Academician Guo Guangcan's team of China University of Science and Technology has made new progress in the research of infrared image conversion: Professor Shi Baosen and Professor Zhou Zhiyuan of the team combined with spiral phase contrast technology, used quasi-phase matching and frequency process to realize up-conversion edge enhancement imaging from infrared image to visible image, and realized field-of-view enhancement by adjusting phase matching. The research results were published in the authoritative journal Physical Review Applied (Phys. Rev. Appl. 11, 044013 (2019) on April 4, 2019. This technology has important potential applications in the fields of bioimaging, pattern recognition and infrared remote sensing.
The image detectors working in infrared band generally have some shortcomings, such as poor sensitivity, low efficiency and high price. It is an effective method to transform infrared image information into visible band by frequency up-conversion, and then use visible band image detector with excellent performance and low price to solve the problem of infrared image detection. Phase contrast enhanced imaging technology is an important image processing technology. It combines spiral phase contrast edge enhancement technology with non-linear sum-frequency process to realize up-conversion edge enhancement of infrared image information, which is of great significance to image processing and detection. Shi Baosen and Zhou Zhiyuan have been engaged in the research of nonlinear frequency conversion of structured light field for a long time. They have successively studied the propagation, evolution and conservation characteristics of vortex beams in frequency doubling and sum process [Opt. Express 22, 20198 (2014); JOSAB 32, 407 (2015); Sci Rep. 4, 5650 (2014)], and developed the frequency up-conversion detection technology of single photon structured light field [Light: Sci. & Appl. 5, e16019].（ 2016; Phys. Rev. Lett. 117, 103601 (2016)]. By introducing the scroll pump light into the up-conversion imaging process and using the quasi-phase matched PPKTP crystal as the spiral filter and the frequency up-conversion medium, the up-conversion detection of object edge enhancement under infrared light illumination is successfully realized. At the same time, the maximum 2.1-fold field of view enhancement is achieved by adjusting the phase matching in the non-linear process. The experimental results are in good agreement with the numerical simulation results of solving the nonlinear coupled wave equation.
Figure 1. Up-conversion edge-enhanced imaging schematic
Figure 2. Experimental results of up-conversion edge-enhanced imaging and field-of-view enhancement
The first author of the thesis is Dr. Liu Shikai. The author of the communication is Professor Shi Baosen and Associate Professor Zhou Zhiyuan. This work is supported by the Ministry of Science and Technology, the National Natural Science Foundation of China, the Chinese Academy of Sciences and Anhui Province.