Reflected Intensity Distribution Research Articles

Thin film characterization by learning-assisted multi-angle polarized microscopy.

Thin film characterization is a necessary step in the semiconductor industry and nanodevice fabrication. In this work, we report a learning-assisted method to conduct the measurement based on a multi-angle polarized microscopy. By illuminating the film with a tightly focused vectorial beam with space-polarization nonseparability, the angle-dependent reflection coefficients are encoded into the reflected intensity distribution. The measurement is then transformed into an optimization problem aiming at minimizing the discrepancy between measured and simulated image features. The proposed approach is validated by numerical simulation and experimental measurements. As the method can be easily implemented with a conventional microscope, it provides a low cost solution to measure film parameters with a high spatial resolution and time efficiency.

Research on Reflection Mechanism of Nonuniform Plasma

The surface of the near-space hypersonic vehicle is covered with a plasma sheath (PSh) with fluid properties. During the radar detection of hypersonic vehicles, the spatial distribution characteristics of PSh parameters affect the reflected wave intensity and the position of the maximum reflection layer of plasma in the vehicle’s different areas, resulting in significant differences in the intensity and frequency offset of echo signals in various areas. In order to further study the reflection characteristics of nonuniform plasma, this article uses the equivalent wave impedance method to calculate the reflection and transmission coefficients of each layer of plasma, analyzes the reflection intensity distribution mechanism of nonuniform plasma, and reveals the EM shielding effect (ES-effect) of plasma. Based on the typical carrier frequency, collision frequency, electron density, and electron density distribution gradient, the variation law of maximum reflection position and maximum reflection intensity in nonuniform plasma is revealed. The research results lay a theoretical foundation for analyzing echo signal characteristics of the PSh-covered target, radar detection anomaly suppression, and EM stealth.

Recurrent Residual Dual Attention Network for Airborne Laser Scanning Point Cloud Semantic Segmentation

Kernel point convolution (KPConv) can effectively represent the point features of point cloud data. However, KPConv-based methods just consider the local information of each point, which is very difficult to characterize the intrinsic properties of ALS point clouds for complex laser scanning conditions. Therefore, we rethink KPConv and propose a recurrent residual dual attention network (RRDAN) based on the encoder-decoder structure for the semantic segmentation of ALS point cloud data. In the encoder stage, we design an attention kernel point convolution (AKPConv) block by using a scaling factor of batch normalization to highlight the significant channel information. Then, we use the AKPConv block to develop a recurrent residual kernel attention (RRKA) module to iteratively aggregate the local neighborhood features. In the decoder stage, we design a global and local channel attention (GLCA) module with global connection and local 1D convolution to interact the global and local information after fusing the upsampled high-level representations and the skip-connected low-level features. In addition, to reduce the influence of the long-tail distribution of reflection intensity, we apply gamma transformation to correct the data as normal distribution. The proposed RRDAN can achieve diversified feature aggregation to implement the refined semantic segmentation of ALS point clouds. We evaluate our method on two ALS datasets (i.e., ISPRS and DCF2019) to demonstrate its performance compared to a few advanced methods. Code: https://github.com/SC-shendazt/RRDAN.

Non-Destructive Inspection of Twisted Wire in Resin Cover Using Terahertz Wave

We proposed a new method for evaluating the deterioration of messenger wires by using terahertz waves. We use terahertz time-domain spectroscopy to measure several twisted wire samples with different levels of deterioration. We find that each twisted wire sample had a different distribution of reflection intensity which was due to the wires' twist structure. We show that it is possible to assess the degradation from the straight lines present in the reflection intensity distribution image. Furthermore, it was confirmed that our method can be applied to wire covered with resin.

