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Flashlight optics and reflectors.

thestug

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Ok, so I'm currently building a 100w LED flashlight. This is what the actual LED itself looks like.



It should be very bright but the light produced by this will be emitted at a very wide angle more like a flood light. I'm looking to make my light produce a beam of light like in this video.

The question is what do I need for optics and reflector and where do I find them? Any help would be greatly appreciated.
 

marcuspeh

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When activated by electricity, the tungsten filament or LED in the lamp begins to glow, producing light that is visible. This light reflects off of the reflector that is positioned around the lamp. The reflector redirects the light rays from the lamp, creating a steady beam of light, which is the light you see emitting from the flashlight. A clear lens covers the lamp on your flashlight so that the glass on the lamp does not get broken.
 

Mattronium

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hmm, I've thought of trying to build one into a flashlight, but didn't actually do anything because it seemed quit difficult.

I'm not that knowledgeable about this, but below are my thoughts.

The problem is that "throw" depends heavily on the emitter size, ie. small emitter will have better throw, a big emitter will have worse throw.
If you compare it to a XML emitter that has like 4mm diameter, your LED has about 1inch diameter?
Also, what driver are you using?
How are you going to heatsink it? (a lot of heat!)
What battery sizes and configuration are you planning on using?

Sounds like an interesting project if it is do-able.:)

EDIT: I know they do have a lens with mounting for the diode, although I don't know what the throw vs flood would be. LINK
 
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Cyparagon

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It can't be done. Your limitation here is emitter size, and those 100W LED are actually an array of 10x10 1W dies. The effective emitting area is enormous compared to a single die. You can add a gargantuan focusing optic (parabolic mirror or convex lens) to bring the divergence down, but that means a very large initial beam diameter. Therefore, you will NEVER get a beam like the one in your video. Physics says it's not possible. Not with that LED.
 
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thestug

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This is definitely not going to be a compact flashlight. In fact it probably should be called a portable spot light. I'm not trying to make a small beam, but just a beam with plenty of throw. The idea here is to get as much illumination as possible at long distance.

As far as getting as much throw as I can out of this LED. Do I need a giant reflector lens or both? I've got a small lense and reflector designed to fit the LED, but they only focus the light just a tiny bit.

Even if the beam is large and high divergence there must be some way to do it moderately effectively.
 

Cyparagon

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In order to get "good throw", you need a small beam at a distance. If your light is spread over a large area, the intensity is very low, comparatively.
 
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thestug

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In order to get "good throw", you need a small beam at a distance. If your light is spread over a large area, the intensity is very low, comparatively.
I got it now. So a small beam put's the more light in a smaller area. I can see why what I said makes no sense now. :/

However, why is it impossible to take a LED that has a somewhat large area and use a reflector or mirror to keep the light concentrated at a distance?
 

Cyparagon

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The larger the emitter size, the larger the beam. It's just physics. You could spend entire university courses on the subject of optics and not cover it all, so I'm not going to do it justice, but I'll give it a shot. You've seen images like this before, yes?



Now, the second part of the phrase "focal point" is important here. This image only works perfectly if the focal point has, indeed, zero dimensions. Real world light emitters cannot have zero size. This means much of the light emitting area will be OUTSIDE of the focal point, and therefore not at an optimal position to be reflected. Some of the light will go slightly to the left, some of it will go slightly to the right, etc.

As the emitter grows larger, more and more of the light emitting area is farther from the focal point. That is why you will NEVER see a fluorescent tube give a narrow beam of light, for example.
 

thestug

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That makes a little more sense now. It is atleast possible to improve from the nearly 170 degree beam angle and reduce it down to something more useful at range? A reflector or lens should at least help direct some of the light that got scattered to the sides forward, right?
 

will manners

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Diagram of a parabolic mirror
Your response: A conveyance of utter indifference to the initial interpretation put forth,
merely a statement so devoid of humour, by its very nature seemed bloody hilarious. Love it ;)

try a build with XPG-2 emitter de-domed using big aspheric head, run it hard with a BIG copper heatsink:eg:
Finally someone gives the bloke a piece of practical advice :D

@thestug. Follow Mr. Cyparagon's advice and ditch that LED. The key here in laymans terms is that the smaller the emission surface relative to the optics (reflector, aspheric, whatever) the further it will throw. In this instance you would require massive optics to achieve any amount of luminous intensity ("throw").

If you are looking for a throwy beam without any spill you should look at starting with an aspheric flashlight (assuming you are looking for a handheld option). The JAX Z1 is an excellent quality host with a big, beautiful AR coated glass aspheric lense. Utilizing a dedomed XP-G2 LED will yield a very tight and "throwy" beam. Dedoming the LED causes the Luminance (emitted intensity per square area, often referred to as 'surface brightness') to almost double since it greatly reduces the perceived emission area, (see here for more on Luminance and the effects of dedoming, Flashlight Optics - Dome, Dedoming and Throw). Here's a list of parts that you would need to complete a build like this:

JAX Z1 host (see here for a review)
CREE XP-G2 S2 1D
FET Driver - 22mm
Efest Purple 26650 3500mAh

With the aforementioned build using the above parts one could expect in excess of 200 kcd (I.e. Luminous intensity/candela,
see here for more on what candela means and how it is calculated). There's also a thread on BLF detailing this exact build
and what one can expect with a setup like this. Jax Z1 XP-G2 S2 dedomed @5A
 
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thestug

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So, it sounds like I'll end up building two different lights. One that utilizes the 100W LED that I mentioned earlier. I'll probably abandon the idea of trying to make that into light with lots of throw. I'll still try and build a decent portable area flood light as I have most of the pieces I think I'll need.

As far as a LED that is suitable for throw, is the CREE XP-G2 S2 as good as it gets for LED's for this application? I'm not opposed to spending more on an LED if I have to.

I may order that JAX Z1 host.

I see that the driver that will manners posted is a FET driver. Does this mean that the LED is driven by battery voltage that is regulated by PWM?
 
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