Real-time fringe pattern demodulation with a second-order digital phase-locked loop.
The use of a second-order digital phase-locked loop (DPLL) to demodulate fringe patterns is presented. The second-order DPLL has better tracking ability and more noise immunity than the first-order loop. Consequently, the second-order DPLL is capable of demodulating a wider range of fringe patterns than the first-order DPLL. A basic analysis of the first- and the second-order loops is given, and a performance comparison between the first- and the second-order DPLL's in analyzing fringe patterns is presented. The implementation of the second-order loop in real time on a commercial parallel image processing system is described. Fringe patterns are grabbed and processed, and the resultant phase maps are displayed concurrently.
Gdeisat
M A
MA
Coherent and Electro Optics Research Group, School of Engineering, Liverpool John Moores University, James Parsons Building Room B1, Byrom Street, Liverpool L3 3AF, UK.
Burton
D R
DR
Lalor
M J
MJ