DOCSLIB.ORG

Astronomical Instrumentation G

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
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. You can do good astronomy without being totally current in physics (but you need to know physics very well). The relevant technology, in comparison, changes rapidly and you absolutely must be up to date on it, or you will rapidly fall behind. 2 Introduction Chapter 1: Introduction 1. Basics of radiometry 1.1 Basic Terms in Radiometry Virtually all we are going to discuss in this book is measuring photons. Therefore, we lead off with a short description of how their production is treated in radiation physics. To compute the emission of an object, consider a projected area of a Figure 1.1. Emission geometry from a radiation source. surface element of it, dA, onto a plane perpendicular to the direction of observation (Figure 1.1). This area is dA cos θ, where θ is the angle between the direction of observation and the outward normal to dA. The specific intensity, Lν, is the power (Watts) leaving a unit projected area of the surface of the source (in m2) into a unit solid angle (in ster) and unit frequency interval (in Hz), and the subscript lets us know this is a frequency-based quantity. It therefore has units of W m-2 Hz-1 ster-1. In physics, the same quantity is usually called the spectral radiance (in frequency units); we will use the common astronomical terminology here and refer the reader to Rieke (2003) for a table of terminology conversions. Similarly, we can define a specific intensity per wavelength interval, Lλ, where indicates a wavelength-based quantity. The intensity, L, is the specific intensity integrated over all frequencies or wavelengths, and the radiant exitance, M, is the integral of the radiance over solid angle. It is a measure of the total power emitted per unit surface area in units of W m-2. For a black body, where is the Stefan-Boltzmann constant and T is the temperature in Kelvin. The integral of the radiant exitance over the source gives the total output, that is, the luminosity of the source. The irradiance, E, is the power received at a unit surface element some distance from the source. It also has units of W m-2, but it is easy to distinguish it from radiant exitance if we think of a source so distant that it is entirely within the field of view of the detection system. In this case, we might find it impossible to determine M, but E still has a straightforward meaning. The most commonly used quantity is the flux density, the irradiance per frequency or wavelength interval, E or E; it has units of W m-2 Hz-1 (frequency units), or W m-3 (wavelength units). In fact, astronomers have their own unit, the Jansky (Jy), which is 10-26 W m-2 Hz-1 . 3 Introduction The energy of a photon is where c is the speed of light and h is Planck’s constant. Conversion to photons/second can be achieved by dividing the various measures of power output just shown by equation (1.2). To make calculations simple, we generally deal only with Lambertian sources. For them, the intensity is constant regardless of the direction from which the source is viewed. In the astronomical context, a Lambertian source has no limb darkening (or brightening). In fact, we usually deal only with the special case of a Lambertian source, a black or grey body (a grey body has the same spectrum as a black body but with an emission efficiency, or emissivity ε, less than 1). We then have for the specific intensities in frequency and wavelength units: where k is the Boltzmann constant, T is the temperature in Kelvin (K), and n is the refractive index (virtually always n = 1 for astronomical sources). We also have Figure 1.2. Terms describing the propagation of a photon, or a light ray. Time has been frozen, but you should imagine that where r is the the photon is moving at the speed of light in the direction of distance to the the arrow. We will often draw the photon as lines marking the source and A is its surfaces of constant phase, called wavefronts. They are surface area. It is separated by the wavelength. The amplitude of the electric also convenient to field, its wavelength and phase, and the direction it is moving convert from characterize the photon. From George Barbastathis, MIT open frequency to course, 2004. wavelength units by means of 4 Introduction which can be derived by differentiating to derive the relation between d and d. An easy way to remember the conversion is that multiplying the flux density in W m-2 Hz-1 by c/2 with c = 2.998 X 1010 cm/s and in m gives the flux density in W cm-2 m-1. 