This PDF file contains the editorial “Rudolf Kingslake „1903–2003” for OE Vol. 42 Issue 05

An externally modulated amplitude modulated-vestigial sideband (AM-VSB) CATV erbium-doped fiber amplifier (EDFA)-repeated system that uses external light injection technique is proposed and demonstrated. Good performances of carrier-to-noise ratio, composite second order, and composite triple beat were achieved with 0-dBm light injection over a 100-km single-mode fiber transport.

A remote strain sensor with a lead fiber length of 3.3 km and an ultraweak fiber Bragg grating with reflectivity of 0.015% was demonstrated. A demodulation technique based on methods of the differential spectroscopy allows interrogating FBG with reflectance much below the Rayleigh backscattering coefficient.

A simplified and effective model for calculating relative diffraction efficiency of a volume hologram is proposed and demonstrated. In comparison with experimental results and the calculation results of other models, the model is useful in predicting the relative diffraction efficiency and spatial/temporal (wavelength) selectivity of volume holograms under weak coupling.

This PDF file contains the editorial “Optical Metrology Developments and Applications in the Transportation Industry” for OE Vol. 42 Issue 05

Shearography is an approved and powerful tool for the nondestructive investigation of technical components with respect to material faults and structural imperfections. An application field of high interest is the inspection of aircraft and automotive components. Both material and structural imperfections can be recognized as typical fringe patterns in the shearogram. However, a reliable fault detection requires a detectable fault response to the applied load at the surface and a sufficient quality of the fringe pattern as well. Therefore, the testing of large-scale technical objects having in general noncooperative surfaces needs a careful design of the following system components: the shearography sensor, the illumination unit, the loading system, and the evaluation software. We report a mobile shearography system that was especially designed for the inspection of aircraft and automotive parts under industrial boundary conditions. Several examples illustrate the efficiency of the system.

Holography and shearography are two useful whole-field noncontacting optical tools for nondestructive flaw detection and precision measurements. Holography serves as a displacement transducer since it gives direct measurements on displacements whereas shearography serves as a strain gage since it gives direct measurements on displacement gradients. This paper views holography and shearography and their variations as a single optical technique having the same basic mathematical formulation and instrumentation. A key optical component used in both techniques is a doubly-refractive prism that combines two angularly separated laser rays to interfere at near collinearity, thereby permitting the use of a low-resolution CCD camera for recording the interference pattern. Shearography uses a doubly-refractive prism with small image shearing so that two neighboring points on the test surface are brought to interfere at the image plane of the camera, whereas holography, on the other hand, uses a doubly-refractive prism with large image shearing so that light scattered from two different objects—a test object and a reference surface (serving as a reference beam)—are brought to interfere at the image plane of the camera. Hence, testing and measurements made using holography may also be made using shearography, and vice versa.

We present a concise and simple account of image formation in digital holography. Imaging in different recording and reconstruction configurations is considered from the point of view of specifying the impulse response of these configurations. Methods for recording large-size objects are briefly reviewed, followed by a brief discussion on the use of digital holography in interferometric measurements.

Measuring mechanical properties of specimens whose dimensions are in the range of micrometers poses a number of difficult and interesting problems. Currently there are a number of developments in this area, especially in connection with microelectromechanical systems (MEMS). Electronic holographic moiré is an ideal tool for micromechanics studies. It does not require a modification of the surface by the introduction of a reference grating. This is of particular value when placing a reference grating becomes a difficult task. Traditional electronic holographic moiré presents some difficult problems when large magnifications are needed and rigid body motion causes the loss of the correlation fringes. We present developments that solve these problems and extend the application of the technique to micromechanics.

