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Articles 1 - 30 of 45
Full-Text Articles in Physical Sciences and Mathematics
A Fringe Period Unwrapping Technique For Digital Fringe Profilometry Based On Spatial Shift Estimation, Pu Cao, Jiangtao Xi, Joe F. Chicharo, Yanguang Yu
A Fringe Period Unwrapping Technique For Digital Fringe Profilometry Based On Spatial Shift Estimation, Pu Cao, Jiangtao Xi, Joe F. Chicharo, Yanguang Yu
Professor Joe F. Chicharo
In this paper we present a review of the phase unwrapping problem in Fringe Pattern Profilometry (FPP), based on which we study the spatial shift wrapping problem in spatial shift estimation (SEE) based FPP. An approach for carrying out the spatial shift unwrapping is proposed with its performance confirmed by experiments.
Toward Automatic Measurement Of The Linewidth-Enhancement Factor Using Optical Feedback Self-Mixing Interferometry With Weak Optical Feedback, Yanguang Yu, Jiangtao Xi, Joe F. Chicharo, Thierry Bosch
Toward Automatic Measurement Of The Linewidth-Enhancement Factor Using Optical Feedback Self-Mixing Interferometry With Weak Optical Feedback, Yanguang Yu, Jiangtao Xi, Joe F. Chicharo, Thierry Bosch
Professor Joe F. Chicharo
This paper proposes an approach for automatically measuring the linewidth-enhancement factor (LEF) of semiconductor lasers using optical feedback self-mixing interferometry (OFSMI), which works in weak optical feedback regime and where the external target is subject to simple harmonic vibration with unknown vibration frequency and magnitude. According to well-known Lang–Kobayashi theory the waveform of the modulated optical output power from the OFSMI system is influenced by multiple parameters, including the LEF, the optical feedback level factor, and the parameters related to the movement of external target. In order to estimate LEF, other parameters must also be considered and, hence, a multiple …
Estimating The Parameters Of Semiconductor Lasers Based On Weak Optical Feedback Interferometry, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo, Thierry Bosch
Estimating The Parameters Of Semiconductor Lasers Based On Weak Optical Feedback Interferometry, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo, Thierry Bosch
Professor Joe F. Chicharo
The paper presents a new approach for measuring the linewidth enhancement factor (LEF) of semiconductor lasers (SL) and the optical feedback level factor C in SLs. The proposed approach is based on the analysis of self-mixing signals observed in self-mixing optical feedback interferometry. Unlike existing approaches, the approach tries to estimate the parameters LEF and C by a gradient-based optimization algorithm that achieves best data-to-theoretical model fitting. The effectiveness and accuracy of the method have been confirmed and tested by theoretical analysis and computer simulations.
Effects Of Fiber Cladding On Uv Beams And Fringe Patterns In Side-Exposure Fbg Writing, Enbang Li, Jiangtao Xi, Joe F. Chicharo, Yanguang Yu, Jianquan Yao
Effects Of Fiber Cladding On Uv Beams And Fringe Patterns In Side-Exposure Fbg Writing, Enbang Li, Jiangtao Xi, Joe F. Chicharo, Yanguang Yu, Jianquan Yao
Professor Joe F. Chicharo
The so-called side-exposure method has been widely used in the fabrication of fiber Bragg gratings (FBGs). The effects of the fiber cladding on the wavefronts of the UV writing beams and the interference fringes formed inside the fiber have been addressed in this study. The wavefronts of the UV beams have been analyzed and it has been demonstrated that the existence of the fiber cladding significantly alters the wavefronts of the UV beams in one plane and makes them highly astigmatic. Based on the calculated wavefront radii of the UV beams, a model has been established for prediction of the …
Optical Feedback Self-Mixing Interferometry With A Large Feedback Factor C: Behavior Studies, Yanguang Yu, Jiangtao Xi, Joe F. Chicharo, Thierry Bosch
Optical Feedback Self-Mixing Interferometry With A Large Feedback Factor C: Behavior Studies, Yanguang Yu, Jiangtao Xi, Joe F. Chicharo, Thierry Bosch
Professor Joe F. Chicharo
This paper studies the behavior of optical feedback self-mixing interferometric (OFSMI) systems, where the semiconductor lasers operate at a single mode (perturbed external cavity mode) with a large optical feedback factor C. Based on analysis of the spectral linewidth associated with all the possible lasing modes at different C values, a set of mode jumping rules are proposed following the minimum linewidth mode competition principle proposed in . According to the rules, the C factor can be classified into different regions, on which an OFSMI system will exhibit distinct phenomena. In particular, for the same amount of displacement associated with …
Eliminating Noises Contained In Sensing Signals From A Self-Mixing Laser Diode, Yanguang Yu, Tiemin Mei, Jiangtao Xi, Joe F. Chicharo, Huiying Ye, Zhao Wang
Eliminating Noises Contained In Sensing Signals From A Self-Mixing Laser Diode, Yanguang Yu, Tiemin Mei, Jiangtao Xi, Joe F. Chicharo, Huiying Ye, Zhao Wang
Professor Joe F. Chicharo
The paper studied the noise elimination methods for the signals observed from a self-mixing-laser diode (SM-LD) based sensing system. The core part of the sensing system consists of a LD, a lens and an external vibrating target. The proposed noise elimination methods are applied on both the simulated and experimental sensing signals. The results presented in the paper show the noise contained in the sensing signals can be effectively eliminated. As a consequence, the vibration trace of the target can be reconstructed with high accuracy using this sensing system.
