Specular Research Articles

Minimizing the Effect of Specular Reflection on Object Detection and Pose Estimation of Bin Picking Systems Using Deep Learning

The rapid evolution towards industrial automation has widened the usage of industrial applications, such as robot arm manipulation and bin picking. The performance of these applications relies on object detection and pose estimation through visual data. In fact, the clarity of those data significantly influences the accuracy of object detection and pose estimation. However, a majority of visual data corresponding to metal or glossy surfaces tend to have specular reflections that reduce the accuracy. Hence, this work aims to improve the performance of industrial bin-picking tasks by reducing the effects of specular reflections. This work proposes a deep learning (DL)-based neural network model named SpecToPoseNet to improve object detection and pose estimation accuracy by intelligently removing specular reflections. The proposed work implements a synthetic data generator to train and test the SpecToPoseNet. The conceptual breakthrough of this work is its ability to remove specular reflections from scenarios with multiple objects. With the use of the proposed method, we could reduce the fail rate of object detection to 7%, which is much less compared to specular images (27%), U-Net (20%), and the basic SpecToPoseNet model (11%). Thus, it is claimable that the performance improvements gained are positive influences of the proposed DL-based contexts such as bin-picking.

Spheroid-based optical cavities for tunable photon recycling and emitter temperature control in robust solar thermophotovoltaic systems

The theoretical efficiency of solar thermophotovoltaic (STPV) systems is much greater than their efficiencies achieved in practice. Optical cavities can improve the performance of STPV systems by increasing the emitter-to-PV cell view factor and by facilitating photon recycling, whereby photons are reflected back to the emitter. Photon recycling reduces losses and increases the temperature of the emitter, thereby increasing efficiency. Our study presents STPV systems comprising optical cavities in the form of oblate and prolate spheroids. The geometry of the optical cavity can be tuned to control the degree of photon recycling, emitter temperature, emission losses, and the emitter-to-PV cell effective view factor and separation distance without using complex nano- or microstructured materials or optical filters. Numerical analysis shows an optical cavity in the form of a prolate spheroid, prolate spheroid with a middle annular aperture specular reflector, and integrated oblate- and prolate-spheroid can be used to achieve efficiencies of 17.7%, 18.9%, and 22%, respectively, under solar irradiation at a concentration factor of 1500X. These robust spheroid-based optical cavities can be used to design improved STPV systems with increased durability and higher performance.

Bidirectional reflectance factor measurement of conifer needles with microscopic spectroscopy imaging

Leaf reflectance is widely used to retrieve leaf chlorophyll content (Cab) and parameterize canopy radiative transfer models. Measurements of broadleaf reflectance are typically made by using integrating sphere devices, but the approach is generally limited in conifer needle measurements due to the narrow needle coverage relative to the sample port of the integrating sphere. In this study, we proposed a method to measure the bidirectional reflectance factor (BRF) of needles by integrating a hyperspectral imaging spectrometer and an optical microscope. Pure needle pixels can be easily extracted from hyperspectral images after microscope magnification. The method was first validated by the narrow strips of broad leaves as proxies of needles, resulting in the difference between the measured BRF of strips and the BRF of whole broad leaves in the visible bands (400–700 nm) and in the near-infrared bands (700–1000 nm) being 0.0043 and 0.019, respectively. The method was also indirectly verified by tracking the variation in the natural needle BRF with its Cab, resulting in the change in BRF being consistent with the change in Cab. In addition, linear relationships between the needle Cab and the classic vegetation indices (i.e., the red-edge simple ratio and normalized difference vegetation index) calculated from the BRF were found. Apart from the above, we found that (1) the BRF of the abaxial side has a discrepancy with that of the adaxial side of needles, (2) the BRF of a needle varies with its azimuth, hence affecting the correlation between vegetation indices and Cab, and (3) filtering the specular reflection on the microsurfaces of the needle could enhance the correlation between the vegetation indices and needle Cab. The method is expected to accurately measure the BRF of needles and hence to improve the applications of needle optical properties in plant sciences, ecology, and remote sensing fields.

Development of Tailored Graphene Nanoparticles: Preparation, Sorting and Structure Assessment by Complementary Techniques.

