What does dedoming mean?
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bshanahan14rulz
Flashlight Enthusiast
http://www.philipslumileds.com/products/luxeon-C
http://www.luminus.com/products/SBT-90.html
not quite the same, but
http://www.cree.com/led-components-and-modules/products/xlamp/discrete-directional/xlamp-xqb
Your thread title is misleading. It would seem that you DO know what dedoming means ;-)
Generally, it is avoided in order to allow more light to escape the package, instead of being reflected off the dome/air interface. A dome is a way for more light to hit that interface surface at a close to perpendicular angle to cut back on internal reflection. Kind of like how you can see an image reflected on a piece of clear glass at shallow angles. You see that image because the light is hitting at an angle that is so shallow that it no longer wants to go through the glass, but instead wants to reflect off of it.
http://en.wikipedia.org/wiki/Snell's_law#Total_internal_reflection_and_critical_angle < here's more information for you :-)
http://www.luminus.com/products/SBT-90.html
not quite the same, but
http://www.cree.com/led-components-and-modules/products/xlamp/discrete-directional/xlamp-xqb
Your thread title is misleading. It would seem that you DO know what dedoming means ;-)
Generally, it is avoided in order to allow more light to escape the package, instead of being reflected off the dome/air interface. A dome is a way for more light to hit that interface surface at a close to perpendicular angle to cut back on internal reflection. Kind of like how you can see an image reflected on a piece of clear glass at shallow angles. You see that image because the light is hitting at an angle that is so shallow that it no longer wants to go through the glass, but instead wants to reflect off of it.
http://en.wikipedia.org/wiki/Snell's_law#Total_internal_reflection_and_critical_angle < here's more information for you :-)
RoGuE_StreaK
Enlightened
From my limited research recently, it seems fair to say that overall performance decreases, but for some applications, specifically behind thrower lenses, it works better because it gives a smaller apparent die; the die brightness drops a bit due to the reasons listed above, but as it's now occupying a smaller (apparent) space the brightness per mm2 (or some term like that) actually increases.
In short, for aspheric throwers de-doming supposedly yields higher output, but for most other applications the performance is actually lower.
I've been trying to decide whether to buy a cheapie zoom-to-throw XM-L torch, as I'd read that XM-Ls are by no means the best behind a lens; trying to figure out if de-doming would give an $8 monster thrower or whether even ye-olde XR-E would outgun it.
In short, for aspheric throwers de-doming supposedly yields higher output, but for most other applications the performance is actually lower.
I've been trying to decide whether to buy a cheapie zoom-to-throw XM-L torch, as I'd read that XM-Ls are by no means the best behind a lens; trying to figure out if de-doming would give an $8 monster thrower or whether even ye-olde XR-E would outgun it.
The question in the op is bolded, I think the OP understands the whys and wherefores.
RoGuE_StreaK
Enlightened
Weird, it doesn't show up bolded here. And woulda thought the whys and wherefores answer the why nots?
Grmnracing
Newly Enlightened
No bold when using the Tapatalk app for me.
Reminds me of the good old days when I would get in trouble for large pictures by using the Tapatalk app.
light-wolff
Newly Enlightened
Because it essentially destroys the LED. Bare chip+phosphor coating exposed to the elements, oxygen, humidity.
The protective dome is there for a reason. No serious mfg would ever even think about removing it.
It's like selling peeled apples.
LOL
So the ones selling LEDs with no dome to improve throw are overstating the expected life times?
I'd bet you that the dome is there to spread the beam out so it hits the reflector the way it describes in the wiki references above...not to protect it.
No dedomed lights have degraded over time that I have at least.
The humidity can still get in from the led side of the board, and so can airflow with oxygen, etc.
When it heats up, the air inside expands, and vents. When it cools, it sucks air back in...its not hermetically sealed with a vacuum, etc.
:D
In a nut shell, the lights for consumers assume that the consumer will want a certain OTF lumen # as a primary shopping criteria if they are using specs and not how "tactical it looks, etc".....and a round regularly shaped beam w/o artifacts is desirable for most of them....and when sold in REELS of LEDs, the domes do help to prevent direct contact with the LED itself during shipping/production/assembly, etc.
