Lecture 10 Monochromatic Aberrations

Question 1

This occurs both when light is reflected and when it is refracted. It leads to a lower than expected image quality.

Answer 1

Monochromatic aberrations

Question 2

This does not appear when monochromatic light is used. It also does not appear on mirrors. It is only caused by dispersion of light after refraction.

Answer 2

chromatic aberration

Question 3

What are the 5 groups of monochromatic aberrations and which are on/off-axis?

Answer 3

1. spherical aberration (on-axis)
2. coma
3. oblique astigmatism
4. curvature of field
5. distortion

Question 4

This is related to static vision. I.e.: all systems are aligned on one common axis.

Answer 4

on-axis; human vision

Question 5

This is related to dynamic vision. I.e.: systems are not aligned on one common axis. The eye will change position relative to the lens.

Answer 5

off-axis

Question 6

For on-axis aberrations and human vision we only take ________ vision into account.

Answer 6

foveal vision

Question 7

In hyperopia the far point (R) is in-front/behind the eye. And you use plus lenses (concave/convex) to correct this because it diverges/converges light.

Answer 7

behind the eye; convex; converges

Question 8

In myopia the far point (R) is in-front/behind the eye. And you use minus lenses (concave/convex) to correct this because it diverges/converges light.

Answer 8

in-front; concave; diverges

Question 9

In the moving eye, the aperture stop is at the ______ of ________ of the eye.

Answer 9

center of rotation of the eye

Question 10

To perfectly correct a refractive error for a moving eye, ______-______ sphere and ________ sphere must coincide.

Answer 10

far-point sphere; Petzval sphere

Question 11

Different zones of a large lens have different power. Blurry image.

Answer 11

spherical aberration (on-axis)

Question 12

Light striking a large lens obliquely, instead of forming a focal point, forms a comet-like image. Blurry image.

Answer 12

coma (off-axis)

Question 13

Light striking a small section of lens obliquely, instead of forming a focal point, forms an astigmatic interval. Blurry image.

Answer 13

oblique astigmatism

Question 14

Curved image of a flat object. Blurry image.

Answer 14

curvature of field

Question 15

Magnification of an extended object varies with its distance from the optical axis. Image is not blurry.

Answer 15

distortion

Question 16

The absolute power of a spherical lens increases/decreases away from its optical axis.

Answer 16

increases away; decreases closer?

Question 17

The LSA is along the optical axis. The TSA is a is a blur circle on screen, _________ to the optical axis.

Answer 17

perpendicular to the optical axis

Question 18

for +LSA
The non-paraxial image is located farther/closer to the lens than paraxial image. The absolute peripheral power of the lens is lower/higher than the central power.

Answer 18

closer; higher

For -LSA it is farther and lower

Question 19

Aspheric (cornea) means a _____ center and a ______ periphery.

Answer 19

steep center and flatter periphery

Question 20

Under dim lighting conditions the pupil dilates, exposing the retina to non paraxial light rays. This can be one contribution factor to _____ ________.

Answer 20

night myopia

Question 21

Diameter of your blur circle is ____ your TSA.

Answer 21

twice TSA

Question 22

What are the options for minimizing SA? And which are the most practical for the human eye?

Answer 22

1. aperture stop
2. best form lens (practical)
3. aplanatic system
4. orthoscopic doublet
5. aspheric lenses (practical)

Question 23

For an aplantic system the lenses have the same SA. Given the reversed setup, the second lens _______ the aberration of the first.

Answer 23

neutralizes

Question 24

For spherical lenses the surface eccentricity (E) is?

Answer 24

E (epsiolon) = 0

Question 25

A coma is an unsymmetrical blur that gets smaller/larger as an object point is moved off-axis.

Answer 25

larger as an object point is moved off-axis

Question 26

Coma is asymmetric/symmetric at the tangential plane of the lens and asymmetric/symmetric at the sagittal plane.

Answer 26

tangential: asymmetric; sagittal: symmetric

Question 27

Ways of minimizing coma? Are the two practical ways the same as SA?

Answer 27

1. aperture stop 2. best form lens 3. aplanatic system 4. orthoscopic doublet 5. aspheric lenses yes, same practical ones: best form lenses and aspheric lenses

Question 28

What sort of lenses are those where OA is fully eliminated and both images (s and t) coincide with Petzval's surface?

Answer 28

Point-focal form

Question 29

What is a lens that is chosen to optimize for power error?

Answer 29

Percival's form

Question 30

Tscherning's ellipses express BCs for minimizing OA. It is a relation between front surface and back vertex power. The idea shape of the lenses depends on:

Answer 30

Refractive index of lens (n); Distance of object; Obliquity of incident light; Position of the stop RDOP

Question 31

Wollaston form is ______ curved.

Answer 31

highly curved; steep BC: not used for spectacle lenses

Question 32

Ostwalt form is ______ curved.

Answer 32

moderately curved; flat BC: cosmetically acceptable lenses

Question 33

Pantoscopic tilt and face form wrap induces/reduces OA.

Answer 33

induces OA

Question 34

Face form tilt, the tilt is along the _______ meridian.

Answer 34

vertical

Question 35

In pantoscopic tilt the tilt is along the ________ meridian.

Answer 35

horizontal; 180 degrees