scholarly journals Random laser speckle pattern projection for non-contact vibration measurements using a single high-speed camera

2021 ◽  
Vol 158 ◽  
pp. 107719
Author(s):  
Pablo Etchepareborda ◽  
Marie-Hélène Moulet ◽  
Manuel Melon
Keyword(s):  
High Speed ◽  
Speckle Pattern ◽  
Laser Speckle ◽  
Random Laser ◽  
High Speed Camera ◽  
Vibration Measurements ◽  
Pattern Projection

Phase Algorithm Integrating Direct-Correlation and Four-Step Phase-Shifting for Electronic Speckle Pattern Interferometry

2013 ◽  
Vol 448-453 ◽  
pp. 3696-3701
Author(s):  
Yan Bin He ◽  
Xin Zhong Li ◽  
Min Zhou
Keyword(s):  
High Speed ◽  
Speckle Pattern ◽  
Phase Shifting ◽  
Electronic Speckle Pattern Interferometry ◽  
High Speed Camera ◽  
Dynamic Measurements ◽  
High Quality ◽  
Correlation Algorithm ◽  
Phase Map

A phase-shifting algorithm, called a (4,4) algorithm, which takes four phase-shifting interferograms before a specimen is deformed and four interferograms after a specimen is deformed, is presented first. This method is most widely used for phase extraction. Its drawback limited it to be used in dynamic measurements. Also shown is an algorithm called a (4,1) algorithm that takes four phase-shifting interferograms before a specimen is deformed and one interferogram after a specimen is deformed. Because a high-speed camera can be used to record the dynamic interferogram of the specimen, this algorithm has the potential to retain the phase-shifting capability for ESPI in dynamic measurements. The quality of the phase map obtained using (4,1) algorithm is quite lower compared to using (4,4) algorithm. In order to obtain high-quality phase map in dynamic measurements, a direct-correlation algorithm was integrated with the (4,1) algorithm to form DC-(4,1) algorithm which is shown to improve significantly the quality of the phase maps. The theoretical and experimental aspects of this newly developed technique, which can extend ESPI to areas such as high-speed dynamic measurements, are examined in detail.

Study on the Double Pulse Laser Dynamic Electronic Speckle Measurement Based on FPGA

2014 ◽  
Vol 900 ◽  
pp. 617-622
Author(s):  
Fu Sheng Yu ◽  
Teng Fei Li ◽  
Yan Chao Wu ◽  
Zhong Guo Sun ◽  
Sheng Jiang Yin
Keyword(s):  
Stress Distribution ◽  
High Speed ◽  
Surface Deformation ◽  
Speckle Pattern ◽  
Dynamic Measurement ◽  
High Accuracy ◽  
Laser Speckle ◽  
Tool Surface ◽  
Milling Tools ◽  
Intermittent Cutting

Speckle pattern interferometry can be used to measure he displacement, strain and vibration, surface deformation and surface roughness. And dynamic laser speckle measurement with high accuracy has been widely used in measurement of surface deformation. Tool breakage is the main bottleneck of high-speed intermittent cutting development, therefore, obtaining stress distribution of milling tools is a base of improving the tool design and tool life. Using a speckle measurement method of double pulsed digital based on FPGA, which involves the laser cutter, tools and CCD, transforms the high-speed dynamic measurement to quasi-static measurement. As a result, we can get two speckle images of front and back milling cutter surface and calculate the deformation ,strain and stress distribution of the tool surface with analysis.

Application of Electronic Speckle Pattern Shearing Interferometry with High-Speed Camera in Vibration Analysis of Piezoelectric Transducer

2019 ◽  
Vol 11 (06) ◽  
pp. 1950056
Author(s):  
Hamidreza Asemani ◽  
Nasser Soltani
Keyword(s):  
Piezoelectric Transducer ◽  
Vibration Amplitude ◽  
High Speed ◽  
Speckle Pattern ◽  
Maximum Amplitude ◽  
Body Motion ◽  
Mode Shapes ◽  
High Speed Camera ◽  
Full Field ◽  
Shearing Interferometry

