Signal processing algorithms for Doppler effect based nanometer positioning systems

Interferometers based on laser Doppler effect are used as the vehicle to ex amine the cross relationship and performance impact among sub-systems such as optical layout, mechanical layout, signal processing algorithm, and sign al processing circuitry. The classification of interferometers into the thr ee main categories (e.g. homodyne, heterodyne and quadrature) and their inf luence on signal processing algorithms and circuitry which impact interfero meter performance is examined, A quadrature configuration, found to have so me unique advantages, is detailed. Also presented is an experimental laser encoder-set-up equipped with a real-time signal processing circuitry based on a high performance field programmable gate array (FPGA) circuitry with a PC interface for quadrature signal decoding that was constructed to verify the quadrature configuration presented. The experimental data obtained tha t verifies how this new system architecture can fulfill the stringent deman ds of today's high performance, high accuracy metrology systems is also exa mined.