Method For Measurement Of Thickness Research Articles

Atmospheric icing measurement and online ice type recognition for aircraft utilizing optical fiber sensor and machine learning algorithms

For the detection of atmospheric icing process, an ice type recognition and thickness measurement method based on optical fiber sensor is proposed and evaluated. Finite element models based on different structures are built for the four corresponding typical ice types in the atmospheric icing environment. Finite element analysis results show the characteristics of sensor response for different ice types and the potential of real-time ice type recognition using optical fiber sensor. In the laboratory test, under the atmospheric icing conditions, 1655 sets of valid data including glazed ice, mixed ice, rime ice and frost are collected. Cascade models based on machine learning algorithms are built and evaluated using a round-robin leave-one-out method. The model realizes instant ice type recognition and thickness measurement without relying on time-domain curve information. The evaluation results show that the proposed method achieves 92.8 % ice type recognition accuracy and 0.27 mm RMSE for ice thickness measurement.

High-frequency ultrasound-based thickness measurement of highly attenuating materials

This paper investigates an effective method for measuring the thickness of highly attenuating materials using the acoustic radiation-induced quasi-static component (QSC) of a primary longitudinal wave (PLW) at high frequency. The generated QSC features lower attenuation than the high-frequency PLW, so the generated QSC pulse with zero carrier frequency can propagate a longer distance at the same group velocity, even in highly attenuating materials. In addition, the method based on the QSC of a high-frequency PLW has better directivity than the low-frequency PLW-based method, making it more suitable for highly attenuated material local thickness measurement. The thickness of highly attenuating materials can be accurately measured by measuring the pulse-echo time-of-flight of the generated QSC pulse using an ultrasound pulse-echo technique. The experimental examinations conducted for highly attenuating silicone rubber blocks with different thicknesses demonstrate that their thicknesses can be accurately measured with the QSC-based method. This paper provides an effective method for thickness measurements of highly attenuating materials.

Nondestructive Wafer Level MEMS Piezoelectric Device Thickness Detection.

This paper introduces a novel nondestructive wafer scale thin film thickness measurement method by detecting the reflected picosecond ultrasonic wave transmitting between different interfacial layers. Unlike other traditional approaches used for thickness inspection, this method is highly efficient in wafer scale, and even works for opaque material. As a demonstration, we took scandium doped aluminum nitride (AlScN) thin film and related piezoelectric stacking layers (e.g. Molybedenum/AlScN/Molybdenum) as the case study to explain the advantages of this approach. In our experiments, a laser with a wavelength of 515 nm was used to first measure the thickness of (1) a single Molybdenum (Mo) electrode layer in the range of 100-300 nm, and (2) a single AlScN piezoelectric layer in the range of 600-1000 nm. Then, (3) the combined stacking layers were measured. Finally, (4) the thickness of a standard piezoelectric composite structure (Mo/AlScN/Mo) was characterized based on the conclusions and derivation extracted from the aforementioned sets of experiments. This type of standard piezoelectric composite has been widely adopted in a variety of Micro-electromechanical systems (MEMS) devices such as the Piezoelectric Micromachined Ultrasonic Transducer (PMUT), the Film Bulk Acoustic Resonator (FBAR), the Surface Acoustic Wave (SAW) and more. A comparison between measurement data from both in-line and off-line (using Scanning Electron Microscope) methods was conducted. The result from such in situ 8-inch wafer scale measurements was in a good agreement with the SEM data.

Differences in Body Composition Analysis by DEXA, Skinfold and BIA Methods in Young Football Players.

