The imaging of extended scenes (wide field), has always been a challenge as optical systems naturally curve the focal surface. Thomas Sutton proposed in 1861 the use of a ball lens, combined with a curved photographic plate for the imaging of landscapes (cf Fig.1). Since then, the bending of photographic plates has been used routinely in many fields, even astronomy with the use of Schmidt telescopes which naturally have a convex focal surface.
The advent of flat electronic sensors has been a revolution, forcing optical designers to introduce additional optics to fit the flatness of these sensors surface. The classical problem of the planisphere appeared then: a huge distortion is created by the imaging system on the edge of the field. Additional complexity came along with the distortion: the field flatteners increase the volume and the mass of systems, and chromatic aberrations appear in wide field images. Also, the imaging response is not uniform across the field.
The development of curved sensors is a bio-inspired approach. Mimicking the eye retina, this new technology impacts every future imaging system. By directly correcting the field curvature in the focal plane of imagers, the use of curved sensors suppresses the field flatteners. Less optics means less misalignments and instrumental errors, increases the stability and image homogeneity, and reduces the dependence to environmental condition. Thereby it improves image acquisition quality and then reduces image post-processing costs.
This PoC project, CURVE-X, has been crucial to support the development of the start-up CURVE, which has been the very first company to bring curved sensors to the market. this project allowed extensive prototyping to improve the precision and repeatability of the curving process. The process has been patented and licensed to the start-up. Market studies have been performed, as well as press releases mentioning this PoC support from EU.
Inspired by our approach, other companies are today rising in this field, triggering the interest of the community. Soon off-the-shelf, Curved sensors are the next big leap in the field of imagers.
