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1、Vision: Subjective and Objective IssuesOleh TretiakMedical Imaging Systems2002Why Study VisionUnderstand how to display imagesUnderstand what is seenUnderstand how vision worksSources of InformationPhysics of visionNeurophysiology of visionPsychology of visionPsychophysicsReferencesDavid Hubel, Eye,
2、 Brain, and Vision, Henry Hold & Company, 1995James P. C. Southall, Physiological Optics, Dover, 1961Vicki Bruce, Patrick R. Green, Mark A. Georgeson, Visual Perception: Physiology, Psychology, and Ecology, Psychology Press, 1996Visual Pathway - AnatomyVisual Pathway - SymbolicThe Retina and the Eye
3、The EyeballVision and Eye Fixation (motion)Half-retina mapsLayers of the Geniculate NucleusSection through Striate CortexMap From Retina to Striate CortexStriate Cortex Input/OutputIndex of refractionCornea (n2)1.376Aqueous humor and vitreous body (n3 = n7)1.336Outer portion of lens (n4 = n6)1.386Co
4、re-lens (n5)1.406The model is due to Gullstrand (1924). The power of the eye in this model ranges from 58.64 dptr (diopters) to 70.57 dptr. Most of the refraction (43 dptr) is due to the cornea.Subjective Intensity (Contrast) ModelsIn a model for subjective intensity, let x by the brightness (power/
5、area) and y the subjective brightness (contrast). Both x and y range from 0 to 100. Logarithmic model:Power law model:On the next slide we show thirty four steps designed to produce uniform contrast with (1) linear, power law with gamma = 1, (2) power law, gamma = 0.7, and (3) logarithmic. Note that
6、 the appearance of this depends on the transfer function of the display.Simultaneous Contrast ExamplesBackground = 245, circles = 210, 225, and 235Background = 70, circle = 60The circles have the same objective intensity.Typical Visual Spatial ResponseObjective value (intensity)Subjective (perceived) valueMach BandsTypical visual temporal responseBoundariesBrightnessTextureShape PerceptionSize Perception
