ASTM E2544-2008a Standard Terminology for Three-Dimensional (3D) Imaging Systems.pdf

1、Designation: E 2544 08aStandard Terminology forThree-Dimensional (3D) Imaging Systems1This standard is issued under the fixed designation E 2544; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number i

2、n parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This terminology contains common terms, definitions ofterms, descriptions of terms, nomenclature, and acronymsassociated with three-dimensional

3、 (3D) imaging systems in aneffort to standardize terminology used for 3D imaging systems.1.2 The definitions of the terms presented in 3.1 are ob-tained from various standard documents developed by variousstandards development organizations. The intent is not tochange these universally accepted defi

4、nitions but to gather, ina single document, terms and their definitions that may be usedin current or future standards for 3D imaging systems.1.2.1 In some cases, definitions of the same term from twostandards have been presented to provide additional reference.The text in parentheses to the right o

5、f each defined term is thename (and, in some cases, the specific section) of the source ofthe definition associated with that term.1.3 The definitions in 3.2 are specific terms developed bythis committee for 3D imaging systems.1.4 A definition in this terminology is a statement of themeaning of a wo

6、rd or word group expressed in a singlesentence with additional information included in notes ordiscussions.1.5 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 a

7、nd health practices and determine the applica-bility of regulatory limitations prior to use.NOTE 1The subcommittee responsible for this standard will reviewdefinitions on a five-year basis to determine if the definition is stillappropriate as stated. Revisions will be made when determined necessary.

8、2. Referenced Documents2.1 ASTM Standard:2E 456 Terminology Relating to Quality and Statistics2.2 ASME Standard:3B89.4.19 Performance Evaluation of Laser Based SphericalCoordinate Measurement Systems2.3 ISO Standard:4VIM International Vocabulary of Basic and General Termsin MetrologyISO 111461 Laser

9、s and laser-related equipment Testmethods for laser beam widths, divergence angles andbeam propagation ratios Part 1: Stigmatic and simpleastigmatic beams2.4 NIST/SEMATECH Standard:5NIST/SEMATECH e-Handbook of Statistical Methods3. Terminology3.1 Definitions:accuracy of measurement, ncloseness of th

10、e agreementbetween the result of a measurement and a true value of themeasurand. (VIM 3.5)DISCUSSION(1) Accuracy is a qualitative concept.(2) The term “precision” should not be used for “accuracy.”bias (of a measuring instrument), nsystematic error of theindication of a measuring instrument. (VIM 3.

11、25)DISCUSSION(1) The bias of a measuring instrument is normallyestimated by averaging the error of indication over an appro-priate number of repeated measurements.bias, ndifference between the average or expected value of adistribution and the true value.(NIST/SEMATECH e-Handbook)DISCUSSION1This ter

12、minology is under the jurisdiction of Committee E57 on 3D ImagingSystems and is the direct responsibility of Subcommittee E57.01 on Terminology.Current edition approved Aug. 1, 2008. Published August 2008. Originallyapproved in 2007. Last previous edition approved in 2008 as E 2544-08.2For reference

13、d 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 American Society of Mechanical Engineers (ASME), ASMEIntern

14、ational Headquarters, Three Park Ave., New York, NY 10016-5990, http:/www.asme.org.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.5Available from National Institute of Standards and Technology (NIST), 100Bureau Dr., Stop

15、 1070, Gaithersburg, MD 20899-1070, http:/www.nist.gov.e-Handbook available at http:/www.itl.nist.gov/div898/handbook/.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.(1) In metrology, the difference between precision andaccuracy is

16、that measures of precision are not affected by bias,whereas accuracy measures degrade as bias increases.calibration, nset of operations that establish, under specifiedconditions, the relationship between values of quantitiesindicated by a measuring instrument or measuring system, orvalues represente

17、d by a material measure or a referencematerial, and the corresponding values realized by standards.(VIM 6.11)DISCUSSION(1) The result of a calibration permits either the assignmentof values of measurands to the indications or the determinationof corrections with respect to indications.(2) A calibrat

18、ion may also determine other metrologicalproperties such as the effect of influence quantities.(3) The result of a calibration may be recorded in adocument, sometimes called a calibration certificate or acalibration pensation, nthe process of determining systematic er-rors in an instrument and then