Recent technological trends based on miniaturization of mechanical, electromechanical, and photonic devices have led to the development of microelectromechanical systems (MEMS). Effective development of MEMS requires the synergism of advanced design, analysis, and fabrication methodologies, with quantitative metrology techniques for characterization of their performance, reliability, and integrity. We describe optoelectronic techniques for measuring, with submicrometer accuracy, shape and changes in states of deformation of MEMS accelerometers used in transportation applications. Using the display and data modes of the described optoelectronic techniques, it is possible to characterize MEMS. This characterization is performed during static and dynamic modes of operation of MEMS. To assure high accuracy of measurements, overlapping regions, i.e., tiles, of MEMS are analyzed and the data (tiles) are patched together to represent the entire component. Preliminary results indicate that the MEMS accelerometer considered in this study deforms 1.48 μm, under the loading conditions used, which represents nearly 50% of its functional dimension in the direction of deformation.

We describe an interference microscope for valve cone angle, roundness, straightness, and waviness using scanning white light interferometry. Our unusual test geometry creates a spherical optical measurement surface centered at an optical datum point that represents the center of curvature of the mating valve needle or ball. A radial scan locates intersections of the measurement surface with respect to the datum point, and software reconstructs the conical sample surface by means of a calibrated mapping function. This flexible approach accommodates a wide range of cone angles and diameters without a change of optics. Experimental results show promising performance, including a 0.02-μm standard deviation for cone roundness, including sample removal and replacement.

Optical metrology has been widely used in quality inspection. However, the sensor setup during part inspection is often done in an ad hoc way. This leads to unnecessarily high signal dynamic range. Consequently, optical sensors do not have sufficient light dynamic range capabilities especially for shiny surface measurement. We present a computational approach for optimal sensor setup that takes into account the sensor/part interaction to decrease signal dynamic range and to increase model coverage for structured light or similar optical inspection systems. First, we transform the signal dynamic range issue into a distance problem in a spherical map. We then present novel algorithms on the spherical map to search a near-optimal sensor orientation. Based on this near-optimal orientation, we use a gradient method to obtain the free-optimal solution that gives the lowest possible dynamic range. Experimental results demonstrated that under the optimal orientation, there is lower signal dynamic range and better model coverage. Future work on extending this method to multiple sensor planning, sensor design, and stage design for large part inspection is also discussed.

The authors propose a new high-speed and accurate phase analysis and subsequent phase unwrapping method for grating projection surface profilometry. In the proposed method, a special grating pattern is used for the projection. The light intensity distribution of this grating pattern has a form of a frequency modulated sinusoidal wave. In this grating pattern, two different phase distributions are included. The frequency modulated grating, which can be generated with an LCD projector or a film projector easily, is projected onto an object. Then, nine frames with phase stepping at a regular interval for a cycle are taken by a CCD camera. From these nine pictures, the two wrapped phase distributions are analyzed simultaneously. Then, using these phase distributions, phase unwrapping is carried out at each pixel independently. The 3-D profile of the object can be reconstructed using the absolute phase distribution. Since this method is suitable for high-speed shape measurement, applications to various inspections and 3-D surface digitizing are expected.

Principles and new developments of 3-D electronic speckle pattern interferometry (3-D ESPI) for strain and stress analysis are presented. The potentials and limitations are discussed, and some applications used in industry are shown. The newly developed 3-D ESPI technique allows rapid measurement of both the shape and the 3-D deformation of complex industrial components. The combination of shape and deformation provides all the necessary data for the accurate and quantitative determination of true strain and thus stress on nearly any industrial component. Based on a lightweight compact sensor design and new glass fiber concepts, the new device has been greatly miniaturized and can be easily attached to the components during testing. It is well suited for the harsh environmental conditions often found in the real test world.

Measurement of shape and deformation of diffusely reflecting surfaces by phase-shifting digital holography is presented that uses an imaging setup. The difference of the reconstructed phases before and after tilt of the object illumination beam provides the contour lines of the surface height, while before and after object deformation delivers those of object displacement. This method enables measurements of both the surface shape and deformation of 3-D objects of various sizes with the same optical system and processing software. Suppression of speckle noise is also discussed. Although the setup is the same as electronic speckle pattern interferometry with a phase-shifted reference beam, the present method is more flexible because phase information can also be used for numerical reconstruction of the defocused region of a 3-D object.

