ASTM E1543-00(2006)
(Test Method)Standard Test Method for Noise Equivalent Temperature Difference of Thermal Imaging Systems
Standard Test Method for Noise Equivalent Temperature Difference of Thermal Imaging Systems
SIGNIFICANCE AND USE
This test method gives an objective measure of the temperature sensitivity of a thermal imaging system (relative to a standard reference filter) exclusive of a monitor, with emphasis on the detector(s) and preamplifier.
Note 1—Test values obtained under idealized laboratory conditions may or may not correlate directly with service performance.
This test method affords a convenient means for periodically monitoring the performance of a given thermal imaging system.
NETD relates to minimum resolvable temperature difference as described in Test Method E 1213. Thus, an increase in NETD may be manifest as a loss of detail in imagery.
Intercomparisons based solely on NETD figures may be misleading.
Note 2—NETD depends on various factors such as spectral bandwidth and background temperature.
SCOPE
1.1 This test method covers the determination of the noise equivalent temperature difference (NETD; NET) of thermal imaging systems of the conventional forward-looking infrared (FLIR) or other types that utilize an optical-mechanical scanner; it does not include charge-coupled devices or pyroelectric vidicons.
1.2 Parts of this test method have been formulated under the assumption of a photonic detector(s) at a standard background temperature of 295K (22C). Besides nonuniformity, tests made at other background temperatures may result in impairment of precision and bias.
1.3 The values stated in SI units are to be regarded as standard.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E1543 – 00 (Reapproved 2006)
Standard Test Method 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 3.1.1 blackbodysimulator—a device that produces an emis-
sion spectrum closely approximating that emitted by a black-
1.1 This test method covers the determination of the noise
body (surface with emissivity of 1.0), usually a cavity or a flat
equivalent temperature difference (NETD; NEDT) of thermal
plate with a structured or coated surface having a stable and
imaging systems of the conventional forward-looking infrared
uniform temperature.
(FLIR) or other types that utilize an optical-mechanical scan-
3.1.2 dwell time—the time spent, during one frame, in
ner; it does not include charge-coupled devices or pyroelectric
scanning one angular dimension of a single pixel (picture
vidicons.
element) of the image within the instantaneous field of view
1.2 Parts of this test method have been formulated under the
(IFOV) of a detector. Thus, for example, if a single pixel is
assumption of a photonic detector(s) at a standard background
scanned n times during one frame, the dwell time is given by
temperature of 295°K (22°C). Besides nonuniformity, tests
n times the duration of a single scan of the pixel.
made at other background temperatures may result in impair-
3.1.3 FLIR—an acronym for forward-looking infrared,
ment of precision and bias.
originally implying airborne, now denoting any fast-frame
1.3 The values stated in SI units are to be regarded as
thermal imaging system comparable to that of television and
standard.
yielding real-time displays. Generally, these systems employ
1.4 This standard does not purport to address all of the
optical-mechanical scanning mechanisms.
safety concerns, if any, associated with its use. It is the
3.1.4 See also Section J: Infrared Examination, of Termi-
responsibility of the user of this standard to establish appro-
nology E1316.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
4. Summary of Test Method
2. Referenced Documents 4.1 The target is a blackbody source of uniform temperature
2 that is viewed by the infrared thermal imaging system through
2.1 ASTM Standards:
an aperture of prescribed size. A specified temperature differ-
E1213 Test Method for Minimum Resolvable Temperature
ence is established between the target and its background.
Difference for Thermal Imaging Systems
Measurements are made of the peak-to-peak signal voltage
E1316 Terminology for Nondestructive Examinations
from the target and the RMS noise voltage from the back-
3. Terminology
ground, both across a standard reference filter, and of the target
andbackgroundtemperatures.Fromthesemeasuredvalues,the
3.1 Definitions:
NETD is calculated.
This test method is under the jurisdiction of ASTM Committee E07 on
5. Significance and Use
Nondestructive Testing and is the direct responsibility of Subcommittee E07.10 on
5.1 This test method gives an objective measure of the
Emerging NDT Methods.
Current edition approved May 1, 2006. Published June 2006. Originally
temperaturesensitivityofathermalimagingsystem(relativeto
approved in 1993. Last previous edition approved in 2000 as E1543 - 00. DOI:
a standard reference filter) exclusive of a monitor, with
10.1520/E1543-00R06.
2 emphasis on the detector(s) and preamplifier.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
NOTE 1—Test values obtained under idealized laboratory conditions
Standards volume information, refer to the standard’s Document Summary page on
may or may not correlate directly with service performance.
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1543 – 00 (2006)
5.2 This test method affords a convenient means for peri- 6.1.4 Standard Reference Filter, consisting of a single RC
odically monitoring the performance of a given thermal imag- low-pass filter whose product RC is equal to twice the dwell
ing system. time; see Fig. 2.
5.3 NETD relates to minimum resolvable temperature dif-
NOTE 3—If the resistance, R, is in ohms and the capacitance, C,isin
ference as described in Test Method E1213. Thus, an increase
farads, RC is in seconds.
in NETD may be manifest as a loss of detail in imagery.
NOTE 4—The purpose of the filter is to standardize and define a
5.4 Intercomparisons based solely on NETD figures may be
reference noise bandwidth, upon which the noise measurement depends in
part.
misleading.
NOTE 5—If convenient, the filter may be a self-contained unit for
NOTE 2—NETD depends on various factors such as spectral bandwidth
external connection.
and background temperature.
6.1.5 Infrared Spot Radiometer or equivalent radiometric
6. Apparatus instrument, calibrated with the aid of a blackbody source to an
accuracy within 0.1°C.
6.1 The apparatus, as shown in Fig. 1, consists of the
6.1.6 Digital Oscilloscope.
following:
6.1.7 Digital True RMS Voltmeter, with high crest factor
6.1.1 Blackbody Simulator, temporally stable and control-
(peak voltage/RMS voltage) so as not to attenuate any noise
lable to within 0.1°C.
peaks, and bandwidth from approximately zero to at least
6.1.2 Target Plate, containing an aperture several times
1.6/RC. See 6.1.4 and X1.1.
larger dimensionally than the IFOV. The target plate should be
at least ten times the dimension of the aperture in both the
7. Procedure
height and width. (The plate forms the target background; the
aperture, in effect, becomes the target as the blackbody 7.1 Mount the target plate at the blackbody simulator, with
simulator is viewed through it.) The material and surface its aperture oriented the same as the IFOV of the imaging
conditions of the target plate must be carefully considered. It is system and centered with
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