Researching the design of a glass-bead retro-reflective material to reduce downward reflection for urban heat island mitigation

Recently, retro-reflective (RR) materials were proposed for building facades rather than using diffuse highly reflective materials for urban heat island mitigation. However, existing research indicated that when using RR materials, retro-reflection starts to decrease and the downward reflection increases when the incident angle of light exceeds approximately 50° with respect to the surface normal, leading to a negative impact on pedestrians and worsening the urban heat island. To improve the negative impact of downward reflection, this study focuses on designing the surface of glass-bead RR materials to reduce the downward reflection component without changing its retro-reflectivity. The angular retro-reflectivity and angular reflection intensity distribution of a newly designed glass-bead (NDGB) RR sample, a normal glass-bead (NGB) RR sample, and a capsule RR sample (that is already sold on the market) are evaluated and compared using a laboratory-based optical experiment. Moreover, the upward and downward reflection ratios of three RR building walls are measured and compared using an outdoor building-wall model experiment. The results show that the angular retro-reflectivity of the NDGB RR sample is almost the same as the NGB RR sample and only 1.4% lower than that of the capsule RR sample; however, when the incident angle exceeds 60°, the downward (or specular) reflection of the NDGB RR sample is significantly reduced by approximately 97% and 98%, respectively, compared with the NGB and the capsule RR samples.

The optical performance of random and periodic textured mono crystalline silicon surfaces for photovoltaic applications

Surface textures that result in high optical yields are crucial for high efficiency photovoltaic (PV) devices. In this work three different texturing approaches are presented that result in smooth concave structures devoid of sharp features. Such features can sustain the crack-free growth of device quality nano- to poly-crystalline materials such as nano-crystalline silicon, perovskites or C(I)GS, facilitating routes towards hybrid multijunction PV devices. A sacrificial implanted poly-c-Si layer is used to develop a random surface texture for the first texturing approach (Tsac). The influence of the processing conditions, such as layer thickness, implantation energy, dose and ion type, annealing time and temperature, of the sacrificial layer on the developed surface features is investigated. Additionally, a photolithographically developed honeycomb texture (Thoney) is presented. The influence of mask design on the honeycomb features is discussed and a relation is established between the honeycomb period and crack formation in nano-crystalline silicon layers. The reflective properties (spectral reflection, haze in reflection and angular intensity distribution) of these approaches are characterized and compared to a third texturing approach, Tsp, the result of chemically smoothened pyramidal <111> features. It was demonstrated that high optical scattering yields can be achieved for both Thoney and Tsp. Additionally, the performance of a-Si/nc-Si tandem devices processed onto the different textures is compared using both optical device simulations and real device measurements. Simulations demonstrate strong improvements in Jsc-sum (≈45%), in reference to a flat surface, and high Voc*FF of over 1 V are demonstrated for Tsp.

Analytical model to evaluate the reflective directional characteristics of retro-reflective materials

In order to mitigate the urban heat islands (UHI) phenomenon, instead of diffuse reflective (DR) building coating material, retro-reflective (RR) coating material is proposed to be applied to external wall surface of buildings. The reflective directional characteristics of RR materials can be usually investigated through optical measurement. In addition to the method of optical experiment, there are other methods of analytical models predication. This study deals with an optical experiment and two analytical models to evaluate the angular distribution of reflection intensity for RR materials. A total of three RR materials, including prism type plate, capsule type plate and glass bead type plate are created, and their angular distribution of reflection intensity were evaluated by using methods of optical experiment and two analytical models (original analytical model; anisotropic body of rotation of the normal distribution function (AND) model). In order to propose an appropriate analytical model of evaluating the reflective directional characteristics of RR materials, regarding the angular reflection intensity obtained by optical experiment as a real value, the results evaluated by two analytical models are compared in this study. It is shown that it is better to apply the AND model to evaluate the reflective directional characteristics of RR materials, compared to original analytical model.

Application of Impact-Echo Method to 3D SIBIE Procedure for Damage Detection in Concrete

In this study, to visualize damage and defects, such as cracks and voids in concrete, the SIBIE (stack imaging of spectral amplitudes based on impact echo) procedure is applied and numerically improved to construct a three-dimensional (3D) model of elastic wave propagation behavior. A unit of arrayed accelerometers is installed to detect multi-channel signal waveforms in the frequency domain. The resonant frequencies due to reflections at each node in 3D lattice nodes are computed by using the distances from elastic wave input to multiple output locations. The amplitudes corresponding to the resonant frequencies in the spectrum are summed up as the reflection intensity of elastic wave at each node. The reflection intensity distribution is visualized finally in the targeted area three-dimensionally. Case studies are carried out on the proposal of the improved 3D-SIBIE procedure, applied to a concrete specimen with simulated-damage as well as in-situ highway RC (Reinforced Concrete) slabs in service. As for the signal detection, a non-contact elastic wave detecting system using a laser doppler vibrometer is also introduced to consider and validate the promising remote sensing and inspection technique for damage evaluation in concrete with the 3D SIBIE procedure.

