Re: Stereo Acuity

[crowell@xxxxxxxxxxxxxxxxx (Jim Crowell)]

At 6:28 PM 2/29/96, John Bercovitz wrote:
>
>>> In vision there is the anomoly that we an see things that cross the
>>> retina, e.g. a telegraph line in the distance, that no way could be
>>> resolved based on its diameter at the distance!! BobH
>
>> Perhaps because it gets blurred out by the optics of the eye to
>> the point where it's resolveable by the retina?  I guess it
>> would have to be high-contrast...
>
>Even a sub-resolvable object will affect the light intensity levels
>by diffraction if nothing else.  This just shows the eye is able
>to discern low contrast, doesn't it?
>

Yes, that's what I meant.  As you know, a linear optical system
can be characterized by an impulse response function, which
basically corresponds to the luminance distribution or image
that would be created by an infinitesimally small point of light
(or an infintesimally narrow line if you're working in 1D).  The
impulse response function describes how the optical system blurs
the image.  In the case of human vision, it's generally referred
to as the point-spread function (or line-spread if you're
working in 1D).  Any line that's significantly narrower than the
line-spread function will be imaged into something about the
same width as the line-spread function, but with lower contrast
than the line had initially.  So if it had a high enough
contrast to begin with, it will still be detectable....Hm.
maybe I should've just said, "Yes."   :-)

-Jim C.


------------------------------------------------
Jim Crowell
U.C. Berkeley School of Optometry
360 Minor Hall, Berkeley, CA 94720
(510) 642-7679
jim@xxxxxxxxxxxxxxxxx



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