We present a thorough structural characterization of Graphene Nano Particles (GNPs) prepared by means of physical procedures, i.e., ball milling and ultra-sonication of high-purity synthetic graphite. UV-vis absorption/extinction spectroscopy, Dynamic Light Scattering, Transmission Electron Microscopy, IR and Raman spectroscopies were performed. Particles with small size were obtained, with an average lateral size <L> = 70−120 nm, formed by few <N> = 1−10 stacked layers, and with a small number of carboxylic groups on the edges. GNPs relatively more functionalized were separated by centrifugation, which formed stable water dispersions without the need for any surfactant. A critical reading and unified interpretation of a wide set of spectroscopic data was provided, which demonstrated the potential of Specular Reflectance Infrared Spectroscopy for the diagnosis and quantification of chemical functionalization of GNPs. Raman parameters commonly adopted for the characterization of graphitic materials do not always follow a monotonic trend, e.g., with the particle size and shape, thus unveiling some limitations of the available spectroscopic metrics. This issue was overcome thanks to a comparative spectra analysis, including spectra deconvolution by means of curve fitting procedures, experiments on reference materials and the exploitation of complementary characterization techniques.

Atomic oxygen exposure effect on carbon nanotubes/epoxy composites for space systems

Structural, optical and EMI shielding properties of epoxy resin reinforced with carbon nanotubes fillers “Taunit-M” and “Taunit-MD” have been studied. To estimate the resistance of nanocomposites operating in low-Earth orbits, the samples were exposed to atomic oxygen (AO) in the fluence range of (1.7–30) × 1020 cm−2. AO exposure results in mass loss of epoxy resin with carbon fillers: the erosion yields (Rm) are 1.07 × 10−23 g/atom and 1.21 × 10−23 g/atom for “Taunit-M″ and “Taunit-MD”, respectively. Diffuse and specular reflectance noticeably decreases after AO exposure which in their turn leads to increase of solar absorptance from 0.940 to 0.996 for “Taunit-M″ and from 0.944 to 0.992 for “Taunit-MD”. AO exposure also results in reduction of EMI shielding effectiveness from ∼5 dB to ∼4.2 dB and ∼4.96 dB for epoxy resin with “Taunit-M″ and “Taunit-MD”, respectively, in the frequency range of 8.2–12.4 GHz (X-band) at room temperature.

Topology optimization design of dual-channel metasurface structure with controllable amplitude of retroreflection and mirror reflection

For oblique incident electromagnetic waves, the generation of double reflection channels including retroreflection channel is of great significance in improving target recognition performance and navigation performance. In double channel reflection, controlling the ratio of retroreflection to specular reflection is the key to realizing reflection power distribution. In order to realize the control of the proportion of the reflected power in each channel, a topology optimization method for designing the reflective metasurface microstructure with dual channel is proposed in this paper. The implementation mechanism is investigated, physical model of metasurface with dual reflection channel including retroreflection channel is established, and the topology optimization model of metasurface microstructure with specific power ratio of the retroreflection to specular reflection is established. As a numerical example, a dual channel metasurface reflector with a 1∶1 ratio of retroreflection power to specular reflection power is designed for a 10 GHz plane wave in the TE mode with a pitch angle of –30°. The designed metasurface exhibits strong directionality in the retroreflective direction, and the reflection amplitudes in both directions are similar. The retroreflective metasurface with the maximum retroreflection ratio is designed. The retroreflection ratio of the designed metasurface is 0.093. There is no specular reflection or other singular reflection, and the strong reflection on the metasurface is concentrated at –30°. The ratio of the main beam power to the total reflection power is 0.900. The simulated and experimental results verify the feasibility of the proposed method.

A design of laser triangulation system with combined diffuse and specular reflection modes for dull and shiny surface measurements

Conventional laser triangulations are designed to measure the depth or height on a dull or rough surface. This can be done by projecting a light perpendicularly to the surface and capturing the spot of the diffuse reflection which is scattered from the surface. However, for a shiny or smooth surface, the specular reflection dominates, and it is difficult to detect diffuse reflection. We may modify the system setting to capture the specular reflection, with the cost of losing the diffuse reflection information. In this article, we proposed a design of dual diffuse and specular reflection mode of laser triangulation. The advantage is that there is no need to repeat alignment and calibration processes when we change the measuring mode, so we can easily select the measuring mode that is suitable for each surface. We have described the system setting and the calibration results where we can achieve the resolution of micrometre for both measuring modes.

Cinematic reflectometry using QIKR, the quite intense kinetics reflectometer.

