Spaceborn Optoelectronic Sensors and Their Radiometric Calibration
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1 the Spectroscopic Toolbox
13 1 The Spectroscopic Toolbox 1.1 Introduction Present spectroscopic instruments use essentially bulk optics, that is, with sizes much greater than the wavelengths at which the instruments are used (0.3–2.4 μm in this book). Diffraction effects – due to the finite size of light wavelength – are then usually negligible and light propagation follows the simple precepts of geometrical optics. A special case is the disperser or interferometer that provides the spectral information: these are also large size optical devices (say 5 cm to 1 m across), but which exhibit periodic structures commensurate with the working wavelengths. The next subsection gives a short reminder of geometrical optics formulae that dictate how light beams propagate in bulk optical systems. It is followed by an introduction of a fundamental global invariant (the optical etendue) that governs the 4D geometrical extent of the light beams that any kind of optical system can accept: it is particularly useful to derive what an instrument can – and cannot – offer in terms of 3D coverage (2D of space and 1 of wavelength). 1.1.1 Geometrical Optics #101 As a short reminder of geometrical optics, that is, again the rules that apply to light propagation when all optical elements (lenses, mirrors, stops) have no fea- tures at scales comparable or smaller than light wavelength are listed: 1) Light beams propagate in straight lines in any homogeneous medium (spa- tially constant index of refraction n). 2) When a beam of light crosses from a dielectric medium of index of refraction n1 (e.g., air with n close to 1) to another dielectric of refractive index n2 (e.g., an optical glass with refractive index roughly in the 1.5–1.75 range), part of the beam is transmitted (refracted) and the remainder is reflected. -
Lecture 6: Spectroscopy and Photochemistry II
Lecture 6: Spectroscopy and Photochemistry II Required Reading: FP Chapter 3 Suggested Reading: SP Chapter 3 Atmospheric Chemistry CHEM-5151 / ATOC-5151 Spring 2005 Prof. Jose-Luis Jimenez Outline of Lecture • The Sun as a radiation source • Attenuation from the atmosphere – Scattering by gases & aerosols – Absorption by gases • Beer-Lamber law • Atmospheric photochemistry – Calculation of photolysis rates – Radiation fluxes – Radiation models 1 Reminder of EM Spectrum Blackbody Radiation Linear Scale Log Scale From R.P. Turco, Earth Under Siege: From Air Pollution to Global Change, Oxford UP, 2002. 2 Solar & Earth Radiation Spectra • Sun is a radiation source with an effective blackbody temperature of about 5800 K • Earth receives circa 1368 W/m2 of energy from solar radiation From Turco From S. Nidkorodov • Question: are relative vertical scales ok in right plot? Solar Radiation Spectrum II From F-P&P •Solar spectrum is strongly modulated by atmospheric scattering and absorption From Turco 3 Solar Radiation Spectrum III UV Photon Energy ↑ C B A From Turco Solar Radiation Spectrum IV • Solar spectrum is strongly O3 modulated by atmospheric absorptions O 2 • Remember that UV photons have most energy –O2 absorbs extreme UV in mesosphere; O3 absorbs most UV in stratosphere – Chemistry of those regions partially driven by those absorptions – Only light with λ>290 nm penetrates into the lower troposphere – Biomolecules have same bonds (e.g. C-H), bonds can break with UV absorption => damage to life • Importance of protection From F-P&P provided by O3 layer 4 Solar Radiation Spectrum vs. altitude From F-P&P • Very high energy photons are depleted high up in the atmosphere • Some photochemistry is possible in stratosphere but not in troposphere • Only λ > 290 nm in trop. -
Astronomical Instrumentation G
