S. H. Djanibekova, I. E. Protsenko, R. N. Rizahanov

Light panel as two-dimensional plane waveguide (light-guide) with the introduction of the light from the side, for example, from array of LEDs, is considered. The light is introduced into waveguide modes of the panel. The light propagated inside the panel is scattered on diffusion scattering strips installed at one (bottom) of large sides of the panel, scattered light goes outside through the opposite (top, or «working») side of the panel. It is supposed to use such panel for lightening, so it is important to reach possibly homogeneous distribution of the light coming from the work side of the panel. This can be obtained by increasing the the density of scatters in strips going from the side of the panel with LEDs: following the decrease of the light beam power propagated inside the panel. One can reach homogeneous radiation from the work side of the panel also another way: by taking the same density of scatters in each strip but increasing the width of strips in the direction out of the side of the panel with LEDs. The method of calculation of the density of diffusion scatters in strips or the width of strips so that the same power scattered by each strip is proposed in the paper. Calculations are made at geometric optics approximation, which is good for light panels with large (respectively to unity) number of waveguide modes. The increment γsc of dumping of the waveguide mode due to the scattering on the strip with the density ρ of scatters in the waveguide of the thickness d is determined first. Analytical expression for γsc is obtained. Next, by using the expression for γsc, the losses of the light in the waveguide due to the scattering on the strip are found. Equating these losses to the difference in the light flux after and before the scattering strip inexplicit expressions determining the densities of scatters or the widths of strips were found. Parameters of seven scattering strips in the rectangular glass waveguide are calculated as an example. It turned to be that for realistic values of parameters, as widths of strips, one has to keep 20 - 30% of the input power in the panel. This means that the maximum «internal» efficiency of the panel will be about 70 - 80 % without taking into account the losses of the light at the introduction into the panel and at the assumption that all scattered light goes outside. Results of the paper can be used for optimization of panels also as initial or test data in numerical analysis with account for all real features. Results can be used also directly at the design of light panels with side introduction of the light also when the light is introduced from opposite sides of panels or from all sides of panels.