Key Engineering Materials Vols. 381-382

Abstract: A new signal-denoising approach based on DT-CWT (Dual-Tree Complex Wavelet Transform) is presented in this paper to extract feature information from microstructure profile. It takes advantage of shift invariance of DT-CWT, non-Gaussian probability distribution for the wavelet coefficients and the statistical dependencies between a coefficient and its parent. This approach substantially improved the performance of classical wavelet denoising algorithms, both in terms of SNR and in terms of visual artifacts. A simulated MEMS microstructure signal is analyzed.

Abstract: The optical measuring device developed in this study is based on laser autocollimation and can measure the radial error motions of a miniature ultra-high-speed spindle having a maximum rotational speed of 200 krpm. The maximum response frequency of this optical measuring device is over 500 kHz, while the frequency of the radial error motion at 200 krpm is 3.33 kHz for 1 undulation per revolution (upr), and 333 kHz for 100 upr. In addition, the optical measuring device is capable of a highly detailed analysis of the radial error motion of a miniature ultra-high-speed spindle since it has a high signal-to-noise ratio due to little susceptibility to electrical noises.

Abstract: The computer aided measuring system is established to evaluate geometrical information of the structure in subsection manufacture. The cloud points data of surface are collected by laser tracker so as to explore continuing data processing software and evaluate the error of dimension and shape, and then the real measuring model, matched by the corner information, is compared with CAD through the best-fit algorithm. The lack of fitting information which will cause the low measuring precision is solved by the least square method constrained by radius in structure with large radius and small central angle. As the research object, the tunnel structure is used in the quality control of manufacturers.

Abstract: The detection technique of small module gears has a very important research and application value. In this paper, a composite measuring method is presented based on combining traditional mechanical contact measurement with optical image non-contact measurement. First of all, this paper analyzes the basic principle of composite probe composed of optical fiber stylus and CCD imaging system. The tail-end of the stylus is shaped into a micro-sphere, where a small refection mirror is designed. When the laser is transmitted through the fiber, a round facula can be seen from the CCD camera. The micro-sphere is kept contact with the surface of the measured gear at the time of measuring and the error of the measured gear will be reflected by the offset of the facula center. Meanwhile, the sub-pixel extraction algorithm for the center of facula image is presented. Then the calibration principle and method of probe system is analyzed in detail. Finally, the data processing principle of the presented method is discussed for gear measurement.

Abstract: A fully automatic and rather flexible mobile vision 3D coordinate online measurement system is presented and analyzed. The system is composed of a high resolution CCD camera, retro-reflective feature points, and an external orientation device. The feature points, which fixed on the measured object and external orientation device, are imaged by camera in several locations and orientations. The initial external locations and orientations of the camera relative to the fixed external orientation device are determined by pose estimate algorithm, and the feature points coordinates, i.e. measured points coordinates on the object, are calculated by bundle adjustment algorithm based on collinear constraint. To improve the measurement accuracy, the locations of the imaging feature points are determined by bilinear centroid sub-pixel algorithm. The effectiveness of the proposed system has been tested by experiments.

Abstract: Interferometry is a meterage technology which is based on light-wave interference theory. In the general interferometry measurements, the procedure of analyzing and studying interferogram depends on a processing system mostly based on PC. In this paper an image processing system based on DSP is conceived, and the entire system consists of a image collecting module, a digital data exchanging interface and a image processing module. A typical interferogram collected from experiments is processed by the system conceived above. Comparing the processed stripe with the ideal pattern, we found that the system is competent for interferometry.

Abstract: Reversal and multiple measurement techniques have been used in dimensional metrology [1]. The reversal technique in straightness measurement is very common method. The techniques are able to reduce the errors which come from a measuring instrument and compensate the errors automatically. The techniques are available to CMM measurements. For ball-plate calibration, the reversal technique is used in National Metrology Institutes (NMIs). The technique automatically eliminates the geometrical errors of a CMM, for example, straightness, perpendicular and angle (pitch, yaw and roll). The multiple measurement technique is used for measuring symmetrical features as cylinders [2]. We tried to apply the technique for the pitch measurement of a gear. In this paper, we describe the multiple measurement techniques for coordinate metrology, especially, application to gear measurement.

Abstract: In this research, a novel high-precision pitch artifact using balls is proposed for calibration of pitch measuring instruments. This pitch artifact is composed of the combination and the alignment of balls and cylinders on a plane. Balls, cylinders and planes are possible to be manufactured with several-ten-nanometer-order accuracy. Therefore, this artifact can accomplish high dimensional accuracy. In addition, manufacturing of this artifact is not difficult because time-consuming special process is not needed. In this report, the concept, structure and feature of this pitch artifact are proposed and theoretical analysis is carried out.

Abstract: This paper introduces a dual-path Mach-Zehnder interferometer for determining refractive index and geometrical thickness of an optical plate. In this interferometer, two parallel incident beams are separated into two interference pairs which are then recombined to generate two interference signals. An optical plate is placed on the path of one wave of an interference pair, so the phase difference of the interference signals is a function of the plate, and the interferometer is thus able to determine the index and thickness of the plate. A setup constructed to realize the proposed interferometer is described. And the experimental results of applying this setup agree the validity of the interferometer.

Abstract: Experiments are carried out on a femtosecond laser micromachining system with the wavelength 775nm. The ablated patterns on Si (100) and Si (111) surfaces affected by femtosecond pulse laser parameters are presented. The periodic structure termed ripples on silicon surface is investigated. Two kinds of ripples on the ablated surface are observed by SEM. The whole ablation region indicates the ablated field of all amount of laser energy. The ablation region forms two circular areas. The cross section image of the ablated region is showed which is cut by FIB in the orthogonal direction of the line of the center ripples. The depth of ripples is measured. Adjusted the laser fluence as about 0.3~0.33J/cm2 and the pulse number as changeable from 1 to 50, the forming process of the ripples is observed and studied by AFM. Another experiment is done that the wave-plates are inserted into the space between the objective and sample, the result of the direction of ripples changed with the wave-plates of 1/2 or 1/4 is reviewed.