1.2 Image formation and the wave nature of light OK, some source has launched a stream of photons in our direction. How are we going to catch it and unlock its secrets? A photon is described in terms that are illustrated in Figure 1.2. The behavior of the electric field can be expressed as where A is the amplitude, is the angular frequency, and is the phase. Another formalism is to express the phase in complex notation: where j is the imaginary square root of -1. In this case, the quantity is envisioned as a vector on a two dimensional diagram with the real component along the usual x-axis and the imaginary one along the usual y- axis. The angle of this vector represents the phase. We will discuss this formulation further in later chapters. Figure 1.3. wave fronts at the focal For efficient detection of this light, we use plane. optics to squeeze it into the smallest possible space. The definition of “the smallest possible space” is a bit complex. We want to map the range of directions toward the target onto a physical surface where we put an instrument or a detector. This goal implies that we form an image, and since light is a wave, images are formed as a product of interference. The collector must bend the rays of light from a distant object and bring them to a focus at the image plane (see Figure 1.3). There, they must interfere constructively, requiring that they arrive at the image having traversed paths of identical length from the object. This requirement is expressed in Fermat’s Principle, which is expressed in a number of ways including: “The optical path from a point on the object through the optical system to the corresponding point on the image must be the same length for all neighboring rays.” 5 Introduction The optical path is defined as the integral of the physical path times the index of refraction of the material that path traverses. What tolerance is there on the optical path length? Figure 1.3 shows how this tolerance can be determined. If the light waves impinge on the focal plane over too wide a range of angle, then the range of path lengths across the area where we detect the light can be large enough to result in a significant level of destructive interference. From the figure, this condition can be expressed as Here, l is some characteristic distance over which we collect the light – say the minimum size of a detector at the focus of a telescope. Equation (1.10) seems to imply that the size of this detector enters into the fundamental performance of a telescope. However, there is another requirement on the optical system. The beam of light entering the telescope is characterized by an area at its base, A, normally the area of the telescope primary mirror, and a solid angle, ≈ πθ2 where θ is the half-angle of the convergence of the beam onto the telescope (i.e., the angular diameter of the beam is 2 θ).
Load more

Recommended publications
  • 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.
    [Show full text]
  • 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.
    [Show full text]
  • 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.
    [Show full text]
  • 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.
    [Show full text]
  • 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.
    [Show full text]
  • Increasing the Brightness of Light Sources
    Increasing the Brightness of Light Sources Ling Fu Increasing the Brightness of Light Sources Dissertation zur Erlangung des Doktorgrades der Naturwissenschaften (Dr. rer. nat.) dem Fachbereich Physik der Philipps-UniversitÄatMarburg vorgelegt von Ling Fu aus der V.R. China Marburg 2006 Vom Fachbereich Physik der Philipps-UniversitÄatMarburg als Dissertation angenommen am: . Erstgutachter: Prof. Dr. H. Ries Zweitgutachter: Prof. Dr. H. JÄansch Tag der mÄundlichen PrÄufung: 16.11.2006 Zusammenfassung Das Ziel dieser Arbeit ist es, die ErhÄohung der spektralen Strahldichte von Licht- quellen mittels Licht-Recycling zu untersuchen und eine AbschÄatzung des Poten- tials dieser Methode zu erarbeiten. Dazu wurde ein physikalisches Modell der Licht- erzeugung in thermischen und lumineszenten