MEASUREMENT CONDITIONS
5.1. The observer shall have normal visual acuity (post-correction defects less than ± 0.25 dioptres) and good colour vision and be experienced in this type of measurement.
5.2. The test pattern shall be a plate containing four (4) rectangular slots, forming a square of four (4) bars and three (3) spaces as shown in Figure 1. The test pattern is positioned in front of a black body, the temperature of which can be varied, giving a temperature difference (ΔT) between the bars and the spaces.
5.2.1. The spatial frequency of the resolving power measurement targets must be within ± 5% of the nominal value.
5.2.2. The emissivities of the test pattern and the black body must both be at least 0.95.
5.2.3. The back body must make it possible to achieve temperature differences of ± 10 ℃. The accuracy must be 0.5% generally, and 0.01 ℃ for Δ Ts between 0 ℃ and ± 2 ℃.
