1、Designation: E1458 12 (Reapproved 2016)Standard Test Method forCalibration Verification of Laser Diffraction Particle SizingInstruments Using Photomask Reticles1This standard is issued under the fixed designation E1458; the number immediately following the designation indicates the year oforiginal a
2、doption 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.INTRODUCTIONThere exists a large variety of techniques and instruments for the si
3、zing of particles and droplets influid suspension. These instruments are based on a number of different physical phenomena andinterlaboratory comparisons of data on, for example, reference liquid sprays have shown significantvariability. This test method evolved in conjunction with efforts to explai
4、n the observed variability.The effectiveness of this test method can be traced to the fact it circumvents difficulties associated withproducing, replicating, and maintaining a standard sample of liquid particles in a spray. This testmethod uses a photomask reticle to provide a simulation of some of
5、the optical properties of areference population of spherical particles.This test method is only applicable to optical particle sizinginstruments that are based on measurement and analysis of light scattered in the forward direction byparticles illuminated by a light beam. Since modern optical instru
6、ments generally use a laser toproduce a light beam, and since the light scattered in the forward direction by particles can often beaccurately described using diffraction theory approximations, the class of instruments for which thistest method applies have become generally known as laser diffractio
7、n particle sizing instruments.Because it is specifically Fraunhofer diffraction theory2,3that is used in the approximation, theseinstruments are also known as Fraunhofer diffraction particle sizing instruments.The diffraction approximation to the general problem of electromagnetic wave scattering by
8、particles is strictly valid only if three conditions are satisfied. The conditions are: particle sizes mustbe significantly larger than the optical wavelength, particle refractive indices must be significantlydifferent than the surrounding medium, and only very small (near-forward) scattering angles
9、 areconsidered. For the case of spherical particles with sizes on the order of the wavelength or for largescattering angles, the complete Lorenz-Mie scattering theory2,3rather than the Fraunhofer diffractionapproximation must be used. If the size and angle constraints are satisfied but the particle
10、refractiveindex is very close to that of the medium, the anomalous diffraction approximation3may be used.A complication is introduced by the fact that the optical systems of most laser diffraction particlesizing instruments can be used, with only minor modifications such as changing a lens or transl
11、atingthe sample, for measurement configurations outside the particle size or scattering angle range forwhich the diffraction approximation is valid. In this situation the scattering inversion software in theinstrument would generally incorporate a scattering model other than Fraunhofer diffraction t
12、heory, inwhich case the term “laser diffraction instrument” might be considered a misnomer. However, such aninstrument is still in essence a laser diffraction instrument, modified to decrease the lower particle sizelimit. A calibration verification procedure as described by this test method would be
13、 applicable to allinstrument configurations (or operational modes) where the photomask reticle accurately simulates therelevant optical properties of the particles.The ideal calibration test samples for laser diffraction particle sizing instruments would becomprised of the actual particle or droplet
14、 material of interest in the actual environment of interestwith size distributions closely approximating those encountered in practice. However, the use of suchcalibration test samples is not currently feasible because multi-phase mixtures may undergo changesduring a test and because actual samples
15、(for example, a spray) are not easily collected and stabilizedfor long periods of time. The subject of this test method is an alternative calibration test samplecomprised of a two-dimensional array of thin, opaque circular discs (particle artifacts) deposited ona transparent substrate (the photograp
16、hic negative, that is, clear apertures in an opaque substrate, maybe used as well). Each disc or particle artifact represents the orthogonal projection of the cross-sectionCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1of one member
17、of a population of spherical particles comprising the reference population. Thecollection of particle artifacts on a reticle represents an orthogonal projection of all the particles in thereference population for one particular three-dimensional arrangement of the population where themember particle
