311 research outputs found
Bondability of processed glass wafers
No full textThe mechanism of direct bonding at room temperature has been attributed to the short range inter-molecular and inter-atomic attraction forces, such as Van der Waals forces. Consequently, the wafer surface smoothness becomes one of the most critical parameters in this process. High surface roughness will result in small real area of contact, and therefore yield voids in the bonding interface. Usually, the root mean square roughness (RMS) or the mean roughness (Ra) are used as parameters to evaluate the wafer bondability. It was found from experience that for a bondable wafer surface the mean roughness must be in the subnanometer range, preferentially less than 0.5 nm. When the surface roughness exceeds a critical value, the wafers will not bond at all. However RMS and Ra were found to be not sufficient for evaluating the wafer bondability. Hence one tried to relate wafer bonding to the spatial spectrum of the wafer surface profile and indeed some empirical relations that have been found. The first, who proposed a theory on the problem of the closing gaps between contacted wafers was Stengl. This gap-closing theory was then further developed by Tong and Gosele. The elastomechanics theory was used to study the balance between the decrease of surface energy due to the bonding and the increase of elastic energy due to the distortion of the wafer. They considered the worst case by assuming that both wafers have a waviness, with a wavelength (lambda) and a height amplitude h, resulting in a gap height of 2h in a head to head position. This theory is simple and can be used in practice, for studying the formation of the voids, or for constructing design rules for the bonding of deliberately structured wafers. But it is insufficient to know what is the real area of contact in the wafer interface after contact at room temperature because the wafer surface always possesses a random distribution of the surface topography. Therefore Gui developed a continuous model on the influence of the surface roughness to wafer bonding, that is based on a statistical surface roughness model Pandraud demonstrated experimentally that direct bonding between processed glass wafers is possible. This result cannot be explained by considering the RMS value of the surfaces only, because the wafers used show a RMS value larger than 1 nm. Based on the approach exposed in reference six, a rigorous analysis of wafer bonding of these processed glass wafers is presented. We will discuss the relation between the bonding process and different waveguide technologies used for implementing optical waveguides into one or both glass wafers, and give examples of optical devices benefiting from such a bonding process
Interferometrical characterization of stress birefringence in germanium
No full textWe report on the characterisation of the refractive index homogeneity in large blanks of Czochralski-grown Germanium, for thermal imaging use. With a phase-measuring Twyman-Green interferometer working at 10.6 mu m, a map of the index of refraction with an accuracy better than 1 10(-5) can be obtained for blanks which do not exhibit high birefringence. Tn the other case, principal stresses in the disks can be determined through the effect of birefringence on the interferogram, if the stresses are distributed cylinder-symmetrically in the plane of the disk. Relations between stresses, transmittance, and electrical resistivity of the material are observed
Research project work plan for investigation of bicycle and pedestrian continuous and short duration count technologies in Oregon
No full textWhile motorized traffic counts are systematic and comprehensive, bicycle and pedestrian counts are often unknown or inaccurate. This research presents recommendations to increase bicycle and pedestrian count accuracy while integrating bicycle and pedestrian counting with existing ODOT traffic counting. Three bicycle counting technologies - pneumatic tubes, inductive loops and thermal cameras - were tested in a controlled environment as well as mixed traffic condition. Test results indicate that all bicycle counting technologies are adequate to count bicycles under controlled, favorable conditions. However, in mixed traffic conditions only the pneumatic tubes were able to count bicycles with less than 20% error. Bicycle counts in mixed traffic conditions with pneumatic tubes are more accurate when bicycle-specific vehicle classification schemes are used and when counting bicycle traffic within 10 feet tube length of the counting device. Two pedestrian counting technologies - passive infrared and pedestrian phase actuations - were tested and attained satisfactory results.by Krista Nordback, Sirisha Kothuri, Miguel Figliozzi, Taylor Phillips, Carson Gorecki, Andrew Schrope, Portland State University for Oregon Department of Transportation, Research Section and Federal Highway Administration.Covers OCLC #1149151589, OCLC #1341404407Title from PDF title page (viewed on August 19, 2022)."FHWA-OR-RD-16-15"--Technical report documentation page.This archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Sponsored by Oregon Department of Transportation, Research Section; Federal Highway Administration SPR 772Mode of access: Internet from the Oregon Government Publications Collection.Text in English
Software tool for developing algorithms for surface inspection systems
No full textIn this paper we present a software tool by which the image processing and defect classification parts of an inspection system can more easily be designed and tested. The user interface of the tool has been programmed using Microsoft Visual Basic to which the C coded development software has been liked as Windows DLL-libraries. At the moment, a texture analysis method based on sum and difference histograms has been implemented as a basic segmentation method, but the addition of other algorithms is quite straight-forward. In addition to texture analysis, the tool includes a set of classification functions for automatic generation of nearest neighbor and decision tree classifiers. Starting from raw image data, generation of an executable decision tree classifier is possible without writing a line of code. The generation of the decision tree classifiers is based on IFD3, which is an extended version of Quinlan's ID3 algorithm. In this extended version, more advanced features of the induction of fuzzy and hybrid decision trees have been introduced
