Determination and Validation of the Spectral Power Distribution (SPD)
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TIE-35: Transmittance of Optical Glass
DATE October 2005 . PAGE 1/12 TIE-35: Transmittance of optical glass 0. Introduction Optical glasses are optimized to provide excellent transmittance throughout the total visible range from 400 to 800 nm. Usually the transmittance range spreads also into the near UV and IR regions. As a general trend lowest refractive index glasses show high transmittance far down to short wavelengths in the UV. Going to higher index glasses the UV absorption edge moves closer to the visible range. For highest index glass and larger thickness the absorption edge already reaches into the visible range. This UV-edge shift with increasing refractive index is explained by the general theory of absorbing dielectric media. So it may not be overcome in general. However, due to improved melting technology high refractive index glasses are offered nowadays with better blue-violet transmittance than in the past. And for special applications where best transmittance is required SCHOTT offers improved quality grades like for SF57 the grade SF57 HHT. The aim of this technical information is to give the optical designer a deeper understanding on the transmittance properties of optical glass. 1. Theoretical background A light beam with the intensity I0 falls onto a glass plate having a thickness d (figure 1-1). At the entrance surface part of the beam is reflected. Therefore after that the intensity of the beam is Ii0=I0(1-r) with r being the reflectivity. Inside the glass the light beam is attenuated according to the exponential function. At the exit surface the beam intensity is I i = I i0 exp(-kd) [1.1] where k is the absorption constant. -
Reflectance and Transmittance Sphere
Reflectance and Transmittance Sphere Spectral Evolution four inch portable reflectance/ transmittance sphere is ideal for measuring vegetation physiological states SPECTRAL EVOLUTION offers a portable, compact four inch reflectance/transmittance (R/T) integrating sphere for measuring the reflectance and transmittance of vegetation. The 4 inch R/T sphere is lightweight and portable so you can take it into the field for in situ meas- urements, delivered with a stand as well as a ¼-20 mount for use with tripods. When used with a SPECTRAL EVOLUTION spectrometer or spectroradiometer such as the PSR+, RS-3500, RS- 5400, SR-6500 or RS-8800, it delivers detailed information for measurements of transmittance and reflectance modes. Two varying light intensity levels (High and Low) allow for a broader range of samples to be measured. Light reflected or transmitted from a sample in a sphere is integrated over a full hemisphere, with measurements insensitive to sample anisotropic directional reflectance (transmittance). This provides repeatable measurements of a variety of samples. The 4 inch portable R/T sphere can be used in vegetation studies such as, deriving absorbance characteristics, and estimating the leaf area index (LAI) from radiation reflected from a canopy surface. The sphere allows researchers to limit destructive sampling and provides timely data acquisition of key material samples. The R/T sphere allows you to collect all diffuse light reflected from a sample – measuring total hemispherical reflectance. You can measure reflectance and transmittance, and calculate absorption. You can select the bulb inten- sity level that suits your sample. A white reference is provided for both reflectance and transmittance measurements. -
Guide for the Use of the International System of Units (SI)
Guide for the Use of the International System of Units (SI) m kg s cd SI mol K A NIST Special Publication 811 2008 Edition Ambler Thompson and Barry N. Taylor NIST Special Publication 811 2008 Edition Guide for the Use of the International System of Units (SI) Ambler Thompson Technology Services and Barry N. Taylor Physics Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899 (Supersedes NIST Special Publication 811, 1995 Edition, April 1995) March 2008 U.S. Department of Commerce Carlos M. Gutierrez, Secretary National Institute of Standards and Technology James M. Turner, Acting Director National Institute of Standards and Technology Special Publication 811, 2008 Edition (Supersedes NIST Special Publication 811, April 1995 Edition) Natl. Inst. Stand. Technol. Spec. Publ. 811, 2008 Ed., 85 pages (March 2008; 2nd printing November 2008) CODEN: NSPUE3 Note on 2nd printing: This 2nd printing dated November 2008 of NIST SP811 corrects a number of minor typographical errors present in the 1st printing dated March 2008. Guide for the Use of the International System of Units (SI) Preface The International System of Units, universally abbreviated SI (from the French Le Système International d’Unités), is the modern metric system of measurement. Long the dominant measurement system used in science, the SI is becoming the dominant measurement system used in international commerce. The Omnibus Trade and Competitiveness Act of August 1988 [Public Law (PL) 100-418] changed the name of the National Bureau of Standards (NBS) to the National Institute of Standards and Technology (NIST) and gave to NIST the added task of helping U.S. -
