1、Designation: E 1175 87 (Reapproved 2003)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 E 1175; the number immediately following the designation
2、indicates 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measureme
3、nt 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. Ma
4、terials that are pat-terned, 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
5、 property 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 ofs
6、emitransparent 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 value
7、s given 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 regu
8、latory limitations prior to use. (For specific safetyhazards, see Note 1.)2. Referenced Documents2.1 ASTM Standards:E 772 Terminology Relating to Solar Energy Conversion2E 892 Tables for Terrestrial Solar Spectral Irradiance at AirMass 1.5 for a 37 Tilted Surface3E 903 Test Method for Solar Absorpta
9、nce, Reflectance, andTransmittance of Materials Using Integrating Spheres23. Terminology3.1 Definitions:3.1.1 absorptance, nsee Terminology E 772.3.1.2 integrating sphereoptical device used to either col-lect flux reflected or transmitted from a sample into a hemi-sphere or to provide isotropic irra
10、diation of a sample 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 properti
11、es, nabsorptance, reflec-tance, and transmittance of a sample evaluated as the weightedaverage of the measured property, with the wavelength bywavelength of the product of the spectral irradiance for themeasurement and the Commission Internationale delEclairage (CIE) photopic spectral response,4as t
12、he weightingfunction.3.1.4 photopic response, nspectral response of the aver-age human eye when fully adapted to daylight conditions.3.1.5 reflectance, nsee Terminology E 772.3.1.6 transmittance, nsee Terminology E 772.4. Summary of Test Method4.1 This test method describes a procedure and apparatus
13、for determining the area-averaged 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.1These test methods are under the jurisdiction of
14、ASTM Committee E44 onSolar, Geothermal, and Other Alternative Energy Sources and is the directresponsibility of Subcommittee E44.05 on Solar Heating and Cooling Subsystemsand Systems.Current edition approved July 31, 1987. Published September 1987. Originallyapproved in 1987. Last previous edition a
15、pproved in 1996 as E 117587(1996).2Annual Book of ASTM Standards, Vol 12.02.3Annual Book of ASTM Standards, Vol 14.02.4Commission Internationale de lEclairage (CIE), International Light Vocabu-lary, 3rd Ed., Bureau Central de la CIE, Paris, 1970.1Copyright ASTM International, 100 Barr Harbor Drive,
16、PO Box C700, West Conshohocken, PA 19428-2959, United States.4.2 Transmittance is determined with the specimen mountedexternally at the sphere entrance port.5,6Reflectance is deter-mined by placing the specimen in the center of the integratingsphere,5in accordance with the diagram in Fig. A1.2 of Te
17、stMethod E 903. For measurement of reflectance of partiallytransmitting samples, the sample should be backed by a blackopaque absorber to eliminate 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
18、solar energydistribution in accordance with Tables E 892.4.4 Relevant optical properties are determined by the ratioof the total sphere flux transmitted 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 sensitive
19、detector determines whether a solar or a photopic opticalcharacteristic is measured.5. Significance and Use5.1 To overcome the inadequacies of conventional spectro-photometric measurement techniques when nonhomogeneousmaterials are measured, a large integrating sphere may beused.5,6Since the beam em
20、ployed in such spheres is large incomparison to the disparaties of the materials being tested, thenonisotropic nature of the specimen being measured is essen-tially averaged, or integrated out of the measurement, in asingle experimental determination.5.2 Solar and photopic optical properties may be
21、measuredeither with monofunctional spheres individually tailored for themeasurement of either transmittance6or reflectance, or may bemeasured with a single multifunctional sphere that is employedto measure both transmittance and reflectance.55.3 A multifunctional sphere is used for making total sola
22、rtransmittance measurements in both a directional-hemispherical and a directional-directional mode. The solarabsorptance can be evaluated in a single measurement as oneminus the sum of the directional hemispherical reflectance andtransmittance. When a sample at the center of the sphere issupported b
23、y 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 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 ap
24、erture area to total spherearea of 1:200. The circular port defining the entrance apertureshall have a diameter of not less than 230 mm (approximately9 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 i
25、llumination of the sample at directions ofincidence from 0 (normal incidence) to 60 from normal in thetransmittance mode, using natural sunlight as source. Whenemploying an artificial source for either simulated solar orphotopic measurements, the off-angle mechanism may eitherbe made a part of the s
26、phere (with a fixed position lamp) or apart of the source assembly (with a fixed position sphere).6.3 For reflectance measurements, a center-positionedsample mount that has two degrees of freedom is required: inand out of the sample beam, and rotation about the samplebeam to provide incident angles
27、from 0 to 660. The samplemount shall be designed so that the flux transmitted by thesample is absorbed, for measurement of reflectance, or so thatthe sample is supported by its rim for simultaneous measure-ment of reflectance plus transmittance.6.4 The interior of the integrating sphere shall be uni
