Ma Xinru, Hu Hao, Wang Xiaolei
Opt Lett. 2024 Sep 15;49(18):5268-5271. doi: 10.1364/OL.536503.
Terahertz (THz) waves show outstanding application value in the nondestructive detection of hidden targets that are impenetrable to visible light. However, the uncertain location of hidden targets puts a higher demand on the zoom function of the THz quasi-optical systems, especially when the object is immovable. This paper proposes a continuous zoom system working in the THz band consisting of a negative axicon disk, a segmented axicon, and a freeform lens. The negative axicon disk and segmented axicon shape THz waves into annular beams with adjustable diameters, which are respectively focused at different positions by the zone-designed freeform lens. Both simulation and experimental results indicate that the zoom range of the system can reach 82 mm while maintaining an imaging resolution of 6 mm. Notably, continuous zooming is achieved by merely rotating the negative axicon disk, instead of the lens moving. Moreover, all devices in the system can be fabricated by 3D printing or machining. This approach offers the advantages of simple adjustment and low cost, providing, to our knowledge, a novel perspective for the design and application of THz quasi-optical imaging systems.
太赫兹（THz）波在对可见光不可穿透的隐藏目标进行无损检测方面展现出卓越的应用价值。然而，隐藏目标位置的不确定性对太赫兹准光学系统的变焦功能提出了更高要求，尤其是当物体不可移动时。本文提出了一种工作在太赫兹频段的连续变焦系统，该系统由一个负轴棱锥盘、一个分段轴棱锥和一个自由曲面透镜组成。负轴棱锥盘和分段轴棱锥将太赫兹波整形为直径可调的环形光束，这些环形光束分别由区域设计的自由曲面透镜聚焦在不同位置。仿真和实验结果均表明，该系统的变焦范围可达82 mm，同时保持6 mm的成像分辨率。值得注意的是，仅通过旋转负轴棱锥盘即可实现连续变焦，而无需移动透镜。此外，系统中的所有器件均可通过3D打印或机械加工制造。这种方法具有调节简单和成本低的优点，据我们所知，为太赫兹准光学成像系统的设计和应用提供了一种新的视角。
