Paraxial ray approx.

1
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y ltlt R
Paraxial ray approx.
f R/2
2
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R
s
so
si
3
Homework

• 1. A spherical glass bottle(n1.5), with very
  thin wall and its diameter is 20 cm, is filled
  with water(1.33) Determine the position of the
  foci
• 2. a) Detemine the focal length of a thin
  bi-concave lens of index 1.5 having radii of 0.5
  and 0.25 m b) Where is the image of a
  point-like object at a distance of 20 cm
  formed by the lense.

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????????(Aberration)

• Spherical aberration (on axis)
• Coma
• Astigmatism (off axis)
• Curvature of field
• Distortion
• Chromatic aberration

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Spherical aberration
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Comatic aberration (CA)
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?????? - Off axis
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(No Transcript)
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Astigmatism
Fs
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??????????????????? 2 ???????????????????????????
??????????? - Off axis
FT
Slc
S
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Curvature of field
p
10
Distortion
orthoscopic
barrel
Pin cushion
11
Curvature of field causes a planar object to
project a curved (non-planar) image. Rays at a
large angle see the lens as having an effectively
smaller diameter and an effectively smaller focal
length, forming the image of the off axis points
closer to the lens.
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Barrel and pincushion distortion
Barrel
Pincushion
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Chromatic aberration (ChA)
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Chromatic aberration can be minimized using
additional lenses
In an Achromat, the second lens cancels the
dispersion of the first.
Achromats use two different materials, and one
has a negative focal length.
15
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