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Articles 1 - 14 of 14
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.