Advance optoelectronic packaging is dependent on the fundamental understanding of the constituent materials behavior during manufacturing and thermal cycling. Such understanding will allow increasing yield and performance of the optoelectronic packages while decreasing their cost. The combination of issues such as dimensional stability, thermal management, electrical connections, and optical access are not yet well understood.
Dimensional stability of the generic optoelectronic package was studied by the in-plane moire interferometry. Using digital image analysis enhanced data processing one can get the in-plane displacement resolution of 20 nm. The 1200 l/mm grating was transferred on the test vehicle surface before it was subjected to the thermal cycling. The effect of the temperature cycling on the test vehicle integrity was analyzed by studying the relative deformation of the components. It was found that ten cycles in the range of 0° C - 100° C resulted in permanent strain of 400 μstrains at the corner of the brass post and the quartz plate. Thus, the obtained results suggest that during thermal cycling there was an irreversible deformation or slip at the corner of the brass post on the boundary with the quartz plate.
The presented here methodology may be used for analysis of the various adhesives under cyclic thermal loading. The obtained data will be very useful for the design of the optoelectronic package, since it will allow for prediction of the possible misalignment and may be used for the reliability studies of the optoelectronic packages.
A whole-field polarimetric method through digital image processing has been developed for mapping the three optical parameters, which determine normalized Jones matrix of an elliptic retarder. The suggested technique conveys measurement data sufficient to describe optical anisotropy in the media exhibiting rotation of birefringence axes along the light path. Particularly, homogeneous or inhomogeneous birefringent gyrotropic objects and initially isotropic transparent samples bearing stress-induced anisotropy can be investigated by use of this technique. Operational principle of the method implies incremental rotation of polarizer and analyzer with the ratio 1:3 over the revolution of the polarizer and collection of 9 intensity images between successive rotation steps. Then thus obtained intensity patterns are digitally processed by use of Fourier analysis. Specifically in this paper we address issues concerning the accuracy of mapping all the three parameters at different values of those. Some ad hoc experiments with test crystalline quartz phase plates are reported. Computer simulations and measurement results are presented and discussed.
The advanced method for straightforward spectral signal processing in interferometric fiber-optic sensors is presented. It is based on the analysis of the output spectrum of sensing interferometer in the domain of Fourier images. The main idea of the proposed method is to use the sensing interferometer with finesse > 2 and process the higher harmonics in addition to the first one. The technique does not suffer from power and spectral fluctuations of LED and sufficiently noise resistant.It is insensitive to the influence of parasitic interferometers appearing in the optical connectors, multimode fibers and other parts of the instrument. Devices based on such principles does not recalibration after switching on and further operation. The optimization of sensor's parameters based on numerical simulations is presented switching on and further operation. The optimization of sensor's parameters based on numerical simulations is presented.
Fiber optic sensors (FOS) for vibration monitoring of smart structures have certain advantages over conventional strain gage based sensors due to electromagnetic environment insensitivity and high response bandwidth. During the present study, a spatially integrating fiber optic sensor was used for vibration monitoring. It is based on the concept that the optimal placement of the sensing element can be sought by using a priori knowledge of the mode shapes of the structure. The applicability of this approach to polarimetric optical fibers is described. The acquired integrating FOS signal was used to sense and control the vibration of an electrorheological adaptive structure subjected to a random external excitation.
Interferometric fiberoptic sensor (FOS) is immune from electromagnetic influence and provides a useful tool for vibration monitoring. In this paper, some problems associated with the vibration sensing for structures are analyzed. A phase drift model was developed and used to investigate the experimental phenomena occurring at the test. This simpler method was utilized to detect the exciting frequency without complicated signal demodulation. The obtained FOS was used to control the vibration of the structure subjected to a random external excitation.
The unilateral axially dynamic fixator (Orthofix) was mounted on a sheep tibial shaft. Three fixation modes: static, dynamic controlled, and dynamic free were examined by means of double exposure holographic interferometry. Simultaneously, the acceleration was measured by an accelerometer and displayed on the monitor together with loading characteristics. The first exposure was made before the acting force was applied to the tibia plateau. The second one after the moment when the acceleration wave started to propagate through the specimen. We stated that in the case of dynamization less torsion occurs at the fracture site. So far, we have not been able to determine any correlation between results of holographic and accelerometric measurements.
A new method (algorithm and computer implementation) has been developed to define the 3-D shape of a surface based on an analysis of the shadow moiré patterns of the object. The approach is based on a phase-shifting technique enhanced by the solution of a set of overdetermined nonlinear equations involving the light intensities acquired by means of the shadow moiré method. Such an approach allows the accuracy of the measurements to be improved by utilizing excess information. Because the method uses a conventional white-light source, it can be applied to measure the geometry of human faces and bodies as well as the out-of-plane surface deformation of a loaded structure. The theory of the algorithm is described, together with test results. The results obtained show that the described approach can resolve the shape of an object with an average error of less than 2%.
A high sensitivity strain measurement procedure that combines moire interferometry and digital image processing, has been successfully implemented to determine thermally induced strains in electronic components. The technique is called Fractional Fringe Moire Interferometry (FFMI). It produces whole field displacement information that are used to compute strains in a certain plane. Displacements in the submicron domain are detected with excellent spatial resolution over the area of interest. An example is presented here to illustrate the use of the technique to monitor thermally induced deformations in a specimen made from a plastic DIP device. The specimen was uniformly heated from room temperature to 90 degree(s)C, and the resulting moire fringe patterns were recorded, analyzed using digital-image-processing and in plane displacements in the package were determined. Strain components were then computed by simple differentiation of the acquired displacement fields. Contour maps showing actual thermo/mechanical strain components in the device were constructed. Those maps can provide an excellent tool for strain analysis of microelectronic devices regardless of the structural complexity of the device.
Recent increase in use of compact discs attracted more attention to the problem of the quality control. Since those discs are made form polycarbonate they may exhibit birefringence introduced during manufacturing process. Such birefringence changes the index of refraction of the polycarbonate, which in turn causes deviation of the reading laser ray from rectilinear path. Currently available devices utilize laser based systems for reading of residual birefringence during disc rotation. As a result, this process is time consuming and provides averaged through the circular track information.
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