Real-time diagnosis of the radiative properties of participatory media, such as flames, is very difficult due to their spatial and temporal complexity. In this paper, we propose a new method to simultaneously reconstruct gas and carbon soot properties using a multispectral light-field camera. Hyperspectral light-field imaging is performed on two targets (a rectangular participating medium and a flame) to analyze the spectral imaging effect of gas-solid radiative properties in the mid-infrared band. The two-color method combined with the nearest-neighbor filtering method was used to reconstruct the medium temperature and carbon soot absorption coefficients, which helps yield the gas mole fractions (H2O and CO2) for a specific mid-infrared band and reconstruct their actual distributions.
With the improvement of stealth and penetration ability of high-speed targets, it is more and more difficult to capture and recognize high-speed targets by relying on traditional optical characteristic signals. It is urgent to expand the characteristic optical elements as an effective complement to the existing detection means. As an optical element, polarization greatly expands the optical information dimension and has high application value in the field of target detection and recognition. This paper presents a method for calculating polarization radiation transmission of rocket plume based on Monte Carlo method. The correctness of the algorithm is verified by an example of L13. The detection wavelength of 1.55 um was selected, and the polarization characteristics of the solid rocket plume at different viewing angles and the imaging characteristics at different viewing angles were calculated using this method. The imaging results show that the characteristics of the polarization degree can reflect the profile of the plume at different observation angles. The point source results show that the polarization degree of the plume is very small in the case of point source radiation, and the polarization Angle changes obviously with the change of the relative detection azimuth, which is helpful to analyze the plume orientation and other information in the case of point source detection.
Based on electromagnetic scattering mechanism, Mie scattering theory and Monte Carlo method are used to analyze the radiation characteristics of SiC particle swarm with different distribution forms. The study find that the form of particle size distribution has a significant impact on the spectral transmittance of particle swarms. The proportion of particles of different sizes in the particle size distribution, the dispersion of particle size distribution, and the span of particle size scale all affect the infrared extinction performance of particle swarms in varying degrees. Among them, the proportion of particles of specific size in the particle size distribution is the most one, which is a necessary factor to ensure the existence and amplitude of particle characteristic spectra. The relationship between particle size distribution and radiation characteristics was deeply analyzed, and the results showed that increasing the proportion of particles in the 0.16~2.5 µm particle size range of SiC particle swarm can comprehensively improve the extinction performance of SiC particle swarm, this is of practical significance for optimizing the infrared radiation performance of particle swarms.
It’s interesting that the artificial structure colors can be actively manipulated by external stimuli such as solvents, temperature, and mechanical force. In this paper, polarization state, the inherent characteristic of incident light, is used to control the structure color by a one-dimension metamaterial perfect absorber with polarized absorption peaks based on the stacked array. The nanostructure, consisting of two metal-dielectric pairs and a bottom metallic film, shows above 90% reflectivity from 652 nm to 750 nm (the red structure color) for TE and above 80% reflectivity from 584 nm to 635 nm (the orange structure color) for TM. Because our designed one-dimension absorber has the absorption peaks at 548 nm and 684 nm for TE and TM, respectively. So the polarization-controllable structure color gradually changes from red to orange when the polarization angles increase from 0° (TE) to 90° (TM). The underlying physical mechanisms of high absorptivity is explained by the electric and magnetic fields distribution.
Based on optical scattering theory of Aden–Kerker method, the extinction efficiencies of submicron hollow particles with 5 kinds of materials, such as graphite(C), brass powder (Cu), cupric oxide (CuO), cuprous oxide(Cu2O) and soot are given in this paper. Some influences of different materials, inner radius (x), outer radius (y), shell thickness (z) and x-z ratio(x/z) on the extinction efficiencies are studied respectively. Owing to lack of literature data, the optical constants of C, Cu, CuO, and Cu2O are firstly obtained by measuring infrared spectral transmittance of material piece and retrieving the equivalent optical constants combined with electromagnetic scattering theory and K-K relation. The results show that particle C, Cu, Cu2O and Soot have a good performance in stability of extinction efficiency distribution within 3-5μm; the extinction efficiencies of C, Cu, Soot decrease gradually with the shortening of the wavelength within 3-5μm; the extinction efficiency of all kinds of particles increase along with outer radius y increased when shell thickness z is fixed.
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