Optical Coherence Tomography

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Optical Coherence Tomography
Andrew Gomez Daniel Kim Jiwon Lee Kenny Tao
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Theory of OCT

Exemplary model for a sample comprising a series
of discrete reflectors.
Schematic of a Michelson interferometer used in
OCT.
Izatt, Joseph A. Theory of Optical Tomography,
2006
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Discrete Reflectors
For z0 at beamsplitter and
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Fourier Domain OCT
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Results
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Experimental Setup

• First Experiment Low-Coherence Interferometry
• Second Experiment Optical Coherence Tomography

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Light Source
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Fiber Coupler (50/50 Beamsplitter)
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Reference Reflector Detector Array (1-D CCD
Camera)
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Microscope

• Dichroic Mirror
• Sample Stage

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Methods

• Experiment 1 Low-Coherence Interferometry
• Purpose to obtain spectral interferogram data to
  measure center wavenumber ko, standard deviation
  ?k and the power reflectivity of the slide
  surface

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Low Coherence Interferometry

• Procedure
• Adjust reference arm micrometer such that there
  are no interference patterns across the spectrum.
• Turn micrometer known distance till a fringe
  pattern similar to the one shown in the theory
  writeup is observed (Fig 1).
• Calibrate spectrogram plot to be able to
  calculate power reflectivity of slide surface.
• Obtain spectrogram (Fig 2) of reference arm only
  by blocking light from reaching the microscope.
  Use to measure ko and ?k. The value of ko is
  where the spectrum is at maximum and ?k is the
  difference in wavenumber between maximum and 1/e
  of maximum.
• Turn on Fourier processing to observe A-scan
  plot.

Figure 1
Figure 2
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Methods

• Experiment II Optical Coherence Tomography
• Purpose to take two and three dimensional images
  of internal biological tissue microstructure.

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Optical Coherence Tomography

• Procedure
• Take B-scan of IR card using DC removal and
  dual-axis scanning mirror.
• Repeat for fingertip. Obtain 3D image by setting
  scan pattern to rectangular volume. This
  allows 100 sequential B-scans to be taken.
• Stop scan and select volume image to obtain 3D
  rendering of data. Try using with a coin.
• Experiment using the 3D rendering program
  3DView on acquired data.

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LCI Results Single Reflector
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LCI Results Reference Arm
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LCI Results A-scan
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OCT Results B-scan
0.2mm
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OCT Results B-scan
Complex conjugate artifacts
Sweat glands
0.2mm
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OCT Results 3D Scan