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Andreas E.,Interstate University of Applied Sciences and Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

Optical measuring techniques for micro structures are limited by the numerical aperture of the objective. Within these limits different techniques can be used: white light interferometry uses an illumination source with short coherence length to determine the absolute position of the surface while confocal profilometry uses the principle of the defocus of light. As a relatively new technique, digital holography offers the simultaneous measurement of intensity and phase of a wave to generate a 3D image with the acquisition of just one single image. We give some application examples of these techniques to micro structures including deformation measurements. © 2011 SPIE. Source


Helsch G.,Clausthal University of Technology | Mos A.,Clausthal University of Technology | Deubener J.,Clausthal University of Technology | Deubener J.,Energie-forschungszentrum Niedersachsen (EFZN) | Holand M.,Interstate University of Applied Sciences and Technology
Solar Energy Materials and Solar Cells | Year: 2010

Quarter-wave anti reflectance (AR) coatings were applied on silica glass by a solgel dip coating process to minimize reflective losses of the receiver cover materials for solar tower power plants. To investigate the thermal resistance of the coatings prepared from silica sols of 20 nm, mean particle sizes, solar transmittance, thickness, and density were determined as a function of isothermal heat treatments using UVvisNIR spectroscopy, profilometry, and X-ray reflectometry, respectively. The initial solar transmittance τ of the AR coated silica glass, cured at 773 K, was 0.973 for a film thickness d=111 nm. Heat treatments in the range from 1273 to 1423 K for 15240 min reduce both film thickness and solar transmittance of the crystal-free films. The isothermal shrinkage rate of the film thickness was described for a relative density >0.634 using MackenzieShuttleworth (MS) model. Viscosity data calculated from the sintering rate constant of the MS model were compared with literature data of silica glasses of known water content prepared by sintering and fusion. This analysis indicates that the sintering kinetics of the nanoporous film were controlled by viscous flow of amorphous silica particles of a water content of ≈1100 ppmw associated with an activation energy of 321 kJ mol-1. © 2010 Elsevier B.V. All rights reserved. Source


Ettemeyer A.,Interstate University of Applied Sciences and Technology
Optical Engineering | Year: 2012

Increasing manufacturing accuracy requirements enforce the development of innovative and highly sensitive measuring tools. Especially for measurement with submicrometer accuracy, the sensor principle has to bechosenappropriately foreachmeasurementsurface.Modernmultisensor coordinatemeasurement systemsallow automatic selection of different sensor heads to measure different areas or properties of a sample. As an example, different types of optical sensors as well as tactile sensors can be used within the same measuring system. I describe different principles of optical sensors used in multisensor coordinate measurement systems as well as a newapproach for tactilemeasurement with submicrometer accuracy.Aspecial fiber probe has been developed. The tip of the fiber probe is formed as a sphere.Thelateral position of this sphereisobservedbyamicroscope objective and can be determined within a fraction of a micrometer. Additionally, a novel optical setup now allows the determination of the z-position of the fiber tipwith submicrometer accuracy. For this purpose, an interferometer setup is used. The laser light is coupled into the optical fiber. The light exiting the fiber tip is collected by themicroscope objective and superposed with a reference wave, generated directly from the laser. The result is an interference signal that is recorded by the cameraandprocessed bya computer.With this setup, thez-displacement of thefiberspherecanbemeasuredwithanaccuracyofa fraction of the laser wavelength used. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). Source


Ghiotti A.,University of Padua | Schoch A.,University of Padua | Schoch A.,Interstate University of Applied Sciences and Technology | Salvadori A.,University of Padua | And 2 more authors.
CIRP Annals - Manufacturing Technology | Year: 2015

Geometrical distortions due to inappropriate setting of process parameters are one of the main causes of variability in manufacturing hot forged thin parts. Their identification and measurement at the earliest steps of the process chain may permit significant benefit especially in case of small batch production. The paper presents a coordinate measuring system for fast inspection of freeform parts at elevated temperatures through high-speed laser triangulation. Main error sources are discussed, including a new method for the correction of systematic errors due to imperfect laser planes alignment. A procedure for testing the metrological performances at elevated temperature is also presented. © 2015 CIRP. Source


Ettemeyer A.,Interstate University of Applied Sciences and Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

Increasing manufacturing accuracy requirements enforce the development of innovative and highly sensitive measuring tools. Especially for measurement with sub micrometer accuracy, the sensor principle has to be chosen appropriately for each measurement surface. Modern multi sensor coordinate measurements systems allow automatic selection of different sensor heads to measure different areas or properties of a sample. As example, different types of optical sensors as well as tactile sensors can be used with the same machine. In this paper we describe different principles of optical sensors used in multi sensor coordinate measurement systems as well as a new approach for tactile measurement with sub micrometer accuracy. A special fiber probe has been developed. The tip of the fiber probe is formed as a sphere. The lateral position of this sphere is observed by a microscope optics and can be determined to a fraction of a micrometer. Additionally, a novel optical set-up now even allows the determination of the z-position of the fiber tip with sub micrometer accuracy. For this purpose we use an interferometric set-up. The light of laser is coupled into the optical fiber. The light, exiting the fiber tip is collected by a microscope optics and superposed with a reference wave, generated directly from the laser. The result is an interferometric signal which is recorded by the camera and processed by a computer. With this set-up, the zdisplacement of the fiber sphere can be measured with an accuracy of a fraction of the used laser wavelength. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE). Source

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