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Measurement of shallow defects using noncontact broadband leaky Lamb wave produced by pulsed laser with ultrasound microphone
摘要： In this study, we propose a convenient noncontact laser ultrasonic system to detect small cracks and estimate the wall-thinning defects of thin plates. The system uses an ultrasound microphone to detect the energy leaked from the broadband Lamb-wave propagation. The broadband characteristics of this wave, produced by a pulsed laser, are used to measure the wavenumber. The cumulative standing-wave energy (CSWE) method that uses a traveling wave is implemented to verify the feasibility of the ultrasound microphone. The excitation energy of the pulsed laser was insufficient compared with that of the continuous-wave contact actuator. Therefore, a modified local wavenumber estimation (LWE) method is proposed, which reconstructs several LWE images at various frequencies. These images are averaged to calculate thicknesses of the plate and defects, by using the wavenumber–thickness relationship. The method has an error of 2.84% and 7.7% for the thickness of the plate and defect area, respectively.
关键词： cumulative standing-wave energy (CSWE),ultrasound microphone,local wavenumber estimation (LWE),wall-thinning defects,noncontact laser ultrasonic system,broadband Lamb-wave propagation,small cracks
更新于2025-09-23 15:19:57
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Noncontact measurement of heart rate using facial video illuminated under natural light and signal weighted analysis
摘要： Non-contact and remote measurements of vital physical signals are important for reliable and comfortable physiological self-assessment. We presented a novel optical imaging-based method to measure the vital physical signals. Using a digital camera and ambient light, the cardiovascular pulse waves were extracted better from human color facial videos correctly. And the vital physiological parameters like heart rate were measured using a proposed signal-weighted analysis method. The measured HRs consistent with those measured simultaneously with reference technologies (r=0.94, p<0.001 for HR). The results show that the imaging–based method is suitable for measuring the physiological parameters, and provide a reliable and comfortable measurement mode. The study lays a physical foundation for measuring multi-physiological parameters of human noninvasively.
关键词： noncontact cardiovascular measurement,heart rate,pulse wave,Biomedical engineering,blood pressure
更新于2025-09-19 17:15:36
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[IEEE 2020 IEEE 33rd International Conference on Micro Electro Mechanical Systems (MEMS) - Vancouver, BC, Canada (2020.1.18-2020.1.22)] 2020 IEEE 33rd International Conference on Micro Electro Mechanical Systems (MEMS) - 3D Laser Nanoprinting
摘要： Digital phantoms are vital for various biomedical researches. Traditional phantoms include theoretical models and voxel models reconstructed from medical images. It has been demonstrated that the homogeneous phantom filled with uniform tissue is accurate enough for wearable antenna design, body-centric channel modeling, etc. Therefore, it is interesting and necessary to investigate the novel approach of generating digital phantoms using an optical noncontact measurement system. In this letter, the point cloud data are first obtained; then, they are simplified via principal component analysis; finally, by applying surface reconstruction and mesh simplification techniques, a digital Chinese phantom is established. To verify the usability of the phantom, numerical calculation is performed to check E-fields at different positions on the body. Results sufficiently prove the feasibility of the train of thought presented in this letter.
关键词： noncontact measurement system,point cloud data,Digital phantom,numerical calculation,surface reconstruction,principal component analysis (PCA)
更新于2025-09-19 17:13:59
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Full noncontact laser ultrasound: first human data
摘要： Full noncontact laser ultrasound (LUS) imaging has several distinct advantages over current medical ultrasound (US) technologies: elimination of the coupling mediums (gel/water), operator-independent image quality, improved repeatability, and volumetric imaging. Current light-based ultrasound utilizing tissue-penetrating photoacoustics (PA) generally uses traditional piezoelectric transducers in contact with the imaged tissue or carries an optical fiber detector close to the imaging site. Unlike PA, the LUS design presented here minimizes the optical penetration and specifically restricts optical-to-acoustic energy transduction at the tissue surface, maximizing the generated acoustic source amplitude. With an appropriate optical design and interferometry, any exposed tissue surfaces can become viable acoustic sources and detectors. LUS operates analogously to conventional ultrasound but uses light instead of piezoelectric elements. Here, we present full noncontact LUS results, imaging targets at ~5 cm depths and at a meter-scale standoff from the target surface. Experimental results demonstrating volumetric imaging and the first LUS images on humans are presented, all at eye- and skin-safe optical exposure levels. The progression of LUS imaging from tissue-mimicking phantoms, to excised animal tissue, to humans in vivo is shown, with validation from conventional ultrasound images. The LUS system design insights and results presented here inspire further LUS development and are a significant step toward the clinical implementation of LUS.
