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The enhancement of Goos-Hanchen shift of graphene coated on a truncated one-dimensional photonic crystal is proposed and theoretically investigated. The proposed band-gap configuration featuring highly electric field enhancement and confinement on the graphene surface enables the excitation of Bloch surface wave mode. By taking full advantages of the remarkable optical properties of the excited optical surface wave mode, a large phase variation appears near the band-gap of the proposed structure, leading to a dramatically enhanced Goos-Hanchen shift. Leveraging this giant Goos-Hanchen shift, the sensing capability of this proposed structure is discussed, implicating a superior performance in Goos-Hanchen shift sensing applications.

Ambient light (AML) limits the usage of absorption spectroscopy to strictly-controlled environments due to its impact on the quality of the signals. In medical applications for Optical instruments that require high reliability and validity results, it is indispensable to control AML impact. In this work, we present a multi-wavelength optical acquisition method, here called SHADE.The technique increases the quality of the optical signals, dynamically assesses AML, and enables mitigating the AML influence on the data. Our proposed technique involves four primary functions: (1) Multiplexing/demultiplexing of target wavelengths using a frequency-division method; (2) Robust signal recovery using inverse notch filters; (3) Concurrent AML intensity estimation; (4) A simple post-processing (offline) suppression of AML interference. We introduce the mathematical framework of SHADE to demonstrate the theoretical scope and limitations. SHADE was also experimentally tested by using a digital signal processing board under different conditions.The results confirmed the performance of the AML reconstruction and the potential of such a method for further improvements of the signal quality. This work was financially supported by the Research Council of Norway and Oslo Metropolitan University/Faculty ofTechnology, Art and Design. The funded Project is “Patient-Centric Engineering in Rehabilitation (PACER)” and project No. is 273599.

Ultra-low reflectance materials are widely applied in the solar energy harvesting, the space instruments, spectrometers and terrestrial telescopes. The ultra-low reflection material of CuO/Cu in UV–vis is designed and achieved via orderly growing ultralong CuO nanowires on copper sheet, constructing the ultra-thick and vertically aligned array. The reflectance of the resultant samples range from 0.078% to 5.31%, via controlling the thickness and density of CuO nanowire arrays at different growth temperature and time. Among them, the blackest sample obtains an ultra-low reflectance of 0.078% in 200–700 nm region and 0.0235% within the 500 nm–600 nm range. The ultra-low reflectivity of CuO nanowire arrays come from the following reasons: 1. the array is so thick and dense that the light can be multiply reflected and absorbed while propagates deep into the interspace of the nanowires, leading to an excellent light trapping. 2. The array can be regarded as air-filled gradient refractive index medium, which is also in favor of the low reflection. The CuO nanowire array represents a new-family of ultra-low reflection material in UV–vis. It will improve the sensitivity of optical instruments efficiently by blackening the inner-wall of drawtube or sample compartment for reducing stray light. Keywords: Ultra-low reflectance materials, Vertically aligned, Light trapping, Solar energy harvesting, Optical instruments

The productivity rate of a manufacturing process is limited by the speed of any measurement processes at the quality control stage. Fast and effective in-line measurements are required to overcome this limitation. Optical instruments are the most promising methods for in-line measurement because they are faster than tactile measurements, able to collect high-density data, can be highly flexible to access complex features and are free from the risk of surface damage. In this paper, a methodology for the development of fast and effective in-line optical measuring instruments for the surfaces of parts with millimetre- to micrometre-size is presented and its implementation demonstrated on an industrial case study in additive manufacturing. Definitions related to in-line measurement and barriers to implementing in-line optical measuring instruments are discussed.

