单驱动二维扫描光纤探头研制

Development of Two Dimensional Scanning Fiber Probe Excited by Single Actuator

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 scanning fiber probe is developed to perform two-dimensional （2D） scanning for optical coherence tomography （OCT）. The probe exploits resonant oscillations of a fiber cantilever, and asymmetry geometrical structure of the fiber cantilever has two distinguished resonant frequencies along orthogonal directions. Orthogonal resonant oscillations are excited simultaneously and 2D scanning patterns are generated when it is actuated by one piece of piezoelectric bimorph through a driving signal with mixed frequencies near above mentioned resonances. The scanning sampling density crucial to imaging quality can be deliberately controlled by setting of the driving frequencies as well as fetching duration. Fine tuning the driving frequencies within the widths of intrinsic resonant curves of the designed fiber cantilever results in large scanning amplitude with different Lissajous trajectories and thus different scanning coverages are produced. For correct image reconstruction, a 2D position sensitive detector is also introduced in the developed probe to record the scanning pattern simultaneously. With the developed probe to the established OCT system, experiments on typical samples for en-face imaging are carried out at 2 frame/s. Those preliminary imaging results are presented in the paper.