It can be quite a challenge trying to see your surrounding in the deep dark night. While you can always feel your way around and hope you don’t trip up and land flat on your face, there are times when being able to see in the dark is essential.
High powered torches are one option, but can seem quite intrusive and draw attention to oneself. Also, there is the issue of your eyes adjusting to the darkness, as I talk about in this post.
Night vision minoculars are another option. When using night vision the adjustment time between green and back to natural darkness is vastly reduced.
So, when is night vision commonly used? It is not just used in call of duty, it present in many things from surveillance cameras, military periscopes and now it’s even in your smartphone.
Part of the reason night vision has so many applications is that it comes in several different forms for the various uses.
How does it work?
When we think of night vision, we think of the green lights we see in action movies or with the military, that is called image intensification or image enhancement. Green is used deliberately as the human eye is more sensitive to green than any other color because green stimulates two of the three kinds of cones, L and M, almost equally.
Image enhancement works by detecting low levels of light and intensifying it. When photons, these are the parties that make up light enter an image enhancer, first enter the device, they will hit a layer called photocathode which releases electrons. These electrons will hit a second layer called the microchannel plate; this plate multiplies the electrons before they move on to the Phosphor screen, that then converts them back into light. As there are more electrons, you will see a brighter image.
But…… What if there is not enough light for image enhancers to…. Enhance?
Well, this is where thermal imaging comes in. Thermal imaging cameras work by detecting heat that comes from different objects and people as they can see an infra-red light.
Heat causes thing to emit photons in the infrared spectrum, although humans cannot see infrared, these cameras take advantage of this in many different ways.
I R cameras produce images called, thermograms, which display a rainbow-colored image using the colors in the picture above. The different colors all represent different temperatures. Thermograms are used for many things, such as medicine, construction, and of course night vision.
Using I.R. For night vision is very useful, as the screen with display the image of different objects likes people and animals in a multitude of colors.
Thermal cameras are great for when the light level is low, but they cannot achieve the same details as the image enhancers. On the other side, the can pick up things that a normal image enhancer can not.
1. A firefighter trying to locate people in a burning building
2. A hunter picking out pray deep in the woods
3. The police are trying to locate a hiding fugitive.
Some cameras can create their own infrared light using a process called active illumination. This process works by lighting up their surroundings with I.R radiation. This additional energy will reflect off what the camera is pointing at; the result is much higher quality images. This comes in very useful for devices such as surveillance cameras.