Imaging with a thick lens

Question 1

why use cardinal points?

Answer 1

the basic imaging properties such as image size, location, and orientation are completely determined by the locations of the cardinal points

Question 2

Where do we act like all the refractions occur at in thick lens?

Answer 2

principal planes

Question 3

nodal points

Answer 3

have the property that a ray aimed at one of them will be refracted by the lens such that it appears to have come from the other. and with the same angle with respect to the optical axis

Question 4

Assumptions of thin lenses

Answer 4

• both sides in same medium
• lens is thin, 0 thickness
• paraxial approximation

Question 5

how can you tell in a thin lens, that the same medium is on both sides of the lens

Answer 5

equal focal lengths on either side of the lens

Question 6

if the focal length is shorter on one side of the thin lens…

Answer 6

the short side is in a medium with higher RI

Question 7

principle plane

Answer 7

• refraction happens at principle plane
• not really a flat surfaces
• curved

Question 8

principal point

Answer 8

where the principle plane intersects the optical axis

Question 9

Rule number 1 in thick lens

Answer 9

parallel then refracts at H’

Question 10

rule number 3 of thick lens

Answer 10

goes towards N, goes straight across to N’ and then comes out of lens at the same angle as it entered lens
ANGLE PRESERVATION
there is a virtual parallel displacement from N’ to N

Question 11

P=N

Answer 11

in a lot of thick lens systems, but not always

Question 12

actual rays

Answer 12

are subjected to two refractions, one per refracting surface

Question 13

conventional rays

Answer 13

change path only when encounter the prinicple planes (parallel and focal ray) or the nodal points (the nodal/radial ray)

Question 14

Ray propagation in a thick lens

Answer 14

rays do not pass through the cardinal points, however it is very useful to follow the rules of conventional rays to find the final path of any ray

Question 15

object distance in thick lens

Answer 15

measured from H

Question 16

image distance in thick lens

Answer 16

measured from H

Question 17

thick lens imaging relationship

Answer 17

1/xo + 1/Feff = 1/xi

Question 18

focal length measurement when rays propagating from right to left

Answer 18

measured from the principal plane H’

Question 19

focal length measurement when rays are propagating from left to right

Answer 19

measured from the principal plane H

Question 20

thin lens in contact optical power

Answer 20

Ptot=P1+P2

Question 21

optical power in a lens system: general

Answer 21

Ptot=P1+P2-(d/n)P1P2

Question 22

optical power in lenses separated by distance in air

Answer 22

Ptot=P1+P2-dP1P2

Question 23

d

Answer 23

the distance from the object space principal plane of the first lens (H’) to the image space principal plane (H’2) of second lens

Question 24

for calculation of the principle point locations as well as nodal point locations

Answer 24

use the object space principal plane of the first lens (H1), and for the image space, the image space principal plane (H’2) of the second lens

Question 25

the origin from which we measure gamma and gamma’ as well as thickness (d)

Answer 25

principal point P1 and the principal point P2 respectively.

these points now have the role of the respective V and V’ points

Question 26

imaging with two or more lenses

Answer 26

1. we find the reduced system cardinal points
2. locate the image by application of the thick ray diagrams
   OR
   employ the analytical expressions

Question 27

use of the intermediate object

Answer 27

1. find the location and size of the primary image by applying summation of beam vergence and optical power (analytical solutions)
   OR
   locate the primary image with ray fiagrams apllicable for a single, thin lens (schematic solution)
2. this is the intermediate object. The pricedure may be repeated for any additional optical element

Question 28

Use of intermediate object

Answer 28

• if 2nd lens appears to block the construction rays, we ignore it for now
• to find final image from intermediate object, we now ignore first lens and trace rays and find image location as normal