OP4 - Multi Wavelength Interferometry for High Precision Distance Measurement

SENSOR+TEST Conferences 2009
2009-05-26 - 2009-05-28
Congress Center Nürnberg
Proceedings OPTO 2009 & IRS² 2009
OPTO Poster Session
J. Petter - Luphos GmbH, Darmstadt, Germany
129 - 132


Precision in mechanical fabrication increased drastically within the last years. In many areas of industrial fabrication these days the precision of production processes reaches beyond the scale of micrometers, while diamond grinded metallic surfaces can be manufactured with optical quality even without finishing polish. High precision optics, aspheric lenses or optical freeforms are produced with only nanometer tolerance while the positioning of bearings and object carriers (e.g. in wafer procession) needs subnanometer resolution. Such high accuracy demands an even higher precision in measurement technology being used e.g. for distance and topology measurements, for the positioning of axis or the quality control of fabricated objects.
Techniques that nowadays are available for these measurement problems are either complicated in adaption or implicate substantial disadvantages slowing down the fabrication process considerably. Futhermore, using tactile measurement systems in topological survey the sensor itself can harm the surface, especially when perfomred in the nanometer precision range; conventional optical measurement systems either are less precise or the dimesions of their sensorheads are to large to be handeled properly. In common they suffer from an only small and fixed workingrange, which makes them not applicable in different and changeable measurement requirements and distances and mutable working areas. Even though simple interferometric methods priinciply are able to measure long distances with high accuracy, it is done only relativlely by counting fringes. Moreover, due to the phase ambiguity they fail when measuring topologies of rough surfaces.
Compared with the aforementioned distance maesurement systems the newly developped Multiwavelength-lnterferometer (MWLI) by Luphos offeres a flexible alternative for high precision measurements for distances and topologies. Using the special method of three interferometers folded into each other the disadvantages of common distance measurement systems are being omitted. The system with its small fibrecoupled sensorhead offers a large flexibility and enables a versatile implementation of the sensor in a whole new area of applications, where measurement hasn't been possible so far.