在300 - 1000 GHz的亞毫米波范圍內的成像對于各種應用（包括安全檢測，通過遮蔽成像和非破壞性評估）都是有用的。在這個頻率范圍內的波長范圍從1mm到0.3mm，能穿透許多光學遮蔽物。形成穿透衣服的高分辨率圖像的能力使得該頻率范圍內的成像對于距離距離的人員安全檢查特別有效。
美國西北太平洋國家實驗室（PNNL）以前已經開發出門控篩選系統，其操作在約30 GHz的毫米波頻率范圍的較低端。這些系統非常適合在門戶內進行篩選，并可在小于1米的范圍內實現約5mm的分辨率。
然而，增加這些系統的范圍將顯著降低由于其相對較長波長的衍射而導致的分辨率。在更高頻率（例如350GHz）下的操作將能夠在給定范圍內提高分辨率的數量級，同時仍然實現足夠的衣服滲透。 PNNL的門戶成像系統依靠波前重建或全息成像技術來數學地集中圖像。在亞毫米波中，由于系統對數據采集期間成像目標位置的微小變化的敏感性，這可能并不總是實用的。在這種情況下，使用透鏡或反射鏡的物理聚焦可能更實用。在本文中，我們研究了350 GHz附近成像安全篩選應用的有效性。使用全息波前重建技術呈現成像結果，以及基于聚焦反射器的成像系統。
Active Imaging at 350 GHz for Security Applications
Sheen DM, DL McMakin, JB Barber, TE Hall, and RH Severtsen. 2008. "Active Imaging at 350 GHz for Security Applications." In Proceedings of the SPIE: Passive Millimeter-Wave Imaging Technology XI , vol. 6948, p. 69480M. International Society for Optical Engineering, Bellingham, WA. doi:10.1117/12.778011
Imaging in the sub-millimeter wave range of 300 – 1000 GHz is useful for a variety of applications including security screening, imaging through obscurations, and non-destructive evaluation. Waves in this frequency range have wavelengths ranging from 1 mm down to 0.3 mm and are able to penetrate many optical obscurants. The ability to form high-resolution images that penetrate clothing makes imaging in this frequency range particularly interesting for personnel security screening at standoff distances. The Pacific Northwest National Laboratory (PNNL) has previously developed portal screening systems that operate at the lower end of the millimeter-wave frequency range around 30 GHz. These systems are well suited for screening within portals and can achieve resolution of about 5 mm at ranges of less than 1 meter. However, increasing the range of these systems would dramatically reduce the resolution due to diffraction at their relatively long wavelength. Operation at much higher frequencies, for example 350 GHz, will enable an order of magnitude improvement of the resolution at a given range, while still achieving adequate clothing penetration. PNNL's portal imaging systems have relied on wavefront reconstruction, or holographic, imaging techniques to mathematically focus the imagery. In the sub-millimeter-wave, this may not always be practical due to sensitivity of the system to slight changes in the position of the imaging target during data collection. In this case, physical focusing using lenses or reflectors may be more practical. In this paper, we examine the effectiveness of imaging near 350 GHz for security screening applications. Imaging results are presented using the holographic wavefront reconstruction technique, as well as a focused reflector-based imaging system.