Analysis of package design of optic modules for automotive cameras to realize reliable image sharpness

To enable future autonomous driving, failure free operation is a requirement for safety relevant electronic and mechanical components. The paper investigates the health indicator (HI), change in sharpness (CIS), used for condition monitoring (CM) of optical modules of automotive stereo cameras. Driven by the cyclic thermo-mechanical stress, strain and displacement, the sharpness of the optical imaging system can change. Different root causes for change in sharpness (CIS) are identified and the contribution of the different failure modes for CIS are investigated. Failure modes are separated in two categories: Changes in the distance between focal and image plane by displacement of the image plane (failure mode -package) and changes in the lens stack of the objective (failure mode - objective). By combining DOE and accelerated life testing the contribution of different stress conditions, i.e. vibrations and temperature cycling, was quantified and compared. Strong evidence was found that vibration induced aging has no influence on optical performance of the objective. Moreover, the comparison showed that vibration induced CIS can be neglected compart to CIS induced by thermo-mechanical cycling. To investigate CIS as a health indicator for the entire camera sensor the specification and development of a novel in situ measurement system for CM of camera sensors is described.