Vasilios Aris Morikis Dan DeLahunta Dr. Hyle Park, Ph.D.

Vasilios Aris MorikisDan DeLahunta

Dr. Hyle Park, Ph.D.

Optical Coherence Tomography◦An Overview of OCT

System Setup◦Sample Arm◦Galvanometer

Project Overview◦Methodology◦Results◦Conclusions

High resolution sub-surface imaging Non-invasive

◦Not harmful to subject Potential in many fields

◦Ophthalmology (RNFL thickness, AMD)◦Dermatology (photoaging, BCC detection)◦Cardiology (assessment of vulnerable

plaques)◦Gastroenterology (Barrett’s esophagus)

Time delay between reflected light is measured to determine depth of the reflecting structure◦ Due to the short time delays between signals OCT must use an

interferometer to detect the reflected light. Interference fringes are formed when the sample and reference

arms are within a small range. A depth profile is formed by the detection of the interference

pattern between the reference and sample arm as the reference arm is scanned.

The intensity of the depth profile is encoded on a logarithmic scale.

A 2D cross section or even a 3D volume can made by scanning the beam across the sample.

Helped to construct the Sample Arm.

Built the box to power and control the Galvo

Video of the Galvo moving

Develop analysis/processing code in MATLAB

Objective: Mathematically focus raw data obtained from the 1310 nanometer system.◦Adjust the incident angle, focal length, and

the wavelength.◦Increase the signal to noise ratio (SNR) to

produce high resolution image.

Collimator

Diffraction Grating

Focusing Lens

Fast Line Scan Cameras

Polarized beamsplitter cube

Read the Image

Flip Matrix (if

necessary)

Zero Padding

FFTDisplay Image

Interpolate

Raw data obtained when the reference and sample arm are 600 microns apart.

Image taken of the mirror.

Pixel Number

Inte

nsi

ty

Completely unprocessed data. To create accurate image

point spread function should be narrow and high (ignore all the noise in the middle).

Creates a blurred black line when the actual image is formed.

Splits the matrix and adds many 0’s in Fourier space.

Doubles the size of the original graph.◦ Used to increase the point density to interpolate

more accurately.

Inte

nsi

ty

Inte

nsi

ty

Pixel Number Pixel Number

Used to find remap the data linearly in wave number (k) to improve the results of a subsequent FFT

Takes the Intensity vs. Pixel number graph and Intensity vs. k.

Fourier transform switches one complex valued function into another.◦Transforming k (wave number) into actual

space.

Side Camera Straight Camera

Incident Angle 49 degrees 51 degrees

Grating Spacing 1.0e-3/1145 1.0e-3/1145

Focal Length 92 millimeters 95 millimeters

Wavelength 1350 nanometers 1350 nanometers

Pixel Width 25 micrometers 25 micrometers

Now that the parameters are correct a much more focused image is created.◦Dark line at the top is thin and not blurry

Image obtained form the 1310 nanometer system before processing (left) and after processing (right).◦ Image width:100 microns◦ Image height: 500 microns

Very first image acquired with either system.

I would like to thank NSF and the UC Riverside BRITE program for funding, as well as the University of California, Riverside and NIH (R00 EB007241), and Dr. Hyle Park and the rest of the Park Research Group for their guidance.

Mr. Jun Wang for organizing and Dr. Victor Rodgers for directing the program.