Aberrations of optical system Flashcards
why do monochromatic aberations happen
from the shapes and positions of optical surfaces and to the positions of limited aperatures
why do chromatic aberrations happen
variation in refractive index w/ wavelength of light (dispersion)
what are the seidel aberrationst hat are most relevant for the eye
SA
coma
radial astig
which seidel aberr are mainly considered in the quality of ophthalmic lenses
curvature of field
distortion
what is positive SA
what lenses does this happen for
marginal rays focus in front of the paraxial rays
marginal zones have more positive power than the central zone
-positive spherical lenses
what is negative SA
what lenses does this happen for
marginal rays focus in back of paraxial rays meaning the marginal zones have less power than the central zone
- positive aspheric surfaces that have a steeper curvature in the center than in the periphery
- negative sph lenses
what is longitudinal SA
the difference in positiion of the marginal and paraxial foci along the optic axis
what is lateral SA
the difference in position of the marg and paraxial rays in the plane of the paraxial focus
how are SA minimized in real eyes
small pupil diameter
aspheric surface
gradient refractive index of lens
what is positive coma
marginal rays meet at a location further from the optic axis
brighttest image on bottom
what is negative coma
marginal rays focus closer to the optic axis than the chief ray, brightest at top
when does pincushion distortion happen
when an off axis ray falls beyond the chief ray
high plus
when does barrel distortion happen
when an off axis ray falls closer to the optic axis than the chief way
high minus
a stop in front of a positive lens will cause what kind of distortion
barrel
a stop in back of the postivie lens will cause
pincushion
