Research On Key Technology In Full-field Optical Coherence Tomography

Optical coherence tomography(OCT)is a label-free,non-invasive imaging technique with the ability of extracting in vivo tomographic images of biological tissue.This work is mainly focused on optimization of FF-OCT(Full-field optical coherence tomography,FFOCT)system,image analysis and rapid three-dimensional imaging speed.The main contents and results are as follows:For optimizing the system performance of FF-OCT,the microscope objective was moved to the optimal position by balancing the spherical aberrations caused by thin tissue and objective,in which the averaged refractive index of thin biological tissue can be estimated by defocus phenomenon that separating coherence plane and focal plane.Then,an achromatic FF-OCT system based on polarization phase-shifting method and Hilbert transform was designed for wavelength-independent phase-shifitng;meanwhile,one two-dimensional tomographic image can be obtained in single-shot.High-resolution tomographic images of onion cell,in vivo human finger tips and mitotic of onion apricot were presented.The designed FF-OCT system reached the spatial resolution of 0.89?m×1.35?m and the sensitivity of 57dB.To explore the diagnosis value of FF-OCT image,the en face images of human liver tissue obtained with FF-OCT were compared with the ones obtained with current histopathology staining methods,the FF-OCT images of liver cell,portal vein and hepatic artery from normal and cancerous tissue were displayed.A three-dimensional size 385×288×80?m3 of portal vein were also shown.For identifying the change of status of nuclei during the mitotic process of onion root tip cells,a program based on round hough transform was developed which was able to mark up the nuclei in each tomographic image automatically.The FF-OCT images were analyzed and it turned out that the fractal parameter varies greatly in cancerous tissue and in the region of portal vein and fiber bands,the difference between the fractal parameters of cancerous and normal tissue decreases with the increase of depth.To improve three-dimensional imaging speed in the in vivo embryo imaging,a higher rate line-scanned CCD and a broadband supercontinuum laser were used for SD-OCT(Spectral Domain Optical Coherence Tomography,SD-OCT).The ratio of fiber coupler was considered theoretically for getting the best SNR(Signal-noise ratio,SNR),also an SNR-coupler ratio curve was drawn in this paper.OCT signal was then computed in wavenumber-linear distribution spectrum and compensating the dispersion after removing fixed pattern noise.Spectral interferometric detection was accomplished by a broadband,a ZEMAX-based spectrometer consisting of a grating,achromatic lenses,and a line-scan camera operating at a 70 kHz A-line rate.This SD-OCT system obtained the axial resolution of 1.92 ?m and sensitivity of 98 dB within the deep range of 500?m,at the same time,the in vivo two-dimensional tomographic images of human skin were presented to demonstrate real-time and high-resolution imaging ability of SD-OCT.