This paper investigates the change in optical performance in a multi-element lens objective from a series production automotive camera, due to elevated temperature. The change in optical performance is evaluated by a coupled thermomechanical and optical finite element (FE) simulation. The change in the overall geometry of the objective at 85°C is calculated by thermo-mechanical simulation and caused by the expansion of individual elements. In addition, the change in the surface geometry of the lenses is obtained after smoothening the distorted FE mesh. Optical simulations are performed afterward on the deformed objective to evaluate the optical parameters including MTF (modulation transfer function) at 60 line pairs per millimeter (lp/mm). A shift of the best focus position of the lens is observed. Simulated MTF values are validated by measuring the MTF at 60 lp/mm of 10 lens samples by heating it in-situ on the measurement system. It is seen that change in MTF is about 10 percent when the lens is heated from room temperature to 85°C. Coupled optical simulations indicate the presence of astigmatism and coma, implying the asymmetric change in lens geometry at elevated temperature and tilt in one or more lens elements.

© (2023) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Amit Pandey, Denis Unruh, Marcel Kettelgerdes, Bernhard Wunderle, and Gordon Elger, "Evaluation of thermally induced change in sharpness of automotive cameras by coupled thermo-mechanical and optical simulation," Proc. SPIE 12327, SPIE Future Sensing Technologies 2023, 123270U (Presented at SPIE Future Sensing Technologies: April 20, 2023; Published: 22 May 2023); https://doi.org/10.1117/12.2665475.