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Thread: Phosphor conversion of photons in LEDs & photon recycling efficiency

  1. #31

    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by The_Driver View Post

    Yes, the collar is not really a very practical thing. It was also overly expensive considering what it does. They could have made it out of aluminium and offered it for a quarter of the price.

    The lasers are already cheap if you are ok with a using multiple diodes in a single light (a laser bank where all the beams are combined using optics). Only the very powerful muliti-watt diodes from Osram and Nichia are actually expensive.

    The Osram Black Flat's luminance has been measured by multiple people and several record braking throwers have been built with it. The highest value ever measured (that I have seen) is 260cd/mm^2 at maximum output (4.5-5A). In the light linked in my we got up to around 240-250cd/mm^2.

    EDIT: your PM box is full!
    Entschuldigen Sie, sehr geeherter Herr! Es it jetzt leer.

    A machined and polished aluminum block (6061T) will get equal to or better than the 99% reflectivity of the collar across the spectrum?
    Last edited by Genzod; 03-04-2018 at 11:51 PM.

  2. #32
    Flashaholic Enderman's Avatar
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    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by Genzod View Post
    A machined and polished aluminum block (6061T) will get equal to or better than the 99% reflectivity of the collar across the spectrum?
    No, only precision dielectric coated glass or silver coated diamond-turned reflectors can get anywhere near 99%.
    Polished aluminum in the best case is 95%.
    Polishing would also decrease the surface accuracy, and normal machining will not give an accurate surface finish.
    You need to electroform the reflector or have it diamond turned.

  3. #33

    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by Enderman View Post
    No, only precision dielectric coated glass or silver coated diamond-turned reflectors can get anywhere near 99%.
    Polished aluminum in the best case is 95%.
    Polishing would also decrease the surface accuracy, and normal machining will not give an accurate surface finish.
    You need to electroform the reflector or have it diamond turned.
    Enderman! I've followed your two light cannon builds with much interest! Thank you for contributing here. You lumen-wizards will make a photon-professor out of me yet!

    Out of curiosity if you know (I imagine you would), which would be cheaper to do--contract for one electroformed reflector to 99% or silver coat one diamond turned reflector?
    Last edited by Genzod; 03-05-2018 at 12:04 AM.

  4. #34
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    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by Genzod View Post
    Enderman! I've followed your two light cannon builds with much interest! Thank you for contributing here. You lumen-wizards will make a photon-professor out of me yet!

    Out of curiosity if you know (I imagine you would), which would be cheaper to do--contract for one electroformed reflector to 99% or silver coat one diamond turned reflector?
    Hahah thanks

    Diamond turning is very expensive and usually only done for stuff like making mandrels.
    Electroforming is a much more budget option, but only if the electroforming company has an already made mandrel for the reflector size you need.
    Making a custom mandrel will cost like 5-10k, so you're limited by the stock options (with the option of having the reflectors cut to smaller sizes too if you need)
    Unfortunately neither optiforms not phoenix have spherical reflectors of the size or angle we need, I may try contacting phoenix to see how expensive it would be for them to make a custom spherical one.

    For the electroformed optics the silver coating is best with ~98% reflectivity but is very delicate, so unless you have it in a completely sealed enclosure it needs to have a protective coating on it making it even more expensive.
    Aluminum coating is ~92% reflectivity and more durable, also cheaper.
    Rhodium coating is what people use for short arc lamps that emit UV and need a durable reflector, but the rhodium is less than 85%.

    If you get glass reflectors then you can have stuff like cold mirror or dielectric coatings which are 95-99% but glass is also more expensive and delicate.
    The reason a cold mirror is ideal for collars is because all the infrared low wavelength light emitted is not reflected back, and this reduces the amount of heat increase due to the collar.
    This low wavelength light does not increase the brightness at all and just heats the LED up needlessly, and more heat means lower output.

    There is, as you noticed, also light that leaks through the cold mirror, which could theoretically still be used to increase intensity.
    Leds however don't output that much infrared energy so I'm curious if using a solid metal collar reflecting all energy back would actually increase or decrease performance.

