I don't really "get" optics for multiple LED's

[SRT Mike]

I see all the charts and diagrams that show point sources of light with diagonal lines showing how they go through an optic, but here's the issue I am having.

I am trying to make as small a light as possible. So I have an 18mm board with 3 Rebels on it in a triangle formation. There is no room on the board for even the smallest off-the-shelf optic, but I am trying to narrow the beam a bit from the 120 degrees down to something a lot less.

I know that I will get a lot of spill if I don't use an optic that covers the dome on the Rebel LED... but what I am wondering is can I put an 18mm fresnel lens over the front so it covers the dies of all three LED's to help narrow up the beam a bit?

I would be putting the lens directly on top of the domes of the LED's.

Does anyone know anywhere that sells small circular fresnel lenses?

 

[znomit]

I am trying to make as small a light as possible. So I have an 18mm board with 3 Rebels on it in a triangle formation. There is no room on the board for even the smallest off-the-shelf optic, but I am trying to narrow the beam a bit from the 120 degrees down to something a lot less.

Can you go 2mm bigger and toss the rebels for Cree XP-Es?
http://www.cutter.com.au/proddetail.php?prod=cut861

 

[Moddoo]

Can you go 2mm bigger and toss the rebels for Cree XP-Es?
http://www.cutter.com.au/proddetail.php?prod=cut861

those should work well with rebels

 

[SRT Mike]

I can't, unfortunately. There is actually 6 LED's on the board, two triangles where only 3 will be lit up at any given time (so I can have a white flashlight for normal use, and a red flashlight for nighttime when I don't want to ruin my night vision).

So I wouldn't be able to do anything like a triple optic. I noticed a few companies make triple or even quad optics for Rebels but I was hoping to have a single lens over the front that would catch the light and give me a more defined beam.

I'm definitely not looking for throw, more flood.. but as you know, the tighter the beam the brighter it is too.

Would the fresnel just not work at all?

 

[saabluster]

Would the fresnel just not work at all?

That is correct. It will not work at all. If you can't fit some teeny tiny lenses in there then you are out of luck.

 

[SRT Mike]

That is correct. It will not work at all. If you can't fit some teeny tiny lenses in there then you are out of luck.

Is it because the point sources are not in the center of the fresnel lens?

I have seen some automotive tail lights that use a sheet of small fresnel lenses in front of the LED"s. Of course they are using 40 or 60 degree LED's, and I guess the distance to the fresnel is such that it focuses the light on the lens (radially around the center of the fresnel).

Does anyone know a company that makes tiny little lenses? much smaller than Carclo, etc.???

 

[saabluster]

Is it because the point sources are not in the center of the fresnel lens?

I have seen some automotive tail lights that use a sheet of small fresnel lenses in front of the LED"s. Of course they are using 40 or 60 degree LED's, and I guess the distance to the fresnel is such that it focuses the light on the lens (radially around the center of the fresnel).

Does anyone know a company that makes tiny little lenses? much smaller than Carclo, etc.???

DX has a nice selection but just be aware you may or may not get shipped anything. I am a bit bitter on this right now. Been waiting 5 months to get an order. There is also Surplus Shed.

 

[saabluster]

Does anyone know a company that makes tiny little lenses? much smaller than Carclo, etc.???

I just remembered I have some lenses that are 8.45mm in diameter. Don't know if that's small enough but if you would like some just PM me.

 

[fyrstormer]

Try taking a lense with the power you want to LensCrafters and having them narrow it down.

 

[saabluster]

Try taking a lense with the power you want to LensCrafters and having them narrow it down.

 

[SRT Mike]

I just remembered I have some lenses that are 8.45mm in diameter. Don't know if that's small enough but if you would like some just PM me.

That is very kind of you, I will PM you!