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Vision 153-158
Structure of the Eye
We only use light energy to see.
Wavelength
• The distance from the peak of one light wave to the peak of the next.
•The distance determines the hue (color) of the light we perceive.
Intensity
The amount of energy in a light wave.
Determined by the height of the wave.
The higher the wave the more intense the light is.
Vision – front of eyeball – phase 1
Pupil- adjustable opening in the center of the eye
Iris- a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil opening
Lens- transparent structure behind pupil that changes shape to focus images on the retina
Nearsighted Vision
Farsighted Vision
Inner eye – phase 2
Accommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retina
Retina- the light-sensitive inner surface of the eye receptor rods and cones layers of neurons that begin the processing
of visual information
The Retina
Rods and Cones – 125 million rods to 7 million cones per eye!
• Rods – sensitive to variations in light, helps us adjust to dark. Full adjustment = 30 minutes
• Cones – sensitive to color, bright light. Full adjustment = 5 minutes
Retina’s Reaction to Light
Optic nerve- nerve that carries neural impulses from the eye to the brain
Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there
Fovea- central point in the retina, around which the eye’s cones cluster. Greatest visual acuity
Blind spot
Processing from retina to the brain – phase 3
• Bipolar Cells – preliminary sensory reception area. Raw data
• Ganglion cells – neurons that are photoreceptive – processes fine details from cones
• From retina cells go to optic nerve and then optic chiasm
158-163Color Processing
Trichromatic (three color) Theory Young and Helmholtz three different retinal color receptors
red green blue
Color-Deficient Vision
People who suffer red-green blindness have trouble perceiving the number within the design
Visual Information Processing
Opponent-Process Theory- opposing retinal processes enable color vision
“ON” “OFF”
red green
green red
blue yellow
yellow blue
black white
white black
Opponent Process Theory – Afterimage effect
Feature Detection
The concept that specific nerve cells in the brain respond to specific features of the stimulus, such
as shape, angle, or movement.
Parallel Processing• The processing of several aspects of a
problem simultaneously.
Color Motion Form Depth