  5. #35
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    Default Re: Phosphor conversion of photons in LEDs

    My comment concerning the price of aluminium vs glass was based on production of larger numbers of aluminium reflectors. I don't think electroforming is needed for such a collar.

    The glass variant from Wavien with dichroic coating leads to highest perfromance, yes. But 5% more output for 4x the price is rarely needed. I think they should have sold both variants.

    The light loss in the Wavien reflector should not be of concern. It has a reflectivity of around 95% if it has a standard cold mirror coating. 5% of the output of a XP-G2 is around 50lm. Thats very easy to see, but it doesn't make much of a difference.

  6. #36

    Default Re: Phosphor conversion of photons in LEDs

    Saabluster said an aluminum core reflector would work, but also added a painted reflector would not. I'm thinking in terms of measured albedo, and I know for white acrylic paint, the albedo is 80%. That's not far removed from 85-95% for coated reflectors. My point isn't to use white paint, but simply say, does the argument about efficiency really boil down to what Saabluster said, yes or no, all or nothing?

    If you take the Wavien collar Sven_m used in his experiment, the gain mathematically described is (0.75*0.4+0.25)/0.25=2.2. That means 40% of the wasted light (light predestined to not make it directly through a lens) is reflected back to the die and is redirected out the opening toward a lens.

    Assuming the reflector's reflectance efficiency is 99%, we can rearrange the equation as [0.75*(0.4040)*0.99+0.25]/0.25=2.2 to say the same thing, but identify where the reflection efficiency plays its role.

    Now if you have a glass or PMMA bubble with a 60 degree beam opening, and you paint the outside with acrylic paint so the interior surface looks smooth, the equation becomes [0.75*(0.4040)*0.8+0.25]/0.25=1.97 That's only a 10% loss in performance over the wavien collar.

    So how is it reflector paint won't work, when white paint only has a 10% performance loss?

    Keep in mind this isn't an assertion! It's a construct designed to give us a medium to dissect and analyze so we can bring out the actual truth. I think I might understand why it won't work, but I'd like to bounce it off everyone here to get a better understanding of the dynamics of the light in the LED and collar.
    Last edited by Genzod; 03-05-2018 at 05:04 PM.

  7. #37

    Default Re: Phosphor conversion of photons in LEDs

    It would be extremely helpful in dissecting the above argument if someone has a link to anyone who has actually experimented with an aluminum core reflector and obtained gain results by experiment.

  8. #38
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    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by Genzod View Post
    Saabluster said an aluminum core reflector would work, but also added a painted reflector would not. I'm thinking in terms of measured albedo, and I know for white acrylic paint, the albedo is 80%. That's not far removed from 85-95% for coated reflectors. My point isn't to use white paint, but simply say, does the argument about efficiency really boil down to what Saabluster said, yes or no, all or nothing?

    If you take the Wavien collar Sven_m used in his experiment, the gain mathematically described is (0.75*0.4+0.25)/0.25=2.2. That means 40% of the wasted light (light predestined to not make it directly through a lens) is reflected back to the die and is redirected out the opening toward a lens.

    Assuming the reflector's reflectance efficiency is 99%, we can rearrange the equation as [0.75*(0.4040)*0.99+0.25]/0.25=2.2 to say the same thing, but identify where the reflection efficiency plays its role.

    Now if you have a glass or PMMA bubble with a 60 degree beam opening, and you paint the outside with acrylic paint so the interior surface looks smooth, the equation becomes [0.75*(0.4040)*0.8+0.25]/0.25=1.97 That's only a 10% loss in performance over the wavien collar.

    So how is it reflector paint won't work, when white paint only has a 10% performance loss?

    Keep in mind this isn't an assertion! It's a construct designed to give us a medium to dissect and analyze so we can bring out the actual truth. I think I might understand why it won't work, but I'd like to bounce it off everyone here to get a better understanding of the dynamics of the light in the LED and collar.

    The equation does not make any sense to me!

    The LED is de-domed, so it is a lambertion emitter. 75% of the total amount of light that exits this LED hits the collar. The remaining 25% goes through the hole in the collar. The blue content of this 75% enters the phosphor again (minus reflection discussed above) and is converted and exits the phosphor in a different angle. This leads to an increase of 120% of the 25% of the light which I already mentioned. The gain of 120% will vary from LED to LED, also depending on drive current, heat, tint etc. It has no direct mathematical relation to the amount of angular light that hits the collar.