Two recent efforts addressing the automated noncontact inspection of both small and large parts is discussed. Also included is a discussion of some of the processes developed to assist in data collection and analysis—uncertainty of implied surfaces, row and row-column filtering for removing edge noise, classification of edges, convolution and Sobel filters for edge detection, and data collection considerations for large point clouds.

We present the results of the analysis and experimental study of defect detection using whole field laser Doppler vibrometry (WFLDV). The nondestructive inspection (NDI) procedure is based on the vibrational mode evaluation for a test object with specified defect parameters. To evaluate the procedure, a clamped aluminum drum with radius R was selected as the test object. The introduced defect was a thickness loss of 2.5, 5.0, and 7.5% at the central part of the drum. The data from computational examination, based on finite element analysis, are compared with experimental data received from tests with LDV. Additionally, we present data from interrogation of a multilayer (carbon composite) element with present defects in a specific layer and examples of corrosion detection. The experiments show that the technique enables reliable defect detection, location, and quantification.

The use of Fourier transforms to delineate displacement information between a pair of shifted random speckle patterns is exploited for applications to the fields of micro/nanotechnology and biomechanics. Examples include crack tip deformation, differential thermal strain distribution in electronic packaging, mechanical properties of MEMS material, and epicardium deformation of globally and regionally ischemic hearts.

The response of wide, thin, center-notched, 2024-T3 aluminum panels undergoing far-field tensile load is investigated. Three panels with a notch length to panel width of 0.33 and widths of 305, 610, and 1016 mm were subjected to far-field tensile loading. As part of the experimental program, two pairs of cameras were configured into separate stereovision systems and used to simultaneously capture both the global response of the sheet and the local response near a notch tip. Global areas, ranging in size from 250×250 mm to 550×550 mm, were imaged for each panel. A second stereovison system recorded images of a small area, 10×20 mm, ahead of one notch tip. Postprocessing of the stereovision measurement data from global and local systems using three-dimensional digital image correlation was used to obtain the complete displacement field at each point in the region of interest. In general, results demonstrate that the combination of stereovision and three-dimensional digital image correlation is capable of accurately measuring true, three-dimensional structural deformations in regions undergoing both large out-of-plane displacements and large displacement gradients. Furthermore, 3-D measurements on the panel specimen near the grip location are shown to provide an independent assessment of the true boundary conditions, with specimen slippage clearly noted in the 1016-mm specimen. Results from the extensive notched, wide panel experimental program demonstrate that (a) each panel has an initial shape that deviates up to 3 mm from planarity, with the greatest deviations occurring at the center of the notch, (b) the global load-displacement response is essentially linear for load levels that are well beyond the onset of large, out-of-plane displacements in the notch region, and (c) increasing the size of the notched, thin panel specimen results in distinctly different surface deformations and deformed shapes, with three separate maxima/minima in the out-of-plane component of the largest panel. The region where tensile opening strains are above 2% extends several millimeters ahead of the hole, while compressive strains parallel to the notch direction are contained within a few millimeters of the hole. The in-plane shear strains are concentrated along circular lobes at ∓45 deg from the horizontal direction, a trend which is generally consistent with plane stress conditions.

Finite element analyses, for comparison with the experimental measurements, were performed for each panel described in Part I. Results indicate that (a) for the 305- and 610-mm panels, the finite element predictions and global experimental measurements for two of the displacement components, U(x, y, 0.80 mm) and W(x, y, 0.80 mm), are in good agreement throughout the panel, (b) for the 305- and 610-mm panels, the finite element predictions for the vertical displacement field V(x, y, 0.80 mm) are ~5% lower than the measurements throughout the panel, (c) for the 1016-mm panel, the finite element predictions did not match the experimental measurements due to the specimen slipping in the grip fixtures, as shown in the full-field measurements, resulting in significant changes in the measured panel deformations, and (d) for all three panels, the local finite element predictions for the in-plane strain components, ∈_xx, ∈_xy, and ∈_yy, including the overall trends in both the size and shape of the large strain regions, are in quantitative agreement with experimental results. In summary, results indicate that an appropriate finite element method, capable of predicting the deformations observed in the structures to be modeled, will be effective in modeling the overall behavior of wide, flawed panels up to the onset of flaw growth. Furthermore, the combination of finite element analysis and three-dimensional measurements for accurate prediction of displacement boundary conditions is shown to be a viable hybrid approach for predicting flawed panel response.