Extraction of Incident Irradiance from LWIR Hyperspectral Imagery Pierre Lahaie, DRDC Valcartier 2459 De La Bravoure Road, Quebec, Qc, Canada
DRDC-RDDC-2015-P140 Extraction of incident irradiance from LWIR hyperspectral imagery Pierre Lahaie, DRDC Valcartier 2459 De la Bravoure Road, Quebec, Qc, Canada ABSTRACT The atmospheric correction of thermal hyperspectral imagery can be separated in two distinct processes: Atmospheric Compensation (AC) and Temperature and Emissivity separation (TES). TES requires for input at each pixel, the ground leaving radiance and the atmospheric downwelling irradiance, which are the outputs of the AC process. The extraction from imagery of the downwelling irradiance requires assumptions about some of the pixels’ nature, the sensor and the atmosphere. Another difficulty is that, often the sensor’s spectral response is not well characterized. To deal with this unknown, we defined a spectral mean operator that is used to filter the ground leaving radiance and a computation of the downwelling irradiance from MODTRAN. A user will select a number of pixels in the image for which the emissivity is assumed to be known. The emissivity of these pixels is assumed to be smooth and that the only spectrally fast varying variable in the downwelling irradiance. Using these assumptions we built an algorithm to estimate the downwelling irradiance. The algorithm is used on all the selected pixels. The estimated irradiance is the average on the spectral channels of the resulting computation. The algorithm performs well in simulation and results are shown for errors in the assumed emissivity and for errors in the atmospheric profiles. The sensor noise influences mainly the required number of pixels. Keywords: Hyperspectral imagery, atmospheric correction, temperature emissivity separation 1. INTRODUCTION The atmospheric correction of thermal hyperspectral imagery aims at extracting the temperature and the emissivity of the material imaged by a sensor in the long wave infrared (LWIR) spectral band. -
Beer-Lambert Law: Measuring Percent Transmittance of Solutions at Different Concentrations (Teacher’S Guide)
TM DataHub Beer-Lambert Law: Measuring Percent Transmittance of Solutions at Different Concentrations (Teacher’s Guide) © 2012 WARD’S Science. v.11/12 For technical assistance, All Rights Reserved call WARD’S at 1-800-962-2660 OVERVIEW Students will study the relationship between transmittance, absorbance, and concentration of one type of solution using the Beer-Lambert law. They will determine the concentration of an “unknown” sample using mathematical tools for graphical analysis. MATERIALS NEEDED Ward’s DataHub USB connector cable* Cuvette for the colorimeter Distilled water 6 - 250 mL beakers Instant coffee Paper towel Wash bottle Stir Rod Balance * – The USB connector cable is not needed if you are using a Bluetooth enabled device. NUMBER OF USES This demonstration can be performed repeatedly. © 2012 WARD’S Science. v.11/12 1 For technical assistance, All Rights Reserved Teacher’s Guide – Beer-Lambert Law call WARD’S at 1-800-962-2660 FRAMEWORK FOR K-12 SCIENCE EDUCATION © 2012 * The Dimension I practices listed below are called out as bold words throughout the activity. Asking questions (for science) and defining Use mathematics and computational thinking problems (for engineering) Constructing explanations (for science) and designing Developing and using models solutions (for engineering) Practices Planning and carrying out investigations Engaging in argument from evidence Dimension 1 Analyzing and interpreting data Obtaining, evaluating, and communicating information Science and Engineering Science and Engineering Patterns -
Irradiance and Beam Transmittance Measurements Off the West Coast of the Americas
VOL. 84, NO. C1 JOURNAL OF GEOPHYSICAL RESEARCH JANUARY 20, 1979 Irradiance and Beam Transmittance Measurements off the West Coast of the Americas RICHARD W. SPINRAD,J. RONALD V. ZANEVELD, AND HASONG PAK Schoolof Oceanography,Oregon State University, Corvallis, Oregon 97331 Measurementsof total irradiance versusdepth and beam transmissionversus depth were made at stationsnear shore along the west coast of the North and South American continents.The water typesat each station were optically classifiedaccording to the systemof Jerlov (1976), thus providingadditional information for the descriptionof the distribution of the world's ocean water types. In addition, the parameterk/c, wherek is the irradianceattenuation coefficient and c is the beamattenuation coefficient, has been shown to be a useful parameterfor determiningthe relative particle concentrationsof ocean water. INTRODUCTION mately 75 m. At two stations(8 and 9), equipmentmalfunc- Optical classificationof oceanwater is an important means tions preventedmeasurements from being taken. of distinguishing water types. Jerlov [1951] presented a The irradiance meter usedhad a flat opal glassdiffuser as a method of classificationaccording to spectraltransmittance of cosinecollector and containeda signallog amplifierto provide downward irradiance at high solar altitude. Downward irra- an outputsignal between +4 V dc. The spectralresponse of the diance is defined as the radiant flux on an infinitesimal element irradiance meter is shown in Figure 3. The transmissivity of the upper face (0 ø-180ø) of a horizontal surfacecontaining meter consistedessentially of a light-emitting diode (wave- the point being considered,divided by the area of that element length = 650 nm), collimatinglenses, and a photodiode.The [Jerlov, 1976]. Jerlov's [1951] classificationdefined three dif- optical path length of the meter was 0.25 m. -
