Just past of 2016, international situation ups and downs, global counter-terrorism situation more severe, "base" Organization of threat still exists, "Islamic country" momentum not reduction, world Shang most national are faced with terrorism of reality threat, although States high pressure combat, but threat still in spread, hundred people above casualties of major terrorist attacks case repeatedly occurred, on international social of security and stable caused huge impact.

On March 23, 2016 at "the heart of Europe" Belgium airports, subway bombings that occurred in the capital, killing at least 34 people were killed and nearly 300 injured. For China, terrorist attacks still occur in the Xinjiang region, foreign terrorist attacks on overseas Chinese interests and pose a serious threat to the security of personnel, "along the way" along the country's deteriorating situation on China's peripheral security environment against terrorism constitutes a major threat to reality.

For the prevention of critical events as much as possible, all to personnel transport, attending important meetings or large venues, implementation of the explosion-proof safety inspection.

At present, the international public security technologies include human review, handheld metal detectors, metal detectors, x-ray machines, explosive trace detection, liquid detector and so on. Which, artificial check accuracy high but efficiency low, and was check personnel easy produced conflict mood; metal detector and detection door cannot on non-metallic dangerous goods for recognition; explosion real marks volume detection and liquid detection instrument are exists function single, and application limited of shortcomings; x light machine only used to check luggage items, can recognition objects of profile, but cannot detection objects of chemical nature, once found suspicious items, only open box check, artificial identify, and, its maximum disadvantages is exists ionization radiation hurt, Abroad has been prohibited for human security. Shuangliu airport in Chengdu after x-ray machine has been formally prohibited by the Ministry of environmental protection for human security.

Therefore, traditional x-ray machines, metal detectors or pat-downs, such as real time check mode, dynamic sense the inherent risks, has been unable to meet the needs of the increasingly critical and complex security situation. So, is there a technology that can quickly identify the various hazardous materials, harmless to human body?

Too Hertz wave, this in electromagnetic waves spectrum is located in mm wave and infrared Zhijian of "vacuum zone", its frequency about for 1 trillion Hertz of mystery spectrum paragraph, its unique of fingerprint spectrum, and wide band, and penetrating sex, and high tell and no against five big characteristics, to communications (broadband communications), and Hertz in electromagnetic waves spectrum in radar, and electronic against, and electromagnetic weapons, and astronomy, and medical imaging (no mark of gene check, and cell level of Imaging), and lossless detection, and security checks (biochemical real of check), field brings has far-reaching of effect.

Terahertz electromagnetic spectrum position

In particular, when the field of Terahertz technology for security checks, and Terahertz waves can not only detect Imaging can also detect substances, drugs, explosives, and no clear evidence has been scanning dream of the Holy Grail.

Active Terahertz Imaging

At present, the Terahertz technology in security testing, material identification, and other fields has been developing rapidly, generally divided into active and passive. Passive receiving human emission of Terahertz Imaging, image resolution is poor and vulnerable to outside interference, had belonged to obsolete technology. Active electromagnetic and receives ECHO imaging the human body, is a hot spot in us-European developed countries, but also the future of mainstream applications. Foreign airports using Terahertz technology scans the clearance of passengers and luggage at the airport, checking the mail for possession of dangerous drugs, or bomb anthrax powder and other prohibited items.

If the large-scale use of this technology in a public place, personnel in the process, achieve large-scale, real-time, dynamic scanning, capture and early warning of suspicious objects to prevent his entering the crowded places or near key objectives, can best avoid the unpredictable storm events in the past.

Active three-dimensional high resolution imaging of Terahertz technology is not only a necessary way of public security technology development, can make up for important areas and cities in the process of rapid development of population influx, key regional counter-terrorism situation, short of public security facilities, lack of skills and ability to solve the massive people's life safety problem in the process of urbanization is of great significance.

刚刚过去的2016年，国际形势跌宕起伏，全球反恐形势愈发严峻，“基地”组织的威胁依然存在，“伊斯兰国”势头不减，世界上多数国家都面临着恐怖主义的现实威胁，虽然各国高压打击，但是威胁仍在蔓延，百人以上伤亡的重大恐怖袭击案件屡屡发生，对国际社会的安全和稳定造成巨大冲击。

特别是2016年3月23日在“欧洲心脏”比利时首都发生的机场、地铁连环爆炸案，致使至少34人死亡、近300人受伤。对于中国，在新疆地区恐怖主义袭击事件仍有发生，境外的恐怖袭击对中国的海外利益和人员安全构成严重威胁，“一带一路”沿线国家的反恐形势恶化对中国的周边安全环境构成现实的重大威胁。

为尽可能的预防各种暴恐事件，各国均要对人员乘坐交通工具、参加重要集会或进入大型场馆，实施防爆安全检查。

目前，国际公共安检技术主要包括人工检查、手持金属探测器、金属探测门、X光机、爆炸物痕量探测、液体检测仪等。其中，人工检查准确度高但效率低，且被检人员易产生抵触情绪；金属探测器和探测门无法对非金属危险品进行识别；爆炸物痕量探测和液体检测仪都存在功能单一、应用局限的缺点；X光机只能用来检查行李物品，可以识别物体的轮廓，但无法侦测物体的化学性质，一旦发现可疑物品，只能开箱检查，人工辨别，并且，其最大弊端是存在电离辐射伤害，国外已禁止用于人体安检。在成都双流机场事件后，X光机已正式被国家环保部明令禁止用于人体安检。

因此，传统的X光机、金属探测或搜身等检查模式无法实时、动态感知潜藏的危险，已不能满足当前日益严峻和复杂的安检形势的需求。那么，有没有一种技术，既能快速辨识各种危险物品，又对人体无害？

太赫兹波，这个在电磁波谱位于毫米波与红外之间的“真空地带”，其频率约为1万亿赫兹的神秘谱段，其独特的指纹谱、宽频带、穿透性、高分辨和无危害五大特性，给通信（宽带通信）、赫兹在电磁波谱里雷达、电子对抗、电磁武器、天文学、医学成像（无标记的基因检查、细胞水平的成像）、无损检测、安全检查（生化物的检查）等领域带来了深远的影响。

太赫兹在电磁波谱里的位置

特别是，当太赫兹技术用于安全检查领域时，太赫兹波不仅能检测成像，还可以检测物质成分，让毒品、爆炸物等无所遁形，一直就是扫描成像梦寐以求的圣杯。

主动式太赫兹扫描成像

目前，太赫兹技术在安防检测、物质识别等领域发展迅猛，一般分为主动式和被动式。被动式只接收人体发射的太赫兹波成像，成像分辨率差且易受外界环境干扰，已属于淘汰技术。主动式发射电磁波并接收人体反射回波成像，是美欧发达国家的研究热点，也是未来的主流应用方向。国外机场已利用太赫兹技术扫描机场通关的旅客与行李,检查邮件中是否藏有毒品、炭疽菌粉或炸弹等违禁物品。

如果在公共场所大规模使用这项技术，对人员行进过程中，实现大范围、实时、动态扫描成像，提前捕获和预警可疑对象，防范其进入人流密集场所或者接近关键要害目标，可以最大程度避免以往无法预知的暴恐事件。

主动式三维太赫兹高分辨成像技术不仅是公共安全技术发展的必经途径，更能弥补重要地区及大中型城市快速发展过程中带来的人口大量涌入，重点地区反恐形势严峻，公共安检设施技术水平和应用能力不足的短板，对解决中国大规模城市化过程中的民众生产生活安全问题有着重要的现实意义。