ABSTRACT
Frequency conversion imaging technology can provide an effective way for infrared detection against the limitations of conventional infrared detectors, such as expense and cooling requirements, but the converted luminescence intensity of frequency conversion materials limits the application of this technology. In this paper, a cascade material (CM) fusion method is proposed to improve the conversion luminous intensity and thus enhance the frequency conversion imaging effect at 1550 nm near infrared (NIR) excitation. First, we derived from the energy level transition mechanism of CM that the CM fusion method can achieve three excitations of substrate materials (SMs). It can improve the conversion luminescence intensity of SM in CM. Then, we experimentally prepared CM and SM films and simultaneously measured the frequency conversion imaging effect of the two films at 1550 nm NIR excitation. It was found that the weight ratio of doped material (DM) to SM affects the imaging enhancement of CM films. Therefore, we compared the imaging grayscale value intensity of CM films with different weight ratios under the same detection conditions. Finally, it was concluded that the best enhancement of frequency conversion imaging was achieved with a DM to SM weight ratio of 0.25 for this mechanism. The enhancement was about 3.11 times compared to SM films.
ABSTRACT
A large number of space activities are generating a high amount of undesirable space debris, which causes inevitable damage to spacecraft and satellites. Moreover, the damage assessment of ultrahigh-speed debris is a challenging task that requires both theoretical and ground-level experimental simulations. One should note that the location and damage degree can be preliminarily determined by measuring the impact flash spectrum, which provides basic data for damage assessment. Herein, the radiation spectrum of an ultrahigh-speed collision between plastic projectile and aluminum target is measured by using spectroscopic technology. The surface temperature of the colliding material, electron temperature, and electron density in the plasma are simultaneously retrieved by using a single-frame spectrum. The single-frame spectrum is separated into a continuous spectrum and a line spectrum by using continuous thermal radiation spectrum inversion material interface temperature and line spectrum inversion electron temperature and electron density in the plasma.
ABSTRACT
The authors have investigated the optical properties of core-shell structure of mist wrapped dust particles based on the method of discrete dipole approximation (DDA). The influence on the thickness of the elliptical core-shell structure were calculated which the ratio of long axis and short axis is 2:1, and the change of scattering angle for scattering characteristics. The results shows that the thickness of outer layer increase from 1.2 to 4.8 µm with the scattering and extinction coefficient of double core-shell layers particles decrease from 3.4 and 3.43 to 2.543 and 2.545, when the size of inner core isn't change. And scattering relative strength also increased obviously. The thickness of inner core increase from 0.6 to 2.4 µm with the of scattering and extinction coefficient change from 2.59 and 2.88 to 2.6 and 2.76 when thickness of outer remain constant. Effect of the thickness of visible outer layer on the scattering characteristics of double core-shell layers particles is greater, because of the interaction between scattering light and outer materials. The scattering relative intensity decrease with wavelength increased, while increased with the scale of core-shell structure increase. The results make a promotion on the study of the transportation characteristics of laser and scattering characteristics when the atmospheric aerosol and water mist interact together.