Optical Instruments Research Articles

Approach to fiber-based optical polarimetry for tissue assessment: system calibration and application.

The potential of optical polarimetry is increasingly explored to unravel the tissue structure through several optical instrument configurations. Fiber-based solutions offer portability and are accommodative in an endoscopic examination environment. Here, we address the challenges in realizing a fiber-based optical polarimetry system through an approach involving an all-fiber polarization controller. The methods of device calibration and application in bulk tissues are discussed, and results are presented.

Into nonlinearity and beyond for Zernike-like wavefront sensors

Context. Telescopes like the Extremely Large Telescope (ELT) and the Giant Magellan Telescope (GMT) will be used together with extreme adaptive optics (AO) instruments to directly image Earth-like planets. The AO systems will need to perform at the fundamental limit in order to image Earth twins. A crucial component is the wavefront sensor. Interferometric wavefront sensors, such as the Zernike wavefront sensor (ZWFS), have been shown to perform close to the fundamental sensitivity limit. However, sensitivity comes at the cost of linearity; the ZWFS has strong nonlinear behavior. Aims. The aim of this work is to increase the dynamic range of Zernike-like wavefront sensors by using nonlinear reconstruction algorithms combined with phase sorting interferometry (PSI) and multi-wavelength measurements. Methods. The response of the ZWFS is explored analytically and numerically. Results. The proposed iterative (non)linear reconstructors reach the machine precision for small aberrations (<0.25 rad rms). Coupling the nonlinear reconstruction algorithm with PSI increases the dynamic range of the ZWFS by a factor of three to about 0.75 rad rms. Adding multiple wavebands doubles the dynamic range again, to 1.4 radians rms. Conclusions. The ZWFS is one of the most sensitive wavefront sensors, but has a limited dynamic range. The ZWFS will be an ideal second-stage wavefront sensor if it is combined with the proposed nonlinear reconstruction algorithm.

Precision of diamond turning sinusoidal structures as measurement standards used to assess topography fidelity

In optical surface metrology, it is crucial to assess the fidelity of the topography measuring signals. One parameter to quantify this is the small-scale fidelity limit T FIL defined in ISO 25 178-600:2019. To determine this parameter, sinusoidal structures are generated, where the wavelengths are modulated according to a discrete chirp series. The objects are produced by means of ultra-precision diamond face turning. Planar areas and regions with slopes below 4° could be produced with form deviations of ≲10 nm. An initial estimate of the cutting tool’s nose radius resulted in a deviation that caused the ridges of the structures to be too narrow by approximately 150 nm, while the trenches were too wide. At the bottom of narrow trenches, deviations are observed in the form of elevations with heights of about 20 to 100 nm. The measurement standard investigated in this study has also been used to characterise optical instruments in a round-robin test within the European project TracOptic, which requires precise knowledge of the geometry of all structures. The geometry of the topography, cosine structures superimposed with form deviations, was measured using the Met. LR-AFM metrological long-range atomic force microscope of the German National Metrology Institute.

Achievement of dynamic tablet defect detection mechanism using biaxial slope symmetry algorithm

An inspection in tablet appearance integrity before bottling is regarded as a routine task in a pharmaceutical factory. Although some methods such as automated optical instrument, video or artificial intelligence (AI) are currently available in industry, it usually pays for a complex computational process as well as high cost. Based on the symmetry of tablet appearance in reality, this study develops a biaxial scanning slope symmetry algorithm to realize a dynamic real-time tablet defect detection with a simple arithmetic operation. First, the tablet is discretely scanned using image sensor in two axes, i.e. X and Y directions, simultaneously. Second, the analogy output signals generated from the sensor during the scanning process is discretely digitized and stored in an array. Third, the coordinate of center point in the series data array is identified from every line scanning. Fourth, every section slope between two nearby center points from the first to last lines is formulated and calculated sequentially. Finally, the square mean error (SME) is used to evaluate the shape defect situation according to all accumulated errors from every slope variation. The experimental results verify that the proposed algorithm can achieve both fast and accurate detection performance.