The most widely used method in professional sports for fat percentage assessment is the skinfold method. However, there is the chance of bias and human error. For this reason, other more precise methods are used, such as single-frequency bioelectrical impedance analysis (BIA) or dual energy X-ray absorptiometry (DEXA). However, there are limited data that demonstrate the methodological shortcomings or congruences in fat and fat-free mass estimates including gender differences and differences in athlete populations. Thus, the aim of the present study was to compare total body fat (%BF) estimated by six skinfold thickness measurement (SKF) and single-frequency bioelectrical impedance analysis (BIA) methods, using three different sets of equations, to that assessed by the dual energy X-ray absorptiometry (DEXA) method using a DEXA Hologic Serie Discovery QDR. For this aim, 76 males and 70 females belonging to the professional Spanish football federation were evaluated. We found significant differences between the three measures. BIA significantly underestimates the fat percentage, followed by skinfolds. With DEXA being the more objective or accurate method, an equation is established by means of linear regression analysis that allows the percentage of adipose tissue to be obtained either through anthropometry or electrical bioimpedance and adjusted to that which would be obtained by the DEXA system.

A new ultrasonic method for synchronous measurement of internal temperature distributions and thickness in high-temperature structures

A new ultrasonic method for synchronous measurement of multiple parameters of heated materials is proposed in this paper. Based on the thermal-acoustic-solid coupling theory, the internal temperature distributions and thickness of solid structures are reconstructed synchronously by an alternate iterative multi-parameter identification method. Firstly, a numerical model of multi-parameter synchronous identification is obtained based on temperature dependence of the velocity of the ultrasonic wave propagating through the heated material. Then, an inverse analysis by the alternate iterative method for estimating equivalent thermal boundary conditions and thickness. In addition, experiments are carried out in order to validate the feasibility and reliability of the developed method, whose stability and accuracy are also analyzed through a comprehensive parameter analysis. The research results show that the structure thickness obtained by the alternate iteration method based on ultrasonic transit time accords with the physical reality and the internal transient temperature profiles determined ultrasonically agrees well with those obtained using thermocouples installed in the steel. It demonstrates that the method proposed in this work is an effective multi-parameter synchronous measurement means to determine the internal transient temperature distribution and thickness of high temperature structures with high accuracy by ultrasonic pulse echo measurements.

High-Precision Thickness Measurement of Cu Film on Si-Based Wafer Using Erasable Printed Eddy Current Coil and High-Sensitivity Associated Circuit Techniques

The eddy current coil is widely adopted to measure the thickness of copper (Cu) film on the silicon (Si) based wafer. However, the lift-off distance (LOD) variation between the coil and Cu film has a strong negative effect on the accuracy and repetitiveness of the thickness measurement. Therefore, it is necessary to eliminate the impact of LOD variation. In this article, a high-precision thickness measurement method is proposed to determine the thickness of Cu film on the Si-based wafer by using the techniques of the erasable printed eddy current coil (EPECC) and the high-sensitivity associated circuit. The theoretical feasibility and sensitivity improvement of the conceptual design are analyzed in detail. As a proof of concept, a prototype of the proposed method is fabricated. The EPECC is prepared on the back surface of the wafer, and the LOD is unvaried during the measurement. Experimental results show that comparing with the traditional eddy current coil, the measurement stability, precision, and accuracy of the Cu film thickness by the proposed method are significantly improved even under severe vibration conditions. The relative error is 2% in repeated measurements.

Non‐invasive on‐site method for thickness measurement of transparent ceramic glazes based on depth from focus

AbstractGlazed ceramics are a common material analyzed through geochemistry, whether in the form of tableware collected during excavations or tiles observed as part of architectural features. Within the framework of these studies, measuring the thickness of the transparent glaze is one of the useful variables available for the characterization of the ceramic, contributing to searches for provenance as well as serialization. However, this task often requires invasive methods performed in the laboratory, which may not always be possible. This paper develops a non‐invasive and portable on‐site system for measuring the thickness of ceramic glazes. Based on the depth from focus technique, this method makes use of a classical camera, a macroscopic lens, a translation stage, and a laptop for system control. In this article, we test this method through the measurement of glaze for ten samples as compared to results obtained for sections through scanning electron microscopy.

Automatic evaluation of endometrial receptivity in three-dimensional transvaginal ultrasound images based on 3D U-Net segmentation.

