Optics, electromagnetic theory Geometrical optics Concept
Etendue
Summary
Etendue measures how spread out a beam of light is, in area and in angle together. It is the volume that the beam occupies in the phase space of Hamiltonian optics. In a lossless optical system etendue cannot decrease, and in an ideal system it is conserved. This limits how far light can be concentrated, and it explains why no lens can make an image brighter than the source. See the definition.
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| Tag | M8FEBN0QSE |
|---|---|
| URI | m2://M8FEBN0QSE |
| Kind | concept |
| Writing | W0 stub |
| MSC | 78A05 |
| Same as | |
| Changed | 3 November 2026 |
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