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'[ee] Re: cell phone cameras'
2006\10\09@144415 by Robert Rolf

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Subject tag added.

David VanHorn wrote:
> I've been asked to come up with a device to prevent cell phone camera use.
>
> Anyone have links/info to share?
>
> This is NOT an RF jammer, this is an optical (probably IR) device to
> "confuse" the camera into unusable pictures.

Not possible! (prove me wrong)

Any CCD/CMOS color camera has an IR cut filter to prevent IR from messing up the red channel.
You would need extremely bright IR to affect the camera's exposure adversely.


Try firing a remote control into cell camera. You will see only a faint glow.
Even if you could make it brilliant, it would only be a small percentage of the
field of view, it would have little effect on exposure.

You will also not likely be able to detect use of the camera since FCC/EC regulations on RF
emissions would make the pixel clock (the usual way spy cams are detected) too faint.

Nothing short of a destructive EMP, or total darkness
(and then only if the camera doesn't have a flash), will prevent a cell camera from working.
Only physical confiscation will. And with the 'airplane mode' on the new multiuse phones
(e.g. MP3 player), you can't even use 'cell phone detectors' to see if the phone is on.
At least not easily.

Robert

2006\10\09@151101 by Steven Howes

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part 1 1676 bytes content-type:text/plain; (decoded quoted-printable)

Strobing a cluster of IR LEDs at well over their rated current will cause the camera to auto adjust the light, making it dark with light flashes, but it is FAR from perfect.


{Original Message removed}

2006\10\09@151114 by David VanHorn

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On 10/9/06, Robert Rolf <spam_OUTRobert.RolfTakeThisOuTspamualberta.ca> wrote:
>
> Subject tag added.


thanks :)

Any CCD/CMOS color camera has an IR cut filter to prevent IR from messing up
> the red channel.
> You would need extremely bright IR to affect the camera's exposure
> adversely.


Extremely bright isn't a problem.
Pulsed banks of high power emitters is within reason, as long as we don't
reach a point where it's dangerous to humans.


> Even if you could make it brilliant, it would only be a small percentage
> of the field of view, it would have little effect on exposure.


I'm thinking in terms of illuminating the room with enough IR, pulsed, so
that the autoexposure is either way too bright, or way too dark. If I push
it into long exposure and motion-blur everything, that's acceptable too.
Mounted camera vs non-moving target is not likely in this area.

>
> Nothing short of a destructive EMP, or total darkness
> (and then only if the camera doesn't have a flash), will prevent a cell
> camera from working.
> Only physical confiscation will.


That's what they are doing now, but some people become upset when you
forcibly separate the halves of their phone and drop the remains in a bucket
of salt water.

2006\10\09@151544 by Shawn Wilton

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You know, I would SWEAR that there was a story a short while ago about
someone at MIT that had come up with a solution to this.  Google for it.

Wish I could provide more information.



On 10/9/06, Robert Rolf <.....Robert.RolfKILLspamspam@spam@ualberta.ca> wrote:
{Quote hidden}

> -

2006\10\09@153013 by Robert Rolf

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>>You would need extremely bright IR to affect the camera's exposure
>>adversely.
>
> Extremely bright isn't a problem.
> Pulsed banks of high power emitters is within reason, as long as we don't
> reach a point where it's dangerous to humans.

It would have to be VERY bright. And pulsing doesn't gain you anything since
the sensor will integrate the exposure over it's frame time.
And all the IR will do is provide MORE illumination to the subject, unless
the emitters are just glaring into the lens. And any good camera will ignore
'lights' in computing the exposure.

> I'm thinking in terms of illuminating the room with enough IR, pulsed, so
> that the autoexposure is either way too bright, or way too dark.

The AE is not going to make it way too bright. Since you are providing more light,
it would cut down the exposure time, darkening that which is not illuminated by the IR.
BUT, what IS illuminated by IR will be nicely exposed.

> If I push
> it into long exposure and motion-blur everything, that's acceptable too.

Only way to do that is to REDUCE the illumination.

> Mounted camera vs non-moving target is not likely in this area.

I suspect you've been asked to protect ladies from cameras in their exercise room?

>>Nothing short of a destructive EMP, or total darkness
>>(and then only if the camera doesn't have a flash), will prevent a cell
>>camera from working.
>>Only physical confiscation will.
>
> That's what they are doing now, but some people become upset when you
> forcibly separate the halves of their phone and drop the remains in a bucket
> of salt water.

Well, that's about the only sure fire method.
Guess it's more serious than peeping toms.

The only reliable method is physically barring entry.
I could just as easily smuggle in a 16mm 'spy' camera and your IR would have ZERO
affect on that. And a metal detector wouldn't find it either.

Robert

2006\10\09@155453 by David VanHorn

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>
>
> It would have to be VERY bright. And pulsing doesn't gain you anything
> since
> the sensor will integrate the exposure over it's frame time.