Digital Image Correlation monitoring of the surface strains, microscopic in-situ observations of the micro-damage on the specimen edge and Acoustic Emission (AE) are utilized simultaneously during tension tests of quasi-isotropic carbon fibre reinforced polymer composites. It is found that the cluster analysis for characteristic parameters of AE events (the main being the signal amplitude and frequency) does not unambiguously identify the type of damage which causes the event. With optical instruments, it is observed that the signatures of AE events depend on the position of the ply where damage happens and on the ply orientation (90 degrees vs 45 degrees). Robust evidences for the variations in AE characteristics of damage modes in different lay-ups are presented. AE events, originated from surface cracks, have high amplitude and low frequency, whereas AE events, originated from transverse cracks in the inner plies, have low amplitude and high frequency characteristics. Any conclusion for fibre breaks are not reached in this study. Therefore, measurements in this study rather point out that the AE events, which could be interpreted as fibre breaks because of their high frequency characteristics, as optical observations prove, correspond to other damage types in quasi-isotropic laminates.

An international comparison of optical instruments measuring polymer surfaces with arithmetic mean height values in the sub-micrometre range has been carried out. The comparison involved sixteen optical surface texture instruments (focus variation instruments, confocal microscopes and coherent scanning interferometers) from thirteen research laboratories worldwide. Results demonstrated that: (i) Agreement among different instruments could be achieved to a limited extent; (ii) standardised guidelines for uncertainty evaluation of areal surface parameters are needed for users; (iii) it is essential that the performance characteristics (and especially the spatial frequency response) of an instrument is understood prior to a measurement.

With the launch of MESSENGER and Venus Express, a new wave of exploration of the inner solar system has begun. Noting the growing number of probes to the inner solar system, it is proposed to connect the expertise of the respective spacecraft teams and the NEO and IEO survey community to best utilize the extended cruise phases and to provide additional data return in support of pure science as well as planetary defence. Several missions to Venus and Mercury are planned to follow in this decade. Increased interest in the inferior planets is accompanied by several missions designed to study the Sun and the interplanetary medium (IPM) from a position near or in Earth orbit, such as the STEREO probes and SDO. These augment established solar observation capabilities at the Sun-Earth L1 Lagrangian point such as the SOHO spacecraft. Thus, three distinct classes of spacecraft operate or observe interior to Earth's orbit. All these spacecraft carry powerful multispectral cameras optimized for their respective primary targets. MESSENGER is scheduled to end its six-year interplanetary cruise in March 2011 to enter Mercury orbit, but a similarly extended cruise with several gravity-assists awaits the European Mercury mission BepiColombo. Unfortunately, the automatic abort of the orbit insertion manoeuvre has also left Akatsuki (a.k.a. Venus Climate Orbiter (VCO), Planet-C) stranded in heliocentric orbit. After an unintended fly-by, the probe will catch up with Venus in approximately six years. Meanwhile, it stays mostly interior to Venus in a planet-leading orbit. In addition to the study of comets and their interaction with the IPM, observations of small bodies akin to those carried out by outer solar system probes are occasionally attempted with the equipment available. The study of structures in the interplanetary dust (IPD) cloud has been a science objective during the cruise phase of the Japanese Venus probe Akatsuki from Earth to Venus. IPD observations in the astronomical H-band (1.65 µm) are supported by its IR2 camera down to 1.5 µW/m2sr in single 2 minute exposures. In the same setting, point sources of 13 mag can be detected. Obviously, a number of large asteroids exceed this threshold. The Earthguard-1 study, completed in 2003 by the DLR Institute of Planetary Research and Kayser-Threde under ESA contract, proposed a dedicated steerable Ø20...35 cm telescope and CCD camera payload on a probe to the inner solar system, to detect Near-Earth and Inner-Earth Objects (NEOs, IEOs) in favourable opposition geometry. A ride-share on a Mercury orbiter and a dedicated low-thrust propulsion spacecraft to a heliocentric 0.5 AU orbit were studied. A similar-sized telescope is presently being developed for the AsteroidFinder satellite of DLR. Therefore, the technical feasibility of a number of asteroid observation scenarios involving spacecraft and targets interior to Earth’s orbit is assessed based on the latest available spacecraft information and asteroid population models. A rough estimate of the required effort in terms of ground-based spacecraft operations and on-board resources is given for selected representative scenarios.

