1、Designation:E121314Standard Practice forMinimum Resolvable Temperature Difference for ThermalImaging Systems1This standard is issued under the fixed designation E1213;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last r
2、evision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This practice covers the determination of the minimumresolvable temperature difference(MRTD)capability of thecompound observer-t
3、hermal imaging system as a function ofspatial frequency.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsib
4、ility 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:2E1316 Terminology for Nondestructive Examinations3.Terminology3.1 Definitions:3.1.1 differential
5、blackbodyan apparatus for establishingtwo parallel isothermal planar zones of different temperatures,and with effective emissivities of 1.0.3.1.2 See also Terminology E1316.4.Summary of Practice4.1 A standard four-bar target is used in conjunction with adifferential blackbody that can establish one
6、blackbody isother-mal temperature for the set of bars and another blackbodyisothermal temperature for the set of conjugate bars,which areformed by the regions between the bars(see Fig.1).The targetis imaged onto the monochrome video monitor of a thermalimaging system where the image is viewed by an
7、observer.Thetemperature difference between the bars and their conjugates,initially zero,is increased incrementally only until the observercan distinguish the four bars.This critical temperature differ-ence is the MRTD.4.2 The spatial distribution of temperature of each targetmust be measured remotel
8、y at the critical temperature differ-ence that determines the MRTD.The mean temperature of eachbar must not differ from that of any other bar by more than themeasured MRTD.A similar requirement applies to the tem-perature of each conjugate bar.Otherwise the MRTD value isunacceptable.4.3 The backgrou
9、nd temperature and the spatial frequencyof each target must be specified together with the measuredvalue of MRTD.4.4 The probability of resolution must be specified togetherwith the reported value of MRTD.5.Significance and Use5.1 This practice relates to a thermal imaging systemseffectiveness for d
10、iscerning details in a scene.5.2 MRTD values provide estimates of resolution capabilityand may be used to compare one system with another.(LowerMRTD values indicate better resolution.)5.3 Due to the partially subjective nature of the procedure,repeatability and reproducibility are apt to be poor and
11、 MRTDdifferences less than 0.2C are considered to be insignificant.NOTE1Values obtained under idealized laboratory conditions may ormay not correlate directly with service performance.6.Apparatus6.1 The apparatus consists of the following:6.1.1 Comparison Charts(Targets),comprised of four pe-riodic
12、bars of aspect ratio(width:height)1:7,as shown in Fig.1.6.1.2 Differential Blackbody,temporally stable and control-lable to within 0.1C.6.1.3 Infrared Spot Radiometer,calibrated with the aid of ablackbody source to an accuracy within 0.1C.NOTE2Comparison charts may be fabricated by cutting slots in
13、metal1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.10 onSpecialized NDT Methods.Current edition approved Oct.1,2014.Published October 2014.Originallyapproved in 1987.Last previous edition approved in 200
14、9 as E1213-97(2009).DOI:10.1520/E1213-14.2For 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.*A Summary of Changes sec
15、tion appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 and coating with black paint of emissivity greater than 0.95.In this casethe slots would constitute the bars.7.Procedure7.1 Mount a comparison chart(t
16、arget)onto the differentialblackbody.NOTE3Differential blackbodies may be used within an environmentalisothermal temperature chamber.Then,at equilibrium the temperature ofthe conjugates approximately equals the temperature of the room,orambient temperature.7.2 Optimally focus the thermal imaging system directly onthe target or on an optical projection of the target.7.3 Adjust the thermal imaging system for quasi-linearoperation.7.4 Adjust the monochrome video monitor controls so thatthe presence
