Wanted - ZnSe flat window to add as a protective shield to front of IR Camera - Page 1
Forum section: electronics / general

author: Liam G
author_rank: Contributor
timestamp: August 29, 2022, 06:18:56 pm
content: I'm looking to ruggedize a camera for a non-profit rental scheme. My plan is to glue it into place, and if it ever gets scratched, just replace it. So, as cheap as possible. Can be any shape; round, square, rectangular etc.Thanks.

author: Liam G
author_rank: Contributor
timestamp: September 01, 2022, 12:32:16 pm
content: bumpAnybody? Surely someone else has constructed an IR transparent lens protector for hostile environments.

author: Fraser
author_rank: Super Contributor
timestamp: September 01, 2022, 12:54:53 pm
content: Yes, but you are looking for something inexpensive and sadly ZnSe and Germanium are expensive materials. The ZnSe lenses we use for close-up work are manufactured for the CO2 laser engraver industry and mass production reduces cost. Flat ZnSe and Germanium windows are less common and so cost more. If you look on eBay for ZnSe or Germanium window you will find them. Non AR coated windows may cause image degradation and reflection issues. Germanium windows need to be AR coated if high transmission losses are to be avoided. ZnSe is less of a problem in this respect.In industry we use disposable lens protectors or expensive Germanium versions. The disposable lens protectors use Polyolefin film that has good transmission at thermal wavelengths and is tough enough to protect against fluid splashes. I tend to buy 12 micron thickness heat shrink Polyolefin film used for food wrapping. For ballistic protection, a Germanium, GaAs or ZnSe lens protector is used. Thin plain silicon may also be used but it’s transmission at LWIR can be an issue, hence it must be thin.It is not difficult to find ZnSe or Germanium windows…. But it is not inexpensive either.ZnSe…..https://www.ebay.co.uk/itm/125305975691?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=OMb9rQOER86&sssrc=2349624&ssuid=BgpdXaaLSkK&var=&widget_ver=artemis&media=COPYhttps://www.ebay.co.uk/itm/393615742684?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=0PkOw1UgR4O&sssrc=2349624&ssuid=BgpdXaaLSkK&var=&widget_ver=artemis&media=COPYhttps://www.ebay.co.uk/itm/224471094066?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=2919eCl2RpO&sssrc=2349624&ssuid=BgpdXaaLSkK&var=&widget_ver=artemis&media=COPYhttps://www.ebay.co.uk/itm/165003861118?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=srsid7sftry&sssrc=2349624&ssuid=BgpdXaaLSkK&var=&widget_ver=artemis&media=COPYGermanium…https://www.ebay.co.uk/itm/224626273792?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=KxdLw-i2R6O&sssrc=2349624&ssuid=BgpdXaaLSkK&var=&widget_ver=artemis&media=COPYhttps://www.ebay.co.uk/itm/225063584367?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=KxdLw-i2R6O&sssrc=2349624&ssuid=BgpdXaaLSkK&var=&widget_ver=artemis&media=COPYhttps://www.ebay.co.uk/itm/265553375530?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=k9uBQzvPQTe&sssrc=2349624&ssuid=BgpdXaaLSkK&var=&widget_ver=artemis&media=COPYNote that adding a window in front of a thermal camera will add a transmission loss and so a temperature measurement error. With some lens protectors the introduced error is small, whilst others produce significant error (Silicon windows at LWIR)Fraser

author: Vipitis
author_rank: Frequent Contributor
timestamp: September 01, 2022, 03:40:18 pm
content: Coating is important. The window I have has a 'diamond like, hard carbon coating' on one side that even claims to be explosion proof. It got quite a few scratches but works just fine. The other side isn't coated and has this shimmering gold-purple look of a few thin layers and they will be ruined if abused.Apart from finding the windows as bare parts, you can probably harvest them from surveillance style camera boxes that are meant for outdoor use, but it's difficult to make that cost effective.And don't be scared about a scratch of two. the element is transparent and close to the lens, well our of focus with all those f/1.2 lenses. it will be difficult to even spot on the image. But it's not superficial. I used mine as a whacky beam splitter before.

author: Liam G
author_rank: Contributor
timestamp: September 01, 2022, 05:52:14 pm
content: Much thanks toFraserEspecially the first ZnSe ebay link - I hadn't found one that cheap.Also, the Polyolefin info; this was unknown to me and I'll certainly try that out first.

author: Liam G
author_rank: Contributor
timestamp: September 01, 2022, 05:57:24 pm
content: Quote from: Vipitis on September 01, 2022, 03:40:18 pmThat's a great idea, will bear that in mind next time I'm at a scrap heap

author: Liam G
author_rank: Contributor
timestamp: September 01, 2022, 10:21:38 pm
content: Just done a test with some Polyolefin shrink wrap from an un-opened box of tea bags. Worked perfectly. A small 2 to 3 degrees C reduction in the captured temperature, but this shouldn't cause too many problems for a basic home inspection use case.