摘要: The scope of this paper is to demonstrate a least square method for optimisation of basic parameters for selected physical experiment design where large input parameter measurement and adjustment is needed. The speed of calculation and experimentally verified results are promising to use this method in many physical projects. We have demonstrated this method for computation of feeding currents of correcting coils for stationary magnetic field used in NMR imaging. A set of linear equation definition and determination of a target function and optimisation computations are presented with procedures that provide optimal values of currents for shim coils. The proposed method, because of its simplicity and speed of computation, is convenient for basic adjustment of the magnetic field homogeneity by the first magnet installation. It is also suitable for periodic testing and magnet inhomogeneity correction for MRI magnets.
摘要: For 3D digital measurement of large scale objects, image mosaic is the key technology to achieve whole measurement for a small measuring field of the sensor unit. A viscous-target-based three-dimensional image mosaic technology is proposed. The screw theory is introduced to realize the spatial image mosaic. The method permits an automatic identification of targets and a better matching for the feature coded technology. In experiments, the method was proved to be valid, with a relatively high precision on three-dimensional image mosaic. The relative error of the space length measurement is less than 0.6%.
摘要: The problem of freeform surface reconstruction starting from a cloud of points measured by a laser scanning system is examined. The objective is to fully integrate reverse engineering and laser scanning for rapid product development. The measuring principle and the configuration of the system are investigated. Based on non-uniform rational B-spline (NURBS) curve and surface, the freeform curve, the surface reconstruction method, the step and parameterization algorithms are introduced. The interfaces between initial graphic exchange specification (IGES) and stereo lithography interface specification (STL) with CAD and rapid prototyping manufacturing (RPM) system are discussed. The system is developed based on an open graphics library (OPEN GL) software environment. A practical case is presented to illustrate the effectiveness of the approach.
摘要: A super resolution measurement technique is proposed to improve the accuracy of the automated stereovision measurement systems. Image super resolution is useful to reconstruct a visually enhanced high resolution image from a set of low resolution images. Due to the ill conditioning problem of the super resolution model, a-priori information is augmented into the model. We examined different a-priori and concluded that the Solution norm is the most suitable apriori to be used with the optimization technique described. Experiment also showed that the super resolution technique could perform measurement on small images, which are not possible without the technique. An increase in measurement accuracy from 99.73% to 99.91% is obtained.
摘要: CCD camera is used in the liquid signature analyzer system to capture images of the liquid drop of the tested sample. The digital image processing work is presented. CCD camera records the variation of the liquid drop during growth. The outline information of the drop is available through image processing. The instantaneous volume of the liquid drop can be gained through mathematical calculation. With the use of CCD camera, the information of the tested sample we can get during the measurement is enhanced. The function of the liquid signature analyzer is enriched and the discrimination ability of this technology is improved.
摘要: A new nonlinear intensity interpolation algorithm is presented to realize sub-pixel edge detection. The interpolation algorithm based on the Canny criteria makes full use of grads information attained by Canny edge detection to perform special interpolation in the grads direction. When the resolution is enhanced, the interpolated image by the new interpolation scheme can efficiently preserve high frequency component in the original image. The edge detection of interpolated image permits high precision localization. The new interpolation algorithm is more effective in reserving the grads information of the step edge of the initial image than the usual linear interpolations. It requires simpler computation than the present non-linear interpolations.
摘要: Temperature variation on accuracy and stability in measurement instruments is an important issue. High performance and miniaturized instruments have rigorous requirements on temperature. Heat transfer and temperature control are important in instruments design. For laser interferometer, temperature variation will adversely affect the frequency stability of the laser and the measuring precision. In order to effectively stabilize the frequency, a simple and effective heat sink design for laser interferometer is presented. It is based on the fractal theory and the heat transfer characteristics to allow higher dissipation for temperature control to generate higher heat transfer area in a finite space. Experimental results in frequency stabilization clearly show that this method is effective.
摘要: A new method for calibrating stereo vision measurement system is presented. By moving a rigid optical reference bar in a pattern in and around the measurement volume, the relative orientation and position of the two cameras can be determined by using the epipolar constraint, the linear normalization eight-point algorithm and the M-estimator method. The scale factor of the translation between the two cameras can be calculated by the distances between the marks on the reference bar. With automatically controlled infrared LED marks, the imaging feature points have a uniform intensity profile and a high contrast with background. The calibration accuracy can be improved. The simulation and experiments have shown that the calibration accuracy can be comparable with the complex off-line calibration.
摘要: A novel 2D pattern used in camera calibration is presented. An array of circles with one feature circle located at the center is photo echoed on the pattern. According to the category of the pattern, an ellipse recognition algorithm is proposed. It facilitates acquisition of the distinguished points without human operation. The 3D space coordinate system of these points can be established automatically and accurately. A series of experiments show that the algorithm is robust and reliable. The calibration error is less than 0.4 pixels. The new ellipse recognition algorithm can be widely used for computer vision applications.
摘要: A rapid calibration method for the parameters of a laser light plane scanning 3D measurement system is proposed. The mathematic model and the calibrated parameters of the measurement system are presented. A novel orthogonal calibration jig composed of two orthogonal planes is designed. The CCD camera parameters and the light plane parameters of the measurement system can be rapidly calibrated with the orthogonal calibration jig. The laser scanning 3D measurement system is calibrated with the calibration jig. A standard plane is measured at different positions. The accuracy is better than 0.1mm.