1. 2 Photometric Units
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Glossary Physics (I-Introduction)
1 Glossary Physics (I-introduction) - Efficiency: The percent of the work put into a machine that is converted into useful work output; = work done / energy used [-]. = eta In machines: The work output of any machine cannot exceed the work input (<=100%); in an ideal machine, where no energy is transformed into heat: work(input) = work(output), =100%. Energy: The property of a system that enables it to do work. Conservation o. E.: Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes. Equilibrium: The state of an object when not acted upon by a net force or net torque; an object in equilibrium may be at rest or moving at uniform velocity - not accelerating. Mechanical E.: The state of an object or system of objects for which any impressed forces cancels to zero and no acceleration occurs. Dynamic E.: Object is moving without experiencing acceleration. Static E.: Object is at rest.F Force: The influence that can cause an object to be accelerated or retarded; is always in the direction of the net force, hence a vector quantity; the four elementary forces are: Electromagnetic F.: Is an attraction or repulsion G, gravit. const.6.672E-11[Nm2/kg2] between electric charges: d, distance [m] 2 2 2 2 F = 1/(40) (q1q2/d ) [(CC/m )(Nm /C )] = [N] m,M, mass [kg] Gravitational F.: Is a mutual attraction between all masses: q, charge [As] [C] 2 2 2 2 F = GmM/d [Nm /kg kg 1/m ] = [N] 0, dielectric constant Strong F.: (nuclear force) Acts within the nuclei of atoms: 8.854E-12 [C2/Nm2] [F/m] 2 2 2 2 2 F = 1/(40) (e /d ) [(CC/m )(Nm /C )] = [N] , 3.14 [-] Weak F.: Manifests itself in special reactions among elementary e, 1.60210 E-19 [As] [C] particles, such as the reaction that occur in radioactive decay. -
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. -
Luminance Requirements for Lighted Signage
Luminance Requirements for Lighted Signage Jean Paul Freyssinier, Nadarajah Narendran, John D. Bullough Lighting Research Center Rensselaer Polytechnic Institute, Troy, NY 12180 www.lrc.rpi.edu Freyssinier, J.P., N. Narendran, and J.D. Bullough. 2006. Luminance requirements for lighted signage. Sixth International Conference on Solid State Lighting, Proceedings of SPIE 6337, 63371M. Copyright 2006 Society of Photo-Optical Instrumentation Engineers. This paper was published in the Sixth International Conference on Solid State Lighting, Proceedings of SPIE and is made available as an electronic preprint with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. Luminance Requirements for Lighted Signage Jean Paul Freyssinier*, Nadarajah Narendran, John D. Bullough Lighting Research Center, Rensselaer Polytechnic Institute, 21 Union Street, Troy, NY 12180 USA ABSTRACT Light-emitting diode (LED) technology is presently targeted to displace traditional light sources in backlighted signage. The literature shows that brightness and contrast are perhaps the two most important elements of a sign that determine its attention-getting capabilities and its legibility. Presently, there are no luminance standards for signage, and the practice of developing brighter signs to compete with signs in adjacent businesses is becoming more commonplace. Sign luminances in such cases may far exceed what people usually need for identifying and reading a sign. Furthermore, the practice of higher sign luminance than needed has many negative consequences, including higher energy use and light pollution. -
Report on Digital Sign Brightness
REPORT ON DIGITAL SIGN BRIGHTNESS Prepared for the Nevada State Department of Transportation, Washoe County, City of Reno and City of Sparks By Jerry Wachtel, President, The Veridian Group, Inc., Berkeley, CA November 2014 1 Table of Contents PART 1 ......................................................................................................................... 3 Introduction. ................................................................................................................ 3 Background. ................................................................................................................. 3 Key Terms and Definitions. .......................................................................................... 4 Luminance. .................................................................................................................................................................... 4 Illuminance. .................................................................................................................................................................. 5 Reflected Light vs. Emitted Light (Traditional Signs vs. Electronic Signs). ...................................... 5 Measuring Luminance and Illuminance ........................................................................ 6 Measuring Luminance. ............................................................................................................................................. 6 Measuring Illuminance. .......................................................................................................................................... -
