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.
© 2000 Optical Society of America
(100.2650) Image processing : Fringe analysis
(100.5070) Image processing : Phase retrieval
(120.4630) Instrumentation, measurement, and metrology : Optical inspection
(200.4960) Optics in computing : Parallel processing
Munther A. Gdeisat, David R. Burton, and Michael J. Lalor, "Real-Time Fringe Pattern Demodulation with a Second-Order Digital Phase-Locked Loop," Appl. Opt. 39, 5326-5336 (2000)