Optimal Spatial Sampling Criterion in a 2D THz Holographic Imaging System

This paper presents our study on the spatial sampling scheme in a 2-D terahertz holographic imaging system operating at 220 GHz, in which the amplitude and phase of reflected/scattered signal from the target are recorded by raster scanning on the aperture plane. The amplitude and phase based image reconstruction has been proved better than the amplitude based image. Traditionally, the spatial sampling interval, which needs to satisfy the Nyquist sampling criterion, has mostly been selected based on the worst case scenario. However, smaller spatial sampling interval will introduce more time consumption in the scanning. We have derived in theory an optimal spatial sampling criterion based on the target size and the threshold power beam width of transmitter/receiver antenna. The optimal spatial sampling interval is much larger than the worst case Nyquist criterion and has been verified in the experiment, leading to a substantially reduced imaging time while maintaining the image quality.