1、Designation: E1175 87 (Reapproved 2015)Standard Test Method forDetermining Solar or Photopic Reflectance, Transmittance,and Absorptance of Materials Using a Large DiameterIntegrating Sphere1This standard is issued under the fixed designation E1175; the number immediately following the designation in
2、dicates the 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.1. Scope1.1 This test method covers the measurement
3、of the absolutetotal solar or photopic reflectance, transmittance, or absorp-tance of materials and surfaces. Although there are severalapplicable test methods employed for determining the opticalproperties of materials, they are generally useful only for flat,homogeneous, isotropic specimens. Mater
4、ials that arepatterned, textured, corrugated, or are of unusual size cannot bemeasured accurately using conventional spectrophotometrictechniques, or require numerous measurements to obtain arelevant optical value. The purpose of this test method is toprovide a means for making accurate optical prop
5、erty measure-ments of spatially nonuniform materials.1.2 This test method is applicable to large specimens ofmaterials having both specular and diffuse optical properties. Itis particularly suited to the measurement of the reflectance ofopaque materials and the reflectance and transmittance ofsemitr
6、ansparent materials including corrugated fiber-reinforcedplastic, composite transparent and translucent samples, heavilytextured surfaces, and nonhomogeneous materials such aswoven wood, window blinds, draperies, etc.1.3 The values stated in SI units are to be regarded as thestandard. The values giv
7、en in parentheses are for informationonly.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulator
8、y limitations prior to use. (For specific safetyhazards, see Note 1.)2. Referenced Documents2.1 ASTM Standards:2E772 Terminology of Solar Energy ConversionE892 Tables for Terrestrial Solar Spectral Irradiance at AirMass 1.5 for a 37 Tilted SurfaceE903 Test Method for Solar Absorptance, Reflectance,
9、andTransmittance of Materials Using Integrating Spheres3. Terminology3.1 Definitions:3.1.1 absorptance, nsee Terminology E772.3.1.2 integrating sphereoptical device used to either col-lect flux reflected or transmitted from a sample into a hemi-sphere or to provide isotropic irradiation of a sample
10、from acomplete hemisphere.3.1.2.1 DiscussionIt consists of a cavity that is approxi-mately spherical in shape with apertures for admitting anddetecting flux and usually having additional apertures overwhich sample and reference specimens are placed.3.1.3 photopic optical properties, nabsorptance,ref
11、lectance, and transmittance of a sample evaluated as theweighted average of the measured property, with the wave-length by wavelength of the product of the spectral irradiancefor the measurement and the Commission Internationale delEclairage (CIE) photopic spectral response,3as the weightingfunction
12、.3.1.4 photopic response, nspectral response of the averagehuman eye when fully adapted to daylight conditions.3.1.5 reflectance, nsee Terminology E772.3.1.6 transmittance, nsee Terminology E772.1This test method is under the jurisdiction of ASTM Committee E44 on Solar,Geothermal and Other Alternati
13、ve Energy Sources and is the direct responsibility ofSubcommittee E44.05 on Solar Heating and Cooling Systems and Materials.Current edition approved March 1, 2015. Published April 2015. Originallyapproved in 1987. Last previous edition approved in 2009 as E117587(2009). DOI:10.1520/E1175-87R15.2For
14、referenced ASTM standards, visit the ASTM website, 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.3Available from Commission Internationale de lEclairage (CIE), Int
15、ernationalLight Vocabulary, 3rd Ed., Bureau Central de la CIE, Paris, 1970.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Summary of Test Method4.1 This test method describes a procedure and apparatusfor determining the area-avera
16、ged optical properties of com-plex or nonuniform materials and surfaces. This test methodemploys a large diameter integrating sphere and a sourcecapable of illuminating a representative area of the testspecimens surface.4.2 Transmittance is determined with the specimen mountedexternally at the spher
17、e entrance port.4,5Reflectance is deter-mined by placing the specimen in the center of the integratingsphere,4in accordance with the diagram in Fig. A1.2 of TestMethod E903. For measurement of reflectance of partiallytransmitting samples, the sample should be backed by a blackopaque absorber to elim
18、inate the transmitted flux from themeasurement.4.3 The source may be either natural sunlight or an artificialsource that closely approximates an Air Mass 1.5 solar energydistribution in accordance with Tables E892.4.4 Relevant optical properties are determined by the ratioof the total sphere flux tr
