skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A Comparison of 2pi and 4pi Photometric Testing of Directional and Omnidirectional Sources in an Integrating Sphere

Abstract

A Comparison of 2pi and 4pi Photometric Testing of Directional and Omnidirectional Sources in an Integrating Sphere. These data will help determine if differences in methods should be addresed in test methods specifically for LED products but applicable to other technologies as well

Authors:
;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1149229
Report Number(s):
PNNL-SA-98453
BT0301000
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: LEUKOS - The Journal of the Illuminating Engineering Society of North America, 10(4):183-191
Country of Publication:
United States
Language:
English
Subject:
LED; SSL; sphere; 2 pi; 4 pi

Citation Formats

Richman, Eric E., and Merzouk, Massine B. A Comparison of 2pi and 4pi Photometric Testing of Directional and Omnidirectional Sources in an Integrating Sphere. United States: N. p., 2014. Web. doi:10.1080/15502724.2014.910126.
Richman, Eric E., & Merzouk, Massine B. A Comparison of 2pi and 4pi Photometric Testing of Directional and Omnidirectional Sources in an Integrating Sphere. United States. doi:10.1080/15502724.2014.910126.
Richman, Eric E., and Merzouk, Massine B. 2014. "A Comparison of 2pi and 4pi Photometric Testing of Directional and Omnidirectional Sources in an Integrating Sphere". United States. doi:10.1080/15502724.2014.910126.
@article{osti_1149229,
title = {A Comparison of 2pi and 4pi Photometric Testing of Directional and Omnidirectional Sources in an Integrating Sphere},
author = {Richman, Eric E. and Merzouk, Massine B.},
abstractNote = {A Comparison of 2pi and 4pi Photometric Testing of Directional and Omnidirectional Sources in an Integrating Sphere. These data will help determine if differences in methods should be addresed in test methods specifically for LED products but applicable to other technologies as well},
doi = {10.1080/15502724.2014.910126},
journal = {LEUKOS - The Journal of the Illuminating Engineering Society of North America, 10(4):183-191},
number = ,
volume = ,
place = {United States},
year = 2014,
month = 6
}
  • To correctly measure the solar transmittance of a material that scatters light, a detector with uniform directional response must be used, and the integrating sphere is often used in combination with an optical detector for this purpose. However, no real optical detector system has a completely uniform directional response; thus a directional response error will always exist. This note analyzes the directional response error in directional-hemispherical transmittance measurements at solar wavelengths and determines this error for transmittance measurements on materials that scatter light in different ways, made with a state-of-the-art integrating-sphere-spectrophotometer system. It is shown that for certain types ofmore » materials, the directional response error is the dominant error in the measurement of directional-hemispherical transmittance. 18 refs., 4 figs.« less
  • Infrared integrating sphere measurements of solid samples are important in providing reference data for contact, standoff and remote sensing applications. At the Pacific Northwest National Laboratory (PNNL) we have developed protocols to measure both the directional-hemispherical ( and diffuse (d) reflectances of powders, liquids, and disks of powders and solid materials using a commercially available, matte gold-coated integrating sphere and Fourier transform infrared spectrometer. Detailed descriptions of the sphere alignment and its use for making these reflectance measurements are given. Diffuse reflectance values were found to be dependent on the bidirectional reflection distribution function (BRDF) of the sample and themore » solid angle intercepted by the sphere’s specular exclusion port. To determine how well the sphere and protocols produce quantitative reflectance data, measurements were made of three diffuse and two specular standards prepared by the National institute of Standards and Technology (NIST, USA), LabSphere Infragold and Spectralon standards, hand-loaded sulfur and talc powder samples, and water. The five NIST standards behaved as expected: the three diffuse standards had a high degree of “diffuseness,” d/ = D > 0.9, whereas the two specular standards had D ≤ 0.03. The average absolute differences between the NIST and PNNL measurements of the NIST standards for both directional-hemispherical and diffuse reflectances are on the order of 0.01 reflectance units. Other quantitative differences between the PNNL-measured and calibration (where available) or literature reflectance values for these standards and materials are given and the possible origins of discrepancies are discussed. Random uncertainties and estimates of systematic uncertainties are presented. Corrections necessary to provide better agreement between the PNNL reflectance values as measured for the NIST standards and the NIST reflectance values for these same standards are also discussed.« less
  • As part of the pre-flight calibration and validation activities for the Ocean Color and Temperature Scanner (OCTS) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color satellite instruments, a radiometric measurement comparison was held in February 1995 at the NEC Corporation in Yokohama, Japan. Researchers from the National Institute of Standards and Technology (NIST), the National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC), the University of Arizona Optical Sciences Center (UA), and the National Research Laboratory of Metrology (NRLM) in Tsukuba, Japan used their portable radiometers to measure the spectral radiance of the OCTS visible and near-infrared integrating spheremore » at four radiance levels. These four levels corresponded to the configuration of the OCTS integrating sphere when the calibration coefficients for five of the eight spectral channels, or bands, of the OCTS instrument were determined. The measurements of the four radiometers differed by {minus}2.7% to 3.9% when compared to the NEC calibration of the sphere and the overall agreement was within the combined measurement uncertainties. A comparison of the measurements from the participating radiometers also resulted in agreement within the combined measurement uncertainties. These results are encouraging and demonstrate the utility of comparisons using laboratory calibration integrating sphere sources. Other comparisons will focus on instruments that are scheduled for spacecraft in the NASA study of climate change, the Earth Observing System (EOS).« less