Message Board Thread - "transparent material used for an infared region?"

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transparent material used for an infared region? Lulu 2/11/2004
I need to burn small fire inside a transparent enclosure, apparently glass is not good because of the reflection. is there any other transparent material I can use to make an enclosure and IR camera can detect the fire inside of it?
 
Re:transparent material used for an infared region? Kim H.A. 2/11/2004
Some type of sapphire glass could be used. You should be able to get a type that can withstand the heat and that is applicapable for thermography. It is sometimes used in viewports at furnaces and boilers.
 
Re:transparent material used for an infared region? Gary Orlove 2/11/2004
What you use depends on several factors:

1. At what wavelengths is your camera sensitive? There are two common regions for commercial infrared cameras, 3-5µm and 8-12 µm. This will dictate choice of materials available, for instance, sapphire, an excellent material for this purpose, is not transparent at longer wavelengths and hence can't be used for 8-12 µm cameras.

2. What temperature and pressure differential is the window expected to withstand?

3. How large is the window going to be, the larger it is, generally the thicker it has to be to withstand pressure differentials. Increased thickness will affect the optical properties.

4. You may have to apply antireflection coatings to the window in order to improve transmission performance. The atmophere and temperatures in your application may be detrimental to the coating.

Discuss all of these topics with your window supplier before choosing a material.

Here are some suppliers to consider:

http://www.ispoptics.com/
http://www.hawk-ir.com/
http://www.crystran.co.uk/index.htm
http://www.cyber.rdg.ac.uk/ISP/infrared/home.htm
http://infrared.als.lbl.gov/IRwindows.html

Gary Orlove
Infrared Training Center

 
Re:transparent material used for an infared region? Lulu 2/11/2004
I am using Thermacam SC 500 camera, the spectral range is 7.5~13 um. the enclosure actually works as a chimney. its top and bottom are hollow. so the pressure is almost atmospheric pressure. the temperature will not exceed 300 degree C. the window size is about 60x100 cm. is there any transparent polyethylene I can use? Thanks for your guys help!
 
Re:transparent material used for an infared region? Gary Orlove 2/12/2004
Given the information you just sent, I would take a look at using Zinc Selenide (ZnSe) window material.

Unfortunately I am not aware of any polyethylene that will withstand high temperatures, at low temps polyethylene works great!

Gary Orlove
Infrared Training Center
 
Re:transparent material used for an infared region? Lulu 2/12/2004
Thanks Gary for your kindness reply. if polyethylene works, how about polypropylene? there are some companies providing polypropylene sheet not polyethylene. I really have no idea where I can get it. I just want to try some experiments without fires. thanks
 
Re:transparent material used for an infared region? Gary Orlove 2/13/2004
I haven't tested it but my gut feeling is that polyproylene is not a great window material for your camera.

See the transmission curve here: http://www.appl-tech.com/Pittcon99HTML/img22.htm

My suggestion is to measure the transmission with your camera and prove it to yourself either way.

Gary Orlove
Infrared Training Center

 
Re:transparent material used for an infared region? Gary Orlove 2/13/2004
One other thought. You might try this IR window material made out of a special plastic. It's transparency in the LW is about 60%. The price is definitely right!

See http://www.edmundoptics.com/IOD/DisplayProduct.cfm?productid=2043

Gary Orlove
Infrared Training Center
 


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