Review
Metallurgy & Metallurgical Engineering
Mei-qi Shao, Dong Xu, Si-yi Li, Xiao-gang Zuo, Chang-ke Chen, Gong-zhuang Peng, Jia-min Zhang, Xiao-chen Wang, Quan Yang
Summary: Surface roughness measurement is crucial for characterizing material microstructure during processing, and the laser speckle method has gained attention as an online non-destructive measurement technique. This review focuses on the improvements in surface roughness measurements based on the laser speckle method, discussing the theory of speckle formation and the statistical properties of speckle patterns related to surface roughness. Three main methods, including speckle contrast method, speckle correlation method, and fractal method, are described in detail, and a comprehensive comparison among these methods is presented. The recent advances and applications of surface roughness measurements are reviewed, and the future prospects and summary of surface roughness measurements based on the laser speckle method are provided.
JOURNAL OF IRON AND STEEL RESEARCH INTERNATIONAL
(2023)
Article
Chemistry, Analytical
Suganandha Bharathi Jayabarathi, Mani Maran Ratnam
Summary: This study compares the correlation between 3D surface roughness and laser speckle pattern using two different experimental setups. The results show that the setup using a He-Ne laser provides better results.
Article
Optics
Leon Schweickhardt, Andreas Tausendfreund, Dirk Stoebener, Andreas Fischer
Summary: This article presents a speckle-based measurement technique for characterizing anisotropic surfaces. By utilizing a specific measurement setup and evaluation algorithm, multiple measurands can be obtained from a speckle image, including the machining direction, the autocorrelation length perpendicular to the machining direction, as well as two root mean square roughness parameters parallel and perpendicular to the machining direction.
Article
Meteorology & Atmospheric Sciences
Mingjie Xie, Xiang Peng, Yue Shang, Li Yang, Yuanyuan Zhang, Yuhang Wang, Hong Liao
Summary: In this study, collocated filter samples of PM2.5 were analyzed for light absorption, and the agreement between the light absorption properties of WSOC and MEOC was found to be good. Correcting for sampling artifacts is necessary but increases heterogeneity in collocated measurements. Additionally, WSOC and MEOC absorption contribute differently to different emission sources.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2022)
Article
Chemistry, Analytical
Suganandha Bharathi Jayabarathi, Mani Maran Ratnam
Summary: Current studies are focused on the correlation between characteristic features extracted from the laser speckle pattern of machined surfaces and 2D surface roughness parameters. The novelties of this work include the use of an inexpensive laser pointer for producing the speckle pattern, the correlation study between the speckle pattern features and 3D surface roughness, and the investigation of the influence of illumination angle, lens aperture size, and shutter speed on the correlation. The highest coefficient of determination of 0.8955 was obtained for the correlation between the energy descriptor from the gray level co-occurrence matrix and the ten-point height S-10z 3D surface roughness parameter.
Article
Engineering, Mechanical
Klemen Zaletelj, Vid Agrez, Janko Slavic, Rok Petkovsek, Miha Boltezar
Summary: The proposed method utilizes laser-light interference to form a speckle pattern for DIC measurements without modifying the surface of the structure, with speckle size depending on factors such as surface roughness.
MECHANICAL SYSTEMS AND SIGNAL PROCESSING
(2021)
Article
Engineering, Electrical & Electronic
Ernst Csencsics, Johannes Schlarp, Tobias Glaser, Tobias Wolf, Georg Schitter
Summary: This article introduces a method for simulating the measurement uncertainty caused by laser speckle and investigates the effects of speckle reduction mechanisms based on spatio-temporal averaging. Simulation studies reveal that a larger triangulation angle reduces the influence of laser speckle and the resulting uncertainty. By integrating a speckle-reducing moving diffuser mechanism into the optical sensor path, a parameter study demonstrates the achievable improvement for various combinations of motion frequency and amplitude. Experimental results validate the accuracy of the simulations and show that the diffuser can reduce the speckle-induced uncertainty by up to 63%.
IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT
(2023)
Article
Optics
Jonathan L. Habif, Arunkumar Jagannathan, Samuel Gartenstein, Phoebe Amory, Saikat Guha
Summary: This study calculates the fundamental limit for discriminating between pure laser light and thermal noise in a photon-starved regime, demonstrating that a generalized Kennedy receiver can closely approach the Helstrom limit, with experimental demonstration showing improvement in discrimination sensitivity and error probability.
Article
Biochemistry & Molecular Biology
Kai Long, Jing Liu, Shuhao Shen, Mark Thong, Deyun Wang, Nanguang Chen
Summary: Mucociliary clearance is essential for maintaining healthy airways. Optical imaging methods, such as LSH-LSI, can be used to assess ciliary movement and provide quantitative indicators without labeling. The proposed inverted LSH-LSI platform has been experimentally confirmed to measure ciliary beating frequency and characterize ciliary beating pattern.
COMPUTATIONAL AND STRUCTURAL BIOTECHNOLOGY JOURNAL
(2023)
Article
Engineering, Multidisciplinary
Vismay Trivedi, Swapnil Mahajan, Mugdha Joglekar, Nirav Joshi, Vani Chhaniwal, Satish Kumar Dubey, Zeev Zalevsky, Bahram Javidi, Arun Anand
Summary: Magnetic field sensing is crucial in various fields, and recent advancements in optical sensors have led to the development of magnetic field sensors based on optical principles. This study presents a simple and cost-effective approach for sensing magnetic field by converting it into mechanical translation and then into optical signals. The magnetic field is quantified by measuring the changes in the speckle pattern of the optical signals. The proposed method can measure both static and time varying magnetic fields with high resolution and accuracy.
Article
Optics
Shanta Hardas Patil, Rishikesh Kulkarni
Summary: This study proposed a roughness measurement method based on singular value decomposition, using objective speckle patterns to quantify surface roughness. Experimental results demonstrated the broad surface roughness measuring capability of the method with a single laser source, comparing different indicators.
OPTICS AND LASERS IN ENGINEERING
(2022)
Article
Chemistry, Multidisciplinary
Majid Masnavi, Martin Richardson
Summary: A series of experiments were conducted to measure the spectral irradiances of laser plasmas created from metal targets over the wavelength region of 123-164 nm. Strong experimental radiations mainly originated from bound-bound transitions of low-ionized charges.
APPLIED SCIENCES-BASEL
(2021)
Article
Optics
Priyanka Satapathy, Ganeswar Nath, Punyatoya Mishra
Summary: This article discusses the method of measuring surface roughness through laser speckle characterization. By recording the sensitivity of speckle signals at different distances from the surfaces, important information about surface conditions can be obtained, and the speckle contrast changes significantly with the change in the incidence laser signal strength and distance.
Article
Optics
Linxiao Deng, Yuhua Yang, Guan Wang, Binghui Yao, Jiafei Ma, Liquan Zhu, Chun Gu, Lixin Xu
Summary: A color speckle measurement method for laser projection systems based on human speckle perception was proposed in this study. The proposed method, which took into account the practical irregular spectrum distribution of a laser projection system, provided more accurate results compared to previous monochromatic light approximation methods. Experimental verification was conducted using a complete laser projector, confirming the effectiveness of the proposed method. It can serve as a basis for standardized color speckle measurement applications in laser projection systems.
OPTICS AND LASER TECHNOLOGY
(2022)
Article
Optics
Priyanka Priyadarsini Singh, Ganeswar Nath
Summary: This research investigates the importance of laser techniques in analyzing the surface roughness of composite materials. The results show that the laser measuring method outperforms the surface profilometry technique in most materials, with lower costs and a scientific-concept-based approach.
Article
Optics
Leon Schweickhardt, Andreas Tausendfreund, Dirk Stoebener, Andreas Fischer
Summary: This article presents a speckle-based measurement technique for characterizing anisotropic surfaces. By utilizing a specific measurement setup and evaluation algorithm, multiple measurands can be obtained from a speckle image, including the machining direction, the autocorrelation length perpendicular to the machining direction, as well as two root mean square roughness parameters parallel and perpendicular to the machining direction.
