Fresnel Lens...What do you know about this

Discussion in 'Displays' started by Jon_Heidbreder, Jan 26, 2004.

  1. Jon_Heidbreder

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    What do you know about fresnel lenses


    What kind of picture do they give?

    What kind of brightness can they give?


    any information about them would be much appreciated
     
  2. jeff peterson

    jeff peterson Supporting Actor

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    oh, oh...you're not thinking about building your own FPTV using a 13" tv, cardboard box and Fresnel lens are you?

    Note this is an OLD scam. Lens themselves have no brightness, the tv doesn't throw enough to be magnified to the 100" they claim in their ads.

    Run, grasshopper. [​IMG]
     
  3. Allan Jayne

    Allan Jayne Cinematographer

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    Almost all rear projection TV sets have a fresnel lens. It is a panel the size of the screen mounted just behind the front screen surface. It has a pattern of concentric circular ridges. A flat magnifying glass with circular ridges is another example of a fresnel lens. Its purpose in an RPTV is to make the picture have a uniform brightness instead of having a hot spot corresponding to the location of the projector lamp and where the hot spot seems to be on the screen depends on where you are sitting or standing.

    How the fresnel lens accomplishes this is to aim the rays of light coming from all parts of the screen to be parallel, where before they are expanding outward as they leave the lens assembly (condensing lenses) down by the lamp.

    The fresnel lens is not enough. For an RPTV there is another screen layer called the lenticular lens to share the light so people sitting to each side of center see a reasonable picture too.

    More:
    http://members.aol.com/ajaynejr/vidfres.htm
     
  4. Jon_Heidbreder

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    Thanks Jeff


    I thought it would be impossible to generate the kind of brightness needed with that setup.




    Im running as fast as my little legs will take me.
     
  5. Jack Ferry

    Jack Ferry Stunt Coordinator

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    Jack Ferry
    Fresnel lenses are really cool - if you're a lighthouse enthusiast.
     
  6. JohnnyG

    JohnnyG Screenwriter

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