28、formlycoated with a spectrally flat paint having a minimum hemi-spherical reflectance of 0.85 in the spectral region of interest.For photopic measurements only, nearly any flat interior whitepaint will suffice. For solar and ultraviolet measurements, agood barium sulfate-pigmented sphere paint is re
29、quired.6.5 A stable source illuminant having a spectral distributionapproximating that of a standard solar spectrum of Air Mass1.5 (Tables E 892) shall be employed for simulated solarmeasurements. Other sources may be employed for photopicmeasurements if the spectral energy distribution is essential
30、lyflat in the 475 to 650-nm region.6.6 For natural sunshine illumination, a solar siderostat (orheliostat) arrangement is required to provide uniform illumi-nation (unless the sphere is itself operated in an altazimuthaltracking mode). Data should be taken during the time of daythat ensures a normal
31、 incident global (hemispherical) irradi-ance of at least 900 W/m2.NOTE 1Warning: Suitable eye protection is required when workingwith concentrated sunlight as would be encountered in using a solarsiderostat. Manipulations of the reflectors for periodic maintenance, or forsample mounting can accident
32、ally reflect concentrated sunlight upon theface. Sunglasses having high extinction for ultraviolet light are the mostimportant precaution. Reflective glasses will prevent accidental burning ofthe retina by concentrated infrared light.6.7 In both natural sunshine and artificial source illumina-tion,
33、suitable circular light baffles are required to focus lightonto the entrance port. Focusing is especially critical in thereflectance mode. The size of the beam shall not exceed 50 %of the size of the entrance port, or 45 % of the verticaldimension of specimens destined for measurements at 60normal i
34、ncidence.6.8 A suitable detector/recorder system capable of measur-ing the flux over the spectral regions of interest is required. Thesystem 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 entra
35、nce port topreclude direct illumination 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 dimensio
36、ns “L” (Fig. 1)should be between one and two sphere radii, the exactdimension depending on the baffle diameters and the solidangle of excitance desired.5Zerlaut, G. A., and Anderson, T. E., “A Large-Multipurpose, Solar-IlluminatedIntegrating Sphere,” Optical Materials Technology for Energy Effciency
37、 and SolarEnergy Conversion III, SPIE Vol 502, 1984, p. 152.6Kessel, J., and Selkowitz, S., “Integrating Sphere Measurements of Directional-Hemispherical Transmittance of Window Systems,” Journal of Illuminant Engineer-ing Society, No. 1, 1984, p. 136.E 1175 87 (2003)27. Test Specimens7.1 Transmitta
38、nce specimens should be of sufficient size toprevent the possibility of light leaks at the edge of the entranceport. Only practical limits apply to the planar dimensions oftransparent specimens. Reflectance specimens should be regu-lar in shape (squares or disks) and shall not exceed 1/200th ofthe s
39、pherical area of the integrating sphere.8. Procedure8.1 Transmittance Mode:8.1.1 In the directional-hemispherical transmittance mode,the principal 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
40、the directional-directional solar transmit-tance by inserting an appropriate occulting tube between thespecimen and the sphere (as shown in Fig. 1(a). 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 i
41、s stable, insert the sample intothe incident beam and record the resulting signal. Repeat themeasurement sequence until the ratios (for example, thetransmittance) are within 0.005 measurement units of eachother (usually 2 or 3 sequences are sufficient).8.2 Reflectance Mode:8.2.1 A removable stanchio
42、n with sample rod permits posi-tioning the sample exactly in the center of the sphere to provideabsolute reflectance measurements. Solar reflectance 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
43、 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-flection impediments that were present when the specimen wasilluminated). Repeat the measurement sequence until the ratios(for example, the reflectance) ar
44、e 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 ReflectanceCompute the transmit-tance or reflectance (solar or photopic) as the ratio of signalswhen the sample and sphere wall are illuminated as follows:T
45、ransmittance: ts5 Vs/ Vw(1)Reflectance: rs5 Vs/ Vw(2)where:Vsand Vw= detector signals when the sample andsphere wall are illuminated, respectively,and are, of course, specific to the mode (forexample, transmittance or reflectance).9.2 Absorptance of transmitting and translucent specimens(by direct m
46、easurement7in reflectance mode) are as follows:as5 1 2 Vs/Vw(3)where:ts+ rs= Vs/Vw10. Report10.1 The report shall contain the following information:10.1.1 The source and identity of the test specimen,10.1.2 A complete description of the test specimen; thick-ness, cross sectional shape, color, and si
47、ze,7Also known as 4p transmittance for transmitting specimens.FIG. 1 Integrating Sphere (Transmittance Modes)FIG. 2 Integrating Sphere (Reflectance Mode)E 1175 87 (2003)310.1.3 The place, date, and solar time of test (if naturalsunlight). If artificial, supply illuminant data (type, spectraldistribu
48、tion, 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 precision of any measurement depends directly onthe stability of the flux and its spectral distrib
49、ution 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 E 903) of homogeneous and nonhomogeneous mate-rials show agreement to within 1 %. The bias of any measure-ment can be shown to be 0.995 for spheres with uniformdiffuse wall reflectance.12.
