1、Designation: E1311 89 (Reapproved 2010)E1311 14Standard Test Method Practice forMinimum Detectable Temperature Difference for ThermalImaging Systems1This standard is issued under the fixed designation E1311; the number immediately following the designation indicates the year oforiginal adoption or,
2、in 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 minimum detectable temperature d
3、ifference (MDTD) capability of acompound observer-thermal imaging system as a function of the angle subtended by the target.1.2 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibilityof the user of this standard to establish app
4、ropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E1316 Terminology for Nondestructive Examinations3. Terminology3.1 Definitions:3.1.1 differential blackbodyan apparatus for establishing two parallel
5、isothermal planar zones of different temperatures, andwith effective emissivities of 1.0.3.1.2 field of view (FOV)the shape and angular dimensions of the cone or the pyramid that define the object space imagedby the system; for example, rectangular, 4-deg wide by 3-deg high.3.1.2.1 DiscussionThe siz
6、e of the field of view is customarily expressed in units of degrees.3.1.3 See also Terminology E1316.4. Summary of Test Method4.1 A standard circular target is used in conjunction with a differential blackbody that can establish one blackbody isothermaltemperature for the target and another blackbod
7、y isothermal temperature for the background by which the target is framed. Thetarget, at an undisclosed orientation, is imaged onto the monochrome video monitor of a thermal imaging system whence the imagemay be viewed by an observer. The temperature difference between the target and the background,
8、 initially zero, is increasedincrementally until the observer, in a limited duration, can just distinguish the target. This critical temperature difference is theMDTD.NOTE 1Observers must have good eyesight and be familiar with viewing thermal imagery.4.2 The temperature distributions of each target
9、 and its background are measured remotely at the critical temperature differencethat defines the MDTD.4.3 The background temperature and the angular subtense for each target are specified together with the measured value ofMDTD. The (fixed) field of view included by the background is also specified.
10、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 edition approved June 1, 2010Oct. 1, 2014. Published November 2010October 2014. Originally approved in 1989.
11、 Last previous edition approved in 20042010as E1311 - 89 (2004).(2010). DOI: 10.1520/E1311-89R10.10.1520/E1311-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the
12、 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 the previous version. Becauseit may not be technically possible to adequately depict all changes acc
13、urately, 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 ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United St
14、ates14.4 The probability of detection is specified together with the reported value of MDTD.5. Significance and Use5.1 This test method gives a measure of a thermal imaging systems effectiveness for detecting a small spot within a largebackground. Thus, it relates to the detection of small material
15、defects such as voids, pits, cracks, inclusions, and occlusions.5.2 MDTD values provide estimates of detection capability that may be used to compare one system with another. (LowerMDTD values indicate better detection capability.)NOTE 2Test values obtained under idealized laboratory conditions may
16、or may not correlate directly with service performance.6. Apparatus6.1 The apparatus consists of the following:6.1.1 Target Plates, containing single or multiple circular targets of area(s) not greater than 5 % of the combined areas of targetand background (that is, FOV area), and with the distance
17、from the center of the target to the center of the FOV equal to one thirdof the height or the diameter of the FOV. See Fig. 1.NOTE 3A target plate may be fabricated by cutting one or more circular apertures in a metal plate of high thermal conductivity, such as aluminum,and coating with black paint
18、of emissivity greater than 0.95. In this case an aperture would constitute a target, and the coated metal surrounding the targetand within the field of view of the thermal imaging system would constitute the targets background.6.1.2 Facility, for mounting target plates and varying the orientation of
19、 any given target through 360.6.1.3 Differential Blackbody, controllable to within 0.1C and stable over the test period to within 0.1C.6.1.4 Infrared Spot Radiometer, calibrated with the aid of a blackbody source to an uncertainty not exceeding 0.1C.7. Procedure7.1 Mount a target plate and orient th
20、e target in correspondence with some integral hour marking on an imaginary clock. Donot divulge the orientation to the observer.NOTE 4Only one observer at a time is to be present during the testing.7.2 Optimally focus the thermal imaging system directly on the target or on an optical projection of t
21、he target.7.3 Adjust the thermal imaging system for quasi-linear operation.7.4 Adjust the monochrome video monitor controls so that the presence of noise is barely perceivable by the observer.7.5 Make the display luminance and the laboratory ambient luminance mutually suitable for visual acuity and
22、viewing comfort.FIG. 1 Schematic Showing 1. Target Plate; 2. FOV; and 3. TargetE1311 1427.6 Advise the observer that a visible spot will eventually appear in the monitors display. Instruct him to signal when he canperceive the spot and to cite its orientation relative to the 12 h of a clock; for exa
23、mple, 1 oclock, 2 oclock, 3 oclock, etc. Refrainfrom further conversation during the test that could conceivably influence or bias the observer.7.7 Set T (the temperature of the target minus the nominal temperature of the background) equal to zero.7.8 Increase T in positive increments not exceeding
24、0.1C every 60 s or until the observer signals. If the identification isincorrect, continue as before.NOTE 5To increase T it is customary to fix the background temperature and raise the target temperature.7.9 If the observer correctly identifies the orientation of the spot, record the diameter of the
