A novel optical-mechanical scanning passive THz imaging system

A novel passive THz imaging system of single channel and optical-mechanical scanning is described. It employs a Cassegrain antenna of 390mm in diameter, and achieves the two-dimensional scanning imaging via the cooperation of a line scanning mirror, driven by a crank-rocker mechanism in a high speed, and the motion of the frame scanning mirror. Thus, the system has many advantages such as low cost, simple structure, efficient and so on. The single frame imaging time of the system is only 20s, the field of view (FOV) is 30°× 36°, and the angle resolution is up to 0.6°. The experimental results show that the system can image the human body, and effectively detect dangerous items concealed under the clothes. For the images, processed by a sparse representation-based image denoising and inpainting algorithm, which generalizing the K-Means clustering process, for adapting dictionaries in order to achieve sparse signal representations. The processed image quality is improved obviously. The experimental results demonstrate, better RMSE and highest Peak Signal-to-Noise Ratio (PSNR) compared with traditional methods can be obtained.