Visual Perception 4 Flashcards
points on the retina that overlap if the eyes are superimposed on each other
corresponding retinal points
if we superimpose the 2 eyes then the two retinal images….
overlap
what is a horopter
hypothetical surface
-objects that fall on the horopter create corresponding retinal points
objects that don’t fall on the horopter create what
non-corresponding points
the difference btwn the non-correspoding retinal points from the hypothetical corresponding points is called
disparity
corresponding retinal points have ___ dispartity while noncorr points have ____ dispartiy
corr: 0
non-corr: greater than 0
the horopter is a surface of ___ disparity and its position in the vf depends on the ____ of the eye (fixation)
0
convergence
objects with 0 disparity are seen as ___ objects
objects w/ dispartiy diff from 0 are seen as ____
single
2-known as diplopia
what is panum’s fusional area
the area close to the horopter that can generate objects w/ 0 disparity
objects that are further away from the horopter have ___ angle of disparity (or abs dispartity) from objects that are closer to it
larger
what does absolute disparity indicate
distance from the horopter (or the plane we are focusing on)
what is relative dispartiy
what can this give us info about
the difference btwn the absolute disparities of 2 objects
-can give us info about the object’s position relatve to each other
relative disparity remains always the ___ btwn 2 objects as we move our eyes and scan a scene
same
-this constant diff in disparity gives us info about the ______ of objects
relative position
for depth perception, we use _____
absolute and relative disparity
for depth perception, we use absolute dispartiy for…
relative disparity for…
absolute: to judge an object’s distance from the plane of focus (horopter)
relative: judge the relative positions of objects
what are the 2 kinds of dispartity
crossed and uncrossed
what dispartiy is the objects always in front of the horopter
crossed disparity
what disparity is it when the object is always behind the horopter
uncrossed
crossed and uncrossed disparity is also called the ….
sign of disparity as we can tell whether an object is (+) or (-) the horopter
what is the perception of depth called
stereopsis
what is the geometrical description of how the objects are projected on the retina
disparity
the stereoscope, view master, 3D movies and 3D tvs all use the same principles, they project lightly diff images on the retina causing…
disparity and therefore depth info
what project different images on each eye through an optical system
stereogram (steroscope?) and view master
how do 3D movies work with imgs of different color
2 slightly diff images are having diff color characteristics
usually one greenish one reddish
-by using tinted filters, one red and one green, the red img will be transmitted through the green filter and a diff image will be projected on each eye
-disparity btwn 2 diff image=depth perception
how do 3D images work with polarized light
one image reflects polarized light in one direction while the other image reflects polarized light in another direction
-polarized lenses used that permit only one polarization to go through
what is the passive method for 3D TV
polarized images are generated by the TV and again by using polarized glasses each image is projected only on one eye
what is the active method for 3D TV
2 images are fast alternating on the screen
- special glasses have an electronic componenet/shutter
- each shutter is synchronized to only be open only when the first image is presented while the other remains shut and therefore there is no image on the other eye
- the alternation must be higher thant he CFF so you don’t detect flicker
how is steropsis used in military and medicine
military: usd to help appreciate the height, size, and shape of a target
medicine: taking x-rays from diff positions to create retinal dispartiy and would be able to see a tumor popping out
all these methods provide steropsis bc of ____
but all the images we see (either in movie theatre, tv, or stereoscope) provide ______
disparity monocular cues (ex. occlusion)
what are random-dot stereograms
presenting only binocular disparity w/ no monocular cues
-the fact that people perceive floating objects here suggest that disparity alone is a sufficient cue for stereopsis
what is the corresponding problem
in order for disparity to work, the visual system matches the corresp points on the left and right retina
-for real world scenes, the visual system may match objects using specific features
ex. round with round, corner w/ corner
-most objects in the real world are discriminable (can tell part from other objects)
-our perceptual system corresponds one point to another even though it is complicated and our visual system calculates disparities
NO ANSWER TO CORRESPONDING PROBLEM.
-dont know how our visual system matches the corresponing points and calculates the disparities to create the perception of depth
why is the visual system unable to calculate disparity for steropsis in stabismus
there are no corresponding points on the left and right retina
the perception of ____ is affected by stereopsis
size
cant judge that an object is distant or near and therefore can’t judge its size
what is the holway and boring experiment
aka hallway experiement
- test stimulus can move back and forth and can change size so as to have the same visual angle on the retina
- task for observer is to look at the stimulus and change the size of the comparison stimulus to be the same size as the test stimulus
when the conditions were ______ the observers did a good job matching the sizes of the 2 stimuli
free-viewing
size estimation is based on the….
physcial sizes of objects when depth cues are available
size estimation is influenced by…
the objects visual angle when depth info isn’t available
what is size constancy
our perception of an objects size is relatively constant, even when we see it from different distances (diff visual angles)
what is it called when a mechanism uses a mathematical equation proposed to explain size constancy
size-distance scaling
size-distance takes what into account
objects distance
what is the equation to size-distnace scaling
which ones change together and what remians the same
S=a(RxD)
S=perceived img
R=retinal img
D=viewing dist
a=constan
R and D chnage together (direct rel’n) so S remains the same
what is emmert’s law
the farther away an afterimage appears, the larger it will be perceived
when the size constancy euqation is not applied correctly, forcing us to perceive different sizes, what is this called
misapplied size constancy
what does the misapplied size contancy fail to explain
similar illusions w/ no obvsious perspceticve
