The Experts below are selected from a list of 81783 Experts worldwide ranked by ideXlab platform
Lorenzo Marrucci - One of the best experts on this subject based on the ideXlab platform.
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measuring the complex orbital angular momentum spectrum and spatial mode decomposition of Structured Light beams
Optica, 2017Co-Authors: Alessio Derrico, Raffaele Damelio, Bruno Piccirillo, Filippo Cardano, Lorenzo MarrucciAbstract:Light beams carrying orbital angular momentum are key resources in modern photonics. In many applications, the ability to measure the complex spectrum of Structured Light beams in terms of these fundamental modes is crucial. Here we propose and experimentally validate a simple method that achieves this goal by digital analysis of the interference pattern formed by the Light beam and a reference field. Our approach allows one to also characterize the beam radial distribution, hence retrieving the entire information contained in the optical field. Setup simplicity and reduced number of measurements could make this approach practical and convenient for the characterization of Structured Light fields.
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measuring the complex orbital angular momentum spectrum and spatial mode decomposition of Structured Light beams
arXiv: Optics, 2017Co-Authors: Alessio Derrico, Raffaele Damelio, Bruno Piccirillo, Filippo Cardano, Lorenzo MarrucciAbstract:Light beams carrying orbital angular momentum are key resources in modern photonics. In many applications, the ability of measuring the complex spectrum of Structured Light beams in terms of these fundamental modes is crucial. Here we propose and experimentally validate a simple method that achieves this goal by digital analysis of the interference pattern formed by the Light beam and a reference field. Our approach allows one to characterize the beam radial distribution also, hence retrieving the entire information contained in the optical field. Setup simplicity and reduced number of measurements could make this approach practical and convenient for the characterization of Structured Light fields.
Song Zhang - One of the best experts on this subject based on the ideXlab platform.
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pixel wise absolute phase unwrapping using geometric constraints of Structured Light system
Optics Express, 2016Co-Authors: Yatong An, Jaesang Hyun, Song ZhangAbstract:This paper presents a method to unwrap phase pixel by pixel by solely using geometric constraints of the Structured Light system without requiring additional image acquisition or another camera. Specifically, an artificial absolute phase map, Φmin, at a given virtual depth plane z = zmin, is created from geometric constraints of the calibrated Structured Light system; the wrapped phase is pixel-by-pixel unwrapped by referring to Φmin. Since Φmin is defined in the projector space, the unwrapped phase obtained from this method is absolute for each pixel. Experimental results demonstrate the success of this proposed novel absolute phase unwrapping method.
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Novel calibration method for Structured-Light system with an out-of-focus projector
Applied Optics, 2014Co-Authors: Beiwen Li, Nikolaus Karpinsky, Song ZhangAbstract:A Structured-Light system with a binary defocusing technique has the potential to have more extensive application due to its high speeds, gamma-calibration-free nature, and lack of rigid synchronization requirements between the camera and projector. However, the existing calibration methods fail to achieve high accuracy for a Structured-Light system with an out-of-focus projector. This paper proposes a method that can accurately calibrate a Structured-Light system even when the projector is not in focus, making it possible for high-accuracy and high-speed measurement with the binary defocusing method. Experiments demonstrate that our calibration approach performs consistently under different defocusing degrees, and a root-mean-square error of about 73 μm can be achieved with a calibration volume of 150(H) mm×250(W) mm×200(D)mm.
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novel method for Structured Light system calibration
Optical Engineering, 2006Co-Authors: Song Zhang, Peisen S HuangAbstract:System calibration, which usually involves complicated and time-consuming procedures, is crucial for any 3-D shape measurement system. In this work, a novel systematic method is proposed for accurate and quick calibration of a 3-D shape measurement system we developed based on a Structured Light technique. The key concept is to enable the projector to "capture" images like a camera, thus making the calibration of a projector the same as that of a camera. With this new concept, the calibration of Structured Light systems becomes essentially the same as the calibration of traditional stereovision systems, which is well estab- lished. The calibration method is fast, robust, and accurate. It signifi- cantly simplifies the calibration and recalibration procedures of struc- tured Light systems. This work describes the principle of the proposed method and presents some experimental results that demonstrate its performance. © 2006 Society of Photo-Optical Instrumentation Engineers.
Andrew Forbes - One of the best experts on this subject based on the ideXlab platform.