Feasibility study of in-line particle image velocimetry

This article describes recent tests and developments of imaging and evaluation techniques for particle image velocimetry (PIV) that exploit the forward scattering of tracer particles by placing the camera in-line with the illuminating light source, such as a laser or a light emitting diode. These techniques have been in use for some time in microscopy and in the design of optical instruments in astronomy. However, they have not yet been used for macroscopic PIV flow measurements. This study highlights the most promising approaches of the various recording configurations and evaluation techniques.

Water vapor condensation in optical instruments on Mars

Modern high-sensitivity spectrometers rely on photons reflecting thousands of times between extremely reflective mirrors to generate absorption pathlengths that are kilometers long. The absorption spectrum of trace gas species is enhanced when cooling the gas sample, however, should any atmospheric volatiles condense within the gas cell, the highly-reflective mirrors may become marred, drastically cutting down the effective optical path length. In the Martian atmosphere, the first volatile to condense is typically water vapor, thus understanding the variability of the water frost point is essential for determining the performance limit of any optical instrument. We will examine these performance limits and map the maximum temperatures at which water vapor will condense on the Martian surface with respect to a model instrument being prepared for flight. The variability of the frost point with time and solar longitude (Ls) therefore reveals areas of the Martian surface at which the precision of a high-sensitivity spectrometer is optimized. We find that the optimal performance is achieved during northern fall and winter (Ls = 180°–360°) at polar and mid-latitude locations in the northern hemisphere, and during northern spring (Ls = 0°–90°) at equatorial and mid-latitude locations in the southern hemisphere when the frost point reaches the lowest maximums.

The Influence of the Project Based Learning (PjBL) Model on Student Learning Outcomes

The purpose of the research to determine the effect of Project Based Learning (PjBL) model on student learning outcomes in optical instruments. The sampling technique used purposive sampling, obtained class XI MIPA 4 as experimental class and XI MIPA 5 as control class. The research design used was a nonequivalent control group design. The experimental class will be given treatment using the Project Based Learning (PjBL) model, while the control class will use the expository model (conventional learning). Learning outcomes abilities measured in the cognitive domain include: C1) remembering, C2) understanding, C3) applying, C4) analyzing, C5) evaluating, and C6) creating. The instrument used was 10 multiple choice questions. Data were analyzed using parametric statistics, namely Manova. The results showed a sinificance value of 0.000 < 0.05 and a value of Rcount > Rtable where 0.359 > 0.350, so H0 was rejected and Ha was accepted. So can be concluded that there is an influence of the Project Based Learning (PjBL) model on scientific literacy and student learning outcomes in optical equipment material.

Impact of Physics Modules Based on Problem Based Learning on The Problem-Solving Abilities of Students in the Material of Optical Instruments

The purpose of this study is to ascertain how students' problem-solving skills are affected by the use of a problem-based learning physics module. A nonequivalent control group design and a quasi-experimental research methodology are used. Test instruments in the form of descriptive questions and non-test instruments in the form of a questionnaire on student replies make up the instruments utilized. Students in grade XI at SMA Darul Falah for the academic year 2022–2023 make up the study population. Purposive sampling was used to choose the research sample, resulting in the experimental group consisting of 21 students from class XI MIPA 2 and the control group consisting of 21 students from class XI MIPA 1. For the experimental group, a customized problem-based learning module in physics was employed. The Problem-Solving Ability instrument consists of descriptive questions that have been tested for validity, reliability, difficulty level, and item discrimination. The experimental group's average post-test score was 83.66, compared to 60.09 for the control group. Both groups' data were uniformly distributed and homogeneous. The hypothesis test results indicated that the calculated t-value was greater than the critical t-value, specifically 6.33, which is higher than 2.02 for the post-test data. Therefore, the alternative hypothesis ( ) is accepted, and the null hypothesis ( ) is rejected, indicating an influence of using the physics module based on problem-based learning on students' problem-solving abilities in the topic of optical instruments. Based on the analysis of the questionnaire responses, students' responses improved after the implementation of the physics module based on problem-based learning, with an implementation percentage of 72%. In conclusion, there is an influence of using the physics module based on problem-based learning on students' problem-solving abilities in the topic of optical instruments.

