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distances d were measured from the aperture plane of the photometer to the front tip of the LED. Studied LEDs: Methods were tested with 17 different LEDs with varying geometries, colors and power levels. LED types are presented in Figure 1. Four of the studied LEDs had temperature stabilization at the temperature of 25°C. Constant-current of 20 mA was used for low power LEDs and 330 mA for the high power LEDs. Measurement results Illuminances were measured at various distances d between 100 mm and 1000 mm depending on the power level of the studied LED. The measurement distance selections also included the CIE recommended distances 316 mm and 100 mm for all LEDs. Modified inverse-square law fitting for the green temperature-stabilized LED is presented in Figure 2 as an example of typical results. Illuminance E v [lx] 160 120 80 40 0 0 100 200 300 400 500 600 700 Distance d [mm] calculated measured Figure 2. Inverse-square law for the green temperature stabilized LED. The analysis was done at various fitting ranges due to different power levels. For the high power LEDs with and without a lens, illuminance values were fitted at the regions 100–3000 mm and 100–1600 mm, respectively. For the low power indicator LEDs, the distance measurements were done by steps of 50 mm between 100 mm and 316 mm. Other studied LEDs were analyzed using the region of 100–700 mm. The results are presented in Table 1. It can be seen that most of the LEDs follow the modified inverse square law with standard deviation smaller than 1 %, biggest standard deviation being 2.1 %. Over more limited regions (e.g. excluding the 100-mm distance) agreement is typically better than 0.1 %. For most LEDs the size of the source can be assumed to be zero. For the LEDs containing powerful lenses this assumption can not be made, but an agreement can be found using r 1 as a free parameter. CIE luminous intensities typically vary quite a lot from each other for each of the studied LEDs. Table 1. Measurement results of the studied LEDs. The first column gives diameter and color of the LEDs. L is the length of the LED housing. studied Modified inverse-square law I LED A / L LED I v ∆d r 1 standard I LED B [mm] [cd] [mm] [mm] deviation 3 mm w 3.6 0.2 0.0 0.85 % 0.989 6.0 3 mm r 1.4 4.8 0.0 0.60 % 1.081 4.6 3 mm g 3.6 5.2 0.0 0.11 % 1.071 4.8 5 mm w 1.9 7.2 0.0 1.23 % 1.089 8.6 5 mm b 0.8 9.5 36.7 0.23 % 1.247 8.7 5 mm g 2.5 13.7 14.4 0.03 % 1.206 8.7 5 mm r 3.4 12.0 0.0 0.48 % 1.179 8.7 5 mm g 1.9 6.2 0.0 0.96 % 1.094 7.0 5 mm g 15.7 7.8 102.7 1.03 % 1.907 9.8 5 mm b/g 6.9 -44.1 85.1 0.18 % 1.278 10.7 10 mm o 69 -23.4 215.8 0.62 % 3.958 15.1 10 mm r 6.5 1.6 65.6 1.28 % 1.378 13.5 1W w 285 -11.0 45.6 0.17 % 1.057 14.1 1W g 403 31.6 0.0 2.09 % 1.337 14.1 1W g 5.5 2.3 0.0 0.14 % 1.029 3.0 sideview g 0.004 5.7 0.0 0.21 % 0.700 5.7 square r 0.026 -0.4 0.0 0.89 % 0.250 5x5 Conclusions Applicability of the modified inverse-square law for the luminous intensity measurements of the LEDs has been studied with seventeen LEDs. Many of the studied LEDs contain a lens which complicates the distance measurements. The analysis removes the effect of the lens by moving the image of the source and allowing its size to vary. The essential information of the LEDs can be included in three parameters, luminous intensity I v , radius of the image of the source r 1 , and location of the image of the source ∆d. Fitting made by the proposed method gives notably more consistent results than the CIE standard, and the solution includes the standardized parameters I LED A and I LED B . The method is therefore useful in applications where more consistency is needed. References 1. K. Muray, “Photometry of diode emitters: light emitting diodes and infrared emitting diodes,” Appl. Opt. 30, 2178-2186 (1991). 2. CIE 127.2, Measurement of LEDs. 3. J. Hovila, M. Mustonen, P. Kärhä, E. Ikonen, “Determination of the diffuser reference plane for accurate illuminance responsivity calibrations,” Appl. Opt. (in press). It should be noted that the obtained values for ∆d and r 1 are far from the physical dimensions. They should be considered merely as parameters in a two-aperture approximation of the optical system instead of true physical dimensions. 212
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NEWRAD PROCEEDINGS OF THE 9 TH INTE
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NEWRAD 2005 Scientific Program Day
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14:50 Hiroshi Shitomi, AIST 5-3 Pho
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NEWRAD 2005 Scientific Program-Post
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33. Drift in the absolute responsiv
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Session 6 Novel Techniques 64. The
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Session 9 Realisation of scales 94.