BackgroundEndometrial thickness is an essential factor affecting female fertility. Clinically, ultrasound imaging is the first choice for the examination of uterine and endometrial-related diseases. However, the boundary of some endometrial is challenging to distinguish due to the effects of image resolution and noise. In addition, the irregular shape of the endometrium makes it more difficult for doctors to measure its thickness. Through the automatic segmentation and extraction of the endometrium, the maximum thickness of the endometrium can be measured automatically and accurately. This provides a quantitative index for doctors to use diagnostically.MethodsIn this study, 85 cases of three-dimensional transvaginal ultrasound (3D TVUS) images were collected retrospectively, including 75 cases of endometrial adhesion and 10 cases of non-adhesion. Firstly, the ultrasound images were filtered by block-matching and 3D filtering and speckle reducing anisotropic diffusion (SRAD). These two kinds of filtered images were combined with the original image to construct a three-channel image. Then, the augmented images were sent to 3D U-Net to realize endometrium segmentation. The performance of the segmentation models was evaluated using the Dice similarity coefficient (DSC), Jaccard, sensitivity, and 95th percentile Hausdorff distance (HD95). Finally, the medial axis transform was used to extract the endometrial centerline, based on which the endometrial thickness could be automatically measured.ResultsThe endometrium segmentation method proposed in this paper achieved 90.83% in Dice, 83.35% in Jaccard, 90.85% in sensitivity, and 12.75 mm in HD95 in the testing set. Taking the doctor’s manual measurement as the gold standard, 94.20% of the automatic endometrial thickness measurements based on the segmentation results were within the allowable error range of clinical diagnosis.ConclusionsThis paper presents an automatic endometrium segmentation and thickness measurement method for 3D TVUS images. The experimental results show that this method has high segmentation accuracy to recognize endometrial adhesion images. Furthermore, the thickness measurement based on the segmentation results has high reliability and repeatability, and the accuracy can meet clinical diagnosis needs.

Comparison of Central Corneal Thickness Measurements by Ultrasound Pachymetry and Non-Contact Specular Microscopy in Normal Eyes

Central corneal thickness measurement plays a crucial role in the assessment and treatment of glaucoma and several corneal diseases in addition to its importance in refractive surgery management. There are various methods for central corneal thickness measurement, which differ in their operating principles and technology beside the difference in their advantages and limitation. This study aims to compare central corneal thickness (CCT) values of healthy eyes measured by two common devices: ultrasound pachymetry (UP) and non-contact specular microscopy (NCSM) and to determine the average difference between the two measurements. The study was conducted in the ophthalmology outpatient clinic in Imam Al-Sadiq Hospital- Hilla city and included 99 healthy individuals (198 eyes) of both genders. Results indicated that NCSM tends to give thinner CCT values compared to UP while providing quicker, safer and more comfortable evaluation for corneal thickness in addition to corneal endothelial cell density.

Experimental helium-beam radiography with a high-energy beam: Water-equivalent thickness calibration and first image-quality results.

A clinical implementation of ion-beam radiography (iRad) is envisaged to provide a method for on-couch verification of ion-beam treatment plans. The aim of this work is to introduce and evaluate a method for quantitative water-equivalent thickness (WET) measurements for a specific helium-ion imaging system for WETs that are relevant for imaging thicker body parts in the future. Helium-beam radiographs (αRads) are measured at the Heidelberg Ion-beam Therapy Center with an initial beam energy of 239.5 MeV/u. An imaging system based on three pairs of thin silicon pixel detectors is used for ion path reconstruction and measuring the energy deposition (dE) of each particle behind the object to be imaged. The dE behind homogeneous plastic blocks is related to their well-known WETs between 280.6 and 312.6 mm with a calibration curve that is created by a fit to measured data points. The quality of the quantitative WET measurements is determined by the uncertainty of the measured WET of a single ion (single-ion WET precision) and the deviation of a measured WET value to the well-known WET (WET accuracy). Subsequently, the fitted calibration curve is applied to an energy deposition radiograph of a phantom with a complex geometry. The spatial resolution (modulation transfer function at 10 % -MTF10% ) and WET accuracy (mean absolute percentage difference-MAPD) of the WET map are determined. In the optimal imaging WET-range from ∼280 to 300 mm, the fitted calibration curve reached a mean single-ion WET precision of 1.55 0.00%. Applying the calibration to an ion radiograph (iRad) of a more complex WET distribution, the spatial resolution was determined to be MTF10% = 0.49 0.03 lp/mm and the WET accuracy was assessed as MAPD to 0.21 %. Using a beam energy of 239.5 MeV/u and the proposed calibration procedure, quantitative αRads of WETs between ∼280 and 300 mm can be measured and show high potential for clinical use. The proposed approach with the resulting image qualities encourages further investigation toward the clinical application of helium-beamradiography.

