Tong Zhaomin, Shen Wenjiang, Song Shaohua, Cheng Wenzhi, Cai Zhuo, Ma Yifei, Wei Lei, Ma Weiguang, Xiao Liantuan, Jia Suotang, Chen Xuyuan
Opt Express. 2017 Feb 20;25(4):3795-3804. doi: 10.1364/OE.25.003795.
In high lumen laser projectors, it is required to use laser diodes coupled to multi-mode fibers (MMFs) to obtain a high power illumination module. In this paper, we have fabricated an electromagnetic micro-scanning mirror (EM-MSM), and we have firstly demonstrated a speckle reduction method by the combination of the EM-MSM and the MMF. With the help of a condenser lens, laser beams modulated and reflected from the EM-MSM are coupled into the MMF within its acceptance angle. Because the fast scanning behavior of the EM-MSM results in the phase modulation and mode coupling among the MMF guided modes, the light intensity field distributions at the exit aperture of the MMF are changing. During the charge-coupled device (CCD) integration time, the random speckle patterns are integrated and homogenized by the CCD camera, and hence speckle is reduced. By driving the EM-MSM in raster scan, the lowest compound speckle contrast ratio at 0.0794 is obtained, where the EM-MSM half scanning angles are 0.4 ° and the optical power loss is lower than 4.5%. The demonstrated technique is compact and can endure the high power of the laser module; thus, it has a promising potential in high lumen laser projector applications.
在高流明激光投影仪中，需要使用耦合到多模光纤（MMF）的激光二极管来获得高功率照明模块。在本文中，我们制作了一个电磁微扫描镜（EM-MSM），并且首次展示了一种通过将EM-MSM与MMF相结合来减少散斑的方法。在聚光透镜的帮助下，从EM-MSM调制和反射的激光束在其接收角内耦合到MMF中。由于EM-MSM的快速扫描行为导致MMF导模之间的相位调制和模式耦合，MMF出射孔径处的光强场分布会发生变化。在电荷耦合器件（CCD）积分时间内，随机散斑图案被CCD相机积分并均匀化，从而减少了散斑。通过以光栅扫描方式驱动EM-MSM，获得了最低为0.0794的复合散斑对比度，其中EM-MSM的半扫描角为0.4°，光功率损耗低于4.5%。所展示的技术结构紧凑，能够承受激光模块的高功率；因此，它在高流明激光投影仪应用中具有广阔的潜力。
