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Light Damage

Light Damage: Causes, how to avoid it, and factors that play into tube performance

One of the most commonly asked questions by new night vision users and those looking to get into night vision is how much light a night vision device can take without damage.  Night vision is a big investment and one of the obvious fears by any night vision user is permanently burning their tubes.  Although it is important to understand there are no guarantees, this article can be used as a guide to help avoid unnecessary burns.  Please note that Licentia Arms Co. does not warranty against light burns and this article is aimed as a guide and is in no way a guarantee.

There are two main types of burns that we will address in this article, temporary and permanent burns.  A temporary burn is a burn that appears in a tube, for any of the various reasons we will address below, that works itself out of the tube and does not last permanently.  Temporary burns mainly show themselves in the form of what looks like a shadow.  These temporary burns typically still give you an image through them but just are not as bright as the rest of the tube.

Permanent burns are burns that once in the tube are permanent and do not go away.  These will be in the tube for the life of the tube.  These typically appear in the form of a black blem where no image is received in that part of the tube.  They also occur when temporary burns do not have time to work themselves out of the tube before the unit is powered off.

Both temporary and permanent burns happen due to three main causes: long exposure of a static image, laser burns, or from concentrated light source exposure.  Night vision tubes are meant to be used and ran in dynamic lighting conditions and modern tubes handle variable light very well.  However, one mistake people make is allowing their night vision to be left in the same position with no movement for long periods of time.  This mistake largely happens in two main scenarios, leaving the unit on while not in use and rifle mounted applications behind a red dot.  Although night vision can handle dynamic lighting conditions very well, if a tube is left on the same image for long period of time, A light source that normally would not burn a tube can indeed leave a burn.  An example of this is leaving a PVS-14 mounted behind a NV compatible red dot for long periods of time.  Since the reticle is brighter than the environment (hence why you can pick it up) over exposure burns can frequently happen.  Another example of this is sitting the unit down on a table or flipping it up on a helmet mount while the unit is still turned on for extended periods of time.  To avoid long exposure burns we recommend that if the unit is not in front of the user’s eye, that it be turned off to prevent unnecessary damage.

In addition to long exposure burns, laser burns are another very common burn that we see.  Laser burns happen in two ways, over exposure and by direct contact with the tube.  Over exposure burns from lasers happen when a unit stares at a laser / illuminator in the same position for long periods of time.  This commonly happens when a unit is set up stationary for filming or with clip on devices on tripods with a constant laser / illuminator throw.  To avoid this, practice good laser discipline and only deploy your laser / illuminator when needed.  The second type of laser burn is when a laser makes direct contact with the image intensifier tube.  This can happen both from reflective surfaces and during training if a laser is pointed directly at your night vision.  Direct contact laser burns are almost always permanent and will not go away with time.  To avoid direct laser burns be mindful of reflective surfaces and angles.  If you blast a laser at a mirror or piece of glass it can bounce right back at you and burn your tubes.

The final cause of light damage is also one of the most common burns that we see and happen when people misunderstand what autogated tubes can handle.  When tubes are autogated they help protect themselves from light damage.  However, autogating can only protect tubes from environmental changes that affect the tube as a whole.  For instance, if a bright flashlight is shined down range the environmental conditions are changing making what is seen through the tube all brighter.  This is where autogating kicks in and helps protect the tubes, however, autogating cannot protect against concentrated light sources that greatly differ from the environment.  A perfect example of this is isolated light sources such as streetlights on dark roads.  Since the environment is dark and the streetlight is very bright, looking directly at the streetlight could burn your tube. 

One thing to note is that environmental lighting conditions play a huge part in what will burn a tube and not.  Concentrated light burns happen because of a large difference in brightness of a light source and the surrounding environmental lighting conditions that the tube can see. Thus, causing the tube to not be able to compensate by autogating, in turn burning the tube.  This means that the variance in brightness from a concentrated light source and the environment is much more important than the actual light source itself. 

If while using night vision you notice a burn in the tube, there are several ways to try and get the burn out of the tube.  If the burn is slight, they often work themselves out.  However, for more intense light damage the best way is to black box the unit by leaving the unit on in a bag or case where no light is hitting the photocathode.  This lets the tube reset and work the burn out.  If a burn happens and the black box technique isn’t possible at the time, a good way is to get burns out is to flash a bright flashlight or illuminator down range a few times which can kick in the autogating and help the tube work the burn out.  As a general rule of thumb, if a unit is black boxed over night after a burn happens and the burn is still in the tube it is likely a permanent burn.

With all of that being said, night vision is meant to be used and current tube technology is very good at handling light.  These are simply examples of common burns we see and how to avoid them.  Although the information in this article can be extremely helpful to those who do not have a lot of time under night vision in varying environments.  The absolute best way to tell what your tubes can handle is to use them.  Temporary burns are inevitable with use and will teach you what their limits are.  Time spent under night vision is the best way to learn.