关键词： photoacoustics,noncontact imaging,volumetric imaging,human imaging,laser ultrasound
更新于2025-09-12 10:27:22
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Noncontact photoacoustic angiography with an air-coupled ultrasonic transducer for evaluation of burn injury
摘要： In vivo identi?cation of viable and thermally coagulated blood in a burn wound can be used to pro?le the type, extent, and site of the burn, thus assisting the removal of necrotic tissue in preparation for skin grafts. Recently, intensive research on photoacoustic imaging (PAI) has been conducted to evaluate burn injury. However, most PAI systems usually take the approach of direct physical contact of an acoustic detector or an impedance matching medium with the vulnerable burned skin, which exposes signi?cant limitations on the diagnosis of burn injuries. Here, we present a noncontact PAI system, based on a custom designed air-coupled ultrasonic transducer, enabling in vivo noncontact vasculature to be imaged without contrast agents. Using the natural difference in light absorption between coagulated and non-coagulated blood at the wavelength of 532 nm, this PAI system possesses an immanent advantage to discriminate viable and thermally coagulated blood in burned tissues. Phantom experiments and burned rabbit’s skin imaging have been implemented to demonstrate that the noncontact PAI technique could be valuable in the adjuvant diagnosis and observation of burns.
关键词： air-coupled ultrasonic transducer,noncontact,photoacoustic imaging,burn injury,vasculature
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE International Conference "Quality Management, Transport and Information Security, Information Technologies" (IT&QM&IS) - Saint Petersburg, Russia (2018.9.24-2018.9.28)] 2018 IEEE International Conference "Quality Management, Transport and Information Security, Information Technologies" (IT&QM&IS) - Algorithms for Detecting Potato Defects Using Images in the Infrared Range of Spectrum
摘要： An automated system for contactless thermal quality testing of potato moving along a chain conveyor is presented. The algorithm of the computer vision system for the recognition of potato defects in real time is described. The method for detecting defects is based on determining the temperature difference between healthy and damaged tissues after short-term heating of the tubers.
关键词： noncontact,computer vision,nondestructive,potato,testing,defect,infrared
更新于2025-09-10 09:29:36
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High-Yield Formation of Graphdiyne Macrocycles Through On-Surface Assembling and Coupling Reaction
摘要： Rationally designed halogenated hydrocarbons are widely used building blocks to fabricate covalent-bonded carbon nanostructures on surface through a reaction pathway involving generation and dissociation of organometallic intermediates and irreversible covalent bond formation. Here we provide a comprehensive picture of the on-surface-assisted homocoupling reaction of 1,3-bis(2-bromoethynyl)benzene on Au(111), aiming for the synthesis of graphdiyne nanostructures. Submolecular resolution scanning tunneling microscopy and noncontact atomic force microscopy observations identify the organometallic intermediates and their self-assemblies formed in the dehalogenation process. The demetallization of the organometallic intermediates at elevated temperatures produces butadiyne moieties that spontaneously formed two different covalent structures, i.e. graphdiyne zigzag chains and macrocycles, whose ratio was found to depend on the initial coverage of organometallic intermediates. At the optimal condition, the stepwise demetallization and cyclization led to a high yield production of graphdiyne macrocycles up to 95 %. Statistical analysis and theoretical calculations suggested that the favored formation of macrocycles was resulted from the complex interplay between thermodynamic and kinetic processes involving the organometallic bonded intermediates and the covalently bonded butadiyne moieties.