The Quite Intense Kinetics Reflectometer (QIKR) will be a general-purpose, horizontal-sample-surface neutron reflectometer. Reflectometers measure the proportion of an incident probe beam reflected from a surface as a function of wavevector (momentum) transfer to infer the distribution and composition of matter near an interface. The unique scattering properties of neutrons make this technique especially useful in the study of soft matter, biomaterials, and materials used in energy storage. Exploiting the increased brilliance of the Spallation Neutron Source Second Target Station, QIKR will collect specular and off-specular reflectivity data faster than the best existing such machines. It will often be possible to collect complete specular reflectivity curves using a single instrument setting, enabling "cinematic" operation, wherein the user turns on the instrument and "films" the sample. Samples in time-dependent environments (e.g., temperature, electrochemical, or undergoing chemical alteration) will be observed in real time, in favorable cases with frame rates as fast as 1Hz. Cinematic data acquisition promises to make time-dependent measurements routine, with time resolution specified during post-experiment data analysis. This capability will be deployed to observe such processes as in situ polymer diffusion, battery electrode charge-discharge cycles, hysteresis loops, and membrane protein insertion into lipid layers.

Wavefront Control of Millimeter Waves With a VO2-Based Reconfigurable Meta-Reflectarray

In this paper, a novel architecture of a reconfigurable metasurface is proposed and numerically assessed for wavefront control in wireless systems working in the millimeter-wave range. We show that a metasurface made of engineered silicon bricks covered with a thin film of vanadium dioxide provides anomalous reflection with an efficiency of 93% at 60 GHz and a relative bandwidth of 15%. After applying a thermal stimulus that triggers the transition of vanadium dioxide from the insulator phase to the metallic phase, the metasurface abruptly changes its response and provides specular reflection. The device shows high efficiency and broadband operation in both VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> states, allowing dynamic control of millimeter waves. Therefore, it finds applications in imaging, sensing, and intelligent wireless communications in 5G and 6G systems, especially for beam-shaping and beam-steering. Moreover, the proposed reconfigurable metasurface has a simple configuration that lends itself to standard fabrication tools, and it has a subwavelength size for integrated and compact communication systems.

About Lanford's theorem in the half-space with specular reflection

&lt;p style='text-indent:20px;'&gt;The present article proposes a rigorous derivation of the Boltzmann equation in the half-space. We show an analog of the Lanford's theorem in this domain, with specular reflection boundary condition, stating the convergence in the low density limit of the first marginal of the density function of a system of N hard spheres towards the solution of the Boltzmann equation associated to the initial data corresponding to the initial state of the one-particle-density function. The original contributions of this work consist in two main points: the rigorous definition of the collision operator and of the functional space in which the BBGKY hierarchy is solved in a strong sense; and the adaptation to the case of the half-space of the control of the recollisions performed by Gallagher, Saint- Raymond and Texier, which is a crucial step to obtain a quantitative version of the Lanford's theorem.&lt;/p&gt;

Influence of collisions on the effect of electromagnetic-induced transparency in cells of finite sizes with anti-relaxation coating of walls

Based on the semiclassical theory of the interaction of two-frequency laser radiation with a resonant atomic medium, an analytical expression is obtained that describes the form of resonances of electromagnetically induced transparency detected in a cell with a finite direction in the longitudinal laser beam direction with an anti-relaxation coating of walls, taking into account the motion of atoms and collisions with walls. The following types of reflection from walls are considered: diffuse, specular, and specular-incoherent. It is found that in a number of cases the diffuse type of reflection exhibits the properties of a mirror-incoherent one. It is also shown that the nondegeneracy of the excited state in a number of cases significantly changes the shape of the transparency resonance. Keywords: Electromagnetically induced transparency, Gas cell, anti-relaxation coating, diffuse reflection, specular reflection, specular-incoherent reflection.

Study on plasma cleaning of surface contaminants on pure copper

To demonstrate the relationship between the type of working gas and the efficiency of plasma cleaning, the kinetic energy of the incident ions was controlled by adjusting the bias, and the effect of different ion sources on the sputtering yield under the same bias was compared. The plasma flow generated by glow discharge was used to clean the sample surface to evaluate the plasma cleaning efficiency. Scanning electron microscope (SEM), x-ray photoelectron spectroscopy (XPS), x-ray Powder Diffraction (XRD), Ultraviolet-visible Spectrophotometer (UV), and Surface Profiler were used to characterize the surface morphology, element types, phase composition, specular reflectance, and three-dimensional (3D) morphology before and after plasma cleaning. The results show that the sputtering yield increases with the increase of bias, and when the bias value is lower than 400 V, the mass of the samples has almost no change before and after cleaning. It takes more energy to remove the surface oxide than the pure metal copper. The results also show that argon plasma has a better effect on removing pollutants on the sample surface than nitrogen plasma. However, a long time of plasma cleaning is often accompanied by re-deposition. The changes in copper reflectance induced by plasma cleaning are also discussed.