Astronomical Instrumentation G. H. Rieke Contents: 0. Preface 1. Introduction, radiometry, basic optics 2. The telescope 3. Detectors 4. Imagers, astrometry 5. Photometry, polarimetry 6. Spectroscopy 7. Adaptive optics, coronagraphy 8. Submillimeter and radio 9. Interferometry, aperture synthesis 10. X-ray instrumentation Introduction Preface Progress in astronomy is fueled by new technical opportunities (Harwit, 1984). For a long time, steady and overall spectacular advances were made in telescopes and, more recently, in detectors for the optical. In the last 60 years, continued progress has been fueled by opening new spectral windows: radio, X-ray, infrared, gamma ray. We haven't run out of possibilities: submillimeter, hard X-ray/gamma ray, cold IR telescopes, multi-conjugate adaptive optics, neutrinos, and gravitational waves are some of the remaining frontiers. To stay at the forefront requires that you be knowledgeable about new technical possibilities. You will also need to maintain a broad perspective, an increasingly difficult challenge with the ongoing explosion of information. Much of the future progress in astronomy will come from combining insights in different spectral regions. Astronomy has become panchromatic. This is behind much of the push for Virtual Observatories and the development of data archives of many kinds. To make optimum use of all this information requires you to understand the capabilities and limitations of a broad range of instruments so you know the strengths and limitations of the data you are working with. As Harwit (1984) shows, before ~ 1950, discoveries were driven by other factors as much as by technology, but since then technology has had a discovery shelf life of only about 5 years! Most of the physics we use is more than 50 years old, and a lot of it is more than 100 years old. -
Optics Microstructured Optics SMS Design Methods Plastic Optics
www.led-professional.com ISSN 1993-890X Review LpR The technology of tomorrow for general lighting applications. Sept/Oct 2008 | Issue 09 Optics Microstructured Optics SMS Design Methods Plastic Optics LED Driver Circuits Display Report Copyright © 2008 Luger Research & LED-professional. All rights reserved. There are over 20 billion light fixtures using incandescent, halogen, Design of LED or fluorescent lamps worldwide. Many of these fixtures are used for directional light applications but are based on lamps that put Optics out light in all directions. The United States Department of Energy (DOE) states that recessed downlights are the most common installed luminaire type in new residential construction. In addition, the DOE reports that downlights using non-reflector lamps are typically only 50% efficient, meaning half the light produced by the lamp is wasted inside the fixture. In contrast, lighting-class LEDs offer efficient, directional light that lasts at least 50,000 hours. Indoor luminaires designed to take advantage of all the benefits of lighting-class LEDs can exceed the efficacy of any incandescent and halogen luminaire. Furthermore, these LEDs match the performance of even the best CFL (compact fluorescent) recessed downlights, while providing a lifetime five to fifty times longer before requiring maintenance. Lastly, this class of LEDs reduces the environmental impact of light (i.e. no mercury, less power-plant pollution, and less landfill waste). Classical LED optics is composed of primary a optics for collimation and a secondary optics, which produces the required irradiance distribution. Efficient elements for primary optics are concentrators, either using total internal reflection or combined refractive/reflective versions. -
Photon Cross Sections, Attenuation Coefficients, and Energy Absorption Coefficients from 10 Kev to 100 Gev*
1 of Stanaaros National Bureau Mmin. Bids- r'' Library. Ml gEP 2 5 1969 NSRDS-NBS 29 . A111D1 ^67174 tioton Cross Sections, i NBS Attenuation Coefficients, and & TECH RTC. 1 NATL INST OF STANDARDS _nergy Absorption Coefficients From 10 keV to 100 GeV U.S. DEPARTMENT OF COMMERCE NATIONAL BUREAU OF STANDARDS T X J ". j NATIONAL BUREAU OF STANDARDS 1 The National Bureau of Standards was established by an act of Congress March 3, 1901. Today, in addition to serving as the Nation’s central measurement laboratory, the Bureau is a principal focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. To this end the Bureau conducts research and provides central national services in four broad program areas. These are: (1) basic measurements and standards, (2) materials measurements and standards, (3) technological measurements and standards, and (4) transfer of technology. The Bureau comprises the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Center for Radiation Research, the Center for Computer Sciences and Technology, and the Office for Information Programs. THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation’s scientific community, industry, and com- merce. The Institute consists of an Office of Measurement Services and the following technical divisions: Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic and Molec- ular Physics—Radio Physics -—Radio Engineering -—Time and Frequency -—Astro- physics -—Cryogenics. -
