Diffractive Optics in Automotive Headlamps – New Design Concepts Including a Special Simulation Process

The properties of diffractive optical elements can be used for new functions and optical concepts that cannot be realized by using refractive optics solely. In case of headlamp systems, these functions could be the chromatic and the thermal correction of refractive lenses and the design of a cut-off-free low beam system. For these two application examples, a simulation has been realized that integrates wave optics in ray-tracing-methods. The presented measurements of diffractive lenses and diffractive gratings show the accuracy of the chosen simplifications. The calculated beam deflection is divided into the waves propagation direction and the diffraction order of the corresponding ray. Based on this simulation principle, a new design concept is presented. This concept combines chromatic and thermal corrections in one lens using two different materials and is extended by an optimization of the Abbe number. The currently chosen wavelengths for the calculation of the Abbe number are optimized for black-body-spectra which are not used in headlamps any more. Therefore the three associated wavelengths are recalculated and optimized for a given spectrum in general.