19、ansmitted or reflected by the specimento the total sphere flux, or both when no specimen is in place.4.5 The use of a spectrally flat or spectrally sensitivedetector determines whether a solar or a photopic opticalcharacteristic is measured.5. Significance and Use5.1 To overcome the inadequacies of
20、conventional spectro-photometric measurement techniques when nonhomogeneousmaterials are measured, a large integrating sphere may beused.4,5Since the beam employed in such spheres is large incomparison to the disparaties of the materials being tested, thenonisotropic nature of the specimen being mea
21、sured is essen-tially averaged, or integrated out of the measurement, in asingle experimental determination.5.2 Solar and photopic optical properties may be measuredeither with monofunctional spheres individually tailored for themeasurement of either transmittance5or reflectance, or may bemeasured w
22、ith a single multifunctional sphere that is employedto measure both transmittance and reflectance.45.3 A multifunctional sphere is used for making total solartransmittance measurements in both a directional-hemispherical and a directional-directional mode. The solarabsorptance can be evaluated in a
23、single measurement as oneminus the sum of the directional hemispherical reflectance andtransmittance. When a sample at the center of the sphere issupported by its rim, the sum of the reflectance and transmit-tance can be measured as a function of the angle of incidence.The solar absorptance is then
24、one minus the measured absorp-tance plus transmittance.6. Apparatus6.1 An integrating sphere having a minimum radius of 1 mand a maximum ratio of entrance aperture area to total spherearea of 1:200. The circular port defining the entrance apertureshall have a diameter of not less than 230 mm (approx
25、imately9 in.), although a port diameter of 300 mm (approximately 12in.) is preferred.6.2 The sphere shall be mounted in such a manner as topermit precision illumination of the sample at directions ofincidence from 0 (normal incidence) to 60 from normal in thetransmittance mode, using natural sunligh
26、t as source. Whenemploying an artificial source for either simulated solar orphotopic measurements, the off-angle mechanism may eitherbe made a part of the sphere (with a fixed position lamp) or apart of the source assembly (with a fixed position sphere).6.3 For reflectance measurements, a center-po
27、sitionedsample mount that has two degrees of freedom is required: inand out of the sample beam, and rotation about the samplebeam to provide incident angles from 0 to 660. The samplemount shall be designed so that the flux transmitted by thesample is absorbed, for measurement of reflectance, or so t
28、hatthe sample is supported by its rim for simultaneous measure-ment of reflectance plus transmittance.6.4 The interior of the integrating sphere shall be uniformlycoated with a spectrally flat paint having a minimum hemi-spherical reflectance of 0.85 in the spectral region of interest.For photopic m
29、easurements only, nearly any flat interior whitepaint will suffice. For solar and ultraviolet measurements, agood barium sulfate-pigmented sphere paint is required.6.5 A stable source illuminant having a spectral distributionapproximating that of a standard solar spectrum of Air Mass1.5 (Tables E892
30、) shall be employed for simulated solarmeasurements. Other sources may be employed for photopicmeasurements if the spectral energy distribution is essentiallyflat in the 475 to 650-nm region.6.6 For natural sunshine illumination, a solar siderostat (orheliostat) arrangement is required to provide un
31、iform illumi-nation (unless the sphere is itself operated in an altazimuthaltracking mode). Data should be taken during the time of daythat ensures a normal incident global (hemispherical) irradi-ance of at least 900 W/m2.NOTE 1Warning: Suitable eye protection is required when workingwith concentrat
32、ed sunlight as would be encountered in using a solarsiderostat. Manipulations of the reflectors for periodic maintenance, or forsample mounting can accidentally reflect concentrated sunlight upon theface. Sunglasses having high extinction for ultraviolet light are the mostimportant precaution. Refle
33、ctive glasses will prevent accidental burning ofthe retina by concentrated infrared light.6.7 In both natural sunshine and artificial sourceillumination, suitable circular light baffles are required to focuslight onto the entrance port. Focusing is especially critical inthe reflectance mode. The siz
34、e of the beam shall not exceed50 % of the size of the entrance port, or 45 % of the verticaldimension of specimens destined for measurements at 60normal incidence.6.8 A suitable detector/recorder system capable of measur-ing the flux over the spectral regions of interest is required. The4Zerlaut, G.
