Optical Principles Research Articles

In Situ Stress Measurement Techniques on Li-ion Battery Electrodes: A Review

Li-ion batteries experience mechanical stress evolution due in part to Li intercalation into and de-intercalation out of the electrodes, ultimately resulting in performance degradation. In situ measurements of electrode stress can be used to analyze stress generation factors, verify mechanical deformation models, and validate degradation mechanisms. They can also be embedded in Li-ion battery management systems when stress sensors are either implanted in electrodes or attached on battery surfaces. This paper reviews in situ measurement methods of electrode stress based on optical principles, including digital image correlation, curvature measurement, and fiber optical sensors. Their experimental setups, principles, and applications are described and contrasted. This literature review summarizes the current status of these stress measurement methods for battery electrodes and discusses recent developments and trends.

Determination of High-affinity Antibody-antigen Binding Kinetics Using Four Biosensor Platforms

Label-free optical biosensors are powerful tools in drug discovery for the characterization of biomolecular interactions. In this study, we describe the use of four routinely used biosensor platforms in our laboratory to evaluate the binding affinity and kinetics of ten high-affinity monoclonal antibodies (mAbs) against human proprotein convertase subtilisin kexin type 9 (PCSK9). While both Biacore T100 and ProteOn XPR36 are derived from the well-established Surface Plasmon Resonance (SPR) technology, the former has four flow cells connected by serial flow configuration, whereas the latter presents 36 reaction spots in parallel through an improvised 6 x 6 crisscross microfluidic channel configuration. The IBIS MX96 also operates based on the SPR sensor technology, with an additional imaging feature that provides detection in spatial orientation. This detection technique coupled with the Continuous Flow Microspotter (CFM) expands the throughput significantly by enabling multiplex array printing and detection of 96 reaction sports simultaneously. In contrast, the Octet RED384 is based on the BioLayer Interferometry (BLI) optical principle, with fiber-optic probes acting as the biosensor to detect interference pattern changes upon binding interactions at the tip surface. Unlike the SPR-based platforms, the BLI system does not rely on continuous flow fluidics; instead, the sensor tips collect readings while they are immersed in analyte solutions of a 384-well microplate during orbital agitation. Each of these biosensor platforms has its own advantages and disadvantages. To provide a direct comparison of these instruments' ability to provide quality kinetic data, the described protocols illustrate experiments that use the same assay format and the same high-quality reagents to characterize antibody-antigen kinetics that fit the simple 1:1 molecular interaction model.

Determination of High-affinity Antibody-antigen Binding Kinetics Using Four Biosensor Platforms

Label-free optical biosensors are powerful tools in drug discovery for the characterization of biomolecular interactions. In this study, we describe the use of four routinely used biosensor platforms in our laboratory to evaluate the binding affinity and kinetics of ten high-affinity monoclonal antibodies (mAbs) against human proprotein convertase subtilisin kexin type 9 (PCSK9). While both Biacore T100 and ProteOn XPR36 are derived from the well-established Surface Plasmon Resonance (SPR) technology, the former has four flow cells connected by serial flow configuration, whereas the latter presents 36 reaction spots in parallel through an improvised 6 x 6 crisscross microfluidic channel configuration. The IBIS MX96 also operates based on the SPR sensor technology, with an additional imaging feature that provides detection in spatial orientation. This detection technique coupled with the Continuous Flow Microspotter (CFM) expands the throughput significantly by enabling multiplex array printing and detection of 96 reaction sports simultaneously. In contrast, the Octet RED384 is based on the BioLayer Interferometry (BLI) optical principle, with fiber-optic probes acting as the biosensor to detect interference pattern changes upon binding interactions at the tip surface. Unlike the SPR-based platforms, the BLI system does not rely on continuous flow fluidics; instead, the sensor tips collect readings while they are immersed in analyte solutions of a 384-well microplate during orbital agitation.Each of these biosensor platforms has its own advantages and disadvantages. To provide a direct comparison of these instruments' ability to provide quality kinetic data, the described protocols illustrate experiments that use the same assay format and the same high-quality reagents to characterize antibody-antigen kinetics that fit the simple 1:1 molecular interaction model.

A free-form side-emitting lens for airfield lighting

Side-emitting lenses are essential devices in some special lighting fields. Two types of side-emitting lenses with refractive and total reflective free-form surfaces are introduced. The principles of geometric optics and non-imaging optics are adopted to construct the free-form surfaces without complex mapping or a differential iteration process. As an example, an elevated taxiway edge light is designed for airfield lighting. A side-emitting lens with two sawtooth additions on top is designed to meet the luminous intensity distribution required by the US Federal Aviation Administration (FAA). An analysis is carried out to determine tolerance limits during manufacture and installation. Computer simulation results show that a side-emitting efficiency of 85.4% is achieved for a Cree XP-E LED. The light distribution of this elevated taxiway edge light complies with the FAA regulations.

Basis-neutral Hilbert-space analyzers

Interferometry is one of the central organizing principles of optics. Key to interferometry is the concept of optical delay, which facilitates spectral analysis in terms of time-harmonics. In contrast, when analyzing a beam in a Hilbert space spanned by spatial modes – a critical task for spatial-mode multiplexing and quantum communication – basis-specific principles are invoked that are altogether distinct from that of ‘delay’. Here, we extend the traditional concept of temporal delay to the spatial domain, thereby enabling the analysis of a beam in an arbitrary spatial-mode basis – exemplified using Hermite-Gaussian and radial Laguerre-Gaussian modes. Such generalized delays correspond to optical implementations of fractional transforms; for example, the fractional Hankel transform is the generalized delay associated with the space of Laguerre-Gaussian modes, and an interferometer incorporating such a ‘delay’ obtains modal weights in the associated Hilbert space. By implementing an inherently stable, reconfigurable spatial-light-modulator-based polarization-interferometer, we have constructed a ‘Hilbert-space analyzer’ capable of projecting optical beams onto any modal basis.

NOMAD spectrometer on the ExoMars trace gas orbiter mission: part 2-design, manufacturing, and testing of the ultraviolet and visible channel.

NOMAD is a spectrometer suite on board the ESA/Roscosmos ExoMars Trace Gas Orbiter, which launched in March 2016. NOMAD consists of two infrared channels and one ultraviolet and visible channel, allowing the instrument to perform observations quasi-constantly, by taking nadir measurements at the day- and night-side, and during solar occultations. Here, in part 2 of a linked study, we describe the design, manufacturing, and testing of the ultraviolet and visible spectrometer channel called UVIS. We focus upon the optical design and working principle where two telescopes are coupled to a single grating spectrometer using a selector mechanism.

Three-dimensional multiple-particle tracking with nanometric precision over tunable axial ranges

The precise localization of nanometric objects in three dimensions is essential to identify functional diffusion mechanisms in complex systems at the cellular or molecular level. However, most optical methods can achieve high temporal resolution and high localization precision only in two dimensions or over a limited axial (z) range. Here we develop a novel wide-field detection system based on an electrically tunable lens that can track multiple individual nanoscale emitters in three dimensions over a tunable axial range with nanometric localization precision. The optical principle of the technique is based on the simultaneous acquisition of two images with an extended depth of field while encoding the z position of the emitters via a lateral shift between images. We provide a theoretical framework for this approach and demonstrate tracking of free diffusing beads and GABAA receptors in live neurons. This approach allows getting nanometric localization precision up to an axial range above 10 μm with a high numerical aperture lens—quadruple that of a typical 3D tracking system. Synchronization or complex fitting procedures are not requested here, which leads to a suitable architecture for localizing single molecules in four dimensions, namely, three dimensions in real-time.

Complementarity in single photon interference \u2013 the role of the mode function and vacuum fields

BackgroundIn earlier experiments the role of the vacuum fields could be demonstrated as the source of complementarity with respect to the temporal properties (Heuer et al., Phys. Rev. Lett. 114:053601, 2015).MethodsSingle photon first order interferences of spatially separated regions from the cone structure of spontaneous parametric down conversion allow for analyzing the role of the mode function in quantum optics regarding the complementarity principle.ResultsHere the spatial coherence properties of these vacuum fields are demonstrated as the physical reason for complementarity in these single photon quantum optical experiments. These results are directly connected to the mode picture in classical optics.ConclusionThe properties of the involved vacuum fields selected via the measurement process are the physical background of the complementarity principle in quantum optics.

MODEL FOR DETERMINATION OF THREE-DIMENSIONAL COORDINATES OF HIDDEN POINTS

One of the problems encountered during surveys is obstruction of points to be monitored, an example of this can be found in industrial environments where there are usually pipes and equipment that do not allow the establishment of straight lines;. An alternative to the application of topographic survey techniques is the use of plane mirrors to diversion of straight lines where the points of interest are observed indirectly. This study presents a new approach to the problem, whose analytical solution is based on the principles of Geometrical Optics and Surveying. The relative positional accuracy achieved in the preliminary tests is submillimetric order, and the absolute positional accuracy is millimetric order.

Technical principles of adaptive optics in ophthalmology

During the last 25years ophthalmic imaging has undergone arevolution. This review gives an overview of the possibilities of adaptive optics (AO) for ophthalmic imaging technologies and their development and illustrates that the role of ophthalmic imaging changed from the documentation of obvious abnormalities to the detection of microscopic yet significant conspicuities. This enables earlier and more precise diagnoses. The implementation of AO for imaging systems like fundus cameras, scanning laser ophthalmoscopy and optical coherence tomography has gained in importance. In recent years acouple of companies started developing commercially available AO systems, thus, indicating afuture use in clinical routine.

Liquid lens-based optical sectioning tomography for three-dimensional flame temperature measurement

Measurement of three-dimensional temperature field of a flame plays a significant role in in-depth insight into combustion process. This paper proposes a novel optical sectioning tomography for the measurement of three-dimensional temperature of flame through a single camera in combination with an ionic electrowetting-based variable focus liquid lens. Firstly, the optical sectioning imaging principle is introduced based on a variable focus liquid lens. Secondly, the calibration works are carried out on a liquid lens-based optical sectioning tomography system for three-dimensional flame temperature measurement to determine the relationship between the working voltages of the liquid lens and its focal planes in combination with entropy function. Further Gaussian model is taken as the defocused model to calibrate the point spread function of the system through edge method, and the CCD sensor is calibrated by a black body furnace to find out the relationship between the image gray and the received radiation energy. The reconstruction algorithms for three-dimensional flame luminosity distribution of the combustion flame are also developed. Finally experimental works are undertaken to evaluate the optical sectioning tomography system. Preliminary experimental results on an ethylene-air co-flow burner verified the feasibility of the optical sectioning tomography for the three-dimensional temperature distribution of a diffusion flame. The developed optical sectioning tomography system is capable of characterizing the structure and combustion characteristics of the diffusion flame.

Bio-physically plausible visualization of highly scattering fluorescent neocortical models for in silico experimentation

BackgroundWe present a visualization pipeline capable of accurate rendering of highly scattering fluorescent neocortical neuronal models. The pipeline is mainly developed to serve the computational neurobiology community. It allows the scientists to visualize the results of their virtual experiments that are performed in computer simulations, or in silico. The impact of the presented pipeline opens novel avenues for assisting the neuroscientists to build biologically accurate models of the brain. These models result from computer simulations of physical experiments that use fluorescence imaging to understand the structural and functional aspects of the brain. Due to the limited capabilities of the current visualization workflows to handle fluorescent volumetric datasets, we propose a physically-based optical model that can accurately simulate light interaction with fluorescent-tagged scattering media based on the basic principles of geometric optics and Monte Carlo path tracing. We also develop an automated and efficient framework for generating dense fluorescent tissue blocks from a neocortical column model that is composed of approximately 31000 neurons.ResultsOur pipeline is used to visualize a virtual fluorescent tissue block of 50 μm3 that is reconstructed from the somatosensory cortex of juvenile rat. The fluorescence optical model is qualitatively analyzed and validated against experimental emission spectra of different fluorescent dyes from the Alexa Fluor family.ConclusionWe discussed a scientific visualization pipeline for creating images of synthetic neocortical neuronal models that are tagged virtually with fluorescent labels on a physically-plausible basis. The pipeline is applied to analyze and validate simulation data generated from neuroscientific in silico experiments.

Reading What the Mind Thinks From How the Eye Sees

Human eyes convey a remarkable variety of complex social and emotional information. However, it is unknown which physical eye features convey mental states and how that came about. In the current experiments, we tested the hypothesis that the receiver’s perception of mental states is grounded in expressive eye appearance that serves an optical function for the sender. Specifically, opposing features of eye widening versus eye narrowing that regulate sensitivity versus discrimination not only conveyed their associated basic emotions (e.g., fear vs. disgust, respectively) but also conveyed opposing clusters of complex mental states that communicate sensitivity versus discrimination (e.g., awe vs. suspicion). This sensitivity-discrimination dimension accounted for the majority of variance in perceived mental states (61.7%). Further, these eye features remained diagnostic of these complex mental states even in the context of competing information from the lower face. These results demonstrate that how humans read complex mental states may be derived from a basic optical principle of how people see.

Radiation force of a high-energy laser and its effects on second-harmonic generation.

The radiation force of a high-energy laser caused by reflection at the input surface of a mounted KH2PO4 (KDP) crystal is studied, along with its effects on the second-harmonic generation (SHG) efficiency of the laser beam. A comprehensive model incorporating principles of momentum transfer, mechanics, and optics is proposed, taking advantage of which, the mechanical stress within the KDP crystal that is caused by the radiation force, and the SHG efficiency that is affected by the stress are successively studied. Moreover, the effects of the intensity of the laser beam on the radiation force, the stress, and the SHG efficiency are determined, respectively. It demonstrates that a high-energy laser beam causes macroscopic radiation force and further contributes negative effects to SHG efficiency.

Recent advances in planar optics: from plasmonic to dielectric metasurfaces

This article reviews recent progress leading to the realization of planar optical components made of a single layer of phase shifting nanostructures. After introducing the principles of planar optics and discussing earlier works on subwavelength diffractive optics, we introduce a classification of metasurfaces based on their different phase mechanisms and profiles and a comparison between plasmonic and dielectric metasurfaces. We place particular emphasis on the recent developments on electric and magnetic field control of light with dielectric nanostructures and highlight the physical mechanisms and designs required for efficient all-dielectric metasurfaces. Practical devices of general interest such as metalenses, beam deflectors, holograms, and polarizing interfaces are discussed, including high-performance metalenses at visible wavelengths. Successful strategies to achieve achromatic response at selected wavelengths and near unity transmission/reflection efficiency are discussed. Dielectric metasurfaces and dispersion management at interfaces open up technology opportunities for applications including wavefront control, lightweight imaging systems, displays, electronic consumer products, and conformable and wearable optics.

Studies of electrochemical interfaces by broadband sum frequency generation

We present a perspective on the use of potential-dependent broadband multiplex vibrational sum-frequency generation spectroscopy (hereafter SFG) to study electrochemical systems. In SFG, a broadband mid-infrared (IR) pulse is combined with a narrowband visible pulse, generating a pulse at the sum frequency, which contains a spectrum that, due to the principles of nonlinear optics, originates solely from the electrified interface. Our SFG spectrometer can obtain one hundred or more spectra during a routine cyclic voltammetry (CV) measurement. We used SFG to study a model for a Li-ion battery anode and a low-overpotential CO2 reduction reactor based on a room-temperature ionic liquid (RTIL). SFG spectra from these complex systems were difficult to interpret, in part due to the organic electrolytes that have a forest of infrared vibrational transitions. Here we discuss a rubric for experimental measurement and interpretation with such systems. We describe the electrified interface, or double layer, as consisting of the electrode surface, a region of adsorbed molecules and an outer diffuse electric double layer. We combined resonant SFG, where the IR pulses were tuned to vibrational transitions of adsorbates, with nonresonant SFG where the IR pulses were tuned away from all vibrational transitions. The former provides information about chemistry on the electrode surface and the latter about the potential-dependent response of the double layer. We show how this rubric can be used to understand solid-electrolyte interphase formation on a model for the Li-ion electrode, and how low-overpotential CO2 reduction on Ag is controlled by potential-driven structural transitions of the RTIL electrolyte.

