Collective Curved CMOS Sensor Process: Application for High-Resolution Optical Design and Assembly Challenges

Curved sensors is a well-adapted technology solution to enhance the vast majority of optical systems. It helps to remove lenses and simplify optical architectures. These advantages open news challenges such as a specific fabrication process applied to curved sensors and new rules for final system integration. In this paper, we first introduce benefits of curved sensors applied on a compact high-resolution camera to define the sensor shape specifications and to reach high performances and compactness (-50% compared to a benchmark system). Mechanical limits and optical modeling are used. Then, based on these curved specifications, a novel collective curving process is described, developed on 1/1.8" format CMOS image sensors with a radius or curvature target R= 55 mm and R=60 mm. This work includes packaging and assembly steps, optimizations, and morphological characterizations in accordance to optical design requirements. Finally, a dedicated optical test bench is used for Modulation Transfer Function (MTF) characterization of the final camera prototype. All these experiments and optical results introduce new opto-mechanical requirements and demonstrate the feasibility and high performances of systems with curved sensors.