Optical Principles Research Articles

Electrically adjustable location of a projected image in augmented reality via a liquid-crystal lens.

An augmented reality (AR) system involving the electrically tunable location of a projected image is implemented using a liquid-crystal (LC) lens. The projected image is either real or virtual. By effectively doubling the LC lens power following light reflection, the position of a projected virtual image can be made to vary from 42 to 360 cm, while the tunable range for a projected real image is from 27 to 52 cm on the opposite side. The optical principle of the AR system is introduced and could be further developed for other tunable focusing lenses, even those with a lower lens power. The benefits of this study could be extended to head-mounted display systems for vision correction or vision compensation. We believe that tunable focusing LC optical elements are promising developments in the thriving field of AR applications.

NOMAD spectrometer on the ExoMars trace gas orbiter mission: part 1--design, manufacturing and testing of the infrared channels.

NOMAD is a spectrometer suite on board ESA's ExoMars trace gas orbiter due for launch in January 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 dayside and nightside, and during solar occultations. In this paper, the design, manufacturing, and testing of the two infrared channels are described. We focus upon the optical working principle in these channels, where an echelle grating, used as a diffractive element, is combined with an acousto-optical tunable filter, used as a diffraction order sorter.

Shining a light on Harriot and Galileo: On the mechanics of reflection and projectile motion

Decades before Newton’s Principia ushered in the age of modern science, Aristotelian physics faced a serious challenge against its weakest point, in the quest to construct a new theory of projectile motion. Yet how were such new principles of motion conceived, without reference to an established theory of mechanics? This paper explores the conceptual space between the rejection of Aristotle’s physics and the appearance of Newton’s physics in which people such as Harriot and Galileo sought new ways to understand mechanical phenomena. This paper seeks to show that both Harriot and Galileo looked to the (early seventeenth-century) zeitgeist of accepting the law of reflection as a law of oblique projection-rebound for all material bodies, for their foundational (non-Aristotelian) conceptual resource. The kinematics and dynamics of light’s compound, oblique motion had been developed over centuries within optics, and constituted the ‘ideal’ resource for novel analyses of oblique projectile motion. Whereas Harriot’s inclusion of air resistance restricted the generalizability of optical principles to his simplest case, the upright parabola, Galileo’s idealized analysis of projectile motion in a vacuum represented all cases of projectile motion as upright parabolas. He was thus able to generalize these optical principles to projectile motion per se.

Specular reflectance (SR) and attenuated total reflectance (ATR) infrared (IR) spectroscopy of transparent flat glass surfaces: A case study for soda lime float glass

This paper describes the optical principles of specular reflection (SR) and attenuated total reflection (ATR)-infrared (IR) spectroscopy, both of which are useful methods for glass surface analyses. It should be noted that the shape, position, and relative intensity of peaks in reflectance spectra vary drastically depending on the IR incidence angle as well as the probe method (SR vs. ATR). For example, in SR-IR analyses of soda lime glass, the Si–O–Si stretch band shows a blue-shift from its original position and a new peak grows at ~1200cm−1 as the IR incidence angle increases. In contrast, the Si–O–Si stretch band appears significantly red-shifted from its original position in the ATR-IR spectra of soda lime glass. SR-IR spectra of thin and flat samples can contain transmission spectral features, due to the reflection from the backside, in the region where the bulk absorption coefficient is low. These artifacts are due to the complex nature of refractive index and should not be interpreted as new peaks or new chemical states of soda lime glass surfaces. An ATR-IR analysis to probe hydrous species in glass surface is demonstrated using two ATR crystals with different refractive indices.

Three‐dimensional information storage of polymer doped with nano‐silver

ABSTRACTFemtosecond laser three‐dimensional optical storage is an important method to realize high‐density optical storage. Based on femtosecond laser microexplosion optical information storage principle, the information was written and readout with Titanium sapphire femtosecond pulsed laser, the storage experiments were performed in the polymer doped with nano‐silver, 11‐layer optical information storage was achieved, the information point spacing was 2 μm and the information layer spacing 14 μm. The experiments showed that polymeric materials doped with nano‐silver can be used for femtosecond laser three‐dimensional optical storage and this had laid a solid foundation for high density and ultrahigh density optical information storage. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2662–2665, 2015

Design of compact LED free-form optical system for aeronautical illumination.