Radiometric and Photometric Measurements with TAOS Photosensors Contributed by Todd Bishop March 12, 2007 Valid
TAOS Inc. is now ams AG The technical content of this TAOS application note is still valid. Contact information: Headquarters: ams AG Tobelbaderstrasse 30 8141 Unterpremstaetten, Austria Tel: +43 (0) 3136 500 0 e-Mail: [email protected] Please visit our website at www.ams.com NUMBER 21 INTELLIGENT OPTO SENSOR DESIGNER’S NOTEBOOK Radiometric and Photometric Measurements with TAOS PhotoSensors contributed by Todd Bishop March 12, 2007 valid ABSTRACT Light Sensing applications use two measurement systems; Radiometric and Photometric. Radiometric measurements deal with light as a power level, while Photometric measurements deal with light as it is interpreted by the human eye. Both systems of measurement have units that are parallel to each other, but are useful for different applications. This paper will discuss the differencesstill and how they can be measured. AG RADIOMETRIC QUANTITIES Radiometry is the measurement of electromagnetic energy in the range of wavelengths between ~10nm and ~1mm. These regions are commonly called the ultraviolet, the visible and the infrared. Radiometry deals with light (radiant energy) in terms of optical power. Key quantities from a light detection point of view are radiant energy, radiant flux and irradiance. SI Radiometryams Units Quantity Symbol SI unit Abbr. Notes Radiant energy Q joule contentJ energy radiant energy per Radiant flux Φ watt W unit time watt per power incident on a Irradiance E square meter W·m−2 surface Energy is an SI derived unit measured in joules (J). The recommended symbol for energy is Q. Power (radiant flux) is another SI derived unit. It is the derivative of energy with respect to time, dQ/dt, and the unit is the watt (W). -
Radiometry and Photometry
Radiometry and Photometry Wei-Chih Wang Department of Power Mechanical Engineering National TsingHua University W. Wang Materials Covered • Radiometry - Radiant Flux - Radiant Intensity - Irradiance - Radiance • Photometry - luminous Flux - luminous Intensity - Illuminance - luminance Conversion from radiometric and photometric W. Wang Radiometry Radiometry is the detection and measurement of light waves in the optical portion of the electromagnetic spectrum which is further divided into ultraviolet, visible, and infrared light. Example of a typical radiometer 3 W. Wang Photometry All light measurement is considered radiometry with photometry being a special subset of radiometry weighted for a typical human eye response. Example of a typical photometer 4 W. Wang Human Eyes Figure shows a schematic illustration of the human eye (Encyclopedia Britannica, 1994). The inside of the eyeball is clad by the retina, which is the light-sensitive part of the eye. The illustration also shows the fovea, a cone-rich central region of the retina which affords the high acuteness of central vision. Figure also shows the cell structure of the retina including the light-sensitive rod cells and cone cells. Also shown are the ganglion cells and nerve fibers that transmit the visual information to the brain. Rod cells are more abundant and more light sensitive than cone cells. Rods are 5 sensitive over the entire visible spectrum. W. Wang There are three types of cone cells, namely cone cells sensitive in the red, green, and blue spectral range. The approximate spectral sensitivity functions of the rods and three types or cones are shown in the figure above 6 W. Wang Eye sensitivity function The conversion between radiometric and photometric units is provided by the luminous efficiency function or eye sensitivity function, V(λ). -
The Determination of Cloud Optical Depth from Multiple Fields of View Pyrheliometric Measurements
The Determination of Cloud Optical Depth from Multiple Fields of View Pyrheliometric Measurements by Robert Alan Raschke and Stephen K. Cox Department of Atmospheric Science Colorado State University Fort Collins, Colorado THE DETERMINATION OF CLOUD OPTICAL DEPTH FROM HULTIPLE FIELDS OF VIEW PYRHELIOHETRIC HEASUREHENTS By Robert Alan Raschke and Stephen K. Cox Research supported by The National Science Foundation Grant No. AU1-8010691 Department of Atmospheric Science Colorado State University Fort Collins, Colorado December, 1982 Atmospheric Science Paper Number #361 ABSTRACT The feasibility of using a photodiode radiometer to infer optical depth of thin clouds from solar intensity measurements was examined. Data were collected from a photodiode radiometer which measures incident radiation at angular fields of view of 2°, 5°, 10°, 20°, and 28 ° • In combination with a pyrheliometer and pyranometer, values of normalized annular radiance and transmittance were calculated. Similar calculations were made with the results of a Honte Carlo radiative transfer model. 'ill!:! Hunte Carlo results were for cloud optical depths of 1 through 6 over a spectral bandpass of 0.3 to 2.8 ~m. Eight case studies involving various types of high, middle, and low clouds were examined. Experimental values of cloud optical depth were determined by three methods. Plots of transmittance versus field of view were compared with the model curves for the six optical depths which were run in order to obtain a value of cloud optical depth. Optical depth was then determined mathematically from a single equation which used the five field of view transmittances and as the average of the five optical depths calculated at each field of view. -
