全光纤频域光学相干层析成像系统优化研究

Optimization of fiber-based spectral domain optical coherence tomography system

针对频域光学相干层析（SD-OCT）系统特有硬件（线阵CCD及分光光栅）参数对成像质量造成的影响,展开了对基于光纤的频域OCT系统中硬件参量的模拟和优化工作,分析了分光计中CCD线列阵像素数及数字化深度、CCD安装偏差等因素对OCT成像质量的影响,并对光谱像素图定位进行了修正。研究表明：纵向分辨率不受CCD线列阵像素数的影响,CCD线列阵像素数的增多将线性地增大最大测量深度;CCD数字化深度小于6bit将直接导致系统纵向分辨率的锐减;线阵CCD偏离聚焦透镜焦面将导致点扩展函数的强度减弱、系统分辨率降低;在较小角度内转动CCD,将使纵向分辨率得到提高;采用氖灯光谱进行像素图定位校正之后,可以相应地提高系统分辨率。部分模拟结论得到实验验证。采用此模拟优化结果,可根据OCT成像的具体要求对系统硬件参量进行优化选择。

The hardware parameters of a spectral domain OCT （SD-OCT） system are analyzed for the optimal OCT imaging. These parameters include pixel number and digitization depth of the line CCD in the spectrometer,and the tolerance of CCD installation. Calibration of the spectrum localization is carried out. The depth resolution is not affected by the CCD linear array pixel number,but with the increasing of CCD linear array pixel number,the maximum probing depth increases linearly. If the digitization depth of CCD is higher than 6bit,it is possible to calculate useful depth cans with good resolutions. When the CCD is moved several millimeters away from the focal plane,the value of point spread function （PSF） will decrease,and the resolution will degrade. When the CCD rotates several degree,full width at half maximum （FWHM） of the PSF will decrease,denoting the increasing of the axial resolution. After calibration using Ne lamp spectrum,the quality of the image will be obviously improved. Some of the results are experimentally verified. For SD-OCT system,the optimal system parameters can be selected for specific application.