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搭建基于光谱光学相干层析术(SDOCT,spectral domain optical coherence tomography)的内窥成像系统,分析SDOCT的理论分辨率和探测深度。根据近轴子午光线方程,利用矩阵法分析自聚焦GRIN(gradient index)透镜成像原理,设计适用于SDOCT扫描探头的GRIN透镜,聚焦距离为10mm,透镜长度为5.31mm,直径为1.8mm。通过光学传递函数(MTF)对比GRIN透镜和传统球面透镜对成像质量的影响。利用内窥成像系统对洋葱内外表皮样品进行成像,获得3.2mm×0.7mm的层析图像。实验结果表明,利用GRIN透镜聚焦光束时,SDOCT系统的横向分辨率可达8μm,成像质量得到提高。
An endoscopic imaging system based on SDOCT was set up to analyze the theoretical resolution and depth of SDOCT. According to the paraxial meridional equation, the GRIN (gradient index) lens imaging principle is analyzed by matrix method. The GRIN lens is designed for SDOCT scanning probe. The focusing distance is 10mm, the lens length is 5.31mm and the diameter is 1.8mm. The influence of the GRIN lens and the conventional spherical lens on the imaging quality was compared by the optical transfer function (MTF). The inner and outer epidermis samples were imaged using the endoscopic imaging system to obtain a tomographic image of 3.2 mm × 0.7 mm. The experimental results show that the lateral resolution of the SDOCT system can be up to 8μm when the beam is focused by the GRIN lens, and the imaging quality is improved.