Research On Polarization-sensitive Optical Coherent Tomography Technology

Polarization-sensitive optical coherence tomography(PS-OCT)is a new medical imaging technology.Based on ordinary optical coherence tomography(OCT),PS-OCT is used to measure and analyze the polarization information of a sample as an additional function?On the one hand,like OCT,PS-OCT is non-invasive and high-resolution,can measure the reflectance at different depths inside the sample,tomography of human tissues such as the retina and skin,which reveals the microstructure inside the sample.PS-OCT can also measure the polarization characteristics of the sample(especially the phase delay of the two polarization directions orthogonal to each other due to birefringence)and use it as an additional contrast mechanism for imaging.People can differentiate different structures in the sample by different polarization characteristics.We build a multiple-incidence-states PS-OCT based on fiber.This type PS-OCT uses two orthogonally polarized incident light to irradiate the sample at the same time and obtain the polarization state of the reflected light respectively.In this way,the interference of the fiber on the measurement of the polarization state is eliminated.At the sample arm,we use a passive polarization delay unit to generate two beams of incident light with orthogonal polarization states.In the detection unit,we build all-fiber polarization detection unit based on fiber-based polarization beam splitters(FPBS).During data processing,we first controlled the acquisition card and galvanometer to obtain the two-dimensional tomographic image data of the sample by a C++program wrote by us,and then used MATLAB to calculate and analyze the polarization information of the sample to generate a sample structure diagram and double-pass phase retardation diagram.And we verify the feasibility of the system by imaging the glass sheet,the 1/4 wave plate working in the 1310nm band and the 1/2 wave plate working in the 512nm band.We generate the structure diagram and the DPPR diagram.The structure diagram and the measured DPPR value are in line with theoretical expectations.Finally,we tried to image biological tissues.We image the skin of fingertips of human forefingers.We see the epidermal layer and dermal layer of the skin in the structure image and DPPR image.The experimental results are in line with theoretical expectations.