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Noncontact detection of concrete flaws by neural network classification of laser doppler vibrometer signals
摘要： This study aimed to develop a non-contact and high-speed damage detection technology for use on concrete structures. A laser Doppler vibrometer was used to obtain the vibrations of a concrete structure at a high signal-to-noise ratio. The observed vibration data were transformed into frequency spectra by Fourier transform. Using the simulation by the finite element method, it was predicted that the characteristic spectrum appeared in the low frequency region for the cracked part. However, the experimental results did not show such a difference clearly. In contrast, in the high-frequency region of the experimental data, a spectrum peculiar to the cracked part tended to appear. Nonetheless, the difference was so small that it was often buried by variations in hammering strength. Therefore, it was difficult to manually determine the signal of the cracked part. Machine learning using a convolutional neural network was carried out in order to judge the location and dimensions of a cracked part with high accuracy. As a result, cracks in the concrete were detected with a high accuracy of more than 90%.
关键词： convolutional neural network,laser doppler vibrometer,concrete,non-destructive inspection
更新于2025-09-23 15:21:01
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Microcirculatory Response to Photobiomodulationa??Why Some Respond and Others Do Not: A Randomized Controlled Study
摘要： Photobiomodulation (PBM), a non‐ionizing, non‐thermal irradiation, used clinically to accelerate wound healing and inhibit pain, was previously shown to increase blood flow. However, some individuals respond to PBM, but others do not. The purpose of this study was to investigate factors affecting this patient‐specific response using advanced, noninvasive methods for monitoring microcirculatory activity. In this prospective, randomized controlled trial (NCT03357523), 20 healthy non‐smoking volunteers (10:10 males:females, 30 ± 8 years old) were randomized to receive either red‐ (633 nm and 70 W/cm2) or near‐infrared light (830 nm and 55 mW/cm2) over the wrist for 5 minutes. Photoplethysmography, laser Doppler flowmetry, and thermal imaging were used to monitor palm microcirculatory blood volume, blood flow, and skin temperature, respectively, before, during, and 20 minutes after irradiation. Participants with skin temperature change ≥0.5°C from baseline were considered “responders”. Near‐infrared PBM was found to induce a 27% increase in microcirculatory flow that increased to 54% during the 20‐minute follow‐up period (P = 0.049 and P = 0.004, respectively), but red light PBM did not increase the median flow. Only 10 of 20 participants were responders by thermal imaging (i.e., ≥0.5°C from baseline), and their initial skin temperature was between 33 and 37.5°C. The non‐responders had either “hot” hands (≥37.5°C) or “cold” hands (≤33°C). In responders, the meantime to 20% increase in microcirculatory blood volume and blood flow was less than 2.5 minutes after initiation of PBM irradiation. We demonstrated that PBM induces arteriolar vasodilatation that results in both immediate and long‐lasting increased capillary flow and tissue perfusion in healthy individuals. This response was wavelength‐dependent and modified by skin temperature. These findings regarding physiological parameters associated with sensitivity or resistance to PBM provide information of direct relevance for patient‐specific therapy.
关键词： body temperature regulation,laser‐Doppler flowmetry,microcirculation,low‐level laser therapy,vasodilation,thermal imaging,photoplethysmography
更新于2025-09-23 15:19:57
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XXIX Messtechnisches Symposium (Arbeitskreis der Hochschullehrer f??r Messtechnik) || Laser-Doppler-Vibrometrie in der Medizin
摘要： Laser-Doppler-Vibrometer (LDV) messen kleinste Schwingungsamplituden. Dieses Messverfahren hat neben technischen auch biomedizinische Anwendungen. Die überwachung des Herzrhythmus wird aktuell mit dem Elektrokardiogramm (EKG) durchgeführt, wobei Elektroden auf der Haut befestigt werden. Eine berührungslose Messung, wie sie mit LDV m?glich ist, hat viele Vorteile und würde die Patientenüberwachung (z.B. verbrannte Haut, Traumata auf den Brustkorb, Frühgeborenen, und Athleten unter Belastung) erheblich vereinfachen. In diesem Beitrag zeigen wir, dass optische Vibrokardiographie (VKG) mit LDV nicht nur wie bereits bekannt die Herzfrequenz und deren Variabilit?t messen kann, sondern auch eine berührungslose Herzrhythmusmessung mit einer robusten AV-Block-Klassifikation erm?glicht.
关键词： Laser Doppler Vibrometrie,Elektrokardiogramm,Herzrhythmus,AV-Bl?cke
更新于2025-09-23 15:19:57
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Repeatability of High Resolution Laser Doppler Images of the hands in patients with systemic sclerosis and secondary Raynaud's phenomenon
摘要： Objectives The objective of the study was to establish the repeatability of baseline diagnostic images of the dorsum of the hands acquired using a high resolution Laser Doppler imager in patients with Raynaud’s phenomenon secondary to Systemic Sclerosis (SSc). Methods The dorsal side of the hands of 22 patients (8 male 14 female) , age range 29-73, median 62, with SSc and secondary Raynaud’s phenomenon were imaged over two consecutive days at approximately the same time using a Moor Instruments High Resolution Laser Doppler imaging unit. The images were analysed by taking regions of interest at discrete locations in the images to calculate dimensionless values of flux(PU). Repeatability of the diagnostic investigation was assessed by using methods described by Bland and Altman and by also plotting the results from visit 1 against visit 2 and calculating the line of best fit. Results and Conclusions Based on the criteria that 95% of all measurement differences should be within a factor of 1.96 of the standard deviations of the mean values, then high resolution Laser Doppler Imaging technique is probably repeatable when acquiring and analysing baseline images of patients with Raynaud’s phenomenon secondary to SSc. However a larger study with more patients is required to prove this conclusively - as only data from 19 patients was analysed [3 patients were not included due to technical issues] - and was therefore susceptible to marked clinical variations in patients presenting on different days for the investigations.
关键词： Laser Doppler imaging,Repeatability,Scleroderma,Raynaud’s
更新于2025-09-23 15:19:57
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Multiple reflection assisted Laser Doppler Vibrometer setup for high resolution displacement measurement
摘要： An experimental design of high resolution non-intrusive displacement sensor working on the principle of basic LDV is being presented. Resolution enhancement has been achieved through phase multiplication using multiple reflections within a high-Q cavity created by a vibrating surface and a high reflection mirror placed parallel to each other. Displacement of 72 nm has been measured with an error range of ±14 nm through direct counting of characteristic peaks in ‘‘half cycle’’ of a interferogram. A linear relationship between displacement and number of reflections has been obtained which offers a straightforward route to measure displacements up to sub-nanometer scale and the resolution is essentially dictated by the reflectivity and physical dimension of moving source.
关键词： Sub-nano scale measurement,Interference,Laser Doppler Vibrometery
更新于2025-09-23 15:19:57
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High-Accuracy SINS/LDV Integration for Long-Distance Land Navigation
摘要： Since the conventional strapdown inertial navigation system (SINS)- and odometer (OD)-integrated navigation has certain limitations, such as suffering from scale factor variation and being affected by wheel slipping and skidding, we present a high-accuracy integrated navigation system that uses both the SINS and laser Doppler velocimeter (LDV) for land vehicles to overcome these problems. We took the lever-arm residual and boresight errors into consideration and formed a complete 21-state Kalman filter to accomplish integrated navigation and precise sensor-to-sensor calibration. The observability analysis of the SINS/LDV system provides valuable insights into the conditions under which the states can be estimated. In addition, the summed measurement model and sequential Kalman filter calculation are deduced to make full use of the nonholonomic constraints (NHC) and LDV measurements. Finally, a long-distance experiment (230 km) with a navigation-grade IMU demonstrated that positioning accuracies of better than 0.02% of the distance travelled can be achieved in both the horizontal and vertical directions.
关键词： land navigation,Inertial navigation system,nonholonomic constraints (NHC),odometer (OD),laser Doppler velocimeter (LDV)
更新于2025-09-19 17:15:36
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Non-Contact Damage Detection under Operational Conditions with Multipoint Laservibrometry
摘要： Scanning laser–Doppler vibrometry (SLDV) can localize and visualize damages in mechanical structures. In order to enable scanning, it is necessary to repeat the vibration. Therefore, this technique is not suited to detect emerging hazards in working machinery that change the vibration behavior. A common technique for such cases is monitoring the vibration excited by machine operation with accelerometers. This technique requires mechanical coupling between sensors and the measurement object, which in?uences the high-frequency vibration responses. However, in the low-frequency range, local damages do not shift resonances or distort operational de?ection shapes (ODS) signi?cantly. These alterations in the vibration behavior are tiny and hard to detect. This paper shows that multipoint laservibrometry (MPV) with laser excitation can measure these e?ects e?ciently, and it further demonstrates that damages in?uence ODSs at frequencies above 20 kHz much stronger than at frequencies below 20 kHz. In addition, ODS-based damage indices are discussed; these are highly sensitive to minute visible changes of the ODSs. In order to enhance the sensitivity of hazard detection, the response vector assurance criterion value is computed and evaluated during operation. The capabilities and limitations of the methodology on the example of a cantilever with manually emerging damage are demonstrated.