Simultaneous measurement of layer thicknesses in thin layered materials using the phase of ultrasonic reflection coefficient spectrum

The wide application of layered materials proposes more requests for their mechanical performance. The measurement of layer thicknesses is an important part of performance evaluation for the layered materials. Ultrasonic testing is an effective method for thickness measurement. However, in thin layered materials, the layer thicknesses are immeasurable due to the overlap of ultrasonic echoes from interlayer interfaces. This work presented an ultrasonic method for simultaneous measurement of layer thicknesses in thin layered materials using the phase of ultrasonic reflection coefficient spectrum (PRCS) at normal incidence, and the other method using the magnitude of ultrasonic reflection coefficient spectrum (MRCS) was also investigated for comparison. The inversion algorithm based on the particle swarm optimization (PSO) was used to avoid convergence to local minima. Both the sensitivities to the thickness parameters and effects of frequency bandwidth of the transducer were studied for PRCS and MRCS. The results indicate that PRCS is sensitive to the layer thicknesses and larger frequency bandwidth is favorable for convergence zones to be produced. Compared with MRCS, the narrower convergence zones can be obtained using PRCS. The experimental measurement results of the thin Al-Ti bi-layered material confirm that the measurement of layer thicknesses using PRCS is more accurate than MRCS. The relative errors of the Al layer and the Ti layer between the PSO estimated values and the real values are −3.77% and +1.91% using PRCS, respectively.

Non-destructive evaluation of uneven coating thickness based on active long pulse thermography

Non-destructive detection of coating thickness is important after coating deposition and during service. The present work is to establish a measurement method for fast inspection, large area detection of coating thickness with an active long pulse thermography. The measurement method was theoretically analyzed based on the equation of 1D heat transfer in the depth direction, accordingly coating thickness can be quantitively evaluated by recording the temperature decay curve in the cooling stage and computing the time at the minimum of its 2nd derivative. Then, the proposed method was experimentally validated by uniform coating specimen with different thicknesses. Furthermore, the thickness measurement method was successfully applied to measure thickness of an uneven coating specimen within a relative error of 5% with sufficient sampling rate. Finally, some key techniques were discussed for accurate measurements including thermal excitation, sampling rate of thermography, thickness ratio of coating and substrate, etc. The results verify that active long pulse thermography is a powerful tool for non-contact and full-field measurement of coating thickness with merits of safe and easy to implement.

Film thickness measurements in the R1233zd film evaporation and flow processes on a quartz plate

The evaporation and flow of refrigerant films widely exists in aviation and aerospace, refrigeration and air-conditioning, consumer electronics, and other fields. Film thickness measurement with high accuracy is helpful to understand heat transfer mechanisms of liquid films, and further improve the relevant industrial devices and processes. Here, R1233zd was taken as the research object, and a novel method of refrigerant film thickness measurement based on absorption spectroscopy was proposed. An inversion model for determination of film thickness was established, and a measurement system was then developed. A calibration tool with known film thicknesses (0-500 μm) was employed to validate the measurement accuracy of the system. It was found that the measurement uncertainty was ±0.5%. Furthermore, the evaporation processes of R1233zd films with three different initial thicknesses on a horizontal quartz plate and the flow processes of R1233zd films at three different flow rates on an inclined quartz plate were investigated, respectively.