Measurement of Scattering Cross Section with a Spectrophotometer with an Integrating Sphere Detector
Volume 117 (2012) http://dx.doi.org/10.6028/jres.117.012 Journal of Research of the National Institute of Standards and Technology Measurement of Scattering Cross Section with a Spectrophotometer with an Integrating Sphere Detector A. K. Gaigalas1, Lili Wang1, V. Karpiak2, Yu-Zhong Zhang2, and Steven Choquette1 1National Institute of Standards and Technology, Gaithersburg, MD 20899 2Life Technologies, 29851 Willow Creek Rd., Eugene, OR 97402 [email protected] [email protected] [email protected] A commercial spectrometer with an integrating sphere (IS) detector was used to measure the scattering cross section of microspheres. Analysis of the measurement process showed that two measurements of the absorbance, one with the cuvette placed in the normal spectrometer position, and the second with the cuvette placed inside the IS, provided enough information to separate the contributions from scattering and molecular absorption. Measurements were carried out with microspheres with different diameters. The data was fitted with a model consisting of the difference of two terms. The first term was the Lorenz-Mie (L-M) cross section which modeled the total absorbance due to scattering. The second term was the integral of the L-M differential cross section over the detector acceptance angle. The second term estimated the amount of forward scattered light that entered the detector. A wavelength dependent index of refraction was used in the model. The agreement between the model and the data was good between 300 nm and 800 nm. The fits provided values for the microsphere diameter, the concentration, and the wavelength dependent index of refraction. -
Regular Spectral Transmittance
NBS Measurement Services: Regular Spectral Transmittance NBS Special Publication 250-6 U.S. Department of Commerce National Bureau of Standards Center for Radiation Research The Center for Radiation Research is a major component of the National Measurement Laboratory in the National Bureau of Standards. The Center provides the Nation with standards and measurement services for ionizing radiation and for ultraviolet, visible, and infrared radiation; coordinates and furnishes essential support to the National Measurement Support Systemfor ionizing radiation; conducts research in radiation related fields to develop improved radiation measurement methodology; and generates, compiles, and critically evaluates data to meet major national needs. The Center consists of five Divisions and one Group. Atomic and Plasma Radiation Division Carries out basic theoretical and experimental research into the • Atomic Spectroscopy spectroscopic and radiative properties of atoms and highly ionized • Atomic Radiation Data species; develops well-defined atomic radiation sources as radiometric • Plasma Radiation or wavelength standards; develops new measurement techniques and methods for spectral analysis and plasma properties; and collects, compiles, and critically evaluates spectroscopic data. The Division consists of the following Groups: Radiation Physics Division Provides the central national basis for the measurement of far ultra- • Far UV Physics violet, soft x-ray, and electron radiation; develops and disseminates • Electron Physics radiation standards, -
Transmittance Four-Up
Transmittance notes Transmittance notes – cont I What is the difference between transmittance and transmissivity? There really isn’t any: see the AMS glossary entry I Review: prove that the total transmittance for two layers is I Review the relationship between the transmittance, absorption Trtot = Tr1 Tr2: cross section, flux and radiance × I Introduce the optical depth, τλ and the differential F2 transmissivity, dTr = dτλ Trtot = − F0 I Show that Fλ = Fλ0 exp( τλ) for “direct beam” flux − F1 Tr1 = F0 F2 F2 Tr2 = = F1 Tr1F0 F2 Tr1Tr2 = = Trtot F0 Transmittance 1/10 Transmittance 2/10 scattering and absorption cross section flux and itensity I Since we know that we are dealing with flux in a very small I Beer’s law for flux absorption comes from Maxwell’s equations: solid angle, we can divide (1) through by ∆ω, recogize that Iλ Fλ/∆ω in this near-parallel beam case and get Beer’s Fλ = Fλ0exp( βas) (1) ≈ − law for intensity: 2 3 where βa m m− is the volume absorption coefficient. 2 We are ignoring the spherical spreading (1/r ) loss in (1) Iλ = Iλ0exp( βas) (2) under the assumption that the source is very far way, so that − I Take the differential of either (1) or (2) and get something s, the distance traveled, is much much smaller than r, the like this: distance from the source. I This limits the applicability of (1) to direct sunlight and laser dIλ = βadsIλ0exp( βas) = Iλβads (3) light. − − − or I The assumption that the source is far away is the same as assuming that it occupies a very small solid angle ∆ω.