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Window screen focuses bricks beyond?

  1. Jan 8, 2007 #1
    Can a uniform diffraction grating (a window screen) alone focus objects (bricks on a building beyond) so that a nearsighted observer (I) can better image them?
  2. jcsd
  3. Jan 9, 2007 #2
    Diffraction gratings don't focus things to my knowladge. However, what you may be expieriencing might have something to do with Morie Patterns.
  4. Jan 9, 2007 #3
    I say this without having read the link (sorry im lazy its late :P) but i think he means that you could change the path of the light rays with defraction and effectively use it as a lens.
  5. Jan 9, 2007 #4


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    If you mean that things seem to be in better focus when you stand right up close to a fine mesh and peer through it at distant objects, then it is likely the pinhole effect is negating your refractive error.

    Read this for a very simple explanation : http://www.myopia.org/pinholes.htm
    Last edited by a moderator: Apr 22, 2017
  6. Jan 9, 2007 #5
    Thanks, folks. It had me fooled! Indeed it must be a Moire pattern rather than a pinhole effect, since there were many apertures contributing to the interference, without substantial loss of light. I guess approximate coherence is cancelled out with many "pinholes." Two great suggestions that I initially overlooked.
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