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Absolute Accuracy of Total Solar Ir
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Low-uncertainty absolute radiometri
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NIST Reference Cryogenic Radiometer
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Measurement of the absorptance of a
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Grooves for Emissivity and Absorpti
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New apparatus for the spectral radi
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VUV and Soft X-ray metrology statio
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The metrology line on the SOLEIL sy
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Cryogenic radiometer developments a
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measured with BiTe thermopiles. Exp
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variations of the spectral sensitiv
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aperture area by I = π·L·F·A, w
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Table 1 Ratio of radiometric power
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Consistency of radiometric temperat
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Project of absolute measuring instr
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Session 2 UV, Vis, and IR Radiometr
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Table 1: Summary of the quality ass
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wavelength / nm U180 @ MLS band wid
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ight half is uncoated. Measurements
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Change [%] 2 1 0 -1 -2 -3 -4 PTFE d
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had been accommodated to industrial
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Relative Uncertainty 0.4% 0.3% 0.2%
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instrument differences or from diff
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3.00E-08 Nomalized radiant flux 2.5
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frequencies, the chopping frequency
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600 mA for each set. In both cases,
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Detailed and comparative results wi
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measurement to an independent spect
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The stability of silicon n-on-p jun
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applied. Reproducibility of measure
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Mutual comparison Mutual comparison
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A comparison of the performance of
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Stray-light correction of array spe
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Characterizing the performance of U
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Optical Radiation Action Spectra fo
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A newly developed double broadband
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On potential discrepancies between
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Correcting for bandwidth effects in
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Establishment of Fiber Optic Measur
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Detector-based NIST-traceable Valid
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Long-term calibration of a New Zeal
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Drift in the absolute responsivitie
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Radiance source for CCD low-uncerta
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Improved NIR spectral responsivity
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Characterization of a portable, fib
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Synchrotron radiation based irradia
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The Spectral Irradiance and Radianc
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NIST BXR I Calibration A. Smith, T.
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NIST BXR II Infrared Transfer Radio
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Proceedings NEWRAD, 17-19 October 2
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Spectral responsivity interpolation
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Monochromator Based Calibration of
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Study of the Infrared Emissivity of
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Radiometric Stability of a Calibrat
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Session 3 Photolithography and UV P
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NEWRAD 2005: Improvements in EUV re
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Measuring pulse energy with solid s
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Vacuum ultraviolet quantum efficien
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Spatial Anisotropy of the Exciton R
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Comparison of spectral irradiance r
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Session 4 Remote sensing Proceeding
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Solar Radiometry from SORCE G. Kopp
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Inter-comparison Study of Terra and
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The Solar Bolometric Imager - Recen
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On measuring the radiant properties
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A Model of the Spectral Irradiance
