Optimization On Imaging Characterics Of Frequency-domain Optical Coherence Tomography With Algorithm

Optical coherence tomography is a kind of two-beam interference imaging technique(Optical Coherence Tomography,OCT)based on Michelson interference principle,which has characteristics of non-contact and non-invasive optical imaging.There is no need for axial scanning of the sample in the frequency domain optical coherence tomography(FD-OCT)that can receive the interference spectrum produced by the object beam and reference light.The structural information in the sample-depth direction is contained within the interference spectrum.By using the Fourier transform to the interference spectrum,scattering potential(axial signal intensity)can be obtained.Frequency domain OCT of no axial scanning has been widely applied in the field of medical imaging and diagnosis in recent years.In this paper,the factors of effect on the imaging depth and axial resolution of frequency domain OCT tomogram are explored,and the causes of reducing tomographic imaging quality are explained.In the experiment,the optical setup is equipped with optical-fiber paths,and the multiple interference spectrums captured with CCD are reconstructed into the complex spectrums by using numerical algorithm.The removal of disturbance terms(such as the DC term,the parasitic term and complex conjugate term)from tomographic images are performed with two-step phase shift and three-step phase shift are performed and compared.Accordingly,the imaging depth of the tomogram is extended.In addition,the causes of the dispersion effect that may reduce the axial resolution of tomographic imaging are analyzed.With Hilbert transform method,the phase of the interference spectrum is extracted and modulated,and the two-order dispersion effect is eliminated from the distribution of phase.After the evaluation of two-order dispersion coefficients in the different depths,the fitting curve of two-order dispersion coefficient can be obtained,and the method of continuous dispersion compensation is presented.The compensation for dispersion-broadened effect of the tomogram over all the depth direction is realized by means of this continuous dispersion compensation,so that under-compensation and over-compensation in FD-OCT tomographic imaging are effectively solved.