1、Designation: E1458 12Standard 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 adoption or, in the
2、 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 sizing of particles
3、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 explain the observed var
4、iability.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 the optical proper
5、ties 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 instruments generally us
6、e 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 diffraction particle sizing
7、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 byparticles is stric
8、tly 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 areconsidered. Fo
9、r 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 refractiveindex is
10、 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 translatingthe sample, f
11、or 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 theory, inwhich cas
12、e 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 applicable to all
13、instrument 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 material of inter
14、est 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 (for example, a sp
15、ray) 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 photographic negative, that
16、 is, clear apertures in an opaque substrate, may1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.be used as well). Each disc or particle artifact represents the orthogonal projection of the cross-sectionof one member of a population o
17、f 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 particles are positioned
18、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 particles, with a size
19、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-forward scattering cha
20、racteristics 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 composition of the particle
21、s 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 properties of the
22、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 would be produced by
23、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 difficult. Forthat
24、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 E799(recall that v
25、olume 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 the truevalues for
26、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 acceptedreference value
27、s. 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 of theaccepted r
28、eference 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 method describes
29、a procedure necessary topermit a user to easily verify that a laser diffraction particlesizing instrument is operating within tolerance limit specifica-tions, for example, such that the instrument accuracy is asstated by the manufacturer. The recommended calibrationverification method provides a dec
30、isive 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 applicationsinvolving spheric
31、al 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 idealconditions. No
32、nideal 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 receiving lens and
33、therefore 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, 2012. Published Novembe
34、r 2012. Originally approved in 1992. Last previous edition approved in 2001 as E1458 92 (2001) which waswithdrawn in February 2010 and reinstated in October 2012.2Bohren, C.F., and Huffman, D.R., Absorption and Scattering of Light by Small Particles, John Wiley and Sons, New York, 1983.3van de Hulst
35、, H.C., Light Scattering by Small Particles, 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 122
36、nonspherical particles, the 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 ve
37、rify quantitative performance 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
38、diffraction. A determination 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. Th
39、us, unitshandled roughly or used under adverse conditions (for ex-ample, exposed to dust, chemical vapors, vibration, or combi-nations thereof) shall undergo a calibration verification morefrequently than those not exposed to such conditions. Thisprocedure shall be performed after any significant re
40、pairs aremade on an instrument, 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, ass
41、ociated 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 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:5A340 Terminology of Symbols and Definitions Relating toM
42、agnetic TestingD123 Terminology 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 Ap
43、pearanceE456 Terminology Relating to Quality and StatisticsE799 Practice for Determining Data Criteria and Processingfor Liquid Drop Size AnalysisE1187 Terminology Relating to Conformity Assessment62.2 Military Standard:7MIL-STD-45662 Calibration Systems Requirements2.3 NIST Standard:8NIST SP 676-1
44、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 Lab.Accreditation3. Terminology3.1 Current ASTM Standard DefinitionsDefinitions of
45、 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).3.1.3 biassee Terminology D123, (Committee D13).3.1.4 calibrationsee Terminology
46、 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, and ANSI-ASQC Z-1 DraftStandard for Calibration Systems). For example, in some
47、 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 between the instrument re-sponse and the accepted value of the standard, for exam
48、ple, 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 stated accuracy specifications.To clarify the situation it is proposed that the m
49、ore 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).3.1.9 standard reference materialsee Terminology E131,(Committee E13).3.1.10 test method, nsee Terminology D123, (CommitteeD13).3.1.11 test