R-based method for quantitative analysis of biofilm thickness by using confocal laser scanning microscopy.

Microscopy is mostly the method of choice to analyse biofilms. Due to the high local heterogeneity of biofilms, single and punctual analyses only give an incomplete insight into the local distribution of biofilms. In order to retrieve statistically significant results a quantitative method for biofilm thickness measurements was developed based on confocal laser scanning microscopy and the programming language R. The R‐script allows the analysis of large image volumes with little hands‐on work and outputs statistical information on homogeneity of surface coverage and overall biofilm thickness. The applicability of the script was shown in microbial fuel cell experiments. It was found that Geobacter sulfurreducens responds differently to poised anodes of different material so that the optimum potential for MFC on poised ITO anodes had to be identified with respect to maximum current density, biofilm thickness and MFC start‐up time. Thereby, a positive correlation between current density and biofilm thickness was found, but with no direct link to the applied potential. The optimum potential turned out to be +0.1 V versus SHE. The script proved to be a valuable stand‐alone tool to quantify biofilm thickness in a statistically valid manner, which is required in many studies.

Polarization Measurement Method Based on Liquid Crystal Variable Retarder (LCVR) for Atomic Thin-Film Thickness

Atomic thickness thin films are critical functional materials and structures in atomic and close-to-atomic scale manufacturing. However, fast, facile, and highly sensitive precision measurement of atomic film thickness remains challenging. The reflected light has a dramatic phase change and extreme reflectivity considering the Brewster angle, indicating the high sensitivity of the optical signal to film thickness near this angle. Hence, the precision polarization measurement method focusing on Brewster angle is vital for the ultrahigh precision characterization of thin films. A precision polarization measurement method based on a liquid crystal variable retarder (LCVR) is proposed in this paper, and a measurement system with a high angular resolution is established. A comprehensive measurement system calibration scheme is also introduced to accommodate ultrahigh precision film thickness measurement. Repeatable measurement accuracy to the subnanometer level is achieved. Standard silicon oxide film samples of different thicknesses were measured around Brewster angle using the self-developed system and compared with a commercial ellipsometer to verify the measurement accuracy. The consistency of the thickness measurement results demonstrates the feasibility and robustness of the measurement method and calibration scheme. This study also demonstrates the remarkable potential of the LCVR-based polarization method for atomic film thickness measurement in ultraprecision manufacturing.

GEOMETRIC MEASUREMENTS USING MICROWAVES

The article presents an overview of methods for measuring geometric parameters – the thickness of dielectric materials and products using ultrahigh frequency radio waves. The main methods of thickness measurement are considered: geometric, amplitude-phase, frequency-phase, ellipsometric, with examples and characteristics of their practical application. The schemes of implemented microwave thickness gauges and converters are given.

Thickness measurement method for the thermal protection layer of a solid rocket motor based on a laser point cloud

The thermal protection layer of the solid rocket motor (SRM) is an important elastic material applied to the adhesive shell and propellant; the thickness of the layer is related to the performance of the SRM. This paper proposes a method of linear laser scanning to realise the precise thickness measurement of the thermal protection layer. The custom-designed data acquisition device separately collects distance values from the inner surface of the thermal protection layer, before and after coating, using a linear laser sensor. The two measured distance values are subtracted and D-H modelling (a classical kinematics modelling method proposed by Denavit and Hartenberg) is conducted, then the system errors are analysed and calibrated to obtain the 3D point cloud data of the profile. The iterative closest point (ICP) algorithm is used to register the point cloud data relating to the internal surface, then an octree-based simplification method is proposed to realise the denoising and simplification of the point cloud data. Next, the normal vector of the point cloud data is calculated and the reference surface is extracted as the projection plane. The simplified point cloud is then projected onto the plane and the geometric information of the point cloud data after projection is extracted. A series of distance differences, namely the thickness of the thermal protection layer, is obtained. Finally, the Poisson surface reconstruction algorithm is used to display the inner surface of the thermal protection layer. The results show that the difference between the calculated values and the measured values is less than 0.1 mm, indicating that the thickness of the thermal protection layer of the SRM can be measured by the proposed non-contact method.