Imaging spectrometer for process industry applications
No full textThis paper presents an imaging spectrometer principle based on a novel prism-grating-prism (PGP) element as the dispersive component and advanced camera solutions for on-line applications. The PGP element uses a volume type holographic plane transmission grating made of dichromated gelatin (DCG). Currently, spectrographs have been realized for the 400-1050 nm region but the applicable spectral region of the PGP is 380-1800 nm. Spectral resolution is typically between 1.5 and 5 nm. The on-axis optical configuration and simple rugged tubular optomechanical construction of the spectrograph provide a good image quality and resistance to harsh environmental conditions. Spectrograph optics are designed to be interfaced to any standard CCD camera. Special camera structures and operating modes can be used for applications requiring on-line data interpretation and process control
Composants micro-optiques popur systèmes miniatures d'imagerie à base de technologie MEMS
No full textLa miniaturisation des systèmes d'imagerie présente aujourd'hui un fort potentiel dans plusieurs domaines, dont le développement de nouveaux dispositifs biomédicaux. Les exigences associées concernant l'imagerie demandent un effort substantiel dans le développement de composants optiques de haute qualité. Un meilleur contrôle de la propagation de la lumière ou de ses caractéristiques dans de tels systèmes est également important. Les composants doivent donc, par exemple, contenir les aberrations optiques pouvant affecter la résolution, la mise en œuvre de composants optiques dont le profil de phase continu est bien contrôlé est une voie intéressante. Ces composants devraient, de plus, être réalisés à partir de matériaux robustes en vue de leur assemblage au sein de dispositifs miniatures. Ce manuscrit de thèse de doctorat porte donc sur la conception et la fabrication parallèle de tels micro-composants optiques réfractifs réalisés en verre. Dans ce but, deux technologies ont été étudiées et optimisées, la lithographie à niveaux de gris et un procédé de soufflage de verre. En exemple, des microaxicons en verre ont été fabriqués et la génération de faisceaux de Bessel démontrée. Ce type de faisceau est caractérisé par une longue distance de propagation non-diffractive le long de l'axe optique, suivie d'une forme de faisceaux creux, qui les rend très utiles dans de nombreux domaines. Ces travaux de thèse ont été soutenus par le projet SMYLE (Small Systems for a Better Life) et le conseil Régional de Franche-Comté.Miniaturization of imaging systems shows nowadays a strong potential for many applications, in particular, e. g., for novel biomedical devices. Related imaging specifications require a substantial effort onto the development of high quality microoptical components. better control of light propagation and features in such system sis also of particular interest. Components should then e.g. contain optical aberrations in order to reach high resolutions. In purpose of searching higher diffraction efficiencies or resolutions, optical components with well-controlled continuous phase profiles are sought. In addition, they also should be made of robust materials to handle their further assembly into miniaturized devices. Consequently, the manuscript focuses on the design and the parallel fabrication of such microoptical components made of glass. To that end, two technologies have been studied and optimized, namely gray-scale lithography and glass-blowing processes. As an example, glass-based microaxicons have been fabricated and Bessel beams generation has been demonstrated. This type of beam exhibits a long non-diffractive propagation distance along the optical axis followed by a dark hollow shape which makes them useful in many different applications. This work has been supported by the SMYLE (Smart Systems for a Better Life) European project and the Ranche-Comté Regional Council
Etude et réalisation d'un magnétomètre isotrope miniature à pompage optique de l'hélium -4
No full textPas de résumé disponibleNo abstract available
Sub-kHz traceable characterization of stroboscopic scanning white light interferometer
No full textScanning white light interferometry (SWLI) is an established methodology for non-destructive testing of MEMS/NEMS. In contrast to monochromatic interference microcopy SWLI can unambiguously resolve surfaces featuring tall vertical steps. Oscillating samples can be imaged using a stroboscopic SWLI (SSWLI) equipped with a pulsed light source. To measure static samples the lateral and vertical scales of the SSWLI can be calibrated using transfer standards with calibrated dimensions such as line scales, 2D gratings, gauge blocks, and step height standards. However, traceable dynamic characterization of SSWLI requires a transfer standard (TS) providing repeatable traceable periodic movement. A TS based on a piezo-scanned flexure guided stage with capacitive feedback was designed and manufactured. The trajectories of the stage motion for different amplitude and frequency settings were characterized to have 2 nm standard uncertainty. Characterization was made using a symmetric differential heterodyne laser interferometer (SDHLI). The TS was first used to characterize quasidynamic measurements across the vertical range of the SSWLI, 100 μm. Dynamic measurement properties of the SSWLI were then characterized using a sinusoidal vertical trajectory with 2 μm nominal amplitude and 50 Hz frequency. The motion amplitude of the TS, 2038 nm, measured with the SSWLI was 6 nm smaller than the amplitude measured with SDHLI. The repeatability of SSWLI expressed as experimental standard deviation of the mean was 8.8 nm. The maximum deviation in instantaneous displacement and oscillation velocity were 49 nm and 27 μm/s, respectively. A traceable method to characterize the capacity of the SSWLI to perform dynamic measurements at sub-kHz frequencies was demonstrated.</p
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