Retinal Spectral Domain OCT Tomography Technique Applied To Several Key Issues

Optical coherence tomography (OCT) is a new non-invasive optical image technique, which is based on partial coherence. The technology has the advantages of micron vertical resolution, high sensitivity, high accuracy, low damage to the human eye and so on, thus, it has been widely used in the field of retinal image.Based on relevant principles of OCT within spectral domain, the article designed an OCT system. In order to remove the noise in interference signal, the experiment takes use of phase shifting method, which is of easier operation and higher accuracy, for noise-removal processing. The experiment confirms PZT phase shifting method and polarizing phase shifting method while compares the difference of both methods on stability and accuracy. The experiment also builds a polarizing phase shifting OCT system with better phase shifting effects within spectral domain, and takes isolated pig retina specimen as sample, extracting interference signal and phasing noise, in order to extract depth information through windowed Fourier transform and Hilbert transform.According to the results of two phase-shift method, this paper confirmed the method of removing Direct Current noise in interferometry signal by three frames phase-shifting. At the same time, we also found that the method of shifting phase by polarization had higher accuracy and stability and was much easier to operation. In the OCT system we built, the phase delay was less than30" due to alignment errors and fast axis offset on wave plate. In the test with pig’s retina, the depth information was obtained through interference signal processing. Data from experiments were pretty fit with references and confirmed the operability of depth extraction algorithm on the other hand. Combined with horizontal scan, tomography image of pig’s retinal was reconstructed and we can see a clear distribution of layer with a total thickness of about0.2mm.