The present study provides an illustration of the use of holographic moiré interferometry in the mechanical evaluation of finger-jointed wood assemblies. Finger joints are critical strength-determining elements in glued laminated structural timber, and are finding an increasing use in construction and transportation industries. These joints are a source of potential structural weakness, and hence it is of utmost importance to test the functioning quality of these joints. The finger-jointed timbers are tested to failure. The key advantage of holographic moiré interferometry resides in its ability to display the real phenomena along with their degree of relative importance.

The application of genetic algorithms for quantitative characterization of a single delamination in composite laminated panels is discussed. The damage identification procedure is formulated as an input-output inverse problem through which system parameters are identified. The input of the inverse problem, the normalized central moments (NCM), is calculated from the surface displacements of a finite element (FE) representation of a delaminated panel in a vacuum chamber. The output parameters, the planar location, diameter, and depth of the flaw, are the solution to the inverse problem to characterize the idealized circular debonding crack. The inverse problem is solved as an optimization procedure. The objective function of the optimization algorithm is defined as the squared difference of the NCM obtained from a FE model with an actual delamination and from a FE model with a trial debonding. The optimum crack parameters are found by minimizing the objective function through the use of a novel implementation of real-coded adaptive range genetic algorithms. Numerical examples are presented to show the effectiveness of the proposed identification procedure.

Active thermography has gained broad acceptance as a nondestructive evaluation method for numerous in-service and manufacturing applications in the aerospace industry. However, because of the diffusive nature of the process, it is subject to blurring and degradation of the signal as one attempts to image deeper subsurface features. Despite this constraint, active thermographic response is deterministic, to the extent that the postexcitation time evolution for a defect-free sample can be accurately predicted using a simple one-dimensional model. In the patented thermal signal reconstruction method, the time history of every pixel in the field of view is compared to such a model in the logarithmic domain, where deviations from ideal behavior are readily identifiable. The process separates temporal and spatial nonuniformity noise components in the image sequence and significantly reduces temporal noise. Time-derivative images derived from the reconstructed data allow detection of subsurface defects at earlier times in the sequence than conventional contrast images, significantly reducing undesirable blurring effects and facilitating detection of low-thermal-contrast features that may not be detectable in the original data sequence.

We review an optical method referred to as 3-D computer vision technique for nondestructive inspection of three-dimensional objects whose surfaces are specularly reflective. In the setup, a computer-generated cosinusoidal fringe pattern in the form of linear, parallel fringe lines of equal spacing is displayed on a TV monitor. The monitor is placed in front of the test object, whose specularly reflective surface behaves as a mirror. A virtual image (or mirror image) of the fringe lines is thus formed. For a planar surface, the fringe pattern of the image is undistorted. The fringe lines, however, are distorted according to the slope distribution if the surface is not flat. By digitizing the distorted fringe lines, employing a phase-shift technique, the fringe phase distribution is determined, hence enabling subsequent determination of the surface slope distribution. When applied to nondestructive flaw detection, two separate recordings of the virtual image of the fringe lines are made, one before and another after an incremental load is applied on the test object. The difference of the two phase-fringe distributions, or the phase change, represents the change in surface slope of the object due to the deformation. As a subsurface flaw also affects surface deformation, both surface and subsurface flaws are thus revealed from anomalies in the surface slope change. The method is simple, robust, and applicable in industrial environments.