Lecture 3: the Sensor
4.430 Daylighting Human Eye ‘HDR the old fashioned way’ (Niemasz) Massachusetts Institute of Technology ChriChristoph RstophReeiinhartnhart Department of Architecture 4.4.430 The430The SeSensnsoror Building Technology Program Happy Valentine’s Day Sun Shining on a Praline Box on February 14th at 9.30 AM in Boston. 1 Happy Valentine’s Day Falsecolor luminance map Light and Human Vision 2 Human Eye Outside view of a human eye Ophtalmogram of a human retina Retina has three types of photoreceptors: Cones, Rods and Ganglion Cells Day and Night Vision Photopic (DaytimeVision): The cones of the eye are of three different types representing the three primary colors, red, green and blue (>3 cd/m2). Scotopic (Night Vision): The rods are repsonsible for night and peripheral vision (< 0.001 cd/m2). Mesopic (Dim Light Vision): occurs when the light levels are low but one can still see color (between 0.001 and 3 cd/m2). 3 VisibleRange Daylighting Hanbook (Reinhart) The human eye can see across twelve orders of magnitude. We can adapt to about 10 orders of magnitude at a time via the iris. Larger ranges take time and require ‘neural adaptation’. Transition Spaces Outside Atrium Circulation Area Final destination 4 Luminous Response Curve of the Human Eye What is daylight? Daylight is the visible part of the electromagnetic spectrum that lies between 380 and 780 nm. UV blue green yellow orange red IR 380 450 500 550 600 650 700 750 wave length (nm) 5 Photometric Quantities Characterize how a space is perceived. Illuminance Luminous Flux Luminance Luminous Intensity Luminous Intensity [Candela] ~ 1 candela Courtesy of Matthew Bowden at www.digitallyrefreshing.com. -
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. -
Light and Illumination
ChapterChapter 3333 -- LightLight andand IlluminationIllumination AAA PowerPointPowerPointPowerPoint PresentationPresentationPresentation bybyby PaulPaulPaul E.E.E. Tippens,Tippens,Tippens, ProfessorProfessorProfessor ofofof PhysicsPhysicsPhysics SouthernSouthernSouthern PolytechnicPolytechnicPolytechnic StateStateState UniversityUniversityUniversity © 2007 Objectives:Objectives: AfterAfter completingcompleting thisthis module,module, youyou shouldshould bebe ableable to:to: •• DefineDefine lightlight,, discussdiscuss itsits properties,properties, andand givegive thethe rangerange ofof wavelengthswavelengths forfor visiblevisible spectrum.spectrum. •• ApplyApply thethe relationshiprelationship betweenbetween frequenciesfrequencies andand wavelengthswavelengths forfor opticaloptical waves.waves. •• DefineDefine andand applyapply thethe conceptsconcepts ofof luminousluminous fluxflux,, luminousluminous intensityintensity,, andand illuminationillumination.. •• SolveSolve problemsproblems similarsimilar toto thosethose presentedpresented inin thisthis module.module. AA BeginningBeginning DefinitionDefinition AllAll objectsobjects areare emittingemitting andand absorbingabsorbing EMEM radiaradia-- tiontion.. ConsiderConsider aa pokerpoker placedplaced inin aa fire.fire. AsAs heatingheating occurs,occurs, thethe 1 emittedemitted EMEM waveswaves havehave 2 higherhigher energyenergy andand 3 eventuallyeventually becomebecome visible.visible. 4 FirstFirst redred .. .. .. thenthen white.white. LightLightLight maymaymay bebebe defineddefineddefined -
Illumination and Distance
PHYS 1400: Physical Science Laboratory Manual ILLUMINATION AND DISTANCE INTRODUCTION How bright is that light? You know, from experience, that a 100W light bulb is brighter than a 60W bulb. The wattage measures the energy used by the bulb, which depends on the bulb, not on where the person observing it is located. But you also know that how bright the light looks does depend on how far away it is. That 100W bulb is still emitting the same amount of energy every second, but if you are farther away from it, the energy is spread out over a greater area. You receive less energy, and perceive the light as less bright. But because the light energy is spread out over an area, it’s not a linear relationship. When you double the distance, the energy is spread out over four times as much area. If you triple the distance, the area is nine Twice the distance, ¼ as bright. Triple the distance? 11% as bright. times as great, meaning that you receive only 1/9 (or 11%) as much energy from the light source. To quantify the amount of light, we will use units called lux. The idea is simple: energy emitted per second (Watts), spread out over an area (square meters). However, a lux is not a W/m2! A lux is a lumen per m2. So, what is a lumen? Technically, it’s one candela emitted uniformly across a solid angle of 1 steradian. That’s not helping, is it? Examine the figure above. The source emits light (energy) in all directions simultaneously. -
