Stray light

Stray light is unwanted light reaching a detector or image plane by a path other than the intended optical path — as a result of scattering off mechanical surfaces, multiple reflections, or diffraction at edges.

How is stray light analyzed?

The analysis requires a full 3D model of the instrument — not just the optical elements, but also the housing, baffles, and mounting elements — with real surface scattering properties (BSDF) based on measurements. A Monte Carlo simulation with a very large number of rays (often billions) can detect stray paths invisible in a simplified model.

Applications

Stray light analysis is critical in space and astronomical instruments (telescopes, satellite cameras), military and night-vision systems, and precision imaging systems, where even a small level of stray light can degrade image contrast.

Related terms

PST

BSDF

Non-sequential ray tracing