The Experimental Evaluation Of Fbg Sensor For Strain Measurement Of Prestressed Steel Strand, Enbang Li, Jiangtao Xi, Joe F. Chicharo, Tiegen Liu, Xin Li, Junfeng Jiang, Lina Li, Yunxin Wang
The Experimental Evaluation Of Fbg Sensor For Strain Measurement Of Prestressed Steel Strand, Enbang Li, Jiangtao Xi, Joe F. Chicharo, Tiegen Liu, Xin Li, Junfeng Jiang, Lina Li, Yunxin Wang
Professor Joe F. Chicharo
Multi-wire steel strands have been widely used in various prestressed concrete structures. In this study, experimental evaluation of fiber Bragg grating (FBG) sensors for strain measurements in a seven-wire prestressed steel strand has been carried out. An installation technique of FBG sensors has been developed to fulfill the special requirements of the prestressed steel strand. The experiment results show that fiber Bragg gratings can represent the overall stress of the prestressed steel strand without being affected by the specific structure of the strand when it is only fixed on one wire. It is also demonstrated that the maximum strain that …
Blind Colour Isolation For Colour-Channel-Based Fringe Pattern Profilometry Using Digital Projection, Y. Hu, Jiangtao Xi, Joe F. Chicharo, Zongkai Yang
Blind Colour Isolation For Colour-Channel-Based Fringe Pattern Profilometry Using Digital Projection, Y. Hu, Jiangtao Xi, Joe F. Chicharo, Zongkai Yang
Professor Joe F. Chicharo
We present an algorithm for estimating the color demixing matrix based on the color fringe patterns captured from the reference plane or the surface of the object. The advantage of this algorithm is that it is a blind approach to calculating the demixing matrix in the sense that no extra images are required for color calibration before performing profile measurement. Simulation and experimental results convince us that the proposed algorithm can significantly reduce the influence of the color cross talk and at the same time improve the measurement accuracy of the color-channel-based phase-shifting profilometry.
