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Video mode: sensor vulnerable to lasers



 
 
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  #1  
Old August 9th 10, 04:23 PM posted to rec.photo.digital.slr-systems
Alan Browne
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Posts: 12,640
Default Video mode: sensor vulnerable to lasers

Be careful when using video mode (or long exposures) when lasers are around.

http://vimeo.com/13450755


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  #2  
Old August 9th 10, 09:07 PM posted to rec.photo.digital.slr-systems
Me
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Posts: 796
Default Video mode: sensor vulnerable to lasers

Alan Browne wrote:
Be careful when using video mode (or long exposures) when lasers are
around.

http://vimeo.com/13450755

Even worse:

http://www.reuters.com/article/idUSL...080714?sp=true
  #3  
Old August 9th 10, 10:57 PM posted to rec.photo.digital.slr-systems
OG
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Posts: 106
Default Video mode: sensor vulnerable to lasers


"Alan Browne" wrote in message
...
Be careful when using video mode (or long exposures) when lasers are
around.

http://vimeo.com/13450755


Would EVF based cameras will have the same vulnerability at all times?


  #4  
Old August 9th 10, 11:01 PM posted to rec.photo.digital.slr-systems
Alan Browne
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Posts: 12,640
Default Video mode: sensor vulnerable to lasers

On 10-08-09 17:57 , OG wrote:
"Alan wrote in message
...
Be careful when using video mode (or long exposures) when lasers are
around.

http://vimeo.com/13450755


Would EVF based cameras will have the same vulnerability at all times?


A good point - I would assume so.

It's germane to note that, in the video shown, only one (or a few) site
failed but all the pixels to the right of it are then rendered useless
as their image data can't be bucket brigaded off of the sensor (this
explains the straight line failure).

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  #5  
Old August 9th 10, 11:08 PM posted to rec.photo.digital.slr-systems
Alan Browne
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Posts: 12,640
Default Video mode: sensor vulnerable to lasers

On 10-08-09 16:07 , Me wrote:
Alan Browne wrote:
Be careful when using video mode (or long exposures) when lasers are
around.

http://vimeo.com/13450755

Even worse:

http://www.reuters.com/article/idUSL...080714?sp=true


I remember seeing a documentary excerpt on setting up lights at rock
concerts in the late 80's. There were always 1 or 2 "laser nazi's" in
charge of making sure the lasers are setup safely and that they "dump"
into something absorbent. I think this discipline is missing in Russia
and likely fading elsewhere. (In a Pink Floyd video a roadie lights his
cigarette with a laser...)

The Russian military (Navy) have been known to light US and Canadian
patrol aircraft with lasers. This resulted in vision damage to a
Canadian helicopter crew in the early 2000's - included a US officer who
was also affected.

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  #6  
Old August 10th 10, 01:08 AM posted to rec.photo.digital.slr-systems
R Davis
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Posts: 42
Default Video mode: sensor vulnerable to lasers

On Mon, 9 Aug 2010 13:51:58 -0700 (PDT), RichA
wrote:

On Aug 9, 4:07*pm, Me wrote:
Alan Browne wrote:
Be careful when using video mode (or long exposures) when lasers are
around.


http://vimeo.com/13450755


Even worse:

http://www.reuters.com/article/idUSL...080714?sp=true


Brainless to fire a Argon laser into a crowd instead of over their
heads. Even those little frequency-shifted green pocket lasers can do
damage, let alone an industrial entertainment laser.


