Half a croissant, on a plate, with a sign in front of it saying '50c'
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Cloud Painting

Use colored lasers to draw pictures on the underside of a cloudy sky.
  (+6, -1)
(+6, -1)
  [vote for,

The technology exists to take different-colored laser beams and scan a reflective screen, yielding a watchable image. See the first link.

With a more-powerful set of lasers, aimed upward, whenever the sky is cloudy-grey in the daytime, (or cloudy-dark at night), the undersides of the clouds themselves can be used as a giant screen, for 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 frown 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.)

Vernon, Jun 13 2015

A laser image-projector http://www.cnet.com...p-projector-series/
As mentioned in the main text. [Vernon, Jun 13 2015]

A searchlight-beam "pixel" painted on a cloud. http://starcannonus...cing-off-clouds.jpg
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. Hyper_20Lasers
As implied by an annotation. [Vernon, Jun 13 2015]

Project air filter ads onto smog http://www.designbo...t-china-06-11-2015/
Xiao Zhu is a Chinese company dedicated to providing clean air to its citizens... [lahosken, Jun 13 2015]


       So now when I look up at the sky I'll see ads for Comcast Cable!
lepton, Jun 13 2015

       If you Google "laser projection clouds", you will get quite a few hits. These are usually single-colour images, admittedly.   

       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, Jun 13 2015

       [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.// [marked-for-tagline] :)
Vernon, Jun 13 2015

       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 equivalent effect.   

       Now make your image 10 x 10 of your "pixels" and we're talking 0.5MW of laser power.
MaxwellBuchanan, Jun 13 2015

       [+] So call it Smog Painting.   

       Oh I see lahosken wrote about it already. Hi lahosken never saw you here before...
pashute, Jun 15 2015

       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, Jun 15 2015

       [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).
Vernon, Jun 15 2015

       //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.
MaxwellBuchanan, Jun 15 2015

       //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).//   

       Actually Max, I seem to remember reading somewhere that illuminating something briefly at higher intensity makes it seem brighter on average than the constant output.
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.
Loris, Jun 16 2015

       *1 - I likey.
xandram, Jun 17 2015

       Creative, interesting, and evil. And it could lead to horrible flaming carnage. I would bun you twice if I could.
Voice, Jun 17 2015

       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 hard.
bs0u0155, Jun 17 2015

       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.
Altoidian, Jun 18 2015

       //sanity would simply evaporate//   

       I'm sure there's a laser frequency that can help that along a little.
bs0u0155, Jun 19 2015


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