Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Adaptive DFT-Based Interferometer Fringe Tracking Edward Wilson | EURASIP Journal on Applied Signal Processing 2005 15 2559-2572 2005 Hindawi Publishing Corporation Adaptive DFT-Based Interferometer Fringe Tracking Edward Wilson Intellization 454 Barkentine Lane Redwood Shores CA 94065 USA Email Ettore Pedretti Harvard-Smithsonian Center for Astrophysics 60 Garden Street Cambridge MA 02138 USA Astronomy Department University of Michigan 914 Dennison Building Ann Arbor MI 48109 USA Email epedrett@ Jesse Bregman NASA Ames Research Center Mail Stop 269-1 Moffett Field CA 94035 USA Email Robert W. Mah NASA Ames Research Center Mail Stop 269-1 Moffett Field CA 94035 USA Email Wesley A. Traub Harvard-Smithsonian Center for Astrophysics 60 Garden Street Cambridge MA 02138 USA Email wtraub@ Received 1 June 2004 Revised 29 October 2004 An automatic interferometer fringe tracking system has been developed implemented and tested at the Infrared Optical Telescope Array IOTA Observatory at Mount Hopkins Arizona. The system can minimize the optical path differences OPDs for all three baselines of the Michelson stellar interferometer at IOTA. Based on sliding window discrete Fourier-transform DFT calculations that were optimized for computational efficiency and robustness to atmospheric disturbances the algorithm has also been tested extensively on offline data. Implemented in ANSI C on the 266 MHz PowerPC processor running the VxWorks real-time operating system the algorithm runs in approximately milliseconds per scan including all three interferograms using the science camera and piezo scanners to measure and correct the OPDs. The adaptive DFT-based tracking algorithm should be applicable to other systems where there is a need to detect or track a signal with an approximately constant-frequency carrier pulse. One example of such an application might be to the field of thin-film measurement by ellipsometry using a broadband light source and a