Especially when they are pot-modded to ~100mw. I had a couple visitors here
yesterday, their son wanted to play with my 405nm and green laser pointers
that I have. ($7.95 w/ free shipping from China on E-Bait, but their
potentiometers are adjusted to 5mw to get them through customs.) I
especially like the green pot-modded ones. The beam (not just terminal dot)
is brightly visible in the air in full sunlight. He was having fun lighting
matches with them. I warned him to not stare at the focused beam on the
paper-matches too intently. He was seeing spots for quite awhile.The 405nm
blue laser (same price) is interesting when pot-modded to ~100mw. It makes
some fist-sized crystals I dug out of my rock-shop phosphoresce in a bright
magenta color. As you sweep the laser over the crystals it leaves a trace
of bright magenta for about 1/4th second. This phosphorescence undetectable
under short and long-wave UV. It must be the intensity of the light that
causes it. A pot-modded 405nm laser should be in every rock-hound's bag of
investigative tools. I've no doubt they'll open up a whole new type of
minerals out there now. Categories of short-wave UV
fluorescence/phosphorescence, long-wave UV fluorescence/phosphorescence,
and blue-laser fluorescence/phosphorescence.

  #7  
Old August 11th 10, 02:39 AM posted to rec.photo.digital.slr-systems
R Davis
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Posts: 42
Default Video mode: sensor vulnerable to lasers

On Tue, 10 Aug 2010 14:05:47 -0700 (PDT), RichA
wrote:

On Aug 9, 8:08*pm, R Davis wrote:
On Mon, 9 Aug 2010 13:51:58 -0700 (PDT), RichA
wrote:

On Aug 9, 4:07*pm, Me wrote:
Alan Browne wrote:
Be careful when using video mode (or long exposures) when lasers are
around.


http://vimeo.com/13450755


Even worse:


http://www.reuters.com/article/idUSL...080714?sp=true


Brainless to fire a Argon laser into a crowd instead of over their
heads. *Even those little frequency-shifted green pocket lasers can do
damage, let alone an industrial entertainment laser.


Especially when they are pot-modded to ~100mw. I had a couple visitors here
yesterday, their son wanted to play with my 405nm and green laser pointers
that I have. ($7.95 w/ free shipping from China on E-Bait, but their
potentiometers are adjusted to 5mw to get them through customs.) I
especially like the green pot-modded ones. The beam (not just terminal dot)
is brightly visible in the air in full sunlight. He was having fun lighting
matches with them. I warned him to not stare at the focused beam on the
paper-matches too intently. He was seeing spots for quite awhile.The 405nm
blue laser (same price) is interesting when pot-modded to ~100mw. It makes
some fist-sized crystals I dug out of my rock-shop phosphoresce in a bright
magenta color. As you sweep the laser over the crystals it leaves a trace
of bright magenta for about 1/4th second. This phosphorescence undetectable
under short and long-wave UV. It must be the intensity of the light that
causes it. A pot-modded 405nm laser should be in every rock-hound's bag of
investigative tools. I've no doubt they'll open up a whole new type of
minerals out there now. Categories of short-wave UV
fluorescence/phosphorescence, long-wave UV fluorescence/phosphorescence,
and blue-laser fluorescence/phosphorescence.


What is the crystal?


I never bothered to ID it, I have many many projects always in the works.
But now that you ask ... (went to go get it) ... it's going to be a little
difficult, because the crystalline structure is trapped in a matrix of what
appears to be a kind of light colored basalt. The cleavage planes of the
crystals are clear and large with a satiny vitreous appearance, but there
are no crystals projecting beyond the conglomerate to determine any clear
planes of growth. All cleavage planes of the large embedded crystals are
also at unique angles to one another. (After more looking, I found one set
of cleavage (or growth) planes at 90 degrees to each other, and another set
at about 60 degrees to each other.) They are a light translucent
grayish-white. Softer than a pocket-knife blade. So I suspect a form of
calcite (many forms of calcite fluoresce yellows or greens, usually with a
long duration phosphorescence) or maybe dolomite. It almost looks like a
pale chabazite, some of the crystals have random inclusions of a rusty
pink.

This is where a further ID key of "blue-laser effects" in rock and mineral
books would come in handy. If under the blue-laser listing it said,
"Phosphoresces for about 1/4th second in bright magenta", then I could tell
you right off what it was.


I know fluorite will fluoresce under UV light,
but I don't know which crystals display phosphorescence.


