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Radiometric and Photometric Concepts Based on Measurement Techniques C
Application Note No. 6 April 1982 Radiometric and Photometric Concepts Based on Measurement Techniques C. Richard Duda Senior Scientist, United Detector Technology 3939 Lanmark Street, Culver City, Cal. 90230 Abstract The value of the fundamental quality in radiometry, the bution of optical radiation. In 1937 the National Bureau watt, is presently realized by electrical substitution in of Standards transferred the luminous intensity produced which the temperature produced in a blackened mate- by a platinium blackbody to a series of lamps. This orig- rial due to absorption of radiant energy is balanced inal calibration has served to this date for standardiza- against that produced by electrical energy whose cur- tion of lamps used by industry to realize the photometric rent and voltage can accurately be measured. A new scale. Recently the fundamental unit in photometry was method to measure optical radiation is being explored changed from the candela, as defined by a blackbody, to by the National Bureau of Standards in which photons the lumen, as defined by the watt, uniting the conceptual are absorbed in a semiconductor and converted with ef- interrelationships between photometry and radiometry. 1 ficiency closely approaching the theoretical maximum Changes in the photometric scale due to redefinition of - 100 percent. its less than one percent difference in NBS lamp inten- sity values. 2 Other radiometric concepts, such as radiance, irradi- ance, and radiant intensity can easily be defined through Because Vλ , the mathematical representations of human simple geometric relationships. Photometry on the other visual spectral response is difficult to realize with a high hand, while sharing these identical relationships also in- degree of accuracy in a practical detector, comparison troduces detector response modeled after human visual of sources with a broad spectral distribution can best be traits; new measurement unit names, and reliance on accomplished with a reference source. -
Foot-Candles: Photometric Units
UPDATED EXTRACT FROM CREG JOURNAL. FILE: FOOT3-UP.DOC REV. 8. LAST SAVED: 01/02/01 15:14 PHOTOMETRICS Foot-Candles: Photometric Units More footnotes on optical topics. David Gibson describes the confusing range of photometric units. A discussion of photometric units may the ratio of luminous efficiency to luminous The non-SI unit mean spherical candle- seem out of place in an electronic journal but efficiency at the wavelength where the eye is power is the intensity of a source if its light engineers frequently have to use light sources most sensitive. Unfortunately, however, this output were spread evenly in all directions. It and detectors. The units of photometry are term can be confused with the term efficacy, is therefore equivalent to the flux [lm] ¸ 4p. some of the most confusing and least which is used to describe the efficiency at standardised of units. converting electrical to luminous power. Luminance Photometric units are not difficult to The candela measures the intensity of a understand, but can be a minefield to the Illumination, Luminous Emittance. point source. We also need to define the uninitiated since many non-SI units are still The illumination of a surface is the properties of an extended source. Each small in use, and there are subtle differences incident power flux density measured in element DS of a diffuse reflective surface will between quantities with similar names, such lumens per square metre. A formal definition scatter the incident flux DF and behave as if as illumination and luminance. would be along the lines of: if a flux DF is it were an infinitesimal point source. -
LEP 2.4.04 Lambert's
R LEP Lambert’s law 2.4.04 Related topics Problems luminous flux, light quantity, light intensity, illuminance, lumi- 1. The luminous flux emitted reflected by a diffusely reflecting nance. surface is to be determined as a function of the angle of observation. Principle and task 2. Lambert’s law (cos-law) is to be verified using the graph of the measurement values. Visible light impinges on a diffusely reflecting surface. The luminance of this surface is determined as a function of the angle of observation. Set up and procedure The stand tube is introduced into the articulated radial holder, Equipment which is fitted with an angular scale, until it goes no further. The articulated radial holder is then attached to the tripod Housing for experiment lamp 08129.01 1 base, after which the tripod rods are clamped each with an Halogen lamp, 12 V/50 W 08129.06 1 edge facing upward. The luxmeter probe is attached to the Holder G 6.35 f. 50/100 W halo.lamp 08129.04 1 short support rod using the universal clamp in such a way that Double condenser, f 60 mm 08137.00 1 it points to the pivoting centre whilst being aligned with the Lens holder 08012.00 1 rod. The rest of the set up is shown in Fig. 1. The distances of Lens, mounted, f +200 mm 08024.01 1 the components from the pivot centre are shown in Fig. 2. Zinc sulfide screen 08450.00 1 Right angle clamp -PASS- 02040.55 4 On the luminous screen, the surface of which is directed per- Tripod base -PASS- 02002.55 1 pendicularly to the optical axis to start with, a circular surface B Barrel base -PASS- 02006.55 1 ( approx. -