We provide a description of four optical systems for metrology using an electronic image processor for generation and display of interferograms. An example is provided of electronic holography on an automobile brake rotor.

In the field of structural testing, optical techniques have already been successfully applied for the determination of the dynamic structure response. Recently electronic speckle pattern interferometry (ESPI) systems using pulsed lasers are increasingly used to replace conventional double pulse holography interferometers. ESPI takes over not only the main benefits of holography toward conventional measuring techniques, such as full-field, noncontact measurement and sensitivity, but also uses modern camera and computer techniques for image capturing and processing. The capabilities of pulsed ESPI have already been further extended to 3-D measurements of the dynamic response and modal analysis of vibrations. An important area of application has already been demonstrated in the field of brake disks analysis, where pulsed ESPI systems provide complete maps of the vibration of any component of brakes during testing (brake disks, drums, calipers, and pads). Using the 3-D technique, completely automatic brake squeal inspection systems have been designed, which capture the squealing signal, automatically set and fire the laser, and provide a complete full-field deformation map of the component under test. We describe recent developments of the 3-D ESPI technique using pulsed lasers, and give examples of applications in the fields of dynamic structure response, with an emphasis in the field of brake squeal analysis. The application for the determination of the complex amplitude of vibration is demonstrated, which opens further potential into the field of operational deflection measurement and modal analysis. Conventional techniques using accelerometers and vibrometers have a very high temporal resolution and therefore are predestined to measure the frequency response of the vibrating object. ESPI overcomes this feature with very high spatial resolution, allowing a full-field measurement also for transient events.

Noise, vibration, and harshness (NVH) can be predominate brake noise described as roughness/judder, brake creep groan, and brake squeal, all of which are important issues and concerns for customer satisfaction in the automotive industry. Brake roughness and groan are low-frequency vibration and noise, while brake squeal is a high-frequency noise. These have been the challenging issues for engineers and researchers for many years due to their complex nature that involves multiple disciplines such as nonlinear dynamics, contact mechanics, and tribology or nanotribology. As in the body/chassis and power-train arena, laser metrology can be uniquely applied in brake NVH to shed light on this complex issue. Engineers can gain insight on NVH fundamental root causes and provide guidance for optimal design resolution. We provide some examples that illustrate the recent progress and novel applications of holographic interferometry, pulsed laser holographic interferometry, pulsed laser electronic speckle pattern interferometry, and laser Doppler vibrometry methodology to identify the root causes of brake concerns and verify engineering solutions.

A five-wavelength hybrid dense-wavelength-division-multiplexing (DWDM) system with four OC-192 (10 Gbit/s) channels and one CATV channel was built and demonstrated for digital and video trunking application. A low bit error rate (BER), <10^–9, was achieved for the four OC-192 digital channels, and good performance with respect to carrier-to-noise ratio (CNR) ≥ 50 dB, composite second order (CSO) ≥ 65 dB, and composite triple beat (CTB) ≥ 65 dB were obtained for the CATV channel over a 100-km large-effective-area fiberlink. A high trunk data rate of 40 Gbit/s was provided with good CATV performance.

Interband wavelet correlation provides one approach to defining edges in an image. Interband wavelet products follow long-tailed density distributions, and in such a context thresholding is very difficult. We show how segmentation using a Markov-field spatial dependence model is a more appropriate approach to demarcating edge and nonedge regions. A key part of this work is quantitative assessment of goodness of edge versus nonedge fit. We introduce a formal assessment framework based on Bayes factors. A detailed example is used to illustrate these results.

