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Wang Z.,CAS Shenyang Institute of Automation
Optics Express | Year: 2015

In this paper, a method is proposed to measure the shapes of specular surfaces with one-shot-projection of structured laser patterns. By intercepting the reflection of the reflected laser pattern twice with two diffusive planes, the closed form solution is achieved for each reflected ray. The points on the specular surface are reconstructed by computing the intersections of the incident rays and the reflected rays. The proposed method can measure both static and dynamic specular shapes due to its oneshot-projection, which is beyond the capability of most of state of art methods that need multiple projections. To our knowledge, the proposed method is the only method so far that could yield the closed form solutions for the dynamic and specular surfaces. © 2015 Optical Society of America. Source


Wang Z.,CAS Shenyang Institute of Automation
Journal of Optics (United Kingdom) | Year: 2014

As one of the most popular non-contact shape measurement methods, phase shift profilometry has been studied for many decades and has found applications in both the scientific and industrial world. However, its measurement accuracy and noise resistance ability are still widely researched topics. In this paper, a method to determine the phase map by calculating the phases from multiple high carrier frequencies is proposed for phase shift profilometry to measure the object's shape. Four-shifted phases are well designed to yield a closed-form solution, and a combination of the computation results from multiple high frequencies can suppress the prevalent noise effectively. Calibration methods are also introduced for practical implementation. A moving kernel filter calculated from the maximum likelihood estimation is used to suppress the noise further. The experimental results verified the effectiveness of the proposed methods. © 2014 IOP Publishing Ltd. Source


Wang Z.,CAS Shenyang Institute of Automation
IEEE Transactions on Industrial Informatics | Year: 2016

With the rapid development of microscopy imaging technology, the requirement for robust segmentation and quantification of cells or nanoparticles increases greatly. It remains challenging due to the diversity of the cell or nanoparticle types, the arbitrary shapes, and the large numbers of cells or nanoparticles. The most existing methods are only capable of segmenting some specific types of cells or nanoparticles. In this paper, we propose a more versatile approach that is capable of segmenting a variety of cells or nanoparticles. It consists of five parts: 1) automatic gradient image formation; 2) automatic threshold selection; 3) manual calibration of the threshold selection method for each specific type of cell or nanoparticle images; 4) manual determination of the segmentation cases for each specific type of cell or nanoparticle images; and 5) automatic quantification by iterative morphological erosion. After the parameter, N is calibrated and the segmentation case is determined manually for each specific type of cell or nanoparticle images with one or several typical images; only parts 1), 2), and 5) are needed for the rest of processing and they are automatic. The proposed approach is tested with different types of cell and nanoparticle images. Experimental results verified its effectiveness. © 2016 IEEE. Source


Wang Z.,CAS Shenyang Institute of Automation
IEEE Transactions on Industrial Informatics | Year: 2014

Controlling the welding process by monitoring the weld pool surface becomes more and more popular in robotic arc welding. In this paper, we propose a monitoring system to infer the P-gas metal arc welding (GMAW) weld pool geometry from the reflected laser lines, which are projected onto the specular weld pool and reflected onto a diffusive plane. The parallel straight lines are distorted according to the shape of the weld pool and thus contain the weld pool's shape information. Accurately computing the equations of the imaged laser lines in the world coordinate system is critical for the subsequent weld pool shape estimation. This paper focuses on accurately segmenting and identifying the reflected laser lines and novel image processing algorithms are proposed to fulfill this specific task. Experimental results verified the effectiveness of the proposed algorithms. © 2014 IEEE. Source


Wang Z.,CAS Shenyang Institute of Automation
IEEE Transactions on Industrial Electronics | Year: 2015

Robust measurement of the specular weld pool surface can help better understand the complex welding processes and provide feedback for robotic welding. The strong arc light and the specular surface of the weld pool make it difficult for the direct sensing measurement. In this paper, a novel imaging and measurement system is proposed, and it makes use of the strong penetrability of the laser to avoid the interference of arc light and obtain the surface information of the weld pool. By intercepting the reflection of a projected laser pattern twice, the proposed system gives a closed-form solution for each reflected ray and a closed-form solution for the corresponding point on the weld pool surface. The weld pool surface can be thus reconstructed by one-shot structured light projection. To increase the robustness of the measurement system, the least deformation principle is proposed to rectify the coefficient errors of the computed plane equation. Finally, a sequence of 3-D weld pools is reconstructed and compared with state-of-art literature. The comparison verifies that our method is significantly better than all the other methods in measuring the 3-D weld pool shapes. © 2015 IEEE. Source

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