Basic Optical Principles Research Articles

Simultaneous Multifocal Plane Fourier Ptychographic Microscopy Utilizing a Standard RGB Camera.

Fourier ptychographic microscopy (FPM) is a computational imaging technology that can acquire high-resolution large-area images for applications ranging from biology to microelectronics. In this study, we utilize multifocal plane imaging to enhance the existing FPM technology. Using an RGB light emitting diode (LED) array to illuminate the sample, raw images are captured using a color camera. Then, exploiting the basic optical principle of wavelength-dependent focal length variation, three focal plane images are extracted from the raw image through simple R, G, and B channel separation. Herein, a single aspherical lens with a numerical aperture (NA) of 0.15 was used as the objective lens, and the illumination NA used for FPM image reconstruction was 0.08. Therefore, simultaneous multifocal plane FPM with a synthetic NA of 0.23 was achieved. The multifocal imaging performance of the enhanced FPM system was then evaluated by inspecting a transparent organic light-emitting diode (OLED) sample. The FPM system was able to simultaneously inspect the individual OLED pixels as well as the surface of the encapsulating glass substrate by separating R, G, and B channel images from the raw image, which was taken in one shot.

Plasmon-enhanced second harmonic generation of metal nanostructures.

As the most common nonlinear optical process, second harmonic generation (SHG) has important application value in the field of nanophotonics. With the rapid development of metal nanomaterial processing and chemical preparation technology, various structures based on metal nanoparticles have been used to achieve the enhancement and modulation of SHG. In the field of nonlinear optics, plasmonic metal nanostructures have become potential candidates for nonlinear optoelectronic devices because of their highly adjustable physical characteristics. In this article, first, the basic optical principles of SHG and the source of surface symmetry breaking in metal nanoparticles are briefly introduced. Next, the related reports on SHG in metal nanostructures are reviewed from three aspects: the enhancement of SHG efficiency by double resonance structures, the SHG effect based on magnetic resonance and the harmonic energy transfer. Then, the applications of SHG in the sensing, imaging and in situ monitoring of metal nanostructures are summarized. Future opportunities for SHG in composite systems composed of metal nanostructures and two-dimensional materials are also proposed.

Comparative evaluation of the clinical performance of conventional and extended depth of focus monofocal intraocular lenses (systematic review)

A systematic review was performed in PubMed using the following keywords monofocal IOLs, monofocal IOLs with extended depth of focus (sharpness), EDOF, cataract phacoemulsification, visual acuity, and quality of life. Studies were selected in accordance with the criteria for prospective or retrospective studies. In a comparative analysis of clinical efficacy, the results of binocular IOL implantation and lens material from the same manufacturer were analyzed as the main sources. In total, 234 studies were analyzed using systematic review filters and authors knowledge of the topic. The duration of the retrospective analysis was 8 years (20172023). A total of 234 papers were analyzed over the last 8 years (20172023), further using systematic review filters and the authors knowledge of the topic.
 Data obtained indicated that traditional monofocal IOLs acted like bifocal lenses because they formed two main focal points for far and near vision, which did not provide the required level of visual acuity at an intermediate distance. The basic optical principle of EDOF (extended depth of focus) was to create a focal point for distance vision and an elongated focal point to increase the depth of field near and at intermediate distances. The results of the literature analysis indicated that the use of EDOF (compared with monofocal IOL) was associated with a higher level of visual acuity at intermediate and near distances and comparable distance visual acuity and increased depth of field, which generally provides a more natural range of vision and less use of glasses. Light phenomena, spectacle independence, and patient satisfaction were comparable among EDOF types.
 Given the above advantages, EDOF implantation can be considered a variant of an individual approach to the selection of IOLs, taking into account the possibility of using it in patients whose professional activity is associated with long-term visual work at intermediate distances (e.g., users of personal computers). In the context of the role and place of EDOF in the general system of aphakia correction following cataract phacoemulsification, further accumulation of clinical material is necessary, taking into account the IOL model and patients professional visual activity level.

