Rotationally shearing interferometer for extra-solar planet detection: preliminary results with a solar system simulator.

We describe preliminary experimental results on the laboratory demonstration of a technique to detect an extrasolar planet using a rotationally shearing interferometer. We simulate a planet and a star in a laboratory solar system. It consists of two laser beams; each passed through a spatial filter, collimated and combined. We confirm the theoretical prediction that the on-axis star generates no fringes for any shear angle. The star generates a uniform wave front that is invariant to the shear angle. Additionally, we demonstrate that the off-axis planet produces straight fringes. Thus, the mere presence of fringes confirms the existence of a planet. Furthermore, we illustrate that the fringe density and their inclination increase with the shear angle in the rotational shearing interferometer. Therefore, the number of fringes and their direction may be changed from the Earth to confirm (or reject) the existence of a planet.

Design method for compact, achromatic, high-performance, solid catadioptric system (SoCatS), from visible to IR.

Maresse described a classical solid catadioptric system (SoCatS) for a lens comprising a solid body and a single-focal Maksutov type construction, characterized by two refractive and two reflective surfaces. Due to ray propagation through the solid block twice, the design is feasible at a single wavelength, otherwise suffering on chromatic aberration induced by dispersion. We design a SoCatS for a telescope and describe a class of solutions to reduce and control chromatic and some spherical aberration in the solid catadioptric system.

Three-dimensional reconstruction of subsurface defects using finite-difference modeling on pulsed thermography.

We develop a technique to analyze pulsed thermography videos in order to detect and reconstruct subsurface defects in homogeneous and layered objects. The technique is based on the analysis of the thermal response of an object to a heat pulse. This thermal response is compared to the predictions of a finite-difference model that is systematically and progressively adjusted to minimize a cost function. With this minimization process, we obtain a depth and a thickness function that allow us to determine the three-dimensional shape, size, depth, thickness, and location of internal defects. The detected defects are reliably reconstructed with graphics of easy interpretation.

Bidimensional fluorescence analysis and thermal design of europium thenoyltrifluoroacetonate based thermal-to-visible converter.

We perform a bidimensional analysis to evaluate the variation of the fluorescence decay of europium thenoyltrifluoroacetonate (EuTTA) with temperature changes. We analyze how a specific thermal distribution modifies the spatial temperature of the sensing film and we study the corresponding fluorescence response using an integral functional of the emission decay. We present experimental results of a thermal distribution registered with the EuTTA-based thermal-to-visible conversion method. Furthermore, we analyze the spatial and temporal response of the proposed sensing element by using heat-transfer theory. Based on the presented analysis, we establish the optimal thermal and physical design for the sensing element of the proposed thermal-to-visible converter.

Reconstruction and analysis of pulsed thermographic sequences for nondestructive testing of layered materials.

We develop a heat transfer model to reconstruct pulsed thermographic data of layered objects. One of its salient features is its incorporation of normalized variables for a generalized approach to such problems. Additionally, we establish a methodology to determine the spatial and temporal limits of the data reconstruction process. Moreover, we describe an effective nondestructive technique for detecting and characterizing internal defects in multilayer objects. This inspection technique is verified on the construction of physical models and their examination. The depth, transverse dimensions, and front-surface shape of the detected defects are straightforwardly obtained from 3D depthgrams.

Risley prisms to control wave-front tilt and displacement in a vectorial shearing interferometer.

A pair of thin prisms is used to deviate a light beam without changing the image orientation in a vectorial shearing interferometer. The relative angle between prisms determines the displacement of the wave front and its tilt. The direction of the beam displacement is controlled by means of changing the relative angle between prisms. This system is employed to control the displacement of a sheared wave front as a vector quantity and to introduce a controlled amount of tilt in what we believe is a novel interferometric shearing system. The predicted performance of this wave-front director is confirmed experimentally.

Phase reconstruction from undersampled intensity patterns.

We demonstrate the uniqueness and convergence of phase recovery from high-spatial-frequency and undersampled intensity data. Furthermore, this is accomplished without the ambiguities that arise in phase unwrapping and without the need to employ a priori information. The method incorporates the technique of line integration of the phase gradient to find the first approximation to the phase and the algorithm of synthetic interferograms to find the unknown phase with high accuracy. The method may be used with any experimental method that at a certain data processing step obtains generalized sine and cosine intensity functions.

Vectorial shearing interferometer.

The vectorial shearing interferometer is based on the Mach-Zehnder configuration; it incorporates a displacement shearing system composed of a pair of wedge prisms that modify the optical path difference and the tilt of the sheared wave front with respect to that of the reference wave front. Variable shear and tilt can be implemented along any direction by choice of displacements Delta x and Delta y. The number of fringes and their orientation can be controlled with the vectorial shear. Knowledge of the prescribed displacements in the x and the y directions permits one to obtain a phase gradient in any direction.

Design of a diluted aperture by use of the practical cutoff frequency.

We analyze the imaging performance of a number of diluted-aperture configurations, using the modulation transfer function. We select a single figure of merit, the practical cutoff frequency, rather than the traditional cutoff frequency, as the more useful frequency for the detection of details. Using this new parameter, we compare the performance of a number of published aperture configurations. On the basis of this analysis a new configuration is proposed for the Polar Stratospheric Telescope primary.

Convergent, recursive phase reconstruction from noisy, modulated intensity patterns by use of synthetic interferograms.

We present a novel method of rapidly convergent phase reconstruction from noisy and high-fringe-density intensity patterns without a priori information. We define an error function that incorporates the measured intensity data to ensure the convergence. The error function is the absolute value of the cosine of the difference of the reconstructed phase and the unknown phase, i.e., a calculated or a synthetic interferogram.

Fringe analysis and phase reconstruction from modulated intensity patterns.

A novel method of determining phase from a modulated intensity pattern is described. A line integral of the gradient of the phase is used to reconstruct the phase, eliminating the necessity for complex methods of phase unwrapping. The new algorithm can be used with any technique that experimentally or theoretically yields the cosine and sine or the tangent of the phase. This phase-reconstruction process works effectively even in the regions of high-intensity gradients and is insensitive to the profile of the illuminating beams and to the shape of the domain boundaries.