    Where do you get your 40% figure from?

    Any standard reflector of the same shape will work. The performance will only vary slightly depending on the reflectivity. The larger the size difference bwteen reflecotr and LED diameter becomes, the more precise the reflector needs to be.

    Photon in the German forum tried selfmade stainless steel collars a few years ago. They worked, but not very good. Why? Because stainless steel only reflects around 30% of 450nm light. Low gain wa salso caused by the larger hole on the top, by the fact that he polished them instead of putting on a real coating, and imperfect shape, small collar size, sub-optimal led tint, maybe imperfect focus etc..

    Concerning paint:
    Easy test for you: take a focussed flashlight and shine it at the kind of surface you are describing (in the dark). Does the reflected "beam" throw as far as the flashlight does by itsself? You can be more precise by using a lux meter. You will have the same losses with a spherical shaped surface. I can't in any way imagine how white paint would ever work!
    Reflective silver-colored paint would certainly work, but it will not be as smooth as a real reflector. This reduces the effective surface area so not all of the available light will actually hit the LED. In addtion to this the (probably lower) reflectivity needs to be accounted for.

  9. #39

    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by The_Driver View Post
    The equation does not make any sense to me!

    Where do you get your 40% figure from?
    40% of the light hitting the collar is added to the opening. 40% * 75% = 30%

    This is the 30% of total light you need to make the added 120% you mentioned, as 30% / 25% =120%

  10. #40

    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by The_Driver View Post
    Concerning paint:
    Easy test for you: take a focused flashlight and shine it at the kind of surface you are describing (in the dark). Does the reflected "beam" throw as far as the flashlight does by itself? You can be more precise by using a lux meter. You will have the same losses with a spherical shaped surface. I can't in any way imagine how white paint would ever work!
    Reflective silver-colored paint would certainly work, but it will not be as smooth as a real reflector. This reduces the effective surface area so not all of the available light will actually hit the LED. In addtion to this the (probably lower) reflectivity needs to be accounted for.
    If the albedo is 80%, it's obvious throw would decrease. I imagine someone has already taken a lux meter to acrylic paint and measured 80% reflectance. But the point was never to use white paint, just illustrate numbers.
    Last edited by Genzod; 03-05-2018 at 09:24 PM.

  11. #41

    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by The_Driver View Post

    Photon in the German forum tried selfmade stainless steel collars a few years ago. They worked, but not very good. Why? Because stainless steel only reflects around 30% of 450nm light. Low gain wa salso caused by the larger hole on the top, by the fact that he polished them instead of putting on a real coating, and imperfect shape, small collar size, sub-optimal led tint, maybe imperfect focus etc..
    I remember reading exactly what you just said here about stainless steel. It's a completely valid point that demonstrates albedo might be high but the important components of the light getting absorbed by the reflector render the albedo by itself misleading.

    What is the ratio on blue photons to yellow photons in the white light headed to the wavien collar?
    Last edited by Genzod; 03-05-2018 at 11:37 PM.

  12. #42
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    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by Genzod View Post
    40% of the light hitting the collar is added to the opening. 40% * 75% = 30%

    This is the 30% of total light you need to make the added 120% you mentioned, as 30% / 25% =120%
    The conversion process is probably not a constant for all LEDs and setups. I wouldn't use this equation. A LED with a reddish tint (less yellow-green) might work better for example than one which already has a very yellow-greenish tint. Who knows...

    Quote Originally Posted by Genzod View Post
    What is the ratio on blue photons to yellow photons in the white light headed to the wavien collar?
    This ratio cannot be easily stated. It depends on the specific LED that is used. Just take a look at the spectrum of any standard cool-white LED (in the datasheet). Chemically de-domed Cree LEDs have a little bit higher-yellow green content. But these are not needed, the Osram Black Flat (it comes from the factory without the dome, no greenish tint) also works nicely.

    To do this you would need to have the measured watt output of the LED (not lumens!) and then put it in relation to the absorbance spectrum of YAG:Ce Phosphor. After this you would apply the conversion loss factor for this type of phosphor. Then you would get the watts that come out after conversion.