Sediment particles suspended in seawater absorb and scatter light, making the water turbid and the underwater light field diffuse. Knowledge of suspended particle concentration is needed for a number of practical applications, including sediment transport, and optical instruments are presently widely used to provide this information. In this chapter, we review methods for deriving the mass concentration of suspended material using direct and remote optical sensing. The relationship between optical properties and suspended sediment concentration, however, is not straightforward: it depends on the size, shape and refractive index of the particles in suspension. Some progress has been made in recent years with the discovery that the size of flocculated particles is controlled, at least to some extent, by turbulence. Knowledge of turbulence conditions may therefore be useful for improving the interpretation of optical signals in terms of suspended sediment load.

Publisher Summary This chapter describes a selection of widely used instruments and techniques. Optical instruments can be conveniently thought of in two categories: those basically involving image formation (for example, microscopes and telescopes) and those that involve intensity measurement (for example, photometers). Many instruments (for example, spectrophotometers) involve both processes, and it is convenient to regard these as falling in the second, intensity measurement category. The development of optical fibers and light guides has enormously broadened the scope of optical techniques. Light sources for use in instruments are grouped under two headings: conventional or incoherent sources and laser or coherent sources. The principal characteristics of a conventional light source for use in instruments are: spectral power distribution, luminance or radiance, stability of light output, ease of control of light output, and stability of position. Other factors that may have to be taken into account in the design of an instrument system are heat dissipation, the nature of auxiliary equipment needed, source lifetime, cost, and ease of replacement.

We consider the influence of physics on the development of the microscope, using the unusual approach of working backwards in time from the present day to the earliest times. Modern microscopes use techniques including stimulated emission depletion microscopy and near-field scanning optical microscopy that relies on the properties of evanescent waves. These instruments allow optical instruments greatly to exceed conventional concepts of resolution, and they rely on computers to drive the system. High-resolution objective lenses, meanwhile, are now being made at very high cost using aspheric lenses. These are not used by microscopists, but are essential for the systems of photollithography used in the printing of microcircuits on computer chips. Apochromatic objectives resulted from the theoretical physics elaborated by Ernst Abbe in the nineteenth century, yet before the development of the color-corrected lens, simple (i.e., single-lens) microscopes were capable of resolving surprisingly fine details. Microscopes made by Bancks of London were used by Darwin, Brown, Bentham, and Hooker and—with careful adjustment—can reveal remarkably fine detail that seems to defy the constraints of the theoretician. Simple microscopes were used by Leeuwenhoek in the Netherlands in the seventeenth century, and here we will see that the design—widely described as a “Leeuwenhoek microscope”—was actually a concept of the London philosopher, Robert Hooke. The chapter will conclude at the earliest days of the microscope, throwing new light on the earliest microscopic descriptions in the literature of science. We learn how the theoretical constraints of physics can be challenged by the use of personal preference and experience.

The rapid expansion of the optical fiber telecommunication industry due to the explosion of the Internet has substantially driven down the cost of optical components, making fiber optic sensors more economically viable. In addition, the rapid development of fiber-optic sensors, particularly the fiber Bragg grating (FBG) sensors offers many advantages and capability that could not be achieved otherwise. In the past few years, fiber Bragg grating sensors have attracted a lot of interest and they are being used in numerous applications. This paper describes the FBG sensors developed for structural health monitoring, and were installed on Hong Kong's landmark Tsing Ma bridge (TMB), which is the world longest (1377 m) suspension bridge that carried both railway and regular road traffic. Forty FBG sensors divided into three arrays were installed on the hanger cable, rocker bearing and truss girders of the TMB. The objectives of the study are to investigate the feasibility of using the developed FBG sensors for structural health monitoring, via monitoring the strain of different parts of the TMB under both the railway and highway loads as well as comparing the FBG sensors' performance with the conventional structural health monitoring system - Wind and Structural Health Monitoring System (WASHMS) that has been operating at TMB since the bridge's commissioning in May 1997. The experimental observations in this project show that the results using FBG sensors were in excellent agreement with those acquired by WASHMS. © 2005 Elsevier Ltd. All rights reserved.

