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Optics II > Achromatic Aberrations > Flashcards

Achromatic Aberrations Flashcards

1
Q

“______ limited” system is considered to be perfect

A

diffraction-limited system

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2
Q

what can diffraction limit?

A

it ultimately limits the quality of an optical system, even if there is no scatter or aberrations and the system is in focus

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3
Q

2 types of aberrations

A

monochromatic and chromatic

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4
Q

for axial points the wavefront aberration has only one component, which is :

A

spherical aberration

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5
Q

for off-axis points there may be one or more additional components, including:

A
  • coma
  • oblique astigmatism
  • curvature of field
  • distortion
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6
Q

rays from outside the paraxial zone form a:

A

rather large “blur patch” around the paraxial focus, P’

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7
Q

what is the smallest blur patch called and what is it analogous to?

A

the “waist” or “clc”, it is analogous to the circle of least confusion

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8
Q

what is special about “fast” optical systems with a wide field of view?

A

they must be of high precision and such systems are object distant dependent

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9
Q

what is a drawback of the precise “fast” optical systems

A

if designed to be aberration-free for distant objects, aberrations will be present for a near object, and vice versa

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10
Q

what are other names for the “5 components resulting from the 3rd order term of the sine expansion”?

A

Seidel aberrations, primary aberrations, 3rd order aberrations, or aberrations of form

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11
Q

all aberrations are _____ ______ dependent

A

object distance (x)

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12
Q

what type of aberration would be important in spectacle lenses and why?

A

oblique aberrations are important since the eye may rotate and look obliquely through the lens

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13
Q

what types of aberrations wouldn’t be as important in spectacle lenses and why?

A

aberrations that are aperture-dependent are small and of less importance because the aperture of these lenses is effectively limited by the pupil

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14
Q

are the monochromatic aberrations in the eye small or large and why?

A

monochromatic aberrations of the eye are rather small, especially if the diameter of the pupil also is small

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15
Q

Δω= magnitude of

A

magnitude of the transverse aberration

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16
Q

Δω is the distance between:

A

point where the actual ray crosses the paraxial image plane and the paraxial image point

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17
Q

y=

A

the distance of the object point from the optical axis

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18
Q

ρ= the ___ _____

A

zone radius

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19
Q

ρ, the zone radius, is the distance of:

A

the distance of the ray from the center of the entrance pupil

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20
Q

C30 ρ^3 =

A

spherical aberration

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21
Q

C21 ρ^2 y =

A

coma

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22
Q

C12 ρ y^2 =

A

oblique astigmatism

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23
Q

D12 ρ y^2 =

A

curvature of field

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24
Q

C03 y^3 -

A

distortion

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25
Q

spherical aberration depends only on the:

A

zone radius (ρ)

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26
Q

spherical aberration applies to what type of axis points?

A

both on and off axis object points

27
Q

ls / ts =

A

xs’ / ρ

28
Q

in SA, the peripheral ray crosses the optical axis at a distance ___ from the paraxial focus

A

ls

29
Q

the term ( ls ) stands for

A

longitudinal spherical aberration for a ray

30
Q

in SA, the distance of the ray from the paraxial focus as it crosses the paraxial image plane is called ____

A

ts

31
Q

the term ( ts ) stands for

A

the transverse spherical aberration

32
Q

if the object is a single point on the optical axis, then all of the primary aberrations are zero except ______

A

spherical aberrations (SA)

33
Q

longitudinal SA may be expressed in dioptric form as

A

(1/xs’) - (1/x)

34
Q

xs’ = the distance from….

A

the distance from the lens to the point where the peripheral ray crosses the OA

35
Q

u= shape factor =

A

(r2 + r1) / (r2-r1)

36
Q

v= position factor =

A

(x’ + x) / (x’ - x)

37
Q

what is the term “lens bending” used to do?

A

lens bending is a term used to denote the selection of an optimum lens shape (surface radii) while holding lens power fixed

38
Q

what is the shape factor for plano-convex, equiconvex, and convex-plano?

A

plano-convex: u= -1
equiconvex: u=0
convex-plano: u= +1

39
Q

what would the ratio of surface radii (r2/r1) value for a lens that minimizes SA for a distant object?

A

about -6

40
Q

shape that best minimizes SA for a distant object is

A

a biconvex shape close to a convex-plano shape

41
Q

shape that best minimizes SA for an image at infinity (near object)

A

close to a plano-convex

42
Q

the principle behind fining an optimum lens shape is: the SA for a lens or system of lenses is minimizes by causing ……

A

by causing deviations to be equally divided between the surfaces

43
Q

the maximum SA when the EP and AS are the same for a single thin lens is proportional to:

A

the square of the AS diameter

44
Q

the Δω for coma is:

A

Δω= C21 ρ^2 y

45
Q

since coma is zero for on-axis image points (y=0)… coma only affects what kind of image points?

A

only affects off-axis image points

46
Q

describe what it means by ‘coma has a fairly strong dependence on zone radius’

A

the rays through the lens periphery will be aberrated much more than rays near the center of the lens

47
Q

describe coma

A

for off-axis pencils, rays passing through peripheral zones of the lens will come to a focus at points laterally displaced from rays through more central zones of the lens

48
Q

the lens shape that causes coma to be zero is

A

close to the lens shape that minimizes SA

49
Q

when an object is at infinity, the shape factor (u) that minimizes coma is:

A

about -9

50
Q

what are the two aberrations that are proportional to y^2ρ

A

oblique astigmatism and curvature of image

51
Q

in oblique astigmatism, what are the orientations of the line foci in the conoid of sturm dependent on?

A

they depend on the orientations of the tangential and sagittal planes and the orientations of these planes depend on the position of the off-axis object point

52
Q

the TLF is defined as

A

the tangential line focus is perpendicular to the tangential plane

53
Q

the SLF is defined as

A

the sagittal line focus is perpendicular to the sagittal plane

54
Q

list the Dt, Dsg and D values in order from greatest to least

A

Dt > Dsg > D

55
Q

(TLF or SLF)

the ____ is always closer to the lens than the _____ and both are closer than the paraxial focus

A

the TLF is always closer to the lens than the SLF

56
Q

an extended object presented to an optical system with no aberrations except curvature of field would be brought to focus how?

A

on a curved surface rather than a plane surface

57
Q

the power Dt and Dsg give the ____ of the line foci but tell us nothing about the ____ of the line foci

A

positons

lengths

58
Q

the lengths of the line foci are directly proportional to the

A

lens aperture diameter

59
Q

oblique astigmatism may be reduced by the choices of the:

A

convergent and divergent surfaces (front and back curves) of a spectacle lens

60
Q

the Δω for distortion is

A

C03 y^3

61
Q

distortion depends only on the:

A

distance of the object from the OA

62
Q

which aberration has no dependence on zone radius (aperture size)?

A

distortion

63
Q

explain distortion

A

the lateral magnification of an image either increases or decreases as one moves off-axis

64
Q

how does distortion affect shape and/ or blur of an image?

A

the shape of the image may differ from that of the object, but imagery is sharp- distortion is not blur or loss of resolution

Optics II (7 decks)

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