The external occulter blocks out much of the direct solar-disk light that would come in nearly parallel to the rays from the extended corona, but there are other rays from the solar disk that can enter the instrument at oblique angles, scatter around, and possibly contaminate observations. These rays are caught by the sunlight trap.
The purpose of the sunlight trap is to intercept direct solar-disk light which enters the entrance aperture and attenuate (i.e., absorb) it. This is accomplished by covering the metal surfaces with a extremely black paint-like coating that absorbs as much as 90% of the UV light and 97% of the visible light. The energy of these photons is either re-radiated at infrared wavelengths or conducted through the metal as heat. The geometric design of the sunlight trap provides for at least seven reflections, or "bounces," each attenuating the light greatly, before any remaining sunlight can exit the trap. The figure below illustrates this geometry.
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