I used to use then years ago for the Counter Drug program. They were bulky, but worked pretty good. We were afraid to use it because it was so expensive that if we dropped it, who was going to pay for it! At that time, it was $25K. I bid on a Thorne EMI european weapon site, but was beat out at the last minute. Almost got it for $1,000 Euros. The problem is that it used compressed air for cooling the seaker and it took a special cylinder. Again, still a expensive proposition.
I've played with and against the big heavy chunky one that had it's own refrigeration unit. It had an ID range of man sized out to 1000m and vehicles out to 5000m. It was noisy as, but very effective in picking up heat signature. Also used a later version that was a bit bigger than a Sony 8 handicam, that let you ID people and objects a lot better. Still made some noise. The dream one at the moment would be the Elcan Spectra 2x for US$14000, 4x for $17000. Weapon mountable and quite handy for what it does.
Yeah I have looked through one, made a really loud clicking noise, and the man target looked like he was on fire, no crisp body lines, cool thing was seeing the heat come up out of the fox holes.
