1. Introduction What is Vision? Active Visual Perception
1. Introduction What is Vision? Active Visual Perception
1. Introduction What is Vision? Active Visual Perception
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Zoltan Kato: Computer V<strong>is</strong>ion<br />
Depth Cues: Binocular D<strong>is</strong>parity<br />
• Each eye receives a slightly different image of the<br />
world from which 3D positions can be inferred.<br />
• D<strong>is</strong>parity - The difference in retinal position<br />
between the corresponding points in two images.<br />
D<strong>is</strong>parity <strong>is</strong> inversely proportional to the depth of the<br />
point in space.<br />
Zoltan Kato: Computer V<strong>is</strong>ion<br />
Theory of V<strong>is</strong>ual <strong>Perception</strong><br />
• The information we receive<br />
by our eyes <strong>is</strong> relatively<br />
impover<strong>is</strong>hed.<br />
• For example, the retina<br />
receives a grainy 2D image of<br />
the v<strong>is</strong>ual scene…<br />
• …that includes large gaps<br />
(blind spots)…<br />
• …and an uneven<br />
representation of colour<br />
(cones) and luminance (rods).<br />
• Th<strong>is</strong> information <strong>is</strong><br />
transformed into a rich<br />
v<strong>is</strong>ual experience.<br />
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Zoltan Kato: Computer V<strong>is</strong>ion<br />
Perceptual Constancy<br />
Size constancy<br />
• We tend to experience objects as the same, despite the<br />
image they produce on the retina may vary greatly.<br />
• Shape constancy – objects seen from different angles do not appear<br />
different or to change shape<br />
• Size constancy – objects do not seem to change size when they move<br />
nearer or further away.<br />
• Color constancy – differing illumination does not affect color despite<br />
changes in the actual reflected light.<br />
Zoltan Kato: Computer V<strong>is</strong>ion<br />
Theory of V<strong>is</strong>ual <strong>Perception</strong>: Marr<br />
• Theories of v<strong>is</strong>ual perception attempt to explain how<br />
th<strong>is</strong> happens.<br />
• David Marr: V<strong>is</strong>ion: A Computational Investigation<br />
into the Human Representation and Processing of<br />
V<strong>is</strong>ual Information, 1982.<br />
• wanted to understand mechan<strong>is</strong>ms of v<strong>is</strong>ion rather<br />
than just behaviours associated with it.<br />
• He took an information processing view of the mind…<br />
• …and aimed to describe perception in terms of<br />
computations on sense data…<br />
• …to extract high level v<strong>is</strong>ual experience.<br />
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