Is there a minimum lens-diameter to get a parallel beam using e.g. Cree T6?

HI,

I have an urgent question.

I have to make a flashlight (including lenses with a small diameter) for a robotic arm and it should be as bright as possible (>500 Lux), without having a diameter of more than 15mm. The thing is, the beam has to be parallel.

I am trying figure out what the minimum diamater must be. all the really bright flashlights have more than 20mm. Is there a reason in principle? heat? lens-related?

If I use e.g. a Cree T6, do you think its possible to make a parallel beam with lenses with 15mm in diameter?

than you very much! I apreciate your help.

If you use an aspherical lens, you can get a VERY collimnated beam.

That way, you can minimize the diameter, and maximize the lux on target.

T6 is more of a Bin than an LED per se...

The smaller the LED, the easier to collimate the beam.

The Cree XP-G2, XP-E, and so forth, are smaller LED's.

The die the LED is on can be a limiting factor depending upon the driver requirements, etc. If you make it direct drive or regulated from the power supply, etc (Driven from the robot, instead of the robot "holding a battery powered flashlight") - you can get around some of that.

Heat dissipation can be an issue in some cases, but can be overcome with heat sinking if the light use is short, or, fans, water cooling, etc, for longer durations. How hard the LED is driven to achieve the desired performance will be a related factor.

You mention 500 lux, did you mean on your target, or, at the std 1 meter reference?

How large a spot of light did you want to appear on your target, with what lux on target at what range?

There's no such thing as a parallel beam, even the most collimated laser with outputs exceed 1 billion watts used in fusion experiments will show divergence and obey the inverse square law to the letter. The T6 is not an LED but a bin, i take it that you're refering to an XML/XML2? The XML2 is 10% brighter and has a 10% die shrink compared to the original XML so it should be easier to focus.

Did you mean 500 lux or 500 candela? Lux depends on distance but if you want 500 candela, that is very easy to do, you don't even need an aspheric, a 15mm OP reflector will be doing at least 2000 candela. With regards to size, you don't see maximally driven high output LEDs like XMLs in less than 15mm diameter because you would be limiting yourself to AA sized or smaller cells. Even with an 14500 IMR, runtime with an XML at 3+A would be 5-7 mins, and will definitely burn your hand. The 18650 is the most common cell used for such applications and it has a diameter of 18mm, so a flashlight would have to be bigger than that. The reward of using an 18650 is more than 5 times the capacity of the 14500IMR, better throw due to the bigger optics and better heatsinking. It's a no brainer really.