Forward-scattering effect on underwater laser imaging

Abstract

AAA: Muon imaging is one of the most promising non-invasive techniques for density structure scanning, specially for large objects reaching the kilometre scale. It has already interesting applications in different fields like geophysics or nuclear safety and has been proposed for some others like engineering or archaeology. One of the approaches of this technique is based on the well-known radiography principle, by reconstructing the incident direction of the detected muons after crossing the studied objects. In this case, muons detected after a previous forward scattering on the object surface represent an irreducible background noise, leading to a bias on the measurement and consequently on the reconstruction of the object mean density. Therefore, a prior characterization of this effect represents valuable information to conveniently correct the obtained results. Although the muon scattering process has been already theoretically described, a general study of this process has been carried out based on Monte Carlo simulations, resulting in a versatile tool to evaluate this effect for different object geometries and compositions. As an example, these simulations have been used to evaluate the impact of forward scattered muons on two different applications of muon imaging: archaeology and volcanology, revealing a significant impact on the latter case. The general way in which all the tools used have been developed can allow to make equivalent studies in the future for other muon imaging applications following the same procedure. KKKK: Models and simulations, Simulations methods and programs AAXXX PPPPP: 1709.05106

Polarization Reconstruction Algorithm of Target Based on the Analysis of Noise in Complex Underwater Environment

“…We use the focal plane polarization camera to take data acquisition, the camera can obtain four intensity images at different polarization direction at one-time, I0, I45, I90, I135 respectively, and can obtain Stokes vector of target reflection and backward scattering light after passing through water at the same time. This paper uses method of curve fitting to obtain the best image of orthogonal polarization, taking Stokes vector and fitting out the curve of relationship between I(θ) and θ, using Equation (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) to compute the corresponding figure of maximum intensity I max with angle is θ max and figure of minimum intensity I min with angle is θ min .…”

“…In an underwater environment, because the forward scattering mechanism are more complicated, the influence extent of backward scattering is greater than the forward scattering this article does not take the forward scattering factor into subsequent process of modeling, and specific content can refer to Section 2. According to Equation (3-2), the maximum intensity expression and minimum intensity expression are shown in Equation (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20):…”

“…Using Equation (3-20) can get intensity expression of underwater scene as shown in Equation (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21):…”

“…For transmission process of forward scattering, we can take approximation θ 0. Similar to derivation process of received power of backward scattering, power of forward scattering received imaging system can be expressed as [15]:…”

“…Similar to definition of effect coefficient of backward scattering in field of underwater imaging, similarly defining power ratio η f P r /P f as effect coefficient of forward scattering in field of underwater imaging. P r represents reflected power of underwater target received by imaging system [15], and is expressed as:…”