1、Designation: E259 06 (Reapproved 2015)Standard Practice forPreparation of Pressed Powder White Reflectance FactorTransfer Standards for Hemispherical and Bi-DirectionalGeometries1This standard is issued under the fixed designation E259; the number immediately following the designation indicates the
2、year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONThe internationally accepted standard of reflectance
3、 is the perfect reflecting diffuser. This idealreflecting surface reflects 100 % of the incident radiant power such that the radiance is the same forall directions within the hemisphere above the surface. No physical realization of this standard exists.Optical properties of standards prepared from p
4、ressed plaques of magnesium carbonate (MgCO3),barium sulfate (BaSO4), or polytetrafluoroethylene (PTFE) can approximate an ideal standard. Forfurther information see CIE Publication No. 46 (1).2The principal use of a white reflectance factorstandard is to transfer an absolute scale of reflectance to
5、 a more durable material or from oneinstrument to another. In theory, it should be easy to do this transfer from first principles. In practice,one is likely to need values for parameters that are unknown, proprietary, or require a high level ofskill. Some, but not all, of those parameters are discus
6、sed in this practice.1. Scope1.1 This practice covers procedures for preparing pressedpowder transfer standards. These standards can be used in thenear-ultraviolet, visible and near-infrared region of the electro-magnetic spectrum. Procedures for calibrating the reflectancefactor of materials on an
7、absolute basis are contained in CIEPublication No. 44 (2). Pressed powder standards are used astransfer standards for such calibrations because they have ahigh reflectance factor that is nearly constant with wavelength,and because the geometric distribution of reflected flux re-sembles that from the
8、 perfect reflecting diffuser.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of th
9、is standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E284 Terminology of Appearance3. Terminology3.1 Terms and definitions in Terminology E284 are appli-cable to this pract
10、ice.3.2 Definitions:3.2.1 The following definitions are particularly important tothis practice:3.2.2 perfect reflecting diffuser, nideal reflecting surfacethat neither absorbs nor transmits light, but reflects diffusely,with the radiance of the reflecting surface being the same for allreflecting ang
11、les, regardless of the angular distribution of theincident light. (1990)3.2.3 reflectance, ,nratio of the reflected radiant orluminous flux to the incident flux in the given conditions.CIEA3.2.4 The term reflectance is often used in a general sense oras an abbreviation for reflectance factor. Such u
12、sage may beassumed unless the above definition is specifically required bythe context. (1989b)1This practice is under the jurisdiction of ASTM Committee E12 on Color andAppearance and is the direct responsibility of Subcommittee E12.02 on Spectro-photometry and Colorimetry.Current edition approved N
13、ov. 1, 2015. Published November 2015. Originallyapproved in 1965. Last previous edition approved in 2011 as E259 06 (2011).DOI: 10.1520/E0259-06R15.2The boldface numbers in parentheses refer to the list of references at the end ofthis practice.3For referenced ASTM standards, visit the ASTM website,
14、www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2
15、.5 reflectance factor, R, nratio of the flux reflected fromthe specimen to the flux reflected from the perfect reflectingdiffuser under the same geometric and spectral conditions ofmeasurement. CIEB(1988)4. Summary of Practice4.1 Procedures are given for the preparation of whitereference standards o
16、f diffuse reflectance factor and diffuseradiance factor. The recommended materials are white powdersthat are pressed into plaques. These plaques provide closeapproximations to the optical properties of the perfect reflect-ing diffuser, and may be used to transfer a scale of absolutereflectance to an
17、other material or to an instrument.5. Significance and Use5.1 All commercial reflectometers measure relative reflec-tance. The instrument reading is the reflectance factor, the ratioof the light reflected by a reference specimen to that reflectedby a test specimen. That ratio is dependent on specifi
18、cinstrument parameters.5.2 National standardizing laboratories and some researchlaboratories measure reflectance on instruments calibratedfrom basic principles, thereby establishing a scale of absolutereflectance as described in CIE Publication No. 44 (2). Thesemeasurements are sufficiently difficul
19、t that they are usually leftto laboratories that specialize in them.5.3 A standard that has been measured on an absolute scalecould be used to transfer that scale to a reflectometer. Whilesuch procedures exist, the constraints placed on the mechanicalproperties restrict the suitability of some optic
20、al properties,especially those properties related to the geometric distributionof the reflected light. Thus, reflectance factor standards whichare sufficiently rugged and able to be cleaned, depart consid-erably from the perfect diffuser in the geometric distribution ofreflected radiance.5.4 The geo
21、metric distribution of reflected radiance from apressed powder plaque is sufficiently diffuse to provide adependable calibration of a directional-hemispherical reflecto-meter. Although pressed powder standards are subject tocontamination and breakage, the directional-hemispherical re-flectance facto
