Max theoretical resolution of scanned images.

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Energize
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May seem like a bizarre question but I was wondering what the maximum possible resolution of a scanned A4 image would be.

A4 paper is 0.297m x 0.21m, average resolution of light is 200nm.

So I get,

(0.297m / 200x10^-9m) x (0.21m / 200x10^-9m) = 1.56 terapixels

Is this about right? Would we be able to use violet light for a greyscale image to achieve a higher resolution, and would we have to stick to the resolution of red light to get an accurate scan with a colour image?
 
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Energize said:
average resolution of light is 200nm.
Visible light has a wavelength of around 400 to 700nm
There are microscopy techniques that will give you position of an edge that is smaller than wavelength and you can detect the position of small high contrast objects that are smaller than a wavelength

And of course some non-light microscopes can resolve individual atoms
 
mgb_phys said:
Visible light has a wavelength of around 400 to 700nm
There are microscopy techniques that will give you position of an edge that is smaller than wavelength and you can detect the position of small high contrast objects that are smaller than a wavelength

And of course some non-light microscopes can resolve individual atoms

The max resolution of a simple optical scanner is half the wavelength though is it not? Giving a max resolution of 200nm and average of 275nm?

russ_watters said:
This all assumes that the image being scanned is that high of a resolution.

How does one determine the max resolution of say a graphite drawing, I assume it is related the size of the graphite molecules?
 
Energize said:
How does one determine the max resolution of say a graphite drawing, I assume it is related the size of the graphite molecules?
I'm not sure you can really say a graphite drawing is an "image" - it is more of a physical object.

The useful resolution is probably limited to the size of the fabric of the canvas or paper pulp particles.
 
Energize said:
The max resolution of a simple optical scanner is half the wavelength though is it not? Giving a max resolution of 200nm and average of 275nm?
The diffraction limit of a NA [tex]\approx[/tex] 1 objective is about 0.5wavelengths
But this is a very simplistic picture of resolution