Basic questions of optics training

«Basic Questions of Optics Training» involves the study of various approaches and strategies for effective teaching of optics to students who do not have prior experience or knowledge in this field. This topic is important because optics is a fundamental aspect of physics and is used in a variety of fields, including medicine, engineering, and telecommunications. The aim of teaching optics from scratch is to help students understand the basic principles of optics and how they are applied in different areas. Some of the key methods used in teaching optics from scratch include using hands-on demonstrations and experiments to help students visualize the concepts, problem-based learning to help students develop critical thinking and problem-solving skills, and the use of technology, such as simulations and interactive software, to enhance the learning experience. Research in this field has focused on identifying effective teaching methods and developing innovative strategies for teaching optics from scratch. The literature on this topic includes studies that explore the use of different teaching methods and technologies, as well as those that investigate the effectiveness of these approaches in enhancing student learning and engagement. Furthermore, the topic of teaching optics from scratch is important for addressing the challenge of increasing diversity and inclusivity in physics education. Many students, particularly those from underrepresented groups, may lack the prior knowledge or background in physics and may face barriers in accessing and succeeding in physics courses. Effective strategies for teaching optics from scratch can help to bridge this gap and provide all students with a strong foundation in physics.

Surgical telescopes: basic optical principles and main features

Surgical telescopes: basic optical principles and main features

Approximation of radial structure of unstable ion-sound modes in rotating magnetized plasma column by eikonal equation

The problem of the correct asymptotic construction of the radial structure of linearly unstable ion-sound electrostatic eigenmodes is studied. The eigenvalue problem with boundary conditions of the first and second kind (electrodynamic and hydrodynamic types) for the oscillations that propagate in a uniform cylindrical column of magnetized plasma along an axial homogeneous magnetic field is formulated. A method for constructing a discrete spectrum of small-scale unstable oscillations of the system based on the basic principles of geometric optics is proposed. The main idea of the method is an explicit idea of the type of boundary conditions - the conductivity and absorbing properties of the wall bounding the plasma cylinder. A dispersion relation for unstable small-scale modes destabilized due to the effects of differential rotation is derived from the Eikonal equation. For the correct construction instability growth rates spectra an universal recipe for the selection of radial wave numbers of small-scale eigenmodes in accordance with any of the types of boundary conditions is proposed.

A design method for direct vision coaxial linear dispersion spectrometers.

A spectrometer design method based on the prism-prism-grating (PPG) dispersion module is proposed in this paper to correct the serious nonlinear dispersion that prism and grating spectrometers and other dispersive spectrometers suffer from. First, we determine the criteria for selecting the optical materials of the PPG module by analyzing the dispersion characteristics of prisms and gratings. Second, a loop traversal algorithm is used to optimize the system structure parameters after selecting optical materials. Next, the direct vision coaxial condition of the PPG module is derived according to basic optical principles and the geometrical relationship between optical elements. Then, the dispersion equation of the PPG module is used to establish the spectral linearity index of the system. Finally, combined with the design index, the structural parameters of the PPG module to meet the linear dispersion requirements are determined. A direct vision coaxial linear dispersion spectrometer is designed and realized under the condition that the working band is 400-990 nm, the deviation angle and offset of the emitted ray with a central wavelength of 695 nm with respect to the optical axis are 0, and the dispersion angle is not less than 15°. The results simulated by ZEMAX show that the actual simulation results are consistent with the theoretical calculation results, the spectral resolution of the spectrometer is less than 1.5 nm, and the spectral smile and keystone are less than 3.89% pixels. In the discussion section, the influences of the dispersion ability of optical materials and the incident angles of prisms and gratings on the spectral dispersion linearity of the PPG module are analyzed and studied. The universality of the spectrometer design method developed in this paper is discussed, and its universality is simulated and verified in the 1000-1600 nm and 1600-2200 nm bands. In addition, some advantages compared with other dispersion structures are analyzed.

Exploring cell and tissue mechanics with optical tweezers.

Cellular and tissue biosystems emerge from the assembly of their constituent molecules and obtain a set of specific material properties. To measure these properties and understand how they influence cellular function is a central goal of mechanobiology. From a bottoms-up, physics or engineering point-of-view, such systems are a composition of basic mechanical elements. However, the sheer number and dynamic complexity of them, including active molecular machines and their emergent properties, makes it currently intractable to calculate how biosystems respond to forces. Because many diseases result from an aberrant mechanotransduction, it is thus essential to measure this response. Recent advances in the technology of optical tweezers have broadened their scope from single-molecule applications to measurements inside complex cellular environments, even within tissues and animals. Here, we summarize the basic optical trapping principles, implementations and calibration procedures that enable force measurements using optical tweezers directly inside cells of living animals, in combination with complementary techniques. We review their versatility to manipulate subcellular organelles and measure cellular frequency-dependent mechanics in the piconewton force range from microseconds to hours. As an outlook, we address future challenges to fully unlock the potential of optical tweezers for mechanobiology.

