Overview: composite optical elements
ray from infinity bends at 2nd PP
ray from then goes FFP BFP the FFP through the BFP
FFL BFL FFP BFP bends at then goes EFL EFL 1st PP on to infinity
1st PP 2nd PP 1st PP 2nd PP
1st PP 2nd PP
BFP image object 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 θ: half-angle subtended by the imaging the physical element which system from limits the angle of acceptance of the imaging an axial object system
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
MIT 2.71/2.710 02/23/09 wk4-a- 3 3 Entrance & exit pupils
image through image through preceding elements succeeding elements
entrance aperture exit pupil stop 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.
C.R.
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 image through preceding elements succeeding elements
M.R.
C.R.
field stop exit entrance window window
MIT 2.71/2.710 02/23/09 wk4-a- 9 9 All together
M.R.
C.R.
field aperture entrance stop stop exit entrance pupil exit window window pupil
MIT 2.71/2.710 02/23/09 wk4-a-10 10 All together
C.R.
FoV
field aperture entrance stop stop exit entrance pupil exit window window 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 MIT 2.71/2.710 02/23/09 wk4-a-11 11 All together
NA
field aperture entrance stop stop exit entrance pupil exit window window pupil 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 object plane or digital detector array
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 Aperture Exit Stop pupil & Entrance (virtual) Pupil image plane
MIT 2.71/2.710 02/23/09 wk4-a-15 15 Example: single-lens camera
marginal ray
chief ray
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
chief ray
2nd FP 1st FP
Field Stop Entrance & Exit Window Window
MIT 2.71/2.710 02/23/09 wk4-a-17 17 Example: single-lens camera
2nd FP 1st FP
Aperture Exit Stop pupil & Entrance (virtual) Pupil Field Stop Entrance & Exit Window Window
MIT 2.71/2.710 02/23/09 wk4-a-18 18 Example: single-lens camera
C.R. from object at field edge
FoV
nd M.R. from on-axis object 2 FP NA 1st FP
Aperture Exit Stop pupil & Entrance (virtual) Pupil Field Stop Entrance & Exit Window 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
M.R. from object Lens, at field edge C.R. from object FL f at field edge
M.R. from on-axis object
FS ExP Aperture & ExW EnW & EnP
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
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