The effectiveness of the laser can be evaluated by the beam quality factor, the beam quality factor is related to the initial parameters of the outgoing laser and various atmospheric parameters on the transmission path. Therefore, the prediction of the beam quality factor can be regarded as a statistical identification problem. Support vector machine has unique advantages in dealing with small sample, nonlinear and high dimensional problems, and can be used to deal with such statistical identification problems. This paper simulates the transmission process of Gaussian laser in the marine atmosphere based on the numerical simulation model of multi-layer phase screen, obtaining simulation data of initial laser radius, initial power, transmission distance, refractive index structure constant, atmospheric visibility, and spot radius, beam drift, and energy circle rate at the receiving surface; then constructing the prediction models of these beam quality factors by support vector machine, the optimal parameter model is obtained by adjusting the kernel function of the model, the insensitive loss coefficient and the penalty factor; finally, the prediction error and accuracy of the model are analyzed. The research results show that the support vector machine can fit the multiple regression relationship between input and output well, and the prediction accuracy of the model is high. The research results can provide a feasible basis for the application of support vector machine in the evaluation of the effectiveness of the laser in the marine atmosphere.
Determining index of refraction of rough surface object is important for target identification and classification by polarization measurement, but it is difficult to directly acquire the imaginary part of complex refractive index. Many numerical inverse methods are proposed, which are Vimal-Milo method and improved Vimal-Milo inversion method. The first method is evaluated by P-G model, which is based on scalar bidirectional reflectance distribution function with a mode of “polarization ratio – angle correlation”. But this method is only applied in almost specular reflection and its defects are explicit in application. The second method named improved Vimal-Milo method is proposed based on the mode of ‘relative polarization component – angle correlation’. In this method, the inversion formula for the complex refraction index was semi-empirical deduced and global search algorithms such as genetic algorithm or Hooke – Jeeves search algorithm were used. Although two inversion methods are same based on P-G model, polarization measurement are different of which one is polarization ratio and the other is S1 component. The simulation results showed that (1) roughness parameters (correlation length and height standard variance of microfacet) have little effect to inversion of complex refraction index, and they must be calibrated accurately. (2) stokes values and reflection angle have smaller effect and they can be measured by polarimeter and angulometer. (3) incident angle is strongly correlated with complex refraction index and must be measured largely and precisely. (4) we must try to avoid poor specular reflection condition and improve degree of polarization.
Laser-induced periodic surface structure (LIPSS) is a universal phenomenon which occurs for both continuous laser and pulsed laser. Recently, most studies are focus on LIPSS irradiated by fs laser. However, LIPSS irradiated by continuous laser still need to be carefully studied. Here, We study LIPSS in silicon wafer irradiated by continuous laser for different duration time and power. For the same power, we can observe the evolution process of LIPSS for different time. It is surprising that the evolution process of LIPSS seems to be layered, which occurs for different power. The inner layer occurs at first, then the outer layer occurs. Our study can be used to control the formation of LIPSS.
When laser propagate in the atmosphere, due to aerosol scattering and absorption, laser energy will continue to decline, affecting the effectiveness of the laser effect. Based on the Monte Carlo method, the relationship between the photon spatial energy distributions of the laser wavelengths of 10.6μm in marine, sand-type, water-soluble and soot aerosols ,and the propagation distance, visibility and the divergence angle were studied. The results show that for 10.6μm laser, the maximum number of attenuation of photons arriving at the receiving plane is sand-type aerosol, the minimal attenuation is water soluble aerosol; as the propagation distance increases, the number of photons arriving at the receiving plane decreases; as the visibility increases, the number of photons arriving at the receiving plane increases rapidly and then stabilizes; in the above cases, the photon energy distribution does not deviated from the Gaussian distribution; as the divergence angle increases, the number of photons arriving at the receiving plane is almost unchanged, but the photon energy distribution gradually deviates from the Gaussian distribution.
Proc. SPIE. 9796, Selected Papers of the Photoelectronic Technology Committee Conferences held November 2015
KEYWORDS: Mathematical modeling, Solar radiation models, Data modeling, Skin, Far infrared, Infrared radiation, Radiation effects, Solar radiation, Performance modeling, Thermal modeling, Atmospheric modeling, Temperature metrology
The characteristic of the self-infrared radiation of airplane-skin is very important for the stealth performance of airplane. Based on the theory of the airplane-skin temperature field, the distribution of the atmospheric temperature field and the principle of the black-body radiation function the self-infrared radiation model was established. In specified flight conditions, the influence of the atmospheric temperature, the speed of flight, the emissivity and the sight angle detection on the self-infrared radiation of the airplane skin were analyzed. Through the simulation of infrared radiation, some results under different flight states are obtained. The simulation results show that skin infrared radiation energy mainly concentrate on the far infrared wavebands, and various factors have different effects on the infrared radiation of skin. This conclusion can help reduce the infrared radiation and improve the stealth performance of airplane in the engineering design and the selection of flight conditions.