Bachmann Adrian, Leitgeb Rainer, Lasser Theo
Opt Express. 2006 Feb 20;14(4):1487-96. doi: 10.1364/oe.14.001487.
One of the main drawbacks of Fourier domain optical coherence tomography (FDOCT) is the limited measurement depth range. Phase shifting techniques allow reconstructing the complex sample signal resulting in a doubled depth range. In current complex FDOCT realizations the phase shift is introduced via a reference path length modulation, which causes chromatic phase errors especially if broad bandwidth light sources are employed. With acousto-optic frequency shifters in the reference and sample arm, and the detector being locked to the resulting beating frequency, the signal is quadrature detected at high speed. The beating signal frequency is the same for all wavelengths allowing for achromatic complex reconstruction. With a Ti:Sapphire laser at 800nm and spectral width of 130nm, a heterodyne complex FDOCT system is realized with 20kHz line rate and an axial resolution of 4mum.
傅里叶域光学相干断层扫描（FDOCT）的主要缺点之一是测量深度范围有限。相移技术允许重建复杂的样本信号，从而使深度范围加倍。在当前复杂的FDOCT实现中，相移是通过参考路径长度调制引入的，这会导致色相位误差，特别是在使用宽带宽光源时。通过在参考臂和样本臂中使用声光频率移位器，并将探测器锁定到产生的拍频，信号可以高速进行正交检测。所有波长的拍频信号频率相同，从而实现消色差复重建。使用波长为800nm、光谱宽度为130nm的钛宝石激光器，实现了线速率为20kHz、轴向分辨率为4μm的外差复FDOCT系统。
