fast development for systems based on fiber optical technology. As consequence, groups of IEEE- PSRC, IEC TC57, CIGRE SC A3, and some others are involved in developing activities in the area of optical systems for protective relaying. This paper provides an overview on those activities discussed by international groups. The document is divided into the four major sections. The first one explains the interaction of sensors within a protection scheme. The second section deals with the designing and components of fiber-optic current sensors (FOCS). Once presented their description, there are divulged general tests identified as relevant. Finally a brief comparison with conventional sensors is presented.

Differential shearing interferometer

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.

High precision phase-shifter modulator in a shearing interferometric system

Shearing interferometers measure small angular variations such as the angle between a star and a planet measured from the Earth. The detected intensity pattern usually presents few fringes or less, often just a fraction of a fringe that may be interpreted as a misalignment error. Exact alignment is a challenge in the calibration of an interferometer. The optical components frequently introduce tilt making it very difficult to retrieve the phase. Spatial light modulators (SLM) are traditionally used to shift the phase to compensate small amounts of tilt, improving the accuracy of the phase measurement. We implement a phase retrieving algorithm to evaluate the accuracy of the phase shifter based on a SLM in a vectorial shearing interferometer (VSI). Our VSI is based on a Mach-Zehnder configuration. With the SLM we are able to compensate the phase error due to the alignment and the fabrication errors. Our results also demonstrate that we may correct error in the OPD and the magnitude of the tilt in the observation plane.

Feature enhanced radar imaging via neural network computing-based sensor fusion

We address a novel neural network (NN) computing-based approach to the problem of feature enhanced (FE) fusion of remote sensing (RS) imagery acquired with different coherent radar/SAR sensing modalities. The novel proposition consists in adapting the Hopfield-type maximum entropy NN (MENN) computational framework to solving the FE image recovery inverse problems with adaptive multiple sensor data fusion that preserves salient radar/SAR image features. The FE fusion is performed via aggregating the descriptive experiment design and the theoretical informatics inspired maximum entropy regularization frameworks for iterative minimization of the energy function of the multistate MENN with adaptive adjustments of the MENNs synaptic weights and bias inputs. We also feature on the computational implementation issues of the MENN-based multi-sensor radar/SAR data fusion and verify the overall image enhancement efficiency via computer simulations with real-world RS imagery.

Engineering intelligent structures for energy efficiency

The current philosophy of designing intelligent buildings emphasizes the use of materials whose performance is compatible with thermal environment that changes daily and seasonally. Ideally, engineering designs should incorporate features to reflect as much energy as feasible and store excess thermal energy. This may be for usage during periods when thermal energy is needed for heating. We show that current construction design methods may be improved for energy efficiency, by incorporating an attic as an transitional space for energy storage during summer, and by employing roof materials with high reflectivity in the visible and in the near IR (up to about 1.9 μm). Thus, traditional red or pink brick roofs, potentially glazed or covered with low reflectivity coating, would likely remain (become again) the preferred construction material.

Vectorial shearing interferometer used in defocus detection

Bringing the image of a static object to the focus of a system is a relative easy task. However, when the object is being moved, the system has to be adapting some parameters according to the object displacement. For small movements, some detection systems are not able to distinguish the new position of the object. The Vectorial Shearing interferometer (VSI) is able to detect small changes in the position through the measurement of the defocus associated with this displacement. We present a method to detect and asses defocus of a wavefront by using a VSI. We present experimental results.

Edge enhancement by unsharp masking using liquid-crystal displays

A new method for real-time edge enhancement is presented. The method is based on the capacity of liquid-crystal displays to generate a contrast-reverted replica of the image displayed on it. When the negative replica is defocused and it is superposed to the original image (displayed in a second liquid-crystal display), one obtains an image with enhanced second derivatives. The proposed technique resembles the classical (photographic) unsharp masking method, but unlike the time-consuming photographic implementation, it can be applied in real-time. The proposed method is potentially interesting for image processing in areas such as microscopy, industrial edge inspection, etc. Validation experiments are presented.