25、 target, the diameter or the heightand width of the FOV, and the observation distance normal to the target plate.7.10 Measure the temperature distribution of the target and the target background with an infrared spot radiometer replacing thethermal imaging system. The target shall be measured in at
26、least three locations, uniformly spaced. The background shall bemeasured at two zones: (1) adjacent to the target (that is, zone 1); (2) beyond zone 1 (that is, zone 2). The measurements in eachzone shall be uniformly distributed, with the number of zone 2 measurements equal to twice that of zone 1
27、(except for the specialcase of 7.12).7.11 Calculate the mean temperature, T, of the target. Calculate the weighted average, TB, of the target background, inaccordance with 8.3. Provisionally, T = T TB is the MDTD. Record T and TB.7.12 If the target size and the field of view of the spot radiometer a
28、re comparable, make double the number of zone 2measurements, in pairs consisting of two adjacent locations. Compare adjacent temperature readings; the difference between anytwo adjacent readings must be less than the MDTD. Otherwise the MDTD test results are unacceptable for this particular targetsi
29、ze.NOTE 6This criterion is intended to guard against spurious spots, that is, false targets.7.13 Replace the target with another of different size. Randomly orient it in accordance with 7.1 and repeat the test (7.2 through7.12).7.14 Repeat step 7.13 one or more times.7.15 Repeat the entire test (7.1
30、 through 7.14) with a different observer.7.16 Repeat step 7.15 one or more times.8. Calculations8.1 Calculate the angular subtenses for rectangular FOVs as follows:w 5 tan21 W/R! deg#,or (1)5103W/R mrad#;h 5 tan21 H/R! deg#,or5103 H/R mrad#,where:W = width of FOV,R = observation distance normal to c
31、enterpoint of FOV,H = height of FOV,R W, andR H.NOTE 7w may be referred to as the horizontal field of view, and denoted HFOV; h may be referred to as the vertical field of view, and denotedVFOV.8.2 Calculate the angular subtenses for circular FOVs and targets as follows:5 tan21 D/R! deg#,or (2)5103
32、D/R mrad#,where:D = diameter of circular FOV or target, as appropriate,R = observation distance normal to centerpoint of FOV or of target, as appropriate, andR D.E1311 1438.3 Calculate the weighted average, TB, of the target background as follows:TB 56(mxi1(nyj6m1n (3)where:xi = temperature measurem
33、ent in zone 1, i = 1, 2, . m,yj = temperature measurement in zone 2, j = 1, 2, . n,m = number of zone 1 temperature measurements,n = number of zone 2 temperature measurements,(m xi = sum of all zone 1 temperature measurements, and(n yj = sum of all zone 2 temperature measurements.NOTE 8Seventy-five
34、percent of TB is weighted in the vicinity of the target.8.4 Calculate the probability of detection as shown by the following illustration:8.4.1 For a given target size, the MDTD results obtained with three different observers are 0.5C, 0.6C, 1.0C. The observerwho detected 0.5C would also be capable
35、of detecting 0.6C and 1.0C. Similarly the observer who detected 0.6C would alsobe capable of detecting 1.0C. Hence, the respective probabilities of detection are: for 0.5C, 13 = 33 %; for 0.6C, 23 = 67 %; for1.0C, 33 = 100 %.9. Report9.1 Report the following information:9.1.1 Target angular subtense
36、,9.1.2 Observation distance to target,9.1.3 FOV,9.1.4 MDTD,9.1.5 (Weighted) background temperature, and9.1.6 Probability of detection.9.2 MDTD values should relate to a probability of detection of at least 50 %.9.3 When comparing different systems, different targets, or different angular subtenses,
37、only a single probability of detectionshould be used throughout.NOTE 9A plot of MDTD versus target angular subtense is a convenient form for reporting the data for a given system or a given target.10. Precision and Bias10.1 PrecisionInsufficient data are available upon which to formulate a precision
38、 statement. Notwithstanding, owing to thepartially subjective nature of the test, repeatability and reproducibility are apt to be poor and MDTD differences less than 0.2Care considered to be insignificant.10.2 BiasThe procedure set forth in this test method for measuring the minimum detectable tempe
39、rature difference for thermalimaging systems has no bias because the minimum detectable temperature difference can be defined only in terms of a test method.11. Keywords11.1 infrared imaging systems; minimum detectable temperature difference; nondestructive testing; thermal imaging systems;thermogra
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45、441. Scope*1.1 This practice covers the determination of the minimum detectable temperature difference (MDTD) capability of a compoundobserver-thermal imaging system as a function of the angle subtended by the target.1.2 The values stated in SI units are to be regarded as standard. No other units of
46、 measurement are included in this standard.1.3 This standard does not purport to address all of the safety problems, 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 regulator
47、ylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E1316 Terminology for Nondestructive Examinations3. Terminology3.1 Definitions:3.1.1 differential blackbodyan apparatus for establishing two parallel isothermal planar zones of different temperatures, andwith effective emissivities
48、 of 1.0.3.1.2 field of view (FOV)the shape and angular dimensions of the cone or the pyramid that define the object space imagedby the system; for example, rectangular, 4-deg wide by 3-deg high.3.1.2.1 DiscussionThe size of the field of view is customarily expressed in units of degrees.3.1.3 See als
49、o Terminology E1316.4. Summary of Practice4.1 A standard circular target is used in conjunction with a differential blackbody that can establish one blackbody isothermaltemperature for the target and another blackbody isothermal temperature for the background by which the target is framed. Thetarget, at an undisclosed orientation, is imaged onto the monochrome video monitor of a thermal imaging system whence the imagemay be viewed by an observer. The temperature difference between the target
