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Old May 25th 2016, 01:53 AM   #1
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Fibre-optics design question

Hello,
I am trying to design something which needs to transfer as light as efficiently as possible from a 1W RGB LED, down 2 metres of a clear acrylic plastic rod/tube (used as an "optical fibre"), to a diffuser at the far end.

The idea is is that total internal reflection will cause the light to go down the plastic rod rather than leak out the sides.

Assume the plastic rod/tube is clear and un-clad, and is 6mm in diameter, and is suspended in free space.

My questions are:
1) Would be the light transfer down the "optical fibre" work better and be more efficient with a solid acrylic rod, or with a hollow rod (e.g. OD=6mm, ID=3.2mm or 4mm).

2) Given that the light-source is a flat-fronted LED which has a wide radiant pattern, what is the best optical arrangement to get most of it's light into the end of the optical fibre in a direction compatible with total-internal-reflection. (e.g. a Ball lens?)

REF: See the Led datasheet for the light distribution pattern http://www.rapidonline.com/pdf/55-2267.pdf

Thank you

Regards,
Nicholas Lee
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Old May 25th 2016, 05:53 AM   #2
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What you're describing is known as a light pipe, and is quite common in the design of electronic equipment. You want to use a solid cylinder of acrylic, not hollow. You do not need a lens at the LED end of the light pipe, but you do need to locate it as close as possible to the surface of the LED. It would also be good if the end of the light pipe could be hollowed out to surround the LED. Here's a reference that may help - note the idea of a "LED retaining wall": http://www.mouser.com/pdfDocs/Lumex_...dule_Part2.pdf
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Old May 25th 2016, 12:42 PM   #3
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Thanks

Thank you, that was most helpful.
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