Evaluating NDIR Optical Cavity Signal Degradation under Field Humidity Exposure
Field humidity degrades NDIR cavities through liquid condensation scattering and mirror oxidation, requiring hydrophobic vents and controlled wall heating.
Gold Mirror Reflectivity
Infrared Efficiency
Metallic surface finishes deliver broad spectral performance for thermal imaging and spectroscopic systems. High gold mirror reflectivity is maintained across the mid to long wave infrared regions, where values frequently exceed 98 percent. The metal is deposited via vacuum evaporation or sputtering onto a polished substrate.
Spectral Range
Reflectance remains high from 650 nanometres through the far infrared. While gold mirror reflectivity is poor in the ultraviolet and blue parts of the spectrum, it is the standard for CO2 laser applications and heat shielding.
Oxidation Resistance
Inert chemical properties prevent the formation of a tarnish layer that would degrade the optical performance. Because gold mirror reflectivity does not drop over time due to corrosion, the component provides a stable reference for infrared sensors. Protective overcoats are sometimes added to increase the physical scratch resistance.
Surface Quality
Metrological assessment of the coating involves using a spectrophotometer with an integrating sphere to capture the total hemispherical reflectance. Achieving peak gold mirror reflectivity requires a substrate with a surface roughness below 2 nanometres. Any scattering caused by pits or scratches reduces the effective signal in the optical system.
Calibration of the instrument is performed against a certified silver or spectralon standard.