| BMEG400C/591C
OCT Signal Processing II
| BMEG400C/591C
Experiment System
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§Retinal OCT system
o 200 kHz swept source
o Dual balanced detection o Calibration interferometer
§Image acquisition parameters o # of points / A-scan: 1536
o # of A-scans / B-scan: 500
o # of B-scan / C-scan: 500
o Reference frame index: 250
L & M : Les & Mirror
FC : Fiber collimator
PC : Polarization controller
GS : Galvanometer scanner
DCP : Dispersion compensation prism
| BMEG400C/591C
Reference B-scan
| BMEG400C/591C
Reference A-scan
| BMEG400C/591C
Extract Calibration Signal
| BMEG400C/591C
OCT Volume Processing
OCT Processing
| BMEG400C/591C
Resampling Process
| BMEG400C/591C
Resampled Reference B-scan
| BMEG400C/591C
OCT Image Before & After Resampling
| BMEG400C/591C
Spectral Shift Compensation
| BMEG400C/591C
Fixed Pattern Noise (FPN) Subtraction & Windowing
| BMEG400C/591C
FPN Subtraction
| BMEG400C/591C
Dispersion Estimation & Compensation
| BMEG400C/591C
Dispersion Compensation
| BMEG400C/591C
Windowing Processing
| BMEG400C/591C
Hanning Windowing
| BMEG400C/591C
Project A – OCT Volume Processing
OCT Processing
| BMEG400C/591C
Amplitude & Intensity (Linear / Log scale)
Amplitude Intensity (linear) Intensity (log)
| BMEG400C/591C
Motion Correction
| BMEG400C/591C
Cross-Correlation
§ In signal processing, cross-correlation is a measure of similarity of two waveforms as a function of time-lag applied to one of them.
§ Also known as a sliding dot product or sliding inner-product. $$
𝐺 𝑖,𝑗 = & & h 𝑢,𝑣 𝐹 𝑖+𝑢,𝑗+𝑣 !”#$ %”#$
Denoted by 𝐺 = h ∗ 𝐹 (Cross-correlation)
§ Filtering an image:
o Replace each pixel with a linear combination of its neighbors
§ Filter “kernel” or “mask”
oh𝑢,𝑣 istheprescriptionforweightsinthelinearcombination
| BMEG400C/591C
Convolution & Fourier Transform
𝑔 𝑖,𝑗 =𝑓⊗h=) ) 𝑓 𝑥,𝑦 h 𝑖−𝑥,𝑗−𝑦 𝑑𝑥𝑑𝑦 !” !”
F𝑔=F𝑓/Fh 𝑔 = F!# F 𝑓 / F h
:Convolution
: Convolution Theorem
| BMEG400C/591C
Cross-Correlation
Max. Cross-correlation
Cross-correlation coefficient map
| BMEG400C/591C
Motion Corrected OCT Volume – Fast Scan Direction Before Motion Correction After Motion Correction
| BMEG400C/591C
Motion Corrected OCT Volume – Slow Scan Direction Before Motion Correction After Motion Correction
| BMEG400C/591C
Tilt Correction
| BMEG400C/591C
Tilt Corrected OCT Volume
Fast Scan Direction Slow Scan Direction
| BMEG400C/591C
ImageJ – Volume Viewer
| BMEG400C/591C
ImageJ – Volume Viewer
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