Characterization and Programming of Doppler OCT and Spectroscopic OCT (Algorithm Design + Phase shift + Fourier transform + Morlet transform + Signal Processing)
This project incorporates characterization and coding for two OCT extensions, Doppler and Spectroscopic OCT, after the critical interference pattern formation step. By using image‐ processing techniques, Doppler or velocity information is found through the Doppler frequency shift, which is extracted by calculating the phase differences of two axial sequential A‐line scans at the same location within a scanning period. It is accomplished by assuming an approximate 90% overlap between A‐line scans, therefore, consecutive A‐line scan can be treated as the same area. Spectroscopic data is obtained through the measurement of the full interference signal by comparing the backscattered light before and after an absorbing medium and a Morlet transform to remove windowing artifacts. Additionally, with the novel hue‐saturation false‐color mapping spectroscopic images can be obtained. Back‐scattered intensity can be mapped as saturation, and the spectral center of mass is mapped into to hue while the luminance is kept constant, therefore, allowing for the visualization of intensity and the spectral shift of back scattered light.23
The scope of this project was to develop processing code for Doppler and spectroscopic OCT for use with the systems under development in the Neuroscience and Optical Imaging Lab, and to do basic characterization and testing of these algorithms.