My setup is:

Night Optics D760 6x gen3, gain adjustable.
Night Optics IRK2 Illuminator

I have found that while hunting, I would like to make a second or third shot on hogs but I am aware that the D760 6x is limited in this respect.  I know that a PVS setup is better for this but in the interest of making those follow up, I purchased a OTAL-C.  The OTAL-C is really nice.  Very small, light and easy to setup.  The IR dot is really bright out at 100y and the adjustments are easy if you read the manual.  Onto my question....

I noticed that through the 760, when I turn the IR laser on for a few seconds and turn it off, it leaves a dark spot that you can see through the tube.  It goes away after about 15-20s.

For those experts on the subject of IR laser damage, what is going on the cause the dark spot?

Can it hurt the tube?  I have heard of laser damaged tubes but never seen it before.

I know lots of guys use them on PVS (unmagnified) setups without problems, am I going to have an issue long term?

I have not seen this topic of laser damage addressed before.  With the intro of the $500 IR laser like the OTAL-C, it seems to be a worthwhiile discussion.  Thanks.

LD

I believe the D760 has a L-3 tube in it and should have an autogated power supplies which is probably causing what you are experiencing if I were to guess.

over the shelf civi lasers have such low power I dont think you could damage a tube even if you tried, especially an autogated tube. short of just sitting there shining a laser right into the optic.

What it sounds like is happening is when you fire the laser up the autogating adjusts your image due to the added light from the laser. When you turn the laser off the autogate relaxes and takes a few seconds to return to the normal image with no added light.
you may get the same result from a street light or headlights, the tube will dim the image to protect itself.

now if you were using a 3b laser and someone was pointing it at you I might see the potential to cause some damage.

Its not the whole tube that gets dark, just a small spot.  I am hopeful that it wont cause damage.  For now, I am using pressure switch for minimal on time.  Thanks for the response.

LD

if its leaving a mark like that , then it will soon become a dark smudge that will stay there , and the laser will always be on the same bit of the tube , if you can turn the gain down on the scope it should help and perhaps use an illuminator or turn the laser down more if it will.      tubes find it hard to protect themselves from small points of light

If it's temporary as you described, it could just be charge depletion of the MCP in that area because of the intensity of the light.  Like the others said if it's exposed too long like that it could become a permanent blemish.

I will start by saying ALL light harms your photo cathode. Light in one spot on the photo cathode will harm that spot. Now the harm is the amount of light X time. The life span of a photo cathode is when the sensitivity of the photo cathode is half of what it was brand new. When a laser reflection always shows up in the same spot as with a laser and night scope mounted on the same rifle, it will quickly make that spot less sensitivity. Using a head mounted PVS14 spreads the loss of sensitivity around so it takes much longer to cause a noticeable problem as the dot does not always show up in the same spot.  

If it's a relatively low-power laser ( and it sounds like it ) then the biggest danger is probably burn-in on the tube. This would be a permanent dark spot on the tube when the laser is off, and it's probably right in the middle of the riflescope crosshairs, so you don't want image burn-in there.


Try not to leave your laser and D760 on at the same time. Autogating won't help, and neither will BSP in this case. Burn in is rather nasty like that.


A few seconds or even a minute from time to time probably won't leave permanent damage, and you'll notice if it starts and can use the sock-drawer method to recover somewhat.


Leaving both on for a few hours will result in a bad outcome, likely including permanent damage.


Regards

David

Out of my depth here, but I'd like to help.

Do you need the total output of the laser?

You could put a neutral density filter or something in front of the laser emit port, and reduce its intensity.


I say that because my pistol laser is way, way, way too hot for what I need, so I think I'll cut a circle out of some window tint with a hole punch and try to knock it down some.

I experience something similar with my PVS14. When I first turn it on, and happen to scan through an area that has a bright light, like a street light far off in the distance, it will leave a temporary dark mark "shadow" in the image. If I'm scanning from side to side across the light source, it will appear as a dark line or dark shape across the image. This goes away quickly though. At first, I was concerned about this but now I realize that it always goes away after a few seconds.

I assume this is something normal for NV.

Plenty of tubes do this. I have tubes that look like a darn road map when scanning across bright lights. It goes away in a minute or so. It is called phosphor persistence. The property of a phosphor that determines its ability to emit light for a period of time time after the stimulus has been removed. I have noticed it more on L3 tubes but ITT tubes are not immune from this. Was pretty common with older tubes but the newer ones seem to be much better.

Just the nature of the beast and some tubes are worse than others. It can also be depleting the photocathode. I am not up on all the science of this and CJ7hawk could explain it in more detail. I just know it is a common condition but not harmful to the tube. I just try not to look at bright lights though it is unavoidable at times.

If memory serves me P20 phosphor used on older tubes was very prone to phosphor persistence. I believe the newer tubes use a P43 phosphor which is not as susceptible to the condition. However, tubes still show the condition and some are worse than others.