Accuracy in dynamic laser speckle: optimum size of speckles for temporal and frequency analyses

Braga, Roberto A.; González-Peña, Rolando J.

doi:10.1117/1.oe.55.12.121702

Cited by 16 publications

(9 citation statements)

References 26 publications

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“…The smoothness of the exponential curve from the proposed device enables us to follow the drying process for a longer time than when using the camera in the optical laboratory. In short, pixel size matters, and can improve the sensitivity of our sensor [ 26 ].…”

Section: Discussionmentioning

confidence: 99%

“…The images were acquired from a TV zoom lens with a focal length of 50 mm, numerical aperture of f/11 (speckle size was 13.57 μm), connected to an AVT Marlin F-145B CCD camera (pixel size of 4.65 μm, Allied Vision Technologies, Stadtroda, Germany) [ 26 ].…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, the challenge is to monitor the speckle phenomenon in situ where external influences create a barrier to many applications, and evaluate the robustness of the portable equipment [ 25 , 26 ]. The adjustment of the speckle analysis must also be considered, particularly for processing events that occur over a long period of time.…”

Section: Introductionmentioning

confidence: 99%

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A Portable Dynamic Laser Speckle System for Sensing Long-Term Changes Caused by Treatments in Painting Conservation

Pérez

González-Peña

Braga

et al. 2018

Sensors

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Dynamic laser speckle (DLS) is used as a reliable sensor of activity for all types of materials. Traditional applications are based on high-rate captures (usually greater than 10 frames-per-second, fps). Even for drying processes in conservation treatments, where there is a high level of activity in the first moments after the application and slower activity after some minutes or hours, the process is based on the acquisition of images at a time rate that is the same in moments of high and low activity. In this work, we present an alternative approach to track the drying process of protective layers and other painting conservation processes that take a long time to reduce their levels of activity. We illuminate, using three different wavelength lasers, a temporary protector (cyclododecane) and a varnish, and monitor them using a low fps rate during long-term drying. The results are compared to the traditional method. This work also presents a monitoring method that uses portable equipment. The results present the feasibility of using the portable device and show the improved sensitivity of the dynamic laser speckle when sensing the long-term process for drying cyclododecane and varnish in conservation.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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A Portable Dynamic Laser Speckle System for Sensing Long-Term Changes Caused by Treatments in Painting Conservation

Pérez

González-Peña

Braga

et al. 2018

Sensors

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“…The terms such as specklepixel size matching [40] or speckle-pixel size ratio [41] are defined as a universal parameter in many speckle imaging systems. According to the Nyquist theorem, the speckle-pixel size ratio should be greater than 2 [42]. However, the higher the speckle-pixel size ratio is, the less information the speckle pattern has in a DSPI system.…”

Section: Requirements For the Speckle-pixel Size Ration In Dspi Systemmentioning

confidence: 99%

Effect of the Speckle Size on the Quality of Speckle Pattern in DSPI System

Zhong

Tang

et al. 2019

IEEE Access

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In order to detect the deformation and strain of materials accurately, the key is to obtain the phase information caused by dynamic loading in digital speckle pattern interferometry (DSPI). In this paper, the evaluation method of quality of the speckle pattern in DSPI system is proposed, and the influence of the size of speckle grain on the stability and contrast of speckle pattern is discussed. And then, the strain detection experiments of inactive and bioactive materials are provided with different aperture slit size under the same detection conditions. The size of speckle grain has an important influence on the quality of speckle pattern. For strain detection of inactive materials, using the small size of speckles can obtain higher quality speckle pattern under the condition of satisfying the Nyquist theorem and spectral separation. For active biomaterials, non-structural factors easily induce the instability of speckle pattern, which leads to the decorrelation of between pre-deformation and post-deformation speckle pattern. So the compromise between the stability and the information capacity of speckle images should be considered in the selection of speckle size. Experiments show that the optimum size of speckles used for strain detection active biomaterials is larger than that of inactive biomaterials under the same conditions in the same DSPI system.

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“…A windowed Fourier ridges algorithm [ 9 , 10 , 11 ] and a windowed Fourier filtering algorithm have been proposed to achieve a low standard deviation for local frequencies and phase distributions in fringe pattern analysis. Morlet wavelet transform has also been used for phase extraction on different types of fringe patterns [ 12 , 13 , 14 ].…”

Section: Introductionmentioning

confidence: 99%

A Fringe Phase Extraction Method Based on Neural Network

Miao

Yan

et al. 2021

Sensors

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In optical metrology, the output is usually in the form of a fringe pattern, from which a phase map can be generated and phase information can be converted into the desired parameters. This paper proposes an end-to-end method of fringe phase extraction based on the neural network. This method uses the U-net neural network to directly learn the correspondence between the gray level of a fringe pattern and the wrapped phase map, which is simpler than the exist deep learning methods. The results of simulation and experimental fringe patterns verify the accuracy and the robustness of this method. While it yields the same accuracy, the proposed method features easier operation and a simpler principle than the traditional phase-shifting method and has a faster speed than wavelet transform method.

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Accuracy in dynamic laser speckle: optimum size of speckles for temporal and frequency analyses

Cited by 16 publications

References 26 publications

A Portable Dynamic Laser Speckle System for Sensing Long-Term Changes Caused by Treatments in Painting Conservation

A Portable Dynamic Laser Speckle System for Sensing Long-Term Changes Caused by Treatments in Painting Conservation

Effect of the Speckle Size on the Quality of Speckle Pattern in DSPI System

A Fringe Phase Extraction Method Based on Neural Network

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