Large depth-of-focus achievement based on an aspheric lens with a ring

Terahertz (THz) imaging technology has been widely studied because of its easy penetration of non-polar materials and low photon energy. To acquire a beam featuring both excellent transverse spatial resolution and a considerable depth-of-focus (DOF) to fulfill the demands of two-dimensional and three-dimensional THz imaging, this paper presents an aspheric lens with ring (ALR). The ALR has a controlled diameter of 50 mm, can be machined by 3Dprinted technology, and does not need to use complex imaging optical paths to achieve the large DOF function. In a transmitted point-scan imaging system with a 140 GHz light source, the lens can achieve both a resolution of 6 mm and an effective DOF of 66.4 mm for objects greater than 27 mm from the lens surface. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.