Quellen erstellt und an verschiedenen Typen von Lichtquellen sowie einem Prototyp der Carambola, einer von uns ent- wickelten und hier vorgestellten Optik furÄ deterministisches Licht-Recycling veri¯- ziert. FurÄ moderne Beleuchtungssysteme sind kompakte GrÄo¼e und hohe Helligkeit (Strahldichte) wichtige Eigenschaften. Licht-Recycling kann die Strahldichte des von einer Lichtquelle ausgesendeten Lichts um den Preis des Verringerns der insgesamt in den Phasenraum abgestrahlten Energie erhÄohen. Licht-Recycling bedeutet die Reflexion eines Teils des ausgestrahlten Lichts zur Quelle. Ein Teil dieses reflektier- ten Lichts entgeht der Absorption in der Quelle und steht weiter zur Verfugung.Ä Infolgedessen kann die Strahldichte eines verkleinerten Phasenraums im
    [Show full text]
  • Nonimaging Optics
    Introduction ho NONIMAGING OPTICS Julio Chaves Light Prescriptions Innovators Madrid, Spain (^oC) CRC Press V*^ / Taylor & Francis Group Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Croup, an Informa business Contents Foreword xv Preface xvii Acknowledgments xix Author xxi List of Symbols xxiii List of Abbreviations and Terms xxv Part I Nonimaging Optics 1 1 Fundamental Concepts 3 1.1 Introduction 3 1.2 Imaging and Nonimaging Optics 3 1.3 The Compound Parabolic Concentrator 8 1.4 Maximum Concentration 17 1.5 Examples 22 References 23 2 Design of Two-Dimensional Concentrators 25 2.1 Introduction 25 2.2 Concentrators for Sources at a Finite Distance 25 2.3 Concentrators for Tubular Receivers 27 2.4 Angle Transformers 29 2.5 The String Method 30 2.6 Optics with Dielectrics 35 2.7 Asymmetrical Optics 37 2.8 Examples 41 References 52 3 Etendue and the Winston-Welford Design Method 55 3.1 Introduction 55 3.2 Conservation of Etendue 57 3.3 Nonideal Optical Systems 63 3.4 Etendue as a Geometrical Quantity 65 3.5 Two-Dimensional Systems 68 3.6 Etendue as an Integral of the Optical Momentum 70 3.7 Etendue as a Volume in Phase Space 75 3.8 Etendue as a Difference in Optical Path Length 78 3.9 Flow Lines 83 3.10 The Winston-Welford Design Method 87 3.11 Caustics as Flow Lines 99 ix Contents 3.12 Maximum Concentration 102 3.13 Etendue and the Shape Factor 106 3.14 Examples 110 References 115 Vector Flux 117 4.1 Introduction 117 4.2 Definition of Vector Flux 121 4.3 Vector Flux as a Bisector of the Edge Rays 126 4.4 Vector
    [Show full text]
  • Spaceborn Optoelectronic Sensors and Their Radiometric Calibration
    Spaceborne Optoelectronic Sensors and their Radiometric Calibration. Terms and Definitions. Part 1. Calibration Techniques Alexander V. Prokhorov Raju U. Datla Vitaly P. Zakharenkov Victor Privalsky Thomas W. Humpherys Victor I. Sapritsky Editors: Albert C. Parr Lev K. Issaev QC NIST too National Institute of Standards and Technology *U,SL Technology Administration, U.S. Department of Commerce * 7*03 *oo 5 NISTIR 7203 Spaceborne Optoelectronic Sensors and their Radiometric Calibration. Terms and Definitions. Part 1. Calibration Techniques Alexander V. Prokhorov Raju U. Datla Vitaly P. Zakharenkov Victor Privalsky Thomas W. Humpherys Victor I. Sapritsky Editors: Albert C. Parr Lev K. Issaev NIST National Institute of Standards and Technology Technology Administration, U.S. Department of Commerce NISTIR 7203 Spaceborne Optoelectronic Sensors and their Radiometric Calibration. Terms and Definitions Part 1. Calibration Techniques Alexander V. Prokhorov Raju U. Datla NIST Vitaly P. Zakharenkov Vavilov State Optical Insitute, S. -Petersburg, Russia Victor Privalsky Thomas W. Humpherys Space Dynamics Laboratory/Utah State University, Logan, UT Victor I. Sapritsky All-Russian Research Institute for Optical and Physical Measurements, Moscow, Russia Editors: Albert C. Parr NIST Lev K. Issaev Russian Institute ofMetrological Seiwice, Moscow, Russia March 2005 U.S. DEPARTMENT OF COMMERCE Carlos M. Gutierrez, Secretary TECHNOLOGY ADMINISTRATION Phillip J. Bond, Under Secretaiy of Commercefor Technology' NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY Hratch G. Semerjian, Acting Director 0imHHKMICKTPOHHbl8 flaT4MKM KOCMMMeCKOlO I83MIMBMNI M MX paAMOMeTPHiecKafl KanuGpoBKa TepMHHbi h onpe^ejieHHH HacTb 1. MeTO/jbi Kajm6poBKH AjieKcaimp IlpoxopoB, Pa^y /JaTJia, HaijHOHajibHbiH HHCTHTyT CTaH^apTOB h TexHOJiorHH, reHTec6epr, niTaT MepHnenr, CUJA BMTajiHH 3axapeHKOB, rocy^apcTBeHHbm ohthhcckhh HHCTHTyT hm. C.
