Table 11 Calculated speckle noise in each wavelength regime.

From: Mid-IR standoff measurement of ageing-related spectroscopic changes in bitumen in the 6 µm (1700 cm−1) region. Part 1: Measurement strategy and instrument design principles

Parameter

Reference region: 3.8 μm

Carbonyl region: 6 μm

Speckle size s

11 μm

18 μm

Speckle noise ΔIspeckle/I0

5.7 × 10–3

9.0 × 10–3

Reduced speckle noise for a 5 mm illuminated spot averaged over a 10 m section of road (N = 10,000)

5.7 × 10–5

9.0 × 10–5

Detected signal for 0.01AU, as ΔI/I0

23 × 10–3

23 × 10–3

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