Methods to assess tooth gingival thickness and diagnose gingival phenotypes: A systematic review.

Measurement of the periodontal soft tissue dimension is crucial for clinical decision-making and aesthetic prognosis. However, the effectiveness of different measuring methods remains unclear. This systematic review aimed to explore the diagnostic accuracy of two non-invasive methods (namely CBCT and ultrasound) for gingival thickness measurement at different tooth positions. A systematic search was performed using PubMed (including Medline), PubMed Central, OVID, Cochrane Library, LILACS and OpenGrey. Studies focusing on comparisons between CBCT, ultrasound and direct transgingival probing were included. The means, SDs and correlation coefficients with 95% confidence intervals were extracted and analyzed using Review Manager and R software. Twelve studies were selected. No significant difference was found between CBCT measurement and transgingival probing in the anterior and posterior dentition, and a moderate correlation was observed between these two methods (r=0.41). A weak correlation was found between ultrasound measurement and transgingival probing (r=0.32), and a slight but statistically significant difference was found when comparing ultrasonic devices and transgingival probing in the posterior area. CBCT can be considered a relatively reliable method for gingival thickness measurement in both the anterior and posterior areas compared with direct probing. Ultrasonic devices provide limited accuracy in the posterior area but are relatively comparable with direct clinical assessments in the anterior area. Measurement location may affect the diagnostic accuracy and repeatability of gingival thickness measurements. Appropriate method selection in different clinical scenarios is crucial to aesthetic outcome prediction and decision-making.

Error Analysis and Correction of Thickness Measurement for Transparent Specimens Based on Chromatic Confocal Microscopy with Inclined Illumination

As a fast, high-accuracy and non-contact method, chromatic confocal microscopy is widely used in micro dimensional measurement. In this area, thickness measurement for transparent specimen is one of the typical applications. In conventional coaxial illumination mode, both the illumination and imaging axes are perpendicular to the test specimen. At the same time, there are also geometric measurement limitations in conventional mode. When measuring high-transparency specimen, the energy efficiency will be quite low, and the reflection will be very weak. This limitation will significantly affect the signal-to-noise ratio. The inclined illumination mode is a good solution to overcome this bottleneck, but the thickness results may vary at different axial positions of the sample. In this paper, an error correction method for thickness measurement of transparent samples is proposed. In the authors’ work, the error correction model was analyzed and simulated, and the influence caused by the different axial positions of sample could be theoretically eliminated. The experimental results showed that the thickness measurement of the samples was practically usable, and the measurement errors were significantly reduced by less than 2.12%, as compared to the uncorrected system. With this error correction model, the standard deviation had decreased significantly, and the axial measurement accuracy of the system can reach the micron level. Additionally, this model has the same correction effect on the samples with different refractive indexes. Therefore, the system can realize the requirement of measurement at different axial positions.

Design of a deep learning visual system for the thickness measurement of each coating layer of TRISO-coated fuel particles

In the new generation of nuclear energy system, the thickness of the coating layer of tristructural isotropic (TRISO)-coated fuel particles is one of the most important parameters. Recently, some visual-based methods have been developed for the thickness measurement of each coating layer, but the existing method still lacks of practicality. In this study, an advanced visual system combined with the ceramographic section method and deep learning algorithms is designed to automatically measure the thickness values of each coating layer. In the designed visual system, an automatic image acquisition method is first achieved. After that, an accurate thickness measurement method is proposed based on the designed image segmentation model. Finally, to enhance the reliability and consistency of the measurement results, a tracing method is developed for the designed measurement system. The experimental results demonstrate that the designed system can accurately automatically measure the thickness values of each coating layer.