Two completely different strategies for taking a wide LED output and turning it into the beam your design needs. One bends photons; the other deletes them. Knowing when to use each saves watts and contrast.
Four ideas to carry into the next specification conversation you have.
TIR (Total Internal Reflection) and Fresnel lenses redirect the LED's full output. Losses ≈ 5–10%. The beam is clean, with a defined edge.
Mechanical flags block unwanted spread. Losses can hit 50% on a tight cut, but the beam edge can be hand-set on site.
Streetlights, downlights, panels, beam is locked at manufacture. Lens does the work.
Where the cut needs to be tuned on site to miss a curtain, a chair, or a face.
Efficiency numbers are typical; real values depend on lens material and barn-door geometry.
| Method | Efficiency | Best use |
|---|---|---|
| TIR lens (PMMA/PC) | ≈ 92% | Streetlight · spot |
| Fresnel lens | ≈ 88% | Stage · concert · spotlight |
| Refractor (textured) | ≈ 85% | Office panel · diffused |
| Reflector (specular) | ≈ 88% | Highbay · downlight |
| Reflector (diffuse white) | ≈ 80% | Office troffer · glare control |
| Barn doors (mech.) | ≈ 50–80% | Theatre · hospitality accent |
| Honeycomb louvre | ≈ 70% | Museum · gallery glare control |
Five framing decisions that pick between refractive optics and mechanical control.
Total Internal Reflection lenses use a refractive shape with a hollow centre. The LED sits in the cavity; photons either pass straight through or hit the side at an angle exceeding the critical angle and reflect internally. Efficiency above 90% with clean cut-off.
A grid of small hexagonal cells in front of the optic. Cuts off-axis light at the cell wall angle. Loses 25–30% efficiency but kills the "cave effect" reflection in computer screens. Standard in offices designed to UGR ≤ 19.
Theatre, film, hotel hospitality, the wall you light tonight is not the wall you light tomorrow. A pre-set lens has no answer. Four hinged flags around the aperture do. Spec barn doors only where reconfigurability is non-negotiable.
A premium retail spot may run a TIR lens for the primary beam (efficient) plus a removable snoot or flag for spill control on the wall (precise). Cost more, look like the work of someone who cared.
An RFQ that says "barn doors" forecloses TIR alternatives. An RFQ that says "beam 15° ± 1°, hard cut-off at 35° from axis, < 50 cd outside" lets the supplier pick the optics, and usually returns a better answer.
Our spec catalogue offers interchangeable TIR-lens options on every spot fixture, plus a snoot/louvre accessory range for fine glare control.
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