Fast Quality-Guided Flood-Fill Phase Unwrapping Algorithm For Three-Dimensional Fringe Pattern Profilometry, Ke Chen, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo
Fast Quality-Guided Flood-Fill Phase Unwrapping Algorithm For Three-Dimensional Fringe Pattern Profilometry, Ke Chen, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo
Professor Joe F. Chicharo
A fast quality-guided flood-fill phase unwrapping algorithm is proposed for real-time 3D Fringe Pattern Profilometry (FPP) system. The proposed approach consists of three steps. First, based on the phase maps acquired by phase shift profilometry (PSP) techniques, a quality map is generated according to the phase variance adjacent pixels on the wrapped phase map. According to the quality map, the phase map is divided into several parts which are categorised as either rapid phase changing areas or smooth phase changing areas. Then quality-guided flood-fill phase unwrapping algorithm is applied to rapid phase changing areas and non-guided path-following algorithm is used …
The Height Variance Range For One Frequency Fringe Pattern Profilometry, Yi Ding, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo, Wenqing Cheng
The Height Variance Range For One Frequency Fringe Pattern Profilometry, Yi Ding, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo, Wenqing Cheng
Professor Joe F. Chicharo
The upper limit on the deepest step of the surface shape that can be accurately determined is an important performance measure associated with the fringe projection profilometry. This metric is evaluated as the variance of height between two adjacent pixels on a fringe patterns reflected from the object surface. This paper presents novel results on this metric based on the Nyquist sampling theorem originally developed in the area of communication theory. Compared to existing results, we indicate that the fringe width and digital image resolution also affect the height variance range significantly. This new result could be used to increase …
Phase Error Correction Based On Inverse Function Shift Estimation In Phase Shifting Profilometry Using A Digital Video Projector, Yang Liu, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo
Phase Error Correction Based On Inverse Function Shift Estimation In Phase Shifting Profilometry Using A Digital Video Projector, Yang Liu, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo
Professor Joe F. Chicharo
Fringe Pattern Profilometry (FPP) is 3D surface measuring technique based on triangulation. The utilization of digital projection in FPP system introduces significant phase distortion for Phase Shifting Profilometry (PSP), because of the nonlinear response of digital video projectors, which is referred as gamma distortion. Considering that the distorted phase has a stable function for a reference plane, this paper proposes an approach based on inverse function shift estimation (IFSE) to detect the spatial shift of the distorted phase caused by object height. This spatial shift is independent of projector’s gamma distortion and accurate surface can be reconstructed based it. The …
Implementation Of A Quasi-Digital Adc On Pld, Fu-Yuan Wang, Yong-Liang Li, Jiangto Xi, Joe F. Chicharo
Implementation Of A Quasi-Digital Adc On Pld, Fu-Yuan Wang, Yong-Liang Li, Jiangto Xi, Joe F. Chicharo
Professor Joe F. Chicharo
This paper presents a new way to implement stochastic logic-based analog-to-digit converters (ADCs) on a programmable logic device (PLD) chip. The proposed implementation is almost all digitalized so that the design can be done by using hardware description language and the results can be easily downloaded into a PLD chip. Both simulation and hardware test results are given.
Novel Two-Dimension Fbg Sensor Based On Rectangle Cantiliver Beam For Simultaneous Measurement Of Force And Temperature, Weigang Zhang, Guiyan Kai, Shuzhong Yuan, Xiaoyi Dong, Enbang Li, Jiangtao Xi, Joe F. Chicharo
Novel Two-Dimension Fbg Sensor Based On Rectangle Cantiliver Beam For Simultaneous Measurement Of Force And Temperature, Weigang Zhang, Guiyan Kai, Shuzhong Yuan, Xiaoyi Dong, Enbang Li, Jiangtao Xi, Joe F. Chicharo
Professor Joe F. Chicharo
In this paper, for the first time to our knowledge, we report a novel FBG-type two-dimensional sensor that is able to simultaneously measure two-dimension (2-D) force and temperature, and the 2-D force sensing process can be tuned by applying rectangular cantilever beam (RCB). In the vertical directions of the RCB axis, the wavelengths shifts of two FBGs bonded to the surface of the RCB are quasi-linear with respect to the 2-D force and temperature, respectively. Two FBGs are experimentally demonstrated to have the 2-D force sensitivities of ~5.32 nm/N and 3.21 nm/N, a temperature sensitivity of ~0.095nm/°C between 0°C and …
Recovering The Absolute Phase Maps Of Two Fringe Patterns With Selected Frequencies, Yi Ding, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo
Recovering The Absolute Phase Maps Of Two Fringe Patterns With Selected Frequencies, Yi Ding, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo
Professor Joe F. Chicharo
Phase unwrapping is an important and challenging issue in fringe pattern profilometry. In this Letter we propose an approach to recover absolute phase maps of two fringe patterns with selected frequencies. Compared to existing temporal multiple frequency algorithms, the two frequencies in our proposed algorithm can be high enough and thus enable efficient and accurate recovery of absolute phase maps. Experiment results are presented to confirm the effectiveness of the proposed technique.
A Data-Fitting Approach For Displacements And Vibration Measurement Using Self-Mixing Interferometers, Yi Zhang, Jiangtao Xi, Joe F. Chicharo, Yanguang Yu
A Data-Fitting Approach For Displacements And Vibration Measurement Using Self-Mixing Interferometers, Yi Zhang, Jiangtao Xi, Joe F. Chicharo, Yanguang Yu
Professor Joe F. Chicharo
This paper presents a signal processing approach for vibration measurement using self-mixing interferometer (SMI). Compared to existing approaches, the proposed approach is able to achieve an accuracy of λ/40 which significantly exceeds the accuracy limit associated with conventional simple SMI systems λ/4.
