Night Vision Devices (NVDs) are complex and delicate optical systems that react to light at a microscopic level. As a result, the image in them may contain certain defects — both manufacturing and those arising during operation. In this article, we will look at the difference between factory spots, blemishes, tracing, emission points, and methods for their detection and prevention.
🔸 Factory Spots
Factory spots are small black dots that appear during the production of the image intensifier tube (IIT).
Manufacturers divide the image into three zones:
- Zone 1 — the center of the image, where the presence of spots is unacceptable.
- Zones 2 and 3 — the edges of the field of view. Here, the presence of spots is acceptable for lower-class NVDs.
The higher the class of the device, the stricter the requirements for allowable defects.
⚠️ Blemishes — why this is dangerous
A blemish is a defect that occurs after the assembly of the NVD.
Main causes:
- Mechanical impact (shock, drop)
- Light damage (laser, prolonged pointing at a light source)
Such damage can look like "bruises" or darkening in the field of view.
🌞 Image Burn-in
If an NVD is pointed at a bright object for a long time, the image can literally "burn into" the screen. This often happens when the device is left on, pointed at car headlights or other light sources.
✏️ Tracing
Tracing is light streaks that "trail" behind bright objects. This is not a permanent defect, however, it can be annoying. Some NVD models exhibit this effect more often than others, especially in the first minutes after switching on.
✴️ Emission Points
These are bright points that glow even in complete darkness. If such a point does not disappear under strong lighting — the microchannel plate is likely damaged. Such defects can increase over time.
Conclusion
Night vision devices require careful and attentive handling. Factory spots are acceptable, however, damage arising during operation can be irreversible. The sooner you detect the problem and take measures (for example, apply the Blackboxing method), the more chances there are to save the device's functionality. Remember: proper storage, avoiding bright light, and removing batteries are simple but effective preventive measures.
