TheThe HumanHuman EyeEye andand VisionVision 11 (Producing(Producing TheThe Image)Image) Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science InIn thisthis sectionsection .. .. .. υ Anatomy of human eye υ Image formation by human eye υ Method of light detection υ Retinal processing υ Eye optical defects and diseases Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science HumanHuman VisualVisual SystemSystem Exposure Image formation Detection Processing Control •Cornea •Iris/pupil •Retina •Brain •Lens •Photoreceptor •Rods sensitivity •Cones Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science HumanHuman EyeEye Ciliary Muscle Sclera Ear side (Temporal) Iris Vitreous Humor Fovea Pupil Eyelens Retina Optic Nerve Cornea Nose side (Nasal) Aqueous Humor Suspensory ligament Choroid υ Human eye is a complete imaging system. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science ImageImage FormationFormation Object Image υ The curved surfaces of the eye focus the image onto the back surface of the eye. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science CorneaCornea υ The outer wall of the eye is formed by the hard, white Sclera sclera. Cornea υ Cornea is the clear portion of the sclera. υ 2/3 of the refraction takes place at the cornea. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science IrisIris andand PupilPupil Iris υ Colored iris controls the size of the opening (pupil) Pupil where the light enters. υ Pupil determines the amount of light, like the aperture of a camera. Iris open Iris closed Dilated pupil Constricted pupil Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science LensLens Ciliary muscle υ Eye lens is made of transparent fibers in a Lens clear membrane. υ Suspended by suspensory ligament. Suspensory Ligament υ Used as a fine focusing mechanism by the eye; Transparent provides 1/3 of eye’s Fibers total refracting power. υ Non-uniform index of refraction. Cross section of the eye lens Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science AccommodationAccommodation Distant object υ The suspensory ligaments attach the lens to the ciliary muscle. υ When the muscle contracts, the lens bulges out in the Relaxed muscle back, decreasing its focal Taut ligaments Near object length. υ The process by which the lens changes shape to focus is called accommodation. Contracted muscle Slack ligaments Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science AqueousAqueous HumorHumor andand VitreousVitreous HumorHumor υ Transparent Vitreous Humor gelatinous liquid filling the eye. υ Provides nutrients to the cornea and eye lens. υ Also helps maintain Aqueous Humor the eyeball shape with its pressure. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science RetinaRetina υ Retina is the photosensitive “detector” for the eye. Retina υ Two types of receptors in the retina: rods for low light level, and cones for color. Fovea υ Located at the center of the retina, fovea contains a greater concentration of Optic Nerve cones. υ Signals from the receptors leave through the optic nerve to the brain. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science.