Think Defence wrote about the apparently new purchase of some laser-based counter-sniper sensor for the UK's army.
It's strange. All counter sniper sensor approaches appear to have substantial deficits (such as acoustic systems failing against subsonic bullets; an example for subsonic sniper rifle is this), but I'm surprised anyone is still looking much at the "laser reflections give away optics" approach. This approach was already used during the early 90's in the "Stingray" modification of Bradley, and kept having troubles in several iterations as far as I can tell.
One of the fundamental problems is that the sniper can basically counter it in a minute with duct tape. You probably know the anti(sun)-reflection device for sniper scopes; cover the lens with something, then add a slit into it. A surprisingly small slit suffices for almost unimpaired view. Example from quick google search:
|anti-reflection slit cover for the scope|
It works also on binoculars. You would likely need to look directly at the sensor for the sensor to detect your optic despite this countermeasure.*
Furthermore, it's like the explosives sniffer dogs patrolling along often-mined railways and getting countered by partisans dispersed TNT granules: You can boost the false alarm rate easily.
All you need to do is to disperse glass balls, 90° angled or curved reflectors (mirrors) and so on in the landscape. A smart opponent will do so once (s)he understands the challenge.
Last but not least, a sniper does NOT need a scope. Open iron sights (such as diopter sights) are accurate enough out to 300 m without much training (I disliked the G3's diopter and have no steady aim, but I was good at least on the 300 m shooting range!), and out to 500 m under fine circumstances in skilled hands. Today's snipers pride themselves in their lethality at long ranges such as 700 m or more than a kilometre. Historically, almsot all sniping was done at much shorter ranges, below 600 m with majority even happening within 300 m. This wasn't because of the limitations of the guns, but because opponents in a real war become careful and simply don't show themselves that much. You simply cannot see them that often at 600+ m.
The likely most deadly sniper ever did most of his kills with open sights.
All too often Western military equipment procurement fails to take into account basic countermeasures, betting on our opponents being incapable anyway. That's probably even a successful bet, but what does this tell about our employment of our military. How can incapable opposition be a threat to our security at all?
2012-03 The missing information on equipment
2011-11 Sniping: History and theory
2010-08 The sense of smell for reconnaissance
2009-03 Acoustic sniper detection systems and their weak spot
*: To be honest, I'm not 100% sure this slit thing would work (I would love to see a test of it), but considering the other examples it doesn't really need to..