Overview: composite optical elements
ray from
infinity
FFP
BFP
FFL
1st
PP
then goes
through the BFP
BFP
bends at
1st PP
EFL
2nd
ray from
the FFP
FFP
BFL
EFL
bends at
2nd PP
1st PP
PP
1st PP
then goes
on to infinity
2nd PP
2nd PP
BFP
object
image
FFP
EFL
EFL
MIT 2.71/2.710
02/23/09 wk4-a- 1
1
Today
•
Apertures & Stops
– Aperture
– Entrance Pupil
– Exit Pupil
– Field Stop
– Entrance Window
– Exit Window
MIT 2.71/2.710
02/23/09 wk4-a- 2
2
Aperture Stop and Numerical Aperture
medium of
refr. index n
Aperture stop
the physical element which
limits the angle of acceptance of the imaging
system
θ: half-angle subtended by the imaging
system from
an axial object
Numerical Aperture
Speed
pronounced f-number, e.g.
f/8 means (f/#)=8.
The Aperture Stop
limits the optical energy
that is admitted through the system
Later we will also learn that the NA also
defines the resolution (or resolving power) of
the optical system
MIT 2.71/2.710
02/23/09 wk4-a- 3
3
Entrance & exit pupils
image through
preceding elements
entrance
pupil
aperture
stop
image through
succeeding elements
exit
pupil
multi-element
optical system
MIT 2.71/2.710
02/23/09 wk4-a- 4
4
The Chief & Marginal Rays
M.R.
C.R
.
Chief Ray: Starts from off-axis object, goes through the center of the Aperture
Marginal Ray: Starts from off-axis object, goes through the edge of the Aperture
Together, the C.R. and M.R. define the angular acceptance of spherical ray bundles
originating from an off-axis object.
MIT 2.71/2.710
02/23/09 wk4-a- 5
5
The Chief & Marginal Rays
M
.
.R
.
R
.
C
Corollaries:
Chief Ray also goes through the center of the Entrance & Exit Pupils
Marginal Ray also goes through the edge of the Entrance & Exit Pupils
The Chief and Marginal Rays meet again at the image
MIT 2.71/2.710
02/23/09 wk4-a- 6
6
The Field Stop
Limits the angular acceptance
of Chief Rays
MIT 2.71/2.710
02/23/09 wk4-a- 7
7
The Field Stop
FoV
Defines the Field of View (FoV)
MIT 2.71/2.710
02/23/09 wk4-a- 8
8
Entrance & Exit Windows
image through
preceding elements
image through
succeeding elements
M.R.
C.
R.
field
stop
entrance
window
exit
window
MIT 2.71/2.710
02/23/09 wk4-a- 9
9
All together
M.R.
C.
R.
entrance
entrance pupil
window
field
stop
aperture
stop
exit
pupil
exit
window
MIT 2.71/2.710
02/23/09 wk4-a-10
10
All together
C.
R.
FoV
field
stop
aperture
stop
entrance
exit
exit window
entrance pupil
pupil
window
The Field of View is the angle between the pair of Chief Rays
that just make it through the edges of the Field Stop
MIT 2.71/2.710
02/23/09 wk4-a- 11
11
All together
NA
field
stop
aperture
stop
entrance
exit
exit window
entrance pupil
pupil
window
The Numerical Aperture is the angle between the pair of Marginal Rays that just make it through the edges of the Aperture Stop MIT 2.71/2.710
02/23/09 wk4-a-12
12
Example: single-lens camera
2nd FP
1st FP
size of
film
or digital
detector
array
object
plane
image
plane
MIT 2.71/2.710
02/23/09 wk4-a-13
13
Example: single-lens camera
2nd FP
1st FP
object
plane
Aperture
Stop
& Entrance
Pupil
image
plane
MIT 2.71/2.710
02/23/09 wk4-a-14
14
Example: single-lens camera
2nd FP
1st FP
object
plane
Exit
pupil
(virtual)
Aperture
Stop
& Entrance
Pupil
image
plane
MIT 2.71/2.710
02/23/09 wk4-a-15
15
Example: single-lens camera
mar
chi
gina
ef r
l ray
ay
2nd FP
1st FP
object
plane
Field Stop
& Exit Window
MIT 2.71/2.710
02/23/09 wk4-a-16
16
Example: single-lens camera
chi
ef r
ay
2nd FP
1st FP
Entrance
Window
Field Stop
& Exit Window
MIT 2.71/2.710
02/23/09 wk4-a-17
17
Example: single-lens camera
2nd FP
1st FP
Exit
pupil
(virtual)
Entrance
Window
Aperture
Stop
& Entrance
Pupil
Field Stop
& Exit Window
MIT 2.71/2.710
02/23/09 wk4-a-18
18
Example: single-lens camera
C.R
. fro
mo
bje
FoV
ct a
t fie
ld e
xis object
n-a
M.R. from o
dge
2nd FP
NA
1st FP
Exit
pupil
(virtual)
Entrance
Window
Aperture
Stop
& Entrance
Pupil
Field Stop
& Exit Window
MIT 2.71/2.710
02/23/09 wk4-a-19
19
Example: single-lens camera
Lens,
FL f
MIT 2.71/2.710
02/23/09 wk4-a-20
20
Example: single-lens camera
Lens,
FL f
M.R. from
ob
at field e ject
dge
C.R. fr
om
at field object
edge
M.R. from on
-axis object
EnW
ExP Aperture
& EnP
FS
& ExW
MIT 2.71/2.710
02/23/09 wk4-a- 21
21
MIT OpenCourseWare
http://ocw.mit.edu
2.71 / 2.710 Optics
Spring 2009
For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms.