为了实现对激光束的准直变倍扩束, 提出了一种基于液晶空间光调制器(Liquid Crystal Spatial Light Modulator, LC-SLM)实现数字变焦透镜的方法, 并利用这种方法搭建了基于LC-SLM的变焦扩束系统。首先根据透镜相位变换原理和LC-SLM的相位调制特性由计算机编程生成不同焦距的数字透镜相位调制图, 实现不同焦距的数字透镜功能, 通过凸透镜对平行光束的汇聚作用, 验证该功能的有效性, 平均误差为095%。上述结果说明LC-SLM能够实现变焦透镜功能。接下来, 通过与汇聚透镜组合实现对激光束的连续变倍率准直扩束。该系统的扩束倍率为2×~5×, 均方根误差为0539 7 mm, 峰谷值为099 mm。实验结果表明, 本文提出的方法可以实现对激光束不同倍率的扩束且扩束比连续可变。该系统解决了传统变焦系统无法满足多变的激光扩束需求的问题, 且结构简单, 精度高, 在激光扩束应用方面具有广泛应用前景。

In order to achieve collimation and zoom expansion in laser beams, a method of creating digital zoom lenses based on LC-SLM(Liquid Crystal Spatial Light Modulator) is proposed and a zoom beam expansion system based on LC-SLM is built using this method. Firstly, according to the principles of lens phase transformation and the phase modulation characteristics of LC-SLM, the phase modulation maps of digital lenses with different focal lengths are generated using computer programming to obtain the function of digital lenses with different focal lengths. The effectiveness of the function is verified with the convergence of convex lenses to parallel beams. The average error is 095%. It can be concluded that LC-SLM can achieve the function of digital lenses with different focal lengths and realize a zoom lens′ function. A 2×~5× continuous magnification collimation of the laser beam is then attained by combining it with the converging lens. The beam expansion error is 0539 7 mm, and the peak valley value is 099 mm. The experimental results show that the method proposed in this paper can be used to expand the laser beam to different multiples and the beam expansion ratio can be varied continuously. This system solves the problem that the traditional zoom systems cannot meet the changing demands of laser beam expansion. It has a simple structure with high precision and has great significance in the applications of laser beam expansion.