关键词： structural health monitoring,multipoint laser-Doppler vibrometer,operational de?ection shape,operational condition,damage detection,laser–Doppler vibrometry,non-destructive testing,laser ablation
更新于2025-09-19 17:13:59
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The preliminary validation of laser Doppler flowmetry in systemic sclerosis in accordance with the OMERACT filter: A systematic review
摘要： Objectives: To investigate the validation status of laser Doppler flowmetry (LDF) in systemic sclerosis (SSc) according to the ‘Outcome Measures in Rheumatologic Clinical Trials’ (OMERACT) filter. Methods: The literature was systematically reviewed to identify all reports assessing the microcirculatory flow in SSc patients. The OMERACT filter (cid:1)including the domains of truth, discrimination and feasibility(cid:1) was applied and a quality assessment was done by the ‘Good Methods Checklist’. To ease the comparison between studies the results were grouped per dynamic test situation: basal, cold/heat challenge and occlusion. Results: The literature search resulted in 4332 hits. Based on title and abstract screening 243 hits were retained and of these, 52 full texts described an assessment by LDF in SSc patients. Finally, 18 studies passed the quality assessment and form the object of this review. The review reveals that expert consensus is lacking on the face and content validity of LDF in SSc. The construct validity of LDF, on the other hand is partially validated. Conflicting results exist on the discriminant capacity of LDF in distinguishing healthy from diseased patients, primary from secondary Raynaud’s phenomenon and in differentiating between disease subsets. Yet, complementing an LDF-measurement with a heat challenge, as well as the evaluation of the post-occlusive hyperaemic response, has the potential to elicit a difference between healthy and diseased patients. Lastly, data on the feasibility of LDF in SSc is lacking in the identified literature. Conclusion: This systematic review emphasizes the very preliminary validation status of LDF in the assessment of the microcirculatory flow in SSc.
关键词： OMERACT,Validity (epidemiology),Microcirculation,Outcome measure,Systemic scleroderma,Laser Doppler flowmetry
更新于2025-09-19 17:13:59
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The Vibration Behavior of Suba??Micrometer Gas Vesicles in Response to Acoustic Excitation Determined via Laser Doppler Vibrometry
摘要： The ability to monitor sub-micrometer gas vesicles’ (GVs) vibration behavior to nonlinear buckling and collapse using laser Doppler vibrometry is reported, providing a precise noncontact technique for monitoring the motion of sub-micrometer objects. The fundamental and first harmonic resonance frequencies of the vesicles are found to be 1.024 and 1.710 GHz, respectively. An interparticle resonance is furthermore identified at ≈300 MHz, inversely dependent upon the agglomerated GV size of around 615 nm. Most importantly, the vesicles amplify and broaden input acoustic signals at far lower frequencies—for example, 7 MHz—associated with medical and industrial applications, and they are found to transition from a linear to nonlinear response at 150 kPa and to collapse at 350 kPa or greater.
关键词： bubble dynamics,gas vesicles,sub-micrometer object metrology,acoustofluidics,laser Doppler vibrometry
更新于2025-09-19 17:13:59
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Differential laser Doppler velocimetry for cross-sectional velocity distribution measurements using 48-channel spatial encoding and nonmechanical scanning
摘要： A differential laser Doppler velocimeter using 48-channel spatial encoded measurement points is proposed for dense cross-sectional velocity distribution measurements. An asymmetrical push–pull configuration and multiple photodiodes are employed to increase the number of the measurement points. The functionality of the proposed structure is experimentally demonstrated. The results indicate that a cross-sectional velocity distribution is successfully measured with the proposed structure.
关键词： Nonmechanical scanning,Spatial encoding,Interferometry,Laser Doppler velocimetry
更新于2025-09-19 17:13:59