Experimental Study On Frequency Domain Optical Coherence Tomography

As a real-time imaging technology for non-invasive detection of livingbiological tissue, optical coherence tomography (OCT) can achieve high spatialresolution of micron dimension and millimeter level imaging depth. Frequencydomain optical coherence tomography (FD-OCT) is an important branch of the OCT,which is characterized by non-mechanical longitudinal scan to speed OCT imagingprosses. Compared with time-domain optical tomography (TD-OCT), there areadvantages such as high sensitivity, and long detection depth in FD-OCT.In the paper, frequency domain coherence tomography is investigated experimentally.The experimental setup of FD-OCT is built based on the Michelson interferometerand the spectrometer by using a super light-emitting diode (SLD) source of centerwavelength850nm, bandwidth50nm. The imaging detections for some samples areperformed.The removal of the complex conjugate image with phase shift method is analyzed toextend the imaing range of FD-OCT, since during the later stage of image processing,half of the imaging range is reduced by complex-conjugate ambiguity that caused byFourier transform to real number data. In order to resolve the complex-conjugateambiguity, traditional phase-shifting technique is used in the work of imageprocessing. Currently, four step phase shift or more steps phase shift method wasutilized by most research, in which the piezoelectric ceramic translation or otherhigh-cost instrument is needed. Therefore the system is high-consuming and costly.The two-step phase shift method is introduced in the experiment, to reduce thenumber of steps in the phase-shift operation, speeding up the imaging of OCT. Theglass revolving shift method is discussed, in which the optical setup of FD-ODC isbuilt without PZT driving machine and other traditional phase shifter in theexperiments.In order to improve the image quality, wavelet denoising principle is studied. Thewavelet technique is applied in denoising processing of OCT image got from theexperiments. Finally, to get more details information from the image, pseudo-colorenhancement is used in the image processing.