18、s are positioned within a finite reference volume. The reference volume is generallydefined such that the area covered by particle artifacts on the reticle is roughly equivalent to thecross-section of the instrument light beam. The reference population would generally contain a largenumber of partic
19、les, with a size distribution that approximates distributions of practical interest,randomly distributed over the reference volume. Large numbers and random positions minimizecomplications that can arise from optical coherence effects (interference).Of importance here is the fact that the near-forwa
20、rd scattering characteristics of the orthogonalprojections of the particle cross-sections onto the reticle plane accurately simulate, in regimes wherethe diffraction approximation is valid, the near-forward scattering characteristics of the referencepopulation (independent of the chemical compositio
21、n of the particles in the reference population). Inother words the photomask reticle, when illuminated with a laser beam of known properties, generatesa reference scattered light signature which can be predicted analytically from a knowledge of the sizedistribution of the reference population. The p
22、roperties of the reference population can be inferredfrom a characterization (using optical microscopy) of the sizes of the particle artifacts on the reticle.As the instrument is operated away from the diffraction regime, the scattering properties of thephotomask reticle diverge from that which woul
23、d be produced by the reference population andinterpretation of the measurements becomes more problematic.The most complete test result for this test method would be a discrete size distribution reported fora very large number of size class intervals, but intercomparisons of such distributions are di
24、fficult. Forthat reason statistical parameters (for example, representative diameters and measures of thedispersion) of the particle size distribution are used. Two examples of statistical parameters are thevolume median diameter DV0.5and the relative span (DV0.9 DV0.1)/DV0.5as defined in Practice E
25、799(recall that volume parameters such as DVffor a photomask reticle are defined in the sense thattwo-dimensional particle artifacts scatter light like spherical particles of the same diameter). Estimatesof the true values of these statistical parameters for a photomask reticle (or more precisely th
26、e truevalues for the reference population simulated by the reticle) can be established using optical orelectron microscope measurements of the diameters of the particle artifacts on the reticle. The valuesso established are termed image-analysis reference values and will be used herein as the accept
27、edreference values. It is the stability of DV0.5, the relative span, and all other statistical parametersrepresentative of the particle artifact size distribution for a reticle and the ability to produce nearlyidentical replicate copies of the reticles that make this test method useful. A comparison
28、 of theaccepted reference value of DV0.5, the relative span, or any other parameter of a reticle with acorresponding test result from the instrument under evaluation can be used to assess the acceptabilityof the instrument and of the data routinely obtained with the instrument.1. Scope1.1 This test
29、method describes a procedure necessary topermit a user to easily verify that a laser diffraction particlesizing instrument is operating within tolerance limitspecifications, for example, such that the instrument accuracyis as stated by the manufacturer. The recommended calibrationverification method
30、 provides a decisive indication of theoverall performance of the instrument at the calibration pointor points, but it is specifically not to be inferred that all factorsin instrument performance are verified. In effect, use of this testmethod will verify the instrument performance for applicationsin
31、volving spherical particles of known refractive index wherethe near-forward light scattering properties are accuratelymodeled by the instrument data processing and data reductionsoftware. The precision and bias limits presented herein are,therefore, estimates of the instrument performance under idea
32、lconditions. Nonideal factors that could be present in actualapplications and that could significantly increase the bias errorsof laser diffraction instruments include vignetting4(that is,where light scattered at large angles by particles far away fromthe receiving lens does not pass through the rec
33、eiving lens andtherefore does not reach the detector plane), the presence of1This test method is under the jurisdiction of ASTM Committee E29 on Particle and Spray Characterization and is the direct responsibility of Subcommittee E29.02 onNon-Sieving Methods.Current edition approved Oct. 1, 2016. Pu