35、 A., and Anderson, T. E., “A Large-Multipurpose, Solar-IlluminatedIntegrating Sphere,” Optical Materials Technology for Energy Effciency and SolarEnergy Conversion III, SPIE Vol 502, 1984, p. 152.5Kessel, J., and Selkowitz, S., “Integrating Sphere Measurements of Directional-Hemispherical Transmitta
36、nce of Window Systems,” Journal of Illuminant Engineer-ing Society, No. 1, 1984, p. 136.E1175 87 (2015)2system should be capable of resolving a signal of 1 part in 200and should be linear to 2 % at full scale illumination.6.9 The detector shall be baffled from the entrance port topreclude direct ill
37、umination of the photoreceptor. The detectorshall be mounted in the sphere wall at 90 to the plane of theentrance aperture either at the bottom or top of the sphere.6.10 For directional-directional measurements of transmit-tance employing an occulting tube, the dimensions “L” (Fig. 1)should be betwe
38、en one and two sphere radii, the exactdimension depending on the baffle diameters and the solidangle of excitance desired.7. Test Specimens7.1 Transmittance specimens should be of sufficient size toprevent the possibility of light leaks at the edge of the entranceport. Only practical limits apply to
39、 the planar dimensions oftransparent specimens. Reflectance specimens should be regu-lar in shape (squares or disks) and shall not exceed 1/200th ofthe spherical area of the integrating sphere.8. Procedure8.1 Transmittance Mode:8.1.1 In the directional-hemispherical transmittance mode,the principal
40、configuration is shown in Fig. 1(b). Rotate thesphere or adjust the source to give the desired angle ofincidence (up to 60 from normal).8.1.2 Determine the directional-directional solar transmit-tance by inserting an appropriate occulting tube between thespecimen and the sphere (as shown in Fig. 1(a
41、). Coat theinterior of the tube with a highly absorbing paint.8.1.3 Record the detector signal without the sample in theincident beam. When the signal is stable, insert the sample intothe incident beam and record the resulting signal. Repeat themeasurement sequence until the ratios (for example, the
42、transmittance) are within 0.005 measurement units of eachother (usually 2 or 3 sequences are sufficient).8.2 Reflectance Mode:8.2.1 A removable stanchion with sample rod permits posi-tioning the sample exactly in the center of the sphere to provideabsolute reflectance measurements. Solar reflectance
43、 may bedetermined as a function of incident angle up to 60 fromnormal. The basic configuration is shown in Fig. 2.8.2.2 Record the detector signal first with the specimen inthe beam, and then with the specimen removed from the beam,but still in the sphere (to provide essentially the same interre-fle
44、ction impediments that were present when the specimen wasilluminated). Repeat the measurement sequence until the ratios(for example, the reflectance) are within 0.005 measurementunits of each other.8.3 Absorptance Mode Use the same procedure as 8.2.9. Calculation of Results9.1 Transmittance and Refl
45、ectanceCompute the transmit-tance or reflectance (solar or photopic) as the ratio of signalswhen the sample and sphere wall are illuminated as follows:Transmittance:s5 Vs/Vw(1)Reflectance:s5 Vs/Vw(2)where:Vsand Vw= detector signals when the sample and spherewall are illuminated, respectively, and ar
46、e, ofcourse, specific to the mode (for example,transmittance or reflectance).9.2 Absorptance of transmitting and translucent specimens(by direct measurement6in reflectance mode) are as follows:s5 1 2 Vs/Vw(3)where:s+ s= Vs/Vw10. Report10.1 The report shall contain the following information:10.1.1 Th
47、e source and identity of the test specimen,6Also known as 4 transmittance for transmitting specimens.FIG. 1 Integrating Sphere (Transmittance Modes)E1175 87 (2015)310.1.2 A complete description of the test specimen;thickness, cross sectional shape, color, and size,10.1.3 The place, date, and solar t
48、ime of test (if naturalsunlight). If artificial, supply illuminant data (type, spectraldistribution, etc.),10.1.4 The irradiance on the sample,10.1.5 Type of detector and data acquisition equipmentused, and10.1.6 Results, including standard deviation (where useful).11. Precision and Bias11.1 The pre
49、cision of any measurement depends directly onthe stability of the flux and its spectral distribution during anyset of measurements. Transmittance measurements taken of aflat (FRP) translucent plastic sheet overa1hperiod from 1100to 1200 h, utilizing natural sunlight, gave a mean solartransmittance of 0.876 with a standard deviation of 60.003 (forn = 14).11.2 Comparative data for a multifunctional sphere versusstandard spectrophometric measurements (employing TestMethod E903) of homogeneous and nonhomogeneous materi-als show agreement to within 1 %. The
