中文摘要：

主要探讨自然界树叶样本的太赫兹透射成像中的对比度与透射频率的关系。运用透射模式的太赫兹时域光谱系统对样本进行了聚焦逐点式的主动扫描,得到样本各部分的太赫兹波透射率,然后进行数据处理和二维成像。通过对样本在8个不同频率下的太赫兹透射率成像的比对分析,表明样本的不同部分对各个频率的太赫兹波的吸收都有较明显的差别。为了得到更清晰的太赫兹成像,必须选取合适的成像频率使样本成像的对比度更佳,实验发现应该选择透射振幅适中的频段,且在此范围内样品的某些部分具有吸收峰的频率附近进行成像。

英文摘要：

In this article,the contrast of the images of leaves scanned by THz time domain spectroscopy is discussed.From the leaf′s transmittance images reconstructed at 8 different THz frequencies,it shows the absorption properties of the sample′s different parts are distinct which give out different image contrasts.Better image contrast will lead to clearer picture.The study demonstrates that to obtain better image contrast,it is better to select the frequency around which the transmission amplitude is moderate and the some part of the sample has an absorption peak within this range.