The LINC-NIRVANA Fringe and Flexure Tracker: the testbed interferometer

Thomas Bertram; Bettina Lindhorst; Evangelia Tremou; Steffen Rost; Yeping Wang; Imke Wank; Gunther Witzel; Christian Straubmeier; Andreas Eckart

doi:10.1117/12.788980

28 July 2008 The LINC-NIRVANA Fringe and Flexure Tracker: the testbed interferometer

Thomas Bertram, Bettina Lindhorst, Evangelia Tremou, Steffen Rost, Yeping Wang, Imke Wank, Gunther Witzel, Christian Straubmeier, Andreas Eckart

Author Affiliations +

Proceedings Volume 7013, Optical and Infrared Interferometry; 701337 (2008) https://doi.org/10.1117/12.788980
Event: SPIE Astronomical Telescopes + Instrumentation, 2008, Marseille, France

Abstract

LINC-NIRVANA is the NIR homothetic imaging camera for the Large Binocular Telescope (LBT). Its Fringe and Flexure Tracking System (FFTS) is mandatory for an effcient interferometric operation of LINC-NIRVANA: the task of this cophasing system is to assure a time-stable interference pattern in the focal plane of the camera. A testbed interferometer, set up as laboratory experiment, is used to develop the FFTS control loop and to test the robustness of the fringe tracking concept. The geometry of the resulting interferometric intensity distribution in the focal plane of the implemented CCD corresponds to that of the LBT PSF. The setup allows to produce monochromatic (He-Ne laser) and polychromatic (halogen lamp) PSFs and allows to actively introduce well defined low-order phase perturbations, namely OPD and differential tip/tilt. Furthermore, all components that are required in a fringe tracking servo loop are included: a sensor for fringe acquisition and an actuator to counteract measured OPD. With this setup it is intended to determine the performance with which a fringe tracking control loop is able to compensate defined OPD sequences, to test different control algorithms, and to optimize the control parameters of an existing servo system. In this contribution we present the design and the realization of the testbed interferometer. Key parameters describing the white light testbed interferometer, such as fringe contrast and thermal sensitivity are discussed. The effects of all controllable phase perturbations are demonstrated.

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Thomas Bertram, Bettina Lindhorst, Evangelia Tremou, Steffen Rost, Yeping Wang, Imke Wank, Gunther Witzel, Christian Straubmeier, and Andreas Eckart "The LINC-NIRVANA Fringe and Flexure Tracker: the testbed interferometer", Proc. SPIE 7013, Optical and Infrared Interferometry, 701337 (28 July 2008); https://doi.org/10.1117/12.788980

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