Papers by Author: Zhi Gang Fan

Abstract: Cold-background multitarget compounding system provides infrared targets for hardware-in-the-loop simulation system, in which large aperture reflective mirrors are employed. In this paper, we proposed a combined belt-back structure and designed the flexible connection to solve support mechanism of large aperture mirrors for 100K temperature variations. By Finite Element Method analysis, root mean square (RMS) of optimized mirror was better than λ/40 under self-gravity and 100K temperature variations. By Zernike polynomial fitting, MTF of multitarget compounding system was over 0.5 and RMS spot diameter was less than 0.05mrad. Results demonstrated that the proposed support mechanism was effective and provided analytical data for 1m level mirror in large environment temperature variations.

Abstract: The possibility of constructing terahertz Fabry-Perot interferometer using metallic meshes with micrometer period and high ratio of linewidth/period is investigated, and the effectivity of traditional equivalent circuit method is verified by FDTD method. Simulation shows that the reflectance and transmittance of this kind of meshes calculated by equivalent circuit method have considerable deviation from those obtained by vector analysis of FDTD, so equivalent circuit method can be used to roughly evaluate the properties of this kind of metallic meshes. By using a metallic mesh with the period of 5 micrometers and the ratio of linewidth/period of 0.8, a finesse larger than 1100 can be achieved while the peak transmittance is still larger than 0.2 for a Fabry-Perot interferometer. It is therefore concluded that a high-quality terahertz Fabry-Perot interferometer can be constructed by using metallic meshes with micrometer period and high ratio of linewidth/period.

Abstract: In this paper, a novel optical method, namely, Coherent Gradient Sensing (CGS) is used to study the fracture properties of IR window materials in the guidance missile. CGS can produce high contrast fringes and provide some degree of control on the sensitivity of measurement during experiment. It is highly attractive for solid mechanics applications, especially to new materials, such as IR window materials. But the accuracy of the fringe order in the CGS interference image will deeply influence the precision of experiment. Because of the different optical principle from other method, the fringe order of CGS can’t be obtained through the phase-shift technology. To satisfy the precision request of IR window materials, a kind of modified CGS method, loading CGS method is introduced and analyzed, which can accurately obtain the fringe order of random position in the CGS interference image. This method doesn’t need additional optical set-up and complicated image processing techniques, but only need two CGS interference images under different loading. Static fracture experiments of ZnS show that this method can evidently improve the precision of the CGS method.