Download Lenses - Mouse Vision

Image formation with lenses
Operating Principle
• Lenses use the principle of refraction to
change the shape of a light beam.
- Bending of light – Why?
n
c
v
c  Speed of light
v  Phase velocity
Operating Principle
• Lenses use the principle of refraction to
change the shape of a light beam.
- Refractive index
Operating Principle
• Lenses use the principle of refraction to
change the shape of a light beam.
- Refractive index
Operating Principle
• Lenses use the principle of refraction to
change the shape of a light beam.
- Refractive index
Operating Principle
• Lenses use the principle of refraction to
change the shape of a light beam.
- Refractive index
n1 sin( 1 )  n2 sin(  2 )
Operating Principle
Operating Principle
• Lenses use the principle of refraction to
change the shape of a light beam.
- Refractive index
- Curvature
Operating Principle
Wavefront picture
Operating Principle
Wave picture
Operating Principle
• Lenses use the principle of refraction to
change the shape of a light beam.
- Refractive index
- Curvature
Operating Principle
• Lenses use the principle of refraction to
change the shape of a light beam.
- Refractive index
- Curvature
Operating Principle
• Lenses use the principle of refraction to
change the shape of a light beam.
- Refractive index
- Curvature
Operating Principle
Consider lens thickness negligible:
1 1 
1
 (n  1)   
f
 R1 R2 
1 1
P  m  Diopters 
f
- Power of the lens
Types of lenses
Convex lens:
Types of lenses
Concave lens:
Types of lenses
Positive meniscus lens:
Types of lenses
Negative meniscus lens:
Fresnel lenses
Image formation
Ray tracing rules:
• In: parallel to the optical axis – Out: through back focal point
• In: through the centre of lens – Out: travel unchanged
• In: through the focal point – Out: parallel to the optical axis
Image formation
Image condition:
• “all” light rays emitted by one point in the sample meet in a
defined point behind the lens -> imaging plane
Image formation
The visualized object:
• Each point reflects (emits) light in all directions
=> multitude of point light sources
Image formation
Ray tracing rules:
1 1 1
 
S o Si f
M
hi Si
f
 
ho S o f  S o
Image formation
Image distance (S2) in focal dist.
Ray tracing rules:
Positive lenses
Negative lenses
Object distance S1 in focal dist.
Lens systems
Compound lenses:
• No distance between them (z=0)
1 1 1
 
f fi fo
Lens systems
Compound lenses:
• when z > fo+fi - Two converging lenses in series -> upright,
scaled image
fo
fi
M  Mo  Mi 

f o  So f i  Sod
Lens systems
Infinite conjugate system:
• if object in the focal point -> the distance between the lenses
is not relevant (can be infinite)
Lens systems
Infinite conjugate system:
• if object in the focal point -> the distance between the lenses
is not relevant (can be infinite)
Lens systems
Beam expanders:
• Collimated light source
Lens systems
Beam expanders:
• Collimated light source – if d  f o  f i , the light beam is
expanded.
fi
M
fo