Search

In optical precision assembly, most optical components are fixed by multi-point adhesive bonding. However, the stress fields generated in lenses by radial stress in the adhesive significantly influence the imaging quality of precision optical lenses. To date, the adhesive bonding process is conducted empirically, meaning that the stress in lenses cannot be actively or quantitatively controlled. Therefore, to improve the current passive process, a theoretical mechanical model of an optical lens was established, and a novel stress potential function was proposed to derive the analytical solution of stress components in lenses under an arbitrary number of multi-point radial stresses. The results revealed a quantitative relationship between the radial stress in the adhesive and the stress field in the optical lens. Furthermore, a new experimental device was developed, and a systematic experimental method was proposed to apply multi-point quantitative radial loads on an optical lens and measure its real-time stress distribution, which further verifies the accuracy and validity of the proposed theoretical model. This study provides a theoretical approach for the quantitative control of lens stress and optimization of adhesive bonding configuration in optical precision assembly process, which is a basis to enhance the imaging accuracy of precision optical instruments.

The cracked morphology and iridescent properties of photonic crystal (PC) films have greatly limited their applications in the field of color pigments and optical instruments. Herein, we fabricated...

The study of the electromagnetic spectrum, how light interacts with matter, and optical instruments such as lenses, mirrors, and gratings are important concepts in the Advanced Placement (AP) physics and introductory undergraduate physics and astronomy courses. The production, control, and analysis of light helps scientists to learn about the natural world. A spectrometer is an instrument that utilizes several components (lenses, mirrors, diffraction grating, or prism) that students commonly study in an introductory optics unit and can be helpful to demonstrate for students how light can be separated on the basis of wavelength. The authors designed and built a simple tabletop spectrometer. The layout is compact so as to make it easy to construct on a rolling cart to be easily transported for classroom demo or lab purposes. Additionally, we focused on keeping the spectrometer affordable, and discuss options for sourcing parts and scavenging for items in existing supplies. We constructed and tested two spectrometers, one at Susquehanna University in Pennsylvania and one at Providence College in Rhode Island. Similar to Isaac Newton leaving Trinity College in 1665 during the bubonic plague outbreak, the final testing and building of these spectrometers was completed in the basements of the authors’ homes amid the COVID-19 shelter-at-home orders.

Critical angle refractometry is an established technique for determining the refractive index of liquids and solids. For transparent samples, the critical angle refractometry precision is limited by incidence angle resolution. For lossy samples, the precision is also affected by reflectance measurement error. In the present study, it is demonstarted that reflectance error can be practically eliminated, provided that the sample’s extinction coefficient is a priori known with sufficient accuracy (typically, better than 5%) through an independent measurement. Then, critical angle refractometry can be as precise with lossy media as with transparent ones.

The understanding of yielding pillar behavior has been well documented in terms of pillar strength. The behavior has been documented using numerical simulations and empirical formulas. Nevertheless, the understanding of how fracture propagates in a matured yielding pillar is not well established. Indeed, very limited studies have striven to study this behavior using numerical simulation; however, the simulation appears to be a complex method and some models do not present the actual distribution. In this study, geophysical and optical instruments (ground-penetrating radar (GPR) and borescope respectively) were used to establish the distribution of extension fractures across the matured yielding pillar. The GPR survey has shown that the distribution of fractures across the length of the matured yielding pillar differs greatly, with extensive fracturing distributed along the middle section of the pillar; this distribution was observed to propagate to a maximum depth of about 1.7 m. However, the situation on the top and lower section of the pillar differs greatly from the middle section; in these sections, extensive fracturing was observed to propagate to the maximum depth of about 0.5 m, with moderate fracturing occurred from 0.6 to about 1.5 m toward the pillar core while the rest of the pillar is therefore dominated with less fracturing to solid rockmass. Borescope analysis was performed to validate the GPR survey; the results from the borescope analysis correlated with the GPR survey. Based on the GPR and borescope results obtained from several yielding pillars, a summation of the results is therefore presented in a form of an empirical chart categorizing the distribution of fractures along the yielding pillar. It is therefore argued that a developed summation chart of fracture distribution could be utilized to classify the maturity of yielding pillars based on fracturing. Indeed, the developed summation chart is simple to use and does not require complex analysis. It is therefore concluded that the developed summation chart could open more doors in exploring other simple alternative ways of classifying the matured yielding pillars.