A type of runway centerline light is designed for the application of light-emitting diode (LED) aeronautical illumination. A total internal reflection collimating lens and an integrated prism are designed, respectively, to meet the intensity distribution of International Convention on Civil Aviation (ICAO) regulations. The principle of geometric optics is adopted to construct the free-form surfaces of a collimating lens, which is simple. Different variations are used in the process of free-form surface calculation. An integrated prism with a diffuser is used for uniformly diffusing rays and then decreasing the central maximum intensity to avoid glare. The structure of the optical system is compact. Computer simulation results show that an optical efficiency of 79.2% is achieved for a 1 mm×1 mm LED source. Tolerance analysis is carried out to determine tolerance limits of manufacture and installation errors. To verify the optical performance of the proposed runway centerline light, the practical illumination distribution is measured by using Cree XP-E2 LED, which can comply with ICAO regulations.

Process analytical technologies in food industry - challenges and benefits: A status report and recommendations.

Process analytical technologies in food industry - challenges and benefits: A status report and recommendations.

Optics demonstrations using cylindrical lenses

In this paper we consider the main properties of cylindrical lenses and propose several demonstrational experiments that can be performed with them. Specifically we use simple glasses full of water to demonstrate some basic geometrical optics principles and phenomena. We also present some less standard experiments that can be performed with such cylindrical lenses. All proposed experiments are accessible and attractive.

Structural design and image processing of a spherical artificial compound eye

This manuscript presents a design method and corresponding image processing algorithms of a spherical artificial compound eye. The artificial compound eye is composed of multi-dimensional sub-eye imaging channels pointing to different directions. By using the principle of geometrical optics and imaging optics, the design method of the multi-dimensional imaging structure was analyzed. To satisfy the practical requirement of the structure, the image processing algorithm based on the segmentation rotation projection technology was studied. In order to validate the above design method and image processing algorithm, a spherical compound eye consisting of 37 imaging channels was fabricated and the corresponding imaging experiments were carried out. The results show that the field of view (FOV) of the imaging structure is up to 118° and the structure meets the practical requirements.

All-optical background subtraction readout method for bimaterial cantilever array sensing.

Optical readout method plays a critical role in bimaterial cantilever array sensing system. The common optical readout methods are based on spectral plane filtering. In the paper an all-optical background subtraction readout approach inspired by total reflection and optical lever principle is presented for the bimaterial cantilever array sensing. Comparing with the spectral plane filtering methods the proposed approach eliminates digital subtraction operation by using optical total reflection instead of digital subtraction and avoids spectral filtering operation. An all-optical background subtraction directly-view infrared sensing system was developed to evaluate the approach. The infrared target can be directly acquired by the visible light CCD. The experimental results and analysis show its unique advantages.

Assessment of minimum permissible geometrical parameters of a near-to-eye display.

Light weight and small dimensions are some of the most important characteristics of near-to-eye displays (NEDs). These displays consist of two basic parts: a microdisplay for generating an image and supplementary optics in order to see the image. Nowadays, the pixel size of microdisplays may be less than 4μm, which makes the supplementary optics the major factor in defining restrictions on a NED dimensions or at least on the distance between the microdisplay and the eye. The goal of the present work is to find answers to the following two questions: how small this distance can be in principle and what is the microdisplay maximum resolution that stays effective to see through the supplementary optics placed in immediate vicinity of the eye. To explore the first question, we consider an aberration-free magnifier, which is the initial stage in elaboration of a real optical system. In this case, the paraxial approximation and the transfer matrix method are ideal tools for simulation of light propagation from the microdisplay through the magnifier and the human eye's optical system to the retina. The human eye is considered according to the Gullstrand model. Parameters of the magnifier, its location with respect to the eye and the microdisplay, and the depth of field, which can be interpreted as the tolerance of the microdisplay position, are determined and discussed. The second question related to the microdisplay maximum resolution is investigated by using the principles of wave optics.

Back scattering interferometry revisited – A theoretical and experimental investigation

A refractive index based detector based on so called back scattering interferometry (BSI) has been described in the literature as a unique optical method for measuring biomolecular binding interactions in solution. In this paper, we take a detailed look at the optical principle underlying this technique to understand fully the constituents and behaviour of the fringe patterns generated. The simulated results are compared and validated with experimental measurements. Hereby, we show that BSI does not operate as a resonant cavity as often stated in the literature. Recently, we have questioned the claims made that BSI in general can be used to measure molecular bindings. Here we explore this topic further in three cases using fluorescence spectroscopy as a reference method. Finally, we explore whether refractive index sensing can be used to measure the enzymatic phosphorylation of glucose to glucose-6-phosphate.

Optimized lens design for small angle uniform illumination from an extended source

Based on the edge-ray principle of non-imaging optics, an optical design method for a lens producing small angle, uniform illumination from a high-power light-emitting diode light source has been developed. The energy correspondence between the light-emitting diode light source and the illuminance distribution on a target plane was established, and a number of discrete points for freeform profile curves which could achieve uniform illumination over a small angle were calculated and fitted to create a lens. Finally, simulations were performed using software. The influence of the size of light source on the emitting angle under uniform illumination was also investigated. The results show that the optical system can achieve uniform illumination with an extended source, the divergence angle being controlled within a minimum range by the optical design method.

Investigation and simulation of photonic crystal directional coupler switch

The photonic crystal optical switch is one of the most important applications of photonic crystals in telecommunication networks. Switching is a main process in digital computers and signal processing systems. The growth of optical signal processing systems draws particular attention to the design of ultra-fast optical switches. In this reported work, first a directional coupler switch based on photonic crystals is designed and the linear state has been analysed and simulated. Then, the principles of nonlinear optics are used to perform optical switching at a wavelength of 1550 nm by COMSOL Multiphysics in micron dimension. The dielectric rods of this photonic crystal lattice are made of AlGaAs. The central row is an important factor for attaining the required power in nonlinear switching performance. Finally, the radius of rods in the central nonlinear row is changed several times and the results are compared with each other. In this switch, the output power ratio, called the extinction ratio, and the required refractive index change for the nonlinear status are taken into account. The former is for the evaluation of directional coupler efficiency and the latter is generally an important factor in optical nonlinear switches.

Active Learning in Fiber Optic Course Using Applied Education Game

The strategy or method used in the learning process affect the result of learning. The wrong strategy will make students feel bored and lazy to attend class. In general, the learning method that is mostly used in universities around the world is center learning where the lecturer will give speak and the students will listen and take notes. This study was done in two classes i.e. a master’s degree module and a bachelor degree course in the Department of Electrical, Electronics and System Engineering, National University of Malaysia. A total of 31 students were used as respondents (sample) that consists of 61.3% male and 38.7% female, where 41.9% of them are doing bachelor degrees and the other 58.1% doing master’s degrees. This research show that 45% of respondents strongly agree and 55% of respondents agree that education games are more enjoyable than conventional lectures. 68% of respondents strongly agree and 29% of respondents agree that they like to study fiber optic using games. Furthermore, 58% of respondents strongly agree and 39% of respondents agree that they could remember fiber optic principles using the educational game.

Processes for design, construction and utilisation of arrays of light-emitting diodes and light-emitting diode-coupled optical fibres for multi-site brain light delivery.

Optogenetics enables light to be used to control the activity of genetically targeted cells in the living brain. Optical fibers can be used to deliver light to deep targets, and LEDs can be spatially arranged to enable patterned light delivery. In combination, arrays of LED-coupled optical fibers can enable patterned light delivery to deep targets in the brain. Here we describe the process flow for making LED arrays and LED-coupled optical fiber arrays, explaining key optical, electrical, thermal, and mechanical design principles to enable the manufacturing, assembly, and testing of such multi-site targetable optical devices. We also explore accessory strategies such as surgical automation approaches as well as innovations to enable low-noise concurrent electrophysiology.

