Dual-phase and three-phase grating x-ray interference is a promising new technique for grating-based x-ray differential phase contrast imaging.Dual-phase grating interferometers have been relatively completely studied...Dual-phase and three-phase grating x-ray interference is a promising new technique for grating-based x-ray differential phase contrast imaging.Dual-phase grating interferometers have been relatively completely studied and discussed.In this paper,the corresponding imaging fringe formula of the three-phase grating interferometer is provided.At the same time,the similarities and differences between the three-phase grating interferometer and the dual-phase grating interferometer are investigated and verified,and that the three-phase grating interferometer can produce large-period moiréfringes without using the analyzing grating is demonstrated experimentally.Finally,a simple method of designing three-phase grating and multi-grating imaging systems from geometric optics based on the thin-lens theory of gratings is presented.These theoretical formulas and experimental results provide optimization tools for designing three-phase grating interferometer systems.展开更多
In this paper, we demonstrate a new optical method for tiny strain measurements based on the principle of carrier fringes of moire interferometry. A cross-line grating with frequency of 1200 lp/mm is replicated on the...In this paper, we demonstrate a new optical method for tiny strain measurements based on the principle of carrier fringes of moire interferometry. A cross-line grating with frequency of 1200 lp/mm is replicated on the specimen surface, and the strain can be deduced from the changes in carrier fringes before and after the deformation of an object. Four coherent laser beams are used to obtain the carrier fringe patterns of field U and V. Both theoretical analysis and numerical simulation indicate that the ideal accuracy of strain can be controlled within a range of ±1με. Case study of a plane extension experiment shows that the measurement accuracy of strain can be controlled within the range of ±10με. The average strain values of every row of field U and every column of field V can be obtained by using this method, and approximated strain of every pixel in the whole-field can be further acquired, and thus it is possible to measure tiny strains occurred in a micro-field. The technology in this paper can provide comprehensive information for analyzing related mechanical content in the field of MEMS.展开更多
In this paper, the optical/digital fringe multiplication (O/DFM) is realized in projection moiré using digital image processing (DIP). Both deformed grating and reference grating are captured using a CCD camera. ...In this paper, the optical/digital fringe multiplication (O/DFM) is realized in projection moiré using digital image processing (DIP). Both deformed grating and reference grating are captured using a CCD camera. The reference grating can also be produced using DIP. With the O/DFM, the pattern is multiplied with an image processing software, which is developed using MATLAB 6.5. Also with DIP, the phase shifting can become much simpler, and the automation can be adopted. The multiplied pattern is much thinner and easier to read, and sensitivity of measurement can be enhanced.展开更多
A novel method to separate and simultaneously record the Moiréinterferometry fringe patterns of three deformation fields with only one CCD camera is developed;details of its operation principle,key points and err...A novel method to separate and simultaneously record the Moiréinterferometry fringe patterns of three deformation fields with only one CCD camera is developed;details of its operation principle,key points and error analysis are presented.With this technique,the deformation in U,V and W fields can be measured simultaneously,so dynamic test with comprehensive information can be performed.The advantage of this technique over other similar techniques lies in its simplicity,easy implementation and low cost.An application of this technique is given to show its feasibility.Technical problems that may be caused with this technique are also analyzed.展开更多
A dual-frequency digital Moiré measurement method(DFDM) is proposed for the three-dimensional(3D) shape measurement of an object.The high-and low-frequency fringes are modulated separately along orthogonal direct...A dual-frequency digital Moiré measurement method(DFDM) is proposed for the three-dimensional(3D) shape measurement of an object.The high-and low-frequency fringes are modulated separately along orthogonal direction using different carrier frequencies before being projected onto the measured object.After collecting and demodulating the composite fringe,the digital π phase shift is used to remove the DC component of the demodulated fringes,resulting in high-precision Moiré fringes for calculating the wrapped phase.The unwrapping of the high-frequency wrapped phase is guided by the low-frequency phase to further realistically reconstruct the surface of the measured object.When compared with existing single-shot digital Moiré profilometry,DFDM effectively removes the DC component of the fringe and calculates the phase more accurately.展开更多