In this study, moth-eye-inspired structures (MISs), which improve optical performance of surfaces, were developed to enhance light efficiency in various optical fields. As the polymer-based soft lithography process can easily optimize MIS materials and nanostructures, 12 MIS/inverse MIS (IMIS) surfaces of 300, 500, and 1000 nm composed of polyurethaneacrylate (PUA) and polydimethylsiloxane (PDMS) polymers were fabricated, and a thin octafluorocyclobutane (C4F8) layer was deposited on the surfaces to reduce their surface energies. The results showed that the 300-nm PDMS-MIS showed excellent optical properties with 94.44 % transmittance and 3.28 % reflectance. Additionally, two theoretical phenomena, the diffraction effect and double-slit diffraction, were experimentally demonstrated using three single-wavelength lasers. Subsequently, contact-angle measurements demonstrated all MIS/IMIS surfaces to possess hydrophobic and superhydrophobic properties, which can protect devices from outdoor liquids. Finally, we confirmed the applicability of MIS by attaching it to a cell phone display and an ITO glass, which is used as a substrate in various optical instruments.

Ultrasound has been used for antifouling on the surface of medical devices or food utensils, but it is rarely applied in marine anti‐biofouling on underwater instruments. To understand whether ultrasonic antifouling is suitable for underwater optical windows, the effect of ultrasonic conditions including frequency, power and duration on the removal of microbiofouling on the surface of polymethyl methacrylate (PMMA), a type of common optical material, was investigated in this study by three‐factor and three‐level orthogonal experiments. Before and after the ultrasonic treatment, both surface morphology and fouling degree of PMMA samples immersed in Escherichia coli suspension and seawater were characterized and quantified using laser scanning microscope. The results showed that ultrasonic treatment can effectively remove microfouling from the PMMA surface under suitable conditions. Ultrasonic technology has a great potential for the control of microfouling on the marine optical instruments. When compared with power and duration, ultrasonic frequency has a more significant effect on antifouling efficacy of ultrasound. It is useful for PMMA samples exposed to seawater within 2 days to conduct an antifouling treatment under the condition of an ultrasonic frequency of 20 kHz, ultrasonic power of 40 W, and ultrasonic duration of 7 min.

Optical glass must satisfy multiple specifications for a given optical instrument. Machine learning has recently been applied to the development of materials. The optimization of compositions with multiple target properties has been investigated. Here, we focus on the trade-off between target properties, namely the refractive index nd and the Abbe number νd, for optical glass and apply a multi-objective Bayesian optimization algorithm called ParEGO to find glass compositions with low target property values using INTERGRAD data. In addition, we examine the effects of normalizing the target properties and descriptors on the search performance of ParEGO. The results reveal that ParEGO can effectively find compositions with low target property values and that normalization is necessary for sufficient ParEGO search performance. The normalization of target properties and descriptors may be effective for other multi-objective Bayesian optimization algorithms and materials. We also discuss how to apply the method to the actual development of optical glass.

It is of great significance to measure the residual stress distribution accurately for optical elements and evaluate its influence on the performance of optical instruments in optical imaging, aviation remote sensing, semiconductor manufacturing, and other fields. The stress of optical elements can be closely related to birefringence based on photoelasticity. Thus, the method of quantifying birefringence to obtain the stress becomes the main method of stress measurement technologies for optical elements. This paper first introduces the basic principle of stress measurement based on photoelasticity. Then, the research progress of stress measurement technologies based on this principle is reviewed, which can be classified into two methods: polarization method and interference method. Meanwhile, the advantages and disadvantages of various stress measurement technologies are analyzed and compared. Finally, the developing trend of stress measurement technologies for optical elements is summarized and prospected.

This article gives a brief overview of optical devices used in shooting. This article is intended to acquaint students (students) of higher, secondary special and secondary education institutions with information about optical devices used in shooting.

Onboard the International Space Station (ISS), as a part of the “Uragan” Earth exploration experiment, various observation devices are used, including photo and video spectral equipment, the orientation of which is carried out manually by the crew through the portholes. However, severe limitations are imposed on the planning of such experiments, primary related to the necessity taking into account the crew’s daily routine and the availability of time allocated for scientific experiments. The solution for expanding the ability to conduct experiments is the employing of automated orientation platforms (OP). One of these OPs is the video spectral equipment orientation system SOVA-1-426. A method for orientation angles forecasting of optical instruments for pointing at predefined objects on the Earth’s surface with SOVA-1-426 is presented. Moreover, in the described method, in addition to the coordinates of the center of mass, the current orientation of the ISS is taken into account, which makes it possible to perform the forecast with better precision. Taking into account the ISS orientation is carried out through the use of the ISS rotation quaternion to control the platform in automatic mode. The presented method for the orientation angles forecasting of high-resolution photo-camera aboard the ISS by employing SOVA-1-426 allows its automatic alignment on the Earth’s surface objects with accuracy up to seven kilometers. The described method is implemented in software and is currently used in the SOVA-1-426 OP aboard the ISS for the remote sensing of the Earth’s surface.

