Plato's Cave: The Conventional View
The Conventional View of Visual Processing
The current view of visual processing is based on a number of
prominent milestones in vision science. One was the
Hodgkin-Huxley neuron
model, which suggests a simple integrate-and-threshold function for
the individual neuron. Another was the finding by
Huebel & Wiesel
of simple, complex, and hyper-complex cells in the visual cortex,
suggesting a hierarchy of successive stages of processing to extract
ever higher order visual features. This concept is exemplified by
recent work like that of
Tanaka (1994)
to map ever higher level features in higher cortical areas.
Conventional Models of Visual Processing
The conventional view has inspired a number of computational models
both in image processing, as in the
Blocks World
model, and
Ballard's Computer Vision,
as well as models of human perception such as
Marr's Vision
model, and
Biederman's Geon
model of visual coding.
The basic idea in all of these systems is that visual perception
involves a feed-forward progression of sensory information through
various stages of feature detection. At each stage the information is
abstracted and compressed, resulting in an ever more symbolic
representation.
Abstraction
and compression generally go hand-in-hand, because abstraction implies
a many-to-one transformation from many possible instances to a single
invariant form, so that a system which is capable of such abstraction
need only remember the canonical form, not the multiple possible
instances of that form. Abstraction, compression, and
invariance
therefore are all desirable properties of a recognition system.
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