The Experts below are selected from a list of 40050 Experts worldwide ranked by ideXlab platform
Wen-hsiang Tsai - One of the best experts on this subject based on the ideXlab platform.
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fold Principal Axis a new tool for defining the orientations of rotationally symmetric shapes
Pattern Recognition Letters, 1991Co-Authors: Sheng-lin Chou, Ja-chen Lin, Wen-hsiang TsaiAbstract:Abstract Chou, S.-L., J.-C. Lin and W.-H. Tsai, Fold Principal Axis—a new tool for defining the orientations of rotationally symmetric shapes, Pattern Recognition Letters 12 (1991) 109–115. A new type of Principal Axis, namely, fold Principal Axis, is introduced in this paper, which can be used to define the orientations of rotationally symmetric shapes. A given shape is first transformed into a new shape on which the well-defined traditional Principal Axis is detected. The traditional Principal Axis is then transformed back to obtain the proposed fold Principal axes of the given shape. The properties of such axes, including the uniqueness, existence, and invariance under rotation, translation, and scaling, are investigated. Some illustrative examples are also given.
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Fold Principal Axis—a new tool for defining the orientations of rotationally symmetric shapes
Pattern Recognition Letters, 1991Co-Authors: Sheng-lin Chou, Ja-chen Lin, Wen-hsiang TsaiAbstract:Abstract Chou, S.-L., J.-C. Lin and W.-H. Tsai, Fold Principal Axis—a new tool for defining the orientations of rotationally symmetric shapes, Pattern Recognition Letters 12 (1991) 109–115. A new type of Principal Axis, namely, fold Principal Axis, is introduced in this paper, which can be used to define the orientations of rotationally symmetric shapes. A given shape is first transformed into a new shape on which the well-defined traditional Principal Axis is detected. The traditional Principal Axis is then transformed back to obtain the proposed fold Principal axes of the given shape. The properties of such axes, including the uniqueness, existence, and invariance under rotation, translation, and scaling, are investigated. Some illustrative examples are also given.
Jing-fung Lin - One of the best experts on this subject based on the ideXlab platform.
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measurements of phase retardation and Principal Axis angle using an electro optic modulated mach zehnder interferometer
Optics and Lasers in Engineering, 2005Co-Authors: Sen Yung Lee, Jing-fung LinAbstract:Abstract This paper presents an electro-optic modulated circular heterodyne modified Mach–Zehnder interferometer and a convenient two-phase signal-processing algorithm for the measurement of variations in the magnitude of phase retardation and the angle of Principal Axis in optical materials. The developed method solves the problems of normalized intensity jump and limited phase retardation measurement range associated with the circular heterodyne interferometer proposed previously. The present method uses a saw-tooth wave signal to drive an electro-optic (EO) modulator, and employs a lock-in amplifier to demodulate the Principal Axis angle and the phase retardation. Specifically, this paper considers two main sources of measurement errors, namely the misorientation of the EO modulator and the reflection phase retardation of the beam splitter. Furthermore, the study develops calibration procedures and identifies a means to minimize measurement errors induced by the reflection phase retardation of the beam splitter.
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Measurements of the Principal Axis and phase retardation using a new circular polariscope and the Senarmont setup
2005Co-Authors: Jing-fung Lin, Sen Yung Lee, Chi Cheng PengAbstract:Measurements of the Principal Axis and phase retardation using a new circular polariscope and the Senarmont setup with electro-optic modulation is presented. In the first step of measurements, we use the electro-optic modulated circular heterodyne interferometer and the phase-lock technique to precisely measure the Principal Axis angle. After removing the first quarter-wave plate in the first setup, a Senarmont setup is designed to determine the phase retardation also using the phase-lock technique. The simple phase extraction algorithm for the Principal Axis angle and the phase retardation measurement is presented. The average absolute errors of the Principal Axis angle and the phase retardation of the λ/8-wave plate are determined to be only 0.4680 and 0.23%.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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Measurements of phase retardation and Principal Axis angle using an electro-optic modulated Mach–Zehnder interferometer
Optics and Lasers in Engineering, 2005Co-Authors: Sen Yung Lee, Jing-fung LinAbstract:Abstract This paper presents an electro-optic modulated circular heterodyne modified Mach–Zehnder interferometer and a convenient two-phase signal-processing algorithm for the measurement of variations in the magnitude of phase retardation and the angle of Principal Axis in optical materials. The developed method solves the problems of normalized intensity jump and limited phase retardation measurement range associated with the circular heterodyne interferometer proposed previously. The present method uses a saw-tooth wave signal to drive an electro-optic (EO) modulator, and employs a lock-in amplifier to demodulate the Principal Axis angle and the phase retardation. Specifically, this paper considers two main sources of measurement errors, namely the misorientation of the EO modulator and the reflection phase retardation of the beam splitter. Furthermore, the study develops calibration procedures and identifies a means to minimize measurement errors induced by the reflection phase retardation of the beam splitter.