A Novel Technique for Estimation and Detection of Specular Reflections Leveraging High Frame Rate Ultrasound Imaging

The clinical interpretability of specular interfaces in ultrasound (US) imaging is heavily influenced by the anatomical knowledge of the operator and the transmit–receive beamforming employed for imaging. The violation of the conventional diffuse assumptions by highly directive specular reflections makes their detection challenging which increases the cognitive burden of operators in tissue characterization or calibrating the beam steering/transducer to ensure their detection. However, the areas for improved operator assistance and related workflow in this regard remain largely unexplored. This work proposes a novel method called tiered subaperture (SA) directivity indexing, which employs a SA-level measurement of energy in the reflections through multiangle plane wave transmissions to automatically identify the directivity of specular reflections. The reflection directivity is vectorized and visually fed as a characterized colored image to the operator to distinguish the specular patterns in the US data. The technique is illustrated for clinical use cases such as needle tracking in guided interventional procedures, anisotropy in MSK US, and bone fracture monitoring. The proposed method improves retention, enables freehand scans, and augmentation of hand–eye coordination for the operators for tissue characterization, beamforming, and transducer calibration thus aiding quicker diagnosis by saving procedure times.

SIPFormer: Segmentation of Multiocular Biometric Traits With Transformers

The advancements in machine vision have opened up new avenues for implementing multimodal biometric identification systems for real-world applications. These systems can address the shortcomings of unimodal biometric systems, which are susceptible to spoofing, noise, nonuniversality, and intraclass variations. Besides, ocular traits among various biometric traits are preferably used in these recognition systems due to their great uniqueness, permanence, and performance. However, segmenting visual biometric features under unconstrained situations remains challenging due to a variety of variables, such as Purkinje reflexes, specular reflections, eye gaze, off-angle pictures, poor resolution, and numerous occlusions. To overcome these challenges, this research presents a novel framework called SIPFormer, comprising the encoder, decoder, and transformer blocks to simultaneously segment three ocular traits (sclera, iris, and pupil) using its discriminative multihead self-attention mechanism. Besides, we used the large publicly available iris database reflecting different unconstrained acquisition settings, with inherent noise effects such as scanner artifacts, intensity and illumination variations, motion blur, and occultations caused by eyelashes, eyelids, and eyeglasses. Furthermore, the simulation results demonstrate the efficacy of the proposed SIPFormer model, where it achieved the mean Dice similarity coefficient scores of 0.9018, 0.9176, and 0.9229 for segmenting the sclera, iris, and pupil classes, respectively.

Электромагнитно-индуцированная прозрачность в ячейках конечных размеров с антирелаксационным покрытием стенок

In this paper, we propose an approach that makes it possible to obtain an analytical expression of the spectral dependence of the resonance of electromagnetically induced transparency detected by bichromatic radiation in a cell of finite size in the longitudinal direction of the laser beam. Specular and diffuse reflections of atoms from walls are considered. It was found that a significant difference between these types of reflections takes place only for cells of small longitudinal dimensions compared to the splitting wavelength of the ground state of atoms. A physical explanation is proposed for the difference between the Stokes and anti-Stokes scattering channels of probe radiation in terms of dressed states.

Deep Highlight Removal Using Temporal Dark Prior in High-Speed Domain

This paper proposes a deep highlight removal method based on the dichromatic model under alternating current (AC) light sources with a new diffuse prior on temporal domain, temporal dark prior. An input image is decomposed into specular and diffuse components using a deep network. Due to AC powered lights, both incident and reflected lights are time-varying. We exploit the periodic variation property of the specular and diffuse reflections as a prior for dichromatic model based image decomposition. In addition, we propose a new temporal dark prior as a pseudo-diffuse reflection. Unlike the conventional prior in the spatial domain, to the best of our knowledge, this is the first study to utilize a diffuse prior on the temporal domain for highlight removal. The blurred version of the temporal dark prior is additionally fed to the network to alleviate hole artifacts. It is demonstrated through diverse experiments that these temporal priors can strongly contribute to accurate image decomposition, leading to better highlight removal.