We present the results of a theoretical numerical analysis of transmission characteristics of a fiber optic refractometric transducer with a hemispherical glass detection element. In this transducer, the internal reflection of light from the element's spherical surface depends on the refractive index of the surrounding medium. We examine the effects of the transducer's geometrical and optical parameters and its refractive index on the transmission function, its nonlinearity, and the transducer's sensitivity to the refractive index of the surrounding medium. We show that through a proper choice of the transducer's material and geometrical parameters, it is possible to obtain a transmission function of any necessary span over a wide interval of the refractive index of the surrounding medium (from n = 1.0 to 1.7), and to modify the form of the transmission function from a linear one to a steplike one in virtually the same device. This permits us to use the proposed transducer for two contrasting applications: assessing the refractive index, and discriminating between two liquids or between air and a liquid, as in the detection of liquids, level measurement, etc. In addition, it is possible to adjust the transducer input range to the refractive index of a particular fluid (or fluids) of interest.

We present an experimental study on the photopolymer poly(methyl methacrylate) doped with phenathrenequinone molecules. Material characteristics for holographic data storage, including optical characteristics, scattering effect, relation between diffraction efficiency and number of holograms, and exposure schedule for multiple storage, are investigated. An experimental demonstration of multiple storage of digital data pages in a polymer cube is presented.

This paper presents a new image coding algorithm for scalable and robust image transmission. The algorithm, termed block-based layered set partitioning in hierarchical tree (B-LSPIHT), has both SNR and resolution scalabilities, and its performance is resilient to transmission errors. In the algorithm, the number of layers and the rate and resolution associated with each layer can be specified before encoding. Starting from the base layer, B-LSPIHT encodes one layer at a time until the design of the top layer is completed. The transmission errors are localized using a block-based method. The bits allocated to each block are determined by a dynamic programming technique based on the rate-distortion function computed from the channel models. Numerical results show that the B-LSPIHT algorithm is effective for constructing layered image transmission systems over noisy channels.

This research is focused on the study of local-type image registration techniques, which concern pixel mapping between two correlated images with both global and local deformations. Our algorithm is object-contour-based, meaning that control points that conduct the transformation are adaptively selected from the matched contour points. It is novel in two important respects. First, we propose to match object contours in the source and target images by using locally-maximal-curvature points and curve projection. Second, the selection of control points is capable of adapting to both global and local deformations, normally being denser in contour segments with substantial local deformations. The proposed scheme is also hybrid in the sense that local contour matching and global surface-spline fitting of control points are combined. Simulations and some comparisons are made by using infrared thermographs and ordinary gray images. Experiments show better registration accuracy of object contours than with traditional methods such as elastic or curvature scale space matching.

A universal digital laser microinterferometer is presented, which can measure the shape, displacement, and strain and stress of microelements and microelectromechanical systems (MEMSs). This device can measure microelements with either a smooth or a rough surface. The method is based on laser interferometry (for smooth surfaces) and laser speckle interferometry (for rough surfaces), incorporating a diode laser, a long-distance microscope, a CCD camera, and a high-precision phase-shifting technique. The measuring system can be utilized to measure shape and out-of-plane displacement for samples with smooth surfaces, and with minor modification it can be applied to investigate out-of-plane and in-plane displacements for samples with rough surfaces. The theory and methodology of the universal digital laser microinterferometer are described. In particular, calibration and error compensation are introduced. The usefulness of the microinterferometer is demonstrated by examples of shape and displacement measurement for different MEMSs and microelements.

We give an up-to-date description of some present development issues, together with an architecture study and a systems engineering analysis, in the area of laser sources for the injection of the Laser Méga-Joule (LMJ), which are a part of the French ICF fusion program. After a brief description of the main concepts, the overview consists of two parts. The first one includes the standard first source (all-fiber design) that will be used for the activation of the facility of Ligne d'Intégration Laser (LIL), the reduced-scale demonstrator under construction for the validation of the concepts and technology to be selected for the LMJ. The second one describes the state of the art in the prototyping of a new source, with extended performance with respect to optical noise and robustness, to be tested on LIL in a second step of the activation.

