Common path continuous terahertz reflection and attenuated total reflection imaging

Abstract

Terahertz imaging technology is one of the candidate technologies for medical imaging. In particular, continuous terahertz reflection and attenuated total reflection imaging are expected to achieve rapid intraoperative imaging, which is hot research topic at present. In order to realize the rapid multi-dimensional and high-quality terahertz imaging detection of sample, it is necessary to study the common optical path continuous terahertz reflection/attenuated total reflection dual-mode imaging system based on point scanning. By using the Fresnel formula and the penetration depth formula of evanescent wave, the influence of imaging angle on the reflected signal and the penetration depth of attenuated total reflection are studied theoretically in this paper. The imaging angle of terahertz wave suitable for both reflection and attenuation total reflection imaging is obtained. Based on this, an isoscele total reflection prism with a base angle of 49° is designed. The dual-mode imaging of common optical path continuous terahertz reflection and attenuated total reflection is realized by quickly switching between reflection window and total reflection prism. The reflection and attenuation total reflection imaging modes have imaging resolutions of 400 μm and 500 μm, respectively. Continuous terahertz reflection and attenuated total reflection imaging are experimentally studied by using distilled water and pork as samples. The results show that the relative reflectance of the sample obtained in the attenuated total reflection imaging mode fluctuates within a range of 1%, and the image contrast is 9 times that of the reflection imaging mode. Moreover, attenuated total reflection imaging can effectively identify the sample with the length less than 1 mm. Thus, compared with reflection imaging, continuous terahertz attenuated total reflection imaging has the advantages of high image resolution, high image contrast and highr signal stability, and can accurately obtain the reflectivity of sample. The terahertz attenuated total reflection imaging technology is more helpful in achieving high sensitivity imaging of samples. By combining reflection and attenuated total reflection imaging modes, the advantages of different imaging modes can be compensated for and the performance of the imaging system can be further improved. This common path continuous terahertz reflection and attenuated total reflection dual mode imaging system is expected to achieve a high sensitivity detection of sample.