提出了基于旋转λ/2波片无色散相移器的理论模型,和实施该相移器功能的全场光学相干层析成像(Optical coherence tomography, OCT)系统,为实现快速、高分辨光学相干层析成像提供了一种有效方法。该相移器能在宽光谱范围内无色散地获得八倍于λ/2波片旋转角的相移量,避免了利用单色光相移算法提取信号时存在的系统误差。针对修正Carré算法和三步相移算法所要求的不同相移量,在240 nm波长范围内,对相移器的性能进行了数值分析。结果表明,在给定光谱范围内,相移量越大,相移误差的绝对值也越大,幅值比变化范围也越大。用于实施无色散相移器功能的全场光学相干层析成像系统结构,与现有结构相比,具有一些有益的特点。

Theoretical model of an achromatic phase shifter based on a rotating half-wave plate and its implementation in a full-field optical coherence tomography (OCT) system are proposed for rapid and high-resolution OCT imaging. The phase shifter that is almost independent of the wavelength over a broad range can provide phase shift at eight times of rotating angle of the half-wave plate. Conventional monochromatic phase-shifting algorithms can thus be adopted without systematic errors. Numerical analysis on phase shifting error and amplitude ratio between orthogonal polarization components versus wavelength over a range of 240 nm for nominal phase shifts required for the revised Carré algorithm and three-step phase-shifting algorithm respectively is conducted. The results demonstrate increased phase shift error and increased fluctnation of amplitude ratio for larger nominal phase shift. The full-field OCT system with the proposed achromatic phase shifter has several advantages compared with previous system.