Research On Synthetic Aperture Algorithm For Spectral Domain OCT

Optical coherence tomography (OCT) is a latest optical imaging technology based on the white-light interferometry, which can acquire cross image for interior microscopic view of biological system. OCT has many advantages such as non-traumatic detection and high resolution, thus it possesses a wide prospect in scientific research and clinic application.In this paper, the scanning model of spectral domain optical coherence tomography (SDOCT) system and effects produced by Gaussian beam itself are discussed. Referring to the data processing methods of synthetic aperture radar (SAR) and the approximate wavenumber domain algorithm which our group has researched, we propose the synthetic aperture algorithm to abate the compromise between resolutions and depth of focus in SDOCT, and achieve image reconstruction with spatially invariant resolution.The researches mainly focus on the following aspects:1. The paper analyzes the fundamental principle and scanning model of SDOCT in detail. Referring to the data processing methods of SAR, the synthetic aperture algorithms for transverse scanning and rotary scanning respectively are proposed to implement image reconstruction with high resolution.2. According to the structure of transverse scanning, the physical model of diffraction is presented, along with the finite beam width and the shape of wavefronts produced by Gaussian beam taken into account. On the basis of scattering forward model, the equations of reference light, sample light and interference spectrum are deduced, as well as the procedure of image reconstruction.3. This paper compares the range Doppler (RD) algorithm and wavenumber domain algorithm. The improved RD algorithm is applied to improve the resolutions in the axial and lateral directions, where the two-dimensional processing of the spectrum data is decomposed into two one-dimensional processings of variable exchange and matched filter. The synthetic aperture algorithm is demonstrated to improve the image quality in the rotary scanning, which makes it possible that OCT can be used in the endoscopic system.4. The simulations are implemented in terms of the key parameters that influence the image quality. Properly selecting optical devices, the fibre-based interference system is built, and images of fresh pig liver are gained, which effectively shows that the algorithm will be competent for imaging.