Aspheric Lenses Flashcards
2 advantages of aspheric lenses:
reduce off axis aberrations
reduce lens thickness
asphericity of Q=0 means:
it’s a circle
Q>0 is a _ ellipse, and _ curved
oblate, more
-1
prolate, less
if a plane cuts through a cone that is parallel to the side of the cone, a _ is created
asphericity Q= _
parabola
-1 (always flatter than circle and ellipse
incident rays parallel to the axis reflect off a paraboloid, and always pass through the focal point; therefore there are no _ aberrations
spherical
if a plane intersects the cone and its base, the curve is a _
Q=_
hyperbola
from flattest to steepest:
hyperbola, parabola, prolate ellipse, circle, oblate ellipse
as Q becomes more negative, sagittal depth _
decreases
power at the tangential meridian of an ellipsoid is the _
power at the sagittal meridian is the _
minimum
increasing.. max, idk? (smaller radius of curvature)
vertex power is _, (greater than tangential and sagittal)
maximum
power drops off faster along the _ meridian
tangential
with full aspheric lenses, the aspericity starts _ at the vertex
immediately
nonfull aspheric lenses have _
central area that is spherical is called: _
outer part of the lens is usually aspheric for _
a spherical component and an aspherical component
cap
progressive add power
aspheric lenses are flatter than spherical, so their sagittal depths are _
smaller
high +: a lens with an aspheric base curve will flatten the front lens which:
- betters the cosmetics
- decreases RA and curvature of field
- reduces _
thickness
plus lenses: periphery of front and back surfaces are _ ,center remains spherical
flattened (entire lens thinner)
minus lenses: peripheral portion of front is _
peripheral portion of back is _
steepened
flattened
(center is not changed)
an aspheric lens will produce _, and is used for _
progressive power changes
PALs (distance portion is spherical)
aspherical lenses are best used for _ rxs
_ lenses are best used if astigmatism is present
spherical
atoric
atoric lenses have _ surface powers
2 aspheric
like aspheric lenses, atoric lenses will
_ peripheral aberrations
reduce
atoric lenses are recommended for >_D of astigmatism
2.00
atoric lenses are never used for _ rxs
spherical
