现有的液晶显示器(LCD)背光模组大多采用侧入式发光二极管(LED)作为背光源，其要求导光板厚度始终大于LED发光截面宽度。为解决这一问题，提出一种用于侧入式LED背光模组的自由曲面光耦合结构，包括浸入式准直透镜与自由曲面反射器，光源出射光先由浸入式准直透镜收集并准直，再经自由曲面反射器反射并聚集到导光板入光面。利用斯涅尔定律、微分几何法以及等光程原理对该模块进行设计，并通过光学仿真验证设计的可行性。实验结果表明，当采用有效发光面积为0.4 mm×0.4 mm的LED芯片作为光源时，导光板厚度减少0.6 mm，导光板入光面处光能利用率达到96.23%，相对于传统结构，光线利用率提高11.22%。该光耦合模块实现了背光模组中导光板的薄型化，同时改善了导光板入光面处光热点现象。

Conventional backlight system of liguid crystal display (LCD) always uses side-in light emitting diodes (LEDs). It requires that the thickness of the light guide plate should be larger than LED′s light-emitting section width. To solve this problem, a free- form optical coupling module for side- LED backlight is proposed, which includes collimator lens and a free- form reflector. The light is firstly collected and collimated by immersing collimator lens, and then reflected and gathered into the LGP′s incident surface. By using Snell′s law, differential geometry method and aplanatic principle, the detailed design of the module is presented, and the feasibility is shown by optical simulation. Simulation results show that by choosing 0.4 mm×0.4 mm LED chip as the light source, the thickness of the light guide plate is reduced 0.6 mm, and the light utilization can still reach 96.23%. Compared with the conventional structure, the light utilization increases by 11.22%. The optical coupling module can realize a thinner backlight module effectively, and simultaneously help to restrain the hot phenomenon.