2D spatial distribution of reflection intensity on the upper surface of the Philippine Sea plate off the Boso Peninsula, Japan

The region off the Boso Peninsula, Japan, is a tectonically complex area where the Pacific plate is subducting beneath both the landward plate and the Philippine Sea plate (PHS) from the Japan trench and the Izu-Bonin trench as the PHS is subducting under the landward plate from the Sagami trough. It is important to better determine the structure of this region to deepen our understanding of its seismicity. Previous seismic reflection studies have shown that reflections from the upper surface of the PHS vary with depth, being stronger in the main slip area of the slow slip events beneath the Boso Peninsula (Boso SSEs). However, the spatial relationship between the reflective area and the SSEs is poorly constrained. This study mapped the distribution of the reflective area using data recorded by ocean bottom seismometers during an active-source seismic experiment. We constructed a 3D P-wave velocity structure by using traveltimes of first arrivals from 18 ocean bottom seismometer records. We also adapted the traveltime mapping method to reflection traveltimes, projecting them to the depth–distance domain, to map the 2D distribution of strong reflections from the top of the PHS. These reflections were concentrated in two areas, one near the main slip area of the Boso SSEs and the other about 60km to the east. In the first area, the absence of strong velocity contrasts near the top of the PHS suggests that the reflections were generated by a thin low-velocity layer. In contrast, the structure of the second area has a convex shape of high velocity with a high velocity gradient near the top of the PHS. This structure may represent boninitic material of the outer-arc high, partially serpentinized peridotite, or gabbro displaced by intraoceanic reverse faults.

Monitoring microstructural evolution in-situ during cyclic loading with high-resolution reciprocal space mapping

High-resolution reciprocal space mapping using high-energy hard x-rays has been developed to investigate the microstructure of grains located in the bulk of a metallic sample in a non-destructive way in-situ during different loading conditions. The technique allows to identify and follow individual grains and subgrains during ongoing deformation such as loading in tension and compression, during repeated cyclic deformation or even individual load cycles while simultaneously monitoring macroscopic stress and strain. Insight in the structural reorganization within single grains is gained by in-situ monitoring of the characteristic intensity distribution of Bragg reflections from individual grains during cyclic deformation of commercially pure polycrystalline aluminium. By reciprocal space mapping with high angular resolution and combined analysis of the radial and azimuthal information, individual subgrains are tracked during single load cycles with different strain amplitudes. Additionally, changes in mean peak position, peak width and asymmetry of integrated radial profiles from individual grains are analyzed as well as their orientation spread. In this manner, the microstructural evolution in grains embedded in the bulk of polycrystalline specimens is traced and linked to the changing mechanical loads during cyclic deformation.

A study on the durability of a glass bead retro-reflective material applied to building facades

Heat from buildings contributes about 1/2 of the city’s anthropogenic heat to the urban heat island (UHI). The ratio of heat emitted from building external walls occupies about 1/3 of the anthropogenic waste heat total in Japan. Retro-reflective (RR) materials applied to building facades instead of highly reflective (HR) materials for UHI mitigation are being studied. Glass bead RR material is one of the main RR material types. In this study, several glass bead RR materials with different refractive indices and different color reflective layers were developed. The long-term change in solar reflectivity and angular distribution of reflection intensity for these glass bead RR materials was evaluated for purpose of durability verification. The result showed that both the solar reflectivity and angular distribution of reflection intensity for these developed glass bead RR materials almost have no significant change after 368 days of exposure in the outdoor environment. Moreover, it is shown that the glass bead RR material with a refractive index of 1.9 has much better RR performance, compared to that with a refractive index of 1.5.

