Low cost material for large window tranparent to both LWIR and visible light?

[hap2001]

ZnSe seems to be good except it cost to much for my desire.
I want something like 50*40cm and still inexpensive. Any ideas?

[mikeselectricstuff]

Polyethylene is probably about the best you'll get

[CatalinaWOW]

Windows always have other needs than transparency.  Simple salt (NaCl) meets the transparency requirement, but obviously fails in the presence of water.  Polyethylene is good for transparency but can't stand much heat or abrasion and can suffer over time from dirt imbedded in the outside surface.  Several other plastics do ok on transparency and are a bit better for abrasion and heat.

What else do you need?  Water resistance, mechanical etc?  Are you imaging through the window, or just measuring radiation quantity?

[hap2001]

Thank you all!

What else do you need?  Water resistance, mechanical etc?  Are you imaging through the window, or just measuring radiation quantity?

I want it to actually replace one of the window glass in my house, so I can imaging through it without let insects in.

[CatalinaWOW]

Thank you all!

What else do you need?  Water resistance, mechanical etc?  Are you imaging through the window, or just measuring radiation quantity?

I want it to actually replace one of the window glass in my house, so I can imaging through it without let insects in.

I think that there are no inexpensive materials that would work for a permanent replacement for a home window.  But if you make the window easily replaceable (similar to the glass panes termed storm windows that are often used in the US, installed in winter to add a layer of insulation, and then removed in summer to allow operation of the normal window), you would find polyethylene a good choice.

Perhaps the best option would be the film used for wrapping food, which could be stretched over a frame.  The material varies, often a polyvinyl, but has decent transmission in the LWIR.   You would just substitute this frame for the glass pane whenever you where using your thermal camera.  Durability isn't much of an issue because it is so cheap and easy to replace. 

[Berni]

Plastic Seran wrap.

It is nicely transparent to visible light. The material might not be super transparent to LWIR but because it is so thin there is not enough material to stop all that much LWIR. Makes a slight shadow, but perfectly usable.

If you are looking for a solid pane of material that is perfectly transparent to LWIR... that is going to be very very very expensive at such a size.

[hap2001]

Thanks everyone.

[nick liu]

thanks everyone