Study On The Phase Modulation Of Reference Light In The FF-OCT System

Optical coherence tomography (OCT) is a diagnostic imaging technology, which was proposed in the early 1990s, it allows for noninvasive visualizing of internal tissue structure and physiology, and reveals great application value in biomedicine. Extracting the weak coherence signal from the background noise is the key part of OCT, and is also the research emphasis in the recent years, moreover, the phase modulation of reference light has a close bearing on the detection of coherence signal.In this paper, for the purpose of reducing all kinds of background noise and increasing the scan rate, the full-field optical coherence tomography (FF-OCT) is selected as the research object, and a method of sinusoidal phase modulation based on PZT controlling reference mirror is presented, which is helpful to extract and process the signal. The main research of this paper are including:At first, on the basis of the basic principle and the key technology of OCT, the imaging features and the background noise of FF-OCT is analyzed, and the process of signal extraction is studied, then, by image processing and algorithm the preponderant incoherence background and scattering noise are eliminated, and the imaging algorithm and optimum modulation parameter are designed.Secondly, in order to obtain the optimum modulation of reference light, an ideal discrete digital sine function with adjustable amplitude is used to adjust the vibrating of PZT, and frequency synchronism detection technology and integral method are also used to extract the coherence signal.Thirdly, according to the optimum modulation parameter, a digital phase shift technique is used to adjust vibrating phase of PZT, which is designed by a single chip computer delaying pulse and has the same frequency and high accuracy with the phase lock technique.Fourthly, considering the effect of PZT self defect, we designed a self-adaptive fuzzy PID controller using in controlling and adjusting PZT.Finally, the results of experiments at the end of the paper demonstrated the feasibility of the phase modulation technology of reference light in the FF-OCT system, achieved the scan control of reference arm, made sure of the reliable detection of the coherence signal, and may be also helpful for the further research.