Under the environment of MATLAB, a closed-loop feedback laser tracking system was established based on the dynamic prediction with Kalman filter and some other filtering processes. Different motion states of the tracked target are simulated to test the tracking performance. The following conclusions are obtained through simulations. After adding the dynamic prediction with Kalman filter, the tracking hysteresis can effectively be avoided when tracking the dynamic object. Taking advantage of the high frequency of PSD, the coordinate value can be read for several times in a feedback loop and then filtered to obtain a more accurate spot coordinate. Under static condition, the instability due to noise can be reduced through segmenting the feedback coefficient by distinguishing between the dynamic and static state of the object. According to the above designs, the results of the laser tracking system simulations show that the dynamic tracking performance is better than 100°/s, and static stability has an order of magnitude improvement than before.
The rapid development of modern science and technology puts forward higher and higher requirements for displacement measurement. As a non-contact measurement technology, laser ranging has played an important role in various fields for the unique advantages and has become a hot topic in the field of measurement research. At present, there are little research on high-precision displacement measurement at medium and long distance, the needs of which are widespread in practical application, so this work has important value. Among various laser ranging technologies, the laser triangulation method has the advantages of high-speed, high precision, simple structure, etc. Therefore, this paper chooses the direct laser triangulation method to carry out the research after analyzed the common types of laser triangulation system. In view of the requirements of high-precision displacement measurement requirements at medium and long distance, this article discussed the design of laser triangulation measuring system and the selection of structural parameters. Then we proposed a direct laser triangulation measurement structure under Scheimpflug conditions. This system selects PSD displacement transducer to collect the position information of the scattered light spot. After that, this paper discusses the principle of laser triangulation distance measurement and simulates the system. Then the influence of different parameters on high-precision displacement measurement and the relationship between them are investigated. Based on the research talked above, we got a set of structural parameters of the displacement measurement system. The measurement accuracy can be ~micron with the working distance of 500mm.
In order to detect weak magnetic field, the demonstration based on all-fiber full polarization Sagnac magnetic sensor was used in our scheme. Beam condense system(BCS) is very meaningful as one of the key technologies in this magnetic sensor. In the paper, we introduce a simple way to design a BCS. Because of the restriction of the system space, the BCS can’t take too much space. However, the common product of beam condense system is kind of complex and will take much space, these disadvantages can’t meet the application. We choose small lenses, design the simple workpiece by ourselves and coupling into our detection system. The workpiece including pressure rings and sleeves. In our plan, we choose telescope system as optical path. After passing the beam condense system, the diameter of beam can be smaller and reflect in magnetic-optical crystal (MOC) many times. In this way, the sensitivity of detection system can be magnified for about 11 times. Overall, the most obvious advantages of this beam condense system are simple structure, small space and low cost. There are two important parameters of beam condense system: The first is called condense ratio, which can be controlled by the choice of lenses. The second is called final beam diffusion angle, which depended on both the condense ratio and beam diffusion angle of collimating lens.
In order to improve the scale factor stability of interferometric fiber optic gyroscope (IFOG), laser is considered to be an alternative to traditional broadband light source because of its excellent frequency stability. Although the performance of IFOG driven directly by laser is inspiring, it is still necessary for further improvement. The main limiting factor is its narrow linewidth and errors of coherent backscattering, polarization coupling and Kerr effect will be reintroduced in laser-driven IFOG. At present, one of the best methods is using Gaussian white noise (GWN) to drive an external electro-optic phase modulator (EOM) and broaden the optical spectrum of laser which will not cause additional frequency drift to the laser. This review studies the mechanism of phase modulation comprehensively based on theory and simulation. The process of broadening is described by numerical calculation and OptiSystem platform. The spectrum is also broadened as expected in the experiment observed by optical spectrum analyzer (OSA). Furthermore, by broadening the linewidth before laser enters the IFOG system, its angular random walk noise and drift are improved by more than 60% compared with no modulation. The test results also show that the drift has reached the level of broadband light source. Related work enriches the application of laser as light source in IFOG and the research about external phase modulation.
In this paper, a new method for analyzing the states of polarization (SOP) distribution characteristics is proposed, which combines the Poincaré sphere measurement method with the improved Delaunay triangulation algorithm, and the specific components and proportions of the SOP of the beam can be quantitatively obtained. On this basis, a numerical parameter, called polarization separation degree (PSD), is introduced to characterize the spatial random dispersion level of partially polarized or unpolarized light. Experimentally, the output SOP distribution of the depolarized erbium-doped superfluorescent fiber source (SFS) is tested, the results show that the PSD of the SFS output light within 2.5 hours is 96.856%, and the proportion of right-handed (left-handed) elliptically polarized light is 49.21% and 50.53%, the proportions of righthanded (left-handed) circularly polarized light and linearly polarized light are 0.05%, 0.11%, and 0.1%, respectively, which provides a valuable numerical reference for further optimizing its structural design and reducing its polarization-dependent wavelength shift. Moreover, the evaluation method proposed in the paper provides an effective way to analyze the dynamic evolution and distribution characteristics of the SOP, and can effectively promote the development and application of polarization imaging and detection, optical fiber communication and sensing technology.
The basic principle of a dynamic goniometer based on fiber optic gyroscope was introduced. According to this principle, the model on uncertainty of angle measurement results was established and the simulation analysis on uncertainty of measurement results was performed. Furthermore, a series of repetitive experiments with this goniometer at different rotational velocities were carried out. Experiments results showed that they were consistent with the uncertainty got from the theoretical analysis when the confidence level was set to 95% and the evaluation model on uncertainty was effective.
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