Terahertz real-time imaging is a promising technology for applications in material characterizations, material reaction analysis, and biomedical imaging^[1,2]. The first, to the best of our knowledge, demonstration of real-time imaging in terahertz region was realized by employing a powerful gas laser^[3]. However, the gas laser is huge and expensive, which makes it difficult to obtain practical application in the imaging system. Therefore, Lee et al.^[4] developed an imaging system by employing the quantum-cascade laser (QCL) that is one of the important terahertz solid-state sources with high output power and compact structure. After that, research on terahertz real-time imaging has been rapidly developed in the past ten or more years^[5–14]. By improving the performance of terahertz arrays^[5,8], the real-time imaging demonstration with a resolution of hundreds of microns is realized. Using a microscope lens and synchronous signal locking, the imaging resolution is improved to less than 100 µm^[6]. Finally, a two-dimensional wobbling mirror has been used to eliminate the interference fringes of the emitting light of terahertz QCL^[11]. Although the performance and imaging effects of terahertz real-time imaging systems have been greatly improved by employing the above improvements in receiver and optical path, the complex optics and high cost make the above imaging system unable to be widely used.