Digital algorithms for parallel pipelined single detector homodyne fringe counting in laser interferometry

0468529 - ÚPT 2017 RIV US eng C - Conference Paper (international conference)
Řeřucha, Šimon - Šarbort, Martin - Holá, Miroslava - Čížek, Martin - Hucl, Václav - Číp, Ondřej - Lazar, Josef
Digital algorithms for parallel pipelined single detector homodyne fringe counting in laser interferometry.
20th Slovak-Czech-Polish Optical Conference on Wave and Quantum Aspects of Contemporary Optics (Proceedings of SPIE 10142). Bellingham: SPIE, 2016, s. 1-11, č. článku 101420Z. ISSN 0277-786X.
[Slovak-Czech-Polish Optical Conference on Wave and Quantum Aspects of Contemporary Optics /20./. Jasná (SK), 05.09.2016-09.09.2016]
R&D Projects: GA MŠMT(CZ) LO1212; GA MŠMT ED0017/01/01; GA ČR GB14-36681G; GA TA ČR TE01020233
Institutional support: RVO:68081731
Keywords : laser interferometry * displacement measurement * optical metrology * nanometrology * homodyne detection * scale linerization
Subject RIV: BH - Optics, Masers, Lasers
http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2595371

The homodyne detection with only a single detector represents a promising approach in the interferometric application which enables a significant reduction of the optical system complexity while preserving the fundamental resolution and dynamic range of the single frequency laser interferometers. We present the design, implementation and analysis of algorithmic methods for computational processing of the single-detector interference signal based on parallel pipelined processing suitable for real time implementation on a programmable hardware platform (e.g. the FPGA - Field Programmable Gate Arrays or the SoC - System on Chip). The algorithmic methods incorporate (a) the single detector signal (sine) scaling, filtering, demodulations and mixing necessary for the second (cosine) quadrature signal reconstruction followed by a conic section projection in Cartesian plane as well as (a) the phase unwrapping together with the goniometric and linear transformations needed for the scale linearization and periodic error correction. The digital computing scheme was designed for bandwidths up to tens of megahertz which would allow to measure the displacements at the velocities around half metre per second. The algorithmic methods were tested in real-time operation with a PC-based reference implementation that employed the advantage pipelined processing by balancing the computational load among multiple processor cores. The results indicate that the algorithmic methods are suitable for a wide range of applications [3] and that they are bringing the fringe counting interferometry closer to the industrial applications due to their optical setup simplicity and robustness, computational stability, scalability and also a cost-effectiveness.
Permanent Link: http://hdl.handle.net/11104/0266504