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. -
Black Body Radiation and Radiometric Parameters
Black Body Radiation and Radiometric Parameters: All materials absorb and emit radiation to some extent. A blackbody is an idealization of how materials emit and absorb radiation. It can be used as a reference for real source properties. An ideal blackbody absorbs all incident radiation and does not reflect. This is true at all wavelengths and angles of incidence. Thermodynamic principals dictates that the BB must also radiate at all ’s and angles. The basic properties of a BB can be summarized as: 1. Perfect absorber/emitter at all ’s and angles of emission/incidence. Cavity BB 2. The total radiant energy emitted is only a function of the BB temperature. 3. Emits the maximum possible radiant energy from a body at a given temperature. 4. The BB radiation field does not depend on the shape of the cavity. The radiation field must be homogeneous and isotropic. T If the radiation going from a BB of one shape to another (both at the same T) were different it would cause a cooling or heating of one or the other cavity. This would violate the 1st Law of Thermodynamics. T T A B Radiometric Parameters: 1. Solid Angle dA d r 2 where dA is the surface area of a segment of a sphere surrounding a point. r d A r is the distance from the point on the source to the sphere. The solid angle looks like a cone with a spherical cap. z r d r r sind y r sin x An element of area of a sphere 2 dA rsin d d Therefore dd sin d The full solid angle surrounding a point source is: 2 dd sind 00 2cos 0 4 Or integrating to other angles < : 21cos The unit of solid angle is steradian. -
Determination of Resistances for Brightness Compensation
www.osram-os.com Application Note No. AN041 Determination of resistances for brightness compensation Application Note Valid for: TOPLED® / Chip LED® / Multi Chip LED® TOPLED E1608® /Mini TOPLED® / PointLED® Advanced Power TOPLED® / FIREFLY® SIDELED® Abstract This application note describes the procedure for adjusting the brightness of light emitting diodes (LEDs) in applications by means of resistors. For better repeatability, the calculation of the required resistance values is shown by means of an example. Author: Hofman Markus / Haefner Norbert 2021-08-10 | Document No.: AN041 1 / 14 www.osram-os.com Table of contents A. Introduction ............................................................................................................ 2 B. Basic procedure ..................................................................................................... 2 C. Possible sources of errors ..................................................................................... 3 Temperature ...................................................................................................... 3 Forward voltage ................................................................................................. 4 D. Application example .............................................................................................. 4 E. Conclusion ........................................................................................................... 12 A. Introduction Due to manufacturing tolerances during production, LEDs cannot be produced -
2.1 Definition of the SI
CCPR/16-53 Modifications to the Draft of the ninth SI Brochure dated 16 September 2016 recommended by the CCPR to the CCU via the CCPR president Takashi Usuda, Wednesday 14 December 2016. The text in black is a selection of paragraphs from the brochure with the section title for indication. The sentences to be modified appear in red. 2.1 Definition of the SI Like for any value of a quantity, the value of a fundamental constant can be expressed as the product of a number and a unit as Q = {Q} [Q]. The definitions below specify the exact numerical value of each constant when its value is expressed in the corresponding SI unit. By fixing the exact numerical value the unit becomes defined, since the product of the numerical value {Q} and the unit [Q] has to equal the value Q of the constant, which is postulated to be invariant. The seven constants are chosen in such a way that any unit of the SI can be written either through a defining constant itself or through products or ratios of defining constants. The International System of Units, the SI, is the system of units in which the unperturbed ground state hyperfine splitting frequency of the caesium 133 atom Cs is 9 192 631 770 Hz, the speed of light in vacuum c is 299 792 458 m/s, the Planck constant h is 6.626 070 040 ×1034 J s, the elementary charge e is 1.602 176 620 8 ×1019 C, the Boltzmann constant k is 1.380 648 52 ×1023 J/K, 23 -1 the Avogadro constant NA is 6.022 140 857 ×10 mol , 12 the luminous efficacy of monochromatic radiation of frequency 540 ×10 hertz Kcd is 683 lm/W.