THz焦平面连续波透射成像系统的成像面积及对比度

研究了THz辐射和THz焦平面器件的特性,分析了THz焦平面探测器连续波透射成像系统的能量传输过程。考虑大气衰减、器件限制等影响因素以及连续激光照射、目标场景与焦平面探测器之间的信号传递关系,推导出了连续波透射成像系统的成像面积及对比度两个重要的参量模型。然后设计并组建了连续波THz透射成像系统。根据所建模型分别对信封中的环三亚甲基三硝铵(RDX)粉末和塑料盒中的金属刀片两种不同被测物体的成像面积及对比度进行了计算。结果表明:基于理论推导的两种实例其最大成像面积可达4.74cm×6.32cm和3.534cm×4.712cm,图像对比度分别为0.242 2和0.306。与美国麻省理工学院(MIT)的成像系统进行了对比,该系统的成像面积为3cm×3cm或4cm×4cm,与本文推导结果处于同一数量级,由此验证了本文提出的模型和方法的合理性和有效性。

Imaging area and contrast of THz focal plan array CW transmission imaging system

The characteristics of THz radiation and a THz Focal Plane Array(FPA) detector were researched, and the energy transmitting processing of a continuous wave imaging system in the FPA detector was analyzed. In consideration of the atmospheric attenuation, device limitation, and the signal transfer relation of continuous laser irradiation, target scene and the FPA detector, two parameter models for the imaging area and contrast ratio of the continuous wave imaging system were derived. Then, a continuous wave imaging system was designed. According to derived models, the imaging areas and contrasts of two different objects(one is the envelope with cyclotrimethylene trinitramine (RDX) powders and the other is the plastic case with metal blades) were calculated. The obtained results show that the imaging areas of the two examples are 4.74 cm×6.32 cm, 3.534 cm×4.712 cm, and the contrasts are 0.242 2 and 0.306 respectively. The results are compared with that of the imaing system with the imaging area of 3 cm×3 cm or 4 cm×4 cm from the Massachusetts Institute of Technology(MIT). They are derived in the same order of magnitude, which verifies that the proposed models and method are reasonable and effective.