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Old 05-21-2012, 02:26 PM   #1
brainhulk
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Default can you use a magnifying glass to make a powerful laser...

Out of a bunch of small laser pointers?

What's the biggest insect I could zap with it?
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Old 05-21-2012, 02:41 PM   #2
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I think that would do the exact opposite of what you'd want, spreading the beam. I think you'd want to focus the beam in, using mirrors and such no? I think that's how most of those experimental stuff is set up anyway.
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Old 05-21-2012, 02:44 PM   #3
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You'd need a lot of laser pointers, but yes, you could focus a bunch of them to a point with a magnifying glass.

Better just to use a more powerful monolithic laser - a typical laser pointer is about 1/100 of the power needed to make a decent burning laser.
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Old 05-21-2012, 02:51 PM   #4
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Simply use a bigger laser. There was a demonstration a year or so ago where some guys (I think it was also on a TED talk) built a mosquito tracking system with a laser zapper. The tracking system was able to identify which bugs were mosquitoes, then zap the mosquitoes out of the air with a burst from a laser. They used 100% off the shelf, easily accessible components - stuff that you or I have easy access to.
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Old 05-21-2012, 02:56 PM   #5
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Quote:
Originally Posted by DrPizza View Post
Simply use a bigger laser. There was a demonstration a year or so ago where some guys (I think it was also on a TED talk) built a mosquito tracking system with a laser zapper. The tracking system was able to identify which bugs were mosquitoes, then zap the mosquitoes out of the air with a burst from a laser. They used 100% off the shelf, easily accessible components - stuff that you or I have easy access to.
you have a video for that?
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Old 05-21-2012, 03:06 PM   #6
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http://www.popsci.com/technology/art...s-pesky-skeets
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Old 05-21-2012, 03:18 PM   #7
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muhahaha, awesome. death to those west nile virus carrying bugs
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Old 05-21-2012, 03:25 PM   #8
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No. You can't obtain the high degree of spatial and temporal coherence of light produced by a Laser simply by focusing light with a magnifying glass.

You can, however, increase optical power to the point where you can set some critters on fire.
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Old 05-21-2012, 03:34 PM   #9
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Legal (FDA) pointers are <4.99mW. Even passing a perfectly focused (waist) beam over most materials will not raise a wisp of smoke.

It's easy to burn. Very easy. However if you want a visible beam it gets a little harder. If you want to burn at distance it gets considerably harder. When dealing with lasers anything that's (harder) means it costs more - sometimes a lot more!

That said you can easily build or buy a class IV burning laser at 445nm (brilliant blue) for $100 or so. They use diodes from small video projectors. These can be combined to produce multi watt beams. They can be focused down to very tiny waists so even a 1W beam can set things on fire. Goggles are an absolute must unless you don't place much value on your eyes.

The TED demo seems impressive but basically it's vapor ware. No pun intended. There are demos of the TRACKING part (search for laser mosquito zapper) on youtube.com. The actual laser zapping part you see impressive video (linked earlier) is under lab conditions where the laser can be focused just right and move/panned slowly in a controlled environment. To see them both working just does not happen. Just as you cannot see a pixar movie rendered in realtime. The lasers used in those movies were 405nm devices which are not available in class IV powers. Their beams can be focused down smaller than multimoded 445nm lasers but the kill range is quite narrow as just a few cm past the waist the beam diameter is larger than the target and power density is simply too low for six legged critter ablation!

If you have a magnifying glass now why not just use the sun?
Even better, get a Fresnel from a projection TV or overhead projector and you can "roast" something quite a bit larger.
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Old 05-21-2012, 03:40 PM   #10
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That laser tracker device totally needs to be marketted and sold. Would be awesome! Now use that same technology with 100 separate lasers, set up near the camp area and watch the clouds of mosquitoes fall. You'd want to bring a big generator and tons of fuel though, that thing would be running at full tilt!

Don't worry about all the dead carcases, the chipmunks take care of em.

As for the OP, you probably could focus the laser point even more but you'd have to be extremely precise and it would probably be very short range, like inches. Then it would just spread out more.
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Old 05-21-2012, 03:43 PM   #11
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Quote:
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muhahaha, awesome. death to those west nile virus carrying bugs
Check out some of the videos on youtube of popping balloons with lasers.
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Old 05-21-2012, 03:48 PM   #12
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Didnít anyone ever tell you to make sure your optics were clean?



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Old 05-21-2012, 03:53 PM   #13
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Didnít anyone ever tell you to make sure your optics were clean?



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I've ruined my fair share of simple acrylic aspheres that were not completely FOD free. Barely a hint of green thinking I had a badly misaligned OC mirror, tried again and then pulled it apart to see a nicely charred aspheric group! That was with a 1.1W pump (808nm). At least they're pretty cheap. Even CASIX junk MCAs are quite expensive in comparison.
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Old 05-21-2012, 04:40 PM   #14
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Quote:
Originally Posted by brainhulk View Post
Out of a bunch of small laser pointers?

What's the biggest insect I could zap with it?
you should go read the wiki on laser...
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Old 05-21-2012, 04:51 PM   #15
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Quote:
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I've ruined my fair share of simple acrylic aspheres that were not completely FOD free. Barely a hint of green thinking I had a badly misaligned OC mirror, tried again and then pulled it apart to see a nicely charred aspheric group! That was with a 1.1W pump (808nm). At least they're pretty cheap. Even CASIX junk MCAs are quite expensive in comparison.
seriously, who are you? are you a female James Bond of coolness? through out the years and thousands of posts it seems as if you have done every thing.
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Old 05-21-2012, 05:43 PM   #16
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Anyone else notice the copywrite in the video?
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Old 05-31-2012, 03:09 PM   #17
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Quote:
Originally Posted by Red Squirrel View Post
That laser tracker device totally needs to be marketted and sold. Would be awesome! Now use that same technology with 100 separate lasers, set up near the camp area and watch the clouds of mosquitoes fall. You'd want to bring a big generator and tons of fuel though, that thing would be running at full tilt!

Don't worry about all the dead carcases, the chipmunks take care of em.

As for the OP, you probably could focus the laser point even more but you'd have to be extremely precise and it would probably be very short range, like inches. Then it would just spread out more.
http://www.youtube.com/watch?v=wSIWpFPkYrk

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Old 05-31-2012, 03:19 PM   #18
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didn't you all see Real Genius? They used ice not a magnifying glass to make a more powerful laser.
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Old 05-31-2012, 03:25 PM   #19
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didn't you all see Real Genius? They used ice not a magnifying glass to make a more powerful laser.
Yes I did see it, Val was the only reason why I didn't eject the tape.
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Old 05-31-2012, 03:30 PM   #20
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My only comment is this thread is a total contractions in terms.

Sure a magnifying glass can focus light to a single point, but before and beyond that point, its no longer true. And worse yet, no lens can focus polychromatic light equally.

But a laser sends a single discrete beam of monochromatic light out that is equally small at all points.
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Old 05-31-2012, 03:32 PM   #21
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Hmm never thought ice could be used as a magnifying glass but I can totally see that working.

If ever I find myself lost in the arctic I'll try to remember that one. Build an igloo, then make a ice roof and shape it so that the sun's beam can be concentrated on a single spot inside the igloo. Free heat!

If I can shape it very good I could even cook stuff with it or start a fire.
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