ALR_Sim_tracks — Trajectory Simulator Software to Assist the Search for Favourable Trajectories for the Exploration of the Triple Asteroid 2001-SN263 From the Laser Altimeter Point of View

This paper presents a simulator tool, named _ALR_Sim_tracks_, dedicated to the preliminary analysis of trajectories planned for a space mission to explore the surface of celestial bodies using optical sensors, such as a laser altimeter. The software offers a prediction of the coverage results obtainable in a simulated exploration campaign carried out along a selected/simulated trajectory, for the set of target and instrument parameters used (in qualitative and quantitative terms, including 2D/3D visualizations). The software was created to perform an analysis that would allow the identification of favourable trajectories for conducting the intended exploration of the triple asteroid 2001-SN263 during Brazil's first deep space mission (ASTER mission) from the point of view of the Laser Altimeter being designed to fly in this mission, which was named ALR. Because there are few tools described and available for this type of analysis in the literature, and these are generally complex, proprietary and of restricted use, this work aims to help broaden the understanding of the process involved and the access to this type of tool. The paper contains the description of the _ALR_Sim_tracks_ software and everything involved in its operation. The illustrative examples presented in this text involve the exploration of an asteroid from the point of view of a laser altimeter, because this was the initial motivation for creating the simulator. However, other optical instruments with similar operation, used to explore other types of targets (e.g. planets or moons), are also considered when suitable modelling is available.

On the variability of the atomic oxygen density in the upper atmosphere under different solar activity and geomagnetic conditions and its impacts on satellite drag

Atomic oxygen (AO) is the most abundant species in the terrestrial thermosphere at altitudes of 180 to 700 km and plays a crucial role in numerous upper atmospheric processes. The drag encountered by a spacecraft is directly influenced by the background atmospheric density, making AO a notable contributor in this regard. The objective of this study is to analyze the variability of the density of AO in the near-Earth space environment under different solar activity conditions, as well as during severe space weather events. The analysis is primarily focused on the altitude range of 300 to 500 km in the Earth’s thermosphere across the globe, which is a crucial operating region for a large number of Low Earth Orbiting satellites. AO exerts significant drag on the Low Earth Orbit (LEO) satellites and reacts with the materials of the satellite body and in situ probes mounted therein, causing considerable degradation to both. Additionally, AO interferes with measurements made by optical instruments through phenomena such as ‘shuttle glow’. Analysis based on NRLMSIS 2.0 model revealed that the concentration of AO displays significant seasonal variations primarily due to the asymmetry in solar insolation. The highest concentration of AO was observed during the spring equinoctial month of the solar maximum year, while the lowest concentration was noted during the winter solstitial month of the solar minimum year. The enhancement seen in AO density contours show an asymmetry in the zonal direction at approximately 50∘ N in June and 50∘ S in December. Similarly, during geomagnetically disturbed days, the AO density shows enhancements along various longitudes, as indicated by the elongated contours. During geomagnetic storms, the heightened Joule heating in the polar region modifies the meridional circulation, which in turn affects the global distribution of AO density. Similarly, an analysis of thermospheric neutral winds obtained from the HWM93 model reveals that the zonal winds exhibit a strong westward acceleration over the region where AO density is enhanced. Furthermore, such an increase in AO density during geomagnetic storms has been found to cause orbital degradation ranging from a few tens of meters to a few hundred meters, depending on the strength and geo-effectiveness of the storms. This study emphasizes the critical contribution of AO density to satellite drag force, necessitating in situ measurements for an accurate estimation of the altitude decay of the spacecraft.

