Optics is nowhere near my specialty, but it does seem to me that you can only capture so much light with a lens, no matter how optically perfect it is, before diffraction causes you to lose information. Of course, bigger / more numerous lenses & sensors would alleviate this, but then that's probably not going to be stealthy. So, I don't see how improved technology (a sudden breakthrough in how light works notwithstanding) will fix this.
Please, could anybody in optics weigh in on this, perhaps with some math? I'm very much curious what the upper limit would be for a typical piece of 3" glass.
Realistically, if this is a goal, then manufacturers will just increase the sensor size until the goal is met. This isn't a cell phone, so the sensor size constraints are pretty forgiving for this platform.
* Note: I am no optics expect, this is just what I've picked up on my own.
It's incredibly tiny. As I understand it they etch individual pixels onto it, each of which can only receive light from a specific angle. As you make it larger and larger you can absorb more and more light at higher and higher resolutions, without dealing with lenses.
Although even lenses can do insane things like magnify individual cells to be human visible, or take pictures of distant galaxies. I don't know why everyone is so skeptical of merely photographing someone's eye.
Typical cell spacing is between 3 and 10 micro meter right now iirc and red light is around 650 nm, so about a factor of 5 to 10 or thereabouts.
Biggest enemies are not incident light quantity but thermal noise, as you get smaller in cell size that becomes a real problem (you can alleviate that with cooling).
That is true--with a single camera.
At some point, we will have so many cameras facing an objective that you can exceed the limits of individual optics.
And that, too, will get better with better hardware. At first, you may only be able to detect hair color and rough hair length in cases where the person being identified has a nice silhouette against an evenly lit sky, but that already is something.
[0] https://en.wikipedia.org/wiki/Diffraction-limited_system
I was remarking the other day about some neighbors who caught the folks who broke into their house because a person across the street had a 1080p video camera which caught them going over the side fence (and fortunately facing the street).
And in my personal experience of "Imagine you could play a game where the graphics card would realistically render the battle from any angle in real time! No way, too much compute needed." where I really missed the notion that multi-core GPUs would grow like they had.
What this research says is that when you have pictures of people from high resolution cameras, that have high dynamic range, you will be able to pull out faces of people near them from corneal reflections. That won't be today obviously, it might not be five years from now, but don't count it out as "never."