Diffractive optics in automotive headlamps – thermal effects and optical system design

Classical design of diffractive optical elements is based on scalar diffraction theory. This concerns also the light source as an ideal light source, namely as a plane or a spherical wave. In this case, the athermalization and achromatisation of refractive lenses with diffractive structures are already being in use. The growing complexity of headlamp systems leads to an increasing influence of these two aberrations to the optical design. Because of this, the integration of diffractive optics in the design process of headlamp systems in case of achromatisation and athermalization are being forced, but there are still some challenges. First of all, the virtual light source of the optical element is a non-ideal light source, neither plane nor spherical. Furthermore, the simulation of diffractive optics has to be integrated in the simulation process of automotive systems. Firstly, studies of the thermal behaviour based on FEM-simulations for athermalization will be presented. It has been shown that the ideal thermal formula is different to the real behaviour of the element. Additionally, the integration of the athermalization to the design process will be presented too.