Many minerals phosphoresce. To the dark-adapted eye, many calcites will
continue to glow a dull green, orange, or yellow for many many minutes
after exposed to UV. Barely visible, but its there. For minerals with very
short duration phosphorescence they polish a sample of the mineral into a
sphere, then spin it rapidly on its axis in the presence of strong
short-wave or long-wave UV light. They determine the duration of
phosphorescence by how far the glow is wrapped around to the back unlit
portion of the spinning sphere, the time calculated from the RPMs.

I had thought it might be an interesting photography dilemma to solve. I've
been wanting to send photos of the mineral's behavior under blue-laser to a
few friends. But how to expose for the bright magenta phosphorescence that
trails behind the bright blue laser played across its surface, and not
overexpose those same traced areas with the 100mw laser. I really can't
think of a simple way around it, other than maybe using a strong orange
filter to filter out the laser frequency. Unfiltered video might work. Then
just pull out a frame with the best example.

Perhaps CHDK might come to the rescue. Using it's motion-detection I could
set it to detect a change of light in the FOV, set shutter for about 1/4th
second. No, that wouldn't work. It would start exposing on the first laser
detection. I need it to expose for the light left behind the moving laser.
Maybe if I move the laser across its surface faster than the
motion-detection trigger time of 45ms. That would do it. The laser would
have left the FOV and the camera would only capture the trail left behind.
Still though, video would be more impressive, it's neat to see the many
swirls of magenta glow all around where the laser was played.

An interesting photography dilemma I've not run into before.

I might try a solve-by-doing tonight, if I get a break in feeding about
50-60 wild critters. My normal 'til sunrise routine. Got some nice infrared
shots last night of a Barred Owl 10 ft. up a tree above where I was feeding
and hand-feeding the critters. It didn't seem to be phased by my being
within a couple yards of it. Perhaps it sensed safety from how many wild
animals would follow me around the yard or eat out of my hands. It was
getting some of the mice and voles that go for the crumbs the larger
critters gluttonously drop into the grass. I watched it catch a couple when
I went back inside. I was a little concerned for all the smaller raccoon
cubs' safety, but the owl itself was on the smaller side. If nothing else,
all the cubs milling around got to learn about owls. Their mothers most
curious about the scent of the owl after it flew back into the tree,
intently checking out where it had landed and subdued its prey for a few
moments.

A random grab, Barred Owl in infrared. (JPG degradation intentional) Note
its posture, it could care less that I was there. It was busy watching all
the raccoons, foxes, opossums, and food dishes. Hoping to spot a darting
mouse or vole amongst them all.

http://farm5.static.flickr.com/4118/4881074056_e8ab34ec2c_z.jpg

The IR videos are more impressive. It was interesting to watch how the owl
would move its face in a full circular motion, in a flat plane to the
direction of what it was trying to detect. Bobbing its head low, then to
the right, up, to the left, and down again in one large and smooth full
circular motion, while keeping its eyes on the same spot. It appeared to be
using its stereo hearing in more than one plane, not just left/right but
top to bottom too. Like making a larger listening-dish out of its hearing
by sweeping a larger area of the received sound.


  #8  
Old August 12th 10, 05:56 PM posted to rec.photo.digital.slr-systems
Kennedy McEwen
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Posts: 639
Default Video mode: sensor vulnerable to lasers

In article , R Davis
writes
Especially when they are pot-modded to ~100mw. I had a couple visitors
here yesterday, their son wanted to play with my 405nm and green laser
pointers that I have. ($7.95 w/ free shipping from China on E-Bait, but
their potentiometers are adjusted to 5mw to get them through customs.)
I especially like the green pot-modded ones. The beam (not just
terminal dot) is brightly visible in the air in full sunlight. He was
having fun lighting matches with them. I warned him to not stare at the
focused beam on the paper-matches too intently. He was seeing spots for
quite awhile.