So, when we want to make the beam project straight out more and concentrate the hot spot, more than we want it to have more spill/corona, etc...we can remove the dome and the lumens may drop a bit, but, the ones that are left do march straight out much better.
A floody beam, overall, is more useful, so, Joe Consumer may not want to make that trade off. Joe Thrower might want to though, and that's who dedomes.
Or you can just buy LEDs made w/o domes to do the same thing, such as the SBT's already linked to as examples...so you don't have to pop off a dome.
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Emphasis was added by Norm. There is no bold in the OP.
To answer the original question:
Why don't LED manufacturers sell LEDs without a dome? Flashlights are a teeny-tiny-itty-bitty piece of the LED market. Throwy flashlights are a teeny-tiny-itty-bitty piece of the flashlight market. The market for LEDs with no dome is so incredibly small that no manufacturer would ever consider selling them that way... for all practical purposes the market doesn't exist to them.
Why don't more flashlight manufacturers use de-domed LEDs? Most likely because it's too expensive (and temperamental) for the relatively small gain in throw. Since LEDs aren't manufactured without a dome, it means they have to be removed by the flashlight manufacturer. I'm guessing that if any of these Chinese manufacturers were willing to de-dome, it would be incredibly expensive. Hobbyists and super-specialized flashlight makers are the only ones left.
This is all conjecture, but that's how I understand it.
As pointed out, MFRs do sell them. They are used in situations where high levels of optical control are needed. I.e. theatrical spots, specialized architectural, etc. No dome does not mean it is not sealed, it just does not have a full dome.
Semiman
Semiman
light-wolff
Newly Enlightened
I was thinking of dedomed XM-Ls (this is very popular in the German flashlight crowd).
XM-L (and all other CRE LEDs) domes are basically glued to the emitter. They ARE sealed. People use solvents to remove the dome. Pulling off the soften and partially dissolved dome stresses the phosphor coating and the wire bonds, somtimes ripping them off. I wouldn't trust a LED that was subjected to this kind of treatment. Plus you never know what the solvent does to the phosphor.
Luminus is different: the domes aren't attached to the chip, but to a frame, and the chips are not selaed (maybe this is one of the reasons for their rather poor lm/W?). Removing the dome on these doesn't do anything to the chip, agreed.
Without a dome and de-domed would be two different things to me but then the differences have already been pointed out. Here's a couple of my favorites that were not mentioned:
http://www.philipslumileds.com/products/luxeon-z
http://www.philipslumileds.com/products/luxeon-z-es
http://www.philipslumileds.com/products/luxeon-z
http://www.philipslumileds.com/products/luxeon-z-es
argleargle
Enlightened
- Joined
- Jan 7, 2013
- Messages
- 321
It wasn't so long ago that I didn't know what the heck a de-domed emiiter meant!
This is, IMHO a fantastic thread! A clear dome over a LED emitter changes its beam characteristics. As has been stated in the thread, it most definitely plays a role in protection of the product while shipped in the logistical requirements of the manufacturers. That bare thin phosphor layer can't take much abuse when bounced around in shipping or what not. If completely protected already in a sealed flashlight head, it might not be so big a deal. As far as I have read and understand, the only de dedoming reason would be honorable and noble flashlight hackers who are trying to create the next generation of ultimate tight-throwing flashlights with whatever is on hand or available by part number.
Then again, maybe I don't know what I'm talking about. Were you really going to try soaking your emmitters in gasoline or acetone? This action by it self? I am sort of an old-timer. I recall an internet hoax about coating your computer modem in wax to make it go faster. For your newcomers, this is the thing that let you get on the internet once-upon-a-time.... with your phone land line. Anyway, I see a real purpose for de-doming. It's for the high end flashlight hackers and flashaholics seeking the ultimate long range throw with whatever parts they can get. We don't give a flip about what can be done 5 years from now. We want it now. Joe Flashlight doesn't need or want it because it introduces too many variables for a non-enthusiast to want.