Role of otoendoscope as a preoperative tool in tympanoplasty

<p class="abstract"><strong>Background:</strong> Chronic suppurative otitis media (CSOM) is one of the common causes for hearing impairment and disability. Despite continuous technical improvement, the basic optical principles and their limitations have remained the same over the past three decades. This study aimed at visualizing and evaluating the middle ear structures with the aid of 0 and 30-degree otoendoscopes preoperatively in cases of chronic suppurative otitis media.</p><p class="abstract"><strong>Methods:</strong> In this prospective study, 70 patients (40 females and 30 males) above the age of 10 years with CSOM were subjected to otoendoscopy using 0- and 30-degree endoscopes. The various middle ear structures and hidden spaces like facial recess, sinus tympani, hypotympanum were visualized preoperatively. </p><p class="abstract"><strong>Results:</strong> Middle ear structures and blind niches were better evaluated preoperatively using 0 and 30-degree otoendoscopes and a definitive operative plan was formulated.</p><p class="abstract"><strong>Conclusions:</strong> Otoendoscopy provided a significant better visualization of all the middle ear structures and various hidden spaces.</p>

Hands-on Curriculum in Optics of Microscopy

ABSTRACT Optics is an important subfield of physics required for instrument design and used in a variety of other disciplines, especially subjects that intersect the life sciences. Students from a variety of disciplines and backgrounds should be educated in the basics of optics to train the next generation of interdisciplinary researchers and instrumentalists who will push the boundaries of discovery or create inexpensive optical-based diagnostics. We present an experimental curriculum developed to teach students the basics of geometric optics, including ray and wave optics. The students learn these concepts in an active, hands-on manner through designing, building, and testing a homebuilt light microscope made from component parts. We describe the experimental equipment and basic measurements students can perform to learn these basic optical principles focusing on good optical design techniques, testing, troubleshooting, and iterative design. Students are also exposed to fundamental concepts of measurement uncertainty inherent in all experimental systems. The project students build is open and versatile to allow advanced projects, such as epifluorescence. We also describe how the equipment and curriculum can be flexibly used for an undergraduate level optics course, an advanced laboratory course, and graduate-level training modules or short courses.

Photochemical On–Off Switching of One-Dimensional Photonic Crystals Consisting of Azo-Functionalized Liquid Crystal Polymer and Polyvinyl Alcohol

One-dimensional (1D) photonic crystals (PCs) are prepared from multi-bilayered films stacked with alternating azo-functionalized liquid crystal polymer (PAz) films and polyvinyl alcohol (PVA) films. Reflection with a wavelength that depends on the thickness of the films is observed, and the reflection can be turned on and off by switching between the two states, based on whether there is a difference in the refractive index between the two films. The refractive index change of PAz can be photochemically caused by a phase transition, based on the alignment states of the liquid crystal (LC). In this review, we focused on an effective photo-induced on–off switching approach in 1D PCs using LC properties and described the basic optical and chemical principles, the experimental results, and further optimizations.

Grundlagen der Optik

As an ophthalmologist, it is very important to know whether limited vision is caused by refractive problems or whether there is another pathology behind it. That's why refraction plays a key role at the beginning of every eye examination. Therefore, it is important to know the basic principles of optics. When fitting spherical and cylindrical lenses, it is interesting to know which properties the respective lenses have. One should also be aware of the optical paths and refraction laws when fitting spectacle lenses and prisms. In addition, when prescribing spectacle lenses, one should consider changes in the distance between corneal apex and spectacle lens and know conversions for the strength of contact lenses. Only if you have a deeper understanding of refraction and correction of refractive errors you will be able to adjust optimal vision aids for more difficult refraction conditions.

Imaging Through Fire Using Narrow-Spectrum Illumination.

This paper demonstrates a simple method to enhance visibility through clean-burning flames that allows new opportunities to perform qualitative and quantitative optical metrology in fire research. The method combines narrow-spectrum, blue illumination and matched optical filters to reduce the influence of optical emissions from a glowing hot target and a large natural gas diffusion flame. The paper describes how the required illumination strength and filtering can be estimated from basic combustion and optical principles. Compared to white light, the required illumination to detect objects 26 engulfed in flames with this method is reduced by a factor of 104. A series of experiments are conducted to determine the effectiveness of this method, successfully demonstrating the ability to take images of objects in natural gas fires up to 1000 kW using 200 W of illumination power.

