Introduction to Optics
part I
Overview Lecture
Space Systems Engineering
presented by: Prof. David Miller
prepared by: Olivier de Weck
Revised and augmented by: Soon-Jo Chung
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16.684 Space Systems Product Development
MIT Space Systems Laboratory
February 13, 2001
Outline
Goal: Give necessary optics background to tackle a
space mission, which includes an optical payload
?Light
?Interaction of Light w/ environment
?Optical design fundamentals
?Optical performance considerations
?Telescope types and CCD design
?Interferometer types
?Sparse aperture array
?Beam combining and Control
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February 13, 2001
Examples - Motivation
Spaceborne Astronomy
Planetary nebulae NGC 6543
September 18, 1994
Hubble Space Telescope
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February 13, 2001
Properties of Light
Wave Nature
Particle Nature
2
2
H P w E
Duality
Energy of
? E
2
0
a photon
Q=h Q
Detector
c wt
2
Solution:
Photons are
(
ikr Zt I) “packets of energy”
EAe
E: Electric field vector
H: Magnetic field vector
Poynting Vector:
S
c
E uH
4 S
Spectral Bands (wavelength O):
Wavelength:
O Q
2 S
QT
Ultraviolet (UV) 300 ? -300 nm
Z
Visible Light 400 nm - 700 nm
2 S
Near IR (NIR) 700 nm - 2.5 Pm
Wave Number: k
O
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MIT Space Systems Laboratory
February 13, 2001
Reflection-Mirrors
Mirrors (Reflective Devices) and Lenses (Refractive Devices)
are both “Apertures” and are similar to each other.
T
i
T
o
Law of reflection:
T
i
= T
o
Mirror Geometry given as
a conic section rot surface:
1
2
z()
r r
k 1
U
U
Reflected wave is also k 1
in the plane of incidence
Circle: k=0 Ellipse -1<k<0
Specular
Reflection
Parabola: k=-1 Hyperbola: k<-1
Detectors resolve Images produced by
(solar) energy reflected from
a target scene* in Visual and NIR.
*rather than self-emissions
Target Scene
sun
mirror
detector
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February 13, 2001
2
Transmission-Refraction
Medium 1
Medium 2
n
2
n
1
Recall Snell’s Law
n
1
sin T n
2
sin T
Incident ray
12
Refracted Ray
E H
2
Light Intensity
S
c
4 S
Dispersion if index of refraction is wavelength dependent n( O)
Refractive devices not popular in space imaging ,
since we need different lenses for UV, visual and IR.
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MIT Space Systems Laboratory
February 13, 2001
Polarization
Light can be represented as a
transverse electromagnetic wave
made up of mutually perpendicular,
fluctuating electric and magnetic
fields.
Ordinary white light is made up of waves that fluctuate
at all possible angles. Light is considered to be
"linearly polarized" when it contains waves that only
fluctuate in one specific plan (Polarizers are shown)
In-phase=> 45 degrees linearly polarized 90 degree out of phase->circular
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February 13, 2001
QuickTime? and a
Cinepak decompressor
are needed to see this picture.
Interference
two or more light waves yielding a resultantInterference: Interaction of
irradiance that deviates from the sum of the component irradiances
If the high part of one wave (its crest) overlaps precisely with the high part
of another wave, we get enhanced light.
(r
1
r
2
) 2 Sm / k m O
Crest + Crest = Strong Light
If the high part of one wave overlaps precisely with the low part of another
wave (its trough), they cancel each other out.
(r
1
r
2
) Sm / k
1
m O
Crest + Trough = Darkness
2
MIT Space Systems Laboratory
(coherent)
each other
Conditions of Interference:
? need not be in phase with each source, but
the initial phase difference remains constant
? A stable fringe pattern must have nearly
the same frequency. But,white light will
produce less sharp, observable interference
? should not be orthogonally polarized to
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16.684 Space Systems Product Development
February 13, 2001
Diffraction
Diffraction occurs at the edges of optical elements
and field stops, this limits the Field-of-View (FOV).
This is THE limiting factor,
Intensity
T
2
§
sin u
·
which causes spreading of
screen I E I
o ¨