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Polariscope for simultaneous measurement of the Principal Axis and the phase retardation by use of two phase-locked extractions
Applied Optics, 2004Co-Authors: Jing-fung Lin, Sen Yung LeeAbstract:A novel polariscope with electro-optic modulation that is capable of simultaneous measurement of the Principal Axis and the phase retardation of an optical linear birefringent medium by means of two phase-locked extractions is described. A phase compensator is used to suppress the transmission phase-retardation effect of the beam splitter, thereby enhancing the precision of the measuring performance. The validity of the proposed design is demonstrated by measurement of the Principal Axis and phase retardation of a quarter-wave plate sample. There are absolute errors of 0.25° on average and 0.58° at maximum in the Principal-Axis measurement and of 0.75° (0.83%) on average and 3.11° at maximum in the phase-retardation measurement. Meanwhile, the retardation error lies within a 5% uncertainty range of a commercial wave plate. The root-mean-square resolutions for the Principal-Axis angle and phase-retardation measurements are 0.042° and 0.081°, respectively. Finally, the dynamic ranges of the Principal-Axis angle measurement and the phase-retardation measurement extend as far as 180°.
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A compact circular heterodyne interferometer for simultaneous measurements of variation in the magnitude of phase retardation and Principal Axis angle
Measurement Science and Technology, 2004Co-Authors: Sen Yung Lee, Jing-fung LinAbstract:This paper presents a compact configuration for simultaneous measurements of variation in the magnitude of phase retardation and Principal Axis angle in optical materials. The configuration comprises a circular heterodyne common-path interferometer, in which a sawtooth voltage waveform is used to regulate an electro-optic (EO) modulator. Changes in phase retardation and in the angle of the Principal Axis are demodulated by a lock-in amplifier via a simple signal-processing algorithm. Compared to the conventional configurations, the proposed interferometer offers an easier setup, has only one detection channel, and employs a simpler signal-processing operation. The validity of the proposed measurement system is demonstrated using a quarter-wave plate as a sample. The results indicate that the average absolute errors of the phase retardation and Principal Axis angle of quarter-wave plate are 4.88% and 0.94°, respectively. Furthermore, the root-mean-square resolutions of the magnitude of phase retardation and the Principal Axis angle are shown to be 1.59° and 0.10°, respectively. The dynamic range of phase retardation measurement is up to 90° and that of the Principal Axis angle measurement is up to 180°.
Fei Gao - One of the best experts on this subject based on the ideXlab platform.
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Principal Axis and crease detection for slap fingerprint segmentation
International Conference on Image Processing, 2010Co-Authors: Yongliang Zhang, Yaping Huang, Gang Xiao, Fei GaoAbstract:In slap fingerprint segmentation, crease is the most difficult edge to correctly detect. In this paper, we present a novel yet simple and accurate algorithm for the Principal Axis and crease detection. Firstly, the Principal Axis of each foreground region is detected using the minimal rotational inertia; Secondly, the crease detection is done based on cost function minimization. This algorithm has been incorporated in a slap fingerprint segmentation scheme, previously developed by the authors, producing successful results.
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ICIP - Principal Axis and crease detection for slap fingerprint segmentation
2010 IEEE International Conference on Image Processing, 2010Co-Authors: Yongliang Zhang, Yaping Huang, Gang Xiao, Fei GaoAbstract:In slap fingerprint segmentation, crease is the most difficult edge to correctly detect. In this paper, we present a novel yet simple and accurate algorithm for the Principal Axis and crease detection. Firstly, the Principal Axis of each foreground region is detected using the minimal rotational inertia; Secondly, the crease detection is done based on cost function minimization. This algorithm has been incorporated in a slap fingerprint segmentation scheme, previously developed by the authors, producing successful results.
Steve Maybank - One of the best experts on this subject based on the ideXlab platform.
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Principal Axis-based correspondence between multiple cameras for people tracking
IEEE Transactions on Pattern Analysis and Machine Intelligence, 2006Co-Authors: Weiming Hu, Jianguang Lou, Tieniu Tan, Xue Zhou, Min Hu, Steve MaybankAbstract:Visual surveillance using multiple cameras has attracted increasing interest in recent years. Correspondence between multiple cameras is one of the most important and basic problems which visual surveillance using multiple cameras brings. In this paper, we propose a simple and robust method, based on Principal axes of people, to match people across multiple cameras. The correspondence likelihood reflecting the similarity of pairs of Principal axes of people is constructed according to the relationship between "ground-points" of people detected in each camera view and the intersections of Principal axes detected in different camera views and transformed to the same view. Our method has the following desirable properties: 1) Camera calibration is not needed. 2) Accurate motion detection and segmentation are less critical due to the robustness of the Principal Axis-based feature to noise. 3) Based on the fused data derived from correspondence results, positions of people in each camera view can be accurately located even when the people are partially occluded in all views. The experimental results on several real video sequences from outdoor environments have demonstrated the effectiveness, efficiency, and robustness of our method.
Jeanbernard Hayet - One of the best experts on this subject based on the ideXlab platform.
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multiple view multiple target tracking with Principal Axis based data association
Advanced Video and Signal Based Surveillance, 2011Co-Authors: Francisco Madrigal, Jeanbernard HayetAbstract:We present a novel method for multi-object tracking that tracks target both in the video streams and in a reference ground frame. This allows to remove ambiguities created by occlusions in one view. Our system takes as a base a recently proposed collaborative scheme and makes it handle multiple targets. We use a fast, simple solution for data association in the ground plane based on Principal Axis and a partly joint probabilistic model with MCMC sampling to ensure that tracked targets are kept separated whenever groups of targets appear. Results are presented on several popular databases of multi-camera, multi-target videos.
