Window screen focuses bricks beyond?

[Loren Booda]

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?

 

[ObsessiveMathsFreak]

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.

 

[FunkyDwarf]

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.

 

[Curious3141]

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

 

[Loren Booda]

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.