If the majority of sensors operate on visible light, their modeling remains a difficult task. Indeed, part of the complexity of the modeling results from the very different shape and size factors between the whole pixel, the micrometric lenses and the nanometric structuring of the surface of the absorbing semiconductor. Moreover, an accurate estimation of light absorption is delicate because it depends on the absorbing material but also on the temperature of the latter and the density of free carriers. We develop a numerical modeling approach based on high order discontinuous Galerkin time-domain methods to study light absorption in the whole imager device, from curved and micrometric lenses to the pyramidal and nanometric texturing of the doped silicon. This study is conducted in collaboration with ST Microlectronics in Crolles, which takes place in the context of the IPCEI (Important Projects of Common European Interest) Microelectronics