Curved detectors for astronomical applications: characterization results on different samples.

Abstract

Due to the increasing dimension, complexity, and cost of future astronomical surveys, new technologies enabling more compact and simpler systems are required. The development of curved detectors allows enhancement of the performances of the optical system used (telescope or astronomical instrument), while keeping the system more compact. We describe here a set of five curved complementary metal-oxide semiconductor (CMOS) detectors developed within a collaboration between CEA-LETI and CNRS-LAM. These fully functional detectors 20Mpix (CMOSIS CMV20000) have been curved to different radii of curvature and spherical shapes (both convex and concave) over a size of 24×32 mm2. Before being able to use them for astronomical observations, we assess the impact of the curving process on their performances. We perform a full electro-optical characterization of the curved detectors, by measuring the gain, the full well capacity, the dynamic range, and the noise properties, such as dark current, readout noise, pixel-relative non-uniformity. We repeat the same process for the flat version of the same CMOS sensor, as a reference for comparison. We find no significant difference among most of the characterization values of the curved and flat samples. We obtain values of readout noise of 10e- for the curved samples compared to the 11e- of the flat sample, which provides slightly larger dynamic ranges for the curved detectors. Additionally, we measure consistently smaller values of dark current compared to the flat CMOS sensor. The curving process for the prototypes shown in this paper does not significantly impact the performances of the detectors. These results represent the first step toward their astronomical implementation.