34、blished October 2016. Originally approved in 1992. Last previous edition approved in 2012 as E1458 12. DOI:10.1520/E1458-12R16.2Bohren, C.F., and Huffman, D.R., Absorption and Scattering of Light by Small Particles, John Wiley and Sons, New York, 1983.3van de Hulst, H.C., Light Scattering by Small P
35、articles, Dover Publications Inc., New York, 1981.4Hirleman, E.D., Oechsle, V., and Chigier, N.A., “Response Characteristics ofLaser Diffraction Particle Sizing Systems: Optical Sample Volume and LensEffects,” Optical Engineering, Vol 23, 1984, pp. 610619.E1458 12 (2016)2nonspherical particles, the
36、presence of particles of unknownrefractive index, and multiple scattering.1.2 This test method shall be used as a significant test of theinstrument performance. While the procedure is not designedfor extensive calibration adjustment of an instrument, it shallbe used to verify quantitative performanc
37、e on an ongoing basis,to compare one instrument performance with that of another,and to provide error limits for instruments tested.1.3 This test method provides an indirect measurement ofsome of the important parameters controlling the results inparticle sizing by laser diffraction. A determination
38、 of allparameters affecting instrument performance would comeunder a calibration adjustment procedure.1.4 This test method shall be performed on a periodic andregular basis, the frequency of which depends on the physicalenvironment in which the instrumentation is used. Thus, unitshandled roughly or
39、used under adverse conditions (forexample, exposed to dust, chemical vapors, vibration, orcombinations thereof) shall undergo a calibration verificationmore frequently than those not exposed to such conditions.This procedure shall be performed after any significant repairsare made on an instrument,
40、such as those involving the optics,detector, or electronics.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesafety problems, if any, associated with its use. It is ther
41、esponsibility of the user of this 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:5A340 Terminology of Symbols and Definitions Relating toMagnetic TestingD123 Terminology
42、Relating to TextilesD3244 Practice for Utilization of Test Data to DetermineConformance with SpecificationsE131 Terminology Relating to Molecular SpectroscopyE135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE284 Terminology of AppearanceE456 Terminology Relatin
43、g to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE799 Practice for Determining Data Criteria and Processingfor Liquid Drop Size AnalysisE1187 Terminology Relating to Conformity Assessment(Withdrawn 2006)62.2 Military Standard:
44、7MIL-STD-45662 Calibration Systems Requirements2.3 NIST Standard:8NIST SP 676-1 Measurement Assurance Programs2.4 ANSI Standard:9ANSI-ASQC Z-1 Standard for Calibration Systems2.5 ISO Standard:10ISO Guide 2A General Terms and Their Definitions Con-cerning Standardization Certification, and Testing La
45、b.Accreditation3. Terminology3.1 Current ASTM Standard DefinitionsDefinitions of theterms listed below, as used in this test method are from theCompilation of ASTM Standard Definitions:113.1.1 accuracysee Terminology D123, (Committee D13).3.1.2 assignable causesee Terminology E456, (Commit-tee E11).
46、3.1.3 biassee Terminology D123, (Committee D13).3.1.4 calibrationsee Terminology E1187, (CommitteeE36).3.1.5 DiscussionThis and many other commonly useddefinitions for calibration are very broad in the sense that theycould encompass a wide range of tasks. (See for exampleMIL-STD-45662, NIST SP 676-1
47、, and ANSI-ASQC Z-1 DraftStandard for Calibration Systems). For example, in some casescalibration is only the determination of whether or not aninstrument is operating within accuracy specifications (toler-ance testing in NIST SP 676-1). In other cases calibrationincludes reporting of differences be
48、tween the instrument re-sponse and the accepted value of the standard, for example, toproduce a “Table of Corrections” to be used with the instru-ment. Finally, calibration can also include any repairs oradjustments required to make the instrument response consis-tent with the standard within the st
49、ated accuracy specifications.To clarify the situation it is proposed that the more specificterms calibration verification and calibration adjustment (see3.4) both of which would fall under these broad definitions ofcalibration.3.1.6 coeffcient of variationsee Terminology D123,(Committee D13). Also known as the relative standard devia-tion (see Terminology E135, Committee E01).3.1.7 reference materialsee Terminology E1187, (Com-mittee E36) (see ISO Guide 2A).3.1.8 scatteringsee Terminology E284, (Committee E12).5For referenced ASTM standards, visit the ASTM website, www.ast
