ASTM E1543-14(2022)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:E1543 −14 (Reapproved 2022)
Standard Practice for
Noise Equivalent Temperature Difference of Thermal
Imaging Systems
This standard is issued under the fixed designation E1543; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This practice covers the determination of the noise 3.1 Definitions:
equivalent temperature difference (NETD; NE∆T) of thermal 3.1.1 blackbody simulator—a device that produces an emis-
imaging systems of the conventional forward-looking infrared sion spectrum closely approximating that emitted by a black-
(FLIR) or other types that utilize an optical-mechanical scan- body (surface with emissivity of 1.0), usually a cavity or a flat
ner; it does not include charge-coupled devices or pyroelectric plate with a structured or coated surface having a stable and
vidicons. uniform temperature.
3.1.2 dwell time—the time spent, during one frame, in
1.2 Parts of this practice have been formulated under the
scanning one angular dimension of a single pixel (picture
assumption of a photonic detector(s) at a standard background
element) of the image within the instantaneous field of view
temperature of 295 °K (22 °C). Besides nonuniformity, exami-
(IFOV) of a detector. Thus, for example, if a single pixel is
nations made at other background temperatures may result in
scanned n times during one frame, the dwell time is given by
impairment of precision and bias.
n times the duration of a single scan of the pixel.
1.3 The values stated in SI units are to be regarded as
3.1.3 FLIR—an acronym for forward-looking infrared,
standard. No other units of measurement are included in this
originally implying airborne, now denoting any fast-frame
standard.
thermal imaging system comparable to that of television and
1.4 This standard does not purport to address all of the
yielding real-time displays. Generally, these systems employ
safety concerns, if any, associated with its use. It is the
optical-mechanical scanning mechanisms.
responsibility of the user of this standard to establish appro-
3.1.4 See also Section J: Infrared Examination, of Termi-
priate safety, health, and environmental practices and deter-
nology E1316.
mine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accor-
4. Summary of Practice
dance with internationally recognized principles on standard-
4.1 The target is a blackbody source of uniform temperature
ization established in the Decision on Principles for the
that is viewed by the infrared thermal imaging system through
Development of International Standards, Guides and Recom-
an aperture of prescribed size. A specified temperature differ-
mendations issued by the World Trade Organization Technical
ence is established between the target and its background.
Barriers to Trade (TBT) Committee.
Measurements are made of the peak-to-peak signal voltage
from the target and the RMS noise voltage from the
2. Referenced Documents
background, both across a standard reference filter, and of the
2.1 ASTM Standards:
target and background temperatures. From these measured
E1213 Practice for Minimum Resolvable Temperature Dif-
values, the NETD is calculated.
ference for Thermal Imaging Systems
5. Significance and Use
E1316 Terminology for Nondestructive Examinations
5.1 Thispracticegivesanobjectivemeasureofthetempera-
ture sensitivity of a thermal imaging system (relative to a
This practice is under the jurisdiction of ASTM Committee E07 on Nonde-
structive Testing and is the direct responsibility of Subcommittee E07.10 on standard reference filter) exclusive of a monitor, with emphasis
Specialized NDT Methods.
on the detector(s) and preamplifier.
Current edition approved Dec. 1, 2022. Published December 2022. Originally
NOTE 1—Test values obtained under idealized laboratory conditions
approved in 1993. Last previous edition approved in 2018 as E1543 – 14(2018).
DOI: 10.1520/E1543-14R22. may or may not correlate directly with service performance.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.2 This practice affords a convenient means for periodi-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
cally monitoring the performance of a given thermal imaging
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. system.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1543−14 (2022)
5.3 NETD relates to minimum resolvable temperature dif-
ference as described in Practice E1213. Thus, an increase in
NETD may be manifest as a loss of detail in imagery.
5.4 Intercomparisons based solely on NETD figures may be
misleading.
NOTE 2—NETD depends on various factors such as spectral bandwidth
and background temperature.
6. Apparatus
6.1 The apparatus, as shown in Fig. 1, consists of the
FIG. 2 Circuit Diagram of Standard Reference Filter
following:
6.1.1 Blackbody Simulator, temporally stable and control-
lable to within 0.1 °C.
6.1.2 Target Plate, containing an aperture several times
NOTE 3—If the resistance, R, is in ohms and the capacitance, C,isin
larger dimensionally than the IFOV. The target plate should be
farads, RC is in seconds.
at least ten times the dimension of the aperture in both the
NOTE 4—The purpose of the filter is to standardize and define a
reference noise bandwidth, upon which the noise measurement depends in
height and width. (The plate forms the target background; the
part.
aperture, in effect, becomes the target as the blackbody
NOTE 5—If convenient, the filter may be a self-contained unit for
simulator is viewed through it.) The material and surface
external connection.
conditions of the target plate must be carefully considered. It is
6.1.5 Infrared Spot Radiometer or equivalent radiometric
helpful for the back side of the target plate to be a highly
instrument, calibrated with the aid of a blackbody source to an
reflective metallic surface to minimize the influence of the
accuracy within 0.1 °C.
blackbody simulator on the temperature of the target back-
6.1.6 Digital Oscilloscope.
ground. The front surface of the
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