Study On Imaging Depth Improvement Method In Frequency Domain Optical Coherence Tomography

In the Spectral Domain Optical Coherence Tomography(SDOCT)system,the system has high transverse resolution only within the depth of field.In order to obtain high resolution in both the lateral and longitudinal directions,it is necessary to use an objective lens with a large numerical aperture.In this case,high resolution can only be reached in the focal depth range of the objective lens.The transverse resolution degrades away from the focal plane.Interferometric synthetic aperture microscopy(ISAM)is a three dimensional image reconstruction algorithm,which can remove the out-of-focus blur by computing.A resolution in all planes that is equivalent to the resolution achieved at the focal plane can be achieved so that the contradiction between the transverse resolution and the depth of field in the SDOCT system can be solved.In this paper,the principle of ISAM and its possible applications were discussed.The comparison between the reconstructed image by using conventional SDOCT method and the one with ISAM were carried out.The Nonuniform Fast Fourier Transforms(NUFFT)algorithm was applied in ISAM to save the operation time.The results showed that it can greatly reduce computational complexity to save the rebuilding time,improving the performance of real-time and high-resolution SDOCT.In order to detect the subsurface damage of the optical elements,the Total Internal Reflection Microscopyx(TIRM)system and the SDOCT system were combined to carry out detection and evaluation analysis.A set of calibration and measurement methods were proposed and tested.In the experiment,the position of the probe arms of the two systems was calibrated to make accurate tomographic imaging of the same point prior to coarse positioning.The parameters of the subsurface damage can then be obtained.