1、Designation: E1543 00 (Reapproved 2011)E1543 14Standard Test Method Practice 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
2、the case of 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 noise equivalent temperature differ
3、ence (NETD; NET) of thermalimaging systems of the conventional forward-looking infrared (FLIR) or other types that utilize an optical-mechanical scanner; itdoes not include charge-coupled devices or pyroelectric vidicons.1.2 Parts of this test method have been formulated under the assumption of a ph
4、otonic detector(s) at a standard backgroundtemperature of 295K (22C). Besides nonuniformity, tests made at other background temperatures may result in impairment ofprecision and bias.1.3 The values stated in SI units are to be regarded as standard.1.4 This standard does not purport to address all of
5、 the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E1213 Practice for Minimum
6、 Resolvable Temperature Difference for Thermal Imaging SystemsE1316 Terminology for Nondestructive Examinations3. Terminology3.1 Definitions:3.1.1 blackbody simulatora device that produces an emission spectrum closely approximating that emitted by a blackbody(surface with emissivity of 1.0), usually
7、 a cavity or a flat plate with a structured or coated surface having a stable and uniformtemperature.3.1.2 dwell timethe time spent, during one frame, in scanning one angular dimension of a single pixel (picture element) ofthe image within the instantaneous field of view (IFOV) of a detector. Thus,
8、for example, if a single pixel is scanned n times duringone frame, the dwell time is given by n 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-frame thermalimaging system comparable to that of te
9、levision and yielding real-time displays. Generally, these systems employ optical-mechanical scanning mechanisms.3.1.4 See also Section J: Infrared Examination, of Terminology E1316.4. Summary of Test Method4.1 The target is a blackbody source of uniform temperature that is viewed by the infrared th
10、ermal imaging system through anaperture of prescribed size.Aspecified temperature difference is established between the target and its background. Measurementsare made of the peak-to-peak signal voltage from the target and the RMS noise voltage from the background, both across a standardreference fi
11、lter, and of the target and background temperatures. From these measured values, the NETD is calculated.1 This test method practice is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.10 onSpecialized NDT Methods.Current edit
12、ion approved Dec. 1, 2011Oct. 1, 2014. Published March 2012October 2014. Originally approved in 1993. Last previous edition approved in 20062011 asE1543 - 00(2006).(2011). DOI: 10.1520/E1543-00R11.10.1520/E154314.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Cus
13、tomer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to t
14、he previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright
15、ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Significance and Use5.1 This test method gives an objective measure of the temperature sensitivity of a thermal imaging system (relative to astandard reference filter) exclusive of a monitor, w
16、ith emphasis on the detector(s) and preamplifier.NOTE 1Test values obtained under idealized laboratory conditions may or may not correlate directly with service performance.5.2 This test method affords a convenient means for periodically monitoring the performance of a given thermal imagingsystem.5.
17、3 NETD relates to minimum resolvable temperature difference as described inTest Method E1213.Thus, an increase in NETDmay be manifest as a loss of detail in imagery.5.4 Intercomparisons based solely on NETD figures may be misleading.NOTE 2NETD depends on various factors such as spectral bandwidth an
18、d background temperature.6. Apparatus6.1 The apparatus, as shown in Fig. 1, consists of the following:6.1.1 Blackbody Simulator, temporally stable and controllable to within 0.1C.6.1.2 Target Plate, containing an aperture several times larger dimensionally than the IFOV. The target plate should be a
19、t leastten times the dimension of the aperture in both the height and width. (The plate forms the target background; the aperture, in effect,becomes the target as the blackbody simulator is viewed through it.) The material and surface conditions of the target plate mustbe carefully considered. It is
20、 helpful for the back side of the target plate to be a highly reflective metallic surface to minimize theinfluence of the blackbody simulator on the temperature of the target background. The front surface of the target plate shouldappear to the infrared imaging system to have a high emissivity. One
21、possibility would be to coat the viewed surface with a highemissivity paint or coating.6.1.3 Target Cover, used to block completely the radiation emanating from the target. The target cover should have front andback surface properties similar to those of the target plate.6.1.4 Standard Reference Fil
22、ter, consisting of a single RC low-pass filter whose product RC is equal to twice the dwell time;see Fig. 2.NOTE 3If the resistance, R, is in ohms and the capacitance, C, is in farads, RC is in seconds.NOTE 4The purpose of the filter is to standardize and define a reference noise bandwidth, upon whi
23、ch the noise measurement depends in part.NOTE 5If convenient, the filter may be a self-contained unit for external connection.6.1.5 Infrared Spot Radiometer or equivalent radiometric instrument, calibrated with the aid of a blackbody source to anaccuracy within 0.1C.FIG. 1 Schematic of NETD TestProc
24、edure Configuration; (a) When Measuring Signal and (b) When Measuring NoiseE1543 1426.1.6 Digital Oscilloscope.6.1.7 Digital True RMS Voltmeter, with high crest factor (peak voltage/RMS voltage) so as not to attenuate any noise peaks, andbandwidth from approximately zero to at least 1.6/RC. See 6.1.
