Non-orthogonal shaft laser theodolite(N-theodolite) measurement system is a new kind of measurement instrument utilized in large-scale metrology, which is made up of two same N-theodolites. To achieve the transformation of N-theodolites’ coordinate systems, a calibration method of extrinsic parameters is proposed. With the help of a scale-bar of a certain length, the calibration can be performed conveniently. The correctness of the calibration method is verified by the measurement experiments of point coordinates and distances. The experimental results show that the RMSE of spatial points and the distances of measured points are 0.319mm and 0.150mm respectively. We demonstrate that the proposed calibration method of extrinsic parameters is feasible for the N-theodolite measurement system.
Fiber-optic interferometers (FOIs) are common methods in the field of sensing. However, several issues hinder the technological advancements and the expansion of the scope of applications, including the polarization fading effect, multimodal interferences, and difficulties in resolving the phase of an optical signal. Aiming at solving these problems, we theoretically and experimentally analyze an original method based on broadband light source carried microwave interferometry. Mathematical models of broadband light source interference, broadband light source modulation, and modulated signal interference are constructed and simulated. Proved that optical interference fringes visibility is small enough to be regarded as zero when using broadband ASE light source. Thus, this method will eliminate the influence of optical interference and achieve accurate OPD measurement by interrogating single frequency microwave interference pattern. Unlike an optical signal with a frequency of hundreds of THz, the phase of a microwave signal can be easily and accurately measured. Therefore, the system provides an easy, convenient, and affordable way to achieve various physical quantities sensing with a satisfactory spatial resolution. Experiment results are in good agreement with theoretical calculations, which proves the superiority of the system in practice
The laser beam is considered as an important technique tool for 3D measurement. For precise 3D measurement, the spatial pose of a laser beam must be calibrated before measurement. To make the spatial pose of a laser beam more precise, an optimization method of a laser beam is proposed in this paper. Utilizing the points measured by a laser tracker as benchmark, the more precise parameters of the laser beams can be obtained through Levenberg-Marquarelt algorithm. Comparing improved results with initial ones, the effect of the method can be shown obviously. The method is considered to be a feasible way to optimize the laser beam through experiment verification.
For the trans-scale three-dimensional (3D) measurement in regular-size space and industrial applications, there are many deficiencies and application limitations for traditional measurement methods. Reference to the three axes architecture of traditional instruments, a novel non-orthogonal shafting laser sensor is proposed. The novel sensor is mainly composed of two non-orthogonal shafting laser sensing modules, and each module is made up of two one-dimensional rotary tables and one collimated laser. In the novel laser sensing module, the three axes represent a non-orthogonal shafting architecture, with no orthogonal and intersecting requirements. The manufacturing and application costs are greatly reduced. A high-accuracy calibration method based on coordinate measuring machine and image processing is introduced. An improved perspective projection transform model and attitude kinetic model described by quaternion are adopted to calculate the 3D coordinates of spatial points. The simulation and experimental results showed that a maximum error less than 0.1 mm was detected from 100 mm to 500 mm. It is proved that trans-scale 3D measurement is feasible with the proposed non-orthogonal shafting laser sensor.
The definition of dynamic envelope curve is the maximum limit outline caused by various adverse effects during the running process of the train. It is an important base of making railway boundaries. At present, the measurement work of dynamic envelope curve of high-speed vehicle is mainly achieved by the way of binocular vision. There are some problems of the present measuring system like poor portability, complicated process and high cost. A new measurement system based on the monocular vision measurement theory and the analysis on the test environment is designed and the measurement system parameters, the calibration of camera with wide field of view, the calibration of the laser plane are designed and optimized in this paper. The accuracy has been verified to be up to 2mm by repeated tests and experimental data analysis. The feasibility and the adaptability of the measurement system is validated. There are some advantages of the system like lower cost, a simpler measurement and data processing process, more reliable data. And the system needs no matching algorithm.
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