## 4 Results and Discussions
### Computer Simulation of the Scattering Process of an Incident Beam  
As a result of calculations performed using the constructed computer model, data were obtained on the spatial propagation of the reflected beam from a flat surface and from a surface with a complex two-periodic structure. Simulation of the scattering process of the reflected beam was performed in the COMSOL Multiphysics software environment. The model was based on a mechanism for calculating optical processes using the Beam Optics calculation module [35], which we described in our previous works [36; 37]. Considering the comparability of the ratio of the scale of the processed microstructure and the wavelength, the effect of the mapping of the diffraction pattern during scattering on a complex structure can be calculated, as was achieved in our previous studies using the ray optics module. We necessarily use wave optics when studying the refraction of a beam in complex inhomogeneous media. Since the formation of diffraction maxima (d), which is shown in Figure 6, pos. b, area 1, and Figure 6, pos. c, is considered in the study to be a negative factor in terms of the surface unmasking characteristic, we use the calculation of the model using the ray optics module without precise determination of the locations of the diffraction maxima. In the process of the presented modeling, the task is to calculate and visualize the reflection trajectory of a narrowly directed light beam incident on [I] a surface with a mono-periodic structure without a coating (Figure 7a), [II] a flat surface with a smooth transparent coating and [III] surface with a complex two-periodic microstructure and a transparent coating. In theoretical modeling, the thickness of the additional transparent coating is set at 70 microns. A transparent coating on the surface of the base material (AISI 321) with a two-periodic microstructure has a similar two-periodic microstructure formed on the external side of the transparent material (Glass fiber) (Figure 7b). The purpose of introducing another rough coating surface with other optical properties into theoretical models is to improve the scattering properties of the surface by complicating the trajectory of the reflected beam. This article presents the results only of theoretical studies of the scattering characteristics of surfaces with a complex surface structure having an additional coating and requires further experimental research. An additional structured layer can be obtained both additively and by spraying with subsequent sintering and repeated laser scanning. The formation of a microstructure on the coating surface can be performed using femtosecond laser processing, which occurs with less thermal impact on the material and does not cause intense melting and uncontrolled surface deformations. Figure 7: Reflective surface: (**a**) with a complex mono-periodic structure; (**b**) with a complex two-periodic structure and a transparent outer coating. The arrow indicates mirror surface. The nature of beam scattering from a surface with a complex microstructure is assessed by the pattern of trajectories of the scattered reflected beam in the plane of its incidence, as well as in comparison with the scattering patterns of the beam reflected from a similar flat surface with a flat transparent surface coating and a surface with a two-periodic microstructure and structured coating. From the diagrams of the distribution of reflected light from reflective surfaces, one can judge the nature of the reflection. In the case of reflection of a beam from a surface with a complex mono-periodic structure, the nature of the reflection becomes scattered (Figure 8a). In this case, it can be noted that, when the beam is incident normal to the surface, intense reflection occurs in a narrow sector oriented in the opposite direction to the direction of incidence. In this case, an intense unmasking reflection is observed. Figure 8: The incident beam scattering pattern: the reflection from a mono-periodic surface without the transparent outer coating.