This paper deals with the mode I crack problem of a cracked rubber sheet under plane stress condition using the delicate digital moiré technique. Through the four step phaseshifting method of automated fringe ana...This paper deals with the mode I crack problem of a cracked rubber sheet under plane stress condition using the delicate digital moiré technique. Through the four step phaseshifting method of automated fringe analysis, the displacement fields in the Cartesian coordinate system are given. By the coordinate-transform equation, the radial and circular displacement distributions in the polar coordinate system are obtained. The displacement isoline distributions and displacement vector distributions near the crack tip are discussed. The strain isoline distributions near the crack tip are also analyzed in this paper. Finally, the distribution rules for the mechanical fields near the crack tip are discussed with the sector division method.展开更多
This study describes a novel fringe-shaping technique developed to alleviate the fringe truncation problem engendered by the acquired saturated and/or weak fringe images from high-/low-reflectance surfaces of three-di...This study describes a novel fringe-shaping technique developed to alleviate the fringe truncation problem engendered by the acquired saturated and/or weak fringe images from high-/low-reflectance surfaces of three-dimensional（3D） objects in phase-shifting profilometry. The particle swarm optimization algorithm is employed to perform the recovery of the truncated fringes with optimal fitting for compensation after single-trial acquisition. The results show that the proposed method improves phase recovery accuracy to accomplish 3 D surface reconstruction with only one set of phase-shifting fringes under different truncation sceneries.展开更多
介绍了一种数字处理技术实现对光栅编码器所产生莫尔条纹信号的细分。莫尔信号经过光电转换后输出两路正余弦信号并通过光栅解码电路对其AD(analog to digital)采样,利用正切值消除正余弦信号的非线性误差,根据正余弦信号的正负将一个...介绍了一种数字处理技术实现对光栅编码器所产生莫尔条纹信号的细分。莫尔信号经过光电转换后输出两路正余弦信号并通过光栅解码电路对其AD(analog to digital)采样,利用正切值消除正余弦信号的非线性误差,根据正余弦信号的正负将一个周期信号分割成8份,通过反正切角度值实现对每一份的细分。最后将此设计应用于单轴转台。实验结果表明,光栅编码器输出的的静态位置精度可以达到0.000 1°,动态位置及速度曲线无跳变,满足使用要求。展开更多
In this study, a displacement measurement method based on digital moiré fringe is described and experimentally demonstrated. The method is formed by only one grating with a constant pitch. First, the magnified gr...In this study, a displacement measurement method based on digital moiré fringe is described and experimentally demonstrated. The method is formed by only one grating with a constant pitch. First, the magnified grating image is received by an imaging array and is sent to a computer. Then, the digital moiré fringes are generated by overlaying the grating image with its mirrored one. Finally, a specifically designed algorithm is used to obtain the fringes' phase difference before and after movement and calculate the displacement. This method has the effects of amplifying displacement and averaging the grating lines error, the same as the traditional moiré technique using two pieces of gratings. At the same time, the proposed system is much easier to assemble and the measurement resolution can be set more flexibly. One displacement measuring system based on this method was built up. Experiment results show that its measurement errors are less than 0.3 μm and less than 0.12 μm at the resolutions of 0.1 μm and 0.03 μm, respectively.展开更多
基金Project supported by LingChuang Research Project of China National Nuclear Corporationthe National Natural Science Foundation of China(Grant No.12027812)。
文摘Dual-phase and three-phase grating x-ray interference is a promising new technique for grating-based x-ray differential phase contrast imaging.Dual-phase grating interferometers have been relatively completely studied and discussed.In this paper,the corresponding imaging fringe formula of the three-phase grating interferometer is provided.At the same time,the similarities and differences between the three-phase grating interferometer and the dual-phase grating interferometer are investigated and verified,and that the three-phase grating interferometer can produce large-period moiréfringes without using the analyzing grating is demonstrated experimentally.Finally,a simple method of designing three-phase grating and multi-grating imaging systems from geometric optics based on the thin-lens theory of gratings is presented.These theoretical formulas and experimental results provide optimization tools for designing three-phase grating interferometer systems.
基金the Basal Research Funds of National Defence Science and Technology
文摘In this paper, we demonstrate a new optical method for tiny strain measurements based on the principle of carrier fringes of moire interferometry. A cross-line grating with frequency of 1200 lp/mm is replicated on the specimen surface, and the strain can be deduced from the changes in carrier fringes before and after the deformation of an object. Four coherent laser beams are used to obtain the carrier fringe patterns of field U and V. Both theoretical analysis and numerical simulation indicate that the ideal accuracy of strain can be controlled within a range of ±1με. Case study of a plane extension experiment shows that the measurement accuracy of strain can be controlled within the range of ±10με. The average strain values of every row of field U and every column of field V can be obtained by using this method, and approximated strain of every pixel in the whole-field can be further acquired, and thus it is possible to measure tiny strains occurred in a micro-field. The technology in this paper can provide comprehensive information for analyzing related mechanical content in the field of MEMS.
