Night Vision
The three basic types
- Active Illumination
- Image Intensification
- Thermal Imaging
Modern technologies used by the military: AN/PVS-5A, AN/PVS-7A, and AN/AVS-31
Active Illumination
Lowest cost. This is basically an infrared camera working with an infrared illuminator. Range is limited to distance of infrared source. Easily detectable. The light source is closer to the visual portion of the spectrum so that it is near visible yet still below human eye perception.
These work well for CCTV cameras, video cameras, and indoor night vision requirements. This is typically a digital technology.
Consumer Example: This is an inexpensive and common technology with examples across many industries.
Image Intensification
Vietnam War era "Starlight Scope" and modern Military NVGS fall into this category. Uses only existing light and through magnification the light level is useful to the human eye. These are lighter and more real time. They produce no detectable light source. Typically there is a limited field of view with no peripheral view. Multiple lens versions that are military grade can retail for up to $40,000 such as those used by Navy S.E.A.L. teams. This is an analog technology using electrical image intensifiers. These will not produce any image if there is no available light, such as in a completely dark room sealed from any light entering.
Resolution is measured by "line pairs to millimeter". Military grade NVGS are required to be a minimum of 64 line pairs per millimeter.
The Vietnam War era Starlight Scope was a Generation 1 night vision technology using a series of Phosphor Screens and Photocathodes making the unit large and somewhat heavy. They were sensitive enough to operate well off of the light from stars on a clear light or moon light. Later in the 1970s Generation 2 technology improved the system by adding a Microchannel Plate thus decreasing the overall size and weight, and increasing sensitivity so that the unit could perform well on darker or cloudy nights. Generation 3 technology was introduced in the 1980s and improvements included a longer useful lifespan of the unit as well as better resolution and greater light sensitivity.
Consumer Example: PVS-14 Night Vision Monocular Gen 3
Thermal Imaging
Requires no external light source so it can be useful when outdoors or in a completely dark room without any light. Operates by detecting long-wave infrared light which is an emissive light source or more commonly thought of as heat. Thermal Imaging works well in fog and smoke unlike the other two night vision types. This technology also offers the longest range as the most distant objects with a heat signature can be easily detected. This is a digital system prone to slight motion delays the same as active illumination systems.
Consumer Example: Pulsar Core RXQ30V Thermal Scope
