ASTM E1213-97

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: E 1213 – 97 An American National Standard
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 bar must not differ from that of any other bar by more than the
measured MRTD. A similar requirement applies to the tem-
1.1 This test method covers the determination of the mini-
perature of each conjugate bar. Otherwise the MRTD value is
mum resolvable temperature difference (MRTD) capability of
unacceptable.
the compound observer-thermal imaging system as a function
4.3 The background temperature and the spatial frequency
of spatial frequency.
of each target must be specified together with the measured
1.2 This standard does not purport to address all of the
value of MRTD.
safety concerns, if any, associated with its use. It is the
4.4 The probability of resolution must be specified together
responsibility of the user of this standard to establish appro-
with the reported value of MRTD.
priate safety and health practices and determine the applica-
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-
tiveness for discerning details in a scene.
2.1 ASTM Standards:
5.2 MRTD values provide estimates of resolution capability
E 1316 Terminology for Nondestructive Examinations
and may be used to compare one system with another. (Lower
3. Terminology
MRTD values indicate better resolution.)
3.1 Definitions:
NOTE 1—Test values obtained under idealized laboratory conditions
3.1.1 differential blackbody—an apparatus for establishing
may or may not correlate directly with service performance.
two parallel isothermal planar zones of different temperatures,
6. Apparatus
and with effective emissivities of 1.0.
3.1.2 See also Terminology E 1316. 6.1 The apparatus consists of the following:
6.1.1 Test Charts (Targets), comprised of four periodic bars
4. Summary of Test Method
of aspect ratio (width:height) 1:7, as shown in Fig. 1.
4.1 A standard four-bar target is used in conjunction with a 6.1.2 Differential Blackbody, temporally stable and control-
differential blackbody that can establish one blackbody isother-
lable to within 0.1°C.
mal temperature for the set of bars and another blackbody 6.1.3 Infrared Spot Radiometer, calibrated with the aid of a
isothermal temperature for the set of conjugate bars, which are
blackbody source to an accuracy within 0.1°C.
formed by the regions between the bars (see Fig. 1). The target
NOTE 2—Test charts may be fabricated by cutting slots in metal and
is imaged onto the monochrome video monitor of a thermal
coating with black paint of emissivity greater than 0.95. In this case the
imaging system where the image is viewed by an observer. The
slots would constitute the bars.
temperature difference between the bars and their conjugates,
7. Procedure
initially zero, is increased incrementally only until the observer
can distinguish the four bars. This critical temperature differ-
7.1 Mount a test chart (target) onto the differential black-
ence is the MRTD.
body.
4.2 The spatial distribution of temperature of each target
NOTE 3—Differential blackbodies may be used within an environmen-
must be measured remotely at the critical temperature differ-
tal isothermal temperature chamber. Then, at equilibrium the temperature
ence that determines the MRTD. The mean temperature of each
of the conjugates approximately equals the temperature of the room, or
ambient temperature.
7.2 Optimally focus the thermal imaging system directly on
This test method is under the jurisdiction of ASTM Committee E-7 on
the target or on an optical projection of the target.
Nondestructive Testing and is the direct responsibility of Subcommittee E07.10 on
7.3 Adjust the thermal imaging system for quasi-linear
Emerging NDT Methods.
Current edition approved Dec. 10, 1997. Published February, 1998. Originally operation.
published as E 1213 – 87. Last previous edition E 1213 – 92.
7.4 Adjust the monochrome video monitor controls so that
Annual Book of ASTM Standards, Vol 03.03.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
E 1213
FIG. 1 Targets Used for MRTD Determinations
NOTE 5—Only one observer at a time shall be present during the
the presence of noise is barely perceivable by the observer.
testing.
7.5 Make the display luminance and the laborato
...