Anyone who has ever watched a movie or television show that involves warfare, surveillance, or covert operations is probably familiar with images seen when operating night vision devices.
Does anyone remember the "The Silence of the Lambs" where Jodi Foster is being chased by her adversary in a pitch black basement? Or maybe you have used a unit yourself and are familiar with the illuminated images on a green screen, but have no idea how it all works.
How are you able to see in the dark, and why does everything appear to be green? There are two types of night vision that are typically used: 'image enhancement', and 'thermal imaging'.
Image enhancement works by amplifying small amounts of light in order to see an image.
The second type, thermal imaging, captures the heat of an object and projects it as an image.
Image enhancement is commercially available and has the familiar green glow that most people are familiar with.
Image enhancement works by capturing visible and infrared light in an image intensifier tube.
The light is captured by the objective lens, or the lens furthest from the user's eye, and is then sent to the image photocathode.
The photocathode then turns the photons from the light energy into electrons.
Once the light energy is converted to electrons, they are paced through a plate made with fiber-optic technology called a micro-channel plate, or MCP.
Once they have paced through the MCP they strike a screen that has been coated with phosphorus.
As the electrons strike the phosphorous it releases green photons which are viewable to humans by looking through the ocular lens of the night vision unit.
Several generations of night vision technology have been invented since the inception of night vision.
Each generation has brought an improvement in the quality of the image, while decreasing the amount of light that is needed to achieve that image.
Generations 1 through 3 are currently available for commercial use.
People buying night vision devices should know that although generation 2 and 3 optical devices do offer much clearer images at lower light levels, the technology improvements enabling these images come with a price tag.
While you can pick up a low magnification night vision scope for a few hundred dollars, you can also easily spend $3,000 for a top end 3rd generation unit.
Discerning which one is right for you is really a matter of what you need the unit for and what you are willing to spend.
As night vision technology continues to improve you can expect the images that are projected to become even clearer, and the light requirements to decrease.
You should also expect the price of later generation models to continue to decline.