An irradiance profile measurement approach and profiling system were developed to measure the solar irradiance profile of the Arctic sea ice using fiber optic spectrometry. The approach involved using a miniature spectrometer to sense light signals collected and transmitted from a fiber probe. The fiber probe was small, and could thus move freely in inclined bore holes drilled in sea ice with its optical entrance pointing upward. The input-output relationship of the system was analyzed and built. Influence factors that determined the system output were analyzed. A correctional system output approach was proposed to correct the influence of these factors, and to obtain the solar irradiance profile based on the measurements outputted by this system. The overall performance of the system was examined in two ice floes in the Arctic during the 9th Chinese National Arctic Research Expedition. The measured solar irradiance profiles were in good agreement with those obtained using other commercially available oceanographic radiometers. The derived apparent optical properties of sea ice were comparable to those of similar sea ice measured by other optical instruments.

Optical coatings are integral components of virtually every optical instrument. However, despite being a century-old technology, there are only a handful of optical coating types. Here, we introduce a type of optical coatings that exhibit photonic Fano resonance, or a Fano-resonant optical coating (FROC). We expand the coupled mechanical oscillator description of Fano resonance to thin-film nanocavities. Using FROCs with thicknesses in the order of 300 nm, we experimentally obtained narrowband reflection akin to low-index-contrast dielectric Bragg mirrors and achieved control over the reflection iridescence. We observed that semi-transparent FROCs can transmit and reflect the same colour as a beam splitter filter, a property that cannot be realized through conventional optical coatings. Finally, FROCs can spectrally and spatially separate the thermal and photovoltaic bands of the solar spectrum, presenting a possible solution to the dispatchability problem in photovoltaics, that is, the inability to dispatch solar energy on demand. Our solar thermal device exhibited power generation of up to 50% and low photovoltaic cell temperatures (~30 °C), which could lead to a six-fold increase in the photovoltaic cell lifetime. A thin-film optical coating exhibits Fano resonance showing promising applications in structural colouring of transparent objects and hybrid thermal and photovoltaic power generation.

The design of optical instruments is an active subject due to improvement in lens techniques, fabrication technology, and data handling capacity. Much remains to do to expand its application to phytopathology, which would be in particular quite useful to improve crop growth monitoring in countries like Mali. An optical multimodal system for plant samples has been developed to improve the characterization of leaf disease symptoms, provide information on their effects, and avoid their spread. Potentially inexpensive components (laser, lens, turntables camera and sample, filter, lens, camera and computer) have been selected, assembled and aligned on an optical table into a multimodal system operating in transmission, reflection, diffusion and fluorescence. The illumination and observation angles can be adjusted to optimize viewing conditions in the four modes. This scientific contribution has been an initiation into the design and implementation of an optical instrument. Initial results are shown and will now be extended in cooperation with agronomic laboratories in African countries for tests on specific plant diseases in relation with prevailing climate conditions.

Background: Optical neuronavigation has been established as a reliable and effective adjunct to many neurosurgical procedures. Operations such as asleep deep brain stimulation (aDBS) benefit from the potential increase in accuracy that these systems offer. Built into these technologies is a degree of tolerated error that may exceed the presumed accuracy resulting in suboptimal outcomes. Objective: The objective of this study was to identify an underlying source of error in neuronavigation and determine strategies to maximize accuracy. Methods: A Medtronic Stealth system (Stealth Station 7 hardware, S8 software, version 3.1.1) was used to simulate an aDBS procedure with the Medtronic Nexframe system. Multiple configurations and orientations of the Nexframe-Nexprobe system components were examined to determine potential sources of, and to quantify navigational error, in the optical navigation system. Virtual entry point and target variations were recorded and analyzed. Finally, off-plan error was recorded with the AxiEM system and visual observation on a phantom head. Results: The most significant source of error was found to be the orientation of the reference marker plate configurations to the camera system, with the presentation of the markers perpendicular to the camera line of site being the most accurate position. Entry point errors ranged between 0.134 ± 0.048 and 1.271 ± 0.0986 mm in a complex, reproducible pattern dependent on the orientation of the Nexprobe reference plate. Target errors ranged between 0.311 ± 0.094 and 2.159 ± 0.190 mm with a similarly complex, repeatable pattern. Representative configurations were tested for physical error at target with errors ranging from 1.2 mm to 1.4 mm. Throughout data acquisition, no orientation was indicated as outside the acceptable tolerance by the Stealth software. Conclusions: Use of optical neuronavigation is expected to increase in frequency and variety of indications. Successful implementation of this technology depends on understanding the tolerances built into the system. In situations that depend on extremely high precision, surgeons should familiarize themselves with potential sources of error so that systems may be optimized beyond the manufacturer’s built-in tolerances. We recommend that surgeons align the navigation reference plate and any optical instrument’s reference plate spheres in the plane perpendicular to the line of site of the camera to maximize accuracy.