3d Face Recognition Based On A Modified Icp Method, Kankan Zhao, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo
3d Face Recognition Based On A Modified Icp Method, Kankan Zhao, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo
Professor Joe F. Chicharo
3D face recognition technique has gained much more attention recently, and it is widely used in security system, identification system, and access control system, etc. The core technique in 3D face recognition is to find out the corresponding points in different 3D face images. The classic partial Iterative Closest Point (ICP) method is iteratively align the two point sets based on repetitively calculate the closest points as the corresponding points in each iteration. After several iterations, the corresponding points can be obtained accurately. However, if two 3D face images with different scale are from the same person, the classic partial …
Signal Processing Methods Implemented In A Novel Fbg Sensing System For Vibration/Dynamic Strain Measurement, Xingyuan Xu, Enbang Li, Jiangtao Xi, Joe F. Chicharo
Signal Processing Methods Implemented In A Novel Fbg Sensing System For Vibration/Dynamic Strain Measurement, Xingyuan Xu, Enbang Li, Jiangtao Xi, Joe F. Chicharo
Professor Joe F. Chicharo
We have demonstrated a novel Fiber Bragg Grating sensing system based on a Fabry-Perot tunable filter for measuring dynamic processes. This system is very suitable for multipoint vibration or dynamic strain detection. However, in some conditions, the response time of Fabry-Perot tunable filter will influence the sensitivity of the sensor that the sensitivity is not kept constant. Therefore, post-processing for the measured vibration signal is necessary to solve this problem. In this paper, the demodulation technique of this system is briefly described and two signal processing methods are introduced to deal with the measured signal to obtain stable measurement of …
The Fourier Spectrum Analysis Of Optical Feedback Self-Mixing Signal Under Weak And Moderate Feedback, Xiaojun Zhang, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo
The Fourier Spectrum Analysis Of Optical Feedback Self-Mixing Signal Under Weak And Moderate Feedback, Xiaojun Zhang, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo
Professor Joe F. Chicharo
The spectrum characteristics of self-mixing signals observed in optical feedback self-mixing interferometry (OFSMI) is studied in this paper. The purpose is to provide guidance for the design of pre-processing techniques for eliminating noise or disturbance. The influence of two important parameters of the OFSMI system on the spectrum, that is, the optical feedback factor and the linewidth enhancment factor, are measured by means of Discrete Fourier transform (DFT). The simulated results show that, at a weak feedback, the OFSMI signals are strictly band limited in nature, with the cut-off frequencies being the vibration frequency and the fringe frequency respectively. Also …
An Energy-Aware Multilevel Clustering Algorithm For Wireless Sensor Networks, Xinfang Yan, Jiangtao Xi, Joe F. Chicharo, Yanguang Yu
An Energy-Aware Multilevel Clustering Algorithm For Wireless Sensor Networks, Xinfang Yan, Jiangtao Xi, Joe F. Chicharo, Yanguang Yu
Professor Joe F. Chicharo
Clustering sensors nodes as the basic of routing is an efficient mechanism for prolonging the lifetime of wireless sensor networks. In this paper, the high-efficient multilevel clustering is abstracted as a root tree which has the performances of the minimal relay set and the maximal weight according to graph theory. A mathematical model for the clustering virtual backbone is built. Based on the model, an algorithm called energy-aware multilevel clustering (EAMC) is proposed. The EAMC can reduce the number of relays used for data transmission by minimizing the amount of the nodes in the root tree (that is cluster-head). Furthermore, …
An Estimation Method For Feedback Level Factor C Of A Self-Mixing Interferometry System, Yuanlong Fan, Yanguang Yu, Jiangtao Xi, Joe F. Chicharo
An Estimation Method For Feedback Level Factor C Of A Self-Mixing Interferometry System, Yuanlong Fan, Yanguang Yu, Jiangtao Xi, Joe F. Chicharo
Professor Joe F. Chicharo
This paper presents a fast estimation method for feedback level factor C of a self-mixing interferometry (SMI) system. The reconstruction of a displacement waveform using a SMI signal needs to know a C value. However, it is difficult to maintain a constant C value during the reconstruction process. We study the features of the reconstructed displacement waveforms incorporating different pre-set C values and classify waveforms into two types. Bisection method is introduced in our method for fast estimating C value. The effectiveness of our proposed method has been verified by both simulation and experimental data.
