光纤探头将发射光纤、接收光纤及自聚焦(GRIN)透镜集成为一体,可替代传统动态光散射装置的光路系统,能有效提高空间相干性,但目前尚缺乏光纤探头结构参数的最优设计方法.依据动态光散射光路系统空间相干性的要求,分析了光纤探头的结构参数,给出了优化设计的方法,确定了光纤探头两透镜间距和夹角的最佳取值范围.实验结果表明：光纤探头两透镜夹角为19°,间距为1.5 mm 时,可满足光路系统空间相干性的要求,接收信号的信噪比最高,相关函数的截距达到0.83,使用最优拟合累积分析法反演的颗粒平均直径相对误差小于2%.

Fiber optic probe is made up of two single mode fibers,one for launch and the other for detection,mounted on one gradient index (GRIN) micro lens.It can replace the optical path of the conventional dynamic light scattering set- up and accord with spatial coherence condition.However,there is a lack of the optimal design method of structural parameters of optical fiber probe.Based on spatial coherence condition of the dynamic light scattering system,we analyze the structural parameters of the optical fiber probe,describe the method of optimal design and determine the best value range of the distance and angle between two lens of optical fiber probe.Experimental data shows that the optical fiber probe,whose angle between two lens is 19° and space is 1.5 mm,can meet the requirement of the spatial coherence.In such a case,the signal-to-noise ratio of the received signal is highest and intercept of the correlation function is 0.83.The relative error of the average particle diameter,which is obtained by the optimal fitting Cumulants method,is less than 2%.