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VISION

VISION. Objectives. Explain the visual process, including the stimulus input, the structure of the eye, and the transduction of light energy Discuss the different levels of visual information processing and the value of parallel processing.

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VISION

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  1. VISION

  2. Objectives • Explain the visual process, including the stimulus input, the structure of the eye, and the transduction of light energy • Discuss the different levels of visual information processing and the value of parallel processing. • Explain the Young-Helmhotz and opponent-processing theories of color vision, and describe the nature of color constancy.

  3. Stimulus Input: Light Energy

  4. Great amplitude (bright colors, loud sounds) Short wavelength=high frequency (bluish colors, high-pitched sounds) Long wavelength=low frequency (reddish colors, low-pitched sounds) Small amplitude (dull colors, soft sounds) Vision- Physical Properties of Waves

  5. Vision • Hue • dimension of color determined by wavelength of light • Intensity • amount of energy in a wave determined by amplitude • brightness • loudness

  6. The spectrum of electromagnetic energy

  7. The Eye

  8. The Eye • 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

  9. The Eye

  10. The Eye • 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, containing receptor rods and cones plus layers of neurons that begin the processing of visual information

  11. The Eye • Farsighted Nearsighted Normal

  12. Receptors in the Human Eye Cones Rods Number 6 million 120 million Location in retina Center Periphery Sensitivity in dim light Low High Color sensitive? Yes No Vision- Receptors

  13. The Eye • 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

  14. Pathways from the Eyes to the Visual Cortex

  15. Visual Information Processing

  16. Visual Information Processing • Parallel Processing • simultaneous processing of several aspects of a problem simultaneously

  17. Cell’s responses Stimulus Visual Information Processing • Feature Detectors • nerve cells in the brain that respond to specific features • shape • angle • movement

  18. Feature Detection

  19. Feature Detection

  20. Feature Detection • On ceup on atim ether eweretwobe ars. The yate aloto fhone yan drest edat nigh t.Oned ayat hird be arap prochedan dye l led "Why arey outwobe arsso fat?"

  21. Facial Recognition

  22. Color Detection

  23. Visual Information Processing • Trichromatic (three color) Theory • Young and Helmholtz • three different retinal color receptors • red • green • blue

  24. Color-Deficient Vision • People who suffer red-green blindness have trouble perceiving the number within the design

  25. Visual Information Processing Opponent-Process Theory- opposing retinal processes enable color vision “ON” “OFF” redgreen greenred blueyellow yellowblue black white white black

  26. Opponent Process- Afterimage Effect

  27. Visual Information Processing • Color Constancy • Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

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