NavList:

   

Reply

Frank,

I am really 30 years behind (or so) in the latest
developments about human eye phisiology.
But at that time, 30 years ago, I was also thinking,
how was it possible. I don't know how, but I don't think
it CONTRADICTS any scientific facts. Including the diffraction.

In principle, I can imagine a mechanism, which will determine
direction to a point source with very high precision,
while the whole mechanism consists of ONLY one cell (receptor),
and not very accurate one.

This is what actually happens in a radar range/direction
finder which I studied at approximately the same time, (as
an officer of anti-aircraft artillery).
The antenna of this radar had a very moderate "resolution",
and it was a "single cell", in the sense it could measure only
one parameter (intensity of the reflected signal.

High precision was achieved by the very fast MOTION of this antenna.
(I can explain more detail about this off list; I think the subject
is somewhat off the topic).
I knew that microscopic fast motion of an eye also occurs when
we look at an object carefully, and I thought this can explain
(in principle) higher than normal resolution.

I never considered the subject rigorously though, from a mathematical
point of view. But my impression
is that the resolution of 1" does not contradict any laws of physics.

Besides, I am sure that all this was carefully studied by
researchers in human vision, and finding it out only
requires some search.

Alex.

P.S. I don't know, what precisely your calculation was,
but I can guess that diffraction creates some spot (instead
of a dot) from a point object in the eye retina.
And you computed the size of this spot? And concluded that
a spot created by two point objects at some very small
angluar distance is indistinguishable from a spot created
by one such object?

On Wed, 16 Feb 2005, Frank Reed wrote:

>
> Alex, you wrote earlier:
> "However there are well documented cases of much higher resolution.
> (One  person tested in XIX century had resolution of 1",
> but this seems to be the  world record. Several people were described
> who could see the phases of Venus  with naked eye)."
>
> I mentioned before that I was skeptical, and it only dawned on me while I
> was throwing out last week's back-of-the-envelope calculations that one
> arc-second resolution is literally impossible. The diffraction limit is  imposed by
> the laws of physics and gives a lower limit of 15 arcseconds under  the very
> best of circumstances (under typical circumstances, this optical limit  is about
> 30"). If Nature chose to pack more cone cells into our foveas than  one for
> every 15" of angle across the retina, they would not yield higher  resolution.
>
> Can anyone think of a loophole I've missed here? The diffraction limit has
> some fuzziness of definition (there's a pun in there somewhere), but I don't
> think it's enough to help.
>
> -FER
> 42.0N  87.7W, or 41.4N 72.1W.
> www.HistoricalAtlas.com/lunars
>
>
>

   

Reply