  13. #43

    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by The_Driver View Post
    The conversion process is probably not a constant for all LEDs and setups. I wouldn't use this equation. A LED with a reddish tint (less yllow green) might work better for example than one which already has a very yellow-greenish tint. Who knows...



    This ratio cannot be easily stated. It depends on the specific LED that is used. Just take a look at the spectrum of any standard cool-white LED (in the datasheet). Chemically de-domed Cree LEDs have a little bit higher-yellow green content. But these are not needed, the Osram Black Flat (it comes form the factory without the dome, no greenish tint) also works nicely.

    To do this you would need to have the measured watt output of the LED (not lumens!) and then put it in relation to the absorbance spectrum of YAG:Ce Phosphor. After this you would apply the conversion loss factor for this type of phosphor. Then you would get the watts that come out after conversion.
    I'm only analyzing one set-up, the Wavien collar and XP-G2, so to clarify, I'm asking if anyone knows the yellow to blue ratio in the XP-G2. The equation is not being used as a general design tool, only to set up discussion and analysis of the dynamics in one set-up. I'm not trying to assert it is correct or useful. I already mentioned I see one thing that might be wrong with it.

    The equation is accurately describing the portioning of light in the set up. It is sending a surviving 40% of the lumens involved in recycling/reflection part out the hole for a 2.2 gain.

    The equation does not (yet) accurately describe the specific details of the dynamic between the reflector and the LED. That is what I'm trying to investigate. The (0.40)*(75) component can be expanded to depict the specifics of the dynamics, like average number of reflections between the LED and reflector, blue to yellow conversions and corresponding heat losses, etc. That is the reason I am asking what the blue to yellow photon conversion ratio is in the XP-G2, so I can start to modify the equation to account for losses.
    Last edited by Genzod; 03-06-2018 at 08:47 PM.

  14. #44
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    Default Re: Phosphor conversion of photons in LEDs

    The 40% collar efficiency is pretty accurate.
    Even between different LEDs most of the light is in the visible range and won't change the output much whether it is warmer or cooler colour temp.

    What is more difficult to estimate is how much light is recycled by angle.
    The areas of the collar closer to vertical will be reflecting light almost straight down, so more light would exit the collar compared to light being reflected from the side of the LED.
    However, the majority of an LED's total output is emitted at 45 degrees.
    Having a collar with a 30 degree opening rather than 60 would therefore give higher intensity, however it is impossible to know how much more without testing because of the non-linearity.

    Of course this would only apply to custom made collars, since all wavien collars are 60 degrees only.
    I guess they found this to be a good compromise between lumen output and intensity increase.

  15. #45

    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by Enderman View Post
    What is more difficult to estimate is how much light is recycled by angle.
    Indeed. I would need a plot of the incidence verses %reflection for a bare, rough, phosphor/silicone surface for that. While I've seen that for glass, I'm doubtful one exists for a hobbyist's dedomed LED.

  16. #46
    Flashaholic* The_Driver's Avatar
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    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by Genzod View Post
    Indeed. I would need a plot of the incidence verses %reflection for a bare, rough, phosphor/silicone surface for that. While I've seen that for glass, I'm doubtful one exists for a hobbyist's dedomed LED.
    I have not found exactly what you are looking for, but I am getting closer:

    Investigation of the Optical Properties of YAG:Ce Phosphor

    Measurement and Numerical Studies of Optical Properties of YAG:Ce Phosphor for White Light-Emitting Diode Packaging

    EDIT:
    Page 130 of this book is interesting in this regard.

  17. #47

    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by The_Driver View Post
    I have not found exactly what you are looking for, but I am getting closer:

    Investigation of the Optical Properties of YAG:Ce Phosphor

    Measurement and Numerical Studies of Optical Properties of YAG:Ce Phosphor for White Light-Emitting Diode Packaging

    EDIT:
    Page 130 of this book is interesting in this regard.
    I appreciate your efforts to help me refine my work, Driver.

    The first paper I found a few days ago and I haven't yet fully digested it. The second is new. The Mie Theory calculations look interesting, but since that is new, it will take me a while to digest it as well.