Article
Instruments & Instrumentation
Axel von Freyberg, Marina Terlau, Dirk Stoebener, Andreas Fischer
Summary: For small quantities of forming large metal sheets, incremental sheet forming is a cost-effective alternative to deep drawing. However, tool deflections can cause increased form deviations. By measuring the tool deflection in real time with an optical multi-sensor system, the geometric deviations of the manufactured part can be minimized. The proposed system uses a large number of inexpensive sensors to measure the angle to a point light source on the tool, allowing for accurate calculation of the tool position in the three-dimensional manufacturing volume.
TM-TECHNISCHES MESSEN
(2023)
Article
Instruments & Instrumentation
Daniel Gleichauf, Felix Oehme, Ann-Marie Parrey, Michael Sorg, Nicholas Balaresque, Andreas Fischer
Summary: Thermographic flow visualization is a well-established imaging method for localizing laminar-turbulent flow transition on wind turbines. This study investigates the potential of using this method to detect changes in flow transition position caused by wind gusts. It is proven through theory and experiments on real wind turbines that flow state changes can be detected within seconds using thermographic flow visualization. This opens up possibilities for analyzing unsteady flow phenomena on wind turbines.
TM-TECHNISCHES MESSEN
(2023)
Article
Chemistry, Multidisciplinary
Friederike Jensen, Elie Abi Aoun, Oliver Focke, Andreas Krenz, Christian Tornow, Mareike Schlag, Catherine Lester, Axel Herrmann, Bernd Mayer, Michael Sorg, Andreas Fischer
Summary: This article investigates the causes and evolution of premature rain erosion damage to the leading edges of wind turbine rotor blades. Non-destructive measurement methods, such as CT and XRM with AI-based evaluation, reveal that premature erosion arises from initial material defects, which act as weak points in the material composite. Additionally, thermographic investigations show that active thermography has potential for in-situ monitoring of rotor blade leading edges.
APPLIED SCIENCES-BASEL
(2022)
Article
Energy & Fuels
Felix Oehme, Daniel Gleichauf, Nicholas Balaresque, Michael Sorg, Andreas Fischer
Summary: This study presents and verifies a thermographic detection and localization method for unsteady flow separation on an operating wind turbine. The method utilizes an infrared thermographic measurement approach to achieve high spatial resolution. By analyzing the thermodynamic response behavior of the surface temperature, a two-step signal processing approach is proposed. The results show that the method successfully detects and localizes unsteady flow separation with high resolution.
FRONTIERS IN ENERGY RESEARCH
(2022)
Article
Optics
Andreas Fischer
Summary: By evaluating the speckle contrast or image auto-correlation, the roughness parameter Sq can be measured. This study derives the measurement uncertainty limits for four sources of uncertainty, including surface roughness, speckle noise, quantum shot noise, and camera noise. The results show that speckle noise is the largest contributor to measurement uncertainty, leading to a minimal achievable relative uncertainty of 1%-2% for Sq = (0.03 - 0.15).
Article
Engineering, Industrial
Andreas Fischer, Andreas Tausendfreund, Raphael Hess, Timm Petersen, Dirk Stoebener
Summary: In electrical discharge machining, measuring the induced mechanical stress is crucial for developing process models to enhance the fatigue strength of the machined part. High-speed digital speckle photography is introduced to measure the load fields on the workpiece side with a lateral displacement resolution of 28 nm and spatiotemporal resolution of 29 μm and 40 μs, respectively. This allows for the temporal resolution of the load effects of individual 100 μs short discharge pulses and characterizes the occurring spatial load inhomogeneities and their dynamics, enriching our understanding of the machining process.
CIRP ANNALS-MANUFACTURING TECHNOLOGY
(2023)
Article
Engineering, Mechanical
Bjoern Espenhahn, Lukas Schumski, Daniel Meyer, Dirk Stoebener, Andreas Fischer
Summary: Investigations on coolant flow in a running grinding machine aim to understand the interaction between fluid, workpiece, and tool and correlate flow dynamics with cooling efficiency. Using Particle Image Velocimetry (PIV), flow measurements of metal working fluid (MWF) are visualized. Without a workpiece, the measurements reveal the deflection and entrainment of MWF with the tool, indicating a maximum cooling capacity at 80% of the tool's circumferential velocity. By implementing an optical transparent workpiece, flow measurements in the decreasing gap between the workpiece and grinding wheel reveal a deceleration stagnation before the contact zone, providing the necessary data to understand flow-based cooling mechanisms in grinding processes.