Study on the mean intensity from a cube corner reflector in atmospheric turbulence

Cube corner reflector is widely used as the cooperative target in laser tracking, location and other systems and its reflected intensity distribution is of great significance to the design of cooperative target as well as to the theoretical study on the performance of laser radar system. An analytic algorithm for calculating the reflected intensity in atmospheric turbulence is presented in this paper, in which the effective reflective area of corner reflector is approximately taken as an ellipse, and the reflected beam is decomposed of a series of complex Gaussian functions. All these, combined with the extended Huygens-Fresnel principle, derive the expression of the mean received intensity from the reflector. The effects of incident angle, off-axis distance of the reflector, propagation distance and the strength of turbulence on the shape, asymmetry, beam width and spreading of the reflected field are calculated and discussed.

In situ assessment of target poisoning evolution in magnetron sputtering

We present an experimental approach for the in situ monitoring of target poisoning through roughness evolution during reactive sputtering by laser reflectometry. Aluminum (Al) and Titanium (Ti) targets were reactively sputtered in the presence of Nitrogen (N2) and Oxygen (O2), separately. From the hysteresis loops of reactive gas flow and discharge voltage, the threshold flow rates of N2 and O2 were determined for partial and complete poisoning of the targets, respectively. These targets were then sputtered up to 60min in metallic and poisoning modes at different flow rate of the reactive gases. For given time intervals, the eroded regions of the cylindrical sputtering targets were hit by a laser beam and reflected images were captured on a screen. Based on ray tracing optics, the reflected intensity distribution of the laser was utilized for the assessment of the poisoned surface. The mean tilt angle of the surface roughness for both nitride and oxide formation on the Al and Ti targets was measured from the reflected intensity profiles. A change in surface roughness of poisoned targets was observed after different sputtering times. As a proof of concept, the deposition rate and de-poisoning time were measured at different poisoning levels. The change in surface roughness of the targets was found to be in good agreement with depoisoning time. This in situ method can be applied for the assessment of target poisoning evolution during reactive sputtering.

Factors Affecting the Statistical Properties of Sea Clutter

SUMMARYWe observed sea clutter in the sea area east of the Daini Kaiho sea fort in Tokyo Bay using an X‐band radar, and obtained data from 21,996 cells by 47 consecutive observations. In order to investigate the statistical properties, we performed estimation of parameters by maximum likelihood estimation and a test of goodness of fit by the Akaike Information Criterion (AIC), as models for the Weibull, log‐Weibull, and log‐Normal distributions. The reflected intensity distribution of sea clutter was found to obey the Weibull distribution better than any other distribution, and we therefore made a study using the shape parameter of the Weibull distribution. It was found that sea conditions such as swells and wind waves affect the statistical properties of sea clutter.

シークラッタの統計的性質に影響を与える要因

We observed sea clutter of sea area in the east of the Daini Kaiho sea fort in Tokyo Bay using an X-band Radar, and we obtained the data of 21,996 cells by observation of consecutive 47 times. In order to investigate the statistical properties, we made estimation of parameters by maximum likelihood estimation and a test of goodness of fit by AIC as models for Weibull, log-Weibull, and log-Normal distributions. As a result, the reflected intensity distribution of sea clutter obeyed Weibull distribution better than any other distributions, and so we made a study using shape parameter of Weibull distribution, it was found that sea condition such as swell and wind wave affect the statistical properties of sea clutter.

Reflected-intensity distribution of angle-tuned thin film filter based on frequency recursive algorithm

For a three-port angle-tuned thin film filter, the characteristic of reflected-port is very important to reflect multiple wavelengths spectrum. As the filter is in tilted incidence, the reflected-facula broadens and the reflectivity decreases. In this paper, we proposed a frequency recursive algorithm based on fast Fourier transform and Fresnel formula. The reflected-intensity distribution of the narrowband filter from normal incidence to 40° tilted incidence was simulated by this frequency recursive algorithm. Meanwhile, the beam field experiments were accordingly performed in this study. Compared with the traditional beam spatial superposition method, the frequency recursive algorithm is more efficient and precise in calculating the reflectivity of the reflected beam, suggesting the frequency recursive algorithm may be more helpful for fabricating the three-port tunable thin film filter.

