Artificially prepared microbial spores have excellent electromagnetic attenuation properties due to their special composition and structure. At present, studies on the optical properties of microbial spores have mainly focused on those with a single band or a single germplasm, which has limitations and cannot reveal the optical properties comprehensively. In this paper, 3 kinds of laboratory-prepared microbial spores were selected for compounding, and the spectral reflectivities of single-germplasm biospores and compound biospores were measured in the wavebands of 0.25–2.4 and 3–15 μm. The complex refractive indices (CRIs) were calculated in combination with the Kramers–Kronig (K-K) algorithm. Relying on the smoke box broadband test system, the transmittance of single-germplasm bioaerosols and compound bioaerosols from the ultraviolet (UV) band to the far-infrared (FIR) band was measured, and the mass extinction coefficients were calculated. The results indicate that the trend of the complex refractive indices of the compound spores is consistent with that of the single-germplasm spores with a larger particle size. For the single-germplasm bioaerosols, the lowest transmittance values were 2.21, 5.70 and 6.27% in the visible (VIS), near-infrared (NIR) and middle-infrared (FIR) bands, and the mass extinction coefficients reached 1.15, 0.87 and 0.84 m²/g, respectively. When AO and BB spores were compounded at 4:1, the extinction performance of the bioaerosols somewhat improved in all wavebands. These results can help to comprehensively analyze the optical properties of bioaerosols and provide ideas for the development of new extinction materials.

Infrared smoke plays a vital role in battlefield photoelectric countermeasures. Transmittance and effective shielding area are crucial indicators in the evaluation of infrared smokescreen shielding performance. The traditional evaluation technique has drawbacks of lacking precision, time consumption, and low automation level. Therefore, an efficient and accurate technique is urgently desired for the evaluation of infrared smokescreen shielding performance in the battlefield environment. We propose a technique based on the grayscale value for evaluating infrared smokescreen shielding performance. First, a description of the field test system is introduced. Second, the transmittance and effective shielding area mathematical models are deduced and constructed. In particular, we discuss the assignment methods of the background and smokescreen grayscale value in the transmittance mathematical model. Finally, the evaluation software is designed, and a field test sample calculation is included to illustrate the procedure of the proposed technique. The results prove to be of enough precision for engineering applications, which is of great significance for engineering guidance.