Fresnel lens based large-diameter terahertz imaging system

Abstract

The invention discloses a Fresnel lens based large-diameter terahertz imaging system. The imaging system comprises a system shell, a scanning light path and a detector, the scanning light path and the detector are arranged in the system shell, and a Fresnel lens is adopted in the scanning light path. The imaging system has the advantages that improvement in a conventional refraction type scanning imaging system is performed on the basis of the Fresnel lens, so that high resolution ratio and imaging quality can be achieved, and the improved imaging system is simple to process and compact in structure and has much higher sensitivity than the conventional refraction type scanning imaging system.

Description

technical field [0001] The invention relates to optical imaging technology, in particular to large-aperture terahertz imaging technology. Background technique [0002] The large-aperture terahertz imaging system mainly includes two types of imaging scanning methods, one is reflective scanning imaging, and the other is refraction imaging. [0003] The former (reflection scanning imaging system) is currently the most widely used in the market and in the field of scientific research. It mainly uses two or one off-axis parabolic mirror to scan and focus the target, and converge the terahertz signal radiated by the human body to the detection. The main advantage is that it is simple to manufacture and design, but the disadvantage is that the imaging resolution and imaging quality are poor. [0004] The key of the refraction imaging system is a terahertz lens made of HDPE (high density polyethylene) material, and it is scanned with two or more flat mirrors, and the terahertz sign...

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Problems solved by technology

[0003] The former (reflective scanning imaging system) is currently the most widely used in the market and scientific research fields. It mainly uses two or one off-axis parabolic mirrors to scan and focus the target, and gathers the terahertz signals radiated by the human body to the detection system. The main advantage is that it is simple to manufacture and design, and the disadvantage is that the imaging resolution and imaging quality are poor

[0004] The key to the refraction imaging system is a terahertz lens made of HDPE (high-density polyethylene) material, which is scanned with two or more flat mirrors to focus the terahertz signal radiated by the human body and then converge it to the detector For imaging, the advantage is that the imaging resolution and imaging quality are better than those of the reflective system, and the mirror only needs to use a flat mirror without additional processing of the curved surface. The disadvantage is that the key component of the imaging system - the terahertz lens, in order to ensure the focal length and imaging As a result, it needs to be processed into a lens with a large diameter and a thick thickness. The processing is difficult, the weight is heavy, and the consumables are large. As the thickness increases, the absorption of terahertz signals increases, and the overall sensitivity of the system is low.

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