消D-alpha线的高性能UV-NIR复合光源的设计与实现

在利用光学原理实现高精密测量的过程中，光是信号的载体，因此光源性能的优劣对测量结果的精确度起着至关重要的作用。采用双光源正交方式，并结合滤光技术消除D-alpha线的影响。利用L6561功率因数校正器设计降压型PFC驱动电路，输出单路基准电压，缩短了整体电路的动态响应时间，使工作电路的效率大大提高。选用电流型UC3843芯片并结合TLC271芯片设计单端反击式高频电路，高精度输出300 mA电流。最终实现UV-NIR复合光源输出连续、平滑、稳定的光谱，光谱波动低于3%，电压波动低于0.05%/h。 The performance of the light source is of great importance to the accuracy of the measurement results for the reason that light is the carrier of the signal for high precision measurement based on optical principle. In this study, the influence of D-alpha line is eliminated by combining the or-thogonal mode of double light source with the filter technology. Using L6561 power factor corrector design of Buck PFC to drive circuit and output single reference voltage shortens the dynamic response time of the whole circuit and improves the work efficiency greatly. A single end counter type high frequency circuit is designed with current type UC3843 chip and TLC271 chip to output 300 mA high precision current. The UV-NIR composite light source is implemented finally to output continuous, smooth and stable spectra. The spectral fluctuation is below 3%, and the voltage fluctuation is less than 0.05%/h.

Survey and Review

Barbora Benešová and Martin Kružík are the authors of “Weak Lower Semicontinuity of Integral Functionals and Applications,” the Survey and Review paper in this issue. The notion of weak lower semicontinuity arises in a natural way when studying the existence of solutions of problems seeking to minimize a real-valued function or functional \(I(u)\) as \(u\) ranges in a suitable set \(\mathcalY\) of admissible candidates. It would be difficult to overemphasize the importance of those problems. Many scientific theories are built upon a minimization principle; Fermat's 1662 least-time principle in geometric optics provides perhaps the earliest example. Algorithms in applied mathematics, from data assimilation to training neural networks, are often based on minimization. What is weak lower semicontinuity and what role does it play in showing the existence of a minimizer of \(I\)? In the simplest case where the set \(\mathcalY\) of admissible candidates is a bounded, closed interval of the real line (or more generally a bounded, closed subset of a Euclidean space), we may start by considering a minimizing sequence, i.e., a sequence \(\u_n\\subset\mathcalY\) such that \(I(u_n)\) converges to \(I_* = \inf\ I(u): u\in\mathcalY\\). By the Bolzano--Weierstrass theorem, there exists a subsequence \(\u_n_k\\) converging to a limit \(u_*\in\mathcalY\), and then, if \(I\) is continuous, \[ I(u_*) = łim_k I(u_n_k), \] or \(I(u_*)=I_*\). In this way, the infimum \(I_*\) is finite and \(u_*\) is a minimizer. The argument hinges both on (i) the continuity of \(I\) and (ii) the possibility of extracting convergent subsequences of sequences in \(\mathcalY\), or, in other words, the compactness of \(\mathcalY\). In the calculus of variations, where \(u\) is a function, \(I\) a functional such as \(\int_a^b f(x,u(x),u^\prime(x))dx\), and \(\mathcalY\) a closed, bounded subset of a normed linear space \(Y\), the same procedure will not work, because \(\mathcalY\) is not compact. The best we may hope for is that \(\mathcalY\) is compact in the weak topology of \(Y\) and extract from the minimizing sequence \(\u_n\\subset\mathcalY\) a weakly convergent subsequence, i.e., a subsequence such that \(łim_k \ell(u_n_k) = \ell(u_*)\) for each bounded, linear functional \(\ell\) on \(Y\). However, \(I\) is typically not continuous with respect to the weak topology (see Example 1.1 in the paper), and then the equation displayed above will not be satisfied. Fortunately, in many applications, \(I\) is weakly lower semicontinuous (lower semicontinuous with respect to the weak topology). This means that for sequences \(v_n\) that converge weakly to a limit \(v\), \(I(v) łeq łiminf_n(v_n)\); the prefix semi- refers to the fact that here we have the symbol \(łeq\) rather than \(=\). For weakly lower semicontinuous \(I\), \[ I(u_*) łeqłiminf_k I(u_n_k). \] Thus \(I(u_*) łeq I_*\), so that the weak limit \(u_*\) is a minimizer. The article, which begins with a very friendly introduction, reviews in detail the literature on weak lower semicontinuity since the 1950s. It also discusses applications, notably to elasticity, including recently studied situations where the energy functional depends on higher derivatives of the deformations.