Put it this way, would you strip the heatsink off of your computer processor because someone told you it would simply make it go faster? In the 386 PC processor days, that would be 100% fine, but it wouldn't have an effect. PC cpus didn't even have a heatsink back then, except for the newfound world of "overclockers." It was arcane magic back in those days, there wasn't a guide on Tomshardware, Anandtech, or HARDOcp to tell you how to do it. Oh wait, I didn't check to see if those sites even still exist! Anyway, those sites came later in the PPP-internet connection days. It was far from the text-only SLIP-unix days. Telnet and lynx? It is far from that simple, friends. It's far from that simple. It's related, however! Electrical engineering doesn't change much, it's just the components that get better! Emacs versus VI? Domed versus de-domed? Is it the same holy war without an understanding of the underlying architecture?
You're mostly exposing the reactive phosphor layer to open air and any contaminants that can get to it. If you had a hermetically sealed and nitrogen purged flashlight head, it should probably be okay... theoretically. Ever heard about nitrogen-purged rifle scopes? It's sort of the same problem and same solution. You *DID* know that phosphorous is used in MATCHES, right? Did you really want this to get super-hot in an oxygen environment? Are you seeing dark spots on the phospor layer of your emitter die? Is the light itself turning blue? People like me remeber the revolution that happened when white 5mm leds became possible. It was a brilliant hacker who CHEATED to make it happen. Everyone wanted a white led and all attempts failed. He made it work by "cheating" and using a blue emitter to blast a custom phosphor layer... it's something we take for granted these days.
I'm sorry. My lawn is full of holes. I try to tell people to get off of it, but I can never seem to do so in time. My poor lawn is half dead.
My lawn.
PS: CPF, I'd quit ya, if I only knew how, younger sister!
This is, IMHO a fantastic thread! A clear dome over a LED emitter changes its beam characteristics. As has been stated in the thread, it most definitely plays a role in protection of the product while shipped in the logistical requirements of the manufacturers. That bare thin phosphor layer can't take much abuse when bounced around in shipping or what not. If completely protected already in a sealed flashlight head, it might not be so big a deal. As far as I have read and understand, the only de dedoming reason would be honorable and noble flashlight hackers who are trying to create the next generation of ultimate tight-throwing flashlights with whatever is on hand or available by part number.
Then again, maybe I don't know what I'm talking about. Were you really going to try soaking your emmitters in gasoline or acetone? This action by it self? I am sort of an old-timer. I recall an internet hoax about coating your computer modem in wax to make it go faster. For your newcomers, this is the thing that let you get on the internet once-upon-a-time.... with your phone land line. Anyway, I see a real purpose for de-doming. It's for the high end flashlight hackers and flashaholics seeking the ultimate long range throw with whatever parts they can get. We don't give a flip about what can be done 5 years from now. We want it now. Joe Flashlight doesn't need or want it because it introduces too many variables for a non-enthusiast to want.
Put it this way, would you strip the heatsink off of your computer processor because someone told you it would simply make it go faster? In the 386 PC processor days, that would be 100% fine, but it wouldn't have an effect. PC cpus didn't even have a heatsink back then, except for the newfound world of "overclockers." It was arcane magic back in those days, there wasn't a guide on Tomshardware, Anandtech, or HARDOcp to tell you how to do it. Oh wait, I didn't check to see if those sites even still exist! Anyway, those sites came later in the PPP-internet connection days. It was far from the text-only SLIP-unix days. Telnet and lynx? It is far from that simple, friends. It's far from that simple. It's related, however! Electrical engineering doesn't change much, it's just the components that get better! Emacs versus VI? Domed versus de-domed? Is it the same holy war without an understanding of the underlying architecture?
You're mostly exposing the reactive phosphor layer to open air and any contaminants that can get to it. If you had a hermetically sealed and nitrogen purged flashlight head, it should probably be okay... theoretically. Ever heard about nitrogen-purged rifle scopes? It's sort of the same problem and same solution. You *DID* know that phosphorous is used in MATCHES, right? Did you really want this to get super-hot in an oxygen environment? Are you seeing dark spots on the phospor layer of your emitter die? Is the light itself turning blue? People like me remeber the revolution that happened when white 5mm leds became possible. It was a brilliant hacker who CHEATED to make it happen. Everyone wanted a white led and all attempts failed. He made it work by "cheating" and using a blue emitter to blast a custom phosphor layer... it's something we take for granted these days.