This chapter discusses several concepts related to the optical properties and to the formation of colors in glasses. The most common applications of glasses are based on their optical properties. It is important to recognize that the optical properties of the glass have to remain time independent for their application. Application of glasses for making optical instruments and lenses is based on properties such as refractive index and its dispersion that can be varied by varying chemical composition. One of the more important applications based on optical properties of glass is in the field of information technology through the use of glass fibers. Although transparency is often associated with the visible region, several classes of glasses are highly transparent at other wavelengths of electromagnetic spectrum. This has led to the development of three important classes of glasses—namely, oxide, chalcogenide, and halide glasses that exhibit different windows of transparency. Glasses are isotropic in annealed state under the action of hydrostatic pressure but they become anisotropic and exhibit birefringent behavior when they are not properly annealed and when subjected to nonhydrostatic pressure. By virtue of the birefringence, such glasses are characterized by two indices of refraction—that is, one along the direction of applied or unannealed stress and the other perpendicular to it.

Publisher Summary Silica fibers can change their optical properties permanently when they are exposed to intense radiation from a laser operating in the blue or ultraviolet spectra region. Fiber gratings can be designed to operate over a wide range of wavelengths extending from the ultraviolet to the infrared region. Diffraction gratings constitute a standard optical component and are used routinely in various optical instruments such as a spectrometer. There is considerable evidence that photosensitivity of optical fibers is due to defect formation inside the core of Ge-doped silica fibers. Using several different techniques can make fiber gratings. There are four major techniques commonly used for making fiber gratings: the single-beam internal technique, the dual-beam holographic technique, the phase mask technique, and the point-by-point fabrication technique. The field of photonic-crystal fibers is in its infancy and is likely to evolve in the near future.

Publisher Summary This chapter describes resolution enhancement by data inversion techniques. The development of micro-informatics and computer-assisted devices has deeply modified the classical concept of resolving power of an optical instrument. In modern instruments, numerical algorithms can be implemented to process—that is, invert the recorded data to get estimates of the probed object with enhanced resolutions. The resolution limits then arise as practical limitations because of the noise amplification inherent in all inversion procedures. The chapter illustrates the way such limits can be assessed and the circumstances under which a significant amount of super-resolution is achievable. Moreover, following the development of Fourier methods in optics, it has become more usual to characterize the resolution of an optical system in terms of its bandwidth. Fourier transform of the object is an entire analytic function and hence, could be uniquely recovered from that piece of spectrum transmitted by the optical system. Finally, the chapter illustrates the way to assess the amount of achievable super-resolution where the object is uniformly illuminated over some finite slit. Before analyzing the conditions under which super-resolution can be achieved, the chapter briefly outlines the required framework and describes the way a mathematical model is defined for the imaging process and the way the associated inverse problem is solved.

Publisher Summary This chapter highlights the two approaches of coherence by considering the propagation of the mutual coherence and cross-spectral density in an optical instrument, (in the transmission electron microscope in particular). Some other practical aspects of coherence are also examined briefly, notably illuminating systems and the role of coherence in scanning transmission electron microscope (STEM) imagery. There are two modes of illumination in common use, critical illumination and Kohler illumination. In the former, the specimen plane is conjugate to the effective source plane (crossover plane) whereas in the Kohler case, the effective source plane is conjugate to the image focal plane of the final condenser lens, which may in fact be the pre-field of the objective.

