Abstract
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.
Highlights
Terahertz technology has many applications in astronomy, biological research, security screening, chemical and explosive detection [1]
All imaging systems in THz spectral ranges can be divided into two main categories: incoherent detection and coherent detection [2], [3]
The raster scanning is adopted in these systems to record the signals reflected from the target on the aperture plane
Summary
Terahertz technology has many applications in astronomy, biological research, security screening, chemical and explosive detection [1]. The spatial sampling interval is an important parameter, which determines the imaging quality and time. The spatial sampling interval is usually chosen to be between λ/4 and λ/2 when considering the worst case scenario, i.e. the aperture plane being close to the target [4].
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