Electronic speckle pattern shearing interferometry, also known as shearography, is a highly sensitive technique that can measure the distribution of the displacement derivatives of the object surface. This method has also been used to describe the mode shapes of vibrating objects. In the current research, electronic speckle pattern shearing interferometry with high-speed camera was proposed for full-field measurement of the derivative of the vibration amplitude. One of the important limitations of time-average shearography is that this method is only able to provide the qualitative measurement of vibration amplitude. Stroboscopic shearography also has an inevitable limitation on the measurement of vibration amplitude at frequencies lower than 50[Formula: see text]Hz. To study the performance of shearography with high-speed camera, the research concerned the low-frequency vibration of a piezoelectric transducer during its operation. The proposed method overcomes the limitations of conventional shearography methods in quantitative measurement of vibration amplitude at low frequencies. Laser Doppler vibrometry (LDV) method was used to verify the measurement results of shearography with high-speed camera. The obtained results indicated good agreement between both shearography with high-speed camera and LDV methods. However, due to the rigid body motion of the piezoelectric transducer, LDV results generally represented more values for the maximum amplitude.

scholarly journals ENHANCEMENT OF STEREO IMAGERY BY ARTIFICIAL TEXTURE PROJECTION GENERATED USING A LIDAR

2016 ◽  
Vol XLI-B5 ◽  
pp. 599-606 ◽  
Author(s):  
Joshua Veitch-Michaelis ◽  
Jan-Peter Muller ◽  
David Walton ◽  
Jonathan Storey ◽  
Michael Foster ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Speckle Pattern ◽  
Ground Truth ◽  
Laser Speckle ◽  
Image Texture ◽  
High Signal ◽  
Optical Elements ◽  
Image Texture Analysis ◽  
Ground Truth Data ◽  
Pattern Projection

Passive stereo imaging is capable of producing dense 3D data, but image matching algorithms generally perform poorly on images with large regions of homogenous texture due to ambiguous match costs. Stereo systems can be augmented with an additional light source that can project some form of unique texture onto surfaces in the scene. Methods include structured light, laser projection through diffractive optical elements, data projectors and laser speckle. Pattern projection using lasers has the advantage of producing images with a high signal to noise ratio. We have investigated the use of a scanning visible-beam LIDAR to simultaneously provide enhanced texture within the scene and to provide additional opportunities for data fusion in unmatched regions. The use of a LIDAR rather than a laser alone allows us to generate highly accurate ground truth data sets by scanning the scene at high resolution. This is necessary for evaluating different pattern projection schemes. Results from LIDAR generated random dots are presented and compared to other texture projection techniques. Finally, we investigate the use of image texture analysis to intelligently project texture where it is required while exploiting the texture available in the ambient light image.

Analyzing the requirements of high-speed camera parameters for enhanced laser speckle sensing of flow dynamics

2020 ◽  
Vol 2 (3) ◽  
pp. 035032
Author(s):  
Mark Golberg ◽  
Ran Califa ◽  
Javier Garcia ◽  
Zeev Zalevsky
Keyword(s):  
High Speed ◽  
Flow Dynamics ◽  
Laser Speckle ◽  
High Speed Camera ◽  
Camera Parameters

scholarly journals ENHANCEMENT OF STEREO IMAGERY BY ARTIFICIAL TEXTURE PROJECTION GENERATED USING A LIDAR

2016 ◽  
Vol XLI-B5 ◽  
pp. 599-606 ◽  
Author(s):  
Joshua Veitch-Michaelis ◽  
Jan-Peter Muller ◽  
David Walton ◽  
Jonathan Storey ◽  
Michael Foster ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Speckle Pattern ◽  
Ground Truth ◽  
Laser Speckle ◽  
Image Texture ◽  
High Signal ◽  
Optical Elements ◽  
Image Texture Analysis ◽  
Ground Truth Data ◽  
Pattern Projection

Passive stereo imaging is capable of producing dense 3D data, but image matching algorithms generally perform poorly on images with large regions of homogenous texture due to ambiguous match costs. Stereo systems can be augmented with an additional light source that can project some form of unique texture onto surfaces in the scene. Methods include structured light, laser projection through diffractive optical elements, data projectors and laser speckle. Pattern projection using lasers has the advantage of producing images with a high signal to noise ratio. We have investigated the use of a scanning visible-beam LIDAR to simultaneously provide enhanced texture within the scene and to provide additional opportunities for data fusion in unmatched regions. The use of a LIDAR rather than a laser alone allows us to generate highly accurate ground truth data sets by scanning the scene at high resolution. This is necessary for evaluating different pattern projection schemes. Results from LIDAR generated random dots are presented and compared to other texture projection techniques. Finally, we investigate the use of image texture analysis to intelligently project texture where it is required while exploiting the texture available in the ambient light image.

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