Development of a Sensor Prototype and Geometry Based Parameters for the Characterization of Riblets Using Angle-resolved Measurement Techniques

The application of periodic microscale-structures, so-called riblets, is a medium-term goal intended to help airplane manufacturers in the modern civil aviation industry to reduce fuel consumption of aircrafts significantly. To reach this goal it is necessary to investigate the quality of riblets during the manufacturing process as well as during the operating time. Thus, it is essential to measure the degradation of those microscopic structures as a function of flight time in order to reach a decision on whether to replace or to rework the existing riblets. Tactile measurement principles are being disqualified for practical applications for several reasons. Instead, optical measurement principles are well-suited for this kind of application. The angle-resolved scattering light principle describes such an optical measurement method, which is suitable for measuring riblet structures and moreover can be virtually modeled. Based on theoretical pre-examinations of the physical measurement principle, a virtual sensor has been developed at the Institute for Measurement and Sensor-Technology at the University of Kaiserslautern to investigate riblet degradation. This was achieved within the framework of the International Research and Trainee Group 2057 (IRTG 2057), founded by the German Research Foundation (DFG). This virtual sensor forms the basis of a prototype, the so-called riblet sensor, which is currently being subjected to practical testing. A comparison between virtual and real measurement data is thus possible.To ultimately get meaningful results regarding the qualitative conditions of the riblets, so-called scatter distributions must be analyzed and interpreted. An unambiguous interpretation of scatter distributions presents difficulties. The development of applicable parameters based on virtual data analysis therefore is a significant aspect, which will be considered within this article. Furthermore detailed physical descriptions of the virtual sensor will be given.

Heliostat attitude angle detection method based on BP neural network

Traditional fossil fuels have dried up, global warming and sustained economic development have led to the rapid growth of clean energy resources. Tower thermal power generation has attracted much attention due to its ability to generate electricity during the night. The traditional tower thermal power generation adopts open-loop control which requires very high mechanical accuracy. In the operation of power station and there may be a settlement, wind load or other factors make the heliostat skew phenomenon. It will eventually lead to a decline in power generation efficiency. Thus, we propose a closed-loop feedback control method based on machine vision and optical reflection principle based on the method of using the correction of heliostat spot acquisition board. To identify the spot and the ellipse fitting method for spot feature extraction using image processing technology, we propose a heliostat to determine the characteristics of the corresponding spot mapping the attitude angle method based on BP neural network. Thus we can provide direct feedback control of heliostat errors. The new method can effectively increase the heliostat tower power generation efficiency and also can make the tower heliostat thermal power generation cost reduced with the popularization and application of significance.