Chapter 5 Flashcards
cornea
hard transparent surface thorugh whichl ligt enters and provides greates optical power
sclera
hard white layer on outer surface of eye
vitreous humor
eye interior that is a transparant gelatinous mass allowing light rays to penetrate with little distortion
aqueous humor
as light rays cross the cornea they pass through this chamber that is transparent and galtinous
lens
cross aqueious humor and hit this through the pupil
size of the pupil is controlled by what
iris - provides aperture regulating amount of ligth allowed to pass
ciliary muscles
optical power of lens altered by these
retina
after lens and vitreous humor hits this which is more than 180 degrees of inner eye boundary
photorecpetors
catch light from output pixels and behave like input pixes
fovea
highest visual acuity and measure of the shapness or clarity of vision- greatest concentration of photoreceptors and almost entirely cones
optic disc
small hole on reitna where neural pulses are transmitted outside of the eye thorugh the optic nerve
types of photoreceptors
rods and cones
rods
triggered by low loevel so flightt
cones
require more light and distinguish between coloes
how many rods and cones does the retina have
120 millions and 6 million respectively
three categories of cones
red green blue
luminance measured in what
si units of candelas per square meter - correspond directly to amount of ligh power per area
scotopic vision
eye take up to 35 mins to fully adapt to low light reulting in monocrhomatic mode
photopic vision
adaptation to trichromatic mode in birght light that takes 10 minutes
peripheral vision
rays that enter cornea from sides alnd on parts of reitna with lower rod density and very low cone density/ better at detecting movement but cannot distinguish colors
blind spot
not photoreceptors - retinas are inside out
layers of neurons
rods and cones to bipolar to amacrine to horizontal cells
inner nuclear layer
holds bipolar amacrine and horizonatl cells
ganglion cell layer
signals from inner nuiclear then reach thie gangilion cells and axons of ganglion are not directly connect to optic nerve but a hole punctured lets them reroute
bipolar cells
tranmit signals from photorecptors to gnaglion. some connect only to cones (1-10) and others connect only to rods (30-50)
types of bipolar cells
on bipolar when rae of photon absorption increases and off for decreasing photon absorption
bipolars connected to cones have what types
on and off
bipolars connected to rods ahve what types
only on
vertical versus horizontal cells
vertical are bipolar but horizontal are connnected by input or dendrites to photorecpetors and bipolar /
lateral inhibition
activation of one photoreceptor tends to decrease activation of neightbors
types of ganglion clels
midget, parasol bistratified
types of filteriing operations performed by ganglion cells
spatial temporal and spectral or color vairations
spatial opponency
nerual structures are disigned to detect local image variations
connection of optic nerve
thalamus called lateral geniculate nucleus
lgn
sends signal sfrom sense to the brain but also processing - send inof to priamry visual cortex (V1)
rotation of each eye controlled by how many muscles attached to the sclera
six
the tendons pull
in opposite pairs
movements based on purpose
saccades, smooth pursuit, vestibulo ocular reflex, optokinetic relfex, vergence, microsacccades
saccades
rapid motion to quickly relocate the fovea so important features from scene are sensed with highest acuity
saccadic masking
hide intervals of time over which saccades occur from our memory - distorted time perception
smooth pursuit
eyes slowly rotate to track moving target features like a car - reduce motion blue (image stabilization)
vestibulo ocular reflex
most important/ eyes rotate to coutneract rotation of head / involuntary/ based on angular accelerations sensed by vestibutlar organs, signals sent ot eyye muslce to counter motion/ provide image stabilitization
optokinetic reflex
occurs when fast object speeds along/ eyes rapidly and involuntarily choose features for tracking while alternating between smooth pursuit and saccade
vergence
align eyes with the object/ if object is closer than previous fixation, then convergence but if object is farther then divergence mtoion (pupils move father)
microsaccades
small involuntary jerks of less than one degree that trace out erratic path/ augment other processes like control of ficaton, reduction of perceptual fading due to adaptation, improve visual acuity and resolve perceptula ambiguityes
factors of good vr visual display
spatial resolution, intensity resolution and range, temporal resolution
spatial resolution
how many pixes per square area are needed
intensity reosltuion
how many intesity values can be produced and what are min and max/ also color resolutionand range
temporal resolutio
how fast do displays need to change their pixels
aliasing
perceive sharp diagoal lines as being jagged (spatial resolution)
screen door effect
image produced by digital lcd projector(spatial resolution)
retina display
326 pixels per linear inch
factors that contribute to acuity tasks
brightness, contrast, eye movements, time exposure, part of retina ctimulated
cycles per degree
corresponds to number of stripes or sinusoidal peaks that can be seen as separate along viewing arc
how much field of view is enough
max is 270, larger than provided by flat screen of less than 180/ inc field of fiew by ringin screenig closer would require high pixed density but lens aberrations at periphery may limit effective/ if eye could be tracked and tiny movable display was always positioned in front of pupil with zero delay, fewer pixels needed
foveated rendering
simulate moving tiny screen by keeping fixed display but focusing graphical rendering only in spot where eye is looking
VOR gain
ratio comparing eye rotation rate numberator to coutner rotation and translation rate of head in denominator
VOR gain is close to
1 with respet to pitch and yaw
rolling scannout
raster scan, rather than glbal because pixels are updated line by line/ dipslays are output analog/ dont perceive the scannout pattern during use because of slow charge and resopnse time of photoreceptors
retinal image slip
eyes move and image of feature may move slightly on retina due to motions and optical distortions
vergence accommodation mismatch
eyes would strongly converge if object redered to screen appeared only 10cm away but theydont need to change optical power of eye lens/ eyes would try to accommodate with effect of blurred perceived image/ stimulus provided by vr is inconsistent with rela world
