well as Hanlon tells you! the ranger combat helmet, gives ranger low light optic focus, so they can see better in the dark ( or like they took cateye)
there should be in the next DLC, the option to use the low light optics in the heltmet, or on power armor helmets, add water breathing or protection of gas or whatnot!
and on the combat helmet mark two, give you the ability to turn on the light!

If your on pc you can download project Nevada from nexus and some helmets are like what it would look like not full screen and you get night vision with come helmets

ahhhh PS3 :\