A GPU parallel computing method for infrared target imaging was established, in which skin and plume was included. The SLG model was used to calculate the infrared characteristics of the radiation gases, and the LOS method was used to solve the infrared radiation transmission equation of the plume. According to the imaging geometry relationship between the surface and the three-dimensional plume, a target projection algorithm was established, in the method the forward ray tracing method was used to calculate the surface radiation imaging, and the reverse ray tracing method was used to calculate the plume radiation imaging. The CUDA parallel method was used to increase the calculation speed in the skin projection calculation module and the plume radiation calculation module, and the fast calculation of the target infrared spectrum image at the entrance of the detector was realized. The results show that the projection imaging algorithm can accurately generate the target image under the set conditions. The radiation distribution of the target infrared image is consistent with the temperature distribution. The calculation result of the tail flame radiation intensity is in good agreement with the experimental results. The CUDA parallel algorithm can effectively improve the computational efficiency of the program, the calculation speed of the skin projection module can be more than hundred times when the amount of calculation is large.
2019, 48(S2): 103-108. doi: 10.3788/IRLA201948.S218001
As the focus of current research on hollow core photonic bandgap fiber, reducing fiber loss is of great importance. In the view of fiber design, taking the 19 cell hollow core photonic bandgap fiber for example, the relationship between structure parameters and loss characteristic was investigated using the finite element method. Simulation results indicate that the confinement loss can be effectively reduced by adjusting the cladding parameters. With the increase of the layer of air holes, the air filling fraction and the fillet diameter at the corners, the confinement loss can be reduced below 10-4 dB/km. While the surface scattering loss, which depends on the coupling between the core mode and the surface mode, increases with the thickness of the core wall as well as the core expansion factor. In addition, the appearance of surface mode also leads to a sacrifice of transmission bandwidth. Limited by the fiber structure, the transmission loss of 19 cell hollow core photonic bandgap fiber is difficult to be reduced to less than 1 dB/km. Further reducing fiber loss can only be achieved by removing more air holes to form a larger hollow core structure. The research achievement provides theoretical basis for the realization of low loss hollow core photonic bandgap fibers.