Etendue Bench

Trace a Lambertian LED through a reflector or TIR optic and up to three lenses. Watch where the light goes, how sharp the beam gets, and why brightness stops growing.

Rays

    Drag to pan, scroll to zoom, double-click to fit. Both axes share one scale in millimetres. Rays are drawn from five points across the LED.

    Light budget

    Source seen from the wall

    Brightness across the beam

    Right after the last optic

    On the wall

    Sweep one parameter

    Vary Everything else stays as set. The dot marks where you are now.

    Rules of thumb from the numbers

      Method: 3D skew-ray trace of the rotationally symmetric system with Snell refraction, unpolarised reflection loss (Fresnel equations) at every glass surface, total internal reflection and mirror absorption. The diagram shows one cross-section of those rays. Brightness is read at the wall as the average over a small central disc, and never above the etendue limit. Sun reference: 100 klx, 0.53° across, 1.6 Gcd/m².