Advanced Physics Laboratory
1 ADVANCED PHYSICS LABORATORY XRF X-Ray Fluorescence: Energy-Dispersive Technique (EDXRF) PART II Optional Experiments Author: Natalia Krasnopolskaia Last updated: N. Krasnopolskaia, January 2017 Spectrum of YBCO superconductor obtained by Oguzhan Can. SURF 2013 2 Contents Introduction ………………………………………………………………………………………3 Experiment 1. Quantitative elemental analysis of coins ……………..………………………….12 Experiment 2. Study of Si PIN detector in the x-ray fluorescence spectrometer ……………….16 Experiment 3. Secondary enhancement of x-ray fluorescence and matrix effects in alloys.……24 Experiment 4. Verification of stoichiometry formula for superconducting materials..………….29 3 INTRODUCTION In Part I of the experiment you got familiar with fundamental ideas about the origin of x-ray photons as a result of decelerating of electrons in an x-ray tube and photoelectric effect in atoms of the x-ray tube and a target. For practical purposes, the processes in the x-ray tube and in the sample of interest must be explained in detail. An X-ray photon from the x-ray tube incident on a target/sample can be either absorbed by the atoms of the target or scattered. The corresponding processes are: (a) photoelectric effect (absorption) that gives rise to characteristic spectrum emitted isotropically; (b) Compton effect (inelastic scattering; energy shifts toward the lower value); and (c) Rayleigh scattering (elastic scattering; energy of the photon stays unchanged). Each event of interaction between the incident particle and an atom or the other particle is characterized by its probability, which in spectroscopy is expressed through the cross section σ of the process. Actually, σ has a dimension of [L2] and in atomic and nuclear physics has a unit of barn: 1 barn = 10-24cm2. -
Remote Sensing
remote sensing Article A Refined Four-Stream Radiative Transfer Model for Row-Planted Crops Xu Ma 1, Tiejun Wang 2 and Lei Lu 1,3,* 1 College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China; [email protected] 2 Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands; [email protected] 3 Key Laboratory of Western China’s Environmental Systems (Ministry of Education), Lanzhou University, Lanzhou 730000, China * Correspondence: [email protected]; Tel.: +86-151-1721-8663 Received: 17 March 2020; Accepted: 14 April 2020; Published: 18 April 2020 Abstract: In modeling the canopy reflectance of row-planted crops, neglecting horizontal radiative transfer may lead to an inaccurate representation of vegetation energy balance and further cause uncertainty in the simulation of canopy reflectance at larger viewing zenith angles. To reduce this systematic deviation, here we refined the four-stream radiative transfer equations by considering horizontal radiation through the lateral “walls”, considered the radiative transfer between rows, then proposed a modified four-stream (MFS) radiative transfer model using single and multiple scattering. We validated the MFS model using both computer simulations and in situ measurements, and found that the MFS model can be used to simulate crop canopy reflectance at different growth stages with an accuracy comparable to the computer simulations (RMSE < 0.002 in the red band, RMSE < 0.019 in NIR band). Moreover, the MFS model can be successfully used to simulate the reflectance of continuous (RMSE = 0.012) and row crop canopies (RMSE < 0.023), and therefore addressed the large viewing zenith angle problems in the previous row model based on four-stream radiative transfer equations. -
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Optics Basics 08 N [Compatibility Mode]