The autoexposure part has to look at light over a time interval. I'm hoping
to find that interval, and do something that's maybe 1/2 Hz off that, so
that it over/under estimates each frame.

And all the IR will do is provide MORE illumination to the subject, unless
> the emitters are just glaring into the lens. And any good camera will ignore
> 'lights' in computing the exposure.


Glaring into the lens is a possibility, and ignoring it would be very hard.


>
> The AE is not going to make it way too bright. Since you are providing
> more light, it would cut down the exposure time, darkening that which is not
> illuminated by the IR.
> BUT, what IS illuminated by IR will be nicely exposed.


My thought is to provide varying illumination so that an averaged reading
will give black stripes in the image, or over and underexposed images, or
something of that effect.


> I suspect you've been asked to protect ladies from cameras in their
> exercise room?


No, but it's close enough to use as a test case.



> Well, that's about the only sure fire method.
> Guess it's more serious than peeping toms.


:)

The only reliable method is physically barring entry.
> I could just as easily smuggle in a 16mm 'spy' camera and your IR would
> have ZERO affect on that. And a metal detector wouldn't find it either.


Minox 8mm would be better, but you'll still have to be more than normally
clever to pull it off.   I have a nice minox B, with handmade motor drive to
close and open the camera after every frame.  BTDT.  My father did film-type
intel work for the military.

Robert
>
> -

2006\10\09@161006 by Jinx

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> You know, I would SWEAR that there was a story a short
> while ago about someone at MIT that had come up with a
> solution to this

Thunderbirds had it licked 40 years ago. And that was for
film cameras too. That Brains, man, clever guy. For a puppet

> > Nothing short of a destructive EMP, or total darkness

Won't be long before the see-anywhere camera phone

Israeli researchers combine IR camera, cell phone

http://www.eetimes.com/news/latest/showArticle.jhtml?articleID=178600334

Dave, if you do manage to work this out, you'll be a multi-
millionaire (every girl with a short skirt will want one). And
I'd like you to remember who your friends, your very best
and caring friends, are ;-)

2006\10\09@161957 by David VanHorn

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>
> The autoexposure part has to look at light over a time interval. I'm
> hoping to find that interval, and do something that's maybe 1/2 Hz off that,
> so that it over/under estimates each frame.
>

A little prelim testing with my Samsung blade phone says this is doable.  An
IRLED pulsed at a low rate does cause the camera's brightness to band and
blank.

Now it's down to engineering. :)

2006\10\09@162306 by Mitch Miller

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www.google.com/search?hs=RZg&hl=en&lr=&safe=off&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&q=defeat+camera+ccd+light&btnG=Search
http://www.livingroom.org.au/photolog/news/new_system_blocks_digital_photography.php

Although neither of these are the original story I read.

-- Mitch



Jinx wrote:
{Quote hidden}

2006\10\09@162943 by David VanHorn

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>
>
> Dave, if you do manage to work this out, you'll be a multi-
> millionaire (every girl with a short skirt will want one). And
> I'd like you to remember who your friends, your very best
> and caring friends, are ;-)


I don't think this will work out to be portable.

I did have some fun with picket signs a while back, putting a message in
IRLEDS underneath a thin paper cover with a different mesage.  The IR
message only shows in camcorders. :)

2006\10\09@165432 by Robert Ussery

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face
GIT, not MIT!
http://gtresearchnews.gatech.edu/newsrelease/anti-camera.htm

That's the original story. No real technical details, but maybe it'll
point you in the right direction, Dave.

Not exactly a portable solution, but great for theaters, classified
areas and such.

Robert
(Georgia Tech undergrad :o) )

Shawn Wilton wrote:
> You know, I would SWEAR that there was a story a short while ago about
> someone at MIT that had come up with a solution to this.  Google for it.
>
> Wish I could provide more information.


2006\10\09@170106 by Herbert Graf

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On Mon, 2006-10-09 at 14:54 -0500, David VanHorn wrote:
> >
> >
> > It would have to be VERY bright. And pulsing doesn't gain you anything
> > since
> > the sensor will integrate the exposure over it's frame time.
>
>
> The autoexposure part has to look at light over a time interval. I'm hoping
> to find that interval, and do something that's maybe 1/2 Hz off that, so
> that it over/under estimates each frame.

Which might have a chance of working, with one particular model of
phone. All the others will likely work just fine.

I find the whole idea pointless. No matter what you do, a SERIOUS
peeping tom will find a way, there's no way to stop it. If just giving a
false sense of security is good enough, then go ahead. Otherwise I
personally believe it to be a waste of resources.

Frankly getting rid of photo cell phones is kinda pointless since it's
so blatantly obvious they are being used. The to worry about and catch
are the ones attaching spy cams to their shoes.

TTYL

2006\10\09@170743 by David VanHorn

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On 10/9/06, Robert Ussery <uavsciencespamKILLspamfrii.com> wrote:
>
> GIT, not MIT!
> http://gtresearchnews.gatech.edu/newsrelease/anti-camera.htm
>
> That's the original story. No real technical details, but maybe it'll
> point you in the right direction, Dave.


