30 April 2008 A compact high-sensitivity heterodyne interferometer for industrial metrology
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For translation and tilt metrology, we developed a compact fiber-coupled polarizing heterodyne interferometer which is based on a highly symmetric design where both, measurement and reference beam have similar optical pathlengths and the same frequency and polarization. The method of differential wavefront sensing is implemented for tilt measurement. With this setup we reached noise levels below 5 pm/square root of Hz; Hz in translation and below 10 nrad/square root of Hz; in tilt measurement, both for frequencies above 10-2 Hz. While this setup is developed with respect to the requirements of the LISA (Laser Interferometer Space Antenna) space mission, we here present the current status of its adoption to industrial applications. We currently design a very compact and quasi-monolithic setup of the interferometer sensor head based on ultra-low expansion glass material. The resulting compact and robust sensor head can be used for nano-positioning control. We also plan to implement a scan of the measurement beam over the surface under investigation enabling high resolution 3D profilometry and surface property measurements (i. e. roughness, evenness and roundness). The dedicated low-noise (≤1nm/square root of Hz) piezo-electric actuator in the measurement beam of the interferometer will be realized using integrated micro-system technology and can either be implemented in one or two dimensions.
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Thilo Schuldt, Thilo Schuldt, Martin Gohlke, Martin Gohlke, Dennis Weise, Dennis Weise, Achim Peters, Achim Peters, Ulrich Johann, Ulrich Johann, Claus Braxmaier, Claus Braxmaier, } "A compact high-sensitivity heterodyne interferometer for industrial metrology", Proc. SPIE 7003, Optical Sensors 2008, 70030Y (30 April 2008); doi: 10.1117/12.781336; https://doi.org/10.1117/12.781336

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