# Lecture 7 - UCSD Jacobs School of Engineering

```How was the field trip to CYMER?
•  A. Excellent
•  B. Very good
•  C. Good
•  D. So so
1
Lecture 7
Manipulation of Light
&quot;
Condition for imaging
&quot;
Pinhole imaging
&quot;
Types of lenses
&quot;
Imaging Equation
&quot;
Magnification, virtual images
&quot;
Liquid Lens
&quot;
Super-resolution imaging
&quot;
Beyond the diffraction limit
&quot;
Near-field Scanning Optical Microscopy (NSOM)
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Things That Image
&quot;
What are things that can image?
&quot;
Camera
&quot;
Eye
&quot;
Microscope
&quot;
Telescope
&quot;
Projector
&quot;
What's the simplest thing that can image?
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What's the Requirement to Form an Image?
&quot;
&quot;
&quot;
Light striking each point on an object bounces
off in all directions.
Hold a sheet of white paper near an object. Each
point on the paper is getting light from every
point on the object - no image.
What if each point on the paper got light from
just one point on the object?
&quot;
Bright -&gt; Bright
Dark -&gt; Dark
Image!
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A Pinhole Meets the Requirements for an Image
Most of the light is blocked
5
Demo:
A Pinhole Camera
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What Can Image Without Wasting Light?
&quot;
A Lens - Almost Magic!
Every ray ends up at the corresponding point on the image
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Anatomy of a Lens
http://www.physicsclassroom.com/class/refrn/Lesson-5/The-Anatomy-of-a-Lens
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Learning Lenses
Biconvex
Positive Lenses
(Converging)
Biconcave
Negative Lenses
(Diverging)
Planoconvex
Positivemeniscus
Planoconcave
Negativemeniscus
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Focusing Light
f
focal length
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Lensmaker’s Equation
d &lt;&lt; R1, R2
&quot;1 1%
1
= ( n −1) \$ − '
f
# R1 R2 &amp;
If R1 &gt; 0 the first surface is convex, and
if R1 &lt; 0 the surface is concave.
For the back surface of the lens: if R2 &gt; 0
the surface is concave, and if R2 &lt; 0 the
surface is convex.
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Works for Negative Lenses Too
d &lt;&lt; R1, R2
&quot;1 1%
1
= ( n −1) \$ − '
f
# R1 R2 &amp;
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f
o
ho
i
Measurements start at lens
and point outward.
Left is negative.
Right is positive.
hi
_1 = _1
i
f
-
_1
o
If the focal length of the lens, f, is 1 cm, the object
distance o is 1.25 cm to the left from the lens, what is
the magnification?
A.  -4
B. -2
C. 2 D. 4
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Negative Lenses?
f
f
If the focal length of the lens, f, is -1 cm, the object
distance o is 2 cm to the left from the lens, what is the
magnification?
A.  - 3
B. – 1/3
C. 1/3 D. 3
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Microscope
http://en.wikipedia.org/wiki/Optical_microscope
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How Human Eyes Focus
http://sciencelearn.org.nz/Contexts/Light-and-Sight/Science-Ideas-and-Concepts/How-the-eye-focuses-light
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Liquid Lens
Wetting
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Contact Angle
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Electrowetting
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http://pubs.rsc.org/en/content/articlelanding/2008/sm/b714994h/unauth#!divAbstract
Tuning Focal Length by Voltage
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http://optilux.com/technology/
Liquid Lens
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Is there a limit to the resolution of microscope?
Minimum Focal Spot Size or Best Resolution
Diffraction Limit
f
focal length
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•  Diffraction limit
d = λ/[2n sin(θ)]
–  For green light, the smallest d ~ 250 nm ! Features
smaller than 250 nm cannot be resolved
http://spie.org/x34468.xml
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Diameter D
Depth of field
F
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Beyond the Diffraction Limit
•  Near Field Scanning Optical Microscopy
Evanescent
wave
https://www.pdx.edu/nano-development-lab/nearfield-optical-microscopy
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What Have We Learned?
&quot;
Condition for imaging
&quot;
Pinhole imaging
&quot;
Types of lenses
&quot;
Imaging Equation
&quot;
Magnification, virtual images
&quot;
Liquid Lens
&quot;
Super-resolution imaging
&quot;
Beyond the diffraction limit
&quot;
Near-field Scanning Optical Microscopy (NSOM)
31
How is today’s content on imaging?
1 (very boring) – 5 (very interesting)
•  A 1
•  B 2
•  C 3
•  D 4
•  E 5
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Photoelectric Effect
If shining the metal with a certain
wavelength of light produces
photoelectrons, increasing the intensity of
light
A. increases the electron kinetic energy
B. has no effect on the electron kinetic
energy
C. decreases the electron kinetic energy
http://hyperphysics.phy-astr.gsu.edu/
hbase/mod1.html
33
Photoelectric Effect
Red light will not cause the ejection of
electrons, no matter what the intensity!
A weak violet light will eject only a few
electrons, but their maximum kinetic
energies are
A.  greater than
B.  the same as
C.  smaller than
http://hyperphysics.phy-astr.gsu.edu/
hbase/mod1.html
those for intense light of longer
wavelengths
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Photoelectric Effect
Electron energy = hν – constant
&agrave; Whatever knocking the electrons out
has an energy proportional to light
frequency
The ejected electron energy is
independent of the total energy of
illumination
&agrave; The interaction must be like that of a
particle which gives all of its energy to
the electron
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Wave-Particle Duality of Light
http://hyperphysics.phy-astr.gsu.edu/hbase/mod1.html
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Homework
•  What is the wavelength of an electron at room
temperature?