What Limits Vision Flashcards
What is the limit of human retina
300 pixels/inch
Which PSF corresponds to a small pupil?
Large airy disc
Between vision is achieved with
A. With a more confined PSF
B. With a less confined PSF
C. PSF size doesn’t matter
With a more confined PSF
The we consider diffraction only, better vision is achieved with
Larger pupil
PSF without aberrations would be what
Airy disc
Aberrations and pupil size
Get worse with larger pupil
Larger pupil with diffraction only
Increased VA
Aberrations and pupil size
Worse with larger pupil
What is the sweet spot for diffraction and aberration
2-3mm pupil
Pupil-dependent limit to vision
About 1 arcmin
What is not taken into consideration when talking about retinal display
Viewing display
The required pixel density to meet the criterion for retinal display
Varies depending on size of display
What kind of screen has potential to be a retinal display?
Any if at the right distance
Resolution limit for the standard vision human eye
1 arcmin
Pixel density for retinal display
1 pixel per 88microns, over an inch, 288 pixels make it 300
What part of the eye os responsible for image formation?
Cornea, lens, pupil
Aberrations and diffraction
Image collection and recording in eye
Retina (photoreceptors)
What is the average cone spacing in fovea
2.6microns, 0.5 arcmin
Cone spacing
Rods and cones behave differently and aren’t dispersed evenly
With half the photosensor pixel size, resolution is
Double
What signal do we perceive
Analog
What signal do we send to the brain
Digital
Limitations imposed by cone signaling
If the signal has more dense info, this wont be picked up
Sensor spacing=cone spacing (fovea)
Digital sampling limit to vision
0.5 arcmin
What do you control with pinhole
Depth of field
What are the two jobs of pinhole
- Sweet spot
2. Increase depth of focus
What does pinhole ultimately do
Aberration and diffraction still there, but all these effects are least possible with pinhole
What does pinhole visual rule out
Pathology
Diffraction effects due to a small pinhole contribute to what
- Increase of the size of the circle of least confusion
- increases the range of acceptable vision (depth of focus)
- reduces effects of aberrations
Pinhole occluder said with a _____ aperture are used during routine ocular examination to benchmark the potential for best refractive visual correction
1.2mm
The pinhole allows individuals with a refractive error up to _______ to see up to ______ logMar
5 diopter
0.17 logMAR
