My unit got a couple sets of combination image intensifying/thermal goggles back in 2008 to try out (long before the AN/PSQ-42s were even in development). The thing that stuck out most to me was how much everyone disliked them without really being able to articulate why.
There was also a rumor that if you turned your head fast enough with them on they’d cause you to vomit and pass out, which is almost certainly not true but boy did we believe it.
We used the PVS-7 monocular devices in the Contingency Response Groups. While it wasn’t anything I’d want to live in, it works ok enough to drive a HMMWV at night safely
These new ones would be wild, I’ll see if I can get a demo this year somewhere.
Basically it said infrared goggles use digital processing, so there's at least one frame of lag for every image, which can cause those issues. Image intensifying googles are totally analog so there's no lag to avoid that issue.
> so there's at least one frame of lag for every image
Well, 24 fps vs 120 fps would technically matter, to the point where at a high enough frame rate you could not possibly tell the difference; I suspect it's more like 48 fps (if it's a constant 48 fps) than 120 *
If there's a digital component to these which causes frame delay, I wonder what the FPS is. Competitive gamers say 120 vs 60 makes a substantial difference. Since the use case is literally first-person shooting...
I could be wrong but I believe 120 vs 60 makes a huge difference only because the framrtate is not actually constant and in certain cases/scenes the framerate can drop significantly, whereas an IR google I immagine will render at a constant framerate regardless of scene.
> There was also a rumor that if you turned your head fast enough with them on they’d cause you to vomit and pass out, which is almost certainly not true but boy did we believe it.
Sounds like (slightly exaggerated) VR sickness symptoms, e.g. when there's too much latency between head movement and vision updates. Some people are more sensitive to this than others.
Perhaps it has to do with the optical center being offset? I don't have one to test it out, but if it works like it says online, the optical center would move from somewhere in the middle of your eye to somewhere in the middle of the device, which would cause changes in parallax, and therefore mismatch in movement between the inner ear and what is inferred from the eyes. Maybe that's what causes the discomfort.
So an IIT doesn’t really have a “refresh rate”, but the thermal component does.
I don’t get any motion sickness with Gen3 IIT’s even moving fast, but with digital systems there’s a latency in refresh rate that becomes very disorienting.
The thermal part of the combined system is digital - in the units I’ve looked at, the image from the thermal is “projected” into the IIT’s lens. So while the image from the IIT alone is lag free, the thermal overlay does have lag and can mess you up a bit.
I should have specified, I meant with the overlay. Do you have any idea what the rate might have been? It's a pretty gucci piece of gear, but in 2008 everything thermal was. A 10 Hz overlay would work fine for observation (those monoculars everyone has now can be about that shitty), but movement would be gross.
I have no idea what it would have been back then, but the current “best” ones I’ve seen on the civilian market have a refresh rate of 50hz and you still experience some “issues”.
I’ve played with some older kit that was somewhere around 14hz or so and was fucking awful, felt like being ill after walking around in them!
