谱域光学相干层析成像中深度分辨相位误差提取及补偿

Extraction and Compensation for Depth-Resolved Phase Error in Spectral Domain Optical Coherence Tomography

提出了一种在谱域光学相干层析成像(SDOCT)中提取随深度变化的相位误差及补偿该误差的方法。对被测样品的干涉谱作加窗傅里叶变换,得到一幅二维深度-频谱图。样品不同界面对应的干涉谱因加窗傅里叶变换的时频特性而被分离开。对各干涉谱相位分别进行多项式拟合,得到一组随深度变化的相位误差分布。将该深度相位误差分布作为补偿因子实现精确补偿。该方法不仅可完成对多个介质层构成的复杂样品的色散补偿,还可以实现对由于波数采样不均引起的随深度非线性变化的相位误差的补偿。仿真实验和对四层盖玻片样品及人体指甲盖的实验结果表明,该方法能简单精确地补偿系统随深度变化的相位误差,有效地抑制因相位误差导致的系统纵向分辨率随深度的恶化,改善成像质量。

A windowed Fourier transform （WFT） based method is proposed for extracting and compensating depth-resolved phase error in spectral domain optical coherence tomography （SDOCT） system. Firstly, by using a WFT to the interference spectrum of the light from the sample and the reference mirror, the depth-frequency distribution of A-scan of the sample is obtained. Due to the time-frequency characteristics of the WFT, the interference spectra corresponding to different interfaces at different depths are separated. The polynomial fitting for the phase variation of each complex interference spectrum is then performed and the phase errors distribution with the change of depth is obtained. Based on these phase errors, a precise numerical compensation for the phase is carried out. This method can not only be applied for extracting and compensating of depth-resolved dispersion phase error, but also can be used for depth-varied phase error compensation resulted from uneven spectrum sampling in wave-number space. A simulation for dispersion phase error extraction is conducted. Finally, the SDOCT images of the 4-layer cover glasses and fingernail of a volunteer are obtained and then used for phase error extraction with the WFT method. The results demonstrate that the proposed method has the capability of extracting the phase errors with high precision, leading to the improvement of the depth resolution and the image quality after phase error compensation.