Drive Formula for Sars Length of Wire Hanging Between Two Electric Poles and Some Applications

Base on sars length of wire hanging between two electric poles makes angles θ & ∝ with horizontal. Drive the formula for sars length of wire makes angles with horizontal θ & ∝ where (θ > ∝). Find the volume, Sars surface area,Total surface area of many kinds of Sars cuboid and Sars cube like as LL-Sars cuboid, UU-Sars cuboid, LU-Sars cuboid, LL-Sars cube, UU-Sars cube, LU-Sars cube . All kind of Sars cuboid and Sars cube used in optics instruments like as Sars lens, Sars mirror. When a ray of light incident on the Sars surface area then it is refracted or reflected depending on the sars surface area and angles θ&∝. Base on Sars length of wire used 170 applications and more. But in this paper some application are used. To find the Sars length of wire hanging between two electric poles. If f(x) is a smooth curve on [a, b] and length of curve y=f(x) from a to b.

A preliminary study on a new approach for measurement of the antioxidant capacity of single molecules in food

Antioxidant activity refers to the rate of reaction between a specific antioxidant and a specific oxidant. On the other hand, antioxidant capacity is a measure of the quantity of a free radical in a concentration, neutralized by antioxidant molecules under examination. All common methods such as: Ferric Reducing Antioxidant Power (FRAP), Total Peroxyl Radical Antioxidant Parameter (TRAP), Oxygen Radical Absorption Capacity (ORAC), Crocin Bleaching Assay (CBA), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and others have some technical limitations. All methods, before any analytical test, require a sample preparation, which is separated into hydrophilic and lipophilic fractions. However, this already represents an artifact, because some of the properties of the biological matrix are lost. The new OXEFIN unit defined as the ratio between the electrical power of the sample and the control allows us to compare the antioxidant capacities of single substances or a mixture of them, without the use of a target molecule and equipment such as a spectrophotometer or other optical detection instruments. Moreover, we are able to detect the total antioxidant capacity in an opaque solution without sample preparation(such as food). The milks range from 2.73 ± 0.02 to 0.20 ± 0.003 at 4 ml and 4.33 ± 0.04 to 0.26 ± 0.003 at 8 ml. The berries and fruit juices range from 5350 ± 38 to 673 ± 5.8 at 4 ml and from 5220 ± 40 to 915 ± 5 at 8 ml. The method proposed in this paper represents a new approach to the antioxidant capacity measurements reducing the cost, analysis time, the amount of reagents and avoid the possible chemical interferences during the radical chain reaction.

High-directivity far-field radiation of quantum dot-based single-photon emitter coupled to polymeric circular waveguide resonant grating

Solid-state single-photon emitters (SPEs) commonly encounter the limitation of quasi-omnidirectional radiation patterns, which poses challenges in utilizing their emission with conventional optical instruments. In this study, we demonstrate the tailoring of the far-field radiation patterns of SPEs based on colloidal quantum dots (QDs), both theoretically and experimentally, by employing a polymer-based dielectric antenna. We introduce a simple and cost-effective technique, namely low one-photon absorption direct laser writing, to achieve precise coupling of a QD into an all-polymer circular waveguide resonance grating. By optimizing the geometry parameters of the structure using 3D finite-difference time-domain simulations, resonance at the emission wavelength of QDs is achieved in the direction perpendicular to the substrate, resulting in photon streams with remarkably high directivity on both sides of the grating. Theoretical calculations predict beam divergence values below 2°, while experimental measurements using back focal plane imaging yield divergence angles of approximately 8°. Our study contributes to the evaluation of concentric circular grating structures employing low refractive index polymer materials, thereby expanding the possibilities for their application.

Effect of Wordwall-Assisted Brain-Based Learning to Cognitive Learning Outcomes on Optical Equipment Material

Improving student learning outcomes will always be influenced by how teachers teach and provide innovation in learning. This study focuses on evaluating the cognitive learning achievements of class XI high school physics students in the Optical Instrument material, using the Wordwall-assisted Brain Based Learning model. The study is a quasi-experiment with all students in class XI of MS SMAN Plus Riau Province. A sample of 59 students with class XI MS 1 as the experimental group and class XI MS 4 as the control group. Daily tests were conducted to collect data on cognitive learning outcomes, which were analyzed both descriptively and inferentially. The findings indicate a significant difference in cognitive learning outcomes between the experimental and control groups, with the former achieving an average outcome of 81.83 and the latter attaining an average of 73.10. These results demonstrate that the Wordwall-assisted BBL learning model can enhance the cognitive learning outcomes of grade XI students in Senior High School, specifically in the Optical Equipment material.

