Week 13 Quiz: Aberrations

pantoscopic and face-form

2 most common types of tilts

1. reduce marginal astig and distortion 2. choose lens curvatures that give the power desired

2 things to do to achieve best performance for lenses

1. refractive index of lens decreases 2. power of lens increases 3. size of aperature increases

3 things that cause spherical aberration to increase

1. only the central 3 mm of the cornea is spherical 2. iris restricts marginal rays 3. lens has a gradient index of refraction

3 ways the eye can correct spherical aberration

1. spherical aberrations 2. coma 3. marginal astigmatism 4. curvature of field 5. distortion

5 types of monochromatic aberrations

true

T/F: as humans, we do not have much problem with spherical aberrations

false ; no because iris limits oblique rays entering the eye

T/F: coma is a problem for human

true

T/F: if a point source of light contains all wavelengths in the visible spectrum then light will not focus at a single point

aberrations

___ cause the image to be blurred and distorted

shorter ; more

blue wavelengths are ___ and bend ___

higher ; myopically

blue wavelengths have a ___ refractive index and focus ___

high plus or high-powered bifocal lenses

chromatic aberrations can be ignored except in these 2 cases

chromatic difference of magnification

clinically: color fringes

cone

coma causes the image to appear blurred in a ___-shaped fashion

bifocals

common example of pantoscopic tilt

retina

curvature of field is desired in the eye because the ___ is curved

dispersion formula

defines how refractive index varies with wavelength

chromostereopsis

depth perception due to chromatic aberration

transverse chromatic aberration

difference in magnification as a function of wavelength

curvature of field

discrepancy between the actual image surface and the far point sphere surface

TCA = h(LCA)

equation used for TCA in fovea

TCA = z(LCA) x sin(w)

equation used for TCA in peripheral retina

further ; negative spherical aberration

for concave surfaces, the marginal rays cross the optical axis ___ from the surface of the lens than the paraxially rays what is this called?

closer ; positive spherical aberration

for convex surfaces, the marginal rays will cross the axis ___ to the surface of the lens than the central, paraxial rays what is this called?

displaced pupil

in the fovea, there is induced TCA for ___

off-axis

in the peripheral retina, there is induced TCA for ___ objects

off-axis

is coma on-axis or off-axis?

on only one that is on-axis

is spherical aberration on-axis or off-axis?

Fe and K'

n(wavelength) will affect both the ___ and ___ of the eye

coma

occurs because each portion of a lens has a different focal power

spherical aberration

occurs when light is incident upon a large diameter lens so that both the paraxial and marginal rays are refracted

marginal (oblique) astigmatism

occurs when rays from an object pass obliquely through a lens; the interval between the tangential and sagittal foci

teacup, saucer, plate

order of 3 surfaces for oblique astig

longer ; less

red wavelengths are ___ and bend ___

lower ; hyperopically

red wavelengths have a ___ refractive index and focus ___

smaller

shorter wavelengths subtend a ___ angle than longer wavelengths

longitudinal chromatic aberration

the chromatic difference of focus when the image of source formed by blue rays is formed in front of the image formed by red rays

curved

the image formed on the retina is ___

location

the images of different wavelengths in a point source of light will vary in ___ along the optical axis (LCA)

size/magnification

the images of different wavelengths in a point source of light will vary in ___ on the curved retina (TCA)

more

the rays that enter the prism closer to the apex are deviated ___ than the rays entering close to the base

petzval surface

the tangential and sagittal surfaces are brought together in one image surface called ___

barrel distortion ; minus

type of distortion? minus or plus lens?

pincushion distortion ; plus

type of distortion? minus or plus lens?

achromatic doublet

type of lens that eliminates chromatic aberrations

pantoscopic tilt

type of tilt where lens is curved away from face

retroscoptic tilt

type of tilt where lens is curved toward the face

face-form tilt

type of tilt where lenses frame the face

anti-face form tilt

type of tilt where the lenses frame away from the face

589 nm

wavelength perfectly focused on the retina in emmetropes