In practice, the wrapped phase in interferometry is often affected by noise and discontinuity, and among the various types of phase unwrapping (PU) method, the weighted least-square (WLS) PU algorithm, as a global strategy, is widely utilized. However, the excessive smoothing effect exists within the process of PU. Therefore, it is necessary to conduct a comprehensively analysis of different WLS PU algorithms, which includes noise resistance, discontinuity characteristics, convergence speed, and accuracy. First, different weighting strategies were compared with detail for the WLS approach. Under slight noise condition, the edge detection map (EDM) and the filtering method both obtained relatively accurate and reliable phase information. However, when it comes to global multiplicative noise such as speckle noise, the filtering method showed better anti-noise performance than the EDM method, whereas EDM was more capable of dealing with discontinuous phase. Second, to improve the iterative convergence speed and accuracy, the initial value selection was analyzed in detail, and a new initial value selection method was proposed. Simulation and experiments were carried out and validated the results of the analysis.
A telephoto structure-based laser autocollimation with common-path compensation method is proposed to compensate laser beam drift of laser autocollimator. According to the analysis, the measurement beam and the reference beam propagate alongside nearly the same path with approximately identical amounts of drift. Moreover, the ellipses fitting algorithm based on least square approach ensures the accuracy of extracting centroid of the beam while the only photodetector (CCD) with the telephoto objective and several reflectors guarantees the compaction and effectiveness of the system. Simulations and experiments demonstrate a significant beam drift compensation result up to 86.5%. In other words, the stability of the laser beam in the process of measurement is improved.
This paper addresses a fundamental, easy but powerful mechanism of Virtual Reality Simulation system on World Wide Web. The basic idea is to use Virtual Reality Modeling Language (VRML) to build the virtual world, and design a specific simulator to complete the common simulation work and drive the VR animation. According to the achievable mathematics and animation function, two types of this VR Simulation system are founded. The first one is to use VRMLScript or JavaScript to code the specific simulator. This mechanism really can be realized, however, the mathematical operations and the simulation model scale are limited. The other is to apply Java for coding the simulator, then use HTML to combine the VR scene and the simulator in the same WebPage, which can harmonize the VR animation running according to the simulation logic. Because Java is fully mathematics functioned and the Java code modules are entirely reusable, this VR simulation system, which is mainly recommended, can be easily realized on desktop PC and meet the basic interactive requirements of VR Technology without any extra hardware. A VR M/M/1/k Queuing simulation system is given to explain the mechanism. Finally, the overall Integrated Development Environment for this VR simulation system is also discussed.
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