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Comment by Mankhool | Hacker News Reader

I believe that the system is actually detecting the lasers that the cameras use for range-finding, and then using a laser to blind the sensor.

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All cameras I've ever owned used purely passive, optical autofocus with rarely activated IR assist off the flash unit, which only fires when it gets really dark and works only for distances under 10-15 feet.

From the article it's completely unclear to me how could that possibly work: those "lasers" would have to scan every square inch of the landscape (possibly a couple square miles) at the rate of about 100-1000 times per second in order to blind an SLR camera during the day.

Any experts here?

You're exactly right (though I'm no expert). SLRs use contrast detection focusing. I have no idea how you could detect a CCD at any point in space all around you for the tiny fraction (1/1000 wouldn't be uncommon outdoors on a sunny day) of a second that it's exposed, _and_ react to it in that same time span. Sounds to me like someone just scammed a rich idiot out of a bunch of money.

SLRs use phase-detect actually, using separate AF sensors. Contrast-detect is used in compact cameras (non-SLRs) and optionally in live-view mode on some DSLRs.

Agreed, this description makes no sense. If you're talking about a point & shoot camera, or any camera with a live preview where the CCD is continually exposed, then it might work. But a plain old SLR is going to expose its CCD for maybe 1/1000 of a second on a sunny day.

I have seen a system like this that worked by detecting flash photography, and firing a flash back at the source of the original flash. If you react quickly enough to a flash, you can blind the CCD while it's still exposed, ruining the image. Can't find the link right now. But if you don't use a flash, then that system doesn't work.

I think you mean this: http://ahprojects.com/exhibitions/anti-paparazzi

No expert, but is it possible that this technology could be coupled with cameras using an object recognition algorithm? Once it had narrowed the space, it could then scan.

IANAN. The sensor detection sounds pretty unlikely. But what about some other possible methods:

The end of an SLR lens is domed/convex, and slightly reflective (even the best ones are slightly). The lens would have to be pointed at the ship for the system to care about it. In that state, shining a laser at the lens and detecting the reflection would pick up the reflection profile of the convex surface (you'd need a 2d array of sensors to pick up the range of return angles as the laser moves from the center of the lens), and finding the center would be fairly easy - so you'd know where to fire. How many other reflective convex surfaces have their axis of rotation pointed straight at the boat?

I imagine this is mostly a problem when in dock, or at anchor, where the paparazzi are probably all in one location (or a few), so the search space could be very quickly narrowed down by a human.

Seems like a pretty frivolous way to spend money, but at least it's being spent.

My eyes are reflective convex surfaces. They're also averse to high intensity laser light.

Yes, that seems to be the case for military use:

"The JD-3 laser dazzler is mounted on the Chinese Type 98 main battle tank. It is coupled with a laser radiation detector, and automatically aims for the enemy's illuminating laser designator, attempting to overwhelm its optical systems or blind the operator. The ZM-87 Portable Laser Disturber is a Chinese electro-optic countermeasure laser device. It can blind enemy troops at up to 2 to 3 km range and temporarily blind them at up to 10 km range."

http://en.wikipedia.org/wiki/Dazzler_%28weapon%29

Though there was also a bizarre spy incident with Russian "merchant" ship blinding US & Canadian helicopter-surveillance operators where it's not clear if they used laser range-finding:

http://en.wikipedia.org/wiki/Strait_of_Juan_de_Fuca_laser_in...

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