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Giant Fresnel Lens

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I found a company that sells giant fresnel lenses. What is a Fresnel lens? Think of a lighthouse or the top of an overhead projector. As light goes through the lens, spiral cut ridges focus the light to a focal point. You end up with the equivalent of a giant magnifying glass or parabolic mirror. There is some really juicy math invovled in calculating how to create a lens, determining the focal length and lens strength.

I framed the lens with some 2“x2“ lumber and secured it with electrical tape. When I carried the lens out of the garage, I knew we were in for a good show. The asphalt driveway started smoking. Our first target was a penny which the lens quickly melted into slag. Next up was a hamburger. We widened the focus and it flash cooked the top of the burger.

 

What I learned:

  1. You really need welding goggles. I have none so we had to use a spotter from a distance to help us focus. If you knelt down and tried to focus it without eye protection, you would surely suffer eye damage.
  2. If the sun is directly overhead, the lens is easier to focus and burns significantly hotter.
  3. Burgers cooked with a giant death ray don't taste very good. It's about like cooking in a microwave: you don't get the smoky taste that a BBQ gives you.

Comments

  • Anonymous
    July 29, 2004
    DEATH RAY OF DOOM ... hmm there's an ebay slot for those I'm sure! ;-)

  • Anonymous
    July 29, 2004
    LOL Giant Death Ray of DOOM. This would make a nice fatality for Sub Zero in MK. :-)

  • Anonymous
    July 29, 2004
    OH man I just saw the website. Their "scientist" look like Unix users.

  • Anonymous
    July 29, 2004
    Wow this is the second post I've read about fresnel lenses in the past few months. It's a good thing blogs hadn't been invented when I was twelve for the sake of my local fire department and my retinas!!!

  • Anonymous
    July 29, 2004
    What on earth are you going to use it for, apart from comedy value ?

  • Anonymous
    July 29, 2004
    I wouldn't wear sandals whilst weilding the thing if I were you...

  • Anonymous
    July 30, 2004
    The comment has been removed

  • Anonymous
    July 30, 2004
    It would be cool to see if you could get it to run a little steam turbine. Micro-solar power.

  • Anonymous
    July 30, 2004

    Probably wreaks havoc on dogs too.

  • Anonymous
    July 30, 2004
    http://blogs.msdn.com/jrule/archive/2004/07/29/201082.aspx...

  • Anonymous
    August 02, 2004
    What?! No Ants!? ;)

  • Anonymous
    August 02, 2004
    Whats the range of those things? (Could I for example mount one on my car...?)

    lol

  • Anonymous
    August 02, 2004
    as for point #3 - this still might be a fun way to start the barbeque for those who don't have liquid oxygen as an option [ http://ep.llnl.gov/msds/Chem120/lox-oxidation.html ]

  • Anonymous
    August 03, 2004
    Jeremy:

    I got your IM but was not at home. "Old Rugged Cross" sounds good. Do you have the sheet music or MP3? I'll get cracking.

    -Paul

  • Anonymous
    August 03, 2004
    TinyScreenfuls Trackback

  • Anonymous
    August 05, 2004
    sooo cool ... I am off to get me one...

  • Anonymous
    August 06, 2004
    Say, WHERE can I buy this GIAN FRESNEL LENS?? Please give me the URL! THANKS!! Eugene

  • Anonymous
    August 07, 2004
    I would love to find out where to buy these also. Please let us know. Thansk!

    John
    john@airwired.net

  • Anonymous
    August 07, 2004
    Guys there's a link right in the first paragraph of the post to alltronics.com.

  • Anonymous
    August 14, 2004
    You didn't mention one of the cooler uses of fresnel lenses: bringing our trusty naval aviators back aboard the carrier on every landing. The "meatball" or "ball" as it is called is an array of fresnel lenses that provide precise visual glideslope information to the pilot from a gyro stabilized platform so that even with pitching decks they can fly down the perfect glideslope to an "OK" 3-wire.

  • Anonymous
    August 19, 2004
    If you want some more information on Fresnel lens applications and other solar uses, check out this site. http://www.knowledgepublications.com. The guy sells smaller 8.8 x 11 fresnel sheets and has some intersting books on solar power and hydrogen stuff.

    Cheers

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    August 26, 2004
    The comment has been removed

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