Monte Carlo simulation of light scattering in the atmosphere and effect of atmospheric aerosols on the point spread function

A boundary migration model for imaging within volumetric scattering media

Effectively imaging within volumetric scattering media is of great importance and challenging especially in macroscopic applications. Recent works have demonstrated the ability to image through scattering media or within the weak volumetric scattering media using spatial distribution or temporal characteristics of the scattered field. Here, we focus on imaging Lambertian objects embedded in highly scattering media, where signal photons are dramatically attenuated during propagation and highly coupled with background photons. We address these challenges by providing a time-to-space boundary migration model (BMM) of the scattered field to convert the scattered measurements in spectral form to the scene information in the temporal domain using all of the optical signals. The experiments are conducted under two typical scattering scenarios: 2D and 3D Lambertian objects embedded in the polyethylene foam and the fog, which demonstrate the effectiveness of the proposed algorithm. It outperforms related works including time gating in terms of reconstruction precision and scattering strength. Even though the proportion of signal photons is only 0.75%, Lambertian objects located at more than 25 transport mean free paths (TMFPs), corresponding to the round-trip scattering length of more than 50 TMFPs, can be reconstructed. Also, the proposed method provides low reconstruction complexity and millisecond-scale runtime, which significantly benefits its application.

Imaging in scattering media is challenging due to signal attenuation and strong coupling of scattered and signal photons. The authors present a boundary migration model of the scattered field, converting scattered measurements in spectral form to scene information in temporal domain, and image Lambertian objects in highly scattering media.

Temporal and spatial domain detection model and method of infrared photoelectric detection target

To improve the detection ability of photoelectric detection targets under low-illumination conditions, based on the traditional infrared photoelectric detection targets, in this paper, we propose a design method for an infrared detection screen by using a double high-power line laser interactive layout auxiliary mode, and we form an active infrared photoelectric detection target. We then establish the calculations of the laser beam's illumination and the emission power of the pulse laser as a projectile passes through the infrared detection screen. According to the relation of the thickness of the infrared detection screen, the time period over which the projectile passes through the infrared detection screen, and the projectile's spatial position, we use the grid division method to establish the temporal- and spatial-domain echo power model and the output signal voltage function of the active infrared photoelectric detection target. Through calculations and experimental analysis, it is found that the echo power is reduced as the detection distance is increased, and the intensity of the echo power is not linear with the thickness of the detection screen or the length of the projectile in the temporal and spatial domains. The detection performance of the proposed active infrared photoelectric detection target is better than the traditional infrared photoelectric detection target, and it can be improved to a certain extent by increasing the laser emission power appropriately.