Page 161 and 162: Determination of Aerosol Optical De
Page 163 and 164: Procedures of absolute calibration
Page 165 and 166: Using a Blackbody to Determine the
Page 167 and 168: On the drifts exhibited by cryogeni
Page 169 and 170: On-orbit Characterization of Terra
Page 171 and 172: Space solar patrol mission for moni
Page 173 and 174: Multi-channel ground-based and airb
Page 175 and 176: Thermal Modelling and Digital Servo
Page 177 and 178: Calibration of Filter Radiometers f
Page 179 and 180: Radiometric Calibration of a Coasta
Page 181 and 182: A Verification of the Ozone Monitor
Page 183 and 184: Session 5 Photometry and Colorimetr
Page 185 and 186: Review on new developments in Photo
Page 187 and 188: Linking Fluorescence Measurements t
Page 189 and 190: Photoluminescence from White Refere
Page 191 and 192: A Simple Stray-light Correction Mat
Page 193 and 194: New robot-based gonioreflectometer
Page 195 and 196: Rotational radiance invariance of d
Page 197 and 198: Minimizing Uncertainty for Traceabl
Page 199 and 200: Development of a total luminous flu
Page 201 and 202: Determination of the diffuser refer
Page 203 and 204: DEVELOPMENT OF A LUMINANCE STANDARD
Page 205 and 206: Measuring photon quantities in the
Page 207 and 208: Session 6 Novel techniques Proceedi
Page 209 and 210: Characterization of germanium photo
Page 211: Determination of luminous intensity
Page 215 and 216: The Measurement of Surface and Volu
Page 217 and 218: The evaluation of a pyroelectric de
Page 219 and 220: UV detector calibration based on an
Page 221 and 222: NEWRAD 2005: Non selective thermal
Page 223 and 224: NEWRAD 2005 Calibration of Current-
Page 225 and 226: Simplified diffraction effects for
Page 227 and 228: Widely Tunable Twin-Beam Light Sour
Page 229 and 230: Measurement of quantum efficiency u
Page 231 and 232: Session 7 International Comparisons
Page 233 and 234: The CCPR K1-a Key Comparison of Spe
Page 235 and 236: Comparison of Measurements of Spect
Page 237 and 238: APMP PR-S1 comparison on irradiance
Page 239 and 240: Comparison Measurements of Spectral
Page 241 and 242: Comparison of mid-infrared absorpta
Page 243 and 244: Comparison of photometer calibratio
Page 245 and 246: A Comparison of Re-C, Pt-C, and Co-
Page 247 and 248: Session 8 Radiometric and Photometr
Page 249 and 250: Application of Metal (Carbide)-Carb
Page 251 and 252: On Estimation of Distribution Tempe
Page 253 and 254: Hyperspectral Image Projectors for
Page 255 and 256: Reproducible Metal-Carbon Eutectic
Page 257 and 258: Thermodynamic temperature determina
Page 259 and 260: Spatial Light Modulator-based Advan
Page 261 and 262: Novel subtractive band-pass filters
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Analysis of the Uncertainty Propaga
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Absolute linearity measurements on
Page 267 and 268:
Comparison of two methods for spect
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Precision Extended-Area Low Tempera
Page 271 and 272:
Flash Measurement System for the 25
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A normal broadband irradiance (Heat
Page 275 and 276:
A laser-based radiance source for c
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Furnace for High-Temperature Metal
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Investigations of Impurities in TiC
Page 281 and 282:
Determining the temperature of a bl
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High-temperature fixed-point radiat
Page 285 and 286:
Long-term experience in using deute
Page 287 and 288:
High-temperature fixed-point radiat
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A comparison of Co-C, Pd-C, Pt-C, R
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Irradiance measurements of Re-C, Ti
Page 293 and 294:
Evaluation and improvement of the p
Page 295 and 296:
The Spectrally Tunable LED light So
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Session 9 Realisation of scales Pro
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The Realization and the Disseminati
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The establishment of the NPL infrar
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The PTB High-Accuracy Spectral Resp
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ÆÛ ÑØÓ ÓÖ Ø ÔÖÑÖÝ ÖÐ
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An integrated sphere radiometer as
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From X-rays to T-rays: Synchrotron
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Infrared Radiometry at LNE: charact
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Transfer standard pyrometers for ra
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Preliminary Realization of a Spectr
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New photometric standards developme
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Distribution temperature scale real
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Gloss standard calibration by spect
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Absolute cryogenic radiometry in th
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Detailed Comparison of Illuminance
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Radiometric Temperature Comparisons
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Characterization of Thermopile for
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Detector Based Traceability Chain E
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Comparison of the PTB Radiometric S
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Spectral Responsivity Scale between
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Realization of the NIST Total Spect
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Goniometric Realisation of Reflecta
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