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Use colored lasers to draw pictures on the underside of a cloudy sky.
The technology exists to take different-colored laser beams and
a reflective screen, yielding a watchable image. See the first
With a more-powerful set of lasers, aimed upward, whenever
is cloudy-grey in the daytime, (or cloudy-dark at night), the
undersides of the
clouds themselves can be used as a giant
making advertising images --even moving images. Remember,
in any partly-cloudy daytime the clouds are white, reflecting
ALL colors. When
the outdoors are dimly-lit or dark, there simply isn't a lot of
normal white light reflecting off clouds, giving us an
opportunity to see reflected colored light --IF it is bright
enough. Which lasers can produce, easily!
The local Governmental Aviation Administration would probably
on this Idea, unless it can be assured that whenever a plane flies
through the area, it is detected and the lasers are shut off.
(For anyone curious about the title of this Idea, when the
military uses a laser to illuminate something, such that the
reflected light can be detected by a "smart" guided missile, the
shining laser is considered to be "painting" the target.)
A laser image-projector
As mentioned in the main text. [Vernon, Jun 13 2015]
A searchlight-beam "pixel" painted on a cloud.
We want lots of rather-smaller (and colored!) pixels, to make whole images. [Vernon, Jun 13 2015]
It's been a long time since I had a good opportunity to link this old Idea.
As implied by an annotation. [Vernon, Jun 13 2015]
Project air filter ads onto smog
Xiao Zhu is a Chinese company dedicated to providing clean air to its citizens... [lahosken, Jun 13 2015]
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||So now when I look up at the sky I'll see ads for Comcast
||If you Google "laser projection clouds", you will get
quite a few hits. These are usually single-colour
||Trying to do this in daylight will be very very
difficult. A lit 100W light-bulb is unlikely to be
visible at 1000ft during even a heavily-overcast day.
Now try to illuminate tens of square metres of cloud
at the same or greater intensity, and you're looking at
kilowatts of laser power.
||[MaxwellBuchanan], there are plenty of folks around here
who think it is quite OK if the lasers need more power.
||//The lasers need more power.//
||At some point, you'll just vaporise the clouds, no?
||Incidentally, re. the necessary laser power, the
searchlights in your linked picture were probably on
the order of 15kW. I'm not sure how the efficiency of
lasers compares to that of filament searchlights, but
you'd need at least 5kW of laser to produce the
||Now make your image 10 x 10 of your "pixels" and
we're talking 0.5MW of laser power.
||Its hard for me to imagine a circumstance where
there arent planes in the sky (being that I live near
EGLC / LCY / London City Airport). Im not really
comfortable with the idea of encouraging people to
point lasers into the sky its a serious and
imprisonable offence to be caught shining a laser at
aircraft. On the other hand, its not hard for me to
||What might work better is if there were a way of
transporting light up to cloud level in a sort of
conveyor belt of haze that connects the light source
with droplets, which connect the droplets to
droplets, which connect the droplets to droplets,
which connect the droplets to droplets, and so on.
||[+] So call it Smog Painting.
||Oh I see lahosken wrote about it already. Hi lahosken never
saw you here before...
||Vernon, did you see Maxwel's remark at the end?
||Sorry but when an idea becomes too long, and the
annotations just as long (not all your fault) it becomes very
hard for serious people to remark on them.
||[pashute], I suspect [MaxwellBuchanan] of forgetting
that laser light can be made to "scan". So only 3 high-
power lasers are needed, having red, green and blue
light respectively. Scanning can happen fast enough for
a large screen to reflect a complete image for the eye
(first link), so I think it can also be done to paint an
image on the underside of a cloud.
||Also, a lens system can expand the diameter of the
laser beams to create larger pixels (of which fewer
would then be needed for the complete image).
||//I suspect [MaxwellBuchanan] of forgetting that
laser light can be made to "scan".//
||I suspect [Vernon] of having unfounded suspicions.
||No, I had not forgotten that lasers can scan.
||However, if you scan a laser over, say, 10 pixels at a
high enough rate to make the scanning invisible, each
pixel will have a mean illumination equivalent to
1/10th of the laser power (assuming there's no "dead
time" between pixels).
||Also, if you expand the beam diameter, your intensity
will go down.
||//However, if you scan a laser over, say, 10 pixels at a
high enough rate to make the scanning invisible, each
pixel will have a mean illumination equivalent to 1/10th
of the laser power (assuming there's no "dead time"
||Actually Max, I seem to remember reading somewhere
that illuminating something briefly at higher intensity
makes it seem brighter on average than the constant
I don't know why that would be, although I can speculate.
||But yes, illuminating a large area of cloud in the daytime
would be a lot of work. Doing it at nightime seems more
feasible - and that is what the idea seems to be implying.
||I also think that for this to work you'd ideally have a very
thick cloud, on an otherwise very clear day. Because not
all the light will be reflected from the base of the cloud,
you'll get a sort of rod effect through it (per pixel). And
possibly some reflective lighting from nearby, which
might look cool, but will limit the resolution.
Anyway, the point is that you'll need more energy to light
it than you would a flat white screen.
||Creative, interesting, and evil. And it could lead to horrible
flaming carnage. I would bun you twice if I could.
||BIG kW class lasers are now routinely used in the metal
working industry. Just kW worth of diodes thrown down a
fibre optic. The scaling up to 1/2 mW isn't conceptually that
||But, come political season, people will begin to kill
themselves in strange and peculiar ways. The ads would get
first nauseating, then a kind of psychosis would take over
and slowly your sanity would simply evaporate.
||//sanity would simply evaporate//
||I'm sure there's a laser frequency that can help that along a