Extraction of interaction parameters from specular neutron reflectivity in thin films of diblock copolymers: an "inverse problem".

Diblock copolymers have been shown to undergo microphase separation due to an interplay of repulsive interactions between dissimilar monomers, which leads to the stretching of chains and entropic loss due to the stretching. In thin films, additional effects due to confinement and monomer-surface interactions make microphase separation much more complicated than in that in bulks (i.e., without substrates). Previously, physics-based models have been used to interpret and extract various interaction parameters from the specular neutron reflectivities of annealed thin films containing diblock copolymers (J. P. Mahalik, J. W. Dugger, S. W. Sides, B. G. Sumpter, V. Lauter and R. Kumar, Interpreting neutron reflectivity profiles of diblock copolymer nanocomposite thin films using hybrid particle-field simulations, Macromolecules, 2018, 51(8), 3116; J. P. Mahalik, W. Li, A. T. Savici, S. Hahn, H. Lauter, H. Ambaye, B. G. Sumpter, V. Lauter and R. Kumar, Dispersity-driven stabilization of coexisting morphologies in asymmetric diblock copolymer thin films, Macromolecules, 2021, 54(1), 450). However, extracting Flory-Huggins χ parameters characterizing monomer-monomer, monomer-substrate, and monomer-air interactions has been labor-intensive and prone to errors, requiring the use of alternative methods for practical purposes. In this work, we have developed such an alternative method by employing a multi-layer perceptron, an autoencoder, and a variational autoencoder. These neural networks are used to extract interaction parameters not only from neutron scattering length density profiles constructed using self-consistent field theory-based simulations, but also from a noisy ad hoc model constructed previously. In particular, the variational autoencoder is shown to be the most promising tool when it comes to the reconstruction and extraction of parameters from an ad hoc neutron scattering length density profile of a thin film containing a symmetric di-block copolymer (poly(deuterated styrene-b-n-butyl methacrylate)). This work paves the way for automated analysis of specular neutron reflectivities from thin films of copolymers using machine learning tools.

MROX 2.0: a software tool to explore quantum heterostructures by combining X-ray reflectivity and diffraction

New software for the fitting of XRR measurements is developed. It is exemplified on 1 to 10 Si/Ge periods grown on Si template samples and on (001) substrates and one complex ZnO/Zn1−xMgxO superlattice grown on a m-ZnO substrate.

Морфология поверхности и структурные свойства кристаллов GaTe после ионно-плазменной обработки

The effect of ion-plasma treatment on the physical properties of the surface of GaTe crystals is investigated. Gallium telluride crystals were grown by vertical zone melting under the pressure of an inert argon gas of 10.0 MPa at a temperature of 1000 °C and a zone displacement velocity of 9 mm/hr. The treatment was carried out in argon plasma in a high-density low-pressure radio frequency (RF) inductively coupled plasma reactor at an argon ion energy of 100-200 eV for 15-120 s. Using scanning electron microscopy methods, it was shown that the formation of nano- and submicron structures of various architectures (nanohillocks, nanocones, droplet structures) occurred on the surface during processing. It is shown that the sputtering processes are accompanied by enrichment of the near-surface layer with metal atoms and a decrease in oxygen content. The formation of nano- and submicron gallium droplets on the surface has been proved by X-ray diffractometry. The analysis of the raman scattering spectra showed a decrease in the oxide phases of tellurium after plasma treatment. It is established that modification of the GaTe surface leads to suppression of specular optical reflection in the range of 0.4-6.2 eV.

Modelling surface light scattering for inverse two-dimensional reflector design

We present a novel approach of modelling surface light scattering in the context of two-dimensional reflector design, relying on energy conservation and optimal transport theory. For isotropic scattering in cylindrically or rotationally symmetric systems with in-plane scattering, the scattered light distribution can be expressed as a convolution between a scattering function, which characterises the optical properties of the surface, and a specular light distribution. Deconvolving this expression allows for traditional specular reflector design procedures to be used, whilst accounting for scattering. This approach thus constitutes solving the inverse problem of light scattering, allowing for direct computation of the reflector surface, without the need for design iterations.