19、applying these values in anerror model that seeks to eliminate or minimize measure-ment errors. (ASME B89.4.19)conventional true value (of a quantity), nvalue attributedto a particular quantity and accepted, sometimes by conven-tion, as having an uncertainty appropriate for a givenpurpose. (VIM 1.20

20、)DISCUSSION(1) Examples: (1) at a given location, the value assigned tothe quantity realized by a reference standard may be taken asa conventional true value and (2) the CODATA (1986) recom-mended value for the Avogadro constant, NA: 6 022 136 7 31023mol-1.(2) Conventional true value is sometimes ca

21、lled assignedvalue, best estimate of the value, conventional value, orreference value.(3) Frequently, a number of results of measurements of aquantity is used to establish a conventional true value.error (of measurement), nresult of a measurement minus atrue value of the measurand. (VIM 3.10)DISCUSS

22、ION(1) Since a true value cannot be determined, in practice, aconventional true value is used (see true value and conven-tional true value).(2) When it is necessary to distinguish “error” from“relative error,” the former is sometimes called “absolute errorof measurement.” This should not be confused

23、 with the“absolute value of error,” which is the modulus of error.indicating (measuring) instrument, nmeasuring instru-ment that displays an indication. (VIM 4.6)DISCUSSION(1) Examples include analog indicating voltmeter, digitalfrequency meter, and micrometer.(2) The display may be analog (continuo

24、us or discontinu-ous) or digital.(3) Values of more than one quantity may be displayedsimultaneously.(4) A displaying measuring instrument may also provide arecord.limiting conditions, nthe manufacturers specified limits onthe environmental, utility, and other conditions within whichan instrument ma

25、y be operated safely and without damage.(ASME B89.4.19)DISCUSSION(1) The manufacturers performance specifications are notassured over the limiting conditions.maximum permissible error (MPE), nextreme values of anerror permitted by specification, regulations, and so forth fora given measuring instrum

26、ent. (VIM 5.21)measurand, nparticular quantity subject to measurement.(VIM 2.6)DISCUSSION(1) Example includes vapor pressure of a given sample ofwater at 20C.(2) The specification of a measurand may require state-ments about quantities such as time, temperature, and pressure.precision, ncloseness of

27、 agreement between independenttest results obtained under stipulated conditions.(ASTM E 456)DISCUSSION(1) Precision depends on random errors and does not relateto the true value or the specified value.(2) The measure of precision is usually expressed in termsof imprecision and computed as a standard

28、 deviation of the testresults. Less precision is reflected by a larger standard devia-tion.(3) “Independent test results” means results obtained in amanner not influenced by any previous result on the same orsimilar test object. Quantitative measures of precision dependcritically on the stipulated c

29、onditions. Repeatability and repro-ducibility conditions are particular sets of extreme stipulatedconditions.precision, nin metrology, the variability of a measurementprocess around its average value.(NIST/SEMATECH e-Handbook)DISCUSSION(1) Precision is usually distinguished from accuracy, thevariabi

30、lity of a measurement process around the true value.Precision, in turn, can be decomposed further into short-termvariation or repeatability and long-term variation or reproduc-ibility.random error, nresult of a measurement minus the meanthat would result from an infinite number of measurementsof the

31、 same measurand carried out under repeatabilityconditions. (VIM 3.13)DISCUSSION(1) Random error is equal to error minus systematic error.E 2544 08a2(2) Because only a finite number of measurements can bemade, it is possible to determine only an estimate of randomerror.rated conditions, nmanufacturer

32、-specified limits on envi-ronmental, utility, and other conditions within which themanufacturers performance specifications are guaranteed atthe time of installation of the instrument.(ASME B89.4.19)relative error, nerror of measurement divided by a truevalue of the measurand. (VIM 3.12)DISCUSSION(1

33、) Since a true value cannot be determined, in practice aconventional true value is used.repeatability (of results of measurements), ncloseness ofthe agreement between the results of successive measure-ments of the same measurand carried out under the sameconditions of measurement. (VIM 3.6)DISCUSSIO

34、N(1) These conditions are called repeatability conditions.(2) Repeatability conditions include: the same measure-ment procedure; the same observer; the same measuringinstrument used under the same conditions; the same location;and repetition over a short period of time.(3) Repeatability may be expre