Estimating The Parameters Of Semiconductor Lasers Based On Weak Optical Feedback Self-Mixing Interferometry, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo, T. Bosch
Estimating The Parameters Of Semiconductor Lasers Based On Weak Optical Feedback Self-Mixing Interferometry, Jiangtao Xi, Yanguang Yu, Joe F. Chicharo, T. Bosch
Professor Joe F. Chicharo
The paper presents a practical approach for measuring the linewidth enhancement factor /spl alpha/ of semiconductor lasers and the optical feedback level factor C in a semiconductor laser with an external cavity. The proposed approach is based on the analysis of the signals observed in an optical feedback self-mixing interferometric system. The parameters /spl alpha/ and C are estimated using a gradient-based optimization algorithm that achieves best data-to-theoretical model match. The effectiveness and accuracy of the method has been confirmed and tested by computer simulations and experiments, which show that the proposed approach is able to estimate /spl alpha/ and …
An Investigation Into Temporal Gamma Luminance For Digital Fringe Fourier Transform Profilometers, J. M. Baker, Joe F. Chicharo, Jiangtao Xi
An Investigation Into Temporal Gamma Luminance For Digital Fringe Fourier Transform Profilometers, J. M. Baker, Joe F. Chicharo, Jiangtao Xi
Professor Joe F. Chicharo
Analysis of the impact of temporal gamma luminance on Fourier Transform Profilometry (FTP) Digital Video Projection (DVP) based structured light profilometers is undertaken. We investigate the spectral harmonic structure for typical DVP fringe d0 images linking projector -y and 2nd order fringe harmonics. The Ep validity of the presented study is verified through simulation, and subsequently we conclude that for typical projector -y, the 2nd order harmonic is the single most significant contribution to reconstruction error for the phase measuring technique. The impact of our analysis is further gauged by empirical measurement of the temporal variation of -y of a …
Displacement Estimation Based On Model Calibration In Weak Feedback Optical Self-Mixing System, L. Wei, Jiangtao Xi, J. Chicharo
Displacement Estimation Based On Model Calibration In Weak Feedback Optical Self-Mixing System, L. Wei, Jiangtao Xi, J. Chicharo
Professor Joe F. Chicharo
This paper presents a novel method to estimate displacement of a moving object based on model calibration in a weak feedback laser diode self-mixing system. A hybrid genetic algorithm is employed to locate the global minimum for the cost function which is constructed as the discrepancy between theoretically calculated system output and the experimental data. In turn, displacement measurement is achieved by identifying the optimal parameters for the system model. The proposed method is tested by both simulation and experimental setup with measuring accuracy better than 25nm.
Multi-Channel Digital Fringe Calibration For Structured Light Profilometers Using Neural Networks, Matthew J. Baker, Jiangtao Xi, Joe F. Chicharo
Multi-Channel Digital Fringe Calibration For Structured Light Profilometers Using Neural Networks, Matthew J. Baker, Jiangtao Xi, Joe F. Chicharo
Professor Joe F. Chicharo
The performance of structured light profilometers is significantly hindered by the generation of distorted sinusoid fringe images, particularly, for multi-channel applications. In this paper we investigate the application of neural network fringe calibration for the multi-channel approach. We analytically review the nature of the major error sources associated with the multi-channel approach and propose afringe calibration technique with emphasis on minimal photometric calibration. The performance of the calibration technique is gauged through both simulation and experimentation.
