Microscopy

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Microscopy Resolution

• Magnification Image size/Object size
• Resolution The fineness of detail that can be
  distinguished in an image.

Highest Typical ResolutionOptical Microscope
200 nmElectron Microscope 0.1 nm
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Definitions

• Acceptance angle ?
• Numerical Aperture NA n sin?
• Rayleigh resolution criterion for a circular
  aperture ?x 0.61 ?/NA

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OPTICAL MICROSCOPES

• Image construction for a simple biconvex lens

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Rayleigh criterion for resolution
Numerical Aperature
Resolution
Rayleigh Criterion
www.microscopy.fsu.edu www.imb-jena.de
See more interactive tutorials at
www.microscopy.fsu.edu
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Comparison
Bright-Field
Dark-Field

• Full apertureis illuminated

• A central obstruction blocks the central cone.

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Dark-FieldOptical Microscopy

• A central obstruction blocks the central cone.
• The sample is only illuminated by the marginal
  rays.
• These marginal rays must be at angles too large
  for the objective lens to collect.
• Only light scattered by the object is collected
  by the lens.

www.microscopy.fsu.edu
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Dark-FieldOpticalMicroscopy
www.microscopy.fsu.edu
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THE ELECTRON MICROSCOPE

• The wavelength of the electron can be tuned by
  changing the accelerating voltage.
• de Broglie ? h/mv
• ? wavelength associated with the particle
• h Planks constant 6.6310-34 Js
• mv momentum of the particle
• me 9.110-31 kg e 1.610-19 coulomb
• P.E eV ½mv2 ? ? h/?(2meV) 12.3/?V (for
  V in KV, ? in Å)
• V of 60 kV, ? 0.05 Å ? ?x 2.5 Å
• Microscopes using electrons as illuminating
  radiation
• TEM SEM

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Components of the TEM

• Electron Gun Filament, Anode/Cathode
• Condenser lens system and its apertures
• Specimen chamber
• Objective lens and apertures
• Projective lens system and apertures
• Correctional facilities (Chromatic, Spherical,
  Astigmatism)
• Desk consol with CRTs and camera
• Transformers 20-100 kV Vacuum pumps 10-6
  10-10 Torr

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Schematic of E Gun EM lens
Magnification 10,000 100,000 Resolution 1 -
0.2 nm www.udel.edu
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TEM IMAGES
www.udel.edu www.nano-lab. com www.thermo.com