aberrations

Question 1

what is aberration

Answer 1

aberration is deviation from perfection

can be part of optical system or in our eyes

Question 2

what is ideal image formation?

Answer 2

all rays meet at same point

Question 3

what is non-ideal image formation?reality

Answer 3

rays diffract by different amount

rays converge to several points

Question 4

what are the two types of aberration?

Answer 4

. monochromatic

. chromatic

Question 5

what is chromatic aberration?

Answer 5

is a consequence of the refractive index if material being function of wave length
effect resulting from dispersion

Question 6

what does the wavelength of light in chromatic aberration determine?

Answer 6

. wavelength of light determines how much the material slows down the light
. higher refractive index=slower speed
. resulting in a blue light having a reduced focal length

Question 7

how to correct chromatic aberration?

Answer 7

achromatic doublet

Question 8

what is monochromatic aberration?

Answer 8

aberration that arises due to geometry

Question 9

what are the 5 types of monochromatic aberration/seidel aberration?

Answer 9

. spherical aberration
. coma
. astigmatism
. field curvature
. distortion

Question 10

what are the effects of monochromatic aberration?

Answer 10

.extended size for a point image
.curved image plane
. extended images are no longer geometrically similar to the object

Question 11

what is spherical aberration?

Answer 11

. affects images off and on axis
. occurs for lenses made with a spherical surface
. can be controlled by using an aperture stop to eliminate the rays further away from the optical axis

Question 12

what is coma?

Answer 12

. affects off-axis objects
.can be corrected by combination of lenses or an aperture stop
.asymmetrical like the tail of a comet

Question 13

what is astigmatism?

Answer 13

. affects off-axis objects
.causes two focus points one in the horizontal and one in the vertical
.light rays are focussed at different points for each of these two axis

Question 14

what is field curvature?

Answer 14

. occurs for off-axis objects
. For the human eye field curvature is an advantage given the shape of the imaging
surface (i.e. the retina is curved)
.every lens has field curvature due to spherical nature
.can only happen along one axis

Question 15

what is distortion?

Answer 15

. occurs due to geometry of lens
. occurs when linear magnification if a function of the off-axis distance
. off-axis

Question 16

what are the two types of distortion?

Answer 16

. barrel distortion

. pincushion distortion

Question 17

what is barrel distortion?

Answer 17

image magnification decreases off-axis

Question 18

what is pincushion distortion?

Answer 18

image magnification increases off-axis

Question 19

what is the relationship between diameter of airy disk and aperture and wavelength?

Answer 19

. diameter of airy disk increases as aperture decreases and wavelength increases

Question 20

what is is the relationship between aperture size and diffraction?

Answer 20

large aperture size=small diffraction