Improving The Performance In An Optical Feedback Self-Mixing Interferometry System Using Digital Signal Pre-Processing, Yanguang Yu, Jiangtao Xi, Joe F. Chicharo
Improving The Performance In An Optical Feedback Self-Mixing Interferometry System Using Digital Signal Pre-Processing, Yanguang Yu, Jiangtao Xi, Joe F. Chicharo
Professor Joe F. Chicharo
This paper considers the issue of noise reduction associated with Optical Feedback Self-mixing Interferometries (OFSMI). The objective is to develop an effective pre-processing filtering solution that can eliminated the inherent noise disturbances. The characteristics of OFSMI signals are described in some detail and two filter solutions are proposed. The latter includes a non-linear median filter and a Kaiser based FIR filter. The performance of the two types of filters are removing sparkle-like noise while Kaiser based FIR filters areeffective in reducing the high frequency noise as well as the slow time-varying signal envelop fluctuation. Interestingly our results show that the …
Linear Prediction Incorporating Simultaneous Masking, J Lukasiak, I. S. Burnett, Joe F. Chicharo, M. M. Thomson
Linear Prediction Incorporating Simultaneous Masking, J Lukasiak, I. S. Burnett, Joe F. Chicharo, M. M. Thomson
Professor Joe F. Chicharo
Whilst linear prediction is the cornerstone of most modern speech coders, few of these coders incorporate the perceptual characteristics of hearing into the calculation of the linear predictor coefficients (LPCs). This paper proposes a method of incorporating simultaneous masking into the calculation of the LPCs. This modification requires only a modest increase in computational complexity and results in the linear predictor removing more perceptually important information from the input speech signal. This results in a filter that better models the formants of the input speech spectrum. The net effect is that an improvement in quality is achieved for a given …
Computing Running Dcts And Dsts Based On Their Second-Order Shift Properties, Jiangtao Xi, Joe F. Chicharo
Computing Running Dcts And Dsts Based On Their Second-Order Shift Properties, Jiangtao Xi, Joe F. Chicharo
Professor Joe F. Chicharo
This paper presents a set of second-order recursive equations which are referred to as the second-order shift (SOS) properties of the discrete cosine transform (DCT) and the discrete sine transform (DST). The proposed SOS properties enable independent updating of the respective DCT and DST coefficients. This is in direct contrast with existing methodology for computing the running DCT and DST where there is an inherent interdependency between the DCT and DST coefficients. The SOS properties provide more efficient algorithms in terms of computational burden and memory requirements when implementing running DCTs and DSTs.
Power Efficient Connected Topologies In Ad-Hoc Networks, G. Srivastava, Joe F. Chicharo, P. Boustead
Power Efficient Connected Topologies In Ad-Hoc Networks, G. Srivastava, Joe F. Chicharo, P. Boustead
Professor Joe F. Chicharo
Power efficient topologies in an ad-hoc network can reduce battery usage and increase the lifetime of a network. Topology control algorithms including a local minimum spanning tree (LMST), distributed relative neighbourhood graph (DRNG) and K-Neigh graphs are computed by using the location or the distance information of the network nodes. Inaccurate distance or location information can lead to disconnected topology graphs. Furthermore, a distance based topology graph may not necessarily be connected due to wireless signal attenuation and propagation characteristics. In a realistic scenario, a small link distance may correspond to a large transmission power as the signal may need …
Optical Signal Processing For Fiber Bragg Grating Based Wear Sensors, Enbang Li, Jiangtao Xi, Joe F. Chicharo
Optical Signal Processing For Fiber Bragg Grating Based Wear Sensors, Enbang Li, Jiangtao Xi, Joe F. Chicharo
Professor Joe F. Chicharo
In this study, we propose a simplified signal processing scheme for fiber Bragg grating (FBG) based wear sensing. Instead of using a chirped FBG and detecting the bandwidth, we use uniform gratings as sensors and measure the optical power reflected by the sensing grating to determine the length of the sensor grating, hence detect the wear. We demonstrate by the experiments that the proposed method is feasible and practical. The advantage of the proposed method lies in the fact that structure of the wear sensing system is simplified and therefore the cost can be significantly reduced. The principle of the …
Study On Generalized Analysis Model For Fringe Pattern Profilometry, Y. Hu, Jiangtao Xi, Z. Yang, Enbang Li, Joe F. Chicharo
Study On Generalized Analysis Model For Fringe Pattern Profilometry, Y. Hu, Jiangtao Xi, Z. Yang, Enbang Li, Joe F. Chicharo
Professor Joe F. Chicharo
This paper presents a generalized analysis model for fringe pattern profilometry. We mathematically derived a new analysis model that gives a more general expression of the relationship between projected and deformed fringe patterns. Meanwhile, based on the proposed generalized model, a new algorithm is presented to retrieve 3-D surfaces from nonlinearly distorted fringes.Without any prior knowledge about the projection system, we still can obtain very accurate measurement results by using a generalized analysis model and a proposed algorithm. Computer simulation and experimental results show that the generalized model and the proposed algorithm can significantly improve the 3-D reconstruction precision, especially …