ASTM E1543-2000(2011) Standard Test Method for Noise Equivalent Temperature Difference of Thermal Imaging Systems《热成像系统的噪声等效温差的标准试验方法》.pdf

1、Designation: E1543 00 (Reapproved 2011)Standard Test Method forNoise Equivalent Temperature Difference of ThermalImaging Systems1This standard is issued under the fixed designation E1543; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis

2、ion, 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 noiseequivalent temperature difference (NETD; NEDT)

3、of thermalimaging systems of the conventional forward-looking infrared(FLIR) or other types that utilize an optical-mechanical scan-ner; it does not include charge-coupled devices or pyroelectricvidicons.1.2 Parts of this test method have been formulated under theassumption of a photonic detector(s)

4、 at a standard backgroundtemperature of 295K (22C). Besides nonuniformity, testsmade at other background temperatures may result in impair-ment of precision and bias.1.3 The values stated in SI units are to be regarded asstandard.1.4 This standard does not purport to address all of thesafety concern

5、s, if any, associated 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:2E1213 Test Method for Minimum Resolvable T

6、emperatureDifference for Thermal Imaging SystemsE1316 Terminology for Nondestructive Examinations3. Terminology3.1 Definitions:3.1.1 blackbody simulatora device that produces an emis-sion spectrum closely approximating that emitted by a black-body (surface with emissivity of 1.0), usually a cavity o

7、r a flatplate with a structured or coated surface having a stable anduniform temperature.3.1.2 dwell timethe time spent, during one frame, inscanning one angular dimension of a single pixel (pictureelement) of the image within the instantaneous field of view(IFOV) of a detector. Thus, for example, i

8、f a single pixel isscanned n times during one frame, the dwell time is given byn times the duration of a single scan of the pixel.3.1.3 FLIRan acronym for forward-looking infrared,originally implying airborne, now denoting any fast-framethermal imaging system comparable to that of television andyiel

9、ding real-time displays. Generally, these systems employoptical-mechanical scanning mechanisms.3.1.4 See also Section J: Infrared Examination, of Termi-nology E1316.4. Summary of Test Method4.1 The target is a blackbody source of uniform temperaturethat is viewed by the infrared thermal imaging syst

10、em throughan aperture of prescribed size. A specified temperature differ-ence is established between the target and its background.Measurements are made of the peak-to-peak signal voltagefrom the target and the RMS noise voltage from the back-ground, both across a standard reference filter, and of t

11、he targetand background temperatures. From these measured values, theNETD is calculated.5. Significance and Use5.1 This test method gives an objective measure of thetemperature sensitivity of a thermal imaging system (relative toa standard reference filter) exclusive of a monitor, withemphasis on th

12、e detector(s) and preamplifier.NOTE 1Test values obtained under idealized laboratory conditionsmay or may not correlate directly with service performance.1This test method is under the jurisdiction of ASTM Committee E07 onNondestructive Testing and is the direct responsibility of Subcommittee E07.10

13、 onSpecialized NDT Methods.Current edition approved Dec. 1, 2011. Published March 2012. Originallyapproved in 1993. Last previous edition approved in 2006 as E1543 - 00(2006).DOI: 10.1520/E1543-00R11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Servic

14、e 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 19428-2959, United States.5.2 This test method affords a convenient mean

15、s for peri-odically monitoring the performance of a given thermal imag-ing system.5.3 NETD relates to minimum resolvable temperature dif-ference as described in Test Method E1213. Thus, an increasein NETD may be manifest as a loss of detail in imagery.5.4 Intercomparisons based solely on NETD figure

16、s may bemisleading.NOTE 2NETD depends on various factors such as spectral bandwidthand background temperature.6. Apparatus6.1 The apparatus, as shown in Fig. 1, consists of thefollowing:6.1.1 Blackbody Simulator, temporally stable and control-lable to within 0.1C.6.1.2 Target Plate, containing an ap

17、erture several timeslarger dimensionally than the IFOV. The target plate should beat least ten times the dimension of the aperture in both theheight and width. (The plate forms the target background; theaperture, in effect, becomes the target as the blackbodysimulator is viewed through it.) The mate

18、rial and surfaceconditions of the target plate must be carefully considered. It ishelpful for the back side of the target plate to be a highlyreflective metallic surface to minimize the influence of theblackbody simulator on the temperature of the target back-ground. The front surface of the target

19、plate should appear tothe infrared imaging system to have a high emissivity. Onepossibility would be to coat the viewed surface with a highemissivity paint or coating.6.1.3 Target Cover, used to block completely the radiationemanating from the target. The target cover should have frontand back surfa

20、ce properties similar to those of the target plate.6.1.4 Standard Reference Filter, consisting of a single RClow-pass filter whose product RC is equal to twice the dwelltime; see Fig. 2.NOTE 3If the resistance, R, is in ohms and the capacitance, C,isinfarads, RC is in seconds.NOTE 4The purpose of th

21、e filter is to standardize and define areference noise bandwidth, upon which the noise measurement depends inpart.NOTE 5If convenient, the filter may be a self-contained unit forexternal connection.6.1.5 Infrared Spot Radiometer or equivalent radiometricinstrument, calibrated with the aid of a black

