PH880 Modern Optical Imaging
• Instructor : YongKeun Park
– Natural Science Bldg. #3305, [email protected]
• Website: http://bmokaist.wordpress.com/ph880/– Lecture notes, references, and so on
• Lectures: Mon, Wed, Fri 2-3PM
• Classroom: Natural Science Bldg. #1320 (9/1)
From 9/3, Changeui-gwan (창의관) #409
• Units: 3-0-3
• Office hour: Mon, Wed, Fri, 3-3:30PM, Natural Science Bldg. #3350 (right after the lecture)
KAIST PH880 9/1/2010
Class objective
- Cover the physical principles of modern optical imaging- Physical intuition and underlying mathematical tools
- Systems approach to analyze and design optical imaging system
- Cover the various modern optical microscopes- From bright-field microscopy to super-resolution microscopy
- Application of the optical imaging systems. - Biology: cellular and sub-cellular imaging
- Chemistry: molecular imaging
- Medicine: disease diagnosis
- Engineering: metrology
KAIST PH880 9/1/2010
KAIST PH880 9/1/2010
Drawings of the instruments used by Robert Hooke.
R. Hooke, Micrographia, 1665
Old optical imaging system (1665)
KAIST PH880 9/1/2010
Recent imaging system (~90s’)
http://www.microscopyu.com
Buccal Epithelial Cells under DIC microscopy
KAIST PH880 9/1/2010
Recent imaging system:Digital holographic microscopy
YK Park et al., Optics Express, 2006YK Park et al, PNAS, 2010
Course schedule
KAIST PH880 9/1/2010
Period Contents Period Contents
week 1Introduction to optical imaging
Geometric opticsweek 9 Nonlinear microscopy
week 2 Fourier optics week 10 Digital holography
week 3 Fourier opticsBright-field
microscopyweek 11
Optical Coherent Tomography
Photo-acoustic microscopy
week 4 Resolution/Abberations week 12 FRET / SNOM
week 5 Intrinsic contrast microscopy week 13 Super resolution microscopy
week 6 Fluorescent microscopy week 14 Synthetic Aperture / Detectors
week 7 Confocal microscopy week 15 Adaptive Optics in Imaging
week 8Mid-term:
critical review paperweek 16
Final:
presentation on topics in modern
optics
Mathematical tool Conventional Recent Current research topics
Administrative: PH880
• Grade:
– mid-term critical review paper (40 %),
– final presentation (50 %),
– lecture participation (10 %)
KAIST PH880 9/1/2010
Mid-term critical review
• Write a short critical review that involves reading at least 5 papers, discussing the methods, problems, conclusions, in any area on which optical imaging may impinge. (wk 8)
• We will hand out a reading list with some suggestions and examples of papers that you might find useful and interesting, but you are welcome to search for any others as well. (wk 5)
• Maximum length: 7 pages including everything (title page and reference list).
KAIST PH880 9/1/2010
Final presentation
• We will hand out the list of recent papers on the related topic. Each student may choose one from the list (wk 12).
• Write a critical review that involves discussing the methods, problems, conclusions, and suggestions. Maximum length: 5 pages. (final week)
• Each student should be prepared to present an overview of your critical review (using PPT slides) in no more than 20 minutes including Q/A (final week).
KAIST PH880 9/1/2010
Overview of week1
• Wednesday
– Course admin.
– Introduction to optical imaging
– Review: Optics (undergraduate level)
• Friday
– Geometric optics II
KAIST PH880 9/1/2010
Optical imaging
KAIST PH880 9/1/2010
Incident light
Scattering
object
Need optics to “undo” the effect of scattering In free space: focus the light
image
Optical imaging : lens
KAIST PH880 9/1/2010
Point sources(object)
Point images
Each point source from the object plane focuses onto a point image at the image planeNote; image inversion
object plane image plane
Ideal optical imaging system
KAIST PH880 9/1/2010
OpticalElements
object
• Ideal imaging system:Each point in the object is mapped onto a single point in the image
• In real world, imaging system do not focus perfectly1. Aberration: an imperfection in image formation2. Diffraction limited resolution
image
Aberration
• an imperfection in image formation by an optical system
KAIST PH880 9/1/2010
Perfect focus DefocusAberration
SphericalAberration
ChromaticAberration
Why optical system do not focus perfectly?
• Aberration & Diffraction
• In Geometrical Optics (paraxial approximation), optical system do focus perfectly
• To deal w/ aberration, we need non-paraxial Geometric optics
• To deal w/ diffraction, we need Wave (Fourier) Optics
KAIST PH880 9/1/2010
What is light?
• Light is a form of electromagnetic energy– Heating of illuminated objects, conversion of light to current,
mechanical pressure (“Maxwell force”) etc.
• Light energy is conveyed through particles: “photon”– Ballistic behavior, e.g. shadow
• Light energy is conveyed through “waves”– Interference, diffraction
• Quantum mechanics reconcile two point of view: “wave/particle duality”
KAIST PH880 9/1/2010
KAIST PH880 9/1/2010
Wave properties of light
E
t z
1/
E: Electric field: wavelength (spatial period) [m]k=2/ : wave number (spatial frequency) [rad/m]: temporal frequency [1/s, Hz]=2 : angular frequency [rad/s]
Wave/Particle duality of light
• Photon = light particle
• Energy E = h
h = Planck’s constant = 6.626210-34 Js
= temporal frequency [1/s]
• Dispersion relation : c = c = speed of light = 299,792,458 m/s
= wavelength [m]
* Holds in vacuum only
KAIST PH880 9/1/2010
Light in matter: refraction/absorption
KAIST PH880 9/1/2010
• Speed c = 3x108 m/s
• Absorption coefficient 0
• Speed = c/n
n : refractive index
(index of refraction)
• Absorption coefficient α
Energy decay after distance L :
e-2αL
Light in vacuum Light in matter
* glass fiber has n 1.5, α 0.25 dB/km = 0.0228/km, * Most biological cell & tissue are transparent:
(α is very small, n provides important contrast. )
Refractive index, n
KAIST PH880 9/1/2010
• Note that refractive index is a function of wavelength: ‘dispersion’
Consequence : chromatic aberration
• Air: n slightly higher than 1
(most commonly assumed n 1 for practical purposes)
• Water: n 1.33
• Cell culture medium : n 1.337 (PBS solution at 633 nm)
• Glass : n 1.45-1.75
• Photorefractive crystal, e.g. Lithium niobate n 2.2-2.3
• Solution: depending on the concentration of solute, C
nX = nw + α · C
nX : n of solution (e.g. Hemoglobin)
nw : n of solvent (e.g. water)
α : specific refractive index increment of solute
Overview of week1
• Wednesday– Course admin.
– Introduction to optical imaging
– Review: Optics (undergraduate level)
• Friday– Geometric optics II
Refractive index, Fermat’s principle, Reflection, Refraction, Ray-tracing, lens
KAIST PH880 9/1/2010
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