Head stabilization apparatus for high-resolution ophthalmic imaging.

Head movement must be stabilized to enable high-quality data collection from optical instrumentation such as eye trackers and ophthalmic imaging devices. Though critically important for imaging, head stabilization is often an afterthought in the design of advanced ophthalmic imaging systems, and experimental devices often adapt used and/or discarded equipment from clinical devices for this purpose. Alternatively, those seeking the most stable solution possible, including many users of adaptive optics ophthalmoscopy systems, utilize bite bars. Bite bars can provide excellent stability but are time consuming to fabricate, decreasing imaging efficiency, and uncomfortable for many patients, especially the elderly and/or those with prosthodontics such as dentures who may refuse participation in a study that requires one. No commercial vendors specifically offer head mount solutions for experimental ophthalmic imaging devices, resulting in nearly every custom device having a different solution for this commonly encountered problem. Parallelizing the head stabilization apparatus across different custom devices may improve standardization of experimental imaging systems for clinical trials and other multicenter investigations. Here we introduce a head mount design for ophthalmic imaging that is modular, adjustable, and customizable to the constraints of different experimental imaging configurations. The three points of head contact in our solution provide excellent stabilization across a range of head sizes and shapes from small children to adults, and the ease of adjustment afforded by our design minimizes the time to get participants stabilized and comfortable.

Self-assembled coating with a metal-polyphenolic network for intraocular lens modification to prevent posterior capsule opacification

Posterior capsule opacification (PCO) is a main complication after cataract surgery and intraocular lens (IOLs) implantation and is attributed to residual lens epithelial cells (LECs) migrating to the IOL surface and posterior capsules. IOL surface modification has been a newly-developing research filed in recent years; however, the applicability and economical acquisition of modified materials remain unsolved. In this study, we first applied a metal-polyphenolic network coating with a self-assembly technique on the IOL surface by using tannic acid (TA) combined with AlCl3, which are easily acquire and applying on the IOL surface to solve the IOL transmittance affair. Using wound healing and Transwell assay to verify AZD0364 inhibits cell migration ( P < 0.05), the lipopolysaccharide-induced macrophage inflammation model to verify pterostilbene (PTE) inhibits the inflammatory reaction ( P < 0.01). By optimizes its self-assembly coating parameters and calculating its drug release kinetics, we successfully loaded these two drugs on the coating, named TA (AZD0364/PTE) IOL. Its surface morphology characteristics were analyzed by scanning electron microscope, x-ray photoelectron spectrometer and water contact angle. The optical performance was carefully investigated by optical instruments and equipment (n= 3). The in vitro results showed that TA (AZD0364/PTE) IOL can significantly inhibit cell adhesion and acute inflammation (n= 3, P < 0.0001). Importantly, after in vivo implantation for 28 d with eight rabbits PCO models in two groups, the TA (AZD0364/PTE) IOL group maintained clear refracting media and decreased the inflammatory reaction compared with the original IOL group ( P < 0.05). This study provides a new applicable and economical strategy for preventing PCO and offers a reference for the next generation of IOLs that benefit cataract patients.

Traceable characterization of hollow organosilica beads as potential reference materials for extracellular vesicle measurements with optical techniques

The concentration of cell-type specific extracellular vesicles (EVs) is a promising biomarker for various diseases. However, concentrations of EVs measured by optical techniques such as flow cytometry (FCM) or particle tracking analysis (PTA) in clinical practice are incomparable. To allow reliable and comparable concentration measurements suitable reference materials (RMs) and SI-traceable (SI—International system of units) methods are required. Hollow organosilica beads (HOBs) are promising RM candidates for concentration measurements of EVs based on light scattering, as the shape, low refractive index, and number concentration of HOBs are comparable to EVs of the respective size range that can be detected with current optical instrumentation. Here, we present traceable methods for measuring the particle size distribution of four HOB types in the size range between 200 and 500 nm by small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM), as well as the number concentration by single-particle inductively coupled plasma mass spectrometry (spICP-MS). Based on the size and shape results, traceable reference values were obtained to additionally determine the refractive index of the shell of the HOB samples by FCM. Furthermore, the estimated refractive indexes of the HOBs plausibly agree with the refractive indexes of EVs of corresponding size. Due to their narrow size distribution and their similar shape, and low refractive index, all HOB samples studied are suitable RM candidates for calibration of the measured sample volume by optical methods within the photon wavelength range used, and thus for calibration of number concentration measurements of EVs in the size range indicated. This was confirmed as the number concentration values obtained by PTA and two independent flow cytometric measurements agreed with the concentration reference values obtained by two independent spICP-MS measurements within the calculated uncertainty limits.

