Table 1.
Specifications of IRTs claimed by the manufacturers.
Table 2.
Specifications of blackbodies claimed by the manufacturer (under normal lab environment,18–24°C)a.
Fig 1.
Block diagram of the experimental setup.
(Red dotted box shows the screening thermograph system. Working distance was d = 0.8 m.).
Fig 2.
Stability results based on one-hour continuous temperature recordings with time interval of 15 seconds.
(a: ST-1 and IRT-1; b: ST-2 and IRT-2).
Table 3.
Stability and drift values for different sampling intervals.
Fig 3.
Sample thermograms of BB-2 fixed at 37°C, and placed at 0.15 m from IRT-1 (a and b) and 0.05 m from IRT-2 (c and d) lenses.
(a and c: focused on BB-2; b and d: focused at 0.8 m; dotted box illustrates the WTP region in each image; the x and y coordinates show the pixel numbers in x and y directions).
Fig 4.
WTP and FOV uniformity values based on different numbers of random pixels.
(a: maximum difference as uniformity; b: SD as uniformity; cameras focused at 0.8 m; BB-2 at 37 °C; error bars show SD of repeated sampling).
Fig 5.
IRT uniformity values versus BB-2 temperature based on the modified-29-pixels (dashed lines), and all-pixels (solid lines) methods.
(Dashed horizontal line at 0.2°C shows the IEC requirement. Cameras were focused at 0.8m).
Fig 6.
Effects of spatial frequency on MRTD.
The conjugate bars were at ambient temperature and positioned in the vertical direction at 0.8 m. Reprinted from [39] under a CC BY license, with permission from SPIE Publications, original copyright [2017].
Fig 7.
Effects of target temperature on MRTD.
(a) vertical and (b) horizontal bars at 0.35 m. MRTD values averaged over five different target temperatures between 31°C and 39°C. Error bars show the data SD. Insets show sample high contrast thermographs acquired from the target at spatial frequencies of 0.018 cycles/mrad.
Fig 8.
Contrast versus ΔT for (a) IRT-1 and (b) IRT-2.
Shaded horizontal bar represents the lowest visible contrast of 10%. The 4-bar target (conjugate bars) maintained at 35°C and positioned in the horizontal direction at distance of 0.35m. Insets show sample thermograms at MRTD threshold for spatial frequency of 0.035 cycles/mrad.
Fig 9.
(a) response graph: TST versus TCS (small error bars are not apparent in the graph), and (b) Bland-Altman graph: offset error versus TCS. Shaded area represents the required evaluation range.
Table 4.
List of standard uncertainties, combined standard uncertainties, and |TST − TCS| values.
Table 5.
Essential performance requirements for STs.