Publisher Summary This chapter discusses the industrial application of modern measurement and estimation techniques in biotechnology. In biotechnology, optical measurement technology and especially the use of fibers may result in the development of more reliable and easily sterilized small size sensors for many of the conventional variables such as temperature, pressure, and level. Optical measurement principles that utilize absorption, fluorescence, reflection, color, turbidity, luminescence to detect different substances will probably have more applications because optical fibers make it possible to locate the main optical instrument far from the process area letting only a simple optical part come into contact with the process itself. This is a great advantage because it means that several of the optical techniques used in laboratories can be essentially linked directly to the process without sample taking and transfer. Spectrophotometers and other similar complex analytical instruments can be used more easily for online measurements because they need not be installed for on-site operation but can be kept in a laboratory environment.

The temperature dependence of the quality factor of three different aluminum alloys suitable for cryogenic optical instruments has been investigated. A leaf spring configuration was formed by the bars fixed on one end and set to a bending mode oscillation. The loose end directed a laser beam onto a position sensitive detector. Using this optical read-out the motion was not affected by disturbing or additional damping forces. During cooldown the fundamental frequency of the bar, amplitude and decay time were monitored. From these measurements the temperature dependence of the resonance and of the quality factor was determined. Two alloys have shown acceptable internal damping.

Publisher Summary This chapter discusses the basic optical instruments. The basic structure and theory of each type of instrument is discussed, as well as performance criteria, limitations, and caveats. The chapter discusses the visual system. A magnifier is a single lens that produces for visual observation an erect virtual image of a nearby object. The purpose of an eyepiece is the same, but its object is an image formed by a preceding optical system. The eyepiece is discussed here as a separate instrument, since its function is the same wherever it is found. Afocal systems, whose power is zero, have a number of unique and useful properties that are not widely known. Afocal systems are also referred to as telescopes, since visual telescopes are afocal. Afocal and focal systems differ in kind, not merely in degree; afocal systems are not merely focal systems with an infinite focal length. Afocal systems have no focal points, no principal planes, and no nodal points, that is, none of the cardinal points of a focal system. The autocollimator, one of the most important instruments in metrology, is used both for measuring small differences in angles and as a nulling device for setting angles. Schlieren systems show variations in the optical path length of light passing through transparent objects or reflecting from the surface of specular objects by causing the path length differences to appear as irradiance variations.

In the last chapter we studied the improvement in signal-to-noise ratio that should be produced by multiplexing. However, in practice the performance of an optical instrument is affected by a great many factors which are difficult to predict and to analyze. In this chapter we discuss some of these factors and their effect on the signal-to-noise ratio.

This chapter begins with a description of multiplexing methods, shows the connections with weighing designs, and describes the best masks for use in optical instruments and the improvements produced by them.

Microprocessor-controlled, optical diagnostic instrumentation systems are being developed at Mississippi State University for the U.S. Department of Energy's (DOE) magnetohydrodynamic (MHD) program and other fossil energy technologies. Three of these instrumentation techniques are described. The sensitivity of the temperature gradient of the combustion flame to a change in stoichiometry indicates a possible optical stoichiometric control technique. A microprocessor-controlled, packaged optical instrument for non-intrusive measurement of nitric oxide (NO) concentration in a combustion gas is described. Experimental results are presented using coherent anti-Stokes Raman spectroscopy (CARS) for spatially and temporally resolved temperature measurements in a simulated coal-fired envi ronment.

Publisher Summary This chapter describes the correction of optical images by compensation of aberrations and spatial frequency filtering. Efforts are being made to reduce the disturbing effects of aberrations on image formation in optical systems and its amount in designing and in the production of optical instruments. Techniques by means of which correcting the aberrant image under given conditions of relative aperture, focusing, and so on can be attained are required. The chapter describes two different methods. In the first method, the aberration is compensated by the use of an optical filter at the pupil of the objective. The second method consists of applying double diffraction (Abbe's experiment) to correction of photographic images. The chapter focuses on the application of these two methods in relation to correction of optical images formed by an aberrant objective.