Basic Optical Concepts Oliver Dross, LPI Europe 1 Refraction- Snell's Law Snell’s Law: n φ φ n i i Sin ( i ) = f φ Media Boundary Sin ( f ) ni n f φ f 90 Refractive Medium 80 internal 70 external 60 50 40 30 angle of exitance 20 10 0 0 10 20 30 40 50 60 70 80 90 angle of incidence 2 Refraction and TIR Exit light ray n f φ φ f f = 90° Light ray refracted along boundary φ φ n c i i φ Totally Internally Reflected ray i Incident light rays Critical angle for total internal reflection (TIR): φ c= Arcsin(1/n) = 42° (For index of refraction ni =1.5,n= 1 (Air)) „Total internal reflection is the only 100% efficient reflection in nature” 3 Fresnel and Reflection Losses Reflection: -TIR is the most efficient reflection: n An optically smooth interface has 100% reflectivity 1 Fresnel Reflection -Metallization: Al (typical): 85%, Ag (typical): 90% n2 Refraction: -There are light losses at every optical interface -For perpendicular incidence: 1 Internal 0.9 2 Reflection − 0.8 External n1 n2 R = 0.7 Reflection + 0.6 n1 n2 0.5 0.4 Reflectivity -For n 1 =1 (air) and n 2=1.5 (glass): R=(0.5/2.5)^2=4% 0.3 -Transmission: T=1-R. 0.2 0.1 -For multiple interfaces: T tot =T 1 *T 2*T 3… -For a flat window: T=0.96^2=0.92 0 -For higher angles the reflection losses are higher 0 10 20 30 40 50 60 70 80 90 Incidence Angle [deg] 4 Black body radiation & Visible Range 3 Visible Range 6000 K 2.5 2 5500 K 1.5 5000 K 1 4500 K Radiance per wavelength [a.u.] [a.u.] wavelength wavelength per per Radiance Radiance 0.5 4000 K 3500 K 0 2800 K 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 Wavelength [nm] • Every hot surface emits radiation • An ideal hot surface behaves like a “black body” • Filaments (incandescent) behave like this. -
The Optical Effective Attenuation Coefficient As an Informative
hv photonics Article The Optical Effective Attenuation Coefficient as an Informative Measure of Brain Health in Aging Antonio M. Chiarelli 1,2,* , Kathy A. Low 1, Edward L. Maclin 1, Mark A. Fletcher 1, Tania S. Kong 1,3, Benjamin Zimmerman 1, Chin Hong Tan 1,4,5 , Bradley P. Sutton 1,6, Monica Fabiani 1,3,* and Gabriele Gratton 1,3,* 1 Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA 2 Department of Neuroscience, Imaging and Clinical Sciences, University G. D’Annunzio of Chieti-Pescara, 66100 Chieti, Italy 3 Psychology Department, University of Illinois at Urbana-Champaign, Champaign, IL 61820, USA 4 Division of Psychology, Nanyang Technological University, Singapore 639818, Singapore 5 Department of Pharmacology, National University of Singapore, Singapore 117600, Singapore 6 Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA * Correspondence: [email protected] (A.M.C.); [email protected] (M.F.); [email protected] (G.G.) Received: 24 May 2019; Accepted: 10 July 2019; Published: 12 July 2019 Abstract: Aging is accompanied by widespread changes in brain tissue. Here, we hypothesized that head tissue opacity to near-infrared light provides information about the health status of the brain’s cortical mantle. In diffusive media such as the head, opacity is quantified through the Effective Attenuation Coefficient (EAC), which is proportional to the geometric mean of the absorption and reduced scattering coefficients. EAC is estimated by the slope of the relationship between source–detector distance and the logarithm of the amount of light reaching the detector (optical density). -
Gamma-Ray Interactions with Matter
2 Gamma-Ray Interactions with Matter G. Nelson and D. ReWy 2.1 INTRODUCTION A knowledge of gamma-ray interactions is important to the nondestructive assayist in order to understand gamma-ray detection and attenuation. A gamma ray must interact with a detector in order to be “seen.” Although the major isotopes of uranium and plutonium emit gamma rays at fixed energies and rates, the gamma-ray intensity measured outside a sample is always attenuated because of gamma-ray interactions with the sample. This attenuation must be carefully considered when using gamma-ray NDA instruments. This chapter discusses the exponential attenuation of gamma rays in bulk mater- ials and describes the major gamma-ray interactions, gamma-ray shielding, filtering, and collimation. The treatment given here is necessarily brief. For a more detailed discussion, see Refs. 1 and 2. 