An integrated image sensor with backside illumination includes a pixel. The pixel is formed by a photodiode within an active semiconductor region having a first face and a second face. A converging lens, lying in front of the first face of the active region, directs received light rays towards a central zone of the active region. At least one diffracting element, having a refractive index different from a refractive index of the active region, is provided at least partly aligned with the central zone at one of the first and second faces.