ASTM E1213-97(2002)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:E1213–97 (Reapproved 2002)
Standard Test Method for
Minimum Resolvable Temperature Difference for Thermal
Imaging Systems
This standard is issued under the fixed designation E 1213; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope encethatdeterminestheMRTD.Themeantemperatureofeach
bar must not differ from that of any other bar by more than the
1.1 This test method covers the determination of the mini-
measured MRTD. A similar requirement applies to the tem-
mum resolvable temperature difference (MRTD) capability of
perature of each conjugate bar. Otherwise the MRTD value is
the compound observer-thermal imaging system as a function
unacceptable.
of spatial frequency.
4.3 The background temperature and the spatial frequency
1.2 This standard does not purport to address all of the
of each target must be specified together with the measured
safety concerns, if any, associated with its use. It is the
value of MRTD.
responsibility of the user of this standard to establish appro-
4.4 The probability of resolution must be specified together
priate safety and health practices and determine the applica-
with the reported value of MRTD.
bility of regulatory limitations prior to use.
5. Significance and Use
2. Referenced Documents
5.1 This test relates to a thermal imaging system’s effec-
2.1 ASTM Standards:
tiveness for discerning details in a scene.
E 1316 Terminology for Nondestructive Examinations
5.2 MRTD values provide estimates of resolution capability
3. Terminology
and may be used to compare one system with another. (Lower
MRTD values indicate better resolution.)
3.1 Definitions:
3.1.1 differential blackbody—an apparatus for establishing
NOTE 1—Test values obtained under idealized laboratory conditions
two parallel isothermal planar zones of different temperatures,
may or may not correlate directly with service performance.
and with effective emissivities of 1.0.
6. Apparatus
3.1.2 See also Terminology E 1316.
6.1 The apparatus consists of the following:
4. Summary of Test Method
6.1.1 Test Charts (Targets), comprised of four periodic bars
4.1 A standard four-bar target is used in conjunction with a
of aspect ratio (width:height) 1:7, as shown in Fig. 1.
differential blackbody that can establish one blackbody isother- 6.1.2 Differential Blackbody, temporally stable and control-
mal temperature for the set of bars and another blackbody
lable to within 0.1°C.
isothermal temperature for the set of conjugate bars, which are 6.1.3 Infrared Spot Radiometer, calibrated with the aid of a
formed by the regions between the bars (see Fig. 1). The target
blackbody source to an accuracy within 0.1°C.
is imaged onto the monochrome video monitor of a thermal
NOTE 2—Test charts may be fabricated by cutting slots in metal and
imaging system where the image is viewed by an observer.The
coating with black paint of emissivity greater than 0.95. In this case the
temperature difference between the bars and their conjugates,
slots would constitute the bars.
initially zero, is increased incrementally only until the observer
7. Procedure
can distinguish the four bars. This critical temperature differ-
ence is the MRTD.
7.1 Mount a test chart (target) onto the differential black-
4.2 The spatial distribution of temperature of each target
body.
must be measured remotely at the critical temperature differ-
NOTE 3—Differential blackbodies may be used within an environmen-
tal isothermal temperature chamber. Then, at equilibrium the temperature
of the conjugates approximately equals the temperature of the room, or
This test method is under the jurisdiction of ASTM Committee E07 on
ambient temperature.
Nondestructive Testing and is the direct responsibility of Subcommittee E07.10 on
Emerging NDT Methods.
7.2 Optimally focus the thermal imaging system directly on
Current edition approved December 10, 1997. Published February, 1998.
the target or on an optical projection of the target.
Originally published as E 1213 – 87. Last previous edition E 1213 – 92.
Annual Book of ASTM Standards, Vol 03.03.
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E1213–97 (2002)
FIG. 1 Targets Used for MRTD Determinations
NOTE 4—Observers must be free of eye disease, have good eyesight,
7.3 Adjust the thermal imaging system for quasi-linear
and be familiar with viewing thermal imagery.
operation.
NOTE 5—Only one observer at a time shall be present during the
7.4 Adjust the monochrome video monitor
...