Papers by Keyword: Interferometry

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Authors: J. Molimard, R. Cordero, A. Vautrin
Abstract: Optical Full Field Techniques (OFFT) are more and more utilized by mechanical laboratories. Among these methods, interferometry techniques (mainly composed of Speckle/Grating Interferometry or Speckle/Grating Shearography) are more difficult to use in a mechanical lab context, because of their sensitivity to external vibrations (except shearography), and because of the global lack of optical culture of mechanical engineers. Speckle-based methods are of great practical interest for the users, but their signal to noise ratio (SNR) is affected by the rigid body motion of the specimen. Here, the speckle decorrelation is minimized at local scale directly using the SNR. First, a shearography experiment is modeled to characterize the recorrelation procedure for a rigid body motion, a constant strain map and finally a high degree of localization. The mean noise level is found to be 6 times higher than a fully-correlated phase map for a 1 pixel speckle size. Last, a first application to a single-ply fabric composite lamina is shown. Resulting strain maps are of high quality with a very low spatial resolution (4 pixels). The local bending / global tension coupling effect is clearly put in evidence.
Authors: Alexander Höink, Karl Meiners-Hagen, Otto Jusko, Ahmed Abou-Zeid
Abstract: The experimental results for the determination of the form of thin cylinders (Ø ~ 2.5 mm) as well as step heights of gauge blocks (~ 100 µm) and roundness profiles of test samples from metal or glass with different diameters between ~ 2.5 mm and 80 mm using two multi-wavelength diode laser interferometers are presented and discussed.
Authors: Nan Zhao, Zhi Yuan Sun
Abstract: Interferometry is a very important method in high accuracy measurement for optical system. This article briefly introduced the conception of interferometry and took a product of 4D Technology as an example to carry on the measurement. A large-scale optic-electrical Theodolite in assemblage was measured, and its primary mirror was 400mm in diameter. With the analysis of the results, some micro adjustments of the mechanical structure proceed, and it made the system perform better. The final results of the whole system is 1.061λ in P-V value and 0.1136λ in RMS value (λ=632.8nm), this meets the demand of optical design and practical application. The result demonstrates that interferometry is a good way to be utilized and optimize in the procedure of assemble.
Authors: Torsten Mai, Guido Bartl, Arnold Nicolaus, Andreas Peter
Abstract: For the aimed redefinition of the SI-unit kilogram the international Avogadro group is to measure the amount of substance of a silicon sphere with a relative uncertainty of better than 2 x 10-8. Up to now 3.0 x 10-8 is reached, mainly caused by the 2.7 x 10-8 uncertainty of the volume determination. Which itself is essentially affected by the uncertainty of wave front distortion caused by optical fabrication errors and possible misalignment. To gain more information on how the wave front distortion influences the result a new interferometer with improved optics and rather large changes in the etalon is built up. A comparison of the measurements of one sphere taken with two different interferometers gives direct access to this information. Additionally a ray tracing software is being developed to simulate the alignment and measurement processes. Following the alignment steps the resulting positioning uncertainties of each element can be simulated and elements which contribute mainly to the uncertainty can be identified. This gives evidence where an improvement of the alignment techniques is most effective and necessary. With the additional use of Monte Carlo method based calculations the influence on the measurement results can be determined.
Authors: Suejit Pechprasarn, Terry W.K. Chow, Kodchakorn Ittipornnuson, Michael G. Somekh, Naphat Albutt
Abstract: In this paper, we firstly explain the concept of surface plasmon resonance imaging and a main key issue in the field of localized SPR imaging, which is the trade-off between resolution and sensitivity. We will then explain how V(z) scanning confocal microscope can overcome the trade-off and enable us to make a localized detection of multiple analytes in small quantities. This paper provides a brief review on a chronological development of the confocal surface plasmon embedded interferometric microscope and highlights the key idea behind each developments. Theoretical detection limit of the confocal system is within a single molecule detection regime, where 100kD molecule can be detected with 100μJ of light in the confocal system. We also discuss some key challenges in achieving the theoretical limit, such as, microphonic vibration and slow scanning speed of the system and how to get around these challenges. Lastly, we discuss some possible future developments to improve the system.
Authors: Michael F. Kuechel, Daniel M. Sykora
Abstract: Recent developments in next generation disc technology, cameras in mobile phones, zoom-lenses for small digital cameras and camcorders, digital SLRs, and television cameras have amplified the demand for affordable optical systems with outstanding image quality, a combination that can only be achieved using aspheric surfaces. The metrology of aspheric surfaces is a classical problem, but solutions so far have not fulfilled all demands for system cost, TACT (Total Average Cycle Time), minimized tooling, measurement uncertainty, spatial resolution, robustness in a production environment and many more. Zygo Corp. presents here a new method [1,2] for measurement of rotationally symmetrical aspheric surfaces using a new commercial system, which has the potential to fulfill these industry requirements. During measurement, the surface is scanned along its symmetry axis in a Fizeau cavity with a spherical reference surface. The coordinates x,y,z at the (moving) zone of normal incidence are derived from simultaneous phase-measurements at the apex and zone. Phase-shifting Fizeau interferometry and displacement interferometry are combined in the new commercial system to realize this new method. Aspheric departure from a best-fitsphere approaching 800 microns can be measured, and absolute measurement is possible with an absolutely calibrated transmission sphere. A custom parabolic artifact is measured with conventional null Fizeau interferometry and by the new commercial system. Data is reported for each technique along with a difference map achieved by fiducialized data subtract where 32.0 nm peak-to-valley (PV) and 3.6 nm R.M.S. are achieved.
Authors: Ian A. Ashcroft, S. Erpolat, J. Tyrer
Authors: L. Devesa, M. Vaz, J. Sousa Cirne, Nuno Ferreira Rilo, Rui M. Leal
Authors: W. Storm, H.A. Gerber, G.-F. Hohl, M. Naujok, R. Schmolke
Authors: Jack R. Little Jr.
Abstract: Advanced ceramic materials are required to meet increasing high temperature demands of components in advanced propulsion engines for high performance aircraft as well as increasing structural demands in ceramic-composite armor. Monitoring the structural performance of these advanced ceramic materials presents challenges. Recently a new technology, Evisive ScanTM, based on microwave interferometry has been developed that allows condition monitoring. The internationally patented Evisive Scan™ method (1, 2, 3, 4, 5, 6), utilizes microwaves to interrogate dielectric materials. The microwaves are reflected at areas of changing dielectric constant. The reflected energy and the interrogating beam are combined to form an interference pattern which is measured in the transceiver as a signal voltage. The signal voltage is sampled at many positions in the inspection area. This point cloud is displayed as an Evisive Scan™ image, which presents volumetric detail of the inspected part. Over the past two years the technology has been demonstrated on Ceramic Matrix Composites and has shown to be an efficient measurement of porosity and manufacturing defects. The method has also been demonstrated to be applicable to ceramic composite armor made of monolithic ceramic tiles in complex, multilayer structures.
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