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VISION
LIGHT
 Electromagnetic
energy
described in wavelengths
 Main colors of the spectrum:
ROYGBIV
PUPIL
 Determines
into eye
amount of light let
LENS
 Focuses
light rays onto the
retina.
 Adjusts to the distance of objects
by changing its thickness (squint)
RETINA
 Nerve
layer that lines the back of the
eye.
 Contains rods, cones, & neurons
(photoreceptors) that process visual
stimuli
 Macula -- a small area in the retina
- allows us to see fine details
clearly.
BLIND SPOT
 Part
of retina that contains no
photoreceptors
 Located where Optic Nerve
leaves the eye
CORNEA
 The
clear front window of the eye.
The cornea transmits and focuses
light into the eye.
IRIS
 The
colored part of the eye. The
iris helps regulate the amount of
light that enters the eye.
 Vitreous
-- the clear, jelly-like
substance that fills the middle of the
eye.
OPTIC NERVE
 Connects
 Carries
the eye to the brain
the impulses formed by
the retina to the brain, which
interprets them as images.
RODS & CONES
 Rods
- night vision; black & white,
light & dark
95% of photoreceptors are rods
Rods - long + narrow
RODS & CONES
 Cones
Responsible for color vision
About 5% of photoreceptors
Rods - thick + tapered
3 Types:


Red, Green/Yellow, Blue/Violet
COLOR BLINDNESS
 Partially
or totally unable to
distinguish color
COLOR BLINDNESS
 People
who see all colors called
trichromats (from the Greek
term meaning “three colors”
 Smaller number of people see only
two colors = dichromats
COLOR BLINDNESS
 Monchromats
-- See the world in
only black and white. Occurs in
about 1 in every 100,000 men.
COLOR VISION
Circle – light spectrum is bent
in a circle – colors across from one
another are complimentary
 Color
COLOR VISION
 Afterimage
=
visual sensation that occurs
after original stimulus has been
removed
Is seen in the complimentary
color
-Stare at the eye of the red parrot while you count
slowly to 20, then look immediately at one spot in the
empty bird cage. The faint, ghostly image of the blue
green bird will appear in the cage.
-Try the same thing with the green cardinal. A faint
magenta bird will appear in the cage.
-Stare at the eye of the red parrot while you count
slowly to 20, then look immediately at one spot in the
empty bird cage. The faint, ghostly image of the blue
green bird will appear in the cage.
-Try the same thing with the green cardinal. A faint
magenta bird will appear in the cage.
ADAPTATION
 Dark
adaptation = rods & cones
become more sensitive to light
(entering a dark room)
 Light
adaptation = r & c become
less sensitive (leaving dark room
into light)
VISUAL ACUITY
 Sharpness
of vision
 Determined by the ability to see
visual details
Corrective Lenses