Very interesting discovery with my DBS...

[cal..45]

hi folks,

today I was going to swap pills on my dereelight DBS. three days ago the CL1H V4 with Q2 A5 emitter arrived and I was going to check how the beam will look like in a DBS smooth.

however, the moment I unscrewed the Q5 pill from the DBS, suddenly the little domed plastic cap (I really don't know how it is called) which is centered at front of the pill came off. here is what I mean:

not a big deal, I never gave much attention to that part, until now...


curious, how the beam would alter without that cap, I screwed the pill back in and really didn't expect what I just saw:

luckily I have another Q5 pill (with cap) which I immediately tried after and the (usual) result looks like this:

one could assume, that in the first pic a smooth reflector was used and in the second an op reflector, but thats not the case. both shots were taken with the same pills (Q5 1S) and with the same light with smooth reflector. the only difference is that little plastic thingy, not attached to one of the pills. btw: both shots were taken about 4,50meters away.

now, I'm far from being an expert and could be wrong, but the hotspot without the cap is so much more focused, that I probably accidently found a way to increase the throw of the DBS quite a few meters. I'm thrilled to see how it will look outside tonight....


regards, holger

 

[UlrikJ]

Interesting discovery!

Please post some beam shots later so we can see if the theory is correct!

 

[saabluster]

suddenly the little domed plastic cap...came off.

now, I'm far from being an expert and could be wrong, but the hotspot without the cap is so much more focused, that I probably accidently found a way to increase the throw of the DBS quite a few meters. I'm thrilled to see how it will look outside tonight....


regards, holger

This is nothing new. The "cap" is the glass dome of the Cree LED. It is a lens and as such magnifies the die. When taken off this effect is gone and the reflector "sees" a smaller light source. Hence the smaller more collimated beam. The downside to this "mod" is that you lose some lumens and there is usually a tint shift to yellow/green. Whether that is a bad thing depends on the user.

 

[cal..45]

@ saabluster,

well, it is new for me, I just haven't lost an emitter lens before

I really thought it was made of plastic, but indeed it seems to be made of glass.

as far as the tint goes - absolutely no difference (at least not noticable) than before.


regards, holger

 

[Pöbel]

head the same thing with my mrv. Ultra small extremely intense hotspot. But the tint soon shifted to very yellow/green so that i finally exchanged the emitter for an intact one with dome.

 

[Glenn7]

head the same thing with my mrv. Ultra small extremely intense hotspot. But the tint soon shifted to very yellow/green so that i finally exchanged the emitter for an intact one with dome.

why does the tint shift - is it because air/contaminates reach the phosphor and degrade it (it cant be heat) - and if so could you not glue a non magnified UCL piece of glass to protect it - so you could have a real top thrower

 

[WadeF]

You might try using the same exposure for both shots so we could have a better comparision. The 1st picture was at 1/13th of a second, the second picture at 1/30th of a second, which means the 1st picture will be over exposed more than the 2nd.

 

[cal..45]

@ wade,

to be honest I have not the slightest idea what are you talking about, I take pictures rather seldom and the camera is only two days old, so I have no photo skills whatsoever...

all I did was pressing the button after the autofocus came on, how can you - or me - tell how long something was exposed to what? :thinking::thinking::thinking:


regards, holger

 

[jirik_cz]

Information about exposure, camera model etc. are saved in EXIF data of every image. To make proper beamshots you must use manual setting and use the same exposure for both shots. Unfortunately your camera doesn't have manual settings...

 

[Fallingwater]

As far as I know, with the lens removed moisture eventually kills the die, or messes up the phosphor, or... y'know, something bad.

 

[saabluster]

As far as I know, with the lens removed moisture eventually kills the die, or messes up the phosphor, or... y'know, something bad.

Moisture gets in regardless of whether the lens is on or off. The the need to bake them sometimes before they are reflow soldered is proof of that. Moisture has nothing to do with tint shift or a decrease in output and it certainly will not kill the die.

 

[Flashlight Aficionado]

Then what causes tint shift in undomed dies?

 

[Flashlight Aficionado]

Then what causes tint shift in undomed LEDs?

Bump, not a double post.

 

[saabluster]

Then what causes tint shift in undomed LEDs?

Bump, not a double post.

I have some theories but I'm not sure exactly. I have done several tests,for various reasons, where I take the dome off. I noticed that the tint does not shift every time the dome is removed. One of them stayed the exact same tint when I removed the dome but after I messed with it some more(trying to couple it to a fiber optic) the tint shifted to the same yellow/green as the others.

 

[Jarl]

When I was screwing round with some luxeon rebels for a bike light, I knocked the dome off one them. I was using optics rather than a reflector, and thought "ahh, screw it" and whacked the optic on (8 degrees). What the optic did is basically magnify the die, rather like an aspheric, and there was a streak of blue in the beam. I'm guessing this is where the gummy dome ripped off some phosphor as it came off, exposing the blue of the LED.

Maybe something similar happens to the crees when you remove the dome- the phosphor becomes damaged, somehow.

 

[saabluster]

Maybe something similar happens to the crees when you remove the dome- the phosphor becomes damaged, somehow.

Yes I am fairly sure it is the phosphor being damaged the question seems to be in what way and how does this create a tint shift. I think the phosphor layer is getting picked up off the surface of the die.

 

[Jarl]

if it were, I would have thought that'd make it more blue, as I experienced with my rebel, rather than yellow/green.

 

[saabluster]

if it were, I would have thought that'd make it more blue, as I experienced with my rebel, rather than yellow/green.

Not if the layer of phosphor stayed over the die and was not ripped. When you knocked the dome off the rebel it probably ripped a piece/pieces of the phosphor off thus creating the blue you saw. I have done this on the Crees too.

 

[Gunner12]

I think if the dome was taken off without affecting the gel under it too much, then the tint shift might not happen. If too much get was taken off, then the phosphor probably reacts to the air and causes the tint shift. This assumption is not based on anything.