Counterfeiting is a growing issue and causes economic losses. Fluorescent inks containing In(Zn)P/ZnS/DDT colloidal nanoparticles are formulated and combined with a convenient optical device for authentication. The particle size and fluorescent colors of the colloidal nanoparticles were tuned by adjusting the reaction temperature. The particle stability and brightness were improved by the addition of dodecanethiol, coating the particle surface with an organic shell. Security patterns were printed on various substrates by applying the screen-printing technique. The patterns were invisible under daylight but observable under UV-light illumination, displaying five different emission colors. By adjusting the concentration of the nanoparticles in the ink, the security patterns were made almost not observable under UV-light illumination but clearly identified by a commercial fiber optics-based spectrometer and a handheld optical device, called a Quantag sensor that was developed in-house. Furthermore, the spectral signatures of barely noticeable patterns are unambiguously validated by the Quantag sensor. Accordingly, low cost and easily applicable anticounterfeiting technology powered by custom-formulated fluorescent inks and a handheld optical instrument are developed to authenticate valuable documents and products.

In this study, a portable optical instrument was designed and developed for real-time nondestructive determination of fruit ripeness. A prototype of the instrument using inexpensive parts was developed and calibrated for apple ripeness detection based on moisture content, soluble solids content, pH, and firmness. An array of six optical point sources (light-emitting diodes (LEDs) that emit light at 520-, 670-, 920-, 970-, 1050-, and 1320-nm wavelengths) were selected using visible/near infrarred (Vis/NIR) spectral analysis on apple samples. The instrument was equipped with optical fibers, optical sensors, and an Arduino board for sending and receiving the waves and processing the received signals, as well as controlling the operation of the instrument. The decision tree method was utilized to create a classification model for training the instrument to classify ripe and unripe apples. Test results showed acceptable performance of the developed instrument for apple ripeness estimation and proved useful in classifying fruits into ripe and unripe groups based on their internal quality.

Industry and governments have deployed computer vision models to make high-stake decisions in society. While they are often presented as neutral and objective, scholars have recognized that bias in these models might lead to the reproduction of racial, social, cultural and economic inequity. A growing body of work situates the provenance of bias in the collection and annotation of datasets that are needed to train computer vision models. This article moves from studying bias in computer vision models to the agency that is commonly attributed to them: the fact that they are universally seen as being able to make biased decisions. Building on the work of Bruno Latour and Jonathan Crary, the authors discuss computer vision models as agential optical instruments in the production of contemporary visuality. They analyse five interconnected research steps – task selection, category selection, data collection, data labelling and evaluation – of six widely cited benchmark datasets, published during a critical stage in the development of the field (2004–2020): Caltech 101, Caltech 256, PASCAL VOC, ImageNet, MS COCO and Google Open Images. They found that, despite all sorts of justifications, the selection of categories is not based on any general notion of visuality, but depends heavily upon perceived practical applications, the availability of downloadable images and, in conjunction with data collection, favours categories that can be unambiguously described by text. Second, the reliance on Flickr for data collection introduces a temporal bias in computer vision datasets. Third, by comparing aggregate accuracy rates and ‘human’ performance, the dataset papers introduce a false dichotomy between the agency of computer vision models and human observers. In general, the authors argue that the agency of datasets is produced by obscuring the power and subjective choices of its creators and the countless hours of highly disciplined labour of crowd workers.

Dielectric reflectors are the passive components that have their potential demands for various purposes, such as back-end reflector in solar cells, the band pass filters in optical instruments, thermal reflector and so on. Though well-established techniques for manufacturing such reflectors are available, the demand for their low-cost production with a minimum number of coatings has attracted the attention of the scientific community. In this framework, this paper addresses the process optimization for the low-cost and rapid fabrication of dielectric TiO2/SiO2 reflectors with 100% reflectance. Numerous studies are carried out to explore the structural, morphological, and optical characteristics of reflectors. We summarize that the desired reflection band of a selective-wavelength range can be realized by varying the precursor and catalyst concentrations, annealing cycle, and the spin rate. With this, we noticed the shifting of reflection window from the visible (Vis) to near-infrared (NIR) wavelength region using reflectors of merely 2.5 stacks of TiO2/SiO2 films. We also performed the thermal response of the reflector by radiating an infrared light source and observed an exceptional performance indicating its thermal shielding application.

