Transparent Plastics

[russellhq]

I'm wondering if all transparent plastics pass IR or if there's any to watch for. I'm planning a build and need to make a small sensor window. Something like perspex or polycarbonate would be ideal, but if it blocks IR then it's of no use ?

[Dr_Ju_ju]

Perspex, is a brand, and according to the Wiki (https://en.wikipedia.org/wiki/Polycarbonate) Polycarbonate transmits IR to quite high frequencies. UV has the potential to break down the polymer bonds, but if its for a small window, just replace after x years.

[russellhq]

Thanks. The window will only about an inch. I'm now thinking that maybe a basic luminance filter would work?

Also, after a bit of googling, a piece of borosilicate would work if I can find a small piece for not much money.

[russellhq]

Something like this should fit the bill I think:

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F142873666801

 

[Astrobits]

Google "ir transmission of plastics"

Nigel

[JamesF]

You can probably get relatively small pieces of borosilicate glass from suppliers of parts for 3d printers as it's often used as a print bed and it shouldn't cost very much.  I'm inclined to think a photographic filter might be a whole lot less hassle though.

James

[Astrobits]

As the window will be it the optical train you will need something better than "window glass". Look here for some quality windows:

https://www.edmundoptics.co.uk/c/visible-windows/669/#Categories=Categories%3ANjY50

Nigel

[wimvb]

5 hours ago, JamesF said:

I'm inclined to think a photographic filter might be a whole lot less hassle though

My thought too. A normal uv filter for a camera lens should do the trick.

[Stub Mandrel]

What's the application?

If you want a window that passes IR but minimises visible light  go to a boot sale and buy and old IR remote with a plastic window.

[russellhq]

It's to protect a TSL2561 luminance sensor and a MLX90614 digital infrared thermometer as part of a sky monitoring station I'm trying to build. I've ordered the £2 UV filter from eBay, so hopefully that should do the job.