22、body source to anaccuracy within 0.1C.6.1.6 Digital Oscilloscope.6.1.7 Digital True RMS Voltmeter, with high crest factor(peak voltage/RMS voltage) so as not to attenuate any noisepeaks, and bandwidth from approximately zero to at least1.6/RC. See 6.1.4 and X1.1.7. Procedure7.1 Mount the target plat

23、e at the blackbody simulator, withits aperture oriented the same as the IFOV of the imagingsystem and centered with the blackbody source, see Fig. 1(a).7.2 Connect the standard reference filter (input) to a pointbeyond the preamplifier and before any multiplexor, video syncpulse generator or pulse-w

24、idth modulator.7.3 The thermal imaging system, including the scanner,shall be in operation. (The monitor need not be connected.)7.4 Set the blackbody simulator target temperature toroughly 7 or 8C above the ambient temperature; the recom-mended ambient temperature is 22C, controlled within 61C.7.5 W

25、ith the spot radiometer at a normal distance of1mtothe target, measure and record the target temperature, T.FIG. 1 Schematic of NETD Test Configuration; (a) When Measuring Signal and (b) When Measuring NoiseE1543 00 (2011)27.6 Replace the radiometer with the thermal imaging systemat the same locatio

26、n.7.7 Connect the standard reference filter output to theoscilloscope. Measure and record the peak-to-peak signalvoltage, S, between the signals from the background and thesignals from the target. Be certain that the range and levelcontrols of the infrared imager are set so that both the targetand b

27、ackground signals are within the working range of theinstrument.7.8 Place the target cover over the entire aperture; see Fig.1(b).7.9 Replace the oscilloscope with the RMS voltmeter.Measure and record the RMS noise voltage, N. The range andlevel control settings on the infrared imager should not bea

28、djusted between the signal measurement in 7.7 and the noisemeasurement in 7.9.7.10 Replace the thermal imaging system with the spotradiometer at the same location. Measure the apparent targetbackground temperature. Record the actual target backgroundtemperature, TB, correcting for emissivity, if war

29、ranted. Thedesired background temperature is 22C.7.11 The difference, TTB, should be between 5 and 10C;otherwise adjust the blackbody simulator target temperatureaccordingly and repeat 7.5 through 7.11.7.12 Calculate the NETD; see 8.1.7.13 With the spot radiometer (or equivalent radiometricinstrumen

30、t) measure the temperature uniformities of the targetand of the target background. The required temperature uni-formities are 60.05C for the target and 60.1C for the targetbackground.7.14 Similarly, measure the temperature stabilities of thetarget and the target background. The target must not vary

31、bymore than 60.05C for the time interval from the temperaturemeasurement, T, to the signal measurement, S. The targetbackground must not vary by more than 60.1C for theduration of the entire test.7.15 Inclusion of 7.13 and 7.14 shall be required for the firstthree tests made with a given installatio

32、n. Subsequent tests mayomit these steps where deemed warranted; for example, afterno significant change in NETD is observed.8. Calculation8.1 Calculate the noise equivalent temperature difference,NETD, as follows:NETD 5T 2 TBS/NC! (1)where:T = target temperature (C),TB= target background temperature

33、 (C), andS/N = signal to noise ratio (dimensionless).8.2 Calculate the noise equivalent bandwidth of the refer-ence filter (reference noise bandwidth), DfR, as follows (seeX1.2):DfR514RCHz! (2)where:R = filter resistance (ohms), andC = filter capacitance (farads).9. Report9.1 Report the following in

34、formation:9.1.1 NETD,9.1.2 Background temperature,9.1.3 Reference noise bandwidth, and9.1.4 Spectral bandwidth.10. Precision and Bias10.1 Insufficient data are available on which to base aprecision and bias statement.11. Keywords11.1 infrared imaging systems; noise equivalent temperaturedifference;

35、nondestructive testing; thermal imaging systems;thermographyFIG. 2 Circuit Diagram of Standard Reference FilterE1543 00 (2011)3APPENDIX(Nonmandatory Information)X1. MATHEMATICAL DERIVATIONS RELATING TO THE STANDARD REFERENCE FILTERX1.1 Characteristic FrequencyThe frequency responseof the standard re

36、ference filter is sketched in Fig. X1.1, whereR/Rois the ratio of output-to-input responsivity, and v is theangular frequency (v =2pf). The frequency at which R/Roequals 0.707 is the characteristic frequency, given by:vc51RCor fc512pRC(X1.1)and:10fc5102pRC51.6RC(X1.2)X1.2 Noise Equivalent BandwidthF

37、or a system charac-terized by exponential decay time, as above, the noise equiva-lent bandwidth is given by:DfR5*0 df1 1 2pft!2514t(X1.3)where:t = RC.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. User

38、s 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 to revision at any time by the responsible technical committee and must be reviewed every

39、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. Your comments will receive careful consideration at a meeting of theresponsible technica

40、l 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 copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,

41、 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).FIG. X1.1 Frequency Response of the Standard Reference FilterE1543 00 (2011)4