    You added the edit for the book while I was looking the second paper over. I'll give that a look as well. Thank you.

  18. #48

    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by The_Driver View Post
    Page 130 of this book is interesting in this regard.
    There was no p 130 in the preview, but I went to the English version on Google and found on p 104 figure 3.36 which provides coefficients that I'm interested in verses volume fraction of phosphor in LEDs. I believe there is an optimal fraction for LEDs like the XP-G2. Do you know what that tends to be?

  19. #49
    Flashaholic* The_Driver's Avatar
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    Default Re: Phosphor conversion of photons in LEDs

    No, and I think Cree would really prefer to keep that a secret . Maybe we will find out at some point though.

  20. #50

    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by The_Driver View Post
    No, and I think Cree would really prefer to keep that a secret . Maybe we will find out at some point though.
    That's interesting. I thought I saw a paper recently that determined the optimal fraction, around 20% if I'm not mistaken. I can't remember where I saw that, but I remember they produced two plots that they made that conclusion from.

  21. #51
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    Default Re: Phosphor conversion of photons in LEDs

    BTW: I just noticed something interesting. The Osram Black Flat, which doesn't have a dome, is very smooth on top of the die. It seems to be much more reflective compared to to chemically de-domed LEDs.

  22. #52

    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by The_Driver View Post
    BTW: I just noticed something interesting. The Osram Black Flat, which doesn't have a dome, is very smooth on top of the die. It seems to be much more reflective compared to to chemically de-domed LEDs.
    Yes, and I believe the XP-G2 and XP-G3 surfaces are now intentionally roughened to change the angle of incidence at the surface for internal photons trying to get out. That works to our advantage with a wavien collar.

    One might use a silicone sealer in discrete bursts to create a roughened surface. Be interesting to see if it would improve the performance of a collar and Oslon Black Flat.

  23. #53

    Default Re: Phosphor conversion of photons in LEDs

    I know that in the original waiven collar, there is a specific reflection efficiency--95 or 99% depending on who you ask (not important for the moment). It looks like this light is getting transmitted through the collar rather than absorbed even though I'd venture a guess the collar is getting very warm under a barrage of nearly 1000 lumens. What is important to me though is, it is lost and does not return to the die.

    When the light goes back to the die, it enters the silicone/phosphor matrix through refraction, even to some extent at a horizontal angle because there is still refraction at that angle of approach. The blue photons are said to undergo conversion to yellow photons to some extent and the energy difference between the two wavelengths gets converted to energy (heat) according to the Planck-Einstein relation E=h*c/λ, and the photons bounce around inside the matrix until they get "recycled" and find an angle out. Chance of direction is 25% out and 75% back to the collar.

    I'm wondering of what photons that go into the die's matrix, what percentage comes back out?

    I realize each phosphor/silicone die has a different concentration ratio, making one exact figure impossible for so many different compositions, but that doesn't preclude a generalized range in the optimal ratio that dies tend to be made at around 10-20%. For example, we may have a coated reflector with unknown efficiency, but if we know it was electrically coated by a manufacturer, we can say it is most likely in the range of 85-95%.
    Last edited by Genzod; 03-13-2018 at 09:30 PM.

  24. #54

    Default Re: Phosphor conversion of photons in LEDs & photon recycling efficiency

    normally the phosphorus layer absorbs specific wavelength and then re-emit the light. if the LED chip is poorly design, leakage may occur
    Let's get into the wonderful world of LED lighting. It is applied to sports field, warehouse, port, garage, airport, tennis court, etc. As for LED advantage, by making the replacement with HID or fluorescent tube lighting fixture.

  25. #55

    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by The_Driver View Post

    The Osram Black Flat's luminance has been measured by multiple people and several record braking throwers have been built with it. The highest value ever measured (that I have seen) is 260cd/mm^2 at maximum output (4.5-5A). In the light linked in my sig we got up to around 240-250cd/mm^2.
    I'm back after a family related medical emergency. Been a month now.

