I'm trying to build a led beam, the same as moving heads on stage lights. It's for a light art installation.This is my job, and you can have a look at collectif-coin.com
(Ok. It's not a flashlight, but you guys know how to build throwers. Right ?)
Objectives:
- very parallel beam (0° - 1.5°)
- very strong, very white beam
- very cold
My first attempt is with a CFT-90-W, an aspheric lens from Optolife (A380 : diam=120mm, f=161.5mm), and a cheap condenser lens taken from a led pin spot.
Above you have a beam from a Martin MH3 (with a philips 5r inside :)on the left, and my beam on the right.
In real life, the results are not so good. My beam is not "white" enought. You see throught it.
I'm pretty sure I have to find the right first condenser lens, but I don't know which one could fit.
Somebody to help me ?
How can I throw a maximum of light to the 120mm lens ?
The MH3 produces 8,786,000 candela. That’s… a lot. Matching it without similarly fancy optics might be tricky. The BLF GT makes about 1.2 Mcd from a similar lens diameter, though it’s using a reflector.
There is no LED that will give that much candela from that optic.
The technology isn’t here yet.
Also a 0 degree beam is impossible, unless you round down below 0.5.
Even with a collar and a perfect focal length lens the most he will get out of it is ~4mcd and 2500 lumens.
Moving heads often do 10-20mcd and about 20000 lumens.
if he wants something that makes a similar beam he will need to use short arc.
Not just candela, also lumens matter.
If you have a 1mm^2 LED making 1000 lumens or a 2mm^2 LED making 2000lm they will have the same intensty and cd/mm^2 giving the same throw (assuming same polar distribution and other stuff).
The second LED will have a beam 2x brighter (initially) because of double the lumens.
The down side is that the beam will diverge more too due to the larger LED area.
My driver is supplying 4.0v / 15A. I can’t get more right now. The LED should handle 4.2V / 27A … I’m not using any wavian collar. We can’t find them anymore, can we ?
ma tumba:
It would be used in a concert hall. Rather dark and with smoke. It would be quite optimal.
Just a quick picture of the first optic. It's on this strange position that I get the narrowest beam (with the 120mm aspheric lens on top)
So what do you think I should do ?
find a more powerfull driver ? (That I'll do)
find some kind of wavien collar ?
work on the first optic ? (maybe a full spheric one ?)
My feeling is that you should check leaving the first optic out and see what you get with just the 120mm lens.
But if a condensor lens is used to get more light in the hotspot (mind that with it the hotspot will be wider, not brighter), in this position it does not work as a condensor, it is way too far from the led to collect a significant amount of light. I reckon it should be right on top of the led.
The connected wire in the picture from first optic looks very thin to me, I estimate around 0.75mm2.
Thats perhaps not enough for suppling 15A+ current to the led? (Depends also on driver type…)
I wonder if there are “smokes” that would fluoresce under uv light? In this case you could use an uv laser instead of a flashlight. More efficient in terms of beam divergence, brightness and there could be a choice of color, too
What color temp of the led is this? I see mouser lists instock the 7800k, stage white, and even 8500k. I would expect these bluer whites to provide greater scatter and a more visible beam.
What would it be too small?
It has an inside diameter of 25mm, the LED is only 3mmx3mm.
It will have the exact same effect as a larger collar, projecting an inverted image on the die.
Because sma, the only guy who actually studied them in detail here , noted this possibilty. He says that they only focus good in the center which might lead to a reduced effect with large LEDs and/or small collars.
I love moving heads and strong LED beams.