Improvement Spatial Resolution Of FMCW Laser Ranging System And Application In Spherical Coordinate Measurement

Large-scale precision coordinate measurement plays an important role in the field of major equipment manufacturing, space technology, energy industry, national defense industry. Non-cooperative, large-scale laser coordinate measuring technology is a significant development direction in laser measurement. One of the limiting factors determining the precision of non-cooperative coordinate measurement is the measuring precision of the commonly used ranging methods, such as pulsed laser ranging method and phase-shift laser ranging method. Frequency modulated continuous wave(FMCW) laser ranging is a large-scale absolute distance measuring technology, with the characteristics of large measuring range, high measuring resolution and non- cooperative. Nowadays, FMCW laser ranging has become a research focus in non-cooperative absolute laser distance measurement.In this paper, firstly FMCW laser ranging is studied in detail and the methods of improving the range resolution is proposed and validated in experiments. Secondly, the structure of non-cooperative coordinate measuring system based on FMCW laser ranging is proposed. At last the experimental system is constructed and some measuring experiment is carried out. The main research contents are shown as follows:1. Firstly, we study the tuning principle of external cavity tunable laser and the measuring method of the dynamic line width of narrow linewidth laser. Secondly several common laser ranging methods are compared, and the principle of FMCW laser ranging is studied. At the same time, we analyze the relationship between the ranging resolution and the tuning properties of laser. At last, the feasibility of non-cooperative ranging is verified.2. We design a dual interferometer FMCW laser ranging system. Using this system, resample the beat signal of the measuring interferometer at equal optical frequency intervals, then the measuring error due to the nonlinearity of optical frequency modulation is eliminated.3. Influence on the measuring resolution of the dispersive characteristic of fiber is analyzed. We present the method of splicing the resampled signal. Using this method, we can reduce the modulation range of the tunable laser without decreasing the resolution. At the same time, the influence of the fiber dispersion is suppressed. In the practical experiments we obtain the resolution of 40μm at the distance of 11 m, and the measurement standard deviation is 15μm. Furthermore, the non-cooperative measurement is realized.4. Firstly, the overall structure and operation principle of the non-cooperative coordinate measuring system based on FMCW laser ranging is designed. Secondly, the error sources of the spherical coordinate transmission system are analyzed. Thirdly, we build an experimental large-scale non-cooperative coordinate measuring system, and the error analysis and error separation experiments are carried out. Fourthly, using the laser tracker, the precision evaluation experiment to evaluate the measurement accuracy of the distance between two points is carried out.