22、r of pressed powder standards can be sufficientlyreproducible from specimen to specimen made from a given lotof powder, so as to allow one to assign absolute reflectancefactor values to all the powder in a lot.5.5 This practice describes how to prepare white reflectancefactor standards from a powder
23、 in a manner that allows astandardizing laboratory to assign the absolute scale of reflec-tance to the plaque.6. Apparatus6.1 The basic apparatus for producing a pressed powderstandard includes a powder press, powder containers and abalance. There are currently two commercial suppliers ofpowder pres
24、ses. The press and receptacles can also be made ina local machine shop. A suggested configuration is shown inFig. 1. The optical surface of the plaque should be pressedagainst a surface of ground glass or poly(methyl methacrylate)to provide a matte finish on the pressed plaque. Powderreceptacles sho
25、uld be at least 5 mm deep for BaSO4and at least10 mm deep for PTFE.7. Reagents and Materials7.1 Barium SulfateThe barium sulfate should be of thehighest purity. It should be specially refined for optical andspectroscopic use (3).7.2 PolytetrafluoroethyleneThe PTFE (4) should also bespecially refined
26、 for optical and spectroscopic use but somecommercial grades have been found to be acceptable substi-tutes. (5) Large quantities (drums) of commercial grade PTFEcan be obtained from manufacturers.8. Procedure8.1 Store all powdered reflectance standards in tightlycapped glass containers. If the powde
27、r is purchased in plasticcontainers, transfer it to a glass container as soon as possible.Before using the powder, place it in a glass blender equippedwith stainless-steel or PTFE-coated blades and pulverize to auniform consistency. Transfer the quantity of powder to beused with stainless steel or P
28、TFE-coated spoons. Perform thewhole operation in a draft-free location, away from sources ofsmall particulate contamination, filters, sweaters, windows,ovens, etc. Perform all measurements (weight, height, width,depth, volume, area, etc.) with adequate precision to ensurethat the final density is wi
29、thin 5 % of the specified value. Themost reproducible standards are made by pressing the powderto a specific density. Thus, determine the mass of the powder tobe used from the volume of the receptacle.8.2 Barium SulfatePress BaSO4to a density of 2000kg/m3(2.0 gm/cm3) and a thickness of at least 5 mm
30、. Pressseveral specimens in succession. Select matched pairs to berepresentative of the contents of the bottle of powder. Keep thepressed plaques in a covered desiccator when not in use. Somesuppliers of BaSO4provide calibration values with each bottleof powder, other suppliers provide only 3 or 4 q
31、uality referencechecks and a reference to published values of referencestandards prepared from the powder. Table 1 gives the 6/diffuse reflectance factor values for EastmanWhite ReflectanceStandard (3).NOTE 1The collar and receptacle should be securely held in placebefore pressing the powder.FIG. 1
32、Example Powder PressE259 06 (2015)28.2.1 Another description of this procedure is found in Ref.(4).8.3 PolytetrafluoroethylenePress PTFE to a density of1000 kg/m3(1.0 gm/cm3) and a thickness of at least 10 mm.The spectral reflectance, which is a function of density, has abroad maximum near this dens
33、ity. Prepare several specimens insuccession. Matched pairs are selected to be representative ofthe contents of the container of powder. Keep the pressedplaques in a desiccator when not in use. PTFE has a highdielectric constant and can be very sensitive to airborneparticulates. Such contamination ca
34、n make the material slightlyfluorescent and reduce its reflectance in the near-ultravioletspectral region. Table 2 lists the 6/diffuse reflectance factorvalues (6) and Table 3 lists the 45/0 reflectance factor values(7) of PTFE as determined by the National Institute ofStandards and Technology (NIST
35、).9. Precision and Bias9.1 The National Institute of Standards and Technology andthe Inter-Society Color Council Project Committee 22, Mate-rials for Instrument Calibration, have carried out collaborativetests to determine the precision and bias of the preparation ofPTFE reflectance factor standards
36、 (8). The standard deviationof three determinations of the reflectance factor of PTFE by theNISTranged from 0.0002 to 0.0008 over the spectral range 300to 1000 nm. The measured reflectances of PTFE from twomanufacturers exhibited differences of from 0.002 to +0.004over the same range with the larges
37、t differences near the endsof the range and a constant measurement uncertainty of60.005. From the 9 laboratories participating in the round-robin experiment, 17 specimens were returned. The results areshown in Table 4 for the wavelength range 300 to 1000 nm.9.2 The National Institute of Standards an
38、d Technologycarried out collaborative tests to determine the uncertainties inthe preparation of PTFE for use as transfer standards ofreflectance factor for the 45/0 geometry. Duplicate pressingswere made of the same PTFE in ten different laboratories. Thestandard deviations of the measured reflectan
39、ce factor, as afunction of wavelength is shown in Table 5. Table 6 shows themeasured reflectance factors, averages, and standard deviationsof four different drums of PTFE. The total uncertainty for thetransfer is approximately 1 % at wavelengths above 500 nmand approximately 1.5 % at wavelengths bel
40、ow 500 nm in thevisible spectral region.TABLE 1 6/Diffuse Reflectance Factor of Eastman WhiteReflectance Standard Pressed BaSO4PowderAWavelength, nm Reflectance Factor300 0.968350 0.979400 0.987450 0.991500 0.991550 0.992600 0.992650 0.992700 0.992750 0.992800 0.992850 0.991900 0.990950 0.9881000 0.