Banana-shaped molecular architecture: Formation of large columns composed of two concentrically enclosed layers

The room-temperature solid phase (X3) of banana-shaped molecules that forms on cooling from the B6 phase is characterized as having an extremely large hexagonal lattice. In this study, we acquired a detailed structure of the X3 phase from synchrotron radiation (SR) micro-beam X-ray and atomic force microscopy (AFM) measurements. Focusing the micro X-ray beam on a single fan-shaped domain, we observed a well-oriented pattern including nine hk0 reflections with spacings of 20–110 A. These can be indexed with a two-dimensional (2-D) hexagonal lattice with an edge length of 126.8 A and incorporating approximately 70 molecules. The hk0 reflections appear in a direction parallel to the long axis of the fan-shaped domain showing that the two-dimensional lattice exists in a plane perpendicular to both the layer and bent direction of the molecules in the preceding B6 phase. An AFM image clearly illustrates the close packing of cylinders with a diameter equal to the hexagonal lattice edge. Further, the electron density map elucidated from the X-ray reflection intensity distribution shows that each cylinder is constructed of two concentrically enclosed layers.

Evolution of deformation structures under varying loading conditions followed in situ by high angular resolution 3DXRD

With high angular resolution three-dimensional X-ray diffraction, individual subgrains are traced in the bulk of a polycrystalline specimen and their dynamics is followed in situ during varying loading conditions. The intensity distribution of single Bragg reflections from an individual grain is analyzed in reciprocal space. It consists of sharp high-intensity peaks arising from subgrains superimposed on a cloud of lower intensity arising from dislocation walls. Individual subgrains can be distinguished by their unique combination of orientation and elastic strain. The responses of polycrystalline copper to different loading conditions are presented: during uninterrupted tensile deformation, formation of subgrains can be observed concurrently with broadening of the Bragg reflection shortly after onset of plastic deformation. With continued tensile deformation, the subgrain structure develops intermittently. When the traction is terminated, stress relaxation occurs and number, size and orientation of subgrains are found to be constant. The subgrain structure freezes and only a minor clean-up of the dislocation structure is observed. When changing the tensile direction after pre-deformation in tension, a systematic correlation between the degree of strain path change and the changes in the dislocation structure quantified by the volume fraction of the subgrains is established. For obtaining the subgrain volume fraction, a new fitting method has been developed for partitioning the contributions of subgrains and dislocation walls.

Control of Refractive Index of Pressure-Sensitive Adhesives for the Optimization of Multilayered Media

We describe the method of controlling the refractive index of pressure sensitive adhesives (PSAs) from 1.461 to 1.531 by changing the ratio of component monomers. The difference in refractive index between recording and PSA layers determines the penetration depth for recording and reading light due to multiple reflections at layer interfaces. We fabricated multilayered media that contained one, five and ten recording layers and measured their transmittances. The readout signal intensities of ten-layered media, which were fabricated using PSA films of various refractive indices, were measured. We found that a smaller refractive-index difference between recording and transparent layers led to a larger transmittance of the medium and that a refractive index difference smaller than 0.01 provided a signal sufficient for distinguishing each layer. We also calculated reflection intensity distribution for the optimization of the structure of multilayered media.

Enantiomorph identification of crystals belonging to the point groups of 622 and 6 by convergent-beam electron diffraction method

A CBED method proposed by the present authors for chiral identification of enantiomorphic crystals has been successfully applied to crystals with the point groups of 622 and 6. The intensity asymmetry of ZOLZ and/or FOLZ reflections of the Bijvoet pairs is utilized for enantiomorph identification and such intensity asymmetry is noted regardless of beam convergence angle but the extent to which the asymmetry is noted depends on crystal thickness and accelerating voltage. The crystal thickness should be smaller than the extinction distance of relevant reflections that constitute ‘umweganregung’ in multiple scattering, which is responsible for the intensity asymmetry. As a result, the maximum crystal thickness, below which the asymmetric intensity distribution of Bijvoet reflections is evident, increases as the accelerating voltage is increased. When the crystal thickness is small, however, the intensity asymmetry is more pronounced as the accelerating voltage is decreased due to the increased propensity of multiple scattering.