    The one case I've seen of a surface brightness test (on TLF) resulting in 250cd/mm2 was tested at 4.5amps. Unfortunately the charts presented as images are no longer available. 4.5 amps corresponds to 891 lm on a scale leading to 937 lm max at max 5.5 amps from another source on TLF. If you increase the lumens about 5% to max, the surface brightness would increase from 250 to 263, had it been tested at peak. That's fairly close to the calculated 266cd/mm2, where you take the Lumens and simply divide by Pi and the emitter surface area (1.122mm2 in this case).

  26. #56
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    Default Re: Phosphor conversion of photons in LEDs

    Sorry to hear that!
    I currently prefer Köf3's tests on BLF. He uses a new method for measuring. He measures the actual luminous intensity with a reflector and lens (always the same one) to get more realistic values (of single-die LEDs) by calculating back from that. It turns out that the LE UW Q8WP actually manages the same luminance (if you get a resonably good sample), but with a bigger die and thus more lumens. Also just recently Osram announced new LEDs which are basically updated versions of these models which are more practical (center solder pad is neutral, no missing corner on the die, die not offset etc.).

  27. #57

    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by The_Driver View Post
    Sorry to hear that!
    I currently prefer Köf3's tests on BLF. He uses a new method for measuring. He measures the actual luminous intensity with a reflector and lens (always the same one) to get more realistic values (of single-die LEDs) by calculating back from that. It turns out that the LE UW Q8WP actually manages the same luminance (if you get a resonably good sample), but with a bigger die and thus more lumens. Also just recently Osram announced new LEDs which are basically updated versions of these models which are more practical (center solder pad is neutral, no missing corner on the die, die not offset etc.).
    That's great to hear.

    Post #19 at BLF is where I get the surface brightness is 250 cd/mm2 @4.5A. I get my 891 lm @4.5A, 937 max lumens @ 5.6A and 1.122mm^2 die size figures from Köf3's tests. The π divisor I use to obtain surface brightness from lumens and die area comes from the limit analysis I explained here.

    My point isn't which of the many measured surface brightnesses is more correct than the others, but rather that the method of determining surface brightness with that limit is. You can see using the numbers the result isn't far removed from these measurements when they are compared at the same amperage.
    Last edited by Genzod; 04-23-2018 at 05:09 AM.

  28. #58
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    Default Re: Phosphor conversion of photons in LEDs

    Yes, dividing the Lumens/mm^2 by Pi is the the formula for the lambertion emitter which a de-domed LED basically is. It gives a very good ballpark value! I have tried it before and is always close, but never 100% precise.

  29. #59

    Default Re: Phosphor conversion of photons in LEDs

    Quote Originally Posted by The_Driver View Post
    Yes, dividing the Lumens/mm^2 by Pi is the the formula for the lambertion emitter which a de-domed LED basically is. It gives a very good ballpark value! I have tried it before and is always close, but never 100% precise.
    Exactly the same problem you have with hobbyist measurements. .

  30. #60
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    Default Re: Phosphor conversion of photons in LEDs

    Hey The_Driver can you do two simulations of a thick vs thin lens of the same diameter in your 3d ray tracing program?

    Genzod claims that the reason the UF-T20 from vinh gets 260kcd is because the equation of lens area * led intensity is incorrect for thicker lenses.
    With 250cd/mm^2 and 32mm diameter the result is 200kcd without taking into account transmission losses.

    He says that the correct equation is

    I(cd)= T*sin2(A)*L*(d0/s0)2

    T=transmittance
    A=half the internal beam angle or arctan[Di/2/(BFL+x0
    L=total raw lumens available in hemisphere.
    d0=object distance
    X0=EFL2/X
    Xi=di-EFL
    EFL=BFL+CT/n
    S0=die dimension

    However this gives incorrect lux values for pretty much everything else I've tried that isn't the L20, and also implies that using a thicker lens will give more lux than a thinner lens at the same diameter.
    This doesn't make any sense to me because the brightness of the LED would need to be amplified when looking at the lens from a distance, more than simply reflecting/refracting using a typical reflector or lens.
    Also the maximum candela has nothing to do with the size of the LED or the distance that the measurement is taken, so I don't know why the equation he is talking about even uses those values.

    Please let me know what you think, thanks.
    Last edited by Enderman; 05-01-2018 at 10:03 AM.

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