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su 2 poincare sphere a generalized representation for multidimensional Structured Light
Physical Review A, 2020Co-Authors: Yijie Shen, Zhaoyang Wang, Darryl Naidoo, Andrew ForbesAbstract:Structured Light, as a general term for arbitrary states of amplitude, phase, and polarization in optical fields, is highly topical because of a myriad of applications it has fostered. A geometric description to graphically group classes of Structured Light has obvious benefits, with some notable advances in analogous Poincar\'e sphere (PS) mapping for both spin and orbital angular momentum (OAM), as well as ray-optical PS approaches for propagation-invariant fields, but all limited in dimensionality they can describe. Here we propose a generalized SU(2) PS for arbitrary dimensional Structured Light. The states on it represent extended families of beams with multidimensional ray-wave structures, accurately described by SU(2) symmetry groups. We outline how to construct this mapping theoretically, revealing insights into mode transformations involving OAM and geometric phase, and fully verify its efficacy experimentally. The generality of our approach is evident by the reduction to prior PS representations as special cases. We also demonstrate an extension of our approach to explain a more general high-dimensional vector beam. This construction naturally accounts for the salient topology of the classical PSs while bringing to more new degrees of freedom and dimensions for tailoring a larger variety of quantum-to-classical Structured beams for a variety of applications.
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evolution and conservation of orbital angular momentum in three dimensional Structured Light
Conference on Lasers and Electro-Optics, 2019Co-Authors: Ahmed H Dorrah, Andrew Forbes, Carmelo Rosalcsouzman, Mo MojahediAbstract:We engineer quasi 3D Structured Light fields in which the orbital angular momentum changes locally in both sign and magnitude along the beam's axis and explain how such transitions occur without violating conservation of angular momentum. © 2019 The Author(s)
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all digital wavefront sensing for Structured Light beams
Optics Express, 2014Co-Authors: Angela Dudley, Giovanni Milione, R R Alfano, Andrew ForbesAbstract:We present a new all-digital technique to extract the wavefront of a Structured Light beam. Our method employs non-homogeneous polarization optics together with dynamic, digital holograms written to a spatial Light modulator to measure the phase relationship between orthogonal polarization states in real-time, thereby accessing the wavefront information. Importantly, we show how this can be applied to measuring the wavefront of propagating Light fields, over extended distances, without any moving components. We illustrate the versatility of the tool by measuring propagating optical vortices, Bessel, Airy and speckle fields. The comparison of the extracted and programmed wavefronts yields excellent agreement.
Guangjun Zhang - One of the best experts on this subject based on the ideXlab platform.
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a novel 1d target based calibration method with unknown orientation for Structured Light vision sensor
Optics and Laser Technology, 2010Co-Authors: Zhenzhong Wei, Lijun Cao, Guangjun ZhangAbstract:The problem associated with calibrating a Structured Light vision sensor is that it is difficult to obtain the coordinates of the world calibration points falling on the Light stripe plane. In this paper, we present a novel method to address this problem by randomly moving a 1D (one-dimension) target within the sensor's view field. At each position where the target is set, the world coordinates with one calibration point on the Light stripe plane that can be obtained based on at least three preset known points on the 1D target by a proposed two-stage technique. Thus, as long as the 1D target is at least set at three different positions, not less than three such calibration points can be obtained to perform the Structured Light vision sensor calibration. The simulation and real experiments conducted reveal that the proposed approach has an accuracy of up to 0.065 mm. The advantages of the proposed method are: (1) 1D target is easily machined with high accuracy, which reduces the cost of the calibration equipment; (2) the method simplifies the calibration operation and can be convenient in on-site calibration; (3) the method is suitable for use in confined spaces.
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3d vision inspection for internal surface based on circle Structured Light
Sensors and Actuators A-physical, 2005Co-Authors: Guangjun ZhangAbstract:Abstract 3D vision inspection plays an important role in industry environment. This paper focus on 3D vision inspection for internal surface based on circle Structured Light. The inspection system, established in this paper, consists of an Olympus industrial endoscope, a digital CCD camera, a single-circle pattern laser, a conic reflector, a transparent thin glass tube with the outer diameter of O4.2 mm, a motorized linear motion stage, a personal computer and a few accessorial brackets. The inspection system is calibrated by a two electronic theodolites system and a plane target efficiently. Based on the mathematic model of the inspection system, the 3D shape of the internal surface is obtained from the 2D Structured Light stripe image on the internal surface. The experimental results show that the inspection system has a calibration accuracy of RMS x = 0.032 mm, RMS y = 0.011 mm, and RMS z = 0.029 mm, and a measurement accuracy of RMS x = 0.041 mm, RMS y = 0.019 mm and RMS z = 0.038 mm. It is proved that the inspection system is applicable to inspecting internal surface with high efficiency and accuracy.