See this before letting anyone "play" with your cheap green laser
pointer.

http://www.nist.gov/customcf/get_pdf.cfm?pub_id=906138

Even if you think your GLP is low power and relatively dim, chances are
it is emitting enough invisible 808 & 1064nm to permanently damage your
retina. You can see the green beam, so blink reflex provides a
significant natural protection against retinal damage. You can't see
808 & 1064nm, so no blink reflex and no natural protection - a real
danger when some GLPs emit more than 10x as much power at these
wavelengths as they do in the green.

Sounds like your GLP is leaking a lot of IR if he was "lighting matches"
with it - very dodgy.

The document link above explains some simple tests to at least check the
808nm output from a GLP using a CD-ROM and a webcam.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
  #9  
Old August 13th 10, 07:54 AM posted to rec.photo.digital.slr-systems
David J Taylor[_16_]
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Posts: 1,116
Default Video mode: sensor vulnerable to lasers

"Kennedy McEwen" wrote in message
...
[]
See this before letting anyone "play" with your cheap green laser
pointer.

http://www.nist.gov/customcf/get_pdf.cfm?pub_id=906138

[]
The document link above explains some simple tests to at least check the
808nm output from a GLP using a CD-ROM and a webcam.
--
Kennedy


As someone who used to work with NdYAG lasers at 1064nm, with outputs
measured in mega-joules rather than milli-watts, I recall how seriously
the chance of eye damage was taken. Thanks for the pointer to that
document - interesting as a description of how the devices work as well as
for the warning it provides.

Cheers,
David

  #10  
Old August 13th 10, 08:10 AM posted to rec.photo.digital.slr-systems
Charles
external usenet poster
 
Posts: 265
Default Video mode: sensor vulnerable to lasers

On Tue, 10 Aug 2010 14:05:47 -0700 (PDT), RichA
wrote:

On Aug 9, 8:08*pm, R Davis wrote:
On Mon, 9 Aug 2010 13:51:58 -0700 (PDT), RichA
wrote:

On Aug 9, 4:07*pm, Me wrote:
Alan Browne wrote:
Be careful when using video mode (or long exposures) when lasers are
around.


http://vimeo.com/13450755


Even worse:


http://www.reuters.com/article/idUSL...080714?sp=true


Brainless to fire a Argon laser into a crowd instead of over their
heads. *Even those little frequency-shifted green pocket lasers can do
damage, let alone an industrial entertainment laser.


Especially when they are pot-modded to ~100mw. I had a couple visitors here
yesterday, their son wanted to play with my 405nm and green laser pointers
that I have. ($7.95 w/ free shipping from China on E-Bait, but their
potentiometers are adjusted to 5mw to get them through customs.) I
especially like the green pot-modded ones. The beam (not just terminal dot)
is brightly visible in the air in full sunlight. He was having fun lighting
matches with them. I warned him to not stare at the focused beam on the
paper-matches too intently. He was seeing spots for quite awhile.The 405nm
blue laser (same price) is interesting when pot-modded to ~100mw. It makes
some fist-sized crystals I dug out of my rock-shop phosphoresce in a bright
magenta color. As you sweep the laser over the crystals it leaves a trace
of bright magenta for about 1/4th second. This phosphorescence undetectable
under short and long-wave UV. It must be the intensity of the light that
causes it. A pot-modded 405nm laser should be in every rock-hound's bag of
investigative tools. I've no doubt they'll open up a whole new type of
minerals out there now. Categories of short-wave UV
fluorescence/phosphorescence, long-wave UV fluorescence/phosphorescence,
and blue-laser fluorescence/phosphorescence.


What is the crystal? I know fluorite will fluoresce under UV light,
but I don't know which crystals display phosphorescence. Some
sulfides emit light when bombarded by energetic radiation.
http://www.pbase.com/andersonrm/image/103477978



I have a rock that responds this way, I believe it is a Terlingua type
calcite. when hit with either the blue or green laser the whole rock
lights up, looks like it is illuminated from inside.
 




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