Thomas Ittner

Bio: Thomas Ittner is an academic researcher from University of Stuttgart. The author has contributed to research in topics: Heterodyne & Interferometry. The author has an hindex of 1, co-authored 6 publications receiving 56 citations.

Two-wavelength double heterodyne interferometry using a matched grating technique.

Abstract: Two-wavelength double heterodyne interferometry is applied for topographic measurements on optically rough target surfaces. A two-wavelength He-Ne laser and a matched grating technique are used to improve system stability and to simplify heterodyne frequency generation.

Heterodynverfahren für hochgenaue Vermessung im Nahbereich

Abstract: Es werden die theoretischen Grundlagen fur ein hochgenaues interferometrisches Distanzmesverfahren, welches auf der Zweilangen-lnterferometrie und der Heterodyn-Technik beruht, dargestellt Des weiteren werden erste Ergebnisse mit einem Demonstrationsmodell prasentiert, die mit einem Helium-Neon-Lasersystem erzielt wurden und dem prinzipiellen Nachweis der Tauglichkeit des Verfahrens fur hochgenaue Abstandsmessungen an technischen Objekten dienten Es wird ein Ausblick auf die Realisierung eines fortgeschrittenen Systems zur Messung bei groser Mesdistanz gegeben In this paper the theoretical fundamentals of a high precision interferometric distance measuring system based on dual wavelength heterodyne interferometry will be given Furthermore first results obtained with a HeNe demonstration set-up will be presented They show that it is possible to use a dual wavelength heterodyne interferometer for high precision ranging A view on an advanced system for large distances which is on progress will be discussed

Doppelheterodyn-Interferometrie für hochgenaue Vermessung im Nahbereich

Abstract: Fur die beruhrungslose Entfernungsmessung bieten sich verschiedene optische Verfahren an. Zu den nicht-koharenten Methoden zahlen die Triangulation /l,2,3,4/, Moire-, Laufzeit-und Phasenmestechniken. Geht man von einer Mesdistanz von 100 m und einer geforderten Auflosung von 0.1 mm aus, so erweisen sich die oben erwahnten Verfahren als nicht geeignet: Die Triangulation und die Moire-Technik benotigt fur die genannten Anforderungen eine zu grose Basis, was einen kompakten Aufbau ausschliest. Bei der Laufzeitmessung und der inkoharenten Phasenmestechnik liegen die derzeit erzielbaren Auflosungen im Millimeterbereich. Eine Verbesserung der Auflosung erfordert einen grosen elektronischen Aufwand.

Dual-wavelength heterodyne interferometry for rough-surface measurements

Abstract: For interferometric topography measurements of optically rough surfaces dual wavelength heterodyne interferometry (DWHI) is a powerful tool. A DWHI system based on a two-wavelength HeNe laser and a matched grating technique is described. This set-Sup improves system stability and allows a simple heterodyne frequency generation. 1.

Dual wavelength heterodyne interferometry using a matched grating set-up

Abstract: Two-wavelength double heterodyne interferometry is applied for topographic measurements on rough target surfaces. A two-wavelength HeNe laser and a matched grating technique are used to improve system stability and to simplify heterodyne frequency generation. Results obtained with an experimental set-up will be presented. The results obtained show that a dual wavelength heterodyne interferometer is appropriate for high precision ranging. Progressing developments for large distances will be discussed.

Extending the unambiguous range of two-color interferometers

Abstract: The unambiguous distance measurement range in two-color interferometry is generally understood to be limited to the equivalent or synthetic wavelength, which is inversely proportional to the wavelength separation of the two colors. Here it is shown that one may extend the unambiguous range well beyond this limit by using optical phase information to determine the synthetic-wavelength fringe order.

Interferometer and method for measuring the refractive index and optical path length effects of air

Abstract: Apparatus and methods particularly suitable for use in electro-optical metrology and other applications to measure and monitor the refractive index of a gas in a measurement path and/or the change in optical path length of the measurement path due to the gas while the refractive index of the gas may be fluctuating due to turbulence or the like and/or the physical length of the measuring path may be changing. More specifically, the invention employs electronic frequency processing to provide measurements of dispersion of the refractive index, the dispersion being substantially proportional to the density of the gas, and/or measurements of dispersion of the optical path length, the dispersion of the optical path length being related to the dispersion of the refractive index and the physical length of the measurement path. The refractive index of the gas and/or the optical path length effects of the gas are subsequently computed from the measured dispersion of the refractive index and/or the measured dispersion of the optical path length, respectively. The information generated by the inventive apparatus is particularly suitable for use in interferometric distance measuring instruments (DMI) to compensate for errors related to refractive index of gas in a measurement path brought about by environmental effects and turbulence induced by rapid stage slew rates. In preferred embodiments, differential plane mirror interferometer architectures are utilized, the operating wavelengths are approximately harmonically related and may be monitored and/or controlled to meet precision requirements, heterodyne and superheterodyne processing are beneficially used, and phase redundancy is resolved.

Distance measurement by multiple-wavelength interferometry

Abstract: Multiple-wavelength interferometry enables us to increase the range of non-ambiguity and to reduce the sensitivity of classical interferometry. It can also be operated on rough surfaces. The accuracy depends on the stability and the calibration of the different wavelengths. An electronically calibrated three-wavelength source for synthetic wavelengths in the millimetre range with an accuracy of better than has been demonstrated. Absolute distance measurements were performed up to 200 mm with a resolution of better than . L'interf?rom?trie ? plusieurs longueurs d'onde permet d'augmenter la zone de non-ambigu?t? et de r?duire la sensibilit? de l'interf?rom?trie classique. Elle peut ?galement ?tre utilis?e sur des surfaces rugueuses. La pr?cision de mesure d?pend de la stabilit? et de la calibration des diff?rentes longueurs d'onde. Une source ? plusieurs longueurs d'onde a ?t? r?alis?e, g?n?rant des longueurs d'onde synth?tiques de quelques millim?tres et permettant une calibration ?lectronique de pr?cision meilleure que . Des mesures de distances absolues ont ?t? effectu?es jusqu'? 200 mm avec une r?solution de environ.

Limits of Optical Range Sensors and How to Exploit Them

Abstract: It appears that only three different physical principles are required to classify all range sensors: (classical) interferometry on smooth surfaces (type III), broad-band interferometry on rough surfaces (type II), and triangulation (type I). We will show that signal formation in classical interferometry is completely different from signal formation in white-light interferometry on rough surfaces. The latter (type II) principle has some remarkable features: the distance uncertainty does not depend on the aperture of observation, and it displays some kind of “superresolution” by acquiring surface roughness, even if the lateral microtopology of the object is unresolved. We will demonstrate this by experiments and theory.