MIT 2.71/2.71009/26/05 wk4-a-1

Imaging systems in nature

• “Physical” architecture matches survival requirements and processing capabilities

• Human eye: evolved for– adaptivity (e.g. brightness adjustment)– transmission efficiency (e.g. mexican hat response)– bypass structural defects (e.g. blind spot)– other functional requirements (e.g. stereo vision)

• Insect eye: similar, but much simpler processor (human brain = ~1011 neurons; insect brain = ~104 neurons)

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Anatomy of the human eye

W. J. Smith, “Modern Optical Engineering,” McGraw-Hill

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Eye schematic with typical dimensions

Photographic camera

FFP1.5cm BFP

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Remote object (unaccommodated eye)

Proximal object (accommodated eye)

Comfortable viewing up to 2.5cm away from the cornea

Accommodation (focusing)

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Eye defects and their correction

from Fundamentals of Opticsby F. Jenkins & H. White

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The eye’s “digital camera”: retina

http://www.mdsupport.org

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The eye’s “digital camera”: retina

http://www.phys.ufl.edu/~avery/

rods: intensity (grayscale) cones: color (R/G/B)

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Retina vs your digital camera

(grossly exaggerated; in actual retinatransition from dense to sparse sampling

is much smoother)

Retina:variant sampling rate

Digital camera:fixed sampling rate

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Retina vs your digital cameraRetina:

blind spot not noticeableDigital camera:

bad pixels destructive

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Retina vs your digital camera

CCD imageRetinal image

http://www.klab.caltech.edu/~itti/

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Spatial response of the retina –lateral connections

http://webvision.med.utah.edu/

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Spatial response of the retina –lateral connections

http://www.phys.ufl.edu/~avery/

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Spatial response of the retina –lateral connections

http://faculty.washington.edu/wcalvin

Explanation of the “flipping dot” illusion: the Mexican hat response

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Temporal response: after-images

http://dragon.uml.edu/psych/

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Seeing 3D

http://www.ccom.unh.edu/vislab/VisCourse

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http://research.microsoft.com/users/antcrim/talks/UWTalk_files/slide0074.htm

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The compound eye

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Elements of the compound eye:ommatidia (=little eyes)

“image” formation:blurry, but

computationally efficientfor moving-edge detection