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An Auto-Focusing Approach for a Dynamic Quadrature Interferometer

Title data

Gollwitzer, Andreas ; Haugg, Susanne ; Fischerauer, Gerhard:
An Auto-Focusing Approach for a Dynamic Quadrature Interferometer.
In: AMA Service GmbH (ed.): Proceedings OPTO 2009 & IRS² 2009 : 9th International Conference on Optical Technologies for Sensing and Measurement & 11th International Conference on Infrared Sensors & Systems. - Wunstorf : AMA Service GmbH , 2009 . - pp. 29-34
ISBN 978-3-9810993-6-2
DOI: https://doi.org/10.5162/opto09/o1.2

Abstract in another language

The measurement of surface vibrations with small amplitudes is often accomplished using interferometric techniques. For a good local resolution of the vibration amplitudes, the laser beam has to be focused on the surface through a high magnification lens. Owing to the small depth of focus of this lens, its distance to the surface has to be controlled accurately and precisely. In order to get rid of the frequency shifting parts of a heterodyne interferometer and to simultaneously eliminate the effects of noise sources such as fluctuations in the surface reflectivity of the device under test, we use a homodyne setup with additional path length modulation. The sensitivity of the setup is increased by quadrature interferometry, i. e., the synchronous measurement of the intensities detected by two photodiodes. We also present a signal processing technique for the control of the distance between lens and surface; this makes sure that the laser beam is optimally focused onto the surface and leads to a high overall signal-to-noise ratio.

Further data

Item Type: Article in a book
Refereed: No
Institutions of the University: Faculties
Faculties > Faculty of Engineering Science
Faculties > Faculty of Engineering Science > Chair Measurement and Control Technology
Faculties > Faculty of Engineering Science > Chair Measurement and Control Technology > Chair Measurement and Control Technology - Univ.-Prof. Dr.-Ing. Gerhard Fischerauer
Result of work at the UBT: Yes
DDC Subjects: 600 Technology, medicine, applied sciences > 620 Engineering
Date Deposited: 13 Jun 2016 08:34
Last Modified: 13 Jun 2016 08:34
URI: https://eref.uni-bayreuth.de/id/eprint/32660