Photometric Calibrations —————————————————————————
NIST Special Publication 250-37 NIST MEASUREMENT SERVICES: PHOTOMETRIC CALIBRATIONS ————————————————————————— Yoshihiro Ohno Optical Technology Division Physics Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899 Supersedes SP250-15 Reprint with changes July 1997 ————————————————————————— U.S. DEPARTMENT OF COMMERCE William M. Daley, Secretary Technology Administration Gary R. Bachula, Acting Under Secretary for Technology National Institute of Standards and Technology Robert E. Hebner, Acting Director PREFACE The calibration and related measurement services of the National Institute of Standards and Technology are intended to assist the makers and users of precision measuring instruments in achieving the highest possible levels of accuracy, quality, and productivity. NIST offers over 300 different calibrations, special tests, and measurement assurance services. These services allow customers to directly link their measurement systems to measurement systems and standards maintained by NIST. These services are offered to the public and private organizations alike. They are described in NIST Special Publication (SP) 250, NIST Calibration Services Users Guide. The Users Guide is supplemented by a number of Special Publications (designated as the “SP250 Series”) that provide detailed descriptions of the important features of specific NIST calibration services. These documents provide a description of the: (1) specifications for the services; (2) design philosophy and theory; (3) NIST measurement system; (4) NIST operational procedures; (5) assessment of the measurement uncertainty including random and systematic errors and an error budget; and (6) internal quality control procedures used by NIST. These documents will present more detail than can be given in NIST calibration reports, or than is generally allowed in articles in scientific journals. In the past, NIST has published such information in a variety of ways. -
Illumination Fundamentals
Illumination Fundamentals The LRC wishes to thank Optical Research Associates for funding this booklet to promote basic understanding of the science of light and illumination. Project Coordinator: John Van Derlofske Author: Alma E. F. Taylor Graphics: Julie Bailey and James Gross Layout: Susan J. Sechrist Cover Design: James Gross Technical Reviewers: Dr. Mark Rea and Dr. John Van Derlofske of the Lighting Research Center; Dr. William Cassarly and Stuart David of Optical Research Associates. Table 2.1 and Figures 2-3 and 2-5 are from Physics for Scientists and Engineers, copyright (c) 1990 by Raymond A. Serway, reproduced by permission of Harcourt, Inc. No portion of this publication or the information contained herein may be duplicated or excerpted in any way in other publications, databases, or any other medium without express written permission of the publisher. Making copies of all or part of this publication for any purpose other than for undistributed personal use is a violation of United States copyright laws. © 2000 Rensselaer Polytechnic Institute. All rights reserved. Illumination Fundamentals 3 Contents 1. Light and Electromagnetic Radiation ...................................... 7 1.1. What is Light? ................................................................... 7 1.2. The “Visible” Spectrum .................................................... 8 1.3. Ultraviolet Radiation ........................................................ 8 1.4. Infrared Radiation ............................................................ 8 2. -
The International System of Units (SI) - Conversion Factors For
NIST Special Publication 1038 The International System of Units (SI) – Conversion Factors for General Use Kenneth Butcher Linda Crown Elizabeth J. Gentry Weights and Measures Division Technology Services NIST Special Publication 1038 The International System of Units (SI) - Conversion Factors for General Use Editors: Kenneth S. Butcher Linda D. Crown Elizabeth J. Gentry Weights and Measures Division Carol Hockert, Chief Weights and Measures Division Technology Services National Institute of Standards and Technology May 2006 U.S. Department of Commerce Carlo M. Gutierrez, Secretary Technology Administration Robert Cresanti, Under Secretary of Commerce for Technology National Institute of Standards and Technology William Jeffrey, Director Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose. National Institute of Standards and Technology Special Publications 1038 Natl. Inst. Stand. Technol. Spec. Pub. 1038, 24 pages (May 2006) Available through NIST Weights and Measures Division STOP 2600 Gaithersburg, MD 20899-2600 Phone: (301) 975-4004 — Fax: (301) 926-0647 Internet: www.nist.gov/owm or www.nist.gov/metric TABLE OF CONTENTS FOREWORD.................................................................................................................................................................v -
EL Light Output Definition.Pdf
