Optical measurement techniques – A push for digitization

Kulkarni, Rishikesh; Rastogi, Pramod K.

doi:10.1016/j.optlaseng.2016.05.002

Cited by 40 publications

(29 citation statements)

References 188 publications

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“…When projected over a 3D object, the phase-shifted open fringes in Eq. (1) become phasemodulated proportionally to the height profile of the surface under test [1][2][3][4][5]. Our ideal mathematical model for the sinusoidal phase-modulated fringe pattern is given by:   remains true if the camera sees just a portion of the region illuminated by the digital projector [9].…”

Section: Theoretical Frameworkmentioning

confidence: 99%

“…Both spatial and temporal carriers are assumed to be known ( ' u is easily calibrated using a reference plane), so we can estimate ( , ) c x y or ( , ) c x y  using synchronous methods. By convention we choose ( , ), c x y from where the searched phase-map and the fringes' contrast function are computed as its argument and amplitude, respectively [1][2][3][4][5]. For the spatial synchronous method, having 0 (0, ), u   the searched analytic signal is given by…”

Section: Theoretical Frameworkmentioning

confidence: 99%

“…Nowadays, structured-light projection profilometry is arguably the most popular technique for tri-dimensional (3D) shape measurement [1][2][3]. Particularly the phase-demodulation methods working with sinusoidal fringe patterns provide the highest-quality dense estimations of the digitized surface [1][2][3][4]. A typical setup for fringe-projection profilometry (FPP) requires an image projector, a camera, and a computing device for control and data processing.…”

Section: Introductionmentioning

confidence: 99%

“…Defocused projection of binary fringes removes the need to calibrate non-linear gamma encoding of most projectors, which is one of the main difficulties for high-quality phase estimations in digital FPP [1][2][3][4][5][6][7][8]. It also impedes us from using many-step phase-shifting algorithms (PSAs) for robust quadrature filtering.…”

Section: Introductionmentioning

confidence: 99%

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Profilometry with digital fringe-projection at the spatial and temporal Nyquist frequencies

Padilla¹,

Servı́n²,

Garnica³

2017

Opt. Express

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A phase-demodulation method for digital fringe-projection profilometry using the spatial and temporal Nyquist frequencies is presented. It allows to digitize tridimensional surfaces using the highest spatial frequency (π radians per pixel) and consequently with the highest sensitivity for a given digital fringe projector. Working with the highest temporal frequency (π radians per temporal sample), the proposed method rejects the DC component and all even-order distorting harmonics using 2-step phase shifting; this robustness against harmonics is similar to that of the popular 4-step least-squares phase-shifting algorithm. The proposed phase-demodulation method is suitable for the digitization of piecewise continuous surfaces because it does not require spatial low-pass filtering. Gamma calibration is also unnecessary because the projected fringes are binary, and the harmonics produced by the binary profile can be attenuated with a slight defocusing on the digital projector. Viability of the proposed method is supported by experimental results showing complete agreement with the predicted behavior.

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Section: Theoretical Frameworkmentioning

confidence: 99%

Section: Theoretical Frameworkmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Profilometry with digital fringe-projection at the spatial and temporal Nyquist frequencies

Padilla¹,

Servı́n²,

Garnica³

2017

Opt. Express

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“…This work focusses on optical techniques that currently are promoted by progress in material science and manufacturing technology, leading for example to smaller and higher resolving lens systems and more possibilities concerning optical accessibility. There are already numerous reviews on the details of measurement techniques in general and on specific techniques available. Therefore, this work seeks to provide an overview on measurement techniques and literature closely related to the problems arising in disperse multiphase systems on different size scales.…”

Section: Introductionmentioning

confidence: 99%

Description of Disperse Multiphase Processes: Quo Vadis?

Hohl

Panckow

Schulz

et al. 2018

Chemie Ingenieur Technik

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The experimental accessibility of disperse systems often is a critical factor when it comes to the development of modeling approaches that intend to converge towards an exact solution. Often, integral or pseudo‐homogeneous values are used to reduce the complexity of the system, but a detailed single particle or interface analysis is crucial to understand relevant effects that also affect the swarm behavior. A high number of experimental techniques with respective limitations and advantages is available to quantify these effects. In this work, an overview on measurement techniques for momentum, heat and mass transfer in particle swarms as well as for the particle size distribution and interface characterization is provided. The industrial applicability is addressed by pointing out the vicinity to the process and the costs of different measurement techniques.

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