Temperature-induced spherical aberration in the athermalization of large-aperture glass-plastic optical systems

Without athermalization, the image quality of optical systems with plastic lenses can significantly degrade due to the unstable thermal properties of plastic materials under temperature fluctuations. Unlike existing research that focuses solely on moderate aperture lens systems for athermalization, this paper investigates glass-plastic hybrid lens systems with large apertures. We investigate the phenomenon of temperature-induced spherical aberration (TiSA), which has not been thoroughly explored. A formula is then derived to quantitatively estimate the amount of TiSA. To mitigate the impact of TiSA on imaging quality, we present methods for fully and partially athermalizing the lens system. Additionally, our study includes two-lens design examples to verify the presence of TiSA and demonstrate the effectiveness of our athermalization approaches. These methods are applied to lenses with large apertures used in automotive pixelated lighting, resulting in fully and partially athermalized designs. The prototype based on partial athermalization shows good performance within the working temperature range, supporting the effectiveness of this approach. The analysis and methods presented can be applied across various fields, including automotive lighting, LiDAR, ADAS systems, surveillance cameras, and mobile phone cameras.