Resolution of human eye?

MrDio007 mrdio007 at aol.com
Thu Jan 23 13:14:28 EST 1997


A neat book that provides refs in this direction 

VISION coding and efficiency
ed Colin Blakemore
Cambridge U Press 1990

I'd agree that post transduction there is significant processing which
plays a role in resolution limits functionaly.  One must also think about
the fact that the eye is NOT a camera or a telescope and that it was not
evolved only to separate lines separated by little spaces but to deal with
the environment and increase the likelyhood of survival (object
recogintion for example).

The above book has a great chapter from MF Land "The design of compound
eyes"

Quotes from this follow
"The feature of an eye that ultimately limits its ability to resolve
detail is the size of the lens.  This is because the larger the lens the
smaller is the diffraction pattern that it produces;  large telescopes
resolve better than small ones.  The diffraction pattern due to a point
scoucr, the AIry disc, has a radius (r) from its centre to the first dark
ring given by

r=1.22 (lambda)/D      radians

or a width (w) at half max intensity of 

w= lamda/D radians

where lambda is the wavelength and D the aperature diameter.  The Raleigh
criterion, used in astronomy, assumes that thetwo point sources can be
separated if the image of one falls on the the first dark ring of the
image of the other, so that they are resolvable if their angular
separation exceeds 1.22 (lambda)/D........For our own eyes, with DAYLIGHT
pupil diameters of 2.5mm, the limit is 0.84 minutes of arc."

Land then later cites Kirschfield (1976) who says that this one minute
res. if true only in the foveal region and falls off drastically.
Kirschfield (1976) "The resolution of lens and compound eyes" In, Neural
Principals of Vision, Ed Zettler and Weiler, pp354-70 Berlin: Springer.

Well this is probably overkill but this stuff is neat.

Matt Sweeney





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