1MIT 2.71/2.71009/26/05 wk4-a-1Imaging 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 = ~1011neurons; insect brain = ~104neurons)MIT 2.71/2.71009/26/05 wk4-a-2Anatomy of the human eyeW. J. Smith, “Modern Optical Engineering,” McGraw-Hill2MIT 2.71/2.71009/26/05 wk4-a-3Eye schematic with typical dimensionsPhotographic cameraFFP1.5cmBFPMIT 2.71/2.71009/26/05 wk4-a-4Remote object (unaccommodated eye)Proximal object (accommodated eye)Comfortable viewing up to 2.5cm away from the corneaAccommodation (focusing)3MIT 2.71/2.71009/26/05 wk4-a-5Eye defects and their correctionfrom Fundamentals of Opticsby F. Jenkins & H. WhiteMIT 2.71/2.71009/26/05 wk4-a-6The eye’s “digital camera”: retinahttp://www.mdsupport.org4MIT 2.71/2.71009/26/05 wk4-a-7The eye’s “digital camera”: retinahttp://www.phys.ufl.edu/~avery/rods: intensity (grayscale) cones: color (R/G/B)MIT 2.71/2.71009/26/05 wk4-a-8Retina vs your digital camera(grossly exaggerated; in actual retinatransition from dense to sparse samplingis much smoother)Retina:variant sampling rateDigital camera:fixed sampling rate5MIT 2.71/2.71009/26/05 wk4-a-9Retina vs your digital cameraRetina:blind spot not noticeableDigital camera:bad pixels destructiveMIT 2.71/2.71009/26/05 wk4-a-10Retina vs your digital cameraCCD imageRetinal imagehttp://www.klab.caltech.edu/~itti/6MIT 2.71/2.71009/26/05 wk4-a-11Spatial response of the retina –lateral connectionshttp://webvision.med.utah.edu/MIT 2.71/2.71009/26/05 wk4-a-12Spatial response of the retina –lateral connectionshttp://www.phys.ufl.edu/~avery/7MIT 2.71/2.71009/26/05 wk4-a-13Spatial response of the retina –lateral connectionshttp://faculty.washington.edu/wcalvinExplanation of the “flipping dot” illusion: the Mexican hat responseMIT 2.71/2.71009/26/05 wk4-a-14Temporal response: after-imageshttp://dragon.uml.edu/psych/8MIT 2.71/2.71009/26/05 wk4-a-15Seeing 3Dhttp://www.ccom.unh.edu/vislab/VisCourseMIT 2.71/2.71009/26/05 wk4-a-16http://research.microsoft.com/users/antcrim/talks/UWTalk_files/slide0074.htm9MIT 2.71/2.71009/26/05 wk4-a-17MIT 2.71/2.71009/26/05 wk4-a-18The compound eye10MIT 2.71/2.71009/26/05 wk4-a-19Elements of the compound eye:ommatidia (=little eyes)“image” formation:blurry, but computationally efficientfor moving-edge
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