2.2 EXPONENTIAL A~ATION Gamma rays were first identified in 1900 by Becquerel and VMard as a component of the radiation from uranium and radium that had much higher penetrability than alpha and beta particles. In 1909, Soddy and Russell found that gamma-ray attenuation followed an exponential law and that the ratio of the attenuation coefficient to the density of the attenuating material was nearly constant for all materials. 2.2.1 The Fundamental Law of Gamma-Ray Attenuation Figure 2.1 illustrates a simple attenuation experiment. When gamma radiation of intensity IO is incident on an absorber of thickness L, the emerging intensity (I) transmitted by the absorber is given by the exponential expression (2-i) 27 28 G. -
A Brief Overview of Non-Imaging Optics
2132-40 Winter College on Optics and Energy 8 - 19 February 2010 Overview of non-imaging optics V. Lakshminarayanan University of Waterloo Waterloo CANADA A Brief Overview of Non- Imaging Optics V. Lakshminarayanan University of Waterloo Waterloo, Canada What is Non-Imaging Optics? • Is the branch of optics which deals with transfer of light between a source and an object. • Techniques do not form an optimized (non-aberrated) image of source. • Optimized for radiative transfer from source to target Some examples • Optical light guides, non-imaging reflectors, nonimaging lenses, etc. • Practical examples: auto headlamps, LCD backlights, illuminated instrument panel displays, fiber optics illumination devices, projection display systems, concentration of sunlight for solar power, illumination by solar pipes, etc. Two major components of a non- imaging optics system •1. Concentration – maximize the amount of energy that “falls” on a target –ie., as in solar power •2. Illumination – control the distribution of light, i.e.,it is evenly spread of some areas and completely blocked in other areas - i.e., automobile lamps • Variables: Total radiant flux, angular distribution of optical radiation, spatial distribution of optical radiation • Collection efficiency An Optimized non-imaging optics example • THE flux at the surface of the Sun, 6.3 kW cm-2, falls off with the square of distance to a value of 137 mW cm-2 above the Earth's atmosphere, or typically 80–100 mW cm-2 at the ground. In principle, the second law of thermodynamics permits an optical device to concentrate the solar flux to obtain temperatures at the Earth's surface not exceeding the Sun's surface temperature. -
Intensity, Brightness And´Etendue of an Aperture Lamp 1 Problem
Intensity, Brightness and Etendue´ of an Aperture Lamp Kirk T. McDonald Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544 (December 8, 2012; updated July 23, 2018) 1Problem An aperture lamp is a variant of a fluorescent bulb in which the phosphor1 is deposited on a reflecting substrate (which acts as a kind of optical insulator), and both of these exist over only a portion of the azimuth of the cylindrical glass housing, as sketched below. Phosphor molecules are excited by ultraviolet light emitted during the steady electrical discharge of the low-pressure gas inside the lamp, and subsequently de-excite via emission of visible light. Some of this light is absorbed and re-emitted by the phosphor. In this problem, assume that there are no losses in this absorption/re-emission. Compare the intensity, brightness and ´etendue of the light from an ordinary fluorescent lamp (with no reflector and phosphor over the full azimuth) with that of an aperture lamp, with small angular aperture Δφ, with the same power output in the visible light. You may assume that the phosphor surface emits radiation according to Lambert’s cosine law [2].2 Note that the principle of this problem applies equally well to a lamp consisting of an array of light-emitting diodes (which also absorb and re-emit light with little loss).3,4 Show that the effect of the phosphor/reflector (optical insulator) is to increase the inten- sity/brightness/temperature of the light inside the lamp (and the light emitted by it) for a 1 The phosphors are typically metal oxides with a PO4 radical, often with rare-earth elements.