New analytical method for the calculation of the LED secondary optics for automotive high-beam lamps is presented. Automotive headlamps should illuminate the road and the curb at the distance of 100-150 meters and create a bright, flat, relatively powerful light beam. To generate intensity distribution of this kind we propose to use TIR optical element (collimator working on the total internal reflection principle) with array of microlenses (optical corrector) on the upper surface. TIR part of the optical element enables reflection of the side rays to the front direction and provides a collimated beam which incidents on the microrelief. Microrelief, in its turn, dissipates the light flux in horizontal direction to meet the requirements of the Regulations 112, 113 and to provide well-illuminated area across the road in the far field. As an example, we computed and simulated the optical element with the diameter of 33 millimeters and the height of 22 millimeters. Simulation data shows that three illuminating modules including Cree XP-G2 LED and lens allow generating an appropriate intensity distribution for the class D of UNECE Regulations.
The new optimization method for design of LED optical elements working on the total internal reflection principle is
proposed. The optimization method includes the quick raytracing technique adapted for axis-symmetrical surfaces and
processing more than hundred thousand rays per second. The raytracing technique based on the approximation of the
surface of revolution by a set of truncated cones is presented. As an example, the compact optical element producing
uniformly illuminated circle region with angular size of 50° for an extended light source 1x1 mm is computed and
simulated. The light efficiency of the designed optical element is about 91.3% and the root-mean-square error of the
generated irradiance distribution is less than 10%.
A method is suggested for design of refractive optical surface intended for generation of the prescribed irradiance
distribution. The method is based on the gradient optimization of the refractive surface represented as a bicubic spline in
spherical coordinates. An optical element for direct-type backlight system was designed. The element produces
uniformly illuminated hexagonal region with angular size of 143° at the distance of 15 mm from the Luxeon® Rebel
Cool-White LED. The RMS error of generated irradiance distribution from the constant value is 3-4% with an energy
efficiency greater than 81%. The simulation data shows that a large, uniformly illuminated region can be formed by
means of a system of the indicated elements, located at the nodes of a rhombic grid.