太赫兹连续波成像的质量改进与降噪

摘要

Terahertz wave imaging has many advantages such as small ionizing radiation and high discrimination of organic mat-ter,so it is very suitable for non-contact,non-destructive imaging detection.However,this imaging method is susceptible to un-avoidableproblems such as disturbance of electromagnetic environment and fluctuation ofequipment power,which makes it diffi-cult to obtain high resolution terahertzimages.In this paper,terahertz imaging is realized by using the terahertz continuous-wave source imaging system.The terahertz images of four samples of cards,leaves,coins and keys are denoised by ourimproved threshold gray-scale transformation algorithm.Then,the images are sharpened and enhanced by the Laplacian operator.The re-sults are evaluated bymean square error and peak signal to noise ratio estimation.After the denoising,the estimated peak signal to noise ratio of some samples increased by 4～5 dB,so the image quality was improved obviously.This research proves that the built-up terahertz imaging system has a pomosing application prospect.%太赫兹波成像具有电离辐射小,对有机物鉴别力高等多种技术优势,因而非常适合应用于非接触式、非破坏性成像检测.然而这种成像手段易受到成像时电磁环境干扰和设备功率变化等问题的影响,因而存在一些特定的干扰模式,导致大部分的太赫兹脉冲扫描图像很难获得高清晰度的图像.利用搭建的太赫兹连续波源透射光路成像系统实现了逐点扫描式太赫兹成像.通过阈值灰度变换算法的改进优化,对卡片、树叶、一元硬币和钥匙四种样品的太赫兹波图像进行了去噪,然后基于拉普拉斯算子对图像进行锐化增强,并用均方误差和峰值信噪比估计等对去噪效果进行评价.去噪后太赫兹波扫描的部分样品峰值信噪比估计值提高可达4～5 dB,图像质量得到明显改善.研究证明所搭建的太赫兹成像系统具有一定的应用前景.