An image sensor is includes a plurality of pixels. Each of the pixels includes a silicon photoconversion region and a material that at least partially surrounds the photoconversion region. The material has a refraction index smaller than the refraction index of silicon, and the interface between the photoconversion region of the pixel and the material is configured so that at least one ray reaching the photoconversion region of the pixel undergoes a total reflection or a plurality of successive total reflections at the interface.