    [Show full text]
  • IAT16 Imaging and Aberration Theory Lecture 2 Fourier and Hamiltonian
    Imaging and Aberration Theory Lecture 2: Fourier- and Hamiltonian Optics 2016-10-26 Herbert Gross Winter term 2016 www.iap.uni-jena.de 2 Preliminary time schedule 1 19.10. Paraxial imaging paraxial optics, fundamental laws of geometrical imaging, compound systems Pupils, Fourier optics, pupil definition, basic Fourier relationship, phase space, analogy optics and 2 26.11. Hamiltonian coordinates mechanics, Hamiltonian coordinates Fermat principle, stationary phase, Eikonals, relation rays-waves, geometrical 3 02.11. Eikonal approximation, inhomogeneous media single surface, general Taylor expansion, representations, various orders, stop 4 09.11. Aberration expansions shift formulas different types of representations, fields of application, limitations and pitfalls, 5 16.11. Representation of aberrations measurement of aberrations phenomenology, sph-free surfaces, skew spherical, correction of sph, aspherical 6 23.11. Spherical aberration surfaces, higher orders phenomenology, relation to sine condition, aplanatic sytems, effect of stop 7 30.11. Distortion and coma position, various topics, correction options 8 07.12. Astigmatism and curvature phenomenology, Coddington equations, Petzval law, correction options Dispersion, axial chromatical aberration, transverse chromatical aberration, 9 14.12. Chromatical aberrations spherochromatism, secondary spoectrum Sine condition, aplanatism and Sine condition, isoplanatism, relation to coma and shift invariance, pupil 10 21.12. isoplanatism aberrations, Herschel condition, relation to Fourier optics 11 04.01. Wave aberrations definition, various expansion forms, propagation of wave aberrations special expansion for circular symmetry, problems, calculation, optimal balancing, 12 11.01. Zernike polynomials influence of normalization, measurement 13 18.01. Point spread function ideal psf, psf with aberrations, Strehl ratio 14 25.01. Transfer function transfer function, resolution and contrast Vectorial aberrations, generalized surface contributions, Aldis theorem, intrinsic 15 01.02.
    [Show full text]
  • Phase Space Treatment of Optical Beams*}
    Zoftfooofh CENTRAL INSTITUTE OF PHYSICS INSTITUTE FOR PHYSICS AND TECHNOLOGY OP RADIATION DEVICES Buckare*t, P.O.Sox MG-6,ROMANIA *) POLYTECHNIC INSTITUTE OF BUCHAREST,ELECTRONICS DEPARTMENT PoUiu Street No. 1tBackarz*tt ROMANIA \FT*fc ' L0P-43-19$4 . January PHASE SPACE TREATMENT OF OPTICAL BEAMS*} G.NEMES, I.E.TEOPORESCU*1, MIRELA MEMES*) ABSTRACT. The lecture reveal* the po**lblllty o{ treating op­ tical beam* and *y*ttm* u&lng the. PS concept. In the lint pant some well known concept* and refjJLt* o{ changed particle optici ane applied to optical beam and systems. Attention It, paled to the PSl concept a* to being a beam Invariant accord­ ing to Llouvllte'* theorem. In the second pant some *lmple op­ tical sources, their PSf and their trans {orm* through simple optical element* are theoretically presented. An experimental method and a device {or PSE measurement* are presented In the third part. In the {ourth part the. main problem* o I the linear *y*tem theory which were apptMtd to ilectrlcal circuit* In the tlMe. {or frequency) domain and to optical *y*tem* In the bldl- men*lonal *pace o{ *patlal coordinate.* [or Apatlal frequencies] are applied to *tl%matlc optical *y*tem* In the bldlmtn*lonal PS [*patlal coordinate., angle). Seat example* o{ applying PS concept* In optic* art presented In the frith part. The lectu­ re Is mainly ba*zd on original rt*ult* *ome o{ them being pnv£ou*ly unpubll*htd. t) Iorited lecture pretested at the 3~rd International School cf Coherent Optice, Bucharest, 30 auguet-8 September 1982.
