Optics Lecture 2 Flashcards
How must receptor units be placed to resolve fine details of the pattern imaged on the retina
Sufficiently close together to correctly interpret the pattern
When the visual system correctly interprets the spatial frequency and orientation of pattern
Veridical
Spatial frequency at which finest light pattern that can be correctly resolved by the retina
Nyquist limit
The nyquist limit of the human visual system
60c/deg
The spatial frequency at which the visual system cannot distinguish between light patterns
Aliasing
The spacing of what cells limit resolution
Ganglion cells
Why are PR not a limiting factor for visual resolution
Because peripheral cones are spaced too closely
If only considering neural blur, can contrast be better than 60 c/deg
Yes
If considering optics and neural blur, can contrast be better than 60 c/deg
No
With laser interferometry, how does the contrast sensitivity change
It increases form 60 to 120 c/deg
The 2 major spatial tasks performed by human system
Resolution and detection
Do gang cells increase or decease away from fovea
Decrease
Detection in the central and peripheral vision is limited by
Size of cones
Resolution and detection at fovea
Patters reliably resolved and detected
Resolution and detection at peripheral (30 deg nasal)
Reliably detect but not resolved
Between detection and resolution is called
Aliasing
3 steps of letter recognition
Detection
Resolution
Identification
Reasons for discrepancy on central visions impact on retinal image quality
- Overestimation bc scattering is being ignored
- emphasis on MTF (ignore PTF)
Most important optical defect affecting retinal image quality is
Defocus
Polychromatic light impact on retinal image quality: max contrast sensitivity loss of ______ and a visual acuity loss of _____
.2 log unit
10 %
TCA causes loss of
Image contrast
What is the stiles-Crawford effect on retinal image quality
Influence optimal refraction in presence of aberrations, but the magnitude is likely to be small
The luminous efficiency of rays entering at the center of the pupil is (>/
Greater than
Influences the VA and visual performances of the eye
Stiles - Crawford apodization
How does pupil decentration affect retinal image quality
Induces additional aberrations, like TCA, which decrease spatial visual performance
How does retinal image quality change with object angle
It steadily declines
