Traditionally reserved for military applications, image intensifier tubes (a.k.a. night vision scopes) are persistently pricey analog devices for amplifying light.
For non-military applications they are largely being overtaken by "digital night-vision," which is essentially a conventional sub-$100 CMOS or CCD sensor without an infrared filter, typically supplemented with active near-infrared illuminators.
Given that a state-of-the-art image intensifier (which may be called 4G, or Gen3+) starts at $3,000, I am wondering: How close are existing digital camera sensors to matching the performance of analog intensifiers, and is there a theoretical limit that would prevent a conventionally-sized CMOS or CCD sensor from matching the low-light performance of an analog intensifier?
I'm not sure how to compare the performance specifications provided for analog intensifiers to a "black-and-white" digital sensor. For example, state-of-the-art intensifier specifications include:
- 64lp/mm (line pairs per mm) resolution
- Signal/Noise about 25.
Note that for "night vision" a monochromatic digital sensor can eschew the anti-aliasing and color filter arrays, presumably increasing sensitivity and reducing noise over the conventional ratings we see with those filters in place. DxO offers a low-light sensor measurement that lists "the highest ISO setting for a camera that allows it to achieve an SNR of 30dB while keeping a good dynamic range of 9 EVs and a color depth of 18bits." (SNR of 30dB equates to a simple multiple of 32. And the color requirements are, I assume, far more demanding than those required for black-and-white resolution.) For current generation full-frame sensors those numbers are up around 3000ISO. For APS-C sensors it looks like they're around 1000ISO.
Perhaps someone with a greater facility for these metrics can find a relationship between the analog and digital ones?