Методика автоматизированного измерения пространственных распределений плотности тока технологических электронных пучков

The importance of developing an automated technique for measuring spatial current density distributions of process electron beams is shown. It has been proven that immediate methods based on directly measuring the electron beam current components are of the main interest for constructing monitoring and control systems in electron beam-based process installations, because it is only these methods that can provide reliable information about the spatial distribution of current density. Experimental investigations of spatial current density distributions for electron beams with power capacities up to 6 kW have been carried out. The distributions obtained by the probe method are analyzed, and their deviations from the normal distribution function and axial symmetry are revealed. The limitations of the probe method based on the heat flux density and beam power are determined, and an express method for measuring the current density radial distribution over the electron beam cross section is proposed, which is based on using the direct edge method and on numerically processing the time dependences of the current. A scheme for quantifying the radial distribution of the electron beam current density is given. The possibility of applying the proposed technique for measuring the characteristics of beams with a power density up to 1.8∙104 W/cm2 using a copper collector has been experimentally confirmed. It is shown that the developed technique is necessary for mathematically reconstructing the current density volume distribution using the basic principles of electronic optics.

Fast auto-focus scheme based on optical defocus fitting model

An optical defocus fitting model-based (ODFM) auto-focus scheme is proposed. Considering the basic optical defocus principle, the optical defocus fitting model is derived to approximate the potential-focus position. By this accurate modelling, the proposed auto-focus scheme can make the stepping motor approach the focal plane more accurately and rapidly. Two fitting positions are first determined for an arbitrary initial stepping motor position. Three images (initial image and two fitting images) at these positions are then collected to estimate the potential-focus position based on the proposed ODFM method. Around the estimated potential-focus position, two reference images are recorded. The auto-focus procedure is then completed by processing these two reference images and the potential-focus image to confirm the in-focus position using a contrast based method. Experimental results prove that the proposed scheme can complete auto-focus within only 5 to 7 steps with good performance even under low-light condition.

Basic Optical and Corpuscular Physical Principles for Lab-on-a-Chip Constructions with Multiple Non-Optical Physical Signal Conversions into OAS (Optical Analytical Signals) in Multiparametric Experimental Biomedical Engineering Customizations

Basic Optical and Corpuscular Physical Principles for Lab-on-a-Chip Constructions with Multiple Non-Optical Physical Signal Conversions into OAS (Optical Analytical Signals) in Multiparametric Experimental Biomedical Engineering Customizations

Optical design and fabrication of palm/fingerprint uniform illumination system with a high-power near-infrared light-emitting diode.

In order to meet the requirements of uniform illumination for optical palm/fingerprint instruments and overcome the shortcomings of the poor uniform illumination on the working plane of the optical palm/fingerprint prism, a novel secondary optical lens with a free-form surface, compact structure, and high uniformity is presented in this paper. The design of the secondary optical lens is based on emission properties of the near-infrared light-emitting diode (LED) and basic principles of non-imaging optics, especially considering the impact of the thickness of the prism in the design. Through the numerical solution of Snell's law in geometric optics, we obtain the profile of the free-form surface of the lens. Using the optical software TracePro, we trace and simulate the illumination system. The results show that the uniformity is 89.8% on the working plane of the prism, and the test results show that the actual uniformity reaches 85.7% in the experiment, which provides an effective way for realizing a highly uniform illumination system with high-power near-infrared LED.

Seismic imaging of the Sun's far hemisphere and its applications in space weather forecasting.

The interior of the Sun is filled acoustic waves with periods of about 5 min. These waves, called “p modes,” are understood to be excited by convection in a thin layer beneath the Sun's surface. The p modes cause seismic ripples, which we call “the solar oscillations.” Helioseismic observatories use Doppler observations to map these oscillations, both spatially and temporally. The p modes propagate freely throughout the solar interior, reverberating between the near and far hemispheres. They also interact strongly with active regions at the surfaces of both hemispheres, carrying the signatures of said interactions with them. Computational analysis of the solar oscillations mapped in the Sun's near hemisphere, applying basic principles of wave optics to model the implied p modes propagating through the solar interior, gives us seismic maps of large active regions in the Sun's far hemisphere. These seismic maps are useful for space weather forecasting. For the past decade, NASA's twin STEREO spacecraft have given us full coverage of the Sun's far hemisphere in electromagnetic (EUV) radiation from the far side of Earth's orbit about the Sun. We are now approaching a decade during which the STEREO spacecraft will lose their farside vantage. There will occur significant periods from thence during which electromagnetic coverage of the Sun's far hemisphere will be incomplete or nil. Solar seismology will make it possible to continue our monitor of large active regions in the Sun's far hemisphere for the needs of space weather forecasters during these otherwise blind periods.

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.