GWENT GROUP ADVANCED MATERIAL SYSTEMS Luminance The candela per square metre (cd/m²) is the SI unit of luminance; nit is a non-SI name also used for this unit. It is often used to quote the brightness of computer displays, which typically have luminance’s of 50 to 300 nits (the sRGB spec for monitor’s targets 80 nits). Modern flat-panel (LCD and plasma) displays often exceed 300 cd/m² or 300 nits. The term is believed to come from the Latin "nitere" = to shine. Candela per square metre 1 Kilocandela per square metre 10-3 Candela per square centimetre 10-4 Candela per square foot 0,09 Foot-lambert 0,29 Lambert 3,14×10-4 Nit 1 Stilb 10-4 Luminance is a photometric measure of the density of luminous intensity in a given direction. It describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle. The SI unit for luminance is candela per square metre (cd/m2). The CGS unit of luminance is the stilb, which is equal to one candela per square centimetre or 10 kcd/m2 Illuminance The lux (symbol: lx) is the SI unit of illuminance and luminous emittance. It is used in photometry as a measure of the intensity of light, with wavelengths weighted according to the luminosity function, a standardized model of human brightness perception. In English, "lux" is used in both singular and plural. Microlux 1000000 Millilux 1000 Lux 1 Kilolux 10-3 Lumen per square metre 1 Lumen per square centimetre 10-4 Foot-candle 0,09 Phot 10-4 Nox 1000 In photometry, illuminance is the total luminous flux incident on a surface, per unit area. -
Notes: D=Distance in Meters A=Pupil Area in Mm2 = 3.14159 Eq
2. Physical and Physiological Optics I. Radiometry Energy (erg = dyne cm; joule = 107 erg) Power P (erg/sec, watt = joule/sec, horsepower, calorie) Radiant flux, also P (watts, passing through an area of a surface coming from one side of the surface) dP Irradiance E = radiant flux/area (watt/cm2) = where S is area e dS Primary/Secondary sources Solid angle ω (steradians) vs angle θ (radians) Point sources dP Radiant intensity I = (watts/steradian emitted in a particular direction) e dω 2 Therefore, irradiance Ee = Iecosθ/r on a surface situated along that direction Extended sources (the sky, a piece of paper, a monitor screen) dP 2 Radiant emittance Me = = watt/cm emitted in all directions A B dS S Next, consider the case when the source is a surface. ∆ Plane A is close to the source, and has a small hole ∆σ of size ∆σ small enough to be treated as a point source. The observer is at plane B a large distance r O x away. Thus, as seen from B, the hole subtends solid θ angle ∆ω=∆σ/r 2. The observers sees a patch of area ∆S of the surface through the hole. r 2 Radiance Le = watt/cm /steradian emitted by a patch in a particular direction = dIe /dσ = radiant intensity per area of hole = dEe /dω = received irradiance per solid angle of source (i.e., per steradian) 2 2 (because ∆Ee=∆Ie /r and ∆ω=∆σ/r ) Lambertian (source/surface), cosine law, here’s the derivation: ∆σ = ∆S cosθ ∆P = ∫Le∆σdω ω Me∆S = ∫Le∆σdω ω Me = ∫Lecosθdω ω Change integration to annuli around the normal, and for Lambertian surface, Le is independent of θ: dω = 2πsinθdθ π 2 Hence: Me = πLe ∫ sin2θdθ = πLe 0 Light as a wave speed of light c ∼ 3 × 1010 cm/sec wavelength λ = c /ν (in nm = 10−9 meters) (visible = blue 400 to red 700) Light as particles Photons, each of energy hν (h = 6.6245 × 10−27 erg sec; ν = cycles/sec) Expected number of quanta = energy/energy-per-photon Spectral content Spectral power distribution (e.g. -
Radiometry and Photometry FAQ
Radiometry and photometry FAQ by James M. Palmer Research Professor Optical Sciences Center University of Arizona Tucson, AZ; 85721 “When I use a word, it means just what I choose it to mean - neither more nor less.” Lewis Carroll (Charles Lutwidge Dodgson) Effective technical communication demands a system of symbols, units and nomenclature (SUN) that is reasonably consistent and that has widespread acceptance. Such a system is the International System of Units (SI). There is no area where words are more important than radiometry and photometry. This document is an attempt to provide necessary and correct information to become conversant. 1. What is the motivation for this FAQ? 2. What is radiometry? What is photometry? How do they differ? 3. What is projected area? What is solid angle? 4. What are the quantities and units used in radiometry? 5. How do I account for spectral quantities? 6. What are the quantities and units used in photometry? 7. What is the difference between lambertian and isotropic? 8. When do the properties of the eye get involved? 9. How do I convert between radiometric and photometric units? 10. Where can I learn more about this stuff? 1. What is the motivation for this FAQ? There is so much misinformation and conceptual confusion regarding photometry and radiometry, particularly on the WWW by a host of “authorities”, it is high time someone got it straight. So here it is, with links to the responsible agencies. RADIOMETRY & PHOTOMETRY FAQ 1 Background: It all started over a century ago. An organization called the General Conference on Weights and Measures (CGPM) was formed by a diplomatic treaty called the Metre Convention. -
Illuminating Terms & Graphics