A model-free method based on RDPG for fiber diameter steady control

Optical fibers have made outstanding contributions to optical instruments such as micro-channel plates (MCPs) and micro-pore optics (MPOs). As the stricter performance requirements for the MCP and MPO, traditional diameter control methods are incapable. Additionally, the partial observation issue of fiber drawing process further limits the outcome of the existing control approaches. Innovative control algorithms are vital for the diameter precision enhancement. We investigate the significance of recurrent deterministic policy gradient (RDPG) on diameter control. RDPG consists of deep deterministic policy gradient (DDPG) and recurrent neural network (RNN) where DDPG is a model-free reinforcement learning algorithm for continuous control and RNN for addressing partial observation. The impact of RNN variants selection on control performance is further discussed. Results illustrate that the application of RNN substantially solves the partial observation and varying RNN variants play a positive role in diameter control, but bidirectional gated recurrent unit (BiGRU) reaches the best accuracy. Comparison experiment results indicate that RDPG is able to learn reasonable control strategies and achieves significantly more accurate and robust diameter control in contrast with the existing methods.

Raman spectroscopic measurements and imaging on sub-newton Berkovich and spherical imprints in fused silica

This paper lays out best practices for evaluating and optimizing a Raman spectroscopy setup to ensure the collection of reliable spectral data and/or Raman images on indented glasses. The Raman spectroscopic measurements and imaging were conducted on residual imprints created with Berkovich and spherical probes at forces in the sub-newton range in fused silica. The capability of a conventional optical instrument for mapping spectral variations in sub-newton imprints on glasses is evaluated by studying the influence of the optical configuration (choice of microscope objective) on the spatial resolution of the spectroscopy setup. The spatial resolution was quantitatively assessed in Z profile measurements and qualitatively evaluated by mapping changes in spectral features and correlated densification within the indented regions of fused silica specimens. The paper discusses the importance of appropriately matching the analysis volume of the Raman spectroscopic setup with the size of the indentation-induced densification zone by demonstrating the detrimental effects a mismatch may have on accurately capturing the magnitude of spectral changes and correlated densification.

Gold-sputtered LPG fiber sensor pulse electroplated with iron-carbon for monitoring passivation and depassivation of carbon steel in concrete pore solutions

Monitoring the passivation and depassivation of reinforcement steel is of significant importance, particularly for certain reinforced concrete structures that define the time of steel rebar depassivation as the end of the durability service life. In this study, a gold-sputtered long-period grating (LPG) optical fiber sensor coated with pulse-electroplated iron-carbon is characterized for continuous monitoring of the surface state of carbon steel from passivation to depassivation in concrete pore solutions. Electrochemical corrosion and optical tests are performed simultaneously using an electrochemical workstation and an optical instrument. A protective passivation film with a thickness of approximately 4.05 nm was formed on the iron-carbon coating after 5 days of immersion in the simulated concrete pore solution, and its thickness is nonlinearly correlated with the wavelength shift of the LPG optical fiber sensor during the passivation process. The resonant wavelength changes in the opposite direction after depassivation, which can be used for the detection of the depassivation time. After depassivation, the wavelength shift and mass loss of the iron-carbon coating can be divided into three phases, and a linear relationship exists in each phase. The gold-sputtered fiber sensor coated with pulse-electroplated iron-carbon investigated in this study, demonstrates better performance than silver-deposited LPG fiber sensors.