I really don't know much about night vision equipment.  Most of what I've seen has an IR illuminator.  It seems to me that's fine as long as the other guy doesn't have NV capability.

Are there passive night vision devices that just amplify ambient light?

In a defensive situation, if you were using an IR illuminator and the other guy saw it you would just be giving him a target.

Just don't turn on the IR illuminator; if it were a concern (rightlly so in a tactical situation, put black tape over it).  I'm assuming you are looking at devices which have the IR as a switch on and off (mine does).  Also, there are the pure infrared devices, but those are $12000.  

Most all the Russian gen-1's have illuminators because they need them; they don't work usefully at all without them. A lot of these illuminators are not-optional (there is only one power switch for both, and the illuminator turns on with the NV tube). And to top it off, alot of these illuminators are not-invisible; they plainly glow a deep red. You don't even need another NV scope to see them.

.....Gen-1's that need active illumination are very-un-tactical. I don't recall reading of any military or police that fields gen-1 equipment anymore. Gen-1's work only slightly better than a big flashlight, but cost a lot more and are not as durable.

If you can afford to buy gen-2 ($1000+) or gen-3 ($2400+) they may have an optional illuminator (with a separate switch). But a lot of the time outdoors, they won't need it.

Good NV is damned fascinating to play with, but the prices are steep and it's not real useful for most of us.
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I have what's called a gen 1+.  Works decently without illumination, looks like a flashlight beam on my target (in the viewfinder) when I flip it on.  Same switch, just an additional position.  I guess a good rule of thumb would be to not buy something where the IR is full-time.  (Never saw one, so I just take your word.)

Illuminators are quite common on current third gen technology as well. My PVS 14 is equipped with one built in. As far as I know all of these units are as well as the 6015.

The thing about illuminators is they are almost always necessary in enclosed areas such as buildings due to less ambient light. You will also find they can be useful when working in wooded areas as they can be darker than the surrounding open field or road areas as well.

IR illuminators are very useful and, in some cases, completely necessary.  Be sure to follow common sense guidelines when employing them and the advantages will be tremendous.

My personal favorite is the little Surefire M1 single cell light. It is dedicated IR and puts out a tremendous amount of light due to no filter.  It is applicable for situations up to about 50-75 yds.

Easily the best accessory you can get for use with NV.

Gen 3 works in most conditions w/out a IR source.


Da Torch, by Victor (on this board), belts out IR past 300 yards