Iluminating a 30cm diameter target from the closest distance possible. Advice needed.

[lothloriel]

Hi there candlepower!

For my light source I have some XPG-2 LEDs. Ideally I want to use 1 LED per coloured disc. Details as follows:

I have an odd sort of problem on my hands. For a project i'm working on I need to illuminate (backlight) a semi-opaque coloured disc (~30cm diam) with a relatively even distribution. I also need to illuminate it from the absolute shortest distance possible; im talking having the LED less than 10cm away from the disc.

This kind of stuff is not my background so I wouldn't know where to start.

I can only thing of 2 options off the top of my head;
1. use the widest reflector I can find (as of this post i've found an 80deg reflector from this website (does that 80deg mean from centre out? so 160deg across the diameter?)) and just shine that directly on the target
2. handmake/order a large flat parabolic reflector with a shallow depth and 30cm diameter, and orient the LED backwards into that reflector which then illuminates the target (Would normal aluminium foil work for this? E.g. create a skeleton in the shape of the parabola with wire and then fasten the aluminium as smoothly (or crumpled for diffusion?) as possible )

Could anyone offer suggestions how I would go about doing this; both in making any required reflectors or sourcing appropriate materials.

regards

 

[jaycyu]

Mule

=LED as close to the frontal glass as possible without a reflector of any kind.
A mule's light distribution is superb. There is no hotspot. The light falls off so evenly, I hardly notice the gradient.
30cm diameter beam profile from 10cm distance is no problem.
You can also cut out and apply a diffusion film on both sides of the glass.

You can buy diffusion films on CPFMarketplace.com sold by Phaserburn.
S1LVA sold out his sublime-looking Mule dropins.

Over at CPF buy/sell/trade, vinhguyen54 is currently accepting custom orders of mules with your selection of LED type.
You can order a XML Mule, Quad Mule, or Color XR-E Mule. Note that smaller the die, the harsher/sharper the shadows.

His stuff are bonded to copper PCB's so they're driven really hardcore. In fact, you might need a McClicky on/off switch upgrade if you want your tailcap's spring to survive when going above 3A current.

You need flashlights that accept P60 LED drop-ins. If you like brandname and quality, go with Surefire's 6P/C2. If you want quality, go with Solarforce's L2P/L2N. If you want budget, go with Ultrafire.

Another possibility is some non-modular lights can have their head+reflector removed but can still function. Those are like $13 each over at places like Manafont, compared to a custom made $80 Mule build.

 

[lothloriel]

Mule

=LED as close to the frontal glass as possible without a reflector of any kind.
A mule's light distribution is superb. There is no hotspot. The light falls off so evenly, I hardly notice the gradient.
30cm diameter beam profile from 10cm distance is no problem.
You can also cut out and apply a diffusion film on both sides of the glass.

You can buy diffusion films on CPFMarketplace.com sold by Phaserburn.
S1LVA sold out his sublime-looking Mule dropins.

Over at CPF buy/sell/trade, vinhguyen54 is currently accepting custom orders of mules with your selection of LED type.
You can order a XML Mule, Quad Mule, or Color XR-E Mule. Note that smaller the die, the harsher/sharper the shadows.

His stuff are bonded to copper PCB's so they're driven really hardcore. In fact, you might need a McClicky on/off switch upgrade if you want your tailcap's spring to survive when going above 3A current.

You need flashlights that accept P60 LED drop-ins. If you like brandname and quality, go with Surefire's 6P/C2. If you want quality, go with Solarforce's L2P/L2N. If you want budget, go with Ultrafire.

Another possibility is some non-modular lights can have their head+reflector removed but can still function. Those are like $13 each over at places like Manafont, compared to a custom made $80 Mule build.

Hi jaycyu,
thank you very much for that information.

Could I get a bit of clarification about what a "mule" is? My understanding from what you said above is that one can place an an emitter (i.e. just the cree bulb, no reflector no lens) as close as possible to the diffusion film.

My intention with it is to effectively make one big car indicator/brake light; i.e the aim of this is to create an illuminated coloured disc that needs to be seen from a short/medium distance away.

Do you think for this purpose I should just get a large sheet from berlin wallpaper (where phaserburn says he gets his) and cut this to size (~30cm diam; i need 4-5 of these) and then place some kind of coloured cellophane on top (something like this ) and then place the LED behind it all.

regards,
loth

 

[jaycyu]

Google "CPF mule," and "mule flashlight." You'll see a lot of McGizmo's customs.
How are you going to power the lights? If you use a 3100maH battery, driving your led at 0.4A will give you about 8 hours. The best way to charge a large number of 18650/26650 is with the Nitecore i4. If you plan to link the torches with some other power source, then I don't know anything about that.
And where is the rig going to operate? Pitch darkness or under streetlights?

 

[lothloriel]

Google "CPF mule," and "mule flashlight." You'll see a lot of McGizmo's customs.
How are you going to power the lights? If you use a 3100maH battery, driving your led at 0.4A will give you about 8 hours. The best way to charge a large number of 18650/26650 is with the Nitecore i4. If you plan to link the torches with some other power source, then I don't know anything about that.
And where is the rig going to operate? Pitch darkness or under streetlights?

Thanks, I understand now.

The disc is actually intended to be seen during daylight overcast/low cloudcover situations clearly from distances up to 10 metres away.

I don't need it to illuminate anything anything like a torch does, so to speak, other than the disk itself, i.e. it needs to be illuminated as much as possible so that the disc itself is visible; much like a car indicator/brake light.

I intend to drive the led at 1.5A which seems to be the the max specified by the datasheet - can they be pushed more with a heatsink? (The Cree XPG-2 that is)

So I think the setup I will use is a wide angle reflector + mule to initially diffuse the light, then offset a tinted colour sheet a few cm away.

 

[jaycyu]

If the flashlight uses a wide angle reflector then it's no longer considered as a mule, unless you mean you'll have some mule flashlights and some reflector flashlights.

There are Cree LED's that produce a single solid color like pure red, pure blue, or pure green. In this case, you can skip the color sheet. I don't know how much light you lose when a white Xpg2 passes a color film, but I'm guessing a lot. You have to figure out which configuration is more energy/intensity efficient. I think the current generation XPG2 is 20% more efficient in a normal circumstance, but not as efficient as a pure color LED if the XPG2 passes through film.

Edit: I came across this just now. In the top photos, you can see how much of the white spectrum is blocked to get one color:
http://en.wikipedia.org/wiki/Color_rendering_index


If this is only a temporary project, you can salvage the white XPG's for normal use (having 4 torches around will qualify you has a flashaholic). Otherwise, you may sell your parts on the CPF buy/sell/trade forum or at CPFMarketplace.

In the past, vihn drives his XR-E's to 2A. Today, with his copper PCB, he's able to drive the XPG2 to 3A. At 3A, the best batteries will only last a little more than an hour. 2A to 2.5A isn't really too much current. Use aluminum or copper strips to wrap the drop-in for better thermal contact.