41、986ADensity = 2000 kg/m3and thickness = 5 mm.TABLE 2 6/Diffuse Reflectance Factor of Pressed PTFE PowderAWavelength, nm Reflectance FactorB300 0.984350 0.990400 0.993450 0.993500 0.994550 0.994600 0.994650 0.994700 0.994750 0.994800 0.994850 0.994900 0.994950 0.9941000 0.994ADensity = 1000 kg/m3and
42、thickness $ 5 mm.BAccurate to 0.002.TABLE 3 45/0 Diffuse Reflectance Factor of Pressed PTFEPowderAWavelength, nm Reflectance FactorB380 1.002390 1.003400 1.005410 1.006420 1.006430 1.007440 1.007450 1.008460 1.008470 1.009480 1.009490 1.009500 1.010510 1.010520 1.010530 1.010540 1.011550 1.011560 1.
43、011570 1.011580 1.011590 1.011600 1.011610 1.011620 1.012630 1.012640 1.012650 1.012660 1.012670 1.012680 1.012690 1.012700 1.012710 1.013720 1.014730 1.015740 1.015750 1.016760 1.016770 1.017ADensity = 1000 kg/m3and thickness $5 mm.BAccurate to 0.003.E259 06 (2015)310. Keywords10.1 bidirectional op
44、tical measuring system; hemisphericaloptical measuring system; integrating sphere; material stan-dards; reflectance and reflectivity; transfer standardsTABLE 4 Average and Standard Deviation of 6/DiffuseReflectance Factors of 17 PTFE Plaques Prepared by 9LaboratoriesWavelength, nmReflectance FactorA
45、verageAStandardDeviationB300 0.9792 0.0063350 0.9883 0.0021400 0.9911 0.0018500 0.9919 0.0020600 0.9915 0.0023700 0.9914 0.0023800 0.9912 0.00241000 0.9910 0.0024AAverage Density = 926.2 kg/m3.BStandard Deviation = 85.7 kg/m3.TABLE 5 Difference From the Average of PTFE Powder Pressings Ten Laborator
46、ies (A-J) and Two Replicates (1-2)Wavelength, nm380 450 600 700 770A1 0.002 0.004 0.002 0.003 0.004A2 0.004 0.006 0.003 0.001 0.003B1 -0.001 0.001 0.000 0.000 -0.007B2 -0.005 0.000 -0.001 0.000 -0.001C1 0.009 0.006 0.004 0.004 0.005C2 -0.005 -0.005 -0.004 -0.006 -0.005D1 0.001 0.002 0.001 0.001 0.00
47、2D2 0.007 0.004 0.003 0.002 0.002E1 -0.003 0.002 0.002 0.003 0.004E2 -0.004 -0.004 -0.005 -0.006 -0.006F1 0.000 -0.011 -0.004 0.008 0.004F2 -0.001 0.000 0.001 0.001 0.001G1 -0.002 -0.004 -0.004 -0.004 -0.005G2 0.009 0.005 0.002 0.002 0.004H1 -0.012 -0.006 -0.006 -0.008 -0.007H2 0.010 0.001 0.000 0.0
48、01 0.002I1 -0.003 0.000 -0.002 -0.001 0.000I2 0.006 -0.002 0.002 0.002 0.005J1 -0.010 -0.007 -0.005 -0.007 -0.004J2 0.003 0.007 0.006 0.008 0.006Standard Deviation (k=2) 0.012 0.010 0.006 0.008 0.008TABLE 6 45/0 Reflectance Factor of Pressed PTFE Powder From Different Drums of PTFEWavelength, nm380
49、420 470 550 630 700 770Drum 1 1.005 1.008 1.011 1.013 1.012 1.013 1.016Drum 2 1.001 1.006 1.009 1.011 1.012 1.012 1.017Drum 3 0.993 0.999 1.006 1.007 1.010 1.011 1.016Drum 4 1.007 1.010 1.011 1.012 1.013 1.013 1.017Mean 1.002 1.006 1.009 1.011 1.012 1.012 1.017Standard Deviation 0.013 0.010 0.008 0.005 0.002 0.002 0.001E259 06 (2015)4REFERENCES(1) Publication CIE No. 46A Review of Publications on Properties andReflection Values of Material Reflection Standards, available fromUSNC/CIE. Request ordering information from Secretary USNC,NIST, Room A317/