    [Show full text]
  • Design of Axisymmetrical Tailored Concentrators for LED Light Source Applications
    Design of axisymmetrical tailored concentrators for LED light source applications Bart Van Giel*, Youri Meuret and Hugo Thienpont Applied physics and photonics department (TONA), Vrije Universiteit Brussel Pleinlaan 2, 1050 Brussel, Belgium ABSTRACT In our contribution we present a solution to an important question in the design of a LED-based illumination engine for projection systems: the collimation of the LED light. We tested the principle in the modification of a common device in non-imaging optics, the compound Parabolic Concentrator. This CPC-like achieves a collection of 72% (ideal reflective coating presumed). This CPC-like was tailored by numerically solving an differential equation. This approach has some serious drawbacks. For a compact collection device with high collimation, an other approach is required. A more elegant design strategy will rely fully on geometrical principles. The result of our work is a compound collection lens that achieves a collection efficiency of 87%, assuming an ideal reflective coating and neglecting Fresnel losses. We study the performance of this device in detail. Further enhancements are suggested. Keywords: light-emitting diode, projection display, edge ray theorem, etendue, collimation, illumination, optimization, optical design, tailored surfaces 1 INTRODUCTION The increase of the emitted light flux of light emitting diodes (LEDs) makes it interesting to use these devices as light sources for projector applications. LEDs are small light sources with a narrow spectral emission band and a low operating voltage, which makes them a ideal light source for compact, very light and inexpensive projector applications. [1] However, LEDs have also an important disadvantage. The optical power per unit of étendue is significantly lower than e.g.
    [Show full text]
  • Etendue and Optical Throughput Calculations Authors: H
    TECHNICAL NOTE #002-2-14-2011 Etendue and Optical Throughput Calculations Authors: H. Zhu and P. Blackborow Introduction This note is intended to help decide whether a Laser-Driven Light Source (LDLS™) is the appropriate source for an application. In this note we will consider only the optical performance and not other benefits of the LDLS, such as stability or ultra-long life. One of the main factors to consider is whether or not the étendue of the LDLS matches the étendue of the optical system. To have an optimized throughput in an optical system, the étendue of the light source, the collecting optics, and the étendue of the light receiving optics, optical fibers or monochromators, need to be closely matched. (In this Application Note, a monochromator can also mean a spectrometer or a spectrograph.) In addition to the term “étendue,” other terms often used are “f-number” (F/#) and “numerical aperture” (NA). Etendue and its relationship to F/# and NA of an optical system will be discussed, in addition to discussions on how to use étendue and throughput calculations to select appropriate LDLS applications. For simplicity, diffraction and coherence effects are excluded in these discussions. What is Etendue and Why Etendue Matching is Important for Effective Light Coupling The term étendue comes from the French word for extent or spread. Other terms used for this property are Geometrical Extent (G), Optical Extent, and Optical Invariant. We will use G to represent étendue. For a LDLS source with relatively small cone of radiation (so paraxial optical approximation is valid), the étendue (G) of a light source is equal to the source emitting area (S) times the solid angle (Ω) from which the light is collected for a specific application, G ≈ SΩ [mm2-sr].
    [Show full text]