关键词： on-surface reaction,graphdiyne macrocycle,organometallic intermediate,scanning tunneling microscopy,noncontact atomic force microscopy,thermodynamic and kinetic control
更新于2025-09-10 09:29:36
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A comparison of NCT, Goldman application tonometry values with and without fluorescein
摘要： Purpose: The aim of the study was to statistically compare intraocular pressure (IOP) values measured using noncontact tonometer (NCT), Goldmann applanation tonometry (GAT) with fluorescein (fGAT), and GAT without fluorescein (nGAT). The study was also performed to test whether the values obtained using each technique change in accordance with the central corneal thickness (CCT) and refractive and keratometric values. Study design: This study was a prospective study of 188 eyes of 94 healthy volunteers. Methods: IOP was measured using fGAT, nGAT and NCT. CCT, refractive values, and keratometric values were measured, and the correlations and differences in the IOP for each tonometer were investigated. Results: The mean IOP values obtained with the NCT, nGAT, and fGAT were 17.5±3.7, 12.3±2.7, and 12.5±2 mmHg. The mean CCT was 538.2±34.4 μm, the mean refractive value was 0.9±1.2 D, and the mean keratometric value was 43.5±1.5 D. NCT was positively correlated with fGAT and GAT values and was significantly higher than both the values. There were no differences between fGAT and GAT values. No correlation was observed between the CCT and keratometric and refractive values and the difference between NCT and nGAT or fGAT. Conclusion: Differences in the measurements obtained using nGAT and fGAT were insignificant (P.0.05). Both values were positively correlated with NCT measurements (r =0.354, P,0.05) and were independent of CCT, keratometry, and refraction values. nGAT appears to be suitable for use in routine clinic practice.
关键词： central corneal thickness,Goldmann applanation tonometry,intraocular pressure,refractive value,noncontact tonometry,fluorescein
更新于2025-09-09 09:28:46
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24-GHz Self-Injection-Locked Vital-Sign Radar Sensor With CMOS Injection-Locked Frequency Divider Based on Push-Push Oscillator Topology
摘要： In this letter, a 24-GHz CMOS injection-locked frequency divider (ILFD) based on the push–push oscillator topology is designed and fabricated. It is further treated as the kernel component of a self-injection-locked (SIL) radar sensor for noncontact vital-sign detection. The push–push topology is employed to double the oscillation frequency of the 12-GHz LC oscillator to provide the 24-GHz transmitting signal of the radar sensor, while the direct injection-locked configuration is used to divide the receiving 24-GHz injection signal by 2. Hence, the 12-GHz output of the ILFD can be connected with a differentiator-based envelope detector for vital-sign demodulation. By packaging the developed ILFD chip and connecting it with two antennas, a gain block, a differentiator-based envelope detector, and a 24-GHz SIL radar sensor can be built to detect the physiological chest movement of a human subject. The feasibility of developing a SIL radar sensor in the millimeter-wave range is also demonstrated.
关键词： self-injection-locked (SIL) radar,push–push oscillator,noncontact vital-sign sensor,Continuous-wave (CW) radar,injection-locked frequency divider (ILFD)
更新于2025-09-09 09:28:46
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Automated, Noncontact Intraocular Pressure Home Monitoring after Implantation of a Novel Telemetric Intraocular Pressure Sensor in Patients with Glaucoma: A Feasibility Study
摘要： Purpose. Reliable and regular assessment of intraocular pressure (IOP) is important for the monitoring of patients with glaucoma. The purpose of this study was to evaluate the feasibility of a novel system for the automated, noncontact measurement of IOP. Patients and Methods. A first-generation telemetric IOP sensor was previously implanted in the ciliary sulcus of six patients with open-angle glaucoma during cataract surgery. Using this technology, automated noninvasive tonometry may be performed in a home setting. In the present study, a modified sleep mask and a modified eyepatch with incorporated coil antennae for measurements during nighttime and daytime, respectively, were tested on a single patient. Results. In this feasibility study, the 24 h wear of the prototype measuring apparatus was well tolerated. Three sequences of 24 h IOP measurements with at least 200 IOP measurements per day were performed (Sequence 1: mean 19.6 ± 2.7 mmHg, range 13.4–28.7 mmHg; Sequence 2: mean 21.0 ± 3.0 mmHg, range 13.1–30.5 mmHg; Sequence 3: mean 19.9 ± 2.4 mmHg, range 12.6–27 mmHg). Conclusions. For the first time, repeated and automated 24-hour measurements are possible using a prototype noncontact reading system after implantation of a novel telemetric IOP sensor in patients with glaucoma.
关键词： noncontact tonometry,glaucoma,intraocular pressure,automated measurement,telemetric sensor
更新于2025-09-09 09:28:46