Optics: Retinal Image Quality 2 Flashcards
Seven factors that affect retinal image quality:
-retinal receptor spacing
-central vision
-aberration
-polychromatic light
-stile-Crawford effect
-pupil de-centration
-peripheral vision
What does the ability to resolve the fine details depend on?
The receptor units within the retina must be sufficiently close together to correctly interpret the pattern
What is the nyquist limit?
The visual system is JUST able to resolve the pattern
When is the system considered veridical?
When the visual system correctly interprets the spatial frequency and orientation pattern
When is the system considered at the nyquist limit?
When the spatial frequency is at the finest light pattern that can correctly be resolved by the retina
What is the nyquist limit of the human visual system (value)?
60cpd or 20/10
What is aliasing?
The spatial frequency at which the visual system cannot distinguish between light patterns
What is visual resolution limited by?
The SPACING of the ganglion cells in the retina
Why is the reason for resolution limits correlating to the ganglion cells spacing?
Because there is a 1:1 correspondence between the cones and ganglion cells
peripheral cones and resolution limitations:
Peripheral cones are spaced too closely to be a limiting factor for visual resolution
Resolution/contrast cannot be better than 60cpd. true or false
-true if considering optics and neural blur
-false if only considering neural blur
What can the contrast sensitivity of the human eye be increases to with laser inferometry?
120 cpd
What are the two major spatial tasks performed by the human system?
Resolution and detection
What is detection?
The ability of the patience to detect that a spot of light is present —> details not important
Detection in the central and peripheral vision is limited by what?
The size of the cone photoreceptors
What are pattern resolution and pattern detection limited by?
Neural architecture of the retina
In the periphery, things can be __________, but not very well _________
Detected, resolved
Hierarchy of vision:
Detection < resolution < identification
Why is there variation in retinal image quality between different eyes?
There is a scattering effect being ignored
What optical defect affects the retinal image quality the most?
Defocus
Pupil decentration affecting retinal image quality:
Decentration of the pupil can induce optical aberrations (transverse chromatic aberration and coma) that decrease spatial visual performance
Why are optics associated with the periopheral retina poor?
Focusing errors in the form of oblique astigmatism and field of curvature
Retinal image quality declines steadily with ______________
Object angle
Improving peripheral optics has ______ improvement in resolution but __________ improvement in detection occurs
Little, marked