Based on a graded-refractive-index lens model, the effects of thermal lensing on the overlap integrals, diffraction loss, pump threshold, and laser efficiency of the TEM₀₀ mode for uniformly pumped solid-state lasers with a flat-flat symmetrical cavity are analyzed. Unlike the end-pumped system, the overlap integral V_th related to the threshold pump power will not change with pump power, due to the uniform pumping. We link the thermal lensing with the laser output power. A dramatic increase of the laser mode radius at the crystal caused by the thermal lensing reduces the Fresnel number and raises the diffraction loss so that the laser output power drops at one value of the pump power.

The transmission characteristics of phase-shifted long-period gratings (LPGs) are simulated theoretically using coupled-mode theory and the fundamental-matrix method. A phase-shifted LPG device cascaded with another uniform LPG can be used to flatten the gain spectrum of an erbium-doped fiber amplifier (EDFA) with three gain peaks. The results of all simulations have shown that a broadband amplifier with a 0.7-dB peak-to-peak gain variation over 36 nm can be realized practically. Using our designed and fabricated device, the experimental results show that the 3-dB bandwidth of the flattened EDFA is increased from 18 to 46 nm for an unequalized spectrum. The gain ripple over that bandwidth is reduced to approximately 0.9 dB. The improvement by a factor of 2 to 3 is realized in the sprectral performance. Such a gain-flattening fiber filter is indeed plausible and has a practical application in dense wavelength-division multiplexed (DWDM) telecommunication systems.

Contactless embossing of microlenses (CEM) is a well-known fabrication method for refractive microlenses. By applying pressure and heat, a thermoplastic material expands into circular holes of a hot embossing tool. Compared to normal hot embossing, the holes for forming the latter microlenses are so deep that the lens surface is never in contact with the embossing tool itself. Surface tension caused by the applied pressure to the outside lens region is the basic mechanism that forms spherical microlenses. Recently published results describe the f-number of such lenses to be always larger than two for microlenses with diameters below 300 μm. In our approach we newly adapted temperature parameters and additionally applied vacuum during the hot embossing process, which yielded microlenses in, e.g., polymethyl methacrylate (PMMA) with f-numbers as small as 1.2 even for large diameters around 1.5 mm.

This study investigates the delamination of polymeric coatings from glass fibers in double-coated optical fibers, induced by long-term thermal interfacial shear stress. The shear stress between the fiber and the primary coating should always be lower than the interfacial shear strength to prevent delamination. It can be minimized by properly selecting the physical properties of the coatings as follows: The thickness and Young's modulus of the secondary coating can be decreased so long as the requirement for the strength of the secondary coating is satisfied. The thickness of the primary coating can be increased if the spring constant of the optical fiber is chosen to prevent microbending of the glass fiber at low temperature. Meanwhile, Poisson's ratio of the primary coating is set very close to 0.5. The Young's modulus and the relaxation time of the primary coating, and the thermal expansion coefficient and the relaxation time of the secondary coating, should all be minimized.

We have studied, assembled, and tested several different types of phase-modulated optical polarimeters capable of transient stress and molecular orientation angle measurements in complex optically anisotropic fluids and materials. The main difference in the instrumentation lies in the applied modulation technique. Three different phase modulation techniques are studied in this paper: the photoelastic effect, the transverse electro-optic effect, and liquid-crystal variable retardation modulation schemes. The precise measurement of a material's retardance and average molecular orientation angle depends on an accurate alignment and calibration within the range of the chosen modulator. Therefore, we address some of the issues associated with the choice of phase modulator as well as applicable alignment and calibration techniques. We also study and test several methods that may be used to ameliorate these issues.

When water is removed from the paper during paper making, a dimensional change occurs in which the paper shrinks in the direction perpendicular to the direction of processing. The dimensional changes vary across the web and influence, e.g., the surface and compression properties of the paper; they also complicate the control of the paper machine. In this article, a robust method for estimating the relative shrinkage profile is presented. The method is based on a one-dimensional recording of the imprints from the forming fabric, using a fluorescence technique. The recording is transformed into a time-frequency spectrum, on which three different frequency estimators have been evaluated. In simulations on synthetic data and measurements on paper profiles the estimator that maximizes the correlation energy showed the most robust and accurate performance of the methods evaluated, even at a low signal-to-noise ratio.

