Experimental Research On Large-Scale Metrology Base On Serial Counting Of Active Optical Loop

Large-scale metrology is one of the basic supporting techniques for manufacturing and installing large-scale mechanical parts with high precision, and one technical challenge to metrologists. Deep and systematical research on optical methods of large-scale metrology is performed after analysis and comparison of present measuring principles and technologies. The mathematical model of the new method named multiple-flight-in-single-shot is established, which is based on the principle of pulsed laser ranging. And the serial counting system of large-scale metrology, based on the structure of an active optical loop, is under research. Performance limitations, from pulse broadening caused by dispersions and from pulse broadening and loss caused by rough surface reflections of objects, are analyzed and resolved. The equivalent model of the large-scale metrology system is created by analyzing noises of active optical loops, and simulated in order to optimize systematic structures. Performance influences of optical loop loss and other factors are profoundly analyzed theoretically and experimentally. And self-pulsation replaces the input pulse in order to improve accuracy further. Measurement precision is promoted, and the high noise immunity and portability of pulsed laser ranging are reserved. The producting and installing costs could be decreased and the efficiency increased with great application prospects. The main contents are discribed as follow:First, the new method's mathematical model of multiple-flight-in-single-shot is established. The clock pulse frequency, which restricts the precision of the time-of-flight measuement, is converted into other physical quantities of the phase shifts. Precision could be promoted further by bypassing the electrical bottleneck of the clock frequency, and meet demand of the large-scale metrology for high accuracy.Second, the serial counting system is designed with high feasibility. Cyclic replication, of a laser pulse for large-scale metrology, is realized by the structure of the active optical loop with the core of an Er-doped fiber amplifier, in order to keep coincidence with the principle. The equivalent model is established by analyzing noises of the active optical loop. And structure optimizations are achieved through the model simulation.Then, experiment system is set up. Performance influences from optical loop loss, input pulse power and pumping power are profoundly analyzed in order to find best conditions for system. Comparison between two system schemes, of the input laser pulse and self-pulsations, is performed through experimental researchs in order to improve precision further.Last, the types and sources of errors are analyzed. Differential measurement algorithm is used according to the structural features, which endows the system with the functions of self-calibration and self errors correction. So, the system could be calibrated by itself easily and correct errors dynamically. Differential algorithm and redundant data obtaining by events recording, jointly correct deterministic and random errors caused by dispersions, refract index of optical fibers and retro-reflector, and surrounding temperature, and so on, to keep best performance.