Window screen focuses bricks beyond?

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Discussion Overview

The discussion revolves around whether a uniform diffraction grating, such as a window screen, can focus distant objects like bricks for a nearsighted observer. The scope includes concepts of diffraction, optical effects, and visual perception.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions if a diffraction grating can focus distant objects for a nearsighted observer.
  • Another participant asserts that diffraction gratings do not focus light but suggests that the observed effect might relate to Moire Patterns.
  • A different participant proposes that diffraction could change the path of light rays, potentially functioning like a lens.
  • One participant suggests that the perceived improvement in focus when viewing distant objects through a fine mesh may be due to the pinhole effect mitigating refractive errors.
  • A later reply acknowledges the possibility of Moire patterns being responsible for the observed effect, noting that multiple apertures contribute to interference without significant light loss.

Areas of Agreement / Disagreement

Participants express differing views on the role of diffraction gratings and the mechanisms behind the observed effects, indicating that multiple competing perspectives remain without consensus.

Contextual Notes

There are unresolved assumptions regarding the nature of the optical effects being discussed, including the definitions of diffraction, Moire patterns, and the pinhole effect.

Loren Booda
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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?
 
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Loren Booda said:
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?
Diffraction gratings don't focus things to my knowladge. However, what you may be expieriencing might have something to do with Morie Patterns.
 
I say this without having read the link (sorry I am 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.
 
Loren Booda said:
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?

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:
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 canceled out with many "pinholes." Two great suggestions that I initially overlooked.
 

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