Narcissus: reflections on retroreflections in thermal imaging systems

Area of Science:

• Optical Engineering
• Infrared Technology
• Radiometry

Background:

• Narcissus is an artifact in scanning thermal imaging systems.
• It arises from background radiation reflecting off optical surfaces and reaching detectors.
• This effect creates self-images or 'ghosts' within the thermal data.

Purpose of the Study:

• To develop a method for quantifying the narcissus effect in thermal imaging systems.
• To determine the narcissus artifact's intensity and size.
• To relate the artifact to system parameters like spectral response and f/No.

Main Methods:

• Derivation of paraxial surface-contribution formulas based on Lagrange invariants.
• Integration of system spectral response with optical surface data.
• Calculation of narcissus equivalent scene temperature difference (NARCDeltaT).

Main Results:

• Formulas accurately predict narcissus intensity and size using paraxial ray data.
• The equivalent scene temperature difference (NARCDeltaT) quantifies the narcissus effect.
• Gaussian formulation simplifies analysis, reducing the need for extensive ray tracing.

Conclusions:

• The developed method provides a radiometrically accurate way to characterize narcissus.
• Paraxial formulas offer an efficient alternative to complex ray tracing for narcissus analysis.
• Understanding and quantifying narcissus is crucial for accurate thermal imaging interpretation.