9 June 1994 LAMP: a concept for the European Southern Observatory VLTI fringe sensor
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In the framework of the development of the Very Large Telescope Interferometer (VLTI) by the European Southern Observatory (ESO) we have proposed the LAMP (Large Amplitude Modulated Path). The sensor is that part of the fringe-tracker which only provides a set of error signals reflecting Optical Path Differences (OPD) at a common focus, between collected fields, the so-called piston effect. LAMP relies on both temporal encoding of OPD on each pair of apertures and on an appropriate spatial encoding which allows simultaneous operation on several apertures. Besides, it has been designed so as to provide at the same time both coherencing error signals and cophasing error signals (these latter when allowed by the source's brightness). Such ability is based on the large amplitude used in the modulation. In this paper, after a short presentation of both initial working conditions and specific capabilities that have driven the design, we describe the principle of LAMP. We also describe a generic setup and we report performances in terms of OPD resolution (minimum detectable piston), response-time and limiting magnitude. Finally advantages and drawbacks of the design are discussed.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jean Gay and Yves Rabbia "LAMP: a concept for the European Southern Observatory VLTI fringe sensor", Proc. SPIE 2200, Amplitude and Intensity Spatial Interferometry II, (9 June 1994); doi: 10.1117/12.177240; https://doi.org/10.1117/12.177240

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