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From: briand@cv.hp.com (Brian Dixon)
Subject: Re: Computer eye
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Date: Thu, 27 Apr 1995 00:01:16 GMT
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Diglio A. Simoni (diglio@npac.syr.edu) wrote:
: -- 

: In article <push-2304951534580001@mind.mit.edu>, push@mit.edu (Pushpinder Singh) writes:
: >In article <3ne26e$ncp@uuneo.neosoft.com>, mckee@starbase.neosoft.com
: >(George McKee) wrote:
: >
: >>         The Caltech silicon retina can't be emulated by a Turing Machine
: >> because it doesn't have a finite set of states or symbols.  It can be
: >> simulated more or less accurately, but it cannot be emulated precisely
: >> in the way that a Universal TM can emulate any other digital computer.
: >
: >Thermal and quantum noise throws out your accuracy, so why bother with
: >precision?  And even if we had perfect accuracy, there's no reason for a
: >retina to need infinite precision anyway.  So you're making a useless
: >assertion.
: >
: >The only advantage such analog machinery may have is speed, since we can
: >translate some operations into forms that take advantage of the natural
: >transformations allowed by solid state devices.
: >
: >-push

FYI: The lady's silicon retina was intended at first to be a fully analog
device, but later became a hybrid of analog and digital.  This was justified
since this IS how the natural system works.  The photons which excite the
sensory cells in the retina (rods/cones) elicit an analog response.  When
the analog response surpasses a threshold, then the sensory cells produce
a train of 'action potentials'...a digital form of the original response.
No, it is not encoded conventionally.  In neural systems the connectivity is
what determines function, not any special encoding.  In the retina, the
connectivity (both the path and excitatory or inhibitory nature of the 
receptive fields) in the eye itself, the lateral geniculate nucleus, and
the 5-part visual cortex provides function decomposition, analysis, and
recombinant analysis.  The silicon eye only modeled the retina I believe.

Brian

--
Brian Dixon, Machine Vision Engineer, Hewlett Packard (Corvallis, Oregon)
503-715-3143 (wk), briand@cv.hp.com (email). "Opinions & attitudes are mine!"