35、ssed quantitatively in termsof the dispersion characteristics of the results.reproducibility (of results of measurements), nclosenessof the agreement between the results of measurements of thesame measurand carried out under changed conditions ofmeasurement. (VIM 3.7)DISCUSSION(1) A value statement

36、of reproducibility requires specifica-tion of the conditions changed.(2) The changed conditions may include: principle ofmeasurement; method of measurement; observer; measuringinstrument; reference standard; location; conditions of use; andtime.(3) Reproducibility may be expressed quantitatively int

37、erms of the dispersion characteristics of the results.(4) Results are usually understood to be corrected results.systematic error, nmean that would result from an infinitenumber of measurements of the same measurand carried outunder repeatability conditions minus a true value of themeasurand. (VIM 3

38、.14)DISCUSSION(1) Systematic error is equal to error minus random error.(2) Like true value, systematic error and its causes cannotbe completely known.(3) For a measuring instrument, see “bias.”true value (of a quantity), nvalue consistent with thedefinition of a given particular quantity. (VIM 1.19

39、)DISCUSSION(1) This is a value that would be obtained by a perfectmeasurement.(2) True values are by nature indeterminate.(3) The indefinite article “a,” rather than the definite article“the,” is used in conjunction with “true value” because theremay be many values consistent with the definition of

40、a givenparticular quantity.uncertainty of measurement, nparameter, associated withthe result of a measurement, that characterizes the dispersionof the values that could reasonably be attributed to themeasurand. (VIM 3.9)DISCUSSION(1) The parameter may be, for example, a standard devia-tion (or a giv

41、en multiple of it) or the half width of an intervalhaving a stated level of confidence.(2) Uncertainty of measurement comprises, in general,many components. Some of these components may be evalu-ated from the statistical distribution of the results of series ofmeasurements and can be characterized b

42、y experimental stan-dard deviations. The other components, which can also becharacterized by standard deviations, are evaluated from as-sumed probability distributions based on experience or otherinformation.(3) It is understood that the result of the measurement is thebest estimate of the value of

43、the measurand, and that allcomponents of uncertainty, including those arising from sys-tematic effects, such as components associated with correctionsand reference standards, contribute to the dispersion.3.2 Definitions of Terms Specific to This Standard:3D imaging system, na non-contact measurement

44、 instru-ment used to produce a 3D representation (for example, apoint cloud) of an object or a site.DISCUSSION(1) Some examples of a 3D imaging system are laserscanners (also known as LADARs or LIDARs or laser radars),optical range cameras (also known as flash LIDARs or 3Drange cameras), triangulati

45、on-based systems such as thoseusing pattern projectors or lasers, and other systems based oninterferometry.(2) In general, the information gathered by a 3D imagingsystem is a collection of n-tuples, where each n-tuple caninclude but is not limited to spherical or Cartesian coordinates,return signal

46、strength, color, time stamp, identifier, polariza-tion, and multiple range returns.(3) 3D imaging systems are used to measure from rela-tively small scale objects (for example, coin, statue, manufac-tured part, human body) to larger scale objects or sites (forexample, terrain features, buildings, br

47、idges, dams, towns,archeological sites).angular increment, nthe angle between samples, Da, whereDa = ai ai-1, in either the azimuth or elevation directions(or a combination of both) with respect to the instrumentsinternal frame of reference.DISCUSSIONE 2544 08a3(1) For scanning instruments, the angu

48、lar increment mayalso be known as the angle step size.beam diameter (ds), nfor a laser beam with a circularirradiance pattern, the beam diameter is the extent of theirradiance distribution in a cross section of the laser beam (ina plane orthogonal to its propagation path) at a distance z andis given

49、 by:dsz! 5 4sz!where:s(z) = sx(z) = sy(z)sx(z),sy(z) = the square roots of the second order mo-mentsDISCUSSION(1) Reference ISO 111461.(2) For a laser beam with a Gaussian distribution ofirradiance, the beam diameter is often defined as the distanceacross the center of the beam for which the irradiance, I, equals1/e2of the maximum irradiance (where e is the base of thenatural logarithm). See Fig. 1. The area inside a circle with thisdiameter and centered at the beam center will contain 86.5 %of the total irrad