Proceedings Article | 12 July 2023
KEYWORDS: Image sensors, Reliability, CMOS sensors, Image processing, Electro optics, Quantum sensors, Manufacturing, Sensors, Astronomical imaging, Optical sensors
Curved imaging sensors bring significant size, weight and cost reduction to imaging systems while mitigating off-axis optical aberrations, as opposed to current flat sensors. Unlocking these key features has captured the interest of major players over the last two decades. SILINA has been developing a CMOS image sensor curving process which adapts to various sensor characteristics. This process enables the deformation of image sensors to various shapes to specifically maximize the performance of every single imaging system. Indeed, curved CMOS image sensors (CIS) help to create compact optical instruments, notably imagers, telescopes and spectrographs. Simplifying optical systems enables to release opto-mechanical constraints from the design to the integration phase. Nowadays, freeform optical elements participate in the development of solutions that meet the common needs of compact, fast, wide-angle and high-resolution systems. Nevertheless, freeform surfaces remain extremely expensive in terms of manufacturing and metrology. Moreover, field curvature aberration is still difficult to correct and curved CIS bring a suitable solution for that. Early 2021, SILINA has demonstrated the manufacturing of spherical and aspherical CIS, opening a new area to optical system design. Optical designers can now consider various sensor shapes to optimize their systems by considering spherical, aspherical or more complex focal surfaces. In 2022, SILINA is generating a data set of electro-optical performances of curved CIS. EMVA1288 compliant CMOS image sensor characterization test beds are being developed in order to fulfill this challenge. Experimental data of dark current, photo-response non-uniformity, fixed pattern noise, quantum efficiency and more can be measured. Furthermore, characterizing a large number of curved CIS will enable to assess the influence of SILINA’s curving process on key performance criteria and extract statistic results. In parallel to the electro-optical characterization campaign, reliability tests such as thermal tests, thermo-vacuum cycle and aging tests, following the ECSS norms, will be performed in order to qualify the robustness of the curving process . This paper gives an overview of SILINA‘s activities. The benefits of curved CIS are illustrated through on-going projects, the main features of the curving process and the electro-optical characterization are introduced. A focus is done on the improvement of shape accuracy and on the performances of visible curved CIS. Finally, the results of reliability tests are presented.
