Overview: composite optical elements
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FFP
1st PP
BFP
2nd PP
FFL BFL
EFL EFL
ray from infinity bends at
2nd PP
then goes through the BFP
ray from the FFP
bends at 1st PP
FFP
1st PP
BFP
2nd PP
then goes on to infinity
object FFP
BFP image
1st PP 2nd PP
EFL EFL
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Today
• Apertures & Stops – Aperture – Entrance Pupil – Exit Pupil
– Field Stop – Entrance Window – Exit Window
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Aperture Stop and Numerical Aperture
medium ofrefr. index n
Aperture stop the physical element which θ: half-angle subtended by the imaging
limits the angle of acceptance of the imaging system from an axial objectsystem
Numerical Aperture
Speed pronounced f-number, e.g.
f/8 means (f/#)=8.
The Aperture Stop Later we will also learn that the NA also limits the optical energy defines the resolution (or resolving power) of
that is admitted through the system the optical system
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Entrance & exit pupils
multi-element optical system
entrance pupil
exit pupil
aperture stop
image through preceding elements
image through succeeding elements
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The Chief & Marginal Rays
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C.R.
M.R.
Together, the C.R. and M.R. define the angular acceptance of spherical ray bundles originating from an off-axis object.
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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
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The Chief & Marginal Rays
Corollaries:
C.R.
M.R.
Chief Ray also goes through the center of the Entrance & Exit PupilsMarginal Ray also goes through the edge of the Entrance & Exit Pupils
The Chief and Marginal Rays meet again at the image
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The Field Stop
Limits the angular acceptance of Chief Rays
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The Field Stop
FoV
Defines the Field of View (FoV)
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Entrance & Exit Windows
image through preceding elements
image through succeeding elements
field stop
C.R.
M.R.
exit windowentrance
window
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All together
entrance window
exit window
field stop
C.R.
M.R.
entrance pupil
aperture stop
exit pupil
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All together
C.R. FoV
entrance window
exit window
field stopentrance
pupil
aperture stop
exit pupil
The Field of View is the angle between the pair of Chief Rays that just make it through the edges of the Field Stop
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All together
NA
entrance window
exit window
field stopentrance
pupil
aperture stop
exit pupil
The Numerical Aperture is the angle between the pair of Marginal Rays that just make it through the edges of the Aperture Stop
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Example: single-lens camera
2nd FP
1st FP size of
object film
plane or digital detector
array
image plane
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Example: single-lens camera
object plane
2nd FP
1st FP
Aperture Stop
& Entrance Pupil image
plane
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Example: single-lens camera
2nd FP
1st FP
object plane Aperture
Exit Stop pupil & Entrance
(virtual) Pupil image plane
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Example: single-lens camera
object plane
2nd FP
1st FP
chief ray
marginal ray
Field Stop& Exit Window
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Example: single-lens camera
Field Stop & Exit Window
2nd FP
1st FP
chief ray
Entrance Window
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Example: single-lens camera
Field Stop & Exit Window
2nd FP
1st FP
Exit pupil
(virtual)
Aperture Stop
& Entrance Pupil
Entrance Window
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Example: single-lens camera
Field Stop
2nd FP
1st FP
Exit pupil
(virtual)
Aperture Stop
& Entrance Pupil
M.R. from on-axis object
C.R. from object at field edge
NA
FoV
Entrance & Exit Window Window
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Example: single-lens camera
Lens, FL f
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Example: single-lens camera
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EnW
FS & ExWExP Aperture
& EnP
Lens, FL f
M.R. from on-axis object
C.R. from objectat field edge
M.R. from objectat field edge
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2.71 / 2.710 Optics Spring 2009
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