The Optical Measurement and Quantitative Analysis of Algesia in Spodoptera litura Larva

Muscle vibration measurement has long been an unique scientific study, in general, and the direct reaction of animals to feel pain (algesia), either from vascular or muscle contraction, is a complex perceptual experience. Thus this paper proposes a way to measure animal algesia quantitatively, by measuring the changes in muscle vibration due to a pinprick on the surface of the skin of a Spodoptera litura larva. Using the laser optical triangulation measurement principle, along with a CMOS image sensor, linear laser, software analysis, and other tools, we quantify the subtle object point displacement, with a precision of up to $10{\mu}m$ , for our chosen Spodoptera litura larva animal model, in which it is not easy to identify the tiny changes in muscle contraction dynamics with the naked eye. We inject different concentrations of formalin reagent (empty needle, 12% formalin, and 37% formalin) to obtain a variety of different muscle vibration frequencies as the experimental results. Because of the high concentrations of reagent applied, we see a high frequency shift of muscle vibration, which can be presented as pain indices, so that the algesia can be quantified.

μ-biomimetic flow-sensors—introducing light-guiding PDMS structures into MEMS

In the area of biomimetics, engineers use inspiration from natural systems to develop technical devices, such as sensors. One example is the lateral line system of fish. It is a mechanoreceptive system consisting of up to several thousand individual sensors called neuromasts, which enable fish to sense prey, predators, or conspecifics. So far, the small size and high sensitivity of the lateral line is unmatched by man-made sensor devices. Here, we describe an artificial lateral line system based on an optical detection principle. We developed artificial canal neuromasts using MEMS technology including thick film techniques. In this work, we describe the MEMS fabrication and characterize a sensor prototype. Our sensor consists of a silicon chip, a housing, and an electronic circuit. We demonstrate the functionality of our -biomimetic flow sensor by analyzing its response to constant water flow and flow fluctuations. Furthermore, we discuss the sensor robustness and sensitivity of our sensor and its suitability for industrial and medical applications. In sum, our sensor can be used for many tasks, e.g. for monitoring fluid flow in medical applications, for detecting leakages in tap water systems or for air and gas flow measurements. Finally, our flow sensor can even be used to improve current knowledge about the functional significance of the fish lateral line.

Concept of a multichannel spin-resolving electron analyzer based on Mott scattering.

The concept of a multichannel electron spin detector based on optical imaging principles and Mott scattering (iMott) is presented. A multichannel electron image produced by a standard angle-resolving (photo) electron analyzer or microscope is re-imaged by an electrostatic lens at an accelerating voltage of 40 kV onto the Au target. Quasi-elastic electrons bearing spin asymmetry of the Mott scattering are imaged by magnetic lenses onto position-sensitive electron CCDs whose differential signals yield the multichannel spin asymmetry image. Fundamental advantages of this concept include acceptance of inherently divergent electron sources from the electron analyzer or microscope focal plane as well as small aberrations achieved by virtue of high accelerating voltages, as demonstrated by extensive ray-tracing analysis. The efficiency gain compared with the single-channel Mott detector can be a factor of more than 10(4) which opens new prospects of spin-resolved spectroscopies in application not only to standard bulk and surface systems (Rashba effect, topological insulators, etc.) but also to buried heterostructures. The simultaneous spin detection combined with fast CCD readout enables efficient use of the iMott detectors at X-ray free-electron laser facilities.

ADVANCES IN FILLER DISPERSION MEASUREMENTS

ABSTRACT It is well documented throughout the literature that filler dispersion significantly influences rubber performance. However, there is no single experimental method to measure dispersion precisely. By presenting new experimental techniques and reviewing several existing ones that measure dispersion at different length scales, steps are undertaken to close the knowledge gap in understanding dispersion. Some methods, such as electrical resistivity, are able to probe only the conductive carbon black network; the others take into consideration all compounding ingredients including mineral fillers and chemicals. One of the techniques discussed in more detail will be surface profilometry, which is based on the noncontact optical interferometry principle. The other technique reviewed in more detail is based on high-resolution field emission scanning electron microscopy imaging. These different techniques were employed to evaluate multiple rubber compounds with varying dispersion levels, and the data will be presented and discussed.