1、Designation: E 1213 97 (Reapproved 2009)Standard Test Method forMinimum Resolvable Temperature Difference for ThermalImaging Systems1This standard is issued under the fixed designation E 1213; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、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.1. Scope1.1 This test method covers the determination of the mini-mum resolvable temperature difference (MRT
3、D) capability ofthe compound observer-thermal imaging system as a functionof spatial frequency.1.2 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 pr
4、actices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 1316 Terminology for Nondestructive Examinations3. Terminology3.1 Definitions:3.1.1 differential blackbodyan apparatus for establishingtwo parallel isothermal planar zones of
5、different temperatures,and with effective emissivities of 1.0.3.1.2 See also Terminology E 1316.4. Summary of Test Method4.1 A standard four-bar target is used in conjunction with adifferential blackbody that can establish one blackbody isother-mal temperature for the set of bars and another blackbo
6、dyisothermal 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 observer. Thetemperature difference between the bars and their conjug
7、ates,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 remotely at the critical temperature differ-ence that determines the MRTD
8、. 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 background temperature and the spatial frequencyof each target must be
9、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 test relates to a thermal imaging systems effec-tiveness for discerning details in a scene.5.2 MRTD values provide estimates o
10、f resolution capabilityand may be used to compare one system with another. (LowerMRTD values indicate better resolution.)NOTE 1Test values obtained under idealized laboratory conditionsmay or may not correlate directly with service performance.6. Apparatus6.1 The apparatus consists of the following:
11、6.1.1 Test Charts (Targets), comprised of four periodic barsof 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.
12、NOTE 2Test charts may be fabricated by cutting slots in metal andcoating with black paint of emissivity greater than 0.95. In this case theslots would constitute the bars.7. Procedure7.1 Mount a test chart (target) onto the differential black-body.1This test method is under the jurisdiction of ASTM
13、Committee E07 onNondestructive Testing and is the direct responsibility of Subcommittee E07.10 onEmerging NDT Methods.Current edition approved March 1, 2009. Published March 2009. Originallyapproved in 1987. Last previous edition approved in 2002 as E 1213 - 97(2002).2For referenced ASTM standards,
14、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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 1942
15、8-2959, United States.NOTE 3Differential blackbodies may be used within an environmen-tal isothermal temperature chamber. Then, at equilibrium the temperatureof the conjugates approximately equals the temperature of the room, orambient temperature.7.2 Optimally focus the thermal imaging system direc
16、tly 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 of noise is barely perceivable by the observer.7.5 Make the display luminance and the laboratory ambientlumi
17、nance mutually suitable for visual acuity and viewingcomfort.7.6 Instruct the observer to signal when he can perceive theappearance of four distinct bars on the monitor. Refrain fromfurther conversation during the test which could conceivablyinfluence or bias the observer.7.7 Record the distances th
18、at determine spatial frequency(see 8.1), and set the nominal DT (the nominal temperature ofthe bars minus the nominal temperature of the conjugate bars,zero or a positive number) equal to zero.7.8 Gradually increase the nominal DT in increments notexceeding 0.1C until the observer signals.7.9 Measur
19、e the spatial distribution of temperature of thetargets with an infrared spot radiometer of accuracy better than0.1C. Each bar and each conjugate must be measured in atleast three locations that include the ends and centerpoint. Ifadditional locations are measured, all must be at regularintervals. T
20、he field of view must be confined to the bar orconjugate being measured.7.10 Calculate the mean temperature of each bar and inter-compare the values, and calculate the mean temperature ofeach conjugate bar and intercompare the values.7.11 Calculate the actual DT (the average temperature of thebars m
21、inus the average temperature of the conjugate bars).Provisionally, this is the MRTD.7.12 Compare the largest difference in the mean tempera-tures of any two bars, or any two conjugate bars, with theMRTD. If this difference exceeds the MRTD, the test resultsare unacceptable for this particular spatia
22、l frequency.7.13 Replace the test chart with another of different spatialfrequency and repeat the test (7.2-7.12).7.14 Repeat 7.13 one or more times.7.15 Repeat the entire test (7.1-7.14) with a different ob-server.7.16 Repeat 7.15 one or more times.NOTE 4Observers must be free of eye disease, have
23、good eyesight,and be familiar with viewing thermal imagery.NOTE 5Only one observer at a time shall be present during thetesting.8. Calculation8.1 Calculate the spatial frequency, F, of the test charts asfollows:F 51023DsFcyclesmradG(1)where:F = spatial frequency,D = distance from target to thermal i
24、maging system, m,s = center line to center line separation of bars, m, and D s.8.2 Calculate the probability of resolution as shown by thefollowing illustration: For a given test chart, the MRTD resultsobtained with three different observers are 0.5C, 0.6C, and1.0C. The observer who resolved 0.5C wo
25、uld also be capableof resolving 0.6C and 1.0C; similarly the observer whoresolved 0.6C would also be capable of resolving 1.0C.Therefore, the respective probabilities of resolution are: for0.5C,13 = 33 %; for 0.6C,23 = 67 %; for 1.0C,33= 100 %.9. Report9.1 Report the following information:9.1.1 Spat
26、ial frequency,9.1.2 MRTD,9.1.3 Probability of resolution, and9.1.4 Background temperature.9.2 MRTD values must relate to a probability of resolutionof at least 50 %.FIG. 1 Targets Used for MRTD DeterminationsE 1213 97 (2009)29.3 Only a single probability of resolution must be usedthroughout.NOTE 6A
27、graph of MRTD versus spatial frequency is a convenientform of reporting the data.10. Precision and Bias10.1 Insufficient data are available on which to base aprecision and bias statement. Notwithstanding, owing to thepartially subjective nature of the test, repeatability and repro-ducibility are apt
28、 to be poor and MRTD differences less than0.2C are considered to be insignificant.11. Keywords11.1 infrared imaging systems; minimum resolvable tem-perature difference; nondestructive testing; thermal imagingsystems; thermography; infraredASTM International takes no position respecting the validity
29、of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject t
30、o revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters.
31、 Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is
32、copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).E 1213 97 (2009)3