FLOW MEASUREMENT AND INSTRUMENTATION
(2023)
Article
Materials Science, Characterization & Testing
Friederike Jensen, Josefa Feline Jerg, Michael Sorg, Andreas Fischer
Summary: Defects such as voids in wind turbine blades affect premature rain erosion, particularly at the leading edge. Active thermography enables non-contact in-situ inspection of leading edges. Thermographic investigations reveal that sub-surface defects make the blades more susceptible to erosion, and erosion onset depends on defect depth. The development from sub-surface to surface defects can be visualized, allowing damage stage to be assigned to an erosion stage.
NDT & E INTERNATIONAL
(2023)
Article
Instruments & Instrumentation
Alina Ross, Nicholas Balaresque, Andreas Fischer
Summary: Cup anemometers are widely used in the wind energy industry, and their performance is classified based on the IEC 61400-50-1:2022 standard. However, this standard does not adequately consider the effects of temperature and density.
TM-TECHNISCHES MESSEN
(2023)
Article
Multidisciplinary Sciences
Daniel Niederer, Natalie Mengis, Max Wiessmeier, Matthias Keller, Wolf Petersen, Andree Ellermann, Tobias Drenck, Christian Schoepp, Amelie Stoehr, Andreas Fischer, Andrea Achtnich, Raymond Best, Lucia Pinggera, Matthias Krause, Daniel Guenther, Maren Janko, Christoph Kittl, Turgay Efe, Karl-Friedrich Schuettler, Lutz Vogt, Michael Behringer, Thomas Stein
Summary: Exploratory moderation-mediation models were used to identify various functional factors that contribute to self-report functional abilities after ACL reconstruction. Pain was found to be the strongest factor in the early rehabilitation phase, while time since reconstruction played a major role in the early and mid phases. Other variables such as COVID-19-associated restrictions and rehabilitation dosage also had an impact.
SCIENTIFIC REPORTS
(2023)
Article
Chemistry, Analytical
Marina Terlau, Axel von Freyberg, Dirk Stoebener, Andreas Fischer
Summary: In order to address the large geometric deviations caused by the deflection of the forming tool, it is necessary to measure the tool tip position in real time. A multi-sensor system based on triangulation is used to accurately measure the tool tip position.
Article
Optics
Leon Schweickhardt, Andreas Tausendfreund, Dirk Stoebener, Andreas Fischer
Summary: Digital speckle photography is a displacement field measurement method using laser speckles as markers. It provides a fast and precise measurement with only one reference image, making it suitable for in-process measurements in manufacturing engineering. The method's accuracy is affected by higher-order displacement gradients, which has been studied through simulations using isotropic Gaussian surface topographies and digital image correlation. The results show that the random error is proportional to the first-order displacement gradient, while the systematic error is influenced by the evaluation algorithm, second-order gradient, and subset size. The findings from the simulative study suggest that the relative error caused by displacement gradients in practical displacement measurements is below 2.5%.
JOURNAL OF THE EUROPEAN OPTICAL SOCIETY-RAPID PUBLICATIONS
(2023)
Article
Green & Sustainable Science & Technology
Paula Helming, Alex Intemann, Klaus-Peter Webersinke, Axel von Freyberg, Michael Sorg, Andreas Fischer
Summary: The size of wind turbines has increased, emphasizing the importance of efficient structural health monitoring. A terrestrial laser scanner (TLS) is used to measure blade deformation and tower-blade tip clearance, allowing for effective monitoring of wind turbine structures.
WIND ENERGY SCIENCE
(2023)
Article
Engineering, Manufacturing
Lukas Schumski, Nikolai Guba, Bjoern Espenhahn, Dirk Stobener, Andreas Fischer, Daniel Meyer
Summary: The free jet and the interaction area during grinding were analyzed using new measurement techniques, which allowed for the assessment of the free jet geometry and velocities, velocity distribution, and the amount of metalworking fluid (MWF) in the interaction area. The main findings indicated that the free jet velocity remained constant, the velocity distribution was influenced by the flow rate, and a new image parameter (black pixel fraction) was derived for evaluating the MWF supply.
JOURNAL OF MANUFACTURING AND MATERIALS PROCESSING
(2022)