After the student has mastered the various techniques of employing “white lights” with both handguns and long guns, the subject of night vision goggles (NVGs) can be introduced. There are quite a few variations of devices that can be employed and their utility depends on the specific environment involved and the characteristics of the object needing to be revealed by the NVG.
Thermal Devices
Thermal night vision devices work by sensing radiation given off by the object itself. Thermal night vision works by sensing the infrared radiation (“heat”) being given off by an object. The object could be a living organism or a mechanical device which produces heat as a byproduct of its operation.
Image Intensifiers
Passive Devices
Passive image intensifiers work by taking the light given off by an object and then “intensifying” that light such that it is then visible by the human eye. One specific example of this is “thermal” device above. Other devices work on the light spectrum outside of the infrared.
Active Devices
In contrast, active night devices work by generating a “light source” which is then projected onto an object and the subsequent reflection is detected. These devices are often also known as “image intensifiers”.