This chapter presents the details of examination of the wave nature of light and the properties of different optical instruments. The resolving power of a telescope is the reciprocal of the smallest angle, which the line joining the two stars subtends at the objective of the telescope for which resolution of the images is just apparent. If a beam of polarized light is passed through solutions of certain substances, for example, sugar, the plane of vibration is turned through a certain angle that is proportional to the length of the path of light in the solution and to its concentration. It depends also on the nature of the substance in solution. The substance is said to be optically active. Some transparent substances become doubly refracting when subjected to stress. Examination under polarized light of models of structures made from such substances enables the amount of strain at certain points of the structure to be estimated.

Publisher Summary This chapter discusses various properties of spherical mirrors. Spherical mirrors are those types of mirrors whose reflecting surfaces form a part of the surface of a sphere. In the convex type, the reflection takes place on the outside surface of the sphere while in the concave type reflection is from the inside surface. The path of a ray of light is always reversible. Thus, an incident ray passing through the principal focus of a concave mirror is reflected parallel to the principal axis. The fundamental property of a convex, or diverging, mirror is to make incident divergent beams more divergent. Use of spherometer is a nonoptical method suitable for both types of mirror. Concave mirrors are used as magnifiers as in shaving mirrors, dentists' inspection mirrors, etc., in which cases the object must be closer to the mirror than the principal focus. Convex mirrors find less application than concave mirrors. They are used as driving mirrors because they give a wide field of view, that is, the diminished image formed is of a large area of the surroundings. They are also used as ornamental mirrors in homes and find occasional use in telescopes and other optical instruments.

Publisher Summary This chapter discusses attitude-sensing techniques. It also discusses the measurement of angular position and angular velocity, and the techniques for the measurement of angular acceleration. The chapter highlights the measurement of the attitude angles and angular velocities of the aircraft with respect to the earth, including the measurement of the aircraft heading and the measurement of pitch and roll angles. The instruments used for flight test purposes can be divided into two groups: (1) optical instruments that measure directly the angles between the aircraft and the earth, or between the aircraft and an astronomical body whose attitude relative to the earth is known and (2) instruments that measure the attitude of the aircraft relative to some reference direction that can be determined inside the aircraft. The chapter discusses the characteristics of the basic instruments and a few of the combined-type instruments regularly used in flight testing.

Publisher Summary This chapter discusses an image intensifier system for direct observation at very low light levels. The performance of the unaided eye at low brightness levels is described, and the improvements in perception are discussed which can theoretically be obtained by the use of visual aids. Two kinds of aid in particular are considered—namely, purely optical instruments and image intensifier systems of the direct viewing type. From these considerations, it is concluded that a major improvement in perception at low light levels can be obtained with the aid of image intensifier systems employing an objective lens with large diameter. In order to achieve the maximum possible improvement in perception under varying conditions of contrast and field luminance, the total angular magnification of the system should be variable. For this purpose, an electrostatically focused image intensifier tube is being developed with a magnification which can be varied between about 0.2 and 0.8. The chapter describes the electron optics of this tube and the optical components of the system in which the tube is intended to be operated.

Publisher Summary This chapter describes certain applications of shearing interferometry. Examinations performed by means of interferometry consist in making the variation of separation between two wavefronts visible and measurable. In shearing interferometers, two superimposed, displaced images of the wavefront under test are made to interfere with each other. They provide a comparison of a wavefront with a sheared image of itself. An advantage of such instruments is that the need for a reference surface is eliminated, so that they can be used for testing wavefronts of any size. The shearing interferometers work without reunion of waves. Wavefront shearing interferometry can be used for testing optical instruments and components and for determining performance and wavefront form. The shape of the wavefront is a function of the optical elements producing it. The aberrations of lenses and the shapes of mirror surfaces are obtainable from the measurement of wavefront shapes. For the examination of extended transparent isotropic objects, shearing interferometers using polarized light are suitable, as they are easy to adjust, insensitive to vibration, and work with a very high precision.