Long time ago I’ve seen someone come up with the idea of painting a collar with reflective paint directly on a LED dome.
I’d like to theorize on that topic…
Let’s first depict the subject in question:
Both LEDs that you see are actually the same model. But they are depicted at different angles, one is straight and the other is rotated by 45°.
Let’s call the green angle α and the red one β.
Let’s call the orange angle γ and the violet one δ.
Let’s call the lens collection angle ε.
Ideally α=β=γ=δ=ε.
When a collar is much larger than a die these are close to each other. When it’s as small as here….that’s not the case.
We need to decice on how high to paint the collar.
One option would be to have no light escaping the LED at off angles (and hitting flashlight head).
That would mean γ=ε.
Depending on your lens (and its ε) this may require painting the entire dome (hmm…not a great option) or a large part of it.
Painting large part of it means that a lot of light emitted at perfectly good angle (even straight up) hits the collar and is reflected back. That means bouncing around a lot of light. And each bounce is a risk of the photon being absorbed somewhere. The effect would be cooking of the LED….not a great option either.
I’ll be calling reflection of a photon that would otherwise hit the lens an ill one.
Another option would be to go to the other extreme. Paint low, so low that we have no ill reflections at all.
δ=ε.
I see no ill effects with this approach and it should improve luminance.
But by painting as low as needed to never capture good light means that we fail to capture a lot of stray light. Painting the collar marginally higher means that only light emitted from the corner of the die and only at barely-good-enough angle is ill-reflected. But we slightly increase the chance of having good reflection for the entire die.
That drives us towards β=ε.
Overall I believe that the optimum would be to choose some height that gives us δ<ε<β. I don’t know whether closer to δ or to β.
Now how does is it related to slicing the LED?
I believe they should be used together. But how? Slice as low as possible? In a LED that doesn’t have bond wires that would compromise collar effectiveness but maximize slicing effectiveness. Make the collar at the perfect height and slice right at that height? That would maximise collar effectiveness but increase risk that a photon reflecting off the silicone-air boundary fails to hit the die.
How much can we gain?
Surely nothing near a full size collar. And since it can be easily applied only to LEDs that have domes - it surely won’t make any domed LED that we tested so far throwier than flat Osrams. But not every aspheric light needs to come with a flat Osram…
Note that IANAL but it seems to me that Wavien patent does not cover collars that are a part of the emitter.