I'm sorry. My lawn is full of holes. I try to tell people to get off of it, but I can never seem to do so in time. My poor lawn is half dead.
My lawn.
PS: CPF, I'd quit ya, if I only knew how, younger sister!
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RoGuE_StreaK
Enlightened
I'll have what he's having! :buddies:
How about concave, um... undomes? To make the die look smaller again? :thinking:
How about concave, um... undomes? To make the die look smaller again? :thinking:
Bullzeyebill
Flashaholic
Alright guys, be nice.
Bill
Bill
argleargle
Enlightened
- Joined
- Jan 7, 2013
- Messages
- 321
Now THAT sounds interesting! I remember back when people said you couldn't have a negative refraction on normal materials.
http://en.wikipedia.org/wiki/Negative_index_metamaterials
A bunch of old men said it couldn't be done. Just to spite them, some youngsters went and did it. I think that they said it just to make some young interns work past their pay grade. The best part is they pulled it off!
TL;DR summary? Those darned kids made a flat lens that shouldn't exist. Good on them!!!
Wake me up if there's a flashlight that uses negative metamaterials and LASER COOLING. While we're at it, why don't we crack how some tech companies managed direct laser excitement of a phosphor laser? It's like a white LED minus the blue LED component, simply using laser light to excite the phosphor layer!
Oh wait... http://www.candlepowerforums.com/vb/showthread.php?352543-Remote-Phosphor-Formulation
When did THIS happen? This is good! I want more stuff like this!
Here's an intro to laser cooling. http://hyperphysics.phy-astr.gsu.edu/hbase/optmod/lascool.html
Basically, you shine a certain kind of laser on a certain substance and it LOWERS IN TEMPERATURE! All it does, really, is move the heat from one part of the design to another. My understanding is that is defeats Peltier coolers at this time.
Did you want the brightest light yet, or what? ... or did you just wonder what this "de doming" thing meant?
I tell you, I'm getting older by the second. I just noticed that my hands looks like gloves typing in the darkness from the light from this newfangled LED-backlit thin screen monitor. My first monitor was green monochrome CGA... later I got one with a switch on the back that let me have 16 color graphics. They called it... EGA. I remember when VGA came out. It would blow a fuse in my EGA monitor if I accidentally tried to run a VGA protected-mode application.
I'm going to go put some lotion on now... or something. I really can't be this old yet. Once upon a time on some linux forums, people said I was an elf! I didn't know at the time that they were insulting me and comparing me to the HAARP project and the conspiracy theories out there. So what if the Earth resonates at a natural frequency that was named after that Schumann guy. http://en.wikipedia.org/wiki/Schumann_resonances
Really, though... my lawn is in shambles. I hired some people to cut it with their high-tech zero-turn radius mowers. One got STUCK and the other had to pull him out with a chain. It was horrible. I have ruts all in the east side of my lawn from that... dead grass everywhere!
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This thread rulz!
Both of my dedomed XML2 lights throw quite well & I've used one in the field extensively without any issues.
The tint can get a little green if u start with a cool white i think but my dedomed 4000K looks VERY similar to a 3200K hiCRI.
Ok back to lawnmowers & lotion!
;)
Both of my dedomed XML2 lights throw quite well & I've used one in the field extensively without any issues.
The tint can get a little green if u start with a cool white i think but my dedomed 4000K looks VERY similar to a 3200K hiCRI.
Ok back to lawnmowers & lotion!
;)
Cree XQD is UN-domed, not DE-domed. In fact, all of these products are UN-domed.
It doesn't make sense for a manufacturer to make an LED with a dome and then TEAR IT OFF! That's just silly! :)
Undomed products generally have superior color over angle as compared to the domed versions of the same part.
In the Philips LumiLEDs domain for example, LUXEON Z ES has better color over angle than the LUXEON T, which is just a LUXEON Z ES with a dome...
It doesn't make sense for a manufacturer to make an LED with a dome and then TEAR IT OFF! That's just silly! :)
Undomed products generally have superior color over angle as compared to the domed versions of the same part.
In the Philips LumiLEDs domain for example, LUXEON Z ES has better color over angle than the LUXEON T, which is just a LUXEON Z ES with a dome...
