针对荧光偏振免疫分析仪对光源的需求，提出使用发光二极管(LED)作为激发光源并设计了口径小、结构紧凑且准直度高的配光系统。根据LED 的发光特性，采用折射自由曲面和反射自由曲面组合的方式实现对光源的准直。利用几何光学理论建立光源与目标面之间的关系方程确定面型参数。仿真分析结果表明，对1 mm×1 mm LED面光源可以实现发散角为±2.4°的准直照明，系统能量利用率可达85%以上。实现了结构紧凑、准直性能高的设计目标，为荧光偏振免疫分析仪激发光学系统的小型化提供了一种有效的设计方案。

Based on the requirements of light source used in fluorescence polarized immunoassay analysis device, light emitting diode (LED) is proposed to use as stimulating source and illuminating system with small size, compact structure and high collimation is designed. Referring to the luminous characteristics of LED, a new system combined with refractive and reflective freeform surfaces is designed for collimating. Equations between the source and target surfaces are presented through the theory of geometrical optics to get the surface parameters. The simulation results show that the collimating system can achieve ± 2.4° diverging angel for a 1 mm × 1 mm LED surface source with efficiency no less than 85%. Accomplishing the expected of compact construction and high collimation, the paper offers an effective reference for compact design of fluorescence polarized immunoassay analysis device.