The benefit of De-dome SST-50 & SST-90 to reflector based lights has been shown many times now. Many posts including some of the lights I made in which that I observed between 30 to 40% increase of lux@ 1 meter using the same Rebel Deep SMO reflector & identical driving current.
It is also known that the de-dome (on any leds) will cause a lose of total lumens for sure, although the % loss is debatable.
With the obvious net gain of throw on reflector based light, I am planning to make transition towards making some de-doomed SST-90 flashlights.
The de-dome obviously send more light sideways, therefore benefit reflector but hurt aspherical applications.
However, there's some questions in my mind: What's the ideal doom-less form for Reflector based flashlight?
Leave it alone?
Coat with another layer of optically clear Silicone?
Silicone + a Flat top doom?
Silicone + a flat thin glass?
With some searching, I found this Report:
http://www.osti.gov/bridge/servlets/purl/963890-7R3mLc/963890.pdf
I think it answered quite a few questions, just a summary on what I've learned when it applies to de-dome.
1. If you apply clears silicone without dome (flat top, silicone alone)
The Silicone layer extract more photons out of led, but it's canceled
out by additional internal reflection at silicon/air junction.
As a result, it actually lost total lumen output, although not by much.
2. When glass doom is applied to the silicone, (Silicone & glass has very close defraction index, allows very little lost from silicone to glass), very little light is lost at glass dome to air junction (This is because the light is hitting the doom surface head-on, not at an angle like the flat top, ie. the least internal reflection possible). As a result, the additional light extraction by silicone is able to escape to the air & increase total lumens.
Because adding the silicon alone made no improvement, The net gain of lumens is almost completed resulted from the shape of the doom.
Therefore, it's not possible to prevent lumen loss when de-dome.
Putting additional silcone won't help (Unless you make a silicone doom, then what's the point of de-dome?
Even the factory doom-less SST has a much lower total lumen output than the doom version, nothing we can do about it, come to think about it, if there's something they can do to keep the lumen out put, then the factory would have done it. So my investigations are kind of pointless, I guess I just needed some data to reassure myself.
There might be an small possibility of improvement: If after de-dome, one add silicone & top it with a flat glass lid but with a AR coating on the air side only, perhaps, that may improve a few % points over the de-doom alone?
May be an optical expert can chime in to see if it make sense?
It is also known that the de-dome (on any leds) will cause a lose of total lumens for sure, although the % loss is debatable.
With the obvious net gain of throw on reflector based light, I am planning to make transition towards making some de-doomed SST-90 flashlights.
The de-dome obviously send more light sideways, therefore benefit reflector but hurt aspherical applications.
However, there's some questions in my mind: What's the ideal doom-less form for Reflector based flashlight?
Leave it alone?
Coat with another layer of optically clear Silicone?
Silicone + a Flat top doom?
Silicone + a flat thin glass?
With some searching, I found this Report:
http://www.osti.gov/bridge/servlets/purl/963890-7R3mLc/963890.pdf
I think it answered quite a few questions, just a summary on what I've learned when it applies to de-dome.
1. If you apply clears silicone without dome (flat top, silicone alone)
The Silicone layer extract more photons out of led, but it's canceled
out by additional internal reflection at silicon/air junction.
As a result, it actually lost total lumen output, although not by much.
2. When glass doom is applied to the silicone, (Silicone & glass has very close defraction index, allows very little lost from silicone to glass), very little light is lost at glass dome to air junction (This is because the light is hitting the doom surface head-on, not at an angle like the flat top, ie. the least internal reflection possible). As a result, the additional light extraction by silicone is able to escape to the air & increase total lumens.
Because adding the silicon alone made no improvement, The net gain of lumens is almost completed resulted from the shape of the doom.
Therefore, it's not possible to prevent lumen loss when de-dome.
Putting additional silcone won't help (Unless you make a silicone doom, then what's the point of de-dome?
Even the factory doom-less SST has a much lower total lumen output than the doom version, nothing we can do about it, come to think about it, if there's something they can do to keep the lumen out put, then the factory would have done it. So my investigations are kind of pointless, I guess I just needed some data to reassure myself.
There might be an small possibility of improvement: If after de-dome, one add silicone & top it with a flat glass lid but with a AR coating on the air side only, perhaps, that may improve a few % points over the de-doom alone?
May be an optical expert can chime in to see if it make sense?
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