Lens info needed

[Jouellet]

I know, it's not really an electronic question, but it started as an electronic idea !!

I'm looking for info on which lens might be needed: I want to group a couple of hi-power LED, let's say on a 2-3" (5-8 cm) diameter, and focus the light as a beam, something like what you see in "disco-fixture" in bars....

I have no knowledge in optic, but I hope that someone here does or has access to one of those fixture....

 

[Bluejets]

Some LEDs already have a lens.
You will need to look at the spec sheet for the particular LED you are using.

 

[Externet]

Imagine you already have in your hands 3 or 4 lenses. How will you mount/held them perfectly aligned and properly spaced... That is the hardest part.
Try to locate an used one; will be cheaper than choosing/buying lenses and housing to hold them properly.
----> http://www.stagespot.com/fixtures-c/lighting-fixtures/followspot-fix.html
Or
----> http://www.ebay.com/sch/items/?_nkw=led follow spot&_sacat=&_ex_kw=&_mPrRngCbx=1&_udlo=&_udhi=&_sop=12&_fpos=&_fspt=1&_sadis=&LH_CAds=&rmvSB=true
There is a LED one listed there, cheap. No way to beat it by buying lenses.

 

[hevans1944]

A good place to start is Edmund Optics.

If you know nothing about optics, they can help bring you up to speed with that too at Scientifics Online.

 

[Jouellet]

Externet: i have a lathe, a CNC and a laser cutter.... Pretty sure I can figure out a way.....

Evans1944: thx for the link... Will look at it !

Bluejets: planning on using 20 watt LED... Will need a lens system

 

[KJ6EAD]

Start by choosing an LED with a narrow viewing angle then follow the guidance in hevans1944's post.

 

[hevans1944]

@Jouellet The lens system will be greatly affected by several parameters: length of beam "throw", size of beam at the desired distance, shape of the beam, sharpness (or lack thereof) of beam edge, diameter of beam at the source, and diameter or effective area of the LED source. It may be difficult to find (and heat sink) a single 20 watt LED, but that is the best choice versus an extended emitter array of smaller wattage LEDs. To improve efficiency and lower costs you should investigate a plastic Fresnel lens as the last optical element. You may need to precede this with plano-convex lenses to expand the image of the LED to fill the output aperture. I believe in good old "trial and error" when it comes to non-imaging optics, but it would certainly help to learn at least the rudiments of lens theory. Do you have any experience with optics? I know you said in your first post that you didn't, but some "back of the napkin" design sketches plus the lens equations will help you determine what is feasible as well as practical.