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Frequency Domain Optical
Coherence Tomography
(FDOCT)
Joon S Kim
IMSURE Summer Research Fellow
At Beckman Laser Institute
University of California at Irvine
Irvine, CA 92612
Email: [email protected]
OCT
• Optical Coherence Tomography
– New field of imaging technology that can
complement conventional imaging techniques
– Based on interference of EM wave
– Provide high spatial resolution cross-sectional
view of tissues without excision
– Endless potential biomedical applications
• Non-invasive Diagnostics
OCT vs. Conventional Imag. Tech
Resolution (log)
Standard
clinical
1 mm
Ultrasound
100 mm
10 mm
High
frequency
Confocal
microscopy
OCT
1 mm
Penetration depth (log)
1 mm
1 cm
10 cm
Two kinds of OCT
• TDOCT
– Time Domain OCT
– Use of Scanning Mirror
• FDOCT
– Fourier (Frequency) Domain OCT
– Use of laser source over band of optical
frequency
– Advantages over TDOCT
My research experience with
FDOCT are in 2 phases…
• First phase:
– Understanding and Replicating FDOCT
experimental setting from scratch
• Second phase:
– Learning the physical and mathematical
reasoning behind the magical DSP algorithm
which extract images out of OCT data!
Part 1
•
Swept source
FDOCT experiment set up
Mirror
Grating
Collimator
2 x 2 Coupler
Phase
Modulator
Attenuator
Fiber Fabry-Perot
interferometer
Probe
Detector1
Detector2
Sample
Current FDOCT System
• No human intervention required
• Everything controlled from execution
module in host computer
• Host computer
– houses NI-6112: A2D Conversion of OCT data
– performs digital signal processing
– controls peripherals
Scanning sample
• Surface of sample is divided into
imaginary grid.
• Each block in grid: Pixel
• Scanning in X direction
Z
– Lateral scan
• Scanning in Z direction
– A scan
X
Y
Scanning sample (cont.)
•
•
•
•
1600 samples / A-scan (pixel)
400 A-scan / Lateral scan
Lateral scanning Frequency: 2 KHz
A-scanning Frequency: 10 MHz
– Limited by A2D converter (NI-6112)
• Pixel size: 10 micron
• Slow process => not applicable in Vivo
With NI-5122
• Max. Sampling Frequency: 100 MS/sec
• A-scanning Frequency: 100 MHz
– More time for DSP
– Boost lateral scanning frequency to 20 KHz
– One step closer to in Vivo application of
FDOCT
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