First a background on Nightscopes which the German military was working
on in the 1930's (YES! That's right - The 1930's!).
Using early optical-based technologies, nightvision became TRULY practical
when collector tubes (photo-multipliers) became available on a more
commercial basis in the mid-1950's and early 1960's.
Types of Nightvision:
1) Passive Optical Intensification
2) Active Scanning Emissions 2D and 3D Image Reconstruction
Five methods of night image amplification is available today:
1) Using Vacuum-tubes where the individual photons entering a tube
hit and excite special pigments/phosphor-like materials that then emit
more numerous photons which then hit a secondary material that creates
an electrical current when photons hit it...These are called photo
multiplier tubes and are BIG, HEAVY, EXPENSIVE and don't last
very long. Generation 1, 2 & 3 nightscopes use variations of these tubes.
2) CCD-based photo amplification - a digital based system
that allows photons to directly hit a grid of Charge-Coupled Device cells
that directly output a charge of a specific strength depending upon
the energy level of photons hitting each cell. This is the way most video
cameras work EXCEPT for night-vision work, the filtering for infrared and
ultraviolet wavelengths are turned OFF so that ALL levels of charge
NO matter how small or large can be interpreted by an analog to
digital convertor circuit that is sent to a digital RGB or mono-chrome
electronic display device.
CCD's are expensive and the filtering and digital signal processing
required to noise-filter and scale up the charge levels is mathematically
intensive and therefore CPU intensive (and expensive)
Plus the individual CCD cells that accept incoming photos and emit
corresponding electrons are not very sensitive to extremely
short or long visible wavelengths thus limiting their effectiveness
in extremely DARK conditions (i.e. NO LIGHT) However images
3) CMOS (Complementary Metal Oxide Semiconductor) has the HUGE
advantage of being low-power, easy to manufacture using
already-in-place circuit fabrication facilities and has a higher level of
sensitivity versus CCD. The disadvantage is that the NOISE level
of the resulting image is MUCH higher and thus the DSP algorithms
that must distinguish between incoming photons and the internal noise
created within the CMOS circuitry itself is much more problematic.
CCD's create a sharper more pronounced image while CMOS circuits
are noisier but MUCH CHEAPER to manufacture and power!
4) Infra-red - registering the Heat emmission of living beings
and machinary and using the DSP processing to amplify the
minsicule differences between temperature ranges and assign
specific greyscale or RGB values to those emmissions that fall
within specified ranges and output that graph to a display device
Infra-red is one of the BEST way to differentiate movement
and foreground objects from static backgrounds.
5) Ultra-violet, acoustic, lidar, radar and other non-visible wavelengths.
By using the active emissions of radio, sound or light one can actively
scan and create a two-dimensional or three-dimensional bitmap
of distance & time values that can be mathematically enhanced
and filtered to create a moving image on a monitor in any RGB
or monochrome colourspace that highlights movement or objects
from a background. The advantage of these techniques is that active
scanning can produce MUCH HIGHER RESOLUTION and sharper images
than passive photomultiplier tubes, CCD's, CMOS chips or Infra-red
imaging. The disadvantage is that active scanning PRODUCES emissions
and thus provides a useful target for attack by enemy forces.