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研制了应用于光学相干层析(OCT)成像的二维扫描光纤探头。该探头利用光纤悬臂的共振特性,结合光纤悬臂的结构不对称性,使光纤悬臂在正交方向具有不同的共振频率。通过对压电双晶片施加接近于上述两种共振频率的混频信号,就能同时激发光纤悬臂两正交方向上的振动,实现光纤悬臂的单驱动二维扫描。扫描采样率对成像质量至关重要,可通过驱动信号的频率选择和图像采集时间的设定来控制。在光纤悬臂固有频率曲线谐振宽度范围内细调驱动信号频率,可形成不同形状因而不同扫描覆盖率的大振幅李萨如轨迹。为实现扫描图像的正确重建,在扫描探头中引入了二维位置敏感探测器,用于扫描轨迹的同步记录。应用所研制的光纤扫描探头于已建立的光学相干层析系统,开展了典型样品的横断面扫描成像实验,在2 frame/s的采样速率获得了初期的实验结果,验证了方案的可行性。
A two-dimensional scanning fiber probe for optical coherence tomography (OCT) imaging was developed. The probe utilizes the resonant characteristics of the fiber cantilever and the structural asymmetry of the fiber cantilever so that the fiber cantilevers have different resonance frequencies in the orthogonal direction. By applying a mixing signal close to the above two resonant frequencies to the piezoelectric bimorph, the vibration in two orthogonal directions of the fiber cantilever can be excited at the same time to realize the single-drive two-dimensional scanning of the fiber cantilever. Scanning sampling rate is crucial for image quality and can be controlled by setting the frequency of the drive signal and the image acquisition time. Fine-tuning the driving signal frequency within the resonant range of the fiber cantilever natural frequency curve can form large amplitude Lissajous traces with different shapes and thus different scanning coverage. In order to achieve the correct reconstruction of the scanned images, a two-dimensional position-sensitive detector was introduced into the scanning probe for the simultaneous recording of the scanning trajectories. The developed optical fiber scanning probe was applied to the established optical coherence tomography system to carry out the cross-sectional scanning imaging experiment of typical samples. The initial experimental results were obtained at a sampling rate of 2 frames / s, which proves the feasibility of the scheme.