文摘In this paper, the optical/digital fringe multiplication (O/DFM) is realized in projection moiré using digital image processing (DIP). Both deformed grating and reference grating are captured using a CCD camera. The reference grating can also be produced using DIP. With the O/DFM, the pattern is multiplied with an image processing software, which is developed using MATLAB 6.5. Also with DIP, the phase shifting can become much simpler, and the automation can be adopted. The multiplied pattern is much thinner and easier to read, and sensitivity of measurement can be enhanced.
文摘A novel method to separate and simultaneously record the Moiréinterferometry fringe patterns of three deformation fields with only one CCD camera is developed;details of its operation principle,key points and error analysis are presented.With this technique,the deformation in U,V and W fields can be measured simultaneously,so dynamic test with comprehensive information can be performed.The advantage of this technique over other similar techniques lies in its simplicity,easy implementation and low cost.An application of this technique is given to show its feasibility.Technical problems that may be caused with this technique are also analyzed.
文摘A dual-frequency digital Moiré measurement method(DFDM) is proposed for the three-dimensional(3D) shape measurement of an object.The high-and low-frequency fringes are modulated separately along orthogonal direction using different carrier frequencies before being projected onto the measured object.After collecting and demodulating the composite fringe,the digital π phase shift is used to remove the DC component of the demodulated fringes,resulting in high-precision Moiré fringes for calculating the wrapped phase.The unwrapping of the high-frequency wrapped phase is guided by the low-frequency phase to further realistically reconstruct the surface of the measured object.When compared with existing single-shot digital Moiré profilometry,DFDM effectively removes the DC component of the fringe and calculates the phase more accurately.
基金Project supported by the National Natural Sciences Foundation of China (No. 10572102).
文摘This paper deals with the mode I crack problem of a cracked rubber sheet under plane stress condition using the delicate digital moiré technique. Through the four step phaseshifting method of automated fringe analysis, the displacement fields in the Cartesian coordinate system are given. By the coordinate-transform equation, the radial and circular displacement distributions in the polar coordinate system are obtained. The displacement isoline distributions and displacement vector distributions near the crack tip are discussed. The strain isoline distributions near the crack tip are also analyzed in this paper. Finally, the distribution rules for the mechanical fields near the crack tip are discussed with the sector division method.
基金supported by the Ministry of Science and Technology(MOST 104-2221-E-034-010-MY3),Taiwan,China
文摘This study describes a novel fringe-shaping technique developed to alleviate the fringe truncation problem engendered by the acquired saturated and/or weak fringe images from high-/low-reflectance surfaces of three-dimensional（3D） objects in phase-shifting profilometry. The particle swarm optimization algorithm is employed to perform the recovery of the truncated fringes with optimal fitting for compensation after single-trial acquisition. The results show that the proposed method improves phase recovery accuracy to accomplish 3 D surface reconstruction with only one set of phase-shifting fringes under different truncation sceneries.
文摘介绍了一种数字处理技术实现对光栅编码器所产生莫尔条纹信号的细分。莫尔信号经过光电转换后输出两路正余弦信号并通过光栅解码电路对其AD(analog to digital)采样,利用正切值消除正余弦信号的非线性误差,根据正余弦信号的正负将一个周期信号分割成8份,通过反正切角度值实现对每一份的细分。最后将此设计应用于单轴转台。实验结果表明,光栅编码器输出的的静态位置精度可以达到0.000 1°,动态位置及速度曲线无跳变,满足使用要求。
基金Project supported by the National Natural Science Foundation of China(No.61205159)
文摘In this study, a displacement measurement method based on digital moiré fringe is described and experimentally demonstrated. The method is formed by only one grating with a constant pitch. First, the magnified grating image is received by an imaging array and is sent to a computer. Then, the digital moiré fringes are generated by overlaying the grating image with its mirrored one. Finally, a specifically designed algorithm is used to obtain the fringes' phase difference before and after movement and calculate the displacement. This method has the effects of amplifying displacement and averaging the grating lines error, the same as the traditional moiré technique using two pieces of gratings. At the same time, the proposed system is much easier to assemble and the measurement resolution can be set more flexibly. One displacement measuring system based on this method was built up. Experiment results show that its measurement errors are less than 0.3 μm and less than 0.12 μm at the resolutions of 0.1 μm and 0.03 μm, respectively.
