arched wedge structures
A. N. Aleksahin, I. E. Protsenko, A. V. Uskov
New kind of secondary optics for LED lightening is suggested and investigated for the external lightening purposes. This optics is a light panel with lateral income of the light. The light from LEDs came into the back-side of the panel and goes outside from its large face side. The light does not go outside through the opposite face side because of the total internal reflection. We consider the case, when the panel is built of cylinders of different radii, the centers of cylinders are slightly shifted with the respect one another. Geometric parameters of the panel and the input beam are selected such that the output radiation has pre-determined angular distribution, for example, a «wide» distribution necessary for optimum lightening of roads. First we present basic principles of optics of arched wedges, build approximated theory based on the combination of optical properties of «straight» wedges and spherical shell. This theory lets us to select geometrical parameters of panel – arched wedge, so that the light goes out of the wedge only through the lateral (external) surface of large radius. Almost all the light goes outside after four reflections from these surface. It turns to be that the light does not go outside at all through the surface of smaller radius at optimum selection of parameters including the apex angle of the input light beam and the angle of the first incidence of the beam on the lateral surface of the panel. We present the dependences of the coefficient of extraction of the light through the external surface of the panel on and determine the region of where , i.e. all light goes outside only through external surface. Next we use analytic estimations of geometric parameters of the panel as initial data for numerical calculations of light panels and for obtaining necessary angular distributions of output light. We obtain a «wide» output angular distribution of the light from cylindrical arched wedge panel, for two such panels placed in front of each other; we suggest also spherical arched wedge light panels. Our results show and justify physical principles of work of arched wedge light panels, they can be used for development of similar structures of secondary optic and can be applied directly to design of LED lightening panels.