Illuminating Terms & Graphics Candela ~ the basic SI unit of luminous intensity; the luminous intensity in a given direction of a source that emits monochromatic radiation Golden Ratio in design ~ an ideal based on Fibonacci. In this case the number 8, which is 3 + 5. Lumen (unit) ~ The lumen (symbol: lm) is the SI derived unit of luminous flux, a measure of the total quantity of visible light emitted by a source. Illuminance ~ the lighting up of a surface area. It is a measure of the amount of light falling onto (illuminating) and spreading over the given surface area. It correlates with how humans perceive brightness of an illuminated area. Illuminance is often called brightness, which leads to confusion, as brightness can be used to also describe luminance. Brightness is a reference to physiological sensations and perceptions of light; it is not to be used for quantitative purposes. The SI unit for illuminance is lux (lx). Sometimes people use the term foot-candle; foot-candle is a non SI unit of illuminance widely used in the United States. The term “foot-candle” means “the illuminance on a surface by a candela source one foot away”. One foot-candle is equivalent to one lumen per square foot which is approximately 10.764 lux. Luminance ~ the measure of the amount of light passing through, emitting or reflected from a particular surface traveling at a solid angle; it indicates how much luminous power can be perceived by a human eye. Thus luminance indicates the brightness of emitted or reflected surface. Luminance is used in the display industry to quantify the brightness of displays. -
Technical Standards Board Standard
TECHNICAL REV. STANDARDS TSB 003 MAY1999 BOARD Issued 1965-06 400 Commonwealth Drive, Warrendale, PA 15096-0001 STANDARD Revised 1999-05 Superseding TSB 003 JUN92 Submitted for recognition as an American National Standard Rules for SAE Use of SI (Metric) Units Foreword—SI denotes The International System of Units (Le Système International d’Unités). SI was established in 1960, under the Treaty of the Meter, by Resolutions and Recommendations of the General Conference on Weights and Measures (Conférence Générale des Poids et Mesures, CGPM) and the International Committee for Weights and Measures (Comité International des Poids et Mesures, CIPM) on The International System of Units. The abbreviation "SI" is used in all languages. In 1969, the SAE Board of Directors issued a directive that "SAE will include SI units in SAE Standards and other technical reports." During the ensuing several decades, SAE metric policy evolved and implementation progressed. The SAE’s current metric policy is, "Operating Boards shall not use any weights and measures system other than metric (SI), except when conversion is not practical, or where a conflicting world industry practice exists." Principal driving forces for SAE metrication were: worldwide movement to metric units; enactment of United States Federal metric legislation and the resultant national metrication activity; the international trend in industry and business throughout the world, and the growing international scope of SAE. Currently, the widespread, strong support for international standards harmonization is another key motivating factor in the global metrication movement. TSB 003 (formerly SAE J916) has been updated periodically, to reflect SAE metric policy evolution—as well as developments in the specific, formal content of SI; and in the correct, consistent usage and application of SI...which sometimes is referred to as "the modern version of the metric measurement system." The content of TSB 003 is consistent with international and U.S. -
1. 2 Photometric Units
4 CHAPTERl INTRODUCTION 1. 2 Photometric units Before starting to describe photomultiplier tubes and their characteristics,this section briefly discusses photometric units commonly used to measurethe quantity of light. This section also explains the wavelength regions of light (spectralrange) and the units to denotethem, as well as the unit systemsused to expresslight intensity. Since information included here is just an overview of major photometric units, please refer to specialty books for more details. 1. 2. 1 Spectral regions and units Electromagneticwaves cover a very wide rangefrom gammarays up to millimeter waves.So-called "light" is a very narrow range of theseelectromagnetic waves. Table 1-1 showsdesignated spectral regions when light is classified by wavelength,along with the conver- sion diagram for light units. In general, what we usually refer to as light covers a range from 102to 106 nanometers(nm) in wavelength. The spectral region between 350 and 70Onmshown in the table is usually known as the visible region. The region with wavelengthsshorter than the visible region is divided into near UV (shorter than 35Onrn),vacuum UV (shorter than 200nm) where air is absorbed,and extremeUV (shorter than 100nm). Even shorter wavelengthsspan into the region called soft X-rays (shorter than IOnrn) and X- rays. In contrast, longer wavelengths beyond the visible region extend from near IR (750nm or up) to the infrared (severalmicrometers or up) and far IR (severaltens of micrometers) regions. Wavelength Spectral Range Frequency Energy nm (Hz) (eV) X-ray Soft X-ray 10 102 1016 ExtremeUV region 102 10 Vacuum UV region 200 Ultravioletregion 10'5 350 Visible region 750 103 Near infraredregion 1 1014 104 Infrared region 10-1 1013 105 10-2 Far infrared region 1012 106 10-3 .