Why there's no cooled LWIR thermal cameras? - Page 1
Forum section: electronics / general

author: naze
author_rank: Newbie
timestamp: June 11, 2019, 02:28:38 pm
content: I think it would be great if we use a very sensitive cooled detector on LWIR which have much more energy, thus will provide very good pictures, but I haven't seen any cooled LWIR camera, why?

author: Spirit532
author_rank: Frequent Contributor
timestamp: June 11, 2019, 05:12:15 pm
content: Because they're very expensive.There's plenty of LWIR cameras based on QWIP and SLS detectors. The FLIR X8500sc SLS for example.

author: David Hess
author_rank: Super Contributor
timestamp: June 11, 2019, 06:03:16 pm
content: Taking advantage of the increased far infrared performance would also require more expensive optics suitable for far infrared.

author: Max Planck
author_rank: Regular Contributor
timestamp: June 11, 2019, 08:38:34 pm
content: Quote from: naze on June 11, 2019, 02:28:38 pmLook at the web pages of manufacturers like FLIR, Infratec or Telops. There is plenty of them. The reason you don't see them too often is their price and the fact that in the LWIR band, in most cases uncooled systems are an acceptable solution.Max

author: Ben321
author_rank: Frequent Contributor
timestamp: June 15, 2019, 06:56:10 am
content: Quote from: Max Planck on June 11, 2019, 08:38:34 pmActually you can get some increased performance using a simple peltier TEC type cooler, just not as good as with a sterling mechanical cooler (or liquid nitrogen cooling).

author: bugi
author_rank: Regular Contributor
timestamp: June 15, 2019, 08:35:34 am
content: Quote from: Ben321 on June 15, 2019, 06:56:10 amEven if the performance increases, the issue is that the performance is good enough as is, so anything that increases cost after that needs to increase the performance a lot. While a peltier itself is cheap, it may need much more power, possibly better case, better cooling (of that peltier), management of the condensation, etc. All that extra design and parts cost and reduced reliability... and it becomes a niche with not enough interest shown from the market for the industry to be too interested, either.Considering that it has all been done in e.g. astro, tech limitations or design difficulty is not stopping it happening.

author: Ben321
author_rank: Frequent Contributor
timestamp: June 15, 2019, 09:21:53 pm
content: Quote from: bugi on June 15, 2019, 08:35:34 amCondensation is manageable in most conditions, as long as you don't live in a humid climate.

author: bugi
author_rank: Regular Contributor
timestamp: June 15, 2019, 10:32:32 pm
content: Quote from: Ben321 on June 15, 2019, 09:21:53 pmUmm.. then why do some cooled devices talk about filling the device (or relevant section of it) with pure nitrogen etc. for avoiding condensation (or even freezing some of the moisture if sub-0C)? (And not specifically in humid climate. I admit, its years since I read about it, so I don't remember specifics.) I guess one could, in some cases, simply cover every sensitive section with proper coating, but the path of light still needs to stay clear of condensation (and it doesn't necessarily need coating if the window doesn't care about occasional water on it).Even moving normal camera in or out from/to a cold outside should use some care (e.g. the slow warmup inside a closed bag with a bit of insulation, or cooldown with just insulation). Especially the move to outside (device and its internals cool with warm humid air inside) is nasty one, since the condensation will be mostly inside. Cooling with peltier corresponds to that effect, just smaller section getting cooled.In any case, even if condensation wasn't an issue, there is still plenty enough other reasons.