1、Designation: E 1543 00 (Reapproved 2006)Standard Test Method forNoise Equivalent Temperature Difference of ThermalImaging Systems1This standard is issued under the fixed designation E 1543; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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; NED
3、T) 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
4、(s) 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 conc
5、erns, 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:2E 1213 Test Method for Minimum Resolvab
6、le TemperatureDifference for Thermal Imaging SystemsE 1316 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 cav
7、ity or 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 examp
8、le, if 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 an
9、dyielding real-time displays. Generally, these systems employoptical-mechanical scanning mechanisms.3.1.4 See also Section J: Infrared Examination, of Termi-nology E 1316.4. Summary of Test Method4.1 The target is a blackbody source of uniform temperaturethat is viewed by the infrared thermal imagin
10、g system 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, an
11、d of the 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
12、 on the detector(s) and preamplifier.NOTE 1Test values obtained under idealized laboratory conditionsmay or may not correlate directly with service performance.5.2 This test method affords a convenient means for peri-odically monitoring the performance of a given thermal imag-ing system.5.3 NETD rel
13、ates to minimum resolvable temperature dif-ference as described in Test Method E 1213. Thus, an increasein NETD may be manifest as a loss of detail in imagery.5.4 Intercomparisons based solely on NETD figures may bemisleading.1This test method is under the jurisdiction of ASTM Committee E07 onNondes
14、tructive Testing and is the direct responsibility of Subcommittee E07.10 onEmerging NDT Methods.Current edition approved May 1, 2006. Published June 2006. Originallyapproved in 1993. Last previous edition approved in 2000 as E 1543 - 00.2For referenced ASTM standards, visit the ASTM website, www.ast
15、m.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 19428-2959, United States.NOTE 2NET
16、D 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 aperture several timeslarger d
17、imensionally 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 material and surfaceconditions o
18、f 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 plate should appear tothe in
19、frared 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 surface properties similar to tho
20、se 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 the filter is to standardize a
21、nd 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 blackbody source to anaccuracy wi
22、thin 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 plate at the blackbody simulator
23、, 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-width modulator.7.3 The therm
24、al imaging system, including the scanner,shall be in operation. (The monitor need not be connected.)FIG. 1 Schematic of NETD Test Configuration; (a) When Measuring Signal and (b) When Measuring NoiseFIG. 2 Circuit Diagram of Standard Reference FilterE 1543 00 (2006)27.4 Set the blackbody simulator t
25、arget temperature toroughly 7 or 8C above the ambient temperature; the recom-mended ambient temperature is 22C, controlled within 61C.7.5 With the spot radiometer at a normal distance of1mtothe target, measure and record the target temperature, T.7.6 Replace the radiometer with the thermal imaging s
26、ystemat the same location.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 t
27、hat both the targetand background 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 infrar
28、ed imager should not beadjusted 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, correctin
29、g for emissivity, if warranted. 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 equival
30、ent radiometricinstrument) 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. T
31、he target must not vary 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
32、with a given installation. 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= targe
33、t background temperature (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
34、 Report the following information: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
35、 temperaturedifference; nondestructive testing; thermal imaging systems;thermographyE 1543 00 (2006)3APPENDIX(Nonmandatory Information)X1. MATHEMATICAL DERIVATIONS RELATING TO THE STANDARD REFERENCE FILTERX1.1 Characteristic FrequencyThe frequency responseof the standard reference filter is sketched
36、 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 BandwidthFor a system charac-terized
37、 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. Users of this standard are exp
38、ressly 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 five years andif not revis
39、ed, 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 technical committee, which you may
40、 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, PA 19428-2959,United Stat
41、es. 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).FIG. X1.1 Frequency Response of the Standard Reference FilterE 1543 00 (2006)4
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