blackbody source to an uncertainty not exceeding 0.1°C.
7.Procedure
7.1Mount a target plate and orient the target in correspon-
dence with some integral hour marking on an imaginary clock.
Do not divulge the orientation to the obrver.
N OTE 4—Only one obrver at a time is to be prent during the testing.
7.2Optimally focus the thermal imaging system directly on
the target or on an optical projection of the target.
7.3Adjust the thermal imaging system for quasi-linear
operation.
7.4Adjust the monochrome video monitor controls so that
the prence of noi is barely perceivable by the obrver.
7.5Make the display luminance and the laboratory ambient
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luminance mutually suitable for visual acuity and viewing
comfort.
7.6Advi the obrver that a visible spot will eventually
怎样做鱼好吃appear in the monitor’s display.Instruct him to signal when he
烫纹理can perceive the spot and to cite its orientation relative to the
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12h of a clock;for example,1o’clock,2o’clock,3o’clock,
etc.Refrain from further conversation during the test that could
conceivably influence or bias the obrver.巴洛克艺术
石牌战役7.7Set D T (the temperature of the target minus the nominal
temperature of the background)equal to zero.
7.8Increa D T in positive increments not exceeding 0.1°C
every 60s or until the obrver signals.If the identification is
incorrect,continue as before.
N OTE 5—To increa D T it is customary to fix the background
temperature and rai the target temperature.
7.9If the obrver correctly identifies the orientation of the
spot,record the diameter of the target,the diameter or the
height and width of the FOV ,and the obrvation distance
normal to the target plate.7.10Measure the temperature distribution of the target and the target background with an infrared spot radiometer replac-ing the thermal imaging system.The target shall be measured in at least three locations,uniformly spaced.The background shall be measured at two zones:(1)adjacent to the target (that is,zone 1);(2)beyond zone 1(that is,zone 2).The measure-ments in each zone shall be uniformly distributed,with the number of zone 2measurements equal to twice that of zone 1(except for the special ca of 7.12).7.11Calculate the mean temperature,T ,of the target.Calculate the weighted average,T B ,of the target background,in accordance with 8.3.Provisionally,D T 5T −T B is the MDTD.Record D T and T B .7.12If the target size and the field of view of the spot radiometer are comparable,make double the number of zone 2measurements,in pairs consisting of two adjacent locations.Compare adjacent temperature readings;the difference be-tween any two adjacent readings must be less than the MDTD.Otherwi the MDTD test results are unacceptable for this particular target size.N OTE 6—This criterion is intended to guard against spurious spots,that is,fal targets.7.13Replace the target with another of different size.Randomly orient it in accordance with 7.1and repeat the test (7.2through 7.12).7.14Repeat step 7.13one or more times.7.15Repeat the entire test (7.1through 7.14)with a differ-ent obrver.7.16Repeat step 7.15one or more times.8.Calculations 8.1Calculate the angular subtens for rectangular FOVs as follows:u w 5tan 21~W /R !@deg #,or (1)5103W /R @mrad #;u h 5tan 21~H /R !@deg #,or 5103H /R
@mrad #,where:W 5width of FOV ,R 5obrvation distance normal to centerpoint of FOV ,H 5height of FOV ,R >>W ,and R >>H .N OTE 7—u w may be referred to as the horizontal field of view,and denoted HFOV;u h may be referred to as the vertical field of view,and denoted VFOV .8.2Calculate the angular subtens for circular FOVs and targets as follows:u 5tan 21~D /R !@deg #,or (2)5103D /R @mrad #,where:D 5diameter of circular FOV or target,as
appropriate,
FIG.1Schematic Showing 1.Target Plate;2.FOV;and 3.
Target
R 5obrvation distance normal to centerpoint of FOV or
of target,as appropriate,and拉斐尔
R >>D .
8.3Calculate the weighted average,T B ,of the target back-
爱莫文蔚歌词ground as follows:
T B 56(m x i 1(n y j 6m 1n (3)
where:x i 5temperature measurement in zone 1,i 51,2,...m ,y j 5temperature measurement in zone 2,j 51,2,...n ,m 5number of zone 1temperature measurements,n 5number of zone 2temperature measurements,(m x i 5sum of all zone 1temperature measurements,and (n y j 5sum of all zone 2temperature measurements.N OTE 8—Seventy-five percent of T B is weighted in the vicinity of the target.8.4Calculate the probability of detection as shown by the following illustration:8.4.1For a given target size,the MDTD results obtained with three different obrvers are 0.5°C,0.6°C,1.0°C.The obrver who detected 0.5°C would also be capable of detect-ing 0.6°C and 1.0°C.Similarly the obrver who detected 0.6°C would also be capable of detecting 1.0°C.Hence,the respective probabilities of detection are:for 0.5°C,1⁄3533%;for 0.6°C,2⁄3567%;for 1.0°C,3⁄35100%.9.Report 9.1Report the following information:
9.1.1Target angular subten,9.1.2Obrvation distance to target,9.1.3FOV ,9.1.4MDTD,9.1.5(Weighted)background temperature,and 9.1.6Probability of detection.9.2MDTD values should relate to a probability of detection of at least 50%.9.3When comparing different systems,different targets,or different angular subtens,only a single probability of detec-tion should be ud throughout.N OTE 9—A plot of MDTD versus target angular subten is a conve-nient form
for reporting the data for a given system or a given target.10.Precision and Bias 10.1Precision —Insufficient data are available upon which
to formulate a precision statement.Notwithstanding,owing to
the partially subjective nature of the test,repeatability and
reproducibility are apt to be poor and MDTD differences less
than 0.2°C are considered to be insignificant.
10.2Bias —The procedure t forth in this test method for
measuring the minimum detectable temperature difference for
thermal imaging systems has no bias becau the minimum
detectable temperature difference can be defined only in terms
of a test method.
11.Keywords
11.1infrared imaging systems;minimum detectable tem-
perature difference;nondestructive testing;thermal imaging
systems;thermography;infrared The American Society for Testing and Materials takes no position respecting the validity of any patent rights asrted in connection with any item mentioned in this standard.Urs of this standard are expressly advid that determination of the validity of any such patent rights,and the risk of 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 and if not revid,either reapproved or withdrawn.Your comments are invited either for revision of this standard or for additional standards and should be addresd to ASTM Headquarters.Your comments will receive careful consideration at a meeting of the responsible technical committee,which you may attend.If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards,100Barr Harbor Drive,West Conshohocken,PA
19428.