The use of three-dimensional (3D) optical instruments to measure soft tissue facial characteristics is increasing, but systematic assessments of their reliability, practical use in research and clinics, outcome measurements, and advantages and limitations are not fully established. Therefore, a review of the current literature was performed on the reliability of facial anthropometric measurements obtained by 3D optical facial reproductions as compared to conventional anthropometry or other optical devices. The systematic literature search was conducted in electronic databases following the PRISMA guidelines (PROSPERO registration: CRD42018085473). Overall, 815 studies were identified, with 27 final papers included. Two meta-analyses were conducted. Tested devices included conventional cameras, laser scanning, stereophotogrammetry, and structured light. Studies measured living people or inanimate objects. Overall, the optical devices were considered reliable for the measurement of linear distances. Some caution is needed for surface assessments. All instruments are suitable for the analysis of inanimate objects, but fast scan devices should be preferred for living subjects to avoid motion artefacts in the orbital and nasolabial areas. Prior facial landmarking is suggested to improve measurement accuracy. Practical needs and economic means should direct the choice of the most appropriate instrument. Considering the increasing interest in surface-to-surface measurements, fast scan devices should be preferred, and dedicated protocols devised.

Literacy skill is needed in the 21st century learning, whereas research about the implementation of Problem Based Learning-Science Technology Engineering and Mathematics (PBL-STEM) to develop students’ ability of scientific literacy is still limited. This research purposed to compare students’ scientific literacy competencies domain improvement through PBL-STEM in the topic of optical instrument. The quasi-experiment non-equivalent group design involved the students of Senior High School 9 Malang Indonesia in three classes called PBL-STEM, PBL, and control class. PBL-STEM class made three products, which were camera obscura, magnifier, and binoculars, which were presented with posters and reports. The PBL class, on the other hand, only made binoculars and presented their work briefly. Scientific Literacy Ability Test was used with 0.88 Cronbach’s alpha reliability. Data analysis with one-way ANOVA, post hoc Tukey test, N-gain, and Cohen’s effect size was conducted. The result showed that three classes had a significantly different ability in scientific literacy. Scientific literacy competencies domain of PBL-STEM was the highest, while PBL class is higher than the control class. The improvement of both PBL-STEM and PBL belonged in medium category, whereas the improvement in the control class was in low category. The effect of the operational implementation of PBL-STEM and PBL pair yielded large result, and both PBL-STEM and control and PBL and control pairs yielded very large category in the improvement of students’ scientific literacy.

Studies of the upper atmosphere have to be performed using optical photometric and spectrometric means. Modern devices allow precise photometry of the glow of the night atmosphere — airglow — with high temporal spatial and spectral resolution. As a result, the obtained airglow parameters make it possible to determine the physicochemical properties of the upper atmosphere and observe their variation under the influence of various factors. The National Heliogeophysical Complex, which is being created in Eastern Siberia, is therefore to include a certain set of modern optical instruments. The paper presents the main phenomena that will be investigated by the optical instruments of the complex, provides information on their composition and scientific goals, presents the results of preliminary studies performed using a prototype of the instruments. As a result of the studies, the presence of a significant (about 10 m/sec) vertical wind at various altitudes (100 and 250 km) was established, the importance of taking into account the vertical wind to study the vertical dynamics of the charged component was demonstrated. The long-term dynamics of the vertical wind at an altitude of about 100 km has a pronounced seasonal variations and the absence of diurnal variations, whereas the dynamics of the vertical wind at an altitude of 250 km has a pronounced diurnal variations, which is mostly clearly defined in winter. This suggests the presumed presence of vertical circulation cells at various altitude levels. The possibilities of optical stereoscopy and differential image analysis methods are demonstrated, as applied to the study of fast luminous formations and conducting active ground and space experiments to modify Earth's ionosphere. We report the results of the determination of a three-dimensional picture of a long-lived meteor track with the use of two wide-angle cameras. We propose an algorithm that allows us to get a stereo image of events occurring in the upper atmosphere, recorded simultaneously from different observation points. The joint work of the tools of this complex and the development of cooperation with third-party organizations are shown to be a good enough direction for further study of the vertical dynamics of Earth’s upper atmosphere and space weather phenomena.