We report a photoacoustic (PA) study of the thermal and transport properties of a GaAs epitaxial layer doped with Si at varying doping concentration, grown on GaAs substrate by molecular beam epitaxy. The data are analyzed on the basis of Rosencwaig and Gersho's theory of the PA effect. The amplitude of the PA signal gives information about various heat generation mechanisms in semiconductors. The experimental data obtained from the measurement of the PA signal as a function of modulation frequency in a heat transmission configuration were fitted with the phase of PA signal obtained from the theoretical model evaluated by considering four parameters—viz., thermal diffusivity, diffusion coefficient, nonradiative recombination time, and surface recombination velocity—as adjustable parameters. It is seen from the analysis that the photoacoustic technique is sensitive to the changes in the surface states depend on the doping concentration. The study demonstrates the effectiveness of the photoacoustic technique as a noninvasive and nondestructive method to measure and evaluate the thermal and transport properties of epitaxial layers.

We have developed and applied a spatiotemporal fusion framework that uses different fusion strategies across time frames (temporal fusion) as well as between sensors (spatial fusion). We have developed, at the feature level, new and different fusion strategies (additive and minmax fusion) in addition to the traditional strategies (multiplicative, min, and max fusion). These different fusion strategies are compared and predicted by their receiver operating characteristics performance in the likelihood-reading domain. Furthermore, by applying the additive fusion strategy, we have developed methods for adaptive sensor weighting using reliability functions to improve fusion performance. Our simulated test and analysis results show that temporal fusion (as well as spatial fusion) can considerably improve target classification, and also show that the adaptive sensor weighting using reliability functions can significantly improve fusion performance when one sensor is much more reliable than the other. Finally, we propose an optimal integrated spatiotemporal multiple sensor fusion system that includes two new processors: the adaptive processor and the fusion selection processor.

Range sensors capable of continuous free motion during surface-geometry measurement have limited access to complex surfaces or must operate in a restricted environment. This is due to the use of secondary sensors to track the range-sensor head. Other free-motion sensors require a complex range-data acquisition process. This paper presents a method of measuring surface geometry by a laser-camera range-sensor head that is permitted continuous unconstrained motion in six degrees of freedom, without requiring measurement of the sensor-head position and orientation by additional sensors. Numerous range views, each containing several profiles captured in a single camera image, are acquired with little motion between viewpoints. This form of range data provides sufficient information at each laser-camera viewpoint, to generate overlap for registration of successive views while minimizing redundant data. Transformations between pairs of adjacent views are computed using a transformation-parameter optimization to minimize the distance between view surfaces. Global registration of all views is carried out by sequentially applying the local transformations. In simulations of the range-sensing method using noiseless and noisy range views, global registration of an open 49-view sequence yielded mean absolute global registration errors that are acceptable for many surface-modeling applications. The method is applicable when the range-sensor head and object have independent continuous unknown motion.

We establish the importance of correlation between successive scenes in dissolve detection and propose a new adaptive dissolve detection method based on the analysis of a dissolve modeling error, which is the difference between an ideally modeled dissolve curve with no correlation and an actual dissolve curve including correlation. The proposed method consists of two steps. First, candidate dissolve regions are extracted using the characteristics of a downward-convex parabola; then each candidate region is checked using the dissolve modeling error. If the dissolve modeling error for a candidate region is less than a threshold equal to the dissolve modeling error with a target correlation, the candidate region is identified as a dissolve region with a lower correlation than the target correlation. The threshold is determined adaptively from the variance at the start and end of the candidate region and the given target correlation. By considering the correlation between successive scenes, the proposed method is able to function as a semantic scene-change detector. The proposed algorithm was tested on various types of data, and its performance proved to be more accurate and reliable than that of other, commonly used methods.