Embodiments of the present application disclose an optical image capturing unit, an optical image capturing system, and an electronic device. The optical image capturing unit includes: a micro lens; a light shielding layer disposed under the micro lens, where the light shielding layer is provided with a window; and a photosensor disposed under the light shielding layer, where the micro lens is configured to converge an optical signal from above the micro lens to the window, and the optical signal is transmitted to the photosensor via the window. Technical solutions of embodiments of the present application could enhance performance of an optical image capturing product.