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Might not be the best forum, but sort of at a loss of where else to try...

I'm trying to find a cover/dome for an IR LED project that I'm working on. The only thing I've found so far is:

http://www.goldmine-elec-products.com/prodinfo.asp?number=G15340

...which is a clear green acrylic dome. My question is, would the green color block/interact with the LED signal in a negative way?

If anyone else has any links to a similar dome/cover for IR LEDS, that would be an acceptable answer as well. :-)

THANKS!

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  • \$\begingroup\$ What are its optical properties? \$\endgroup\$ – Andy aka Feb 6 '18 at 15:21
  • \$\begingroup\$ The link says that cover is for projection TVs...perhaps it was a color filter? If so, I'd fully expect it to filter out most of the IR. \$\endgroup\$ – Bort Feb 6 '18 at 15:26
  • \$\begingroup\$ Does it have to be green? I am not sure about the colored kinds, but I am pretty sure all clear acrylic/plexiglas will let IR go through. And finding sources just a matter of googling the "Acrylic Dome Plastic Hemisphere" terms. \$\endgroup\$ – dim Feb 6 '18 at 15:46
  • \$\begingroup\$ Yes, unfortunately all they have is green. \$\endgroup\$ – ZacWolf Feb 6 '18 at 22:23
  • \$\begingroup\$ @ZacWolf. I wasn't asking for what this online shop have. I was asking for what you actually need. If you don't really need green, then use clear acrylic, and you can be confident that IR can go through. And finding sources for clear acrylic hemispeheres is actualy very easy, as I said. This kind of things is used a lot for presenting products in showcases. \$\endgroup\$ – dim Feb 7 '18 at 8:23
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The colour of a cover will not tell you anything about the IR properties you are looking for.

There are black covers which allow IR transmission and you can find clear covers which will block IR transmission.

What you have to look for is:

  • wavelength of your LED
  • transmission of that wavelength of the cover you want to use

Now, you can hope that they have not modified the transmission of acrylic outside of the visible spectrum while tinting it green and use a sample of a PMMA transmission curve, which will look something like this:

Tranmission sample of Acrylic taken from https://www.thorlabs.de/newgrouppage9.cfm?objectgroup_id=16

Source

As you can see it has a wide transmission range from 350 nm to 1600 nm - which should cover your IR LED (usually around 950 nm).

The green will have an effect in the range from 390 nm to 700 nm (visible spectrum) but not necessarily in the IR range.

For example there is this: black material with IR transmission, http://www.eplastics.com/Plexiglass_Acrylic_Sheet_Infrared_Transmitting

Source

Which starts to transmit really only after 800 nm, which means it is black (maybe you can see it as very dark red in bright enough light) but IR will still pass through.


And when guessing the question remains, is it even acrylic to begin with or did they just label it that way...

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  • \$\begingroup\$ For the cost I'm willing to take the change based on this EXCELLENT information. I've had good luck with this vendor in the past, so if they say acrylic I tend to give them the benefit of the doubt. Thank you very much for the explanation, it was exactly what I was hoping for! \$\endgroup\$ – ZacWolf Feb 6 '18 at 22:27

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