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Complete calibration of a Structured Light stripe vision sensor through planar target of unknown orientations
Image and Vision Computing, 2004Co-Authors: Fuqiang Zhou, Guangjun ZhangAbstract:Abstract Structured Light 3D vision inspection is a commonly used method for various 3D surface profiling techniques. In this paper, the mathematical model of the Structured Light stripe vision sensor is established. We propose a flexible new approach to easily determine all primitive parameters of a Structured Light stripe vision sensor. It is well suited for use without specialized knowledge of 3D geometry. The technique only requires the sensor to observe a planar target shown at a few (at least two) different orientations. Either the sensor or the planar target can be freely moved. The motion need not be known. A novel approach is proposed to generate sufficient non-collinear control points for Structured Light stripe vision sensor calibration. Real data has been used to test the proposed technique, and very good result has been obtained. Compared with classical techniques, which use expensive equipment such as two or three orthogonal planes, the proposed technique is easy to use and flexible. It advances Structured Light vision one step from laboratory environments to real engineering 3D metrology applications.
Joaquim Salvi - One of the best experts on this subject based on the ideXlab platform.
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a state of the art in Structured Light patterns for surface profilometry
Pattern Recognition, 2010Co-Authors: Joaquim Salvi, Sergio Fernandez, Tomislav Pribanic, Xavie LladoAbstract:Shape reconstruction using coded Structured Light is considered one of the most reliable techniques to recover object surfaces. Having a calibrated projector-camera pair, a Light pattern is projected onto the scene and imaged by the camera. Correspondences between projected and recovered patterns are found and used to extract 3D surface information. This paper presents an up-to-date review and a new classification of the existing techniques. Some of these techniques have been implemented and compared, obtaining both qualitative and quantitative results. The advantages and drawbacks of the different patterns and their potentials are discussed.
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a new optimised de bruijn coding strategy for Structured Light patterns
International Conference on Pattern Recognition, 2004Co-Authors: J Pages, Joaquim SalviAbstract:Coded Structured Light is an optical technique based on active stereovision that obtains the shape of objects. One shot techniques are based on projecting a unique Light pattern with an LCD projector so that grabbing an image with a camera, a large number of correspondences can be obtained. Then, a 3D reconstruction of the illuminated object can be recovered by means of triangulation. The most used strategy to encode one-shot patterns is based on De Bruijn sequences. In This work a new way to design patterns using this type of sequences is presented. The new coding strategy minimises the number of required colours and maximises both the resolution and the accuracy.
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pattern codification strategies in Structured Light systems
Pattern Recognition, 2004Co-Authors: Joaquim Salvi, J Pages, J BatlleAbstract:Coded Structured Light is considered one of the most reliable techniques for recovering the surface of objects. This technique is based on projecting a Light pattern and viewing the illuminated scene from one or more points of view. Since the pattern is coded, correspondences between image points and points of the projected pattern can be easily found. The decoded points can be triangulated and 3D information is obtained. We present an overview of the existing techniques, as well as a new and definitive classification of patterns for Structured Light sensors. We have implemented a set of representative techniques in this field and present some comparative results. The advantages and constraints of the different patterns are also discussed.
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uncalibrated reconstruction an adaptation to Structured Light vision
Pattern Recognition, 2003Co-Authors: David Fofi, Joaquim Salvi, El Mustapha MouaddibAbstract:Abstract Euclidean reconstruction from two uncalibrated stereoscopic views is achievable from the knowledge of geometrical constraints about the environment. Unfortunately, these constraints may be quite difficult to obtain. In this paper, we propose an approach based on Structured Lighting, which has the advantage of providing geometrical constraints independent of the scene geometry. Moreover, the use of Structured Light provides a unique solution to the tricky correspondence problem present in stereovision. The projection matrices are first computed by using a canonical representation, and a projective reconstruction is performed. Then, several constraints are generated from the image analysis and the projective reconstruction is upgraded into an Euclidean one—as we will demonstrate, it is assumed that the sensor behaviour is affine without loss of generality so that the constraints generation is simplified. The method provides our sensor with adaptive capabilities and permits to be used in the measurement of moving scenes such as dynamic visual inspection or mobile robot navigation. Experimental results obtained from both simulated and real data are presented.
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robust segmentation and decoding of a grid pattern for Structured Light
Iberian Conference on Pattern Recognition and Image Analysis, 2003Co-Authors: J Pages, Joaquim Salvi, Carles MataboschAbstract:This paper describes the implementation details of a coded Structured Light system useful for one-shot measurements of a surface. Since a unique pattern is projected, the technique is useful for measuring moving surfaces. A pattern based on grid structure is used. The main advantage of such structure is that redundant codification is applied to the cross-points. Since both pattern axis are coded, decoding errors can be corrected thanks to the proposed algorithm. Moreover, not only the cross-points of the grid can be reconstructed but also the pixels belonging to vertical and horizontal slits. A description of the segmentation and decoding stage is given in order to take profit of the advantages of the pattern codification.
