Three-Dimensional Terahertz Coded-Aperture Imaging in Space Domain

As a promising radar imaging technique, terahertz coded-aperture imaging (TCAI) can achieve high-resolution, forward-looking, and staring imaging by producing spatiotemporal independent signals with coded apertures. However, traditional 3-DTCAI working in time domain, has two problems, that is, heavy computational burden caused by large-scale reference-signal matrix, and poor resolving ability under low signal-to-noise ratio (SNR). Frequency-domain (FD)-TCAI (FD-TCAI) is able to reduce the two problems only in a limited degree. Therefore, this paper first proposes a space-domain (SD)-TCAI (SD-TCAI) method, which achieves more effective and efficient 3-D imaging than FD-TCAI under low SNR. With correlation operation, SD-TCAI transforms the echo signals from frequency domain to space domain, where spike pulses appear in the target positions. According to different spike pulses, the 3-D imaging areas can be divided and reconstructed in parallel, and finally synthesized together to obtain the whole 3-D target. In this way, the computational burden is further reduced, leading to an improved SNR. In this paper, we build and present the imaging models and procedures of TD-TCAI, FD-TCAI, and SD-TCAI, respectively. The experimental results demonstrate that SD-TCAI has overwhelming superiority over TD-TCAI and FD-TCAI. Therefore, SD-TCAI has great potential in applications, such as security screening, nondestructive detection, and medical diagnosis.