Laser Scanner Can Detect Someone Watching You A Kilometer Away

I can think of a few inexpensive methods of covering a lens that would neutralize this.

you're right to a point, but if you work in defense a lot of the time an advantage you demonstrate forces opposing forces to either change their game or up their technology to keep up. As for lesser capable forces it might be years before they recognize why or how they lost a man, tank, radar installation etc. I applaud this system, not scoff at it.

It's a bit like radar and stealth. There are materials, coatings and angled surfaces that will deflect and attenuate laser energy.

A simple example is a broad-spectrum neutral gray filter angled at 45 degrees. Let's say it has a transmission of 20%. That would still let enough light through for me to see my target. BUT - The primary reflection of the laser is lost at that 45 degree angle. The laser energy that goes through it has to make 2 passes, once in and once back out, before getting back to the sensor. That means only 4% of the energy returns, multiplied by the low reflectance (less than 0.5%) off the lens surfaces of my 'scope. And if I have my lenses coated with 'moth-eye' coatings, the reflectances are even lower.

In addition to this simple example there are notch filters and circular polarizing schemes, neither very expensive, that would attenuate the beam. If I then locate a bunch of dummy lenses nearby (think chaff) the sensor won't see me since it will be busy sorting out the clutter.

I appreciate the idea, I just don't see it as practical. The countermeasures are too easily obtained and any decent optics engineer would know them.

would those be some of the same engineers that protected the 10's of thousands of Republican guard that were wiped out with low tech carpet bombing in Iraq? it's an endless argument, The Cole had huge firepower and was almost taken out by a very low tech, low speed attack, I agree with almost every point you made but I think another layer always causes problems for an enemy. I love tech and don't think for a moment this system is an "answer all", just a cool tool along the lines of a "firefinder"...it wasn't perfect but it resulted in plenty of great counter attacks but would never stop them all as The Cole incident proved

No, those would be the Engineers at Lockheed who developed the stealth technology used in the F-117 that blew up many of the radar installations.

I think this works quite differently than you expect. If i am correct in my assumption about how this works, then your methods intended to defeat this system, will actually make you even more detectable rather than less! I'm assuming that this works by detecting scattering rather than reflection. We found out by accident how well this idea works when we were experimenting with laser based long range listening devices....

My comments were based on what the article said - how it described the operation of the device - and based on my knowledge of lasers, filters, lenses and optical coatings. I've been doing this kind of work for 25+ years, mostly in opto-electronics for military applications. So I've had experience with a lot of this stuff.

Could I have overlooked something? Sure. If the DOD decides to spend $Ms or $Bs of our tax dollars on this, I would hope it is not as easily counter-measured as I suspect it is.

What we discovered by accident is that any optics that our listening beam hit acted as a dead zone! We were unable to "listen" to vibrations when the beam accidentally encountered a telescope lens in the room we were targeting. Even though it was first passing through a plate glass window that should have returned a good signal! I'm not an optics expert, just someone who happened to observe this phenomena....

And a simple laser detector will let you know if someone else is trying to find out if you are watching them.

Terrorists already use simple cell phone cameras to detect targeting lasers and their sources.

Are eyeglasses optical glass? Magnifying glasses?

The article says the system can tell optical glass from broken bottles and so forth.

Could it be confused by scattering old eyeglasses around? Save the lenses from broken cameras, binoculars, hunting scopes to use to create decoys?

Mirrors work wonders for disrupting laser beam "intelligence" especially fresnel lensed mirrors.