How Do Night Vision Goggles Work?
Everybody saw how spies and soldiers in the movies use special glasses to see more clearly in the dark. These night vision goggles use technological advancements to allow people who wear them to see in the dark. Some people even disputed that this is just some science fiction gadget that is not real. Well they are real and they can allow a person to see over 200 meters in a pitch dark. Here is how exactly do these green goggles work and what technologies are used in them.
How it works
The way night vision goggles work depends on the type of technology that is being used. Currently, we have two different types of technology that allows us to see during the night. But first we need to understand certain things about light, in order to understand how night vision works. Not all light is visible, visible light is only a part of electromagnetic spectrum (which includes all types of light). We also have ultraviolet and infrared light, which are not visible to the naked eye.
The amount of energy in a light wave is directly connected to the wavelength. Longer wavelengths have higher energy. In the visible light spectrum, violet has the highest amount of energy, while the red has the least amount. Right next to the infrared spectrum. The two types of technologies that allow us to see better in the dark are image enhancement and thermal imaging.
Thermal imaging
All beings emit energy, inanimate objects like engines also emit heat waves. Expenditure of energy produces heat, and that heat makes atoms in that object to fire off photons in the thermal-infrared spectrum. The more heat there is the shorter the wavelength of the photons, objects that are really heat will emit photons that are visible to the naked eye. Thermal imaging uses this infrared emission and produces a picture based on heat.
Here’s how thermal imaging works: All the infrared light emissions in the view are focused through a special lens. Infrared-detector elements scan the focused light. These elements produce a comprehensive temperature pattern, a thermo gram. These elements work fast and it only takes one thirtieth of a second to produce the thermo gram. This is obtained from several thousand points from the view of the detector array.
These detector elements convert the thermo gram into electric impulses, which are sent to a signal processing unit. This unit contains a chip that will use this information and make a display out of it. The unit later sends this information to the display, and there depending on the strength of the infrared emission various colors appear. This combination from the impulses make an image.
Image enhancement
This technology collects all the light, even the lower portion of the infrared spectrum which cannot be seen by the naked eye, and amplifies the image to the point when we can see it. Objective lens catches the light and sends it to an image-intensifier tube. Most night vision devices (NVDs) receive power from AA batteries. Image-intensifier tube has a photocathode, which translates the photons of light to electrons. After the tube, electrons come in contact with phosphor coated screen. Electrons react with the phosphors to release photons. These phosphors create a green image that is very characteristic for night vision. All this is viewed through the ocular lens. If you are interested to find out even more about these technologies and devices you could check out some night vision goggles review online.
The reason that the image is green is because human eyes are more sensitive to green light, and it is easier to look at for a prolonged period of time. Night vision technology is used in military and law enforcement agencies. It can be used for navigation and surveillance, hunting and animal watching also. Now you know how it works.
