The camera lens detector is quite ingenious, though it only works for locally monitored cameras. You look through the hole in the device and slowly scan the room for camera lenses while listening for the uncontrolled guffaws of the camera operator. An advanced Audio Ribaldry Locator algorithm will then pinpoint the source.
Yes, but ...
If the hidden camera works in the IR, but reflects into a wide beam in the visible, there won't be any cat-eye retroreflector effect to reveal the hidden camera to the eye.
An IR camera detector with coaxial IR source can see the cat-eye effect. For sensitivity, it may be useful to modulate the IR source and synchronous detect the detector output.
Some video cameras (Sony?) can be modified to do this, by removing the IR absorbing filter on the image sensor.
Joe Gwinn
A lens with a scatterer at the focus works like a cat's eye. (Which, not coincidentally, is also a lens with a scatterer at the focus.) Back in the film camera days, pictures of people taken with direct flash usually showed 'red eye', due to precisely this effect.
Some years ago, I worked on a patent case (*) at the International Trade Commission. (The ITC is an administrative law 'court' operating as part of the Commerce Department. The fancy-schmancy name probably lets them pay the judges less.) ;)
This one was a real beast.
Back in 1967, during the Vietnam War and soon after the invention of the laser, some bright spark working for the military came up with this scheme for killing enemy snipers: you send out a broad collimated laser beam from a scope, and shoot a .50-caliber round at the places where you see those bright red-eye glints. With perfect aim, that would send a bullet right through the poor guy's sniper scope, but anywhere close would probably be sufficient. So naturally our bright spark filed a patent on the idea of sending out a collimated laser beam and detecting the back-reflection.
Of course, the patent was immediately classified, and so nobody knew about it for over 40 years. Lots and lots of laser applications developed in which this technique was used, including essentially all optical disk systems, laser radars, long-distance lidars, and many, many others.
Then in the mid-teens it got declassified again, and suddenly there was this patent that covered a good third of all laser applications, amounting to tens of billions of dollars per year, *and had 20 years to run.*
I got hired to help defend Samsung against this one. ITC cases are real rocket dockets, typically taking nine months to a year to reach final judgment, versus two or three years for a normal district court case. I did only a part of the work on it, but kept an eye on its progress.
Samsung settled out of the case, but the other defendants soldiered on and eventually won on a technical legal point: the plaintiffs lacked 'prudential standing', i.e. they hadn't made sure they had clear ownership of the patent. That was a huge black eye for the plaintiffs, and especially their lawyers: it looked like they owned the world, and they wound up with zilch.
Lucky escape for everybody else, of course.
Cheers
Phil Hobbs
(*) Optical Devices LLC v. Lenovo Group et al. Investigation 337-TA-897, US International Trade Commission, 2014
Classifying a patent is a direct conflict with the concept.
But happens all the time, especially when a shooting war is involved, and there is nothing the inventor can do to stop it. One would hope that the inventor is compensated for this taking, but the government's opinion of worth may differ from the inventor's opinion.
Phil: What is the patent number?
Joe Gwinn
The patents were issued to Norman R. Wild and Paul M. Leavy.
RE40,927 RE42,913 RE43,681
Cheers
Phil Hobbs
Thanks. I'll be off reading.
Joe
I've read them. It would seem that they were trying to patent the idea of retro-reflectors, and I wondered about that, retroreflectors having been patented in 1934:
.
Two of the reissues eliminate those claims, but one does not, so I'm missing something.
Also there was a lot made of the mechanical position of the retroreflection within the optical system. What are they getting at?
As for secret patents, I notice that all the assignees were all defense contractors, originally the rubble from the collapse of Sanders, so I bet they made significant money on this, only uncloaking when this trick was general knowledge.
Joe
The red eye effect is distinct due to its much larger angular subtense and lack of cube corners. Back in 1967, highway signs weren't nearly as bright--they were just paint. Somebody thought of putting glass beads in the paint, which made them much brighter, but not like today's.
They want to shoot the enemy sniper right in the eyeball.
Yeah, if you're an employee you don't get much of anything from a patent. IBM used to have a fairly generous patent awards program--over the years I probably made about 2 years of one kid's college tuition off it.
Naturally they recently gutted it.
Cheers
Phil Hobbs
Sounds like one would want a scope that is not only telescopic but also periscopic.
Yes. That's one of the alternatives shown in the patents.
Joe Gwinn
Sure, but it was prior art to all that.
Cheers
Phil Hobbs
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