25、4 and X1.1.7. Procedure7.1 Mount the target plate at the blackbody simulator, with its aperture oriented the same as the IFOV of the imaging systemand centered with the blackbody source, see Fig. 1(a).7.2 Connect the standard reference filter (input) to a point beyond the preamplifier and before any
26、 multiplexor, video sync pulsegenerator or pulse-width 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 to roughly 7 or 8C above the ambient temperature; the recommendedambie
27、nt temperature is 22C, controlled within 61C.7.5 With the spot radiometer at a normal distance of 1 m to the target, measure and record the target temperature, T.7.6 Replace the radiometer with the thermal imaging system at the same location.7.7 Connect the standard reference filter output to the os
28、cilloscope. Measure and record the peak-to-peak signal voltage, S,between the signals from the background and the signals from the target. Be certain that the range and level controls of the infraredimager are set so that both the target and background signals are within the working range of the ins
29、trument.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 and levelcontrol settings on the infrared imager should not be adjusted between the signal measurement in 7.7 and the
30、 noise measurementin 7.9.7.10 Replace the thermal imaging system with the spot radiometer at the same location. Measure the apparent target backgroundtemperature. Record the actual target background temperature, TB, correcting for emissivity, if warranted. The desired backgroundtemperature is 22C.7.
31、11 The difference, T TB, 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 radiometric instrument) measure the temperature uniformities of the t
32、arget and ofthe target background. The required temperature uniformities are 60.05C for the target and 60.1C for the target background.7.14 Similarly, measure the temperature stabilities of the target and the target background. The target must not vary by morethan 60.05C for the time interval from t
33、he temperature measurement, T, to the signal measurement, S. The target backgroundmust not vary by more than 60.1C for the duration of the entire test.7.15 Inclusion of 7.13 and 7.14 shall be required for the first three tests made with a given installation. Subsequent tests mayomit these steps wher
34、e deemed warranted; for example, after no significant change in NETD is observed.8. Calculation8.1 Calculate the noise equivalent temperature difference, NETD, as follows:NETD5T 2TBS/N C! (1)where:T = target temperature (C),FIG. 2 Circuit Diagram of Standard Reference FilterE1543 143TB = target back
35、ground temperature (C), andS/N = signal to noise ratio (dimensionless).8.2 Calculate the noise equivalent bandwidth of the reference filter (reference noise bandwidth), fR, as follows (see X1.2):fR 5 14RC Hz! (2)where:R = filter resistance (ohms), andC = filter capacitance (farads).9. Report9.1 Repo
36、rt 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 a precision and bias statement.11. Keywords11.1 infrared imaging systems; noise equivalent tem
37、perature difference; nondestructive testing; thermal imaging systems;thermographyAPPENDIX(Nonmandatory Information)X1. MATHEMATICAL DERIVATIONS RELATING TO THE STANDARD REFERENCE FILTERX1.1 Characteristic FrequencyThe frequency response of the standard reference filter is sketched in Fig. X1.1, wher
38、eR/Ro isthe ratio of output-to-input responsivity, and is the angular frequency ( = 2pif). The frequency at which R/Ro equals 0.707 isthe characteristic frequency, given by:c 5 1RC or fc 5 12piRC (X1.1)and:10fc 5 102piRC 51.6RC (X1.2)X1.2 Noise Equivalent BandwidthFor a system characterized by expon
39、ential decay time, as above, the noise equivalentbandwidth is given by:FIG. X1.1 Frequency Response of the Standard Reference FilterE1543 144f R 5*0 df112pif!2 5 14 (X1.3)where: = RC.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any ite
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43、 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)
44、. Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ Scope*1.1 This practice covers the determination of the noise equivalent temperature difference (NETD; NET) of thermal imagingsyste
45、ms of the conventional forward-looking infrared (FLIR) or other types that utilize an optical-mechanical scanner; it does notinclude charge-coupled devices or pyroelectric vidicons.1.2 Parts of this practice have been formulated under the assumption of a photonic detector(s) at a standard background
46、temperature of 295K (22C). Besides nonuniformity, examinations made at other background temperatures may result inimpairment of precision and bias.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This standard does not
47、purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E
48、1213 Practice for Minimum Resolvable Temperature Difference for Thermal Imaging SystemsE1316 Terminology for Nondestructive Examinations3. Terminology3.1 Definitions:3.1.1 blackbody simulatora device that produces an emission spectrum closely approximating that emitted by a blackbody(surface with em
49、issivity of 1.0), usually a cavity or a flat plate with a structured or coated surface having a stable and uniformtemperature.3.1.2 dwell timethe time spent, during one frame, in scanning one angular dimension of a single pixel (picture element) ofthe image within the instantaneous field of view (IFOV) of a detector. Thus, for example, if a single pixel is scanned n times duringone frame, the dwell time is given by n times the duration of a single scan of the pixel.3.1.3 FLIRan acronym for forward-looking in