I read something years back, about crystals, like you'd find in a DPSS
laser, that would lase against any shiny surface.  The reflections were
"time reversed" somehow.  They showed it lasing against a spoon.  They could
track the object in realtime, without any electronics, mechanics, or
anything (within limits, i'm sure)   The researchers had to cover all shiny
surfaces, and wear what amounted to an "optical gillie suit" to work with
them..

Cute, but lasing into people's eyes would probably be frowned on.

2006\10\09@171738 by Sergey Dryga

face picon face
Jinx <joecolquitt <at> clear.net.nz> writes:

> Dave, if you do manage to work this out, you'll be a multi-
> millionaire (every girl with a short skirt will want one). And
> I'd like you to remember who your friends, your very best
> and caring friends, are

New fashion - mini-skirt with IR LED cluster!

Sergey




2006\10\09@205359 by Martin K

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There might be interesting (adverse) human effects to very "bright"
flashes of IR, no?
--
Martin K

David VanHorn wrote:
{Quote hidden}

2006\10\09@213846 by Mario Mendes

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If anything, those exposed may get a tan ;)

-----Original Message-----
From: .....piclist-bouncesKILLspamspam.....mit.edu [EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu] On Behalf Of
Martin K
Sent: Monday, October 09, 2006 8:51 PM
To: Microcontroller discussion list - Public.
Subject: Re: [ee] Re: cell phone cameras


There might be interesting (adverse) human effects to very "bright"
flashes of IR, no?
--
Martin K

David VanHorn wrote:
{Quote hidden}

2006\10\09@214813 by David VanHorn

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On 10/9/06, Martin K <martin-distlistsspamspam_OUTnnytech.net> wrote:
>
> There might be interesting (adverse) human effects to very "bright"
> flashes of IR, no?


Doubtful.

2006\10\09@214854 by David VanHorn

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On 10/9/06, Mario Mendes <@spam@piclistKILLspamspammmendes.com> wrote:
>
> If anything, those exposed may get a tan ;)


If we cut the wavelength by a factor of three, maybe.

2006\10\09@232058 by William Chops Westfield

face picon face

On Oct 9, 2006, at 6:48 PM, David VanHorn wrote:

>> There might be interesting (adverse) human effects to very "bright"
>> flashes of IR, no?
>
> Doubtful.
>
Near IR, as emitted by semiconductor lasers, etc, can be especially
dangerous to human eyesight because it is close enough to optical
wavelengths to be focused to high-intensity points on the retina
but not "visible" enough to trigger iris, blink reflex, or conscious
avoidance.  Or so I recall hearing somewhere...  High intensity LEDs
would probably have the same problem.

BillW

2006\10\10@081026 by Martin K

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Well, you better be sure before putting it around people for the sake of
"security"
This is some manufacturing facility and your client is really worried
about their IP getting out, right?
These days everything is considered a vital trade secret.
--
Martin K

David VanHorn wrote:
> On 10/9/06, Martin K <KILLspammartin-distlistsKILLspamspamnnytech.net> wrote:
>  
>> There might be interesting (adverse) human effects to very "bright"
>> flashes of IR, no?
>>    
>
>
> Doubtful.
>  

2006\10\10@095418 by Mike Hord

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> >> There might be interesting (adverse) human effects to very "bright"
> >> flashes of IR, no?
> >
> > Doubtful.
> >
> Near IR, as emitted by semiconductor lasers, etc, can be especially
> dangerous to human eyesight because it is close enough to optical
> wavelengths to be focused to high-intensity points on the retina
> but not "visible" enough to trigger iris, blink reflex, or conscious
> avoidance.  Or so I recall hearing somewhere...  High intensity LEDs
> would probably have the same problem.

It takes an awful lot.  I'm not an ophtalmologist, or an optical engineer,
but I do know that low-power lasers (1mW and less) stand almost no
chance of damaging the eye, even with fairly long exposures (this from
an eye doctor), and I think any diffuse light source would be hard
pressed to match a 1 mW laser in energy per unit area density.

Plus, I looked into this once for a project using IR as an eye sensor.
The amount of light required to even move toward eye damage is
truly huge.

Of course, it may take a lot of light to ensure the cameras don't
work.

Mike H.

2006\10\10@113116 by David VanHorn

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>
>
> Plus, I looked into this once for a project using IR as an eye sensor.
> The amount of light required to even move toward eye damage is
> truly huge.
>
> Of course, it may take a lot of light to ensure the cameras don't
> work.


I'll check into that once I have a better handle on the modulaton and light
levels required to be effective.

It's a pity that the cam chip folks don't implement a "denial" signal. That
would be pretty easy for them, just detect a standard pattern of level
shifts over time, and simply refuse to take a picture.  It would go a ways
to curb the negative reactions to camera phones.

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